Science.gov

Sample records for laboratory natural selection

  1. Demonstrating Natural Selection

    ERIC Educational Resources Information Center

    Hinds, David S.; Amundson, John C.

    1975-01-01

    Describes laboratory exercises with chickens selecting their food from dyed and natural corn kernels as a method of demonstrating natural selection. The procedure is based on the fact that organisms that blend into their surroundings escape predation. (BR)

  2. A Natural Selection: Partnering Teachers and Scientists in the Classroom Laboratory Creates a Dynamic Learning Community

    ERIC Educational Resources Information Center

    Siegel, Marcelle A.; Mlynarczyk-Evans, Susanna; Brenner, Tamara J.; Nielsen, Katherine M.

    2005-01-01

    The high school science laboratory provides a natural environment for students to learn through scientist-teacher partnerships. Scientists represent an excellent resource for teachers and students: They possess specialized knowledge and skills, have access to laboratory equipment and materials, and are immersed in a culture of collaborative…

  3. A Natural Selection: Partnering Teachers and Scientists in the Classroom Laboratory Creates a Dynamic Learning Community

    ERIC Educational Resources Information Center

    Siegel, Marcelle A.; Mlynarczyk-Evans, Susanna; Brenner, Tamara J.; Nielsen, Katherine M.

    2005-01-01

    The high school science laboratory provides a natural environment for students to learn through scientist-teacher partnerships. Scientists represent an excellent resource for teachers and students: They possess specialized knowledge and skills, have access to laboratory equipment and materials, and are immersed in a culture of collaborative…

  4. Adaptive value of phenological traits in stressful environments: predictions based on seed production and laboratory natural selection.

    PubMed

    Brachi, Benjamin; Aimé, Carla; Glorieux, Cédric; Cuguen, Joel; Roux, Fabrice

    2012-01-01

    Phenological traits often show variation within and among natural populations of annual plants. Nevertheless, the adaptive value of post-anthesis traits is seldom tested. In this study, we estimated the adaptive values of pre- and post-anthesis traits in two stressful environments (water stress and interspecific competition), using the selfing annual species Arabidopsis thaliana. By estimating seed production and by performing laboratory natural selection (LNS), we assessed the strength and nature (directional, disruptive and stabilizing) of selection acting on phenological traits in A. thaliana under the two tested stress conditions, each with four intensities. Both the type of stress and its intensity affected the strength and nature of selection, as did genetic constraints among phenological traits. Under water stress, both experimental approaches demonstrated directional selection for a shorter life cycle, although bolting time imposes a genetic constraint on the length of the interval between bolting and anthesis. Under interspecific competition, results from the two experimental approaches showed discrepancies. Estimation of seed production predicted directional selection toward early pre-anthesis traits and long post-anthesis periods. In contrast, the LNS approach suggested neutrality for all phenological traits. This study opens questions on adaptation in complex natural environment where many selective pressures act simultaneously. PMID:22403624

  5. Adaptive Value of Phenological Traits in Stressful Environments: Predictions Based on Seed Production and Laboratory Natural Selection

    PubMed Central

    Glorieux, Cédric; Cuguen, Joel; Roux, Fabrice

    2012-01-01

    Phenological traits often show variation within and among natural populations of annual plants. Nevertheless, the adaptive value of post-anthesis traits is seldom tested. In this study, we estimated the adaptive values of pre- and post-anthesis traits in two stressful environments (water stress and interspecific competition), using the selfing annual species Arabidopsis thaliana. By estimating seed production and by performing laboratory natural selection (LNS), we assessed the strength and nature (directional, disruptive and stabilizing) of selection acting on phenological traits in A. thaliana under the two tested stress conditions, each with four intensities. Both the type of stress and its intensity affected the strength and nature of selection, as did genetic constraints among phenological traits. Under water stress, both experimental approaches demonstrated directional selection for a shorter life cycle, although bolting time imposes a genetic constraint on the length of the interval between bolting and anthesis. Under interspecific competition, results from the two experimental approaches showed discrepancies. Estimation of seed production predicted directional selection toward early pre-anthesis traits and long post-anthesis periods. In contrast, the LNS approach suggested neutrality for all phenological traits. This study opens questions on adaptation in complex natural environment where many selective pressures act simultaneously. PMID:22403624

  6. Laboratory Activities to Support Student Understanding of the Molecular Mechanisms of Mutation & Natural Selection

    ERIC Educational Resources Information Center

    Hubler, Tina; Adams, Patti; Scammell, Jonathan

    2015-01-01

    The molecular basis of evolution is an important and challenging concept for students to understand. In a previous article, we provided some of the scientific background necessary to teach this topic. This article features a series of laboratory activities demonstrating that molecular events can alter the genomes of organisms. These activities are…

  7. Laboratory Activities to Support Student Understanding of the Molecular Mechanisms of Mutation & Natural Selection

    ERIC Educational Resources Information Center

    Hubler, Tina; Adams, Patti; Scammell, Jonathan

    2015-01-01

    The molecular basis of evolution is an important and challenging concept for students to understand. In a previous article, we provided some of the scientific background necessary to teach this topic. This article features a series of laboratory activities demonstrating that molecular events can alter the genomes of organisms. These activities are…

  8. The Pretorious fault, Mponeng mine, South Africa: A site selected for the establishment of a natural earthquake laboratory

    NASA Astrophysics Data System (ADS)

    Reches, Z.; van Aswegen, G.; Jordan, T. H.; Johnston, M.; Zoback, M.

    2004-12-01

    One major obstacle in earthquake investigations is the lack of direct and near-field observations. To reduce this limitation, we initiated the NELSAM project (Natural Earthquake Laboratory in South African Mines) for in-situ seismic observations at 3.5 km depth (session S11 this meeting). The project includes instrumentation of the complete frequency range (creepmeters, seismometers, strain meters, accelerometers, temperature sensors, acoustic emission transducers). This dense 3D array is designed to monitor fault activity before, during, and after M = 2.5-3.5 earthquakes at distances of 1-100 m from their anticipated hypocenters. The site characterization will include 3D mapping, in-situ stress measurements on local and regional scales, and rock mechanics analysis. We describe here the structural and seismic features of the first site where monitoring is planned to start circa April, 2005.We screened and ranked 12 active faults in South African mines according to dimensions, internal structure, accessibility, and likelihood of M 3.0 seismic events. The selected site is on the Pretorius fault, one of the largest faults in the Western Deep Levels gold mines, WSW of Johannesburg. This fault-zone is at least 10 km long; it is very steep and inclined toward the SSE with throw up to 70 m. It contains many individual fault surfaces that vary in inclination from 40 deg to vertical; some have thin breccia zones with quartz cementation, and a few display a fine-grain gouge, but there is no major, well-developed gouge zone. The Pretorius fault accommodated some amount of strike-slip displacement as indicated by frequent inversion of the sense of fault throw, the occurrence of horizontal slickenside striations, and its steepness. The Pretorius fault-zone was active in Archaean times, and it has been locally reactivated by the mining operations in Mponeng and Tautona mines, which provide access to depths of 3.0-3.5 km. Our monitoring site will be established where both sides of the Pretorius fault will be mined during the next few years; the practice in the deep mines and numerical modeling predict profound increase of the seismic activity at the site during the next 2-4 years. The associated increase of shear stresses on the fault is expected to generate a few earthquakes of M>3.0 along surfaces of hundreds to thousands of sq. meters within the fault zone. Monitoring the fault zone activity and particularly the larger events is the main objective of NELSAM.

  9. Mouse mammary tumor virus-induced tumorigenesis in sag transgenic mice: a laboratory model of natural selection.

    PubMed Central

    Golovkina, T V; Prescott, J A; Ross, S R

    1993-01-01

    Transgenic mice that expressed the superantigen protein encoded in the C3H exogenous mouse mammary tumor virus long terminal repeat deleted their V beta 14+ T cells during the shaping of their immune repertoire and showed no evidence of virus production in their mammary glands after infection by milk-borne C3H exogenous virus. However, they developed mammary gland tumors that had newly integrated copies of C3H exogenous virus, although the latency of tumor formation was much longer than in their nontransgenic littermates that retained their V beta 14+ T cells. After four generations, infectious C3H virus was completely eliminated from the transgenic mouse pedigree. These data support the hypothesis that endogenous mouse mammary tumor proviruses are retained in the genome as protection against exogenous virus infection and subsequent tumorigenesis and show that there may be natural selection against the virus in vivo. Images PMID:8230492

  10. Reinventing Natural Selection

    ERIC Educational Resources Information Center

    Geraedts, Caspar L.; Boersma, Kerst Th.

    2006-01-01

    Although many research studies report students' Lamarckian misconceptions, only a few studies present learning and teaching strategies that focus on the successful development of the concept of natural selection. The learning and teaching strategy for upper secondary students (aged 15-16) presented in this study conducted in The Netherlands is…

  11. Reinventing Natural Selection

    ERIC Educational Resources Information Center

    Geraedts, Caspar L.; Boersma, Kerst Th.

    2006-01-01

    Although many research studies report students' Lamarckian misconceptions, only a few studies present learning and teaching strategies that focus on the successful development of the concept of natural selection. The learning and teaching strategy for upper secondary students (aged 15-16) presented in this study conducted in The Netherlands is…

  12. Reinventing Natural Selection

    NASA Astrophysics Data System (ADS)

    Geraedts, Caspar L.; Boersma, Kerst Th.

    2006-06-01

    Although many research studies report students’ Lamarckian misconceptions, only a few studies present learning and teaching strategies that focus on the successful development of the concept of natural selection. The learning and teaching strategy for upper secondary students (aged 15 16) presented in this study conducted in The Netherlands is based on the idea of guided reinvention, rather than on the conceptual change strategy. In guided reinvention, students reinvent the concept of natural selection by answering a sequence of questions based on the logical nature of Darwin’s theory. The results show that few Lamarckian explanations for evolution were recorded in the study and that the majority of the students developed a Darwinian or neo-Darwinian conception. The status of Lamarckian misconceptions is challenged.

  13. Naturally selecting solutions

    PubMed Central

    Manning, Timmy; Sleator, Roy D; Walsh, Paul

    2013-01-01

    For decades, computer scientists have looked to nature for biologically inspired solutions to computational problems; ranging from robotic control to scheduling optimization. Paradoxically, as we move deeper into the post-genomics era, the reverse is occurring, as biologists and bioinformaticians look to computational techniques, to solve a variety of biological problems. One of the most common biologically inspired techniques are genetic algorithms (GAs), which take the Darwinian concept of natural selection as the driving force behind systems for solving real world problems, including those in the bioinformatics domain. Herein, we provide an overview of genetic algorithms and survey some of the most recent applications of this approach to bioinformatics based problems. PMID:23222169

  14. A Natural Selection Game.

    ERIC Educational Resources Information Center

    Tashiro, Mark E.

    1984-01-01

    Provides rules for a game which simulates selection pressures on a hominid group. Objectives include an appreciation of how selectivity works, an understanding of how abiotic factors are able to influence a population, and how interactions within the population can influence the group. (JM)

  15. Modeling Natural Selection

    ERIC Educational Resources Information Center

    Bogiages, Christopher A.; Lotter, Christine

    2011-01-01

    In their research, scientists generate, test, and modify scientific models. These models can be shared with others and demonstrate a scientist's understanding of how the natural world works. Similarly, students can generate and modify models to gain a better understanding of the content, process, and nature of science (Kenyon, Schwarz, and Hug…

  16. Modeling Natural Selection

    ERIC Educational Resources Information Center

    Bogiages, Christopher A.; Lotter, Christine

    2011-01-01

    In their research, scientists generate, test, and modify scientific models. These models can be shared with others and demonstrate a scientist's understanding of how the natural world works. Similarly, students can generate and modify models to gain a better understanding of the content, process, and nature of science (Kenyon, Schwarz, and Hug…

  17. Friendship and natural selection

    PubMed Central

    Christakis, Nicholas A.; Fowler, James H.

    2014-01-01

    More than any other species, humans form social ties to individuals who are neither kin nor mates, and these ties tend to be with similar people. Here, we show that this similarity extends to genotypes. Across the whole genome, friends’ genotypes at the single nucleotide polymorphism level tend to be positively correlated (homophilic). In fact, the increase in similarity relative to strangers is at the level of fourth cousins. However, certain genotypes are also negatively correlated (heterophilic) in friends. And the degree of correlation in genotypes can be used to create a “friendship score” that predicts the existence of friendship ties in a hold-out sample. A focused gene-set analysis indicates that some of the overall correlation in genotypes can be explained by specific systems; for example, an olfactory gene set is homophilic and an immune system gene set is heterophilic, suggesting that these systems may play a role in the formation or maintenance of friendship ties. Friends may be a kind of “functional kin.” Finally, homophilic genotypes exhibit significantly higher measures of positive selection, suggesting that, on average, they may yield a synergistic fitness advantage that has been helping to drive recent human evolution. PMID:25024208

  18. Friendship and natural selection.

    PubMed

    Christakis, Nicholas A; Fowler, James H

    2014-07-22

    More than any other species, humans form social ties to individuals who are neither kin nor mates, and these ties tend to be with similar people. Here, we show that this similarity extends to genotypes. Across the whole genome, friends' genotypes at the single nucleotide polymorphism level tend to be positively correlated (homophilic). In fact, the increase in similarity relative to strangers is at the level of fourth cousins. However, certain genotypes are also negatively correlated (heterophilic) in friends. And the degree of correlation in genotypes can be used to create a "friendship score" that predicts the existence of friendship ties in a hold-out sample. A focused gene-set analysis indicates that some of the overall correlation in genotypes can be explained by specific systems; for example, an olfactory gene set is homophilic and an immune system gene set is heterophilic, suggesting that these systems may play a role in the formation or maintenance of friendship ties. Friends may be a kind of "functional kin." Finally, homophilic genotypes exhibit significantly higher measures of positive selection, suggesting that, on average, they may yield a synergistic fitness advantage that has been helping to drive recent human evolution. PMID:25024208

  19. A quantum of natural selection

    NASA Astrophysics Data System (ADS)

    Lloyd, Seth

    2009-03-01

    The modern evolutionary synthesis, which marries Darwin's theory of natural selection with Mendel's genetics, was developed around the same time as quantum mechanics. Is there any connection between the two?

  20. Laboratory selection quickly erases historical differentiation.

    PubMed

    Fragata, Inês; Simões, Pedro; Lopes-Cunha, Miguel; Lima, Margarida; Kellen, Bárbara; Bárbaro, Margarida; Santos, Josiane; Rose, Michael R; Santos, Mauro; Matos, Margarida

    2014-01-01

    The roles of history, chance and selection have long been debated in evolutionary biology. Though uniform selection is expected to lead to convergent evolution between populations, contrasting histories and chance events might prevent them from attaining the same adaptive state, rendering evolution somewhat unpredictable. The predictability of evolution has been supported by several studies documenting repeatable adaptive radiations and convergence in both nature and laboratory. However, other studies suggest divergence among populations adapting to the same environment. Despite the relevance of this issue, empirical data is lacking for real-time adaptation of sexual populations with deeply divergent histories and ample standing genetic variation across fitness-related traits. Here we analyse the real-time evolutionary dynamics of Drosophila subobscura populations, previously differentiated along the European cline, when colonizing a new common environment. By analysing several life-history, physiological and morphological traits, we show that populations quickly converge to the same adaptive state through different evolutionary paths. In contrast with other studies, all analysed traits fully converged regardless of their association with fitness. Selection was able to erase the signature of history in highly differentiated populations after just a short number of generations, leading to consistent patterns of convergent evolution. PMID:24788553

  1. Laboratory Selection Quickly Erases Historical Differentiation

    PubMed Central

    Lopes-Cunha, Miguel; Lima, Margarida; Kellen, Bárbara; Bárbaro, Margarida; Santos, Josiane; Rose, Michael R.; Santos, Mauro; Matos, Margarida

    2014-01-01

    The roles of history, chance and selection have long been debated in evolutionary biology. Though uniform selection is expected to lead to convergent evolution between populations, contrasting histories and chance events might prevent them from attaining the same adaptive state, rendering evolution somewhat unpredictable. The predictability of evolution has been supported by several studies documenting repeatable adaptive radiations and convergence in both nature and laboratory. However, other studies suggest divergence among populations adapting to the same environment. Despite the relevance of this issue, empirical data is lacking for real-time adaptation of sexual populations with deeply divergent histories and ample standing genetic variation across fitness-related traits. Here we analyse the real-time evolutionary dynamics of Drosophila subobscura populations, previously differentiated along the European cline, when colonizing a new common environment. By analysing several life-history, physiological and morphological traits, we show that populations quickly converge to the same adaptive state through different evolutionary paths. In contrast with other studies, all analysed traits fully converged regardless of their association with fitness. Selection was able to erase the signature of history in highly differentiated populations after just a short number of generations, leading to consistent patterns of convergent evolution. PMID:24788553

  2. Natural Selection in Large Populations

    NASA Astrophysics Data System (ADS)

    Desai, Michael

    2011-03-01

    I will discuss theoretical and experimental approaches to the evolutionary dynamics and population genetics of natural selection in large populations. In these populations, many mutations are often present simultaneously, and because recombination is limited, selection cannot act on them all independently. Rather, it can only affect whole combinations of mutations linked together on the same chromosome. Methods common in theoretical population genetics have been of limited utility in analyzing this coupling between the fates of different mutations. In the past few years it has become increasingly clear that this is a crucial gap in our understanding, as sequence data has begun to show that selection appears to act pervasively on many linked sites in a wide range of populations, including viruses, microbes, Drosophila, and humans. I will describe approaches that combine analytical tools drawn from statistical physics and dynamical systems with traditional methods in theoretical population genetics to address this problem, and describe how experiments in budding yeast can help us directly observe these evolutionary dynamics.

  3. Human evolution: new playgrounds for natural selection.

    PubMed

    Milot, Emmanuel; Pelletier, Fanie

    2013-05-20

    Despite popular misconceptions, natural selection does operate in modern human populations. New studies even show that changes associated with modernization are deeply reshaping selection pressures and, perhaps, bits of our biological nature. PMID:23701687

  4. Populations, Natural Selection, and Applied Organizational Science.

    ERIC Educational Resources Information Center

    McKelvey, Bill; Aldrich, Howard

    1983-01-01

    Deficiencies in existing models in organizational science may be remedied by applying the population approach, with its concepts of taxonomy, classification, evolution, and population ecology; and natural selection theory, with its principles of variation, natural selection, heredity, and struggle for existence, to the idea of organizational forms…

  5. From Nature to the Laboratory and Into the Clinic

    PubMed Central

    Nicolaou, K. C.; Chen, Jason S.; Dalby, Stephen M.

    2009-01-01

    Natural products possess a broad diversity of structure and function, and they provide inspiration for chemistry, biology, and medicine. In this review article, we highlight and place in context our laboratory’s total syntheses of, and related studies on, complex secondary metabolites that were clinically important drugs, or have since been developed into useful medicines, namely amphotericin B (1, Figure 1), calicheamicin ?1I (2), rapamycin (3), Taxol® (4), the epothilones [e.g. epothilones A (5) and B (6)], and vancomycin (7). We also briefly highlight our research with other selected inspirational natural products possessing interesting biological activities [i.e. dynemicin A (8, Figure 2), uncialamycin (9), eleutherobin (10), sarcodictyin A (11), azaspiracid-1 (12), thiostrepton (13), abyssomicin C (14), platensimycin (15), platencin (16), and palmerolide A (17)]. PMID:19028103

  6. Natural resource economics: Selected papers

    SciTech Connect

    Ciriacy-Wantrup, S.V.

    1985-01-01

    This volume was assembled by two of Dr. Wantrup's students as a complement to his textbook, Resource Conservation: Economics and Policies. Wantrup's ideas on conservation economics continued to evolve in ways that were never fully reflected in the textbook and, although for the student of natural resource economics it is still essential reading, to stop there is to have missed some of his most valuable insights. Part 1 of this book deals with various aspects of the ''commons'' problem and includes Wantrup's key contributions to the literature on ''common property,'' which he brought to its current place of prominence in natural resource economics. Parts 2 and 3 focus on water-related issues; Part 4 looks at recent writings in the conservation area, with particular emphasis on irreversibility and uncertainty; and the final section examines the role of natural resources in economic development. Each part is introduced by one of Wantrup's students, and their special insights help guide the reader toward the most significant of Wantrup's ideas.

  7. Natural Selection in a Petri Dish.

    ERIC Educational Resources Information Center

    McCarty, Robbie V.; Marek, Edmund A.

    1997-01-01

    Presents an activity to teach natural selection that involves students in a microbiological investigation. Students discover that a change in environmental conditions tests a species' range of adaptations. (DDR)

  8. The negative view of natural selection.

    PubMed

    Birch, Jonathan

    2012-06-01

    An influential argument due to Elliott Sober, subsequently strengthened by Denis Walsh and Joel Pust, moves from plausible premises to the bold conclusion that natural selection cannot explain the traits of individual organisms. If the argument were sound, the explanatory scope of selection would depend, surprisingly, on metaphysical considerations concerning origin essentialism. I show that the Sober-Walsh-Pust argument rests on a flawed counterfactual criterion for explanatory relevance. I further show that a more defensible criterion for explanatory relevance recently proposed by Michael Strevens lends support to the view that natural selection can be relevant to the explanation of individual traits. PMID:22520205

  9. Can natural selection favour altruism between species?

    PubMed

    Wyatt, G A K; West, S A; Gardner, A

    2013-09-01

    Darwin suggested that the discovery of altruism between species would annihilate his theory of natural selection. However, it has not been formally shown whether between-species altruism can evolve by natural selection, or why this could never happen. Here, we develop a spatial population genetic model of two interacting species, showing that indiscriminate between species helping can be favoured by natural selection. We then ask if this helping behaviour constitutes altruism between species, using a linear-regression analysis to separate the total action of natural selection into its direct and indirect (kin selected) components. We show that our model can be interpreted in two ways, as either altruism within species, or altruism between species. This ambiguity arises depending on whether or not we treat genes in the other species as predictors of an individual's fitness, which is equivalent to treating these individuals as agents (actors or recipients). Our formal analysis, which focuses upon evolutionary dynamics rather than agents and their agendas, cannot resolve which is the better approach. Nonetheless, because a within-species altruism interpretation is always possible, our analysis supports Darwin's suggestion that natural selection does not favour traits that provide benefits exclusively to individuals of other species. PMID:23848844

  10. Comparing Patterns of Natural Selection across Species Using Selective Signatures

    SciTech Connect

    Shapiro, Jesse; Alm, Eric J.

    2007-12-01

    Comparing gene expression profiles over many different conditions has led to insights that were not obvious from single experiments. In the same way, comparing patterns of natural selection across a set of ecologically distinct species may extend what can be learned from individual genome-wide surveys. Toward this end, we show how variation in protein evolutionary rates, after correcting for genome-wide effects such as mutation rate and demographic factors, can be used to estimate the level and types of natural selection acting on genes across different species. We identify unusually rapidly and slowly evolving genes, relative to empirically derived genome-wide and gene family-specific background rates for 744 core protein families in 30 c-proteobacterial species. We describe the pattern of fast or slow evolution across species as the"selective signature" of a gene. Selective signatures represent aprofile of selection across species that is predictive of gene function: pairs of genes with correlated selective signatures are more likely to share the same cellular function, and genes in the same pathway can evolve in concert. For example,glycolysis and phenylalanine metabolism genes evolve rapidly in Idiomarina loihiensis, mirroring an ecological shift in carbon source from sugars to amino acids. In a broader context, our results suggest that the genomic landscape is organized into functional modules even at the level of natural selection, and thus it may be easier than expected to understand the complex evolutionary pressures on a cell.

  11. Comparing Patterns of Natural Selection Across Species Using Selective Signatures

    SciTech Connect

    Alm, Eric J.; Shapiro, B. Jesse; Alm, Eric J.

    2007-12-18

    Comparing gene expression profiles over many different conditions has led to insights that were not obvious from single experiments. In the same way, comparing patterns of natural selection across a set of ecologically distinct species may extend what can be learned from individual genome-wide surveys. Toward this end, we show how variation in protein evolutionary rates, after correcting for genome-wide effects such as mutation rate and demographic factors, can be used to estimate the level and types of natural selection acting on genes across different species. We identify unusually rapidly and slowly evolving genes, relative to empirically derived genome-wide and gene family-specific background rates for 744 core protein families in 30 gamma-proteobacterial species. We describe the pattern of fast or slow evolution across species as the 'selective signature' of a gene. Selective signatures represent a profile of selection across species that is predictive of gene function: pairs of genes with correlated selective signatures are more likely to share the same cellular function, and genes in the same pathway can evolve in concert. For example, glycolysis and phenylalanine metabolism genes evolve rapidly in Idiomarina loihiensis, mirroring an ecological shift in carbon source from sugars to amino acids. In a broader context, our results suggest that the genomic landscape is organized into functional modules even at the level of natural selection, and thus it may be easier than expected to understand the complex evolutionary pressures on a cell.

  12. Reducing environmental bias when measuring natural selection.

    PubMed

    Scheiner, Samuel M; Donohue, Kathleen; Dorn, Lisa A; Mazer, Susan J; Wolfe, Lorne M

    2002-11-01

    Crucial to understanding the process of natural selection is characterizing phenotypic selection. Measures of phenotypic selection can be biased by environmental variation among individuals that causes a spurious correlation between a trait and fitness. One solution is analyzing genotypic data, rather than phenotypic data. Genotypic data, however, are difficult to gather, can be gathered from few species, and typically have low statistical power. Environmental correlations may act through traits other than through fitness itself. A path analytic framework, which includes measures of such traits, may reduce environmental bias in estimates of selection coefficients. We tested the efficacy of path analysis to reduce bias by re-analyzing three experiments where both phenotypic and genotypic data were available. All three consisted of plant species (Impatiens capensis, Arabidopsis thaliana, and Raphanus sativus) grown in experimental plots or the greenhouse. We found that selection coefficients estimated by path analysis using phenotypic data were highly correlated with those based on genotypic data with little systematic bias in estimating the strength of selection. Although not a panacea, using path analysis can substantially reduce environmental biases in estimates of selection coefficients. Such confidence in phenotypic selection estimates is critical for progress in the study of natural selection. PMID:12487346

  13. Complete genetic linkage can subvert natural selection.

    PubMed

    Gerrish, Philip J; Colato, Alexandre; Perelson, Alan S; Sniegowski, Paul D

    2007-04-10

    The intricate adjustment of organisms to their environment demonstrates the effectiveness of natural selection. But Darwin himself recognized that certain biological features could limit this effectiveness, features that generally reduce the efficiency of natural selection or yield suboptimal adaptation. Genetic linkage is known to be one such feature, and here we show theoretically that it can introduce a more sinister flaw: when there is complete linkage between loci affecting fitness and loci affecting mutation rate, positive natural selection and recurrent mutation can drive mutation rates in an adapting population to intolerable levels. We discuss potential implications of this finding for the early establishment of recombination, the evolutionary fate of asexual populations, and immunological clearance of clonal pathogens. PMID:17405865

  14. THE LANGUAGE LABORATORY--SELECTED READINGS.

    ERIC Educational Resources Information Center

    Modern Language Association of America, New York, NY.

    THIS PACKET OF ARTICLES AND BOOKLETS, PUBLISHED FROM 1961 TO 1965, IS DESIGNED FOR PERSONS INTERESTED IN THE USE OF THE LANGUAGE LABORATORY IN THEIR FOREIGN LANGUAGE PROGRAMS. INCLUDED ARE--(1) "A DOZEN DO'S AND DON'TS FOR PLANNING AND OPERATING A LANGUAGE LAB OR AN ELECTRONIC CLASSROOM IN A HIGH SCHOOL," (2) "MODERN FOREIGN LANGUAGES IN HIGH…

  15. A Selected Bibliography on Microbiological Laboratory Design.

    ERIC Educational Resources Information Center

    Laboratory Design Notes, 1967

    1967-01-01

    Reference sources on microbiological laboratory design are cited. Subjects covered include--(1) policies and general requirements, (2) ventilated cabinets, (3) animal isolation equipment, (4) air handling, ventilation, and filtration, (5) germicidal ultraviolet irradiation, (6) aerosol test facilities, (7) process production of microorganisms, and…

  16. A Selected Bibliography on Microbiological Laboratory Design.

    ERIC Educational Resources Information Center

    Laboratory Design Notes, 1967

    1967-01-01

    Reference sources on microbiological laboratory design are cited. Subjects covered include--(1) policies and general requirements, (2) ventilated cabinets, (3) animal isolation equipment, (4) air handling, ventilation, and filtration, (5) germicidal ultraviolet irradiation, (6) aerosol test facilities, (7) process production of microorganisms, and…

  17. THE LANGUAGE LABORATORY--SELECTED READINGS.

    ERIC Educational Resources Information Center

    Modern Language Association of America, New York, NY.

    THIS PACKET OF ARTICLES AND BOOKLETS, PUBLISHED FROM 1961 TO 1965, IS DESIGNED FOR PERSONS INTERESTED IN THE USE OF THE LANGUAGE LABORATORY IN THEIR FOREIGN LANGUAGE PROGRAMS. INCLUDED ARE--(1) "A DOZEN DO'S AND DON'TS FOR PLANNING AND OPERATING A LANGUAGE LAB OR AN ELECTRONIC CLASSROOM IN A HIGH SCHOOL," (2) "MODERN FOREIGN LANGUAGES IN HIGH…

  18. Natural and sexual selection against hybrid flycatchers

    PubMed Central

    Svedin, Nina; Wiley, Chris; Veen, Thor; Gustafsson, Lars; Qvarnström, Anna

    2008-01-01

    While sexual selection is generally assumed to quickly cause or strengthen prezygotic barriers between sister species, its role in causing postzygotic isolation, through the unattractiveness of intermediate hybrids, is less often examined. Combining 24 years of pedigree data and recently developed species-specific molecular markers from collared (Ficedula albicollis) and pied (Ficedula hypoleuca) flycatchers and their hybrids, we were able to quantify all key components of fitness. To disentangle the relative role of natural and sexual selection acting on F1 hybrid flycatchers, we estimated various fitness components, which when combined represent the total lifetime reproductive success of F1 hybrids, and then compared the different fitness components of F1 hybrids to that of collared flycatchers. Female hybrid flycatchers are sterile, with natural selection being the selective force involved, but male hybrids mainly experienced a reduction in fitness through sexual selection (decreased pairing success and increased rate of being cuckolded). To disentangle the role of sexual selection against male hybrids from a possible effect of genetic incompatibility (on the rate of being cuckolded), we compared male hybrids with pure-bred males expressing intermediate plumage characters. Given that sexual selection against male hybrids is a result of their intermediate plumage, we expect these two groups of males to have a similar fitness reduction. Alternatively, hybrids have reduced fitness owing to genetic incompatibility, in which case their fitness should be lower than that of the intermediate pure-bred males. We conclude that sexual selection against male hybrids accounts for approximately 75% of the reduction in their fitness. We discuss how natural and sexual selection against hybrids may have different implications for speciation and conclude that reinforcement of reproductive barriers may be more likely when there is sexual selection against hybrids. PMID:18211878

  19. Midbrain auditory selectivity to natural sounds.

    PubMed

    Wohlgemuth, Melville J; Moss, Cynthia F

    2016-03-01

    This study investigated auditory stimulus selectivity in the midbrain superior colliculus (SC) of the echolocating bat, an animal that relies on hearing to guide its orienting behaviors. Multichannel, single-unit recordings were taken across laminae of the midbrain SC of the awake, passively listening big brown bat, Eptesicus fuscus. Species-specific frequency-modulated (FM) echolocation sound sequences with dynamic spectrotemporal features served as acoustic stimuli along with artificial sound sequences matched in bandwidth, amplitude, and duration but differing in spectrotemporal structure. Neurons in dorsal sensory regions of the bat SC responded selectively to elements within the FM sound sequences, whereas neurons in ventral sensorimotor regions showed broad response profiles to natural and artificial stimuli. Moreover, a generalized linear model (GLM) constructed on responses in the dorsal SC to artificial linear FM stimuli failed to predict responses to natural sounds and vice versa, but the GLM produced accurate response predictions in ventral SC neurons. This result suggests that auditory selectivity in the dorsal extent of the bat SC arises through nonlinear mechanisms, which extract species-specific sensory information. Importantly, auditory selectivity appeared only in responses to stimuli containing the natural statistics of acoustic signals used by the bat for spatial orientation-sonar vocalizations-offering support for the hypothesis that sensory selectivity enables rapid species-specific orienting behaviors. The results of this study are the first, to our knowledge, to show auditory spectrotemporal selectivity to natural stimuli in SC neurons and serve to inform a more general understanding of mechanisms guiding sensory selectivity for natural, goal-directed orienting behaviors. PMID:26884152

  20. Natural selection. IV. The Price equation*

    PubMed Central

    Frank, Steven A.

    2012-01-01

    The Price equation partitions total evolutionary change into two components. The first component provides an abstract expression of natural selection. The second component subsumes all other evolutionary processes, including changes during transmission. The natural selection component is often used in applications. Those applications attract widespread interest for their simplicity of expression and ease of interpretation. Those same applications attract widespread criticism by dropping the second component of evolutionary change and by leaving unspecified the detailed assumptions needed for a complete study of dynamics. Controversies over approximation and dynamics have nothing to do with the Price equation itself, which is simply a mathematical equivalence relation for total evolutionary change expressed in an alternative form. Disagreements about approach have to do with the tension between the relative valuation of abstract versus concrete analyses. The Price equation’s greatest value has been on the abstract side, particularly the invariance relations that illuminate the understanding of natural selection. Those abstract insights lay the foundation for applications in terms of kin selection, information theory interpretations of natural selection, and partitions of causes by path analysis. I discuss recent critiques of the Price equation by Nowak and van Veelen. PMID:22487312

  1. A Lesson on Evolution & Natural Selection

    ERIC Educational Resources Information Center

    Curtis, Anthony D.

    2010-01-01

    I describe three activities that allow students to explore the ideas of evolution, natural selection, extinction, mass extinction, and rates of evolutionary change by engaging a simple model using paper, pens, chalk, and a chalkboard. As a culminating activity that supports expository writing in the sciences, the students write an essay on mass…

  2. A Lesson on Evolution & Natural Selection

    ERIC Educational Resources Information Center

    Curtis, Anthony D.

    2010-01-01

    I describe three activities that allow students to explore the ideas of evolution, natural selection, extinction, mass extinction, and rates of evolutionary change by engaging a simple model using paper, pens, chalk, and a chalkboard. As a culminating activity that supports expository writing in the sciences, the students write an essay on mass…

  3. Darwin's explanation of design: from natural theology to natural selection.

    PubMed

    Ayala, Francisco J

    2010-08-01

    Copernicus, Galileo, Newton and other physical scientists ushered in a conception of the universe as matter in motion governed by natural laws. Their discoveries brought about a fundamental revolution, namely a commitment to the postulate that the universe obeys immanent laws that can account for natural phenomena. The workings of the universe were brought into the realm of science: explanation through natural laws. Darwin completed the Copernican revolution by extending it to the living world. Darwin demonstrated the evolution of organisms. More important yet is that he discovered natural selection, the process that explains the "design" of organisms. The adaptations and diversity of organisms, the origin of novel and complex species, even the origin of mankind, could now be explained by an orderly process of change governed by natural laws. The origin of species and the exquisite features of organisms had previously been explained as special creations of an Omniscient God. Darwin brought them into the domain of science. Evolution is a creative process that produces genuine novelty. The creative power of evolution arises from a distinctive interaction between chance and necessity, between random mutation and natural selection. PMID:19800418

  4. Natural Codeswitching Knocks on the Laboratory Door

    ERIC Educational Resources Information Center

    Myers-Scotton, Carol

    2006-01-01

    This contribution discusses findings and hypotheses from empirical data of naturally-occurring codeswitching. The discussion is framed by some comparisons of the approaches of contact linguists and psycholinguists to bilingual production data. However, it emphasizes the relevance of naturally-occurring codeswitching to the theoretical questions…

  5. Respirator selection for clandestine methamphetamine laboratory investigation.

    PubMed

    Nelson, Gary O; Bronder, Gregory D; Larson, Scott A; Parker, Jay A; Metzler, Richard W

    2012-01-01

    First responders to illicit drug labs may not always have SCBA protection available. Air-purifying respirators using organic vapor cartridges with P-100 filters may not be sufficient. It would be better to use a NIOSH-approved CBRN respirator with its required multi-purpose cartridge system, which includes a P-100 filter. This would remove all the primary drug lab contaminants—organic vapors, acid gases, ammonia, phosphine, iodine, and airborne meth particulates. To assure the proper selection and use of a respirator, it is recommended that the contaminants present be identified and quantified and the OSHA 29 CFR 1910.134 respirator protection program requirements followed. PMID:22571884

  6. Natural selection in action during speciation.

    PubMed

    Via, Sara

    2009-06-16

    The role of natural selection in speciation, first described by Darwin, has finally been widely accepted. Yet, the nature and time course of the genetic changes that result in speciation remain mysterious. To date, genetic analyses of speciation have focused almost exclusively on retrospective analyses of reproductive isolation between species or subspecies and on hybrid sterility or inviability rather than on ecologically based barriers to gene flow. However, if we are to fully understand the origin of species, we must analyze the process from additional vantage points. By studying the genetic causes of partial reproductive isolation between specialized ecological races, early barriers to gene flow can be identified before they become confounded with other species differences. This population-level approach can reveal patterns that become invisible over time, such as the mosaic nature of the genome early in speciation. Under divergent selection in sympatry, the genomes of incipient species become temporary genetic mosaics in which ecologically important genomic regions resist gene exchange, even as gene flow continues over most of the genome. Analysis of such mosaic genomes suggests that surprisingly large genomic regions around divergently selected quantitative trait loci can be protected from interrace recombination by "divergence hitchhiking." Here, I describe the formation of the genetic mosaic during early ecological speciation, consider the establishment, effects, and transitory nature of divergence hitchhiking around key ecologically important genes, and describe a 2-stage model for genetic divergence during ecological speciation with gene flow. PMID:19528641

  7. [Perspectives of selective laboratory screening in children with joint pathology].

    PubMed

    Pychkova, T A; Taloverova, L I

    2014-01-01

    The article highlights the problematic issues of the laboratory diagnostic possibilities in children with joint pathology with moden tests (anti-cyclic citrullinated peptide antibodies and antibodies to mutated citrullinated vimentin). The expediency and effectiveness of the proposed laboratory tests is justified for improvement of the early differential diagnosis, joint pathology treatment optimization, and discuss the prospect of selective laboratory screening in families burdened by rheumatic diseases genealogy. PMID:25796875

  8. Darwinian natural selection: its enduring explanatory power.

    PubMed

    Dimijian, Gregory G

    2012-04-01

    Evolutionary theory has never had a stronger scientific foundation than it does today. In a short review I hope to portray the deep commitment of today's biologists to Darwinian natural selection and to discoveries made since Darwin's time. In spite of the scientific advances in the century and a half since the publication of On the Origin of Species, Darwin still remains the principal author of modern evolutionary theory. He is one of the greatest contributors of all time to our understanding of nature. PMID:22481845

  9. Darwinian natural selection: its enduring explanatory power

    PubMed Central

    2012-01-01

    Evolutionary theory has never had a stronger scientific foundation than it does today. In a short review I hope to portray the deep commitment of today's biologists to Darwinian natural selection and to discoveries made since Darwin's time. In spite of the scientific advances in the century and a half since the publication of On the Origin of Species, Darwin still remains the principal author of modern evolutionary theory. He is one of the greatest contributors of all time to our understanding of nature. PMID:22481845

  10. Symbiogenesis, natural selection, and the dynamic Earth.

    PubMed

    Kutschera, U

    2009-08-01

    One century ago, Constantin S. Mereschkowsky introduced the symbiogenesis theory for the origin of chloroplasts from ancient cyanobacteria which was later supplemented by Ivan E. Wallin's proposal that mitochondria evolved from once free-living bacteria. Today, this Mereschkowsky-Wallin principle of symbiogenesis, which is also known as the serial primary endosymbiosis theory, explains the evolutionary origin of eukaryotic cells and hence the emergence of all eukaryotes (protists, fungi, animals and plants). In 1858, the concept of natural selection was described independently by Charles Darwin and Alfred R. Wallace. In the same year, Antonio Snider-Pellegrini proposed the idea of shifting continents, which was later expanded by Alfred Wegener, who published his theory of continental drift eight decades ago. Today, directional selection is accepted as the major cause of adaptive evolution within natural populations of micro- and macro-organisms and the theory of the dynamic Earth (plate tectonics) is well supported. In this article, I combine the processes and principles of symbiogenesis, natural selection and the dynamic Earth and propose an integrative 'synade-model' of macroevolution which takes into account organisms from all five Kingdoms of life. PMID:19399544

  11. Optimization of gene expression by natural selection.

    PubMed

    Bedford, Trevor; Hartl, Daniel L

    2009-01-27

    It is generally assumed that stabilizing selection promoting a phenotypic optimum acts to shape variation in quantitative traits across individuals and species. Although gene expression represents an intensively studied molecular phenotype, the extent to which stabilizing selection limits divergence in gene expression remains contentious. In this study, we present a theoretical framework for the study of stabilizing and directional selection using data from between-species divergence of continuous traits. This framework, based upon Brownian motion, is analytically tractable and can be used in maximum-likelihood or Bayesian parameter estimation. We apply this model to gene-expression levels in 7 species of Drosophila, and find that gene-expression divergence is substantially curtailed by stabilizing selection. However, we estimate the selective effect, s, of gene-expression change to be very small, approximately equal to Ns for a change of one standard deviation, where N is the effective population size. These findings highlight the power of natural selection to shape phenotype, even when the fitness effects of mutations are in the nearly neutral range. PMID:19139403

  12. COMPUTATIONAL SCIENCE AT BROOKHAVEN NATIONAL LABORATORY: THREE SELECTED TOPICS.

    SciTech Connect

    DAVENPORT,J.W.DENG,Y.GLIMM,J.SAMULYAK,R.

    2003-09-15

    We present an overview of computational science at Brookhaven National Laboratory (BNL), with selections from three areas: fluids, nanoscience, and biology. The work at BNL in each of these areas is itself very broad, and we select a few topics for presentation within each of them.

  13. Scaling in natural and laboratory earthquakes

    NASA Astrophysics Data System (ADS)

    Nielsen, S.; Spagnuolo, E.; Smith, S. A. F.; Violay, M.; Di Toro, G.; Bistacchi, A.

    2016-02-01

    Laboratory experiments reproducing seismic slip conditions show extreme frictional weakening due to the activation of lubrication processes. Due to a substantial variability in the details of the weakening transient, generalization of experimental results and comparison to seismic observations have not been possible so far. Here we show that during the weakening, shear stress τ is generally well matched by a power law of slip u in the form τ∝u-α (with 0.35 < α < 0.6). The resulting fracture energy Gf can be approximated by a power law in some aspects in agreement with the seismological estimates G'. It appears that Gf and G' are comparable in the range 0.01 < u < 0.3 m. However, G' surpasses Gf at larger slips: at u≈10 m, G'≈108 and Gf≈106. Possible interpretations of this misfit involve the complexity of damage and weakening mechanisms within mature fault zone structures.

  14. Darwin's finches: population variation and natural selection.

    PubMed Central

    Grant, P R; Grant, B R; Smith, J N; Abbott, I J; Abbott, L K

    1976-01-01

    Van Valen's model, which relates morphological variation to ecological variation in an adaptive scheme, was investigated with individually marked and measured Darwin's finches on two adjacent Galápagos islands, Santa Cruz and Daphne Major. Results show that environmental heterogeneity is correlated with large continuous, morphological variation: variation in bill dimensions of Geospiza fortis is greater on Santa Cruz than on Daphne, as is environmental heterogeneity. Within populations of this species, different phenotypes distribute themselves in different habitat patches, select foods of different sizes and hardness, and exploit them with efficiencies that are phenotype- (bill size) dependent. These data constitute indirect evidence that natural selection has a controlling influence over the level of phenotypic variation exhibited by a population. Further evidence is that phenotypes did not survive equally well during the study period; on Daphne island G. fortis was apparently subjected to directional selection on bill tip length and G. scandens to normalizing selection on body weight and bill depth. Other factors which may have contributed to the establishment of a difference in variation between Santa Cruz and Daphne populations are the founder effect, genetic drift, and assortative mating. Annual climatic unpredictability is considered a source of environmental heterogeneity which, through its effect upon food supply, favors large morphological variation. It is predicted that species of large individual size are more influenced by this than are small species, and consequently exhibit greater size-corrected variation. The prediction is tested with data from six Geospiza species, and found to be correct. PMID:1061123

  15. Natural Gas Storage Research at Savannah River National Laboratory

    SciTech Connect

    Anton, Don; Sulic, Martin; Tamburello, David A.

    2015-05-04

    As an alternative to imported oil, scientists at the Department of Energy’s Savannah River National Laboratory are looking at abundant, domestically sourced natural gas, as an alternative transportation fuel. SRNL is investigating light, inexpensive, adsorbed natural gas storage systems that may fuel the next generation of automobiles.

  16. Mate Choice in Soldier Beetles: Field & Laboratory Experiments that Demonstrate Sexual Selection in Action

    ERIC Educational Resources Information Center

    Eason, Perri K.; Sherman, Peter T.

    2003-01-01

    Although the theory of evolution is the foundation of modern biology, students too rarely have an opportunity to watch selection operate in natural populations of animals. This lack may be partially responsible for the unfortunate ignorance of many people regarding the significance of evolution in biology. Laboratory exercises that directly study…

  17. The natural selection of altruistic traits.

    PubMed

    Boehm, C

    1999-09-01

    Proponents of the standard evolutionary biology paradigm explain human "altruism" in terms of either nepotism or strict reciprocity. On that basis our underlying nature is reduced to a function of inclusive fitness: human nature has to be totally selfish or nepotistic. Proposed here are three possible paths to giving costly aid to nonrelatives, paths that are controversial because they involve assumed pleiotropic effects or group selection. One path is pleiotropic subsidies that help to extend nepotistic helping behavior from close family to nonrelatives. Another is "warfare"-if and only if warfare recurred in the Paleolithic. The third and most plausible hypothesis is based on the morally based egalitarian syndrome of prehistoric hunter-gatherers, which reduced phenotypic variation at the within-group level, increased it at the between-group level, and drastically curtailed the advantages of free riders. In an analysis consistent with the fundamental tenets of evolutionary biology, these three paths are evaluated as explanations for the evolutionary development of a rather complicated human social nature. PMID:26196335

  18. Recoding of the stop codon UGA to glycine by a BD1-5/SN-2 bacterium and niche partitioning between Alpha- and Gammaproteobacteria in a tidal sediment microbial community naturally selected in a laboratory chemostat

    PubMed Central

    Hanke, Anna; Hamann, Emmo; Sharma, Ritin; Geelhoed, Jeanine S.; Hargesheimer, Theresa; Kraft, Beate; Meyer, Volker; Lenk, Sabine; Osmers, Harald; Wu, Rong; Makinwa, Kofi; Hettich, Robert L.; Banfield, Jillian F.; Tegetmeyer, Halina E.; Strous, Marc

    2014-01-01

    Sandy coastal sediments are global hotspots for microbial mineralization of organic matter and denitrification. These sediments are characterized by advective porewater flow, tidal cycling and an active and complex microbial community. Metagenomic sequencing of microbial communities sampled from such sediments showed that potential sulfur oxidizing Gammaproteobacteria and members of the enigmatic BD1-5/SN-2 candidate phylum were abundant in situ (>10% and ~2% respectively). By mimicking the dynamic oxic/anoxic environmental conditions of the sediment in a laboratory chemostat, a simplified microbial community was selected from the more complex inoculum. Metagenomics, proteomics and fluorescence in situ hybridization showed that this simplified community contained both a potential sulfur oxidizing Gammaproteobacteria (at 24 ± 2% abundance) and a member of the BD1-5/SN-2 candidate phylum (at 7 ± 6% abundance). Despite the abundant supply of organic substrates to the chemostat, proteomic analysis suggested that the selected gammaproteobacterium grew partially autotrophically and performed hydrogen/formate oxidation. The enrichment of a member of the BD1-5/SN-2 candidate phylum enabled, for the first time, direct microscopic observation by fluorescent in situ hybridization and the experimental validation of the previously predicted translation of the stop codon UGA into glycine. PMID:24904545

  19. Recoding of the stop codon UGA to glycine by a BD1-5/SN-2 bacterium and niche partitioning between Alpha- and Gammaproteobacteria in a tidal sediment microbial community naturally selected in a laboratory chemostat

    SciTech Connect

    Hanke, Anna; Hamann, Emmo; Sharma, Ritin; Geelhoed, Jeanine; Hargesheimer, Theresa; Kraft, Beate; Meyer, Volker; Lenk, Sabine; Osmers, Harald; Wu, Rong; Makinwa, Kofi; Hettich, Robert {Bob} L; Banfield, Jillian F.; Tegetmeyer, Halina; Strouss, Marc

    2014-01-01

    Sandy coastal sediments are global hot spots for microbial mineralization of organic matter and denitrification. These sediments are characterized by advective pore water flow, tidal cycling and an active and complex microbial community. Metagenomic sequencing of microbial communities sampled from such sediments showed that potential sulfuroxidizing Gammaproteobacteria and members of the enigmaticBD1-5/ SN-2 candidatephylumwereabundantinsitu (>10% and 2% respectively). By mimicking the dynamic oxic/anoxic environmental conditions of the sedimentin a laboratory chemostat, a simplified microbial community was selected from the more complex inoculum. Metagenomics, proteomics and fluorescenceinsituhybridization showed that this simplified community contained both a potential sulfuroxidizing Gamma proteobacteria (at 24 2% abundance) and a member of the BD1-5 / SN-2candidatephylum (at 7 6%abundance). Despite the abundant supply of organic substrates to the chemostat, proteomic analysis suggested that the selected gamma proteobacterium grew partially auto trophically and performed hydrogen/formate oxidation. The enrichment of a member of the BD1-5/SN-2candidatephylum enabled, for the first time, direct microscopic observation by fluorescent insitu hybridization and the experimental validation of the previously predicted translation of the stop codon UGA into glycine.

  20. Natural selection and cultural rates of change

    PubMed Central

    Rogers, Deborah S.; Ehrlich, Paul R.

    2008-01-01

    It has been claimed that a meaningful theory of cultural evolution is not possible because human beliefs and behaviors do not follow predictable patterns. However, theoretical models of cultural transmission and observations of the development of societies suggest that patterns in cultural evolution do occur. Here, we analyze whether two sets of related cultural traits, one tested against the environment and the other not, evolve at different rates in the same populations. Using functional and symbolic design features for Polynesian canoes, we show that natural selection apparently slows the evolution of functional structures, whereas symbolic designs differentiate more rapidly. This finding indicates that cultural change, like genetic evolution, can follow theoretically derived patterns. PMID:18287028

  1. Leprosy and the natural selection for psoriasis.

    PubMed

    Bassukas, Ioannis D; Gaitanis, Georgios; Hundeiker, Max

    2012-01-01

    Psoriasis is a genetically determined, almost worldwide-distributed inflammatory skin disease with overall higher prevalence among people of northern European ancestry. Since enhanced innate immunity is an important feature of the pathophysiology of this disease, it has been proposed that differences in the prevalence of psoriasis in different populations mainly result from differences in natural selection for gene polymorphisms associated with more vigorous immunity against infectious agents. However the infectious agent(s) that could have acted upon human population as selection pressure for psoriasis is still obscure. Based on the remarkable clinical observation that psoriasis and leprosy are almost mutually exclusive, a fact that is further supported by divergent HLA patterns in patients with psoriasis and leprosy we propose that "resisting leprosy" may have been the evolutionary advantage that favoured the expansion of some psoriasis-associated genotypes especially in the progenitors of modern Europeans. Moreover, we suggest that the spreading out of a certain genetic resistance trait may offer a supplementary explanation for the better understanding of the relatively rapid decline of leprosy in the late medieval epoch in Europe. Both genetic and paleoepidemiologic methods could be employed in order to challenge the present hypothesis. PMID:22079652

  2. Using Card Games to Simulate the Process of Natural Selection

    ERIC Educational Resources Information Center

    Grilliot, Matthew E.; Harden, Siegfried

    2014-01-01

    In 1858, Darwin published "On the Origin of Species by Means of Natural Selection." His explanation of evolution by natural selection has become the unifying theme of biology. We have found that many students do not fully comprehend the process of evolution by natural selection. We discuss a few simple games that incorporate hands-on…

  3. Using Card Games to Simulate the Process of Natural Selection

    ERIC Educational Resources Information Center

    Grilliot, Matthew E.; Harden, Siegfried

    2014-01-01

    In 1858, Darwin published "On the Origin of Species by Means of Natural Selection." His explanation of evolution by natural selection has become the unifying theme of biology. We have found that many students do not fully comprehend the process of evolution by natural selection. We discuss a few simple games that incorporate hands-on…

  4. Reproduction of natural corrosion by accelerated laboratory testing methods

    SciTech Connect

    Luo, J.S.; Wronkiewicz, D.J.; Mazer, J.J.; Bates, J.K.

    1996-05-01

    Various laboratory corrosion tests have been developed to study the behavior of glass waste forms under conditions similar to those expected in an engineered repository. The data generated by laboratory experiments are useful for understanding corrosion mechanisms and for developing chemical models to predict the long-term behavior of glass. However, it is challenging to demonstrate that these test methods produce results that can be directly related to projecting the behavior of glass waste forms over time periods of thousands of years. One method to build confidence in the applicability of the test methods is to study the natural processes that have been taking place over very long periods in environments similar to those of the repository. In this paper, we discuss whether accelerated testing methods alter the fundamental mechanisms of glass corrosion by comparing the alteration patterns that occur in naturally altered glasses with those that occur in accelerated laboratory environments. This comparison is done by (1) describing the alteration of glasses reacted in nature over long periods of time and in accelerated laboratory environments and (2) establishing the reaction kinetics of naturally altered glass and laboratory reacted glass waste forms.

  5. The snowmaker: nature identical snow production in the laboratory

    NASA Astrophysics Data System (ADS)

    Schleef, S.; Jaggi, M.; Loewe, H.; Schneebeli, M.

    2013-12-01

    Using natural snow for laboratory experiments can be tricky due to shortage of winter periods and snowfall, difficulties of sample casting and transport, and the great variability of natural snow due to the varying conditions of crystal growth in the clouds. This hinders repeatable laboratory experiments with reproducible specimen and microstructural characteristics. To minimize experimental uncertainties we designed an improved machine called snowmaker, which enables us to produce nature-identical snow in a cold laboratory under well defined conditions. The snowmaker is based on well-known principles: warm humid air from a heated water basin is advected into a cold nucleation chamber where the vapor resublimates on stretched Nylon wires. Crystals are automatically harvested by a motor driven brush rack and collected in a box, thereby several kilograms of snow can be produced per day with minimum maintenance. The excess vapor is collected in a moisture trap to avoid frost in the laboratory. The entire construction is designed as a rolling, modular assembly system which can easily carried out of the laboratory for defrosting. In addition to previous attempts we focus on the reproducibility of the samples and the comparison to natural snow down to the microscale. We show that the settings of water temperature and cold laboratory temperature facilitates the production of different crystal shapes like dendrites and needles in a reproducible way. Besides photography, we analyzed the microstructure of snowmaker crystals in aggregated specimen by X-ray microtomography. Depending on the settings we can create reproducible samples with density of 50-170 kg/m3 and specific surface areas of 50-80 mm-1. We briefly touch similarities between artificial and natural snow samples with respect to crystal habit, microstructural parameters and short-time metamorphism.

  6. Correlation between laboratory services and reporting requirements for selected zoonoses

    PubMed Central

    Schnurrenberger, Paul R.; Hubbert, William T.

    1981-01-01

    Questionnaires on the reporting required and the diagnostic services provided for selected zoonoses were completed by all departments of public health and all departments of agriculture in the 50 States. The public health departments offered services for a larger number of zoonoses than did the agricultural agencies. The correlation between the required reporting of a disease and the availability of services for that disease was stronger in the case of public health laboratories. All of the public health laboratories offered assistance with brucellosis and tularemia. The agricultural laboratories had services available for brucellosis in 47 States and for leptospriosis in 45 States. Fifteen public health agencies and 11 agricultural agencies provided laboratory services for all the zoonoses that were reportable in their respective States. The public health laboratories in 12 States will test specimens from nonhuman patients. Laboratory resources might be conserved by elimination of some of the duplication of services within a State that results when both the public health and agricultural agencies provide assistance for the same disease. PMID:7193893

  7. The Nature of Laboratory Learning Experiences in Secondary Science Online

    ERIC Educational Resources Information Center

    Crippen, Kent J.; Archambault, Leanna M.; Kern, Cindy L.

    2013-01-01

    Teaching science to secondary students in an online environment is a growing international trend. Despite this trend, reports of empirical studies of this phenomenon are noticeably missing. With a survey concerning the nature of laboratory activities, this study describes the perspective of 35-secondary teachers from 15-different U.S. states who…

  8. NATURAL RESOURCE MANAGEMENT PLAN FOR BROOKHAVEN NATIONAL LABORATORY.

    SciTech Connect

    GREEN,T.ET AL.

    2003-12-31

    Brookhaven National Laboratory (BNL) is located near the geographic center of Long Island, New York. The Laboratory is situated on 5,265 acres of land composed of Pine Barrens habitat with a central area developed for Laboratory work. In the mid-1990s BNL began developing a wildlife management program. This program was guided by the Wildlife Management Plan (WMP), which was reviewed and approved by various state and federal agencies in September 1999. The WMP primarily addressed concerns with the protection of New York State threatened, endangered, or species of concern, as well as deer populations, invasive species management, and the revegetation of the area surrounding the Relativistic Heavy Ion Collider (RHIC). The WMP provided a strong and sound basis for wildlife management and established a basis for forward motion and the development of this document, the Natural Resource Management Plan (NRMP), which will guide the natural resource management program for BNL. The body of this plan establishes the management goals and actions necessary for managing the natural resources at BNL. The appendices provide specific management requirements for threatened and endangered amphibians and fish (Appendices A and B respectively), lists of actions in tabular format (Appendix C), and regulatory drivers for the Natural Resource Program (Appendix D). The purpose of the Natural Resource Management Plan is to provide management guidance, promote stewardship of the natural resources found at BNL, and to integrate their protection with pursuit of the Laboratory's mission. The philosophy or guiding principles of the NRMP are stewardship, adaptive ecosystem management, compliance, integration with other plans and requirements, and incorporation of community involvement, where applicable.

  9. Towards Fully Integrated Natural and Virtual Hydrologic Laboratories

    NASA Astrophysics Data System (ADS)

    Vivoni, E. R.

    2014-12-01

    A key challenge facing hydrologic research and education is the integrated use of natural and virtual laboratories to advance theory and process understanding, develop and test new modeling approaches and provide compelling materials for educational and outreach activities. Too often, the experimental and modeling activities in the hydrologic community are carried out in isolation of each other. This talk will describe our long-term efforts in building two natural watershed laboratories in the Sonoran and Chihuahuan Deserts for the purpose of studying the hydrologic effects of woody plant encroachment. Through the common use of environmental sensor networks, unmanned areal vehicles and spatial sampling methods, the two small watersheds provide unprecedented detail on the hydrologic responses to the bimodal precipitation regime in the southwestern United States in the presence of varying woody plant cover. By designing each natural laboratory using hydrologic modeling criteria, sensor and remote sensing data products and their analyses have been immediately useful for testing and developing meaningful applications of a distributed hydrologic model, the Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator (tRIBS). After building confidence in the model applications, the virtual laboratories at each site are used to test hypotheses on the spatial controls on hydrologic patterns and to infer underlying hydrologic mechanisms. Furthermore, the model-data comparisons allow for detailed investigation of the model improvements that are required related processes, parameters or forcings. Examples are provided to illustrate the information content of the natural and virtual laboratories, the identification of model deficiencies and their resolution, and the process understanding gained from combining the distributed observations and modeling approaches.

  10. Microbial Resistance to Triclosan: A Case Study in Natural Selection

    ERIC Educational Resources Information Center

    Serafini, Amanda; Matthews, Dorothy M.

    2009-01-01

    Natural selection is the mechanism of evolution caused by the environmental selection of organisms most fit to reproduce, sometimes explained as "survival of the fittest." An example of evolution by natural selection is the development of bacteria that are resistant to antimicrobial agents as a result of exposure to these agents. Triclosan, which…

  11. Microbial Resistance to Triclosan: A Case Study in Natural Selection

    ERIC Educational Resources Information Center

    Serafini, Amanda; Matthews, Dorothy M.

    2009-01-01

    Natural selection is the mechanism of evolution caused by the environmental selection of organisms most fit to reproduce, sometimes explained as "survival of the fittest." An example of evolution by natural selection is the development of bacteria that are resistant to antimicrobial agents as a result of exposure to these agents. Triclosan, which…

  12. A Working Model of Natural Selection Illustrated by Table Tennis

    ERIC Educational Resources Information Center

    Dinc, Muhittin; Kilic, Selda; Aladag, Caner

    2013-01-01

    Natural selection is one of the most important topics in biology and it helps to clarify the variety and complexity of organisms. However, students in almost every stage of education find it difficult to understand the mechanism of natural selection and they can develop misconceptions about it. This article provides an active model of natural…

  13. Natural and sexual selection in a wild insect population.

    PubMed

    Rodríguez-Muñoz, R; Bretman, A; Slate, J; Walling, C A; Tregenza, T

    2010-06-01

    The understanding of natural and sexual selection requires both field and laboratory studies to exploit the advantages and avoid the disadvantages of each approach. However, studies have tended to be polarized among the types of organisms studied, with vertebrates studied in the field and invertebrates in the lab. We used video monitoring combined with DNA profiling of all of the members of a wild population of field crickets across two generations to capture the factors predicting the reproductive success of males and females. The factors that predict a male's success in gaining mates differ from those that predict how many offspring he has. We confirm the fundamental prediction that males vary more in their reproductive success than females, and we find that females as well as males leave more offspring when they mate with more partners. PMID:20522773

  14. Seal formation in arid soil under natural and laboratory conditions

    NASA Astrophysics Data System (ADS)

    Sarah, Pariente; Sachs, Eyal

    2013-04-01

    Runoff is of considerable importance in the functioning of a desert ecosystem. The hydrological characteristics of runoff developing on arid soil under natural field conditions and those of runoff occurring in laboratory-controlled rain simulation experiments using the same type of soil were investigated. Runoff and erosion measurements were carried out in small plots (0.2-0.8 m2) on a south-facing hillslope in the northern Negev, Israel (90 mm ave. annual rainfall). Soil from the area near to the runoff plots was collected for the rain simulation experiments conducted in the laboratory. The soil was collected from 0-1 cm and 1-5 cm depths, and then placed within boxes (1.16 m long and 0.55 m wide) in the laboratory in the same order as they had been in the field. Representative surface stones were collected in the field and scattered randomly on the soil surface in the laboratory boxes. In some of the laboratory experiments soil, 5 cm in depth, was placed on a geotechnical sheet on a metal screen, while in other experiments, soil of 5 cm depth was placed on a Terzaghi filter. Rain simulator used had a rotating disk with a tilted nozzle to simulate raindrop size dispersion and kinetic energy of natural rain. The sprinkling intensity was set at a rate of 18 mm/hour. Soil crusts in the field were more stable than those created in the lab for two standard tests: Emerson - immersion test, and the 'single water drop' test. Whereas weak activity of microphytes was found in the field there was no such activity in the lab. The rain depth until runoff in the field was less than under laboratory conditions, while the sediment yield was greater in the field than in the laboratory (8.64 g/m2 versus 0.58 g/m2). The rain simulator experiments that had included a Terzaghi filter showed significantly higher final infiltration rate (7.5 mm/h versus 4.2 mm/h), shorter accumulated watering depth until stabilization of soil seal formation (100-200 mm versus 50 mm), and smaller fraction of clay in the crust (4.2% versus 6.8%), than the experiments that done without this filter. Therefore, it is conceivable that there is a suction of thin material from the surface while capillary pressures are activated, result in sub-surface seal formation (washed-in layer). This can lead to differences between runoff-forming processes existing in the laboratory set-up and processes that occur under natural field conditions.

  15. ENHANCEMENTS TO NATURAL ATTENUATION: SELECTED CASE STUDIES

    SciTech Connect

    Vangelas, K; W. H. Albright, W; E. S. Becvar, E; C. H. Benson, C; T. O. Early, T; E. Hood, E; P. M. Jardine, P; M. Lorah, M; E. Majche, E; D. Major, D; W. J. Waugh, W; G. Wein, G; O. R. West, O

    2007-05-15

    In 2003 the US Department of Energy (DOE) embarked on a project to explore an innovative approach to remediation of subsurface contaminant plumes that focused on introducing mechanisms for augmenting natural attenuation to achieve site closure. Termed enhanced attenuation (EA), this approach has drawn its inspiration from the concept of monitored natural attenuation (MNA).

  16. Laboratory selection for an accelerated mosquito sexual development rate

    PubMed Central

    2011-01-01

    Background Separating males and females at the early adult stage did not ensure the virginity of females of Anopheles arabiensis (Dongola laboratory strain), whereas two years earlier this method had been successful. In most mosquito species, newly emerged males and females are not able to mate successfully. For anopheline species, a period of 24 h post-emergence is generally required for the completion of sexual maturation, which in males includes a 180° rotation of the genitalia. In this study, the possibility of an unusually shortened sexual maturity period in the laboratory-reared colony was investigated. Methods The effect of two different sex-separation methods on the virginity of females was tested: females separated as pupae or less than 16 h post-emergence were mated with males subjected to various doses of radiation. T-tests were performed to compare the two sex-separation methods. The rate of genitalia rotation was compared for laboratory-reared and wild males collected as pupae in Dongola, Sudan, and analysed by Z-tests. Spermatheca dissections were performed on females mated with laboratory-reared males to determine their insemination status. Results When the sex-separation was performed when adults were less than 16 h post-emergence, expected sterility was never reached for females mated with radio-sterilized males. Expected sterility was accomplished only when sexes were separated at the pupal stage. Observation of genitalia rotation showed that some males from the laboratory strain Dongola were able to successfully mate only 11 h after emergence and 42% of the males had already completed rotation. A small proportion of the same age females were inseminated. Wild males showed a much slower genitalia rotation rate. At 17 h post-emergence, 96% of the laboratory-reared males had completed genitalia rotation whereas none of the wild males had. Conclusion This colony has been cultured in the laboratory for over one hundred generations, and now has accelerated sexual maturation when compared with the wild strain. This outcome demonstrates the kinds of selection that can be expected during insect colonization and maintenance, particularly when generations are non-overlapping and similar-age males must compete for mates. PMID:21595988

  17. BSL-3 Laboratory Practices in the United States: Comparison of Select Agent and Non–Select Agent Facilities

    PubMed Central

    Pompei, Victoria C.; Anderson, Alice

    2014-01-01

    New construction of biosafety level 3 (BSL-3) laboratories in the United States has increased in the past decade to facilitate research on potential bioterrorism agents. The Centers for Disease Control and Prevention inspect BSL-3 facilities and review commissioning documentation, but no single agency has oversight over all BSL-3 facilities. This article explores the extent to which standard operating procedures in US BSL-3 facilities vary between laboratories with select agent or non–select agent status. Comparisons are made for the following variables: personnel training, decontamination, personal protective equipment (PPE), medical surveillance, security access, laboratory structure and maintenance, funding, and pest management. Facilities working with select agents had more complex training programs and decontamination procedures than non–select agent facilities. Personnel working in select agent laboratories were likely to use powered air purifying respirators, while non–select agent laboratories primarily used N95 respirators. More rigorous medical surveillance was carried out in select agent workers (although not required by the select agent program) and a higher level of restrictive access to laboratories was found. Most select agent and non–select agent laboratories reported adequate structural integrity in facilities; however, differences were observed in personnel perception of funding for repairs. Pest management was carried out by select agent personnel more frequently than non–select agent personnel. Our findings support the need to promote high quality biosafety training and standard operating procedures in both select agent and non–select agent laboratories to improve occupational health and safety. PMID:24552359

  18. BSL-3 laboratory practices in the United States: comparison of select agent and non-select agent facilities.

    PubMed

    Richards, Stephanie L; Pompei, Victoria C; Anderson, Alice

    2014-01-01

    New construction of biosafety level 3 (BSL-3) laboratories in the United States has increased in the past decade to facilitate research on potential bioterrorism agents. The Centers for Disease Control and Prevention inspect BSL-3 facilities and review commissioning documentation, but no single agency has oversight over all BSL-3 facilities. This article explores the extent to which standard operating procedures in US BSL-3 facilities vary between laboratories with select agent or non-select agent status. Comparisons are made for the following variables: personnel training, decontamination, personal protective equipment (PPE), medical surveillance, security access, laboratory structure and maintenance, funding, and pest management. Facilities working with select agents had more complex training programs and decontamination procedures than non-select agent facilities. Personnel working in select agent laboratories were likely to use powered air purifying respirators, while non-select agent laboratories primarily used N95 respirators. More rigorous medical surveillance was carried out in select agent workers (although not required by the select agent program) and a higher level of restrictive access to laboratories was found. Most select agent and non-select agent laboratories reported adequate structural integrity in facilities; however, differences were observed in personnel perception of funding for repairs. Pest management was carried out by select agent personnel more frequently than non-select agent personnel. Our findings support the need to promote high quality biosafety training and standard operating procedures in both select agent and non-select agent laboratories to improve occupational health and safety. PMID:24552359

  19. Getting to Darwin: Obstacles to Accepting Evolution by Natural Selection

    ERIC Educational Resources Information Center

    Thagard, Paul; Findlay, Scott

    2010-01-01

    Darwin's theory of evolution by natural selection is central to modern biology, but is resisted by many people. This paper discusses the major psychological obstacles to accepting Darwin's theory. Cognitive obstacles to adopting evolution by natural selection include conceptual difficulties, methodological issues, and coherence problems that…

  20. Are Humans Still Evolving? A Natural Selection Discussion Lesson

    ERIC Educational Resources Information Center

    Shields, Martin

    2004-01-01

    A study is conducted to develop sound comprehension of natural selection theory by prompting students to use its concept to explain the evolutionary status of humans. In relation to the current existence of human it is stated that human populations currently undergo microevolutionary changes in allele frequencies due to natural selection and other…

  1. Getting to Darwin: Obstacles to Accepting Evolution by Natural Selection

    ERIC Educational Resources Information Center

    Thagard, Paul; Findlay, Scott

    2010-01-01

    Darwin's theory of evolution by natural selection is central to modern biology, but is resisted by many people. This paper discusses the major psychological obstacles to accepting Darwin's theory. Cognitive obstacles to adopting evolution by natural selection include conceptual difficulties, methodological issues, and coherence problems that…

  2. Development and Evaluation of the Conceptual Inventory of Natural Selection.

    ERIC Educational Resources Information Center

    Anderson, Dianne L.; Fisher, Kathleen M.; Norman, Gregory J.

    2002-01-01

    Presents a diagnostic test to assess students' understanding of natural selection. Field-tests the Conceptual Inventory of Natural Selection (CINS) with nonmajors and biology majors at community colleges. Compares test scores of nonmajors with performances in interviews and discusses the correlation between the test scores and the interview…

  3. A Working Model of Natural Selection Illustrated by Table Tennis

    ERIC Educational Resources Information Center

    Dinc, Muhittin; Kilic, Selda; Aladag, Caner

    2013-01-01

    Natural selection is one of the most important topics in biology and it helps to clarify the variety and complexity of organisms. However, students in almost every stage of education find it difficult to understand the mechanism of natural selection and they can develop misconceptions about it. This article provides an active model of natural…

  4. Natural Selection in the Field and the Classroom

    ERIC Educational Resources Information Center

    Andrews, Tessa Marie

    2012-01-01

    This dissertation examined natural selection in westslope cutthroat trout ("Oncorhynchus clarkii lewisi") and undergraduate learning in the subject area natural selection. Translocation--moving individuals to a new habitat to establish, re-establish or supplement a population--is a crucial management strategy for cutthroat trout. One of…

  5. Are Humans Still Evolving? A Natural Selection Discussion Lesson

    ERIC Educational Resources Information Center

    Shields, Martin

    2004-01-01

    A study is conducted to develop sound comprehension of natural selection theory by prompting students to use its concept to explain the evolutionary status of humans. In relation to the current existence of human it is stated that human populations currently undergo microevolutionary changes in allele frequencies due to natural selection and other…

  6. Natural Selection in the Field and the Classroom

    ERIC Educational Resources Information Center

    Andrews, Tessa Marie

    2012-01-01

    This dissertation examined natural selection in westslope cutthroat trout ("Oncorhynchus clarkii lewisi") and undergraduate learning in the subject area natural selection. Translocation--moving individuals to a new habitat to establish, re-establish or supplement a population--is a crucial management strategy for cutthroat trout. One of…

  7. Laboratory facility design and microbial indoor air quality in selected hospital laboratories.

    PubMed

    Luksamijarulkul, Pipat; Kiennukul, Nuchanard; Vatthanasomboon, Pisit

    2014-05-01

    Hospital laboratory is one of workplace areas contaminated with a variety of biohazards. A cross sectional study was conducted to assess the microbial air quality and facility design in the laboratories of four selected governmental hospitals (Hospitals A, B, C, and D) in Bangkok, Thailand. One hundred eighty-eight indoor air samples were collected from 40 laboratory rooms to investigate bacterial and fungal counts using the Millipore air tester. Forty air samples were collected from the waiting areas of those laboratories, and 16 outdoor air samples were collected to use for comparison. Additionally, those laboratory facilities were assessed following biosafety facility design (10 items). Results indicated that the facility design of laboratory in the Hospital A met most of items of the biosafety facility criteria. The rest met only seven items of the criteria. Means +/- standard deviation (SD) of bacterial counts of 253.1 +/- 247.7 cfu/m3, 236.8 +/- 200.1 cfu/m3, 304.4 +/- 264.2 cfu/m3, and 146.7 +/- 127.0 cfu/m3, and fungal counts of 500.8 +/- 64.2 cfu/ m3, 425.0 +/- 21.2 cfu/m3, 357.0 +/- 121.2 cfu/m3, and 355.7 +/- 86.8 cfu/m3 were found in hospital laboratories A, B, C and D, respectively. The isolated colonies of bacteria and fungi were identified as group or genus. It was found that the most common bacteria was Staphylococcus spp (84.1%, 76.0%, 72.1% and 80.5%, respectively), whereas, the most common fungi were Aspergillus spp and septate hyphae fungi (42.0%, 37.5%, 39.5%, and 45.7%; vs 38.6%, 56.2%, 52.1%, and 37.2%, respectively). These data may be valuable to develop interventions to improve the microbial indoor air quality among hospital laboratories and for preventing the laboratory-acquired infections. PMID:24974659

  8. Natural Resource Management Plan for Brookhaven National Laboratory

    SciTech Connect

    green, T.

    2011-08-15

    This comprehensive Natural Resource Management Plan (NRMP) for Brookhaven National Laboratory (BNL) was built on the successful foundation of the Wildlife Management Plan for BNL, which it replaces. This update to the 2003 plan continues to build on successes and efforts to better understand the ecosystems and natural resources found on the BNL site. The plan establishes the basis for managing the varied natural resources located on the 5,265 acre BNL site, setting goals and actions to achieve those goals. The planning of this document is based on the knowledge and expertise gained over the past 10 years by the Natural Resources management staff at BNL in concert with local natural resource agencies including the New York State Department of Environmental Conservation, Long Island Pine Barrens Joint Planning and Policy Commission, The Nature Conservancy, and others. The development of this plan is an attempt at sound ecological management that not only benefits BNL's ecosystems but also benefits the greater Pine Barrens habitats in which BNL is situated. This plan applies equally to the Upton Ecological and Research Reserve (Upton Reserve). Any difference in management between the larger BNL area and the Upton Reserve are noted in the text. The purpose of the Natural Resource Management Plan (NRMP) is to provide management guidance, promote stewardship of the natural resources found at BNL, and to sustainably integrate their protection with pursuit of the Laboratory's mission. The philosophy or guiding principles of the NRMP are stewardship, sustainability, adaptive ecosystem management, compliance, integration with other plans and requirements, and the incorporation of community involvement, where applicable. The NRMP is periodically reviewed and updated, typically every five years. This review and update was delayed to develop documents associated with a new third party facility, the Long Island Solar Farm. This two hundred acre facility will result in significant changes to this plan warranting the delay. The body of this plan establishes the management goals and actions necessary for managing the natural resources at BNL in a sustainable manner. The appendices provide specific management requirements for threatened and endangered amphibians and fish (Appendices A and B, respectively), and lists of actions in tabular format - including completed items as well as ongoing and new action items (Appendices C and D, respectively).

  9. Natural selection in populations subject to a migration load.

    PubMed

    Bolnick, Daniel I; Nosil, Patrik

    2007-09-01

    Migration tends to oppose the effects of divergent natural selection among populations. Numerous theoretical and empirical studies have demonstrated that this migration-selection balance constrains genetic divergence among populations. In contrast, relatively few studies have examined immigration's effects on fitness and natural selection within recipient populations. By constraining local adaptation, migration can lead to reduced fitness, known as a "migration load," which in turn causes persistent natural selection. We develop a simple two-island model of migration-selection balance that, although very general, also reflects the natural history of Timema cristinae walking-stick insects that inhabit two host plant species that favor different cryptic color patterns. We derive theoretical predictions about how migration rates affect the level of maladaptation within populations (measured as the frequency of less-cryptic color-pattern morphs), which in turn determines the selection differential (the within-generation morph frequency change). Using data on color morph frequencies from 25 natural populations, we confirm previous results showing that maladaptation is higher in populations receiving more immigrants. We then present novel evidence that this increased maladaptation leads to larger selection differentials, consistent with our model. Our results provide comparative evidence that immigration elevates the variance in fitness, which in turn leads to larger selection differentials, consistent with Fisher's Theorem of Natural Selection. However, we also find evidence that recurrent adult migration between parapatric populations may tend to obscure the effects of selection. PMID:17767592

  10. The Nature of Laboratory Learning Experiences in Secondary Science Online

    NASA Astrophysics Data System (ADS)

    Crippen, Kent J.; Archambault, Leanna M.; Kern, Cindy L.

    2013-06-01

    Teaching science to secondary students in an online environment is a growing international trend. Despite this trend, reports of empirical studies of this phenomenon are noticeably missing. With a survey concerning the nature of laboratory activities, this study describes the perspective of 35-secondary teachers from 15-different U.S. states who are teaching science online. The type and frequency of reported laboratory activities are consistent with the tradition of face-to-face instruction, using hands-on and simulated experiments. While provided examples were student-centered and required the collection of data, they failed to illustrate key components of the nature of science. The features of student-teacher interactions, student engagement, and nonverbal communications were found to be lacking and likely constitute barriers to the enactment of inquiry. These results serve as a call for research and development focused on using existing communication tools to better align with the activity of science such that the nature of science is more clearly addressed, the work of students becomes more collaborative and authentic, and the formative elements of a scientific inquiry are more accessible to all participants.

  11. Biological activities of selected marine natural products.

    PubMed

    König, G M; Wright, A D; Sticher, O; Angerhofer, C K; Pezzuto, J M

    1994-12-01

    Sixty-nine natural products derived from Phaeophyta (brown algae), Rhodophyta (red algae), Porifera (sponges), Cnidaria (soft corals), and Mollusca (nudibranchs) were investigated for their cytotoxic, antimalarial, and antimicrobial effects. Fifty-six were found to mediate a positive response in one or more of these test systems. PMID:7809206

  12. Administration of Substances to Laboratory Animals: Equipment Considerations, Vehicle Selection, and Solute Preparation

    PubMed Central

    Turner, Patricia V; Pekow, Cynthia; Vasbinder, Mary Ann; Brabb, Thea

    2011-01-01

    Administration of substances to laboratory animals requires careful consideration and planning to optimize delivery of the agent to the animal while minimizing potential adverse experiences from the procedure. The equipment selected to deliver substances to animals depends on the length of the study and the nature of the material being administered. This selection provides a significant opportunity for refining animal treatment. Similarly, when substances are administered as solutions or suspensions, attention should be given to selection of vehicles and methods used for preparing the solutions and suspensions. The research team, veterinarian, technical personnel, and IACUC members should be aware of reasons underlying selection of equipment for substance delivery and should consider carefully how substances will be prepared and stored prior to administration to animals. Failure to consider these factors during experimental planning may result in unintentional adverse effects on experimental animals and confounded results. PMID:22330706

  13. Canine Evolution in Sabretoothed Carnivores: Natural Selection or Sexual Selection?

    PubMed Central

    Randau, Marcela; Carbone, Chris; Turvey, Samuel T.

    2013-01-01

    The remarkable elongated upper canines of extinct sabretoothed carnivorous mammals have been the subject of considerable speculation on their adaptive function, but the absence of living analogues prevents any direct inference about their evolution. We analysed scaling relationships of the upper canines of 20 sabretoothed feliform carnivores (Nimravidae, Barbourofelidae, Machairodontinae), representing both dirk-toothed and scimitar-toothed sabretooth ecomorphs, and 33 non-sabretoothed felids in relation to body size in order to characterize and identify the evolutionary processes driving their development, using the scaling relationships of carnassial teeth in both groups as a control. Carnassials display isometric allometry in both sabretooths and non-sabretooths, supporting their close relationship with meat-slicing, whereas the upper canines of both groups display positive allometry with body size. Whereas there is no statistical difference in allometry of upper canine height between dirk-toothed and scimitar-toothed sabretooth ecomorphs, the significantly stronger positive allometry of upper canine height shown by sabretooths as a whole compared to non-sabretooths reveals that different processes drove canine evolution in these groups. Although sabretoothed canines must still have been effective for prey capture and processing by hypercarnivorous predators, canine morphology in these extinct carnivores was likely to have been driven to a greater extent by sexual selection than in non-sabretooths. Scaling relationships therefore indicate the probable importance of sexual selection in the evolution of the hypertrophied sabretooth anterior dentition. PMID:23951334

  14. Selection of the Mars Science Laboratory landing site

    USGS Publications Warehouse

    Golombek, M.; Grant, J.; Kipp, D.; Vasavada, A.; Kirk, Randolph L.; Fergason, Robin L.; Bellutta, P.; Calef, F.; Larsen, K.; Katayama, Y.; Huertas, A.; Beyer, R.; Chen, A.; Parker, T.; Pollard, B.; Lee, S.; Hoover, R.; Sladek, H.; Grotzinger, J.; Welch, R.; Dobrea, E. Noe; Michalski, J.; Watkins, M.

    2012-01-01

    The selection of Gale crater as the Mars Science Laboratory landing site took over five years, involved broad participation of the science community via five open workshops, and narrowed an initial >50 sites (25 by 20 km) to four finalists (Eberswalde, Gale, Holden and Mawrth) based on science and safety. Engineering constraints important to the selection included: (1) latitude (±30°) for thermal management of the rover and instruments, (2) elevation (<-1 km) for sufficient atmosphere to slow the spacecraft, (3) relief of <100-130 m at baselines of 1-1000 m for control authority and sufficient fuel during powered descent, (4) slopes of <30° at baselines of 2-5 m for rover stability at touchdown, (5) moderate rock abundance to avoid impacting the belly pan during touchdown, and (6) a radar-reflective, load-bearing, and trafficable surface that is safe for landing and roving and not dominated by fine-grained dust. Science criteria important for the selection include the ability to assess past habitable environments, which include diversity, context, and biosignature (including organics) preservation. Sites were evaluated in detail using targeted data from instruments on all active orbiters, and especially Mars Reconnaissance Orbiter. All of the final four sites have layered sedimentary rocks with spectral evidence for phyllosilicates that clearly address the science objectives of the mission. Sophisticated entry, descent and landing simulations that include detailed information on all of the engineering constraints indicate all of the final four sites are safe for landing. Evaluation of the traversabilty of the landing sites and target “go to” areas outside of the ellipse using slope and material properties information indicates that all are trafficable and “go to” sites can be accessed within the lifetime of the mission. In the final selection, Gale crater was favored over Eberswalde based on its greater diversity and potential habitability.

  15. Using the FAR Guide to Teach Simulations: An Example with Natural Selection

    ERIC Educational Resources Information Center

    Sickel, Aaron J.; Friedrichsen, Patricia J.

    2012-01-01

    Engaging students in a predator-prey simulation to teach natural selection is a common activity in secondary biology classrooms. The purpose of this article is to demonstrate how the authors have changed their approach to teaching this activity from a laboratory investigation to a class-constructed simulation. Specifically, the authors drew upon a…

  16. Using the FAR Guide to Teach Simulations: An Example with Natural Selection

    ERIC Educational Resources Information Center

    Sickel, Aaron J.; Friedrichsen, Patricia J.

    2012-01-01

    Engaging students in a predator-prey simulation to teach natural selection is a common activity in secondary biology classrooms. The purpose of this article is to demonstrate how the authors have changed their approach to teaching this activity from a laboratory investigation to a class-constructed simulation. Specifically, the authors drew upon a…

  17. Natural selection on floral morphology can be influenced by climate.

    PubMed

    Campbell, Diane R; Powers, John M

    2015-06-01

    Climate has the potential to influence evolution, but how it influences the strength or direction of natural selection is largely unknown. We quantified the strength of selection on four floral traits of the subalpine herb Ipomopsis sp. in 10 years that differed in precipitation, causing extreme temporal variation in the date of snowmelt in the Colorado Rocky Mountains. The chosen floral traits were under selection by hummingbird and hawkmoth pollinators, with hawkmoth abundance highly variable across years. Selection for flower length showed environmental sensitivity, with stronger selection in years with later snowmelt, as higher water resources can allow translation of pollination success into fitness based on seed production. Selection on corolla width also varied across years, favouring narrower corolla tubes in two unusual years with hawkmoths, and wider corollas in another late snowmelt year. Our results illustrate how changes in climate could alter natural selection even when the primary selective agent is not directly influenced. PMID:25972465

  18. Bayesian natural selection and the evolution of perceptual systems.

    PubMed Central

    Geisler, Wilson S; Diehl, Randy L

    2002-01-01

    In recent years, there has been much interest in characterizing statistical properties of natural stimuli in order to better understand the design of perceptual systems. A fruitful approach has been to compare the processing of natural stimuli in real perceptual systems with that of ideal observers derived within the framework of Bayesian statistical decision theory. While this form of optimization theory has provided a deeper understanding of the information contained in natural stimuli as well as of the computational principles employed in perceptual systems, it does not directly consider the process of natural selection, which is ultimately responsible for design. Here we propose a formal framework for analysing how the statistics of natural stimuli and the process of natural selection interact to determine the design of perceptual systems. The framework consists of two complementary components. The first is a maximum fitness ideal observer, a standard Bayesian ideal observer with a utility function appropriate for natural selection. The second component is a formal version of natural selection based upon Bayesian statistical decision theory. Maximum fitness ideal observers and Bayesian natural selection are demonstrated in several examples. We suggest that the Bayesian approach is appropriate not only for the study of perceptual systems but also for the study of many other systems in biology. PMID:12028784

  19. Frequency selective bolometer development at Argonne National Laboratory.

    SciTech Connect

    Datesman, A.; Pearson, J.; Wang, G.; Yefremenko, V.; Divan, R.; Downes, T.; Chang, C.; McMahon, J.; Meyer, S.; Carlstrom, J.; Logan, D.; Perera, T.; Wilson, G.; Novosad, V.; Univ. of Chicago; Univ. of Massachusetts

    2008-07-01

    We discuss the development, at Argonne National Laboratory, of a four-pixel camera suitable for photometry of distant dusty galaxies located by Spitzer and SCUBA, and for study of other millimeter-wave sources such as ultra-luminous infrared galaxies, the Sunyaev-Zeldovich (SZ) effect in clusters, and galactic dust. Utilizing Frequency Selective Bolometers (FSBs) with superconducting Transition-Edge Sensors (TESs), each of the camera's four pixels is sensitive to four colors, with frequency bands centered approximately at 150, 220, 270, and 360 GHz. The current generation of these devices utilizes proximity effect superconducting bilayers of Mo/Au or Ti/Au for TESs, along with frequency selective circuitry on membranes of silicon nitride 1 cm across and 1 micron thick. The operational properties of these devices are determined by this circuitry, along with thermal control structures etched into the membranes. These etched structures do not perforate the membrane, so that the device is both comparatively robust mechanically and carefully tailored in terms of its thermal transport properties. In this paper, we report on development of the superconducting bilayer TES technology and characterization of the FSB stacks. This includes the use of new materials, the design and testing of thermal control structures, the introduction of desirable thermal properties using buried layers of crystalline silicon underneath the membrane, detector stability control, and optical and thermal test results. The scientific motivation, FSB design, FSB fabrication, and measurement results are discussed.

  20. Frequency selective bolometer development at Argonne National Laboratory

    NASA Astrophysics Data System (ADS)

    Datesman, Aaron; Pearson, John; Wang, Gensheng; Yefremenko, Volodymyr; Divan, Ralu; Downes, Thomas; Chang, Clarence; McMahon, Jeff; Meyer, Stephan; Carlstrom, John; Logan, Daniel; Perera, Thushara; Wilson, Grant; Novosad, Valentyn

    2008-07-01

    We discuss the development, at Argonne National Laboratory, of a four-pixel camera suitable for photometry of distant dusty galaxies located by Spitzer and SCUBA, and for study of other millimeter-wave sources such as ultra-luminous infrared galaxies, the Sunyaev-Zeldovich (SZ) effect in clusters, and galactic dust. Utilizing Frequency Selective Bolometers (FSBs) with superconducting Transition-Edge Sensors (TESs), each of the camera's four pixels is sensitive to four colors, with frequency bands centered approximately at 150, 220, 270, and 360 GHz. The current generation of these devices utilizes proximity effect superconducting bilayers of Mo/Au or Ti/Au for TESs, along with frequency selective circuitry on membranes of silicon nitride 1 cm across and 1 micron thick. The operational properties of these devices are determined by this circuitry, along with thermal control structures etched into the membranes. These etched structures do not perforate the membrane, so that the device is both comparatively robust mechanically and carefully tailored in terms of its thermal transport properties. In this paper, we report on development of the superconducting bilayer TES technology and characterization of the FSB stacks. This includes the use of new materials, the design and testing of thermal control structures, the introduction of desirable thermal properties using buried layers of crystalline silicon underneath the membrane, detector stability control, and optical and thermal test results. The scientific motivation, FSB design, FSB fabrication, and measurement results are discussed.

  1. Darwin, microbes and evolution by natural selection.

    PubMed

    Moxon, E Richard

    2011-01-01

    Born 200 years ago, Darwin's revolutionary ideas were derived largely from his observations on life forms that evolved relatively recently, including various flowering plants, worms, birds and domesticated animals. Yet, life appeared on planet earth close to 4 billion years ago in the form of unicellular organisms collectively called bacteria. It was only shortly after "On the Origin of Species" was published (1859) that the "germ theory" of infectious diseases was formulated. Microbes (viruses, bacteria, fungi and microparasites) received scant mention in Darwin's writings, although pioneers of the Golden Age of Bacteriology, such as Louis Pasteur (1822-1895), were contemporaries. Today, microbes offer extraordinary testimony and powerful model systems of direct relevance to the essentials of Darwinian selection, such as understanding microbial-host interactions, the evolution of pathogens and the emergence of drug- or vaccine-related resistance. PMID:21120720

  2. Natural Selection Is a Sorting Process: What Does that Mean?

    ERIC Educational Resources Information Center

    Price, Rebecca M.

    2013-01-01

    To learn why natural selection acts only on existing variation, students categorize processes as either creative or sorting. This activity helps students confront the misconception that adaptations evolve because species need them.

  3. The Unit of Natural Selection: Groups, Families, Individuals, or Genes?

    ERIC Educational Resources Information Center

    Reiss, Michael J.

    1985-01-01

    Offers perspectives on natural selection and the phenomenon of altruism. Presents evidence for and against the theories that evolution acts essentially on genes, on individuals, on kin, or on larger groups. (ML)

  4. A network of schools for a natural hazard laboratory

    NASA Astrophysics Data System (ADS)

    Occhipinti, S.

    2012-04-01

    With the Department of Education of the Aosta Valley - Italy - I have been engaged, for a long time, to promote initiatives with the aim to disseminate scientific culture in order to support teachers in their work and to foster in students the acquisition of scientific knowledge, skills and literacy, as required by the international standards of OECD and TIMSS. For this purpose, a network including all schools has been built, with the aim to promote the co-construction of standards of knowledge, a shared and effective use of resources and tools, of good practices, particularly those experiences based on a deductive, constructivist and Inquiry based approach. SCIENCE IN THE NETWORK: a Regional Science Centre has been built, with the aim to share experimental protocols and scientific instruments, to rationalize expenses, with hands-on individual workstations, high level instruments, but also rough materials. Students of all classes and all ages learn how to use scientific instruments, as required by an "up to date" school. A NETWORK OF PROJECTS: A NATURAL HAZARDS LABORATORY, with many others, has been set up, in cooperation with all regional stakeholders, with the aim to promote in all the schools a shared knowledge of the landscape, of its geological and geomorphologic evolution, with the aim to spread the culture of natural hazards and of prevention, to increase the sensitivity for an intelligent, supportive and sustainable use of the territory, environmentally aware of the natural dynamics. Students can experiment, using technical or wooden made instruments, the effects that natural phenomena, action of waters, ice and gravity can product on outcrops and landscape and to apply to local contest the relationship between the concept of hazard, risk and vulnerability.

  5. Annotated selected references on natural resources investigations, Collier County, Florida

    USGS Publications Warehouse

    Swayze, L.J.

    1981-01-01

    A data base for future natural resources investigations in Collier County, Fla., was initiated by compiling a selected annotated bibliography. This report provides references and annotations for selected reports released between 1950 and 1978. The references are presented by subject material as follows: biologic, ecologic, geologic, geochemical, and hydrologic. (USGS)

  6. A Survey of Curriculum Laboratories in Selected Colleges in Pennsylvania.

    ERIC Educational Resources Information Center

    Nevil, Leota

    This report defines a curriculum laboratory to be a center where educational materials are developed, modified, and stored. Included in the document are a history of the curriculum laboratory, a study of its characteristics, and a survey of the curriculum laboratories in the colleges and universities of Pennsylvania. The Wilkes College curriculum…

  7. The genetic consequences of selection in natural populations.

    PubMed

    Thurman, Timothy J; Barrett, Rowan D H

    2016-04-01

    The selection coefficient, s, quantifies the strength of selection acting on a genetic variant. Despite this parameter's central importance to population genetic models, until recently we have known relatively little about the value of s in natural populations. With the development of molecular genetic techniques in the late 20th century and the sequencing technologies that followed, biologists are now able to identify genetic variants and directly relate them to organismal fitness. We reviewed the literature for published estimates of natural selection acting at the genetic level and found over 3000 estimates of selection coefficients from 79 studies. Selection coefficients were roughly exponentially distributed, suggesting that the impact of selection at the genetic level is generally weak but can occasionally be quite strong. We used both nonparametric statistics and formal random-effects meta-analysis to determine how selection varies across biological and methodological categories. Selection was stronger when measured over shorter timescales, with the mean magnitude of s greatest for studies that measured selection within a single generation. Our analyses found conflicting trends when considering how selection varies with the genetic scale (e.g., SNPs or haplotypes) at which it is measured, suggesting a need for further research. Besides these quantitative conclusions, we highlight key issues in the calculation, interpretation, and reporting of selection coefficients and provide recommendations for future research. PMID:26836758

  8. Hard and Soft Selection Revisited: How Evolution by Natural Selection Works in the Real World.

    PubMed

    Reznick, David

    2016-01-01

    The modern synthesis of evolutionary biology unified Darwin's natural selection with Mendelian genetics, but at the same time it created the dilemma of genetic load. Lewontin and Hubby's (1966) and Harris's (1966) characterization of genetic variation in natural populations increased the apparent burden of this load. Neutrality or near neutrality of genetic variation was one mechanism proposed for the revealed excessive genetic variation. Bruce Wallace coined the term "soft selection" to describe an alternative way for natural selection to operate that was consistent with observed variation. He envisioned nature as presenting ecological vacancies that could be filled by diverse genotypes. Survival and successful reproduction was a combined function of population density, genotype, and genotype frequencies, rather than a fixed value of the relative fitness of each genotype. My goal in this review is to explore the importance of soft selection in the real world. My motive and that of my colleagues as described here is not to explain what maintains genetic variation in natural populations, but rather to understand the factors that shape how organisms adapt to natural environments. We characterize how feedbacks between ecology and evolution shape both evolution and ecology. These feedbacks are mediated by density- and frequency-dependent selection, the mechanisms that underlie soft selection. Here, I report on our progress in characterizing these types of selection with a combination of a consideration of the published literature and the results from my collaborators' and my research on natural populations of guppies. PMID:26424874

  9. The Limits of Natural Selection in a Nonequilibrium World.

    PubMed

    Brandvain, Yaniv; Wright, Stephen I

    2016-04-01

    Evolutionary theory predicts that factors such as a small population size or low recombination rate can limit the action of natural selection. The emerging field of comparative population genomics offers an opportunity to evaluate these hypotheses. However, classical theoretical predictions assume that populations are at demographic equilibrium. This assumption is likely to be violated in the very populations researchers use to evaluate selection's limits: populations that have experienced a recent shift in population size and/or effective recombination rates. Here we highlight theory and data analyses concerning limitations on the action of natural selection in nonequilibrial populations and argue that substantial care is needed to appropriately test whether species and populations show meaningful differences in selection efficacy. A move toward model-based inferences that explicitly incorporate nonequilibrium dynamics provides a promising approach to more accurately contrast selection efficacy across populations and interpret its significance. PMID:26874998

  10. Selection at 6-PGD locus in laboratory populations of Bactrocera oleae.

    PubMed

    Cosmidis, Nikos; Goulielmos, George; Eliopoulos, Elias; Loukas, Michael

    2008-10-01

    We have previously shown that laboratory populations of the olive fruitfly Bactrocera oleae come to equilibrium with allele frequencies at the 6-phosphogluconate dehydrogenase (6-PGD) locus markedly different from those of wild populations. In this study, we present new evidence from perturbation experiments in support of the notion that the locus is under selective pressure under laboratory conditions. Eleven populations were started with frequencies at the 6-PGD locus different from the laboratory equilibrium. Over 12 generations, the populations showed a return to the previous equilibrium, indicating a direct and powerful selection pressure on the naturally occurring allozymes of this locus. That is, a marked increase of the F allele followed by a compensatory decrease of allele I. Populations were set up to minimize the effects of associative overdominance, and we discuss the possible influence of this factor. Nucleotide sequence for the 6-PGD F and I alleles revealed two missense mutations at positions 501 and 730 leading to different amino acids among the two alleles. PMID:19061528

  11. Natural and sexual selection in a monogamous historical human population.

    PubMed

    Courtiol, Alexandre; Pettay, Jenni E; Jokela, Markus; Rotkirch, Anna; Lummaa, Virpi

    2012-05-22

    Whether and how human populations exposed to the agricultural revolution are still affected by Darwinian selection remains controversial among social scientists, biologists, and the general public. Although methods of studying selection in natural populations are well established, our understanding of selection in humans has been limited by the availability of suitable datasets. Here, we present a study comparing the maximum strengths of natural and sexual selection in humans that includes the effects of sex and wealth on different episodes of selection. Our dataset was compiled from church records of preindustrial Finnish populations characterized by socially imposed monogamy, and it contains a complete distribution of survival, mating, and reproductive success for 5,923 individuals born 1760-1849. Individual differences in early survival and fertility (natural selection) were responsible for most variation in fitness, even among wealthier individuals. Variance in mating success explained most of the higher variance in reproductive success in males compared with females, but mating success also influenced reproductive success in females, allowing for sexual selection to operate in both sexes. The detected opportunity for selection is in line with measurements for other species but higher than most previous reports for human samples. This disparity results from biological, demographic, economic, and social differences across populations as well as from failures by most previous studies to account for variation in fitness introduced by nonreproductive individuals. Our results emphasize that the demographic, cultural, and technological changes of the last 10,000 y did not preclude the potential for natural and sexual selection in our species. PMID:22547810

  12. Natural and sexual selection in a monogamous historical human population

    PubMed Central

    Courtiol, Alexandre; Pettay, Jenni E.; Jokela, Markus; Rotkirch, Anna; Lummaa, Virpi

    2012-01-01

    Whether and how human populations exposed to the agricultural revolution are still affected by Darwinian selection remains controversial among social scientists, biologists, and the general public. Although methods of studying selection in natural populations are well established, our understanding of selection in humans has been limited by the availability of suitable datasets. Here, we present a study comparing the maximum strengths of natural and sexual selection in humans that includes the effects of sex and wealth on different episodes of selection. Our dataset was compiled from church records of preindustrial Finnish populations characterized by socially imposed monogamy, and it contains a complete distribution of survival, mating, and reproductive success for 5,923 individuals born 1760–1849. Individual differences in early survival and fertility (natural selection) were responsible for most variation in fitness, even among wealthier individuals. Variance in mating success explained most of the higher variance in reproductive success in males compared with females, but mating success also influenced reproductive success in females, allowing for sexual selection to operate in both sexes. The detected opportunity for selection is in line with measurements for other species but higher than most previous reports for human samples. This disparity results from biological, demographic, economic, and social differences across populations as well as from failures by most previous studies to account for variation in fitness introduced by nonreproductive individuals. Our results emphasize that the demographic, cultural, and technological changes of the last 10,000 y did not preclude the potential for natural and sexual selection in our species. PMID:22547810

  13. The Slumgullion Natural Laboratory for Observing Slip Phenomena

    NASA Astrophysics Data System (ADS)

    Gomberg, J. S.; Schulz, W. H.; Bodin, P.; Kean, J. W.; Wang, G.; Coe, J. A.; MacQueen, P.; Foster, K.; Creager, K.

    2009-12-01

    Many natural systems release stresses by failure and sliding across surfaces; examples include landslides, glaciers, crustal- and plate-scale faults. Observational advances continue to reveal diversity in the seismic signals associated with fault slip and how such stress relaxation can occur, even on a single fault system. A particularly rich example are the episodes of slow fault slip near major subduction and transform plate boundaries that manifest as geodetically observed aseismic deformation abetted by a family of seismic signals depleted in high-frequencies relative to those from earthquakes (named ‘episodic tremor and slip’ or ETS). While the driving forces and scales differ, there are striking parallels between some observations and models of ETS and of landslide behaviors; e.g. in both, postulated key controls include rate-dependent friction and strength modulated by pore-pressure changes, dilatancy during rapid shear, and subsequent consolidation. To explore common features and the underlying processes we are studying the Slumgullion landslide, an ideal natural laboratory for observing fault slip and associated seismic and aseismic phenomena. Unlike crustal- or plate-scale studies significant deformation can be measured within a single field season, because the Slumgullion moves at average rates of cm/day. Moreover, pore pressures, displacements, material properties, and environmental variables may be measured directly and continuously at several locations on the landslide (albeit not at the basal sliding surface). We have just completed a field experiment on the Slumgullion to test several hypotheses, particularly that slip along the basal surface and side-bounding faults occurs with comparable richness of aseismic and seismic modes as crustal- and plate-scale boundaries. To do so from August 18-26, 2009 we continuously monitored the displacement-field using a robotic electronic displacement meter and the seismic radiation with 88 vertical-component seismographs [see Bodin et al., companion abstract]. Although we have only begun examining the data thus far, the seismic data contain an abundance of network-wide coherent signals with an amazing variety of characteristics. Significant unsteady movement in the displacement field is evident in the geodetic data, as well as fluctuations in the pore-pressures and relevant environmental parameters. Schulz et al. (companion abstract) presents initial landslide observations. We will form and present implications for understanding the likely mechanisms of failure and slip within natural systems.

  14. Getting to Darwin: Obstacles to Accepting Evolution by Natural Selection

    NASA Astrophysics Data System (ADS)

    Thagard, Paul; Findlay, Scott

    2010-06-01

    Darwin’s theory of evolution by natural selection is central to modern biology, but is resisted by many people. This paper discusses the major psychological obstacles to accepting Darwin’s theory. Cognitive obstacles to adopting evolution by natural selection include conceptual difficulties, methodological issues, and coherence problems that derive from the intuitiveness of alternative theories. The main emotional obstacles to accepting evolution are its apparent conflict with valued beliefs about God, souls, and morality. We draw on the philosophy of science and on a psychological theory of cognitive and emotional belief revision to make suggestions about what can be done to improve acceptance of Darwinian ideas.

  15. Selecting Landing Sites for the 2009 Mars Science Laboratory

    NASA Astrophysics Data System (ADS)

    Grant, J. A.; Golombek, M. P.; Vasavada, A. R.; Watkins, M. M.; Mars Landing Site Steering Committee

    2006-12-01

    Landing site selection for the 2009 Mars Science Laboratory (MSL) is underway and includes a series of open workshops for soliciting science community input regarding the landing site. The first workshop was held in Spring 2006 and focused on prioritizing 33 proposed sites for imaging by orbital spacecraft. It should be noted that the number of potential landing sites is high because MSL entry, descent, and landing (EDL) capabilities enable a small landing error circle (20 km in diameter), high landing site altitude (below 1 km, MOLA datum), and wide latitudes (plus/minus 45 degrees). The primary scientific goal of MSL is to assess the present and past habitability of environments accessed by the mission. In particular, MSL will assess the biological potential of the landing site, characterize the geology and geochemistry at appropriate spatial scales, investigate planetary processes that influence habitability, including the role of water, and characterize the broad spectrum of surface radiation. The geological, chemical, and/or biological evidence for habitability should be expected to be preserved for, accessible to and interpretable by the MSL investigations at the landing site. Because landing safely is paramount, all engineering constraints for the mission must be adhered to for a proposed site to be viewed favorably. For example, areas with potentially high winds will need to be compared with landing system tolerance during development. Slopes across length scales of 2 to 5 km, 20 meters, and 5 meters must be less than 3 degrees, 15 degrees, and 15 degrees, respectively. Rocks at the landing site should be less than 0.6 m high and in intermediate to lower abundance terrains. The landing surface must be load-bearing, radar reflective, trafficable and not be dominated by dust. Persistent cold surface temperatures and CO2 frost will negatively impact performance and areas with very low thermal inertia and very high albedo are excluded. Finally planetary protection requirements limit the MSL landing site to areas not known to have extant water or water-ice within one meter of the surface. Many of the sites proposed at the first workshop may comply with these science and engineering constraints and ongoing imaging at a variety of spatial and spectral resolutions will enable more rigorous assessment of their relative merits. In addition, the mission engineering constraints will continue to be refined during MSL design and development of the spacecraft. A second open workshop is planned for Fall 2007 and will emphasize evaluation of acquired image data, discuss any new sites revealed by orbital assets (e.g., Mars Reconnaissance Orbiter), and pare the list under consideration to a smaller number of primary and back-up sites subject to additional evaluation. An overview of the MSL mission is available at http://mars.jpl.nasa.gov/msl/overview. More information on the MSL landing site selection activities and process and proposed landing sites can be viewed at http://marsoweb.nas.nasa.gov/landingsites/and http://webgis.wr.usgs.gov/.

  16. Evolution of particle angularity in natural and laboratory debris flows

    NASA Astrophysics Data System (ADS)

    Mclaughlin, M. K.; Arabnia, O.; Sklar, L. S.

    2014-12-01

    The sizes of particles entrained in debris flows influence flow dynamics, affecting erosive power and runout distance. Particle size distributions evolve due to wear by abrasion and fracturing, and by gains or losses of sediment mass during transport. To tease apart these factors, we need a better understanding of the controls on rates and patterns of particle wear in debris flows. Here we focus on changes in particle angularity with travel distance, combining laboratory experiments with field study of a rocky debris flow at Inyo Creek, Sierra Nevada California. Angularity can indicate proximity to sediment source, assuming abrasion leads to progressive smoothing of particle surfaces. However, particle fracture can create fresh angular surfaces, confounding estimates of travel distance from angularity. This study is a component of an ongoing set of experiments using a 4 m diameter rotating drum to create near-prototype-scale debris flows. We load the drum with 1.7 Mg of highly angular granodiorite clasts, with median b-axis diameter of 100 mm. The 0.75 m deep, shearing mass flows at 1 m/s. After each 250 m travel distance, we measure mass and length of principal axes for every particle >19 mm, and sieve all smaller particles, to track evolution of the size distribution. We document the angularity of subsamples of selected particle sizes, using several techniques, including analysis of 2D photographs, 3D laser scans, and hand-placed equilibrium points. We use the same techniques in analyzing particles collected in the field study of the downstream evolution of rock clasts along a 1 km length of Inyo Creek. In this catchment, underlain by granodiorite, sediment transport is dominated by debris flows, which leave deposits on the bed and channel margins at slopes >20%. Preliminary laboratory results show rapid smoothing of large particle surfaces combined with creation of smaller angular particles by fracture. In contrast, downstream evolution of angularity in the field is more variable, possibly due to mixing of particles from multiple source areas. Results suggest that downstream changes in angularity contain information about proximity to sources and intensity of particle interactions in transport, and may be useful for constraining predictive relations for particle size evolution in debris flows.

  17. When natural selection gives gene function the cold shoulder.

    PubMed

    Cutter, Asher D; Jovelin, Richard

    2015-11-01

    It is tempting to invoke organismal selection as perpetually optimizing the function of any given gene. However, natural selection can drive genic functional change without improvement of biochemical activity, even to the extinction of gene activity. Detrimental mutations can creep in owing to linkage with other selectively favored loci. Selection can promote functional degradation, irrespective of genetic drift, when adaptation occurs by loss of gene function. Even stabilizing selection on a trait can lead to divergence of the underlying molecular constituents. Selfish genetic elements can also proliferate independent of any functional benefits to the host genome. Here we review the logic and evidence for these diverse processes acting in genome evolution. This collection of distinct evolutionary phenomena - while operating through easily understandable mechanisms - all contribute to the seemingly counterintuitive notion that maintenance or improvement of a gene's biochemical function sometimes do not determine its evolutionary fate. PMID:26411745

  18. Measuring Natural Selection on Genotypes and Phenotypes in the Wild

    PubMed Central

    Linnen, Catherine R.; Hoekstra, Hopi E.

    2013-01-01

    A complete understanding of the role of natural selection in driving evolutionary change requires accurate estimates of the strength of selection acting in the wild. Accordingly, several approaches utilizing a variety of data—including patterns of DNA variability, spatial and temporal changes in allele frequencies, and fitness estimates—have been developed to identify and quantify selection on both genotypes and phenotypes. Here, we review these approaches, drawing on both recent and classic examples to illustrate their utility and limitations. We then argue that by combining estimates of selection at multiple levels—from individual mutations to phenotypes—and at multiple timescales—from ecological to evolutionary—with experiments that demonstrate why traits are under selection, we can gain a much more complete picture of the adaptive process. PMID:20413707

  19. Using Different Examples of Natural Selection When Teaching Biology.

    ERIC Educational Resources Information Center

    Perry, Robert T.

    1993-01-01

    Describes the following examples of natural selection for use in science instruction: sickle-cell anemia and human beings, clogged crabs, the rounding of the human head, shell color in land snails, pollinator behavior and flower color, copper tolerance in a grass, lizards and quick change, and Darwin's finches. (PR)

  20. The Nature of Selected English Teachers' Online Participation

    ERIC Educational Resources Information Center

    Rodesiler, Luke

    2015-01-01

    This article documents an investigation into the nature of selected secondary English teachers' online participation across platforms (i.e., blogs, microblogs, social networking sites) as they explored issues related to teaching, learning, and literacy. Ethnographic content analysis of online artifacts generated over approximately 10 months…

  1. Reconsidering the logical structure of the theory of natural selection

    PubMed Central

    Hunt, Tam

    2014-01-01

    Natural selection has been criticized as a tautology. This would be a major problem for evolutionary biology, if true, because tautological statements can't be falsified and, therefore, can't be scientific. There is merit to this critique insofar as the theory of natural selection is indeed generally described in a tautological manner. However, natural selection can be described non-tautologically if we’re careful. Natural selection should be defined as the theory that attempts to predict and retrodict evolutionary change through environmental forces acting upon organisms. However, this re-framing comes at a cost: it reveals, based on our current knowledge of evolutionary forces, the lack of ability to make accurate predictions about expected changes except in the most simple of circumstances. I suggest that evolutionary biologists should work to develop “principles of evolution,” based on an expanded and more focused research program designed to identify common trends in evolution, which will ultimately allow us to make more accurate predictions and retrodictions about evolution. PMID:26478764

  2. The Nature of Selected English Teachers' Online Participation

    ERIC Educational Resources Information Center

    Rodesiler, Luke

    2015-01-01

    This article documents an investigation into the nature of selected secondary English teachers' online participation across platforms (i.e., blogs, microblogs, social networking sites) as they explored issues related to teaching, learning, and literacy. Ethnographic content analysis of online artifacts generated over approximately 10 months…

  3. Effective Assessment: Probing Students' Understanding of Natural Selection

    ERIC Educational Resources Information Center

    Stern, Luli

    2004-01-01

    Evolution by natural selection provides the conceptual framework upon which much of modern biology is based: therefore understanding core ideas about biological evolution is an essential part of scientific literacy. Nonetheless, research repeatedly shows that high school and college students have difficulties understanding the notion of natural…

  4. Biological fitness and the fundamental theorem of natural selection.

    PubMed

    Grafen, Alan

    2015-07-01

    Fisher's fundamental theorem of natural selection is proved satisfactorily for the first time, resolving confusions in the literature about the nature of reproductive value and fitness. Reproductive value is defined following Fisher, without reference to genetic variation, and fitness is the proportional rate of increase in an individual's contribution to the demographic population size. The mean value of fitness is the same in each age class, and it also equals the population's Malthusian parameter. The statement and derivation are regarded as settled here, and so the general biological significance of the fundamental theorem can be debated. The main purpose of the theorem is to find a quantitative measure of the effect of natural selection in a Mendelian system, thus founding Darwinism on Mendelism and identifying the design criterion for biological adaptation, embodied in Fisher's ingenious definition of fitness. The relevance of the newly understood theorem to five current research areas is discussed. PMID:26098334

  5. The Divergence and Natural Selection of Autocatalytic Primordial Metabolic Systems

    NASA Astrophysics Data System (ADS)

    Marakushev, Sergey A.; Belonogova, Ol'ga V.

    2013-06-01

    The diversity of the central metabolism of modern organisms is caused by the existence of a few metabolic modules, combination of which produces multiple metabolic pathways. This paper analyzes biomimetically reconstructed coupled autocatalytic cycles as the basis of ancestral metabolic systems. The mechanism for natural selection and evolution in autocatalytic chemical systems may be affected by natural homeostatic parameters such as ambient chemical potentials, temperature, and pressure. Competition between separate parts of an autocatalytic network with positive-plus-negative feedback resulted in the formation of primordial autotrophic, mixotrophic, and heterotrophic metabolic systems. This work examined the last common ancestor of a set of coupled metabolic cycles in a population of protocells. Physical-chemical properties of these cycles determined the main principles of natural selection for the ancestral Bacteria and Archaea taxa.

  6. Natural selection drives the evolution of ant life cycles

    PubMed Central

    Wilson, Edward O.; Nowak, Martin A.

    2014-01-01

    The genetic origin of advanced social organization has long been one of the outstanding problems of evolutionary biology. Here we present an analysis of the major steps in ant evolution, based for the first time, to our knowledge, on combined recent advances in paleontology, phylogeny, and the study of contemporary life histories. We provide evidence of the causal forces of natural selection shaping several key phenomena: (i) the relative lateness and rarity in geological time of the emergence of eusociality in ants and other animal phylads; (ii) the prevalence of monogamy at the time of evolutionary origin; and (iii) the female-biased sex allocation observed in many ant species. We argue that a clear understanding of the evolution of social insects can emerge if, in addition to relatedness-based arguments, we take into account key factors of natural history and study how natural selection acts on alleles that modify social behavior. PMID:25114217

  7. Safety in the Chemical Laboratory: The Selection of Eyewash Stations for Laboratory Use.

    ERIC Educational Resources Information Center

    Walters, Douglas B.; And Others

    1988-01-01

    Evaluates and compares common eyewash stations currently being used in laboratories. Discusses types available, installation, water supply needs, and maintenance. Lists current OSHA eyewash station standards. (ML)

  8. Compressed natural gas and liquefied petroleum gas conversions: The National Renewable Energy Laboratory`s experience

    SciTech Connect

    Motta, R.C.; Kelly, K.J.; Warnock, W.W.

    1996-04-01

    The National Renewable Energy Laboratory (NREL) contracted with conversion companies in six states to convert approximately 900 light-duty Federal fleet vehicles to operate on compressed natural gas (CNG) or liquefied petroleum gas (LPG). The contracts were initiated in order to help the Federal government meet the vehicle acquisition requirements of the Energy Policy Act of 1992 (EPACT) during a period of limited original equipment manufacturer (OEM) model availability. Approximately 90% of all conversions were performed on compact of full-size vans and pickups, and 90% of the conversions were to bi-fuel operation. With a positive response from the fleet managers, this program helped the Federal government meet the vehicle acquisition requirements of EPACT for fiscal years 1993 and 1994, despite limited OEM model availability. The conversions also helped to establish the infrastructure needed to support further growth in the use of alternative fuel vehicles. In conclusion, the program has been successful in helping the Federal government meet the vehicle acquisition requirements of EPACT, establishing infrastructure, increasing the displacement of imported oil, and evaluating the emissions performance of converted vehicles. With the relatively widespread availability of OEM vehicles in the 1996 model year, the program is now being phased out.

  9. Survey and analysis of materials research and development at selected federal laboratories

    SciTech Connect

    Reed, J.E.; Fink, C.R.

    1984-04-01

    This document presents the results of an effort to transfer existing, but relatively unknown, materials R and D from selected federal laboratories to industry. More specifically, recent materials-related work at seven federal laboratories potentially applicable to improving process energy efficiency and overall productiviy in six energy-intensive manufacturing industries was evaluated, catalogued, and distributed to industry representatives to gauge their reaction. Laboratories surveyed include: Air Force Wright Aeronautical Laboratories Material Laboratory (AFWAL). Pacific Northwest Laboratory (PNL), National Aeronautics and Space Administration Marshall Flight Center (NASA Marshall), Oak Ridge National Laboratory (ORNL), Brookhaven National Laboratory (BNL), Idaho National Engineering Laboratory (INEL), and Jet Propulsion Laboratory (JPL). Industries included in the effort are: aluminum, cement, paper and allied products, petroleum, steel and textiles.

  10. A model for selecting a clinical laboratory information system. A four-phase process.

    PubMed

    Rose, W; Maffetone, M; Suarez, E; Whisler, K; Bielitzki, L D

    1992-01-01

    Laboratory information systems (LISs) have become an essential part of an efficient and effective laboratory. In the past, selecting an LIS was a relatively simple procedure because there were only a few candidates to select from. Now, however, selecting an LIS from the myriad available has become a time-consuming and complex process. This article presents a multi-attribute utility (MAU) method for selecting an LIS. This MAU method has four phases: identifying LIS vendors and disseminating requests for proposals (RFPs), analyzing RFP responses and selecting the top three vendors, validating responses of the top three vendors, and selecting a primary vendor and preparing a formal recommendation. By following this four-phase process, laboratories will simplify the complex LIS selection process and increase their chances of selecting the best LIS for their needs. PMID:10116931

  11. Natural Selection VS. Random Drift: Evidence from Temporal Variation in Allele Frequencies in Nature

    PubMed Central

    Mueller, Laurence D.; Barr, Lorraine G.; Ayala, Francisco J.

    1985-01-01

    We have obtained monthly samples of two species, Drosophila pseudoobscura and Drosophila persimilis, in a natural population from Napa County, California. In each species, about 300 genes have been assayed by electrophoresis for each of seven enzyme loci in each monthly sample from March 1972 to June 1975. Using statistical methods developed for the purpose, we have examined whether the allele frequencies at different loci vary in a correlated fashion. The methods used do not detect natural selection when it is deterministic (e.g., overdominance or directional selection), but only when alleles at different loci vary simultaneously in response to the same environmental variations. Moreover, only relatively large fitness differences (of the order of 15%) are detectable. We have found strong evidence of correlated allele frequency variation in 13–20% of the cases examined. We interpret this as evidence that natural selection plays a major role in the evolution of protein polymorphisms in nature. PMID:4054608

  12. Effects of Laboratory Videotaping Procedures on Selected Conversation Behaviors.

    ERIC Educational Resources Information Center

    Wiemann, John M.

    1981-01-01

    Concludes that in the laboratory, participants' conversation behavior is not discernably affected by videotaping, no matter how overt or obvious the taping procedure is. Study focuses on behaviors out of conscious awareness: gestures, head nods, speaking turns, self or object manipulations, and shifts to reclining posture or to forward lean. (PD)

  13. Priorities for selection and representation in natural tasks

    PubMed Central

    Tatler, Benjamin W.; Hirose, Yoriko; Finnegan, Sarah K.; Pievilainen, Riina; Kirtley, Clare; Kennedy, Alan

    2013-01-01

    Selecting and remembering visual information is an active and competitive process. In natural environments, representations are tightly coupled to task. Objects that are task-relevant are remembered better due to a combination of increased selection for fixation and strategic control of encoding and/or retaining viewed information. However, it is not understood how physically manipulating objects when performing a natural task influences priorities for selection and memory. In this study, we compare priorities for selection and memory when actively engaged in a natural task with first-person observation of the same object manipulations. Results suggest that active manipulation of a task-relevant object results in a specific prioritization for object position information compared with other properties and compared with action observation of the same manipulations. Experiment 2 confirms that this spatial prioritization is likely to arise from manipulation rather than differences in spatial representation in real environments and the movies used for action observation. Thus, our findings imply that physical manipulation of task relevant objects results in a specific prioritization of spatial information about task-relevant objects, possibly coupled with strategic de-prioritization of colour memory for irrelevant objects. PMID:24018727

  14. Ontogenetic selection on hatchery salmon in the wild: natural selection on artificial phenotypes

    PubMed Central

    Bailey, Michael M; Lachapelle, Kevin A; Kinnison, Michael T

    2010-01-01

    Captive rearing often alters the phenotypes of organisms that are destined for release into the wild. Natural selection on these unnatural phenotypes could have important consequences for the utility of captive rearing as a restoration approach. We show that normal hatchery practices significantly advance the development of endangered Atlantic salmon (Salmo salar) fry by 30+ days. As a result, hatchery fry might be expected to face strong natural selection resulting from their developmental asynchrony. We investigated patterns of ontogenetic selection acting on hatchery produced salmon fry by experimentally manipulating fry development stage at stocking. Contrary to simple predictions, we found evidence for strong stabilizing selection on the ontogeny of unfed hatchery fry, with weaker evidence for positive directional selection on the ontogeny of fed fry. These selection patterns suggest a seasonally independent tradeoff between abiotic or biotic selection favoring advanced development and physiological selection linked to risk of starvation in unfed fry. We show, through a heuristic exercise, how such selection on ontogeny may exacerbate problems in restoration efforts by impairing fry productivity and reducing effective population sizes by 13–81%. PMID:25567929

  15. Preventing Alzheimer's disease by means of natural selection

    PubMed Central

    Demetrius, Lloyd A.; Driver, Jane A.

    2015-01-01

    The amyloid cascade model for the origin of sporadic forms of Alzheimer's disease (AD) posits that the imbalance in the production and clearance of beta-amyloid is a necessary condition for the disease. A competing theory called the entropic selection hypothesis asserts that the primary cause of sporadic AD is age-induced mitochondrial dysregulation and the following cascade of events: (i) metabolic reprogramming—the upregulation of oxidative phosphorylation in compensation for insufficient energy production in neurons, (ii) natural selection—competition between intact and reprogrammed neurons for energy substrates and (iii) propagation—the spread of the disease due to the selective advantage of neurons with upregulated metabolism. Experimental studies to evaluate the predictions of the amyloid cascade model are being continually retuned to accommodate conflicts of the predictions with empirical data. Clinical trials of treatments for AD based on anti-amyloid therapy have been unsuccessful. We contend that these anomalies and failures stem from a fundamental deficit of the amyloid hypothesis: the model derives from a nuclear-genomic perspective of sporadic AD and discounts the bioenergetic processes that characterize the progression of most age-related disorders. In this article, we review the anomalies of the amyloid model and the theoretical and empirical support for the entropic selection theory. We also discuss the new therapeutic strategies based on natural selection which the model proposes. PMID:25551134

  16. Natural selection on thermal performance in a novel thermal environment.

    TOXLINE Toxicology Bibliographic Information

    Logan ML; Cox RM; Calsbeek R

    2014-09-30

    Tropical ectotherms are thought to be especially vulnerable to climate change because they are adapted to relatively stable temperature regimes, such that even small increases in environmental temperature may lead to large decreases in physiological performance. One way in which tropical organisms may mitigate the detrimental effects of warming is through evolutionary change in thermal physiology. The speed and magnitude of this response depend, in part, on the strength of climate-driven selection. However, many ectotherms use behavioral adjustments to maintain preferred body temperatures in the face of environmental variation. These behaviors may shelter individuals from natural selection, preventing evolutionary adaptation to changing conditions. Here, we mimic the effects of climate change by experimentally transplanting a population of Anolis sagrei lizards to a novel thermal environment. Transplanted lizards experienced warmer and more thermally variable conditions, which resulted in strong directional selection on thermal performance traits. These same traits were not under selection in a reference population studied in a less thermally stressful environment. Our results indicate that climate change can exert strong natural selection on tropical ectotherms, despite their ability to thermoregulate behaviorally. To the extent that thermal performance traits are heritable, populations may be capable of rapid adaptation to anthropogenic warming.

  17. Genome-wide polymorphisms show unexpected targets of natural selection.

    PubMed

    Pespeni, Melissa H; Garfield, David A; Manier, Mollie K; Palumbi, Stephen R

    2012-04-01

    Natural selection can act on all the expressed genes of an individual, leaving signatures of genetic differentiation or diversity at many loci across the genome. New power to assay these genome-wide effects of selection comes from associating multi-locus patterns of polymorphism with gene expression and function. Here, we performed one of the first genome-wide surveys in a marine species, comparing purple sea urchins, Strongylocentrotus purpuratus, from two distant locations along the species' wide latitudinal range. We examined 9112 polymorphic loci from upstream non-coding and coding regions of genes for signatures of selection with respect to gene function and tissue- and ontogenetic gene expression. We found that genetic differentiation (F(ST)) varied significantly across functional gene classes. The strongest enrichment occurred in the upstream regions of E3 ligase genes, enzymes known to regulate protein abundance during development and environmental stress. We found enrichment for high heterozygosity in genes directly involved in immune response, particularly NALP genes, which mediate pro-inflammatory signals during bacterial infection. We also found higher heterozygosity in immune genes in the southern population, where disease incidence and pathogen diversity are greater. Similar to the major histocompatibility complex in mammals, balancing selection may enhance genetic diversity in the innate immune system genes of this invertebrate. Overall, our results show that how genome-wide polymorphism data coupled with growing databases on gene function and expression can combine to detect otherwise hidden signals of selection in natural populations. PMID:21993504

  18. Natural selection on thermal performance in a novel thermal environment.

    PubMed

    Logan, Michael L; Cox, Robert M; Calsbeek, Ryan

    2014-09-30

    Tropical ectotherms are thought to be especially vulnerable to climate change because they are adapted to relatively stable temperature regimes, such that even small increases in environmental temperature may lead to large decreases in physiological performance. One way in which tropical organisms may mitigate the detrimental effects of warming is through evolutionary change in thermal physiology. The speed and magnitude of this response depend, in part, on the strength of climate-driven selection. However, many ectotherms use behavioral adjustments to maintain preferred body temperatures in the face of environmental variation. These behaviors may shelter individuals from natural selection, preventing evolutionary adaptation to changing conditions. Here, we mimic the effects of climate change by experimentally transplanting a population of Anolis sagrei lizards to a novel thermal environment. Transplanted lizards experienced warmer and more thermally variable conditions, which resulted in strong directional selection on thermal performance traits. These same traits were not under selection in a reference population studied in a less thermally stressful environment. Our results indicate that climate change can exert strong natural selection on tropical ectotherms, despite their ability to thermoregulate behaviorally. To the extent that thermal performance traits are heritable, populations may be capable of rapid adaptation to anthropogenic warming. PMID:25225361

  19. Genome-wide polymorphisms show unexpected targets of natural selection

    PubMed Central

    Pespeni, Melissa H.; Garfield, David A.; Manier, Mollie K.; Palumbi, Stephen R.

    2012-01-01

    Natural selection can act on all the expressed genes of an individual, leaving signatures of genetic differentiation or diversity at many loci across the genome. New power to assay these genome-wide effects of selection comes from associating multi-locus patterns of polymorphism with gene expression and function. Here, we performed one of the first genome-wide surveys in a marine species, comparing purple sea urchins, Strongylocentrotus purpuratus, from two distant locations along the species' wide latitudinal range. We examined 9112 polymorphic loci from upstream non-coding and coding regions of genes for signatures of selection with respect to gene function and tissue- and ontogenetic gene expression. We found that genetic differentiation (FST) varied significantly across functional gene classes. The strongest enrichment occurred in the upstream regions of E3 ligase genes, enzymes known to regulate protein abundance during development and environmental stress. We found enrichment for high heterozygosity in genes directly involved in immune response, particularly NALP genes, which mediate pro-inflammatory signals during bacterial infection. We also found higher heterozygosity in immune genes in the southern population, where disease incidence and pathogen diversity are greater. Similar to the major histocompatibility complex in mammals, balancing selection may enhance genetic diversity in the innate immune system genes of this invertebrate. Overall, our results show that how genome-wide polymorphism data coupled with growing databases on gene function and expression can combine to detect otherwise hidden signals of selection in natural populations. PMID:21993504

  20. Preventing Alzheimer's disease by means of natural selection.

    PubMed

    Demetrius, Lloyd A; Driver, Jane A

    2015-01-01

    The amyloid cascade model for the origin of sporadic forms of Alzheimer's disease (AD) posits that the imbalance in the production and clearance of beta-amyloid is a necessary condition for the disease. A competing theory called the entropic selection hypothesis asserts that the primary cause of sporadic AD is age-induced mitochondrial dysregulation and the following cascade of events: (i) metabolic reprogramming—the upregulation of oxidative phosphorylation in compensation for insufficient energy production in neurons, (ii) natural selection—competition between intact and reprogrammed neurons for energy substrates and (iii) propagation—the spread of the disease due to the selective advantage of neurons with upregulated metabolism. Experimental studies to evaluate the predictions of the amyloid cascade model are being continually retuned to accommodate conflicts of the predictions with empirical data. Clinical trials of treatments for AD based on anti-amyloid therapy have been unsuccessful. We contend that these anomalies and failures stem from a fundamental deficit of the amyloid hypothesis: the model derives from a nuclear-genomic perspective of sporadic AD and discounts the bioenergetic processes that characterize the progression of most age-related disorders. In this article, we review the anomalies of the amyloid model and the theoretical and empirical support for the entropic selection theory. We also discuss the new therapeutic strategies based on natural selection which the model proposes. PMID:25551134

  1. Natural selection on thermal performance in a novel thermal environment

    PubMed Central

    Logan, Michael L.; Cox, Robert M.; Calsbeek, Ryan

    2014-01-01

    Tropical ectotherms are thought to be especially vulnerable to climate change because they are adapted to relatively stable temperature regimes, such that even small increases in environmental temperature may lead to large decreases in physiological performance. One way in which tropical organisms may mitigate the detrimental effects of warming is through evolutionary change in thermal physiology. The speed and magnitude of this response depend, in part, on the strength of climate-driven selection. However, many ectotherms use behavioral adjustments to maintain preferred body temperatures in the face of environmental variation. These behaviors may shelter individuals from natural selection, preventing evolutionary adaptation to changing conditions. Here, we mimic the effects of climate change by experimentally transplanting a population of Anolis sagrei lizards to a novel thermal environment. Transplanted lizards experienced warmer and more thermally variable conditions, which resulted in strong directional selection on thermal performance traits. These same traits were not under selection in a reference population studied in a less thermally stressful environment. Our results indicate that climate change can exert strong natural selection on tropical ectotherms, despite their ability to thermoregulate behaviorally. To the extent that thermal performance traits are heritable, populations may be capable of rapid adaptation to anthropogenic warming. PMID:25225361

  2. Efficacy of selected natural products as therapeutic agents against cancer.

    PubMed

    Banerjee, Sanjeev; Wang, Zhiwei; Mohammad, Mussop; Sarkar, Fazlul H; Mohammad, Ramzi M

    2008-03-01

    With emerging sophistication in the exploration of ocean environment, a number of marine bioactive products have been identified with promising anticancer activity. Many of these are in active phase I or phase II clinical trials or have been terminated because of adverse side effects, mainly hematological in nature. Nonetheless, the information derived has aided enormously in providing leads for laboratory synthesis with modifications in the parent structure affecting compound solubility, absorption, and toxicity, resulting in less severe toxicity while achieving maximum efficacy in smaller doses. We describe herein, a few of the compounds obtained from marine and terrestrial sources [bryostatin 1 ( 1), dolastatin 10 ( 2), auristatin PE ( 3), and combretastatin A4 ( 4)] that have been extensively investigated in our laboratory and continue to be investigated for their sensitization effects with other cytotoxic agents in several different site-specific tumors employing murine models or human subjects. PMID:18302335

  3. Male Mating Success: Preference or Prowess? Investigating Sexual Selection in the Laboratory Using "Drosophila melanogaster"

    ERIC Educational Resources Information Center

    Coleman, Seth; Jensen, Jeffrey

    2007-01-01

    Sexual selection is the primary force affecting the evolution of the elaborate sexual displays common in animals, yet sexual selection experiments are largely absent from introductory biology laboratories. Here we describe the rationale, methodology, and results of several experiments using "Drosophila melanogaster" to demonstrate sexual selection…

  4. The theory of natural selection of Alfred Russel Wallace FRS.

    PubMed

    Bulmer, Michael

    2005-05-22

    Wallace's 1858 paper 'On the tendency of varieties to depart indefinitely from the original type' is often thought to present a theory of natural selection identical with that of Darwin. Examination of Wallace's argument shows that it is different from Darwin's because Wallace thought that an inferior variety could coexist with a superior variety until environmental deterioration forced the extinction of the inferior one. Other interpretations of Wallace's argument are re-examined in the light of this finding. PMID:16116703

  5. Programed Death is Favored by Natural Selection in Spatial Systems

    NASA Astrophysics Data System (ADS)

    Werfel, Justin; Ingber, Donald E.; Bar-Yam, Yaneer

    2015-06-01

    Standard evolutionary theories of aging and mortality, implicitly based on mean-field assumptions, hold that programed mortality is untenable, as it opposes direct individual benefit. We show that in spatial models with local reproduction, programed deaths instead robustly result in long-term benefit to a lineage, by reducing local environmental resource depletion via spatiotemporal patterns causing feedback over many generations. Results are robust to model variations, implying that direct selection for shorter life span may be quite widespread in nature.

  6. Evolution: natural selection in the evolution of humans and chimps.

    PubMed

    Ellegren, Hans

    2005-11-22

    We now have more or less full sequences of both human and chimp genomes, allowing comparison that sheds light on their evolution. A few hundred genes show significant evidence for adaptive evolution in the two lineages, but the actual number might be much higher. Natural selection has eliminated about 75% of amino acid changes in coding sequence since the split of the human and chimpanzee genomes. PMID:16303548

  7. Genomic mutation rates that neutralize adaptive evolution and natural selection

    PubMed Central

    Gerrish, Philip J.; Colato, Alexandre; Sniegowski, Paul D.

    2013-01-01

    When mutation rates are low, natural selection remains effective, and increasing the mutation rate can give rise to an increase in adaptation rate. When mutation rates are high to begin with, however, increasing the mutation rate may have a detrimental effect because of the overwhelming presence of deleterious mutations. Indeed, if mutation rates are high enough: (i) adaptive evolution may be neutralized, resulting in a zero (or negative) adaptation rate despite the continued availability of adaptive and/or compensatory mutations, or (ii) natural selection may be neutralized, because the fitness of lineages bearing adaptive and/or compensatory mutations—whether established or newly arising—is eroded by excessive mutation, causing such lineages to decline in frequency. We apply these two criteria to a standard model of asexual adaptive evolution and derive mathematical expressions—some new, some old in new guise—delineating the mutation rates under which either adaptive evolution or natural selection is neutralized. The expressions are simple and require no a priori knowledge of organism- and/or environment-specific parameters. Our discussion connects these results to each other and to previous theory, showing convergence or equivalence of the different results in most cases. PMID:23720539

  8. Networking of Icelandic Earth Infrastructures - Natural laboratories and Volcano Supersites

    NASA Astrophysics Data System (ADS)

    Vogfjörd, K. S.; Sigmundsson, F.; Hjaltadóttir, S.; Björnsson, H.; Arason, Ø.; Hreinsdóttir, S.; Kjartansson, E.; Sigbjörnsson, R.; Halldórsson, B.; Valsson, G.

    2012-04-01

    The back-bone of Icelandic geoscientific research infrastructure is the country's permanent monitoring networks, which have been built up to monitor seismic and volcanic hazard and deformation of the Earth's surface. The networks are mainly focussed around the plate boundary in Iceland, particularly the two seismic zones, where earthquakes of up to M7.3 have occurred in centuries past, and the rift zones with over 30 active volcanic systems where a large number of powerful eruptions have occurred, including highly explosive ones. The main observational systems are seismic, strong motion, GPS and bore-hole strain networks, with the addition of more recent systems like hydrological stations, permanent and portable radars, ash-particle counters and gas monitoring systems. Most of the networks are owned by a handful of Icelandic institutions, but some are operated in collaboration with international institutions and universities. The networks have been in operation for years to decades and have recorded large volumes of research quality data. The main Icelandic infrastructures will be networked in the European Plate Observing System (EPOS). The plate boundary in the South Iceland seismic zone (SISZ) with its book-shelf tectonics and repeating major earthquakes sequences of up to M7 events, has the potential to be defined a natural laboratory within EPOS. Work towards integrating multidisciplinary data and technologies from the monitoring infrastructures in the SISZ with other fault regions has started in the FP7 project NERA, under the heading of Networking of Near-Fault Observatories. The purpose is to make research-quality data from near-fault observatories available to the research community, as well as to promote transfer of knowledge and techical know-how between the different observatories of Europe, in order to create a network of fault-monitoring networks. The seismic and strong-motion systems in the SISZ are also, to some degree, being networked nationally to strengthen their early warning capabilities. In response to the far-reaching dispersion of ash from the 2010 Eyjafjallajökull eruption and subsequent disturbance to European air-space, the instrumentation of the Icelandic volcano observatory was greatly improved in number and capability to better monitor sub-surface volcanic processes as well as the air-borne products of eruptions. This infrastructure will also be networked with other European volcano observatories in EPOS. Finally the Icelandic EPOS team, together with other European collaborators, has responded to an FP7 call for the establishment of an Icelandic volcano supersite, where land- and space-based data will be made available to researchers and hazard managers, in line with the implementation plan of the GEO. The focus of the Icelandic volcano supersite are the active volcanoes in Iceland's Eastern volcanic zone.

  9. Natural selection against a circadian clock gene mutation in mice

    PubMed Central

    Spoelstra, Kamiel; Wikelski, Martin; Daan, Serge; Loudon, Andrew S. I.; Hau, Michaela

    2016-01-01

    Circadian rhythms with an endogenous period close to or equal to the natural light–dark cycle are considered evolutionarily adaptive (“circadian resonance hypothesis”). Despite remarkable insight into the molecular mechanisms driving circadian cycles, this hypothesis has not been tested under natural conditions for any eukaryotic organism. We tested this hypothesis in mice bearing a short-period mutation in the enzyme casein kinase 1ε (tau mutation), which accelerates free-running circadian cycles. We compared daily activity (feeding) rhythms, survivorship, and reproduction in six replicate populations in outdoor experimental enclosures, established with wild-type, heterozygous, and homozygous mice in a Mendelian ratio. In the release cohort, survival was reduced in the homozygote mutant mice, revealing strong selection against short-period genotypes. Over the course of 14 mo, the relative frequency of the tau allele dropped from initial parity to 20%. Adult survival and recruitment of juveniles into the population contributed approximately equally to the selection for wild-type alleles. The expression of activity during daytime varied throughout the experiment and was significantly increased by the tau mutation. The strong selection against the short-period tau allele observed here contrasts with earlier studies showing absence of selection against a Period 2 (Per2) mutation, which disrupts internal clock function, but does not change period length. These findings are consistent with, and predicted by the theory that resonance of the circadian system plays an important role in individual fitness. PMID:26715747

  10. Natural selection against a circadian clock gene mutation in mice.

    PubMed

    Spoelstra, Kamiel; Wikelski, Martin; Daan, Serge; Loudon, Andrew S I; Hau, Michaela

    2016-01-19

    Circadian rhythms with an endogenous period close to or equal to the natural light-dark cycle are considered evolutionarily adaptive ("circadian resonance hypothesis"). Despite remarkable insight into the molecular mechanisms driving circadian cycles, this hypothesis has not been tested under natural conditions for any eukaryotic organism. We tested this hypothesis in mice bearing a short-period mutation in the enzyme casein kinase 1? (tau mutation), which accelerates free-running circadian cycles. We compared daily activity (feeding) rhythms, survivorship, and reproduction in six replicate populations in outdoor experimental enclosures, established with wild-type, heterozygous, and homozygous mice in a Mendelian ratio. In the release cohort, survival was reduced in the homozygote mutant mice, revealing strong selection against short-period genotypes. Over the course of 14 mo, the relative frequency of the tau allele dropped from initial parity to 20%. Adult survival and recruitment of juveniles into the population contributed approximately equally to the selection for wild-type alleles. The expression of activity during daytime varied throughout the experiment and was significantly increased by the tau mutation. The strong selection against the short-period tau allele observed here contrasts with earlier studies showing absence of selection against a Period 2 (Per2) mutation, which disrupts internal clock function, but does not change period length. These findings are consistent with, and predicted by the theory that resonance of the circadian system plays an important role in individual fitness. PMID:26715747

  11. Selection and implementation of a laboratory computer system.

    PubMed

    Moritz, V A; McMaster, R; Dillon, T; Mayall, B

    1995-07-01

    The process of selection of a pathology computer system has become increasingly complex as there are an increasing number of facilities that must be provided and stringent performance requirements under heavy computing loads from both human users and machine inputs. Furthermore, the continuing advances in software and hardware technology provide more options and innovative new ways of tackling problems. These factors taken together pose a difficult and complex set of decisions and choices for the system analyst and designer. The selection process followed by the Microbiology Department at Heidelberg Repatriation Hospital included examination of existing systems, development of a functional specification followed by a formal tender process. The successful tenderer was then selected using predefined evaluation criteria. The successful tenderer was a software development company that developed and supplied a system based on a distributed network using a SUN computer as the main processor. The software was written using Informix running on the UNIX operating system. This represents one of the first microbiology systems developed using a commercial relational database and fourth generation language. The advantages of this approach are discussed. PMID:8532393

  12. Natural selection in the field and the classroom

    NASA Astrophysics Data System (ADS)

    Andrews, Tessa Marie

    This dissertation examined natural selection in westslope cutthroat trout (Oncorhynchus clarkii lewisi) and undergraduate learning in the subject area natural selection. Translocation---moving individuals to a new habitat to establish, re-establish or supplement a population---is a crucial management strategy for cutthroat trout. One of the major questions managers face in a translocation is which population(s) should contribute individuals? Unfortunately, we often know little about the differences among potential contributing population. The goal of the first half of this dissertation was to look for differences in performance among individuals from five populations of westslope cutthroat trout. I assessed survival, growth, and condition (Chapter 2) and dispersal (Chapter 3) following the translocation of embryos from these five populations to six introduction sites in Cherry Creek. No differences existed among these populations in relative survival, growth, or condition at age 1 or 2. In contrast, statistically significant differences existed in dispersal distance among these populations. These differences were consistent across some, but not all, introduction locations. As our knowledge of evolutionary biology has continued to grow, so too has our knowledge of how students learn evolution. Students taught using active learning strategies can learn substantially more about complex scientific concepts than students taught using primarily lectures. The goal of the second half of this dissertation was to further examine how students learn natural selection and how instructors facilitate that learning. I conducted a national survey of the relationship between an instructor's use of active learning strategies and how much students learned about natural selection (Chapter 4). I used a random sample of instructors from the largest and most prestigious universities in the country so that my results could be inferred to this large population of instructors. The degree to which instructors used active learning was NOT associated with student learning in this population of typical biology instructors. However, I found that a discussion of contemporary human evolution that used active learning strategies could effectively facilitate student learning of natural selection (Chapter 5).

  13. Using David Lack's Observations of Finch Beak Size to Teach Natural Selection & the Nature of Science

    ERIC Educational Resources Information Center

    Bierema, Andrea M.-K.; Rudge, David W.

    2014-01-01

    One of the key aspects of natural selection is competition, yet the concept of competition is not necessarily emphasized in explanations of natural selection. Because of this, we developed an activity for our class that focuses on competition and provides an example of the effects of competition on natural selection. This hands-on activity models…

  14. Using David Lack's Observations of Finch Beak Size to Teach Natural Selection & the Nature of Science

    ERIC Educational Resources Information Center

    Bierema, Andrea M.-K.; Rudge, David W.

    2014-01-01

    One of the key aspects of natural selection is competition, yet the concept of competition is not necessarily emphasized in explanations of natural selection. Because of this, we developed an activity for our class that focuses on competition and provides an example of the effects of competition on natural selection. This hands-on activity models…

  15. Laboratory Experiences in an Introduction to Natural Science Course.

    ERIC Educational Resources Information Center

    Barnard, Sister Marquita

    1984-01-01

    Describes a two-semester course designed to meet the needs of future elementary teachers, home economists, and occupational therapists. Laboratory work includes homemade calorimeters, inclined planes, and computing. Content areas of the course include measurement, physics, chemistry, astronomy, biology, geology, and meteorology. (JN)

  16. Use of Laboratory-Supplied Natural Gas in Breakthrough Phenomena.

    ERIC Educational Resources Information Center

    Eiceman, G. A.; And Others

    1985-01-01

    Natural gas from regular commercial lines contains enough carbon-8 and above hydrocarbon contaminants to serve as a satisfactory sample for breakthrough experiments. Procedures used, typical results obtained, and theoretical background information are provided. (JN)

  17. The nature of selection on the major histocompatibility complex.

    PubMed

    Apanius, V; Penn, D; Slev, P R; Ruff, L R; Potts, W K

    1997-01-01

    Only natural selection can account for the extreme genetic diversity of genes of the major histocompatibility complex (MHC). Although the structure and function of classic MHC genes is well understood at the molecular and cellular levels, there is controversy about how MHC diversity is selectively maintained. The diversifying selection can be driven by pathogen interactions and inbreeding avoidance mechanisms. Pathogen-driven selection can maintain MHC polymorphism based on heterozygote advantage or frequency-dependent selection due to pathogen evasion of MHC-dependent immune recognition. Empirical evidence demonstrates that specific MHC haplotypes are resistant to certain infectious agents, while susceptible to others. These data are consistent with both heterozygote advantage and frequency-dependent models. Additional research is needed to discriminate between these mechanisms. Infectious agents can precipitate autoimmunity and can potentially contribute to MHC diversity through molecular mimicry and by favoring immunodominance. MHC-dependent abortion and mate choice, based on olfaction, can also maintain MHC diversity and probably functions both to avoid genome-wide inbreeding and produce MHC-heterozygous offspring with increased immune responsiveness. Although this diverse set of hypotheses are often treated as competing alternatives, we believe that they all fit into a coherent, internally consistent thesis. It is likely that at least in some species, all of these mechanisms operate, leading to the extreme diversification found in MHC genes. PMID:9094452

  18. Natural selection by pulsed predation: survival of the thickest.

    PubMed

    Bijleveld, Aller I; Twietmeyer, Sönke; Piechocki, Julia; van Gils, Jan A; Piersma, Theunis

    2015-07-01

    Selective predation can lead to natural selection in prey populations and may alleviate competition among surviving individuals. The processes of selection and competition can have substantial effects on prey population dynamics, but are rarely studied simultaneously. Moreover, field studies of predator-induced short-term selection pressures on prey populations are scarce. Here we report measurements of density dependence in body composition in a bivalve prey (edible cockle, Cerastoderma edule) during bouts of intense predation by an avian predator (Red Knot, Calidris canutus). We measured densities, patchiness, morphology, and body composition (shell and flesh mass) of cockles in a quasi-experimental setting, i.e., before and after predation in three similar plots of 1 ha each, two of which experienced predation, and one of which remained unvisited in the course of the short study period and served as a reference. An individual's shell and flesh mass declined with cockle density (negative density dependence). Before predation, cockles were patchily distributed. After predation, during which densities were reduced by 78% (from 232 to 50 cockles/m2), the patchiness was substantially reduced, i.e., the spatial distribution was homogenized. Red Knots selected juvenile cockles with an average length of 6.9 ± 1.0 mm (mean ± SD). Cockles surviving predation had heavier shells than before predation (an increase of 21.5 percentage points), but similar flesh masses. By contrast, in the reference plot shell mass did not differ statistically between initial and final sampling occasions, while flesh mass was larger (an increase of 13.2 percentage points). In this field study, we show that Red Knots imposed a strong selection pressure on cockles to grow fast with thick shells and little flesh mass, with selection gradients among the highest reported in the literature. PMID:26378316

  19. Exploring the nature of collisionless shocks under laboratory conditions

    PubMed Central

    Stockem, A.; Fiuza, F.; Bret, A.; Fonseca, R. A.; Silva, L. O.

    2014-01-01

    Collisionless shocks are pervasive in astrophysics and they are critical to understand cosmic ray acceleration. Laboratory experiments with intense lasers are now opening the way to explore and characterise the underlying microphysics, which determine the acceleration process of collisionless shocks. We determine the shock character – electrostatic or electromagnetic – based on the stability of electrostatic shocks to transverse electromagnetic fluctuations as a function of the electron temperature and flow velocity of the plasma components, and we compare the analytical model with particle-in-cell simulations. By making the connection with the laser parameters driving the plasma flows, we demonstrate that shocks with different and distinct underlying microphysics can be explored in the laboratory with state-of-the-art laser systems. PMID:24488212

  20. Laboratory study of selected personal inhalable aerosol samplers.

    PubMed

    Görner, Peter; Simon, Xavier; Wrobel, Richard; Kauffer, Edmond; Witschger, Olivier

    2010-03-01

    Assessment of inhalable dust exposure requires reliable sampling methods in order to measure airborne inhalable particles' concentrations. Many inhalable aerosol samplers can be used but their performances widely vary and remain unknown in some cases. The sampling performance of inhalable samplers is strongly dependent on particle size and ambient air velocity. Five inhalable aerosol samplers have been studied in two laboratory wind tunnels using polydisperse glass-beads' test aerosol. Samplers tested were IOM sampler (UK), two versions of CIP 10-I sampler, v1 and v2 (F), 37-mm closed face cassette sampler (USA), 37-mm cassette fitted up with an ACCU-CAP insert (USA), and Button sampler (USA). Particle size-dependent sampling efficiencies were measured in a horizontal wind tunnel under a 1 m s(-1) wind velocity and in a vertical tunnel under calm air, using a specific method with Coulter(R) counter particle size number distribution determinations. Compared with CEN-ISO-ACGIH sampling criteria for inhalable dust, the experimental results show fairly high sampling efficiency for the IOM and CIP 10-I v2 samplers and slightly lower efficiencies for the Button and CIP 10-I v1 samplers. The closed face cassette (4-mm orifice) produced the poorest performances of all the tested samplers. This can be improved by using the ACCU-CAP internal capsule, which prevents inner wall losses inside the cassette. Significant differences between moving air and calm air sampling efficiency were observed for all the studied samplers. PMID:20147627

  1. Direct laboratory tensile testing of select yielding rock bolt systems

    SciTech Connect

    VandeKraats, J.D.; Watson, S.O.

    1996-12-01

    Yielding rock bolt support systems have been developed to accommodate ground movement in shifting ground such as in coal operations; in creeping ground such as salt, trona, and potash; and in swelling ground associated with some clays. These systems, designed to remain intact despite ground movement, should enhance mine safety and help contain costs in areas where revolting of rigid non-yielding systems is typically required. Four such systems were tested in straight tensile pulls in the laboratory. They include the Slip Nut System from Dywidag Systems International USA, Inc., Ischebeck`s bolt mounted Titan Load Indicator, Rocky Mountain Bolt Company`s Yielding Cable Bolt, and a rock bolt installed variation of the yielding steel post developed by RE/SPEC Inc. The first two systems are currently marketed products and the latter two are prototype systems. Each system responds to load and displacement by yielding in a unique manner. All are designed to yield at predetermined loads. A description of each system and its yield function is provided. Each system was tested over its prescribed yield range in a test machine. At least five tests were performed on each system. Each system yielded and continued to provide support according to its design. Each shows promise for ground control use in shifting or creeping rock. This work helps to illustrate the comparative differences in performance between these specialized systems and the applications where they may be most useful.

  2. Direct laboratory tensile testing of select yielding rock bolt systems

    SciTech Connect

    VandeKraats, J.D.; Watson, S.O.

    1996-08-01

    Yielding rock bolt support systems have been developed to accommodate ground movement in shifting ground such as in coal operations; in creeping ground such as salt, trona, and potash; and in swelling ground associated with some clays. These systems, designed to remain intact despite ground movement, should enhance mine safety and help contain costs in areas where rebolting of rigid non-yielding systems is typically required. Four such systems were tested in straight tensile pulls in the laboratory. They include the Slip Nut System from Dywidag Systems International USA, Inc., Ischebeck`s bolt mounted Titan Load Indicator, Rocky Mountain Bolt Company`s Yielding Cable Bolt, and a rock bolt installed variation of the yielding steel post developed by RE/SPEC Inc. The first two systems are currently marketed products and the latter two are prototype systems. Each system responds to load and displacement by yielding in an unique manner. All are designed to yield at predetermined loads. A description of each system and its yield function is provided. Each system was tested over its prescribed yield range in a test machine. At least five tests were performed on each system. Each system yielded and continued to provide support according to its design. Each shows promise for ground control use in shifting or creeping rock. This work helps to illustrate the comparative differences in performance between these specialized systems and the applications where they may be most useful.

  3. 42 CFR 493.565 - Selection for validation inspection-laboratory responsibilities.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 5 2014-10-01 2014-10-01 false Selection for validation inspection-laboratory... HEALTH AND HUMAN SERVICES (CONTINUED) STANDARDS AND CERTIFICATION LABORATORY REQUIREMENTS Accreditation by a Private, Nonprofit Accreditation Organization or Exemption Under an Approved State...

  4. 42 CFR 493.565 - Selection for validation inspection-laboratory responsibilities.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 5 2013-10-01 2013-10-01 false Selection for validation inspection-laboratory... HEALTH AND HUMAN SERVICES (CONTINUED) STANDARDS AND CERTIFICATION LABORATORY REQUIREMENTS Accreditation by a Private, Nonprofit Accreditation Organization or Exemption Under an Approved State...

  5. 42 CFR 493.565 - Selection for validation inspection-laboratory responsibilities.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 5 2012-10-01 2012-10-01 false Selection for validation inspection-laboratory... HEALTH AND HUMAN SERVICES (CONTINUED) STANDARDS AND CERTIFICATION LABORATORY REQUIREMENTS Accreditation by a Private, Nonprofit Accreditation Organization or Exemption Under an Approved State...

  6. 42 CFR 493.565 - Selection for validation inspection-laboratory responsibilities.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 5 2010-10-01 2010-10-01 false Selection for validation inspection-laboratory... HEALTH AND HUMAN SERVICES (CONTINUED) STANDARDS AND CERTIFICATION LABORATORY REQUIREMENTS Accreditation by a Private, Nonprofit Accreditation Organization or Exemption Under an Approved State...

  7. 42 CFR 493.565 - Selection for validation inspection-laboratory responsibilities.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 5 2011-10-01 2011-10-01 false Selection for validation inspection-laboratory... HEALTH AND HUMAN SERVICES (CONTINUED) STANDARDS AND CERTIFICATION LABORATORY REQUIREMENTS Accreditation by a Private, Nonprofit Accreditation Organization or Exemption Under an Approved State...

  8. Immunobiological properties of selected natural and chemically modified phenylpropanoids

    PubMed Central

    Harmatha, Juraj; Zídek, Zden?k; Kmoní?ková, Eva; Šmidrkal, Jan

    2011-01-01

    Effects of natural and structurally transformed lignans compared with stilbenes or stilbenoids on production of nitric oxide (NO) triggered by lipopolysaccharide (LPS) and interferon-? (IFN-?), tested under in vitro conditions using murine resident peritoneal macrophages, are reviewed. Relation between the molecular structure and immunobiological activity was investigated, and implication of substituents, double bond stereochemistry, or cyclic attachments (double bond geometry fixation) was assessed. The focus was on lignans and stilbenoids because they were originally selected for a joint project of common interest to phytochemical and pharmacological investigation and because they represent well interesting and universally attractive groups of polyphenols with a feasible potential for therapeutic or nutraceutic utilization. PMID:21577277

  9. Programed Death is Favored by Natural Selection in Spatial Systems.

    PubMed

    Werfel, Justin; Ingber, Donald E; Bar-Yam, Yaneer

    2015-06-12

    Standard evolutionary theories of aging and mortality, implicitly based on mean-field assumptions, hold that programed mortality is untenable, as it opposes direct individual benefit. We show that in spatial models with local reproduction, programed deaths instead robustly result in long-term benefit to a lineage, by reducing local environmental resource depletion via spatiotemporal patterns causing feedback over many generations. Results are robust to model variations, implying that direct selection for shorter life span may be quite widespread in nature. PMID:26196833

  10. Kaon condensation, black holes, and cosmological natural selection.

    PubMed

    Brown, G E; Lee, Chang-Hwan; Rho, Mannque

    2008-08-29

    It is argued that a well-measured double neutron-star binary in which the two neutron stars are more than 4% different from each other in mass or a massive neutron star with mass M > or approximately 2M(middle dot in circle) would put in serious doubt or simply falsify the following chain of predictions: (1) a nearly vanishing vector meson mass at chiral restoration, (2) kaon condensation at a density n-3n0, (3) the Brown-Bethe maximum neutron-star mass Mmax approximately 1.5M(middle dot in circle), and (4) Smolin's "cosmological natural selection" hypothesis. PMID:18851598

  11. Male Mating Success: Preference or Prowess? Investigating Sexual Selection in the Laboratory Using "Drosophila melanogaster"

    ERIC Educational Resources Information Center

    Coleman, Seth; Jensen, Jeffrey

    2007-01-01

    Sexual selection is the primary force affecting the evolution of the elaborate sexual displays common in animals, yet sexual selection experiments are largely absent from introductory biology laboratories. Here we describe the rationale, methodology, and results of several experiments using "Drosophila melanogaster" to demonstrate sexual selection…

  12. The physical nature of Titan's aerosols: Laboratory simulations

    NASA Technical Reports Server (NTRS)

    Scattergood, T. W.

    1995-01-01

    The atmosphere of Titan is known to contain aerosols, as evidenced by the Voyager observations of at least three haze layers. Such aerosols can have significant effects on the reflection spectrum of Titan and on the chemistry and thermal structure of its atmosphere. To investigate some of these effects laboratory simulations of the chemistry of Titan's atmosphere have been done. The results of these studies show that photolysis of acetylene, ethylene, and hydrogen cyanide, known constituents of Titan's atmosphere, yields sub-micron sized spheres, with mean diameters ranging from 0.4 to 0.8 micron, depending on the pressures of the reactant gases. Most of the spheres are contained in near-linear aggregates. The formation of the aggregates is consistent with models of Titan's reflection spectrum and polarization, which are best fit with non-spherical particles. At room temperature, the particles are very sticky, but their properties at low temperatures on Titan are presently not known.

  13. Competition and natural selection in a mathematical model of cancer.

    PubMed

    Nagy, John D

    2004-07-01

    A malignant tumor is a dynamic amalgamation of various cell phenotypes, both cancerous (parenchyma) and healthy (stroma). These diverse cells compete over resources as well as cooperate to maintain tumor viability. Therefore, tumors are both an ecological community and an integrated tissue. An understanding of how natural selection operates in this unique ecological context should expose unappreciated vulnerabilities shared by all cancers. In this study I address natural selection's role in tumor evolution by developing and exploring a mathematical model of a heterogenous primary neoplasm. The model is a system of nonlinear ordinary differential equations tracking the mass of up to two different parenchyma cell types, the mass of vascular endothelial cells from which new tumor blood vessels are built and the total length of tumor microvessels. Results predict the possibility of a hypertumor-a focus of aggressively reproducing parenchyma cells that invade and destroy part or all of the tumor, perhaps before it becomes a clinical entity. If this phenomenon occurs, then we should see examples of tumors that develop an aggressive histology but are paradoxically prone to extinction. Neuroblastoma, a common childhood cancer, may sometimes fit this pattern. In addition, this model suggests that parenchyma cell diversity can be maintained by a tissue-like integration of cells specialized to provide different services. PMID:15210312

  14. Emergence and natural selection of drug-resistant prions.

    PubMed

    Shorter, James

    2010-07-01

    Drug resistance is a refractory barrier in the battle against many fatal diseases caused by rapidly evolving agents, including HIV, apicomplexans and specific cancers. Emerging evidence suggests that drug resistance might extend to lethal prion disorders and related neurodegenerative amyloidoses. Prions are self-replicating protein conformers, usually 'cross-beta' amyloid polymers, which are naturally transmitted between individuals and promote phenotypic change. Prion conformers are catalytic templates that specifically convert other copies of the same protein to the prion form. Once in motion, this chain reaction of conformational replication can deplete all non-prion copies of a protein. Typically, prions exist as ensembles of multiple structurally distinct, self-replicating forms or 'strains'. Each strain confers a distinct phenotype and replicates at different rates depending on the environment. As replicators, prions are units of selection. Thus, natural selection inescapably enriches or depletes various prion strains from populations depending on their conformational fitness (ability to self-replicate) in the prevailing environment. The most successful prions confer advantages to their host as with numerous yeast prions. Here, I review recent evidence that drug-like small molecules can antagonize some prion strains but simultaneously select for drug-resistant prions composed of mammalian PrP or the yeast prion protein, Sup35. For Sup35, the drug-resistant strain configures original intermolecular amyloid contacts that are not ordinarily detected. Importantly, a synergistic small-molecule cocktail counters prion diversity by eliminating multiple Sup35 prion strains. Collectively, these advances illuminate the plasticity of prionogenesis and suggest that synergistic combinatorial therapies might circumvent this pathological vicissitude. PMID:20422111

  15. Making a Natural Product Chemistry Course Meaningful with a Mini Project Laboratory

    ERIC Educational Resources Information Center

    Hakim, Aliefman; Liliasari; Kadarohman, Asep; Syah, Yana Maolana

    2016-01-01

    This paper discusses laboratory activities that can improve the meaningfulness of natural product chemistry course. These laboratory activities can be useful for students from many different disciplines including chemistry, pharmacy, and medicine. Students at the third-year undergraduate level of chemistry education undertake the project to…

  16. Assessment of Application Technology of Natural User Interfaces in the Creation of a Virtual Chemical Laboratory

    ERIC Educational Resources Information Center

    Jagodzinski, Piotr; Wolski, Robert

    2015-01-01

    Natural User Interfaces (NUI) are now widely used in electronic devices such as smartphones, tablets and gaming consoles. We have tried to apply this technology in the teaching of chemistry in middle school and high school. A virtual chemical laboratory was developed in which students can simulate the performance of laboratory activities similar…

  17. Assessment of Application Technology of Natural User Interfaces in the Creation of a Virtual Chemical Laboratory

    ERIC Educational Resources Information Center

    Jagodzinski, Piotr; Wolski, Robert

    2015-01-01

    Natural User Interfaces (NUI) are now widely used in electronic devices such as smartphones, tablets and gaming consoles. We have tried to apply this technology in the teaching of chemistry in middle school and high school. A virtual chemical laboratory was developed in which students can simulate the performance of laboratory activities similar…

  18. Making a Natural Product Chemistry Course Meaningful with a Mini Project Laboratory

    ERIC Educational Resources Information Center

    Hakim, Aliefman; Liliasari; Kadarohman, Asep; Syah, Yana Maolana

    2016-01-01

    This paper discusses laboratory activities that can improve the meaningfulness of natural product chemistry course. These laboratory activities can be useful for students from many different disciplines including chemistry, pharmacy, and medicine. Students at the third-year undergraduate level of chemistry education undertake the project to…

  19. Granular Mechanisms for Faulting in Nature and the Laboratory

    NASA Astrophysics Data System (ADS)

    Hayman, N. W.; Daniels, K. E.; Gibson, G. I.

    2006-12-01

    The Black Mountain detachments in Death Valley, CA, are type localities for large displacement faults that deformed by granular mechanisms. The granular mechanisms likely exerted a first-order control on the strength and stability of the faults. The granular hypothesis arises from: (1) A lack of mineralogical and geochemical data evidence for large fluid fluxes and, by inference, elevated fluid pressure; (2) Microstructural data that show that the fault rocks accommodated strain mostly by interparticle rotation, translation, and grain- boundary abrasion; (3) Structural relationships between the low-angle detachments and high-angle faults (including earthquake scarps) that illustrate that the strength and sliding-stability of the detachments changed over time. To further test the granular hypothesis a shear apparatus was constructed containing polymer disks that are birefringent (photoelastic) under stress. As an aggregate of the disks accumulates strain, the stress is observed by this method to be localized in "force chains" that evolve with deformation. At present the experiment is set up in a strike-slip reference frame with sigma-1 imposed horizontally. A split in the center of the apparatus prevents localization to the shear zone boundaries. A mixture of elliptical and circular particles allows for tracking particle orientations as well as positions, and will ultimately allow the apparatus to test the influence of grain shape on mechanics. Results to date show that stick-slip events coincide with abrupt localization of shear strain to the center of the apparatus, with little change to the force chain geometry near the shear zone boundaries. To simulate the Black Mountain detachments, future runs will find the conditions of large shear strains accommodated by more distributed deformation, while tracking the changes in bulk friction. The approach will be fruitful in combining geologic and laboratory observations to better understand shallow crustal faulting.

  20. More than Meets the Eye--a Simulation of Natural Selection.

    ERIC Educational Resources Information Center

    Allen, J. A.; And Others

    1987-01-01

    Presents experiments using wild birds as predators and pastry as prey and colored stones as background to demonstrate natural selection. Describes the exercise as an exercise in simulating natural selection. (Author/CW)

  1. Natural Selection for Operons Depends on Genome Size

    PubMed Central

    Nuñez, Pablo A.; Romero, Héctor; Farber, Marisa D.; Rocha, Eduardo P.C.

    2013-01-01

    In prokaryotes, genome size is associated with metabolic versatility, regulatory complexity, effective population size, and horizontal transfer rates. We therefore analyzed the covariation of genome size and operon conservation to assess the evolutionary models of operon formation and maintenance. In agreement with previous results, intraoperonic pairs of essential and of highly expressed genes are more conserved. Interestingly, intraoperonic pairs of genes are also more conserved when they encode proteins at similar cell concentrations, suggesting a role of cotranscription in diminishing the cost of waste and shortfall in gene expression. Larger genomes have fewer and smaller operons that are also less conserved. Importantly, lower conservation in larger genomes was observed for all classes of operons in terms of gene expression, essentiality, and balanced protein concentration. We reached very similar conclusions in independent analyses of three major bacterial clades (?- and ?-Proteobacteria and Firmicutes). Operon conservation is inversely correlated to the abundance of transcription factors in the genome when controlled for genome size. This suggests a negative association between the complexity of genetic networks and operon conservation. These results show that genome size and/or its proxies are key determinants of the intensity of natural selection for operon organization. Our data fit better the evolutionary models based on the advantage of coregulation than those based on genetic linkage or stochastic gene expression. We suggest that larger genomes with highly complex genetic networks and many transcription factors endure weaker selection for operons than smaller genomes with fewer alternative tools for genetic regulation. PMID:24201372

  2. Spatially-Correlated Risk in Nature Reserve Site Selection

    PubMed Central

    Albers, Heidi J.; Busby, Gwenlyn M.; Hamaide, Bertrand; Ando, Amy W.; Polasky, Stephen

    2016-01-01

    Establishing nature reserves protects species from land cover conversion and the resulting loss of habitat. Even within a reserve, however, many factors such as fires and defoliating insects still threaten habitat and the survival of species. To address the risk to species survival after reserve establishment, reserve networks can be created that allow some redundancy of species coverage to maximize the expected number of species that survive in the presence of threats. In some regions, however, the threats to species within a reserve may be spatially correlated. As examples, fires, diseases, and pest infestations can spread from a starting point and threaten neighboring parcels’ habitats, in addition to damage caused at the initial location. This paper develops a reserve site selection optimization framework that compares the optimal reserve networks in cases where risks do and do not reflect spatial correlation. By exploring the impact of spatially-correlated risk on reserve networks on a stylized landscape and on an Oregon landscape, this analysis demonstrates an appropriate and feasible method for incorporating such post-reserve establishment risks in the reserve site selection literature as an additional tool to be further developed for future conservation planning. PMID:26789127

  3. Spatially-Correlated Risk in Nature Reserve Site Selection.

    PubMed

    Albers, Heidi J; Busby, Gwenlyn M; Hamaide, Bertrand; Ando, Amy W; Polasky, Stephen

    2016-01-01

    Establishing nature reserves protects species from land cover conversion and the resulting loss of habitat. Even within a reserve, however, many factors such as fires and defoliating insects still threaten habitat and the survival of species. To address the risk to species survival after reserve establishment, reserve networks can be created that allow some redundancy of species coverage to maximize the expected number of species that survive in the presence of threats. In some regions, however, the threats to species within a reserve may be spatially correlated. As examples, fires, diseases, and pest infestations can spread from a starting point and threaten neighboring parcels' habitats, in addition to damage caused at the initial location. This paper develops a reserve site selection optimization framework that compares the optimal reserve networks in cases where risks do and do not reflect spatial correlation. By exploring the impact of spatially-correlated risk on reserve networks on a stylized landscape and on an Oregon landscape, this analysis demonstrates an appropriate and feasible method for incorporating such post-reserve establishment risks in the reserve site selection literature as an additional tool to be further developed for future conservation planning. PMID:26789127

  4. Mosquito management in the face of natural selection.

    PubMed

    Agusto, Folashade B; Bewick, Sharon; Parshad, Rana D

    2012-09-01

    The sterile insect technique (SIT) is an appealing method for managing mosquito populations while avoiding the environmental and social costs associated with more traditional control strategies like insecticide application. Success of SIT, however, hinges on sterile males being able to compete for females. As a result, heavy and/or continued use of SIT could potentially diminish its efficacy if prolonged treatments result in selection for female preference against sterile males. In this paper we extend a general differential equation model of mosquito dynamics to consider the role of female choosiness in determining the long-term usefulness of SIT as a management option. We then apply optimal control theory to our model and show how natural selection for female choosiness fundamentally alters management strategies. Our study calls into question the benefits associated with developing SIT as a management strategy, and suggests that effort should be spent studying female mate choice in order to determine its relative importance and how likely it is to impact SIT treatment goals. PMID:22617381

  5. Mixed strategies and natural selection in resource allocation.

    PubMed

    Kareva, Irina; Berezovkaya, Faina; Karev, Georgy

    2013-01-01

    An appropriate choice of strategy for resource allocation may frequently determine whether a population will be able to survive under the conditions of severe resource limitations. Here we focus on two classes of strategies allocation of resources towards rapid proliferation, or towards slower proliferation but increased physiological and environmental maintenance. We propose a generalized framework, where individuals within a population can use either strategy in different proportion for utilization of a common dynamical resource in order to maximize their fitness. We use the model to address two major questions, namely, whether either strategy is more likely to be selected for as a result of natural selection, and, if one allows for the possibility of resource over-consumption, whether either strategy is preferable for avoiding population collapse due to resource exhaustion. Analytical and numerical results suggest that the ultimate choice of strategy is determined primarily by the initial distribution of individuals in the population, and that while investment in physiological and environmental maintenance is a preferable strategy in a homogeneous population, no generalized prediction can be made about heterogeneous populations. PMID:24245635

  6. Thermodynamic Cycle Selection for Distributed Natural Gas Liquefaction

    NASA Astrophysics Data System (ADS)

    Barclay, M. A.; Gongaware, D. F.; Dalton, K.; Skrzypkowski, M. P.

    2004-06-01

    Natural gas liquefaction plants with cooling capacities of approximately 100 kW are facilitating the development of a distributed LNG infrastructure. To be economically viable, liquefiers of this scale must be able to operate on a variety of feed gases while offering relatively low capital costs, short delivery time, and good performance. This paper opens with a discussion of a natural gas liquefier design focusing on the refrigeration system. Linde, cascade, mixed refrigerant, and modified-Brayton cycle refrigeration systems are then discussed in context of the overall plant design. Next, a detailed comparison of the modified-Brayton and mixed refrigerant cycles is made including cycle selection's impact on main system components like the recuperative heat exchanger and compressors. In most cases, a reverse-Brayton or a mixed refrigerant cycle refrigerator is the best-suited available technology for local liquefaction. The mixed refrigerant cycle liquefier offers the potential of better real performance at lower capital costs but requires more know-how in the areas of two-phase flow and refrigerant composition management, heat exchanger design, and process control.

  7. Natural selection shaped regional mtDNA variation in humans

    PubMed Central

    Mishmar, Dan; Ruiz-Pesini, Eduardo; Golik, Pawel; Macaulay, Vincent; Clark, Andrew G.; Hosseini, Seyed; Brandon, Martin; Easley, Kirk; Chen, Estella; Brown, Michael D.; Sukernik, Rem I.; Olckers, Antonel; Wallace, Douglas C.

    2003-01-01

    Human mtDNA shows striking regional variation, traditionally attributed to genetic drift. However, it is not easy to account for the fact that only two mtDNA lineages (M and N) left Africa to colonize Eurasia and that lineages A, C, D, and G show a 5-fold enrichment from central Asia to Siberia. As an alternative to drift, natural selection might have enriched for certain mtDNA lineages as people migrated north into colder climates. To test this hypothesis we analyzed 104 complete mtDNA sequences from all global regions and lineages. African mtDNA variation did not significantly deviate from the standard neutral model, but European, Asian, and Siberian plus Native American variations did. Analysis of amino acid substitution mutations (nonsynonymous, Ka) versus neutral mutations (synonymous, Ks) (ka/ks) for all 13 mtDNA protein-coding genes revealed that the ATP6 gene had the highest amino acid sequence variation of any human mtDNA gene, even though ATP6 is one of the more conserved mtDNA proteins. Comparison of the ka/ks ratios for each mtDNA gene from the tropical, temperate, and arctic zones revealed that ATP6 was highly variable in the mtDNAs from the arctic zone, cytochrome b was particularly variable in the temperate zone, and cytochrome oxidase I was notably more variable in the tropics. Moreover, multiple amino acid changes found in ATP6, cytochrome b, and cytochrome oxidase I appeared to be functionally significant. From these analyses we conclude that selection may have played a role in shaping human regional mtDNA variation and that one of the selective influences was climate. PMID:12509511

  8. Natural selection shaped regional mtDNA variation in humans.

    PubMed

    Mishmar, Dan; Ruiz-Pesini, Eduardo; Golik, Pawel; Macaulay, Vincent; Clark, Andrew G; Hosseini, Seyed; Brandon, Martin; Easley, Kirk; Chen, Estella; Brown, Michael D; Sukernik, Rem I; Olckers, Antonel; Wallace, Douglas C

    2003-01-01

    Human mtDNA shows striking regional variation, traditionally attributed to genetic drift. However, it is not easy to account for the fact that only two mtDNA lineages (M and N) left Africa to colonize Eurasia and that lineages A, C, D, and G show a 5-fold enrichment from central Asia to Siberia. As an alternative to drift, natural selection might have enriched for certain mtDNA lineages as people migrated north into colder climates. To test this hypothesis we analyzed 104 complete mtDNA sequences from all global regions and lineages. African mtDNA variation did not significantly deviate from the standard neutral model, but European, Asian, and Siberian plus Native American variations did. Analysis of amino acid substitution mutations (nonsynonymous, Ka) versus neutral mutations (synonymous, Ks) (kaks) for all 13 mtDNA protein-coding genes revealed that the ATP6 gene had the highest amino acid sequence variation of any human mtDNA gene, even though ATP6 is one of the more conserved mtDNA proteins. Comparison of the kaks ratios for each mtDNA gene from the tropical, temperate, and arctic zones revealed that ATP6 was highly variable in the mtDNAs from the arctic zone, cytochrome b was particularly variable in the temperate zone, and cytochrome oxidase I was notably more variable in the tropics. Moreover, multiple amino acid changes found in ATP6, cytochrome b, and cytochrome oxidase I appeared to be functionally significant. From these analyses we conclude that selection may have played a role in shaping human regional mtDNA variation and that one of the selective influences was climate. PMID:12509511

  9. Effects of natural and sexual selection on adaptive population divergence and premating isolation in a damselfly.

    PubMed

    Svensson, Erik I; Eroukhmanoff, Fabrice; Friberg, Magne

    2006-06-01

    The relative strength of different types of directional selection has seldom been compared directly in natural populations. A recent meta-analysis of phenotypic selection studies in natural populations suggested that directional sexual selection may be stronger in magnitude than directional natural selection, although this pattern may have partly been confounded by the different time scales over which selection was estimated. Knowledge about the strength of different types of selection is of general interest for understanding how selective forces affect adaptive population divergence and how they may influence speciation. We studied divergent selection on morphology in parapatric, natural damselfly (Calopteryx splendens) populations. Sexual selection was stronger than natural selection measured on the same traits, irrespective of the time scale over which sexual selection was measured. Visualization of the fitness surfaces indicated that population divergence in overall morphology is more strongly influenced by divergent sexual selection rather than natural selection. Courtship success of experimental immigrant males was lower than that of resident males, indicating incipient sexual isolation between these populations. We conclude that current and strong sexual selection promotes adaptive population divergence in this species and that premating sexual isolation may have arisen as a correlated response to divergent sexual selection. Our results highlight the importance of sexual selection, rather than natural selection in the adaptive radiation of odonates, and supports previous suggestions that divergent sexual selection promotes speciation in this group. PMID:16892974

  10. Definition of experiments and instruments for a communication/navigation research laboratory. Volume 2: Experiment selection

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The selection and definition of candidate experiments and the associated experiment instrumentation requirements are described. Information is presented that addresses the following study objectives: (1) determine specific research and technology needs in the comm/nav field through a survey of the scientific/technical community; (2) develop manned low earth orbit space screening criteria and compile lists of potential candidate experiments; (3) in Blue Book format, define and describe selected candidate experiments in sufficient detail to develop laboratory configuration designs and layouts; and (4) develop experiment time phasing criteria and recommend a payload for sortie can/early laboratory missions.

  11. Materials research at selected Japanese laboratories. Based on a 1992 visit: Overview, summary of highlights, notes on laboratories and topics

    SciTech Connect

    Not Available

    1994-02-01

    I visited Japan from June 29 to August 1, 1992. The purpose of this visit was to assess the status of materials science research at selected governmental, university and industrial laboratories and to established acquaintances with Japanese researchers. The areas of research covered by these visits included ceramics, oxide superconductors, intermetallics alloys, superhard materials and diamond films, high-temperature materials and properties, mechanical properties, fracture, creep, fatigue, defects, materials for nuclear reactor applications and irradiation effects, high pressure synthesis, self-propagating high temperature synthesis, microanalysis, magnetic properties and magnetic facilities, and surface science.

  12. A User Assessment of Workspaces in Selected Music Education Computer Laboratories.

    ERIC Educational Resources Information Center

    Badolato, Michael Jeremy

    A study of 120 students selected from the user populations of four music education computer laboratories was conducted to determine the applicability of current ergonomic and environmental design guidelines in satisfying the needs of users of educational computing workspaces. Eleven categories of workspace factors were organized into a…

  13. Natural Energy Laboratory of Hawaii Authority (NELHA): Hawaii Ocean Science & Technology Park; Kailua-Kona, Hawaii

    DOE Data Explorer

    Olson, K.; Andreas, A.

    2012-11-01

    A partnership with the Natural Energy Laboratory of Hawaii Authority and U.S. Department of Energy's National Renewable Energy Laboratory (NREL) to collect solar data to support future solar power generation in the United States. The measurement station monitors global horizontal horizontal irradiance to define the amount of solar energy that hits this particular location. The solar measurement instrumentation is also accompanied by meteorological monitoring equipment to provide scientists with a complete picture of the solar power possibilities.

  14. Natural selection of cooperation and degree hierarchy in heterogeneous populations.

    PubMed

    Gómez-Gardeñes, Jesús; Poncela, Julia; Mario Floría, Luis; Moreno, Yamir

    2008-07-21

    One of the current theoretical challenges to the explanatory powers of Evolutionary Theory is the understanding of the observed evolutionary survival of cooperative behavior when selfish actions provide higher fitness (reproductive success). In unstructured populations natural selection drives cooperation to extinction. However, when individuals are allowed to interact only with their neighbors, specified by a graph of social contacts, cooperation-promoting mechanisms (known as lattice reciprocity) offer to cooperation the opportunity of evolutionary survival. Recent numerical works on the evolution of Prisoner's Dilemma in complex network settings have revealed that graph heterogeneity dramatically enhances the lattice reciprocity. Here we show that in highly heterogeneous populations, under the graph analog of replicator dynamics, the fixation of a strategy in the whole population is in general an impossible event, for there is an asymptotic partition of the population in three subsets, two in which fixation of cooperation or defection has been reached and a third one which experiences cycles of invasion by the competing strategies. We show how the dynamical partition correlates with connectivity classes and characterize the temporal fluctuations of the fluctuating set, unveiling the mechanisms stabilizing cooperation in macroscopic scale-free structures. PMID:18423491

  15. Maintenance of an aminopeptidase allele frequency cline by natural selection.

    PubMed Central

    Koehn, R K; Newell, R I; Immermann, F

    1980-01-01

    The product of the Lap locus in the marine bivalve Mytilus edulis is a neutral, membrane-associated aminopeptidase that is primarily localized on intestinal microvilli and in digestive cell lysosomes. Natural populations are genetically differentiated at the Lap locus between areas of differing salinity. A steep (0.55-0.15) allele frequency cline connects differentiated populations between the Atlantic Ocean and Long Island Sound. We demonstrate an annual gene flow/mortality cycle in cline populations whereby gene frequencies after mortality are correlated with salinity and enzyme activity. The cline is spatially and temporally unstable in immigrants, but stable in residents after mortality. Mortality is nonrandom with regard to the Lap locus; genotype-dependent properties of the aminopeptidase enzyme apparently led to a differential rate of the utilizaiton of nutrient reserves because selected genotypes exhibited an increased rate of tissue weight loss. Aminopeptidase genotypes are differentially adapted to different temperatures and salinities, which provides a mechanism for the relationship among biochemical, physiological, and population phenotypes. PMID:6933563

  16. Natural Pathogens of Laboratory Mice, Rats, and Rabbits and Their Effects on Research

    PubMed Central

    Baker, David G.

    1998-01-01

    Laboratory mice, rats, and rabbits may harbor a variety of viral, bacterial, parasitic, and fungal agents. Frequently, these organisms cause no overt signs of disease. However, many of the natural pathogens of these laboratory animals may alter host physiology, rendering the host unsuitable for many experimental uses. While the number and prevalence of these pathogens have declined considerably, many still turn up in laboratory animals and represent unwanted variables in research. Investigators using mice, rats, and rabbits in biomedical experimentation should be aware of the profound effects that many of these agents can have on research. PMID:9564563

  17. The use of bioluminescent biotests for study of natural and laboratory aquatic ecosystems.

    PubMed

    Kratasyuk, V A; Esimbekova, E N; Gladyshev, M I; Khromichek, E B; Kuznetsov, A M; Ivanova, E A

    2001-03-01

    A set of bioluminescent tests was developed to monitor water quality in natural and laboratory ecosystems. It consisted of four bioluminescent systems: luminous bacteria, coupled enzyme system NADH:FMN-oxidoreductase-luciferase and triplet enzyme systems with alcohol dehydrogenase and trypsin. The set of biotests was applied for a small forest pond (Siberia, Russia), laboratory microecosystems polluted with benzoquinone and a batch culture of blue-green algae. Thereby effects of natural water compared to those of models of heavy pollution and "bloom" of blue-greens on the bioluminescent tests were revealed. The set of biotests was not affected by a natural seasonal variability of water quality in the unpolluted pond, but responded to the heavy pollution and the "bloom" of blue-greens. The set of biotests could be recommended as the alarm test to control the acute toxicity of natural water bodies. PMID:11272913

  18. Preventing and Removing Contamination in a Natural Radiocarbon Sample Preparation Laboratory

    SciTech Connect

    Zermeno, P; Kurdyla, D K; Buchholz, B A; Heller, S J; Frantz, B R; Brown, T A; Kashgarian, M

    2002-10-25

    The introduction of elevated {sup 14}C contamination into a natural radiocarbon sample preparation laboratory can occur through many different pathways. The most difficult to control is the introduction of contaminated samples from outside labs. Laboratories can remain {sup 14}C contaminated as a result of earlier tracer based research, even if ''hot'' work has not occurred in the laboratories in decades. Prior to accepting samples from outside collaborators, it is recommended that the collaborators test their labs for {sup 14}C contamination. Any surface in a lab that has high use by multiple people has the potential to be contaminated. The standard procedure for determining whether a collaborator's lab is contaminated consists of swiping lab surfaces with small glass fiber filters wetted with alcohol and measuring them for {sup 14}C content using AMS. Volatile {sup 14}C can be detected by using aerosol monitors consisting of fine soot that is depleted in {sup 14}C. These monitors can be set out in the laboratory in question to check for volatile {sup 14}C contamination. In the event that a hot sample is introduced in the natural radiocarbon sample prep laboratory, all sample submission should be stopped until the lab is declared clean. Samples already being processed should be completed along with {sup 14}C depleted material and measured by AMS. This will help determine if the contaminated samples have affected other samples in the laboratory. After a contamination event, the laboratory and associated equipment requires cleaning or disposal. All surfaces and equipment should be wiped down with acetone or ethanol. All chemicals in use should be disposed of in the appropriate waste containers and those waste containers removed from the lab. Once the natural radiocarbon laboratory has been thoroughly ''cleaned'', several background samples consisting of {sup 14}C depleted material should be processed through the lab and measured by AMS before unknown samples are processed again.

  19. Laboratory selection of resistance to spinosad in Culex quinquefasciatus (Diptera: Culicidae).

    PubMed

    Su, Tianyun; Cheng, Min-Lee

    2014-03-01

    A southern house mosquito Culex quinquefasciatus Say colony was established from surviving late instars and pupae from a semifield evaluation on Natular XRG (a granular formulation containing 2.5% spinosad). The initial lethal levels ofNatular XRG against this colony were determined in the laboratory for the first-generation progeny (designated as F1). Selection pressure was applied at LC70-90 levels to 10,000-15,000 late third- and early fourth-instar larvae of each generation with Natular XRG. Susceptibility changes in response to selection were determined every other generation, where a gradual and steady decline in susceptibility occurred from generation F1 to F35, followed by significant decline from generations F37 to F45 For reference purposes, susceptibility of freshly collected wild populations as well as a laboratory colony of the same species was also determined concurrently, which fluctuated within a slightly wider range for the wild populations and a tighter range for the laboratory colony. By comparing with wild populations and laboratory reference colony, tolerance to spinosad was observed from generations up to F9 in the selected population. Resistance levels increased gradually from generation F11 to F35, and elevated significantly from generations F37 to F45, when resistance ratios reached 1,415.3- to 2,229.9-fold at LC50 and 9,613.1- to 17,062.6-fold at LC90. Possible mechanisms of resistance development to spinosad were discussed. PMID:24724292

  20. Six Classroom Exercises to Teach Natural Selection to Undergraduate Biology Students

    ERIC Educational Resources Information Center

    Kalinowski, Steven T.; Leonard, Mary J.; Andrews, Tessa M.; Litt, Andrea R.

    2013-01-01

    Students in introductory biology courses frequently have misconceptions regarding natural selection. In this paper, we describe six activities that biology instructors can use to teach undergraduate students in introductory biology courses how natural selection causes evolution. These activities begin with a lesson introducing students to natural…

  1. Human Fertility, Molecular Genetics, and Natural Selection in Modern Societies

    PubMed Central

    Tropf, Felix C.; Stulp, Gert; Barban, Nicola; Visscher, Peter M.; Yang, Jian; Snieder, Harold; Mills, Melinda C.

    2015-01-01

    Research on genetic influences on human fertility outcomes such as number of children ever born (NEB) or the age at first childbirth (AFB) has been solely based on twin and family-designs that suffer from problematic assumptions and practical limitations. The current study exploits recent advances in the field of molecular genetics by applying the genomic-relationship-matrix based restricted maximum likelihood (GREML) methods to quantify for the first time the extent to which common genetic variants influence the NEB and the AFB of women. Using data from the UK and the Netherlands (N = 6,758), results show significant additive genetic effects on both traits explaining 10% (SE = 5) of the variance in the NEB and 15% (SE = 4) in the AFB. We further find a significant negative genetic correlation between AFB and NEB in the pooled sample of –0.62 (SE = 0.27, p-value = 0.02). This finding implies that individuals with genetic predispositions for an earlier AFB had a reproductive advantage and that natural selection operated not only in historical, but also in contemporary populations. The observed postponement in the AFB across the past century in Europe contrasts with these findings, suggesting an evolutionary override by environmental effects and underscoring that evolutionary predictions in modern human societies are not straight forward. It emphasizes the necessity for an integrative research design from the fields of genetics and social sciences in order to understand and predict fertility outcomes. Finally, our results suggest that we may be able to find genetic variants associated with human fertility when conducting GWAS-meta analyses with sufficient sample size. PMID:26039877

  2. Sexual dichromatism in frogs: natural selection, sexual selection and unexpected diversity

    PubMed Central

    Bell, Rayna C.; Zamudio, Kelly R.

    2012-01-01

    Sexual dichromatism, a form of sexual dimorphism in which males and females differ in colour, is widespread in animals but has been predominantly studied in birds, fishes and butterflies. Moreover, although there are several proposed evolutionary mechanisms for sexual dichromatism in vertebrates, few studies have examined this phenomenon outside the context of sexual selection. Here, we describe unexpectedly high diversity of sexual dichromatism in frogs and create a comparative framework to guide future analyses of the evolution of these sexual colour differences. We review what is known about evolution of colour dimorphism in frogs, highlight alternative mechanisms that may contribute to the evolution of sexual colour differences, and compare them to mechanisms active in other major groups of vertebrates. In frogs, sexual dichromatism can be dynamic (temporary colour change in males) or ontogenetic (permanent colour change in males or females). The degree and the duration of sexual colour differences vary greatly across lineages, and we do not detect phylogenetic signal in the distribution of this trait, therefore frogs provide an opportunity to investigate the roles of natural and sexual selection across multiple independent derivations of sexual dichromatism. PMID:22993253

  3. [Genomic variation of laboratory strains and natural populations of Drosophila melanogaster exposed to X-irradiation].

    PubMed

    Shokhanov, S O; Shcherbata, G R; Chernik, Ia I

    1997-01-01

    The spontaneous and X-ray-induced mutation rates and spectrums were estimated in laboratory strains and natural populations of Drosophila melanogaster from the Chernobyl meltdown area. Laboratory strains Oregon R and y2w alpha 4 were stable. In all natural populations, the spontaneous mutation rate was an order of magnitude higher (10(-3)) than in laboratory strains. Irradiation at a total dose of 3000 R was shown to induce genetic instability in the stable laboratory strain y2w alpha 4 and to increase the mutation rate and spectrum range in the unstable natural population P1. A high level of genetic instability was observed both in the first and second generations. Genetic analysis by means of classical genetic and molecular methods was performed; in crosses, a collection of spontaneous and induced mutants was used. The molecular genetic nature of mutations at the white and cut loci was analyzed by Southern blot-hybridization. Mutations at the white locus were shown to result both from transposition and recombination events; cut mutations were caused by deletions. PMID:9162688

  4. Blindisms: Treatment by Punishment and Reward in Laboratory and Natural Settings.

    ERIC Educational Resources Information Center

    Blasch, Bruce B.

    1978-01-01

    Separate experiments were done with six blind students (ages 16-20 years) to test the effectiveness of using punishment (prerecorded sound of chalk screeching on a blackboard) and positive reinforcement (money) in natural and laboratory settings to reduce "blindisms" (stereotypic behaviors). (Author/DLS)

  5. High School Chemistry Students' Scientific Epistemologies and Perceptions of the Nature of Laboratory Inquiry

    ERIC Educational Resources Information Center

    Vhurumuku, Elaosi

    2011-01-01

    This quantitative study investigated the relationship between Chemistry students' scientific epistemologies and their perceptions of the nature of laboratory inquiry. Seventy-two Advanced Level Chemistry students were surveyed. The students were sampled from twelve schools in three of Zimbabwe's nine administrative provinces. Students' scientific…

  6. High School Chemistry Students' Scientific Epistemologies and Perceptions of the Nature of Laboratory Inquiry

    ERIC Educational Resources Information Center

    Vhurumuku, Elaosi

    2011-01-01

    This quantitative study investigated the relationship between Chemistry students' scientific epistemologies and their perceptions of the nature of laboratory inquiry. Seventy-two Advanced Level Chemistry students were surveyed. The students were sampled from twelve schools in three of Zimbabwe's nine administrative provinces. Students' scientific…

  7. Using Natural Selection to Explore the Adaptive Potential of Chlamydomonas reinhardtii

    PubMed Central

    Price, Dana C.; Levitan, Orly; Boyd, Jeffrey; Bhattacharya, Debashish

    2014-01-01

    Improving feedstock is critical to facilitate the commercial utilization of algae, in particular in open pond systems where, due to the presence of competitors and pests, high algal growth rates and stress tolerance are beneficial. Here we raised laboratory cultures of the model alga Chlamydomonas reinhardtii under serial dilution to explore the potential of crop improvement using natural selection. The alga was evolved for 1,880 generations in liquid medium under continuous light (EL population). At the end of the experiment, EL cells had a growth rate that was 35% greater than the progenitor population (PL). The removal of acetate from the medium demonstrated that EL growth enhancement largely relied on efficient usage of this organic carbon source. Genome re-sequencing uncovered 1,937 polymorphic DNA regions in the EL population with 149 single nucleotide polymorphisms resulting in amino acid substitutions. Transcriptome analysis showed, in the EL population, significant up regulation of genes involved in protein synthesis, the cell cycle and cellular respiration, whereas the DNA repair pathway and photosynthesis were down regulated. Like other algae, EL cells accumulated neutral lipids under nitrogen depletion. Our work demonstrates transcriptome and genome-wide impacts of natural selection on algal cells and points to a useful strategy for strain improvement. PMID:24658261

  8. Effects of implant angulation, material selection, and impression technique on impression accuracy: a preliminary laboratory study.

    PubMed

    Rutkunas, Vygandas; Sveikata, Kestutis; Savickas, Raimondas

    2012-01-01

    The aim of this preliminary laboratory study was to evaluate the effects of 5- and 25-degree implant angulations in simulated clinical casts on an impression's accuracy when using different impression materials and tray selections. A convenience sample of each implant angulation group was selected for both open and closed trays in combination with one polyether and two polyvinyl siloxane impression materials. The influence of material and technique appeared to be significant for both 5- and 25-degree angulations (P < .05), and increased angulation tended to decrease impression accuracy. The open-tray technique was more accurate with highly nonaxially oriented implants for the small sample size investigated. PMID:22930776

  9. Amdinocillin (Mecillinam) Resistance Mutations in Clinical Isolates and Laboratory-Selected Mutants of Escherichia coli

    PubMed Central

    Thulin, Elisabeth; Sundqvist, Martin

    2015-01-01

    Amdinocillin (mecillinam) is a β-lactam antibiotic that is used mainly for the treatment of uncomplicated urinary tract infections. The objectives of this study were to identify mutations that confer amdinocillin resistance on laboratory-isolated mutants and clinical isolates of Escherichia coli and to determine why amdinocillin resistance remains rare clinically even though resistance is easily selected in the laboratory. Under laboratory selection, frequencies of mutation to amdinocillin resistance varied from 8 × 10−8 to 2 × 10−5 per cell, depending on the concentration of amdinocillin used during selection. Several genes have been demonstrated to give amdinocillin resistance, but here eight novel genes previously unknown to be involved in amdinocillin resistance were identified. These genes encode functions involved in the respiratory chain, the ribosome, cysteine biosynthesis, tRNA synthesis, and pyrophosphate metabolism. The clinical isolates exhibited significantly greater fitness than the laboratory-isolated mutants and a different mutation spectrum. The cysB gene was mutated (inactivated) in all of the clinical isolates, in contrast to the laboratory-isolated mutants, where mainly other types of more costly mutations were found. Our results suggest that the frequency of mutation to amdinocillin resistance is high because of the large mutational target (at least 38 genes). However, the majority of these resistant mutants have a low growth rate, reducing the probability that they are stably maintained in the bladder. Inactivation of the cysB gene and a resulting loss of cysteine biosynthesis are the major mechanism of amdinocillin resistance in clinical isolates of E. coli. PMID:25583718

  10. Artificial selection for structural color on butterfly wings and comparison with natural evolution

    PubMed Central

    Wasik, Bethany R.; Liew, Seng Fatt; Lilien, David A.; Dinwiddie, April J.; Noh, Heeso; Cao, Hui; Monteiro, Antónia

    2014-01-01

    Brilliant animal colors often are produced from light interacting with intricate nano-morphologies present in biological materials such as butterfly wing scales. Surveys across widely divergent butterfly species have identified multiple mechanisms of structural color production; however, little is known about how these colors evolved. Here, we examine how closely related species and populations of Bicyclus butterflies have evolved violet structural color from brown-pigmented ancestors with UV structural color. We used artificial selection on a laboratory model butterfly, B. anynana, to evolve violet scales from UV brown scales and compared the mechanism of violet color production with that of two other Bicyclus species, Bicyclus sambulos and Bicyclus medontias, which have evolved violet/blue scales independently via natural selection. The UV reflectance peak of B. anynana brown scales shifted to violet over six generations of artificial selection (i.e., in less than 1 y) as the result of an increase in the thickness of the lower lamina in ground scales. Similar scale structures and the same mechanism for producing violet/blue structural colors were found in the other Bicyclus species. This work shows that populations harbor large amounts of standing genetic variation that can lead to rapid evolution of scales’ structural color via slight modifications to the scales’ physical dimensions. PMID:25092295

  11. Artificial selection for structural color on butterfly wings and comparison with natural evolution.

    PubMed

    Wasik, Bethany R; Liew, Seng Fatt; Lilien, David A; Dinwiddie, April J; Noh, Heeso; Cao, Hui; Monteiro, Antónia

    2014-08-19

    Brilliant animal colors often are produced from light interacting with intricate nano-morphologies present in biological materials such as butterfly wing scales. Surveys across widely divergent butterfly species have identified multiple mechanisms of structural color production; however, little is known about how these colors evolved. Here, we examine how closely related species and populations of Bicyclus butterflies have evolved violet structural color from brown-pigmented ancestors with UV structural color. We used artificial selection on a laboratory model butterfly, B. anynana, to evolve violet scales from UV brown scales and compared the mechanism of violet color production with that of two other Bicyclus species, Bicyclus sambulos and Bicyclus medontias, which have evolved violet/blue scales independently via natural selection. The UV reflectance peak of B. anynana brown scales shifted to violet over six generations of artificial selection (i.e., in less than 1 y) as the result of an increase in the thickness of the lower lamina in ground scales. Similar scale structures and the same mechanism for producing violet/blue structural colors were found in the other Bicyclus species. This work shows that populations harbor large amounts of standing genetic variation that can lead to rapid evolution of scales' structural color via slight modifications to the scales' physical dimensions. PMID:25092295

  12. Toxicity of naturally-contaminated manganese soil to selected crops.

    PubMed

    Kováčik, Jozef; Štěrbová, Dagmar; Babula, Petr; Švec, Pavel; Hedbavny, Josef

    2014-07-23

    The impact of manganese excess using naturally contaminated soil (Mn-soil, pseudototal Mn 6494 vs 675 μg g(-1) DW in control soil) in the shoots of four crops was studied. Mn content decreased in the order Brassica napus > Hordeum vulgare > Zea mays > Triticum aestivum. Growth was strongly depressed just in Brassica (containing 13696 μg Mn g(-1) DW). Some essential metals (Zn, Fe) increased in Mn-cultured Brassica and Zea, while macronutrients (K, Ca, Mg) decreased in almost all species. Toxic metals (Ni and Cd) were rather elevated in Mn-soil. Microscopy of ROS, NO, lipid peroxidation, and thiols revealed stimulation in all Mn-cultured crops, but changes were less visible in Triticum, a species with low shoot Mn (2363 μg g(-1) DW). Antioxidative enzyme activities were typically enhanced in Mn-cultured plants. Soluble phenols increased in Brassica only while proteins rather decreased in response to Mn excess. Inorganic anions (chloride, sulfate, and phosphate) were less accumulated in almost all Mn-cultured crops, while the nitrate level rather increased. Organic anions (malate, citrate, oxalate, acetate, and formate) decreased or remained unaffected in response to Mn-soil culture in Brassica, Hordeum, and Triticum but not in Zea. However, the role of organic acids in Mn uptake in these species is not assumed. Because control and Mn-soil differed in pH (6.5 and 3.7), we further studied its impact on Mn uptake in solution culture (using Mn concentration ∼5 mM deducted from water-soluble fraction of Mn-soil). Shoot Mn contents in Mn-treated plants were similar to those observed in soil culture (high in Brassica and low in Triticum) and pH had negligible impact. Fluorescence indicator of "general ROS" revealed no extensive or pH-dependent impact either in control or Mn-cultured roots. Observed toxicity of Mn excess to common crops urges for selection of cultivars with higher tolerance. PMID:24965550

  13. Polycyclic aromatic hydrocarbons at selected burning grounds at Los Alamos National Laboratory

    SciTech Connect

    Harris, B.W.; Minor, L.K.M.; Flucas, B.J.

    1998-02-01

    A commercial immunoassay field test (IFT) was used to rapidly assess the total concentrations of polycyclic aromatic hydrocarbons (PAHs) in the soil at selected burning grounds within the explosives corridor at Los Alamos National Laboratory (LANL). Results were compared with analyses obtained from LANL Analytical Laboratory and from a commercial laboratory. Both used the Environmental Protection Agency`s (EPA`s) Methods 8270 and 8310. EPA`s Method 8270 employs gas chromatography and mass spectral analyses, whereas EPA`s Method 8310 uses an ultraviolet detector in a high-performance liquid chromatography procedure. One crude oil sample and one diesel fuel sample, analyzed by EPA Method 8270, were included for references. On an average the IFT results were lower for standard samples and lower than the analytical laboratory results for the unknown samples. Sites were selected to determine whether the PAHs came from the material burned or the fuel used to ignite the burn, or whether they are produced by a high-temperature chemical reaction during the burn. Even though the crude oil and diesel fuel samples did contain measurable quantities of PAHs, there were no significant concentrations of PAHs detected in the ashes and soil at the burning grounds. Tests were made on fresh soil and ashes collected after a large burn and on aged soil and ashes known to have been at the site more than three years. Also analyzed were twelve-year-old samples from an inactive open burn cage.

  14. Natural laboratory NW Bohemia: Comprehensive fluid studies between 1992 and 2005 used to trace geodynamic processes

    NASA Astrophysics Data System (ADS)

    BräUer, Karin; KäMpf, Horst; Niedermann, Samuel; Strauch, Gerhard; Tesa?, Ji?I.

    2008-04-01

    Comprehensive studies of CO2-rich fluids close to the swarm earthquake region Nový Kostel at the Czech-German border have been started 15 years ago and have in particular included two extended chemical and isotope monitoring studies lasting for several years each. The regional surface distribution patterns of the fluid signatures including the identification of the origin of fluid components are the focus of the detailed studies. Three degassing centers (Cheb basin, Mariánské Lázn?, and Karlovy Vary) with high CO2 flux and the same level of ?13C values, but different levels of 3He/4He ratios, have been identified. The studies have located the CO2 source and have investigated seismically induced changes in fluid characteristics on the basis of unique weekly sampling campaigns at selected locations. A seismically triggered release of crustal helium was confirmed by both monitoring campaigns. Finally, indications for a presently active magmatic process beneath the Cheb basin have been found. In contrast to volcanically active regions, magma accumulation in the study area takes place at the crust-mantle boundary and is not yet accompanied by heat transfer to the surface. Likewise, reactive magma-derived components are absent in the degassing fluids. The area of investigation has the potential to be a natural laboratory for fundamental studies of active geodynamic processes. The results of our fluid monitoring, including the stunning observation of mantle-derived free fluids marked by 3He/4He ratios within the subcontinental mantle range, are supported by geophysical findings from seismic studies and geologic indications.

  15. North American Natural Gas Markets: Selected technical studies

    SciTech Connect

    Huntington, H.G.; Schuler, G.E.

    1989-04-01

    The Energy Modeling Forum (EMF) was established in 1976 at Stanford University to provide a structural framework within which energy experts, analysts, and policymakers could meet to improve their understanding of critical energy problems. The ninth EMF study, North American Natural Gas Markets, was conducted by a working group comprised of leading natural gas analysts and decision-makers from government, private companies, universities, and research and consulting organizations. The EMF 9 working group met five times from October 1986 through June 1988 to discuss key issues and analyze natural gas markets. This third volume includes technical papers that support many of the conclusions discussed in the EMF 9 summary report (Volume 1) and full working group report (Volume 2). These papers discuss the results from the individual models as well as some nonmodeling analysis related to US natural gas imports and industrial natural gas demand. Individual papers have been processed separately for inclusion in the Energy Science and Technology Database.

  16. North American Natural Gas Markets: Selected technical studies. Volume 3

    SciTech Connect

    Huntington, H.G.; Schuler, G.E.

    1989-04-01

    The Energy Modeling Forum (EMF) was established in 1976 at Stanford University to provide a structural framework within which energy experts, analysts, and policymakers could meet to improve their understanding of critical energy problems. The ninth EMF study, North American Natural Gas Markets, was conducted by a working group comprised of leading natural gas analysts and decision-makers from government, private companies, universities, and research and consulting organizations. The EMF 9 working group met five times from October 1986 through June 1988 to discuss key issues and analyze natural gas markets. This third volume includes technical papers that support many of the conclusions discussed in the EMF 9 summary report (Volume 1) and full working group report (Volume 2). These papers discuss the results from the individual models as well as some nonmodeling analysis related to US natural gas imports and industrial natural gas demand. Individual papers have been processed separately for inclusion in the Energy Science and Technology Database.

  17. Idaho National Laboratory Materials and Fuels Complex Natural Phenomena Hazards Flood Assessment

    SciTech Connect

    Gerald Sehlke; Paul Wichlacz

    2010-12-01

    This report presents the results of flood hazards analyses performed for the Materials and Fuels Complex (MFC) and the adjacent Transient Reactor Experiment and Test Facility (TREAT) located at Idaho National Laboratory. The requirements of these analyses are provided in the U.S. Department of Energy Order 420.1B and supporting Department of Energy (DOE) Natural Phenomenon Hazard standards. The flood hazards analyses were performed by Battelle Energy Alliance and Pacific Northwest National Laboratory. The analyses addressed the following: • Determination of the design basis flood (DBFL) • Evaluation of the DBFL versus the Critical Flood Elevations (CFEs) for critical existing structures, systems, and components (SSCs).

  18. Six Classroom Exercises to Teach Natural Selection to Undergraduate Biology Students

    PubMed Central

    Kalinowski, Steven T.; Leonard, Mary J.; Andrews, Tessa M.; Litt, Andrea R.

    2013-01-01

    Students in introductory biology courses frequently have misconceptions regarding natural selection. In this paper, we describe six activities that biology instructors can use to teach undergraduate students in introductory biology courses how natural selection causes evolution. These activities begin with a lesson introducing students to natural selection and also include discussions on sexual selection, molecular evolution, evolution of complex traits, and the evolution of behavior. The set of six topics gives students the opportunity to see how natural selection operates in a variety of contexts. Pre- and postinstruction testing showed students’ understanding of natural selection increased substantially after completing this series of learning activities. Testing throughout this unit showed steadily increasing student understanding, and surveys indicated students enjoyed the activities. PMID:24006396

  19. Assessment of Application Technology of Natural User Interfaces in the Creation of a Virtual Chemical Laboratory

    NASA Astrophysics Data System (ADS)

    Jagodziński, Piotr; Wolski, Robert

    2015-02-01

    Natural User Interfaces (NUI) are now widely used in electronic devices such as smartphones, tablets and gaming consoles. We have tried to apply this technology in the teaching of chemistry in middle school and high school. A virtual chemical laboratory was developed in which students can simulate the performance of laboratory activities similar to those that they perform in a real laboratory. Kinect sensor was used for the detection and analysis of the student's hand movements, which is an example of NUI. The studies conducted found the effectiveness of educational virtual laboratory. The extent to which the use of a teaching aid increased the students' progress in learning chemistry was examined. The results indicate that the use of NUI creates opportunities to both enhance and improve the quality of the chemistry education. Working in a virtual laboratory using the Kinect interface results in greater emotional involvement and an increased sense of self-efficacy in the laboratory work among students. As a consequence, students are getting higher marks and are more interested in the subject of chemistry.

  20. Assessment of Application Technology of Natural User Interfaces in the Creation of a Virtual Chemical Laboratory

    NASA Astrophysics Data System (ADS)

    Jagodziński, Piotr; Wolski, Robert

    2014-09-01

    Natural User Interfaces (NUI) are now widely used in electronic devices such as smartphones, tablets and gaming consoles. We have tried to apply this technology in the teaching of chemistry in middle school and high school. A virtual chemical laboratory was developed in which students can simulate the performance of laboratory activities similar to those that they perform in a real laboratory. Kinect sensor was used for the detection and analysis of the student's hand movements, which is an example of NUI. The studies conducted found the effectiveness of educational virtual laboratory. The extent to which the use of a teaching aid increased the students' progress in learning chemistry was examined. The results indicate that the use of NUI creates opportunities to both enhance and improve the quality of the chemistry education. Working in a virtual laboratory using the Kinect interface results in greater emotional involvement and an increased sense of self-efficacy in the laboratory work among students. As a consequence, students are getting higher marks and are more interested in the subject of chemistry.

  1. Natural selection on a major armor gene in threespine stickleback.

    PubMed

    Barrett, Rowan D H; Rogers, Sean M; Schluter, Dolph

    2008-10-10

    Experimental estimates of the effects of selection on genes determining adaptive traits add to our understanding of the mechanisms of evolution. We measured selection on genotypes of the Ectodysplasin locus, which underlie differences in lateral plates in threespine stickleback fish. A derived allele (low) causing reduced plate number has been fixed repeatedly after marine stickleback colonized freshwater from the sea, where the ancestral allele (complete) predominates. We transplanted marine sticklebacks carrying both alleles to freshwater ponds and tracked genotype frequencies over a generation. The low allele increased in frequency once lateral plates developed, most likely via a growth advantage. Opposing selection at the larval stage and changing dominance for fitness throughout life suggest either that the gene affects additional traits undergoing selection or that linked loci also are affecting fitness. PMID:18755942

  2. Parallel shifts in ecology and natural selection in an island lizard

    PubMed Central

    Calsbeek, Ryan; Buermann, Wolfgang; Smith, Thomas B

    2009-01-01

    Background Natural selection is a potent evolutionary force that shapes phenotypic variation to match ecological conditions. However, we know little about the year-to-year consistency of selection, or how inter-annual variation in ecology shapes adaptive landscapes and ultimately adaptive radiations. Here we combine remote sensing data, field experiments, and a four-year study of natural selection to show that changes in vegetation structure associated with a severe drought altered both habitat use and natural selection in the brown anole, Anolis sagrei. Results In natural populations, lizards increased their use of vegetation in wet years and this was correlated with selection on limb length but not body size. By contrast, a die-back of vegetation caused by drought was followed by reduced arboreality, selection on body size, and relaxed selection on limb length. With the return of the rains and recovery of vegetation, selection reverted back to pre-drought pattern of selection acting on limb length but not body size. To test for the impact of vegetation loss on natural selection during the drought, we experimentally removed vegetation on a separate study island in a naturally wet year. The experiment revealed similar inter-annual changes in selection on body size but not limb length. Conclusion Our results illustrate the dynamic nature of ecology driving natural selection on Anolis morphology and emphasize the importance of inter-annual environmental variation in shaping adaptive variation. In addition, results illustrate the utility of using remote sensing data to examine ecology's role in driving natural selection. PMID:19126226

  3. Gene expression of ABC transporters in Cooperia oncophora after field and laboratory selection with macrocyclic lactones.

    PubMed

    Tydén, Eva; Skarin, Moa; Höglund, Johan

    2014-12-01

    The most widespread helminth parasites of grazing cattle in northern Europe are the gastrointestinal nematodes Ostertagia ostertagi and Cooperia oncophora. Heavy reliance on the use of macrocyclic lactone (ML) in cattle has led to world-wide emergence of resistance to this drug class in C. oncophora. There is evidence that members of the ATP-binding cassette (ABC) transporter family, such as P-glycoproteins (P-gp) and multidrug-resistant proteins (MRP), play a role in resistance to ML. In this study gene expression of Con-pgp9, Con-pgp11, Con-pgp12, Con-pgp16 and Con-mrp1 was examined in two isolates of C. oncophora sharing the same genetic background but exposed to ML differently. For isolate one (Laboratory-selected), adult worms were recovered before and after treatment with ML in vivo. For isolate two (Field-selected), adult worms were collected from tracer animals that had never received anthelmintics themselves. One group grazed together with untreated animals and one group grazed with animals that received suppressive prophylactic treatment with ML at monthly intervals for up to two consecutive grazing seasons. Real-time PCR data demonstrated differences in gene expression after ML selection, with the highest constitutive expression levels for Con-pgp16 and Con-mrp1. Remarkably, the same pattern of increasing expression levels of the ABC transport genes was observed in both Laboratory- and Field-selected isolates, despite the Field-selected isolate not being directly exposed to ML. The higher expression levels of ABC transporters observed in the Field-selected isolate was thus not a response to direct exposure to ML, but rather appeared to reflect a genetic characteristic inherited from worms in the previous generation which had survived exposure to ML in the co-grazing treated animals. PMID:25619799

  4. Mini-conference on Angular Momentum Transport in Laboratory and Nature

    SciTech Connect

    Ji, Hantao; Kronberg, Philipp; Prager, Stewart C.; Uzdensky, Dmitri A.

    2008-05-06

    This paper provides a concise summary of the current status of the research and future perspectives discussed in the Mini-Conference on Angular Momentum Transport in Laboratory and Nature. This Mini-conference, sponsored by the Topical Group on Plasma Astrophysics, was held as part of the American Physical Society's Division of Plasma Physics 2007 Annual Meeting (November 12{16, 2007). This Mini-conference covers a wide range of phenomena happening in fluids and plasmas, either in laboratory or in nature. The purpose of this paper is not to comprehensively review these phenomena, but to provide a starting point for interested readers to refer to related research in areas other than their own.

  5. Six Classroom Exercises to Teach Natural Selection to Undergraduate Biology Students

    ERIC Educational Resources Information Center

    Kalinowski, Steven T.; Leonard, Mary J.; Andrews, Tessa M.; Litt, Andrea R.

    2013-01-01

    Students in introductory biology courses frequently have misconceptions regarding natural selection. In this paper, we describe six activities that biology instructors can use to teach undergraduate students in introductory biology courses how natural selection causes evolution. These activities begin with a lesson introducing students to natural…

  6. A Hands-On Exercise to Demonstrate Evolution by Natural Selection & Genetic Drift

    ERIC Educational Resources Information Center

    Young, Helen J.; Young, Truman P.

    2003-01-01

    Although students "learn" (i.e., hear about) the components of evolution by natural selection in high school biology courses, few of them truly understand or remember them. Evolution by natural selection, although seemingly simple, requires that several conditions be met. The trait of concern must exhibit variation within the population; this…

  7. A Hands-On Exercise to Demonstrate Evolution by Natural Selection & Genetic Drift

    ERIC Educational Resources Information Center

    Young, Helen J.; Young, Truman P.

    2003-01-01

    Although students "learn" (i.e., hear about) the components of evolution by natural selection in high school biology courses, few of them truly understand or remember them. Evolution by natural selection, although seemingly simple, requires that several conditions be met. The trait of concern must exhibit variation within the population; this…

  8. Evolution of Students' Ideas about Natural Selection through a Constructivist Framework

    ERIC Educational Resources Information Center

    Baumgartner, Erin; Duncan, Kanesa

    2009-01-01

    Educating students about the process of evolution through natural selection is vitally important because not only is it the unifying theory of biological science, it is also widely regarded as difficult for students to fully comprehend. Anderson and colleagues (2002) describe alternative ideas and misconceptions about natural selection as highly…

  9. Evolution of Students' Ideas about Natural Selection through a Constructivist Framework

    ERIC Educational Resources Information Center

    Baumgartner, Erin; Duncan, Kanesa

    2009-01-01

    Educating students about the process of evolution through natural selection is vitally important because not only is it the unifying theory of biological science, it is also widely regarded as difficult for students to fully comprehend. Anderson and colleagues (2002) describe alternative ideas and misconceptions about natural selection as highly…

  10. Genome-wide scans for footprints of natural selection

    PubMed Central

    Oleksyk, Taras K.; Smith, Michael W.; O'Brien, Stephen J.

    2010-01-01

    Detecting recent selected ‘genomic footprints’ applies directly to the discovery of disease genes and in the imputation of the formative events that molded modern population genetic structure. The imprints of historic selection/adaptation episodes left in human and animal genomes allow one to interpret modern and ancestral gene origins and modifications. Current approaches to reveal selected regions applied in genome-wide selection scans (GWSSs) fall into eight principal categories: (I) phylogenetic footprinting, (II) detecting increased rates of functional mutations, (III) evaluating divergence versus polymorphism, (IV) detecting extended segments of linkage disequilibrium, (V) evaluating local reduction in genetic variation, (VI) detecting changes in the shape of the frequency distribution (spectrum) of genetic variation, (VII) assessing differentiating between populations (FST), and (VIII) detecting excess or decrease in admixture contribution from one population. Here, we review and compare these approaches using available human genome-wide datasets to provide independent verification (or not) of regions found by different methods and using different populations. The lessons learned from GWSSs will be applied to identify genome signatures of historic selective pressures on genes and gene regions in other species with emerging genome sequences. This would offer considerable potential for genome annotation in functional, developmental and evolutionary contexts. PMID:20008396

  11. Predator-mediated natural selection on the wings of the damselfly Calopteryx splendens: differences in selection among trait types.

    PubMed

    Kuchta, Shawn R; Svensson, Erik I

    2014-07-01

    Traits that increase mating success in males may come at a cost, such as an increased risk of predation. However, predator-mediated selection is challenging to document in natural populations, hampering our understanding of the trade-offs between sexual selection and predation. Here we report on a study of predator-mediated natural selection on wing traits in the damselfly Calopteryx splendens, the males of which possess conspicuous wing patches. Wagtails (genus Motacilla) are important avian predators of C. splendens, capturing them in flight and removing the wings prior to consumption. Using geometric morphometric techniques, we quantified the strength and mode of selection on wing traits by comparing wings from depredated individuals with the standing variation present in the population. Our results reveal that predator-mediated selection is stronger on secondary sexual characters than on size and shape, suggesting that traits related to flight performance are closer to their adaptive peaks. This could be a consequence of the long-term evolutionary association with avian predators, whereas stronger selection on conspicuous secondary sexual traits may reflect trade-offs between sexual and natural selection. Finally, even though C. splendens possesses nearly identical fore- and hindwings, we found evidence for divergent selection between them. PMID:24921603

  12. An Investigation of Zimbabwe High School Chemistry Students' Laboratory Work-Based Images of the Nature of Science

    ERIC Educational Resources Information Center

    Vhurumuku, Elaosi; Holtman, Lorna; Mikalsen, Oyvind; Kolsto, Stein D.

    2006-01-01

    This study investigates the proximal and distal images of the nature of science (NOS) that A-level students develop from their participation in chemistry laboratory work. We also explored the nature of the interactions among the students' proximal and distal images of the NOS and students' participation in laboratory work. Students' views of the…

  13. An Investigation of Zimbabwe High School Chemistry Students' Laboratory Work-Based Images of the Nature of Science

    ERIC Educational Resources Information Center

    Vhurumuku, Elaosi; Holtman, Lorna; Mikalsen, Oyvind; Kolsto, Stein D.

    2006-01-01

    This study investigates the proximal and distal images of the nature of science (NOS) that A-level students develop from their participation in chemistry laboratory work. We also explored the nature of the interactions among the students' proximal and distal images of the NOS and students' participation in laboratory work. Students' views of the…

  14. The Eye of the Laboratory Mouse Remains Anatomically Adapted for Natural Conditions

    PubMed Central

    Shupe, Jonathan M.; Kristan, Deborah M.; Austad, Steven N.; Stenkamp, Deborah L.

    2008-01-01

    Evolutionary effects of domestication have been demonstrated for several body systems, including the eye, and for several vertebrate species, including the mouse. Given the importance of the laboratory mouse to vision science, we wished to determine whether the anatomical and histological features of the eyes of laboratory mice are distinct from those of their naturally adapted, wild counterparts. We measured dimensions and masses of whole eyes and lenses from a wild population plus three inbred strains (C57BL/6J, NZB/BINJ, and DBA/1J) of the house house, Mus musculus, as well as wild and outbred laboratory-domesticated stock of the deer mouse, Peromyscus maniculatus. Histological preparations from these eyes were used to determine outer nuclear layer thickness, linear density of the ganglion cell layer, and for indirect immunofluorescence evaluation of cone opsin expression. For all of these traits, no statistically significant differences were found between any laboratory strain and its wild counterpart. The evolutionary effects of domestication of mice therefore do not include changes to the eye in any variable measured, supporting the continued use of this animal as a model for a naturally adapted visual system. PMID:16219997

  15. Design and validation of laboratory-scale simulations for selecting tribomaterials and surface treatments

    SciTech Connect

    Blau, P.J.

    1997-05-01

    Engineering approaches to solving tribology problems commonly involve friction, lubrication, or wear testing, either in the field or in a laboratory setting. Since wear and friction are properties of the materials in the larger context of the tribosystem, the selection of appropriate laboratory tribotesting procedures becomes critically important. Laboratory simulations must exhibit certain key characteristics of the application in order for the test results to be relevant, but they may not have to mimic all operating conditions. The current paper illustrates a step-by-step method to develop laboratory-scale friction and wear simulations based on a tribosystem analysis. Quantitative or qualitative metrics are established and used to validate the effectiveness of the tribosimulation. Sometimes standardized test methods can be used, but frequently a new type of test method or procedure must be developed. There are four factors to be addressed in designing effective simulations: (1) contact macrogeometry and the characteristics of relative motion, (2) pressure--velocity relationships, (3) thermal and chemical environment (including type of lubrication), and (4) the role of third-bodies. In addition, there are two typical choices of testing philosophy: (1) the worst-case scenario and, (2) the nominal-operations scenario. Examples of the development and use of simulative friction and wear tests are used to illustrate major points.

  16. Spatial patterns of variation due to natural selection in humans

    PubMed Central

    Novembre, John; Di Rienzo, Anna

    2013-01-01

    Empowered by technology and sampling efforts designed to facilitate genome-wide association mapping, human geneticists are now studying the geography of genetic variation with unprecedented detail. With high genomic coverage and geographic resolution, these studies are identifying loci with spatial signatures of selection, such as extreme levels of differentiation and correlations with environmental variables. Collectively, patterns at these loci are beginning to provide novel insights into the process of human adaptation. Here we review the challenges of these studies and emerging results, including how human population structure has influenced the response to novel selective pressures. PMID:19823195

  17. Absence of selective brain cooling in free-ranging zebras in their natural habitat.

    PubMed

    Fuller, A; Maloney, S K; Kamerman, P R; Mitchell, G; Mitchell, D

    2000-03-01

    We used implanted miniature data loggers to measure brain and arterial blood temperatures in three free-ranging zebras (Equus burchelli) in their natural habitat, every 5 min for 9 days. The animals experienced globe temperatures exceeding 40 C, and radiant heat load of about 1000 W m-2. Arterial blood exhibited a moderate amplitude (1.7 C) nychthemeral rhythm, with an acrophase at 19.00 h and a nadir late in the morning, at 10.00 h. Brain temperature consistently exceeded blood temperature, on average by 0.2-0.4 C, and changes in brain temperature closely tracked changes in blood temperature. There was no evidence of selective brain cooling, even during the hyperthermia which followed surgery or that associated with intense, short-duration exercise. The relationship between brain and arterial blood temperatures in free-ranging zebras was unlike that reported for horses in the laboratory. Our results do not support the view that mammals lacking a carotid rete can achieve selective brain cooling. PMID:10751518

  18. Performance audit in the selection and management of personnel in the physician's office laboratory.

    PubMed

    Crowley, J R; Tillman, M

    1986-12-01

    The performance audit does not contain any startling news about human performance. It does, however, provide a unique perspective from which to view human performance. It asks the user to relate systematically each part to the whole, to test a hypothesis against actual data, and to formulate solutions based on a strong rationale. We have of necessity described this process very briefly, suggesting how specific tools may be derived for immediate use in the office laboratory. We conclude with a reminder that much useful information in the performance audit can be captured by constructing three tables with the following headings: 1. Job Description, Requirements, Standards; 2. Requirements, Standards, Deficiencies, Potential Impact; 3. Deficiencies, Possible Causes, Possible Solutions. Thus, the performance audit can provide useful information in regard to selecting personnel (item 1), monitoring the performance of laboratory personnel (item 2), and trouble-shooting specific problems (item 3). PMID:3642611

  19. Natural selection on genes that underlie human disease susceptibility.

    PubMed

    Blekhman, Ran; Man, Orna; Herrmann, Leslie; Boyko, Adam R; Indap, Amit; Kosiol, Carolin; Bustamante, Carlos D; Teshima, Kosuke M; Przeworski, Molly

    2008-06-24

    What evolutionary forces shape genes that contribute to the risk of human disease? Do similar selective pressures act on alleles that underlie simple versus complex disorders [1-3]? Answers to these questions will shed light onto the origin of human disorders (e.g., [4]) and help to predict the population frequencies of alleles that contribute to disease risk, with important implications for the efficient design of mapping studies [5-7]. As a first step toward addressing these questions, we created a hand-curated version of the Mendelian Inheritance in Man database (OMIM). We then examined selective pressures on Mendelian-disease genes, genes that contribute to complex-disease risk, and genes known to be essential in mouse by analyzing patterns of human polymorphism and of divergence between human and rhesus macaque. We found that Mendelian-disease genes appear to be under widespread purifying selection, especially when the disease mutations are dominant (rather than recessive). In contrast, the class of genes that influence complex-disease risk shows little signs of evolutionary conservation, possibly because this category includes targets of both purifying and positive selection. PMID:18571414

  20. Evolutionary stasis in pollen morphogenesis due to natural selection.

    PubMed

    Matamoro-Vidal, Alexis; Prieu, Charlotte; Furness, Carol A; Albert, Béatrice; Gouyon, Pierre-Henri

    2016-01-01

    The contribution of developmental constraints and selective forces to the determination of evolutionary patterns is an important and unsolved question. We test whether the long-term evolutionary stasis observed for pollen morphogenesis (microsporogenesis) in eudicots is due to developmental constraints or to selection on a morphological trait shaped by microsporogenesis: the equatorial aperture pattern. Most eudicots have three equatorial apertures but several taxa have independently lost the equatorial pattern and have microsporogenesis decoupled from aperture pattern determination. If selection on the equatorial pattern limits variation, we expect to see increased variation in microsporogenesis in the nonequatorial clades. Variation of microsporogenesis was studied using phylogenetic comparative analyses in 83 species dispersed throughout eudicots including species with and without equatorial apertures. The species that have lost the equatorial pattern have highly variable microsporogenesis at the intra-individual and inter-specific levels regardless of their pollen morphology, whereas microsporogenesis remains stable in species with the equatorial pattern. The observed burst of variation upon loss of equatorial apertures shows that there are no strong developmental constraints precluding variation in microsporogenesis, and that the stasis is likely to be due principally to selective pressure acting on pollen morphogenesis because of its implication in the determination of the equatorial aperture pattern. PMID:26248868

  1. Selected References on Asbestos: Its Nature, Hazards, Detection, and Control.

    ERIC Educational Resources Information Center

    National Education Association, Washington, DC.

    This document provides teachers with sources of information about the nature, hazards, detection, and control of asbestos. Because many school buildings include asbestos-containing materials, teachers and other school personnel must be aware of the potential dangers to students and to themselves and take steps to have asbestos hazards contained or…

  2. Natural and sexual selection act on different axes of variation in avian plumage color

    PubMed Central

    Dunn, Peter O.; Armenta, Jessica K.; Whittingham, Linda A.

    2015-01-01

    The bright colors of birds are often attributed to sexual selection on males, but in many species both sexes are colorful and it has been long debated whether sexual selection can also explain this variation. We show that most evolutionary transitions in color have been toward similar plumage in both sexes, and the color of both sexes (for example, bright or dull) was associated with indices of natural selection (for example, habitat type), whereas sexual differences in color were primarily associated with indices of sexual selection on males (for example, polygyny and large testes size). Debate about the evolution of bird coloration can be resolved by recognizing that both natural and sexual selection have been influential, but they have generally acted on two different axes: sexual selection on an axis of sexual differences and natural selection on both sexes for the type of color (for example, bright or dull). PMID:26601146

  3. Genome Sequencing Reveals Loci under Artificial Selection that Underlie Disease Phenotypes in the Laboratory Rat

    PubMed Central

    Atanur, Santosh S.; Diaz, Ana Garcia; Maratou, Klio; Sarkis, Allison; Rotival, Maxime; Game, Laurence; Tschannen, Michael R.; Kaisaki, Pamela J.; Otto, Georg W.; Ma, Man Chun John; Keane, Thomas M.; Hummel, Oliver; Saar, Kathrin; Chen, Wei; Guryev, Victor; Gopalakrishnan, Kathirvel; Garrett, Michael R.; Joe, Bina; Citterio, Lorena; Bianchi, Giuseppe; McBride, Martin; Dominiczak, Anna; Adams, David J.; Serikawa, Tadao; Flicek, Paul; Cuppen, Edwin; Hubner, Norbert; Petretto, Enrico; Gauguier, Dominique; Kwitek, Anne; Jacob, Howard; Aitman, Timothy J.

    2013-01-01

    Summary Large numbers of inbred laboratory rat strains have been developed for a range of complex disease phenotypes. To gain insights into the evolutionary pressures underlying selection for these phenotypes, we sequenced the genomes of 27 rat strains, including 11 models of hypertension, diabetes, and insulin resistance, along with their respective control strains. Altogether, we identified more than 13 million single-nucleotide variants, indels, and structural variants across these rat strains. Analysis of strain-specific selective sweeps and gene clusters implicated genes and pathways involved in cation transport, angiotensin production, and regulators of oxidative stress in the development of cardiovascular disease phenotypes in rats. Many of the rat loci that we identified overlap with previously mapped loci for related traits in humans, indicating the presence of shared pathways underlying these phenotypes in rats and humans. These data represent a step change in resources available for evolutionary analysis of complex traits in disease models. PaperClip PMID:23890820

  4. Genome sequencing reveals loci under artificial selection that underlie disease phenotypes in the laboratory rat.

    PubMed

    Atanur, Santosh S; Diaz, Ana Garcia; Maratou, Klio; Sarkis, Allison; Rotival, Maxime; Game, Laurence; Tschannen, Michael R; Kaisaki, Pamela J; Otto, Georg W; Ma, Man Chun John; Keane, Thomas M; Hummel, Oliver; Saar, Kathrin; Chen, Wei; Guryev, Victor; Gopalakrishnan, Kathirvel; Garrett, Michael R; Joe, Bina; Citterio, Lorena; Bianchi, Giuseppe; McBride, Martin; Dominiczak, Anna; Adams, David J; Serikawa, Tadao; Flicek, Paul; Cuppen, Edwin; Hubner, Norbert; Petretto, Enrico; Gauguier, Dominique; Kwitek, Anne; Jacob, Howard; Aitman, Timothy J

    2013-08-01

    Large numbers of inbred laboratory rat strains have been developed for a range of complex disease phenotypes. To gain insights into the evolutionary pressures underlying selection for these phenotypes, we sequenced the genomes of 27 rat strains, including 11 models of hypertension, diabetes, and insulin resistance, along with their respective control strains. Altogether, we identified more than 13 million single-nucleotide variants, indels, and structural variants across these rat strains. Analysis of strain-specific selective sweeps and gene clusters implicated genes and pathways involved in cation transport, angiotensin production, and regulators of oxidative stress in the development of cardiovascular disease phenotypes in rats. Many of the rat loci that we identified overlap with previously mapped loci for related traits in humans, indicating the presence of shared pathways underlying these phenotypes in rats and humans. These data represent a step change in resources available for evolutionary analysis of complex traits in disease models. PMID:23890820

  5. Comparison of in situ and laboratory gamma spectroscopy of natural radionuclides in desert soil.

    PubMed

    Benke, R R; Kearfott, K J

    1997-08-01

    In situ and laboratory gamma spectroscopy were used to characterize natural background levels of radiation in the soil at eight sites around the Yucca Mountain Range. The purpose of this practical field analysis was to determine if published empirical in situ calibration factors would yield accurate quantitative specific activities (Bq kg(-1)) in a desert environment. Corrections were made to the in situ calibration factors to account for the on-axis response of a detector with a thin beryllium end window. The in situ gamma spectroscopy results were compared to laboratory gamma spectroscopy of soil samples gathered from each site. Five natural radionuclides were considered: 40K, 214Pb, 214Bi, 208Tl, and 228Ac. The in situ determined specific activities were consistently within +/-15% of the laboratory soil sample results. A quantitative discussion of the factors contributing to the uncertainty in the in situ and laboratory results is included. Analysis on the specific activity data using statistical hypothesis tests determined that three nuclides, 214Pb, 214Bi, and 228Ac showed a weak site dependence while the other two nuclides, 40K and 208Tl, did not exhibit a site dependence. Differing radiation background levels from site to site along with in situ and laboratory uncertainties in excess of 10% are two factors that account for the weak site dependence. Despite the good correlation between data, it was recommended that the in situ detector be calibrated by a detector-specific Monte Carlo code which would accurately model more complex geometries and source distributions. PMID:9228170

  6. Laboratory reproduction of potential ennoblement of stainless steels in natural seawater

    SciTech Connect

    Amaya, Hisashi; Miyuki, Hideaki

    1999-11-01

    The localized corrosion susceptibility of stainless steels, such as type 3 16L, immersed in natural seawater is higher than those in synthetic seawater. It is widely observed that the corrosion potential of stainless steels in natural seawater becomes noble over +0.3V vs SCE. This phenomenon is caused by the influence of the microorganisms in the natural seawater, and therefore it is considered as Microbially Influenced Corrosion (MIC). In this paper, the laboratory reproduction of the corrosion potential ennoblement was examined on the basis of the metabolize of aerobic bacteria (pH, dissolved oxygen and metabolize). The electrochemical measurements in natural seawater and synthetic seawater with bacterial mediums were carried out. The corrosion potential of stainless steels became noble in only natural seawater, and cathodic current density increased around corrosion potential, these results suggest that the presence of oxidizer on the metal surface which has higher redox potential than that of oxygen. As the corrosion potential became noble during the logarithmic phase of bacterial growth in the result of the examination with isolated bacteria, it is suggested that the aerobic metabolism of bacteria effects the ennoblement of corrosion potential. The ennoblement was also reproduced in laboratory by the addition of oxidase simulated the metabolism of aerobic bacteria. The oxidase produced the peroxide by the reduction of oxygen which has higher redox potential than that of oxygen, therefore it is considered that the corrosion potential ennoblement is caused by the peroxide generated by the metabolism of aerobic bacteria included in the biofilm formed on the surface of the stainless steels in natural seawater.

  7. Darwin, natural selection and the biological essentiality of aluminium and silicon.

    PubMed

    Exley, Christopher

    2009-12-01

    If one was asked to produce a set of 'Trump Cards' based upon 'Forces of Nature Defining Life on Earth' then which card would be 'Top Trump'? I was recently chastised on the Darwin Today website for suggesting Darwin and 'natural selection' rather than, for example, Newton and 'gravity'. Although there is no denying the significance of gravity, my argument in favour of natural selection is simply that gravity is just one factor that contributes towards an outcome which ultimately is defined by natural selection. Both the beauty and the brilliance of natural selection are reflected in its omnipotence to explain the myriad observations of life and, as I will affirm herein, its explanation of the biological essentiality of aluminium and silicon is no exception. PMID:19773172

  8. Salinity selection and preference of the grey snapper Lutjanus griseus: field and laboratory observations.

    PubMed

    Serrano, X; Grosell, M; Serafy, J E

    2010-05-01

    Field observations were supplemented with laboratory experiments to reveal patterns of salinity selection and preference for grey snapper Lutjanus griseus (c. 21 cm total length, L(T)), an ecologically and economically important species in the south-eastern U.S.A. Fish abundance data were examined from a long-term field survey conducted in the mangrove habitats of Biscayne Bay, Florida, where salinities ranged from <1 to 40. First, regression analyses indicated significant, positive linear relationships with salinity for both L. griseus frequency of occurrence and concentration (density when present). These patterns are inconsistent with physiological expectations of minimizing energetic osmoregulatory costs. Next, the salinity preference and swimming activity of 11 L. griseus (ranging from 18 to 23 cm L(T)) were investigated using a newly developed electronic shuttlebox system. In the laboratory, fish preferred intermediate salinities in the range of 9-23. Swimming activity (measured in terms of spontaneous swimming speed) followed a parabolic relationship with salinity, with reduced activity at salinity extremes perhaps reflecting compensation for higher osmoregulatory costs. It is suspected that the basis of the discrepancy between laboratory and field observations for size classes at or near maturity ultimately relates to the reproductive imperative to move towards offshore (high-salinity) coral-reef habitats, a necessity that probably overrides the strategy of minimizing osmoregulatory energetic costs. PMID:20557618

  9. Selective looking at natural scenes: Hedonic content and gender.

    PubMed

    Bradley, Margaret M; Costa, Vincent D; Lang, Peter J

    2015-10-01

    Choice viewing behavior when looking at affective scenes was assessed to examine differences due to hedonic content and gender by monitoring eye movements in a selective looking paradigm. On each trial, participants viewed a pair of pictures that included a neutral picture together with an affective scene depicting either contamination, mutilation, threat, food, nude males, or nude females. The duration of time that gaze was directed to each picture in the pair was determined from eye fixations. Results indicated that viewing choices varied with both hedonic content and gender. Initially, gaze duration for both men and women was heightened when viewing all affective contents, but was subsequently followed by significant avoidance of scenes depicting contamination or nude males. Gender differences were most pronounced when viewing pictures of nude females, with men continuing to devote longer gaze time to pictures of nude females throughout viewing, whereas women avoided scenes of nude people, whether male or female, later in the viewing interval. For women, reported disgust of sexual activity was also inversely related to gaze duration for nude scenes. Taken together, selective looking as indexed by eye movements reveals differential perceptual intake as a function of specific content, gender, and individual differences. PMID:26156939

  10. Natural selection of altruism in inelastic viscous homogeneous populations.

    PubMed

    Grafen, Alan; Archetti, Marco

    2008-06-21

    Biological explanations are given of three main uninterpreted theoretical results on the selection of altruism in inelastic viscous homogeneous populations, namely that non-overlapping generations hinder the evolution of altruism, fecundity effects are more conducive to altruism than survival effects, and one demographic regime (so-called death-birth) permits altruism whereas another (so-called birth-death) does not. The central idea is 'circles of compensation', which measure how far the effects of density dependence extend from a focal individual. Relatednesses can then be calculated that compensate for density dependence. There is very generally a 'balancing circle of compensation', at which the viscosity of the population slows up selection of altruism, but does not affect its direction, and this holds for altruism towards any individual, not just immediate neighbours. These explanations are possible because of recent advances in the theory of inclusive fitness on graphs. The assumption of node bitransitivity in that recent theory is relaxed to node transitivity and symmetry of the dispersal matrix, and new formulae show how to calculate relatedness from dispersal and vice versa. PMID:18371985

  11. Magnesium isotope fractionation by chemical diffusion in natural settings and in laboratory analogues

    NASA Astrophysics Data System (ADS)

    Chopra, Rahul; Richter, Frank M.; Bruce Watson, E.; Scullard, Christian R.

    2012-07-01

    Laboratory experiments are used to document isotopic fractionation of magnesium by chemical diffusion in a silicate melt and the results compared to the magnesium isotopic composition across contacts between igneous rocks of different composition in natural settings. The natural samples are from transects from felsic to mafic rocks at Vinal Cove in the Vinalhaven Intrusive Complex, Maine and from the Aztec Wash pluton in Nevada. Two laboratory diffusion couples made by juxtaposing melts made from powders of the felsic and mafic compositions sampled at Vinal Cove were annealed at about 1500 °C for 22.5 and 10 h, respectively. The transport of magnesium in the diffusion couples resulted in easily measured magnesium isotopic fractionations at the interface (δ26Mg∼1.5‰). These isotopic fractionations provide a distinctive isotopic “fingerprint” that we use to determine whether chemical gradients in natural settings where melts of different composition were juxtaposed were due to chemical diffusion. The magnesium isotopic fractionation along one profile at Vinal Cove is exactly what one would expect based on the fractionations found in the laboratory experiments. This is an important result in that it shows that the isotope fractionation by chemical diffusion found in highly controlled laboratory experiments can be found in a natural setting. This correspondence implies that chemical diffusion was the dominant process responsible for the transport of magnesium across this particular contact at Vinal Cove. A second Vinal Cove profile has a very similar gradient in magnesium concentration but with significantly less magnesium isotopic fractionation than expected. This suggests that mass transport at this location was only partly by diffusion and that some other mass transport mechanism such as mechanical mixing must have also played a role. The magnesium isotopic composition of samples from Aztec Wash shows no resolvable isotopic fractionation across the contact between the mafic and felsic rocks. The different degrees of magnesium isotopic fractionation associated with otherwise similar composition gradients in natural settings show that kinetic isotope fractionations provide a key discriminator for establishing whether or not molecular diffusion was the process responsible for an observed elemental gradient. In the one case of a contact at Vinal Cove where we are confident that the magnesium elemental and isotopic gradients were produced by diffusion, we deduced a cooling rate of about 1.5 °C per day.

  12. From prebiotic chemistry to cellular metabolism--the chemical evolution of metabolism before Darwinian natural selection.

    PubMed

    Meléndez-Hevia, Enrique; Montero-Gómez, Nancy; Montero, Francisco

    2008-06-01

    It is generally assumed that the complex map of metabolism is a result of natural selection working at the molecular level. However, natural selection can only work on entities that have three basic features: information, metabolism and membrane. Metabolism must include the capability of producing all cellular structures, as well as energy (ATP), from external sources; information must be established on a material that allows its perpetuity, in order to safeguard the goals achieved; and membranes must be able to preserve the internal material, determining a selective exchange with external material in order to ensure that both metabolism and information can be individualized. It is not difficult to understand that protocellular entities that boast these three qualities can evolve through natural selection. The problem is rather to explain the origin of such features under conditions where natural selection could not work. In the present work we propose that these protocells could be built by chemical evolution, starting from the prebiotic primordial soup, by means of chemical selection. This consists of selective increases of the rates of certain specific reactions because of the kinetic or thermodynamic features of the process, such as stoichiometric catalysis or autocatalysis, cooperativity and others, thereby promoting their prevalence among the whole set of chemical possibilities. Our results show that all chemical processes necessary for yielding the basic materials that natural selection needs to work may be achieved through chemical selection, thus suggesting a way for life to begin. PMID:18160077

  13. Sperm selection in natural conception: what can we learn from Mother Nature to improve assisted reproduction outcomes?

    PubMed Central

    Sakkas, Denny; Ramalingam, Mythili; Garrido, Nicolas; Barratt, Christopher L.R.

    2015-01-01

    BACKGROUND In natural conception only a few sperm cells reach the ampulla or the site of fertilization. This population is a selected group of cells since only motile cells can pass through cervical mucus and gain initial entry into the female reproductive tract. In animals, some studies indicate that the sperm selected by the reproductive tract and recovered from the uterus and the oviducts have higher fertilization rates but this is not a universal finding. Some species show less discrimination in sperm selection and abnormal sperm do arrive at the oviduct. In contrast, assisted reproductive technologies (ART) utilize a more random sperm population. In this review we contrast the journey of the spermatozoon in vivo and in vitro and discuss this in the context of developing new sperm preparation and selection techniques for ART. METHODS A review of the literature examining characteristics of the spermatozoa selected in vivo is compared with recent developments in in vitro selection and preparation methods. Contrasts and similarities are presented. RESULTS AND CONCLUSIONS New technologies are being developed to aid in the diagnosis, preparation and selection of spermatozoa in ART. To date progress has been frustrating and these methods have provided variable benefits in improving outcomes after ART. It is more likely that examining the mechanisms enforced by nature will provide valuable information in regard to sperm selection and preparation techniques in vitro. Identifying the properties of those spermatozoa which do reach the oviduct will also be important for the development of more effective tests of semen quality. In this review we examine the value of sperm selection to see how much guidance for ART can be gleaned from the natural selection processes in vivo. PMID:26386468

  14. Biochemical characterization of chlorantraniliprole and spinetoram resistance in laboratory-selected obliquebanded leafroller, Choristoneura rosaceana (Harris)(Lepidoptera:Tortricidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Neonate larvae of obliquebanded leafroller, Choristoneura rosaceana, from a laboratory colony were exposed to two reduced-risk insecticides, chlorantraniliprole and spinetoram. After nine generations of selection, significant levels of resistance to each insecticide were observed. Biochemical assa...

  15. Fault healing promotes high-frequency earthquakes in laboratory experiments and on natural faults

    USGS Publications Warehouse

    McLaskey, Gregory C.; Thomas, Amanda M.; Glaser, Steven D.; Nadeau, Robert M.

    2012-01-01

    Faults strengthen or heal with time in stationary contact and this healing may be an essential ingredient for the generation of earthquakes. In the laboratory, healing is thought to be the result of thermally activated mechanisms that weld together micrometre-sized asperity contacts on the fault surface, but the relationship between laboratory measures of fault healing and the seismically observable properties of earthquakes is at present not well defined. Here we report on laboratory experiments and seismological observations that show how the spectral properties of earthquakes vary as a function of fault healing time. In the laboratory, we find that increased healing causes a disproportionately large amount of high-frequency seismic radiation to be produced during fault rupture. We observe a similar connection between earthquake spectra and recurrence time for repeating earthquake sequences on natural faults. Healing rates depend on pressure, temperature and mineralogy, so the connection between seismicity and healing may help to explain recent observations of large megathrust earthquakes which indicate that energetic, high-frequency seismic radiation originates from locations that are distinct from the geodetically inferred locations of large-amplitude fault slip

  16. Genome-wide transcription profile of field- and laboratory-selected dichlorodiphenyltrichloroethane (DDT)-resistant Drosophila

    PubMed Central

    Pedra, J. H. F.; McIntyre, L. M.; Scharf, M. E.; Pittendrigh, Barry R.

    2004-01-01

    Genome-wide microarray analysis (Affymetrix array) was used (i) to determine whether only one gene, the cytochrome P450 enzyme Cyp6g1, is differentially transcribed in dichlorodiphenyltrichloroethane (DDT)-resistant vs. -susceptible Drosophila; and (ii) to profile common genes differentially transcribed across a DDT-resistant field isolate [Rst(2)DDTWisconsin] and a laboratory DDT-selected population [Rst(2)DDT91-R]. Statistical analysis (ANOVA model) identified 158 probe sets that were differentially transcribed among Rst(2)DDT91-R, Rst(2)DDTWisconsin, and the DDT-susceptible genotype Canton-S (P < 0.01). The cytochrome P450 Cyp6a2 and the diazepam-binding inhibitor gene (Dbi) were over transcribed in the two DDT-resistant genotypes when compared to the wild-type Drosophila, and this difference was significant at the most stringent statistical level, a Bonferroni correction. The list of potential candidates differentially transcribed also includes 63 probe sets for which molecular function ontology annotation of the probe sets did not exist. A total of four genes (Cyp6a2, Dbi, Uhg1, and CG11176) were significantly different (P < 5.6 e-06) between Rst(2)DDT91-R and Canton-S. Additionally, two probe sets encoding Cyp12d1 and Dbi were significantly different between Rst(2)DDTWisconsin and Canton-S after a Bonferroni correction. Fifty-two probe sets, including those associated with pesticide detoxification, ion transport, signal transduction, RNA transcription, and lipid metabolism, were commonly expressed in both resistant lines but were differentially transcribed in Canton-S. Our results suggest that more than Cyp6g1 is overtranscribed in field and laboratory DDT-resistant genotypes, and the number of commonalities suggests that similar resistance mechanisms may exist between laboratory- and field-selected DDT-resistant fly lines. PMID:15118106

  17. Survival and catabolic activity of natural and genetically engineered bacteria in a laboratory-scale activated-sludge unit.

    PubMed Central

    McClure, N C; Fry, J C; Weightman, A J

    1991-01-01

    The survival of selected naturally occurring and genetically engineered bacteria in a fully functional laboratory-scale activated-sludge unit (ASU) was investigated. The effect of the presence of 3-chlorobenzoate (3CB) on the survival of Pseudomonas putida UWC1, with or without a chimeric plasmid, pD10, which encodes 3CB catabolism, was determined. P. putida UWC1(pD10) did not enhance 3CB breakdown in the ASU, even following inoculation at a high concentration (3 x 10(8) CFU/ml). The emergence of a natural, 3CB-degrading population appeared to have a detrimental effect on the survival of strain UWC1 in the ASU. The fate of two 3CB-utilizing bacteria, derived from activated-sludge microflora, was studied in experiments in which these strains were inoculated into the ASU. Both strains, AS2, an unmanipulated natural isolate which flocculated readily in liquid media, and P. putida ASR2.8, a transconjugant containing the recombinant plasmid pD10, survived for long periods in the ASU and enhanced 3CB breakdown at 15 degrees C. The results reported in this paper illustrate the importance of choosing strains which are well adapted to environmental conditions if the use of microbial inoculants for the breakdown of target pollutants is to be successful. Images PMID:2014987

  18. Climate change and geothermal ecosystems: natural laboratories, sentinel systems, and future refugia.

    PubMed

    O'Gorman, Eoin J; Benstead, Jonathan P; Cross, Wyatt F; Friberg, Nikolai; Hood, James M; Johnson, Philip W; Sigurdsson, Bjarni D; Woodward, Guy

    2014-11-01

    Understanding and predicting how global warming affects the structure and functioning of natural ecosystems is a key challenge of the 21st century. Isolated laboratory and field experiments testing global change hypotheses have been criticized for being too small-scale and overly simplistic, whereas surveys are inferential and often confound temperature with other drivers. Research that utilizes natural thermal gradients offers a more promising approach and geothermal ecosystems in particular, which span a range of temperatures within a single biogeographic area, allow us to take the laboratory into nature rather than vice versa. By isolating temperature from other drivers, its ecological effects can be quantified without any loss of realism, and transient and equilibrial responses can be measured in the same system across scales that are not feasible using other empirical methods. Embedding manipulative experiments within geothermal gradients is an especially powerful approach, informing us to what extent small-scale experiments can predict the future behaviour of real ecosystems. Geothermal areas also act as sentinel systems by tracking responses of ecological networks to warming and helping to maintain ecosystem functioning in a changing landscape by providing sources of organisms that are preadapted to different climatic conditions. Here, we highlight the emerging use of geothermal systems in climate change research, identify novel research avenues, and assess their roles for catalysing our understanding of ecological and evolutionary responses to global warming. PMID:24729541

  19. Disruptive selection in natural populations: the roles of ecological specialization and resource competition.

    PubMed

    Martin, Ryan A; Pfennig, David W

    2009-08-01

    Disruptive selection is potentially critical in maintaining variation and initiating speciation. Yet there are few convincing examples of disruptive selection from nature. Moreover, relatively little is known about the causes of disruptive selection. Here, we document disruptive selection and its causes in natural populations of spadefoot toad tadpoles (Spea multiplicata), which are highly variable in trophic phenotype and resource use. Using a mark-recapture experiment in a natural pond, we show that selection favors extreme trophic phenotypes over intermediate individuals. We further show that such disruptive selection likely reflects both ecological specialization and resource competition. Evidence for ecological specialization comes from two field experiments, which demonstrate that extreme phenotypes forage more effectively on the main alternative resource types. Support for competition's role in disruptive selection comes from two additional experiments, which demonstrate that intermediate phenotypes, which are often the most common phenotype, compete more with each other than with extreme forms and that the intensity of disruptive selection increases with conspecific density. Generally, ecological specialization and competition are widespread, suggesting that many populations may experience some level of disruptive selection. Thus, disruptive selection may be a more common force contributing to phenotypic variation in natural populations than is currently recognized. PMID:19527118

  20. Assessing the alignment of sexual and natural selection using radiomutagenized seed beetles.

    PubMed

    Power, D J; Holman, L

    2015-05-01

    A major unsolved question in evolutionary biology concerns the relationship between natural and sexual selection. Sexual selection might augment natural selection, for example if mutations that harm female fecundity also reduce male mating success. Conversely, sexual selection might favour traits that impair naturally selected fitness components. We induced detrimental mutations in Callosobruchus maculatus beetles using X-ray irradiation and then experimentally measured the effect of precopulatory sexual selection on offspring number and survival rate. Sexual selection treatment had a negative effect on egg-to-adult survivorship, although the number of progeny reaching adulthood was unaffected, perhaps because eggs and juveniles that failed to develop lessened competition on the survivors. We hypothesize that the negative effect of sexual selection arose because sexually competitive males transmitted a smaller nuptial gift or carried alleles that conferred reduced survival. Although we found no evidence that sexual selection on males can purge alleles that are detrimental to naturally selected fitness components, such benefits might exist in other environmental or genetic contexts. PMID:25808294

  1. Developments of the Price equation and natural selection under uncertainty.

    PubMed

    Grafen, A

    2000-06-22

    Many approaches to the study of adaptation, following Darwin, centre on the number of offspring of individuals. Population genetics theory makes clear that predicting gene frequency changes requires more detailed knowledge, for example of linkage and linkage disequilibrium and mating systems. Because gene frequency changes underlie adaptation, this can lead to a suspicion that approaches ignoring these sophistications are approximate or tentative or wrong. Stochastic environments and sexual selection are two topics in which there are widespread views that focusing on number of offspring of individuals is not enough, and that proper treatments require the introduction of further details, namely variability in offspring number and linkage disequilibrium, respectively. However, the bulk of empirical research on adaptation and a great deal of theoretical work continue to employ these approaches. Here, a new theoretical development arising from the Price equation provides a formal justification in very general circumstances for focusing on the arithmetic average of the relative number of offspring of individuals. PMID:10902688

  2. Infant crying: nature, physiologic consequences, and select interventions.

    PubMed

    Ludington-Hoe, Susan M; Cong, Xiaomei; Hashemi, Fariba

    2002-03-01

    This article describes the nature of infant crying, the physiologic events and changes associated with it, and appropriate nursing interventions for infant crying. A cry is a series of four movements that basically resembles a Valsalva maneuver. Documented immediate and long-term sequelae of crying include increased heart rate and blood pressure, reduced oxygen level, elevated cerebral blood pressure, initiation of the stress response, depleted energy reserves and oxygen, interrupted mother-infant interaction, brain injury, and cardiac dysfunction. Caregivers are encouraged to answer infant cries swiftly, consistently, and comprehensively. Kangaroo care is an efficient method for preventing, minimizing, and halting crying. Other interventions for crying include swaddled holding, a pacifier, sugar water, a sweet-tasting nonsucrose solution, heartbeat sounds, distraction by lullabies or mother's voice, rhythmic movement, and reduction of external stimuli. PMID:11923998

  3. Affective Neuronal Selection: The Nature of the Primordial Emotion Systems

    PubMed Central

    Toronchuk, Judith A.; Ellis, George F. R.

    2013-01-01

    Based on studies in affective neuroscience and evolutionary psychiatry, a tentative new proposal is made here as to the nature and identification of primordial emotional systems. Our model stresses phylogenetic origins of emotional systems, which we believe is necessary for a full understanding of the functions of emotions and additionally suggests that emotional organizing systems play a role in sculpting the brain during ontogeny. Nascent emotional systems thus affect cognitive development. A second proposal concerns two additions to the affective systems identified by Panksepp. We suggest there is substantial evidence for a primary emotional organizing program dealing with power, rank, dominance, and subordination which instantiates competitive and territorial behavior and is an evolutionary contributor to self-esteem in humans. A program underlying disgust reactions which originally functioned in ancient vertebrates to protect against infection and toxins is also suggested. PMID:23316177

  4. Natural selectivity of Nickel and Vanadium in crude oil

    NASA Astrophysics Data System (ADS)

    Fernandez, Olienka Patricia De La O.

    Nickel and Vanadium have always been found in crude oil all around the world. The metal content is found mainly in porphyrin structures in the asphaltene fraction of the petroleum. In order to determine the reason for this natural preference, a set of experiments testing thermodynamics, kinetics, and other factors were performed. Candidate metalloporphyrins containing Vanadyl, Chromium, Iron, Nickel, Copper and Zinc were analyzed through chemical reactions characterized using Silica Column Chromatography, HPLC, MS and UV-Visible. Theoretical analysis of the stability of metalloporphyrins was conducted using DFT/NRLMOL for computational calculation. The analysis of all factors leads us to conclude that the presence of Nickel and Vanadium in petroleum depend on different factors, not only on the stability of the structures, but mainly on abundance in the medium rising from biological processes.

  5. The Nature of Irac-selected Extremely Red Objects

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Huang, J.; Gu, Q.

    2010-05-01

    Using deep U-8um photometry from GEMs, MUSYC and SIMPLE surveys, we investigate properties of a large sample of IRAC-selected extremely red galaxies(IEROs). The sample comprises 304 brightest IEROs distributed over the GEMS field with a total area of 800 arcmin2, which satisfy ([3.6]+[4.5]/2)<21.2 and z-[3.6] > 3.25). Combined with the deepest Chandra and Spitzer surveys in this field, we are able to determine relative contributions of AGNs, (dusty) star-forming galaxies and passively evolving systems to the RED population; 51 sources are detected in at least one of three X-ray bands, leaving 253 non-Xray sources with 179 detected in 24um( 20uJy, 3sigma), indicating that at most 25% of these IEROs are passively evolving.We derive and examine photometric redshift using different methods; their redshift range from 1 to 2.6 with the median value at 1.5. Stellar masses of non-Xray sources are also derived with SED fitting methods, achieving a median value of 0.4*1011 Msun for a chrabrier initial mass function. The properties of best-fitting BC03 models are consistent with templates used for estimating redshifts, which have on average E(B-V) of 0.5 for 24um-deteced galaxies. The corresponding star-formation rates of these star-forming galaxies through SED fitting are within 40-100 Msun yr-1, consistent with that derived from their 24?m flux, which show a median total infrared luminosity 1*1011Lsun. We argue that such selected IEROs may represent a transient population from ULIRGs to LIRGs, and are likely descents of SMGs or DOGs.

  6. Ant Queen Egg-Marking Signals: Matching Deceptive Laboratory Simplicity with Natural Complexity

    PubMed Central

    van Zweden, Jelle S.; Heinze, Jürgen; Boomsma, Jacobus J.; d'Ettorre, Patrizia

    2009-01-01

    Background Experiments under controlled laboratory conditions can produce decisive evidence for testing biological hypotheses, provided they are representative of the more complex natural conditions. However, whether this requirement is fulfilled is seldom tested explicitly. Here we provide a lab/field comparison to investigate the identity of an egg-marking signal of ant queens. Our study was based on ant workers resolving conflict over male production by destroying each other's eggs, but leaving queen eggs unharmed. For this, the workers need a proximate cue to discriminate between the two egg types. Earlier correlative evidence indicated that, in the ant Pachycondyla inversa, the hydrocarbon 3,11-dimethylheptacosane (3,11-diMeC27) is more abundant on the surface of queen-laid eggs. Methodology We first tested the hypothesis that 3,11-diMeC27 functions as a queen egg-marking pheromone using laboratory-maintained colonies. We treated worker-laid eggs with synthetic 3,11-diMeC27 and found that they were significantly more accepted than sham-treated worker-laid eggs. However, we repeated the experiment with freshly collected field colonies and observed no effect of treating worker-laid eggs with 3,11-diMeC27, showing that this compound by itself is not the natural queen egg-marking pheromone. We subsequently investigated the overall differences of entire chemical profiles of eggs, and found that queen-laid eggs in field colonies are more distinct from worker-laid eggs than in lab colonies, have more variation in profiles, and have an excess of longer-chain hydrocarbons. Conclusions Our results suggest that queen egg-marking signals are significantly affected by transfer to the laboratory, and that this change is possibly connected to reduced queen fertility as predicted by honest signaling theory. This change is reflected in the worker egg policing response under field and laboratory conditions. PMID:19262683

  7. Redox-sensitivity and mobility of selected pharmaceutical compounds in a laboratory column experiment

    NASA Astrophysics Data System (ADS)

    Banzhaf, S.; Nödler, K.; Licha, T.; Krein, A.; Scheytt, T.

    2012-04-01

    Laboratory column experiments are suitable to investigate the sediment water interaction and to study the transport behaviour of solutes. Processes like retardation and degradation can be identified and quantified. The conducted experiment, which is closely connected to a field study in Luxembourg, investigated the transport behaviour of selected pharmaceutical compounds and their redox-dependent metabolism under water saturated conditions. Fine-grained natural sediment with a low hydraulic conductivity from a study site in Luxembourg was filled into the column. The water for the experiment was taken from a small stream at the same fieldsite. It was spiked with four pharmaceutical compounds (carbamazepine, diclofenac, ibuprofen, sulfamethoxazole) with concentrations between 170 and 300 ng/L for the different substances. The chosen pharmaceuticals were also detected in groundwater and surface water samples at the study site and used to qualify exchange/mixing of surface water and groundwater (BANZHAF et al., 2011). As some of the substances are known to exhibit redox-sensitive degradation, the redox-conditions were systematically varied throughout the experiment. This was realised by adding nitrate at the inflow of the column. During the experiment, which lasted for 2.5 months, four different nitrate concentrations (20-130 mg/L) were applied, beginning with the highest concentration. During the experiment water from the reservoir tank was sampled daily in order to detect a potential degradation of the pharmaceutical compounds before they enter the column. The effluent water was sampled every three hours to guarantee a maximum resolution for the analysis of the pharmaceuticals where necessary. In addition, major ions were analysed in the influent and effluent samples. Throughout the experiment physicochemical parameters (oxidation reduction potential (ORP), dissolved oxygen, electrical conductivity, and pH-value) were measured and logged at the outflow of the column. At the beginning, the ORP was positive (200 mV) and then dropped continuously. Negative values were reached after 1 month and at the end of the experiment -300 mV were measured. Apart from nitrate and nitrite no significant changes in ion concentrations were detected in the effluent. However, the added pharmaceuticals showed very different behaviour in the column. Diclofenac and especially carbamazepine were highly absorbed by the sediment. They were detected significantly later at the outflow of the column than sulfamethoxazole and ibuprofen. Sulfamethoxazole was heavily influenced by the redox-conditions. Its time variation curve in the effluent is negatively correlated with nitrite and nitrate: during nitrite formation the concentrations of sulfamethoxazole dropped considerably. The presented experiment yields a better understanding of the processes influencing the occurrence and transport behaviour of the studied compounds. In addition, some general findings on redox-dependent transport behaviour and metabolism of the antibiotic sulfamethoxazole are gained. This emphasizes the role of the ORP as a key parameter for the behaviour of this compound, which has to be considered. BANZHAF, S., KREIN, A. & SCHEYTT, T. (2011). Investigative approaches to determine exchange processes in the hyporheic zone of a low permeability riverbank. Hydrogeology Journal 19 (3), pp. 591-601.

  8. Opportunity for natural selection among some selected population groups of Northeast India

    PubMed Central

    Das, Farida Ahmed; Mithun, Sikdar

    2010-01-01

    BACKGROUND: Selection potential based on differential fertility and mortality has been computed for seven population groups inhabiting different geographical locations of Northeast India. MATERIALS AND METHODS: Crow’s as well as Johnston and Kensinger’s index have been used for the present purpose. RESULTS AND CONCLUSION: Irrespective of the methodology, the total index of selection was found to be highest among the Deoris followed by the Kaibartas. The lowest selection index was found among the Oraon population. If the relative contribution of fertility and mortality components to the total index is considered to be multiplicative, it is observed that in all these communities the fertility component exceeds that of mortality component, which may indicate initiation of demographic transitional phase in the selected populations with the betterment of healthcare and socioeconomic condition within the last few decades. PMID:21031053

  9. Chaotic population dynamics can result from natural selection.

    PubMed

    Ferrière, R; Gatto, M

    1993-01-22

    The question of whether animal populations display chaotic dynamics has motivated a thriving body of research for two decades. Yet unambiguous evidence for chaos in the wild remains scarce. Accordingly, it has been proposed that evolutionary forces act to preserve populations from chaos as well as oscillations. We have tested for this hypothesis by considering the dynamics associated with evolutionarily stable life histories (including age of maturity, adult survivorship and recruitment to adulthood) in a simple, but general, demographic model. Contrary to expectation, individual selection operating on demographic traits should often lead to oscillatory or chaotic dynamics for species with late feasible ages of maturity and many age classes. Also, the optimality of chaos is more likely whenever trade-offs constrain recruitment to rapidly decrease with increasing adult survival or decreasing age of maturity. Our results bring evolutionary support to the possibility that chaotic population dynamics might be much more widespread than inferred until now from data analyses. Furthermore, these findings provide novel support for the view that chaos could be an optimal regime for several biological systems. PMID:8094563

  10. Effects of selected bioactive natural products on the vascular endothelium.

    PubMed

    Ahmad, Ajaz; Khan, Rao M A; Alkharfy, Khalid M

    2013-08-01

    The endothelium, a highly active structure, regulates vascular homeostasis through the release of numerous vasoactive factors that control vascular tone and vascular smooth cell proliferation. A larger number of medicinal plants and their isolated chemical constituents have been shown to beneficially affect the endothelium. For example, flavonoids in black tea, green tea, and concord grape cause a vasodilation possibly through their antioxidant properties. Allicin, a by-product of the enzyme alliinase, has been proposed to be the main active metabolite and responsible for most of the biological activities of garlic, including a dose-dependent dilation on the isolated coronaries. Thymoquinone, the principal phytochemical compound found in the volatile oil of the black seed, and the hawthorn extract have also been shown to improve aging-related impairment of endothelium-dependent relaxations in animal models. In this review, the effect of some of the natural products, including Camellia sinensis (black tea and green tea), Vitis labrusca (concord grape), Allium sativum (garlic), and Nigella sativa (black seed) and Crataegus ssp (hawthorn extract), is explored. The molecular mechanisms behind these potential therapeutic effects are also discussed. PMID:23599064

  11. Natural radioactivity levels for selected kinds of Egyptian sand.

    TOXLINE Toxicology Bibliographic Information

    El-Bahi SM; El-Dine NW; Ahmed F; Sroor A; Abdl Salaam MM

    2005-06-01

    The monitoring and evaluation of natural radioactivity content of sixty-five different samples of sand used in building materials, black sand and its components, and therapy sand collected from different locations in Egypt have been investigated. The specific radioactivity concentration of 238U, 232Th series, and 40K were measured by gamma-ray spectrometer using a shielded HPGe. The obtained results of 238U and 232Th series as well as 40K are discussed. The absorbed dose rate of gamma radiation ranged from 15.1 to 64.1, 9.3 to 109, 751, and 32.9 to 63.4 nGy h(-1) for sand used in building materials, black sand with its components, and therapy sand samples, respectively. The representative external hazard index (H ex) for the corresponding values are also estimated and tabulated. The present results are compared with other data previously obtained from different sand areas in both Egyptian and foreign locations.

  12. The 'Natural Laboratory', a tool for deciphering growth, lifetime and population dynamics in larger benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Hohenegger, Johann

    2015-04-01

    The shells of symbiont-bearing larger benthic Foraminifera (LBF) represent the response to physiological requirements in dependence of environmental conditions. All compartments of the shell such as chambers and chamberlets accommodate the growth of the cell protoplasm and are adaptations for housing photosymbiotic algae. Investigations on the biology of LBF were predominantly based on laboratory studies. The lifetime of LBF under natural conditions is still unclear. LBF, which can build >100 chambers during their lifetime, are thought to live at least one year under natural conditions. This is supported by studies on population dynamics of eulittoral foraminifera. In species characterized by a time-restricted single reproduction period the mean size of specimens increases from small to large during lifetime simultaneously reducing individual number. This becomes more complex when two or more reproduction times are present within a one-year cycle leading to a mixture of abundant small individuals with few large specimens during the year, while keeping mean size more or less constant. This mixture is typical for most sublittoral megalospheric (gamonts or schizonts) LBF. Nothing is known on the lifetime of agamonts, the diploid asexually reproducing generation. In all hyaline LBF it is thought to be significantly longer than 1 year based on the large size and considering the mean chamber building rate of the gamont/schizonts. Observations on LBF under natural conditions have not been performed yet in the deeper sublittoral. This reflects the difficulties due to intense hydrodynamics that hinder deploying technical equipment for studies in the natural environment. Therefore, studying growth, lifetime and reproduction of sublittoral LBF under natural conditions can be performed using the so-called 'natural laboratory' in comparison with laboratory investigations. The best sampling method in the upper sublittoral from 5 to 70 m depth is by SCUBA diving. Irregular sampling intervals caused by differing weather conditions may range from weeks to one month, whereby the latter represents the upper limit: larger intervals could render the data set worthless. The number of sampling points at the location must be more than 4, randomly distributed and approximately 5m apart to smooth the effects of patchy distributions, which are typical for most LBF. Only three simple measurements are necessary to determine chamber building rate and population dynamics under natural conditions. These are the number of individuals, number of chambers and the largest diameter of the individual. The determination of a standardized sample surface area, which is necessary for population dynamic investigations, depends on the sampling method. Reproduction and longevity can be estimated based on shell size using the date where the mean abundance of specimens with minimum size (expected after a one month's growth) characterizes the reproduction period. Then the difference to the date with the mean abundance of specimens characterized by large size indicating readiness for reproduction marks the life time. Calculation of the chamber-building rate based on chamber number is more complex and depends on the reproduction period and longevity. This can be fitted with theoretical growth functions (e.g. Michaelis Menten Function). According to the above mentioned methods, chamber building rates, longevity and population dynamics can be obtained for the shallow sublittoral symbiont-bearing LBF using the 'natural laboratory'.

  13. Assessment of laboratory logistics management information system practice for HIV/AIDS and tuberculosis laboratory commodities in selected public health facilities in Addis Ababa, Ethiopia

    PubMed Central

    Desale, Adino; Taye, Bineyam; Belay, Getachew; Nigatu, Alemayehu

    2013-01-01

    Introduction Logistics management information system for health commodities remained poorly implemented in most of developing countries. To assess the status of laboratory logistics management information system for HIV/AIDS and tuberculosis laboratory commodities in public health facilities in Addis Ababa. Methods A cross-sectional descriptive study was conducted from September 2010-January 2011 at selected public health facilities. A stratified random sampling method was used to include a total of 43 facilities which, were investigated through quantitative methods using structured questionnaires interviews. Focus group discussion with the designated supply chain managers and key informant interviews were conducted for the qualitative method. Results There exists a well-designed logistics system for laboratory commodities with trained pharmacy personnel, distributed standard LMIS formats and established inventory control procedures. However, majority of laboratory professionals were not trained in LMIS. Majority of the facilities (60.5%) were stocked out for at least one ART monitoring and TB laboratory reagents and the highest stock out rate was for chemistry reagents. Expired ART monitoring laboratory commodities were found in 25 (73.5%) of facilities. Fifty percent (50%) of the assessed hospitals and 54% of health centers were currently using stock/bin cards for all HIV/AIDS and TB laboratory commodities in main pharmacy store, among these only 25% and 20.8% of them were updated with accurate information matching with the physical count done at the time of visit for hospitals and health centers respectively. Conclusion Even though there exists a well designed laboratory LMIS, keeping quality stock/bin cards and LMIS reports were very low. Key ART monitoring laboratory commodities were stock out at many facilities at the day of visit and during the past six months. Based on findings, training of laboratory personnel's managing laboratory commodities and keeping accurate inventory control procedures were recommended. PMID:24106574

  14. Laboratory investigations on hydrate formation and dissociation in sediments - analogies and differences to natural systems

    NASA Astrophysics Data System (ADS)

    Schicks, J. M.; Spangenberg, E.; Priegnitz, M.; Heeschen, K. U.; Thaler, J.; Abendroth, S.

    2014-12-01

    In natural sediments changes in pressure and temperature may induce the dissociation of naturally occurring gas hydrates. The dissociation of the solid hydrates as well as the increase of a gas phase due to hydrate dissociation may cause or facilitate geo hazards such as slope failure [1]. Therefore, the understanding of hydrate distribution, dissociation and (re-) formation processes which in turn may alter the geomechanical properties of the sediments are of great importance for the prediction on hydrate behavior. During the last decades both, hydrate formation and dissociation, have been studied manifold in laboratory experiments to get a better understanding of these processes. However, the experimental set ups and chosen conditions such as pressure, temperature, sediments, and water saturation vary significantly and do not always simulate natural systems. Within the German national project SUGAR we developed a large LAboratory Reservoir Simulator LARS to study hydrate behavior in sediments. LARS has a total volume of 425 L and has been successfully equipped with an electrical resistivity tomography (ERT). The hydrates form from methane saturated saline water in absence of a free gas phase. Measurements of the dissolved methane at the sample in- and outlet together with temperature monitoring at different locations inside the sediment and ERT measurements are used to describe and characterize the formation process. The ERT and temperature measurements allow for a detection of spatial differences. It could be shown that in this laboratory simulation hydrate forms as it is assumed for natural scenarios. Dissociation processes induced by pressure decrease or temperature increase as well as the consecutive migration of gases and fluids were also studied. To complete the understanding of decisive factors on hydrate formation and fluid flow we investigated the influence of grain sizes on hydrate formation and the influence of hydrate saturation on permeability. In this contribution we present the experimental set up and discuss the results with regard to the analogies and differences to natural systems. [1] Jürgen Mienert, Maarten Vanneste, Stefan Bünz, Karin Andreassen, Haflidi Haflidason, Hans Petter Sejrup, Marine and Petroleum Geology 22 (2005) 233-244.

  15. Epistasis and Natural Selection Shape the Mutational Architecture of Complex Traits

    PubMed Central

    Jones, Adam G.; Bürger, Reinhard; Arnold, Stevan J.

    2014-01-01

    The evolutionary trajectories of complex traits are constrained by levels of genetic variation as well as genetic correlations among traits. Because the ultimate source of all genetic variation is mutation, the distribution of mutations entering populations profoundly affects standing variation and genetic correlations. Here, we use an individual-based simulation model to investigate how natural selection and gene interactions (i.e., epistasis) shape the evolution of mutational processes affecting complex traits. We find that the presence of epistasis allows natural selection to mold the distribution of mutations, such that mutational effects align with the selection surface. Consequently, novel mutations tend to be more compatible with the current forces of selection acting on the population. These results suggest that in many cases mutational effects should be seen as an outcome of natural selection rather than as an unbiased source of genetic variation that is independent of other evolutionary processes. PMID:24828461

  16. Phenotypic heterogeneity is a selected trait in natural yeast populations subject to environmental stress

    PubMed Central

    Holland, Sara L; Reader, Tom; Dyer, Paul S; Avery, Simon V

    2014-01-01

    Populations of genetically uniform microorganisms exhibit phenotypic heterogeneity, where individual cells have varying phenotypes. Such phenotypes include fitness-determining traits. Phenotypic heterogeneity has been linked to increased population-level fitness in laboratory studies, but its adaptive significance for wild microorganisms in the natural environment is unknown. Here, we addressed this by testing heterogeneity in yeast isolates from diverse environmental sites, each polluted with a different principal contaminant, as well as from corresponding control locations. We found that cell-to-cell heterogeneity (in resistance to the appropriate principal pollutant) was prevalent in the wild yeast isolates. Moreover, isolates with the highest heterogeneity were consistently observed in the polluted environments, indicating that heterogeneity is positively related to survival in adverse conditions in the wild. This relationship with survival was stronger than for the property of mean resistance (IC50) of an isolate. Therefore, heterogeneity could be the major determinant of microbial survival in adverse conditions. Indeed, growth assays indicated that isolates with high heterogeneities had a significant competitive advantage during stress. Analysis of yeasts after cultivation for ??500 generations additionally showed that high heterogeneity evolved as a heritable trait during stress. The results showed that environmental stress selects for wild microorganisms with high levels of phenotypic heterogeneity. PMID:24000788

  17. Selection of yeasts with multifunctional features for application as starters in natural black table olive processing.

    PubMed

    Bonatsou, S; Benítez, A; Rodríguez-Gómez, F; Panagou, E Z; Arroyo-López, F N

    2015-04-01

    Yeasts are unicellular eukaryotic microorganisms with a great importance in the elaboration on many foods and beverages. In the last years, researches have focused their attention to determine the favourable effects that these microorganisms could provide to table olive processing. In this context, the present study assesses, at laboratory scale, the potential technological (resistance to salt, lipase, esterase and ?-glucosidase activities) and probiotic (phytase activity, survival to gastric and pancreatic digestions) features of 12 yeast strains originally isolated from Greek natural black table olive fermentations. The multivariate classification analysis carried out with all information obtained (a total of 336 quantitative input data), revealed that the most promising strains (clearly discriminated from the rest of isolates) were Pichia guilliermondii Y16 (which showed overall the highest resistance to salt and simulated digestions) and Wickerhamomyces anomalus Y18 (with the overall highest technological enzymatic activities), while the rest of strains were grouped together in two clearly differentiated clusters. Thus, this work opens the possibility for the evaluation of these two selected yeasts as multifunctional starters, alone or in combination with lactic acid bacteria, in real table olive fermentations. PMID:25475268

  18. Natural selection constrains neutral diversity across a wide range of species.

    PubMed

    Corbett-Detig, Russell B; Hartl, Daniel L; Sackton, Timothy B

    2015-04-01

    The neutral theory of molecular evolution predicts that the amount of neutral polymorphisms within a species will increase proportionally with the census population size (Nc). However, this prediction has not been borne out in practice: while the range of Nc spans many orders of magnitude, levels of genetic diversity within species fall in a comparatively narrow range. Although theoretical arguments have invoked the increased efficacy of natural selection in larger populations to explain this discrepancy, few direct empirical tests of this hypothesis have been conducted. In this work, we provide a direct test of this hypothesis using population genomic data from a wide range of taxonomically diverse species. To do this, we relied on the fact that the impact of natural selection on linked neutral diversity depends on the local recombinational environment. In regions of relatively low recombination, selected variants affect more neutral sites through linkage, and the resulting correlation between recombination and polymorphism allows a quantitative assessment of the magnitude of the impact of selection on linked neutral diversity. By comparing whole genome polymorphism data and genetic maps using a coalescent modeling framework, we estimate the degree to which natural selection reduces linked neutral diversity for 40 species of obligately sexual eukaryotes. We then show that the magnitude of the impact of natural selection is positively correlated with Nc, based on body size and species range as proxies for census population size. These results demonstrate that natural selection removes more variation at linked neutral sites in species with large Nc than those with small Nc and provides direct empirical evidence that natural selection constrains levels of neutral genetic diversity across many species. This implies that natural selection may provide an explanation for this longstanding paradox of population genetics. PMID:25859758

  19. Natural Selection Constrains Neutral Diversity across A Wide Range of Species

    PubMed Central

    Corbett-Detig, Russell B.; Hartl, Daniel L.; Sackton, Timothy B.

    2015-01-01

    The neutral theory of molecular evolution predicts that the amount of neutral polymorphisms within a species will increase proportionally with the census population size (Nc). However, this prediction has not been borne out in practice: while the range of Nc spans many orders of magnitude, levels of genetic diversity within species fall in a comparatively narrow range. Although theoretical arguments have invoked the increased efficacy of natural selection in larger populations to explain this discrepancy, few direct empirical tests of this hypothesis have been conducted. In this work, we provide a direct test of this hypothesis using population genomic data from a wide range of taxonomically diverse species. To do this, we relied on the fact that the impact of natural selection on linked neutral diversity depends on the local recombinational environment. In regions of relatively low recombination, selected variants affect more neutral sites through linkage, and the resulting correlation between recombination and polymorphism allows a quantitative assessment of the magnitude of the impact of selection on linked neutral diversity. By comparing whole genome polymorphism data and genetic maps using a coalescent modeling framework, we estimate the degree to which natural selection reduces linked neutral diversity for 40 species of obligately sexual eukaryotes. We then show that the magnitude of the impact of natural selection is positively correlated with Nc, based on body size and species range as proxies for census population size. These results demonstrate that natural selection removes more variation at linked neutral sites in species with large Nc than those with small Nc and provides direct empirical evidence that natural selection constrains levels of neutral genetic diversity across many species. This implies that natural selection may provide an explanation for this longstanding paradox of population genetics. PMID:25859758

  20. Estimating selection through male fitness: three complementary methods illuminate the nature and causes of selection on flowering time.

    PubMed

    Austen, Emily J; Weis, Arthur E

    2016-02-24

    Our understanding of selection through male fitness is limited by the resource demands and indirect nature of the best available genetic techniques. Applying complementary, independent approaches to this problem can help clarify evolution through male function. We applied three methods to estimate selection on flowering time through male fitness in experimental populations of the annual plant Brassica rapa: (i) an analysis of mating opportunity based on flower production schedules, (ii) genetic paternity analysis, and (iii) a novel approach based on principles of experimental evolution. Selection differentials estimated by the first method disagreed with those estimated by the other two, indicating that mating opportunity was not the principal driver of selection on flowering time. The genetic and experimental evolution methods exhibited striking agreement overall, but a slight discrepancy between the two suggested that negative environmental covariance between age at flowering and male fitness may have contributed to phenotypic selection. Together, the three methods enriched our understanding of selection on flowering time, from mating opportunity to phenotypic selection to evolutionary response. The novel experimental evolution method may provide a means of examining selection through male fitness when genetic paternity analysis is not possible. PMID:26911957

  1. Natural hazard management high education: laboratory of hydrologic and hydraulic risk management and applied geomorphology

    NASA Astrophysics Data System (ADS)

    Giosa, L.; Margiotta, M. R.; Sdao, F.; Sole, A.; Albano, R.; Cappa, G.; Giammatteo, C.; Pagliuca, R.; Piccolo, G.; Statuto, D.

    2009-04-01

    The Environmental Engineering Faculty of University of Basilicata have higher-level course for students in the field of natural hazard. The curriculum provides expertise in the field of prediction, prevention and management of earthquake risk, hydrologic-hydraulic risk, and geomorphological risk. These skills will contribute to the training of specialists, as well as having a thorough knowledge of the genesis and the phenomenology of natural risks, know how to interpret, evaluate and monitor the dynamic of environment and of territory. In addition to basic training in the fields of mathematics and physics, the course of study provides specific lessons relating to seismic and structural dynamics of land, environmental and computational hydraulics, hydrology and applied hydrogeology. In particular in this course there are organized two connected examination arguments: Laboratory of hydrologic and hydraulic risk management and Applied geomorphology. These course foresee the development and resolution of natural hazard problems through the study of a real natural disaster. In the last year, the work project has regarded the collapse of two decantation basins of fluorspar, extracted from some mines in Stava Valley, 19 July 1985, northern Italy. During the development of the course, data and event information has been collected, a guided tour to the places of the disaster has been organized, and finally the application of mathematical models to simulate the disaster and analysis of the results has been carried out. The student work has been presented in a public workshop.

  2. Chemical composition of selected core samples, Idaho National Engineering Laboratory, Idaho

    SciTech Connect

    Knobel, L.L.; Cecil, L.D.; Wood, T.R.

    1995-11-01

    This report presents chemical compositions determined from 84 subsamples and 5 quality-assurance split subsamples of basalt core from the eastern Snake River Plain. The 84 subsamples were collected at selected depths from 5 coreholes located on the Idaho National Engineering Laboratory, Idaho. This report was jointly prepared by Lockheed Idaho Technologies Company and the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, Idaho Operations Office. Ten major elements and as many as 32 trace elements were determined for each subsample either by wavelength dispersive X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, or by both methods. Descriptive statistics for each element were calculated and tabulated by analytical method for each corehole.

  3. Mobile laboratory measurements of atmospheric emissions from agriculture, oil, and natural gas activities in northeastern Colorado

    NASA Astrophysics Data System (ADS)

    Eilerman, S. J.; Peischl, J.; Neuman, J. A.; Ryerson, T. B.; Wild, R. J.; Perring, A. E.; Brown, S. S.; Aikin, K. C.; Holloway, M.; Roberts, O.

    2014-12-01

    Atmospheric emissions from agriculture are important to air quality and climate, yet their representation in inventories is incomplete. Increased fertilizer use has lead to increased emissions of nitrogen compounds, which can adversely affect ecosystems and contribute to the formation of fine particulates. Furthermore, extraction and processing of oil and natural gas continues to expand throughout northeastern Colorado; emissions from these operations require ongoing measurement and characterization. This presentation summarizes initial data and analysis from a summer 2014 campaign to study emissions of nitrogen compounds, methane, and other species in northeastern Colorado using a new mobile laboratory. A van was instrumented to measure NH3, N2O, NOx, NOy, CH4, CO, CO2, O3, and bioaerosols with high time resolution. By sampling in close proximity to a variety of emissions sources, the mobile laboratory facilitated accurate source identification and quantification of emissions ratios. Measurements were obtained near agricultural sites, natural gas and oil operations, and other point sources. Additionally, extensive measurements were obtained downwind from urban areas and along roadways. The relationship between ammonia and other trace gases is used to characterize sources and constrain emissions inventories.

  4. Composition of Bacterial Communities Associated with Natural and Laboratory Populations of Asobara tabida Infected with Wolbachia? †

    PubMed Central

    Zouache, Karima; Voronin, Denis; Tran-Van, Van; Mavingui, Patrick

    2009-01-01

    Asobara tabida wasps are fly endoparasitoids that naturally harbor three Wolbachia strains, which induce cytoplasmic incompatibility and control oogenesis. To investigate whether other bacteria play a role in wasp biology, we surveyed the bacterial communities of wild A. tabida populations originating from different regions of France and of laboratory colonies using PCR-denaturing gradient gel electrophoresis and culture methods. Proteobacteria and Firmicutes were found to be the main phyla represented in these populations. Among these were several cultured and uncultured representatives of the genera Acetobacter, Acidomonas, Bacillus, Brevibacillus, Duganella, Herbaspirillum, Pseudomonas, Staphylococcus, and Streptococcus. In addition to Wolbachia, wild individuals harbored Rickettsia, which tended to be lost when insects were reared in the laboratory. The antibiotic treatment used to generate wasp sublines singly infected with Wolbachia also affected the overall bacterial composition, with most fingerprint sequences being characteristic of the family Enterobacteriaceae. We also screened for potentially heritable endosymbionts by PCR and fluorescence in situ hybridization in stable laboratory lines, with only Wolbachia being consistently found in wasp ovaries. PMID:19376923

  5. From nature to the laboratory: the impact of founder effects on adaptation.

    PubMed

    Santos, J; Pascual, M; Simões, P; Fragata, I; Lima, M; Kellen, B; Santos, M; Marques, A; Rose, M R; Matos, M

    2012-12-01

    Most founding events entail a reduction in population size, which in turn leads to genetic drift effects that can deplete alleles. Besides reducing neutral genetic variability, founder effects can in principle shift additive genetic variance for phenotypes that underlie fitness. This could then lead to different rates of adaptation among populations that have undergone a population size bottleneck as well as an environmental change, even when these populations have a common evolutionary history. Thus, theory suggests that there should be an association between observable genetic variability for both neutral markers and phenotypes related to fitness. Here, we test this scenario by monitoring the early evolutionary dynamics of six laboratory foundations derived from founders taken from the same source natural population of Drosophila subobscura. Each foundation was in turn three-fold replicated. During their first few generations, these six foundations showed an abrupt increase in their genetic differentiation, within and between foundations. The eighteen populations that were monitored also differed in their patterns of phenotypic adaptation according to their immediately ancestral founding sample. Differences in early genetic variability and in effective population size were found to predict differences in the rate of adaptation during the first 21 generations of laboratory evolution. We show that evolution in a novel environment is strongly contingent not only on the initial composition of a newly founded population but also on the stochastic changes that occur during the first generations of colonization. Such effects make laboratory populations poor guides to the evolutionary genetic properties of their ancestral wild populations. PMID:23110657

  6. The Effectiveness of Selective and Non-Selective Schools: An Experiment of Nature.

    ERIC Educational Resources Information Center

    Reynolds, David

    Comprehensive or nonselective schools have been in existence in the United Kingdom for over 40 years, having gradually replaced the old selective system of grammar schools for able pupils and secondary modern schools for less able pupils. In spite of their growth in numbers, comprehensive schools have been subject to continual controversy, and…

  7. Response to selection under controlled environment versus natural selection in diverse regions across Canada

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Red clover is a widely adaptable and productive forage legume species found in most temperate regions of the world. To date, specific selection techniques for identifying genotypes with superior persistence have not been successful in improving the general adaptation and the long-term persistence o...

  8. The Nature of Selection and Judging for the Teacher of the Year Award.

    ERIC Educational Resources Information Center

    McKenna, Bonnie; And Others

    This paper reports on the investigation of the operation of the Teacher of the Year Award program in 28 states. It focuses on the method of selection for recipients of this award, and explores the nature of the judging process used in selecting candidates at both the state and national levels. Specific objectives are: (1) to determine the criteria…

  9. The Nature of Selection and Judging for the Teacher of the Year Award.

    ERIC Educational Resources Information Center

    McKenna, Bonnie; And Others

    This paper reports on the investigation of the operation of the Teacher of the Year Award program in 28 states. It focuses on the method of selection for recipients of this award, and explores the nature of the judging process used in selecting candidates at both the state and national levels. Specific objectives are: (1) to determine the criteria…

  10. Comment on "Bateman in nature: predation on offspring reduces the potential for sexual selection".

    PubMed

    Arnqvist, Göran

    2013-05-01

    Byers and Dunn (Reports, 9 November 2012, p. 802) reported that sexual selection and natural selection are closely related in a wild population of pronghorns. Here, I argue that this conclusion is incorrect. Their main finding is due to the fact that, unsurprisingly, juvenile mortality and juvenile survival are negatively related across years. PMID:23641095

  11. Rational selection of structurally diverse natural product scaffolds with favorable ADME properties for drug discovery.

    PubMed

    Samiulla, D S; Vaidyanathan, V V; Arun, P C; Balan, G; Blaze, M; Bondre, S; Chandrasekhar, G; Gadakh, A; Kumar, R; Kharvi, G; Kim, H O; Kumar, S; Malikayil, J A; Moger, M; Mone, M K; Nagarjuna, P; Ogbu, C; Pendhalkar, D; Rao, A V S Raja; Rao, G Venkateshwar; Sarma, V K; Shaik, S; Sharma, G V R; Singh, S; Sreedhar, C; Sonawane, R; Timmanna, U; Hardy, L W

    2005-01-01

    Natural product analogs are significant sources for therapeutic agents. To capitalize efficiently on the effective features of naturally occurring substances, a natural product-based library production platform has been devised at Aurigene for drug lead discovery. This approach combines the attractive biological and physicochemical properties of natural product scaffolds, provided by eons of natural selection, with the chemical diversity available from parallel synthetic methods. Virtual property analysis, using computational methods described here, guides the selection of a set of natural product scaffolds that are both structurally diverse and likely to have favorable pharmacokinetic properties. The experimental characterization of several in vitro ADME properties of twenty of these scaffolds, and of a small set of designed congeners based upon one scaffold, is also described. These data confirm that most of the scaffolds and the designed library members have properties favorable to their utilization for creating libraries of lead-like molecules. PMID:15789560

  12. From Ends to Causes (and Back Again) by Metaphor: The Paradox of Natural Selection

    ERIC Educational Resources Information Center

    Blancke, Stefaan; Schellens, Tammy; Soetaert, Ronald; Van Keer, Hilde; Braeckman, Johan

    2014-01-01

    Natural selection is one of the most famous metaphors in the history of science. Charles Darwin used the metaphor and the underlying analogy to frame his ideas about evolution and its main driving mechanism into a full-fledged theory. Because the metaphor turned out to be such a powerful epistemic tool, Darwin naturally assumed that he could also…

  13. From Ends to Causes (and Back Again) by Metaphor: The Paradox of Natural Selection

    ERIC Educational Resources Information Center

    Blancke, Stefaan; Schellens, Tammy; Soetaert, Ronald; Van Keer, Hilde; Braeckman, Johan

    2014-01-01

    Natural selection is one of the most famous metaphors in the history of science. Charles Darwin used the metaphor and the underlying analogy to frame his ideas about evolution and its main driving mechanism into a full-fledged theory. Because the metaphor turned out to be such a powerful epistemic tool, Darwin naturally assumed that he could also…

  14. SELECTIVE NOx RECIRCULATION FOR STATIONARY LEAN-BURN NATURAL GAS ENGINES

    SciTech Connect

    Nigel Clark; Gregory Thompson; Richard Atkinson; Chamila Tissera; Matt Swartz; Emre Tatli; Ramprabhu Vellaisamy

    2005-01-01

    The research program conducted at the West Virginia University Engine and Emissions Research Laboratory (EERL) is working towards the verification and optimization of an approach to remove nitric oxides from the exhaust gas of lean burn natural gas engines. This project was sponsored by the US Department of Energy, National Energy Technology Laboratory (NETL) under contract number: DE-FC26-02NT41608. Selective NOx Recirculation (SNR) involves three main steps. First, NOx is adsorbed from the exhaust stream, followed by periodic desorption from the aftertreatment medium. Finally the desorbed NOx is passed back into the intake air stream and fed into the engine, where a percentage of the NOx is decomposed. This reporting period focuses on the NOx decomposition capability in the combustion process. Although researchers have demonstrated NOx reduction with SNR in other contexts, the proposed program is needed to further understand the process as it applies to lean burn natural gas engines. SNR is in support of the Department of Energy goal of enabling future use of environmentally acceptable reciprocating natural gas engines through NOx reduction under 0.1 g/bhp-hr. The study of decomposition of oxides of nitrogen (NOx) during combustion in the cylinder was conducted on a 1993 Cummins L10G 240 hp lean burn natural gas engine. The engine was operated at different air/fuel ratios, and at a speed of 800 rpm to mimic a larger bore engine. A full scale dilution tunnel and analyzers capable of measuring NOx, CO{sub 2}, CO, HC concentrations were used to characterize the exhaust gas. Commercially available nitric oxide (NO) was used to mimic the NOx stream from the desorption process through a mass flow controller and an injection nozzle. The same quantity of NOx was injected into the intake and exhaust line of the engine for 20 seconds at various steady state engine operating points. NOx decomposition rates were obtained by averaging the peak values at each set point minus the baseline and finding the ratio between the injected NO amounts. It was observed that the air/fuel ratio, injected NO quantity and engine operating points affected the NOx decomposition rates of the natural gas engine. A highest NOx decomposition rate of 27% was measured from this engine. A separate exploratory tests conducted with a gasoline engine with a low air/fuel ratio yielded results that suggested, that high NOx decomposition rates may be possible if a normally lean burn engine were operated at conditions closer to stoichiometric, with high exhaust gas recirculation (EGR) for a brief period of time during the NOx decomposition phase and with a wider range of air/fuel ratios. Chemical kinetic model predictions using CHEMKIN were performed to relate the experimental data with the established rate and equilibrium models. NOx decomposition rates from 35% to 42% were estimated using the CHEMKIN software. This provided insight on how to maximize NOx decomposition rates for a large bore engine. In the future, the modeling will be used to examine the effect of higher NO{sub 2}/NO ratios that are associated with lower speed and larger bore lean burn operation.

  15. Evaluation of Cavity Collapse and Surface Crater Formation for Selected Lawrence Livermore National Laboratory Tests - 2011

    SciTech Connect

    Pawloski, G A

    2011-02-28

    This report evaluates collapse evolution for selected Lawrence Livermore National Laboratory (LLNL) underground nuclear tests at the Nevada National Security Site (NNSS, formerly called the Nevada Test Site). The work is being done at the request of National Security Technologies, LLC (NSTec) and supports the Department of Energy, National Nuclear Security Administration for the Nevada Site Office Borehole Management Program (BMP). The primary objective of this program is to close (plug) weapons program legacy boreholes that are deemed no longer useful. Safety decisions must be made before a crater area, or potential crater area, can be reentered for any work. Our statements on cavity collapse and crater formation are input into their safety decisions. The BMP is an on-going program to address hundreds of boreholes at the NTS. Each year NSTec establishes a list of holes to be addressed. They request the assistance of the Lawrence Livermore National Laboratory and Los Alamos National Laboratory Containment Programs to provide information related to the evolution of collapse history and make statements on completeness of collapse as relates to surface crater stability. These statements do not include the effects of erosion that may modify the collapse craters over time. They also do not address possible radiation dangers that may be present. Subject matter experts from the LLNL Containment Program who had been active in weapons testing activities performed these evaluations. Information used included drilling and hole construction, emplacement and stemming, timing and sequence of the selected test and nearby tests, geology, yield, depth of burial, collapse times, surface crater sizes, cavity and crater volume estimations, ground motion, and radiological release information. Both classified and unclassified data were reviewed. Various amounts of information are available for these tests, depending on their age and other associated activities. Lack of data can hamper evaluations and introduce uncertainty. We make no attempt to quantify this uncertainty. The following unclassified summary statements describe collapse evolution and crater stability in response to a recent request to review 3 LLNL test locations in areas 2 and 12: Kennebec in U2af, Cumberland in U2e, and Yuba in U12b.10.

  16. Gas detection and migration in geological media: lessons learned from the Roselend Natural Laboratory (Invited)

    NASA Astrophysics Data System (ADS)

    Pili, E.; Guillon, S.; Agrinier, P.; Sabroux, J.; Adler, P. M.

    2013-12-01

    The Roselend Natural Laboratory (French Alps) is a unique facility for studying gas transport in the subsurface and across the geosphere-atmosphere interface. At 55 m depth, a sealed cavity allows for gas release experiments across fractured porous rocks in the unsaturated zone. While many parameters controlling the state of the geological system are known, analogous gas-tracer experiments were conducted at the field-scale with SF6 and 3He. Water infiltration, permeability and the concentrations of many gases, naturally occurring or injected, are recorded via long-term and high-resolution monitoring. The fracture network is characterized thanks to extensive drilling, logging and modeling. These experiments are used to determine the physical and chemical processes that would control the noble gas source term after an underground nuclear explosion in the framework of the Comprehensive nuclear-Test-Ban Treaty (CTBT) and to develop and validate the corresponding numerical models. The Roselend Natural Laboratory also provides a test bed for sampling protocols and instrument developments. Detection of gases relevant to CTBT issues requires that their baseline concentration is understood. Experiments and subsequent modeling demonstrated that baselines are a highly dynamical process resulting from gas sources, sinks and modulation by barometric pressure and water movements. Gas migration from underground cavities occurs as early venting through fractures due to advection driven by gas overpressure. It is associated with very large dilution which requires very low detection limits. Late-time seepage occurs through fractured porous media thanks to barometric pumping, which is only efficient for a narrow window of parameter values. Full calculation for real fractured porous media is now available.

  17. Natural selection reduces energy metabolism in the garden snail, helix aspersa (cornu aspersum).

    PubMed

    Artacho, Paulina; Nespolo, Roberto F

    2009-04-01

    Phenotypic selection is widely recognized as the primary cause of adaptive evolution in natural populations, a fact that has been documented frequently over the last few decades, mainly in morphological and life-history traits. The energetic definition of fitness predicts that natural selection will maximize the residual energy available for growth and reproduction, suggesting that energy metabolism could be a target of selection. To address this problem, we chose the garden snail, Helix aspersa (Cornu aspersum). We performed a seminatural experiment for measuring phenotypic selection on standard metabolic rate (SMR), the minimum cost of maintenance in ectotherm organisms. To discount selection on correlated traits, we included two additional whole-organism performance traits (mean speed and maximum force of dislodgement). We found a combination of linear (negative directional selection, beta=-0.106 +/- 0.06; P= 0.001) and quadratic (stabilizing selection, gamma=-0.012 +/- 0.033; P= 0.061) selection on SMR. Correlational selection was not significant for any possible pair of traits. This suggests that individuals with average-to-reduced SMRs were promoted by selection. To the best of our knowledge, this is the first study showing significant directional selection on the obligatory cost of maintenance in an animal, providing support for the energetic definition of fitness. PMID:19236475

  18. Natural selection affects multiple aspects of genetic variation at putatively neutral sites across the human genome.

    PubMed

    Lohmueller, Kirk E; Albrechtsen, Anders; Li, Yingrui; Kim, Su Yeon; Korneliussen, Thorfinn; Vinckenbosch, Nicolas; Tian, Geng; Huerta-Sanchez, Emilia; Feder, Alison F; Grarup, Niels; Jørgensen, Torben; Jiang, Tao; Witte, Daniel R; Sandbæk, Annelli; Hellmann, Ines; Lauritzen, Torsten; Hansen, Torben; Pedersen, Oluf; Wang, Jun; Nielsen, Rasmus

    2011-10-01

    A major question in evolutionary biology is how natural selection has shaped patterns of genetic variation across the human genome. Previous work has documented a reduction in genetic diversity in regions of the genome with low recombination rates. However, it is unclear whether other summaries of genetic variation, like allele frequencies, are also correlated with recombination rate and whether these correlations can be explained solely by negative selection against deleterious mutations or whether positive selection acting on favorable alleles is also required. Here we attempt to address these questions by analyzing three different genome-wide resequencing datasets from European individuals. We document several significant correlations between different genomic features. In particular, we find that average minor allele frequency and diversity are reduced in regions of low recombination and that human diversity, human-chimp divergence, and average minor allele frequency are reduced near genes. Population genetic simulations show that either positive natural selection acting on favorable mutations or negative natural selection acting against deleterious mutations can explain these correlations. However, models with strong positive selection on nonsynonymous mutations and little negative selection predict a stronger negative correlation between neutral diversity and nonsynonymous divergence than observed in the actual data, supporting the importance of negative, rather than positive, selection throughout the genome. Further, we show that the widespread presence of weakly deleterious alleles, rather than a small number of strongly positively selected mutations, is responsible for the correlation between neutral genetic diversity and recombination rate. This work suggests that natural selection has affected multiple aspects of linked neutral variation throughout the human genome and that positive selection is not required to explain these observations. PMID:22022285

  19. Darwin's principles of divergence and natural selection: Why Fodor was almost right.

    PubMed

    Richards, Robert J

    2012-03-01

    Darwin maintained that the principles of natural selection and divergence were the "keystones" of his theory. He introduced the principle of divergence to explain a fundamental feature of living nature: that organisms cluster into hierarchical groups, so as to be classifiable in the Linnaean taxonomic categories of variety, species, genus, and so on. Darwin's formulation of the principle of divergence, however, induces many perplexities. In his Autobiography, he claimed that he had neglected the problem of divergence in his Essay of 1844 and only solved it in a flash during a carriage ride in the 1850s; yet he does seem to have stated the problem in the Essay and provided the solution. This initial conundrum sets three questions I wish to pursue in this essay: (1) What is the relationship of the principle of divergence to that of natural selection? Is it independent of selection, derivative of selection, or a type of selection, perhaps comparable to sexual selection? (2) What is the advantage of divergence that the principle implies-that is, why is increased divergence beneficial in the struggle for life? And (3) What led Darwin to believe he had discovered the principle only in the 1850s? The resolution of these questions has implications for Darwin's other principle, natural selection, and permits us to readjust the common judgment made about Jerry Fodor's screed against that latter principle. PMID:22326095

  20. The build up of mutation-selection- drift balance in laboratory Drosophila populations.

    PubMed

    García-Dorado, Aurora; Avila, Victoria; Sánchez-Molano, Enrique; Manrique, Antonio; López-Fanjul, Carlos

    2007-03-01

    The build up of an equilibrium between mutation, selection, and drift in populations of moderate size is an important evolutionary issue, and can be critical in the conservation of endangered populations. We studied this process in two Drosophila melanogaster populations initially lacking genetic variability (C1 and C2) that were subsequently maintained during 431 or 165 generations with effective population size N(e) approximately 500 (estimated by lethal complementation analysis). Each population originated synchronously to a companion set of full-sib mutation accumulation (MA) lines, C1 and MA1 were derived from an isogenic origin and C2 and MA2 from a single MA1 line at generation 265. The results suggest that both C1 and C2 populations were close to the mutation-selection-drift balance for viability and bristle traits, and are consistent with a 2.5-fold increase of the mutation rate in C2 and MA2. Despite this increase, the average panmictic viability in C2 was only slightly below that of C1, indicating that the expressed loads due to segregating deleterious mutation were small, in agreement with the low deleterious mutation rate (0.015-0.045) previously reported for the MA1 lines. In C1, the nonlethal inbreeding depression rate for viability was 30% of that usually estimated in segregating populations. The genetic variance for bristles regenerated in C1 and C2 was moderately smaller than the average value reported for natural populations, implying that they have accumulated a substantial adaptive potential. In light of neutral and selective predictions, these results suggest that bristle additive variance was predominantly due to segregation of mutations with deleterious effects of the order of 10(-3), and is consistent with relatively weak causal stabilizing selection (V(s) approximately 30). PMID:17348928

  1. A highly selective biosynthetic pathway to non-natural C50 carotenoids assembled from moderately selective enzymes

    PubMed Central

    Furubayashi, Maiko; Ikezumi, Mayu; Takaichi, Shinichi; Maoka, Takashi; Hemmi, Hisashi; Ogawa, Takuya; Saito, Kyoichi; Tobias, Alexander V; Umeno, Daisuke

    2015-01-01

    Synthetic biology aspires to construct natural and non-natural pathways to useful compounds. However, pathways that rely on multiple promiscuous enzymes may branch, which might preclude selective production of the target compound. Here, we describe the assembly of a six-enzyme pathway in Escherichia coli for the synthesis of C50-astaxanthin, a non-natural purple carotenoid. We show that by judicious matching of engineered size-selectivity variants of the first two enzymes in the pathway, farnesyl diphosphate synthase (FDS) and carotenoid synthase (CrtM), branching and the production of non-target compounds can be suppressed, enriching the proportion of C50 backbones produced. We then further extend the C50 pathway using evolved or wild-type downstream enzymes. Despite not containing any substrate- or product-specific enzymes, the resulting pathway detectably produces only C50 carotenoids, including ?90% C50-astaxanthin. Using this approach, highly selective pathways can be engineered without developing absolutely specific enzymes. PMID:26168783

  2. Natural Selection

    ERIC Educational Resources Information Center

    Hall, Julie

    2006-01-01

    For education administrators, summer break is the time to regroup and prepare facilities for the next influx of students. Ensuring that facilities are equipped with proper furnishings is part of this preparation. Through careful research and planning, education administrators can choose furniture that will become a lasting investment. This article…

  3. Natural Selection

    ERIC Educational Resources Information Center

    Hall, Julie

    2006-01-01

    For education administrators, summer break is the time to regroup and prepare facilities for the next influx of students. Ensuring that facilities are equipped with proper furnishings is part of this preparation. Through careful research and planning, education administrators can choose furniture that will become a lasting investment. This article…

  4. Assessing drug-induced dyskinesia in the clinic, the laboratory and the natural environment of patients.

    PubMed

    Carignan, Benoit; Daneault, Jean-François; Duval, Christian

    2011-01-01

    The assessment of drug-induced dyskinesia (DID) in Parkinson's disease represents a formidable challenge for clinicians and researchers alike. The present review describes the current assessment tools used in the clinic, where different scales have been developed for monitoring levels of DID in patients. We also review laboratory tools used to assess the quantity and characteristics of DID. Finally, we review assessment methods currently in development for monitoring DID and voluntary mobility in the natural living environment of patients. Here, we discuss the strengths and weaknesses of these tools as it pertains to their efficacy in assessing the quantity of DID, its characteristics, as well as its impact on the quality of life of patients. Finally, we discuss ongoing challenges and research questions that may guide future development of assessment methods aimed at monitoring DID and its impact on daily lives of patients. PMID:23939342

  5. Laser system for natural gas detection. Phase 1: Laboratory feasibility studies

    NASA Technical Reports Server (NTRS)

    Grant, W. B.; Hinkley, E. D., Jr.

    1982-01-01

    This project demonstrated the feasibility of using laser remote sensing technology as a tool for leak survey work in natural gas distribution systems. A laboratory device was assembled using a pair of helium neon (HeNe) lasers to measure methane. One HeNe laser emits radiation at a wavelength of 3.3922 micrometers, which corresponds to a strong absorption feature of methane, while the other emits radiation at a wavelength of 3.3911 micrometers, which corresponds to a weak absorption by methane. As a particular area is scanned for leaks, the laser is pointed at convenient topographic targets within its operating range, about 25 m. A portion of the backscattered radiation is collected by a receiver and focused onto an indium antimonide (InSb) photodetector, cooled to 77K. Methane concentrations were determined from the differential absorption at the two wavelengths for the backscattered radiation.

  6. 3D Magnetic Reconnection and Turbulence Study on Natural and Laboratory Plasmas at RSX

    NASA Astrophysics Data System (ADS)

    Liu, D. T.; Intrator, T. P.; Weber, T. E.; Sears, J. A.; Adams, C. S.; Los Alamos Nat'l Lab Team

    2011-10-01

    In natural and laboratory plasmas, magnetic reconnection and turbulence are difficult 3-dimensional problems and data from the Reconnection Scaling Experiment (RSX) can help address these questions. The data from RSX are fully 3D (no symmetries)and capture the unsteady, dynamic plasma physics of colliding flux ropes that reconnect and form turbulent modes. Data obtained from RSX via B-dot and triple Langmuir probes will be used to determine the time-integrated magnetic field, plasma density, floating potential, and electrostatic field. Additionally, there exist related reconnection and turbulence data from spacecraft that must be downloaded and distilled from large, cumbersome datasets, a process hampered by low telemetry rates. Simulated spacecraft trajectories through the RSX datasets provide insight for data acquisition, analysis, and download aboard spacecraft missions. Supported by US DOE OFES under a National Undergraduate Fellowship, DE-AC52-06NA25396 and NASA grant NNH10A044.

  7. Astrophysical Black Holes as Natural Laboratories for Fundamental Physics and Strong-Field Gravity

    NASA Astrophysics Data System (ADS)

    Berti, Emanuele

    2013-12-01

    Astrophysical tests of general relativity belong to two categories: 1) "internal", i.e. consistency tests within the theory (for example, tests that astrophysical black holes are indeed described by the Kerr solution and its perturbations), or 2) "external", i.e. tests of the many proposed extensions of the theory. I review some ways in which astrophysical black holes can be used as natural laboratories for both "internal" and "external" tests of general relativity. The examples provided here (ringdown tests of the black hole "no-hair" theorem, bosonic superradiant instabilities in rotating black holes and gravitational-wave tests of massive scalar-tensor theories) are shamelessly biased towards recent research by myself and my collaborators. Hopefully this colloquial introduction aimed mainly at astrophysicists will convince skeptics (if there are any) that space-based detectors will be crucial to study fundamental physics through gravitational-wave observations.

  8. Natural selection on quantitative immune defence traits: a comparison between theory and data.

    PubMed

    Seppälä, O

    2015-01-01

    Parasites present a threat for free-living species and affect several ecological and evolutionary processes. Immune defence is the main physiological barrier against infections, and understanding its evolution is central for predicting disease dynamics. I review theoretical predictions and empirical data on natural selection on quantitative immune defence traits in the wild. Evolutionary theory predicts immune traits to be under stabilizing selection owing to trade-offs between immune function and life-history traits. Empirical data, however, support mainly positive directional selection, but also show variation in the form of selection among study systems, immune traits and fitness components. I argue that the differences between theory and empirical data may at least partly arise from methodological difficulties in testing stabilizing selection as well as measuring fitness. I also argue that the commonness of positive directional selection and the variation in selection may be caused by several biological factors. First, selection on immune function may show spatial and temporal variation as epidemics are often local/seasonal. Second, factors affecting the range of phenotypic variation in immune traits could alter potential for selection. Third, different parasites may impose different selective pressures depending on their characteristics. Fourth, condition dependence of immune defence can obscure trade-offs related to it, thus possibly modifying observed selection gradients. Fifth, nonimmunological defences could affect the form of selection by reducing the benefits of strong immune function. To comprehensively understand the evolution of immune defence, the role of above factors should be considered in future studies. PMID:25400248

  9. Darwin and his pigeons. The analogy between artificial and natural selection revisited.

    PubMed

    Theunissen, Bert

    2012-01-01

    The analogy between artificial selection of domestic varieties and natural selection in nature was a vital element of Darwin's argument in his Origin of Species. Ever since, the image of breeders creating new varieties by artificial selection has served as a convincing illustration of how the theory works. In this paper I argue that we need to reconsider our understanding of Darwin's analogy. Contrary to what is often assumed, nineteenth-century animal breeding practices constituted a highly controversial field that was fraught with difficulties. It was only with considerable effort that Darwin forged his analogy, and he only succeeded by downplaying the importance of two other breeding techniques - crossing of varieties and inbreeding - that many breeders deemed essential to obtain new varieties. Part of the explanation for Darwin's gloss on breeding practices, I shall argue, was that the methods of his main informants, the breeders of fancy pigeons, were not representative of what went on in the breeding world at large. Darwin seems to have been eager to take the pigeon fanciers at their word, however, as it was only their methods that provided him with the perfect analogy with natural selection. Thus while his studies of domestic varieties were important for the development of the concept of natural selection, the reverse was also true: Darwin's comprehension of breeding practices was moulded by his understanding of the working of natural selection in nature. Historical studies of domestic breeding practices in the eighteenth and nineteenth century confirm that, besides selection, the techniques of inbreeding and crossing were much more important than Darwin's interpretation allowed for. And they still are today. This calls for a reconsideration of the pedagogic use of Darwin's analogy too. PMID:22037999

  10. Earthquake nests as natural laboratories for the study of intermediate-depth earthquake mechanics

    NASA Astrophysics Data System (ADS)

    Prieto, Germán A.; Beroza, Gregory C.; Barrett, Sarah A.; López, Gabriel A.; Florez, Manuel

    2012-10-01

    The physical mechanism of intermediate-depth earthquakes is still under debate. In contrast to conditions in the crust and shallow lithosphere, at temperatures and pressures corresponding to depths > 50 km, rocks ought to yield by creep or flow rather than brittle failure. Some physical process has to enable brittle or brittle-like failure for intermediate-depth earthquakes. The two leading candidates for that are dehydration embrittlement and thermal shear runaway. Given their great depth, intermediate-depth earthquake processes can't be observed directly. Instead we must rely on a combination of seismology and the study of laboratory analogs to understand them. Earthquake nests are regions of highly concentrated seismicity that are isolated from nearby activity. In this paper we focus on three intermediate-depth earthquake nests - Vrancea, Hindu Kush and Bucaramanga, and what they reveal about the mechanics of intermediate-depth earthquakes. We review published studies of tectonic setting, focal mechanisms, precise earthquake locations and earthquake source physics at these locations, with an emphasis on the Bucaramanga nest. All three nests are associated with subducting lithosphere and at least two of the nests have consistently larger stress drops compared to shallow seismicity. In contrast, the Bucaramanga nest has a larger b-value, larger variability of focal mechanisms and shows no evidence of aftershock sequences unlike the other two. We also report for the first time finding a significant number of repeating earthquakes, some with reverse polarity. Given the nature and characteristics of earthquake nests, they can be thought as natural laboratories. Future seismological studies of intermediate-depth earthquakes in nests will likely enlighten our understanding of their physical mechanisms.

  11. Seismic and geodetic signatures of fault slip at the Slumgullion Landslide Natural Laboratory

    USGS Publications Warehouse

    Gomberg, J.; Schulz, W.; Bodin, P.; Kean, J.

    2011-01-01

    We tested the hypothesis that the Slumgullion landslide is a useful natural laboratory for observing fault slip, specifically that slip along its basal surface and side-bounding strike-slip faults occurs with comparable richness of aseismic and seismic modes as along crustal- and plate-scale boundaries. Our study provides new constraints on models governing landslide motion. We monitored landslide deformation with temporary deployments of a 29-element prism array surveyed by a robotic theodolite and an 88-station seismic network that complemented permanent extensometers and environmental instrumentation. Aseismic deformation observations show that large blocks of the landslide move steadily at approximately centimeters per day, possibly punctuated by variations of a few millimeters, while localized transient slip episodes of blocks less than a few tens of meters across occur frequently. We recorded a rich variety of seismic signals, nearly all of which originated outside the monitoring network boundaries or from the side-bounding strike-slip faults. The landslide basal surface beneath our seismic network likely slipped almost completely aseismically. Our results provide independent corroboration of previous inferences that dilatant strengthening along sections of the side-bounding strike-slip faults controls the overall landslide motion, acting as seismically radiating brakes that limit acceleration of the aseismically slipping basal surface. Dilatant strengthening has also been invoked in recent models of transient slip and tremor sources along crustal- and plate-scale faults suggesting that the landslide may indeed be a useful natural laboratory for testing predictions of specific mechanisms that control fault slip at all scales.

  12. In situ and laboratory toxicity of coalbed natural gas produced waters with elevated sodium bicarbonate

    USGS Publications Warehouse

    Farag, Aida M.; Harper, David D.; Skaar, Don

    2014-01-01

    Some tributaries in the Powder River Structural Basin, USA, were historically ephemeral, but now contain water year round as a result of discharge of coalbed natural gas (CBNG)-produced waters. This presented the opportunity to study field sites with 100% effluent water with elevated concentrations of sodium bicarbonate. In situ experiments, static renewal experiments performed simultaneously with in situ experiments, and static renewal experiments performed with site water in the laboratory demonstrated that CBNG-produced water reduces survival of fathead minnow (Pimephales promelas) and pallid sturgeon (Scaphirhynchus albus). Age affected survival of fathead minnow, where fish 2 d posthatch (dph) were more sensitive than 6 dph fish, but pallid sturgeon survival was adversely affected at both 4 and 6 dph. This may have implications for acute assays that allow for the use of fish up to 14 dph. The survival of early lifestage fish is reduced significantly in the field when concentrations of NaHCO3 rise to more than 1500 mg/L (also expressed as >1245 mg HCO3 (-) /L). Treatment with the Higgin's Loop technology and dilution of untreated water increased survival in the laboratory. The mixing zones of the 3 outfalls studied ranged from approximately 800 m to 1200 m below the confluence. These experiments addressed the acute toxicity of effluent waters but did not address issues related to the volumes of water that may be added to the watershed.

  13. Natural infection of murine norovirus in conventional and specific pathogen-free laboratory mice.

    PubMed

    Ohsugi, Takeo; Matsuura, Kumi; Kawabe, Satomi; Nakamura, Naoko; Kumar, Jerald M; Wakamiya, Makoto; Morikawa, Saki; Urano, Toru

    2013-01-01

    Noroviruses cause most cases of acute viral gastroenteritis worldwide. The lack of a cell culture infection model for human norovirus necessitates the use of molecular methods and/or viral surrogate models amenable to cell culture to predict norovirus inactivation. Murine norovirus (MNV) may be used to construct a small animal model for studying the biology and pathogenesis of noroviruses because MNV is the only norovirus that replicates in cell culture and a small animal model. However, recent studies have shown that natural MNV infection is widespread in laboratory mouse colonies. We investigated MNV infection in both conventional and specific pathogen-free (SPF) genetically modified mice from Japan and the US, and commercial mice from several animal breeders in Japan, using serological and molecular techniques. MNV antibodies were detected in 67.3% of conventional mice and 39.1% of SPF mice from Japan and 62.5% of conventional mice from the US. MNV antibodies were also found in 20% of commercial SPF C57BL/6 mice from one of three breeders. Partial gene amplification of fecal isolates from infected animals showed that the isolates were homologous to reported MNV sequences. These results suggest that both conventional and SPF laboratory mice, including commercial mice, are widely infected with MNV, which might require considerable attention as an animal model of human disease. PMID:23386847

  14. The sleep of the baboon, Papio papio, under natural conditions and in the laboratory.

    PubMed

    Bert, J; Balzamo, E; Chase, M; Pegram, V

    1975-12-01

    The sleep pattern of sixteen baboons (Papio papio) was studied under two very different conditions: (1) in a laboratory at Marseilles, the monkey being immobilized in a restraining chair in a soundproof cubicle; (2) in an African reserve, the monkey being housed in a large cage placed in its natural environment. Some very marked differences emerged. Sleep in the laboratory was longer (by 24 min) and richer in stage 3 and paradoxical sleep. In Africa, however, the sleep showed much more stage 1, was more fragmented and stages 2 and 3 and paradoxical sleep episodes were of shorter duration. Records made in Africa indicate that sleep is independent of slight environmental changes (day length, brightness of the moon, variations in temperature, calls of predators). But the comparison of the two series of results reveals the reorganization which occurs when the monkey is exposed to such different conditions. This adaptation to the environment affects, unequally, the various slow sleep stages and paradoxical sleep. In fact, the major modifications occur in stages 1 and 3 of slow sleep and in paradoxical sleep, while stage 2 appears to constitute the stable, unmodifiable nucleus of sleep. PMID:53145

  15. Improved laboratory test selection and enhanced perception of test results as tools for cost-effective medicine.

    PubMed

    Mayer, M; Wilkinson, I; Heikkinen, R; Orntoft, T; Magid, E

    1998-09-01

    Inconsistencies in the way physicians perceive and handle identical laboratory results have untoward effects on morbidity, mortality and cost of medical care. In this context, the selection of suitable tests to answer definite clinical questions, and the manner in which laboratory results are presented have great impact on the action taken by the clinician. This review addresses preferred methods to improve laboratory test selection, and examines methods that more effectively convey laboratory results to clinicians. It is anticipated that refined selection of tests, and presentation of the test results in a configuration that is easily perceived by the clinician, will facilitate interpretation of laboratory reports. Furthermore, any measures that promote the application of laboratory information in medical practice improve economics at the laboratory-clinical interface. The presently described methods to optimize test selection and interpretation are: likelihood ratios to provide estimates of the ability of a test to identify a clinical condition; consensus- and discriminant function-analysis to estimate the performance of tests in diagnosing a particular disease or condition; receiver operating characteristic (ROC) curves to assess discrimination capabilities. The methods which improve test result perception are expression of results as multiples of the upper normal limit, utilizing signal strength to provide prognostic probabilities, and presentation of results in graphic forms that display mutually interrelated functions, with a specific cluster of results being highly suggestive of a given condition. In addition, we discuss application of expert systems to provide rules based on knowledge and experience to analyze results of tests and suggest diagnosis and action, including additional tests when required. It is anticipated that judicious utilization of laboratory services by application of the reviewed methodologies will help to achieve medically justified responses at a lower cost and help to achieve a proper balance between cost of tests and their clinical usefulness. PMID:9804391

  16. Natural selection in a population group of Andaman and Nicobar Islands

    PubMed Central

    Kapoor, Anup K.; Kaur, Jaspreet

    2012-01-01

    Background: Natural selection is a continuous process that operates in populations to weed out deleterious genes and preserve the genes that increase the chances of survival, procreation, and multiplication. The fitness of a population group is measured in terms of its differential fertility and mortality. These are the most fundamental events through which the natural selection is operative. Selection intensity, which is a measure of the fitness of a population, is expressed in terms of differential fertility, and differential mortality, assuming that the heritability of fitness is complete and that the birth and death rates are all selective. These indices are influenced by a number of socio-cultural conditions, religious, ethnic, and environmental factors which have been studied by different researchers in different parts of the world, including India. Objective: In this paper, an attempt was made to study the index of total selection, index of selection due to mortality, and index of selection due to fertility among the Andaman Indians, an island population of Andaman and Nicobar Islands and we highlight the variability of selection intensity in different ecological zones of India, namely the island, coastal, plains and plateau, Himalayan region, and the desert ecologies. Materials and Methods: Data were collected on pre-designed questionnaire, from women aged 40 + years, on various demographic parameters. Results: The value of the Index of Total Selection was found to be 1.263, the component due to fertility was 1.020, and that of mortality was found to be 0.120 PMID:22690055

  17. Selection of an omnivorous diet by the mangrove tree crab Aratus pisonii in laboratory experiments

    NASA Astrophysics Data System (ADS)

    Erickson, Amy A.; Feller, Ilka C.; Paul, Valerie J.; Kwiatkowski, Lisa M.; Lee, Woody

    2008-02-01

    Observational studies on leaf damage, gut content analyses, and crab behaviour have demonstrated that like numerous other mangrove and salt-marsh generalists, the mangrove tree crab Aratus pisonii feeds on a variety of food resources. This study is the first that experimentally tests feeding preferences of A. pisonii, as well as the first to test experimentally whether chemical composition of food resources is responsible for food selection. Feeding preferences were determined among a variety of plant, algal, and animal resources available in the field both in Florida and Belize, using multiple-choice feeding assays, where male and female crabs simultaneously were offered a variety of food items. To test whether chemistry of food resources was responsible for feeding preferences, chemical extracts of food resources were incorporated in an agar-based artificial food, and used in feeding assays. Results of feeding assays suggest that crabs prefer animal matter from ˜ 2.5 to 13× more than other available resources, including leaves of the red mangrove Rhizophora mangle, which contribute the most to their natural diet. Artificial feeding assays also demonstrated that chemical cues were responsible for selection of animal matter, up to 25× more than other available resources. Non-polar extracts (derived from extraction in 1:1 ethyl actetate:methanol) stimulated feeding the most, suggesting that fatty acids, triglycerides, or sterols may be important for growth, reproduction, or survival. Results for both sexes were similar across most assays. While chemical composition of food resources appears to play some role in selection, this does not discount the potential role of other factors, such as resource availability, competition, predation, or reproductive requirements in influencing feeding preferences. Bioassay-guided fractionation of extracts should aid in determining chemical constituents that play the greatest role in determining feeding preferences.

  18. Selective Aptamers for Detection of Estradiol and Ethynylestradiol in Natural Waters.

    PubMed

    Akki, Spurti U; Werth, Charles J; Silverman, Scott K

    2015-08-18

    We used in vitro selection to identify new DNA aptamers for two endocrine-disrupting compounds often found in treated and natural waters, 17β-estradiol (E2) and 17α-ethynylestradiol (EE). We used equilibrium filtration to determine aptamer sensitivity/selectivity and dimethyl sulfate (DMS) probing to explore aptamer binding sites. The new E2 aptamers are at least 74-fold more sensitive for E2 than is a previously reported DNA aptamer, with dissociation constants (Kd values) of 0.6 μM. Similarly, the EE aptamers are highly sensitive for EE, with Kd of 0.5-1.0 μM. Selectivity values indicate that the E2 aptamers bind E2 and a structural analogue, estrone (E1), equally well and are up to 74-fold selective over EE. One EE aptamer is 53-fold more selective for EE over E2 or E1, but the other binds EE, E2, and E1 with similar affinity. The new aptamers do not lose sensitivity or selectivity in natural water from a local lake, despite the presence of natural organic matter (∼4 mg/L TOC). DMS probing suggests that E2 binding occurs in relatively flexible single-stranded DNA regions, an important finding for rational redesign of aptamers and their incorporation into sensing platforms. This is the first report of aptamers with strong selectivity for E2 and E1 over EE, or with strong selectivity for EE over E2 and E1. Such selectivity is important for achieving the goal of creating practically useful DNA-based sensors that can distinguish structurally similar estrogenic compounds in natural waters. PMID:26182235

  19. How relevant are house dust mite-fungal interactions in laboratory culture to the natural dust system?

    PubMed

    Hay, D B; Hart, B J; Pearce, R B; Kozakiewicz, Z; Douglas, A E

    1992-11-01

    Both house dust and house dust mites Dermatophagoides pteronyssinus contained a wider range of fungi than laboratory mite cultures. In total, nine species of fungi were isolated from D. pteronyssinus in house dust, and these included three xerophilic species (Eurotium amstelodami, Aspergillus penicillioides and Wallemia sebi) commonly found in laboratory cultures of D. pteronyssinus. It is concluded that mites do interact with a similar range of fungi in natural dust and in laboratory culture, but that the diversity of fungal species in the laboratory is reduced and the density of individual fungal species in culture exceeds that of house dust. In a second experiment, dust samples were incubated at room temperature with 75% relative humidity. The diversity of fungi invariably declined from up to 13 genera to the few species recorded in laboratory culture. This suggests that the dominance of xerophilic fungi in laboratory mite rearings is mediated primarily by low relative humidity, and the exclusion of air-borne spores. PMID:1493747

  20. Image statistics underlying natural texture selectivity of neurons in macaque V4

    PubMed Central

    Okazawa, Gouki; Tajima, Satohiro; Komatsu, Hidehiko

    2015-01-01

    Our daily visual experiences are inevitably linked to recognizing the rich variety of textures. However, how the brain encodes and differentiates a plethora of natural textures remains poorly understood. Here, we show that many neurons in macaque V4 selectively encode sparse combinations of higher-order image statistics to represent natural textures. We systematically explored neural selectivity in a high-dimensional texture space by combining texture synthesis and efficient-sampling techniques. This yielded parameterized models for individual texture-selective neurons. The models provided parsimonious but powerful predictors for each neuron’s preferred textures using a sparse combination of image statistics. As a whole population, the neuronal tuning was distributed in a way suitable for categorizing textures and quantitatively predicts human ability to discriminate textures. Together, we suggest that the collective representation of visual image statistics in V4 plays a key role in organizing the natural texture perception. PMID:25535362

  1. Natural attenuation of pharmaceuticals and an illicit drug in a laboratory column experiment.

    PubMed

    Greenhagen, Andrew M; Lenczewski, Melissa E; Carroll, Monica

    2014-11-01

    Trace amounts of pharmaceutical compounds have been detected in waters across the United States. Many compounds are released as the result of human ingestion and subsequent excretion of over-the-counter and prescription medications, and illicit drugs. This research utilized columns (30×30cm) of sand and undisturbed fine-grained sediments to simulate injection of wastewater containing pharmaceuticals and an illicit drug, such as would be found in a septic system, leaky sewer, or landfill. The columns were placed in a temperature-controlled laboratory and each was injected with natural groundwater containing known concentrations of caffeine, methamphetamine, and acetaminophen. Natural attenuation of each chemical was observed in all columns. The highest amount removed (approximately 90%) occurred in the undisturbed column injected with methamphetamine, compared with little reduction in the sand column. When the suite of drugs was injected, loss of methamphetamine was less than when methamphetamine was injected alone. The subsurface sediments exhibit the ability to remove a substantial amount of the injected pharmaceuticals and illicit drug; however, complete removal was not achieved. There was little attenuation of injected pharmaceuticals in the sand column which demonstrates a concern for water quality in the environment if pharmaceuticals were to contaminate a sandy aquifer. Understanding the transport of pharmaceuticals in the subsurface environment is an important component of protecting drinking water supplies from contamination. PMID:24594486

  2. Laboratory evaluation of engine ring wear under natural gas and gasoline operation. Topical report, November 1991

    SciTech Connect

    Treuhaft, M.B.; Buckingham, J.P.

    1991-11-01

    A series of laboratory tests to measure piston ring wear, on a real-time basis, as a function of engine operating conditions (speed, load, and coolant temperature) and oil type, are reported. Two types of tests were performed: one after converting a gasoline engine to run on natural gas, and the other while operating the same engine on gasoline. Piston ring wear was measured using radioactive tracer technology, whereby the small wear particles themselves are monitored as they abrade from the irradiated piston rings and accumulate in the lubrication system. The test data were statistically analyzed and examined on the basis of wear rate as calculated from the instantaneous data showing cumulative wear as a function of test time for a given set of operating conditions. Both independent and synergistic effects were examined. While it was statistically possible to compare wear rates with gasoline and its oil to those for natural gas and its oils, it was not possible to make a distinction with respect to fuel or oil type alone.

  3. Natural vertical transmission of dengue viruses in Aedes aegypti in selected sites in Cebu City, Philippines.

    PubMed

    Edillo, Frances E; Sarcos, Janet R; Sayson, Stephanie L

    2015-12-01

    We attempted to determine the vertical transmission of dengue virus (DENV) in Aedes aegypti in selected sites in Cebu City, Philippines. Mosquito sub-adults were collected monthly from households and the field during the wet-dry-wet season from November, 2011 to July, 2012 and were laboratory-reared to adults. Viral RNA extracts in mosquitoes were assayed by hemi-nested RT-PCR. Results showed that 62 (36.26%; n=679) out of 171 mosquito pools (n=2,871) were DENV+. The minimum infection rate (MIR) of DENV ranged from 0 in wet months to 48.22/1,000 mosquitoes in April, 2012 (mid-dry). DENVs were detected in larvae, pupae, and male and female adults, with DENV-4, DENV-3, and DENV-1, in that rank of prevalence. DENV-1 co-infected with either DENV-3 or -4 or with both in April, 2012; DENV-3 and -4 were present in both seasons. More DENV+ mosquitoes were collected from households than in field premises (p<0.001) and in the dry than in the wet season (p<0.05), with significant interaction (p<0.05) between sites and premises but no interaction between sites and seasons (p>0.05). By Generalized Linear Mixed models, the type of premises nested in sites and monthly total rainfall were significant predictors of monthly dengue cases (p<0.05) and not MIR, season, temperature, and relative humidity. Surveillance of DENV prevalence in Ae. aegypti and detecting their natural foci in the dry season provide an early warning signal of dengue outbreak. PMID:26611963

  4. Natural and laboratory compaction bands in porous carbonates: a three-dimensional characterization using synchrotron X-ray computed microtomography

    NASA Astrophysics Data System (ADS)

    Cilona, A.; Arzilli, F.; Mancini, L.; Emanuele, T.

    2014-12-01

    Porous carbonates form important reservoirs for water and hydrocarbons. The fluid flow properties of carbonate reservoirs may be affected by post-depositional processes (e.g., mechanical and chemical), which need to be quantified. Field-based studies described bed-parallel compaction bands (CBs) within carbonates with a wide range of porosities. These burial-related structures accommodate volumetric strain by grain rotation, translation, pore collapse and pressure solution. Recently, the same structures have been reproduced for the first time in the laboratory by performing triaxial compaction experiments on porous grainstones. These laboratory studies characterized and compared the microstructures of natural and laboratory CBs, but no analysis of pore connectivity has been performed. In this paper, we use an innovative approach to characterize the pore networks (e.g. porosity, connectivity) of natural and laboratory CBs and compare them with the host rock one. We collected the data using the synchrotron X-ray computed microtomography technique at the SYRMEP beamline of the Elettra-Sincrotrone Trieste Laboratory (Italy). Quantitative analyses of the samples were performed with the Pore3D software library. The porosity was calculated from segmented 3D images of pristine and deformed carbonates. A process of skeletonization was then applied to quantify the number of connected pores within the rock volume. The analysis of the skeleton allowed us to highlight the differences between natural and laboratory CBs, and to investigate how pore connectivity evolves as a function of different deformation pathways. Both pore volume and connectivity are reduced within the CBs respect to the pristine rock and the natural CB has a lower porosity with respect to the laboratory one. The grain contacts in the natural CB are welded, whereas in the laboratory one they have more irregular shapes and grain crushing is the predominant process.

  5. Laboratory study of the response of select insecticides to toxicity identification evaluation procedures

    USGS Publications Warehouse

    Kuivila, Kathryn M.; Crepeau, Kathryn L.

    1999-01-01

    A laboratory study was used to evaluate the response of select insecticides to toxicity identification evaluation procedures. Fourteen insecticides, one degradation product, and one synergist were spiked into organic-grade water and carried through toxicity identification evaluation procedures. Concentrations of each compound were analyzed by gas chromatography/mass spectrometry. During Phase I, the water sample was pumped through a C-8 solid-phase extraction cartridge and then eluted with methanol. Dimethoate was not removed by the extraction, but remained in the rinsate. In contrast, permethrin was removed by the extraction, but was not recovered by the methanol elution, and 80 percent of the permethrin remained on the cartridge, teflon tubing, and glassware. Chlorpyrifos also was not recovered completely with the methanol elution (only 62 percent was recovered). The other insecticides were extracted by C-8 solid-phase extraction cartridge and recovered by elution with methanol (80 percent or greater). During Phase II, a new spiked water sample was extracted by C-8 solid-phase extraction cartridge and then eluted with varying concentrations of methanol and water into different fractions. Each methanol:water fraction was analyzed for the added compounds. Most of the insecticides eluted in two fractions, with concentrations of 10 percent or greater. The largest number of insecticides eluted in the 75 percent methanol:water fraction.

  6. Maintenance of a genetic polymorphism with disruptive natural selection in stickleback.

    PubMed

    Marchinko, Kerry B; Matthews, Blake; Arnegard, Matthew E; Rogers, Sean M; Schluter, Dolph

    2014-06-01

    The role of natural selection in the maintenance of genetic variation in wild populations remains a major problem in evolution. The influence of disruptive natural selection on genetic variation is especially interesting because it might lead to the evolution of assortative mating or dominance [1, 2]. In theory, variation can persist at a gene under disruptive natural selection, but the process is little studied and there are few examples [3, 4]. We report a stable polymorphism in the bony armor of threespine stickleback maintained with a deficit of heterozygotes at the major underlying gene, Ectodysplasin (Eda) [5]. The deficit vanishes at the embryo life stage only to re-emerge in adults, indicating that disruptive natural selection, rather than nonrandom mating, is the cause. The mechanism enabling long-term persistence of the polymorphism is unknown, but disruptive selection is predicted to be frequency dependent, favoring homozygous genotypes when they become rare. Further research on the ecological and evolutionary processes affecting individual genes will ultimately lead to a better understanding of the causes of genetic variation in populations. PMID:24856211

  7. The interaction of sexually and naturally selected traits in the adaptive radiations of cichlid fishes.

    PubMed

    Salzburger, Walter

    2009-01-01

    The question of how genetic variation translates into organismal diversity has puzzled biologists for decades. Despite recent advances in evolutionary and developmental genetics, the mechanisms that underlie adaptation, diversification and evolutionary innovation remain largely unknown. The exceptionally diverse species flocks of cichlid fishes are textbook examples of adaptive radiation and explosive speciation and emerge as powerful model systems to study the genetic basis of animal diversification. East Africa's hundreds of endemic cichlid species are akin to a natural mutagenesis screen and differ greatly not only in ecologically relevant (hence naturally selected) characters such as mouth morphology and body shape, but also in sexually selected traits such as coloration. One of the most fascinating aspects of cichlid evolution is the frequent occurrence of evolutionary parallelisms, which has led to the question whether selection alone is sufficient to produce these parallel morphologies, or whether a developmental or genetic bias has influenced the direction of diversification. Here, I review fitness-relevant traits that could be responsible for the cichlids' evolutionary success and assess whether these were shaped by sexual or natural selection. I then focus on the interaction and the relative importance of sexual vs. natural selection in cichlid evolution. Finally, I discuss what is currently known about the genes underlying the morphogenesis of adaptively relevant traits and highlight the importance of the forthcoming cichlid genomes in the quest of the genetic basis of diversification in this group. PMID:18992003

  8. Differential effects of inbreeding and selection on male reproductive phenotype associated with the colonization and laboratory maintenance of Anopheles gambiae

    PubMed Central

    2014-01-01

    Background Effective mating between laboratory-reared males and wild females is paramount to the success of vector control strategies aiming to decrease disease transmission via the release of sterile or genetically modified male mosquitoes. However mosquito colonization and laboratory maintenance have the potential to negatively affect male genotypic and phenotypic quality through inbreeding and selection, which in turn can decrease male mating competitiveness in the field. To date, very little is known about the impact of those evolutionary forces on the reproductive biology of mosquito colonies and how they ultimately affect male reproductive fitness. Methods Here several male reproductive physiological traits likely to be affected by inbreeding and selection following colonization and laboratory rearing were examined. Sperm length, and accessory gland and testes size were compared in male progeny from field-collected females and laboratory strains of Anopheles gambiae sensu stricto colonized from one to over 25 years ago. These traits were also compared in the parental and sequentially derived, genetically modified strains produced using a two-phase genetic transformation system. Finally, genetic crosses were performed between strains in order to distinguish the effects of inbreeding and selection on reproductive traits. Results Sperm length was found to steadily decrease with the age of mosquito colonies but was recovered in refreshed strains and crosses between inbred strains therefore incriminating inbreeding costs. In contrast, testes size progressively increased with colony age, whilst accessory gland size quickly decreased in males from colonies of all ages. The lack of heterosis in response to crossing and strain refreshing in the latter two reproductive traits suggests selection for insectary conditions. Conclusions These results show that inbreeding and selection differentially affect reproductive traits in laboratory strains overtime and that heterotic ‘supermales’ could be used to rescue some male reproductive characteristics. Further experiments are needed to establish the exact relationship between sperm length, accessory gland and testes size, and male reproductive success in the laboratory and field settings. PMID:24418094

  9. Contemporary evolution during invasion: evidence for differentiation, natural selection, and local adaptation.

    PubMed

    Colautti, Robert I; Lau, Jennifer A

    2015-05-01

    Biological invasions are 'natural' experiments that can improve our understanding of contemporary evolution. We evaluate evidence for population differentiation, natural selection and adaptive evolution of invading plants and animals at two nested spatial scales: (i) among introduced populations (ii) between native and introduced genotypes. Evolution during invasion is frequently inferred, but rarely confirmed as adaptive. In common garden studies, quantitative trait differentiation is only marginally lower (~3.5%) among introduced relative to native populations, despite genetic bottlenecks and shorter timescales (i.e. millennia vs. decades). However, differentiation between genotypes from the native vs. introduced range is less clear and confounded by nonrandom geographic sampling; simulations suggest this causes a high false-positive discovery rate (>50%) in geographically structured populations. Selection differentials (¦s¦) are stronger in introduced than in native species, although selection gradients (¦?¦) are not, consistent with introduced species experiencing weaker genetic constraints. This could facilitate rapid adaptation, but evidence is limited. For example, rapid phenotypic evolution often manifests as geographical clines, but simulations demonstrate that nonadaptive trait clines can evolve frequently during colonization (~two-thirds of simulations). Additionally, QST-FST studies may often misrepresent the strength and form of natural selection acting during invasion. Instead, classic approaches in evolutionary ecology (e.g. selection analysis, reciprocal transplant, artificial selection) are necessary to determine the frequency of adaptive evolution during invasion and its influence on establishment, spread and impact of invasive species. These studies are rare but crucial for managing biological invasions in the context of global change. PMID:25891044

  10. Strong natural selection during plant restoration favors an unexpected suite of plant traits

    PubMed Central

    Kulpa, Sarah M; Leger, Elizabeth A

    2013-01-01

    Restoration is an opportunity to study natural selection: One can measure the distribution of traits in source propagules used to found populations, compare this with the distribution of traits in successful recruits, and determine the strength and direction of selection on potentially adaptive traits. We investigated whether natural selection influenced seedling establishment during postfire restoration in the Great Basin, an area where large-scale restoration occurs with a few widely available cultivars planted over a large range of environmental conditions. We collected seeds from established plants of the perennial grass Elymus elymoides ssp. californicus (squirreltail) at two restoration sites and compared the distribution of phenotypic traits of surviving plants with the original pool of restoration seeds. Seeds were planted in common gardens for two generations. Plants grown from seeds that established in the field were a nonrandom subset of the original seeds, with directional selection consistently favoring a correlated suite of traits in both field sites: small plant and seed size, and earlier flowering phenology. These results demonstrate that natural selection can affect restoration establishment in strong and predictable ways and that adaptive traits in these sites were opposite of the current criteria used for selection of restoration material in this system. PMID:23745142

  11. Imprints of Natural Selection Along Environmental Gradients in Phenology-Related Genes of Quercus petraea

    PubMed Central

    Alberto, Florian J.; Derory, Jérémy; Boury, Christophe; Frigerio, Jean-Marc; Zimmermann, Niklaus E.; Kremer, Antoine

    2013-01-01

    We explored single nucleotide polymorphism (SNP) variation in candidate genes for bud burst from Quercus petraea populations sampled along gradients of latitude and altitude in Western Europe. SNP diversity was monitored for 106 candidate genes, in 758 individuals from 32 natural populations. We investigated whether SNP variation reflected the clinal pattern of bud burst observed in common garden experiments. We used different methods to detect imprints of natural selection (FST outlier, clinal variation at allelic frequencies, association tests) and compared the results obtained for the two gradients. FST outlier SNPs were found in 15 genes, 5 of which were common to both gradients. The type of selection differed between the two gradients (directional or balancing) for 3 of these 5. Clinal variations were observed for six SNPs, and one cline was conserved across both gradients. Association tests between the phenotypic or breeding values of trees and SNP genotypes identified 14 significant associations, involving 12 genes. The results of outlier detection on the basis of population differentiation or clinal variation were not very consistent with the results of association tests. The discrepancies between these approaches may reflect the different hierarchical levels of selection considered (inter- and intrapopulation selection). Finally, we obtained evidence for convergent selection (similar for gradients) and clinal variation for a few genes, suggesting that comparisons between parallel gradients could be used to screen for major candidate genes responding to natural selection in trees. PMID:23934884

  12. Interactions between natural selection, recombination and gene density in the genes of Drosophila.

    PubMed Central

    Hey, Jody; Kliman, Richard M

    2002-01-01

    In Drosophila, as in many organisms, natural selection leads to high levels of codon bias in genes that are highly expressed. Thus codon bias is an indicator of the intensity of one kind of selection that is experienced by genes and can be used to assess the impact of other genomic factors on natural selection. Among 13,000 genes in the Drosophila genome, codon bias has a slight positive, and strongly significant, association with recombination--as expected if recombination allows natural selection to act more efficiently when multiple linked sites segregate functional variation. The same reasoning leads to the expectation that the efficiency of selection, and thus average codon bias, should decline with gene density. However, this prediction is not confirmed. Levels of codon bias and gene expression are highest for those genes in an intermediate range of gene density, a pattern that may be the result of a tradeoff between the advantages for gene expression of close gene spacing and disadvantages arising from regulatory conflicts among tightly packed genes. These factors appear to overlay the more subtle effect of linkage among selected sites that gives rise to the association between recombination rate and codon bias. PMID:11861564

  13. From Ends to Causes (and Back Again) by Metaphor: The Paradox of Natural Selection

    NASA Astrophysics Data System (ADS)

    Blancke, Stefaan; Schellens, Tammy; Soetaert, Ronald; Van Keer, Hilde; Braeckman, Johan

    2014-04-01

    Natural selection is one of the most famous metaphors in the history of science. Charles Darwin used the metaphor and the underlying analogy to frame his ideas about evolution and its main driving mechanism into a full-fledged theory. Because the metaphor turned out to be such a powerful epistemic tool, Darwin naturally assumed that he could also employ it as an educational tool to inform his contemporaries about his findings. Moreover, by using the metaphor Darwin was able to bring his theory in accordance with both the dominant philosophy of science in his time and the respected tradition of natural theology. However, as he introduced his theory of evolution by natural selection in On the origin of species in 1859, the metaphor also turned out to have a serious downside. Because of its intentional overtones, his contemporaries systematically misunderstood his metaphor not as a natural mechanism causing evolution to occur but as an agent who works towards particular ends. The difference in success between natural selection as an epistemic tool and its failure as an educational tool is labelled as a paradox. We explain the paradox from a cognitive perspective and discuss the implications for teaching evolution.

  14. Using a semi-natural stream to produce young sturgeons for conservation stocking: Maintaining natural selection during spawning and rearing

    USGS Publications Warehouse

    Kynard, B.; Pugh, D.; Parker, T.; Kieffer, M.

    2011-01-01

    Young sturgeons used for conservation stocking are presently produced using the same methods used for commercial culture. To determine if young sturgeons could be produced without relaxing natural selection factors, we developed a semi-natural stream where we annually studied mating of wild shortnose sturgeon (Acipenser brevirostrum) observed movement of gametes released freely during spawning, and estimated the number of larvae produced by various densities of spawned eggs. The stream had a bottom area of 18.8m2, a rubble-gravel bottom, and a mean bottom current at 0.6 depth during spawning of 48cms-1 (range, 17-126cms-1). Wild adults successfully spawned in the stream each year for 7years (2002-2008). Some females and males were more successful during spawning than others, suggesting an unequal fitness during spawning among wild individuals, which is different than the controlled spawning fitness of individuals in hatcheries. Male and female gametes spawned naturally must connect quickly in the fast current or fail, a selection factor absent in hatcheries. The number of larvae produced was inversely related to spawned egg densitym-2 (R2=0.65) and the maximum number of larvae produced was 8000-16000 (425-851larvaem-2 of bottom). Artificial spawning streams have the potential to contribute to sturgeon restoration. ?? 2011 Blackwell Verlag, Berlin.

  15. The GIST Model for Selection and Modification of Scientific Research for the College Teaching Laboratory Based on Root Competition Investigations

    ERIC Educational Resources Information Center

    Elliott, Shannon Snyder

    2007-01-01

    The purpose of this study is to first develop an 8-week college teaching module based on root competition literature. The split-root technique is adapted for the teaching laboratory, and the Sugar Ann English pea (Pisum sativum var. Sugar Ann English) is selected as the species of interest prior to designing experiments, either original or…

  16. West Florida Shelf: A natural laboratory for the study of ocean acidificiation

    USGS Publications Warehouse

    Hallock, Pamela; Robbins, Lisa L.; Larson, Rebekka A.; Beck, Tanya; Schwing, Patrick; Martinez-Colon, Michael; Gooch, Brad

    2010-01-01

    Declining oceanic pH and carbonate-ion concentrations are well-known consequences of increased atmospheric and surface-ocean partial pressure of carbon dioxide (pCO2). The possible subject of shifts in seawater carbonate chemistry on biocalcification and survival rates of marine organisms provides questions amenable to both experimental and field study (Kleypas and Langdon, 2006). To date, limited quantitative data exist with which to formalize and test hypotheses regarding such impacts, particularly in continental-shelf settings. The continental shelves of Florida provide an ideal natural laboratory in which to test latitudinal (and temperature and depth) shifts in habitat ranges of calcifying organisms. Both the east and west Florida shelves extend from warm temperate to subtropical latitudes; additionally, the west Florida shelf has very little siliciclastic influx to mask the carbonate production. This study utilizes the natural laboratory of the west and southwest Florida shelf (fig 1.1) to examine the transition from foramol (predominately foraminifera and molluscan) carbonate sediments, characteristic of the west-central Florida shelf, to chlorozoan (algal and coral) sediments characteristic of the southwest Florida shelf. The west Florida shelf is a mixed siliciclastic carbonate ramp that to the south transitions to the carbonate-dominated southwest Florida shelf (Enos, 1977; Brooks and others, 2003). The west Florida shelf is a distally steepened carbonate ramp that is ~250 kilometers (km) wide (Read, 1985). It is covered by a veneer of unconsolidated sediment consisting of mainly biogenic carbonate and quartz in the near shore, with subordinate amounts of phosphate. The sediment-distribution pattern is largely a function of proximity to source, with physical processes playing a minor role in distribution. The carbonate sand-and-gravel fraction is produced by organisms within the depositional basin of the west Florida shelf (Brooks and others, 2003). The southwest Florida shelf is a rimmed carbonate margin where organisms produce virtually all of the substrate; it also exhibits a greater sediment thickness as compared to the west Florida shelf (Enos, 1977). Temperature, which is usually associated with latitude, plays a major role in locations of foramol versus chlorozoan assemblages, but other factors beyond latitude influence temperature on the west and southwest Florida shelves. The potential of cooler, deep-water upwelling and transport over the bottom waters of the shelf may have a significant role in the species assemblage at the sediment/water interface and ultimately on location of foramol versus chlorozoan production. Deep water transported onto and over the shelf may also have environmental ramifications beyond temperature by bringing in water of different chemistry.

  17. Effects of environmental changes on natural selection active on human polygenic traits.

    PubMed

    Ulizzi, L

    1993-06-01

    During the last century, industrialized countries experienced such an improvement in socioeconomic conditions and in sanitation that it is likely that the selective forces active on human metric traits have been modified. Perinatal mortality as a function of birth weight is one of the clearest examples of natural selection in humans. Here, trends over time of stabilizing and directional selection associated with birth weight have been analyzed in Japan from 1969 to 1989. The population of newborns has been subdivided according to gestational age, which is one of the main covariates of birth weight. The results show that in full-term babies both stabilizing and directional selection are coming to an end, whereas in babies born after 8 months of gestation these selective forces are still active, even if at much lower levels than in the past. The peculiar results found in the 7-month-gestation population are probably due to grossly abnormal cases of immaturity. PMID:8319942

  18. Investigation of iron-containing products from natural and laboratory cultivated Sphaerotilus-Leptothrix bacteria.

    PubMed

    Angelova, R; Groudeva, V; Slavov, L; Iliev, M; Nedkov, I; Sziklai-László, I; Krezhov, K

    2015-09-01

    Bacterial biomass collected from sheath-forming bacteria of the genera Sphaerotilus and Leptothrix was collected from a high-mountain natural stream water source. The elemental constitution and oxide phases of the products after selective cultivation of the bacteria on two different elective media using neutron activation analysis (NAA), electron microscopy (SEM, TEM), and X-ray diffraction (XRD) were studied. A high enrichment level of iron was revealed by the NAA technique in cultivated isolates as compared to the reference sample from nature. Three types of iron oxide compounds were established after cultivation in Adler's medium: lepidocrocite (?-FeOOH), magnetite (Fe3O4), and goethite (?-FeOOH). The cultivation in the Isolation medium yielded a single phase, that of goethite, excluding one sample with a distinguishable amount of lepidocrocite. XRD and EM investigations show that the biogenic oxides are nanosized. Our study exemplifies the possibilities of the biotechnology approach for obtaining, under artificial conditions, large quantities of iron-containing by-products that could be of further used in appropriate nano- and biotechnologies. PMID:25724989

  19. Analysis of environmental contamination resulting from catastrophic incidents: part 2. Building laboratory capability by selecting and developing analytical methodologies.

    PubMed

    Magnuson, Matthew; Campisano, Romy; Griggs, John; Fitz-James, Schatzi; Hall, Kathy; Mapp, Latisha; Mullins, Marissa; Nichols, Tonya; Shah, Sanjiv; Silvestri, Erin; Smith, Terry; Willison, Stuart; Ernst, Hiba

    2014-11-01

    Catastrophic incidents can generate a large number of samples of analytically diverse types, including forensic, clinical, environmental, food, and others. Environmental samples include water, wastewater, soil, air, urban building and infrastructure materials, and surface residue. Such samples may arise not only from contamination from the incident but also from the multitude of activities surrounding the response to the incident, including decontamination. This document summarizes a range of activities to help build laboratory capability in preparation for sample analysis following a catastrophic incident, including selection and development of fit-for-purpose analytical methods for chemical, biological, and radiological contaminants. Fit-for-purpose methods are those which have been selected to meet project specific data quality objectives. For example, methods could be fit for screening contamination in the early phases of investigation of contamination incidents because they are rapid and easily implemented, but those same methods may not be fit for the purpose of remediating the environment to acceptable levels when a more sensitive method is required. While the exact data quality objectives defining fitness-for-purpose can vary with each incident, a governing principle of the method selection and development process for environmental remediation and recovery is based on achieving high throughput while maintaining high quality analytical results. This paper illustrates the result of applying this principle, in the form of a compendium of analytical methods for contaminants of interest. The compendium is based on experience with actual incidents, where appropriate and available. This paper also discusses efforts aimed at adaptation of existing methods to increase fitness-for-purpose and development of innovative methods when necessary. The contaminants of interest are primarily those potentially released through catastrophes resulting from malicious activity. However, the same techniques discussed could also have application to catastrophes resulting from other incidents, such as natural disasters or industrial accidents. Further, the high sample throughput enabled by the techniques discussed could be employed for conventional environmental studies and compliance monitoring, potentially decreasing costs and/or increasing the quantity of data available to decision-makers. PMID:24568927

  20. Aging is neither a failure nor an achievement of natural selection.

    PubMed

    Aledo, Juan Carlos; Blanco, José María

    2015-01-01

    In contraposition to the view of aging as a stochastic time-dependent accumulation of damage, phenoptotic theories of aging postulate that senescence may provide supra-individual advantages, and therefore it might have been promoted by natural selection. We reason that although programmed aging theories are subjectively appealing because they convey a cure for aging, they also raise a number of objections that need to be dealt with, before we may be entitled to contemplate aging as an adaptive function evolved through natural selection. As an alternative view, we present metabolism as an endless source of by-products and errors causing cellular damage. Although this damage accumulation event is a spontaneous entropy-driven process, its kinetics can be genetically and environmentally modulated, giving place to the wide range of lifespans we observe. Mild forms of damage may be accumulating during a long enough period of time to allow reproduction before the fatal failure happens. Hence, aging would be a stochastic process out of the reach of natural selection. However, those genetic pathways influencing the rate of aging and consequently determining longevity may be targets of natural selection and may contribute to shaping the optimal strategy according to the ecological context. In this sense, short- and long-lived organisms represent two extreme strategies that, in terms of biological fitness, can perform equally well, each within its own niche. PMID:26054343

  1. Evolving Better Cars: Teaching Evolution by Natural Selection with a Digital Inquiry Activity

    ERIC Educational Resources Information Center

    Royer, Anne M.; Schultheis, Elizabeth H.

    2014-01-01

    Evolutionary experiments are usually difficult to perform in the classroom because of the large sizes and long timescales of experiments testing evolutionary hypotheses. Computer applications give students a window to observe evolution in action, allowing them to gain comfort with the process of natural selection and facilitating inquiry…

  2. Instructional Design Consequences of an Analogy between Evolution by Natural Selection and Human Cognitive Architecture

    ERIC Educational Resources Information Center

    Sweller, John

    2004-01-01

    Evolution by natural selection may be characterized as a system in which a large store of genetic information will persist indefinitely while it remains coordinated with its environment but will continuously produce small random variations that are tested for environmental effectiveness. In any environment, effective variations will persist while…

  3. The Power of Natural Selection: A Guided Investigation of Three Case Studies

    ERIC Educational Resources Information Center

    Beachly, William

    2010-01-01

    I describe a quantitative approach to three case studies in evolution that can be used to challenge college freshmen to explore the power of natural selection and ask questions that foster a deeper understanding of its operation and relevance. Hemochromatosis, the peppered moth, and hominid cranial capacity are investigated with a common algebraic…

  4. Unweaving Misconceptions: Guided Learning, Simulations, and Misconceptions in Learning Principles of Natural Selection

    ERIC Educational Resources Information Center

    Weeks, Brian E.

    2013-01-01

    College students often come to the study of evolutionary biology with many misconceptions of how the processes of natural selection and speciation occur. How to relinquish these misconceptions with learners is a question that many educators face in introductory biology courses. Constructivism as a theoretical framework has become an accepted and…

  5. Darwin's Arguments in Favour of Natural Selection and against Special Creationism

    ERIC Educational Resources Information Center

    Nola, Robert

    2013-01-01

    In many places in "The Origin of Species", Darwin compares his own theory of Natural Selection favourably with Special Creationism which comes off as a bad second best. He does this using some version of the argument form known as "Inference to the Best Explanation". The first part of this paper is methodological. It considers Whewell's notion of…

  6. Student Conceptions of Natural Selection and Its Role in Evolution, Research Series No. l65.

    ERIC Educational Resources Information Center

    Bishop, Beth A.; Anderson, Charles W.

    Pretests and posttests on the topic of evolution through natural selection were administered to students in a college nonmajors' biology course. Analysis of test responses revealed that most students understood evolution as a process in which species respond to environmental conditions by changing gradually over time. Student thinking differed…

  7. The Future of Natural Selection Knowledge Measurement: A Reply to Anderson et al. (2010)

    ERIC Educational Resources Information Center

    Nehm, Ross H.; Schonfeld, Irvin Sam

    2010-01-01

    The development of rich, reliable, and robust measures of the composition, structure, and stability of student thinking about core scientific ideas (such as natural selection) remains a complex challenge facing science educators. In their recent article (Nehm & Schonfeld 2008), the authors explored the strengths, weaknesses, and insights provided…

  8. Reasoning about Natural Selection: Diagnosing Contextual Competency Using the ACORNS Instrument

    ERIC Educational Resources Information Center

    Nehm, Ross H.; Beggrow, Elizabeth P.; Opfer, John E.; Ha, Minsu

    2012-01-01

    Studies of students' thinking about natural selection have revealed that the scenarios in which students reason evoke different types, magnitudes, and arrangements of knowledge elements and misconceptions. Diagnostic tests are needed that probe students' thinking across a representative array of evolutionary contexts. The ACORNS is a diagnostic…

  9. Plant mortality and natural selection may increase biomass yield in switchgrass swards

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Switchgrass (Panicum virgatum L.) is an important candidate for bioenergy feedstock production, prompting significant efforts to increase the number of breeding programs and the output of those programs. The objective of this experiment was to determine the potential utility of natural selection for...

  10. Unweaving Misconceptions: Guided Learning, Simulations, and Misconceptions in Learning Principles of Natural Selection

    ERIC Educational Resources Information Center

    Weeks, Brian E.

    2013-01-01

    College students often come to the study of evolutionary biology with many misconceptions of how the processes of natural selection and speciation occur. How to relinquish these misconceptions with learners is a question that many educators face in introductory biology courses. Constructivism as a theoretical framework has become an accepted and…

  11. Human vs. Computer Diagnosis of Students' Natural Selection Knowledge: Testing the Efficacy of Text Analytic Software

    ERIC Educational Resources Information Center

    Nehm, Ross H.; Haertig, Hendrik

    2012-01-01

    Our study examines the efficacy of Computer Assisted Scoring (CAS) of open-response text relative to expert human scoring within the complex domain of evolutionary biology. Specifically, we explored whether CAS can diagnose the explanatory elements (or Key Concepts) that comprise undergraduate students' explanatory models of natural selection with…

  12. The Future of Natural Selection Knowledge Measurement: A Reply to Anderson et al. (2010)

    ERIC Educational Resources Information Center

    Nehm, Ross H.; Schonfeld, Irvin Sam

    2010-01-01

    The development of rich, reliable, and robust measures of the composition, structure, and stability of student thinking about core scientific ideas (such as natural selection) remains a complex challenge facing science educators. In their recent article (Nehm & Schonfeld 2008), the authors explored the strengths, weaknesses, and insights provided…

  13. The Power of Natural Selection: A Guided Investigation of Three Case Studies

    ERIC Educational Resources Information Center

    Beachly, William

    2010-01-01

    I describe a quantitative approach to three case studies in evolution that can be used to challenge college freshmen to explore the power of natural selection and ask questions that foster a deeper understanding of its operation and relevance. Hemochromatosis, the peppered moth, and hominid cranial capacity are investigated with a common algebraic…

  14. Developing Conceptual Understanding of Natural Selection: The Role of Interest, Efficacy, and Basic Prior Knowledge

    ERIC Educational Resources Information Center

    Linnenbrink-Garcia, Lisa; Pugh, Kevin J.; Koskey, Kristin L. K.; Stewart, Victoria C.

    2012-01-01

    Changes in high school students' (n = 94) conceptions of natural selection were examined as a function of motivational beliefs (individual interest, academic self-efficacy), basic prior knowledge, and gender across three assessments (pre, post, follow-up). Results from variable-centered analyses suggested that these variables had relatively little…

  15. Influences of Teleological and Lamarckian Thinking on Student Understanding of Natural Selection

    ERIC Educational Resources Information Center

    Stover, Shawn K.; Mabry, Michelle L.

    2007-01-01

    Previous research has demonstrated creationist, Lamarckian, and teleological reasoning in high school and college students. These lines of thinking conflict with the Darwinian notion of natural selection, which serves as the primary catalyst for biological evolution. The current study assessed evolutionary conceptions in non-science majors,…

  16. Darwin's Arguments in Favour of Natural Selection and against Special Creationism

    ERIC Educational Resources Information Center

    Nola, Robert

    2013-01-01

    In many places in "The Origin of Species", Darwin compares his own theory of Natural Selection favourably with Special Creationism which comes off as a bad second best. He does this using some version of the argument form known as "Inference to the Best Explanation". The first part of this paper is methodological. It considers Whewell's notion of…

  17. Mutation pressure, natural selection, and the evolution of base composition in Drosophila.

    PubMed

    Akashi, H; Kliman, R M; Eyre-Walker, A

    1998-01-01

    Genome sequencing in a number of taxa has revealed variation in nucleotide composition both among regions of the genome and among functional classes of sites in DNA. Mutational biases, biased gene conversion, and natural selection have been proposed as causes of this variation. Here, we review patterns of base composition in Drosophila DNA. Nucleotide composition in Drosophila melanogaster varys regionally, and base composition is correlated between introns and exons. Drosophila species also show striking patterns of non-random codon usage. Patterns of synonymous codon usage and the biochemistry of translation suggest that natural selection may act at 'silent' sites. A relationship between recombination rates and codon usage and comparisons of the evolutionary dynamics of silent mutations within and between species support natural selection discriminating among synonymous codons. The causes of regional base composition variation are less clear. Progress in functional studies of non-coding DNA, further investigations of genome patterns, and statistical tests based on evolutionary theory will lead to a greater understanding of the contributions of mutational processes and natural selection in patterning genome-wide nucleotide composition. PMID:9720271

  18. Evolving Better Cars: Teaching Evolution by Natural Selection with a Digital Inquiry Activity

    ERIC Educational Resources Information Center

    Royer, Anne M.; Schultheis, Elizabeth H.

    2014-01-01

    Evolutionary experiments are usually difficult to perform in the classroom because of the large sizes and long timescales of experiments testing evolutionary hypotheses. Computer applications give students a window to observe evolution in action, allowing them to gain comfort with the process of natural selection and facilitating inquiry…

  19. Young children can be taught basic natural selection using a picture-storybook intervention.

    PubMed

    Kelemen, Deborah; Emmons, Natalie A; Seston Schillaci, Rebecca; Ganea, Patricia A

    2014-04-01

    Adaptation by natural selection is a core mechanism of evolution. It is also one of the most widely misunderstood scientific processes. Misconceptions are rooted in cognitive biases found in preschoolers, yet concerns about complexity mean that adaptation by natural selection is generally not comprehensively taught until adolescence. This is long after untutored theoretical misunderstandings are likely to have become entrenched. In a novel approach, we explored 5- to 8-year-olds' capacities to learn a basic but theoretically coherent mechanistic explanation of adaptation through a custom storybook intervention. Experiment 1 showed that children understood the population-based logic of natural selection and also generalized it. Furthermore, learning endured 3 months later. Experiment 2 replicated these results and showed that children understood and applied an even more nuanced mechanistic causal explanation. The findings demonstrate that, contrary to conventional educational wisdom, basic natural selection is teachable in early childhood. Theory-driven interventions using picture storybooks with rich explanatory structure are beneficial. PMID:24503874

  20. Human vs. Computer Diagnosis of Students' Natural Selection Knowledge: Testing the Efficacy of Text Analytic Software

    ERIC Educational Resources Information Center

    Nehm, Ross H.; Haertig, Hendrik

    2012-01-01

    Our study examines the efficacy of Computer Assisted Scoring (CAS) of open-response text relative to expert human scoring within the complex domain of evolutionary biology. Specifically, we explored whether CAS can diagnose the explanatory elements (or Key Concepts) that comprise undergraduate students' explanatory models of natural selection with…

  1. Instructional Design Consequences of an Analogy between Evolution by Natural Selection and Human Cognitive Architecture

    ERIC Educational Resources Information Center

    Sweller, John

    2004-01-01

    Evolution by natural selection may be characterized as a system in which a large store of genetic information will persist indefinitely while it remains coordinated with its environment but will continuously produce small random variations that are tested for environmental effectiveness. In any environment, effective variations will persist while…

  2. Physical properties and rock physics models of sediment containing natural and laboratory-formed methane gas hydrate

    USGS Publications Warehouse

    Winters, W.J.; Pecher, I.A.; Waite, W.F.; Mason, D.H.

    2004-01-01

    This paper presents results of shear strength and acoustic velocity (p-wave) measurements performed on: (1) samples containing natural gas hydrate from the Mallik 2L-38 well, Mackenzie Delta, Northwest Territories; (2) reconstituted Ottawa sand samples containing methane gas hydrate formed in the laboratory; and (3) ice-bearing sands. These measurements show that hydrate increases shear strength and p-wave velocity in natural and reconstituted samples. The proportion of this increase depends on (1) the amount and distribution of hydrate present, (2) differences, in sediment properties, and (3) differences in test conditions. Stress-strain curves from the Mallik samples suggest that natural gas hydrate does not cement sediment grains. However, stress-strain curves from the Ottawa sand (containing laboratory-formed gas hydrate) do imply cementation is present. Acoustically, rock physics modeling shows that gas hydrate does not cement grains of natural Mackenzie Delta sediment. Natural gas hydrates are best modeled as part of the sediment frame. This finding is in contrast with direct observations and results of Ottawa sand containing laboratory-formed hydrate, which was found to cement grains (Waite et al. 2004). It therefore appears that the microscopic distribution of gas hydrates in sediment, and hence the effect of gas hydrate on sediment physical properties, differs between natural deposits and laboratory-formed samples. This difference may possibly be caused by the location of water molecules that are available to form hydrate. Models that use laboratory-derived properties to predict behavior of natural gas hydrate must account for these differences.

  3. LABORATORY PROCESS CONTROLLER USING NATURAL LANGUAGE COMMANDS FROM A PERSONAL COMPUTER

    NASA Technical Reports Server (NTRS)

    Will, H.

    1994-01-01

    The complex environment of the typical research laboratory requires flexible process control. This program provides natural language process control from an IBM PC or compatible machine. Sometimes process control schedules require changes frequently, even several times per day. These changes may include adding, deleting, and rearranging steps in a process. This program sets up a process control system that can either run without an operator, or be run by workers with limited programming skills. The software system includes three programs. Two of the programs, written in FORTRAN77, record data and control research processes. The third program, written in Pascal, generates the FORTRAN subroutines used by the other two programs to identify the user commands with the user-written device drivers. The software system also includes an input data set which allows the user to define the user commands which are to be executed by the computer. To set the system up the operator writes device driver routines for all of the controlled devices. Once set up, this system requires only an input file containing natural language command lines which tell the system what to do and when to do it. The operator can make up custom commands for operating and taking data from external research equipment at any time of the day or night without the operator in attendance. This process control system requires a personal computer operating under MS-DOS with suitable hardware interfaces to all controlled devices. The program requires a FORTRAN77 compiler and user-written device drivers. This program was developed in 1989 and has a memory requirement of about 62 Kbytes.

  4. Examining beginning biology teachers' knowledge, beliefs, and practice for teaching natural selection

    NASA Astrophysics Data System (ADS)

    Sickel, Aaron J.

    The teacher is the most important school-based factor in student learning. Thus, in order to improve student learning, we must examine how teachers learn to teach. My overarching research agenda centers upon K-16 science teacher learning and development. Within this agenda, I conduct studies focused on two strands of research: 1) How teachers learn to teach science using constructivist and inquiry-oriented teaching strategies; and 2) How teachers learn to teach biological evolution. This dissertation merges the two strands together, and consists of four related manuscripts that address how beginning biology teachers learn to teach natural selection using constructivist and inquiry-oriented teaching strategies. In the first manuscript, I reviewed the evolution education literature focused on K-12 teachers’ knowledge, beliefs, and practice for teaching evolution. Based upon findings across the studies, I articulated five goals for preparing teachers to teach evolution. The second and third manuscripts are longitudinal empirical studies focused on three beginning biology teachers learning to teach natural selection using the 5E instructional model and interactive classroom simulations. The fourth manuscript is a practitioner article that explains how to teach natural selection simulations using a constructivist, analogy-based teaching strategy. Findings that cut across the four manuscripts are organized into the following themes: (A) The participants developed some common types of knowledge for teaching natural selection, yet also developed in unique ways. All participants developed knowledge of the horizontal curriculum. Yet, participants also developed different types of knowledge. For example, participants who had taken an evolution course developed more integrated pedagogical content knowledge for teaching the core concepts of natural selection. The participant who integrated discipline-level knowledge for teaching science through inquiry with topic-level knowledge for teaching natural selection had taken an undergraduate evolution course and possessed a student-centered orientation, demonstrating the importance of both subject matter preparation and orientations for teaching science in reform-based ways. Differences I observed among the participants highlight the need for more in-depth case studies in addition to large-scale studies to understand beginning science teacher development. (B) Beliefs about science teaching and learning shaped the participants’ knowledge and practice for teaching natural selection. Participants who possessed student-centered science teaching orientations developed more integrated pedagogical content knowledge for teaching natural selection. However, one participant with a student-centered orientation possessed beliefs in which it was the students’ role to discover natural selection with little intervention from the teacher. This finding supports the need to help teachers develop constructivist orientations to facilitate students’ conceptual understandings of science in addition to engaging in inquiry processes. (C) Learning to teach evolution requires a complex amalgam of knowledge, beliefs, and practice. The literature highlights the types of knowledge and beliefs that teachers must develop to be willing to teach evolution, including content knowledge, understandings of the nature of science, and knowledge of teaching controversial topics. In addition, teachers need to develop pedagogical content knowledge for teaching evolution in ways that support students’ conceptual understanding of evolution. Based upon my review of the literature, secondary science majors should be required to take a course designed for teaching evolution, with the following goals: 1) Develop content knowledge of evolution; 2) Accept evolution as scientifically valid; 3) Develop understandings of the nature of science related to evolution; 4) Develop strategies for handling the public controversy; and 5) Develop pedagogical content knowledge for teaching evolution. This collection of work has implications for using the construct of pedagogical content knowledge to understand teacher learning, improving teacher preparation, and policy efforts regarding teacher quality.

  5. Mobile laboratory “Explosive destruction of natural materials”: Investigation of the behavior of ice and limestone under explosive loading

    NASA Astrophysics Data System (ADS)

    Orlov, M. Yu; Orlova, Yu N.; Tolkachev, V. F.

    2015-11-01

    In the paper, the behavior of ice and natural limestone under explosion condition was investigated. The objects of study were the river ice and natural limestone quarry on Siberia. The practical significance of research due to the need to increase production of oil and gas in permafrost regions, the fight against ice jams, etc. We organized a mobile laboratory ’’Explosive destruction of the natural materials” at the National Research Tomsk State University. The main purpose of the laboratory is express analyzing of explosive destruction of natural materials. The diameters and depths of explosive craters in the limestone and explosive lane in the ice were obtained. The results can be used to test new models and numerical methods for calculating shock and explosive loading of different materials, including ice.

  6. Natural selection, plasticity and the emergence of a behavioural syndrome in the wild.

    PubMed

    Adriaenssens, Bart; Johnsson, Jörgen I

    2013-01-01

    Individuals often show consistent behavioural differences where behaviours can form integrated units across functionally different contexts. However, the factors causing and maintaining behavioural syndromes in natural populations remain poorly understood. In this study, we provide evidence for the emergence of a behavioural syndrome during the first months of life in wild brown trout (Salmo trutta). Behavioural traits of trout were scored before and after a 2-month interval covering a major survival bottleneck, whereupon the consistency and covariance of behaviours were analysed. We found that selection favoured individuals with high activity levels in an open-field context, a personality trait consistent throughout the duration of the experiment. In addition, a behavioural syndrome emerged over the 2 months in the wild, linking activity to aggressiveness and exploration tendency. These novel results suggest that behavioural syndromes can emerge rapidly in nature from interaction between natural selection and behavioural plasticity affecting single behaviours. PMID:23034098

  7. Unweaving misconceptions: Guided learning, simulations, and misconceptions in learning principles of natural selection

    NASA Astrophysics Data System (ADS)

    Weeks, Brian E.

    College students often come to the study of evolutionary biology with many misconceptions of how the processes of natural selection and speciation occur. How to relinquish these misconceptions with learners is a question that many educators face in introductory biology courses. Constructivism as a theoretical framework has become an accepted and promoted model within the epistemology of science instruction. However, constructivism is not without its skeptics who see some problems of its application in lacking necessary guidance for novice learners. This study within a quantitative, quasi-experimental format tested whether guided online instruction in a video format of common misconceptions in evolutionary biology produced higher performance on a survey of knowledge of natural selection versus more constructivist style learning in the form of student exploration of computer simulations of the evolutionary process. Performances on surveys were also explored for a combination of constructivist and guided techniques to determine if a consolidation of approaches produced higher test scores. Out of the 94 participants 95% displayed at least one misconception of natural selection in the pre-test while the study treatments produced no statistically significant improvements in post-test scores except within the video (guided learning treatment). These overall results demonstrated the stubbornness of misconceptions involving natural selection for adult learners and the difficulty of helping them overcome them. It also bolsters the idea that some misconceptions of natural selection and evolution may be hardwired in a neurological sense and that new, more long-term teaching techniques may be warranted. Such long-term strategies may not be best implemented with constructivist techniques alone, and it is likely that some level of guidance may be necessary for novice adult learners. A more substantial, nuanced approach for undergraduates is needed that consolidates successful teaching strategies to adult students that is based on current research.

  8. Genetic polymorphism and natural selection in the malaria parasite Plasmodium falciparum.

    PubMed Central

    Escalante, A A; Lal, A A; Ayala, F J

    1998-01-01

    We have studied the genetic polymorphism at 10 Plasmodium falciparum loci that are considered potential targets for specific antimalarial vaccines. The polymorphism is unevenly distributed among the loci; loci encoding proteins expressed on the surface of the sporozoite or the merozoite (AMA-1, CSP, LSA-1, MSP-1, MSP-2, and MSP-3) are more polymorphic than those expressed during the sexual stages or inside the parasite (EBA-175, Pfs25, PF48/45, and RAP-1). Comparison of synonymous and nonsynonymous substitutions indicates that natural selection may account for the polymorphism observed at seven of the 10 loci studied. This inference depends on the assumption that synonymous substitutions are neutral, which we test by analyzing codon bias and G+C content in a set of 92 gene loci. We find evidence for an overall trend towards increasing A+T richness, but no evidence for mutation bias. Although the neutrality of synonymous substitutions is not definitely established, this trend towards an A+T rich genome cannot explain the accumulation of substitutions at least in the case of four genes (AMA-1, CSP, LSA-1, and PF48/45) because the Gleft and right arrow C transversions are more frequent than expected. Moreover, the Tajima test manifests positive natural selection for the MSP-1 and, less strongly, MSP-3 polymorphisms; the McDonald-Kreitman test manifests natural selection at LSA-1 and PF48/45. We conclude that there is definite evidence for positive natural selection in the genes encoding AMA-1, CSP, LSA-1, MSP-1, and Pfs48/45. For four other loci, EBA-175, MSP-2, MSP-3, and RAP-1, the evidence is limited. No evidence for natural selection is found for Pfs25. PMID:9584096

  9. On the interpretation and relevance of the Fundamental Theorem of Natural Selection.

    PubMed

    Ewens, Warren J; Lessard, Sabin

    2015-09-01

    The attempt to understand the statement, and then to find the interpretation, of Fisher's "Fundamental Theorem of Natural Selection" caused problems for generations of population geneticists. Price's (1972) paper was the first to lead to an understanding of the statement of the theorem. The theorem shows (in the discrete-time case) that the so-called "partial change" in mean fitness of a population between a parental generation and an offspring generation is the parental generation additive genetic variance in fitness divided by the parental generation mean fitness. In the continuous-time case the partial rate of change in mean fitness is equal to the parental generation additive genetic variance in fitness with no division by the mean fitness. This "partial change" has been interpreted by some as the change in mean fitness due to changes in gene frequency, and by others as the change in mean fitness due to natural selection. (Fisher variously used both interpretations.) In this paper we discuss these interpretations of the theorem. We indicate why we are unhappy with both. We also discuss the long-term relevance of the Fundamental Theorem of Natural Selection, again reaching a negative assessment. We introduce and discuss the concept of genic evolutionary potential. We finally review an optimizing theorem that involves changes in gene frequency, the additive genetic variance in fitness and the mean fitness itself, all of which are involved in the Fundamental Theorem of Natural Selection, and which is free of the difficulties in interpretation of the Fundamental Theorem of Natural Selection. PMID:26220589

  10. Influence of pesticides and herbicides presence on phosphatase activity and selected bacterial microbiota of a natural lake system.

    PubMed

    López, L; Pozo, C; Rodelas, B; Calvo, C; González-López, J

    2006-07-01

    Phosphatase activities (cell-bounded phosphatases "BP" and freely dissolved phosphatases "D P") in water samples from a natural lake "Laguna Grande" (Antequera, Málaga, Spain) amended with 50 microg/ml of selected insecticides, herbicides and fungicide captan were studied under laboratory controlled conditions (temperature and agitation). Our data show that dissolved alkaline phosphatase was the enzymatic activity that contributed in higher proportion to total lake water samples phosphatase status. The presence of organochlorinated insecticides (aldrin and lindane), organophosphorous insecticides (dimetoate, methidation and methyl-parathion), herbicide atrazine and fungicide captan significantly increased phosphatase activities after 28 days of incubation. However, these activities were not affected as a consequence of the addition of the herbicide simazine to the water samples. Heterotrophic mesophilic and psychrophilic aquatic bacteria counts as well as culturable phosphate solubilizing microorganisms, increased when the pesticides were added to lake water samples with herbicide simazine exception. PMID:16786390

  11. Pedagogy and performativity: Rendering laboratory lives in the documentary "Naturally obsessed: the making of a scientist".

    PubMed

    Myers, Natasha

    2010-12-01

    A recently released documentary on life in a protein crystallography laboratory offers an exemplary opportunity to examine how a popular account of scientific training models narrowly defined norms of masculinity and mentorship and simultaneously sets these as the tacit conditions for success in science. Rather than treating this documentary as a good or bad representation of what life in the lab is actually like, this analysis draws attention to how the scientists featured in the film perform for the camera and how the filmmakers splice together the action to animate an engaging story. This essay shows how this popular and widely circulating documentary frames science as a game to be won and stages scientific success on an agonistic playing field. Those who can "make it" are those who are tough enough and those who are willing and able to get entangled in the taunting, jesting, and jostling relationships that appear to be required for mentorship in this lab. The essay argues that this documentary tethers this model of success in science to restrictive norms of masculinity and in so doing promotes a pedagogical culture that fosters competition, rivalry, and ritualized shame. Feminist theories of performativity are engaged to consider the iterative processes through which narrowly circumscribed masculinities and styles of pedagogy are sedimented and naturalized. This essay aims to spur renewed attention to the care historians and anthropologists might take to examine the often hidden tropes that are lurking inside the stories about science that we find so salient. PMID:21409989

  12. Induction of atrazine tolerance in a natural soil assemblage of microalgae reared in the laboratory.

    PubMed

    García-Villada, Libertad; Reboud, Xavier

    2007-01-01

    We investigated the occurrence of tolerance to atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) in soil microalgae by means of the pollution-induced community tolerance methodology. To this end, a natural soil assemblage of microalgae, reared under laboratory conditions, was used as experimental model. Experimental cultures were exposed to 0.46, 0.93, 1.85, 2.70, and 5.40 mg atrazine/L medium for 40 days. After this chronic exposure, both untreated and atrazine-pretreated cultures were subjected to a short-term dose-effect study with atrazine using average growth rate as endpoint. Results showed that chronic exposure to atrazine induced significant changes at the community level, increasing its atrazine tolerance. In addition, atrazine-pretreated assemblages seemed to display, on average, a reduced growth rate compared with untreated assemblages in the absence of atrazine. Response to the presence of atrazine could thus be achieved with some fitness cost. This suggests that the soil microalgal productivity could be diminished after exposure to atrazine. PMID:16249030

  13. Experimental and theoretical study of microalgal competition in laboratory and natural ecosystems

    NASA Astrophysics Data System (ADS)

    Pisman, T. I.; Somova, L. A.

    An important aspect of studying mixed cultures of microalgae is the artificial ecosystems containing algal culture as a regeneration link and a source of vegetable substances. The peculiarities of studying the stability of microalgae mixed cultures in the laboratory and natural environment have been considered in the work. The role of factors most essentially affecting the species structure of phytoplankton community (temperature factor, light intensity, pH environments, elements of mineral nutrition, algal metabolites, predation and fluctuation of environmental conditions) has been displayed. As a result of experimental and theoretical modelling of the microalgae Chlorella vulgaris and Scenedesmus quadricauda competition under limitation on nitrogen, the impossibility of their co-existence has been revealed. Under these conditions Chl. vulgaris turned out to be less competitive than Sc. quadricauda. The influence of the ratio of biogenic elements concentration in the environment, which should be recognized as an independent regulatory factor limiting growth of populations in the community and, thus affecting its structure, has been analyzed.

  14. Theory testing in prehistoric North America: fruits of one of the world's great archeological natural laboratories.

    PubMed

    Bingham, Paul M; Souza, Joanne

    2013-01-01

    This paper has several interconnected goals. First and most generally, we will review the project represented by the papers in this dedicated issue and the SAA Symposium (2012) on Social Complexity and the Bow. This project centers on the ever-stronger and broader theory testing now becoming feasible in archeology and anthropology, in this case exploiting the unique natural laboratory represented by what we refer to as the North American Neolithic transitions. Second, we will strive to synopsize the papers in this issue as opportunities to falsify two general theories of the cause of increases in social complexity associated with the North American Neolithic: warfare and social coercion theories.(1) We argue that, though much work remains to be done, the current evidence supports one of the central predictions of both these theories, that the local arrival of elite bow technology was a central driver of local transitions to increased social complexity. This conclusion, if ultimately verified, has profound implications for the possibility of general theories of history. Third, we will argue that several important details of this evidence falsify warfare theory and support (fail to falsify) social coercion theory (the authors' favored perspective). Moreover, several potential falsifications of social coercion theory are amenable to alternative interpretations, leading to new falsifiable predictions. Finally, we discuss how interactions with our colleagues in this project produced new insights into several details of the predictions of social coercion theory, improving our interpretative capacity. PMID:23776052

  15. Paternity analyses in wild-caught and laboratory-reared Caribbean cricket females reveal the influence of mating environment on post-copulatory sexual selection.

    PubMed

    Oneal, E; Knowles, L L

    2015-12-01

    Polyandry is ubiquitous in insects and provides the conditions necessary for male- and female-driven forms of post-copulatory sexual selection to arise. Populations of Amphiacusta sanctaecrucis exhibit significant divergence in portions of the male genitalia that are inserted directly into the female reproductive tract, suggesting that males may exercise some post-copulatory control over fertilization success. We examine the potential for male-male and male-female post-copulatory interactions to influence paternity in wild-caught females of A. sanctaecrucis and contrast our findings with those obtained from females reared in a high-density laboratory environment. We find that female A. sanctaecrucis exercise control by mating multiple times (females mount males), but that male-male post-copulatory interactions may influence paternity success. Moreover, post-copulatory interactions that affect reproductive success of males are not independent of mating environment: clutches of wild-caught females exhibit higher sire diversity and lower paternity skew than clutches of laboratory-reared females. There was no strong evidence for last male precedence in either case. Most attempts at disentangling the contributions of male-male and male-female interactions towards post-copulatory sexual selection have been undertaken in a laboratory setting and may not capture the full context in which they take place - such as the relationship between premating and post-mating interactions. Our results reinforce the importance of designing studies that can capture the multifaceted nature of sexual selection for elucidating the role of post-copulatory sexual selection in driving the evolution of male and female reproductive traits, especially when different components (e.g. precopulatory and post-copulatory interactions) do not exert independent effects on reproductive outcomes. PMID:26348983

  16. Kinetic Studies with Ion Selective Electrodes: Determination of Creatinine in Urine with a Picrate Ion Selective Electrode: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Diamandis, E. P.; And Others

    1983-01-01

    The kinetic of the Jaffe reaction with picrate ion selective electrode (ISE) and a kinetic method for determining creatinine in urine is presented. The experiment could be used to familarize students with the application of ISE in kinetic studies and chemical analysis. (Author/JN)

  17. Gene expression levels are a target of recent natural selection in the human genome.

    PubMed

    Kudaravalli, Sridhar; Veyrieras, Jean-Baptiste; Stranger, Barbara E; Dermitzakis, Emmanouil T; Pritchard, Jonathan K

    2009-03-01

    Changes in gene expression may represent an important mode of human adaptation. However, to date, there are relatively few known examples in which selection has been shown to act directly on levels or patterns of gene expression. In order to test whether single nucleotide polymorphisms (SNPs) that affect gene expression in cis are frequently targets of positive natural selection in humans, we analyzed genome-wide SNP and expression data from cell lines associated with the International HapMap Project. Using a haplotype-based test for selection that was designed to detect incomplete selective sweeps, we found that SNPs showing signals of selection are more likely than random SNPs to be associated with gene expression levels in cis. This signal is significant in the Yoruba (which is the population that shows the strongest signals of selection overall) and shows a trend in the same direction in the other HapMap populations. Our results argue that selection on gene expression levels is an important type of human adaptation. Finally, our work provides an analytical framework for tackling a more general problem that will become increasingly important: namely, testing whether selection signals overlap significantly with SNPs that are associated with phenotypes of interest. PMID:19091723

  18. Patterns of phenoloxidase activity in insecticide resistant and susceptible mosquitoes differ between laboratory-selected and wild-caught individuals

    PubMed Central

    2013-01-01

    Background Insecticide resistance has the potential to alter vector immune competence and consequently affect the transmission of diseases. Methods Using both laboratory isogenic strains and field-caught Culex pipiens mosquitoes, we investigated the effects of insecticide resistance on an important component of the mosquito immune system: the phenoloxidase (PO) activity. As infection risk varies dramatically with the age and sex of mosquitoes, allocation to PO immunity was quantified across different stages of the mosquito life cycle. Results Our results were consistent in showing that larvae have a higher PO activity than adults, females have a higher PO activity than males, and PO activity declines with adult age. We obtained, however, a marked discrepancy between laboratory and field-collected mosquitoes on the effect of insecticide resistance on PO activity. In the laboratory selected strains we found evidence of strong interactions between insecticide resistance and the age and sex of mosquitoes. In particular, 7 and 14 day old esterase-resistant adult females and acetylcholine-esterase resistant males had significantly higher PO activities than their susceptible counterparts. No such effects were, however, apparent in field-caught mosquitoes. Conclusions Combined, the field and laboratory-based approaches employed in this study provide a powerful test of the effect of insecticide resistance on PO-mediated immunity. The use of laboratory-selected insecticide-resistant strains is still the most widely used method to investigate the pleiotropic effects of insecticide resistance. Our results suggest that the outcome of these laboratory-selected mosquitoes must be interpreted with caution and, whenever possible, compared with mosquitoes captured from the field. PMID:24499651

  19. Coated-Wire Ion Selective Electrodes and Their Application to the Teaching Laboratory.

    ERIC Educational Resources Information Center

    Martin, Charles R.; Freiser, Henry

    1980-01-01

    Describes the procedures for construction of a nitrate coated-wire ion selective electrode and suggests experiments for evaluation of electrode response and illustration of typical analytical applications of ion selective electrodes. (CS)

  20. Genome-wide inference of natural selection on human transcription factor binding sites

    PubMed Central

    Arbiza, Leonardo; Gronau, Ilan; Aksoy, Bulent A; Hubisz, Melissa J; Gulko, Brad; Keinan, Alon; Siepel, Adam

    2013-01-01

    For decades, it has been hypothesized that gene regulation has had central role in human evolution, yet much remains unknown about the genome-wide impact of regulatory mutations. Here we use whole-genome sequences and genome-wide chromatin immunoprecipitation and sequencing data to demonstrate that natural selection has profoundly influenced human transcription factor binding sites since the divergence of humans from chimpanzees 4–6 million years ago. Our analysis uses a new probabilistic method, called INSIGHT, for measuring the influence of selection on collections of short, interspersed noncoding elements. We find that, on average, transcription factor binding sites have experienced somewhat weaker selection than protein-coding genes. However, the binding sites of several transcription factors show clear evidence of adaptation. Several measures of selection are strongly correlated with predicted binding affinity. Overall, regulatory elements seem to contribute substantially to both adaptive substitutions and deleterious polymorphisms with key implications for human evolution and disease. PMID:23749186

  1. Detecting the Genetic Signature of Natural Selection in Human Populations: Models, Methods, and Data

    PubMed Central

    Hancock, Angela M.; Rienzo, Anna Di

    2010-01-01

    Patterns of DNA sequence variation in the genome contain a record of past selective events. The ability to collect increasingly large data sets of polymorphisms has allowed investigators to perform hypothesis-driven studies of candidate genes as well as genome-wide scans for signatures of adaptations. This genetic approach to the study of natural selection has identified many signals consistent with predictions from anthropological studies. Selective pressures related to variation in climate, diet, and pathogen exposure have left strong marks on patterns of human variation. Additional signals of adaptations are observed in genes involved in chemosensory perception and reproduction. Several ongoing projects aim to sequence the complete genome of 1000 individuals from different human populations. These large-scale projects will provide data for more complete genome scans of selection, but more focused studies aimed at testing specific hypotheses will continue to hold an important place in elucidating the history of adaptations in humans. PMID:20622977

  2. Joint phenotypes, evolutionary conflict and the fundamental theorem of natural selection

    PubMed Central

    Queller, David C.

    2014-01-01

    Multiple organisms can sometimes affect a common phenotype. For example, the portion of a leaf eaten by an insect is a joint phenotype of the plant and insect and the amount of food obtained by an offspring can be a joint trait with its mother. Here, I describe the evolution of joint phenotypes in quantitative genetic terms. A joint phenotype for multiple species evolves as the sum of additive genetic variances in each species, weighted by the selection on each species. Selective conflict between the interactants occurs when selection takes opposite signs on the joint phenotype. The mean fitness of a population changes not just through its own genetic variance but also through the genetic variance for its fitness that resides in other species, an update of Fisher's fundamental theorem of natural selection. Some similar results, using inclusive fitness, apply to within-species interactions. The models provide a framework for understanding evolutionary conflicts at all levels. PMID:24686940

  3. Laboratory Evaluation of Ion-Selective Electrodes for Simultaneous Analysis of Macronutrients in Hydroponic Solution

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Automated sensing of macronutrients in hydroponic solution would allow more efficient management of nutrients for crop growth in closed hydroponic systems. Ion-selective microelectrode technology requires an ion-selective membrane or a solid metal material that responds selectively to one analyte in...

  4. Reassigning the Structures of Natural Products Using NMR Chemical Shifts Computed with Quantum Mechanics: A Laboratory Exercise

    ERIC Educational Resources Information Center

    Palazzo, Teresa A.; Truong, Tiana T.; Wong, Shirley M. T.; Mack, Emma T.; Lodewyk, Michael W.; Harrison, Jason G.; Gamage, R. Alan; Siegel, Justin B.; Kurth, Mark J.; Tantillo, Dean J.

    2015-01-01

    An applied computational chemistry laboratory exercise is described in which students use modern quantum chemical calculations of chemical shifts to assign the structure of a recently isolated natural product. A pre/post assessment was used to measure student learning gains and verify that students demonstrated proficiency of key learning…

  5. Reassigning the Structures of Natural Products Using NMR Chemical Shifts Computed with Quantum Mechanics: A Laboratory Exercise

    ERIC Educational Resources Information Center

    Palazzo, Teresa A.; Truong, Tiana T.; Wong, Shirley M. T.; Mack, Emma T.; Lodewyk, Michael W.; Harrison, Jason G.; Gamage, R. Alan; Siegel, Justin B.; Kurth, Mark J.; Tantillo, Dean J.

    2015-01-01

    An applied computational chemistry laboratory exercise is described in which students use modern quantum chemical calculations of chemical shifts to assign the structure of a recently isolated natural product. A pre/post assessment was used to measure student learning gains and verify that students demonstrated proficiency of key learning…

  6. Computer-aided molecular selection and design of natural bioactive molecules.

    PubMed

    Bernard, P; Berthon, J Y; Chrétien, J R

    1999-05-01

    The search for natural bioactive compounds has led to a renewal of interest in exploring the plant kingdom. Indeed, a more rational search for innovative natural active compounds has become a priority. This review describes the search for new, natural, active compounds by combining the classical ethnopharmacology approach with newer strategies. The proposed computer-aided molecular selection and design (CAMSD) strategy is based on an in-depth exploitation of all the ethnopharmacological, chemical and biological information available. In the first step, the information extracted from various complementary sources - private, literature, Internet - is organized within a database called Phytotech. In the second step, bioinformatic technologies are used to search for new leads based on the molecular and/or the botanical diversity analysis of the Phytotech database. Once a lead is found, the knowledge of involved protein/ligand interaction is improved by molecular modeling. Finally, the activity of the derived bioactive compounds is optimized by pharmacomodulation of the previously selected leads with the help of two- or three-dimensional quantitative structure-activity relationships (2D- or 3D-QSAR) database exploitation. This coherent and global strategy, specially designed for selecting and designing natural bioactive molecules, is based on the hybridization of various chemometric strategies and supported by our own recent examples dealing with acetylcholinesterase inhibition. PMID:19649949

  7. Natural selection on plant resistance to herbivores in the native and introduced range.

    PubMed

    Valverde, Pedro L; Arroyo, Juan; Núñez-Farfán, Juan; Castillo, Guillermo; Calahorra, Adriana; Pérez-Barrales, Rocío; Tapia-López, Rosalinda

    2015-01-01

    When plants are introduced into new regions, the absence of their co-evolved natural enemies can result in lower levels of attack. As a consequence of this reduction in enemy pressure, plant performance may increase and selection for resistance to enemies may decrease. In the present study, we compared leaf damage, plant size and leaf trichome density, as well as the direction and magnitude of selection on resistance and plant size between non-native (Spain) and native (Mexico) populations of Datura stramonium. This species was introduced to Spain about five centuries ago and constitutes an ideal system to test four predictions of the enemy release hypothesis. Compared with native populations, we expected Spanish populations of D. stramonium to have (i) lower levels of foliar damage; (ii) larger plant size; (iii) lower leaf trichome density that is unrelated to foliar damage by herbivores; and (iv) weak or no selection on resistance to herbivores but strong selection on plant size. Our results showed that, on average, plants from non-native populations were significantly less damaged by herbivores, were less pubescent and were larger than those from native populations. We also detected different selection regimes on resistance and plant size between the non-native and native ranges. Positive selection on plant size was detected in both ranges (though it was higher in the non-native area), but consistent positive selection on relative resistance was detected only in the native range. Overall, we suggest that changes in selection pressure on resistance and plant size in D. stramonium in Spain are a consequence of 'release from natural enemies'. PMID:26205526

  8. Natural selection on plant resistance to herbivores in the native and introduced range

    PubMed Central

    Valverde, Pedro L.; Arroyo, Juan; Núñez-Farfán, Juan; Castillo, Guillermo; Calahorra, Adriana; Pérez-Barrales, Rocío; Tapia-López, Rosalinda

    2015-01-01

    When plants are introduced into new regions, the absence of their co-evolved natural enemies can result in lower levels of attack. As a consequence of this reduction in enemy pressure, plant performance may increase and selection for resistance to enemies may decrease. In the present study, we compared leaf damage, plant size and leaf trichome density, as well as the direction and magnitude of selection on resistance and plant size between non-native (Spain) and native (Mexico) populations of Datura stramonium. This species was introduced to Spain about five centuries ago and constitutes an ideal system to test four predictions of the enemy release hypothesis. Compared with native populations, we expected Spanish populations of D. stramonium to have (i) lower levels of foliar damage; (ii) larger plant size; (iii) lower leaf trichome density that is unrelated to foliar damage by herbivores; and (iv) weak or no selection on resistance to herbivores but strong selection on plant size. Our results showed that, on average, plants from non-native populations were significantly less damaged by herbivores, were less pubescent and were larger than those from native populations. We also detected different selection regimes on resistance and plant size between the non-native and native ranges. Positive selection on plant size was detected in both ranges (though it was higher in the non-native area), but consistent positive selection on relative resistance was detected only in the native range. Overall, we suggest that changes in selection pressure on resistance and plant size in D. stramonium in Spain are a consequence of ‘release from natural enemies’. PMID:26205526

  9. Interrogating a High-Density SNP Map for Signatures of Natural Selection

    PubMed Central

    Akey, Joshua M.; Zhang, Ge; Zhang, Kun; Jin, Li; Shriver, Mark D.

    2002-01-01

    Identifying genomic regions that have been targets of natural selection remains one of the most important and challenging areas of research in genetics. To this end, we report an analysis of 26,530 single nucleotide polymorphisms (SNPs) with allele frequencies that were determined in three populations. Specifically, we calculated a measure of genetic differentiation, FST, for each locus and examined its distribution at the level of the genome, the chromosome, and individual genes. Through a variety of analyses, we have found statistically significant evidence supporting the hypothesis that selection has influenced extant patterns of human genetic variation. Importantly, by contrasting the FST of individual SNPs to the empirical genome-wide distribution of FST, our results are not confounded by tenuous assumptions of population demographic history. Furthermore, we have identified 174 candidate genes with distribution of genetic variation that indicates that they have been targets of selection. Our work provides a first generation natural selection map of the human genome and provides compelling evidence that selection has shaped extant patterns of human genomic variation. [Supplemental material is available online at www.genome.org.] PMID:12466284

  10. Evidence for evolution in response to natural selection in a contemporary human population

    PubMed Central

    Milot, Emmanuel; Mayer, Francine M.; Nussey, Daniel H.; Boisvert, Mireille; Pelletier, Fanie; Réale, Denis

    2011-01-01

    It is often claimed that modern humans have stopped evolving because cultural and technological advancements have annihilated natural selection. In contrast, recent studies show that selection can be strong in contemporary populations. However, detecting a response to selection is particularly challenging; previous evidence from wild animals has been criticized for both applying anticonservative statistical tests and failing to consider random genetic drift. Here we study life-history variation in an insular preindustrial French-Canadian population and apply a recently proposed conservative approach to testing microevolutionary responses to selection. As reported for other such societies, natural selection favored an earlier age at first reproduction (AFR) among women. AFR was also highly heritable and genetically correlated to fitness, predicting a microevolutionary change toward earlier reproduction. In agreement with this prediction, AFR declined from about 26–22 y over a 140-y period. Crucially, we uncovered a substantial change in the breeding values for this trait, indicating that the change in AFR largely occurred at the genetic level. Moreover, the genetic trend was higher than expected under the effect of random genetic drift alone. Our results show that microevolution can be detectable over relatively few generations in humans and underscore the need for studies of human demography and reproductive ecology to consider the role of evolutionary processes. PMID:21969551

  11. Cyclone Tolerance in New World Arecaceae: Biogeographic Variation and Abiotic Natural Selection

    PubMed Central

    Griffith, M. Patrick; Noblick, Larry R.; Dowe, John L.; Husby, Chad E.; Calonje, Michael A.

    2008-01-01

    Background and Aims Consistent abiotic factors can affect directional selection; cyclones are abiotic phenomena with near-discrete geographic limits. The current study investigates selective pressure of cyclones on plants at the species level, testing for possible natural selection. Methods New World Arecaceae (palms) are used as a model system, as plants with monopodial, unbranched arborescent form are most directly affected by the selective pressure of wind load. Living specimens of known provenance grown at a common site were affected by the same cyclone. Data on percentage mortality were compiled and analysed in biogeographic and phylogenetic contexts. Key Results Palms of cyclone-prone provenance exhibited a much lower (one order of magnitude) range in cyclone tolerance, and significantly lower (P < 0·001) mean percentage mortality than collections from cyclone-free areas. Palms of cyclone-free provenance had much greater variation in tolerance, and significantly greater mean percentage mortality. A test for serial independence recovered no significant phylogenetic autocorrelation of percentage mortality. Conclusions Variation in cyclone tolerance in New World Arecaceae correlates with biogeography, and is not confounded with phylogeny. These results suggest natural selection of cyclone tolerance in cyclone-prone areas. PMID:18669575

  12. Natural selection of autocatalytic systems in flow as the universal mechanism of prebiotic evolution

    NASA Astrophysics Data System (ADS)

    Bartsev, S.; Mezhevikin, V.

    The problem of searching for extraterrestrial life is closely associated with the problem of origin of life in general and on the Earth. However convincing scientific concept of this event does not exist till now. The probability of casual occurrence of the elementary living cell from a set of abiogenous substances is so small, that from the point of natural-science methodological positions this variant of life origin should be excluded. It is necessary to assume the predecessors of cells were very simple, and their development, perfecting and thickening occurred gradually and in the certain sense neatly via natural selection. An assumption, that the predecessors of cells were elementary autocatalytic systems on the basis of the phase-isolated particles, and the mechanism of their selection was selection in flow with respect to kinetics parameters is put forward. In the paper probable directions of autocatalytic systems selection in flow inside a reactor of deal mixing are considered. As reali analog of in flow system of the kind the hydrothermal vent tube worms found in deep-sea waters could be considered. Thus, it is possible to select certain types of autocatalytic systems admitting an opportunity of "mutagenesis", and to plan experimental modeling of initial stages of prebiotic evolution under various physical-chemical conditions, including extraterrestrial ones. According to the concept, the life origin under the certain physical-chemical planetary conditions is the inevitable planetary phenomenon and key stages of this phenomenon allow not only theoretical, but also experimental analysis.

  13. Strong natural selection on juveniles maintains a narrow adult hybrid zone in a broadcast spawner.

    PubMed

    Prada, Carlos; Hellberg, Michael E

    2014-12-01

    Natural selection can maintain and help form species across different habitats, even when dispersal is high. Selection against inferior migrants (immigrant inviability) acts when locally adapted populations suffer high mortality on dispersal to unsuitable habitats. Habitat-specific populations undergoing divergent selection via immigrant inviability should thus show (1) a change in the ratio of adapted to nonadapted individuals among age/size classes and (2) a cline (defined by the environmental gradient) as selection counterbalances migration. Here we examine the frequencies of two depth-segregated lineages in juveniles and adults of a Caribbean octocoral, Eunicea flexuosa. Distributions of the two lineages in both shallow and deep environments were more distinct when inferred from adults than juveniles. Despite broad larval dispersal, we also found an extremely narrow hybrid zone (<100 m), with coincident clines for molecular and morphological characters of the host coral and its algal symbiont. Effective dispersal estimates derived from the hybrid zone are remarkably small (<20 m) for a broadcast spawner. The large selection coefficient against mismatched genotypes derived from cohort data is consistent with that from field transplant experiments. Narrow hybrid zones and limited effective dispersal may be a common outcome of long periods of postsettlement, prereproductive selection across steep ecological gradients. Strong diversifying selection provides a mechanism to explain the prevalence of depth-segregated sibling species in the sea. PMID:25438171

  14. Divergent natural selection promotes immigrant inviability at early and late stages of evolutionary divergence.

    PubMed

    Ingley, Spencer J; Johnson, Jerald B

    2016-03-01

    Natural selection's role in speciation has been of fundamental importance since Darwin first outlined his theory. Recently, work has focused on understanding how selection drives trait divergence, and subsequently reproductive isolation. "Immigrant inviability," a barrier that arises from selection against immigrants in their nonnative environment, appears to be of particular importance. Although immigrant inviability is likely ubiquitous, we know relatively little about how selection acts on traits to drive immigrant inviability, and how important immigrant inviability is at early-versus-late stages of divergence. We present a study evaluating the role of predation in the evolution of immigrant inviability in recently diverged population pairs and a well-established species pair of Brachyrhaphis fishes. We evaluate performance in a high-predation environment by assessing survival in the presence of a predator, and swimming endurance in a low-predation environment. We find strong signatures of local adaptation and immigrant inviability of roughly the same magnitude both early and late in divergence. We find remarkably conserved selection for burst-speed swimming (important in predator evasion), and selection for increased size in low-predation environments. Our results highlight the consistency with which selection acts during speciation, and suggest that similar factors might promote initial population differentiation and maintain differentiation at late stages of divergence. PMID:26831519

  15. Host Species and Environmental Effects on Bacterial Communities Associated with Drosophila in the Laboratory and in the Natural Environment

    PubMed Central

    Staubach, Fabian; Baines, John F.; Künzel, Sven; Bik, Elisabeth M.; Petrov, Dmitri A.

    2013-01-01

    The fruit fly Drosophila is a classic model organism to study adaptation as well as the relationship between genetic variation and phenotypes. Although associated bacterial communities might be important for many aspects of Drosophila biology, knowledge about their diversity, composition, and factors shaping them is limited. We used 454-based sequencing of a variable region of the bacterial 16S ribosomal RNA gene to characterize the bacterial communities associated with wild and laboratory Drosophila isolates. In order to specifically investigate effects of food source and host species on bacterial communities, we analyzed samples from wild Drosophila melanogaster and D. simulans collected from a variety of natural substrates, as well as from adults and larvae of nine laboratory-reared Drosophila species. We find no evidence for host species effects in lab-reared flies; instead, lab of origin and stochastic effects, which could influence studies of Drosophila phenotypes, are pronounced. In contrast, the natural Drosophila–associated microbiota appears to be predominantly shaped by food substrate with an additional but smaller effect of host species identity. We identify a core member of this natural microbiota that belongs to the genus Gluconobacter and is common to all wild-caught flies in this study, but absent from the laboratory. This makes it a strong candidate for being part of what could be a natural D. melanogaster and D. simulans core microbiome. Furthermore, we were able to identify candidate pathogens in natural fly isolates. PMID:23967097

  16. Laboratory Constraints on the Stability of Petroleum at Elevated Temperatures: Implications for the Origin of Natural Gas

    SciTech Connect

    Seewald, Jeffrey, S.

    2011-03-14

    Results of prior DOE supported research conducted at the Woods Hole Oceanographic Institution have demonstrated the participation of sedimentary minerals and water as reactants and catalysts in chemical transformations associated with the degradation of oil and the formation of low molecular weight organic compounds. The occurrence of such processes in natural environments can be difficult to recognize because the composition of organic alteration products may not be substantially different than those produced by thermal cracking. The goals of this study were the development of diagnostic tools based on hydrogen and carbon isotopes that can be used to identify geochemical processes responsible for the formation of thermogenic natural gas. In addition, our activities were expanded to include experimental investigation of CO2 reduction in aqueous systems at elevated temperature and pressures and an assessment of microbial activity in relatively low temperature (<70°C) natural gas reservoirs in southeastern Oklahoma. Specific objectives included: ● A laboratory investigation of geochemical processes that regulate the hydrogen isotope composition of low molecular weight hydrocarbons in natural gas at elevated temperatures and pressures. ● A laboratory investigation of factors that regulate the carbon isotope composition of organic acids in basinal brines. ● A laboratory assessment of the role of methanol during reduction of CO2 to CH4 under hydrothermal conditions. ● Characterization of microbial ecosystems in coproduced fluids from the Potato Hills gas field to assess the role of microbes in the generation of natural gas.

  17. Hands-On Laboratory Simulation of Evolution: An Investigation of Mutation, Natural Selection, & Speciation

    ERIC Educational Resources Information Center

    Hildebrand, Terri J.; Govedich, Fredric R.; Bain, Bonnie A.

    2010-01-01

    Evolutionary theory is the foundation of the biological sciences, yet conveying it to General Biology students often presents a challenge, especially at larger institutions where student numbers in foundation courses can exceed several hundred per lecture section. We present a pedagogically sound exercise that utilizes a series of simple and…

  18. Hands-On Laboratory Simulation of Evolution: An Investigation of Mutation, Natural Selection, & Speciation

    ERIC Educational Resources Information Center

    Hildebrand, Terri J.; Govedich, Fredric R.; Bain, Bonnie A.

    2010-01-01

    Evolutionary theory is the foundation of the biological sciences, yet conveying it to General Biology students often presents a challenge, especially at larger institutions where student numbers in foundation courses can exceed several hundred per lecture section. We present a pedagogically sound exercise that utilizes a series of simple and…

  19. ENVIRONMENTAL PATHWAYS OF SELECTED CHEMICALS IN FRESHWATER SYSTEMS. PART II. LABORATORY STUDIES

    EPA Science Inventory

    Environmental exposure assessment models and laboratory procedures for predicting the pathways of potentially harmful chemicals in freshwater environments were described in Part I of this report (PB-274 548). Procedures were developed for measuring the rates of volatilization, ph...

  20. Foraminiferal Range Expansions: The Mediterranean Sea as a natural laboratory for climate induced invasions

    NASA Astrophysics Data System (ADS)

    Hortense Mouanga, Gloria; Langer, Martin R.

    2015-04-01

    Climate change and biological invasions are key processes that modify biodiversity. One of the most severely affected areas of global change is the Mediterranean Sea, where global warming and the opening of the Suez Canal triggered a mass invasion of tropical Red Sea taxa into Mediterranean territories. Climate models prognosticate that the Mediterranean Sea will be one of the most affected ocean regions and may thus serve as a natural laboratory of future global changes. Among the key taxa that are rapidly expanding their latitudinal range in the Mediterranean Sea are symbiont-bearing foraminifera of the genus Amphistegina. Their range expansion strongly correlates with rising sea surface temperatures and mirrors processes of global change. Amphisteginid foraminifera are among the most prolific foraminiferal species and contribute significantly to shallow-water carbonate sediments. Given their prominent environmental role, rapid biogeographic range expansion, and impact on native ecosystems, amphisteginid range expansion and invasion into new territory are likely to trigger changes in ecosystem functioning. Among the uncertainties, it is not known whether all parts of the Mediterranean will be affected equally and to what extent amphisteginid invasions will impact native biotas. We have initiated a new baseline study to explore the effects of invasive amphisteginids on native foraminiferal biotas and to monitor expansion rates and effects on ecosystem functioning along the current range expansion front. We will present new data on recent shift along the range expansion front and discuss cascading effects on community structures and species richness of native foraminiferal biotas. The magnitude and effects that climate change will have on the Mediterranean foraminiferal faunas may ultimately serve as an example of what would happen along expansion fronts in global oceans.

  1. Comets as natural laboratories: Interpretations of the structure of the inner heliosphere

    NASA Astrophysics Data System (ADS)

    Ramanjooloo, Yudish; Jones, Geraint H.; Coates, Andrew J.; Owens, Mathew J.

    2015-11-01

    Much has been learnt about the heliosphere’s structure from in situ solar wind spacecraft observations. Their coverage is however limited in time and space. Comets can be considered to be natural laboratories of the inner heliosphere, as their ion tails trace the solar wind flow. Solar wind conditions influence comets’ induced magnetotails, formed through the draping of the heliospheric magnetic field by the velocity shear in the mass-loaded solar wind.I present a novel imaging technique and software to exploit the vast catalogues of amateur and professional images of comet ion tails. My projection technique uses the comet’s orbital plane to sample its ion tail as a proxy for determining multi-latitudinal radial solar wind velocities in each comet’s vicinity. Making full use of many observing stations from astrophotography hobbyists to professional observatories and spacecraft, this approach is applied to several comets observed in recent years. This work thus assesses the validity of analysing comets’ ion tails as complementary sources of information on dynamical heliospheric phenomena and the underlying continuous solar wind.Complementary velocities, measured from folding ion rays and a velocity profile map built from consecutive images, are derived as an alternative means of quantifying the solar wind-cometary ionosphere interaction, including turbulent transient phenomena such as coronal mass ejections. I review the validity of these techniques by comparing near-Earth comets to solar wind MHD models (ENLIL) in the inner heliosphere and extrapolated measurements by ACE to the orbit of comet C/2004 Q2 (Machholz), a near-Earth comet. My radial velocities are mapped back to the solar wind source surface to identify sources of the quiescent solar wind and heliospheric current sheet crossings. Comets were found to be good indicators of solar wind structure, but the quality of results is strongly dependent on the observing geometry.

  2. Natural Gamma Emitters after a Selective Chemical Separation of a TENORM residue: Preliminary Results

    NASA Astrophysics Data System (ADS)

    de Freitas, Antonio Alves; dos Santos, Adir Janete Godoy; Pecequilo, Brigitte Roxana Soreanu; Abrão, Alcídio

    2008-08-01

    An analytical procedure was established in order to obtain selective fractions containing radium isotopes (228Ra), thorium (232Th), and rare earths from RETOTER (REsíduo de TÓrio e TErras Raras), a solid residue rich in rare earth elements, thorium isotopes and small amount of natural uranium generated from the operation of a thorium pilot plant for purification and production of pure thorium nitrate at IPEN -CNEN/SP. The paper presents preliminary results of 228Ra, 226Ra, 238U, 210Pb, and 40K concentrations in the selective fractions and total residue determined by high-resolution gamma spectroscopy, considering radioactive equilibrium of the samples.

  3. Natural Gamma Emitters after a Selective Chemical Separation of a TENORM residue: Preliminary Results

    SciTech Connect

    Alves de Freitas, Antonio; Abrao, Alcidio; Godoy dos Santos, Adir Janete; Pecequilo, Brigitte Roxana Soreanu

    2008-08-07

    An analytical procedure was established in order to obtain selective fractions containing radium isotopes ({sup 228}Ra), thorium ({sup 232}Th), and rare earths from RETOTER (REsiduo de TOrio e TErras Raras), a solid residue rich in rare earth elements, thorium isotopes and small amount of natural uranium generated from the operation of a thorium pilot plant for purification and production of pure thorium nitrate at IPEN -CNEN/SP. The paper presents preliminary results of {sup 228}Ra, {sup 226}Ra, {sup 238}U, {sup 210}Pb, and {sup 40}K concentrations in the selective fractions and total residue determined by high-resolution gamma spectroscopy, considering radioactive equilibrium of the samples.

  4. Material selection for wellhead equipment exposed to chlorinated and natural seawater

    SciTech Connect

    Olsen, S.; Nice, P.; Strandmyr, O.; Maligas, M.; Vicic, J.

    1996-08-01

    Corrosion resistant alloys have been used in marine environments for their corrosion resistance. However, some of these materials are prone to localized corrosion, in particular crevice and pitting corrosion, in natural seawater. Injection water normally consists of de-oxygenated seawater, but, more recently either continuously or batch chlorinated and fully oxygenated seawater has been selected for this purpose because of their cost benefits. This investigation covers testing of corrosion resistant materials to aid in the selection of materials for wellhead equipment in an oxygenated and chlorinated seawater injection environment.

  5. Metabolic correlates of selection on aerobic capacity in laboratory mice: a test of the model for the evolution of endothermy.

    PubMed

    Gebczy?ski, Andrzej K; Konarzewski, Marek

    2009-09-01

    According to the aerobic capacity model of the evolution of endothermy, high levels of basal/resting metabolic rate (BMR/RMR) underlying endothermy have evolved as a correlated response to selection for high rates of aerobic metabolism (V(O(2)max)). To test the model we studied metabolic, behavioural and morphological correlates of replicated selection on maximum body mass-corrected metabolism elicited by swimming (V(O(2)swim)) in male laboratory mice. While 10 generations of selection did not change body mass, it resulted in a 12% difference in V(O(2)swim) between mice of selected and control line types and significant, correlated responses in maximum metabolic rates elicited by exposure to cold in a helium-oxygen atmosphere (V(O(2)He)), and during forced running on a motorized treadmill (V(O(2)run)). Selected and control lines also significantly differed with respect to duration of running (a measure of stamina, t(run)), and the distance run to exhaustion (d(e)). However, the selection protocol did not result in elevated BMR and voluntary activity. Higher V(O(2)max) in selected animals was positively correlated with higher masses of gastrocnemius muscles and heart but not of other visceral organs (intestine, stomach, liver and kidneys). These findings provide a mechanistic explanation for the lack of correlation between basal and maximal metabolic rates in selected mice. Overall, our study does not support the assumptions of the aerobic capacity model for the evolution of endothermy. PMID:19684223

  6. Comparing the Slaking of Clay-Bearing Rocks Under Laboratory Conditions to Slaking Under Natural Climatic Conditions

    NASA Astrophysics Data System (ADS)

    Gautam, T. P.; Shakoor, A.

    2016-01-01

    The objective of this study was to compare the laboratory slaking behavior of common clay-bearing rocks to their slaking behavior under natural climatic conditions observed during a 1-year experimental study. Five-cycle slake durability tests were performed in the laboratory on five claystones, five mudstones, five siltstones, and five shales. Twelve replicate specimens of each of these 20 rocks were also exposed to natural climatic conditions for 12 months. After each month of exposure, one replicate specimen of each rock was removed from natural exposure and its grain size distribution was determined. The results of laboratory tests and field experiment were compared in terms of 1st, 2nd, 3rd, 4th, and 5th cycle slake durability indices (Id1, Id2, Id3, Id4, Id5), grain size distribution of slaked material, and disintegration ratio ( D R), where D R is the ratio of the area under the grain size distribution curve of slaked material for a given specimen to the total area encompassing all grain size distribution curves of the specimens tested. Correlations of Id1, Id2, Id3, Id4, and Id5 with D R values for laboratory specimens exhibit R 2 values of 0.87, 0.88, 0.83, 0.75, and 0.70, respectively. However, the relationship between Id2 and D R, determined after 1, 3, 6, and 12 months of natural exposure, becomes weaker with increasing time of exposure, with R 2 values of 0.65, 0.63, 0.63, and 0.25, respectively. The fifth-cycle slake durability index (Id5) for laboratory tested specimens shows a better correlation with D R values for naturally exposed specimens ( R 2 up to 0.80). A comparison of grain size distribution curves of slaked material for laboratory specimens, after the 2nd cycle slake durability test, with those of specimens exposed to natural climatic conditions shows that the laboratory test underestimates the field durability for claystones, and overestimates it for siltstones.

  7. Stochastic effects in adaptive reconstruction of body damage: implied the creativity of natural selection.

    PubMed

    Xiao, Bo; Cui, Li-Qiang; Chen, Tian-Ming; Lian, Bin

    2015-11-01

    After an injury occurs, mechanical/biochemical loads on muscles influence the composition and structure of recovering muscles; this effect likely occurs in other tissues, cells and biological molecules as well owing to the similarity, interassociation and interaction among biochemical reactions and molecules. The 'damage and reconstruction' model provides an explanation for how an ideal cytoarchitecture is created by reducing components not suitable for bearing loads; in this model, adaptive changes are induced by promoting the stochasticity of biochemical reactions. Biochemical and mechanical loads can direct the stochasticity of biochemical reactions, which can in turn induce cellular changes. Thus, mechanical and biochemical loads, under natural selection pressure, modify the direction of cell- and tissue-level changes and guide the formation of new structures and traits, thereby influencing microevolution. In summary, the 'damage and reconstruction' model accounts for the role of natural selection in the formation of new organisms, helps explain punctuated equilibrium, and illustrates how macroevolution arises from microevolution. PMID:26153081

  8. Effects of Heterogeneous Adsorption Affinity on Natural Organic Matter (NOM) Transport in Laboratory Sand Columns

    NASA Astrophysics Data System (ADS)

    McInnis, D. P.; Bolster, D.; Maurice, P. A.

    2012-12-01

    Transport of reactive sorbing solutes through porous media is commonly quantified by implementing an effective retardation coefficient in the advection-dispersion equation (ADE), which describes dispersion in accordance with Fick's law. However, anomalous (non-Fickian) transport behavior can be observed in systems with heterogeneous retardation coefficients (Dentz & Castro, 2009). In such systems, the ADE is unable to reproduce the non-Fickian nature of plume shapes and breakthrough curves, motivating the development and application of alternative solute transport theories, such as the continuous time random walk (CTRW) or multi-rate mass transfer (MRMT). Heterogeneity in retardation coefficients in practice arises from variability in the geochemical properties controlling sorption-desorption kinetics between the solute and mineral surfaces. These distributions have been described in the context of heterogeneity of the porous medium, but to date little attention has been given to the potential role of a geochemically heterogeneous solute. In this work, we consider a system in which anomalous transport arises during the passage of natural organic matter (NOM), a polydisperse mixture of compounds derived from the breakdown of plants and microorganisms in the environment, through homogeneous laboratory sand columns. NOM solutions were passed through columns containing either hematite, corundum, or a naturally-coated quartz sand at a variety of pH and ionic strength conditions. Influent and effluent NOM concentration was measured as UV absorbance at 254 nm. The resulting breakthrough curves are non-Fickian, displaying power-law tailing at late times. Such curves cannot be predicted by the ADE model. Reactivity of NOM components is known to be related to their molecular weight (MW), which tends to be log-normally distributed in aquatic NOM isolates (Cabaniss et al., 2000). Low-MW compounds are more water-soluble, have a higher diffusion coefficient, and due to their smaller structure, are able to enter nanopores which exclude macromolecules. Conversely, high-MW components are hydrophobic, less mobile, and have a greater affinity for metal binding than their smaller counterparts. By analyzing the transport of different NOM components in the effluent solution over time we see that there is a clear heterogeneity in the retardation of the different NOM components. Using the approaches of Dentz & Castro (2009) and Dentz & Bolster (2011) we can show that the effective upscaled transport can be modeled as a CTRW. To this end we demonstrate that the CTRW and MRMT models (which can be shown to be intricately related) can indeed faithfully capture the observed behavior. From a practical perspective, our experiments demonstrate increased mobility of low-MW fractions of NOM relative to high-MW fractions, which - given the ability of NOM to bind to organic compounds, metals, and radionuclides - could have important implications for contaminant transport in groundwater systems.

  9. Coding of Electronic Laboratory Reports for Biosurveillance, Selected United States Hospitals, 2011

    PubMed Central

    Dhakal, Sanjaya; Burrer, Sherry L.; Winston, Carla A.; Dey, Achintya; Ajani, Umed; Groseclose, Samuel L.

    2015-01-01

    Objective Electronic laboratory reporting has been promoted as a public health priority. The Office of the U.S. National Coordinator for Health Information Technology has endorsed two coding systems: Logical Observation Identifiers Names and Codes (LOINC) for laboratory test orders and Systemized Nomenclature of Medicine-Clinical Terms (SNOMED CT) for test results. Materials and Methods We examined LOINC and SNOMED CT code use in electronic laboratory data reported in 2011 by 63 non-federal hospitals to BioSense electronic syndromic surveillance system. We analyzed the frequencies, characteristics, and code concepts of test orders and results. Results A total of 14,028,774 laboratory test orders or results were reported. No test orders used SNOMED CT codes. To describe test orders, 77% used a LOINC code, 17% had no value, and 6% had a non-informative value, “OTH”. Thirty-three percent (33%) of test results had missing or non-informative codes. For test results with at least one informative value, 91.8% had only LOINC codes, 0.7% had only SNOMED codes, and 7.4% had both. Of 108 SNOMED CT codes reported without LOINC codes, 45% could be matched to at least one LOINC code. Conclusion Missing or non-informative codes comprised almost a quarter of laboratory test orders and a third of test results reported to BioSense by non-federal hospitals. Use of LOINC codes for laboratory test results was more common than use of SNOMED CT. Complete and standardized coding could improve the usefulness of laboratory data for public health surveillance and response. PMID:26392850

  10. Darwin's passionate environmentalism or the dangerous fallacy of the 'All-sufficiency of natural selection' theory.

    PubMed

    Marsh, David

    2012-01-01

    Following his last edition of the Origin of Species in 1872, Darwin spent much of the rest of his life searching for possible mechanisms, such as the pangenes in the blood, which would communicate information from the environment to the genome. In each of his six editions of the 'Origin', he stated that there were two forces in evolution - natural selection and conditions of existence. Of the two, he claims that the latter is the more powerful. In so doing, he recognized that natural selection could only operate within the bounds of possibility, that is the environment. August Weismann claimed that conditions of existence had no place in evolution. His publication, the 'All-sufficiency of natural selection', was based on mutilation (cutting tails of rodents and watching the next generation grow tails), which has nothing to do with Darwin's concept of conditions of existence. Nonetheless, evolutionary biologists in general followed the line of the 'all sufficiency' theory and ignored Darwin's conditions of existence, which in other words means the environment. Natural selection has a weak predictive power as it is based on random events. However, the conditions of existence have, by contrast, strong predictive powers that can be tested. The environmental views of two of the greatest evolutionists, Lamarck and Darwin, have been consistently ignored by most evolution theorists who came after them, continuing for over 200 years. Looking at the fossil record through the eyes of Darwin's conditions of existence, not to mention the recent changes in height and shape over the last century, it is possible to draw important conclusions about the past and predictions of the future. With new knowledge of epigenetics, it is perhaps time that Darwin's conditions of existence were given a second hearing. PMID:22544777

  11. Darwin's Arguments in Favour of Natural Selection and Against Special Creationism

    NASA Astrophysics Data System (ADS)

    Nola, Robert

    2013-02-01

    In many places in The Origin of Species, Darwin compares his own theory of Natural Selection favourably with Special Creationism which comes off as a bad second best. He does this using some version of the argument form known as `Inference to the Best Explanation'. The first part of this paper is methodological. It considers Whewell's notion of consilience, that is, the way in which theories can get additional confirmation through unifying otherwise disparate and independent facts. Then it considers various forms of inference to the best explanation. The second part of the paper applies these methodological considerations to an analysis of some of the many passages in Origin where Darwin presents his case in favour of Natural Selection. This gives a far superior explanation of biological facts compared with Special Creationism which provides either an inferior explanation or no explanation at all. Contrary to the view that Creationism should not be taught, the passages from Darwin show at least that it should be understood if only to show that it offers no explanation of a wide range of obvious biological facts. As such the passages in Origin in which Darwin presents his case against Creationism can serve as a series of excellent exercises in getting students to think about Natural Selection as opposed to Creationism. For this reason alone they ought to be better known. In addition, Darwin's point in these passages can only be understood using principles of scientific method, such as inference to the best explanation, which are essential in showing that Natural Selection is to be preferred to Creationism.

  12. MHC studies in nonmodel vertebrates: what have we learned about natural selection in 15 years?

    PubMed

    Bernatchez, L; Landry, C

    2003-05-01

    Elucidating how natural selection promotes local adaptation in interaction with migration, genetic drift and mutation is a central aim of evolutionary biology. While several conceptual and practical limitations are still restraining our ability to study these processes at the DNA level, genes of the major histocompatibility complex (MHC) offer several assets that make them unique candidates for this purpose. Yet, it is unclear what general conclusions can be drawn after 15 years of empirical research that documented MHC diversity in the wild. The general objective of this review is to complement earlier literature syntheses on this topic by focusing on MHC studies other than humans and mice. This review first revealed a strong taxonomic bias, whereby many more studies of MHC diversity in natural populations have dealt with mammals than all other vertebrate classes combined. Secondly, it confirmed that positive selection has a determinant role in shaping patterns of nucleotide diversity in MHC genes in all vertebrates studied. Yet, future tests of positive selection would greatly benefit from making better use of the increasing number of models potentially offering more statistical rigour and higher resolution in detecting the effect and form of selection. Thirdly, studies that compared patterns of MHC diversity within and among natural populations with neutral expectations have reported higher population differentiation at MHC than expected either under neutrality or simple models of balancing selection. Fourthly, several studies showed that MHC-dependent mate preference and kin recognition may provide selective factors maintaining polymorphism in wild outbred populations. However, they also showed that such reproductive mechanisms are complex and context-based. Fifthly, several studies provided evidence that MHC may significantly influence fitness, either by affecting reproductive success or progeny survival to pathogens infections. Overall, the evidence is compelling that the MHC currently represents the best system available in vertebrates to investigate how natural selection can promote local adaptation at the gene level despite the counteracting actions of migration and genetic drift. We conclude this review by proposing several directions where future research is needed. PMID:14635837

  13. Implications of quantum metabolism and natural selection for the origin of cancer cells and tumor progression

    NASA Astrophysics Data System (ADS)

    Davies, Paul; Demetrius, Lloyd A.; Tuszynski, Jack A.

    2012-03-01

    Empirical studies give increased support for the hypothesis that the sporadic form of cancer is an age-related metabolic disease characterized by: (a) metabolic dysregulation with random abnormalities in mitochondrial DNA, and (b) metabolic alteration - the compensatory upregulation of glycolysis to offset mitochondrial impairments. This paper appeals to the theory of Quantum Metabolism and the principles of natural selection to formulate a conceptual framework for a quantitative analysis of the origin and proliferation of the disease. Quantum Metabolism, an analytical theory of energy transduction in cells inspired by the methodology of the quantum theory of solids, elucidates the molecular basis for differences in metabolic rate between normal cells, utilizing predominantly oxidative phosphorylation, and cancer cells utilizing predominantly glycolysis. The principles of natural selection account for the outcome of competition between the two classes of cells. Quantum Metabolism and the principles of natural selection give an ontogenic and evolutionary rationale for cancer proliferation and furnish a framework for effective therapeutic strategies to impede the spread of the disease.

  14. Natural selection and inheritance of breeding time and clutch size in the collared flycatcher.

    PubMed

    Sheldon, B C; Kruuk, L E B; Merilä, J

    2003-02-01

    Many characteristics of organisms in free-living populations appear to be under directional selection, possess additive genetic variance, and yet show no evolutionary response to selection. Avian breeding time and clutch size are often-cited examples of such characters. We report analyses of inheritance of, and selection on, these traits in a long-term study of a wild population of the collared flycatcher Ficedula albicollis. We used mixed model analysis with REML estimation ("animal models") to make full use of the information in complex multigenerational pedigrees. Heritability of laying date, but not clutch size, was lower than that estimated previously using parent-offspring regressions, although for both traits there was evidence of substantial additive genetic variance (h2 = 0.19 and 0.29, respectively). Laying date and clutch size were negatively genetically correlated (rA = -0.41 +/- 0.09), implying that selection on one of the traits would cause a correlated response in the other, but there was little evidence to suggest that evolution of either trait would be constrained by correlations with other phenotypic characters. Analysis of selection on these traits in females revealed consistent strong directional fecundity selection for earlier breeding at the level of the phenotype (beta = -0.28 +/- 0.03), but little evidence for stabilising selection on breeding time. We found no evidence that clutch size was independently under selection. Analysis of fecundity selection on breeding values for laying date, estimated from an animal model, indicated that selection acts directly on additive genetic variance underlying breeding time (beta = -0.20 +/- 0.04), but not on clutch size (beta = 0.03 +/- 0.05). In contrast, selection on laying date via adult female survival fluctuated in sign between years, and was opposite in sign for selection on phenotypes (negative) and breeding values (positive). Our data thus suggest that any evolutionary response to selection on laying date is partially constrained by underlying life-history trade-offs, and illustrate the difficulties in using purely phenotypic measures and incomplete fitness estimates to assess evolution of life-history trade-offs. We discuss some of the difficulties associated with understanding the evolution of laying date and clutch size in natural populations. PMID:12683536

  15. The importance of selection at the level of the pair over 25 years in a natural population of birds

    PubMed Central

    Björklund, Mats; Gustafsson, Lars

    2013-01-01

    Knowledge of the pattern of selection in natural populations is fundamental for our understanding of the evolutionary process. Selection at higher levels has gained considerable theoretical support in recent years, and one possible level of selection is the breeding pair where fitness is a function of the pair and cannot be reduced to single individuals. We analyzed the importance of pair-level selection over 25 years in a natural population of the collared flycatcher. Pair-level selection was significant in five and probably in another 9 years. The relative importance of pair-level selection varied over years and can have stronger or the same strength as directional selection. This means that selection can act on the combination of the breeding pair in addition to selection on each individual separately. Overall, the conservative estimates obtained here show that this is a potentially important form of selection. PMID:24340199

  16. Capturing Naturally Occurring Superior Performance in the Laboratory: Translational Research on Expert Performance

    ERIC Educational Resources Information Center

    Ericsson, K. Anders; Williams, A. Mark

    2007-01-01

    One of the central challenges to studying highly skilled performance in the laboratory is methodological. It is necessary to develop standardized methods that allow investigators to make experts repeatedly reproduce their superior performance in the laboratory. The recent increase in demand for translational research has raised related issues of…

  17. Introgression of mitochondrial DNA promoted by natural selection in the Japanese pipistrelle bat (Pipistrellus abramus).

    PubMed

    Dong, Ji; Mao, Xiuguang; Sun, Haijian; Irwin, David M; Zhang, Shuyi; Hua, Panyu

    2014-12-01

    Introgression of mitochondrial DNA (mtDNA) between closely related taxa can be promoted by either neutral processes or natural selection. Since mitochondrial gene-encoded proteins play critical roles in oxidative metabolism, mtDNA genes are commonly considered to experience strong selective constraint. However, metabolic requirements vary across climatic and ecological gradients, thus modifying potential selective pressures acting on mtDNA genes. Here we conducted tests to detect adaptive evolution occurring in two mtDNA genes (Cytb and ND5) in individuals of Japanese pipistrelle bat (Pipistrellus abramus) across the mainland of China and Hainan Island. Nuclear DNA markers identified two clades in both the mainland and Hainan Island populations, whereas each of these regions had a specific mtDNA clade. This cyto-nuclear discordance is most likely caused by introgression of the mtDNA by ruling out two other alternative scenarios (incomplete lineage sorting and sex-biased gene flow). Although population-based analyses revealed purifying selection acting on Cytb and neutrality in ND5, multiple nonsynonymous substitutions in both Cytb and ND5 were suggested to have been caused by positive selection by a divergence-based analysis. Our study supports the view that molecular adaptation can occur at genes under strong purifying selection if nonsynonymous substitutions cause radical changes in the physicochemical properties of amino acids. PMID:25266707

  18. Form and nature of precopulatory sexual selection in both sexes of a moth

    NASA Astrophysics Data System (ADS)

    Xu, Jin; Wang, Qiao

    2010-07-01

    Sexual selection is a process that operates through intrasexual competition and intersexual choice for reproduction in both sexes. Here, we report our work on a polygamous moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), aiming to infer the form and nature of precopulatory sexual selection in males and females. We show that, although a number of traits measured in each sex are correlated with mating success, the primary selection trait in females appears to be abdominal thickness and that in males is aedeagus length. As the female’s abdominal thickness is a reliable signal about the number and developmental stage of eggs, males who select females with thicker abdomens for mating will gain reproductive benefit, i.e., fertilizing more mature eggs. For females, earlier maturation of their eggs makes the females more likely to achieve mating earlier in an uncertain world where there is no guarantee that they will find more males in the future. Sexual selection appears to be the important force behind the evolution of fast egg maturation in females. We show that, under a male-biased sex ratio, more than 20% of mating fails within a few minutes after the aedeagus has penetrated into the female’s genitalia, suggesting that females can assess the features of the male aedeagus before allowing insemination to occur. Dissection and examination of both sexes suggest that a longer aedeagus enhances mating and fertilization efficiency in this species, supporting the notion that sexual selection is a primary force in the evolution of genital variance.

  19. Does natural selection organize ecosystems for the maintenance of high productivity and diversity?

    PubMed Central

    Leigh, Egbert Giles; Vermeij, Geerat Jacobus

    2002-01-01

    Three types of evidence suggest that natural ecosystems are organized for high productivity and diversity: (i) changes not previously experienced by a natural ecosystem, such as novel human disturbances, tend to diminish its productivity and/or diversity, just as 'random' changes in a machine designed for a function usually impair its execution of that function; (ii) humans strive to recreate properties of natural ecosystems to enhance productivity of artificial ones, as farmers try to recreate properties of natural soils in their fields; and (iii) productivity and diversity have increased during the Earth's history as a whole, and after every major biotic crisis. Natural selection results in ecosystems organized to maintain high productivity of organic matter and diversity of species, just as competition among individuals in Adam Smith's ideal economy favours high production of wealth and diversity of occupations. In nature, poorly exploited energy attracts more efficient users. This circumstance favours the opening of new ways of life and more efficient recycling of resources, and eliminates most productivity-reducing 'ecological monopolies'. Ecological dominants tend to be replaced by successors with higher metabolism, which respond to more stimuli and engage in more varied interactions. Finally, increasingly efficient predators and herbivores favour faster turnover of resources. PMID:12079531

  20. Comparative Analysis of Transcriptional Profiles of Adult Schistosoma japonicum from Different Laboratory Animals and the Natural Host, Water Buffalo

    PubMed Central

    Wu, Chuang; Hou, Nan; Chen, Qijun

    2015-01-01

    Background Schistosomiasis is one of the most widely distributed parasitic diseases in the world. Schistosoma japonicum, a zoonotic parasite with a wide range of mammalian hosts, is one of the major pathogens of this disease. Although numerous studies on schistosomiasis japonica have been performed using laboratory animal models, systematic comparative analysis of whole-genome expression profiles in parasites from different laboratory animals and nature mammalian hosts is lacking to date. Methodology/Principal Findings Adult schistosomes were obtained from laboratory animals BALB/c mice, C57BL/6 mice, New Zealand white rabbits and the natural host, water buffaloes. The gene expression profiles of schistosomes from these animals were obtained and compared by genome-wide oligonucleotide microarray analysis. The results revealed that the gene expression profiles of schistosomes from different laboratory animals and buffaloes were highly consistent (r>0.98) genome-wide. Meanwhile, a total of 450 genes were identified to be differentially expressed in schistosomes which can be clustered into six groups. Pathway analysis revealed that these genes were mainly involved in multiple signal transduction pathways, amino acid, energy, nucleotide and lipid metabolism. We also identified a group of 1,540 abundantly and stably expressed gene products in adult worms, including a panel of 179 Schistosoma- or Platyhelminthes-specific genes that may be essential for parasitism and may be regarded as novel potential anti-parasite intervention targets for future research. Conclusions/Significance This study provides a comprehensive database of gene expression profiles of schistosomes derived from different laboratory animals and water buffaloes. An expanded number of genes potentially affecting the development of schistosomes in different animals were identified. These findings lay the foundation for schistosomiasis research in different laboratory animals and natural hosts at the transcriptional level and provide a valuable resource for screening anti-schistosomal intervention targets. PMID:26285138

  1. Can natural phenotypic variances be estimated reliably under homogeneous laboratory conditions?

    PubMed

    St Juliana, J R; Janzen, F J

    2007-07-01

    The phenotypic variance is assumed to be greater in a more heterogeneous environment. The validity of this assumption is important for microevolutionists to extrapolate results from the laboratory to field environments. We subjected clutches of eggs from common snapping turtles (Chelydra serpentina) to a split-family design to evaluate the variability in incubation time and four size traits of neonates from eggs incubated in the laboratory and those left in situ. Mean size measurements were similar between the laboratory and the field, but incubation time was systematically longer in the field. We found no tendency among clutches for hatchlings resulting from eggs incubated in laboratory or field environments to demonstrate greater variability. Also contrary to expectation, clutches that experienced greater thermal variation in the field did not exhibit greater variation in phenotypic traits. Consequently, extrapolating results from the laboratory to the field may not always be problematic for microevolutionary analyses. PMID:17584235

  2. An Easily Constructed Salicylate-Ion-Selective Electrode for Use in the Instructional Laboratory.

    ERIC Educational Resources Information Center

    Creager, Stephen E.; And Others

    1995-01-01

    Describes an electrode, selective for the salicylate ion, that can be prepared and used by undergraduate students. Discusses the preparation of the electrode, typical response characteristics obtained, and results of a limited study using the electrode to estimate the selectivity coefficient for an interfering ion and to determine the amount of…

  3. INSECTICIDE RESISTANCE MECHANISMS AFTER LABORATORY SELECTION WITH CYPERMETHRIN IN THE GERMAN COCKROACH, BLATTELLA GERMANICA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A cross resistant strain of German cockroach (Marietta) expressing multiple resistance mechanisms was subjected to intense cypermethrin selection pressure. Resistance to cypermethrin increased incrementally from 3.6-fold in the parental strain to 35-fold after 4 rounds of selection. Piperonyl butox...

  4. Evaluating the role of natural selection in the evolution of gene regulation.

    PubMed

    Fay, J C; Wittkopp, P J

    2008-02-01

    Surveys of gene expression reveal extensive variability both within and between a wide range of species. Compelling cases have been made for adaptive changes in gene regulation, but the proportion of expression divergence attributable to natural selection remains unclear. Distinguishing adaptive changes driven by positive selection from neutral divergence resulting from mutation and genetic drift is critical for understanding the evolution of gene expression. Here, we review the various methods that have been used to test for signs of selection in genomic expression data. We also discuss properties of regulatory systems relevant to neutral models of gene expression. Despite some potential caveats, published studies provide considerable evidence for adaptive changes in gene expression. Future challenges for studies of regulatory evolution will be to quantify the frequency of adaptive changes, identify the genetic basis of expression divergence and associate changes in gene expression with specific organismal phenotypes. PMID:17519966

  5. DRIFTSEL: an R package for detecting signals of natural selection in quantitative traits.

    PubMed

    Karhunen, M; Merilä, J; Leinonen, T; Cano, J M; Ovaskainen, O

    2013-07-01

    Approaches and tools to differentiate between natural selection and genetic drift as causes of population differentiation are of frequent demand in evolutionary biology. Based on the approach of Ovaskainen et al. (2011), we have developed an R package (DRIFTSEL) that can be used to differentiate between stabilizing selection, diversifying selection and random genetic drift as causes of population differentiation in quantitative traits when neutral marker and quantitative genetic data are available. Apart from illustrating the use of this method and the interpretation of results using simulated data, we apply the package on data from three-spined sticklebacks (Gasterosteus aculeatus) to highlight its virtues. DRIFTSEL can also be used to perform usual quantitative genetic analyses in common-garden study designs. PMID:23656704

  6. Tropolones As Lead-Like Natural Products: The Development of Potent and Selective Histone Deacetylase Inhibitors

    PubMed Central

    2013-01-01

    Natural products have long been recognized as a rich source of potent therapeutics but further development is often limited by high structural complexity and high molecular weight. In contrast, at the core of the thujaplicins is a lead-like tropolone scaffold characterized by relatively low molecular weight, ample sites for diversification, and metal-binding functionality poised for targeting a range of metalloenzyme drug targets. Here, we describe the development of this underutilized scaffold for the discovery of tropolone derivatives that function as isozyme-selective inhibitors of the validated anticancer drug target, histone deacetylase (HDAC). Several monosubstituted tropolones display remarkable levels of selectivity for HDAC2 and potently inhibit the growth of T-cell lymphocyte cell lines. The tropolones represent a new chemotype of isozyme-selective HDAC inhibitors. PMID:24900743

  7. Footprints of divergent selection in natural populations of Castanopsis fargesii (Fagaceae)

    PubMed Central

    Li, C; Sun, Y; Huang, H W; Cannon, C H

    2014-01-01

    Given predicted rapid climate change, an understanding of how environmental factors affect genetic diversity in natural populations is important. Future selection pressures are inherently unpredictable, so forest management policies should maintain both overall diversity and identify genetic markers associated with the environmental factors expected to change most rapidly, like temperature and rainfall. In this study, we genotyped 648 individuals in 28 populations of Castanopsis fargesii (Fagaceae) using 32 expressed sequence tag (EST)-derived microsatellite markers. After removing six loci that departed from Hardy–Weinberg equilibrium, we measured genetic variation, population structure and identified candidate loci putatively under selection by temperature and precipitation. We found that C. fargesii populations possessed high genetic diversity and moderate differentiation among them, indicating predominant outcrossing and few restrictions to gene flow. These patterns reduce the possible impact of stochastic effects or the influence of genetic isolation. Clear footprints of divergent selection at four loci were discovered. Frequencies of five alleles at these loci were strongly correlated with environmental factors, particularly extremes in precipitation. These alleles varied from being near fixation at one end of the gradient to being completely absent at the other. Our study species is an important forest tree in the subtropical regions of China and could have a major role in future management and reforestation plans. Our results demonstrate that the gene flow is widespread and abundant in natural populations, maintaining high diversity, while diversifying selection is acting on specific genomic regions. PMID:24984608

  8. Experimental evolution can unravel the complex causes of natural selection in clinical infections.

    PubMed

    Brockhurst, Michael A

    2015-06-01

    It is increasingly clear that rapid evolutionary dynamics are an important process in microbial ecology. Experimental evolution, wherein microbial evolution is observed in real-time, has revealed many instances of appreciable evolutionary change occurring on very short timescales of a few days or weeks in response to a variety of biotic and abiotic selection pressures. From clinical infections, including the chronic bacterial lung infections associated with cystic fibrosis that form a focus of my research, there is now abundant evidence suggesting that rapid evolution by infecting microbes contributes to host adaptation, treatment failure and worsening patient prognosis. However, disentangling the drivers of natural selection in complex infection environments is extremely challenging and limits our understanding of the selective pressures acting upon microbes in infections. Controlled evolution experiments can make a vital contribution to this by determining the causal links between predicted drivers of natural selection and the evolutionary responses of microbes. Integration of experimental evolution into studies of clinical infections is a key next step towards a better understanding of the causes and consequences of rapid microbial evolution in infections, and discovering how these evolutionary processes might be influenced to improve patient health.A video of this Prize Lecture, presented at the Society for General Microbiology Annual Conference 2015, can be viewed via this link: Michael A. Brockhurst https://www.youtube.com/watch?v=N1bodVSl27E. PMID:25957311

  9. Footprints of divergent selection in natural populations of Castanopsis fargesii (Fagaceae).

    PubMed

    Li, C; Sun, Y; Huang, H W; Cannon, C H

    2014-12-01

    Given predicted rapid climate change, an understanding of how environmental factors affect genetic diversity in natural populations is important. Future selection pressures are inherently unpredictable, so forest management policies should maintain both overall diversity and identify genetic markers associated with the environmental factors expected to change most rapidly, like temperature and rainfall. In this study, we genotyped 648 individuals in 28 populations of Castanopsis fargesii (Fagaceae) using 32 expressed sequence tag (EST)-derived microsatellite markers. After removing six loci that departed from Hardy-Weinberg equilibrium, we measured genetic variation, population structure and identified candidate loci putatively under selection by temperature and precipitation. We found that C. fargesii populations possessed high genetic diversity and moderate differentiation among them, indicating predominant outcrossing and few restrictions to gene flow. These patterns reduce the possible impact of stochastic effects or the influence of genetic isolation. Clear footprints of divergent selection at four loci were discovered. Frequencies of five alleles at these loci were strongly correlated with environmental factors, particularly extremes in precipitation. These alleles varied from being near fixation at one end of the gradient to being completely absent at the other. Our study species is an important forest tree in the subtropical regions of China and could have a major role in future management and reforestation plans. Our results demonstrate that the gene flow is widespread and abundant in natural populations, maintaining high diversity, while diversifying selection is acting on specific genomic regions. PMID:24984608

  10. Natural selection for the Duffy-null allele in the recently admixed people of Madagascar

    PubMed Central

    Hodgson, Jason A.; Pickrell, Joseph K.; Pearson, Laurel N.; Quillen, Ellen E.; Prista, António; Rocha, Jorge; Soodyall, Himla; Shriver, Mark D.; Perry, George H.

    2014-01-01

    While gene flow between distantly related populations is increasingly recognized as a potentially important source of adaptive genetic variation for humans, fully characterized examples are rare. In addition, the role that natural selection for resistance to vivax malaria may have played in the extreme distribution of the protective Duffy-null allele, which is nearly completely fixed in mainland sub-Saharan Africa and absent elsewhere, is controversial. We address both these issues by investigating the evolution of the Duffy-null allele in the Malagasy, a recently admixed population with major ancestry components from both East Asia and mainland sub-Saharan Africa. We used genome-wide genetic data and extensive computer simulations to show that the high frequency of the Duffy-null allele in Madagascar can only be explained in the absence of positive natural selection under extreme demographic scenarios involving high genetic drift. However, the observed genomic single nucleotide polymorphism diversity in the Malagasy is incompatible with such extreme demographic scenarios, indicating that positive selection for the Duffy-null allele best explains the high frequency of the allele in Madagascar. We estimate the selection coefficient to be 0.066. Because vivax malaria is endemic to Madagascar, this result supports the hypothesis that malaria resistance drove fixation of the Duffy-null allele in mainland sub-Saharan Africa. PMID:24990677

  11. Natural selection for the Duffy-null allele in the recently admixed people of Madagascar.

    PubMed

    Hodgson, Jason A; Pickrell, Joseph K; Pearson, Laurel N; Quillen, Ellen E; Prista, António; Rocha, Jorge; Soodyall, Himla; Shriver, Mark D; Perry, George H

    2014-08-22

    While gene flow between distantly related populations is increasingly recognized as a potentially important source of adaptive genetic variation for humans, fully characterized examples are rare. In addition, the role that natural selection for resistance to vivax malaria may have played in the extreme distribution of the protective Duffy-null allele, which is nearly completely fixed in mainland sub-Saharan Africa and absent elsewhere, is controversial. We address both these issues by investigating the evolution of the Duffy-null allele in the Malagasy, a recently admixed population with major ancestry components from both East Asia and mainland sub-Saharan Africa. We used genome-wide genetic data and extensive computer simulations to show that the high frequency of the Duffy-null allele in Madagascar can only be explained in the absence of positive natural selection under extreme demographic scenarios involving high genetic drift. However, the observed genomic single nucleotide polymorphism diversity in the Malagasy is incompatible with such extreme demographic scenarios, indicating that positive selection for the Duffy-null allele best explains the high frequency of the allele in Madagascar. We estimate the selection coefficient to be 0.066. Because vivax malaria is endemic to Madagascar, this result supports the hypothesis that malaria resistance drove fixation of the Duffy-null allele in mainland sub-Saharan Africa. PMID:24990677

  12. Episodic Selection and the Maintenance of Competence and Natural Transformation in Bacillus subtilis

    PubMed Central

    Johnsen, P. J.; Dubnau, D.; Levin, B. R.

    2009-01-01

    We present a new hypothesis for the selective pressures responsible for maintaining natural competence and transformation. Our hypothesis is based in part on the observation that in Bacillus subtilis, where transformation is widespread, competence is associated with periods of nongrowth in otherwise growing populations. As postulated for the phenomenon of persistence, the short-term fitness cost associated with the production of transiently nongrowing bacteria can be compensated for and the capacity to produce these competent cells can be favored due to episodes where the population encounters conditions that kill dividing bacteria. With the aid of a mathematical model, we demonstrate that under realistic conditions this “episodic selection” for transiently nongrowing (persisting) bacteria can maintain competence for the uptake and expression of exogenous DNA transformation. We also show that these conditions for maintaining competence are dramatically augmented even by rare episodes where selection favors transformants. Using experimental populations of B. subtilis and antibiotic-mediated episodic selection, we test and provide support for the validity of the assumptions behind this model and the predictions generated from our analysis of its properties. We discuss the potential generality of episodic selection for the maintenance of competence in other naturally transforming species of bacteria and critically evaluate other hypotheses for the maintenance (and evolution) of competence and their relationship to this hypothesis. PMID:19189946

  13. Present status of understanding on the G6PD deficiency and natural selection.

    PubMed

    Tripathy, V; Reddy, B M

    2007-01-01

    G6PD deficiency is a common hemolytic genetic disorder, particularly in the areas endemic to malaria. Individuals are generally asymptomatic and hemolytic anemia occurs when some anti-malarial drugs or other oxidizing chemicals are administered. It has been proposed that G6PD deficiency provides protection against malaria. Maintaining of G6PD deficient alleles at polymorphic proportions is complicated because of the X-linked nature of G6PD deficiency. A comprehensive review of the literature on the hypothesis of malarial protection and the nature of the selection is being presented. Most of the epidemiological, in vitro and in vivo studies report selection for G6PD deficiency. Analysis of the G6PD gene also reveals that G6PD-deficient alleles show some signatures of selection. However, the question of how this polymorphism is being maintained remains unresolved because the selection/fitness coefficients for the different genotypes in the two sexes have not been established. Prevalence of G6PD deficiency in Indian caste and tribal populations and the different variants reported has also been reviewed. PMID:17699998

  14. Selection with minimal bias, of an experimental control from natural wetland environments. Technical report (Final)

    SciTech Connect

    Tiedemann, R.B.

    1988-01-01

    The goal of wetland restoration and creation projects is to replicate the native wetland vegetation. The objective evaluation of wetland revegetation, as well as experiments designed to assess the ability of various wetland revegetation methods to replicate the native community, require a representative control site to distinguish between natural variability and that attributable to a treatment. The bias of the investigator often plagues what is intended to be a subjective selection of a control site. This study is designed to census vegetation species compositive of the native community. The study tests the following hypotheses: intentional revegetation as compared to natural colonization will establish a community of vegetation that more closely resembles a native wetland community, and intentional revegetation will establish a community of vegetation more rapidly than natural colonization.

  15. Polymer Selection Approach for Commonly and Uncommonly Used Natural Fibers Under Uncertainty Environments

    NASA Astrophysics Data System (ADS)

    AL-Oqla, Faris M.; Sapuan, S. M.

    2015-07-01

    Factors like awareness of the scarcity of non-renewable natural resources, high petroleum prices, and demands for environmental sustainability, as well as reducing the amount of environmental pollution, have led to a renewed interest in natural fiber reinforced polymer composites as a potential bio-based material type. The best polymer matrix type in view of the wide range of conflicting criteria to form a polymeric-based composite material suitable for sustainable industry under an uncertainty environment has still not been sufficiently determined. This work introduces a selection model to evaluate the available polymers for natural fibers to enhance the industrial sustainability theme. The model built was developed to evaluate various polymer types and to determine their relative merits taking account of various conflicting criteria for both commonly used and uncommonly used natural fibers utilizing the analytical hierarchy process technique. It was found that the choice of the best polymer type for a certain fiber type depends strongly on the polymers' intrinsic desirable conflicting characteristics. Polymers evaluations are illustrated for different technical criteria in order to facilitate the polymer selection process for various industrial applications with high confidence levels.

  16. Selecting the Best Mobile Information Service with Natural Language User Input

    NASA Astrophysics Data System (ADS)

    Feng, Qiangze; Qi, Hongwei; Fukushima, Toshikazu

    Information services accessed via mobile phones provide information directly relevant to subscribers’ daily lives and are an area of dynamic market growth worldwide. Although many information services are currently offered by mobile operators, many of the existing solutions require a unique gateway for each service, and it is inconvenient for users to have to remember a large number of such gateways. Furthermore, the Short Message Service (SMS) is very popular in China and Chinese users would prefer to access these services in natural language via SMS. This chapter describes a Natural Language Based Service Selection System (NL3S) for use with a large number of mobile information services. The system can accept user queries in natural language and navigate it to the required service. Since it is difficult for existing methods to achieve high accuracy and high coverage and anticipate which other services a user might want to query, the NL3S is developed based on a Multi-service Ontology (MO) and Multi-service Query Language (MQL). The MO and MQL provide semantic and linguistic knowledge, respectively, to facilitate service selection for a user query and to provide adaptive service recommendations. Experiments show that the NL3S can achieve 75-95% accuracies and 85-95% satisfactions for processing various styles of natural language queries. A trial involving navigation of 30 different mobile services shows that the NL3S can provide a viable commercial solution for mobile operators.

  17. Investigating the Disney Effect: Are Students Reluctant To Apply Natural Selection Principles to Life Forms with Which They Identify?

    ERIC Educational Resources Information Center

    Jensen, Murray; And Others

    This study was designed to investigate whether a student's responses to test questions about natural selection were influenced by the extent of the student's identification with the organism. The hypothesis was that a student would be reluctant to invoke the ravages of natural selection upon species with which they possessed a greater empathy than…

  18. Measuring Knowledge of Natural Selection: A Comparison of the CINS, an Open-Response Instrument, and an Oral Interview

    ERIC Educational Resources Information Center

    Nehm, Ross H.; Schonfeld, Irvin Sam

    2008-01-01

    Growing recognition of the central importance of fostering an in-depth understanding of natural selection has, surprisingly, failed to stimulate work on the development and rigorous evaluation of instruments that measure knowledge of it. We used three different methodological tools, the Conceptual Inventory of Natural Selection (CINS), a modified…

  19. Measuring Knowledge of Natural Selection: A Comparison of the CINS, an Open-Response Instrument, and an Oral Interview

    ERIC Educational Resources Information Center

    Nehm, Ross H.; Schonfeld, Irvin Sam

    2008-01-01

    Growing recognition of the central importance of fostering an in-depth understanding of natural selection has, surprisingly, failed to stimulate work on the development and rigorous evaluation of instruments that measure knowledge of it. We used three different methodological tools, the Conceptual Inventory of Natural Selection (CINS), a modified…

  20. The Himalayas of Nepal, a natural laboratory for the search and measurement of CO2 discharge

    NASA Astrophysics Data System (ADS)

    Girault, Frédéric; Koirala, Bharat P.; Bhattarai, Mukunda; Rajaure, Sudhir; Richon, Patrick; Perrier, Frédéric

    2010-05-01

    Large CO2 flux has been found in the Trisuli Valley, North of Kathmandu, Central Nepal, in 2005. This leakage zone is located in the vicinity of the Syabru-Bensi hot springs, and is characterized by an average flux of CO2 of 6500±1100 g m-2 day-1 over an area of 15 m × 15 m (Perrier et al., Earth and Planetary Science Letters, 2009). The site is also located close to the Main Central Thrust Zone (MCT Zone), one of the large Himalayan thrust, connected at depth to the Main Himalayan Thrust, the main thrust currently accommodating the India-Tibet collision (Bollinger et al., Journal of Geophysical Research, 2004). Isotopic carbon ratios (?13C) indicate that this CO2 may come from metamorphic reactions at about 15 km of depth (Becker et al., Earth and Planetary Science Letters, 2008; Evans et al., Geochemistry Geophysics Geosystems, 2008). Actually, this zone was originally found because of the large ?13C found in the water of the hot springs suggesting degassing (Evans et al., Geochemistry Geophysics Geosystems, 2008). In 2007, another zone of CO2 discharge was discovered 250 m away from the main Syabru-Bensi hot springs. This new zone, located next to the road and easy to access all over the year, was intensely studied, from the end of 2007 to the beginning of 2009. In this zone, an average value of CO2 flux of 1700±300 g m-2 d-1 was obtained over an area of about 40 m × 10 m. Using CO2 flux data from repeated measurements, similar flux values were observed during the dry winter season and the wet summer period (monsoon) (Girault et al., Journal of Environmental Radioactivity, 2009). Thus, in addition to fundamental issues related to global CO2 balance in orogenic belts and tectonically active zones, these small scale (100-meter) CO2 discharge sites emerge as a potentially useful laboratory for detailed methodological studies of diffusive and advective gas transport. Recently, the search for further gas discharge zones has been carried out using various clues: the presence of a hot spring with high ?13C, of H2S smell, of hot spots in thermal images, of a geological contact, of self-potential anomalies (Byrdina et al., Journal of Geophysical Research, 2009) or of large radon-222 flux. Preliminary results about the failures or successes of the various methods will be given in the Trisuli and Langtang valleys (Central Nepal), in the Kali Gandaki valley (Western Nepal) and in the Thuli Bheri valley (Lower Dolpo, Far Western Nepal). These various sites also offer an opportunity to test the optimal estimation of total CO2 flux, using the least amount of experimental measurements. Preliminary results complemented by simulations will also be given on the total CO2 flux. In parallel, monitoring methods are being studied in the Syabru-Bensi pilot site. First, CO2 flux has been studied as a function of time using repeated measurements. Furthermore, the high radon content of the geological CO2 allows cost-effective monitoring using BARASOL probes. More than two years of data are already available and give hints on the use of radon to follow CO2 discharge as a function of time. These first results show how experimental studies carried out in natural discharge zones provide a rich laboratory to test the methodological approaches useful for CO2 leakage and monitoring.

  1. Identifying Signatures of Natural Selection in Tibetan and Andean Populations Using Dense Genome Scan Data

    PubMed Central

    Bigham, Abigail; Bauchet, Marc; Pinto, Dalila; Mao, Xianyun; Akey, Joshua M.; Mei, Rui; Scherer, Stephen W.; Julian, Colleen G.; Wilson, Megan J.; López Herráez, David; Brutsaert, Tom; Parra, Esteban J.; Moore, Lorna G.; Shriver, Mark D.

    2010-01-01

    High-altitude hypoxia (reduced inspired oxygen tension due to decreased barometric pressure) exerts severe physiological stress on the human body. Two high-altitude regions where humans have lived for millennia are the Andean Altiplano and the Tibetan Plateau. Populations living in these regions exhibit unique circulatory, respiratory, and hematological adaptations to life at high altitude. Although these responses have been well characterized physiologically, their underlying genetic basis remains unknown. We performed a genome scan to identify genes showing evidence of adaptation to hypoxia. We looked across each chromosome to identify genomic regions with previously unknown function with respect to altitude phenotypes. In addition, groups of genes functioning in oxygen metabolism and sensing were examined to test the hypothesis that particular pathways have been involved in genetic adaptation to altitude. Applying four population genetic statistics commonly used for detecting signatures of natural selection, we identified selection-nominated candidate genes and gene regions in these two populations (Andeans and Tibetans) separately. The Tibetan and Andean patterns of genetic adaptation are largely distinct from one another, with both populations showing evidence of positive natural selection in different genes or gene regions. Interestingly, one gene previously known to be important in cellular oxygen sensing, EGLN1 (also known as PHD2), shows evidence of positive selection in both Tibetans and Andeans. However, the pattern of variation for this gene differs between the two populations. Our results indicate that several key HIF-regulatory and targeted genes are responsible for adaptation to high altitude in Andeans and Tibetans, and several different chromosomal regions are implicated in the putative response to selection. These data suggest a genetic role in high-altitude adaption and provide a basis for future genotype/phenotype association studies necessary to confirm the role of selection-nominated candidate genes and gene regions in adaptation to altitude. PMID:20838600

  2. Complex and changing patterns of natural selection explain the evolution of the human hip.

    PubMed

    Grabowski, Mark; Roseman, Charles C

    2015-08-01

    Causal explanations for the dramatic changes that occurred during the evolution of the human hip focus largely on selection for bipedal function and locomotor efficiency. These hypotheses rest on two critical assumptions. The first-that these anatomical changes served functional roles in bipedalism-has been supported in numerous analyses showing how postcranial changes likely affected locomotion. The second-that morphological changes that did play functional roles in bipedalism were the result of selection for that behavior-has not been previously explored and represents a major gap in our understanding of hominin hip evolution. Here we use evolutionary quantitative genetic models to test the hypothesis that strong directional selection on many individual aspects of morphology was responsible for the large differences observed across a sample of fossil hominin hips spanning the Plio-Pleistocene. Our approach uses covariance among traits and the differences between relatively complete fossils to estimate the net selection pressures that drove the major transitions in hominin hip evolution. Our findings show a complex and changing pattern of natural selection drove hominin hip evolution, and that many, but not all, traits hypothesized to play functional roles in bipedalism evolved as a direct result of natural selection. While the rate of evolutionary change for all transitions explored here does not exceed the amount expected if evolution was occurring solely through neutral processes, it was far above rates of evolution for morphological traits in other mammalian groups. Given that stasis is the norm in the mammalian fossil record, our results suggest that large shifts in the adaptive landscape drove hominin evolution. PMID:26164108

  3. Genetic Diversity and Natural Selection of the Plasmodium knowlesi Circumsporozoite Protein Nonrepeat Regions

    PubMed Central

    Fong, Mun Yik; Ahmed, Md Atique; Wong, Shen Siang; Lau, Yee Ling; Sitam, Frankie

    2015-01-01

    Background Plasmodium knowlesi is a simian malaria parasite that has been identified to cause malaria in humans. To date, several thousand cases of human knowlesi malaria have been reported around Southeast Asia. Thus far, there is no detailed study on genetic diversity and natural selection of P. knowlesi circumsporozoite protein (CSP), a prominent surface antigen on the sporozoite of the parasite. In the present study, the genetic diversity and natural selection acting on the nonrepeat regions of the gene encoding P. knowlesi CSP were investigated, focusing on the T-cell epitope regions at the C-terminal of the protein. Methods Blood samples from 32 knowlesi malaria patients and 2 wild monkeys (Macaca fascicularis) were used. The CSP of the P. knowlesi isolates was amplified by PCR, cloned into Escherichia coli, and sequenced. The nonrepeat regions of the CSP gene were analysed for genetic diversity, natural selection and haplotypic grouping using MEGA5 and DnaSP version 5.10.00 programmes. A haplotype network was constructed based on the C-terminal (Th2R/Th3R) T-cell epitope regions using the Median-Joining method in the NETWORK version 4.6.1.2 programme. Previously published sequences from other regions (Malaysia Borneo, Singapore) were also included in the analysis. Results A total of 123 P. knowlesi CSP sequences were analysed. Multiple sequence alignment revealed 58 amino acid changes, and 42 novel amino acid haplotypes were identified. Polymorphism was higher in the C-terminal Th2R/Th3R epitope (? = 0.0293, n = 123) region compared to the overall combined nonrepeat regions (? = 0.0120, n = 123). Negative natural selection was observed within the nonrepeat regions of the CSP gene. Within the C-terminal Th2R/Th3R epitope regions, there was evidence of slight positive selection. Based on haplotype network analysis of the Th2R/Th3R regions, five abundant haplotypes were identified. Sharing of haplotypes between humans and macaques were observed. Conclusion This study contributes to the understanding of the type and distribution of naturally occurring polymorphism in the P. knowlesi CSP gene. This study also provides a measurement of the genetic diversity of P. knowlesi and identifies the predominant haplotypes within Malaysia based on the C-terminal Th2R/Th3R regions. PMID:26379157

  4. A Natural Laboratory for Earth Scientists: Anatolia and Its Surroundings (Invited)

    NASA Astrophysics Data System (ADS)

    Turkelli, N.; Sandvol, E. A.

    2009-12-01

    Anatolia and its surroundings is a tectonically complex region resulting from the collision of Arabian and Eurasian plates in the east, slab roll back along the Hellenic arc, and escape of the Anatolian plate along two transform faults, the North Anatolian Fault and East Anatolian Fault Zones. The continental collision in eastern Anatolia has led to crustal thickening and shortening, uplift, and volcanism. The Mediterranean Sea is a remnant of the Tethyan Ocean basinthat is being subducted beneath the Anatolian plate along the Hellenic and Cyprian arcs. The Isparta Angle as a convex intersection of the Hellenic and Cyprian Arcs and thus an important tectonic feature. The rift basins and recent metamorphic core complexes in western Anatolia are a result of the rapid retreat of the Hellenic arc. The entire region, because of the relatively high rates of deformation, has been subjected large devastating earthquakes, associated with fault zones, in the past and will be subjected to earthquakes in the future. This complex tectonic environment makes the region an excellent natural laboratory to study a diverse set of deformational regimes. This wide variety of tectonics has also created a complex upper mantle and crustal structure that affects regional wave propagation both in terms of amplitude and travel times, and also seismic anisotropy. During the last decade, many of the permanent seismic networks in the region has been modernized, number of stations increased and their data became available to the whole scientific community. This has led to improved event and source parameter determination. In addition to data provided by the permanent networks earth scientists have focused on seismic experiments, such as Eastern Turkey Experiment, Isparta Angle seismic experiment, North Anatolian Fault Zone passive seismic experiment, Zagros Lithospheric Transect, DESERT2000 Transect. Data from these projects have led to a better picture of the region in terms of crust and upper mantle structure. In order to better undetstand these diverse tectonic terrain we need to better resolve the thickness of the Moho , regional wave propagation and blockage characteristics, mantle flow as inferred from mantle anisotropy.

  5. Integrated data search and access to geophysical data for Geohazards Supersites and Natural Laboratories

    NASA Astrophysics Data System (ADS)

    Rowan, L.; Baker, S.; Wier, S.; Boler, F. M.; Meertens, C. M.; Amelung, F.

    2013-12-01

    The Geohazards Supersites and Natural Laboratories (GSNL) are committed to sharing space-based and ground-based geophysical data and building collaborations to better understand Earth processes and mitigate the societal hazards related to the dynamic Earth. GSNL is global with locations in Turkey, Japan, China, Italy, Haiti the United States (e.g. Hawaii and the western U.S.) and elsewhere. The UNAVCO Data Center in Boulder, Colorado, archives and distributes geodesy data and products in the GPS/GNSS, InSAR, and LiDAR domains. UNAVCO has an open access data policy and strives to provide catalogs and data access tools for all users. In an effort to create a unified data and metadata access capability for geodesy data centers in general and for GSNL in particular, UNAVCO and our partners, have designed and implemented software for simplified access called the Geodesy Seamless Archive Centers (GSAC). GSAC is a web services based technology to facilitate data discovery and access. The GSAC technology leverages several well-accepted geodesy data and metadata formats, and identifies a relatively small set of required and recommended metadata for the basic installation. Additional optional metadata can be defined at individual data centers. The GSAC services utilize a repository layer implemented at each data center, and a service layer to identify and present the required metadata elements along with any data center-specific services and capabilities. The software for the GSAC is available through SourceForge, and any geodesy data archive can download the code and implement GSAC services for their repository; doing so will provide the data center's users with the ability to use common query and access mechanisms with other GSAC data centers. Further, optional federation of individual GSAC data centers is facilitated through the GSAC software. GSAC would significantly simplify data access and integration, while enhancing data sharing around the world. GSAC is an excellent tool for advancing the goals of GSNL and helping to make the world a safer place through simple data integration.

  6. Simulating intracrater ash recycling during mid-intensity explosive activity: high temperature laboratory experiments on natural basaltic ash

    NASA Astrophysics Data System (ADS)

    D'Oriano, Claudia; Pompilio, Massimo; Bertagnini, Antonella; Cioni, Raffaello; Pichavant, Michel

    2010-05-01

    Direct observations of mid-intensity eruptions, in which a huge amount of ash is generated, indicate that ash recycling is quite common. The recognition of juvenile vs. recycled fragments is not straightforward, and no unequivocal, widely accepted criteria exist to support this. The presence of recycled glassy fragments can hide primary magmatic information, introducing bias in the interpretations of the ongoing magmatic and volcanic activity. High temperature experiments were performed at atmospheric pressure on natural samples to investigate the effects of reheating on morphology, texture and composition of volcanic ash. Experiments simulate the transformation of juvenile glassy fragments that, falling into the crater or in the upper part of the conduit, are recycled by following explosions. Textural and compositional modifications obtained in laboratory are compared with similar features observed in natural samples in order to identify some main general criteria to be used for the discrimination of recycled material. Experiments were carried out on tephra produced during Strombolian activity, fire fountains and continuous ash emission at Etna, Stromboli and Vesuvius. Coarse glassy clasts were crushed in a nylon mortar in order to create an artificial ash, and then sieved to select the size interval of 1-0.71 mm. Ash shards were put in a sealed or open quartz tube, in order to prevent or to reproduce effects of air oxidation. The tube was suspended in a HT furnace at INGV-Pisa and kept at different temperatures (up to to 1110°C) for increasing time (0.5-12 hours). Preliminary experiments were also performed under gas flux conditions. Optical and electron microscope observations indicate that high temperature and exposure to the air induce large modifications on clast surface, ranging from change in color, to incipient plastic deformation till complete sintering. Significant change in color of clasts is strictly related to the presence of air, irrespective of temperature while sintering is favored by the high temperature and low fO2. Re-heating promotes nucleation and growth of crystals in the groundmass and associated change of glass composition, sometimes accompanied by growth and coalescence of vesicles in the size of 10-50 µm and cracking of the external surface.

  7. 75 FR 53277 - Notice of Intent To Terminate Selected National Voluntary Laboratory Accreditation Program (NVLAP...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-31

    ... testing: paints and related coatings, paper and related products, building seals and sealants, plastics... related products, building seals and sealants, plastics, plumbing, roofing, and mattresses. The purpose of... plumbing laboratories are also accredited for plastic and paint testing in support of plumbing...

  8. ORGANOTIN TOXICITY STUDIES CONDUCTED WITH SELECTED MARINE ORGANISMS AT EPA'S ENVIRONMENTAL RESEARCH LABORATORY, GULF BREEZE, FLORIDA

    EPA Science Inventory

    Studies on effect of bis(tri-n-butyltin)oxide (TBTO) and other organotins on marine species have been conducted at the U.S. Environmental Protection Agency's laboratory at Gulf Breeze, Florida, since 1983. First studies were done on two species of algae, Skeletonema costatum and ...

  9. CPT Profiling and Laboratory Data Correlations for Deriving of Selected Geotechnical Parameter

    NASA Astrophysics Data System (ADS)

    Bulko, Roman; Drusa, Marián; Vl?ek, Jozef; Me?ár, Martin

    2015-12-01

    Currently, can be seen a new trend in engineering geological survey, where laboratory analysis are replaced by in situ testing methods, which are more efficient and cost effective, and time saving too. A regular engineering geological survey cannot be provided by simple core drillings, macroscopic description (sometimes very subjective), and then geotechnical parameters are established based on indicative standardized values or archive values from previous geotechnical standards. The engineering geological survey is trustworthy if is composed of laboratory and in-situ testing supplemented by indirect methods of testing, [1]. The prevalence of rotary core drilling for obtaining laboratory soil samples from various depths (every 1 to 3 m), cannot be a more enhanced as continues evaluation of strata and properties e.g. by CPT Piezocone (every 1 cm). Core drillings survey generally uses small amounts of soil samples, but this is resulting to a lower representation of the subsoil and underestimation of parameters. Higher amounts of soil samples make laboratory testing time-consuming and results from this testing can be influenced by the storage and processing of the soil samples. Preference for geotechnical surveys with in situ testing is therefore a more suitable option. In situ testing using static and dynamic penetration tests can be used as a supplement or as a replacement for the (traditional) methods of surveying.

  10. Determination of natural versus laboratory human infection with Mayaro virus by molecular analysis.

    PubMed

    Junt, T; Heraud, J M; Lelarge, J; Labeau, B; Talarmin, A

    1999-12-01

    A laboratory worker developed clinical signs of infection with Mayaro virus (Togaviridae), an arbovirus of South and Central America, 6 days after preparation of Mayaro viral antigen and 10 days after a trip to a rain forest. There was no evidence of skin lesions during the antigen preparation, and level 3 containment safety measures were followed. Therefore, molecular characterization of the virus was undertaken to identify the source of infection. RT-PCR and DNA sequence comparisons proved the infection was with the laboratory strain. Airborne Mayaro virus contamination is thus a hazard to laboratory personnel. PMID:10694165

  11. Select Agent and Toxin Regulations: Beyond the Eighth Edition of the Guide for the Care and Use of Laboratory Animals

    PubMed Central

    Kastenmayer, Robin J; Moore, Rashida M; Bright, Allison L; Torres-Cruz, Rafael; Elkins, William R

    2012-01-01

    In the interval between the publication of the seventh and eighth editions of the Guide for the Care and Use of Laboratory Animals (Guide), much has changed with regard to the regulation and funding of highly pathogenic biologic agents and toxins (Select Agents). Funding of research involving highly pathogenic agents has increased dramatically during this time, thus increasing the demand for facilities capable of supporting this work. The eighth edition of the Guide briefly mentions Select Agents and provides a limited set of references. Here we provide some background information regarding the relevant laws and regulations, as well as an overview of the programmatic requirements pertaining to the use of Select Agents, with a focus on use in animals. PMID:22776191

  12. Evaluation of toxicity of selected insecticides against thrips on cotton in laboratory bioassays

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Adult vial technique (AVT) and spray table bioassays were conducted to evaluate toxicity of selected insecticides against immature and adult Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). In AVT, technical insecticides comprising of organophosphates (d...

  13. Isolating "Unknown" Bacteria in the Introductory Microbiology Laboratory: A New Selective Medium for Gram-Positives.

    ERIC Educational Resources Information Center

    McKillip, John L.; Drake, MaryAnne

    1999-01-01

    Describes the development, preparation, and use of a medium that can select against a wide variety of Gram-negative bacteria while still allowing growth and differentiation of a wide range of Gram-positives. (WRM)

  14. Moving from the laboratory to the field: Adding natural environmental conditions to toxicology testing

    EPA Science Inventory

    While laboratory toxicology tests are generally easy to perform, cost effective and readily interpreted, they have been criticized for being unrealistic. In contrast, field tests are considered realistic while producing results that are difficult to interpret and expensive. To ...

  15. Highly Variable Recombinational Landscape Modulates Efficacy of Natural Selection in Birds

    PubMed Central

    Gossmann, Toni I.; Santure, Anna W.; Sheldon, Ben C.; Slate, Jon; Zeng, Kai

    2014-01-01

    Determining the rate of protein evolution and identifying the causes of its variation across the genome are powerful ways to understand forces that are important for genome evolution. By using a multitissue transcriptome data set from great tit (Parus major), we analyzed patterns of molecular evolution between two passerine birds, great tit and zebra finch (Taeniopygia guttata), using the chicken genome (Gallus gallus) as an outgroup. We investigated whether a special feature of avian genomes, the highly variable recombinational landscape, modulates the efficacy of natural selection through the effects of Hill–Robertson interference, which predicts that selection should be more effective in removing deleterious mutations and incorporating beneficial mutations in high-recombination regions than in low-recombination regions. In agreement with these predictions, genes located in low-recombination regions tend to have a high proportion of neutrally evolving sites and relaxed selective constraint on sites subject to purifying selection, whereas genes that show strong support for past episodes of positive selection appear disproportionally in high-recombination regions. There is also evidence that genes located in high-recombination regions tend to have higher gene expression specificity than those located in low-recombination regions. Furthermore, more compact genes (i.e., those with fewer/shorter introns or shorter proteins) evolve faster than less compact ones. In sum, our results demonstrate that transcriptome sequencing is a powerful method to answer fundamental questions about genome evolution in nonmodel organisms. PMID:25062920

  16. Natural Selection in a Bangladeshi Population from the Cholera-Endemic Ganges River Delta

    PubMed Central

    Karlsson, Elinor K.; Harris, Jason B.; Tabrizi, Shervin; Rahman, Atiqur; Shlyakhter, Ilya; Patterson, Nick; O'Dushlaine, Colm; Schaffner, Stephen F.; Gupta, Sameer; Chowdhury, Fahima; Sheikh, Alaullah; Shin, Ok Sarah; Ellis, Crystal; Becker, Christine E.; Stuart, Lynda M.; Calderwood, Stephen B.; Ryan, Edward T.; Qadri, Firdausi; Sabeti, Pardis C.; LaRocque, Regina C.

    2015-01-01

    As an ancient disease with high fatality, cholera has likely exerted strong selective pressure on affected human populations. We performed a genome-wide study of natural selection in a population from the Ganges River Delta, the historic geographic epicenter of cholera. We identified 305 candidate selected regions using the Composite of Multiple Signals (CMS) method. The regions were enriched for potassium channel genes involved in cyclic AMP-mediated chloride secretion and for components of the innate immune system involved in NF-κB signaling. We demonstrate that a number of these strongly selected genes are associated with cholera susceptibility in two separate cohorts. We further identify repeated examples of selection and association in an NF-kB / inflammasome-dependent pathway that is activated in vitro by Vibrio cholerae. Our findings shed light on the genetic basis of cholera resistance in a population from the Ganges River Delta and present a promising approach for identifying genetic factors influencing susceptibility to infectious diseases. PMID:23825302

  17. Vegetation-derived cues for the selection of oviposition substrates by Anopheles albimanus under laboratory conditions.

    PubMed

    Torres-Estrada, José Luis; Meza-Alvarez, R Amanda; Cibrián-Tovar, Juan; Rodríguez-López, Mario H; Arredondo-Jiménez, Juan I; Cruz-López, Leopoldo; Rojas-Leon, Julio C

    2005-12-01

    Oviposition response of gravid Anopheles albimanus Wiedemman (Diptera: Culicidae) females to water containing Brachiaria mutica, Cynodon dactylon, Jouvea straminea, Fimbristylis spadicea, and Ceratophyllum demersum was investigated. Gravid An. albimanus females deposited similar egg numbers in cups containing natural plants in water from natural breeding sites and in cups containing natural plants in distilled water. Gravid mosquitoes deposited significantly more eggs in cups containing natural plants in water from natural breeding sites than in cups containing artificial plants in water from the corresponding natural breeding sites. These results were confirmed in experiments conducted in a wind tunnel, indicating that female response is mediated by chemical cues from plants. Bioassays with organic extracts of all 5 plant species indicated that these extracts at 100%, 10%, and 1% concentrations had an oviposition repellent effect, while attractiveness was observed at 0.1%, 0.01%, and 0.001%. Gas chromatography and mass spectrometry analysis of the organic extracts found in all 5 plants showed a mixture of terpenoid and alcohol compounds, among them: guaiacol, phenol, isoeugenol, longifolene, caryophyllene, phenyl ethyl alcohol, and p-cresol. These results suggest that middle-range volatiles from plants may function as chemical cues for the female's oviposition response in this mosquito species. PMID:16506557

  18. Sorption selectivity in natural organic matter studied with nitroxyl paramagnetic relaxation probes.

    PubMed

    Lattao, Charisma; Cao, Xiaoyan; Li, Yuan; Mao, Jingdong; Schmidt-Rohr, Klaus; Chappell, Mark A; Miller, Lesley F; dela Cruz, Albert Leo; Pignatello, Joseph J

    2012-12-01

    Sorption site selectivity and mechanism in natural organic matter (NOM) were addressed spectroscopically by the sorption of paramagnetic nitroxyl compounds (spin probes) of different polarity, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) and HTEMPO (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl). The sorbents were Pahokee peat, Beulah-Zap lignite, and a polystyrene-poly(vinyl methyl ether) (PS-PVME) polymer blend representing the mixed aliphatic-aromatic, polar-nonpolar character of NOM. Nuclear-electron spin interaction serves as an efficient relaxation pathway, resulting in attenuation of the (13)C-CP/TOSS NMR signal for (13)C nuclei in proximity to the N-O· group (r(-6) dependence). In the natural solids the spin probes sorbed more specifically (greater isotherm nonlinearity) and had lower rotational mobility (broader electron paramagnetic resonance signals) than in PS-PVME. Titration with spin probe indicated almost no selectivity for the different carbon functional groups of PS-PVME, and little to no selectivity for the different carbon moieties of Pahokee and Beulah, including aromatic, alkyl, O-alkyl, di-O-alkyl, and O-methyl. In any case, sorption site selectivity of spin probes to NOM was always weaker than partition selectivity found in model solvent-water (toluene, hexadecane, anisole, octanol) and cellulose-water systems. The results indicate little or no preferential sorption in NOM based on functional group chemistry or putative microdomain character, but rather are consistent with the filling of pores whose walls have an average chemical environment reflecting the bulk chemical composition of the solid. This work demonstrates for the first time the use of paramagnetic probes to study sorption specificity. PMID:23078290

  19. Patterns of population differentiation and natural selection on the celiac disease background risk network.

    PubMed

    Sams, Aaron; Hawks, John

    2013-01-01

    Celiac disease is a common small intestinal inflammatory condition induced by wheat gluten and related proteins from rye and barley. Left untreated, the clinical presentation of CD can include failure to thrive, malnutrition, and distension in juveniles. The disease can additionally lead to vitamin deficiencies, anemia, and osteoporosis. Therefore, CD potentially negatively affected fitness in past populations utilizing wheat, barley, and rye. Previous analyses of CD risk variants have uncovered evidence for positive selection on some of these loci. These studies also suggest the possibility that risk for common autoimmune conditions such as CD may be the result of positive selection on immune related loci in the genome to fight infection. Under this evolutionary scenario, disease phenotypes may be a trade-off from positive selection on immunity. If this hypothesis is generally true, we can expect to find a signal of natural selection when we survey across the network of loci known to influence CD risk. This study examines the non-HLA autosomal network of gene loci associated with CD risk in Europe. We reject the null hypothesis of neutrality on this network of CD risk loci. Additionally, we can localize evidence of selection in time and space by adding information from the genome of the Tyrolean Iceman. While we can show significant differentiation between continental regions across the CD network, the pattern of evidence is not consistent with primarily recent (Holocene) selection across this network in Europe. Further localization of ancient selection on this network may illuminate the ecological pressures acting on the immune system during this critically interesting phase of our evolution. PMID:23936230

  20. Natural Product Total Synthesis in the Organic Laboratory: Total Synthesis of Caffeic Acid Phenethyl Ester (CAPE), a Potent 5-Lipoxygenase Inhibitor from Honeybee Hives

    ERIC Educational Resources Information Center

    Touaibia, Mohamed; Guay, Michel

    2011-01-01

    Natural products play a critical role in modern organic synthesis and learning synthetic techniques is an important component of the organic laboratory experience. In addition to traditional one-step organic synthesis laboratories, a multistep natural product synthesis is an interesting experiment to challenge students. The proposed three-step…

  1. Natural Product Total Synthesis in the Organic Laboratory: Total Synthesis of Caffeic Acid Phenethyl Ester (CAPE), a Potent 5-Lipoxygenase Inhibitor from Honeybee Hives

    ERIC Educational Resources Information Center

    Touaibia, Mohamed; Guay, Michel

    2011-01-01

    Natural products play a critical role in modern organic synthesis and learning synthetic techniques is an important component of the organic laboratory experience. In addition to traditional one-step organic synthesis laboratories, a multistep natural product synthesis is an interesting experiment to challenge students. The proposed three-step…

  2. Detection of electrically failed photovoltaic modules at selected MIT Lincoln Laboratory test sites

    SciTech Connect

    Forman, S. E.

    1981-01-01

    The US Department of Energy has set a 20-year lifetime goal for terrestrial photovoltaic modules. In its capacity as a Photovoltaic Field Tests and Applications Center, Massachusetts Institute of Technology Lincoln Laboratory has established various experimental test sites throughout the United States, ranging in size from 1.5 to 100 kW of peak power. These sites contain modules from several manufacturers and serve as test beds for photovoltaic system components. From May 1977 to date, over 11,000 modules have been placed in service at these sites, of which a total of 250 have suffered electrical failures. In previous reports emphasis has been placed on failure modes and the types of physical and electrical degradation found in modules. The methods used to detect failures in operational photovoltaic power-generating systems are reported for several Lincoln Laboratory test sites.

  3. Strong and consistent natural selection associated with armour reduction in sticklebacks.

    PubMed

    LE Rouzic, Arnaud; Østbye, Kjartan; Klepaker, Tom O; Hansen, Thomas F; Bernatchez, Louis; Schluter, Dolph; Vøllestad, L Asbjørn

    2011-06-01

    Measuring the strength of natural selection is tremendously important in evolutionary biology, but remains a challenging task. In this work, we analyse the characteristics of selection for a morphological change (lateral-plate reduction) in the threespine stickleback Gasterosteus aculeatus. Adaptation to freshwater, leading with the reduction or loss of the bony lateral armour, has occurred in parallel on numerous occasions in this species. Completely-plated and low-plated sticklebacks were introduced into a pond, and the phenotypic changes were tracked for 20 years. Fish from the last generation were genotyped for the Ectodysplasin-A (Eda) locus, the major gene involved in armour development. We found a strong fitness advantage for the freshwater-type fish (on average, 20% fitness advantage for the freshwater morph, and 92% for the freshwater genotype). The trend is best explained by assuming that this fitness advantage is maximum at the beginning of the invasion and decreases with time. Such fitness differences provide a quantifiable example of rapid selection-driven phenotypic evolution associated with environmental change in a natural population. PMID:21443674

  4. Seed Predators, not Herbivores, Exert Natural Selection on Solidago spp. in an Urban Archipelago.

    PubMed

    Bode, R F; Gilbert, A B

    2016-02-01

    The effects of urbanization on biodiversity are well established, as a growing city will reduce the size and diversity of patches of native plants. Recolonization of old patches and discovery of new ones by arthropod herbivores should occur as predicted by island biogeography theory. Although colonization represents an increase in biodiversity, such arrivals may exert new forms of natural selection on plants through herbivory and seed predation. Using a single species of old-field aster (Solidago altissima L.), we found that the level of natural selection by seed predators and herbivores follows patterns of island biogeography, with lower amounts of damage on smaller islands, where there are fewer species, and hypothetically smaller populations of arthropods. We also found that in an urban system, levels of herbivory are far below the tolerance levels of Solidago, and that seed predators are likely to be the only arthropod to cause reduced fitness. The pattern seen also implies that as a patch of Solidago grows through clonal expansion, it will come under higher selective pressure. PMID:26494854

  5. Warning signals are under positive frequency-dependent selection in nature.

    PubMed

    Chouteau, Mathieu; Arias, Mónica; Joron, Mathieu

    2016-02-23

    Positive frequency-dependent selection (FDS) is a selection regime where the fitness of a phenotype increases with its frequency, and it is thought to underlie important adaptive strategies resting on signaling and communication. However, whether and how positive FDS truly operates in nature remains unknown, which hampers our understanding of signal diversity. Here, we test for positive FDS operating on the warning color patterns of chemically defended butterflies forming multiple coexisting mimicry assemblages in the Amazon. Using malleable prey models placed in localities showing differences in the relative frequencies of warningly colored prey, we demonstrate that the efficiency of a warning signal increases steadily with its local frequency in the natural community, up to a threshold where protection stabilizes. The shape of this relationship is consistent with the direct effect of the local abundance of each warning signal on the corresponding avoidance knowledge of the local predator community. This relationship, which differs from purifying selection acting on each mimetic pattern, indicates that predator knowledge, integrated over the entire community, is saturated only for the most common warning signals. In contrast, among the well-established warning signals present in local prey assemblages, most are incompletely known to local predators and enjoy incomplete protection. This incomplete predator knowledge should generate strong benefits to life history traits that enhance warning efficiency by increasing the effective frequency of prey visible to predators. Strategies such as gregariousness or niche convergence between comimics may therefore readily evolve through their effects on predator knowledge and warning efficiency. PMID:26858416

  6. Natural Attenuation of Anthropogenic Chromium in Selected Puye Formation in Regional Aquifer System of LOS Alamos, New Mexico

    NASA Astrophysics Data System (ADS)

    Brown, D. B.; Ding, M.; WoldeGabriel, G. W.; Cheshire, M.; Rearick, M.; Conradson, S.; Kluk, E.; Katzman, D.

    2014-12-01

    Routine groundwater monitoring conducted in 2005 revealed significant chromium (Cr) contamination in regional groundwater in Los Alamos, New Mexico. Previous use of potassium dichromate (K2Cr2O7) in cooling towers at Los Alamos National Laboratory's main power plant is believed to be the source of the elevated chromium levels. From 1956 to 1972 between 31,000 and 72,000 Kg of toxic Cr(IV) was released into Sandia Canyon. Initial investigations of the vadose zone using chromium isotopes indicated that reduction of anthropogenic Cr(IV) had occurred. However, to justify the use of Monitoring Natural Attenuation (MNA) as a valid remediation strategy, the Cr attenuation mechanism and the reduction capacity of the regional aquifer needs to be determined. Conventional batch sorption and synchrotron-based X-ray absorption spectroscopy studies were performed. Two samples were selected from the Puye formation, a silicoclastic sedimentary rock sequence located within the contaminated aquifer. Additionally, two Los Alamos Puye outcrop samples with no chromium exposure were selected for comparison. Each sample was subsequently sorted based on grain size, magnetic, and clay fractions. Groundwater with a known concentration of Cr(IV) was used in the batch experiments. Spectroscopy measurements of Puye samples before and after exposure to the same contaminated groundwater were conducted at the Stanford Synchrotron Radiation Lightsource (SSRL). Batch sorption results indicated little to no attenuation, as indicated by the small measured sorption coefficient (Kd < 5 Kg/L). Spectroscopic measurements suggest that attenuation of hexavalent chromium in groundwater is due to reduction of Cr(VI) to Cr(III) in the Puye and may be attributed almost exclusively to the clay fraction. These results indicate that the tested Puye sediments occurring in the regional aquifer have minor ability to naturally attenuate anthropogenic Cr(IV), with the clay fraction dominating the reduction process. This study provides a field prediction model with reliable chromium reactive transport parameters in relevant geological settings.

  7. Genome-wide Selective Sweeps in Natural Bacterial Populations Revealed by Time-series Metagenomics

    SciTech Connect

    Chan, Leong-Keat; Bendall, Matthew L.; Malfatti, Stephanie; Schwientek, Patrick; Tremblay, Julien; Schackwitz, Wendy; Martin, Joel; Pati, Amrita; Bushnell, Brian; Foster, Brian; Kang, Dongwan; Tringe, Susannah G.; Bertilsson, Stefan; Moran, Mary Ann; Shade, Ashley; Newton, Ryan J.; Stevens, Sarah; McMcahon, Katherine D.; Mamlstrom, Rex R.

    2014-05-12

    Multiple evolutionary models have been proposed to explain the formation of genetically and ecologically distinct bacterial groups. Time-series metagenomics enables direct observation of evolutionary processes in natural populations, and if applied over a sufficiently long time frame, this approach could capture events such as gene-specific or genome-wide selective sweeps. Direct observations of either process could help resolve how distinct groups form in natural microbial assemblages. Here, from a three-year metagenomic study of a freshwater lake, we explore changes in single nucleotide polymorphism (SNP) frequencies and patterns of gene gain and loss in populations of Chlorobiaceae and Methylophilaceae. SNP analyses revealed substantial genetic heterogeneity within these populations, although the degree of heterogeneity varied considerably among closely related, co-occurring Methylophilaceae populations. SNP allele frequencies, as well as the relative abundance of certain genes, changed dramatically over time in each population. Interestingly, SNP diversity was purged at nearly every genome position in one of the Chlorobiaceae populations over the course of three years, while at the same time multiple genes either swept through or were swept from this population. These patterns were consistent with a genome-wide selective sweep, a process predicted by the ecotype model? of diversification, but not previously observed in natural populations.

  8. Genome-wide Selective Sweeps in Natural Bacterial Populations Revealed by Time-series Metagenomics

    SciTech Connect

    Chan, Leong-Keat; Bendall, Matthew L.; Malfatti, Stephanie; Schwientek, Patrick; Tremblay, Julien; Schackwitz, Wendy; Martin, Joel; Pati, Amrita; Bushnell, Brian; Foster, Brian; Kang, Dongwan; Tringe, Susannah G.; Bertilsson, Stefan; Moran, Mary Ann; Shade, Ashley; Newton, Ryan J.; Stevens, Sarah; McMahon, Katherine D.; Malmstrom, Rex R.

    2014-06-18

    Multiple evolutionary models have been proposed to explain the formation of genetically and ecologically distinct bacterial groups. Time-series metagenomics enables direct observation of evolutionary processes in natural populations, and if applied over a sufficiently long time frame, this approach could capture events such as gene-specific or genome-wide selective sweeps. Direct observations of either process could help resolve how distinct groups form in natural microbial assemblages. Here, from a three-year metagenomic study of a freshwater lake, we explore changes in single nucleotide polymorphism (SNP) frequencies and patterns of gene gain and loss in populations of Chlorobiaceae and Methylophilaceae. SNP analyses revealed substantial genetic heterogeneity within these populations, although the degree of heterogeneity varied considerably among closely related, co-occurring Methylophilaceae populations. SNP allele frequencies, as well as the relative abundance of certain genes, changed dramatically over time in each population. Interestingly, SNP diversity was purged at nearly every genome position in one of the Chlorobiaceae populations over the course of three years, while at the same time multiple genes either swept through or were swept from this population. These patterns were consistent with a genome-wide selective sweep, a process predicted by the ‘ecotype model’ of diversification, but not previously observed in natural populations.

  9. Evidence of natural selection acting on a polymorphic hybrid incompatibility locus in Mimulus.

    PubMed

    Sweigart, Andrea L; Flagel, Lex E

    2015-02-01

    As a common cause of reproductive isolation in diverse taxa, hybrid incompatibilities are fundamentally important to speciation. A key question is which evolutionary forces drive the initial substitutions within species that lead to hybrid dysfunction. Previously, we discovered a simple genetic incompatibility that causes nearly complete male sterility and partial female sterility in hybrids between the two closely related yellow monkeyflower species Mimulus guttatus and M. nasutus. In this report, we fine map the two major incompatibility loci-hybrid male sterility 1 (hms1) and hybrid male sterility 2 (hms2)-to small nuclear genomic regions (each <70 kb) that include strong candidate genes. With this improved genetic resolution, we also investigate the evolutionary dynamics of hms1 in a natural population of M. guttatus known to be polymorphic at this locus. Using classical genetic crosses and population genomics, we show that a 320-kb region containing the hms1 incompatibility allele has risen to intermediate frequency in this population by strong natural selection. This finding provides direct evidence that natural selection within plant species can lead to hybrid dysfunction between species. PMID:25428983

  10. Differential Evolutionary Selection and Natural Evolvability Observed in ALT Proteins of Human Filarial Parasites.

    PubMed

    Devoe, Neil C; Corbett, Ian J; Barker, Linsey; Chang, Robert; Gudis, Polyxeni; Mullen, Nathan; Perez, Kailey; Raposo, Hugo; Scholz, John; May, Meghan

    2016-01-01

    The abundant larval transcript (ALT-2) protein is present in all members of the Filarioidea, and has been reported as a potential candidate antigen for a subunit vaccine against lymphatic filariasis. To assess the potential for vaccine escape or heterologous protection, we examined the evolutionary selection acting on ALT-2. The ratios of nonsynonymous (K(a)) to synonymous (K(s)) mutation frequencies (?) were calculated for the alt-2 genes of the lymphatic filariasis agents Brugia malayi and Wuchereria bancrofti and the agents of river blindness and African eyeworm disease Onchocerca volvulus and Loa loa. Two distinct Bayesian models of sequence evolution showed that ALT-2 of W. bancrofti and L. loa were under significant (P<0.05; P < 0.001) diversifying selection, while ALT-2 of B. malayi and O. volvulus were under neutral to stabilizing selection. Diversifying selection as measured by ? values was notably strongest on the region of ALT-2 encoding the signal peptide of L. loa and was elevated in the variable acidic domain of L. loa and W. bancrofti. Phylogenetic analysis indicated that the ALT-2 consensus sequences formed three clades: the first consisting of B. malayi, the second consisting of W. bancrofti, and the third containing both O. volvulus and L. loa. ALT-2 selection was therefore not predictable by phylogeny or pathology, as the two species parasitizing the eye were selected differently, as were the two species parasitizing the lymphatic system. The most immunogenic regions of L. loa and W. bancrofti ALT-2 sequence as modeled by antigenicity prediction analysis did not correspond with elevated levels of diversifying selection, and were not selected differently than predicted antigenic epitopes in B. malayi and O. volvulus. Measurements of ALT-2 evolvability made by ?2 analysis between alleles that were stable (O. volvulus and B. malayi) and those that were under diversifying selection (W. bancrofti and L. loa) indicated significant (P<0.01) deviations from a normal distribution for both W. bancrofti and L. loa. The relationship between evolvability and selection in L. loa followed a second order polynomial distribution (R2 = 0.89), indicating that the two factors relate to one another in accordance with an additional unknown factor. Taken together, these findings indicate discrete evolutionary drivers acting on ALT-2 of the four organisms examined, and the described variation has implications for design of novel vaccines and diagnostic reagents. Additionally, this represents the first mathematical description of evolvability in a naturally occurring setting. PMID:26890364

  11. Differential Evolutionary Selection and Natural Evolvability Observed in ALT Proteins of Human Filarial Parasites

    PubMed Central

    Devoe, Neil C.; Corbett, Ian J.; Barker, Linsey; Chang, Robert; Gudis, Polyxeni; Mullen, Nathan; Perez, Kailey; Raposo, Hugo; Scholz, John; May, Meghan

    2016-01-01

    The abundant larval transcript (ALT-2) protein is present in all members of the Filarioidea, and has been reported as a potential candidate antigen for a subunit vaccine against lymphatic filariasis. To assess the potential for vaccine escape or heterologous protection, we examined the evolutionary selection acting on ALT-2. The ratios of nonsynonymous (K(a)) to synonymous (K(s)) mutation frequencies (ω) were calculated for the alt-2 genes of the lymphatic filariasis agents Brugia malayi and Wuchereria bancrofti and the agents of river blindness and African eyeworm disease Onchocerca volvulus and Loa loa. Two distinct Bayesian models of sequence evolution showed that ALT-2 of W. bancrofti and L. loa were under significant (P<0.05; P < 0.001) diversifying selection, while ALT-2 of B. malayi and O. volvulus were under neutral to stabilizing selection. Diversifying selection as measured by ω values was notably strongest on the region of ALT-2 encoding the signal peptide of L. loa and was elevated in the variable acidic domain of L. loa and W. bancrofti. Phylogenetic analysis indicated that the ALT-2 consensus sequences formed three clades: the first consisting of B. malayi, the second consisting of W. bancrofti, and the third containing both O. volvulus and L. loa. ALT-2 selection was therefore not predictable by phylogeny or pathology, as the two species parasitizing the eye were selected differently, as were the two species parasitizing the lymphatic system. The most immunogenic regions of L. loa and W. bancrofti ALT-2 sequence as modeled by antigenicity prediction analysis did not correspond with elevated levels of diversifying selection, and were not selected differently than predicted antigenic epitopes in B. malayi and O. volvulus. Measurements of ALT-2 evolvability made by χ2 analysis between alleles that were stable (O. volvulus and B. malayi) and those that were under diversifying selection (W. bancrofti and L. loa) indicated significant (P<0.01) deviations from a normal distribution for both W. bancrofti and L. loa. The relationship between evolvability and selection in L. loa followed a second order polynomial distribution (R2 = 0.89), indicating that the two factors relate to one another in accordance with an additional unknown factor. Taken together, these findings indicate discrete evolutionary drivers acting on ALT-2 of the four organisms examined, and the described variation has implications for design of novel vaccines and diagnostic reagents. Additionally, this represents the first mathematical description of evolvability in a naturally occurring setting. PMID:26890364

  12. Selective NOx Recirculation for Stationary Lean-Burn Natural Gas Engines

    SciTech Connect

    Nigel Clark; Gregory Thompson; Richard Atkinson; Richard Turton; Chamila Tissera; Emre Tatli; Andy Zimmerman

    2005-12-28

    Selective NOx Recirculation (SNR) involves cooling the engine exhaust gas and then adsorbing the oxides of nitrogen (NOx) from the exhaust stream, followed by the periodic desorption of NOx. By returning the desorbed, concentrated NOx into the engine intake and through the combustion chamber, a percentage of the NOx is decomposed during the combustion process. An initial study of NOx decomposition during lean-burn combustion was concluded in 2004 using a 1993 Cummins L10G 240hp natural gas engine. It was observed that the air/fuel ratio, injected NO (nitric oxide) quantity and engine operating points affected NOx decomposition rates of the engine. Chemical kinetic modeling results were also used to determine optimum NOx decomposition operating points and were published in the 2004 annual report. A NOx decomposition rate of 27% was measured from this engine under lean-burn conditions while the software model predicted between 35-42% NOx decomposition for similar conditions. A later technology 1998 Cummins L10G 280hp natural gas engine was procured with the assistance of Cummins Inc. to replace the previous engine used for 2005 experimental research. The new engine was equipped with an electronic fuel management system with closed-loop control that provided a more stable air/fuel ratio control and improved the repeatability of the tests. The engine was instrumented with an in-cylinder pressure measurement system and electronic controls, and was adapted to operate over a range of air/fuel ratios. The engine was connected to a newly commissioned 300hp alternating current (AC) motoring dynamometer. The second experimental campaign was performed to acquire both stoichiometric and slightly rich (0.97 lambda ratio) burn NOx decomposition rates. Effects of engine load and speed on decomposition were quantified, but Exhaust Gas Recirculation (EGR) was not varied independently. Decomposition rates of up to 92% were demonstrated. Following recommendations at the 2004 ARES peer review meeting at Argonne National Laboratories, in-cylinder pressure was measured to calculate engine indicated mean effective pressure (IMEP) changes due to NOx injections and EGR variations, and to observe conditions in the cylinder. The third experimental campaign gathered NOx decomposition data at 800, 1200 and 1800 rpm. EGR was added via an external loop, with EGR ranging from zero to the point of misfire. The air/fuel ratio was set at both stoichiometric and slightly rich conditions, and NOx decomposition rates were calculated for each set of runs. Modifications were made to the engine exhaust manifold to record individual exhaust temperatures. The three experimental campaigns have provided the data needed for a comprehensive model of NOx decomposition during the combustion process, and data have confirmed that there was no significant impact of injected NO on in-cylinder pressure. The NOx adsorption system provided by Sorbent Technologies Corp. (Twinsburg, OH), comprised a NOx adsorber, heat exchanger and a demister. These components were connected to the engine, and data were gathered to show both the adsorption of NOx from the engine, and desorption of NOx from the carbon-based sorbent material back into the engine intake, using a heated air stream. In order to quantify the NOx adsorption/desorption characteristics of the sorbent material, a bench top adsorption system was constructed and instrumented with thermocouples and the system output was fed into a NOx analyzer. The temperature of this apparatus was controlled while gathering data on the characteristics of the sorbent material. These data were required for development of a system model. Preliminary data were gathered in 2005, and will continue in early 2006. To assess the economic benefits of the proposed SNR technology the WVU research team has been joined in the last quarter by Dr Richard Turton (WVU-Chemical Engineering), who is modeling, sizing and costing the major components. The tasks will address modeling and preliminary design of the heat exchanger, demister and NOx sorbent chamber suitable for a given engine. A simplified linear driving force model was developed to predict NOx adsorption into the sorbent material as cooled exhaust passes over fresh sorbent material. This aspect of the research will continue into 2006, and the benefits and challenges of SNR will be compared with those of competing systems, such as Selective Catalytic Reduction. Chemical kinetic modeling using the CHEMKIN software package was extended in 2005 to the case of slightly rich burn with EGR. Simulations were performed at 10%, 20%, 30% and 40% of the intake air replaced with EGR. NOx decomposition efficiency was calculated at the point in time where 98% of fuel was consumed, which is believed to be a conservative approach. The modeling data show that reductions of over 70% are possible using the ''98% fuel burned'' assumption.

  13. Aggression and feeding of hatchery-reared and naturally reared steelhead (Oncorhynchus mykiss) fry in a laboratory flume and a comparison with observations in natural streams

    USGS Publications Warehouse

    Riley, S.C.; Tatara, C.P.; Scheurer, J.A.

    2005-01-01

    We quantified the aggression and feeding of naturally reared steelhead (Oncorhynchus mykiss) fry stocked into a laboratory flume with naturally reared fry or hatchery-reared fry from conventional and enriched rearing environments at three densities in the presence and absence of predators, and compared the aggression and feeding observed in the flume to that observed in two streams. Steelhead fry attack rate increased with density and was reduced in the presence of predators, but was not affected by rearing treatment. Threat rate appeared to increase with density and was significantly affected by rearing treatment combination, but was not significantly affected by predator presence. Feeding rate was not affected by density or rearing treatment, but was reduced in the presence of predators. The rate of aggression by steelhead fry in two streams was lower than that observed in the laboratory and did not increase with density. Rates of aggression and feeding of hatchery-reared and wild steelhead fry were not significantly different in the streams. Overall, we found no evidence that hatchery rearing environments caused higher aggression in steelhead fry. Laboratory observations of salmonid aggression, particularly at high density, may not reflect aggression levels in the wild. ?? 2005 NRC.

  14. Early history of laboratory breeding of Aedes aegypti (Diptera: Culicidae) focusing on the origins and use of selected strains.

    PubMed

    Kuno, Goro

    2010-11-01

    The yellow fever mosquito, Aedes aegypti (L.) (Diptera: Culicidae), is well recognized for its extensive adaptation to diverse ecological conditions and for genetic variation. Recognizing the importance of strain variation of this mosquito, researchers have established a large number of laboratory strains. Some of the popular strains have been used for research for years in many laboratories around the world. However, the exact origins of many of these strains are unknown. In this review, publications and archival records were examined to report the early laboratory mosquito rearing practices around the world and to identify the origins of selected strains. The records showed that inter-laboratory sharing of strains was already underway in the early part of the 20th century because of the ease of breeding Ae. aegypti and of sending eggs by mail. It also was found that the four strains established in major U.S. institutions by the mid-1930s, including the "ROCK" (short for Rockefeller) strain, had been derived from Cuba, Nigeria, Philippines, or Puerto Rico, all known for a long history of transmission of yellow fever virus or dengue virus rather than from North America. The strains used for research in Europe were primarily derived from West Africa, but strains of Asian, Caribbean, and South American origins also were used for comparative experiments among geographic strains. Neglected issues related to strain designation and original source identification in scientific publications were found and their relevance to current research is discussed. PMID:21175042

  15. Wavelength selection and spectral discrimination for paddy rice, with laboratory measurements of hyperspectral leaf reflectance

    NASA Astrophysics Data System (ADS)

    Song, Shalei; Gong, Wei; Zhu, Bo; Huang, Xin

    2011-09-01

    The objective of this research is to select the most sensitive wavelengths for the discrimination of the imperceptible spectral variations of paddy rice under different cultivation conditions. The paddy rice was cultivated under four different nitrogen cultivation levels and three water irrigation levels. There are 2151 hyperspectral wavelengths available, both in hyperspectral reflectance and energy space transformed spectral data. Based on these two data sets, the principal component analysis (PCA) and band-band correlation methods were used to select significant wavelengths with no reference to leaf biochemical properties, while the partial least squares (PLS) method assessed the contribution of each narrow band to leaf biochemical content associated with each loading weight across the nitrogen and water stresses. Moreover, several significant narrow bands and other broad bands were selected to establish eight kinds of wavelength (broad-band) combinations, focusing on comparing the performance of the narrow-band combinations instead of broad-band combinations for rice supervising applications. Finally, to investigate the capability of the selected wavelengths to diagnose the stress conditions across the different cultivation levels, four selected narrow bands (552, 675, 705 and 776 nm) were calculated and compared between nitrogen-stressed and non-stressed rice leaves using linear discriminant analysis (LDA). Also, wavelengths of 1158, 1378 and 1965 nm were identified as the most useful bands to diagnose the stress condition across three irrigation levels. Results indicated that good discrimination was achieved. Overall, the narrow bands based on hyperspectral reflectance data appear to have great potential for discriminating rice of differing cultivation conditions and for detecting stress in rice vegetation; these selected wavelengths also have great potential use for the designing of future sensors.

  16. Isolation gowns in health care settings: Laboratory studies, regulations and standards, and potential barriers of gown selection and use.

    PubMed

    Kilinc Balci, F Selcen

    2016-01-01

    Although they play an important role in infection prevention and control, textile materials and personal protective equipment (PPE) used in health care settings are known to be one of the sources of cross-infection. Gowns are recommended to prevent transmission of infectious diseases in certain settings; however, laboratory and field studies have produced mixed results of their efficacy. PPE used in health care is regulated as either class I (low risk) or class II (intermediate risk) devices in the United States. Many organizations have published guidelines for the use of PPE, including isolation gowns, in health care settings. In addition, the Association for the Advancement of Medical Instrumentation published a guidance document on the selection of gowns and a classification standard on liquid barrier performance for both surgical and isolation gowns. However, there is currently no existing standard specific to isolation gowns that considers not only the barrier resistance but also a wide array of end user desired attributes. As a result, infection preventionists and purchasing agents face several difficulties in the selection process, and end users have limited or no information on the levels of protection provided by isolation gowns. Lack of knowledge about the performance of protective clothing used in health care became more apparent during the 2014 Ebola epidemic. This article reviews laboratory studies, regulations, guidelines and standards pertaining to isolation gowns, characterization problems, and other potential barriers of isolation gown selection and use. PMID:26391468

  17. Interaction-based evolution: how natural selection and nonrandom mutation work together

    PubMed Central

    2013-01-01

    Background The modern evolutionary synthesis leaves unresolved some of the most fundamental, long-standing questions in evolutionary biology: What is the role of sex in evolution? How does complex adaptation evolve? How can selection operate effectively on genetic interactions? More recently, the molecular biology and genomics revolutions have raised a host of critical new questions, through empirical findings that the modern synthesis fails to explain: for example, the discovery of de novo genes; the immense constructive role of transposable elements in evolution; genetic variance and biochemical activity that go far beyond what traditional natural selection can maintain; perplexing cases of molecular parallelism; and more. Presentation of the hypothesis Here I address these questions from a unified perspective, by means of a new mechanistic view of evolution that offers a novel connection between selection on the phenotype and genetic evolutionary change (while relying, like the traditional theory, on natural selection as the only source of feedback on the fit between an organism and its environment). I hypothesize that the mutation that is of relevance for the evolution of complex adaptation—while not Lamarckian, or “directed” to increase fitness—is not random, but is instead the outcome of a complex and continually evolving biological process that combines information from multiple loci into one. This allows selection on a fleeting combination of interacting alleles at different loci to have a hereditary effect according to the combination’s fitness. Testing and implications of the hypothesis This proposed mechanism addresses the problem of how beneficial genetic interactions can evolve under selection, and also offers an intuitive explanation for the role of sex in evolution, which focuses on sex as the generator of genetic combinations. Importantly, it also implies that genetic variation that has appeared neutral through the lens of traditional theory can actually experience selection on interactions and thus has a much greater adaptive potential than previously considered. Empirical evidence for the proposed mechanism from both molecular evolution and evolution at the organismal level is discussed, and multiple predictions are offered by which it may be tested. Reviewers This article was reviewed by Nigel Goldenfeld (nominated by Eugene V. Koonin), Jürgen Brosius and W. Ford Doolittle. PMID:24139515

  18. Evolvability Is an Evolved Ability: The Coding Concept as the Arch-Unit of Natural Selection

    NASA Astrophysics Data System (ADS)

    Jankovi?, Srdja; ?irkovi?, Milan M.

    2015-09-01

    Physical processes that characterize living matter are qualitatively distinct in that they involve encoding and transfer of specific types of information. Such information plays an active part in the control of events that are ultimately linked to the capacity of the system to persist and multiply. This algorithmicity of life is a key prerequisite for its Darwinian evolution, driven by natural selection acting upon stochastically arising variations of the encoded information. The concept of evolvability attempts to define the total capacity of a system to evolve new encoded traits under appropriate conditions, i.e., the accessible section of total morphological space. Since this is dependent on previously evolved regulatory networks that govern information flow in the system, evolvability itself may be regarded as an evolved ability. The way information is physically written, read and modified in living cells (the "coding concept") has not changed substantially during the whole history of the Earth's biosphere. This biosphere, be it alone or one of many, is, accordingly, itself a product of natural selection, since the overall evolvability conferred by its coding concept (nucleic acids as information carriers with the "rulebook of meanings" provided by codons, as well as all the subsystems that regulate various conditional information-reading modes) certainly played a key role in enabling this biosphere to survive up to the present, through alterations of planetary conditions, including at least five catastrophic events linked to major mass extinctions. We submit that, whatever the actual prebiotic physical and chemical processes may have been on our home planet, or may, in principle, occur at some time and place in the Universe, a particular coding concept, with its respective potential to give rise to a biosphere, or class of biospheres, of a certain evolvability, may itself be regarded as a unit (indeed the arch-unit) of natural selection.

  19. Evolvability Is an Evolved Ability: The Coding Concept as the Arch-Unit of Natural Selection.

    PubMed

    Janković, Srdja; Ćirković, Milan M

    2016-03-01

    Physical processes that characterize living matter are qualitatively distinct in that they involve encoding and transfer of specific types of information. Such information plays an active part in the control of events that are ultimately linked to the capacity of the system to persist and multiply. This algorithmicity of life is a key prerequisite for its Darwinian evolution, driven by natural selection acting upon stochastically arising variations of the encoded information. The concept of evolvability attempts to define the total capacity of a system to evolve new encoded traits under appropriate conditions, i.e., the accessible section of total morphological space. Since this is dependent on previously evolved regulatory networks that govern information flow in the system, evolvability itself may be regarded as an evolved ability. The way information is physically written, read and modified in living cells (the "coding concept") has not changed substantially during the whole history of the Earth's biosphere. This biosphere, be it alone or one of many, is, accordingly, itself a product of natural selection, since the overall evolvability conferred by its coding concept (nucleic acids as information carriers with the "rulebook of meanings" provided by codons, as well as all the subsystems that regulate various conditional information-reading modes) certainly played a key role in enabling this biosphere to survive up to the present, through alterations of planetary conditions, including at least five catastrophic events linked to major mass extinctions. We submit that, whatever the actual prebiotic physical and chemical processes may have been on our home planet, or may, in principle, occur at some time and place in the Universe, a particular coding concept, with its respective potential to give rise to a biosphere, or class of biospheres, of a certain evolvability, may itself be regarded as a unit (indeed the arch-unit) of natural selection. PMID:26419865

  20. Evolvability Is an Evolved Ability: The Coding Concept as the Arch-Unit of Natural Selection

    NASA Astrophysics Data System (ADS)

    Janković, Srdja; Ćirković, Milan M.

    2016-03-01

    Physical processes that characterize living matter are qualitatively distinct in that they involve encoding and transfer of specific types of information. Such information plays an active part in the control of events that are ultimately linked to the capacity of the system to persist and multiply. This algorithmicity of life is a key prerequisite for its Darwinian evolution, driven by natural selection acting upon stochastically arising variations of the encoded information. The concept of evolvability attempts to define the total capacity of a system to evolve new encoded traits under appropriate conditions, i.e., the accessible section of total morphological space. Since this is dependent on previously evolved regulatory networks that govern information flow in the system, evolvability itself may be regarded as an evolved ability. The way information is physically written, read and modified in living cells (the "coding concept") has not changed substantially during the whole history of the Earth's biosphere. This biosphere, be it alone or one of many, is, accordingly, itself a product of natural selection, since the overall evolvability conferred by its coding concept (nucleic acids as information carriers with the "rulebook of meanings" provided by codons, as well as all the subsystems that regulate various conditional information-reading modes) certainly played a key role in enabling this biosphere to survive up to the present, through alterations of planetary conditions, including at least five catastrophic events linked to major mass extinctions. We submit that, whatever the actual prebiotic physical and chemical processes may have been on our home planet, or may, in principle, occur at some time and place in the Universe, a particular coding concept, with its respective potential to give rise to a biosphere, or class of biospheres, of a certain evolvability, may itself be regarded as a unit (indeed the arch-unit) of natural selection.

  1. Chemoselective Reactions of Citral: Green Syntheses of Natural Perfumes for the Undergraduate Organic Laboratory

    ERIC Educational Resources Information Center

    Cunningham, Anna D.; Ham, Eun Y.; Vosburg, David A.

    2011-01-01

    Chemoselectivity is a central concept in organic synthesis and may be readily appreciated in the context of the fragrant, polyfunctional natural product citral. We describe three single-step reactions students may perform on citral to synthesize other natural perfumes: citronellal, geraniol, nerol, or epoxycitral. Each of the reactions uses a…

  2. Chemoselective Reactions of Citral: Green Syntheses of Natural Perfumes for the Undergraduate Organic Laboratory

    ERIC Educational Resources Information Center

    Cunningham, Anna D.; Ham, Eun Y.; Vosburg, David A.

    2011-01-01

    Chemoselectivity is a central concept in organic synthesis and may be readily appreciated in the context of the fragrant, polyfunctional natural product citral. We describe three single-step reactions students may perform on citral to synthesize other natural perfumes: citronellal, geraniol, nerol, or epoxycitral. Each of the reactions uses a…

  3. Genomic signatures of geographic isolation and natural selection in coral reef fishes.

    PubMed

    Gaither, Michelle R; Bernal, Moisés A; Coleman, Richard R; Bowen, Brian W; Jones, Shelley A; Simison, W Brian; Rocha, Luiz A

    2015-04-01

    The drivers of speciation remain among the most controversial topics in evolutionary biology. Initially, Darwin emphasized natural selection as a primary mechanism of speciation, but the architects of the modern synthesis largely abandoned that view in favour of divergence by geographic isolation. The balance between selection and isolation is still at the forefront of the evolutionary debate, especially for the world's tropical oceans where biodiversity is high, but isolating barriers are few. Here, we identify the drivers of speciation in Pacific reef fishes of the genus Acanthurus by comparative genome scans of two peripheral populations that split from a large Central-West Pacific lineage at roughly the same time. Mitochondrial sequences indicate that populations in the Hawaiian Archipelago and the Marquesas Islands became isolated approximately 0.5 Ma. The Hawaiian lineage is morphologically indistinguishable from the widespread Pacific form, but the Marquesan form is recognized as a distinct species that occupies an unusual tropical ecosystem characterized by upwelling, turbidity, temperature fluctuations, algal blooms and little coral cover. An analysis of 3737 SNPs reveals a strong signal of selection at the Marquesas, with 59 loci under disruptive selection including an opsin Rh2 locus. While both the Hawaiian and Marquesan populations indicate signals of drift, the former shows a weak signal of selection that is comparable with populations in the Central-West Pacific. This contrast between closely related lineages reveals one population diverging due primarily to geographic isolation and genetic drift, and the other achieving taxonomic species status under the influence of selection. PMID:25753379

  4. Natural Selection on Individual Variation in Tolerance of Gastrointestinal Nematode Infection

    PubMed Central

    Hayward, Adam D.; Nussey, Daniel H.; Wilson, Alastair J.; Berenos, Camillo; Pilkington, Jill G.; Watt, Kathryn A.; Pemberton, Josephine M.; Graham, Andrea L.

    2014-01-01

    Hosts may mitigate the impact of parasites by two broad strategies: resistance, which limits parasite burden, and tolerance, which limits the fitness or health cost of increasing parasite burden. The degree and causes of variation in both resistance and tolerance are expected to influence host–parasite evolutionary and epidemiological dynamics and inform disease management, yet very little empirical work has addressed tolerance in wild vertebrates. Here, we applied random regression models to longitudinal data from an unmanaged population of Soay sheep to estimate individual tolerance, defined as the rate of decline in body weight with increasing burden of highly prevalent gastrointestinal nematode parasites. On average, individuals lost weight as parasite burden increased, but whereas some lost weight slowly as burden increased (exhibiting high tolerance), other individuals lost weight significantly more rapidly (exhibiting low tolerance). We then investigated associations between tolerance and fitness using selection gradients that accounted for selection on correlated traits, including body weight. We found evidence for positive phenotypic selection on tolerance: on average, individuals who lost weight more slowly with increasing parasite burden had higher lifetime breeding success. This variation did not have an additive genetic basis. These results reveal that selection on tolerance operates under natural conditions. They also support theoretical predictions for the erosion of additive genetic variance of traits under strong directional selection and fixation of genes conferring tolerance. Our findings provide the first evidence of selection on individual tolerance of infection in animals and suggest practical applications in animal and human disease management in the face of highly prevalent parasites. PMID:25072883

  5. Automated ion-selective electrode method for determining fluoride in natural waters

    USGS Publications Warehouse

    Erdmann, D.E.

    1975-01-01

    An automated fluoride method which uses AutoAnalyzer modules in conjunction with a fluoride ion-selective electrode was evaluated. The results obtained on 38 natural water samples are in excellent agreement with those determined by a similar manual method (average difference = 0.026 mg/l). An average fluoride concentration of 0.496 mg/l was found when several natural water samples were spiked with 0.50 mg/l fluoride. Aluminum is the only significant interfering substance, and it can be easily tolerated if its concentration does not exceed 2 mg/l. Thirty samples were analyzed per hour over a concentration range of 0-2 mg/l.

  6. Process for selecting NEAMS applications for access to Idaho National Laboratory high performance computing resources

    SciTech Connect

    Michael Pernice

    2010-09-01

    INL has agreed to provide participants in the Nuclear Energy Advanced Mod- eling and Simulation (NEAMS) program with access to its high performance computing (HPC) resources under sponsorship of the Enabling Computational Technologies (ECT) program element. This report documents the process used to select applications and the software stack in place at INL.

  7. Novel Experiments in Physics II. A Selection of Laboratory Notes Now Used in Colleges and Universities.

    ERIC Educational Resources Information Center

    American Association of Physics Teachers, Washington, DC.

    This second volume, a compilation of reprints of experimental notes in physics, was prepared by the American Association of Physics Teachers (AAPT) Committee on Apparatus and by the AAPT Executive Office in response to requests received by the Association for a completely new edition. The goal of the Committee was to provide a selection of…

  8. Novel Experiments in Physics II. A Selection of Laboratory Notes Now Used in Colleges and Universities.

    ERIC Educational Resources Information Center

    American Association of Physics Teachers, Washington, DC.

    This second volume, a compilation of reprints of experimental notes in physics, was prepared by the American Association of Physics Teachers (AAPT) Committee on Apparatus and by the AAPT Executive Office in response to requests received by the Association for a completely new edition. The goal of the Committee was to provide a selection of…

  9. Goal-Side Selection in Soccer Penalty Kicking When Viewing Natural Scenes

    PubMed Central

    Weigelt, Matthias; Memmert, Daniel

    2012-01-01

    The present study investigates the influence of goalkeeper displacement on goal-side selection in soccer penalty kicking. Facing a penalty situation, participants viewed photo-realistic images of a goalkeeper and a soccer goal. In the action selection task, they were asked to kick to the greater goal-side, and in the perception task, they indicated the position of the goalkeeper on the goal line. To this end, the goalkeeper was depicted in a regular goalkeeping posture, standing either in the exact middle of the goal or being displaced at different distances to the left or right of the goal’s center. Results showed that the goalkeeper’s position on the goal line systematically affected goal-side selection, even when participants were not aware of the displacement. These findings provide further support for the notion that the implicit processing of the stimulus layout in natural scenes can effect action selection in complex environments, such in soccer penalty shooting. PMID:22973246

  10. Seasonal and diel habitat selection by bluegills in a shallow natural lake

    USGS Publications Warehouse

    Paukert, C.P.; Willis, D.W.

    2002-01-01

    Habitat use by bluegill Lepomis macrochirus may be dictated by the avoidance of predators and the availability of prey. Previous work suggests that bluegills large enough to avoid predators will select habitats based on foraging profitability. However, these studies focused on smaller fish (200 mm total length [TL]) bluegills in a shallow (mean depth = 1.2 m), 332-ha, natural lake (Pelican Lake, Nebraska) with both emergent and submergent vegetation distributed throughout. A total of 78 bluegills (200-273 mm TL) were implanted with radio transmitters and relocated daily for 6 d per month (April-September); up to 20 of the tagged fish were relocated every 2 h for a 24-h period once each month. Regardless of diel period, bluegills used open-water, emergent vegetation, submergent vegetation, and mixed emergent - submergent vegetation habitat types in similar proportions. During April, June, and July, male bluegills positively selected emergent vegetation, whereas female bluegills showed no vegetation selection preference during any month. Throughout the study period, bluegills never avoided open-water habitats, suggesting that larger individuals may continue to use open-water habitats in proportion to their availability. In addition, emergent vegetation appeared to be important, particularly for male bluegills. Although the mechanism for the positive selection of emergent vegetation by males was unclear, the protection or enhancement of such habitats may facilitate the preservation of quality bluegill populations in shallow lakes.

  11. On the causal efficacy of natural selection: A response to Richards' critique of the standard interpretation.

    PubMed

    Sullivan-Clarke, Andrea

    2013-12-01

    Given the amount of literature devoted to the reasoning used in Darwin's Origin of Species, an interpretation seeking to revise the standard take on Darwin's methodology is unexpected. Yet, Richards (1997, 1998, 2005) challenges the view that Darwin drew an analogy in the Origin on the grounds that such a strategy could not support the possibility of a new species emerging. I suggest, however, that how one interprets causal efficacy is intimately connected with Darwin's use of analogy. A more robust conception of natural selection, as found in the Origin, supports the standard interpretation, significantly weakening Richards' charge of a paradox. PMID:24231184

  12. The age-specific force of natural selection and biodemographic walls of death

    PubMed Central

    Wachter, Kenneth W.; Evans, Steven N.; Steinsaltz, David

    2013-01-01

    W. D. Hamilton’s celebrated formula for the age-specific force of natural selection furnishes predictions for senescent mortality due to mutation accumulation, at the price of reliance on a linear approximation. Applying to Hamilton’s setting the full nonlinear demographic model for mutation accumulation recently developed by Evans, Steinsaltz, and Wachter, we find surprising differences. Nonlinear interactions cause the collapse of Hamilton-style predictions in the most commonly studied case, refine predictions in other cases, and allow walls of death at ages before the end of reproduction. Haldane’s principle for genetic load has an exact but unfamiliar generalization. PMID:23657010

  13. Conceptualizing the autism spectrum in terms of natural selection and behavioral ecology: the solitary forager hypothesis.

    PubMed

    Reser, Jared Edward

    2011-01-01

    This article reviews etiological and comparative evidence supporting the hypothesis that some genes associated with the autism spectrum were naturally selected and represent the adaptive benefits of being cognitively suited for solitary foraging. People on the autism spectrum are conceptualized here as ecologically competent individuals that could have been adept at learning and implementing hunting and gathering skills in the ancestral environment. Upon independence from their mothers, individuals on the autism spectrum may have been psychologically predisposed toward a different life-history strategy, common among mammals and even some primates, to hunt and gather primarily on their own. Many of the behavioral and cognitive tendencies that autistic individuals exhibit are viewed here as adaptations that would have complemented a solitary lifestyle. For example, the obsessive, repetitive and systemizing tendencies in autism, which can be mistakenly applied toward activities such as block stacking today, may have been focused by hunger and thirst toward successful food procurement in the ancestral past. Both solitary mammals and autistic individuals are low on measures of gregariousness, socialization, direct gazing, eye contact, facial expression, facial recognition, emotional engagement, affiliative need and other social behaviors. The evolution of the neurological tendencies in solitary species that predispose them toward being introverted and reclusive may hold important clues for the evolution of the autism spectrum and the natural selection of autism genes. Solitary animals are thought to eschew unnecessary social contact as part of a foraging strategy often due to scarcity and wide dispersal of food in their native environments. It is thought that the human ancestral environment was often nutritionally sparse as well, and this may have driven human parties to periodically disband. Inconsistencies in group size must have led to inconsistencies in the manner in which natural selection fashioned the social minds of humans, which in turn may well be responsible for the large variation in social abilities seen in human populations. This article emphasizes that individuals on the autism spectrum may have only been partially solitary, that natural selection may have only favored subclinical autistic traits and that the most severe cases of autism may be due to assortative mating. PMID:22947969

  14. If You Don't Have a Good Laboratory, Find a Good Volcano: Mount Vesuvius as a Natural Chemical Laboratory in Eighteenth-Century Italy.

    PubMed

    Guerra, Corinna

    2015-08-01

    This essay that examines the role of the volcano as a chemical site in the late eighteenth century, as the "new chemistry" spread throughout the southern Italian Kingdom of Naples, resulting in lively debates. In Naples itself, these scientific debates were not confined to academies, courts, and urban spaces. In the absence of well-equipped chemical laboratories, Neapolitan scholars also carried out research on chemistry on the slopes of Mount Vesuvius, a natural site that furnished them with all the tools and substances necessary for practising chemistry. By examining various Neapolitan publications on Vesuvius and the chemical reactions and products associated with its periodic eruptions, I argue that the volcano's presence contributed to a distinctive, local approach to chemical theory and practice. Several case studies examine the ways in which proximity to Vesuvius was exploited by Neapolitan scholars as they engaged with the new chemistry, including Giuseppe Vairo, Michele Ferrara, Francesco Semmola, and Emanuele Scotti. PMID:26307910

  15. A simple method for selecting spawning-ready individuals out from laboratorial cultured amphioxus population.

    PubMed

    Li, Guang; Wang, Jing; Yuan, Liang; Wang, Hui; Wang, Yi-Quan

    2015-11-01

    Amphioxus is an emerging model organism for evolutionary developmental (Evo-Dev) studies owing to its key phylogenetic position in chordates. However, the rare supply of living embryonic materials is a major drawback for using amphioxus as a laboratorial model animal. Although the problem has been partially resolved in several recent reports, the spawning of amphioxus still remains unpredictable to some extent. In the present study, we reported an accurate method to distinguish spawning-ready and non-spawning-ready individuals of amphioxus Branchiostoma belcheri. In comparison with non-spawning-ready amphioxus, all spawning-ready individuals display following features several hours before their spawning: 1) for both males and females, the interstices between two adjacent gonads are obvious and relatively wide; and 2) the connections among eggs are loose and the crannies appear in each individual ovary of females. These morphological features were also observed in B. japonicum, indicating their conservation among different lancelet species. Based on this observable criterion, we made predictions on the spawning of about 600 ripe B. belcheri individuals and acquired an accuracy of 86.7% for females and 80.4% for males. In addition, we found that advancing or delaying onset of darkness has no detectable effect on the timing of spawning of B. belcheri. Our study makes amphioxus spawning more amenable for our experiments and will greatly facilitate its utilization as a laboratorial model animal. J. Exp. Zool. (Mol. Dev. Evol.) 324B: 629-635, 2015. © 2015 Wiley Periodicals, Inc. PMID:26299898

  16. LABORATORY STUDIES ON THE STABILITY AND TRANSPORT OF INORGANIC COLLOIDS THROUGH NATURAL AQUIFER MATERIAL

    EPA Science Inventory

    The stability and transport of radio-labeled Fe2O3 particles were studied using laboratory batch and column techniques. Core material collected from shallow sand and gravel aquifer was used as the immobile column matrix material. Variables in the study included flow rate, pH, i...

  17. Outdoors--Nature's Learning Center. A Guide for Implementing an Outdoor Laboratory School Program.

    ERIC Educational Resources Information Center

    Banks, Dorothy E.

    The Round Meadow Environmental Laboratory School is an exemplary project designed to aid District of Columbia 6th grade children in overcoming the educational disadvantages of urban minority group isolation, both cultural and geographical, through a school-based and camp-based interracial and intercultural environmental awareness program. During…

  18. PROJECTS IN IMAGINATIVE NATURE EDUCATION, SURVEY REPORT AND OUTDOOR LABORATORY PLAN.

    ERIC Educational Resources Information Center

    National Audubon Society, New York, NY.

    THIS PLAN SUGGESTS HOW THE MID HUDSON-CATSKILLS MUSEUM CAN WORK CREATIVELY WITH COOPERATING SCHOOL DISTRICTS TO STRENGTHEN THEIR CURRICULUMS THROUGH OUTDOOR EDUCATION. THE RESULT OF THIS COOPERATIVE ENDEAVOR IS TO BE AN OUTDOOR LABORATORY CALLED "GATEWAY CENTER" LOCATED NEAR NEW PALTZ, NEW YORK. PART 1 CONTAINS (1) BACKGROUND INFORMATION, (2)…

  19. RESPONSES OF ZOOPLANKTON AND CHAOBORUS TO TEMEPHOS IN A NATURAL POND AND IN THE LABORATORY

    EPA Science Inventory

    Application of the organophosphorus insecticide temephos to a natural pond in central Minnesota was followed by reduction within 24 hr in all cladocerans, in Diaptomus leptopus and in Chaoborus americanus, and increases in cyclopoid copepods, copepod nauplii and rotifer Keratella...

  20. Genetic drift and natural selection in an isolated Zapotec-speaking community in the Valley of Oaxaca, southern Mexico.

    PubMed

    Little, B B; Malina, R M

    1989-01-01

    Genetic drift and natural selection were analyzed in a genetically isolated Zapotec-speaking community in the Valley of Oaxaca, southern Mexico. Moderately intense genetic drift and selection potentials were found. Potential for drift was related to (1) the small effective size of the population, and (2) the exceptionally low number of migrants into the population. Potential for selection was due to (1) an unusually high variance in fertility, and (2) a high contribution of prereproductive mortality. Significant potential for genetic evolution was found due to genetic drift and natural selection. PMID:2759638