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1

Natural Selection  

Microsoft Academic Search

IN NATURE of June 8 there appears a letter from my friend Prof. Poulton in which he replies to my statement that `natural selection' affords no explanation of evolution. He quotes in extenso a letter from Darwin to the distinguished American botanist Asa Gray, in which Darwin endeavours to deal with the objection that natural selection is a truism and

E. W. MacBride

1929-01-01

2

Natural Selection  

NSDL National Science Digital Library

Learners simulate the process of natural selection using a variety of beans and a bowl with a hole cut into it. The variety of beans represents the variation in a population of microbes, and the bowl with a hole represents an antibiotic or some other selective pressure on the population. Only the beans that survive (don't fall through the hole) are allowed to reproduce for the next generation. Learners record and plot the number of each kind of bean through multiple generations. This activity also addresses the process of scientific investigation as learners are encouraged to design their own method of experimentation, make a hypothesis, record data, and share their results.

Thiel-Cobbey, Heather

2012-01-01

3

Addressing Undergraduate Student Misconceptions about Natural Selection with an Interactive Simulated Laboratory  

Microsoft Academic Search

Although evolutionary theory is considered to be a unifying foundation for biological education, misconceptions about basic\\u000a evolutionary processes such as natural selection inhibit student understanding. Even after instruction, students harbor misconceptions\\u000a about natural selection, suggesting that traditional teaching methods are insufficient for correcting these confusions. This\\u000a has spurred an effort to develop new teaching methods and tools that effectively confront

Joel K. Abraham; Eli Meir; Judy Perry; Jon C. Herron; Susan Maruca; Derek Stal

2009-01-01

4

A Natural Selection  

NSDL National Science Digital Library

The high school science laboratory provides a natural environment for students to learn through scientist-teacher partnerships. A dynamic learning community, authentic inquiry, a deeper understanding of the nature of science, and learning about scientific careers are all benefits of scientist-teacher partnerships. This article focuses on the benefits of partnerships while describing how one specific partnership team developed a natural selection laboratory to integrate with a high school biology curriculum.

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

2005-10-01

5

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

PubMed

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

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

2012-03-05

6

Natural Selection  

Microsoft Academic Search

IN NATURE of November 21, Prof. E. W. MacBride states that ``Ordinary fluctuating variations which can be graphically represented on a `curve of error' are certainly not inherited''. He bases this statement on the work of Johannsen on pure lines of beans, and of Agar and Jennings on clones of Simocephalus and Paramecium. He does not mention the fact that

J. B. S. Haldane

1936-01-01

7

Drosophila and Selection in Nature: From Laboratory Fitness Components to Field Assessments  

Microsoft Academic Search

Studies on Drosophila model organisms are producing a wealth of information on the genetic basis of complex traits and on patterns of genetic divergence\\u000a in specific genes. This emerging information is interpreted within an evolutionary framework but direct connections with fitness\\u000a in nature are usually tenuous. Drosophila fitness under natural conditions can be difficult to define partly because of the

Ary A. Hoffmann

8

``Evolution without Natural Selection''  

Microsoft Academic Search

BELIEVING as I do that the words of a reviewer should be final, it is with no small amount of hesitation that I pen the following few remarks on the review of my little work entitled ``Evolution without Natural Selection,'' which appeared in NATURE of November 12 (p. 26). The curious way in which my book has been misunderstood, and

Charles Dixon

1885-01-01

9

Multicellular microorganisms: laboratory versus nature  

PubMed Central

Our present in-depth knowledge of the physiology and regulatory mechanisms of microorganisms has arisen from our ability to remove them from their natural, complex ecosystems into pure liquid cultures. These cultures are grown under optimized laboratory conditions and allow us to study microorganisms as individuals. However, microorganisms naturally grow in conditions that are far from optimal, which causes them to become organized into multicellular communities that are better protected against the harmful environment. Moreover, this multicellular existence allows individual cells to differentiate and acquire specific properties, such as forming resistant spores, which benefit the whole population. The relocation of natural microorganisms to the laboratory can result in their adaptation to these favourable conditions, which is accompanied by complex changes that include the repression of some protective mechanisms that are essential in nature. Laboratory microorganisms that have been cultured for long periods under optimized conditions might therefore differ markedly from those that exist in natural ecosystems.

Palkova, Zdena

2004-01-01

10

``Evolution without Natural Selection''  

Microsoft Academic Search

I FREELY admit that the impression left upon my mind after reading Mr. Dixon's essay was the same as that which was first conveyed by its title-viz, that the author supposed his work to be, if not ``antagonistic to Darwin's theory of Natural Selection,'' at all events, as I expressed it, ``an important emendation of Darwinism.'' My object, therefore, while

George J. Romanes

1885-01-01

11

Reinventing Natural Selection  

NASA Astrophysics Data System (ADS)

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.

Geraedts, Caspar L.; Boersma, Kerst Th.

2006-06-01

12

Down with natural selection?  

PubMed

Biologists are increasingly reexamining the conceptual structure of evolutionary theory, which dates back to the so-called Modern Synthesis of the 1930s and 1940s. Calls for an Extended Evolutionary Synthesis (EES) cite a number of empirical and theoretical advances that need to be accounted for, including evolvability, evolutionary novelties, capacitors of phenotypic evolution, developmental plasticity, and phenotypic attractors. In Biological Emergences, however, Robert Reid outlines a theory of evolution in which natural selection plays no role or-worse-actually impedes evolution by what Reid calls "natural experimentation." For Reid, biological complexity emerges because of intrinsic mechanisms that work in opposition to natural selection, a view that would reopen old questions of orthogenesis and Lamarckism. This review outlines why we do need an EES, but also why it is unlikely to take the shape that Reid advocates. PMID:19271349

Pigliucci, Massimo

2009-01-01

13

Introduction to Natural Selection  

NSDL National Science Digital Library

This lesson is an introduction to natural selection and is suited to any student who is just beginning his or her discovery of evolution. The motivation introduces a species of bird that became (over millions of years) numerous species, through adaptation. The development is a hands-on activity that demonstrates how populations change little by little, generation by generation, due to survival of species that have traits that are beneficial in an environment.

Science Netlinks;

2002-03-28

14

Natural Selection Simulation  

NSDL National Science Digital Library

This classroom activity introduces the concept of natural selection and how it relates to evolution. Students will use a variety of utensils including clothespins, tweezers and spoons to mimic animals with differently shaped mouths. The class will go through several trials, picking up at least twenty beans in one minute with their assigned utensil. If they fail to do so, their creature has died, demonstrating what happens to animals that cannot compete in the wild. Several discussion questions are included along with the activity.

2012-05-29

15

Natural selection maximizes Fisher information  

Microsoft Academic Search

In biology, information flows from the environment to the genome by the\\u000aprocess of natural selection. But it has not been clear precisely what sort of\\u000ainformation metric properly describes natural selection. Here, I show that\\u000aFisher information arises as the intrinsic metric of natural selection and\\u000aevolutionary dynamics. Maximizing the amount of Fisher information about the\\u000aenvironment captured by

Steven A. Frank

2009-01-01

16

Modeling Natural Selection  

ERIC Educational Resources Information Center

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…

Bogiages, Christopher A.; Lotter, Christine

2011-01-01

17

``Evolution without Natural Selection''  

Microsoft Academic Search

Two or three points in Mr. Romanes's letter in your issue of December 3 (p. 100), leave me no other alternative than to again ask you to insert the following few remarks. I beg to inform Mr. Romanes that with Darwinism my book has very little to do. It neither attempts to refute nor confirm the Darwinian hypothesis of Natural

Charles Dixon

1885-01-01

18

A quantum of natural selection  

NASA Astrophysics Data System (ADS)

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?

Lloyd, Seth

2009-03-01

19

Natural selection in chemical evolution.  

PubMed

We propose that chemical evolution can take place by natural selection if a geophysical process is capable of heterotrophic formation of liposomes that grow at some base rate, divide by external agitation, and are subject to stochastic chemical avalanches, in the absence of nucleotides or any monomers capable of modular heredity. We model this process using a simple hill-climbing algorithm, and an artificial chemistry that is unique in exhibiting conservation of mass and energy in an open thermodynamic system. Selection at the liposome level results in the stabilization of rarely occurring molecular autocatalysts that either catalyse or are consumed in reactions that confer liposome level fitness; typically they contribute in parallel to an increasingly conserved intermediary metabolism. Loss of competing autocatalysts can sometimes be adaptive. Steady-state energy flux by the individual increases due to the energetic demands of growth, but also of memory, i.e. maintaining variations in the chemical network. Self-organizing principles such as those proposed by Kauffman, Fontana, and Morowitz have been hypothesized as an ordering principle in chemical evolution, rather than chemical evolution by natural selection. We reject those notions as either logically flawed or at best insufficient in the absence of natural selection. Finally, a finite population model without elitism shows the practical evolutionary constraints for achieving chemical evolution by natural selection in the lab. PMID:17399743

Fernando, Chrisantha; Rowe, Jonathan

2007-02-12

20

Natural selection in chemical evolution  

Microsoft Academic Search

We propose that chemical evolution can take place by natural selection if a geophysical process is capable of heterotrophic formation of liposomes that grow at some base rate, divide by external agitation, and are subject to stochastic chemical avalanches, in the absence of nucleotides or any monomers capable of modular heredity. We model this process using a simple hill-climbing algorithm,

Chrisantha Fernando; Jonathan Rowe

2007-01-01

21

Natural Selection in Large Populations  

NASA Astrophysics Data System (ADS)

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.

Desai, Michael

2011-03-01

22

From Nature to the Laboratory and Into the Clinic  

PubMed Central

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)].

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

2009-01-01

23

Inheritance and Natural Selection on Functional Traits  

Microsoft Academic Search

We surveyed the literature published since 1985 for evidence of natural selection and heritability in vegetative functional traits and performance. Our goals were to (1) review patterns of selection on specific functional traits and (2) assess general evolutionary questions about selection and heritability for broad classes of traits. While generalizations about the functional significance of specific traits are premature, several

Monica A. Geber; Lauren R. Griffen

2003-01-01

24

From nature to the laboratory and into the clinic.  

PubMed

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), calicheamicin gamma(1)(I) (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), 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

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

2008-11-06

25

Network growth for enhanced natural selection  

NASA Astrophysics Data System (ADS)

Natural selection and random drift are competing phenomena for explaining the evolution of populations. Combining a highly fit mutant with a population structure that improves the odds that the mutation spreads through the whole population tips the balance in favor of natural selection. The probability that the spread occurs, known as the fixation probability, depends heavily on how the population is structured. Certain topologies, albeit highly artificially contrived, have been shown to exist that favor fixation. We present a randomized mechanism for network growth that is loosely inspired in some of these topologies’ key properties and demonstrate, through simulations, that it is capable of giving rise to structured populations for which the fixation probability significantly surpasses that of an unstructured population. This discovery provides important support to the notion that natural selection can be enhanced over random drift in naturally occurring population structures.

Barbosa, Valmir C.; Donangelo, Raul; Souza, Sergio R.

2009-08-01

26

The Aegean: A natural laboratory for tectonics  

NASA Astrophysics Data System (ADS)

The Aegean, a young and active tectonic region, is a natural laboratory for analyzing many tectonic processes that occur in backarc extensional regimes, and the correlation of these processes from landscape development to deeper mantle dynamics. Cenozoic development of the Aegean region was dominated by subduction beneath Europe and coeval upper plate extension modified by westward extrusion of Anatolia. Intraorogenic and backarc extension began during early Cenozoic time within the Balkans and NW Turkey during closure of the Vardar ocean. Extension was manifested by core complex formation and a change in volcanism caused by the evolution of the lithosphere and mantle wedge. Following a short period of local (?) shortening in ~ early Miocene time, regional extension began and continued to the present. Within the Hellenides, E-W extension and the subduction zone migrated westward as thick and thin crustal units were progressively accreted and were complexly rotated up to 40° CW. Within the eastern Balkans and NW Turkey, N-S extension migrated westward and southward, and in the Aegean the volcanic arc and subduction zone migrated southward. Turkish crustal elements rotated complexly CCW, which in concert with the CW rotation in the Hellenides increased the curvature of the subduction zone and lengthened the orogen causing greater subsidence and extension in the Aegean Sea. Westward extrusion of Anatolia from the Arabian collision zone was enhanced by slab roll back in west moving Aegean crust more rapidly westward. Abundant evidence supports slab rollback at different velocities along the subduction zone. In Pliocene time, the North Anatolian fault crossed the Hellenides in a complex transtensional zone and a diffuse zone of left-lateral shear crossed western Turkey at present isolating a relatively undeforming Aegean plate. Major tectonic questions include: What is the geometry and fate of subducted slabs?, How much crust is accreted during subduction of thick and thin crust?, Does crustal accretion cause slab break off or only changes in slab dip?, How does the mantle wedge evolve and how is this expressed in the volcanism?, How much lateral mantle flow occurs during changes in slab geometry and rotation of crustal elements?, and What is the relation of mantle and crustal structure to first order landscape development?

Burchfiel, B. C.

2008-07-01

27

Comparing Patterns of Natural Selection across Species Using Selective Signatures  

SciTech Connect

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.

Shapiro, Jesse; Alm, Eric J.

2007-12-01

28

Comparing Patterns of Natural Selection Across Species Using Selective Signatures  

SciTech Connect

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.

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

2007-12-18

29

Comparing patterns of natural selection across species using selective signatures.  

PubMed

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. PMID:18266472

Shapiro, B Jesse; Alm, Eric J

2008-02-01

30

Microsatellites as targets of natural selection.  

PubMed

The ability to survey polymorphism on a genomic scale has enabled genome-wide scans for the targets of natural selection. Theory that connects patterns of genetic variation to evidence of natural selection most often assumes a diallelic locus and no recurrent mutation. Although these assumptions are suitable to selection that targets single nucleotide variants, fundamentally different types of mutation generate abundant polymorphism in genomes. Moreover, recent empirical results suggest that mutationally complex, multiallelic loci including microsatellites and copy number variants are sometimes targeted by natural selection. Given their abundance, the lack of inference methods tailored to the mutational peculiarities of these types of loci represents a notable gap in our ability to interrogate genomes for signatures of natural selection. Previous theoretical investigations of mutation-selection balance at multiallelic loci include assumptions that limit their application to inference from empirical data. Focusing on microsatellites, we assess the dynamics and population-level consequences of selection targeting mutationally complex variants. We develop general models of a multiallelic fitness surface, a realistic model of microsatellite mutation, and an efficient simulation algorithm. Using these tools, we explore mutation-selection-drift equilibrium at microsatellites and investigate the mutational history and selective regime of the microsatellite that causes Friedreich's ataxia. We characterize microsatellite selective events by their duration and cost, note similarities to sweeps from standing point variation, and conclude that it is premature to label microsatellites as ubiquitous agents of efficient adaptive change. Together, our models and simulation algorithm provide a powerful framework for statistical inference, which can be used to test the neutrality of microsatellites and other multiallelic variants. PMID:23104080

Haasl, Ryan J; Payseur, Bret A

2012-10-27

31

Complete genetic linkage can subvert natural selection.  

PubMed

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

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

2007-04-03

32

Complete genetic linkage can subvert natural selection  

PubMed Central

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.

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

2007-01-01

33

Clippy Island: An Investigation into Natural Selection  

NSDL National Science Digital Library

In this activity, leaners will observe the process of natural selection on a population of birds called 'Springbeaks' over four seasons of breeding on an isolated environment called 'Clippy Island.' Learners will simulate feeding in a timed exercise to illustrate how a limited food supply and the introduction of genetic variants can lead to natural selection and adaptation. Learners will examine whether or not beak size affects the ability of a Springbeak to gather food and how this variation can affect successive generations in the population. This activity is designed for large groups of 30 learners but can work for smaller groups of at least 16 learners.

Furness, Lauren; Sutherland, Louise; Chalk, Hannah; Bulleid, Susan; Bamford, Amanda; Mcghie, Henry

2012-04-09

34

Nullomers: Really a Matter of Natural Selection?  

Microsoft Academic Search

BackgroundNullomers are short DNA sequences that are absent from the genomes of humans and other species. Assuming that nullomers are the signatures of natural selection against deleterious sequences in humans, the use of nullomers in drug target identification, pesticide development, environmental monitoring, and forensic applications has been envisioned.ResultsHere, we show that the hypermutability of CpG dinucleotides, rather than the natural

Claudia Acquisti; George Poste; David Curtiss; Sudhir Kumar; Steven Salzberg

2007-01-01

35

Natural selection. IV. The Price equation*  

PubMed Central

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.

Frank, Steven A.

2012-01-01

36

Natural and Sexual Selection on Many Loci  

PubMed Central

A method is developed that describes the effects on an arbitrary number of autosomal loci of selection on haploid and diploid stages, of nonrandom mating between haploid individuals, and of recombination. We provide exact recursions for the dynamics of allele frequencies and linkage disequilibria (nonrandom associations of alleles across loci). When selection is weak relative to recombination, our recursions provide simple approximations for the linkage disequilibria among arbitrary combinations of loci. We show how previous models of sex-independent natural selection on diploids, assortative mating between haploids, and sexual selection on haploids can be analyzed in this framework. Using our weak-selection approximations, we derive new results concerning the coevolution of male traits and female preferences under natural and sexual selection. In particular, we provide general expressions for the intensity of linkage-disequilibrium induced selection experienced by loci that contribute to female preferences for specific male traits. Our general results support the previous observation that these indirect selection forces are so weak that they are unlikely to dominate the evolution of preference-producing loci.

Barton, N. H.; Turelli, M.

1991-01-01

37

The Natural Selection of Bean Hunters  

NSDL National Science Digital Library

This lesson on natural selection shows students that population characteristics can change as a result of selective pressures operating over several generations. In the lesson, groups of students go hunting for beans in the lawn. Each group has a different tool (e.g. hand, spoon, fork, etc). There are three different colors of beans. The hunting goes for three rounds (generations), with extinctions and reproduction occurring between rounds.

38

A Selected Bibliography on Microbiological Laboratory Design.  

ERIC Educational Resources Information Center

|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,…

Laboratory Design Notes, 1967

1967-01-01

39

THE LANGUAGE LABORATORY--SELECTED READINGS.  

ERIC Educational Resources Information Center

|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…

Modern Language Association of America, New York, NY.

40

Natural selection for resistance to mercury pollution  

Microsoft Academic Search

Summary The survival under conditions of mercury pollution of two natural populations of the marine gastropodCerithium rupestre, derived from mercury-polluted and mercury-free sites, was tested in the laboratory. The results indicate a significantly higher survival rate for animals derived from the mercury-polluted site, in each of six repetitive experiments. We conclude that mercury resistance in marine organisms is reinforced in

R. Baker; B. Lavie; E. Nevo

1985-01-01

41

Readings on Natural Beauty: A Selected Bibliography.  

National Technical Information Service (NTIS)

This bibliography was compiled in response to many requests for an up-to-date list of references on natural beauty and related subjects. It is a selected list and by no means complete. With only a few exceptions all of the references listed appeared after...

S. R. Ottersen

1967-01-01

42

Discussion note: Darwin, Whewell, and natural selection  

Microsoft Academic Search

Reporting on an article of mine (Hodge 1987) Michael Ruse (Biology and Philosophy, Booknotes, Vol. 6 No. 2) recently made some friendly, provocative remarks about three topics: (a) Darwin's possible debts to Whewell's methodological doctrines; (b) the question of the lawfulness of natural selection in relation to the semantic view of scientific theories; and (c) the present state of philosophy

M. J. S. Hodge

1991-01-01

43

Sir Wyville Thomson and Natural Selection  

Microsoft Academic Search

I AM sorry to find that Sir Wyville Thomson does not under stand the principle of natural selection, as explained by Mr.Wallace and. myself. If he had done so, he could not have written the following sentence in the Introduction to the Voyage of the Challenger:-``The character of the abyssal fauna refuses to give the least support to the theory

Charles Darwin

1880-01-01

44

Natural Selection and the Molecular Clock  

Microsoft Academic Search

This paper concludes that the statistical properties of protein evolution are com- patible with a particular model of evolution by natural selection. The argument begins with a statistical description of the molecular clock based on a Poisson process with a randomly varying tick rate. If the time scale of the change of the tick rate of the molecular clock is

John H. Gillespie

1986-01-01

45

Exploiting a Natural Auxotrophy for Genetic Selection  

PubMed Central

We exploited the natural histidine auxotrophy of Francisella species to develop hisD (encodes histidinol dehydrogenase) as a positive selection marker. A shuttle plasmid (pBR103) carrying Escherichia coli hisD and designed for cloning of PCR fragments replicated in both attenuated and highly virulent Francisella strains. During this work, we formulated a simplified defined growth medium for Francisella novicida.

Ramage, Elizabeth; Gallagher, Larry

2012-01-01

46

Laboratory Estimates of Heritabilities and Genetic Correlations in Nature  

PubMed Central

A lower bound on heritability in a natural environment can be determined from the regression of offspring raised in the laboratory on parents raised in nature. An estimate of additive genetic variance in the laboratory is also required. The estimated lower bounds on heritabilities can sometimes be used to demonstrate a significant genetic correlation between two traits in nature, if their genetic and phenotypic correlations in nature have the same sign, and if sample sizes are large, and heritabilities and phenotypic and genetic correlations are high.

Riska, B.; Prout, T.; Turelli, M.

1989-01-01

47

Natural Resource Management Plan for Brookhaven National Laboratory.  

National Technical Information Service (NTIS)

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. The plan establishes the basis for managing the varied n...

2003-01-01

48

The Mechanisms of Evolution: Natural Selection and Natural Conventions  

Microsoft Academic Search

The mechanisms of evolution have been one of the most controversial issues in Biology and the great debate about them has\\u000a culminated, in the 1930s and 1940s, in the Modern Synthesis, the theoretical framework where natural selection is regarded\\u000a as the sole mechanism of evolutionary change. Here it is shown that a new approach to these great problems is provided

Marcello Barbieri

49

Respirator selection for clandestine methamphetamine laboratory investigation.  

PubMed

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

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

2012-01-01

50

Darwinian natural selection: its enduring explanatory power  

PubMed Central

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.

2012-01-01

51

Darwinian natural selection: its enduring explanatory power.  

PubMed

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

Dimijian, Gregory G

2012-04-01

52

The Structure of Evolution by Natural Selection  

Microsoft Academic Search

We attempt a conclusive resolution of the debate over whether the principle of natural selection (PNS), especially conceived\\u000a as the `principle' of the `survival of the fittest', is a tautology. This debate has been largely ignored for the past 15 years\\u000a but not, we think, because it has actually been settled. We begin by describing the tautology objection, and situating the

Richmond Campbell; Jason Scott Robert

2005-01-01

53

Symbiogenesis, natural selection, and the dynamic Earth.  

PubMed

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

Kutschera, U

2009-04-28

54

Natural Resource Management Plan for Brookhaven National Laboratory  

Microsoft Academic Search

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

2011-01-01

55

Laboratory production of early hatching Artemia sp. cysts by selection  

Microsoft Academic Search

The goal of this study was to test whether it is possible to produce early hatching cysts of Artemia franciscana from San Francisco Bay (SFB) by truncation selection. The starting material was an SFB cyst sample, harvested in nature. After selection of early hatching nauplii had taken place, these selected individuals were cultured to maturity, and the hatching rate of

Elizabeta Briski; Gilbert Van Stappen; Peter Bossier; Patrick Sorgeloos

2008-01-01

56

[Nature's healing power--natural selection in protein turnover].  

PubMed

For millennia, medical practitioners, healthy people and the sick have known that there is an inner force that keeps us sound and also cures us. However, neither medicine nor natural sciences have been able to define this curative power. It can not be captured by experiments or assigned with dimensions or numbers. The answer can be found in the quintessential process of all living systems, the interaction of genes and proteins in every single cell. Genes encode proteins; proteins are the ubiquitous instruments of life. Protein molecules undergo rapid turnover: their median lifetime is about 2 days, and in every second so many proteins are synthesized in each of us that their number equals the number of seconds that have passed since the big bang 15 billion years ago. The biochemical dogma that says that after their synthesis proteins are degraded at random - blindly, quasi - is wrong. The experimental results have not been interpreted correctly. In the first instance, proteins are stable and functional, since they have to fulfill numerous tasks. Only aged, severely damaged, non-functioning proteins are discarded. Protein turnover is subject to selection, not to chance. By selecting fresh, functional proteins, the quality of cellular proteins is kept at a high level. The principle of selection in protein turnover is the crucial component in the scientific groundwork of naturopathy therapeutics. With natural influencies and measures (e.g. food processing, intermediate metabolism, exercise, light, warmth, coldness) the steady process of regeneration is accelerated - in contrast to medical therapy, which restricts and blocks protein activities. Natural healing power and self-organization energy are basic phenomena of a therapeutically used physiology. Naturopathy is natural science. PMID:14605483

Pirlet, K

2003-10-01

57

Learning natural selection from the site frequency spectrum.  

PubMed

Genetic adaptation to external stimuli occurs through the combined action of mutation and selection. A central problem in genetics is to identify loci responsive to specific selective constraints. Many tests have been proposed to identify the genomic signatures of natural selection by quantifying the skew in the site frequency spectrum (SFS) under selection relative to neutrality. We build upon recent work that connects many of these tests under a common framework, by describing how selective sweeps affect the scaled SFS. We show that the specific skew depends on many attributes of the sweep, including the selection coefficient and the time under selection. Using supervised learning on extensive simulated data, we characterize the features of the scaled SFS that best separate different types of selective sweeps from neutrality. We develop a test, SFselect, that consistently outperforms many existing tests over a wide range of selective sweeps. We apply SFselect to polymorphism data from a laboratory evolution experiment of Drosophila melanogaster adapted to hypoxia and identify loci that strengthen the role of the Notch pathway in hypoxia tolerance, but were missed by previous approaches. We further apply our test to human data and identify regions that are in agreement with earlier studies, as well as many novel regions. PMID:23770700

Ronen, Roy; Udpa, Nitin; Halperin, Eran; Bafna, Vineet

2013-06-14

58

LABORATORY SELECTION FOR BEET ARMYWORM (LEPIDOPTERA: NOCTUIDAE) RESISTANCE TO METHOXYFENOZIDE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Beet armyworms, Spodoptera exigua (Hubner), were artificially selected in the laboratory for resistance to the insect growth regular, methoxyfenozide. A field collected beet armyworm colony was separated into three cohorts that were independently selected with three concentrations (0.033 ppm, 0.064...

59

COMPUTATIONAL SCIENCE AT BROOKHAVEN NATIONAL LABORATORY: THREE SELECTED TOPICS.  

SciTech Connect

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.

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

2003-09-15

60

The strength of postcopulatory sexual selection within natural populations of field crickets  

Microsoft Academic Search

Sperm competition and cryptic female choice are likely to exert strong postcopulatory sexual selection and may amplify or ameliorate selection acting via male mating success. However, relatively few studies have estimated the potential strength of postcopulatory sexual selection acting within natural populations. Field crickets in the genus Teleogryllus have been used extensively as laboratory models to study the evolution of

Leigh W. Simmons; Maxine Beveridge

2010-01-01

61

Natural Selection: Monarch/Viceroy Case  

NSDL National Science Digital Library

This lesson will provide students with an opportunity to use their understanding of the natural selection model to explain phenomena. For this case they will be asked to account for the bright coloration of and the similarity between monarch and viceroy butterflies. In order to do this, they will work in groups to develop a Darwinian explanation using the narrative structure developed in previous material. Each group will receive a folder with information on species that exhibit a particularly interesting biological phenomenon. The materials in the folders will include narrative descriptions of the organisms and their natural history, pictures, and data tables or graphs to help understand the biology of the characteristics under study. Groups will then present their ideas to their peers and discuss the different explanations in a round table forum. The site also includes detailed instructional notes for the teachers and all of the student handouts required for the folders.

2007-05-19

62

Natural Selection: Monarch/Viceroy Case  

NSDL National Science Digital Library

This lesson will provide students with an opportunity to use their understanding of the natural selection model to explain phenomena. For this case they will be asked to account for the bright coloration of and the similarity between monarch and viceroy butterflies. In order to do this, they will work in groups to develop a Darwinian explanation using the narrative structure developed in previous material. Each group will receive a folder with information on species that exhibit a particularly interesting biological phenomenon. The materials in the folders will include narrative descriptions of the organisms and their natural history, pictures, and data tables or graphs to help understand the biology of the characteristics under study. Groups will then present their ideas to their peers and discuss the different explanations in a round table forum. The site also includes detailed instructional notes for the teachers and all of the student handouts required for the folders.

63

Natural Selection Drives Drosophila Immune System Evolution  

Microsoft Academic Search

ABSTRACT Evidence from,disparate sources suggests that natural selection may,often play a role in the evolution of host immune system proteins. However, there have been few attempts to make general population genetic inferences on the basis of analysis of several immune-system-related genes,from,a single species. Here we present DNA polymorphism,and divergence,data from 34 genes thought,to function,in the innate immune,system,of Drosophila simulans,and,compare,these data

Todd A. Schlenke; David J. Begun

64

Natural selection and cultural rates of change  

PubMed Central

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.

Rogers, Deborah S.; Ehrlich, Paul R.

2008-01-01

65

Darwin's finches: population variation and natural selection.  

PubMed Central

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.

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

1976-01-01

66

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

ERIC Educational Resources Information Center

|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…

Eason, Perri K.; Sherman, Peter T.

2003-01-01

67

Sexual and Natural Selection Both Influence Male Genital Evolution  

PubMed Central

Rapid and divergent evolution of male genital morphology is a conspicuous and general pattern across internally fertilizing animals. Rapid genital evolution is thought to be the result of sexual selection, and the role of natural selection in genital evolution remains controversial. However, natural and sexual selection are believed to act antagonistically on male genital form. We conducted an experimental evolution study to investigate the combined effects of natural and sexual selection on the genital-arch lobes of male Drosophila simulans. Replicate populations were forced to evolve under lifetime monogamy (relaxed sexual selection) or lifetime polyandry (elevated sexual selection) and two temperature regimes, 25°C (relaxed natural selection) or 27°C (elevated natural selection) in a fully factorial design. We found that natural and sexual selection plus their interaction caused genital evolution. Natural selection caused some aspects of genital form to evolve away from their sexually selected shape, whereas natural and sexual selection operated in the same direction for other shape components. Additionally, sexual and natural selection tended to favour larger genitals. Thus we find that the underlying selection driving genital evolution is complex, does not only involve sexual selection, and that natural selection and sexual selection do not always act antagonistically.

Hodgson, Dave J.; Wedell, Nina; Sharma, Manmohan D.; Hunt, John; Hosken, David J.

2013-01-01

68

Laboratory evidence for microbially mediated silicate mineral dissolution in nature  

Microsoft Academic Search

Bacteria may potentially enhance or inhibit silicate mineral dissolution in nature by a variety of mechanisms. In the laboratory, some microbial metabolites enhanced dissolution rates by a factor of ten above the expected proton-promoted rate by an additional ligand-promoted mechanism focussed principally at Al sites at the mineral surface. In investigations with bacteria, it was found that organic acids are

William J. Ullman; David L. Kirchman; Susan A. Welch; Philippe Vandevivere

1996-01-01

69

When environmental variation short-circuits natural selection  

Microsoft Academic Search

The development of a coherent framework for measuring natural selection was one of the major advances in evolutionary biology in the 1970s and 1980s. However, for evolution to occur, natural selection must act on underlying genetic variation, whereas most measurements of natural selection are limited to phenotypes. Two new papers now show that environmentally induced covariances between phenotypes and fitness

Loeske E. B. Kruuk; Juha Merilä; Ben C. Sheldon

2003-01-01

70

Detecting the signature of natural selection with microsatellites  

Microsoft Academic Search

Natural selection is one of the major factors in the evolution of all organisms. Detecting the signature of natural selection has been a central theme in evolutionary genetics. With the availability of microsatellite data, it is of interest to study how natural selection can be detected with microsatellites. ^ The overall aim of this research is to detect signatures of

Hongyan Xu

2003-01-01

71

Reinforcement in chorus frogs: lifetime fitness estimates including intrinsic natural selection and sexual selection against hybrids.  

PubMed

Maladaptive hybridization is hypothesized to be an important force driving the evolution of reproductive isolation between closely related species. Because the magnitude and direction of selection can vary across a life cycle, an accurate understanding of the ubiquity of reinforcement requires fitness to be estimated across the life cycle, but the literature is surprisingly depauperate of such studies. We present fitness estimates of laboratory-raised hybrids between the chorus frogs Pseudacris feriarum and Pseudacris nigrita--two species that have undergone reproductive character displacement where they come into secondary contact. By studying viability, mating success, and fertility across the life cycle, we find strong support for reinforcement as the force driving displacement in this system. Specifically, we find hybrid fitness is reduced by 44%. This reduction results from both sexual selection against hybrid males and natural selection on male fertility, but not viability selection. Sexual selection against hybrid males is four times stronger than natural selection. Hybrid female fitness is not reduced, however, suggesting that Haldane's rule may be operating in this system if males are heterogametic. We also found higher variation in hybrid male fertilization success relative to P. feriarum males, suggesting that the hybrid incompatibility genes are polymorphic within one or both of the parent species. PMID:20100218

Lemmon, Emily Moriarty; Lemmon, Alan R

2010-01-20

72

NATURAL RESOURCE MANAGEMENT PLAN FOR BROOKHAVEN NATIONAL LABORATORY.  

SciTech Connect

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.

GREEN,T.ET AL.

2003-12-31

73

Natural selection and the elusiveness of happiness.  

PubMed Central

The quest for happiness has expanded from a focus on relieving suffering to also considering how to promote happiness. However, both approaches have yet to be conducted in an evolutionary framework based on the situations that shaped the capacities for happiness and sadness. Because of this, the emphasis has almost all been on the disadvantages of negative states and the benefits of positive states, to the nearly total neglect of 'diagonal psychology', which also considers the dangers of unwarranted positive states and the benefits of negative emotions in certain situations. The situations that arise in goal pursuit contain adaptive challenges that have shaped domain-general positive and negative emotions that were partially differentiated by natural selection to cope with the more specific situations that arise in the pursuit of different kinds of goals. In cultures where large social groups give rise to specialized and competitive social roles, depression may be common because regulation systems are pushed far beyond the bounds for which they were designed. Research on the evolutionary origins of the capacities for positive and negative emotions is urgently needed to provide a foundation for sensible decisions about the use of new mood-manipulating technologies.

Nesse, Randolph M

2004-01-01

74

Natural selection and the elusiveness of happiness.  

PubMed

The quest for happiness has expanded from a focus on relieving suffering to also considering how to promote happiness. However, both approaches have yet to be conducted in an evolutionary framework based on the situations that shaped the capacities for happiness and sadness. Because of this, the emphasis has almost all been on the disadvantages of negative states and the benefits of positive states, to the nearly total neglect of 'diagonal psychology', which also considers the dangers of unwarranted positive states and the benefits of negative emotions in certain situations. The situations that arise in goal pursuit contain adaptive challenges that have shaped domain-general positive and negative emotions that were partially differentiated by natural selection to cope with the more specific situations that arise in the pursuit of different kinds of goals. In cultures where large social groups give rise to specialized and competitive social roles, depression may be common because regulation systems are pushed far beyond the bounds for which they were designed. Research on the evolutionary origins of the capacities for positive and negative emotions is urgently needed to provide a foundation for sensible decisions about the use of new mood-manipulating technologies. PMID:15347525

Nesse, Randolph M

2004-09-29

75

Selective particle ingestion by oyster larvae ( Crassostrea virginica ) feeding on natural seston and cultured algae  

Microsoft Academic Search

I investigated selective particle ingestion by oyster larvae (Crassostrea virginica) feeding on natural seston from Chesapeake Bay and laboratory-cultured algae of different sizes or chemical content. In 15 of 16 experiments with complex natural suspensions as food, small(150 µm) larvae selected most strongly for small (2 to 4 µm) food particles, but in the presence of a large (>10 µm)-cell

B. S. Baldwin

1995-01-01

76

Microbial Resistance to Triclosan: A Case Study in Natural Selection  

ERIC Educational Resources Information Center

|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…

Serafini, Amanda; Matthews, Dorothy M.

2009-01-01

77

Geographic distribution of human skin colour: A selective compromise between natural selection and sexual selection?  

Microsoft Academic Search

Modern humans have been shaped by the cumulative action of natural selection, non-adaptive random change, and sexual selection.\\u000a The last of these is not universal and has prevailed in one of two circumstances: (1) A surplus of females due to high male\\u000a mortality, combined with ecological constraints on female participation in food procurement which discourage males from taking\\u000a second wives;

P. Frost

1994-01-01

78

Natural Resource Management Plan for Brookhaven National Laboratory  

SciTech Connect

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).

green, T.

2011-08-15

79

Understanding Natural Selection: Essential Concepts and Common Misconceptions  

Microsoft Academic Search

Natural selection is one of the central mechanisms of evolutionary change and is the process responsible for the evolution\\u000a of adaptive features. Without a working knowledge of natural selection, it is impossible to understand how or why living things\\u000a have come to exhibit their diversity and complexity. An understanding of natural selection also is becoming increasingly relevant\\u000a in practical contexts,

T. Ryan Gregory

2009-01-01

80

Sexual selection, natural selection and the evolution of dimorphic coloration and ornamentation in agamid lizards  

Microsoft Academic Search

Both sexual selection and natural selection can influence the form of dimorphism in secondary sexual traits. Here, we used a comparative approach to examine the relative roles of sexual selection and natural selection in the evolution of sexually dimorphic coloration (dichromatism) and ornamentation in agamid lizards. Sex- ual dimorphism in head and body size were used as indirect indicators of

Devi M. Stuart-Fox; Terry J. Ord

2004-01-01

81

The Nature of Laboratory Learning Experiences in Secondary Science Online  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

82

Laboratory selection for increased longevity in Drosophila melanogaster reduces field performance.  

PubMed

Drosophila melanogaster is frequently used in ageing studies to elucidate which mechanisms determine the onset and progress of senescence. Lines selected for increased longevity have often been shown to perform as well as or superior to control lines in life history, stress resistance and behavioural traits when tested in the laboratory. Functional senescence in longevity selected lines has also been shown to occur at a slower rate. However, it is known that performance in a controlled laboratory setting is not necessarily representative of performance in nature. In this study the effect of ageing, environmental temperature and longevity selection on performance in the field was tested. Flies from longevity selected and control lines of different ages (2, 5, 10 and 15days) were released in an environment free of natural food sources. Control flies were tested at low, intermediate and high temperatures, while longevity selected flies were tested at the intermediate temperature only. The ability of flies to locate and reach a food source was tested. Flies of intermediate age were generally better at locating resources than both younger and older flies, where hot and cold environments accelerate the senescent decline in performance. Control lines were better able to locate a resource compared to longevity selected lines of the same age, suggesting that longevity comes at a cost in early life field fitness, supporting the antagonistic pleiotropy theory of ageing. PMID:23916841

Wit, Janneke; Kristensen, Torsten Nygaard; Sarup, Pernille; Frydenberg, Jane; Loeschcke, Volker

2013-08-02

83

ENHANCEMENTS TO NATURAL ATTENUATION: SELECTED CASE STUDIES  

SciTech Connect

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).

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

84

Enhancements to Natural Attenuation: Selected Case Studies.  

National Technical Information Service (NTIS)

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 enh...

C. H. Benson E. Hood E. S. Beevar T. O. Early W. H. Albright

2007-01-01

85

Laboratory selection for an accelerated mosquito sexual development rate  

PubMed Central

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.

2011-01-01

86

Getting to Darwin: Obstacles to Accepting Evolution by Natural Selection  

ERIC Educational Resources Information Center

|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…

Thagard, Paul; Findlay, Scott

2010-01-01

87

FREQUENCY DEPENDENT NATURAL SELECTION DURING CHARACTER DISPLACEMENT IN STICKLEBACKS  

Microsoft Academic Search

We know little about how natural selection on a species is altered when a closely related species consuming similar resources appears in its environment. In a pond experiment with threespine sticklebacks I tested the prediction that divergent natural selection between competitors is frequency-dependent, changing with the distribution of phe- notypes in the environment. Differential growth and survival of phenotypes in

Dolph Schluter

2003-01-01

88

Historical Intensity of Natural Selection for Resistance to Tuberculosis  

Microsoft Academic Search

Infections have long been thought to exert natural selection on humans. Infectious disease resistance is frequently invoked as a mechanism shaping human genetic diversity, but such hypotheses have rarely been quantitatively evaluated with direct measures of disease-related mortality. Enhancement of genetically deter- mined resistance to tuberculosis by natural selection has been proposed as a factor explaining the decline of tuberculosis

Marc Lipsitch; Alexandra O. Sousa

2002-01-01

89

Development and evaluation of the conceptual inventory of natural selection  

Microsoft Academic Search

Natural selection as a mechanism of evolution is a central concept in biology; yet, most nonbiology-majors do not thoroughly understand the theory even after instruction. Many alternative conceptions on this topic have been identified, indicating that the job of the instructor is a difficult one. This article presents a new diagnostic test to assess students' understanding of natural selection. The

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

2002-01-01

90

SELECTIVE NOx RECIRCULATION FOR STATIONARY LEAN-BURN NATURAL GAS ENGINES  

Microsoft Academic Search

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

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

2005-01-01

91

Selection Is Entailed by Self-Organization and Natural Selection Is a Special Case  

Microsoft Academic Search

In their book, Darwinism Evolving: Systems Dynamics and the Genealogy of Natural Selection, Depew and Weber (1995) argued for the need to address the relationship between self-organization and natural selection in evolutionary theory, and focused on seven visions for doing so. Recently, Batten et al. (2008) in a paper in this journal, entitled Visions of evolution: self-organization proposes what natural

Rod Swenson

2010-01-01

92

Evaluations of selected text references to natural selection by high school biology teachers  

Microsoft Academic Search

For decades researchers have warned of problems associated with using anthropomorphic and teleological formulations to explain natural selection. This study investigates how high school biology teachers evaluate potentially useful text containing canonical, anthropomorphic and teleological formulations that purport to explain biological adaptation through natural selection. Twenty-four teachers were randomly selected from a stratified sample of all high school biology teachers

George L. Preston

1997-01-01

93

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

PubMed Central

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.

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

2011-01-01

94

Natural Selection: Introduction to the Nature of Explanatory Models  

NSDL National Science Digital Library

This information is designed to connect what students have learned about scientific arguments to the role and nature of explanatory models in science. They will be asked to read and discuss a brief handout about scientific models and their function in science. They will discover that models are ideas that scientists use to explain patterns they see in the natural world, a model is an idea that has predictive and explanatory power and is consistent with other ideas about how the world works, and that models can be compared based on data, the inferences made in the model, and the prior knowledge and beliefs upon which they are based. This site includes instructional notes for the teacher and student handouts.

95

Chemistry and biology of selected natural products  

Microsoft Academic Search

Natural products often offer excitement, stimulation, challenges and op- portunities for chemists, biologists and medical investigators. The study of their chemistry, biology and medicine provides, more often than not, rewards imagined and unimagined, and is still a major frontier in organic chemistry. In this article we summa- rize some of our recent work in this area and project ahead to

K. C. Nicolaou; E. A. Theodorakis; C. F. Claiborne

1996-01-01

96

Discrepancies Between Laboratory Shock Experiments on Minerals and Natural Events  

NASA Astrophysics Data System (ADS)

Numerous laboratory shock recovery experiments performed over the past 50 years have provided substantial data on the effects of shock waves on rocks and minerals. However, it has become increasingly clear that the pressure "calibrations" based on shock effects observed in these experiments are inconsistent with interpretations based on static high-pressure data. A fundamental question is whether shock pressures are somehow different from static high pressures. Fifty years ago, many journal reviewers doubted that phase transformations could take place on a sub-microsecond time scale. Shock wave workers responded by invoking "special" properties of shock compression. However, all available evidence is consistent with the hypothesis that phase transitions under shock pressure are no different from phase transitions under static high pressures. The discrepancies noted above result from the fact that the parameter space, especially shock pressure duration, accessible to shock recovery experiments is so small by comparison with natural events. Furthermore virtually all shock recovery experiments on rocks and minerals have used high impedance sample containers, with the result that the samples have been subjected to thermodynamic loading paths substantially from a natural event. Consider the case of a chondritic meteorite made up of minerals having a wide range of shock properties. In a natural shock event the transient (nano-second scale) shock pressure at the shock front can vary by as much as an order of magnitude from grain to grain or even within a single grain. There are corresponding local differences in shock temperature. Assuming a mineral grain size of about a mm, the pressure inhomogeneities will equilibrate in less than a microsecond, wheras the temperature inhomogenities will require seconds to equilibrate. Recent studies of high-pressure phases in meteorites have provided evidence for pressure durations in the range of seconds, long enough for high pressure phases to crystallize from a melt or transform via solid-solid mechanisms. In contrast, the sample shock loaded in a laboratory experiment in a high impedance container reaches peak pressure via a series of shock reflections. As a result, shock and post-shock temperatures correspond to a sample naturally shocked to a substantially lower ( 20-60 %, dependent on sample mineralogy and porosity) equilibrium pressure. The effect of differences in the shock properties of the individual minerals is also greatly reduced. Shock pressure durations in the range of seconds have been inferred from studies of naturally shocked meteorites, whereas the effective duration of a shock recovery experiment is about a microsecond. Shock effects that involve reconstructive phase transformations, and therefore nucleation and growth, are highly dependent on both temperature and duration. Finally, the laboratory experiments are conducted on a small scale; samples cool from their equilibrium post-shock temperature in seconds. In a large natural event, the cooling time can be thousands of years.

de Carli, P. S.; Xie, Z.; Sharp, T. G.

2009-12-01

97

Natural Selection in Protected and Unprotected Populations  

NSDL National Science Digital Library

In this simulation, learners model two elephant seal populations and how they change over time. Learners start with cards representing a variety of seals. Each generation, some seals survive to reproduce, passing on their traits to new seals. The amount of variation in the protected seal population stays high, while the unprotected population becomes more limited by selective pressure. In the related activity, learners can graph their data about the seal populations to show how they change over time.

Huffard, Crissy

2011-01-01

98

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

PubMed Central

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.

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

2013-01-01

99

Canine evolution in sabretoothed carnivores: natural selection or sexual selection?  

PubMed

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

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

2013-08-08

100

Pollinator-mediated natural selection in Penstemon digitalis  

PubMed Central

Measuring the agents of natural selection is important because it allows us to understand not only which traits are expected to evolve but also why they will evolve. Natural selection by pollinators on floral traits is often assumed because in outcrossing animal-pollinated plants flowers are generally thought to function as advertisements of rewards directed at pollinators. We tested the role of bee pollinators in selection on Penstemon digitalis and found that pollinators were driving selection for larger and more flowers. However, what makes our publication unique is the additional information we gained from reviewing the few other studies that also directly tested whether pollinators were agents of selection on floral traits. As we would expect if pollinators are important agents of selection, selection on floral traits was significantly stronger when pollinators were present than when their choices were experimentally removed. Taken together, these results suggest that pollinators can be important drivers of selection in contemporary populations.

Kessler, Andre

2010-01-01

101

Laboratory observation of naturally occurring dust-density waves  

NASA Astrophysics Data System (ADS)

Dust-density waves are electrostatic compressional waves that propagate in dusty plasma. Compared to the more familiar ion-acoustic waves, in dust-density waves, inertia is provided by dust particles (instead of ions) while pressure is provided by the ions as well as electrons (not just electrons). In a laboratory experiment, we observed dust density waves in a 3D void-free dusty plasma. The waves occur naturally due to an ion-flow instability. Dust particles (4.8 microns) are levitated within the volume of a glass box that rests atop an electrode in a radio-frequency glow discharge plasma. Horizontal confinement of dust particles is provided by the plasma's natural electric field that is enhanced by the walls of the glass box, while vertical confinement is due to the electrode's sheath. We observed dust-density waves with planar wave fronts propagating in alignment with flowing ions. By directly imaging the dust particles with a 500 frame-per-second camera, we monitor the dust density modulations in both space and time. A typical wave propagates at 40 mm/s with a frequency of 24 Hz. In this work, we characterize these waves and their growth as they propagate.

Flanagan, Tim; Goree, John

2010-11-01

102

Frequency selective bolometer development at Argonne National Laboratory  

NASA Astrophysics Data System (ADS)

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.

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

2008-08-01

103

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

ERIC Educational Resources Information Center

|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.|

Price, Rebecca M.

2013-01-01

104

Thermal Conductivity of Soft Vulcanized Natural Rubber: Selected Values.  

National Technical Information Service (NTIS)

The published literature on the thermal conductivity of natural rubber was assembled and the results critically evaluated. Best values of thermal conductivity as a function of temperature were selected. These are presented in both graphical and tabular fo...

L. C. K. Carwile H. J. Hoge

1966-01-01

105

Natural Selection: A Case for the Counterfactual Approach  

Microsoft Academic Search

This paper investigates the conception of causation required in order to make sense of natural selection as a causal explanation\\u000a of changes in traits or allele frequencies. It claims that under a counterfactual account of causation, natural selection\\u000a is constituted by the causal relevance of traits and alleles to the variation in traits and alleles frequencies. The “statisticalist”\\u000a view of

Philippe Huneman

106

Natural selection in brain evolution of early hominids  

Microsoft Academic Search

Directional effect of natural selection on the arrangement of brain of anthropoids and man is reviewed. It is demonstrated\\u000a that the evolution of the human nervous system is an integrated result of several multidirectional processes. At the early\\u000a stages of the evolution of primates, the general biological principles of survival of the fittest, i.e., natural selection\\u000a of the most adapted

S. V. Saveliev

2010-01-01

107

Getting to Darwin: Obstacles to Accepting Evolution by Natural Selection  

Microsoft Academic Search

Darwin’s theory of evolution by natural selection is central to modern biology, but is resisted by many people. This paper\\u000a discusses the major psychological obstacles to accepting Darwin’s theory. Cognitive obstacles to adopting evolution by natural\\u000a selection include conceptual difficulties, methodological issues, and coherence problems that derive from the intuitiveness\\u000a of alternative theories. The main emotional obstacles to accepting evolution

Paul Thagard; Scott Findlay

2010-01-01

108

Naturalization Test Redesign Project: Civics Item Selection Analysis  

ERIC Educational Resources Information Center

"Naturalization Test Redesign Project: Civics Item Selection Analysis" provides an overview of the development of content items for the U.S. history and government (civics) portion of the redesigned naturalization test. This document also reviews the process used to gather and analyze data from multiple studies to determine which civics test items…

US Citizenship and Immigration Services, 2008

2008-01-01

109

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

USGS Publications Warehouse

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)

Swayze, L. J.

1981-01-01

110

Selective feeding of four zooplankton species on natural lake phytoplankton  

Microsoft Academic Search

Grazing experiments evaluated by microscopical counting were conducted with different size classes of Daphnia hyalina, D. galeata, Eudiaptomus gracilis, and Cyclops sp., all from Lake Constance, using natural lake phytoplankton as food. Species-specific grazing selectivity coefficients were calculated for the dominant phytoplankton species from weekly experiments. Specific selectivities were found to be largely invariant through the growing season. All zooplankters

Karin Knisely; Walter Geller

1986-01-01

111

Methodological Problems in Evolutionary Biology. X. Natural Selection Without Selective Agents  

Microsoft Academic Search

On a common view of evolution, natural selection is the major force that produces evolutionary change. Selection is thought to operate on different types (genotypes or phenotypes) in populations so as to generate differential reproductive survival of these types. This should engender changes in population composition. The conception of selection as a \\

Wim J. van der Steen

1998-01-01

112

Natural selection and the genetics of adaptation in threespine stickleback.  

PubMed

Growing knowledge of the molecular basis of adaptation in wild populations is expanding the study of natural selection. We summarize ongoing efforts to infer three aspects of natural selection--mechanism, form and history--from the genetics of adaptive evolution in threespine stickleback that colonized freshwater after the last ice age. We tested a mechanism of selection for reduced bony armour in freshwater by tracking genotype and allele frequency changes at an underlying major locus (Ectodysplasin) in transplanted stickleback populations. We inferred disruptive selection on genotypes at the same locus in a population polymorphic for bony armour. Finally, we compared the distribution of phenotypic effect sizes of genes underlying changes in body shape with that predicted by models of adaptive peak shifts following colonization of freshwater. Studies of the effects of selection on genes complement efforts to identify the molecular basis of adaptive differences, and improve our understanding of phenotypic evolution. PMID:20643737

Schluter, Dolph; Marchinko, Kerry B; Barrett, R D H; Rogers, Sean M

2010-08-27

113

Natural Selection on Functional Modules, a Genome-Wide Analysis  

PubMed Central

Classically, the functional consequences of natural selection over genomes have been analyzed as the compound effects of individual genes. The current paradigm for large-scale analysis of adaptation is based on the observed significant deviations of rates of individual genes from neutral evolutionary expectation. This approach, which assumed independence among genes, has not been able to identify biological functions significantly enriched in positively selected genes in individual species. Alternatively, pooling related species has enhanced the search for signatures of selection. However, grouping signatures does not allow testing for adaptive differences between species. Here we introduce the Gene-Set Selection Analysis (GSSA), a new genome-wide approach to test for evidences of natural selection on functional modules. GSSA is able to detect lineage specific evolutionary rate changes in a notable number of functional modules. For example, in nine mammal and Drosophilae genomes GSSA identifies hundreds of functional modules with significant associations to high and low rates of evolution. Many of the detected functional modules with high evolutionary rates have been previously identified as biological functions under positive selection. Notably, GSSA identifies conserved functional modules with many positively selected genes, which questions whether they are exclusively selected for fitting genomes to environmental changes. Our results agree with previous studies suggesting that adaptation requires positive selection, but not every mutation under positive selection contributes to the adaptive dynamical process of the evolution of species.

Serra, Francois; Arbiza, Leonardo; Dopazo, Joaquin; Dopazo, Hernan

2011-01-01

114

Natural and sexual selection in a monogamous historical human population.  

PubMed

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

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

2012-04-30

115

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

SciTech Connect

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.

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

1996-04-01

116

Getting to Darwin: Obstacles to Accepting Evolution by Natural Selection  

NASA Astrophysics Data System (ADS)

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.

Thagard, Paul; Findlay, Scott

2010-06-01

117

High temperature superconductivity research in selected laboratories in West Germany  

NASA Astrophysics Data System (ADS)

The superconductivity work at eight West German laboratories is reviewed. The laboratories are (or located at): the University of Giessen; the Technical University at Darmstadt; Hoechst AG; Siemens AG; KFA Julich; KFK, Karlsruhe; the Walter Meissner Institute, Garching; and the Max Planck Institute, Stuttgart.

Liebenberg, Donald H.; Clark, Alan

1988-07-01

118

The Chips Are Down: A Natural Selection Simulation  

NSDL National Science Digital Library

This lesson demonstrates how natural selection operates, using different colored paper chips to represent prey and a piece of fabric as a background (the environment). The predator (student) will hunt (select chips) to show that the best adapted, by color, are NOT chosen, and others which are poorly adapted (by standing out) ARE chosen (removed). Thus, the best adapted survive and reproduce to pass on their traits. Survivors then reproduce and subsequent generations are preyed upon.

Digiovanni, Nick

119

Aspergillus flavus dose–response curves to selected natural and synthetic antimicrobials  

Microsoft Academic Search

The effects of selected concentrations of antimicrobials from natural (vanillin, thymol, eugenol, carvacrol or citral) or synthetic (potassium sorbate or sodium benzoate) origin on Aspergillus flavus lag time inoculated in laboratory media formulated at water activity (aw) 0.99 and pH 4.5 or 3.5, were evaluated. Time to detect a colony with a diameter >0.5 mm was determined. Mold response was

Aurelio López-Malo; Stella M Alzamora; Enrique Palou

2002-01-01

120

Selecting Landing Sites for the 2009 Mars Science Laboratory  

NASA Astrophysics Data System (ADS)

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/.

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

2006-12-01

121

Clinical Practice as Natural Laboratory for Psychotherapy Research  

Microsoft Academic Search

Both researchers and practitioners need to know more about how laboratory treatment protocols translate to real- world practice settings and how clinical innovations can be systematically tested and communicated to a skeptical sci- entific community. The single-case time-series study is well suited to opening a productive discourse between practice and laboratory. The appeal of case-based time-series stud- ies, with multiple

Jeffrey J. Borckardt; Michael R. Nash; Martin D. Murphy; Darlene Shaw; Patrick O'Neil

122

Selected Topics in Laboratory Animal Medicine. Volume VIII. Parasitology.  

National Technical Information Service (NTIS)

The major parasites of laboratory animals are divided into eight groups: Insects, arachnids, pentastomes, acanthocephalids, unicellular parasites (protozoan), cestodes, trematodes, and nematodes. A broad review is presented of the major characteristics th...

G. W. Irving

1972-01-01

123

Natural selection on floral volatile production in Penstemon digitalis  

PubMed Central

Natural selection is thought to have shaped the evolution of floral scent; however, unlike other floral characters, we have a rudimentary knowledge of how phenotypic selection acts on scent. We found that floral scent was under stronger selection than corolla traits such as flower size and flower color in weakly scented Penstemon digitalis. Our results suggest that to understand evolution in floral phenotypes, including scent in floral selection, studies are crucial. For P. digitalis, linalool was the direct target of selection in the scent bouquet. Therefore, we determined the enantiomeric configuration of linalool because interacting insects may perceive the enantiomers differentially. We found that P. digitalis produces only (S)-(+)-linalool and, more interestingly, it is also taken up into the nectar. Because the nectar is scented and flavored with (S)-(+)-linalool, it may be an important cue for pollinators visiting P. digitalis flowers.

Parachnowitsch, Amy L.; Burdon, Rosalie C. F.; Raguso, Robert A.; Kessler, Andre

2013-01-01

124

Natural Selection and the Reinforcement of Mate Recognition  

Microsoft Academic Search

Natural selection on mate recognition may often contribute to speciation, resulting in reproductive character displacement. Field populations of Drosophila serrata display reproductive character displacement in cuticular hydrocarbons when sympatric with Drosophila birchii. We exposed field sympatric and allopatric populations of D. serrata to experimental sympatry with D. birchii for nine generations. Cuticular hydrocarbons of field allopatric D. serrata populations evolved

Megan Higgie; Steve Chenoweth; Mark W. Blows

2000-01-01

125

Role of evolution by natural selection in population dynamics  

Microsoft Academic Search

Using a Monte Carlo approach we study the role of inheritance and natural selection in the dynamics of populations. We show that a population subject to inheritance has a much better chance of survival in a given condition than a population where new generations do not inherit genomes of their parents. The dependence of the survival chance on such factors

Michel Droz; Andrzej Pekalski

2004-01-01

126

Evolution without Natural Selection: Further Implications of the Daisyworld Parable  

Microsoft Academic Search

Daisyworld is a model dynamical system in which very simple mechanisms interact to produce complex behaviour. It was devised to show how regulation can arise without natural selection. Here we investigate the model in greater detail. We analyze the possible steady states and study the response of the system under dierent conditions, we consider the implications of the hysteresis which

Peter T. Saunders

1994-01-01

127

Natural Selection and Genetic Drift in Protein Polymorphism  

Microsoft Academic Search

THE Kimura theory1 that protein polymorphism is mainly due to random genetic drift acting on a number of neutral isoalleles has been recently discussed by many authors2-4. The electrophoretic study of populations of the same species having different geographical origin and showing great fluctuations in number offers possibilities for testing the relative importance of natural selection and genetic drift in

Luciano Bullini; MARIO COLUZZI

1972-01-01

128

Using Different Examples of Natural Selection When Teaching Biology.  

ERIC Educational Resources Information Center

|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)|

Perry, Robert T.

1993-01-01

129

The Divergence and Natural Selection of Autocatalytic Primordial Metabolic Systems  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

130

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

ERIC Educational Resources Information Center

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)

Walters, Douglas B.; And Others

1988-01-01

131

Networking of Icelandic Earth Infrastructures - Natural laboratories and Volcano Supersites  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

132

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

SciTech Connect

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.

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

1984-04-01

133

Viability selection prior to trait expression is an essential component of natural selection  

PubMed Central

Natural selection operates throughout the life cycle of an organism. Correlative studies typically fail to consider the effects of viability selection prior to trait expression. A 3-year field experiment on the wildflower Mimulus guttatus demonstrates that this unmeasured component of selection can be very strong. As in previous studies, we find that fecundity is positively related to flower size. However, survival to flowering is much lower in large-flowered genotypes than in small-flowered genotypes. Aggregating viability and fecundity, lifetime fitness through female function generally favoured smaller flowered genotypes. This result differs from the great majority of field studies, which suggest strong positive selection on flower size. It has important cautionary implications for studies of natural and sexual selection on adult characters generally, in both plants and animals.

Mojica, Julius P.; Kelly, John K.

2010-01-01

134

Use of Laboratory-Supplied Natural Gas in Breakthrough Phenomena.  

ERIC Educational Resources Information Center

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)

Eiceman, G. A.; And Others

1985-01-01

135

Genome-wide polymorphisms show unexpected targets of natural selection  

PubMed Central

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.

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

2012-01-01

136

Adding Dynamical Sufficiency to Fisher's Fundamental Theorem of Natural Selection  

NASA Astrophysics Data System (ADS)

Fisher's ``fundamental theorem of natural selection'' is famously robust and versatile but, frustratingly, it is dynamically insufficient: it can only predict how fitness will evolve over the course of a single generation. Consequently, his theorem has not been used for predicting the course of evolution but instead for detecting natural selection. His theorem employs only one facet of the fitness distribution, namely, the variance, and thus does not take advantage of all the available information. The theory we have developed shares some common ground with Fisher's theorem, but takes full advantage of the available information by employing the higher moments of the fitness distribution in addition to the variance. The theory developed here suggests: 1) a way to non-parametrically infer the distribution of mutational effects that feeds ongoing evolution, and 2) a framework for predicting fitness (and fitness-related) evolution.

Gerrish, Philip J.; Sniegowski, Paul D.

2011-09-01

137

Geomicrobial kinetics: Extrapolating laboratory studies to natural environments  

Microsoft Academic Search

Predicting metabolic rates and population sizes of microorganisms in natural environments is a central problem in geomicrobiology. Such predictions can be made on the basis of a thermodynamically consistent rate law that accounts for both kinetic and thermodynamic controls on microbial metabolism. Application of the rate law requires kinetic and growth parameters, the values of which have been determined for

Qusheng Jin; Eric E. Roden; Jonathan R. Giska

2012-01-01

138

Genomic mutation rates that neutralize adaptive evolution and natural selection.  

PubMed

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

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

2013-05-29

139

Natural selection in the field and the classroom  

NASA Astrophysics Data System (ADS)

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).

Andrews, Tessa Marie

140

Human facial temperatures in natural and laboratory cold.  

PubMed

Asian, European, and American Indian men were subjected to craniofacial cooling to determine relative ranking and temperature curves for various facial skin sites. Moving and still air 0 degrees C to -35 degrees C in both laboratory and subarctic outdoor settings were used. The objective was to examine resistance to facial frostbite. Facial temperatures stabilize well above freezing even under quite cold conditions and this conclusion is congruent with low incidences of facial frostbite. Racial differences in face temperatures were clearly shown at only the malar eminence, and there was some evidence that exercise can be used to enhance facial circulation. These results and those of other studies reviewed demonstrate that facial sites cooled by convection are usually ranked from forehead (warmest) through malar, cheek, and chin, to nose (coldest). When cooled by still air, the sites tend to retain that same ranking, but there is more variation in ranking. PMID:454321

Steegmann, A T

1979-03-01

141

Genomic landscape of positive natural selection in Northern European populations  

PubMed Central

Analyzing genetic variation of human populations for detecting loci that have been affected by positive natural selection is important for understanding adaptive history and phenotypic variation in humans. In this study, we analyzed recent positive selection in Northern Europe from genome-wide data sets of 250?000 and 500?000 single-nucleotide polymorphisms (SNPs) in a total of 999 individuals from Great Britain, Northern Germany, Eastern and Western Finland, and Sweden. Coalescent simulations were used for demonstrating that the integrated haplotype score (iHS) and long-range haplotype (LRH) statistics have sufficient power in genome-wide data sets of different sample sizes and SNP densities. Furthermore, the behavior of the FST statistic in closely related populations was characterized by allele frequency simulations. In the analysis of the North European data set, 60 regions in the genome showed strong signs of recent positive selection. Out of these, 21 regions have not been discovered in previous scans, and many contain genes with interesting functions (eg, RAB38, INFG, NOS1AP, and APOE). In the putatively selected regions, we observed a statistically significant overrepresentation of genetic association with complex disease, which emphasizes the importance of the analysis of positive selection in understanding the evolution of human disease. Altogether, this study demonstrates the potential of genome-wide data sets to discover loci that lie behind evolutionary adaptation in different human populations.

Lappalainen, Tuuli; Salmela, Elina; Andersen, Peter M; Dahlman-Wright, Karin; Sistonen, Pertti; Savontaus, Marja-Liisa; Schreiber, Stefan; Lahermo, Paivi; Kere, Juha

2010-01-01

142

Preventing and Removing Contamination in a Natural Radiocarbon Sample Preparation Laboratory  

Microsoft Academic Search

The introduction of elevated ¹⁴C 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 ¹⁴C contaminated as a result of earlier tracer based research, even if ''hot'' work has not occurred in the laboratories in decades. Prior to

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

2002-01-01

143

Signatures of selection in natural populations adapted to chronic pollution  

PubMed Central

Background Populations of the teleost fish Fundulus heteroclitus appear to flourish in heavily polluted and geographically separated Superfund sites. Populations from three Superfund sites (New Bedford Harbor, MA, Newark Bay, NJ, and Elizabeth River, VA) have independently evolved adaptive resistance to chemical pollutants. In these polluted populations, natural selection likely has altered allele frequencies of loci that affect fitness or that are linked to these loci. The aim of this study was to identify loci that exhibit non-neutral behavior in the F. heteroclitus genome in polluted populations versus clean reference populations. Results To detect signatures of natural selection and thus identify genetic bases for adaptation to anthropogenic stressors, we examined allele frequencies for many hundreds of amplified fragment length polymorphism markers among populations of F. heteroclitus. Specifically, we contrasted populations from three Superfund sites (New Bedford Harbor, MA, Newark Bay, NJ, and Elizabeth River, VA) to clean reference populations flanking the polluted sites. When empirical FST values were compared to a simulated distribution of FST values, 24 distinct outlier loci were identified among pairwise comparisons of pollutant impacted F. heteroclitus populations and both surrounding reference populations. Upon removal of all outlier loci, there was a strong correlation (R2 = 0.79, p < 0.0001) between genetic and geographical distance. This apparently neutral evolutionary pattern was not evident when outlier loci were included (R2 = 0.092, p = 0.0721). Two outlier loci were shared between New Bedford Harbor and Elizabeth River populations, and two different loci were shared between Newark Bay and Elizabeth River populations. Conclusion In total, 1% to 6% of loci are implicated as being under selection or linked to areas of the genome under selection in three F. heteroclitus populations that reside in polluted estuaries. Shared loci among polluted sites indicate that selection may be acting on multiple loci involved in adaptation, and loci shared between polluted sites potentially are involved in a generalized adaptive response.

2008-01-01

144

Brookhaven National Laboratory Selected Cryogenic Data Notebook: Volume 1, Sections 1-9.  

National Technical Information Service (NTIS)

The Selected Cryogenic Data Notebook has been designed to meet the general needs of the engineers and scientists working with cryogenic systems at Brookhaven National Laboratory. The objective in the preparation of this collection of data tables and chart...

A. G. Prodell H. Brechna J. E. Jensen R. B. Stewart W. A. Tuttle

1980-01-01

145

Brookhaven National Laboratory Selected Cryogenic Data Notebook. Volume 2. Sections 10-18.  

National Technical Information Service (NTIS)

The Selected Cryogenic Data Notebook has been designed to meet the general needs of the engineers and scientists working with cryogenic systems at Brookhaven National Laboratory. The objective in the preparation of this collection of data tables and chart...

A. G. Prodell H. Brechna J. E. Jensen R. B. Stewart W. A. Tuttle

1980-01-01

146

Population thinking and natural selection in dual-inheritance theory.  

PubMed

A deflationary perspective on theories of cultural evolution, in particular dual-inheritance theory, has recently been proposed by Lewens. On this 'pop-culture' analysis, dual-inheritance theorists apply population thinking to cultural phenomena, without claiming that cultural items evolve by natural selection. This paper argues against this pop-culture analysis of dual-inheritance theory. First, it focuses on recent dual-inheritance models of specific patterns of cultural change. These models exemplify population thinking without a commitment to natural selection of cultural items. There are grounds, however, for doubting the added explanatory value of the models in their disciplinary context-and thus grounds for engaging in other potentially explanatory projects based on dual-inheritance theory. One such project is suggested by advocates of the theory. Some of the motivational narratives that they offer can be interpreted as setting up an adaptationist project with regard to cumulative change in cultural items. We develop this interpretation here. On it, dual-inheritance theory features two interrelated selection processes, one on the level of genetically inherited learning mechanisms, another on the level of the cultural items transmitted through these mechanisms. This interpretation identifies a need for further modelling efforts, but also offers scope for enhancing the explanatory power of dual-inheritance theory. PMID:22523438

Houkes, Wybo

2012-01-26

147

Transport and selective uptake of radium into natural clay minerals  

NASA Astrophysics Data System (ADS)

Understanding of the environmental behavior of Ra is important from the viewpoint of the long-termed repository safety of radioactive waste, but investigation of Ra behavior in natural environment is difficult to detect. We found isotopic evidence of Ra transportation and its selective uptake into clay minerals from Pb isotopic analyses. Illite grains found in calcite veins included in sandstone near the Oklo uranium deposit, Republic of Gabon, show extremely low 207Pb/ 206Pb (˜ 0.0158) isotopic ratios. Although the Pb isotopic ratios of calcite and quartz coexisting with illite indicate the formation age of each component, those of illite do not. In addition, illite grains having low 207Pb/ 206Pb isotopic ratios contain a strongly large amount of Ba (1230 to 6010 ppm) in contrast with low contents of Ba in calcite and quartz (< 0.26 ppm). Considering the chemical similarity between Ba and Ra, the 207Pb/ 206Pb isotopic data suggest an excess of 206Pb due to selective adsorption of 226Ra (and also Ba) into illite grains. This is a very rare example to show evidence of the selective adsorption behavior of Ra from the isotopic excesses of 206Pb, although the adsorption ability of Ra itself in nature was largely reported.

Hidaka, Hiroshi; Horie, Kenji; Gauthier-Lafaye, Françoise

2007-12-01

148

The Effects of Selective Breeding on the Laboratory Propagation of Insect Parasites  

Microsoft Academic Search

The formal application of certain animal breeding methods has been investigated in the laboratory propagation of a chalcid parasite, Microplectron fuscipennis Zett. An account is given of the methods used with reference to their value in the propagation of other insect parasites. Through selective breeding, laboratory production permitted the distribution of 889 million parasites over the spruce sawfly infested area

A. Wilkes

1947-01-01

149

Laboratory study of selected personal inhalable aerosol samplers.  

PubMed

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

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

2010-02-10

150

Immunobiological properties of selected natural and chemically modified phenylpropanoids  

PubMed Central

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.

Harmatha, Juraj; Zidek, Zdenek; Kmonickova, Eva; Smidrkal, Jan

2011-01-01

151

Selection maintains MHC diversity through a natural population bottleneck.  

PubMed

A perceived consequence of a population bottleneck is the erosion of genetic diversity and concomitant reduction in individual fitness and evolutionary potential. Although reduced genetic variation associated with demographic perturbation has been amply demonstrated for neutral molecular markers, the effective management of genetic resources in natural populations is hindered by a lack of understanding of how adaptive genetic variation will respond to population fluctuations, given these are affected by selection as well as drift. Here, we demonstrate that selection counters drift to maintain polymorphism at a major histocompatibility complex (MHC) locus through a population bottleneck in an inbred island population of water voles. Before and after the bottleneck, MHC allele frequencies were close to balancing selection equilibrium but became skewed by drift when the population size was critically low. MHC heterozygosity generally conformed to Hardy-Weinberg expectations except in one generation during the population recovery where there was a significant excess of heterozygous genotypes, which simulations ascribed to strong differential MHC-dependent survival. Low allelic diversity and highly skewed frequency distributions at microsatellite loci indicated potent genetic drift due to a strong founder affect and/or previous population bottlenecks. This study is a real-time examination of the predictions of fundamental evolutionary theory in low genetic diversity situations. The findings highlight that conservation efforts to maintain the genetic health and evolutionary potential of natural populations should consider the genetic basis for fitness-related traits, and how such adaptive genetic diversity will vary in response to both the demographic fluctuations and the effects of selection. PMID:22323362

Oliver, Matthew K; Piertney, Stuart B

2012-02-09

152

Space Allocation Guidelines for Selected Vocational Laboratories in Secondary Comprehensive High Schools in Michigan  

ERIC Educational Resources Information Center

The study aims to help establish minimum guidelines for the allocation of instructional space in selected vocational laboratories (machine shop, auto mechanics, welding, sheet metal, drafting) contained in comprehensive high schools, based on the perceptions of educational facility planners, a review of selected literature, and where possible,…

Arcy, Thomas H.

1978-01-01

153

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

ERIC Educational Resources Information Center

|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…

Coleman, Seth; Jensen, Jeffrey

2007-01-01

154

Laboratory Model of Adaptive Radiation: A Selection Experiment in the Bank Vole  

Microsoft Academic Search

In a laboratory colony of a wild rodent, the bank vole Myodes (pClethrionomys) glareolus, a multiway artificial selection ex- periment was applied to mimic evolution toward high aerobic metabolism achieved during locomotor activity, predatory be- havior, and ability to cope with herbivorous diet. Four lines for each of the selection directions and four unselected control lines have been maintained. After

Pawe? Koteja

2008-01-01

155

X-ray CT observations of methane hydrate distribution in natural sediment and laboratory formed compacted sand samples  

Microsoft Academic Search

Synthesizing methane hydrate in the laboratory is necessary due to the limited availability of natural hydrate bearing samples. Creating samples closely simulating natural hydrate distribution patterns is important when properties measured using the lab-synthesized samples are to be used for predictions of natural hydrate behavior. We have observed methane hydrate in many samples including recovered natural sediment cores, and laboratory-formed

Y. Seol; T. J. Kneafsey; E. V. Rees

2009-01-01

156

Emergence and natural selection of drug-resistant prions  

PubMed Central

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-?’ 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.

2010-01-01

157

Detecting Selective Sweeps in Naturally Occurring Escherichia Coli  

PubMed Central

The nucleotide sequences of the gapA and pabB genes (separated by approximately 32.5 kb) were determined in 12 natural isolates of Escherichia coli. Three analyses were performed on the data. First, the levels of polymorphism at the loci were compared within and between E. coli and Salmonella strains relative to their degrees of constraint. Second, the gapA and pabB loci were analyzed by the Hudson-Kreitman-Aguade (HKA) test for selective neutrality. Four additional dispersed genes (crr, putP, trp and gnd) were added to the analysis to provide the necessary frame of reference. Finally, the gene genealogies of gapA and pabB were examined for topological consistency within and between the loci. These lines of evidence indicate that some evolutionary event has recently purged the variability in the region surrounding the gapA and pabB loci in E. coli. This can best be explained by the spread of a selected allele through the global E. coli population by directional selection and the resulting loss in variability in the surrounding regions due to genetic hitchhiking.

Guttman, D. S.; Dykhuizen, D. E.

1994-01-01

158

Differential survival and natural selection: their impact upon aging and cancer mortality  

Microsoft Academic Search

Evidence for natural selection is often presented from the perspective of evolution. However, evolution is not the purpose of natural selection. Natural selection might also impact upon the manifestation of senescence via differential survival. The relationship between age-specific cancer mortality rates and corresponding age group population size in the USA from 1951 to 1989 for age groups over age 45

Jack E Riggs

1996-01-01

159

Evaluations of selected text references to natural selection by high school biology teachers  

NASA Astrophysics Data System (ADS)

For decades researchers have warned of problems associated with using anthropomorphic and teleological formulations to explain natural selection. This study investigates how high school biology teachers evaluate potentially useful text containing canonical, anthropomorphic and teleological formulations that purport to explain biological adaptation through natural selection. Twenty-four teachers were randomly selected from a stratified sample of all high school biology teachers in three counties surrounding a major city in upstate New York. Each teacher evaluated 16 canonical, anthropomorphic and teleological formulations in a questionnaire and then participated in a semi-structured interview to explain why choices were made and how they might modify some items. Goals of this study were to understand teacher standards regarding these formulations by means of determining: (1) How teachers evaluate canonical, anthropomorphic and teleologlcal presented on a questionnaire (2) Do teachers recognize phrases that imply anthropomorphic and teleological meanings? (3) How does content effect teachers' evaluation of statement usefulness? And (4) Do years of experience influence teachers' sensitivity to anthropomorphic and teleological meanings? Conclusions of this study show that: (1) Concern about potential misconceptions was the most important factor influencing teachers' judgment of statements. (2) Vocabulary appears to be an important factor in teachers' judgment of text usefulness. (3) Teachers who are more sensitive to the anthropomorphic or teleological phrases were more likely to reject their use. (4) The content area of natural selection (i.e., animal, microbe, human and plant) does not appear to influence teachers' use of canonical, anthropomorphic or teleological formulations of statements. (5) Inexperienced teachers have a high tolerance for some non-literal formulations (i.e., anthropomorphic and teleological).

Preston, George L.

1997-09-01

160

Contributions of natural and sexual selection to the evolution of premating reproductive isolation: a research agenda.  

PubMed

Speciation by divergent natural selection is well supported. However, the role of sexual selection in speciation is less well understood due to disagreement about whether sexual selection is a mechanism of evolution separate from natural selection, as well as confusion about various models and tests of sexual selection. Here, we outline how sexual selection and natural selection are different mechanisms of evolutionary change, and suggest that this distinction is critical when analyzing the role of sexual selection in speciation. Furthermore, we clarify models of sexual selection with respect to their interaction with ecology and natural selection. In doing so, we outline a research agenda for testing hypotheses about the relative significance of divergent sexual and natural selection in the evolution of reproductive isolation. PMID:24054911

Safran, Rebecca J; Scordato, Elizabeth S C; Symes, Laurel B; Rodríguez, Rafael L; Mendelson, Tamra C

2013-09-19

161

Laboratory studies on natural restoration of ground water after in-situ leach uranium mining  

Microsoft Academic Search

When uranium is mined using in-situ leach techniques, the chemical quality of the ground water in the ore-zone aquifer is affected. This could lead to long-term degradation of the ground water if restoration techniques are not applied after the leaching is completed. Pacific Northwest Laboratory (PNL), is conducting an NRC-sponsored research project on natural restoration and induced-restoration techniques. Laboratory studies

N. E. Bell; W. J. Deutsch; R. J. Serne

1983-01-01

162

Numerical, Laboratory And Field Studiesof Gas Production FromNatural Hydrate Accumulations in Geologic Media  

SciTech Connect

We discuss the range of activities at Lawrence BerkeleyNational Laboratory in support of gas production from natural hydrates.Investigations of production from the various classes of hydrate depositsby numerical simulation indicate their significant promise as potentialenergy sources. Laboratory studies are coordinated with the numericalstudies and are designed to address knowledge gaps that are important tothe prediction of gas production. Our involvement in field tests is alsobriefly discussed.

Moridis, George J.; Kneafsey, Timothy J.; Kowalsky, Michael; Reagan, Matthew

2006-10-17

163

Thermodynamic Cycle Selection for Distributed Natural Gas Liquefaction  

NASA Astrophysics Data System (ADS)

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.

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

2004-06-01

164

Natural selection and self-organization in complex adaptive systems.  

PubMed

The central theme of this work is self-organization "interpreted" both from the point of view of theoretical biology, and from a philosophical point of view. By analysing, on the one hand, those which are now considered--not only in the field of physics--some of the most important discoveries, that is complex systems and deterministic chaos and, on the other hand, the new frontiers of systemic biology, this work highlights how large thermodynamic systems which are open can spontaneously stay in an orderly regime. Such systems can represent the natural source of the order required for a stable self-organization, for homoeostasis and for hereditary variations. The order, emerging in enormous randomly interconnected nets of binary variables, is almost certainly only the precursor of similar orders emerging in all the varieties of complex systems. Hence, this work, by finding new foundations for the order pervading the living world, advances the daring hypothesis according to which Darwinian natural selection is not the only source of order in the biosphere. Thus, the article, by examining the passage from Prigogine's dissipative structures theory to the contemporary theory of biological complexity, highlights the development of a coherent and continuous line of research which is set to individuate the general principles marking the profound reality of that mysterious self-organization characterizing the complexity of life. PMID:20882479

Di Bernardo, Mirko

165

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

PubMed Central

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.

Baker, David G.

1998-01-01

166

Natural selection shaped regional mtDNA variation in humans  

PubMed Central

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.

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

167

Natural selection for costly nutrient recycling in simulated microbial metacommunities.  

PubMed

Recycling of essential nutrients occurs at scales from microbial communities to global biogeochemical cycles, often in association with ecological interactions in which two or more species utilise each others' metabolic by-products. However, recycling loops may be unstable; sequences of reactions leading to net recycling may be parasitised by side-reactions causing nutrient loss, while some reactions in any closed recycling loop are likely to be costly to participants. Here we examine the stability of nutrient recycling loops in an individual-based ecosystem model based on microbial functional types that differ in their metabolism. A supplied nutrient is utilised by a "source" functional type, generating a secondary nutrient that is subsequently used by two other types-a "mutualist" that regenerates the initial nutrient at a growth rate cost, and a "parasite" that produces a refractory waste product but does not incur any additional cost. The three functional types are distributed across a metacommunity in which separate patches are linked by a stochastic diffusive migration process. Regions of high mutualist abundance feature high levels of nutrient recycling and increased local population density leading to greater export of individuals, allowing the source-mutualist recycling loop to spread across the system. Individual-level selection favouring parasites is balanced by patch-level selection for high productivity, indirectly favouring mutualists due to the synergistic productivity benefits of the recycling loop they support. This suggests that multi-level selection may promote nutrient cycling and thereby help to explain the apparent ubiquity and stability of nutrient recycling in nature. PMID:22842011

Boyle, Richard A; Williams, Hywel T P; Lenton, Timothy M

2012-07-26

168

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

SciTech Connect

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.

Not Available

1994-02-01

169

Effect of insecticide resistance on development, longevity and reproduction of field or laboratory selected Aedes aegypti populations.  

PubMed

Aedes aegypti dispersion is the major reason for the increase in dengue transmission in South America. In Brazil, control of this mosquito strongly relies on the use of pyrethroids and organophosphates against adults and larvae, respectively. In consequence, many Ae. aegypti field populations are resistant to these compounds. Resistance has a significant adaptive value in the presence of insecticide treatment. However some selected mechanisms can influence important biological processes, leading to a high fitness cost in the absence of insecticide pressure. We investigated the dynamics of insecticide resistance and its potential fitness cost in five field populations and in a lineage selected for deltamethrin resistance in the laboratory, for nine generations. For all populations the life-trait parameters investigated were larval development, sex ratio, adult longevity, relative amount of ingested blood, rate of ovipositing females, size of egglaying and eggs viability. In the five natural populations, the effects on the life-trait parameters were discrete but directly proportional to resistance level. In addition, several viability parameters were strongly affected in the laboratory selected population compared to its unselected control. Our results suggest that mechanisms selected for organophosphate and pyrethroid resistance caused the accumulation of alleles with negative effects on different life-traits and corroborate the hypothesis that insecticide resistance is associated with a high fitness cost. PMID:22431967

Martins, Ademir Jesus; Ribeiro, Camila Dutra e Mello; Bellinato, Diogo Fernandes; Peixoto, Alexandre Afranio; Valle, Denise; Lima, José Bento Pereira

2012-03-14

170

Composition of Bacterial Communities Associated with Natural and Laboratory Populations of Asobara tabida Infected with Wolbachia  

Microsoft Academic Search

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

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

2009-01-01

171

Field and laboratory measurements of bivalve filtration of natural marine bacterioplankton  

Microsoft Academic Search

Ahstruct Clearance of natural bacterioplankton and phytoplankton by Mytihs edulis, Geukensia demissa, and Myu arenuriu was measured in the laboratory. Of the three, only Geukensia proved capable of efficient clearance of bacteria. Field measurements of clearance across a 46-m-wide Myths bed showed substantial removal of phytoplankton but no effect on bnc- terial concentrations. Measurements of the living gill tissue of

RICHARD T. WRIGHT; RICHARD B. COFFIN; CURTIS P. ERSING; DANIEL PEARSON

1982-01-01

172

Context-dependent fright reactions in captive European minnows: the importance of naturalness in laboratory experiments  

Microsoft Academic Search

The responses of ostariophysan fish to alarm substance (Schreckstoff) have been investigated extensively in the laboratory but there have been few tests of its role under natural conditions. Furthermore, existing studies of the efficacy of Schreckstoff as an alarm substance in the wild have typically employed indirect approaches and have failed to document specific behaviour in a quantitative manner. European

PHILIP W IRVING; ANNE E MAGURRAN

1997-01-01

173

Naturally occurring high chloride coal and superheater corrosion - a laboratory study  

Microsoft Academic Search

The fireside corrosion potential of commercial boiler tube alloys at elevated temperatures when exposed to the combustion products from a series of coals was investigated. The results of the laboratory and field tests were previously reported. In a supplementary phase of the program, the effect of chloride on similar alloys while firing a naturally occurring high chloride Midwestern bituminous coal

A. L. Plumley; W. R. Roczniak

1981-01-01

174

Safety in the Chemical Laboratory: Selecting Chemical Protective Gloves Properly in the Lab.  

ERIC Educational Resources Information Center

Discusses the selection of gloves for the chemistry laboratory. Provides checklists for the purposes of the gloves, and the factors including permeation rate, breakthrough time, friction, and cost. Lists eight rules for preventing skin exposure and minimizing area contamination. Lists six references. (YP)

Hart, Charles

1989-01-01

175

A Selective, Annotated Bibliography for the Language Laboratory, 1959-1971.  

ERIC Educational Resources Information Center

This annotated bibliography lists 163 selected books, articles, and research reports concerning the language laboratory published from 1959 to 1972. It is intended for foreign language teachers and administrators seeking information on the planning, administration, operation, and installation of mediated language instruction. The bibliography is…

Keck, Mary Ellen B., Comp.; Smith, William Flint, Comp.

176

MEASUREMENTS OF NATURAL SELECTION ON FLORAL TRAITS IN WILD RADISH (RAPHANUS RAPHANISTRUM). I. SELECTION THROUGH LIFETIME FEMALE FITNESS  

Microsoft Academic Search

Although the role of natural selection in the evolution of floral traits has been of great interest to biologists since Darwin, studies of selection on floral traits through differences in lifetime fitness have been rare. We measured selection acting on flower number, flower size, stigma exsertion, and ovule number per flower using field data on lifetime female fitness (seed production)

JEFFREY K. CONNER; PETER JENNET; E. Healey

177

Temperature, phenotype, and the evolution of temperature-dependent sex determination: how do natural incubations compare to laboratory incubations?  

PubMed

Phenotypic variation is a fundamental component of the process of evolution and understanding the factors that create this variation is critical to investigations of this process. We test the hypothesis that phenotypic variation created under natural incubation conditions will differ from that created under constant laboratory conditions in a reptile species with temperature-dependent sex determination (TSD), the red-eared slider turtle (Trachemys scripta). Using a split clutch design, we demonstrate that offspring morphology, behavior, and sex differed between hatchlings incubated in the field and those from the laboratory, but immune response did not. The interactions between different phenotypic parameters will ultimately determine how natural selection acts upon offspring, and consequently our data suggest that offspring developing under these differing conditions should have different fitnesses. The relationship between offspring sex and phenotype serves as the theoretical foundation on which most investigations into the evolution of TSD are built. Thus, it may be necessary to use natural incubation conditions to accurately examine how offspring sex relates to other phenotypic parameters if we are to understand the evolution of this sex determining mechanism. PMID:19606486

Paitz, Ryan T; Gould, Amelia C; Holgersson, Mikael C N; Bowden, Rachel M

2010-01-15

178

Modifying effects of phenotypic plasticity on interactions among natural selection, adaptation and gene flow  

Microsoft Academic Search

Divergent natural selection, adaptive divergence and gene flow may interact in a number of ways. Recent studies have focused on the balance between selection and gene flow in natural populations, and empirical work has shown that gene flow can constrain adaptive divergence, and that divergent selection can constrain gene flow. A caveat is that phenotypic diversification may be under the

E. CRISPO

2008-01-01

179

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

NASA Astrophysics Data System (ADS)

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.

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

2008-04-01

180

Natural selection on floral traits of Lobelia (Lobeliaceae): spatial and temporal variation.  

PubMed

The strength and direction of natural selection on floral traits can vary spatially and temporally because of variation in the biotic and abiotic environment. High spatial variation in selection should lead to differentiation of floral traits among populations. In contrast, high temporal variation in selection should retard the evolution of population-specific floral phenotypes. To determine the relative importance of spatial vs. temporal variation in natural selection, we measured phenotypic selection on seven floral traits of the wildflowers Lobelia cardinalis and L. siphilitica in 1999 and 2000. Lobelia cardinalis experienced significant temporal variation in selection, whereas L. siphilitica experienced spatial variation in selection on the same traits. This variation in selection on floral traits was associated with spatial and temporal differences in the soil microenvironment. Although few studies of natural selection include spatial or temporal replicates, our results suggest that such replication is critical for understanding the distribution of phenotypes in nature. PMID:21659233

Caruso, Christina M; Peterson, S Brook; Ridley, Caroline E

2003-09-01

181

Laboratory simulation of natural leaching processes of eastern USA oil shale  

NASA Astrophysics Data System (ADS)

Raw and retorted spent oil shales from Kentucky, as well as soil and overburden materials, were subjected to laboratory and field leaching tests. Standard batch leaching tests grossly undervalue the amount of dissolved ions as measured in the field, being too brief to enable slow reactions of the mineral matrix, such as hydrolysis and oxidation of sulfides or reactions of acidic leachates with soluble components of the clays. Laboratory column tests, devised to closely simulate natural leaching processes, achieved concentration levels and elemental release patterns similar to those found in field tests. The column tests provide a reliable means to assess the leachability of metals in these materials.

Shirav (Schwartz), M.; Robl, T. L.

1993-09-01

182

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

SciTech Connect

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).

Gerald Sehlke; Paul Wichlacz

2010-12-01

183

Mercury selection of allozymes in marine organisms: prediction and verification in nature. [Palaemon elegans; Monodonte turnbinata  

SciTech Connect

The geographic distributions of mercury-tolerant allozyme genotypes of the enzyme phosphoglucomutase in the shrimp Palaemon elegans and the enzyme phosphoglucose isomerase in the marine gastropod Monodonta turbinata were compared in a mercury-polluted site versus several unpolluted sites on the Israeli coast of the Mediterranean sea. It was concluded that in both phosphoglucomutase and phosphoglucose isomerase, the level of the mercury-tolerant allozyme genotypes was higher in the polluted as compared with the unpolluted sites. These results suggest that mercury selection is operating in nature on allozyme genotypes of these marine organisms along patterns comparable with those found previously in laboratory experiments. The authors suggest that the enzymes studied here display an adaptive pattern in polluted environments. Therefore, they may be used as potential indicators and monitors of marine pollution. 13 references, 2 tables.

Nevo, E.; Ben-Shlomo, R.; Lavie, B.

1984-02-01

184

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

PubMed

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

Bell, Rayna C; Zamudio, Kelly R

2012-09-19

185

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

PubMed Central

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.

Bell, Rayna C.; Zamudio, Kelly R.

2012-01-01

186

“Are Humans Evolving?” A Classroom Discussion to Change Student Misconceptions Regarding Natural Selection  

Microsoft Academic Search

Natural selection is an important mechanism in the unifying biological theory of evolution, but many undergraduate students\\u000a struggle to learn this concept. Students enter introductory biology courses with predictable misconceptions about natural\\u000a selection, and traditional teaching methods, such as lecturing, are unlikely to dispel these misconceptions. Instead, students\\u000a are more likely to learn natural selection when they are engaged in

Tessa M. Andrews; Steven T. Kalinowski; Mary J. Leonard

187

Mini-conference on Angular Momentum Transport in Laboratory and Nature  

SciTech Connect

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.

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

2008-05-06

188

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

ERIC Educational Resources Information Center

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…

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

2006-01-01

189

Transgenic Insecticidal Crops and Natural Enemies: A Detailed Review of Laboratory Studies  

Microsoft Academic Search

This review uses a data-driven, quantitative method to summarize the published, peer-reviewed literature about the impact of genetically modiÞed (GM) plants on arthropod natural enemies in laboratory experiments. The method is similar to meta-analysis, and, in contrast to a simple author-vote counting method used by several earlier reviews, gives an objective, data-driven summary of existing knowledge about these effects. SigniÞcantly

Gabor L. Lövei; David A. Andow; Salvatore Arpaia

2009-01-01

190

A Comparison of Water Quality between Natural, Modified, and Manmade Ponds within Brookhaven National Laboratory  

Microsoft Academic Search

Brookhaven National Laboratory (BNL) is located in the center of the Long Island Pine Barrens. Within BNL's 5,265-acre site there are 26 wetlands. Included are coastal plain ponds, vernal ponds, recharge basins, and streams, making it an ideal ecological site to study water chemistry. We tested water samples from seven coastal plain ponds on BNL: four natural (BP1, BP2, BP6,

Priscilla D. Randolph; Roy J. Coomans; Tim Green

191

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

Microsoft Academic Search

BackgroundExperiments 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

Jelle S. van Zweden; Jürgen Heinze; Jacobus J. Boomsma; Patrizia D'Ettorre; Tom Tregenza

2009-01-01

192

Inorganic carbon acquisition in algal communities: are the laboratory data relevant to the natural ecosystems?  

Microsoft Academic Search

Most of the experimental work on the effects of ocean acidification on the photosynthesis of algae has been performed in the\\u000a laboratory using monospecific cultures. It is frequently assumed that the information obtained from these cultures can be\\u000a used to predict the acclimation response in the natural environment. CO2 concentration is known to regulate the expression and functioning of the

Jesús M. Mercado; F. J. L. Gordillo

193

Genetic Load in Natural Populations: Is It Compatible with the Hypothesis That Many Polymorphisms Are Maintained by Natural Selection?  

PubMed Central

Recent studies of genetically controlled enzyme variation lead to an estimation that at least 30 to 60% of the structural genes are polymorphic in natural populations of many vertebrate and invertebrate species. Some authors have argued that a substantial proportion of these polymorphisms cannot be maintained by natural selection because this would result in an unbearable genetic load. If many polymorphisms are maintained by heterotic natural selection, individuals with much greater than average proportion of homozygous loci should have very low fitness. We have measured in Drosophila melanogaster the fitness of flies homozygous for a complete chromosome relative to normal wild flies. A total of 37 chromosomes from a natural population have been tested using 92 experimental populations. The mean fitness of homozygous flies is 0.12 for second chromosomes, and 0.13 for third chromosomes. These estimates are compatible with the hypothesis that many (more than one thousand) loci are maintained by heterotic selection in natural populations of D. melanogaster.

Tracey, Martin L.; Ayala, Francisco J.

1974-01-01

194

Clients and clinician satisfaction with laboratory services at selected government hospitals in eastern Ethiopia  

PubMed Central

Background In clinical laboratory service, patients and clinical service providers are the primary focus of survey of satisfaction in many countries. The objective of the study was to assess clients’ and clinicians’ satisfaction with laboratory services at selected government hospitals in eastern Ethiopia from May to June, 2010. Findings A cross sectional study was conducted at Dil Chora, Jugal, Hiwot Fana and Bisidimo hospitals. Data were collected from 429 patients and 54 clinical service providers. A statistical analysis was conducted using Likert Scale and SPSS Version 16 software. Most of the patients (87.6%) were satisfied with the laboratory services. The lowest [2.48?±?1.39] and highest [4.27?±?0.83] rate satisfaction were on cleanness of latrine to collect specimens and availability of laboratory staff on working hours respectively. The extent of the patients’ satisfaction was different among the study hospitals (P-value?laboratory services. The lowest [3.02?±?1.36] and highest [3.78?±?1.03] rate of satisfaction were found on critical value notification and timely test results for HIV/AIDS patients care respectively. Conclusion The overall degree of customers’ satisfaction with laboratory services was high. But there were some services such as the cleanness of latrines, information given during specimen collection outside laboratory and critical value notification which need attention. Therefore, the hospital administrations and the laboratory departments should work harder and closely to solve the identified problems. Further study with a larger sample size and more factors is recommended.

2013-01-01

195

Examining undergraduate understanding of natural selection and evolution  

NASA Astrophysics Data System (ADS)

This dissertation explores the understanding of evolution and natural selection by zoology and biological sciences education majors in two upper-division undergraduate courses. To date, there has been little research on evolution misconceptions held by these two populations. Students' misconceptions regarding evolution typically revolve around teleological and Lamarckian explanations for adaptations, origin of variation, and fitness. There are other misconceptions, however, that are described in this dissertation. The overarching objective of the dissertation was to identify variables that might influence the conceptual change. A mixed-method analysis was developed to identify instances of conceptual change that go undetected when only quantitative analyses are used. Through interpretations of in-depth interviews, written discourse, diagnostic tests, instructor interviews, and field notes, it was discovered that students' professional and personal affiliations influenced their motivation to resolve misconceptions. There were three main findings of this doctoral study. First, the effects of direct instruction on misconceptions enabled students to identify incorrect teleological wording but did not necessarily change students' writing about evolution. Higher-achieving students with career interests in biology were more likely to resolve their teleological misconceptions than lower-achieving students. Second, zoology student written discourse could be divided into subjective, objective, and authentic categories based on personal and professional connections that students made in their writing. Students who wrote authentically expressed intentions of pursuing professional biological research. Third, biological sciences education students were found to have composite identities based on personal and professional affiliations, which either hindered or enhanced their motivation to resolve evolution misconceptions. Students' personal affiliations to religious communities of practice did not hinder their motivation to understand evolution. However, students' fears of (a) not being able to resolve competing religious and scientific explanations for diversity of life and/or (b) not being prepared to defend evolution concepts to their employers and students were factors that influenced their motivation to learn. Biological sciences education students appeared to identify themselves as "sharers of scientific knowledge," not as "producers of scientific knowledge." I posit that identity plays a role in the conceptual change process.

Balgopal, Meena Michelle

196

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

SciTech Connect

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.

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

1998-02-01

197

North American Natural Gas Markets: Selected technical studies  

SciTech Connect

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.

Huntington, H.G.; Schuler, G.E. (eds.)

1989-04-01

198

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

SciTech Connect

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.

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

1989-04-01

199

Pseudogene evolution and natural selection for a compact genome  

Microsoft Academic Search

Pseudogenes are nonfunctional copies of protein-coding genes that are presumed to evolve without selective constraints on their coding function. They are of con- siderable utility in evolutionary genetics because, in the absence of selection, dif- ferent types of mutations in pseudogenes should have equal probabilities of fixa- tion. This theoretical inference justifies the estimation of patterns of spontaneous mutation from

D. A. Petrov; D. L. Hartl

2000-01-01

200

Light field and water clarity simulation of natural environments in laboratory conditions  

NASA Astrophysics Data System (ADS)

Simulation of natural oceanic conditions in a laboratory setting is a challenging task, especially when that environment can be miles away. We present an attempt to replicate the solar radiation expected at different latitudes with varying water clarity conditions up to 30 m in depth using a 2.5 m deep engineering tank at the University of New Hampshire. The goals of the study were: 1) to configure an underwater light source that produced an irradiance spectrum similar to natural daylight with the sun at zenith and at 60° under clear atmospheric conditions, and 2) to monitor water clarity as a function of depth. Irradiance was measured using a spectra-radiometer with a cosine receiver to analyze the output spectrum of submersed lamps as a function of distance. In addition, an underwater reflection method was developed to measure the diffuse attenuation coefficient in real time. Two water clarity types were characterized, clear waters representing deep, open-ocean conditions, and murky waters representing littoral environments. Results showed good correlation between the irradiance measured at 400 nm to 600 nm and the natural daylight spectrum at 3 m from the light source. This can be considered the water surface conditions reference. Using these methodologies in a controlled laboratory setting, we are able to replicate illumination and water conditions to study the physical, chemical and biological processes on natural and man-made objects and/or systems in simulated, varied geographic locations and environments.

Pe'eri, Shachak; Shwaery, Glenn

2012-05-01

201

Selective NOx Recirculation for Stationary Lean-Burn Natural Gas Engines. Annual Technical Progress Report.  

National Technical Information Service (NTIS)

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 engine...

N. Clark G. Thompson R. Atkinson C. Tissera

2005-01-01

202

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

SciTech Connect

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{sup -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: {sup 40}K, {sup 214}Pb, {sup 214}Bi, {sup 208}Tl, and {sup 228}Ac. 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, {sup 214}Pb, {sup 214}Bi, and {sup 228}Ac showed a weak site dependence while the other two nuclides, {sup 40}K, and {sup 208}Tl, 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. 19 refs., 4 figs., 7 tabs.

Benke, R.R.; Kearfott, K.J. [Univ. of Michigan, Ann Arbor, MI (United States)

1997-08-01

203

Natural selection and the function of genome imprinting: beyond the silenced minority  

Microsoft Academic Search

Most hypotheses of the evolutionary origin of genome imprinting assume that the biochemical character on which natural selection has operated is the expression of the allele from only one parent at an affected locus. We propose an alternative – that natural selection has operated on differences in the chromatin structure of maternal and paternal chromosomes to facilitate pairing during meiosis

Fernando Pardo-Manuel de Villena; Elena de la Casa-Esperón; Carmen Sapienza

2000-01-01

204

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

ERIC Educational Resources Information Center

|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…

Baumgartner, Erin; Duncan, Kanesa

2009-01-01

205

Natural selection theory in non-majors' biology: Instruction, assessment and conceptual difficulty  

Microsoft Academic Search

Evolution by natural selection is the dominant and unifying theme in biology, yet many college students hold alternative conceptions about the topic even after completing general biology. To develop effective instructional strategies and track conceptual understanding, it is useful to have a detailed assessment tool easily used with large classes. This study presents the Conceptual Inventory of Natural Selection (CINS),

Dianne L. Anderson

2003-01-01

206

Visions of Evolution: Self-organization Proposes What Natural Selection Disposes  

Microsoft Academic Search

This article reviews the seven visions of evolution proposed by Depew and Weber (1995, Darwinism Evolving: Systems Dynamics and the Genealogy of Natural Selection, Cambridge, MA: MIT Press), concluding that each posited relationship between natural selection and self-organization has suited different aims and approaches. In the second section of the article, we show that these seven viewpoints may be collapsed

David Batten; Fabio Boschetti

2008-01-01

207

Ecological Mechanisms of Evolution by Natural Selection: Causal Processes Generating Density-and-frequency Dependent Fitness  

Microsoft Academic Search

The current theory of natural selection explains that adaptive evolution occurs because genotypes with greater survival or reproductive tendencies, due to their particular biological properties, tend to increase in frequency over the lesser ones in a common environment; therefore, the former will eventually replace the latter. In nature, such a selection process most often occurs in a local population which

Toshiyuki Nakajima

1998-01-01

208

From prebiotic chemistry to cellular metabolism—The chemical evolution of metabolism before Darwinian natural selection  

Microsoft Academic Search

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

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

2008-01-01

209

PROBING THE ADAPTIVE LANDSCAPE USING EXPERIMENTAL ISLANDS: DENSITY-DEPENDENT NATURAL SELECTION ON LIZARD BODY SIZE  

Microsoft Academic Search

Anolis lizards in the Greater Antilles are thought to have diversified through natural selection on body size and shape, presumably due to interspecific competition and variation in locomotor performance. Here we measure natural selection on body size over three years and across seven replicate populations of the brown anole, A. sagrei. We experimentally manipulated an important component of the environment

Ryan Calsbeek; Thomas B. Smith

2007-01-01

210

WHEN CAN INTELLIGENT DESIGN OF CROPS BY HUMANS OUTPERFORM NATURAL SELECTION?  

Microsoft Academic Search

Natural selection operated on the wild ancestors of crop plants for millions of years. Many seemingly intelligent design changes that we could make to enzyme structure or gene expression would duplicate (at least in phenotypic effect) variants already rejected by past natural selection. These variants died out because they decreased individual plant survival or reproduction under preagricultural conditions. Many of

R. F. DENISON

211

Natural selection and rational decision: two concepts of optimization  

Microsoft Academic Search

There are two different kinds of optimization: “selection” and “rationality” optimization. Selection optimization characterizes\\u000a competition in human and nonhuman societies sharing the same market or niche. “Rationality optimization”, on the other hand,\\u000a characterizes human and nonhuman decision making processes. The two kinds of optimization generate the same result: agents\\u000a end up behaving efficiently. Nonetheless, we should not downplay the differences

Elias L. Khalil

2009-01-01

212

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

NASA Astrophysics Data System (ADS)

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 (?26Mg˜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.

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

2012-07-01

213

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

PubMed

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. PMID:2014987

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

1991-02-01

214

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

USGS Publications Warehouse

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

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

2012-01-01

215

Laboratory studies on natural restoration of ground water after in-situ leach uranium mining  

SciTech Connect

When uranium is mined using in-situ leach techniques, the chemical quality of the ground water in the ore-zone aquifer is affected. This could lead to long-term degradation of the ground water if restoration techniques are not applied after the leaching is completed. Pacific Northwest Laboratory (PNL), is conducting an NRC-sponsored research project on natural restoration and induced-restoration techniques. Laboratory studies were designed to evaluate the ability of the natural system (ore-zone sediments and groundwater) to mitigate the effects of mining on aquifer chemistry. Using batch and flow-through column experiments (performed with lixiviant (leaching solution) and sediments from the reduced zone of an ore-zone aquifer), we found that the natural system can lower uranium and bicarbonate concentrations in solutions and reduce the lixiviant redox potential (Eh). The change in redox potential could cause some of the contaminants that were dissolved during the uranium leaching operation to precipitate, thereby lowering their solution concentration. The concentrations of other species such as calcium, potassium, and sulfate increased, possibly as a result of mineral dissolution and ion exchange. In this paper, we describe the experimentally determined mobility of contaminants after in-situ leach mining, and discuss the possible chemical process affecting mobility.

Bell, N.E.; Deutsch, W.J.; Serne, R.J.

1983-05-01

216

Genome-wide scans for footprints of natural selection  

PubMed Central

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.

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

2010-01-01

217

Critical-like self-organization and natural selection: Two facets of a single evolutionary process?  

Microsoft Academic Search

We argue that critical-like dynamics self-organize relatively easily in non-equilibrium systems, and that in biological systems such dynamics serve as templates upon which natural selection builds further elaborations. These critical-like states can be modified by natural selection in two fundamental ways, reflecting the selective advantage (if any) of heritable variations either among avalanche participants or among whole systems. First, reproducing

Julianne D. Halley; David A. Winkler

2008-01-01

218

Naturally occurring high chloride coal and superheater corrosion - a laboratory study  

SciTech Connect

The fireside corrosion potential of commercial boiler tube alloys at elevated temperatures when exposed to the combustion products from a series of coals was investigated. The results of the laboratory and field tests were previously reported. In a supplementary phase of the program, the effect of chloride on similar alloys while firing a naturally occurring high chloride Midwestern bituminous coal in the same laboratory furnace were studied. On the basis of exposure in the convection pass at temperatures from 1100 to 1700 F, Inconel Alloy 690 was very good while Incoloy 800 and Tp-310 S.S. were good transitional materials. Poor materials were T-22, 316S.S., Inconel 617, and Inconel 671. 4 refs.

Plumley, A.L.; Roczniak, W.R.

1981-01-01

219

Natural Antioxidants in Edible Flours of Selected Small Millets  

Microsoft Academic Search

Investigations were carried out on the natural antioxidants in edible flours of small millets. Total carotenoids content varied from 78–366 ?g\\/100 g in the millet varieties with an average of 199 + 77, 78 + 19, 173 + 25, and 366 + 104 ?g\\/100 g in finger, little, foxtail, and proso millets respectively. Analysis of carotenoids by HPLC for the

V. T. Asharani; A. Jayadeep; N. G. Malleshi

2010-01-01

220

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

ERIC Educational Resources Information Center

|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…

National Education Association, Washington, DC.

221

NATURAL SELECTION ON FLORAL TRAITS OF LOBELIA (LOBELIACEAE): SPATIAL AND TEMPORAL VARIATION1  

Microsoft Academic Search

The strength and direction of natural selection on floral traits can vary spatially and temporally because of variation in the biotic and abiotic environment. High spatial variation in selection should lead to differentiation of floral traits among populations. In contrast, high temporal variation in selection should retard the evolution of population-specific floral phenotypes. To determine the relative importance of spatial

CHRISTINA M. CARUSO; S. BROOK PETERSON; CAROLINE E. RIDLEY

222

Comparing artificial and natural selection in rate of adaptation to genetic stress in Aspergillus nidulans  

Microsoft Academic Search

In an experimental study of adaptation to negative pleiotropic effects of a major fungicide resistance mutation in the filamentous fungus Aspergillus nidulans we have investigated the relative effectiveness of artificial selection vs. natural selection on the rate of compensatory evolution. Using mycelial growth rate as a fitness measure, artificial selection involved the weekly transfer of the fastest growing sector onto

S. E. Schoustra; S. M. Slakhorst-Wandel; A. J. M. Debets; R. F. Hoekstra

2005-01-01

223

Spatial patterns of variation due to natural selection in humans  

Microsoft Academic Search

Empowered by technology and sampling efforts designed to facilitate genome-wide association mapping, human geneticists are now studying the geography of genetic variation in 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

John Novembre; Anna Di Rienzo

2009-01-01

224

The Impacts of Selected Natural Plant Chemicals on Terrestrial Invertebrates  

Microsoft Academic Search

Plants produce thousands of chemicals that are not necessarily involved in their primary metabolism, but are likely to be\\u000a involved in plant defence, communication and competition. These chemicals may be stored within plant tissues, e.g. to act\\u000a as a defence from herbivorous predators, or may be actively released into the surrounding environment. Natural chemicals can\\u000a enter the environment via a

Neal Sorokin; Jeanette Whitaker

225

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

NASA Astrophysics Data System (ADS)

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.

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

2009-04-01

226

The Evolution of Recombination: Removing the Limits to Natural Selection  

PubMed Central

One of the oldest hypotheses for the advantage of recombination is that recombination allows beneficial mutations that arise in different individuals to be placed together on the same chromosome. Unless recombination occurs, one of the beneficial alleles is doomed to extinction, slowing the rate at which adaptive mutations are incorporated within a population. We model the effects of a modifier of recombination on the fixation probability of beneficial mutations when beneficial alleles are segregating at other loci. We find that modifier alleles that increase recombination do increase the fixation probability of beneficial mutants and subsequently hitchhike along as the mutants rise in frequency. The strength of selection favoring a modifier that increases recombination is proportional to ?(2)S?r/r when linkage is tight and ?(2)S(3)? r/N when linkage is loose, where ? is the beneficial mutation rate per genome per generation throughout a population of size N, S is the average mutant effect, r is the average recombination rate, and ?r is the amount that recombination is modified. We conclude that selection for recombination will be substantial only if there is tight linkage within the genome or if many loci are subject to directional selection as during periods of rapid evolutionary change.

Otto, S. P.; Barton, N. H.

1997-01-01

227

Transgenic insecticidal crops and natural enemies: a detailed review of laboratory studies.  

PubMed

This review uses a data-driven, quantitative method to summarize the published, peer-reviewed literature about the impact of genetically modified (GM) plants on arthropod natural enemies in laboratory experiments. The method is similar to meta-analysis, and, in contrast to a simple author-vote counting method used by several earlier reviews, gives an objective, data-driven summary of existing knowledge about these effects. Significantly more non-neutral responses were observed than expected at random in 75% of the comparisons of natural enemy groups and response classes. These observations indicate that Cry toxins and proteinase inhibitors often have non-neutral effects on natural enemies. This synthesis identifies a continued bias toward studies on a few predator species, especially the green lacewing, Chrysoperla carnea Stephens, which may be more sensitive to GM insecticidal plants (16.8% of the quantified parameter responses were significantly negative) than predators in general (10.9% significantly negative effects without C. carnea). Parasitoids were more susceptible than predators to the effects of both Cry toxins and proteinase inhibitors, with fewer positive effects (18.0%, significant and nonsignificant positive effects combined) than negative ones (66.1%, significant and nonsignificant negative effects combined). GM plants can have a positive effect on natural enemies (4.8% of responses were significantly positive), although significant negative (21.2%) effects were more common. Although there are data on 48 natural enemy species, the database is still far from adequate to predict the effect of a Bt toxin or proteinase inhibitor on natural enemies. PMID:19389277

Lövei, Gabor L; Andow, David A; Arpaia, Salvatore

2009-04-01

228

A Nature of Gravitation and the Problem of the Laboratory Gravitational Waves Generation  

NASA Astrophysics Data System (ADS)

This work sheds light on nature of gravitation and vacuum structure to offer new possibilities for the laboratory HFGWs generation, since neither Einstein's GR nor any another theory of gravity not make answer on this question. Well-known hypothesis about non-materiality of gravitation field unambiguously leads to representation that the elemental particles (EPs) are gravitational stabilized substance. By their nature EPs would constitute microscopic black holes with extreme curved space-time into their bulk and in the vicinity. Since EPs birth take place at interaction of photons with polarized vacuum, this latter represents medium consisting from massless gravitational skeletons of known EPs. So the particle can be not born without its antiparticle and vacuum is gravitationally neutral, particle and antiparticle skeleton, must possess gravitation and antigravitation, correspondingly. GWs would be represented oscillations of the EPs gravitational and antigravitational skeletons around the common centre and in consequence they would be transverse. The high penetrating ability of GWs is a result that neither vacuum, in which HFGWs are propagated, nor HFGWs, does not have mass (energy). In the concept frameworks a new RTG, which must be confirmed these representations, is developed. However, already the fact by itself the laboratory generation of GWs is the direct proof of correctness of these representations.

Kanibolotsky, Valentyn

2010-01-01

229

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

PubMed

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

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

2012-10-30

230

Temperature-related natural selection in a wind-pollinated tree across regional and continental scales.  

PubMed

Adaptive genetic variation is a key factor in evolutionary biology, but the detection of signatures of natural selection remains challenging in nonmodel organisms. We used a genome scan approach to detect signals of natural selection in the Black alder (Alnus glutinosa), a widespread wind-pollinated tree. Gene flow through pollen dispersal is believed to be high in this species, and we therefore expected to find a clear response to natural selection. In combination with two different landscape genetic approaches, we determined which environmental variables were most associated with the inferred selection. This analysis was performed on a regional scale (northern Belgium) and on a continental scale (Europe). Because climate-related differences are much more pronounced at the continental scale, we expected to find more selection-sensitive genetic markers across Europe than across northern Belgium. At both spatial scales, a substantial number of genetic loci were considered outliers, with respect to neutral expectations, and were therefore identified as selective. Based on results from our combined approach, four putative selective loci (or 2.5%) were recovered with high statistical support. Although these loci seemed to be associated with different environmental variables, they were mainly temperature-related. Our study demonstrates that the use of complementary methods in landscape genetics allows the discovery of selective loci which otherwise might stay hidden. In combination with a genome scan, the selective loci can be verified and the nature of the selection pressure can be identified. PMID:21623981

Cox, K; Vanden Broeck, A; Van Calster, H; Mergeay, J

2011-05-30

231

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

PubMed

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

Martin, Ryan A; Pfennig, David W

2009-08-01

232

Concentration-mortality responses of Myzus persicae and natural enemies to selected insecticides.  

PubMed

The toxicity of six insecticides was determined for the peach-potato aphid, Myzus persicae (Hemiptera: Aphididae), and some of its natural enemies - the predatory beetles Cycloneda sanguinea (Coccinellidae) and Acanthinus sp. (Anthicidae), and the wasp parasitoid Diaeretiella rapae (Aphidiidae). Natural enemies from these groups are important natural biological control agents in a number of agroecosystems, and insecticides potentially safe to these non-target organisms should be identified using standardized tests. Thus, concentration-mortality bioassays were carried out with both the aphid and its natural enemies to assess the toxicity and selectivity of acephate, deltamethrin, dimethoate, methamidophos, methyl parathion, and pirimicarb. The latter insecticide was highly selective to all natural enemies tested, and its LC(90) for M. persicae was 14-fold lower than the field rate recommended for control of the aphid in brassica crops. Methyl parathion also showed selectivity to C. sanguinea and Acanthinus sp., but not to D. rapae. Acephate was the least potent insecticide against M. persicae and was equally or more toxic to the natural enemies relative to the aphid. Pirimicarb and methyl parathion were efficient against M. persicae and selective in favor of two of the natural enemies tested. Acanthinus sp. and C. sanguinea were more tolerant to the insecticides than was the parasitoid D. rapae. This study shows that there are selective insecticides that may be compatible with conservation of natural enemies in brassica crops, which is important practical information to improve integrated pest management systems in these crops. PMID:22755540

Bacci, Leandro; Rosado, Jander F; Picanço, Marcelo C; Pereira, Eliseu J G; Silva, Gerson A; Martins, Júlio C

2012-01-01

233

Inorganic carbon acquisition in algal communities: are the laboratory data relevant to the natural ecosystems?  

PubMed

Most of the experimental work on the effects of ocean acidification on the photosynthesis of algae has been performed in the laboratory using monospecific cultures. It is frequently assumed that the information obtained from these cultures can be used to predict the acclimation response in the natural environment. CO(2) concentration is known to regulate the expression and functioning of the CCMs in the natural communities; however, ambient CO(2) can become quite variable in the marine ecosystems even in the short- to mid-term. We propose that the degree of saturation of the photosynthesis for a given algal community should be defined in relation to the particular characteristics of its habitat, and not only in relation to its taxonomic composition. The convenience of high CO(2) experiments to infer the degree of photosynthesis saturation by CO(2) in the natural algal communities under the present ocean conditions, as well as its trend in a coming future is discussed taking into account other factors such as the availability of light and nutrients, and seasonality. PMID:21445608

Mercado, Jesús M; Gordillo, F J L

2011-03-29

234

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

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.

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

2013-01-01

235

Hoarding habitat selection of squirrels ( Sciurus vulgaris) in Liangshui Nature Reserve, China  

Microsoft Academic Search

This study was conducted during October 2003–April 2004 in the Liangshui National Nature Reserve of the Xiao Xing'an Mountains of Northeast China. Results showed that hoarding behavior of squirrels exhibited selectivity. The preference order of hoarding habitat selection of squirrels is as follows: original Korean pine forest, secondary natural fir forest, artificial fir forest, mix-conifer leaf forest, artificial fallen leaves

Jianzhang Ma; Cheng Zong; Qingming Wu; Hongfei Zou; Yan Sun; Xin Zheng

2006-01-01

236

Acoustic and resistivity measurements on rock samples containing tetrahydrofuran hydrates: laboratory analogues to natural gas hydrate deposits  

Microsoft Academic Search

In this paper we report laboratory acoustic velocity and electrical resistivity measurements on Berea Sandstone and Austin Chalk samples saturated with a stoichiometric mixture of tetrahydofuran (THF) and water. The and water is an excellent experimental analogue to natural gas hydrates because THF solutions form hydrates similar to natural gas hydrates readily at atmospheric pressures. Hydrate formation in both the

C. Pearson; J. Murphy; R. Hermes

1986-01-01

237

Successful sex pre-selection using natural family planning.  

PubMed

The objective of the study was to test the hypothesis that gender can be preselected by timing coitus in relation to ovulation, the marker of ovulation being the Peak symptom according to the Billings Method. A blind prospective study of 99 couples wishing to preselect the sex of their child was conducted in Nigeria, using the Post-Peak approach of Billings Method for males and Pre-Peak for females. Research co-ordinators examined the 'post-conception' form within four months of conception. This form recorded the timing of coitus prior to conception, and from this, the sex of child was predicted. 94 of the couples had a child of pre-selected sex showing a method success of 94.9%. 78 of 81 predicting a male were successful (96.3%) and 16 of the 18 predicting a female (88.9%). There was one user-failure, a couple who wanted a girl, timed coitus as for a boy, which they had. The study indicates that where comprehensive instruction is provided, the sex of a child can be preselected with a high degree of confidence by timing coitus, using the Post-Peak approach of Billings Method for males and Pre-Peak for females. PMID:21987941

McSweeney, Léonie

2011-03-01

238

Suppressing damage identification errors from selected natural frequencies and mode shape points  

Microsoft Academic Search

This article presents a damage identification method based on structural natural frequencies and mode shape points. According to the well-posedness analysis of this method, an algorithm is proposed to find the optimal combination of natural frequencies and mode shape points. Then, an integrated scheme that consists of the optimal point selection, the damage identification and the measurement noise updating is

Zhihai Xiang; Longqi Wang; Masheng Zhou

2011-01-01

239

Did Natural Selection or Genetic Drift Produce the Cranial Diversification of Neotropical Monkeys?  

Microsoft Academic Search

A central controversy among biologists is the relative importance of natural selection and genetic drift as creative forces shaping biological diversification (Fisher 1930; Wright 1931). His- torically, this controversy has been an effective engine powering sev- eral evolutionary research programs during the last century (Provine 1989). While all biologists agree that both processes operate in nature to produce evolutionary change,

Gabriel Marroig

2004-01-01

240

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

NASA Astrophysics Data System (ADS)

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.

Liu, D. T.; Intrator, T. P.; Weber, T. E.; Sears, J. A.; Adams, C. S.

2011-11-01

241

Elimination of laboratory-acquired cadmium by the oyster Crassostrea virginica in the natural environment  

SciTech Connect

Many productive shellfish-growing areas along the coast of the United States are closed because of pollution from domestic and industrial wastes. Many estuarine areas that are closed to shellfish harvesting because of bacterial pollution contain productive shellfish beds. These shellfish can be used as commercial food products after they have been relayed to approved growing waters and allowed to eliminate the polluting organisms. Relaying is not presently applied to shellfish contaminated with toxic metals for several reasons: There are no standards to control metal pollution (other than mercury) in seafood; few public health problems in this country involve toxic levels of trace metals in oysters; and not enough information is available to indicate the feasibility of such a project. This study demonstrates the feasibility of relaying cadmium-contaminated oysters to observe cadmium elimination. Because oysters containing naturally acquired cadmium were not readily available, oysters containing laboratory-incurred cadmium were studied.

Mowdy, D.E.

1981-03-01

242

Reduced Natural Selection Associated with Low Recombination in Drosophila melanogaster 1  

Microsoft Academic Search

for translational efficiency. We link this model of varying selection intensity to the population-genetics prediction that the effectiveness of natural selection is decreased under reduced recombination. In analyses of 385 D. melunoguster loci, we find that codon bias is reduced in regions of low recombination (i.e., near centromeres and telomeres and on the fourth chromosome). The effect does not appear

Richard Ml Kliman; Jody Hey

243

Detecting natural selection by empirical comparison to random regions of the genome  

Microsoft Academic Search

Historical episodes of natural selection can skew the frequencies of genetic variants, leaving a signature that can persist for many tens or even hundreds of thousands of years. However, formal tests for selection based on allele frequency skew require strong assumptions about demographic history and mutation, which are rarely well understood. Here, we develop an empirical approach to test for

Fuli Yu; Alon Keinan; Hua Chen; Russell J. Ferland; Robert S. Hill; Andre A. Mignault; Christopher A. Walsh; David Reich

2009-01-01

244

Density?Dependent Variation in Lifetime Breeding Success and Natural and Sexual Selection in Soay Rams  

Microsoft Academic Search

Variation in male lifetime breeding success (LBS) is cen- tral to understanding selection, yet it has rarely been measured in natural populations of large mammals. Here, we first describe var- iation in the opportunity for selection in cohorts of Soay rams (Ovis aries) on the archipelago of St. Kilda, Scotland, that were born during years of varying population density. Variation

D. W. Coltman; J. A. Smith; D. R. Bancroft; J. Pilkington; A. D. C. MacColl; J. M. Pemberton

1999-01-01

245

The relative influence of natural selection and geography on gene flow in guppies  

Microsoft Academic Search

Two general processes may influence gene flow among populations. One involves divergent selection, wherein the maladaptation of immigrants and hybrids impedes gene flow between ecological environments (i.e. ecological speciation). The other involves geographic features that limit dispersal. We determined the relative influence of these two processes in natural populations of Trinidadian guppies ( Poecilia reticulata ). If selection is important,

ERIKA CRISPO; PAUL BENTZEN; DAVID N. R EZNICK; MICHAEL T. K INNISON; ANDREW P. H ENDRY

246

Probabilistic optimization of phenotype distributions: a general solution for the effects of uncertainty on natural selection?  

Microsoft Academic Search

Summary Explorations of optimizing selection often find discrepancies between the theoretically expected and observed phenotypes. Such discrepancies are usually attributed to a variety of potential constraints. We suggest that one common constraint, environmental uncertainty, may reduce the applicability of traditional deterministic or stochastic optimization methods and that many apparent discrepancies might be artifacts of these methods. Since natural selection is

Jin Yoshimura; William M. Shields

1987-01-01

247

Evaluating the role of natural selection in the evolution of gene regulation  

Microsoft Academic Search

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

J C Fay; P J Wittkopp

2008-01-01

248

Evaluating the role of natural selection in the evolution of gene regulation  

Microsoft Academic Search

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. Distinguish- ing adaptive changes driven by positive selection from neutral divergence resulting from mutation and genetic drift is critical for understanding

JC Fay; PJ Wittkopp

2007-01-01

249

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

NASA Astrophysics Data System (ADS)

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.

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

2012-10-01

250

How selection pressure changes the nature of social dilemmas in structured populations  

NASA Astrophysics Data System (ADS)

When members of a population engage in dyadic interactions reflecting a prisoner's dilemma game, the evolutionary dynamics depends crucially on the population structure, described by means of graphs and networks. Here, we investigate how selection pressure contributes to change the fate of the population. We find that homogeneous networks, in which individuals share a similar number of neighbors, are very sensitive to selection pressure, whereas strongly heterogeneous networks are more resilient to natural selection, dictating an overall robust evolutionary dynamics of coordination. Between these extremes, a whole plethora of behaviors is predicted, showing how selection pressure can change the nature of dilemmas populations effectively face. We further show how the present results for homogeneous networks bridge the existing gap between analytic predictions obtained in the framework of the pair-approximation from very weak selection and simulation results obtained from strong selection.

Pinheiro, Flávio L.; Santos, Francisco C.; Pacheco, Jorge M.

2012-07-01

251

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

SciTech Connect

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.

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

1995-11-01

252

SELECTIVE NOx RECIRCULATION FOR STATIONARY LEAN-BURN NATURAL GAS ENGINES  

SciTech Connect

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.

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

2005-01-01

253

Host selection and lethality of attacks by sea lampreys (Petromyzon marinus) in laboratory studies  

USGS Publications Warehouse

Parasitic-phase sea lampreys (Petromyzon marinus) are difficult to study in the wild. A series of laboratory studies (1984-1995) of single attacks on lake trout (Salvelinus namaycush), rainbow trout (Oncorhynchus mykiss), and burbot (Lota lota) examined host size selection; determined the effects of host size, host species, host strain, and temperature on host mortality; and estimated the weight of hosts killed per lamprey. Rainbow trout were more able and burbot less able to survive attacks than lake trout. Small sea lampreys actively selected the larger of two small hosts; larger sea lampreys attacked larger hosts in proportion to the hosts' body sizes, but actively avoided shorter hosts (a?? 600 mm) when larger were available. Host mortality was significantly less for larger (43-44%) than for smaller hosts (64%). However, the yearly loss of hosts per sea lamprey was less for small hosts (range, 6.8-14.2 kg per sea lamprey) than larger hosts (range, 11.4-19.3 kg per sea lamprey). Attacks at the lower of two temperature ranges (6.1-11.8A?C and 11.1-15.0A?C) did not significantly reduce the percentage of hosts killed (54% vs. 69%, p > 0.21), but longer attachment times at lower temperatures reduced the number of hosts attacked (33 vs. 45), and produced the lowest loss of hosts (6.6 kg per sea lamprey). Low temperature appeared to offset other factors that increase host mortality. Reanalysis of 789 attacks pooled from these studies, using forward stepwise logistic regression, also identified mean daily temperature as the dominant factor affecting host mortality. Observations in Lakes Superior, Huron, and Ontario support most laboratory results.

Swink, William D.

2003-01-01

254

Laboratory and Field Experiments on Expulsion of Selected Ions along Divergent Polar Geomagnetic Fields  

NASA Astrophysics Data System (ADS)

Laboratory and Field Experiments on Expulsion of Selected Ions along Divergent Polar Geomagnetic Fields. Laboratory experiments have shown significant gyro-resonance acceleration of minority ion species in a magnetized plasma. Field aligned elctron drifts can provide free energy needed to make this process efficient. The linear magnetized device has a uniform magnetic field linked to two adjustable mirrors at the ends. Outdoor experiments at HIPAS Facility Ak(1) ( 84 MW ERP ) are used to test this process in the earth's "chimneys" at the two poles. The divergent polar geomagnetic field converts the perpendicular ion velocity into an upward motion. Satellites and ground-based ELF receivers,supplemented by UHF radars, LIDARs and infrared diagnostics , will monitor low-frequency EM waves and upflows of ions. The upward transport of ions in the lower atmosphere by field-induced diffusion and convection and the coupling to the free energy in the auroral region will be discussed. Computer modeling and theoeries complement our experiments. 1. Wong, A.Y. et al. AIP CIP 96-27719, Chap 3, pp 41-75, 1997

Wong, A. Y.; Deng, B.; Quon, B.; Wang, R.; Hartzell, J.; Rosenthal, G.; Hazelton, L. R.

2007-12-01

255

Fisher's fundamental theorem of inclusive fitness and the change in fitness due to natural selection when conspecifics interact  

Microsoft Academic Search

Competition and cooperation is fundamental to evolution by natural selection, both in animals and plants. Here, I investigate the consequences of such interactions for response in fitness due to natural selection. I provide quantitative genetic expressions for heritable variance and response in fitness due to natural selection when conspecifics interact. Results show that interactions among conspecifics generate extra heritable variance

P. Bijma

2010-01-01

256

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

PubMed

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

Artacho, Paulina; Nespolo, Roberto F

2009-01-06

257

Natural selection in the water: freshwater invasion and adaptation by water colour in the Amazonian pufferfish.  

PubMed

Natural selection and ecological adaptation are ultimately responsible for much of the origin of biodiversity. Yet, the identification of divergent natural selection has been hindered by the spatial complexity of natural systems, the difficulty in identifying genes under selection and their relationship to environment, and the confounding genomic effects of time. Here, we employed genome scans, population genetics and sequence-based phylogeographic methods to identify divergent natural selection on population boundaries in a freshwater invader, the Amazonian pufferfish, Colomesus asellus. We sampled extensively across markedly different hydrochemical settings in the Amazon Basin and use 'water colour' to test for ecological isolation. We distinguish the relative contribution of natural selection across hydrochemical gradients from biogeographic history in the origin and maintenance of population boundaries within a single species and across a complex ecosystem. We show that spatially distinct population structure generated by multiple forces (i.e. water colour and vicariant biogeographic history) can be identified if the confounding effects of genetic drift have not accumulated between selective populations. Our findings have repercussions for studies aimed at identifying engines of biodiversity and assessing their temporal progression in understudied and ecologically complex tropical ecosystems. PMID:22551113

Cooke, G M; Chao, N L; Beheregaray, L B

2012-05-03

258

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

ERIC Educational Resources Information Center

|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…

Reynolds, David

259

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

ERIC Educational Resources Information Center

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…

Reynolds, David

260

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

SciTech Connect

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.

Pawloski, G A

2011-02-28

261

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

PubMed

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

Richards, Robert J

2011-10-29

262

Natural Selection Affects Multiple Aspects of Genetic Variation at Putatively Neutral Sites across the Human Genome  

PubMed Central

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.

Lohmueller, Kirk E.; Albrechtsen, Anders; Li, Yingrui; Kim, Su Yeon; Korneliussen, Thorfinn; Vinckenbosch, Nicolas; Tian, Geng; Huerta-Sanchez, Emilia; Feder, Alison F.; Grarup, Niels; J?rgensen, Torben; Jiang, Tao; Witte, Daniel R.; Sandbaek, Annelli; Hellmann, Ines; Lauritzen, Torsten; Hansen, Torben

2011-01-01

263

SOS induction of selected naturally occurring substances in Escherichia coli (SOS chromotest)  

Microsoft Academic Search

Naturally occurring substances were tested for genotoxicity using a modified laboratory protocol of the Escherichia coli PQ37 genotoxicity assay (SOS chromotest) in the presence and in the absence of an exogenous metabolizing system from rat liver S9-mix. Aristolochic acid I, II, the plant extract aristolochic acid and psoralene were genotoxic; cycasine, emodine, monocrotaline and retrorsine were classified as marginal genotoxic

Sebastian Kevekordes; Volker Mersch-Sundermann; Christian M Burghaus; Jan Spielberger; Heinz H Schmeiser; Volker M Arlt; Hartmut Dunkelberg

1999-01-01

264

Natural selection acts on Atlantic salmon major histocompatibility (MH) variability in the wild  

PubMed Central

Pathogen-driven balancing selection is thought to maintain polymorphism in major histocompatibility (MH) genes. However, there have been few empirical demonstrations of selection acting on MH loci in natural populations. To determine whether natural selection on MH genes has fitness consequences for wild Atlantic salmon in natural conditions, we compared observed genotype frequencies of Atlantic salmon (Salmo salar) surviving in a river six months after their introduction as eggs with frequencies expected from parental crosses. We found significant differences between expected and observed genotype frequencies at the MH class II alpha locus, but not at a MH class I-linked microsatellite or at seven non-MH-linked microsatellite loci. We therefore conclude that selection at the MH class II alpha locus was a result of disease-mediated natural selection, rather than any demographic event. We also show that survival was associated with additive allelic effects at the MH class II alpha locus. Our results have implications for both the conservation of wild salmon stocks and the management of disease in hatchery fish. We conclude that natural or hatchery populations have the best chance of dealing with episodic and variable disease challenges if MH genetic variation is preserved both within and among populations.

de Eyto, Elvira; McGinnity, Philip; Consuegra, Sofia; Coughlan, Jamie; Tufto, Jarle; Farrell, Killian; Megens, Hendrik-Jan; Jordan, William; Cross, Tom; Stet, Rene J.M

2007-01-01

265

Nest-site selection pattern of Grus japonensis in Zhalong Nature Reserve of northeast China  

Microsoft Academic Search

Nest-site selection patterns of Red-crowned cranes (Grus japonensis) and the effects of environmental variables were studied during the years of 2002–2008 in Zhalong Nature Reserve, Qiqihar\\u000a city, northeast China. The nest-site selection pattern of Red-crowned cranes included two orders and three choices: the choice\\u000a of nest-site habitat type within the macro-habitat order, nest zone selection and nest-site microhabitat selection within

Qing-ming Wu; Hong-fei Zou

2011-01-01

266

An example of a natural laboratory for studying the microstructural and petrophysical properties in mylonitic leucogneiss  

NASA Astrophysics Data System (ADS)

In the southern border of the Calabrian Peloritani Orogen (southern Italy) near to the mount Montalto, a thick alpine shear zone crops out interposed between two units: the Aspromonte Unit at the top and the Madonna di Polsi Unit at the bottom, respectively. The crustal-scale shear zone involves different rock types of these two units and can be considered as a natural laboratory for studying the changes in microstructural features and elastic properties of progressively deformed mylonitic rocks. In order to evaluate the relationship between rock fabric and seismic anisotropy, we collected a suite of myonitic leucogneiss belonging to the Aspromonte Unit. They are mostly made up of Qtz+Ab+Wm+Kfs together with subordinate amounts of Bt+Ep+Chl+Tur. The texture of these leucocratic gneisses ranges from weakly deformed mylonite to ultramylonite; the progressive mylonitization is demonstrated by decreasing in grain-size of the pre-kinematic porphyroclasts associated with increase in SPO and syn-mylonitic growth of high phengite white mica and plagioclase albitization. We present here the results of an integrated microstructural study which combines both modern and classical techniques (e.g. C.I.P. method and U-stage approach) and petrophysical investigation consisting of laboratory seismic measurements at various pressure conditions (up to 600MPa) as well as calculations of elastic properties of the mylonitc rock considered as a poly-mineral and poly-crystalline aggregate. Our data suggest that a close relationship exists between bulk seismic anisotropy and petrofabric features. The most important consideration that we can set out is that the mineralogical changes, together with the strain partitioning, are the main factors responsible for the changes in elastic properties observed in the studied mylonitic leucogneiss during the progressive deformation.

Punturo, Rosalda; Cirrincione, Rosolino; Fazio, Eugenio; Heilbronner, Renée.; Kern, Hartmut; Mengel, Kurt; Ortolano, Gaetano; Pezzino, Antonino

2010-05-01

267

Robust Metabolic Responses to Varied Carbon Sources in Natural and Laboratory Strains of Saccharomyces cerevisiae  

PubMed Central

Understanding factors that regulate the metabolism and growth of an organism is of fundamental biologic interest. This study compared the influence of two different carbon substrates, dextrose and galactose, on the metabolic and growth rates of the yeast Saccharomyces cerevisiae. Yeast metabolic and growth rates varied widely depending on the metabolic substrate supplied. The metabolic and growth rates of a yeast strain maintained under long-term laboratory conditions was compared to strain isolated from natural condition when grown on different substrates. Previous studies had determined that there are numerous genetic differences between these two strains. However, the overall metabolic and growth rates of a wild isolate of yeast was very similar to that of a strain that had been maintained under laboratory conditions for many decades. This indicates that, at in least this case, metabolism and growth appear to be well buffered against genetic differences. Metabolic rate and cell number did not co-vary in a simple linear manner. When grown in either dextrose or galactose, both strains showed a growth pattern in which the number of cells continued to increase well after the metabolic rate began a sharp decline. Previous studied have reported that O2 consumption in S. cerevisiae grown in reduced dextrose levels were elevated compared to higher levels. Low dextrose levels have been proposed to induce caloric restriction and increase life span in yeast. However, there was no evidence that reduced levels of dextrose increased metabolic rates, measured by either O2 consumption or CO2 production, in the strains used in this study.

Van Voorhies, Wayne A.

2012-01-01

268

Inferring natural selection operating on conservative and radical substitution at single amino acid sites.  

PubMed

Natural selection operating on amino acid substitution at single amino acid sites can be detected by comparing the rates of synonymous (r(S)) and nonsynonymous (r(N)) nucleotide substitution at single codon sites. Amino acid substitutions can be classified as conservative or radical according to whether they retain the properties of the substituted amino acid. Here methods for comparing the rates of conservative (r(C)) and radical (r(R)) nonsynonymous substitution with r(S) at single codon sites were developed to detect natural selection operating on these substitutions at single amino acid sites. A method for comparing r(C) and r(R) at single codon sites was also developed to detect biases toward these substitutions at single amino acid sites. Charge was used as the property of the amino acids. In a computer simulation, false-positive rates of these methods were always < 5%, unless termination sites were included in the computation of the numbers of sites and estimates of transition/transversion rate ratio were highly biased. The frequency of detection of natural selection operating on conservative substitution was almost independent of the presence of natural selection operating on radical substitution, and vice versa. Natural selection operating specifically on conservative and radical substitution was detected more efficiently by comparing r(S) with r(C) and r(S) with r(R) than by comparing r(S) with r(N). These methods also appeared to be robust against the occurrence of recombination during evolution. In an analysis of class I human leukocyte antigen, negative selection operating on conservative substitution, but not positive selection operating on radical substitution, was observed at some of the codon sites with r(R) > r(C), suggesting that r(R) > r(C) may not necessarily be an indicator of positive selection operating on radical substitution. PMID:17895585

Suzuki, Yoshiyuki

2007-08-01

269

Physical properties and rock physics models of sediment containing natural and laboratory-formed methane gas hydrate  

USGS Publications Warehouse

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.

Winters, W. J.; Pecher, I. A.; Waite, W. F.; Mason, D. H.

2004-01-01

270

Natural selection on molar size in a wild population of howler monkeys (Alouatta palliata).  

PubMed Central

Dental traits have long been assumed to be under selection in mammals, based on the macroevolutionary correlation between dental morphology and feeding behaviour. However, natural selection acting on dental morphology has rarely, if ever, been documented in wild populations. We investigated the possibility of microevolutionary selection on dental traits by measuring molar breadth in a sample of Alouatta palliata (mantled howler monkey) crania from Barro Colorado Island (BCI), Panama. The age at death of the monkeys is an indicator of their fitness, since they were all found dead of natural causes. Howlers with small molars have significantly decreased fitness as they die, on average, at an earlier age (well before sexual maturity) than those with larger molars. This documents the existence of phenotypic viability selection on molar tooth size in the BCI howlers, regardless of causality or heritability. The selection is further shown to occur during the weaning phase of A. palliata life history, establishing a link between this period of increased mortality and selection on a specific morphological feature. These results provide initial empirical support for the long-held assumption that primate molar size is under natural selection.

DeGusta, David; Everett, Melanie A; Milton, Katharine

2003-01-01

271

Immune versus natural selection: antibody aldolases with enzymic rates but broader scope.  

PubMed

Structural and mechanistic studies show that when the selection criteria of the immune system are changed, catalytic antibodies that have the efficiency of natural enzymes evolve, but the catalytic antibodies are much more accepting of a wide range of substrates. The catalytic antibodies were prepared by reactive immunization, a process whereby the selection criteria of the immune system are changed from simple binding to chemical reactivity. This process yielded aldolase catalytic antibodies that approximated the rate acceleration of the natural enzyme used in glycolysis. Unlike the natural enzyme, however, the antibody aldolases catalyzed a variety of aldol reactions and decarboxylations. The crystal structure of one of these antibodies identified the reactive lysine residue that was selected in the immunization process. This lysine is deeply buried in a hydrophobic pocket at the base of the binding site, thereby accounting for its perturbed pKa. PMID:9405338

Barbas, C F; Heine, A; Zhong, G; Hoffmann, T; Gramatikova, S; Björnestedt, R; List, B; Anderson, J; Stura, E A; Wilson, I A; Lerner, R A

1997-12-19

272

Natural image understanding using algorithm selection and high-level feedback  

NASA Astrophysics Data System (ADS)

Natural Image processing and understanding encompasses hundreds or even thousands of different algorithms. Each algorithm has a certain peak performance for a particular set of input features and configurations of the objects/regions of the input image (environment). To obtain the best possible result of processing, we propose an algorithm selection approach that permits to always use the most appropriate algorithm for the given input image. This is obtained by at first selecting an algorithm based on low level features such as color intensity, histograms, spectral coefficients. The resulting high level image description is then analyzed for logical inconsistencies (contradictions) that are then used to refine the selection of the processing elements. The feedback created from the contradiction information is executed by a Bayesian Network that integrates both the features and a higher level information selection processes. The selection stops when the high level inconsistencies are all resolved or no more different algorithms can be selected.

Lukac, Martin; Kameyama, Michitaka; Hiura, Kosuke

2013-01-01

273

The Antei uranium deposit: A natural analogue of an SNF repository and an underground geodynamic laboratory in granite  

Microsoft Academic Search

The estimation of the long-term stability of crystalline rock massifs with respect to natural and technogenic loads in the\\u000a course of long-term storage of spent nuclear fuel (SNF) is a special area of surveys at underground research laboratories\\u000a (URLs). In parallel with these surveys, data on uranium deposits—natural analogues of repositories of SNF consisting of 95%\\u000a UO2—are used for obtaining

N. P. Laverov; V. A. Petrov; V. V. Poluektov; R. M. Nasimov; J. Hammer; A. A. Burmistrov; S. I. Shchukin

2008-01-01

274

Laboratory studies of groundwater degassing in replicas of natural fractured rock for linear flow geometry  

SciTech Connect

Laboratory experiments to simulate two-phase (gas and water) flow in fractured rock evolving from groundwater degassing were conducted in transparent replicas of natural rock fractures. These experiments extend the work by Geller et al. (1995) and Jarsjo and Geller (1996) that tests the hypothesis that groundwater degassing caused observed flow reductions in the Stripa Simulated Drift Experiment (SDE). Understanding degassing effects over a range of gas contents is needed due to the uncertainty in the gas contents of the water at the SDE. The main objectives of this study were to: (1) measure the effect of groundwater degassing on liquid flow rates for lower gas contents than the values used in Geller for linear flow geometry in the same fracture replicas of Geller; (2) provide a data set to develop a predictive model of two-phase flow in fractures for conditions of groundwater degassing; and (3) improve the certainty of experimental gas contents (this effort included modifications to the experimental system used by Geller et al. and separate gas-water equilibration tests). The Stripa site is being considered for a high-level radioactive waste repository.

Geller, J.T.

1998-02-01

275

Laboratory chemical remanent magnetization in a natural claystone: a record of two magnetic polarities  

NASA Astrophysics Data System (ADS)

A record of two magnetic polarities during the acquisition by heating of a laboratory chemical remanent magnetization (CRM) in a natural pyrite-rich claystone was investigated. The samples were heated for 22 hr at 250 °C in a controlled magnetic field (1.0 mT) under an argon atmosphere. We interpret the origin of CRM as the surface oxidation of pyrite to magnetite, which in turn is progressively oxidized into haematite. We carried out experiments under a constant-polarity magnetic field and under two opposite polarities. The resulting CRM was measured after cooling in zero field: it is parallel to the applied field and has the direction of the last polarity. Thermal demagnetization under an argon atmosphere isolates an unexpected low-unblocking-temperature component (TUB < 220 °C). This component probably results from thermal alteration of magnetic carriers during subsequent thermal demagnetization. In the one-polarity experiments, thermal demagnetization of CRM above 220 °C isolates a well-defined component parallel to the imparted field direction. In the experiments with two magnetic polarities thermal demagnetization of CRM reveals two components of opposite polarity. The component which is parallel to the direction of the last applied field is well defined, while the other component, which has the polarity of the first applied field, is ill defined. Oppositely directed components are also detected by using alternating field demagnetization.

Cairanne, G.; Aubourg, C.; Pozzi, J.-P.; Moreau, M.-G.; Decamps, T.; Marolleau, G.

2004-12-01

276

Selection on floral traits through male fertility in a natural plant population  

Microsoft Academic Search

Most studies on selection in plants estimate female fitness components and neglect male mating success, although the latter\\u000a might also be fundamental to understand adaptive evolution. Information from molecular genetic markers can be used to assess\\u000a determinants of male mating success through parentage analyses. We estimated paternal selection gradients on floral traits\\u000a in a large natural population of the herb

Mark van Kleunen; Jaroslaw Burczyk

2008-01-01

277

Form and nature of precopulatory sexual selection in both sexes of a moth  

Microsoft Academic Search

Sexual selection is a process that operates through intrasexual competition and intersexual choice for reproduction in both\\u000a 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.\\u000a We show that, although a number of traits measured in each sex are

Jin Xu; Qiao Wang

2010-01-01

278

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

USGS Publications Warehouse

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.

Kuivila, Kathryn M.; Crepeau, Kathryn L.

1999-01-01

279

Binding of Bacillus thuringiensis proteins to a laboratory-selected line of Heliothis virescens.  

PubMed Central

A laboratory-selected colony of Heliothis virescens displaying a 20- to 70-fold level of resistance to Bacillus thuringiensis proteins was evaluated to identify mechanism(s) of resistance. Brush-border membrane vesicles were isolated from larval midgut epithelium from the susceptible and resistant strains of H. virescens. Two B. thuringiensis proteins, CryIA(b) and CryIA(c), were iodinated and shown to specifically bind to brush-border membrane vesicles of both insect strains. Multiple changes in the receptor-binding parameters were seen in the resistant strain as compared with the susceptible strain. A 2- to 4-fold reduction in binding affinity was accompanied by a 4- to 6-fold increase in binding-site concentration for both proteins. Although these two B. thuringiensis proteins competed for the same high-affinity binding site, competition experiments revealed different receptor specificity toward these proteins in the resistant H. virescens line. The H. virescens strains were not sensitive to a coleopteran-active protein, CryIIIA, nor did these proteins compete with the CryIA proteins for binding. Complexity of the mechanism of resistance is consistent with the complex mode of action of B. thuringiensis proteins.

MacIntosh, S C; Stone, T B; Jokerst, R S; Fuchs, R L

1991-01-01

280

Evolution of premating reproductive isolation among conspecific populations of the sea rock-pool beetle Ochthebius urbanelliae driven by reinforcing natural selection.  

PubMed

How natural selection might be involved in speciation remains a fundamental question in evolutionary biology. When two or more species co-occur in the same areas, natural selection may favor divergence in mating traits. By acting in sympatric but not allopatric populations, natural selection can also affect mate choice within species and ultimately initiate speciation among conspecific populations. Here, we address this potential effect in the sea rock-pool beetles Ochthebius quadricollis and O. urbanelliae. The two species, which inhabit the Mediterranean coasts, co-occurr syntopically in an area along the Italian Tyrrhenian coast and completed reproductive isolation by reinforcement. In this article, through mating trials under laboratory conditions between conspecific populations, we found in O. quadricollis no deviations from random mating. Conversely, in O. urbanelliae, we found a clear pattern of premating isolation between the reinforced populations sympatric with O. quadricollis and those nonreinforced allopatric. This pattern is consistent with the view that natural selection, which completed the reproductive isolation between the two species in sympatry, led incidentally also to partial premating reproductive isolation (I(PSI) estimator from 0.683 to 0.792) between conspecific populations of O. urbanelliae. This case study supports an until recently underappreciated role of natural selection resulting from species interactions in initiating speciation. PMID:22486705

Porretta, Daniele; Urbanelli, Sandra

2012-01-03

281

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

PubMed

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

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

2013-08-09

282

Active habitat selection by megalopae and juvenile shore crabs Carcinus maenas: a laboratory study in an annular flume  

Microsoft Academic Search

We studied megalopae (postlarvae) and young juveniles of the shore crab ( Carcinus maenas L.) in laboratory experiments to\\u000a examine four potentially important processes for juvenile distribution and recruitment: (1) hydrodynamic processes and passive\\u000a deposition of megalopae, (2) active habitat selection of megalopae, (3) habitat specific predation rates, and (4) active habitat\\u000a selection by juveniles. In an annular flume, simulating

Ola Hedvall; Per-Olav Moksnes; Leif Pihl

1998-01-01

283

The External Validity of Behavioral Fear AssessmentThe Problem of Generalizing from the Laboratory to the Natural Environment  

Microsoft Academic Search

This article reviews the literature relevant to the external validity of laboratory tests: (a) the degree to which the fear-eliciting stimuli in behavior tests adequately represent the phobia-relevant situations that subjects encounter in the natural environment, and (b) the effects of measurement reactivity on subjects' responses to these stimuli. We then review the small amount of empirical research correlating subjects'

John R. Lick; Thomas E. Unger

1977-01-01

284

[Variability of reproduction examined in the laboratory between natural populations of Helix aspersa Müller from the Brittany region].  

PubMed

Laboratory experiments were conducted to investigate the effects of geographical localization of natural populations and sampling dates on the reproduction of the garden snail Helix aspersa Müller. In Brittany, reproductive variability between populations shows the adaptive flexibility of characters describing reproductive activity and the relative stability of reproductive ability. PMID:1768314

Madec, L; Daguzan, J

1991-01-01

285

Implementation of the Lawrence Livermore National Laboratory Elementary Science Study of Nature (LESSON) in North Alabama elementary and middle schools  

Microsoft Academic Search

The Alabama A M University - Lawrence Livermore National Laboratory (LLNL) Elementary Science Study of Nature (ALALESSON) was designed to improve elementary and middle school science in North Alabama by involving teachers in two-week summer workshop as well as other follow-up activities. The purpose of the activities was to increase the science knowledge of the teachers and to provide them

McGuire

1989-01-01

286

A Method for Studying Natural Ventilation by Thermal Effects in a Tunnel Greenhouse using Laboratory-Scale Models  

Microsoft Academic Search

A laboratory method for the physical simulation of natural ventilation by thermal effects in greenhouses is presented. Scale models of a tunnel greenhouse were constructed and immersed in a water tank. A solution of salty water and black dye was injected to produce density differences that simulated the buoyancy flux due to the heating of the greenhouse air. Flow was

J. Oca; J. I. Montero; A. Antón; D. Crespo

1999-01-01

287

Improvement of the Resistance of Lactobacillus delbrueckii ssp. bulgaricus to Freezing by Natural Selection  

Microsoft Academic Search

Lactic acid bacteria are often produced as frozen or freeze-dried cultures that can be used for the direct inoculation of milk in cheese and fermented milk pro- duction processes. The objective of this study was to investigate whether the resistance of Lactobacillus del- brueckii ssp. bulgaricus to freezing could be improved by natural selection. Three parallel cultures of strain CFL1

C. Monnet; C. Béal; G. Corrieu

2003-01-01

288

The genomics of natural selection and adaptation: Christmas past, present and future(?)  

Microsoft Academic Search

Background: Genomic analyses are being applied to ‘non-model’ species. These complexes are now ‘models’ for applying genomic approaches to test evolutionary hypotheses. These approaches have revealed the genetic underpinnings of natural selection and adaptation.Aims: We wish to illustrate that the newest techniques in genomics would not be possible without older technological and methodological advances. We also point to the necessity

Michael L. Arnold; Evangeline S. Ballerini; Amanda N. Brothers; Jennafer A. P. Hamlin; Caitlin D. A. Ishibashi; Matthew P. Zuellig

2012-01-01

289

Winter Habitat Selection of Mule Deer Before and During Development of a Natural Gas Field  

Microsoft Academic Search

Increased levels of natural gas exploration, development, and production across the Intermountain West have created a variety of concerns for mule deer (Odocoileus hemionus) populations, including direct habitat loss to road and well-pad construction and indirect habitat losses that may occur if deer use declines near roads or well pads. We examined winter habitat selection patterns of adult female mule

HALL SAWYER; RYAN M. NIELSON; FRED LINDZEY; LYMAN L. McDONALD

2006-01-01

290

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

ERIC Educational Resources Information Center

|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…

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

2012-01-01

291

Species Recommended for Highway Plantings Selected from a Natural Vegetation Survey in the Panhandle in Nebraska.  

National Technical Information Service (NTIS)

A natural flora survey was made in western Nebraska from which selected species are recommended for propagation on the highway right of ways. Only species found to be successfully self-sustaining in the semi-arid portion of the region are described. Inclu...

J. M. B. McGowan

1973-01-01

292

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

ERIC Educational Resources Information Center

|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…

Nehm, Ross H.; Haertig, Hendrik

2012-01-01

293

Haemophilus influenzae: Genetic Variability and Natural Selection To Identify Virulence Factors  

Microsoft Academic Search

The evolutionary processes of natural selection govern the nucleotide sequences of bacterial genes such that during rep- lication over many generations, bacterial virulence factor genes change and their products become diverse. This diversity, which both facilitates and reflects an organism's ability to sur- vive in a variety of ecologic niches and under different envi- ronmental conditions, occurs through two general

Janet R. Gilsdorf; Carl F. Marrs; Betsy Foxman

2004-01-01

294

EVALUATION OF THE SELECT SYNCH PROTOCOL WITH NATURAL SERVICE IN BEEF COWS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objective of this study was to evaluate the Select Synch estrous synchronization protocol with natural service in beef cowherds. This study was conducted in four cowherds ranging in size from 151 to 285 cows located in central Colorado and central and eastern Montana. Within each herd, approxi...

295

Common Garden and Natural Selection Experiments Support Ecotypic Differentiation in the Dominican Anole ( Anolis oculatus )  

Microsoft Academic Search

The theory behind ecotypic differentiation and ecological speciation assumes a predominant role for natural selection working on characteristics with genetic variance, but experimental support for these assumptions is limited. Lesser Antillean anoles show marked ecotypic variation within islands and the potential for ecological spe- ciation. Common garden rearing experiments on the Dominican anole (Anolis oculatus) suggest that the characters showing

Anita Malhotra

2005-01-01

296

Population genetics of marine species: the interaction of natural selection and historically differentiated populations  

Microsoft Academic Search

High gene flow, particularly as mediated by larval dispersal, has usually been viewed as sufficient to limit geographic isolation as a major source of population differentiation among marine species. Despite the general observation of relatively little geographic variation among populations of high dispersal marine species many cases of divergence have been observed and natural selection has usually been invoked to

Thomas J. Hilbish

1996-01-01

297

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

Microsoft Academic Search

Evolution by natural selection may becharacterized as a system in which a largestore of genetic information will persistindefinitely while it remains coordinated withits environment but will continuously producesmall random variations that are tested forenvironmental effectiveness. In anyenvironment, effective variations will persistwhile ineffective variations will disappear.Similarly, human cognitive architectureincludes a large store of information held inlong-term memory that coordinates our cognitiveactivities.

John Sweller

2004-01-01

298

Mutation pressure, natural selection, and the evolution of base composition in Drosophila  

Microsoft Academic Search

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 melanogastervarys regionally, and

Hiroshi Akashi; Richard M. Kliman

1998-01-01

299

The effect of natural selection on the performance of maximum parsimony  

Microsoft Academic Search

BACKGROUND: Maximum parsimony is one of the most commonly used and extensively studied phylogeny reconstruction methods. While current evaluation methodologies such as computer simulations provide insight into how well maximum parsimony reconstructs phylogenies, they tell us little about how well maximum parsimony performs on taxa drawn from populations of organisms that evolved subject to natural selection in addition to the

Dehua Hang; Eric Torng; Charles Ofria; Thomas M Schmidt

2007-01-01

300

On Theoretical Models of Gene Expression Evolution with Random Genetic Drift and Natural Selection  

Microsoft Academic Search

BackgroundThe relative contributions of natural selection and random genetic drift are a major source of debate in the study of gene expression evolution, which is hypothesized to serve as a bridge from molecular to phenotypic evolution. It has been suggested that the conflict between views is caused by the lack of a definite model of the neutral hypothesis, which can

Osamu Ogasawara; Kousaku Okubo; Justin C. Fay

2009-01-01

301

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

ERIC Educational Resources Information Center

|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…

Bishop, Beth A.; Anderson, Charles W.

302

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

ERIC Educational Resources Information Center

|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…

Sweller, John

2004-01-01

303

Were neandertal and modern human cranial differences produced by natural selection or genetic drift?  

Microsoft Academic Search

Most evolutionary explanations for cranial differences between Neandertals and modern humans emphasize adaptation by natural selection. Features of the crania of Neandertals could be adaptations to the glacial climate of Pleistocene Europe or to the high mechanical strains produced by habitually using the front teeth as tools, while those of modern humans could be adaptations for articulate speech production. A

Timothy D. Weaver; Charles C. Roseman; Chris B. Stringer

2007-01-01

304

The use of naturally occurring selectively isolated bacteria for inhibiting paraffin deposition  

Microsoft Academic Search

One of the most severe problems at any oil fields producing paraffinic oils is that of paraffin depositions. Romania which has a long experience in oil production is also faced with this problem in many oil fields. The microbial treatment, based on the activity of naturally occurring, selectively isolated bacteria, is already proved as an effective alternative to conventional methods

I Lazar; A Voicu; C Nicolescu; D Mucenica; S Dobrota; I. G Petrisor; M Stefanescu; L Sandulescu

1999-01-01

305

Natural and sexual selection against immigrants maintains differentiation among micro-allopatric populations  

Microsoft Academic Search

Local adaptation to divergent environmental conditions can promote popu- lation genetic differentiation even in the absence of geographic barriers and hence lead to speciation. But what mechanisms contribute to reproductive isolation among diverging populations? We tested for natural and sexual selection against immigrants in a fish species inhabiting (and adapting to) nonsulphidic surface habitats, sulphidic surface habitats and a sulphidic

M. TOBLER; R. RIESCH; C. M. TOBLER; T. SCHULZ-MIRBACH

2009-01-01

306

An Experimental Comparison of Direct-Detailed Versus Directed Discovery Laboratory Exercises in Teaching Selected Elements of Basic Electricity.  

ERIC Educational Resources Information Center

|The purpose of this study was to ascertain the ef"ects of direct-detailed and directed discovery laboratory methods on selected behavior characteristics of college students during a 3-week period. The 120 students wer" enrolled in three sections of an electricity course under three teachers. During the first 3 weeks of the experiment, 20 students…

Brenner, Charles J.

307

Host Species and Environmental Effects on Bacterial Communities Associated with Drosophila in the Laboratory and in the Natural Environment  

PubMed Central

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.

Staubach, Fabian; Baines, John F.; Kunzel, Sven; Bik, Elisabeth M.; Petrov, Dmitri A.

2013-01-01

308

Laboratory Constraints on the Stability of Petroleum at Elevated Temperatures: Implications for the Origin of Natural Gas  

SciTech Connect

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.

Seewald, Jeffrey, S.

2011-03-14

309

Low pH Springs - A Natural Laboratory for Ocean Acidification  

NASA Astrophysics Data System (ADS)

Recent increases in atmospheric carbon dioxide of 40% above pre-industrial levels has resulted in rising aqueous CO2 concentrations that lower the pH of the oceans. Currently, the surface ocean has an average pH between 8.1 and 8.2: it is estimated that over the next 100 years this value will decrease by ~0.4 pH units. Previous studies have highlighted the negative impacts that changes in pH (and the resulting CaCO3 saturation state) have on marine organisms; however, to date, very little is known about the long-term impacts of ocean acidification on ecosystems as a whole. The Yucatán Peninsula of Quintana Roo, Mexico, represents an ecosystem where naturally low pH groundwater (7.25-8.07) has been discharging offshore at highly localized points (called ojos) since the last deglaciation. We present preliminary chemical and biological data on a selection of ojos from lagoon sites in Puerto Morelos, Mexico. We address the potential long-term implications of low pH waters on marine ecosystems.

Derse, E.; Rebolledo-Vieyra, M.; Potts, D. C.; Paytan, A.

2009-12-01

310

Process for flexibly rejecting selected components obtained from natural gas streams  

SciTech Connect

A continuous process is described for treating a raw inlet natural gas stream to produce: (a) a liquid C/sub 2/+hydrocarbon product having a composition that is selectively adjustable to substantially any selected degree, as the market price for each individual hydrocarbon liquid falls below its fuel price, by selectively rejecting a consecutive molecular weight string of C/sub 2/-C/sub 4/ components and then returning the desirable price component or components to the liquid products stream and (b) a sweet, dry residue natural gas stream of pipeline quality which includes the rejected C/sub 2/, C/sub 3/, and/or C/sub 4/ hydrocarbon components.

Mehra, Y. R.

1985-07-02

311

Genetic polymorphism and natural selection of Duffy binding protein of Plasmodium vivax Myanmar isolates  

PubMed Central

Background Plasmodium vivax Duffy binding protein (PvDBP) plays an essential role in erythrocyte invasion and a potential asexual blood stage vaccine candidate antigen against P. vivax. The polymorphic nature of PvDBP, particularly amino terminal cysteine-rich region (PvDBPII), represents a major impediment to the successful design of a protective vaccine against vivax malaria. In this study, the genetic polymorphism and natural selection at PvDBPII among Myanmar P. vivax isolates were analysed. Methods Fifty-four P. vivax infected blood samples collected from patients in Myanmar were used. The region flanking PvDBPII was amplified by PCR, cloned into Escherichia coli, and sequenced. The polymorphic characters and natural selection of the region were analysed using the DnaSP and MEGA4 programs. Results Thirty-two point mutations (28 non-synonymous and four synonymous mutations) were identified in PvDBPII among the Myanmar P. vivax isolates. Sequence analyses revealed that 12 different PvDBPII haplotypes were identified in Myanmar P. vivax isolates and that the region has evolved under positive natural selection. High selective pressure preferentially acted on regions identified as B- and T-cell epitopes of PvDBPII. Recombination may also be played a role in the resulting genetic diversity of PvDBPII. Conclusions PvDBPII of Myanmar P. vivax isolates displays a high level of genetic polymorphism and is under selective pressure. Myanmar P. vivax isolates share distinct types of PvDBPII alleles that are different from those of other geographical areas. These results will be useful for understanding the nature of the P. vivax population in Myanmar and for development of PvDBPII-based vaccine.

2012-01-01

312

Genetic polymorphism and natural selection in the malaria parasite Plasmodium falciparum.  

PubMed Central

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.

Escalante, A A; Lal, A A; Ayala, F J

1998-01-01

313

Natural selection influences AFLP intraspecific genetic variability and introgression patterns in Atlantic eels.  

PubMed

Investigating patterns of genetic variation in hybridizing species provides an opportunity to understand the impact of natural selection on intraspecific genetic variability and interspecific gene exchange. The Atlantic eels Anguilla rostrata and A. anguilla each occupy a large heterogeneous habitat upon which natural selection could differentially shape genetic variation. They also produce viable hybrids only found in Iceland. However, the possible footprint of natural selection on patterns of genetic variation within species and introgressive hybridization in Icelandic eels has never been assessed. We revisited amplified fragment length polymorphism data collected previously using population genomics and admixture analyses to test if (i) genetic variation could be influenced by non-neutral mechanisms at both the intra- and interspecific levels, and if (ii) selection could shape the spatio-temporal distribution of Icelandic hybrids. We first found candidate loci for directional selection within both species. Spatial distributions of allelic frequencies displayed by some of these loci were possibly related with the geographical patterns of life-history traits in A. rostrata, and could have been shaped by natural selection associated with an environmental gradient along European coasts in A. anguilla. Second, we identified outlier loci at the interspecific level. Non-neutral introgression was strongly suggested for some of these loci. We detected a locus at which typical A. rostrata allele hardly crossed the species genetic barrier, whereas three other loci showed accelerated patterns of introgression into A. anguilla in Iceland. Moreover, the level of introgression at these three loci increased from the glass eel to the yellow eel stage, supporting the hypothesis that differential survival of admixed genotypes partly explains the spatio-temporal pattern of hybrid abundance previously documented in Iceland. PMID:19302349

Gagnaire, P A; Albert, V; Jónsson, B; Bernatchez, L

2009-03-17

314

The Role of Natural Selection in Genetic Differentiation of Worldwide Populations of Drosophila ananassae  

PubMed Central

The main evolutionary forces leading to genetic differentiation between populations are generally considered to be natural selection, random genetic drift, and limited migration. However, little empirical evidence exists to help explain the extent, mechanism, and relative role of these forces. In this study, we make use of the differential migration behavior of genes located in regions of low and high recombination to infer the role and demographic distribution of natural selection in Drosophila ananassae. Sequence data were obtained from 13 populations, representing almost the entire range of cosmopolitan D. ananassae. The pattern of variation at a 5.1-kb fragment of the furrowed gene, located in a region of very low recombination, appears strikingly different from that of 10 noncoding DNA fragments (introns) in regions of normal to high recombination. Most interestingly, two main haplotypes are present at furrowed, one being fixed in northern populations and the other being fixed or in high frequency in more southern populations. A cline in the frequency of one of these haplotypes occurs in parallel latitudinal transects. Taken together, significant clinal variation and a test against alternative models of natural selection provide evidence of two independent selective sweeps restricted to specific regions of the species range.

Baines, John F.; Das, Aparup; Mousset, Sylvain; Stephan, Wolfgang

2004-01-01

315

Inference of natural selection from interspersed genomic elements based on polymorphism and divergence.  

PubMed

Complete genome sequences contain valuable information about natural selection, but this information is difficult to access for short, widely scattered noncoding elements such as transcription factor binding sites or small noncoding RNAs. Here, we introduce a new computational method, called Inference of Natural Selection from Interspersed Genomically coHerent elemenTs (INSIGHT), for measuring the influence of natural selection on such elements. INSIGHT uses a generative probabilistic model to contrast patterns of polymorphism and divergence in the elements of interest with those in flanking neutral sites, pooling weak information from many short elements in a manner that accounts for variation among loci in mutation rates and coalescent times. The method is able to disentangle the contributions of weak negative, strong negative, and positive selection based on their distinct effects on patterns of polymorphism and divergence. It obtains information about divergence from multiple outgroup genomes using a general statistical phylogenetic approach. The INSIGHT model is efficiently fitted to genome-wide data using an approximate expectation maximization algorithm. Using simulations, we show that the method can accurately estimate the parameters of interest even in complex demographic scenarios, and that it significantly improves on methods based on summary statistics describing polymorphism and divergence. To demonstrate the usefulness of INSIGHT, we apply it to several classes of human noncoding RNAs and to GATA2-binding sites in the human genome. PMID:23386628

Gronau, Ilan; Arbiza, Leonardo; Mohammed, Jaaved; Siepel, Adam

2013-02-05

316

The Himalayas of Nepal, a natural laboratory for the search and measurement of CO2 discharge  

NASA Astrophysics Data System (ADS)

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.

Girault, Frédéric; Koirala, Bharat P.; Bhattarai, Mukunda; Rajaure, Sudhir; Richon, Patrick; Perrier, Frédéric

2010-05-01

317

Detecting the Genetic Signature of Natural Selection in Human Populations: Models, Methods, and Data  

PubMed Central

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.

Hancock, Angela M.; Rienzo, Anna Di

2010-01-01

318

Genome-wide inference of natural selection on human transcription factor binding sites.  

PubMed

For decades, it has been hypothesized that gene regulation has had a 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

Arbiza, Leonardo; Gronau, Ilan; Aksoy, Bulent A; Hubisz, Melissa J; Gulko, Brad; Keinan, Alon; Siepel, Adam

2013-06-09

319

Goal-Side Selection in Soccer Penalty Kicking When Viewing Natural Scenes  

PubMed Central

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.

Weigelt, Matthias; Memmert, Daniel

2012-01-01

320

Elevated Bacterial Abundance in Laboratory-Grown and Naturally Occurring Frost Flowers Under Late Winter Conditions  

NASA Astrophysics Data System (ADS)

Sea ice has been identified as an important microbial habitat, with bacteria and other microbes concentrated in the brine inclusions between ice crystals. Frost flowers, thought to draw brine from underlying sea ice, have not been characterized from a microbial standpoint. To test whether frost flowers serve as an upward vector of bacteria contained within sea ice brines we grew frost flowers in a freezer laboratory (air temperature of -21°C) from saline water spiked with the mesophilic (and thus passive under experimental conditions) bacterium Halomonas pacifica. Salinity of melted samples was measured and bacterial abundance determined by epifluorescent microscopy. Bacterial counts scaled to ice-melt volume averaged 2.82 x 106 ml-1 for frost flowers, compared to 9.47 x 105 ml-1 for underlying ice (3 x higher). Bacterial counts also correlated significantly with salinity (maximum value of 62.5 psu) for frost flowers, brine skim, and ice (df = 17, r = 0.59, p < 0.0001). Segregation coefficients were calculated to describe the efficiency of transport of both cells and salt from the starting solution into frost flowers. From these coefficients an enrichment index was calculated to test for bacterial concentration into frost flowers at a different rate than salt. Analysis with a Student’s T-test (df = 24, t = 0.306, p = .76) indicated that cells and salt were not transported into frost flowers with a significantly different efficiency. To test these findings in the field we then collected frost flowers (and related samples) from new sea ice near Barrow, Alaska in April 2009. Bacterial counts were significantly elevated (again, a 3-fold increase) in natural frost flowers (mean = 2.73 x 105 ml-1) compared to underlying sea ice (mean = 8.46 x 104 cells ml-1). For all field samples collected (frost flowers, underlying brine skim and sea ice, as well as snow), bacterial abundance correlated significantly with salinity (maximum value 124 psu, df = 40, r = 0.60, p < 0.0001). The presence of elevated numbers of bacteria in frost flowers may have implications for the previously observed chemical reactions that take place in them, especially if microbial activity can be shown to occur in this unique low temperature, low water activity microbial habitat.

Bowman, J. S.; Deming, J. W.

2009-12-01

321

Critical laboratory and field evaluation of selected surface prospecting techniques for locating oil and natural gas  

Microsoft Academic Search

The theoretical basis for the radiation HALO method in geochemical exploration for oil and gas is largely unproven but has been covered extensively in the literature. An evaluation of the method was conducted by direct field examination of some of the variables. The variables chosen were surface radiometry, magnetometry, gravity, and near-surface soil sampling. The radiometry included measurements of potassium-40,

R. J. Heemstra; R. M. Ray; T. C. Wesson; J. R. Abrams; G. A. Moore

1979-01-01

322

Coated-Wire Ion Selective Electrodes and Their Application to the Teaching Laboratory.  

ERIC Educational Resources Information Center

|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)|

Martin, Charles R.; Freiser, Henry

1980-01-01

323

Selected NASA (National Aeronautics and Space Administration) JPL (Jet Propulsion Laboratory) Mission Video Images (Videodisc).  

National Technical Information Service (NTIS)

The Selected JPL Mission Video Images-Videodisc consists of a one sided color recording of selected motion picture and television clips. It contains one hour of film and video clips from selected JPL flight missions: Ranger 9 photos of the Moon; Surveyor,...

F. Bristow

1982-01-01

324

Evidence for evolution in response to natural selection in a contemporary human population.  

PubMed

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

Milot, Emmanuel; Mayer, Francine M; Nussey, Daniel H; Boisvert, Mireille; Pelletier, Fanie; Réale, Denis

2011-10-03

325

Interrogating a High-Density SNP Map for Signatures of Natural Selection  

PubMed Central

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.

Akey, Joshua M.; Zhang, Ge; Zhang, Kun; Jin, Li; Shriver, Mark D.

2002-01-01

326

Identification of innate immunity elicitors using molecular signatures of natural selection  

PubMed Central

The innate immune system is an ancient and broad-spectrum defense system found in all eukaryotes. The detection of microbial elicitors results in the up-regulation of defense-related genes and the elicitation of inflammatory and apoptotic responses. These innate immune responses are the front-line barrier against disease because they collectively suppress the growth of the vast majority of invading microbes. Despite their critical role, we know remarkably little about the diversity of immune elicitors. To address this paucity, we reasoned that hosts are more likely to evolve recognition to “core” pathogen proteins under strong negative selection for the maintenance of essential cellular functions, whereas repeated exposure to host–defense responses will impose strong positive selective pressure for elicitor diversification to avoid host recognition. Therefore, we hypothesized that novel bacterial elicitors can be identified through these opposing forces of natural selection. We tested this hypothesis by examining the genomes of six bacterial phytopathogens and identifying 56 candidate elicitors that have an excess of positively selected residues in a background of strong negative selection. We show that these positively selected residues are atypically clustered, similar to patterns seen in the few well-characterized elicitors. We then validated selected candidate elicitors by showing that they induce Arabidopsis thaliana innate immunity in functional (virulence suppression) and cellular (callose deposition) assays. These finding provide targets for the study of host–pathogen interactions and applied research into alternative antimicrobial treatments.

McCann, Honour C.; Nahal, Hardeep; Thakur, Shalabh; Guttman, David S.

2012-01-01

327

Natural Gamma Emitters after a Selective Chemical Separation of a TENORM residue: Preliminary Results  

NASA Astrophysics Data System (ADS)

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.

de Freitas, Antonio Alves; Dos Santos, Adir Janete Godoy; Pecequilo, Brigitte Roxana Soreanu; Abra~O, Alcídio

2008-08-01

328

Natural selection on mitochondrial DNA in Parus and its relevance for phylogeographic studies.  

PubMed

I examined mitochondrial ND2 sequences in species of tits (genus Parus) to determine whether substitutions were neutral or under selection. Haplotype trees in these species are shallow and geographically unstructured, which could be a signature of recent demographic expansion or purifying selection. McDonald-Kreitman tests revealed a pattern of excess replacement polymorphisms for closely related taxa. Replacement substitutions tended to be less common in the basal parts of haplotype trees, suggesting that they are selected against over evolutionary time. Thus, the pattern of selection is consistent with a model of mildly deleterious haplotypes. To investigate the significance of this selection, the ND2 gene was subdivided into surface and transmembrane portions, and synonymous-non-synonymous sites, and F(ST)-values (the amount of variance distributed among populations) computed for each. Among sampling localities in P. major, both partitions gave similar estimates of F(ST), which is consistent with demographic expansion as the cause of the shallow trees. In P. montanus, two localities contained high percentages of individuals that had a single replacement substitution in the transmembrane portion of the gene, which inflated F(ST)-values relative to the surface sites. Thus, the interpretation of the genetic differentiation of these two sites could be either geographical isolation or selection. Given that the sole substitution causing the high F(ST)-values was a replacement one, selection is implicated. However, this substitution occurred in only 2 of 12 localities, revealing that overall the phylogeographic pattern was not biased by selection, once the cause of the two high pairwise F(ST)-comparisons was recognized. Investigators should consider the source of significant genetic heterogeneity within species, to determine if the variation is likely caused by demographic isolation or selection. However, it seems unlikely that most phylogeographic analyses are invalidated by the effects of natural selection. PMID:15875572

Zink, Robert M

2005-01-01

329

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 ...

330

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

|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…

Touaibia, Mohamed; Guay, Michel

2011-01-01

331

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

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…

Touaibia, Mohamed; Guay, Michel

2011-01-01

332

Selected Topics in Laboratory Animal Medicine. Volume XVIII. The Squirrel Monkey.  

National Technical Information Service (NTIS)

A summary of the husbandry, diseases, and uses of the squirrel monkey in biomedical research is presented. The fifty-seven references provide source information for this species of laboratory animal. (Author)

J. L. Kupper W. E. Britz

1972-01-01

333

75 FR 53277 - Notice of Intent To Terminate Selected National Voluntary Laboratory Accreditation Program (NVLAP...  

Federal Register 2010, 2011, 2012, 2013

...products, building seals and sealants, plastics, plumbing, roofing, and mattresses...products, building seals and sealants, plastics, plumbing, roofing, and mattresses...laboratories are also accredited for plastic and paint testing in support of...

2010-08-31

334

Multi-robots to micro-surgery: Selected robotic applications at Sandia National Laboratories.  

National Technical Information Service (NTIS)

The Intelligent Systems and Robotics Center (ISRC) at Sandia National Laboratories is a multi-program organization, pursuing research, development and applications in a wide range of field. Activities range from large-scale applications such as nuclear fa...

P. C. Bennett

1996-01-01

335

The Role of Selection in Shaping Diversity of Natural M. tuberculosis Populations  

PubMed Central

Mycobacterium tuberculosis (M.tb), the cause of tuberculosis (TB), is estimated to infect a new host every second. While analyses of genetic data from natural populations of M.tb have emphasized the role of genetic drift in shaping patterns of diversity, the influence of natural selection on this successful pathogen is less well understood. We investigated the effects of natural selection on patterns of diversity in 63 globally extant genomes of M.tb and related pathogenic mycobacteria. We found evidence of strong purifying selection, with an estimated genome-wide selection coefficient equal to ?9.5×10?4 (95% CI ?1.1×10?3 to ?6.8×10?4); this is several orders of magnitude higher than recent estimates for eukaryotic and prokaryotic organisms. We also identified different patterns of variation across categories of gene function. Genes involved in transport and metabolism of inorganic ions exhibited very low levels of non-synonymous polymorphism, equivalent to categories under strong purifying selection (essential and translation-associated genes). The highest levels of non-synonymous variation were seen in a group of transporter genes, likely due to either diversifying selection or local selective sweeps. In addition to selection, we identified other important influences on M.tb genetic diversity, such as a 25-fold expansion of global M.tb populations coincident with explosive growth in human populations (estimated timing 1684 C.E., 95% CI 1620–1713 C.E.). These results emphasize the parallel demographic histories of this obligate pathogen and its human host, and suggest that the dominant effect of selection on M.tb is removal of novel variants, with exceptions in an interesting group of genes involved in transportation and defense. We speculate that the hostile environment within a host imposes strict demands on M.tb physiology, and thus a substantial fitness cost for most new mutations. In this respect, obligate bacterial pathogens may differ from other host-associated microbes such as symbionts.

Pepperell, Caitlin S.; Casto, Amanda M.; Kitchen, Andrew; Granka, Julie M.; Cornejo, Omar E.; Holmes, Eddie C.; Birren, Bruce; Galagan, James; Feldman, Marcus W.

2013-01-01

336

Selective testing of ?-galactosidase activity in the laboratory identification of Salmonella and Shigella species  

Microsoft Academic Search

BackgroundSalmonella and Shigella species are pathogens of great medical and public health importance. However, laboratory identification of these organisms is time consuming. Using current standard laboratory algorithms, the vast majority of organisms submitted for serological typing with Salmonella-specific and Shigella-specific antisera are not clinically significant.AimsTo assess the addition of the O-nitrophenyl-?-d-galactopyranoside (ONPG) test to the standard screening protocol for identification

Samuel Boadi; Mike W D Wren; Stephen Morris-Jones

2010-01-01

337

Laboratory methods for evaluating migrated high molecular weight hydrocarbons in marine sediments at naturally occurring oil seeps  

Microsoft Academic Search

A laboratory study has been conducted to determine the best methods for the detection of C10–C40 hydrocarbons at naturally occurring oil seeps in marine sediments. The results indicate that a commercially available method using n-C6 to extract sediments and gas chromatography–flame ionization detection (GC–FID) to screen the resulting extract is effective at recognizing the presence of migrated hydrocarbons at concentrations

Graham A. Logan; Michael A. Abrams; Nicola F. Dahdah; Emmanuelle Grosjean

2009-01-01

338

Idiosyncratic variations in eye–head coupling observed in the laboratory also manifest during spontaneous behavior in a natural setting  

Microsoft Academic Search

The tendency to generate head movements during saccades varies from person to person. Head movement tendencies can be measured\\u000a as subjects fixate sequences of illuminated targets, but the extent to which such measures reflect eye–head coupling during\\u000a more natural behaviors is unknown. We quantified head movement tendencies in 20 normal subjects in a conventional laboratory\\u000a experiment and in an outdoor

Zachary C. Thumser; Brian S. Oommen; Igor S. Kofman; John S. Stahl

2008-01-01

339

Effects of Natural and Sexual Selection on the Evolution of Guenon Loud Calls  

Microsoft Academic Search

In the Taï Forest, most guenon loud calls show many properties of classic alarm calls: they advertise perception to predators\\u000a and warn recipients about the presence of specific predators, suggesting that they have evolved through natural selection.\\u000a However, several lines of evidence, such as sexual dimorphism in call structure, consistent call usage in non-predatory situations,\\u000a and ontogenetic evidence suggest that

Klaus Zuberbühler

340

Proteolysis on Reggianito Argentino cheeses manufactured with natural whey cultures and selected strains of Lactobacillus helveticus.  

PubMed

Reggianito Argentino cheese is traditionally manufactured with whey starter cultures that provide typical and intense flavor but can cause poor quality standardization. In this study, the influence of natural and selected starters on Reggianito Argentino cheese proteolysis was investigated. Cheeses were manufactured with three strains of Lactobacillus helveticus (SF133, SF138 and SF209) cultured individually in sterile whey and used as single or mixed starters. Control cheeses were made with natural whey starter culture. Cheeses were analyzed to determine gross composition, as well as total thermophilic lactic flora. Proteolysis was assessed by N fractions, electrophoresis and liquid chromatography. Gross composition of the cheeses did not significantly differ, while viable starter cell counts were lower for cheeses made with strain SF209 alone or combined with other strains. Soluble N at pH 4.6 was the same for cheeses made with natural or selected starters, but soluble N in 12% trichloroacetic acid and 2.5% phosphotungstic acid was significantly higher in cheeses made with starters containing strain SF209. Nitrogen fractions results indicated that natural whey starter cultures could be replaced by several starters composed of the selected strains without significant changes to proteolysis patterns. Starter cultures prepared only with SF209 or with the three selected L. helveticus strains produced cheese products with significantly more proteolysis than control cheeses. Chromatographic profiles analyzed by principal components showed that three main peaks on chromatograms, presumptively identified as Tyr, Phe, and Trp, explained most of variability. Principal component scores indicated that cheese samples were grouped by ripening time, which was confirmed by linear discriminant analysis. On the contrary, samples did not cluster by Lactobacillus strain or type of starter. PMID:14740817

Hynes, E R; Bergamini, C V; Suárez, V B; Zalazar, C A

2003-12-01

341

Natural selection theory in non-majors' biology: Instruction, assessment and conceptual difficulty  

NASA Astrophysics Data System (ADS)

Evolution by natural selection is the dominant and unifying theme in biology, yet many college students hold alternative conceptions about the topic even after completing general biology. To develop effective instructional strategies and track conceptual understanding, it is useful to have a detailed assessment tool easily used with large classes. This study presents the Conceptual Inventory of Natural Selection (CINS), a distractor-driven twenty item multiple-choice test that assesses understanding of ten concepts related to natural selection: biotic potential, stable populations, limited natural resources, limited survival, variation within a population, variation inherited, differential survival, change in populations, origin of variation, and origin of species. Development, refinement, and field-testing of individual CINS items are presented, and validity, readability, reliability and factor analysis of the CINS are described. There was significant correlation between student performance on the posttest CINS and end-of-semester interviews suggesting that the CINS is a useful classroom tool. The CINS was used as both a pretest and posttest to determine relative difficulty of the concepts among college students. The three most challenging concepts were random origin of variation, how populations change over time due to changing proportions of alleles, and how new species originate. Many students chose distractors including "need" as a driving force. Results support the use of non-traditional methods, as only students in such classes demonstrated any improvement on the CINS posttest. Pre and posttesting with the CINS was also used to assess relative effectiveness of using two types of supplemental reading materials (selections from narrative, non-textbook sources or from other general biology textbooks) in a general biology course. These results suggest that specific content of readings was more important than style of the readings. Implications for teaching both students and pre-service teachers are described.

Anderson, Dianne L.

342

Darwin's passionate environmentalism or the dangerous fallacy of the 'All-sufficiency of natural selection' theory.  

PubMed

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

Marsh, David

2012-01-01

343

Trace metals in natural iron oxides from laterites: A study using selective kinetic extraction  

Microsoft Academic Search

To determine the extent of metal association in natural iron oxides, a combination of XRD and chemical selective dissolution techniques was applied to four samples from laterites developed on peridotites in East Africa. The reagents used were dithionite-citrate-bicarbonate (DCB), citrate-bicarbonate (CB), hydroxylamine hydrochloride (HH), and oxalic acid-oxalate (Tamm). From the results obtained, it appears that: (1) the difference DCB minus

Fabienne Trolard; Guilhem Bourrie; Emmanuel Jeanroy; Adrien J. Herbillon; Henri Martin

1995-01-01

344

Natural Image Coding in V1: How Much Use is Orientation Selectivity?  

Microsoft Academic Search

Orientation selectivity is the most striking feature of simple cell coding in V1 which has been shown to emerge from the reduction of higher-order correlations in natural images in a large variety of statistical image models. The most parsimonious one among these models is linear Independent Component Analysis (ICA), whereas second-order decorrelation transformations such as Principal Component Analysis (PCA) do

Jan Eichhorn; Fabian Sinz; Matthias Bethge

2008-01-01

345

Evolutionarily stable sets in the single-locus frequency-dependent model of natural selection  

Microsoft Academic Search

Recent developments in the static theory of evolutionarily stable sets (ESSets) are applied to the single-locus frequency-dependent model of natural selection. Particular emphasis is paid to the ESSet properties of the preimage of an ESS (or ESSet) under the genotype-phenotype map. When an ESS is realized in genetic equilibrium with redundancy in a diploid sexual population, the basic problem in

Ross Cressman; József Garay; Zoltán Varga

2003-01-01

346

Zooplanktophagy in the natural diet and selectivity of the invasive mollusk Limnoperna fortunei  

Microsoft Academic Search

Since the 1990s the Río de La Plata basin has been widely colonized by the invader mollusk Limnoperna fortunei. In spite of a relatively well-developed knowledge of the biology and ecology of this mollusk, not much is known about its\\u000a natural diet and possible food selectivity. Stomach contents of 120 specimens attached to the roots of Eichhornia crassipes, and available

Florencia Rojas Molina; Juan César Paggi; Melina Devercelli

2010-01-01

347

QC Validator 2.0: a computer program for automatic selection of statistical QC procedures for applications in healthcare laboratories.  

PubMed

A computer program has been developed to help healthcare laboratories select statistical control rules and numbers of control measurements that will assure the quality required by clinical decision interval criteria or analytical total error criteria. The program (QC Validator 2.0 (QC Validator and OPSpecs are registered trademarks of Westgard Quality Corporation, which has applied for a patent for this automatic QC selection process. Windows is a registered trademark of Microsoft Corporation)) runs on IBM compatible personal computers operating under Windows. The user enters information about the method imprecision, inaccuracy, and expected frequency of errors, defines the quality required in terms of a medically important change (clinical decision interval) or an analytical allowable total error, then initiates automatic selection by indicating the number of control materials that are to be analyzed (1, 2, or 3). The program returns with a chart of operating specifications (OPSpecs chart) that displays the selected control rules and numbers of control measurements. The automatic QC selection process is based on user editable criteria for the types of control rules that can be implemented by the laboratory, total numbers of control measurements that are practical, maximum levels of false rejections that can be tolerated and minimum levels of error detection that are acceptable for detection of medically important systematic or random errors. PMID:9230452

Westgard, J O; Stein, B; Westgard, S A; Kennedy, R

1997-07-01

348

Does natural selection organize ecosystems for the maintenance of high productivity and diversity?  

PubMed

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

Leigh, Egbert Giles; Vermeij, Geerat Jacobus

2002-05-29

349

Probing feature selectivity of neurons in primary visual cortex with natural stimuli  

PubMed Central

One way to characterize neural feature selectivity is to model the response probability as a nonlinear function of the output of a set of linear filters applied to incoming signals. Traditionally these linear filters are measured by probing neurons with correlated Gaussian noise ensembles and calculating correlation functions between incoming signals and neural responses. It is also important to derive these filters in response to natural stimuli, which have been shown to have strongly non-Gaussian spatiotemporal correlations. An information-theoretic method has been proposed recently for reconstructing neural filters using natural stimuli in which one looks for filters whose convolution with the stimulus ensemble accounts for the maximal possible part of the overall information carried the sequence of neural responses. Here we give a first-time demonstration of this method on real neural data, and compare responses of neurons in cat primary visual cortex driven with natural stimuli, noise ensembles, and moving gratings. We show that the information-theoretic method achieves the same quality of filter reconstruction for natural stimuli as that of well-established white-noise methods. Major parameters of neural filters derived from noise ensembles and natural stimuli, as well as from moving gratings are consistent with one another. We find that application of the reverse correlation method to natural stimuli ensembles leads to significant distortions in filters for a majority of studied cells with non-zero reverse-correlation filter.

Sharpee, T.; Sugihara, H.; Kurgansky, A.V.; Rebrik, S.; Stryker, M. P.; Miller, K. D.

2008-01-01

350

Does natural selection organize ecosystems for the maintenance of high productivity and diversity?  

PubMed Central

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.

Leigh, Egbert Giles; Vermeij, Geerat Jacobus

2002-01-01

351

Investigating the Disney Effect: Are Students Reluctant To Apply Natural Selection Principles to Life Forms with Which They Identify?  

ERIC Educational Resources Information Center

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…

Jensen, Murray; And Others

352

Statistical tests for natural selection on regulatory regions based on the strength of transcription factor binding sites  

Microsoft Academic Search

BACKGROUND: Although cis-regulatory changes play an important role in evolution, it remains difficult to establish the contribution of natural selection to regulatory differences between species. For protein coding regions, powerful tests of natural selection have been developed based on comparisons of synonymous and non-synonymous substitutions, and analogous tests for regulatory regions would be of great utility. RESULTS: Here, tests for

Alan M Moses

2009-01-01

353

Beyond the ecological: biological invasions alter natural selection on a native plant species.  

PubMed

Biological invasions can have strong ecological effects on native communities by altering ecosystem functions, species interactions, and community composition. Even though these ecological effects frequently impact the population dynamics and fitness of native species, the evolutionary consequences of biological invasions have received relatively little attention. Here, I show that invasions impose novel selective pressures on a native plant species. By experimentally manipulating community composition, I found that the exotic plant Medicago polymorpha and the exotic herbivore Hypera brunneipennis alter the strength and, in some instances, the direction of natural selection on the competitive ability and anti-herbivore defenses of the native plant Lotus wrangelianus. Furthermore, the community composition of exotics influenced which traits were favored. For example, high densities of the exotic herbivore Hypera selected for increased resistance to herbivores in the native Lotus; however, when Medicago also was present, selection on this defense was eliminated. In contrast, selection on tolerance, another plant defense trait, was highest when both Hypera and Medicago were present at high densities. Thus, multiple exotic species may interact to influence the evolutionary trajectories of native plant populations, and patterns of selection may change as additional exotic species invade the community. PMID:18481527

Lau, Jennifer A

2008-04-01

354

A positively selected APOBEC3H haplotype is associated with natural resistance to HIV-1 infection.  

PubMed

APOBEC3 genes encode cytidine deaminases endowed with the ability to inhibit retroviruses and retrotransposons. These genes have been targets of natural selection throughout primate evolutionary history. We analyzed their selection pattern in human populations observing that APOBEC3F and 3G are neutrally evolving. Conversely, nucleotide diversity was extremely high for APOBEC3H, and most tests rejected the hypothesis of selective neutrality in Eurasian populations. Haplotype analysis and the derived intraallelic nucleotide diversity test indicated that positive selection has driven the increase in frequency of one haplotype (Hap I) outside Africa. Consistently, population genetic differentiation between African and non-African populations was higher than expected under neutrality. A case-control association analysis indicated that Hap I is associated with protection from sexually transmitted HIV-1 infection. Hap I carries a protein-destabilizing variant and a residue conferring resistance to Vif-mediated degradation. Data herein suggest that lower protein stability might have been traded-off with a higher ability to circumvent Vif-mediated hijacking. Alternatively, transcription regulatory variants might represent the selection target. Our data represent an example of how the selective pressures exerted by extinct or unknown viral agents can be exploited to provide valuable information on the allelic determinants of susceptibility to modern infections. PMID:22023594

Cagliani, Rachele; Riva, Stefania; Fumagalli, Matteo; Biasin, Mara; Caputo, Sergio Lo; Mazzotta, Francesco; Piacentini, Luca; Pozzoli, Uberto; Bresolin, Nereo; Clerici, Mario; Sironi, Manuela

2011-06-28

355

Form and nature of precopulatory sexual selection in both sexes of a moth  

NASA Astrophysics Data System (ADS)

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.

Xu, Jin; Wang, Qiao

2010-07-01

356

Chemoselective Reactions of Citral: Green Syntheses of Natural Perfumes for the Undergraduate Organic Laboratory  

ERIC Educational Resources Information Center

|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…

Cunningham, Anna D.; Ham, Eun Y.; Vosburg, David A.

2011-01-01

357

Chemoselective Reactions of Citral: Green Syntheses of Natural Perfumes for the Undergraduate Organic Laboratory  

ERIC Educational Resources Information Center

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…

Cunningham, Anna D.; Ham, Eun Y.; Vosburg, David A.

2011-01-01

358

Identifying signatures of natural selection in Tibetan and Andean populations using dense genome scan data.  

PubMed

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

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

2010-09-09

359

Genome-wide detection of natural selection in African Americans pre- and post-admixture  

PubMed Central

It is particularly meaningful to investigate natural selection in African Americans (AfA) due to the high mortality their African ancestry has experienced in history. In this study, we examined 491,526 autosomal single nucleotide polymorphisms (SNPs) genotyped in 5210 individuals and conducted a genome-wide search for selection signals in 1890 AfA. Several genomic regions showing an excess of African or European ancestry, which were considered the footprints of selection since population admixture, were detected based on a commonly used approach. However, we also developed a new strategy to detect natural selection both pre- and post-admixture by reconstructing an ancestral African population (AAF) from inferred African components of ancestry in AfA and comparing it with indigenous African populations (IAF). Interestingly, many selection-candidate genes identified by the new approach were associated with AfA-specific high-risk diseases such as prostate cancer and hypertension, suggesting an important role these disease-related genes might have played in adapting to a new environment. CD36 and HBB, whose mutations confer a degree of protection against malaria, were also located in the highly differentiated regions between AAF and IAF. Further analysis showed that the frequencies of alleles protecting against malaria in AAF were lower than those in IAF, which is consistent with the relaxed selection pressure of malaria in the New World. There is no overlap between the top candidate genes detected by the two approaches, indicating the different environmental pressures AfA experienced pre- and post-population admixture. We suggest that the new approach is reasonably powerful and can also be applied to other admixed populations such as Latinos and Uyghurs.

Jin, Wenfei; Xu, Shuhua; Wang, Haifeng; Yu, Yongguo; Shen, Yiping; Wu, Bailin; Jin, Li

2012-01-01

360

Reference site selection report for the advanced liquid metal reactor at the Idaho National Engineering Laboratory  

Microsoft Academic Search

This Reference Site Selection Report was prepared by EG G, Idaho Inc., for General Electric (GE) to provide information for use by the Department of Energy (DOE) in selecting a Safety Test Site for an Advanced Liquid Metal Reactor. Similar Evaluation studies are planned to be conducted at other potential DOE sites. The Power Reactor Innovative Small Module (PRISM) Concept

Sivill

1990-01-01

361

Fish sperm cryopreservation in France: from laboratory studies to application in selective breeding programs  

Microsoft Academic Search

Application of sperm cryopreservation by the fish farming industry is still limited, despite great interest in optimising genetic resource conservation; limiting risks associated with horizontal disease transmission; increasing genetic progress; and accelerating genetic selection from prime specimens, as in other livestock production. Several factors are listed. With the aim of developing coherent broodstock selection programmes, SYSAAF (Union of the French

Pierrick Haffray; Catherine Labbe; Gérard MaIsse

362

An Easily Constructed Salicylate-Ion-Selective Electrode for Use in the Instructional Laboratory.  

ERIC Educational Resources Information Center

|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…

Creager, Stephen E.; And Others

1995-01-01

363

Selecao Natural E Fisica de Particulas: Uma Direcao de Pesquisa Em Inteligencia Artificial (Natural Selection and Particle Physics: A Thrust for Artificial Intelligence Research).  

National Technical Information Service (NTIS)

This article presents a proposal for application of the principles of natural selection and particle physics to orient research in artificial intelligence. An elementary model developed in accordance with this proposal is also presented.

G. Bittencourt

1991-01-01

364

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...

365

Diurnality and nocturnality in nonhuman primates: comparative chronobiological studies in laboratory and nature  

Microsoft Academic Search

Looking for differences in circadian clock characteristics of diurnal and nocturnal nonhuman primates, this article summarizes results of chronobiological studies carried out in various nocturnal, diurnal, and cathemeral prosimian and anthropoid primate species under controlled laboratory conditions, under seminatural conditions, and in the wild. In almost all circadian parameters investigated, no differences were discernible between the two main chrono-ecotypes, either

Hans G. Erkert

2008-01-01

366

A naturally acquired infection of laboratory mice with Klebsiella Capsule type 6  

Microsoft Academic Search

SUMMARY An epizootic causing high morbidity and high mortality in Swiss White and Nude mice over a period of 3 weeks was caused by Klebsiella pneumoniae Capsule type 6, which is considered to be nonpathogenic for mice. Experimental inoculation of this organism into laboratory animals caused death within 36 hours, further substantiating its virulence. 305

Helen D. Schneemilch

1976-01-01

367

Naturally occurring high-chloride coal and superheater corrosion - a laboratory study  

Microsoft Academic Search

An investigation was carried out on the fireside corrosion potential of commercial boiler tube alloys at elevated temperatures when exposed to the combustion products from a series of coals. The results of these laboratory and field tests were reported previously. In some supplementary tests, the effect of chloride was investigated on similar alloys while firing a high-chloride mid-western US bituminous

A. L. Plumley; W. R. Roczniak

1982-01-01

368

Synthesis Laboratory for the U.S. Army Medical Research Institute of Infectious Diseases Selection Panel.  

National Technical Information Service (NTIS)

A synthesis laboratory has been established for the preparation of compounds to be evaluated against viruses of interest to U.S. Army Medical Research Institute of Infectious Diseases. The synthesis of known compounds as well as new compounds has been und...

J. A. Secrist C. D. Kwong C. A. Krauth A. G. Ford Y. H. Jois

1990-01-01

369

Laboratory evaluation of avermectin as a selective acaricide for use with Metaseiulus occidentalis (Nesbitt) (acarina: Phytoseiidae)  

Microsoft Academic Search

The suggestion that adding a light oil to avermectin B1 would increase the toxicity of avermectin to spider mites and reduce its effect on predaceous mites was tested in laboratory trials withTetranychus urticae Koch andMetaseiulus occidentalis (Nesbitt) on almond and bean foliage. No differences were found in the toxicity of avermectin + oil vs. avermectin alone at the doses tested

Marjorie A. Hoy; Frances E. Cave

1985-01-01

370

Laboratory toxicity and field efficacy of selected insecticides against fall armyworm (Lepidoptera: Notctuidae)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Fall armyworm, Spodoptera frugiperda (J. E. Smith), is an occasional but often serious pest of several southern row crops, including: cotton, field corn, and grain sorghum. The objective of these studies was to generate baseline dose-mortality responses for fall armyworm larvae in laboratory bioas...

371

SELECTION AND GENETIC ANALYSIS OF LABORATORY MUTANTS OF BOTRYOTINIA FUCKELIANA RESISTANT TO FENHEXAMID  

Microsoft Academic Search

SUMMARY Ten monoascosporic strains of Botryotinia fuckeliana were used in mycelium growth tests to evaluate baseline sensitivity to Fenhexamid, a fungicide recently intro- duced in the control of grey mould. Their response to the fungicide was EC 50 = 0.1-0.3 µg ml -1 and MIC = 0.3-3 µg ml -1 . Eight laboratory mutants resistant to the fungicide were obtained

M. A. De Guido; R. M. De; Miccolis Angelini; S. Pollastro; A. Santomauro; F. Faretra

2007-01-01

372

Synthesis Laboratory for the U.S. Army Medical Research Institute of Infectious Diseases Selection Panel.  

National Technical Information Service (NTIS)

A synthesis laboratory has been established for the preparation of compounds to be evaluated against viruses of interest to U.S. Army medical Research Institute of Infectious Diseases. The synthesis of known compounds as well as new compounds has been und...

J. A. Secrist C. D. Kwong C. A. Krauth A. G. Ford Y. H. Jois

1989-01-01

373

Multi-robots to micro-surgery: Selected robotic applications at Sandia National Laboratories  

Microsoft Academic Search

The Intelligent Systems and Robotics Center (ISRC) at Sandia National Laboratories is a multi-program organization, pursuing research, development and applications in a wide range of field. Activities range from large-scale applications such as nuclear facility dismantlement for the US Department of Energy (DOE), to aircraft inspection and refurbishment, to automated script and program generation for robotic manufacturing and assembly, to

1996-01-01

374

Host laboratory functions for the DoD 2400 bps vocoder selection process  

Microsoft Academic Search

In order for a test method to yield meaningful results the equipment and procedures used to collect and format data for that test must be accurate and consistent. A laboratory evaluating narrowband digital voice coders must be prepared to generate data for a variety of test methods across numerous voice systems without introducing extraneous variability. This paper describes the functions

Paul D. Gatewood; Philip A. LaFollette

1996-01-01

375

Host selection by shrimps symbiotic with sea anemones: A field survey and experimental laboratory analysis  

Microsoft Academic Search

In three coastal areas of the Republic of China, we found six species of anemoneshrimps and five of host sea anemones in 13 symbiotic combinations; four of the 13 combinations were previously documented. In the laboratory, we tested host preference of the three common shrimps, Periclimenes ornatus Bruce, P. brevicarpalis (Schenkel), and Thor amboinensis (De Man), for anemones of three

Chau-Chih Guo; Jiang-Shiou Hwang; Daphne Gail Fautin

1996-01-01

376

Evaluation of Macroinvertebrate Communities and Habitat for Selected Stream Reaches at Los Alamos National Laboratory  

Microsoft Academic Search

This is the second aquatic biological monitoring report generated by Los Alamos National Laboratory's (LANL's) Water Quality and Hydrology Group. The study has been conducted to generate impact-based assessments of habitat and water quality for LANL waterways. The monitoring program was designed to allow for the detection of spatial and temporal trends in water and habitat quality through ongoing, biannual

L. J. Henne; K. J. Buckley

2005-01-01

377

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 ...

378

Genetic Architecture of a Reinforced, Postmating, Reproductive Isolation Barrier between Neurospora Species Indicates Evolution via Natural Selection  

Microsoft Academic Search

A role for natural selection in reinforcing premating barriers is recognized, but selection for reinforcement of postmating barriers remains controversial. Organisms lacking evolvable premating barriers can theoretically reinforce postmating isolation, but only under restrictive conditions: parental investment in hybrid progeny must inhibit subsequent reproduction, and selected postmating barriers must restore parents' capacity to reproduce successfully. We show that reinforced postmating

Elizabeth Turner; David J. Jacobson; John W. Taylor

2011-01-01

379

Varying signals of the effects of natural selection during teleost growth hormone gene evolution.  

PubMed

The growth hormone (GH) gene of teleost fish exhibits a higher degree of variability compared with other vertebrate groups. However, the different selective constraints at the sequence level are not well understood. In this study, maximum-likelihood (ML) models of codon substitutions were used to investigate Darwinian adaptive evolution of the GH gene in teleost fishes. Complete GH gene sequences of 54 fish species were classified into 4 orders, and the variable nature of GH was examined by determining the dN and dS rate variation and the rates of molecular evolution for each teleost order. The results indicate that although the overall evolution rate for teleost GH is high ((1.15 +/- 0.01) x 10(-9) substitutions/(aa site x y)) compared with the "slow phases" in mammals ((0.21 to 0.28 +/- 0.05) x 10(-9)), the vital structure of this gene has been retained. While the majority of the amino acid changes appear to be due to relaxation of purifying selection, some positively selected sites were detected in regions with no specifically identified role in protein function. The positively selected regions observed in salmoniformes lineage suggests a possible role for positive selection driving functional divergence in paralogous forms of the GH gene after whole-genome duplication in this lineage. PMID:16462900

Ryynänen, Heikki J; Primmer, Craig R

2006-01-01

380

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

PubMed

Sexual selection is driven by competition for mates, and the advantage of a competitor is determined by the number of offspring it produces. Early experiments by Angus Bateman characterized this interaction, and the quantitative relationship between a male's number of mates and number of offspring is known as the Bateman slope. Sexual dimorphism, one of the most obvious results of sexual selection, largely requires a positive Bateman relationship, and the slope provides an estimate of the potential for sexual selection. However, natural selection from the environment can also influence male success, as can random effects, and some have argued for inclusion of the latter in calculations of mate success. Data from pronghorn (Antilocapra americana) reveal the presence of a positive Bateman slope in each year of a 10-year study. We found no evidence that random effects skewed male mating success; however, substantial yearly variation in the Bateman slope due to predation on fawns was evident. These results support the validity of the Bateman relationship, yet they also demonstrate that environmental or extrinsic influences can limit the potential for sexual selection. PMID:23139332

Byers, John; Dunn, Stacey

2012-11-01

381

REtools: A laboratory program for restriction enzyme work: enzyme selection and reaction condition assistance  

PubMed Central

Background Restriction enzymes are one of the everyday tools used in molecular biology. The continuously expanding panel of known restriction enzymes (several thousands) renders their optimal use virtually impossible without computerized assistance. Several manufacturers propose on-line sites that assist scientists in their restriction enzyme work, however, none of these sites meet all the actual needs of laboratory workers, and they do not take into account the enzymes actually present in one's own laboratory. Results Using FileMaker Pro, we developed a stand-alone application which can run on both PCs and Macintoshes. We called it REtools, for Restriction Enzyme tools. This program, which references all currently known enzymes (>3500), permits the creation and update of a personalized list of restriction enzymes actually available in one's own laboratory. Upon opening the program, scientists will be presented with a user friendly interface that will direct them to different menus, each one corresponding to different situations that restriction enzyme users commonly encounter. We particularly emphasized the ease of use to make REtools a solution that laboratory members would actually want to use. Conclusion REtools, a user friendly and easily customized program to organize any laboratory enzyme stock, brings a software solution that will make restriction enzyme use and reaction condition determination straightforward and efficient. The usually unexplored potential of isoschizomers also becomes accessible to all, since REtools proposes all possible enzymes similar to the one(s) chosen by the user. Finally, many of the commonly overlooked subtleties of restriction enzyme work, such as methylation requirement, unusual reaction conditions, or the number of flanking bases required for cleavage, are automatically provided by REtools.

Martin, Patrick; Boulukos, Kim E; Pognonec, Philippe

2006-01-01

382

Sorption selectivity in natural organic matter studied with nitroxyl paramagnetic relaxation probes.  

PubMed

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

Lattao, Charisma; Cao, Xiaoyan; Li, Yuan; Mao, Jingdong; Schmidt-Rohr, Klaus; Chappell, Mark A; Miller, Lesley F; dela Cruz, Albert Leo; Pignatello, Joseph J

2012-11-14

383

Isolating "Unknown" Bacteria in the Introductory Microbiology Laboratory: A New Selective Medium for Gram-Positives.  

ERIC Educational Resources Information Center

|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)|

McKillip, John L.; Drake, MaryAnne

1999-01-01

384

Patterns of population differentiation and natural selection on the celiac disease background risk network.  

PubMed

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

Sams, Aaron; Hawks, John

2013-07-31

385

Response to 30 generations of selection for open-field activity in laboratory mice  

Microsoft Academic Search

High and low lines resulting from 30 generations of bidirectional selection for open-field activity have nonoverlapping distributions and more than a thirtyfold difference in mean activity. Open-field defecation scores of lowactive lines are approximately 7 times higher than those of high-active lines, substantiating earlier reports of a large, negative genetic correlation between these characters. Since the selection experiment is replicated,

J. C. DeFries; Mary Cook Gervais; E. A. Thomas

1978-01-01

386

Inspection of the handling of selected chemicals at Lawrence Livermore National Laboratory  

SciTech Connect

The subject report is provided to inform of our findings and recommendations as a result of our inspection, and to give an opportunity to comment. The purpose of this inspection was to examine the potential for manufacture and/or diversion of 49 selected chemicals which were either controlled drugs or precursors that could be illegally used for the manufacture of such drugs, and to determine whether controls in place were adequate to detect misuse of these selected chemicals.

Not Available

1988-02-19

387

Non-obese diabetic mice select a low-diversity repertoire of natural regulatory T cells.  

PubMed

Thymus-derived Foxp3(+) natural regulatory CD4 T cells (nTregs) prevent autoimmunity through control of pathogenic, autoreactive T cells and other immune effector cells. Using T cell receptor (TCR) transgenic models, diversity within this lineage has been found to be similar to that of conventional CD4 T cells. To determine whether balanced TCR diversity may be perturbed in autoimmunity, we have analyzed receptor composition in C57BL/6 and autoimmune non-obese diabetic (NOD) mice. The natural regulatory and conventional CD4 repertoires of C57BL/6 had similar diversities. Despite the apparently normal thymic development of the NOD nTreg lineage, TCR diversity within the selected repertoire was markedly restricted. Detailed analysis of TCRalpha and -beta chain composition is consistent with positive selection into the natural regulatory lineage being under stringent audition for interaction with MHC class II/self-peptide. The NOD MHC region, including the unique H2-A(g7) class II molecule, partly accounts for the reduction in diversity, but additional NOD genetic contribution(s) are required for complete repertoire compaction. Mechanistic links between MHC, autoimmunity, and nTreg diversity identified in this study are discussed. PMID:19359477

Ferreira, Cristina; Singh, Yogesh; Furmanski, Anna L; Wong, F Susan; Garden, Oliver A; Dyson, Julian

2009-04-09

388

Non-obese diabetic mice select a low-diversity repertoire of natural regulatory T cells  

PubMed Central

Thymus-derived Foxp3+ natural regulatory CD4 T cells (nTregs) prevent autoimmunity through control of pathogenic, autoreactive T cells and other immune effector cells. Using T cell receptor (TCR) transgenic models, diversity within this lineage has been found to be similar to that of conventional CD4 T cells. To determine whether balanced TCR diversity may be perturbed in autoimmunity, we have analyzed receptor composition in C57BL/6 and autoimmune non-obese diabetic (NOD) mice. The natural regulatory and conventional CD4 repertoires of C57BL/6 had similar diversities. Despite the apparently normal thymic development of the NOD nTreg lineage, TCR diversity within the selected repertoire was markedly restricted. Detailed analysis of TCR? and -? chain composition is consistent with positive selection into the natural regulatory lineage being under stringent audition for interaction with MHC class II/self-peptide. The NOD MHC region, including the unique H2-Ag7 class II molecule, partly accounts for the reduction in diversity, but additional NOD genetic contribution(s) are required for complete repertoire compaction. Mechanistic links between MHC, autoimmunity, and nTreg diversity identified in this study are discussed.

Ferreira, Cristina; Singh, Yogesh; Furmanski, Anna L.; Wong, F. Susan; Garden, Oliver A.; Dyson, Julian

2009-01-01

389

Natural attenuation of metals and radionuclides: Report from a workshop held by Sandia National Laboratories  

SciTech Connect

Natural attenuation is increasingly applied to remediate contaminated soils and ground waters. Roughly 25% of Superfund groundwater remedies in 1995 involved some type of monitored natural attenuation, compared to almost none 5 years ago. Remediation by natural attenuation (RNA) requires clear evidence that contaminant levels are decreasing sufficiently over time, a defensible explanation of the attenuation mechanism, long-term monitoring, and a contingency plan at the very least. Although the primary focus of implementation has to date been the biodegradation of organic contaminants, there is a wealth of scientific evidence that natural processes reduce the bioavailability of contaminant metals and radionuclides. Natural attenuation of metals and radionuclides is likely to revolve around sorption, solubility, biologic uptake and dilution controls over contaminant availability. Some of these processes can be applied to actively remediate sites. Others, such as phytoremediation, are likely to be ineffective. RNA of metals and radionuclides is likely to require specialized site characterization to construct contaminant and site-specific conceptual models of contaminant behavior. Ideally, conceptual models should be refined such that contaminant attenuation can be confidently predicted into the future. The technical approach to RNA of metals and radionuclides is explored here.

Brady, P.V.; Borns, D.J. [Sandia National Labs., Albuquerque, NM (United States). Geochemistry Dept.

1997-11-01

390

Naturally occurring high-chloride coal and superheater corrosion - a laboratory study  

SciTech Connect

An investigation was carried out on the fireside corrosion potential of commercial boiler tube alloys at elevated temperatures when exposed to the combustion products from a series of coals. The results of these laboratory and field tests were reported previously. In some supplementary tests, the effect of chloride was investigated on similar alloys while firing a high-chloride mid-western US bituminous coal in the same laboratory furnace. On the basis of exposure in the convection pass at temperatures from 1100-1700 F, Inconel Alloy 690 was found to have very good corrosion resistance, while Incoloy 800 H and Tp-310 s.s. were good transitional materials. Poor materials were T-22, 316 s.s., Inconel 617 and Inconel 671.

Plumley, A.L.; Roczniak, W.R.

1982-10-01

391

Vermicompost as natural adsorbent for removing metal ions from laboratory effluents  

Microsoft Academic Search

The use of vermicompost as an adsorbent to remove Cd(II), Cu(II), Pb(II) and Zn(II) ions from laboratory effluents is proposed. Parameters such as adsorption pH, vermicompost amount, flow rate and particle size range were studied. An optimum pH range (2.5–5.0) was found for metal removal. The flow rate affected only slightly the removal of Cd(II) ions (about 10%). A decrease

G. D Matos; M. A. Z Arruda

2003-01-01

392

Chemical aspects of iron oxide coagulation in water: Laboratory studies and implications for natural systems  

Microsoft Academic Search

Initial coagulation rates of colloidal hematite (a-Fe2O3) particles (diameter less than 0.1 µm) were measured experimentally in well-defined laboratory systems at constant temperature. The relative stability ratio,W, was obtained at various ionic strengths in NaCl medium and at pH values in the range from 3 to 12. ExperimentalW values ranged from 1 to 104 in various systems. The results delineate

Liyuan Liang; James J. Morgan

1990-01-01

393

Incipient balancing selection through adaptive loss of aquaporins in natural Saccharomyces cerevisiae populations.  

PubMed

A major goal in evolutionary biology is to understand how adaptive evolution has influenced natural variation, but identifying loci subject to positive selection has been a challenge. Here we present the adaptive loss of a pair of paralogous genes in specific Saccharomyces cerevisiae subpopulations. We mapped natural variation in freeze-thaw tolerance to two water transporters, AQY1 and AQY2, previously implicated in freeze-thaw survival. However, whereas freeze-thaw-tolerant strains harbor functional aquaporin genes, the set of sensitive strains lost aquaporin function at least 6 independent times. Several genomic signatures at AQY1 and/or AQY2 reveal low variation surrounding these loci within strains of the same haplotype, but high variation between strain groups. This is consistent with recent adaptive loss of aquaporins in subgroups of strains, leading to incipient balancing selection. We show that, although aquaporins are critical for surviving freeze-thaw stress, loss of both genes provides a major fitness advantage on high-sugar substrates common to many strains' natural niche. Strikingly, strains with non-functional alleles have also lost the ancestral requirement for aquaporins during spore formation. Thus, the antagonistic effect of aquaporin function-providing an advantage in freeze-thaw tolerance but a fitness defect for growth in high-sugar environments-contributes to the maintenance of both functional and nonfunctional alleles in S. cerevisiae. This work also shows that gene loss through multiple missense and nonsense mutations, hallmarks of pseudogenization presumed to emerge after loss of constraint, can arise through positive selection. PMID:20369021

Will, Jessica L; Kim, Hyun Seok; Clarke, Jessica; Painter, John C; Fay, Justin C; Gasch, Audrey P

2010-04-01

394

Automated ion-selective electrode method for determining fluoride in natural waters  

USGS Publications Warehouse

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.

Erdmann, D. E.

1975-01-01

395

Supervised and Unsupervised Feature Selection for Inferring Social Nature of Telephone Conversations from Their Content  

PubMed Central

The ability to reliably infer the nature of telephone conversations opens up a variety of applications, ranging from designing context-sensitive user interfaces on smartphones, to providing new tools for social psychologists and social scientists to study and understand social life of different subpopulations within different contexts. Using a unique corpus of everyday telephone conversations collected from eight residences over the duration of a year, we investigate the utility of popular features, extracted solely from the content, in classifying business-oriented calls from others. Through feature selection experiments, we find that the discrimination can be performed robustly for a majority of the calls using a small set of features. Remarkably, features learned from unsupervised methods, specifically latent Dirichlet allocation, perform almost as well as with as those from supervised methods. The unsupervised clusters learned in this task shows promise of finer grain inference of social nature of telephone conversations.

Stark, Anthony; Shafran, Izhak; Kaye, Jeffrey

2012-01-01

396

Interfamily variation in amphibian early life-history traits: raw material for natural selection?  

PubMed Central

The embryonic development and time to hatching of eggs can be highly adaptive in some species, and thus under selective pressure. In this study, we examined the underlying interfamily variation in hatching timing and embryonic development in a population of an oviparous amphibian, the rough-skinned newt (Taricha granulosa). We found significant, high variability in degree of embryonic development and hatching timing among eggs from different females. Patterns of variation were present regardless of temperature. We also could not explain the differences among families by morphological traits of the females or their eggs. This study suggests that the variation necessary for natural selection to act upon is present in the early life history of this amphibian.

Hopkins, Gareth R; Gall, Brian G; French, Susannah S; Brodie, Edmund D

2012-01-01

397

Conceptualizing the autism spectrum in terms of natural selection and behavioral ecology: the solitary forager hypothesis.  

PubMed

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

Reser, Jared Edward

2011-05-21

398

The Nature of Faint Spitzer-selected Dust-obscured Galaxies  

Microsoft Academic Search

We use deep far-IR, submillimeter, radio, and X-ray imaging and mid-IR spectroscopy to explore the nature of a sample of Spitzer-selected dust-obscured galaxies (DOGs) in GOODS-N. A sample of 79 galaxies satisfy the criteria R-[24]>14 (Vega) down to S24>100 muJy (median flux density S24=180 muJy). Twelve of these galaxies have IRS spectra available, which we use to measure redshifts and

Alexandra Pope; R. Shane Bussmann; Arjun Dey; Nicole Meger; David M. Alexander; Mark Brodwin; Ranga-Ram Chary; Mark E. Dickinson; David T. Frayer; Thomas R. Greve; Minh Huynh; Lihwai Lin; Glenn Morrison; Douglas Scott; Chi-Hung Yan

2008-01-01

399

Immobilization of selected heavy metals in sewage sludge by natural zeolites.  

PubMed

This contribution presents the possibility of application of natural sorbent (Transcarpathian clinoptylolite (KL)) for immobilization of selected heavy metals in the sewage sludge. The influence of ion-exchange parameters (e.g. time, amount of zeolite) were discussed. Process of immobilization was performed using a static method (Batch). It was found that best possible conditions for immobilization of heavy metal ions were as follows: zeolite fraction 0.7-1.0mm, 5h of shaking, zeolite/sewage sludge ratio 2/98. PMID:18083511

Kosobucki, Przemys?aw; Kruk, Magdalena; Buszewski, Bogus?aw

2007-12-21

400

Detection and characterization of Wolbachia infections in laboratory and natural populations of different species of tsetse flies (genus Glossina).  

PubMed

BACKGROUND: Wolbachia is a genus of endosymbiotic ?-Proteobacteria infecting a wide range of arthropods and filarial nematodes. Wolbachia is able to induce reproductive abnormalities such as cytoplasmic incompatibility (CI), thelytokous parthenogenesis, feminization and male killing, thus affecting biology, ecology and evolution of its hosts. The bacterial group has prompted research regarding its potential for the control of agricultural and medical disease vectors, including Glossina spp., which transmits African trypanosomes, the causative agents of sleeping sickness in humans and nagana in animals. RESULTS: In the present study, we employed a Wolbachia specific 16S rRNA PCR assay to investigate the presence of Wolbachia in six different laboratory stocks as well as in natural populations of nine different Glossina species originating from 10 African countries. Wolbachia was prevalent in Glossina morsitans morsitans, G. morsitans centralis and G. austeni populations. It was also detected in G. brevipalpis, and, for the first time, in G. pallidipes and G. palpalis gambiensis. On the other hand, Wolbachia was not found in G. p. palpalis, G. fuscipes fuscipes and G. tachinoides. Wolbachia infections of different laboratory and natural populations of Glossina species were characterized using 16S rRNA, the wsp (Wolbachia Surface Protein) gene and MLST (Multi Locus Sequence Typing) gene markers. This analysis led to the detection of horizontal gene transfer events, in which Wobachia genes were inserted into the tsetse flies fly nuclear genome. CONCLUSIONS: Wolbachia infections were detected in both laboratory and natural populations of several different Glossina species. The characterization of these Wolbachia strains promises to lead to a deeper insight in tsetse flies-Wolbachia interactions, which is essential for the development and use of Wolbachia-based biological control methods. PMID:22376025

Doudoumis, Vangelis; Tsiamis, George; Wamwiri, Florence; Brelsfoard, Corey; Alam, Uzma; Aksoy, Emre; Dalaperas, Stelios; Abd-Alla, Adly; Ouma, Johnson; Takac, Peter; Aksoy, Serap; Bourtzis, Kostas

2012-01-18

401

Laboratory simulation of natural sulphurization: II. Reaction of multifunctionalized lipids with inorganic polysulphides at low temperatures  

Microsoft Academic Search

A number of geochemically relevant model compounds (alkenes, ketones, aldehydes, acids, alcohols and esters) have been subjected to a reaction with sodium hydrogen polysulphide either in one solvent or mediated by a phase transfer reagent. This reaction, referred to as the hydrosulphurization reaction, is regarded as a simulation of a natural sulphurization reaction of functionalized lipids in early stages of

J. S. Sinninghe Damsté; S. Schouten; W. de Graaf; G. B. van Driel; Leeuw. J. W. de

1994-01-01

402

Observations on Natural and Laboratory Infection of Rodents with the Etiologic Agent of Korean Hemorrhagic Fever.  

National Technical Information Service (NTIS)

Studies were conducted to define the natural host range of Korean hemorrhagic fever (KHF) agent in South Korea, and to identify colonized rodents susceptible to this infection. Eight species of field rodents were captured in areas of Korea endemic for KHF...

H. W. Lee G. R. French P. W. Lee L. J. Baek K. Tsuchiya

1980-01-01

403

The Earth-Moon-Sun natural laboratory for testing of gravitational and electromagnetic fields coupling  

Microsoft Academic Search

Experimental investigations of electromagnetic fields in the atmosphere boundary layer are done at the distance spaced stations, situated on VSU test ground, at Main Geophysical Observa-tory(St. Petersburg), on Kamchatka pen., on Lake Baikal. The distance spaced reception of electrical and magnetic fields will allow to analyze more widely the nature of the investigated interactions. Monitoring of electromagnetic fields in the

Lubov Grunskaya; Valiriy Isakevich; Vladislav Efimov; Alexander Zakirov

2010-01-01

404

The Great Smoky Mountains National Park: Its Use as a Natural Laboratory for General Biology.  

ERIC Educational Resources Information Center

Extended field trips have the potential to provide students with direct experience in learning about the natural world, as well as opportunities for the development of group cohesiveness. This document describes a program developed by a community college in which general biology students spend 3 days in the Great Smoky Mountains National Park. The…

Adams, Harold S.; Lipford, Michael L.

405

Demography and natural selection have shaped genetic variation in Drosophila melanogaster: a multi-locus approach.  

PubMed

Demography and selection have been recognized for their important roles in shaping patterns of nucleotide variability. To investigate the relative effects of these forces in the genome of Drosophila melanogaster, we used a multi-locus scan (105 fragments) of X-linked DNA sequence variation in a putatively ancestral African and a derived European population. Surprisingly, we found evidence for a recent size expansion in the African population, i.e., a significant excess of singletons at a chromosome-wide level. In the European population, such an excess was not detected. In contrast to the African population, we found evidence for positive natural selection in the European sample: (i) a large number of loci with low levels of variation and (ii) a significant excess of derived variants at the low-variation loci that are fixed in the European sample but rare in the African population. These results are consistent with the hypothesis that the European population has experienced frequent selective sweeps in the recent past during its adaptation to new habitats. Our study shows the advantages of a genomic approach (over a locus-specific analysis) in disentangling demographic and selective forces. PMID:14668381

Glinka, Sascha; Ometto, Lino; Mousset, Sylvain; Stephan, Wolfgang; De Lorenzo, David

2003-11-01

406

Community complexity drives patterns of natural selection on a chemical defense of Brassica nigra.  

PubMed

Plants interact with many different species throughout their life cycle. Recent work has shown that the ecological effects of multispecies interactions are often not predictable from studies of the component pairwise interactions. Little is known about how multispecies interactions affect the evolution of ecologically important traits. We tested the direct and interactive effects of inter- and intraspecific competition, as well as of two abundant herbivore species (a generalist folivore and a specialist aphid), on the selective value of a defensive chemical compound in Brassica nigra. We found that investment in chemical defense was favored in interspecific competition but disfavored in intraspecific competition and that this pattern of selection was dependent on the presence of both herbivores, suggesting that selection will depend on the rarity or commonness of these species. These results show that the selective value of ecologically important traits depends on the complicated web of interactions present in diverse natural communities and that fluctuations in community composition may maintain genetic variation in such traits. PMID:18197768

Lankau, Richard A; Strauss, Sharon Y

2008-02-01

407

[Habitat selection of four sympatric pheasants in Guanshan National Nature Reserve, Jiangxi, China].  

PubMed

Habitat selection of four sympatric pheasants (Syrmaticus ellioti, Lophura nycthemera, Pucrasia macrolopha and Bumbusicola thoracica) was studied in Guanshan National Nature Reserve, Jiangxi, China from October 2009 to November 2010. We measured seventeen ecological factors across 388 sites used by the four pheasants by direct observation in six transects. The results show that the pheasants preferred broad-leaved forest and coniferous forest and a sunny or semi-shaded slope. There were differences in elevation, degree of slope, arbor coverage, shrub coverage, shrub quantity, shrub height, herbage cover, herbage species, herbage quantity, leaf litter coverage, distance to water and arbor species between the habitat selected by the four pheasants. Canonical scores indicated that the four pheasants differed in habitat selection to some extent. A stepwise discriminant analysis revealed that elevation, herbage quantity, shrub height, distance to water, shrub cover, arbor cover, degree of slope, leaf litter cover, shrub quantity and herbage cover were the critical factors distinguishing habitat selection between the species. Predicted classification accuracy of the model was 74.7%. PMID:22467392

Liu, Peng; Huang, Xiao-Feng; Gu, Shu-Sheng; Lu, Chang-Hu

2012-04-01

408

Signatures of Demographic History and Natural Selection in the Human Major Histocompatibility Complex Loci  

PubMed Central

Many lines of evidence show that several HLA loci have experienced balancing selection. However, distinguishing among demographic and selective explanations for patterns of variation observed with HLA genes remains a challenge. In this study we address this issue using data from a diverse set of human populations at six classical HLA loci and, employing a comparative genomics approach, contrast results for HLA loci to those for non-HLA markers. Using a variety of analytic methods, we confirm and extend evidence for selection acting on several HLA loci. We find that allele frequency distributions for four of the six HLA loci deviate from neutral expectations and show that this is unlikely to be explained solely by demographic factors. Other features of HLA variation are explained in part by demographic history, including decreased heterozygosity and increased LD for populations at greater distances from Africa and a similar apportionment of genetic variation for HLA loci compared to putatively neutral non-HLA loci. On the basis of contrasts among different HLA loci and between HLA and non-HLA loci, we conclude that HLA loci bear detectable signatures of both natural selection and demographic history.

Meyer, Diogo; Single, Richard M.; Mack, Steven J.; Erlich, Henry A.; Thomson, Glenys

2006-01-01

409

A Review of the Natural History and Laboratory Culture Methods for the Yellow Dung Fly, Scathophaga stercoraria  

PubMed Central

The yellow dung fly Scathophaga stercoraria (L.) (Diptera: Scathophagidae) is a widespread and locally abundant fly associated with the dung of large mammals, especially farm animals. This species has recently become a standard test organism for evaluating toxic effects of veterinary pharmaceuticals in livestock dung. In this context, a review of its natural history and a general description of the field and laboratory rearing methods of this species are provided here to benefit the scientific community as well as government regulators and applicants of eco-toxicological studies. For guidance, means and ranges are included for all relevant standard life history traits stemming from previously published data on Swiss populations.

Blanckenhorn, WU; Pemberton, AJ; Bussiere, LF; Roembke, J; Floate, KD

2010-01-01

410

Occurrence and nature of thermolabile compounds in the Boom Clay kerogen (Oligocene, underground Mol Laboratory, Belgium)  

Microsoft Academic Search

The Boom Clay Formation has been selected as a model for studying the long term disposal of high activity nuclear waste in clay. During the resulting storage, the immature kerogen in the clay would be subjected to thermal stress and some of the products which could be generated might affect the efficiency of the geological barrier. The kerogen isolated from

I Deniau; S Derenne; C Beaucaire; H Pitsch; C Largeau

2004-01-01

411

Novel Experiments in Physics II. A Selection of Laboratory Notes Now Used in Colleges and Universities.  

ERIC Educational Resources Information Center

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…

American Association of Physics Teachers, Washington, DC.

412

Summary Report on State, Local, Private, and Commercial Laboratories' Compliance with Select Agent Regulations.  

National Technical Information Service (NTIS)

The Public Health Security and Bioterrorism Preparedness and Response Act of 2002, Public Law 107-188 (the Act), charges the Department of Health and Human Services (HHS) with the responsibility to regulate select agents, which are materials that have the...

D. R. Levinson

2008-01-01

413

Evolution in action in the classroom: Engaging students in scientific practices to develop a conceptual understanding of natural selection  

NASA Astrophysics Data System (ADS)

Public understanding and acceptance of the theory of evolution in the United States is not commensurate with its acceptance in the scientific community and its role as the central organizing principle of the biological sciences. There are a multitude of factors that affect student understanding of the theory of evolution documented in the literature including the proposition that understanding of evolution is intimately linked to understanding the nature of science. This study describes the development, implementation, and assessment of learning activities that address the process of natural selection and the scientific methodology that illuminates these mechanisms. While pre and post-test scores were higher for students in an Advanced Placement Biology course than students in a general biology course, similar learning gains were observed in both groups. Learning gains were documented in understanding the random nature of mutations and their importance to the process of natural selection, explaining selection as a competitive advantage of one variation over another type and specifically linking this to reproductive success, and in connecting inheritance, variation, and selection to explain the process of natural selection. Acceptance of the scientific validity of the theory of evolution as measured by the Measure of Acceptance of the Theory of Evolution (MATE) Instrument also increased significantly in both groups over the course of the school year. These findings suggest that the sequence of activities implemented in this study promote conceptual change about the nature of science and the process of evolution by natural selection in students.

Johnson, Wendy Renae

414

Gross-beta activity in ground water: natural sources and artifacts of sampling and laboratory analysis  

Microsoft Academic Search

Gross-beta activity has been used as an indicator of beta-emitting isotopes in water since at least the early 1950s. Originally designed for detection of radioactive releases from nuclear facilities and weapons tests, analysis of gross-beta activity is widely used in studies of naturally occurring radioactivity in ground water. Analyses of about 800 samples from 5 ground-water regions of the United

Ann H. Mullin; Z SZABO; D PARKHURST; P VANMETRE

1995-01-01

415

Transport of radionuclides in natural fractures: some aspects of laboratory migration experiments  

Microsoft Academic Search

Results are reported for a series of migration experiments performed in a hydraulically characterized, single, natural fracture in a block of granite with overall dimensions of 1 × 1 × 0.7 m (all approximate), using the conservative, poorly sorbing and strongly sorbing radionuclides 3H20, 131I, 22Na, 85Sr, 137Cs, 60Co, 154,155Eu, 237Np, and 238Pu. The volumetric flow velocity of the transport

T. T. Vandergraaf; D. J. Drew; D. Archambault; K. V. Ticknor

1997-01-01

416

Naturally occurring high-chloride coal and superheater corrision laboratory study  

SciTech Connect

Commerical boiler tube alloys were tested for the corrosive effect of chloride while firing a naturally occurring high chloride Midwestern bituminous coal. On the basis of exposure in the convection pass at temperatures from 1100-1700/sup 0/F, Inconel Alloy 690 was found to have very good resistance to corrosion while Incoloy 800H and Tp-310 s. s. were good transitional materials. Poor materials were T-22, 316 s. s., Inconel 617, and Inconel 671.

Plumley, A.L.; Roczniak, W.R.

1982-10-01

417

Naturally occurring high-chloride coal and superheater corrision laboratory study  

Microsoft Academic Search

Commerical boiler tube alloys were tested for the corrosive effect of chloride while firing a naturally occurring high chloride Midwestern bituminous coal. On the basis of exposure in the convection pass at temperatures from 1100-1700°F, Inconel Alloy 690 was found to have very good resistance to corrosion while Incoloy 800H and Tp-310 s. s. were good transitional materials. Poor materials

A. L. Plumley; W. R. Roczniak

1982-01-01

418

Complementary effect of natural and sexual selection against immigrants maintains differentiation between locally adapted fish  

NASA Astrophysics Data System (ADS)

Adaptation to ecologically heterogeneous environments can drive speciation. But what mechanisms maintain reproductive isolation among locally adapted populations? Using poeciliid fishes in a system with naturally occurring toxic hydrogen sulfide, we show that (a) fish from non-sulfidic sites ( Poecilia mexicana) show high mortality (95 %) after 24 h when exposed to the toxicant, while locally adapted fish from sulfidic sites ( Poecilia sulphuraria) experience low mortality (13 %) when transferred to non-sulfidic water. (b) Mate choice tests revealed that P. mexicana females exhibit a preference for conspecific males in non-sulfidic water, but not in sulfidic water, whereas P. sulphuraria females never showed a preference. Increased costs of mate choice in sulfidic, hypoxic water, and the lack of selection for reinforcement due to the low survival of P. mexicana may explain the absence of a preference in P. sulphuraria females. Taken together, our study may be the first to demonstrate independent—but complementary—effects of natural and sexual selection against immigrants maintaining differentiation between locally adapted fish populations.

Plath, Martin; Riesch, Rüdiger; Oranth, Alexandra; Dzienko, Justina; Karau, Nora; Schießl, Angela; Stadler, Stefan; Wigh, Adriana; Zimmer, Claudia; Arias-Rodriguez, Lenin; Schlupp, Ingo; Tobler, Michael

2010-08-01

419

Darwinian natural selection for orange bioluminescent color in a Jamaican click beetle  

PubMed Central

The Jamaican click beetle Pyrophorus plagiophthalamus (Coleoptera: Elateridae) is unique among all bioluminescent organisms in displaying a striking light color polymorphism [Biggley, W. H., Lloyd, J. E. & Seliger, H. H. (1967) J. Gen. Physiol. 50, 1681–1692]. Beetles on the island vary in the color of their ventral light organs from yellow–green to orange and their dorsal organs from green to yellow–green. The genetic basis for the color variation involves specific amino acid substitutions in the enzyme luciferase. Here, we show that dorsal and ventral light color in P. plagiophthalamus are under separate genetic control, we resolve the allelic basis for color variation, and, through analyses of luciferase sequence variation, we demonstrate that natural selection has produced a long-term adaptive trend for longer wavelength (more orange) ventral light on Jamaica. Our results constitute a novel example connecting the selective fixation of specific nucleotides in nature to their precisely determined phenotypic effects. We also present evidence suggesting that a recently derived ventral orange luciferase allele on the island has deterministically increased in frequency. Thus, the current luciferase polymorphism for P. plagiophthalamus appears to be mirroring the long-term anagenic trend on Jamaica, revealing a possible ongoing adaptive color transition in progress.

Stolz, Uwe; Velez, Sebastian; Wood, Keith V.; Wood, Monika; Feder, Jeffrey L.

2003-01-01

420

Fluctuating natural selection accounts for the evolution of diversification bet hedging.  

PubMed

Natural environments are characterized by unpredictability over all time scales. This stochasticity is expected on theoretical grounds to result in the evolution of 'bet-hedging' traits that maximize the long term, or geometric mean fitness even though such traits do not maximize fitness over shorter time scales. The geometric mean principle is thus central to our interpretation of optimality and adaptation; however, quantitative empirical support for bet hedging is lacking. Here, I report a quantitative test using the timing of seed germination-a model diversification bet-hedging trait-in Lobelia inflata under field conditions. In a phenotypic manipulation study, I find the magnitude of fluctuating selection acting on seed germination timing-across 70 intervals throughout five seasons-to be extreme: fitness functions for survival are complex and multimodal within seasons and significantly dissimilar among seasons. I confirm that the observed magnitude of fluctuating selection is sufficient to account for the degree of diversification behaviour characteristic of individuals of this species. The geometric mean principle has been known to economic theory for over two centuries; this study now provides a quantitative test of optimality of a bet-hedging trait in nature. PMID:19324774

Simons, Andrew M

2009-03-04

421

Complementary effect of natural and sexual selection against immigrants maintains differentiation between locally adapted fish.  

PubMed

Adaptation to ecologically heterogeneous environments can drive speciation. But what mechanisms maintain reproductive isolation among locally adapted populations? Using poeciliid fishes in a system with naturally occurring toxic hydrogen sulfide, we show that (a) fish from non-sulfidic sites (Poecilia mexicana) show high mortality (95 %) after 24 h when exposed to the toxicant, while locally adapted fish from sulfidic sites (Poecilia sulphuraria) experience low mortality (13 %) when transferred to non-sulfidic water. (b) Mate choice tests revealed that P. mexicana females exhibit a preference for conspecific males in non-sulfidic water, but not in sulfidic water, whereas P. sulphuraria females never showed a preference. Increased costs of mate choice in sulfidic, hypoxic water, and the lack of selection for reinforcement due to the low survival of P. mexicana may explain the absence of a preference in P. sulphuraria females. Taken together, our study may be the first to demonstrate independent-but complementary-effects of natural and sexual selection against immigrants maintaining differentiation between locally adapted fish populations. PMID:20574847

Plath, Martin; Riesch, Rüdiger; Oranth, Alexandra; Dzienko, Justina; Karau, Nora; Schiessl, Angela; Stadler, Stefan; Wigh, Adriana; Zimmer, Claudia; Arias-Rodriguez, Lenin; Schlupp, Ingo; Tobler, Michael

2010-06-24

422

Natural selection in utero induced by mass layoffs: the hCG evidence  

PubMed Central

Evolutionary theory, when coupled with research from epidemiology, demography, and population endocrinology, suggests that contracting economies affect the fitness and health of human populations via natural selection in utero. We know, for example, that fetal death increases more among males than females when the economy unexpectedly contracts; that unexpected economic contraction predicts low secondary sex ratios; and that males from low sex ratio birth cohorts live, on average, longer than those from high sex ratio cohorts. We also know that low levels of human chorionic gonadotropin (i.e., hCG) measured in the serum of pregnant women predict fetal death. We do not, however, know whether male survivors of conception cohorts subjected to contracting economies exhibit, as theory predicts, higher hCG than those from other cohorts. We show, in 71 monthly conception cohorts including nearly two million California births, that they do. We thereby add to the literature suggesting that the economy, a phenomenon over which we collectively exercise at least some control, affects population health. Our findings imply that the effect arises via natural selection – a mechanism we largely ignore when attempting to explain, or alter, how collective choice affects our biology.

Catalano, Ralph; Margerison-Zilko, Claire; Goldman-Mellor, Sidra; Pearl, Michelle; Anderson, Elizabeth; Saxton, Katherine; Bruckner, Tim; Subbaraman, Meenakshi; Goodman, Julia; Epstein, Mollie; Currier, Robert; Kharrazi, Martin

2012-01-01

423

Preliminary delineation of natural geochemical reactions, Snake River Plain aquifer system, Idaho National Engineering Laboratory and vicinity, Idaho  

SciTech Connect

The U.S. Geological Survey, in cooperation with the U.S. Department of Energy, is conducting a study to determine the natural geochemistry of the Snake River Plain aquifer system at the Idaho National Engineering Laboratory (INEL), Idaho. As part of this study, a group of geochemical reactions that partially control the natural chemistry of ground water at the INEL were identified. Mineralogy of the aquifer matrix was determined using X-ray diffraction and thin-section analysis and theoretical stabilities of the minerals were used to identify potential solid-phase reactants and products of the reactions. The reactants and products that have an important contribution to the natural geochemistry include labradorite, olivine, pyroxene, smectite, calcite, ferric oxyhydroxide, and several silica phases. To further identify the reactions, analyses of 22 representative water samples from sites tapping the Snake River Plain aquifer system were used to determine the thermodynamic condition of the ground water relative to the minerals in the framework of the aquifer system. Principal reactions modifying the natural geochemical system include congruent dissolution of olivine, diopside, amorphous silica, and anhydrite; incongruent dissolution of labradorite with calcium montmorillonite as a residual product; precipitation of calcite and ferric oxyhydroxide; and oxidation of ferrous iron to ferric iron. Cation exchange reactions retard the downward movement of heavy, multivalent waste constituents where infiltration ponds are used for waste disposal.

Knobel, L.L.; Bartholomay, R.C.; Orr, B.R.

1997-05-01

424

Laboratory mating trials indicate incipient speciation by sexual selection among populations of the cichlid fish Pseudotropheus zebra from Lake Malawi.  

PubMed Central

It has been suggested that sexual selection may have played a major role in the rapid evolution of hundreds of species of cichlid fishes in Lake Malawi. We report the results of a laboratory test of assortative mating among Lake Malawi cichlid fishes from five closely related geographical populations differing in male courtship colour. Paternity of clutches was tested using microsatellite DNA typing of offspring. Out of 1955 offspring typed, 1296 (66.3%) were sired by the male from the same population as the female, which is more than three times the rate expected if females do not differentiate among males of the different populations (20%). This result indicates that mate preferences of geographical races are strongly differentiated, consistent with the races representing incipient geographical species diverging under sexual selection exerted by female preferences for different male courtship colours.

Knight, Mairi E; Turner, George F

2004-01-01

425

Natural selection on EPAS1 (HIF2?) associated with low hemoglobin concentration in Tibetan highlanders  

PubMed Central

By impairing both function and survival, the severe reduction in oxygen availability associated with high-altitude environments is likely to act as an agent of natural selection. We used genomic and candidate gene approaches to search for evidence of such genetic selection. First, a genome-wide allelic differentiation scan (GWADS) comparing indigenous highlanders of the Tibetan Plateau (3,200–3,500 m) with closely related lowland Han revealed a genome-wide significant divergence across eight SNPs located near EPAS1. This gene encodes the transcription factor HIF2?, which stimulates production of red blood cells and thus increases the concentration of hemoglobin in blood. Second, in a separate cohort of Tibetans residing at 4,200 m, we identified 31 EPAS1 SNPs in high linkage disequilibrium that correlated significantly with hemoglobin concentration. The sex-adjusted hemoglobin concentration was, on average, 0.8 g/dL lower in the major allele homozygotes compared with the heterozygotes. These findings were replicated in a third cohort of Tibetans residing at 4,300 m. The alleles associating with lower hemoglobin concentrations were correlated with the signal from the GWADS study and were observed at greatly elevated frequencies in the Tibetan cohorts compared with the Han. High hemoglobin concentrations are a cardinal feature of chronic mountain sickness offering one plausible mechanism for selection. Alternatively, as EPAS1 is pleiotropic in its effects, selection may have operated on some other aspect of the phenotype. Whichever of these explanations is correct, the evidence for genetic selection at the EPAS1 locus from the GWADS study is supported by the replicated studies associating function with the allelic variants.

Beall, Cynthia M.; Cavalleri, Gianpiero L.; Deng, Libin; Elston, Robert C.; Gao, Yang; Knight, Jo; Li, Chaohua; Li, Jiang Chuan; Liang, Yu; McCormack, Mark; Montgomery, Hugh E.; Pan, Hao; Robbins, Peter A.; Shianna, Kevin V.; Tam, Siu Cheung; Tsering, Ngodrop; Veeramah, Krishna R.; Wang, Wei; Wangdui, Puchung; Weale, Michael E.; Xu, Yaomin; Xu, Zhe; Yang, Ling; Zaman, M. Justin; Zeng, Changqing; Zhang, Li; Zhang, Xianglong; Zhaxi, Pingcuo; Zheng, Yong Tang

2010-01-01

426

Natural selection on EPAS1 (HIF2alpha) associated with low hemoglobin concentration in Tibetan highlanders.  

PubMed

By impairing both function and survival, the severe reduction in oxygen availability associated with high-altitude environments is likely to act as an agent of natural selection. We used genomic and candidate gene approaches to search for evidence of such genetic selection. First, a genome-wide allelic differentiation scan (GWADS) comparing indigenous highlanders of the Tibetan Plateau (3,200-3,500 m) with closely related lowland Han revealed a genome-wide significant divergence across eight SNPs located near EPAS1. This gene encodes the transcription factor HIF2alpha, which stimulates production of red blood cells and thus increases the concentration of hemoglobin in blood. Second, in a separate cohort of Tibetans residing at 4,200 m, we identified 31 EPAS1 SNPs in high linkage disequilibrium that correlated significantly with hemoglobin concentration. The sex-adjusted hemoglobin concentration was, on average, 0.8 g/dL lower in the major allele homozygotes compared with the heterozygotes. These findings were replicated in a third cohort of Tibetans residing at 4,300 m. The alleles associating with lower hemoglobin concentrations were correlated with the signal from the GWADS study and were observed at greatly elevated frequencies in the Tibetan cohorts compared with the Han. High hemoglobin concentrations are a cardinal feature of chronic mountain sickness offering one plausible mechanism for selection. Alternatively, as EPAS1 is pleiotropic in its effects, selection may have operated on some other aspect of the phenotype. Whichever of these explanations is correct, the evidence for genetic selection at the EPAS1 locus from the GWADS study is supported by the replicated studies associating function with the allelic variants. PMID:20534544

Beall, Cynthia M; Cavalleri, Gianpiero L; Deng, Libin; Elston, Robert C; Gao, Yang; Knight, Jo; Li, Chaohua; Li, Jiang Chuan; Liang, Yu; McCormack, Mark; Montgomery, Hugh E; Pan, Hao; Robbins, Peter A; Shianna, Kevin V; Tam, Siu Cheung; Tsering, Ngodrop; Veeramah, Krishna R; Wang, Wei; Wangdui, Puchung; Weale, Michael E; Xu, Yaomin; Xu, Zhe; Yang, Ling; Zaman, M Justin; Zeng, Changqing; Zhang, Li; Zhang, Xianglong; Zhaxi, Pingcuo; Zheng, Yong Tang

2010-06-07

427

The magnitude and selectivity of natural and multiple anthropogenic mortality causes in hunted brown bears.  

PubMed

1. The population dynamic and evolutionary effects of harvesting are receiving growing attention among biologists. Cause-specific estimates of mortality are necessary to determine and compare the magnitude and selectivity of hunting and other types of mortalities. In addition to the logistic and financial constraints on longitudinal studies, they are complicated by the fact that nonhunting mortality in managed populations usually consists of a mix of natural and human-caused factors. 2. We used multistate capture-recapture (MCR) models to estimate cause-specific survival of brown bears (Ursus arctos) in two subpopulations in Sweden over a 23-year period. In our analysis, we distinguished between legal hunting and other sources of mortality, such as intraspecific predation, accidents, poaching, and damage control removals. We also tested whether a strong increase in harvest quotas after 1997 in one of the subpopulations affected vulnerability to legal hunting. 3. Although only a fraction of mortalities other than legal hunting could be considered natural, this group of causes showed a general pattern of demographic selectivity expected from natural mortality regimes in populations of long-lived species, namely greater vulnerability of young animals. On the other hand, demographic effects on hunting vulnerability were weak and inconsistent. Our findings support the assumption that hunting and other mortalities were additive. 4. As expected, an increase in hunting pressure coincided with a correspondingly large increase in vulnerability to hunting in the affected subpopulation. Because even unbiased harvest can lead to selective pressures on life-history traits, such as size at primiparity, increasing harvest quotas may not only affect population growth directly, but could also alter optimal life-history strategies in brown bears and other carnivores. 5. Legal hunting is the most conveniently assessed and the most easily managed cause of mortality in many wild populations of large mammals. Although legal hunting is the single-most important cause of mortality for brown bears in Sweden, the combined mortality from other causes is of considerable magnitude and additionally shows greater selectivity in terms of sex and age than legal hunting. Therefore, its role in population dynamics and evolution should not be underestimated. PMID:19220565

Bischof, Richard; Swenson, Jon E; Yoccoz, Nigel G; Mysterud, Atle; Gimenez, Olivier

2009-05-01

428

Screening and selection of most potent diazotrophic cyanobacterial isolate exhibiting natural tolerance to rice field herbicides for exploitation as biofertilizer.  

PubMed

Periodic applications of heavy dosages of herbicides in modern rice-agriculture are a necessary evil for obtaining high crop productivity. Such herbicides are not only detrimental to weeds but biofertilizer strains of diazotrophic cyanobacteria also. It is therefore, essential to screen and select such biofertilizer strains of diazotrophic cyanobacteria exhibiting natural tolerance to common rice-field herbicides that can be further improved by mutational techniques to make biofertilizer technology a viable one. Therefore, efforts have been made to screen five dominant diazotrophic cyanobacterial forms e.g. filamentous heterocystous Nostoc punctiforme , Nostoc calcicola , Anabaena variabilis and unicellular Gloeocapsa sp. and Aphanocapsa sp. along with standard laboratory strain Nostoc muscorum ISU against increasing concentrations (0-100 mg l(-1) of four commercial grade common rice-field herbicides i.e. Arozin, Butachlor, Alachlor and 2,4-D under diazotrophic growth conditions. The lethal and IGC(50) concentrations for all four herbicides tested were found highest for A. variabilis as compared to other test cyanobacteria. The lowest reduction in chlorophyll a content, photosynthetic oxygen evolution, and N(2)-fixation was found in A. variabilis as compared to other rice field isolates and standard laboratory strain N. muscorum ISU. On the basis of prolong survival potential and lowest reductions in vital metabolic activities tested at IGC(50) concentration of four herbicides, it is concluded that A. variabilis is the most potent and promising cyanobacterial isolate as compared with other forms. This could be further improved by mutational techniques for exploitation as most potential and viable biofertilizer strain. PMID:16721882

Singh, Surendra; Datta, Pallavi

2006-01-01

429

A potential bias in the temporal method for estimating Ne in admixed populations under natural selection.  

PubMed

Indirect genetic methods are frequently used to estimate the effective population size (N(e)) or effective number of breeders (N(b)) in natural populations. Although assumptions behind these methods are often violated, there have been few attempts to evaluate how accurate these estimates really are in practice. Here we investigate the influence of natural selection following a population admixture on the temporal method for estimating N(e). Our analytical and simulation results suggest that N(e) is often underestimated in this method when subpopulations differ substantially in allele frequencies and in reproductive success. The underestimation is exacerbated when true N(e) and the fraction of the low-fitness group are large. As an empirical example, we compared N(b) estimated in natural populations of steelhead trout (Oncorhynchus mykiss) using the temporal method (N(b[temp])) with estimates based on direct demographic methods (N(b[demo])) and the linkage disequilibrium method (N(b[LD])). While N(b[LD]) was generally in close agreement with N(b[demo]), N(b[temp]) was much lower in sample sets that were dominated by nonlocal hatchery fish with low reproductive success, as predicted by the analytical results. This bias in the temporal method, which arises when genes associated with a particular group of parents are selected against in the offspring sample, has not been widely appreciated before. Such situations may be particularly common when artificial propagation or translocations are used for conservation. The linkage disequilibrium method, which requires data from only one sample, is robust to this type of bias, although it can be affected by other factors. PMID:17561889

Araki, Hitoshi; Waples, Robin S; Blouin, Michael S

2007-06-01

430

Investigating the genetics of Bti resistance using mRNA tag sequencing: application on laboratory strains and natural populations of the dengue vector Aedes aegypti  

PubMed Central

Mosquito control is often the main method used to reduce mosquito-transmitted diseases. In order to investigate the genetic basis of resistance to the bio-insecticide Bacillus thuringiensis subsp. israelensis (Bti), we used information on polymorphism obtained from cDNA tag sequences from pooled larvae of laboratory Bti-resistant and susceptible Aedes aegypti mosquito strains to identify and analyse 1520 single nucleotide polymorphisms (SNPs). Of the 372 SNPs tested, 99.2% were validated using DNA Illumina GoldenGate® array, with a strong correlation between the allelic frequencies inferred from the pooled and individual data (r = 0.85). A total of 11 genomic regions and five candidate genes were detected using a genome scan approach. One of these candidate genes showed significant departures from neutrality in the resistant strain at sequence level. Six natural populations from Martinique Island were sequenced for the 372 tested SNPs with a high transferability (87%), and association mapping analyses detected 14 loci associated with Bti resistance, including one located in a putative receptor for Cry11 toxins. Three of these loci were also significantly differentiated between the laboratory strains, suggesting that most of the genes associated with resistance might differ between the two environments. It also suggests that common selected regions might harbour key genes for Bti resistance.

Paris, Margot; Marcombe, Sebastien; Coissac, Eric; Corbel, Vincent; David, Jean-Philippe; Despres, Laurence

2013-01-01

431

Multi-robots to micro-surgery: Selected robotic applications at Sandia National Laboratories  

SciTech Connect

The Intelligent Systems and Robotics Center (ISRC) at Sandia National Laboratories is a multi-program organization, pursuing research, development and applications in a wide range of field. Activities range from large-scale applications such as nuclear facility dismantlement for the US Department of Energy (DOE), to aircraft inspection and refurbishment, to automated script and program generation for robotic manufacturing and assembly, to miniature robotic devices and sensors for remote sensing and micro-surgery. This paper describes six activities in the large and small scale that are underway and either nearing technology transfer stage or seeking industrial partners to continue application development. The topics of the applications include multiple arm coordination for intuitively maneuvering large, ungainly work pieces; simulation, analysis and graphical training capability for CP-5 research reactor dismantlement; miniature robots with volumes of 16 cubic centimeters and less developed for inspection and sensor deployment; and biomedical sensors to enhance automated prosthetic device production and fill laparoscopic surgery information gap.

Bennett, P.C. [Sandia National Labs., Albuquerque, NM (United States). Intelligent Systems and Robotics Center

1996-11-01

432

Liquid-gas partitioning of the gasoline oxygenate methyl tert-butyl ether (MTBE) under laboratory conditions and its effect on growth of selected algae.  

PubMed

The partitioning of the widely used gasoline additive methyl tert-butyl ether (MTBE) between liquid growth media and gaseous phase was measured daily under laboratory conditions to determine how closely dissolved MTBE concentrations matched nominal concentrations. Total (gaseous and dissolved) MTBE averaged across 6 days for 29.6, 503.2, and 1005.7 mg L-1 MTBE treatments were 89.9, 90.3, and 73.0% of nominal, respectively, and mean dissolved MTBE in these same treatments were 74.6, 73.8, and 69.6% of total MTBE, respectively. This suggests that dissolved MTBE concentrations can vary substantially from nominal. The effect of MTBE on the growth of selected algae was also evaluated under laboratory conditions. Three unicellular algae, Selenastrum capricornutum (Chlorophyta), Navicula pelliculosa (Bacillariophyta), and Synechococcus leopoliensis (= Anacystic nidulans, Cyanophyta = Cyanobacteria), representative of three taxonomic groups, were used as test organisms. Toxicity tests were acute and increase in cell number was used as an indicator of growth. Algal species were exposed by injection of MTBE into sealed vessels containing defined liquid growth media. The growth of N. pelliculosa and S. leopoliensis was negatively affected at nominal 2400 mg L-1 MTBE, whereas the growth of S. capricornutum was negatively affected at nominal 4800 mg L-1 MTBE and positively affected at nominal 600 mg L-1 MTBE. The differential sensitivity of the growth of these representative species suggests that MTBE may alter algal community composition in the natural environment. PMID:9419267

Rousch, J M; Sommerfeld, M R

1998-01-01

433

The relative influence of natural selection and geography on gene flow in guppies.  

PubMed

Two general processes may influence gene flow among populations. One involves divergent selection, wherein the maladaptation of immigrants and hybrids impedes gene flow between ecological environments (i.e. ecological speciation). The other involves geographic features that limit dispersal. We determined the relative influence of these two processes in natural populations of Trinidadian guppies (Poecilia reticulata). If selection is important, gene flow should be reduced between different selective environments. If geography is important, gene flow should be impeded by geographic distance and physical barriers. We examined how genetic divergence, long-term gene flow, and contemporary dispersal within a watershed were influenced by waterfalls, geographic distance, predation, and habitat features. We found that waterfalls and geographic distance increased genetic divergence and reduced dispersal and long-term gene flow. Differences in predation or habitat features did not influence genetic divergence or gene flow. In contrast, differences in predation did appear to reduce contemporary dispersal. We suggest that the standard predictions of ecological speciation may be heavily nuanced by the mating behaviour and life history strategies of guppies. PMID:16367829

Crispo, Erika; Bentzen, Paul; Reznick, David N; Kinnison, Michael T; Hendry, Andrew P

2006-01-01

434

Selective silencing of autoreactive B lymphocytes-Following the Nature's way.  

PubMed

A novel approach for the selective silencing of targeted autoreactive B lymphocytes is reviewed that mimics the physiological mechanisms for suppressing B cell activity. It is based on the use of bi- or tri-specific chimeric antibodies that cross-link BCRs with a pre-selected antigen-binding specificity with one or more inhibitory types of receptors on the surface of the same disease-associated B lymphocyte. The effect of these engineered antibodies was proved to be specific as they only suppressed the production of the targeted pathological antibodies while sparing those with other specificities. The administration of the chimeric molecules to lupus-prone MRL/lpr mice resulted in decreased levels of disease-associated IgG autoantibodies and of proteinuria, in the prevention of cutaneous lesions, in decreased sizes of the lymphoid organs and in prolonged survival. These results prove that it is indeed possible to selectively silence unwanted B lymphocytes as well as to significantly delay the natural course of a spontaneous antibody-mediated autoimmune disease. PMID:20601201

Nikolova, Kalina A; Mihaylova, Nikolina M; Voynova, Elisaveta N; Tchorbanov, Andrey I; Voll, Reinhard E; Vassilev, Tchavdar L

2010-07-01

435