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1

natural selection  

NSDL National Science Digital Library

Charles Darwin's theory of natural selection was the first plausible mechanism to explain the change of species over time, however, in it's original form it did not explain how new traits could form, or how traits that had formed could be passed on to successive generations. The rise in modern genetics helped to modify biologists understanding of evolution by attributing the origin of new traits in a species to random genetic processes of mutation and sexual recombination, with the survivability of species with the new traits subject to natural selection. This combination of random mutation and natural selection is often referred to as Neodarwinism.

Joiner, David; The Shodor Education Foundation, Inc.

2

Response to natural and laboratory selection at the Drosophila hsp70 genes.  

PubMed

To determine whether and how laboratory and natural selection act on the hsp70 (70-Kd heat-shock protein) genes of Drosophila melanogaster, we examined hsp70 allele frequencies in two sets of populations. First, five populations reared at different temperatures for more than 20 years differentially fixed both a large insertion/deletion (indel) polymorphism at the 87A7 hsp70 cluster ("56H8"/"122") and a single nucleotide polymorphism at the 87C1 hsp70 cluster. In both cases, the 18 degrees C and 25 degrees C populations fixed one allele and the 28 degrees C populations the other, consistent with previously described evolved differences among these populations in Hsp70 expression and thermotolerance. Second, we examined 56H8 and 122 frequencies in a set of 11 populations founded from flies collected along a latitudinal transect of eastern Australia. The 56H8 allele frequencies are positively associated with latitude, consistent with maintenance of the 56H8/122 polymorphism by natural selection. Thermal extremes and average values are negatively correlated with latitude. These results suggest that natural selection imposed by temperature and thermal variability may affect hsp70 allele frequencies. PMID:12389724

Bettencourt, Brian R; Kim, InYoung; Hoffmann, Ary A; Feder, Martin E

2002-09-01

3

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

ERIC Educational Resources Information Center

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

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

2005-01-01

4

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

5

Natural Selection  

NSDL National Science Digital Library

A common criticism of natural selection is: How can it produce novel complex useful structures by pure random chance? Darwin argued that selection is not a random process, and furthermore, it is cumulative. This lesson provides a way for students to actually compare the cumulative non-random selection of Darwin with the non-cumulative version so often erroneously implied. Students attempt to produce a full sequence of 13 cards of one suit (ace - to king). This must be done by shuffling the suit of cards for each round, then checking the cards. Half the teams must look for the full sequence each time, and repeat the process until this is accomplished. The other teams start to build their sequence by pulling the ace when it first appears as the top card, then adding to the stack whenever the next card for the sequence is shuffled to the top. Discussion reveals how the second method mimics Darwinian natural selection, while the first does not.

Heim, Werner

2007-12-12

6

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

7

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

8

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

PubMed Central

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

Glorieux, Cedric; Cuguen, Joel; Roux, Fabrice

2012-01-01

9

Natural Resource Ecology Laboratory  

NSDL National Science Digital Library

The Natural Resource Ecology Laboratory (NREL) at Colorado State University conducts multi-disciplinary research in ecosystem science, with the purpose of improving knowledge of "the complex interactions between humans, management activities, and ecosystems." The recently launched homepage, which is still under construction, includes background information on NREL; descriptions of research projects (a substantial and diverse list); publications, reports, and data; teaching and outreach; and contact information.

10

Argonne National Laboratory's Natural Convection  

E-print Network

Argonne National Laboratory's Natural Convection Shutdown Heat Removal Test Facility #12;Scaling Basis Full Scale Half Scale NSTF ArgonneNationalLaboratory's NaturalConvection will incorporate passive safety systems, many in the form of natural circulation loops, to ensure safe and long

Kemner, Ken

11

Natural Selection Lesson  

NSDL National Science Digital Library

The Natural Selection lesson uses a Monte Carlo model of spot size with variability between generations in an environment with predators to study how variation and environment can affect a species over time.

Joiner, David; The Shodor Education Foundation, Inc.

12

Introduction to Natural Selection  

NSDL National Science Digital Library

This lesson will help students develop an understanding of natural selection, specifically, how it unfolds from generation to generation. The Motivation section introduces a species of bird that became (over millions of years) numerous species, through adaptation. The Development section 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. Students will learn why organisms evolve over time, how natural selection works, and how certain factors determine survival and differences in organisms.

13

Reinventing Natural Selection  

ERIC Educational Resources Information Center

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…

Geraedts, Caspar L.; Boersma, Kerst Th.

2006-01-01

14

Investigating Natural Selection  

NSDL National Science Digital Library

In this activity, students experience one mechanism for evolution through a simulation that models the principles of natural selection and helps answer the question 'how might biological change have occurred and been reinforced over time?' Students will discover that species evolve over time and evolution is the consequence of the interaction of the potential for a species to increase in number, the genetic variability of offspring due to mutation and recombination of genes, a finite supply of the resources required for life, and the ensuing selection of those offspring better able to survive and leave offspring in a particular environment. Natural selection and its evolutionary consequences provide a scientific explanation for the fossil record of ancient life forms, as well as for the striking molecular similarities observed among the diverse species of living organisms. The site also contains a list of materials and all information and instructions required to complete this activity.

15

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

16

Naturally selecting solutions  

PubMed Central

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

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

2013-01-01

17

Extending cosmological natural selection  

E-print Network

The purpose of this paper is to propose an extension to Lee Smolin's hypothesis that our own universe belongs to a population of universes evolving by natural selection. Smolin's hypothesis explains why the parameters of physics possess the values we observe them to possess, but depends upon the contingent fact that the universe is a quantum relativistic universe. It is proposed that the prior existence of a quantum relativistic universe can itself be explained by postulating that a process of cosmogenic drift evolves universes towards stable ('rigid') mathematical structures.

Gordon McCabe

2006-10-05

18

Natural Selection: Unit Introduction  

NSDL National Science Digital Library

This lesson provides an overview for a unit on natural selection. As part of the introduction to the unit, students will have a chance to participate in a discussion around their ideas about evolution. They will also be given information about the goals and expectations for the unit, both in terms of the topics covered and the kinds of work that will be expected from them. Finally, they will be asked to complete a written assignment that will help them and the teacher determine some of the ideas they already have about how evolution operates. Students will prepare a written explanation for a change in shell morphology observed between two subspecies of Galapagos Island tortoises. The site also includes instructional notes for the teacher and a student handout with an introduction to the unit.

19

Visualizing and quantifying natural selection  

Microsoft Academic Search

Modern methods of analysis are enabling researchers to study natural selection at a new level of detail. Multivariate statistical techniques can Identify specific targets of selection and provide parameter estimates that fit into equations for evolutionary change. A more Intuitive understanding of the form of selection can be provided through graphical representation of selection surfaces. Combinations of quantitative and visual

Edmund D. Brodie; Allen J. Moore; Fredric J. Janzen

1995-01-01

20

A Natural Selection Game.  

ERIC Educational Resources Information Center

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

Tashiro, Mark E.

1984-01-01

21

On cosmic natural selection  

E-print Network

The rate of black hole formation can be increased by increasing the value of the cosmological constant. This falsifies Smolin's conjecture that the values of all constants of nature are adjusted to maximize black hole production.

Alexander Vilenkin

2006-10-04

22

Modeling Natural Selection  

NSDL National Science Digital Library

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 bet

Lotter, Christine; Bogiages, Christopher A.

2011-02-01

23

Darwin's Second Idea Natural Selection  

E-print Network

is a scientific theory well supported by the evidence 68%This class #12;Darwin's Ideas "a naturalists...might comeDarwin's Second Idea ­ Natural Selection · Evolution: controversial? · Natural selection ­ Darwin's postulates ­ Controversial? ­ Two examples of NS #12;Charles Darwin Darwin's Ideas 1. Species evolve over

24

Natural Selection and Geology 230  

E-print Network

legs · e.g., human body hair, a ves;Natural Selection · The theory of natural selection was proposed by Charles Darwin in 1859, in his book the same theory as Darwin in the 1850s. #12;One of the most famous and influential books of science. #12

Kammer, Thomas

25

Evolution Through Natural Selection  

NSDL National Science Digital Library

This workbook simulates the population genetics of a single gene with two alleles, allowing the user to set the initial allele frequencies and enter parameters for a variety of different selection models; the program then tracks the population through up to 10,000 generations.

Tim Comar (Benedictine University;Mathematics)

2005-04-17

26

Genetic Algorithms: Artificial Selection vs Natural Selection  

Microsoft Academic Search

Genetic Algorithms (GAs) are a stochastic searching and optimizing method inspired by the biological mechanism of natural selection and evolution. To improve the searching power of GAs for complicated problems, many deterministic measures, particularly, experience and\\/or expert knowledge-based heuristic rules, have been studied in the existing literature. This paper proposes a potentially more useful general methodology of integrating deterministic strategy

Xiao-Bing Hu; Ezequiel Di Paolo

27

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

28

Friendship and natural selection  

PubMed Central

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

Christakis, Nicholas A.; Fowler, James H.

2014-01-01

29

Natural Selection: How Evolution Works  

NSDL National Science Digital Library

The issue-focused interview demonstrates how natural selection is a very efficient, predictable mechanism of evolution. It illustrates how species adapt to their environment, the reproductive success of a species, design in nature and presents evidence of evolution in action, e.g., antibiotic resistance.

Douglas Futuyma (State University of New York at Stony Brook;)

2004-12-01

30

Natural Selection Promotes Antigenic Evolvability  

PubMed Central

The hypothesis that evolvability - the capacity to evolve by natural selection - is itself the object of natural selection is highly intriguing but remains controversial due in large part to a paucity of direct experimental evidence. The antigenic variation mechanisms of microbial pathogens provide an experimentally tractable system to test whether natural selection has favored mechanisms that increase evolvability. Many antigenic variation systems consist of paralogous unexpressed ‘cassettes’ that recombine into an expression site to rapidly alter the expressed protein. Importantly, the magnitude of antigenic change is a function of the genetic diversity among the unexpressed cassettes. Thus, evidence that selection favors among-cassette diversity is direct evidence that natural selection promotes antigenic evolvability. We used the Lyme disease bacterium, Borrelia burgdorferi, as a model to test the prediction that natural selection favors amino acid diversity among unexpressed vls cassettes and thereby promotes evolvability in a primary surface antigen, VlsE. The hypothesis that diversity among vls cassettes is favored by natural selection was supported in each B. burgdorferi strain analyzed using both classical (dN/dS ratios) and Bayesian population genetic analyses of genetic sequence data. This hypothesis was also supported by the conservation of highly mutable tandem-repeat structures across B. burgdorferi strains despite a near complete absence of sequence conservation. Diversification among vls cassettes due to natural selection and mutable repeat structures promotes long-term antigenic evolvability of VlsE. These findings provide a direct demonstration that molecular mechanisms that enhance evolvability of surface antigens are an evolutionary adaptation. The molecular evolutionary processes identified here can serve as a model for the evolution of antigenic evolvability in many pathogens which utilize similar strategies to establish chronic infections. PMID:24244173

Graves, Christopher J.; Ros, Vera I. D.; Stevenson, Brian; Sniegowski, Paul D.; Brisson, Dustin

2013-01-01

31

The cost of natural selection  

Microsoft Academic Search

Summary  Unless selection is very intense, the number of deaths needed to secure the substitution, by natural selection, of one gene\\u000a for another at a locus, is independent of the intensity of selection. It is often about 30 times the number of organisms in\\u000a a generation. It is suggested that, in horotelic evolution, the mean time taken for each gene substitution

J. B. S. Haldane

1957-01-01

32

Natural Selection and Applied Genetics  

NSDL National Science Digital Library

Natural Selection and Applied Genetics is a graduate-level professional development course designed to enhance your understanding and teaching of life science. In two sessions, you will investigate life science topics using hands-on activities and online resources including video segments, interactive activities, readings, and other multimedia materials. These resources are drawn from Teachers' Domain, WGBH's digital library service.

2010-01-01

33

Graduate Fellowship Opportunities Natural Resource Ecology Laboratory  

E-print Network

, and team building skills while enriching STEM learning and instruction in K-12 schools. ThroughGraduate Fellowship Opportunities Natural Resource Ecology Laboratory The Natural Resource Ecology and augmentation awards pay a stipend based on your level of involvement. The fellowships provide funding

MacDonald, Lee

34

Scavenger Hunt: Simulating Natural Selection  

NSDL National Science Digital Library

This kinesthetic activity simulates the process of evolution by natural selection. Students take on the roles of crab-like predators that exhibit one of four variants of feeding appendage: a spoon, fork, knife, and chopsticks. The simulation runs for three trials, as the predators use their appendages to harvest pinto beans, with varying success. Students track the frequency of each appendage type through three generations. This resource is from PUMAS - Practical Uses of Math and Science - a collection of brief examples created by scientists and engineers showing how math and science topics taught in K-12 classes have real world applications.

35

Simulate Natural Selection With Beetles  

NSDL National Science Digital Library

In this simulation activity, students experiment with a population of M&M candies or paper dot "beetles" to test how well each color is adapted to survive on a field of colorful wrapping paper or fabric. Students act as predators and see that camouflaged beetles survive predation preferentially. Students reflect on how the activity could be modified to better simulate the process of predation-based natural selection. This activity is supported by a textbook chapter, "Origin of Species," part of the unit, "Losing Biodiversity," in Global Systems Science (GSS), an interdisciplinary course for high school students that emphasizes how scientists from a wide variety of fields work together to understand significant problems of global impact.

36

Shade selection. Communicating with the laboratory technician.  

PubMed

Shade selection for anterior crowns has always set up a communications problem between the dentist and laboratory technician. Over the years, many different techniques have been formulated to help overcome the problem. These techniques include picture taking, drawing diagrams and using multiple porcelain shade guides. However, they have not completely erased the difficulty of communicating the choice of the proper shade of an anterior crown. This was especially true in the 1990's when all-ceramic crowns were introduced. Popular techniques dentists use for communicating shade selections will be reviewed, along with guidelines for making the proper selection. Many dentists are familiar only with the techniques they were taught in dental school and/or residency program and are unaware of the superior methods that can be used. This type of review can be extremely helpful to restorative dentists. PMID:10874837

Lichter, J A; Solomowitz, B H; Sher, M

2000-05-01

37

Natural Selection: Exploring Variation and Heritability  

NSDL National Science Digital Library

This lesson has students think about two important components of Darwin's model of natural selection in greater detail. First, they will have an opportunity to explore the natural variations present in a variety of organisms. Specifically, they will examine sunflower seeds and Wisconsin Fast Plants. Next, they will use data and graphs of that data from an artificial selection experiment to consider the role of heredity in natural selection. They will answer questions related to a graph and review the statistical concepts of mean, median, mode, and range and will work in groups to examine and answer questions about graphs. The site includes instructional notes for the teacher and the required student handouts.

38

Experiencing Natural Selection: Will You Survive?  

NSDL National Science Digital Library

This video from the Teaching Channel demonstrates the concept of natural selection. The engaging classroom activity, led by instructor Ceri Evans, addresses survival and natural selection and relates these ideas to the larger concept of evolution. The video may be shown to students to demonstrate these concepts, or may be used as the basis for a similar classroom activity. Running time for the video is 27:29.

2011-01-01

39

The Natural Selection of Stick-Worms  

NSDL National Science Digital Library

This lesson teaches students that traits are usually favored by natural selection only when they result in more reproductively successful offspring. Students go out onto the school lawn and play the role of birds, picking up toothpick stick worms which have been previously scattered in equal numbers of green-stained and unstained. Birds are chased away before the worm population drops too low. Back in the classroom, the number of green and non-green worms are compared individually and for the whole class. Discussion relates the experience to the elements of natural selection. As presented here, it does not lend itself to demonstrating the effects of selection over multiple generations.

Dutton, Don; Fisher, Fred; Flammer, Larry

40

The negative view of natural selection.  

PubMed

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

Birch, Jonathan

2012-06-01

41

Sex ratio, sex change, and natural selection.  

PubMed Central

We describe the analogy between the theory of natural selection on sex ratio in newborn gonochores (which will not change sex), and on the age of sex change in sequential hermaphrodites (which are all born into one sex and change to the other later on). We also discuss the conditions under which natural selection favors sequential hermaphrodites over gonochores and vice versa. We show that, in a nearly stable population of nearly constant age composition, selection favors a rare mutant if it increases the prospective reproduction of its newborn bearers that are (or while they are) members of one sex by a percentage exceeding the percentage loss to the other sex. PMID:1068478

Leigh, E G; Charnov, E L; Warner, R R

1976-01-01

42

Can natural selection favour altruism between species?  

PubMed

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

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

2013-09-01

43

Natural and sexual selection against hybrid flycatchers  

PubMed Central

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

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

2008-01-01

44

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

45

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. PMID:22487312

Frank, Steven A.

2012-01-01

46

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.

47

Natural selection in the field and the classroom.  

E-print Network

??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… (more)

Andrews, Tessa Marie.

2012-01-01

48

Natural selection and the regulation of defenses  

Microsoft Academic Search

Many of the body's adaptive responses, such as pain, fever, and fear, are defenses that remain latent until they are aroused by cues that indicate the presence of a threat. Natural selection should shape regulation mechanisms that express defenses only in situations where their benefits exceed their costs, but defenses are often expressed in situations where they seem unnecessary, with

Randolph M. Nesse

2005-01-01

49

A Lesson on Evolution & Natural Selection  

ERIC Educational Resources Information Center

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

Curtis, Anthony D.

2010-01-01

50

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

51

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

PubMed

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

Ayala, Francisco J

2010-08-01

52

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.

53

Natural Selection 9-149 Chapter 9. NATURAL SELECTION AND BIOLOGICAL  

E-print Network

Huxley (1825-1895), about Darwin's theory of Evolution by Nat- ural Selection. I. Introduction A selection into the category of a discovery. Charles Darwin developed his basic theory of evolution created. B. Darwin's Contribution Natural selection is a model of how evolution works. Darwin is sometimes

Richerson, Peter J.

54

The nature of selection during plant domestication.  

PubMed

Plant domestication is an outstanding example of plant-animal co-evolution and is a far richer model for studying evolution than is generally appreciated. There have been numerous studies to identify genes associated with domestication, and archaeological work has provided a clear understanding of the dynamics of human cultivation practices during the Neolithic period. Together, these have provided a better understanding of the selective pressures that accompany crop domestication, and they demonstrate that a synthesis from the twin vantage points of genetics and archaeology can expand our understanding of the nature of evolutionary selection that accompanies domestication. PMID:19212403

Purugganan, Michael D; Fuller, Dorian Q

2009-02-12

55

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

56

The status of cosmological natural selection  

E-print Network

The problem of making predictions from theories that have landscapes of possible low energy parameters is reviewed. Conditions for such a theory to yield falsifiable predictions for doable experiments are given. It is shown that the hypothesis of cosmological natural selection satisfies these conditions, thus showing that it is possible to continue to do physics on a landscape without invoking the anthropic principle. In particular, this is true whether or not the ensemble of universes generated by black holes bouncing is a sub-ensemble of a larger ensemble that might be generated by a random process such as eternal inflation. A recent criticism of cosmological natural selection made by Vilenkin in hep-th/0610051 is discussed. It is shown to rely on assumptions about both the infrared and ultraviolet behavior of quantum gravity that are very unlikely to be true.

Lee Smolin

2006-12-18

57

Machine Learning and Inference Laboratory Natural Induction and Conceptual Clustering  

E-print Network

Reports Machine Learning and Inference Laboratory Natural Induction and Conceptual Clustering University #12;NATURAL INDUCTION AND CONCEPTUAL CLUSTERING: A REVIEW OF APPLICATIONS Ryszard S. Michalski}@mli.gmu.edu; samitchell@verizon.net; wdseeman@braemarnet.com http://www.mli.gmu.edu Abstract Natural induction

Michalski, Ryszard S.

58

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

2009-08-01

59

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. PMID:2515111

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

1989-01-01

60

Natural Selection: Developing a Darwinian Explanation  

NSDL National Science Digital Library

This lesson asks students to take their understanding of Darwin's model of natural selection and begin to think about how it can be used to explain natural phenomena. They will do this by first attempting individually to explain the case of lizard camouflage to provide a concrete example from which to work. Next, they will work within their groups to compile an explanation based on all of their work and, finally, they will be asked to develop a set of criteria for acceptable explanations. Each individual student will develop a Darwinian explanation and each group will write a complete explanation and a list of criteria for a good explanation. The site includes instructional notes for teachers and a student handout.

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

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. PMID:1061123

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

1976-01-01

64

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

SciTech Connect

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

Hanke, Anna [Max Planck Institute for Marine Microbiology; Hamann, Emmo [Max Planck Institute for Marine Microbiology; Sharma, Ritin [ORNL; Geelhoed, Jeanine [Max Planck Institute for Marine Microbiology; Hargesheimer, Theresa [Max Planck Institute for Marine Microbiology; Kraft, Beate [Max Planck Institute for Marine Microbiology; Meyer, Volker [Max Planck Institute for Marine Microbiology; Lenk, Sabine [Max Planck Institute for Marine Microbiology; Osmers, Harald [Max Planck Institute for Marine Microbiology; Wu, Rong [Delft University of Technology, Delft, Netherlands; Makinwa, Kofi [Delft University of Technology, Delft, Netherlands; Hettich, Robert {Bob} L [ORNL; Banfield, Jillian F. [University of California, Berkeley; Tegetmeyer, Halina [Max Planck Institute for Marine Microbiology; Strouss, Marc [University of Calgary, ALberta, Canada

2014-01-01

65

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

PubMed

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

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

2014-01-01

66

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

2010-06-01

67

The snowmaker: nature identical snow production in the laboratory  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

68

SERUM ALBUMIN POLYMORPHISMS IN NATURAL AND LABORATORY POPULATIONS OF PEROMYSCUS  

E-print Network

to estimate frequencies of coat color alleles in Peromyscus maniculatus, and the studies of antigenic the codominantmode of inheritance. From left to right: homozygous Peromyscus maniculatus, homozygous P. maniculatusSERUM ALBUMIN POLYMORPHISMS IN NATURAL AND LABORATORY POPULATIONS OF PEROMYSCUS JAMES H. BROWN

Brown, James H.

69

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. PMID:15347525

Nesse, Randolph M

2004-01-01

70

Good genes sexual selection in nature  

PubMed Central

Whether the mate sampling and choice performed by females in nature influences offspring performance is a controversial issue in theory and an open empirical question. Pronghorn (Antilocapra americana) females engage in an obvious and energetically expensive mate sampling process to identify vigorous males. Although individual females sample independently, their choices converge on a small proportion of males that sire most young. Offspring of attractive males were more likely to survive to weaning and to age classes as late as 5 years, resulting in a selection differential, calculated by expected differences in lifetime number of offspring weaned, of 0.32 against random mating. Enhanced survival to weaning appeared to be accomplished by faster growth rates. Females compensated for matings with a less attractive mate by elevating rates of milk delivery to their young. Because pronghorn males do not have costly ornaments, we conclude that female choice for good genes can exist in the absence of ornaments. Furthermore, female choice may be important and unrecognized as a force that can lower population genetic load. PMID:17060640

Byers, John A.; Waits, Lisette

2006-01-01

71

Good genes sexual selection in nature.  

PubMed

Whether the mate sampling and choice performed by females in nature influences offspring performance is a controversial issue in theory and an open empirical question. Pronghorn (Antilocapra americana) females engage in an obvious and energetically expensive mate sampling process to identify vigorous males. Although individual females sample independently, their choices converge on a small proportion of males that sire most young. Offspring of attractive males were more likely to survive to weaning and to age classes as late as 5 years, resulting in a selection differential, calculated by expected differences in lifetime number of offspring weaned, of 0.32 against random mating. Enhanced survival to weaning appeared to be accomplished by faster growth rates. Females compensated for matings with a less attractive mate by elevating rates of milk delivery to their young. Because pronghorn males do not have costly ornaments, we conclude that female choice for good genes can exist in the absence of ornaments. Furthermore, female choice may be important and unrecognized as a force that can lower population genetic load. PMID:17060640

Byers, John A; Waits, Lisette

2006-10-31

72

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

73

Selective phonotaxis of female crickets under natural outdoor conditions.  

PubMed

Acoustic mate choice in insects has been extensively studied under laboratory conditions, using different behavioural paradigms. Ideally, however, mate choice designs should reflect natural conditions, including the physical properties of the transmission channel for the signal. Since little is known about the discrimination ability of females between male song variants under natural conditions, we performed phonotaxis experiments with female field crickets (Gryllus bimaculatus) outdoors, using two-choice decisions based on differences in carrier frequency, sound pressure level, and chirp rate. For all three song parameters, minimum differences necessary for a significant preference between two song models were considerably larger outdoors compared to laboratory conditions. A minimum amplitude difference of 5 dB was required for a significant choice in the field, compared to only 1-2 dB reported for lab-based experiments. Due to the tuned receiver system, differences in carrier frequency equal differences in perceived loudness, and the results on choice for differences in carrier frequency corroborate those in amplitude. Similarly, chirp rate differences of 50 chirps/min were required outdoors compared to only 20 chirps/min in the lab. For predictions about patterns of sexual selection, future studies need to consider the different outcomes of mate choice decisions in lab and field trials. PMID:24488017

Hirtenlehner, Stefan; Römer, Heiner

2014-03-01

74

NATURAL SELECTION ON COLOR PATTERNS IN POECILIA RETICULATA  

Microsoft Academic Search

All too often in evolutionary biology we are led to speculate or infer the mode of action of natural selection; we usually do not know why some individuals are more adaptive than others. Very often attempts to measure natural selection are unsuc- cessful, leading to heated arguments about the relative importance of selection, ge- netic drift, and epistasis in evolution

JOHN A. ENDLER

1980-01-01

75

A Working Model of Natural Selection Illustrated by Table Tennis  

ERIC Educational Resources Information Center

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

Dinc, Muhittin; Kilic, Selda; Aladag, Caner

2013-01-01

76

Patterns and Power of Phenotypic Selection in Nature  

NSDL National Science Digital Library

This article from the July/August 2007 issue of BioScience is about natural selection and quantifies the strength of selection in nature. Phenotypic selection occurs when individuals with certain characteristics produce more surviving offspring than individuals with other characteristics. Although selection is regarded as the chief engine of evolutionary change, scientists have only recently begun to measure its action in the wild. These studies raise numerous questions: How strong is selection, and do different types of traits experience different patterns of selection? Is selection on traits that affect mating success as strong as selection on traits that affect survival? Does selection tend to favor larger body size, and, if so, what are its consequences? We explore these questions and discuss the pitfalls and future prospects of measuring selection in natural populations.

Joel G. Kingsolver, David W. Pfennig (;)

2007-07-01

77

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

78

Sexual selection and natural selection in bird speciation  

PubMed Central

The role of sexual selection in speciation is investigated, addressing two main issues. First, how do sexually selected traits become species recognition traits? Theory and empirical evidence suggest that female preferences often do not evolve as a correlated response to evolution of male traits. This implies that, contrary to runaway (Fisherian) models of sexual selection, premating isolation will not arise as an automatic side effect of divergence between populations in sexually selected traits. I evaluate premating isolating mechanisms in one group, the birds. In this group premating isolation is often a consequence of sexual imprinting, whereby young birds learn features of their parents and use these features in mate choice. Song, morphology and plumage are known recognition cues. I conclude that perhaps the main role for sexual selection in speciation is in generating differences between populations in traits. Sexual imprinting then leads to these traits being used as species recognition mechanisms. The second issue addressed in this paper is the role of sexual selection in adaptive radiation, again concentrating on birds. Ecological differences between species include large differences in size, which may in themselves be sufficient for species recognition, and differences in habitat, which seem to evolve frequently and at all stages of an adaptive radiation. Differences in habitat often cause song and plumage patterns to evolve as a result of sexual selection for efficient communication. Therefore sexual selection is likely to have an important role in generating premating isolating mechanisms throughout an adaptive radiation. It is also possible that sexual selection, by creating more allopatric species, creates more opportunity for ecological divergence to occur. The limited available evidence does not support this idea. A role for sexual selection in accelerating ecological diversification has yet to be demonstrated.

Price, T.

1998-01-01

79

Seal formation in arid soil under natural and laboratory conditions  

NASA Astrophysics Data System (ADS)

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

Sarah, Pariente; Sachs, Eyal

2013-04-01

80

ORIGINAL PAPER Interactions between sexual and natural selection  

E-print Network

natural selection on badge evolution. Across both subspecies the extent of rusty feathers in the cap patchORIGINAL PAPER Interactions between sexual and natural selection on the evolution of a plumage than an inland-marsh sparrow, M. g. georgiana. Studies of feather- degrading bacteria and convergent

Walters, Jeffrey R.

81

The Nature of Selection on Anhydrobiotic Capacityin Tardigrades  

Microsoft Academic Search

Tardigrades are well known for their capacity to enter an anhydrobiotic state, and remain ametabolic for several years. Yet the evolutionary background, and the forces of natural selection that act on anhydrobiotic capacity have remained unexplored. In this paper, I review the basic problem of anhydrobiosis and the phenotypic traits that may be the main targets of natural selection for

K. Ingemar Jönsson

2001-01-01

82

ORIGINAL PAPER Synthetic analyses of phenotypic selection in natural  

E-print Network

ORIGINAL PAPER Synthetic analyses of phenotypic selection in natural populations: lessons.V. 2012 Abstract There are now thousands of estimates of phenotypic selection in natural pop- ulations, resulting in multiple synthetic reviews of these data. Here we consider several major lessons

Carlson, Stephanie

83

Development and Evaluation of the Conceptual Inventory of Natural Selection.  

ERIC Educational Resources Information Center

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

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

2002-01-01

84

Are Humans Still Evolving? A Natural Selection Discussion Lesson  

ERIC Educational Resources Information Center

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

Shields, Martin

2004-01-01

85

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

86

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

87

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

88

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

ERIC Educational Resources Information Center

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

Sickel, Aaron J.; Friedrichsen, Patricia J.

2012-01-01

89

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. PMID:21150291

Kessler, André

2010-01-01

90

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

91

Bayesian natural selection and the evolution of perceptual systems.  

PubMed Central

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

Geisler, Wilson S; Diehl, Randy L

2002-01-01

92

Natural SelectionsDepartment of Defense Natural Resources Program Spring 2013  

E-print Network

Natural SelectionsDepartment of Defense Natural Resources Program Spring 2013 How will climate to species ranges and distribution. Consequently, today's natural resource planners--both civilian other issues, but they must now also consider if and how climate change will affect their natural

93

The College Language Laboratory: Selected Work Papers Presented at the Conference on the College Language Laboratory, November 1960.  

ERIC Educational Resources Information Center

Selected papers of a conference dealing with development and use of language laboratories in the early 1960's are presented in this publication. Selections include: (1) F. R. Morton's "Recent Developments in Language Laboratory Equipment for Teaching and Research", (2) Pierre Delattre's "Testing the Oral Production of Language Students", (3)…

Morton, F. Rand, Ed.

94

Snapping shrimp prefer natural as opposed to artificial materials as their habitat in laboratory conditions  

NASA Astrophysics Data System (ADS)

This study analyzed the habitat selection behavior of the snapping shrimp, Alpheus spp., comparing natural shelters (Rocks with oysters attached on the surface Sh; rocks with smooth surface, Ro and coral rubble, Co with plastic bottle. Controlled laboratory experiments were conducted to assess the habitat preference, effect of photoperiod and shrimp orientation at shelter. The current study indicated that snapping shrimp preferred natural materials but rejected plastic bottle as their shelter. Among the natural shelters, coral rubble was the most preferred habitat followed by shell and rock. Photoperiod showed minimum effect on the shrimp where they spend most of the time inside and underneath the shelters. In conclusion the current study showed that snapping shrimp preferred coral rubble as opposed to other natural material and plastic bottle. The result also suggested that plastic debris in the marine environment is not an alternative habitat for snapping shrimp.

Sim, Lai Kean; Ghazali, Shahriman M.

2014-09-01

95

Selection of the Mars Science Laboratory Landing Site  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

96

Selection of the Mars Science Laboratory landing site  

USGS Publications Warehouse

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

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

2012-01-01

97

Characterization of radiation environments at selected Pacific Northwest Laboratory facilities  

SciTech Connect

This report is based on a study conducted by Pacific Northwest Laboratory (PNL) from December 15, 1990 to December 15, 1991, to characterize the radiation environments at selected locations within PNL facilities. Thermoluminescent dosimeters were placed at 72 locations to measure non-productive radiation exposure to identify areas in which continuous occupation by a staff member would expose the staff member to radiation exceeding the 100 mrem/yr limit. The areas measured were found to be below the 0.05 mR/hr limit with the exception of three locations. At these three locations above the limit, radiation exposure was reduced by changing office locations and by additional shielding around radiation sources. Evaluations are recommended to determine the causes of elevated exposure rate readings.

Oxley, C.L.

1992-10-01

98

Darwin, microbes and evolution by natural selection.  

PubMed

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

Moxon, E Richard

2011-01-01

99

Natural selective attention: Orienting and emotion  

PubMed Central

The foundations of orienting and attention are hypothesized to stem from activation of defensive and appetitive motivational systems that evolved to protect and sustain the life of the individual. Motivational activation initiates a cascade of perceptual and motor processes that facilitate the selection of appropriate behavior. Among these are detection of significance, indexed by a late centro-parietal positivity in the event-related potential, enhanced perceptual processing, indexed by a initial cardiac deceleration, and preparation for action, indexed by electrodermal changes. Data exploring the role of stimulus novelty and significance in orienting are presented that indicate different components of the orienting response habituate at different rates. Taken together, it is suggested that orienting is mediated by activation of fundamental motivational systems that have evolved to support survival. PMID:18778317

BRADLEY, MARGARET M.

2013-01-01

100

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

101

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

102

Natural and sexual selection in a monogamous historical human population  

E-print Network

those applying evolutionary theory in humans, some scientists consider recent selective pressures weakNatural and sexual selection in a monogamous historical human population Alexandre Courtiola,b,c,1, Cambridge, MA, and approved March 28, 2012 (received for review November 4, 2011) Whether and how human

Lummaa, Virpi

103

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

104

Effective Assessment: Probing Students' Understanding of Natural Selection  

ERIC Educational Resources Information Center

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

Stern, Luli

2004-01-01

105

A network of schools for a natural hazard laboratory  

NASA Astrophysics Data System (ADS)

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

Occhipinti, S.

2012-04-01

106

A Survey of Curriculum Laboratories in Selected Colleges in Pennsylvania.  

ERIC Educational Resources Information Center

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

Nevil, Leota

107

Natural selection on testosterone production in a wild songbird population.  

PubMed

Because of their role in mediating life-history trade-offs, hormones are expected to be strongly associated with components of fitness; however, few studies have examined how natural selection acts on hormonal variation in the wild. In a songbird, the dark-eyed junco (Junco hyemalis), field experiments have shown that exogenous testosterone alters individuals' resolution of the survival-reproduction trade-off, enhancing reproduction at the expense of survival. Here we used standardized injections of gonadotropin-releasing hormone (GnRH) to assay variation in the testosterone production of males. Using measurements of annual survival and reproduction, we found evidence of strong natural selection acting on GnRH-induced increases in testosterone. Opposite to what would be predicted from the survival-reproduction trade-off, patterns of selection via survival and reproduction were remarkably similar. Males with GnRH-induced testosterone production levels that were slightly above the population mean were more likely to survive and also produced more offspring, leading to strong stabilizing selection. Partitioning reproduction into separate components revealed positive directional selection via within-pair siring success and stabilizing selection via extrapair mating success. Our data represent the most complete demonstration of natural selection on hormones via multiple fitness components, and they complement previous experiments to illuminate testosterone's role in the evolution of life-history trade-offs. PMID:20394524

McGlothlin, Joel W; Whittaker, Danielle J; Schrock, Sara E; Gerlach, Nicole M; Jawor, Jodie M; Snajdr, Eric A; Ketterson, Ellen D

2010-06-01

108

Nonconsumptive predator-driven mortality causes natural selection on prey.  

PubMed

Predators frequently exert natural selection through differential consumption of their prey. However, predators may also cause prey mortality through nonconsumptive effects, which could cause selection if different prey phenotypes are differentially susceptible to this nonconsumptive mortality. Here we present an experimental test of this hypothesis, which reveals that nonconsumptive mortality imposed by predatory dragonflies causes selection on their damselfly prey favoring increased activity levels. These results are consistent with other studies of predator-driven selection, however, they reveal that consumption alone is not the only mechanism by which predators can exert selection on prey. Uncovering this mechanism also suggests that prey defensive traits may represent adaptations to not only avoid being consumed, but also for dealing with other sources of mortality caused by predators. Demonstrating selection through both consumptive and nonconsumptive predator mortality provides us with insight into the diverse effects of predators as an evolutionary force. PMID:24152082

Siepielski, Adam M; Wang, Jason; Prince, Garrett

2014-03-01

109

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

110

Fitness landscape of Atlantic cod shaped by harvest selection and natural selection  

Microsoft Academic Search

Harvesting may lead to evolutionary changes in life histories on a contemporary time scale, changes that could be maladaptive\\u000a in natural contexts. However, our understanding of the strength and direction of harvest-induced selection versus natural\\u000a selection is still limited, partly due to the difficulty of tracking the fate of individuals in the wild. Here, we present\\u000a direct estimates of harvest

Esben Moland Olsen; Even Moland

2011-01-01

111

Natural Image Statistics and Low-Complexity Feature Selection  

Microsoft Academic Search

Low-complexity feature selection is analyzed in the context of visual recognition. It is hypothesized that high-order dependences of bandpass features contain little information for discrimination of natural images. This hypothesis is characterized formally, by introduction of the concepts of conjunctive inter- ference and decomposability order of a feature set. Necessary and sufficient conditions, for the feasibility of low-complexity feature selection,

Manuela Vasconcelos; Nuno Vasconcelos

2009-01-01

112

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

113

The Slumgullion Natural Laboratory for Observing Slip Phenomena  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

114

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

115

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. PMID:23221753

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

2013-01-01

116

Measuring Natural Selection on Genotypes and Phenotypes in the Wild  

PubMed Central

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

Linnen, Catherine R.; Hoekstra, Hopi E.

2013-01-01

117

The Role of Metaphor in the Darwin Debates: Natural Theology, Natural Selection, and Christian Production of Counter-Metaphor  

E-print Network

' emotional adherence to natural theology. Many of the interpreters of Darwin's work, both secular and Christian, saw natural selection as a rival to natural theology. The works of three prominent Victorians who attempted to defend natural theology against...

Neumann, Juliet

2012-07-16

118

Natural Selection Reduced Diversity on Human Y Chromosomes  

E-print Network

Natural Selection Reduced Diversity on Human Y Chromosomes Melissa A. Wilson Sayres1,2 *, Kirk E of America Abstract The human Y chromosome exhibits surprisingly low levels of genetic diversity. This could chromosome. Here, using genome-wide analyses of X, Y, autosomal and mitochondrial DNA, in combination

Nielsen, Rasmus

119

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

120

Signatures of natural selection in the human genome  

Microsoft Academic Search

During their dispersal from Africa, our ancestors were exposed to new environments and diseases. Those who were better adapted to local conditions passed on their genes, including those conferring these benefits, with greater frequency. This process of natural selection left signatures in our genome that can be used to identify genes that might underlie variation in disease resistance or drug

Michael Bamshad; Stephen P. Wooding

2003-01-01

121

Ocean waves, nearshore ecology, and natural selection Mark W. Denny*  

E-print Network

-1 Ocean waves, nearshore ecology, and natural selection Mark W. Denny* Stanford University and Helmuth 2002). At high tide, ocean waves break on the shore, imposing large hydrodynamic forces, Intertidal communities, Lift, Wave theory Abstract Although they are subjected to one of the most stressful

Denny, Mark

122

Signatures of selection in natural populations adapted to chronic pollution  

Microsoft Academic Search

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

Larissa M Williams; Marjorie F Oleksiak

2008-01-01

123

Natural Selection: It's Not Darwin's (Or Wallace'S) Theory  

Microsoft Academic Search

For nearly 150 years, since soon after the appearance of the On the Origin of Species, we have known that neither Charles Darwin nor Alfred Russel Wallace originated the theory of natural selection. This certainty is based on the fact that both of these great naturalists admitted that they were beaten to the theory by at least two other naturalists.

Milton Wainwright

2008-01-01

124

Natural selection drives the evolution of ant life cycles.  

PubMed

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

Wilson, Edward O; Nowak, Martin A

2014-09-01

125

Natural selection drives the evolution of ant life cycles  

PubMed Central

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

Wilson, Edward O.; Nowak, Martin A.

2014-01-01

126

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

127

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

PubMed Central

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

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

1985-01-01

128

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. PMID:20462906

Mojica, Julius P.; Kelly, John K.

2010-01-01

129

Priorities for selection and representation in natural tasks  

PubMed Central

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

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

2013-01-01

130

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

PubMed Central

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

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

2010-01-01

131

Natural selection on thermal performance in a novel thermal environment.  

PubMed

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

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

2014-09-30

132

Medicine, evolution, and natural selection: an historical overview.  

PubMed

Contemporary Darwinian medicine is a still-expanding new discipline, one of whose principal aims is to arrive at an evolutionary understanding of those aspects of the body that leave it vulnerable to disease. Historically, there was a precedent for this research; between 1880 and 1940, several scientists tried to develop some general evolutionary theories of disease as arising from deleterious traits that escape elimination by natural selection. In contrast, contemporary Darwinian medicine uses evolutionary theory to consider all the possible reasons why selection has left humans vulnerable to disease. PMID:20039527

Zampieri, Fabio

2009-12-01

133

Copyright 2006 by Machine Learning and Inference Laboratory Application of Natural Induction and Conceptual  

E-print Network

Copyright © 2006 by Machine Learning and Inference Laboratory Application of Natural Induction and Conceptual Clustering to Pattern Discovery in Data Examples of Application to Medicine, Bioinformatics Research Projects in the Machine Learning and Inference Laboratory (www.mli.gmu.edu) Natural Induction (AQ

Michalski, Ryszard S.

134

Natural selection and infectious disease in human populations.  

PubMed

The ancient biological 'arms race' between microbial pathogens and humans has shaped genetic variation in modern populations, and this has important implications for the growing field of medical genomics. As humans migrated throughout the world, populations encountered distinct pathogens, and natural selection increased the prevalence of alleles that are advantageous in the new ecosystems in both host and pathogens. This ancient history now influences human infectious disease susceptibility and microbiome homeostasis, and contributes to common diseases that show geographical disparities, such as autoimmune and metabolic disorders. Using new high-throughput technologies, analytical methods and expanding public data resources, the investigation of natural selection is leading to new insights into the function and dysfunction of human biology. PMID:24776769

Karlsson, Elinor K; Kwiatkowski, Dominic P; Sabeti, Pardis C

2014-06-01

135

Natural selection shaped regional mtDNA variation in humans  

Microsoft Academic Search

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

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

2002-01-01

136

Compactifying de Sitter Naturally Selects a Small Cosmological Constant  

E-print Network

We study compactifications of $D$-dimensional de Sitter space with a $q$-form flux down to $D-Nq$ dimensions. We show that for $(N-1)(q-1)\\geq 2$ there are double-exponentially or even infinitely many compact de Sitter vacua, and that their effective cosmological constants accumulate at zero. This population explosion of $\\Lambda \\ll 1$ de Sitters arises by a mechanism analogous to natural selection.

Adam R. Brown; Alex Dahlen; Ali Masoumi

2013-11-11

137

Genomic mutation rates that neutralize adaptive evolution and natural selection  

PubMed Central

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.

2013-01-01

138

Birth-order differences can drive natural selection on aging.  

PubMed

Senescence-the deterioration of survival and reproductive capacity with increasing age-is generally held to be an evolutionary consequence of the declining strength of natural selection with increasing age. The diversity in rates of aging observed in nature suggests that the rate at which age-specific selection weakens is determined by species-specific ecological factors. We propose that, in iteroparous species, relationships between parental age, offspring birth order, and environment may affect selection on senescence. Later-born siblings have, on average, older parents than do first borns. Offspring born to older parents may experience different environments in terms of family support or inherited resources, factors often mediated by competition from siblings. Thus, age-specific selection on parents may change if the environment produces birth-order related gradients in reproductive success. We use an age-and-stage structured population model to investigate the impact of sibling environmental inequality on the expected evolution of senescence. We show that accelerated senescence evolves when later-born siblings are likely to experience an environment detrimental to lifetime reproduction. In general, sibling inequality is likely to be of particular importance for the evolution of senescence in species such as humans, where family interactions and resource inheritance have important roles in determining lifetime reproduction. PMID:24274174

Gillespie, Duncan O S; Trotter, Meredith V; Krishna-Kumar, Siddharth; Tuljapurkar, Shripad D

2014-03-01

139

Laboratory security and emergency response guidance for laboratories working with select agents. Centers for Disease Control and Prevention.  

PubMed

In recent years, concern has increased regarding use of biologic materials as agents of terrorism, but these same agents are often necessary tools in clinical and research microbiology laboratories. Traditional biosafety guidelines for laboratories have emphasized use of optimal work practices, appropriate containment equipment, well-designed facilities, and administrative controls to minimize risk of worker injury and to ensure safeguards against laboratory contamination. The guidelines discussed in this report were first published in 1999 (U.S. Department of Health and Human Services/CDC and National Institutes of Health. Biosafety in microbiological and biomedical laboratories [BMBL]. Richmond JY, McKinney RW, eds. 4th ed. Washington, DC: US Department of Health and Human Services, 1999 [Appendix F]). In that report, physical security concerns were addressed, and efforts were focused on preventing unauthorized entry to laboratory areas and preventing unauthorized removal of dangerous biologic agents from the laboratory. Appendix F of BMBL is now being revised to include additional information regarding personnel risk assessments, and inventory controls. The guidelines contained in this report are intended for laboratories working with select agents under biosafety-level 2, 3, or 4 conditions as described in Sections II and III of BMBL. These recommendations include conducting facility risk assessments and developing comprehensive security plans to minimize the probability of misuse of select agents. Risk assessments should include systematic, site-specific reviews of 1) physical security; 2) security of data and electronic technology systems; 3) employee security; 4) access controls to laboratory and animal areas; 5) procedures for agent inventory and accountability; 6) shipping/transfer and receiving of select agents; 7) unintentional incident and injury policies; 8) emergency response plans; and 9) policies that address breaches in security. The security plan should be an integral part of daily operations. All employees should be well-trained and equipped, and the plan should be reviewed annually, at least. PMID:12515340

Richmond, Jonathan Y; Nesby-O'Dell, Shanna L

2002-12-01

140

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

141

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 selection

Coleman, Seth; Jensen, Jeffrey

2007-01-01

142

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

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. PMID:18847479

2008-01-01

144

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

2012-05-01

145

Implications of the Reduction Principle for Cosmological Natural Selection  

E-print Network

Smolin (1992) proposed that the fine-tuning problem for parameters of the Standard Model might be accounted for by a Darwinian process of universe reproduction - Cosmological Natural Selection (CNS) - in which black holes give rise to offspring universes with slightly altered parameters. The laws for variation and inheritance of the parameters are also subject to CNS if variation in transmission laws occurs. This is the strategy introduced by Nei (1967) to understand genetic transmission, through the evolutionary theory of modifier genes, whose methodology is adopted here. When mechanisms of variation themselves vary, they are subject to Feldman's (1972) evolutionary Reduction Principle that selection favors greater faithfulness of replication. A theorem of Karlin (1982) allows one to generalize this principle beyond biological genetics to the unknown inheritance laws that would operate in CNS. The reduction principle for CNS is illustrated with a general multitype branching process model of universe creation containing competing inheritance laws. The most faithful inheritance law dominates the ensemble of universes. The Reduction Principle thus provides a mechanism to account for high fidelity of inheritance between universes. Moreover, it reveals that natural selection in the presence of variation in inheritance mechanisms has two distinct objects: maximization of both fitness and faithful inheritance. Tradeoffs between fitness and faithfulness open the possibility that evolved fundamental parameters are compromises, and not local optima to maximize universe production, in which case their local non-optimality may point to their involvement in the universe inheritance mechanisms.

Lee Altenberg

2013-02-06

146

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

147

Exploring the nature of collisionless shocks under laboratory conditions.  

PubMed

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

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

2014-01-01

148

Exploring the nature of collisionless shocks under laboratory conditions  

PubMed Central

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

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

2014-01-01

149

Darwin's Principles of Divergence and Natural Selection: Why Fodor was Almost Right  

E-print Network

0 Darwin's Principles of Divergence and Natural Selection: Why Fodor was Almost Right Robert J. Richards University of Chicago Abstract Darwin maintained that the principles of natural selection of the principle of divergence to that of natural selection? Is it independent of selection, derivative

Richards, Robert J.

150

[Liver cell function test based on selective laboratory studies].  

PubMed

Laboratory tests have been carried out in 517 workers of a Chemical Fibres Plant. This was aimed at the detection of the changes resulting from cumulative exposure to caprolactam, dowtherm and physical factors. There have been performed hematological investigations, uninalyses and biochemical tests: total protein level, activity of enzymes: ASPAT, ALAT, PA, ChE, thymol test. The results have been analysed as the mean values for particular divisions and workstands; then they have been compared with standards. In order to evaluate the degree of occupational exposure of particular groups of workers, an index of the liver cell damage has been calculated. It was expressed in % of the results exceeding the standards in relation to all results in a given group of workers. The highest values of the index were those in the group employed at the polymerization division. The authoresses promote the advisability of special care for this group of workers. PMID:7289867

Sliwi?ska-Przyjemska, H; Pilawska, H

1981-01-01

151

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. PMID:21577277

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

2011-01-01

152

Kaon Condensation, Black Holes and Cosmological Natural Selection  

E-print Network

It is argued that a well measured double neutron star binary in which the two neutron stars are more than 4% different from each other in mass or a massive neutron star with mass M > 2 M_sun would put in serious doubt or simply falsify the following chain of predictions: (1) nearly vanishing vector meson mass at chiral restoration, (2) kaon condensation at a density n ~ 3 n_0, (3) the Brown-Bethe maximum neutron star mass M_max ~ 1.5 M_sun and (4) Smolin's `Cosmological Natural Selection' hypothesis.

G. E. Brown; C. -H. Lee; M. Rho

2008-02-21

153

Summer Field Assistant (Two positions) Natural Resource Ecology Laboratory  

E-print Network

) experience in backcountry environments and conditions; (2) the ability to work independently and as a team, Ecology, or Natural Resource Management. Experience in backpacking, GIS, GPS and/or orienteering, forest recommendations. The quality of the work directly affects the quality and accuracy of final research findings

154

Darwin’s analogy between artificial and natural selection: how does it go?  

Microsoft Academic Search

The analogy Darwin drew between artificial and natural selection in On the Origin of Species has a detailed structure that has not been appreciated. In Darwin’s analogy, the kind of artificial selection called Methodical selection is analogous to the principle of divergence in nature, and the kind of artificial selection called Unconscious selection is analogous to the principle of extinction

Susan G. Sterrett

2002-01-01

155

Evidence for natural selection in a fern hybrid zone.  

PubMed

Morphological characters, chloroplast DNA, and allozymes were used to analyze the distribution of individuals within a hybrid population of the ferns Polystichum munitum and P. imbricans in northwestern California. Microsites within the population were characterized according to soil moisture and light levels reaching the plants. In sites with low soil moisture and high light levels, all of the ferns were genetically and morphologically like P. imbricans. In contrast, ferns with the genetic and morphological identity of P. munitum predominated in moist shady sites. Intermediate sites supported very few P.munitum, a wide variety of hybrid recombinants, and a majority of ferns with P. imbricans characteristics. The pattern of variation within the population is noteworthy because of the close proximity of the habitat extremes and the long-range dispersal of fern spores. We conclude that natural selection along environmental gradients must be a major factor in determining the ecological and genetic associations within the hybrid zone. The results of this study are evaluated in the context of the fern life cycle and compared to the assumptions of models explaining the establishment and maintenance of hybrid zones, which vary in the role attributed to environmentally mediated natural selection. PMID:10948001

Kentner, E K; Mesler, M R

2000-08-01

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. PMID:20422111

2010-01-01

157

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

158

Segment selection in the L&h Realspeak laboratory TTS system  

Microsoft Academic Search

The L&H RealSpeak Laboratory TTS (RSLab) system is a corpus based speech synthesis system comprising components that deal with linguistic processing, prosody prediction, segment selection, concatenation and modification. In this paper we focus on the segment selection process. During segment selection, the units in a large database of speech are scored with a cost according to their prosodic\\/phonetic mismatch with

Geert Coorman; Justin Fackrell; Peter Rutten; Bert Van Coile

2000-01-01

159

Adaptive speciation: the role of natural selection in mechanisms of geographic and  

E-print Network

Adaptive speciation: the role of natural selection in mechanisms of geographic and non the scope of particular speciation mechanisms which assign different roles to natural selection at various; Reproductive isolation; Natural selection; Adaptation; Spandrels 1369-8486/$ - see front matter Ã? 2005 Elsevier

Machery, Edouard

160

Impact of natural genetic variation on enhancer selection and function  

PubMed Central

The mechanisms by which genetic variation affects transcription regulation and phenotypes at the nucleotide level are incompletely understood. Here, we use natural genetic variation as an in vivo mutagenesis screen to assess the genome-wide effects of sequence variation on lineage-determining and signal-specific transcription factor binding, epigenomics, and transcriptional outcomes in primary macrophages from different mouse strains. We find substantial genetic evidence supporting the concept that lineage-determining transcription factors (LDTFs) define epigenetic and transcriptomic states by selecting enhancer-like regions in the genome in a collaborative fashion and facilitating binding of signal-dependent factors. This hierarchical model of transcription factor function suggests that limited sets of genomic data for LDTFs and informative histone modifications can be used for prioritization of disease-associated regulatory variants. PMID:24121437

Heinz, S.; Romanoski, C.E.; Benner, C.; Allison, K.A.; Kaikkonen, M.U.; Orozco, L.D.; Glass, C.K.

2014-01-01

161

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

162

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

2012-11-01

163

Correlation of selected rock and fluid properties with residual oil saturation obtained by laboratory waterfloods  

E-print Network

CORRELATION OF SELECTED ROCK AND FLUID PROPERTIES NITH RESIDUAL OIL SATURATION OBTAINED BY LABORATORY HATERFLOODS A Thesis By JASON NONROE EDGLNGTON Subxi t ted to the Graduate College of the Texas AKi University in partial fulfi' leant... of the recuire~aents for the deSree of iEASTER OF SCIENCE January 1)68 NaJor Su'bract. Petroleum?' EnpineerinS CORRELATION OF SELECTED ROCK AND FLUID PROPERTIES WITH RESIDUAL OIL SATURATION OBTAINED BY LABORATORY ?ATERFLOODS A Thesis JASON MONROE...

Edgington, Jason Monroe

2012-06-07

164

This booklet has been developed to serve as an aid in selecting a laboratory fume hood ventilation system.  

E-print Network

HowTo SelectThe Right Laboratory HoodSystem #12;Foreword This booklet has been developed to serve as an aid in selecting a laboratory fume hood ventilation system. The information is intended to be unbiased and laboratory hood users. The basic understanding of hood systems you gain from reviewing this book- let should

Farritor, Shane

165

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

166

The removal of natural organic matter from selected Turkish source waters using magnetic ion exchange resin (MIEX ®)  

Microsoft Academic Search

The primary objective of this work was to evaluate the effectiveness of the MIEX® process in removing natural organic matter (NOM) from selected drinking water sources of the City of Istanbul. Raw water samples from five drinking water treatment plants (Elmal?, B.Çekmece, Ömerli, ?kitelli, and Ka??thane) serving to about 10 million people were collected and jar-tested in laboratory. The kinetics

Mehmet Kitis; B. ?lker Harman; Nevzat O. Yigit; Mehmet Beyhan; Hung Nguyen; Beryn Adams

2007-01-01

167

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. PMID:9564563

Baker, David G.

1998-01-01

168

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.

169

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

170

Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes  

Microsoft Academic Search

Identifying regions of the human genome that have been targets of natural selection will provide important insights into human evolutionary history and may facilitate the identification of complex disease genes. Although the signature that natural selection imparts on DNA sequence variation is difficult to disentangle from the effects of neutral processes such as population demographic history, selective and demographic forces

Joshua M. Akey; Michael A. Eberle; Mark J. Rieder; Christopher S. Carlson; Mark D. Shriver; Deborah A. Nickerson; Leonid Kruglyak

2004-01-01

171

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

172

Patterns of natural selection on morphology of male and female collared flycatchers ( Ficedula albicollis )  

Microsoft Academic Search

Natural selection may act in different directions among years, life stages, or classes of individuals. Fluctuating selection of this kind is potentially an important mechanism by which additive genetic variation for quantitative traits is maintained, and can prevent populations reaching local adaptive peaks. We analysed natural selection acting on three morphological traits of male and female collared flycatchers via both

ROBERT PRZYBYLO; BEN C. SHELDON; JUHA MERILÄ

2000-01-01

173

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

174

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

SciTech Connect

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 was developed for ALMR by GE. A ALMR Safety Test is planned to be performed on a DOE site to demonstrate features and meet Nuclear Regulatory Commission Requirements. This study considered possible locations at the Idaho National Engineering Laboratory that met the ALMR Prototype Site Selection Methodology and Criteria. Four sites were identified, after further evaluation one site was eliminated. Each of the remaining three sites satisfied the criteria and was graded. The results were relatively close. Thus concluding that the Idaho National Engineering Laboratory is a suitable location for an Advanced Liquid Metal Reactor Safety Test. 23 refs., 13 figs., 9 tabs.

Sivill, R.L.

1990-03-01

175

Music Scope Headphones: Natural User Interface for Selection of Music  

Microsoft Academic Search

This paper describes a novel audio only interface for selecting music which enables us to select songs without having to click a mouse. Using previous music players with normal headphones, we can hear only one song at a time and we thus have to play pieces individually to select the one we want to hear from numerous new music files,

Masatoshi Hamanaka

2006-01-01

176

Using Natural Selection to Explore the Adaptive Potential of Chlamydomonas reinhardtii  

PubMed Central

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

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

2014-01-01

177

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. PMID:22993253

Bell, Rayna C.; Zamudio, Kelly R.

2012-01-01

178

Cold Spring Harbor Laboratory Press NATURE METHODS | VOL.2 NO.11 | NOVEMBER 2005 | 885 CLASSIC PROTOCOL  

E-print Network

© Cold Spring Harbor Laboratory Press NATURE METHODS | VOL.2 NO.11 | NOVEMBER 2005 | 885 CLASSIC chain reaction In 1992, investigators working on mixing and fusing various domains of different DNA (with proofreading activity) such as Deep Vent, Vent or Pfu1. Among other factors that improve LA PCR

Cai, Long

179

“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

180

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

PubMed

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

Su, Tianyun; Cheng, Min-Lee

2014-03-01

181

Identification of innate immunity elicitors using molecular signatures of natural selection  

E-print Network

Identification of innate immunity elicitors using molecular signatures of natural selection Honour hypothesized that novel bacterial elicitors can be identified through these opposing forces of natural­pathogen interactions and applied research into alternative antimicrobial treatments. evolutionary genomics | pathogen

Guttman, David S.

182

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

183

Toxicity of naturally-contaminated manganese soil to selected crops.  

PubMed

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

Ková?ik, Jozef; Št?rbová, Dagmar; Babula, Petr; Švec, Pavel; Hedbavny, Josef

2014-07-23

184

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

185

Six Classroom Exercises to Teach Natural Selection to Undergraduate Biology Students  

PubMed Central

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

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

2013-01-01

186

Six classroom exercises to teach natural selection to undergraduate biology students.  

PubMed

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

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

2013-01-01

187

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

188

Hidden Evolution: Progress and Limitations in Detecting Multifarious Natural Selection  

Microsoft Academic Search

From illustrative examples of research on the best-studied group of species to date, Drosophila melanogaster and its closest relatives, we argue that selection is multifarious, but often hidden. Selective fixation of new, highly advantageous alleles is the most parsimonious explanation for a typical pattern of molecular variation observed in genomic regions characterized by very low recombination: drastically reduced DNA sequence

Norman A. Johnson; Richard M. Kliman

2002-01-01

189

Widespread Genomic Signatures of Natural Selection in Hominid Evolution  

PubMed Central

Selection acting on genomic functional elements can be detected by its indirect effects on population diversity at linked neutral sites. To illuminate the selective forces that shaped hominid evolution, we analyzed the genomic distributions of human polymorphisms and sequence differences among five primate species relative to the locations of conserved sequence features. Neutral sequence diversity in human and ancestral hominid populations is substantially reduced near such features, resulting in a surprisingly large genome average diversity reduction due to selection of 19–26% on the autosomes and 12–40% on the X chromosome. The overall trends are broadly consistent with “background selection” or hitchhiking in ancestral populations acting to remove deleterious variants. Average selection is much stronger on exonic (both protein-coding and untranslated) conserved features than non-exonic features. Long term selection, rather than complex speciation scenarios, explains the large intragenomic variation in human/chimpanzee divergence. Our analyses reveal a dominant role for selection in shaping genomic diversity and divergence patterns, clarify hominid evolution, and provide a baseline for investigating specific selective events. PMID:19424416

McVicker, Graham; Gordon, David; Davis, Colleen; Green, Phil

2009-01-01

190

Toward Selecting and Recognizing Natural Landmarks \\Lambda Erliang Yeh  

E-print Network

the problem of automatically selecting from a set of 3D features the subset which is most likely cost is selected as the most distinguishable landmark. We show implementation results for real 3D objects. Some issues, improvements and extensions to the method are discussed. \\Lambda This work

Kriegman, David J.

191

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

PubMed

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

Rutkunas, Vygandas; Sveikata, Kestutis; Savickas, Raimondas

2012-01-01

192

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. PMID:23324260

2013-01-01

193

Parallel shifts in ecology and natural selection in an island lizard  

PubMed Central

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

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

2009-01-01

194

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

195

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

196

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

NASA Astrophysics Data System (ADS)

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

Jagodzi?ski, Piotr; Wolski, Robert

2014-09-01

197

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

198

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

199

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

ERIC Educational Resources Information Center

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

Young, Helen J.; Young, Truman P.

2003-01-01

200

Laboratory divergence of Methylobacterium extorquens AM1 through unintended domestication and past selection for antibiotic resistance  

PubMed Central

Background A common assumption of microorganisms is that laboratory stocks will remain genetically and phenotypically constant over time, and across laboratories. It is becoming increasingly clear, however, that mutations can ruin strain integrity and drive the divergence or “domestication” of stocks. Since its discovery in 1960, a stock of Methylobacterium extorquens AM1 (“AM1”) has remained in the lab, propagated across numerous growth and storage conditions, researchers, and facilities. To explore the extent to which this lineage has diverged, we compared our own “Modern” stock of AM1 to a sample archived at a culture stock center shortly after the strain’s discovery. Stored as a lyophilized sample, we hypothesized that this Archival strain would better reflect the first-ever isolate of AM1 and reveal ways in which our Modern stock has changed through laboratory domestication or other means. Results Using whole-genome re-sequencing, we identified some 29 mutations – including single nucleotide polymorphisms, small indels, the insertion of mobile elements, and the loss of roughly 36 kb of DNA - that arose in the laboratory-maintained Modern lineage. Contrary to our expectations, Modern was both slower and less fit than Archival across a variety of growth substrates, and showed no improvement during long-term growth and storage. Modern did, however, outperform Archival during growth on nutrient broth, and in resistance to rifamycin, which was selected for by researchers in the 1980s. Recapitulating selection for rifamycin resistance in replicate Archival populations showed that mutations to RNA polymerase B (rpoB) substantially decrease growth in the absence of antibiotic, offering an explanation for slower growth in Modern stocks. Given the large number of genomic changes arising from domestication (28), it is somewhat surprising that the single other mutation attributed to purposeful laboratory selection accounts for much of the phenotypic divergence between strains. Conclusions These results highlight the surprising degree to which AM1 has diverged through a combination of unintended laboratory domestication and purposeful selection for rifamycin resistance. Instances of strain divergence are important, not only to ensure consistency of experimental results, but also to explore how microbes in the lab diverge from one another and from their wild counterparts. PMID:24384040

2014-01-01

201

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

202

NATURE METHODS | VOL.2 NO.11 | NOVEMBER 2005 | 863 Cold Spring Harbor Laboratory Press PUBLISHED IN ASSOCIATION WITH  

E-print Network

NATURE METHODS | VOL.2 NO.11 | NOVEMBER 2005 | 863© Cold Spring Harbor Laboratory Press PROTOCOL PUBLISHED IN ASSOCIATION WITH COLD SPRING HARBOR LABORATORY PRESS Liquid-based free-flow electrophoresis­ reversed-phase HPLC: a proteomic tool Robert L Moritz & Richard J Simpson Joint Proteomics Laboratory

Cai, Long

203

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

204

Caprylate-thallous agar medium for selectively isolating Serratia and its utility in the clinical laboratory.  

PubMed Central

A defined agar medium (hereinafter designated caprylate-thallous [CT5 agar) containing 0.01% yeast extract, 0.1% caprylic (n-octanoic) acid, and 0.025% thallous sulfate is highly selective for all Serratia species and effectively discriminates against most non-Serratia strains likely to be in the same habitats. The selectivity of CT agar is demonstrated by the very high efficiency of colony formation (mean, 80.7% of that on a nonselective complex medium) on CT agar by known Serratia strains and the very low efficiency of colony formation (close to zero) on CT agar by bacterial strains known not to be Serratia. The utility of this medium in actual clinical laboratory practice is demonstrated by the more rapid and higher recovery of Serratia on this selective medium as compared to conventional procedures of in-tandem runs of 513 consecutive urine, feces, and sputum specimens. Pigmented and nonpigmented Serratia strains deliberately added to fecal specimens can be selectively and quantitatively recovered on CT agar. CT agar compares favorably with, or in some cases is an improvement over, other selective media which have been recommended for isolating Serratia. This selective CT agar medium could be quite useful in ecological surveys, especially those related to hospital-acquired infections. PMID:972193

Starr, M P; Grimont, P A; Grimont, F; Starr, P B

1976-01-01

205

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

PubMed Central

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

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

2008-01-01

206

I'm Looking Over a White-Striped Clover: A Natural Selection Case  

NSDL National Science Digital Library

This case study examines the process of natural selection, using the example of white clover. Students will learn the concepts of variation, natural selection, fitness, selection pressure, evolution, and adaptation.The lesson would be useful for high school or lower level undergraduate students studying biology or botany. The case study and teaching notes may be downloaded in PDF format. The site also includes a section for instructor feedback where general comments may be read and contributed.

Evarts, Susan; Krufka, Alison; Wilson, Chester

2006-11-28

207

Spatial patterns of variation due to natural selection in humans  

PubMed Central

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

Novembre, John; Di Rienzo, Anna

2013-01-01

208

Natural or Internal Selection? The Case of Canalization in Complex Evolutionary Systems  

Microsoft Academic Search

Using biological examples and theoretical arguments, the case is presented for extending the notion of natural selection to include internal selection in order to account for the evolution of complex systems. It is suggested that we take into consideration internal factors that arise from the hierarchical dynamics of complex systems. In addition to environmental selection, it is argued, decisive constraints

Alexander Riegler

2008-01-01

209

LIFETIME SELECTION ON HERITABLE LIFE-HISTORY TRAITS IN A NATURAL POPULATION OF RED SQUIRRELS  

Microsoft Academic Search

Despite their importance in evolutionary biology, heritability and the strength of natural selection have rarely been estimated in wild populations of iteroparous species or have usually been limited to one particular event during an organism's lifetime. Using an animal-model restricted maximum likelihood and phenotypic selection models, we estimated quantitative genetic parameters and the strength of lifetime selection on parturition date

D. Réale; D. Berteaux; A. G. McAdam; S. Boutin

2003-01-01

210

The natural history of hypotheses about the selection task: towards a philosophy of science  

E-print Network

The natural history of hypotheses about the selection task: towards a philosophy of science, K. & Chung, M. (eds.) Psychology of rea- soning. Psychology Press. Abstract Wason's (1968) selection's account of science and Wason's account of the ab- stract selection task have lived full lives

van Lambalgen, Michiel

211

Parental assessment and treatment of food selectivity in natural settings.  

PubMed Central

This study evaluated the effects of a parent-conducted functional analysis and treatment consisting of differential reinforcement of an alternative behavior, escape extinction, and demand fading on food selectivity in a young child with autism. Increases in food acceptance at home and in a restaurant were obtained. PMID:14596582

Najdowski, Adel C; Wallace, Michele D; Doney, Janice K; Ghezzi, Patrick M

2003-01-01

212

Gene flow and the limits to natural selection  

Microsoft Academic Search

In general, individuals who survive to reproduce have genotypes that work relatively well under local conditions. Migrating or dispersing offspring elsewhere is likely to decrease an individual's or its offspring's fitness, not to mention the intrinsic costs and risks of dispersal. Gene flow into a population can counteract gene frequency changes because of selection, imposing a limit on local adaptation.

Thomas Lenormand

2002-01-01

213

The nature of faint submm-selected galaxies  

E-print Network

We present the source catalogue for the SCUBA Lens Survey. We summarise the results of extensive multi-wavelength observations of the 15 submillimetre-selected galaxies in the catalogue, from X-rays to radio. We discuss the main observational characteristics of faint submillimetre galaxies as a population, and consider their interpretation within the framework of our understanding of galaxy formation and evolution.

Ian Smail; R. J. Ivison; A. W. Blain; J. -P. Kneib

2001-12-05

214

Mortality among Plants and its Bearing on Natural Selection  

Microsoft Academic Search

I HAVE read with great interest the letters from Prof. Salisbury and Dr. J. Phillips which have appeared in NATURE dealing with mortality in plants at different stages of their life histories. The observations are of the greatest importance, but I doubt whether the interpretation advanced by Prof. Salisbury in his letter of May 31, 1930, is supported by the

R. Weatherall

1931-01-01

215

Selective whole genome amplification for resequencing target microbial species from complex natural samples.  

PubMed

Population genomic analyses have demonstrated power to address major questions in evolutionary and molecular microbiology. Collecting populations of genomes is hindered in many microbial species by the absence of a cost effective and practical method to collect ample quantities of sufficiently pure genomic DNA for next-generation sequencing. Here we present a simple method to amplify genomes of a target microbial species present in a complex, natural sample. The selective whole genome amplification (SWGA) technique amplifies target genomes using nucleotide sequence motifs that are common in the target microbe genome, but rare in the background genomes, to prime the highly processive phi29 polymerase. SWGA thus selectively amplifies the target genome from samples in which it originally represented a minor fraction of the total DNA. The post-SWGA samples are enriched in target genomic DNA, which are ideal for population resequencing. We demonstrate the efficacy of SWGA using both laboratory-prepared mixtures of cultured microbes as well as a natural host-microbe association. Targeted amplification of Borrelia burgdorferi mixed with Escherichia coli at genome ratios of 1:2000 resulted in >10(5)-fold amplification of the target genomes with <6.7-fold amplification of the background. SWGA-treated genomic extracts from Wolbachia pipientis-infected Drosophila melanogaster resulted in up to 70% of high-throughput resequencing reads mapping to the W. pipientis genome. By contrast, 2-9% of sequencing reads were derived from W. pipientis without prior amplification. The SWGA technique results in high sequencing coverage at a fraction of the sequencing effort, thus allowing population genomic studies at affordable costs. PMID:25096321

Leichty, Aaron R; Brisson, Dustin

2014-10-01

216

Idaho National Engineering Laboratory materials in inventory natural and enriched uranium management and storage costs  

SciTech Connect

On July 13, 1994, the Office of Environmental Management (EM) was requested to develop a planning process that would result in management policies for dealing with nuclear materials in inventory. In response to this request, EM launched the Materials In Inventory (MIN) Initiative. A Headquarters Working Group was established to develop the broad policy framework for developing MIN management policies. MIN activities cover essentially all nuclear materials within the DOE complex, including such items as spent nuclear fuel, depleted uranium, plutonium, natural and enriched uranium, and other materials. In August 1995, a report discussing the natural and enriched uranium portion of the Initiative for the Idaho National Engineering Laboratory (INEL) was published. That report, `Idaho National Engineering Laboratory Materials-in-Inventory, Natural and Enriched Uranium`.` identified MIN under the control of Lockheed Idaho Technologies Company at the INEL. Later, additional information related to the costs associated with the storage of MIN materials was requested to supplement this report. This report provides the cost information for storing, disposing, or consolidating the natural and enriched uranium portion of the MIN materials at the INEL. The information consists of eight specific tables which detail present management costs and estimated costs of future activities.

Nebeker, R.L.

1995-11-01

217

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

SciTech Connect

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

Blau, P.J. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1997-05-01

218

The Nature and Evolution of Absorption-Selected Galaxies  

E-print Network

We present results of surveys for high redshift galaxies selected by their having produced detectable Mg~II and Lyman limit absorption in the spectra of background QSOs. We discuss the properties of the absorbing galaxies, the connection between galaxy properties and absorption line signatures, and how a combination of QSO absorption line and conventional faint galaxy techniques can be used to study field galaxy evolution to very large redshifts.

C. Steidel

1995-09-19

219

Natural selection of mitochondria during somatic lifetime promotes healthy aging  

PubMed Central

Stimulation of mitochondrial biogenesis during life-time challenges both eliminates disadvantageous properties and drives adaptive selection of advantageous phenotypic variations. Intermittent fission and fusion of mitochondria provide specific targets for health promotion by brief temporal stressors, interspersed with periods of recovery and biogenesis. For mitochondria, the mechanisms of selection, variability, and heritability, are complicated by interaction of two independent genomes, including the multiple copies of DNA in each mitochondrion, as well as the shared nuclear genome of each cell. The mechanisms of stress-induced fission, followed by recovery-induced fusion and biogenesis, drive the improvement of mitochondrial functions, not only as directed by genotypic variations, but also as enabled by phenotypic diversity. Selective adaptation may explain unresolved aspects of aging, including the health effects of exercise, hypoxic and poisonous preconditioning, and tissue-specific mitochondrial differences. We propose that intermittent purposeful enhancement of mitochondrial biogenesis by stressful episodes with subsequent recovery paradoxically promotes adaptive mitochondrial health and continued healthy aging. PMID:23964235

Rodell, Anders; Rasmussen, Lene J.; Bergersen, Linda H.; Singh, Keshav K.; Gjedde, Albert

2013-01-01

220

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. PMID:9335621

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

1997-01-01

221

Four decades of opposing natural and human-induced artificial selection acting on Windermere pike (Esox lucius)  

Microsoft Academic Search

The ability of natural selection to drive local adaptation has been appreciated ever since Darwin. Whether human impacts can impede the adaptive process has received less attention. We tested this hypothesis by quantifying natural selection and harvest selection acting on a freshwater fish (pike) over four decades. Across the time series, directional natural selection tended to favour large individuals whereas

Stephanie M. Carlson; Eric Edeline; L. Asbjørn Vøllestad; Thrond. O. Haugen; Ian J. Winfield; Janice M. Fletcher; J. Ben James; Nils Chr. Stenseth

2007-01-01

222

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

PubMed

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. PMID:23128232

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

2012-11-01

223

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

224

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

PubMed

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

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

2014-11-01

225

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

226

Selective scenarios for the emergence of natural language.  

PubMed

The recent blossoming of evolutionary linguistics has resulted in a variety of theories that attempt to provide a selective scenario for the evolution of early language. However, their overabundance makes many researchers sceptical of such theorising. Here, we suggest that a more rigorous approach is needed towards their construction although, despite justified scepticism, there is no agreement as to the criteria that should be used to determine the validity of the various competing theories. We attempt to fill this gap by providing criteria upon which the various historical narratives can be judged. Although individually none of these criteria are highly constraining, taken together they could provide a useful evolutionary framework for thinking about the evolution of human language. PMID:16828925

Számadó, Szabolcs; Szathmáry, Eörs

2006-10-01

227

Natural selectivity of Nickel and Vanadium in crude oil  

NASA Astrophysics Data System (ADS)

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

Fernandez, Olienka Patricia De La O.

228

The selective adsorption of hydrogen sulfide from natural gas streams  

E-print Network

determination Run 1 A 2)( mixture of H2S in 002 flowed at 38 ~ 75 cc/min. at std. cond. of 492 F and 1 atm. for 24 min. The titration used 1. 84 cc of 0, 9042 N NaOH. Wt. H2S (Run 1) Gas Measurement 0. 0283 Titration 0+0283 Run 2 A 30$ mixture of H2S... in 002 flowed at 40 cc/min. at std. cond. for 20 min. The titration used 23. 55 cc of 0. 9042 N NaOH. Wt. H2S (Run 2) 0. 364 0. 363 Run 3 of H2S in 002 flowed at 40 cc/min. at std. cond. with approx. 440 cc/min. of natural Sas for 20 min...

Fails, James Clayton

2012-06-07

229

Affective Neuronal Selection: The Nature of the Primordial Emotion Systems  

PubMed Central

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

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

2013-01-01

230

Nucleation of Laboratory Earthquakes: Observation, Characterization, and Scaling up to the Natural Earthquakes Dimensions  

NASA Astrophysics Data System (ADS)

In this work we observe the nucleation phase of in-plane ruptures in the laboratory and characterize its dynamics. We use a laboratory toy-model, where mode II shear ruptures are produced on a pre-cut fault in a plate of polycarbonate. The fault is cut at the critical angle that allows a stick-slip behavior under uniaxal loading. The ruptures are thus naturally nucleated. The material is birefringent under stress, so that the rupture propagation can be followed by ultra-rapid elastophotometry. A network of acoustic sensors and accelerometers is disposed on the plate to measure the radiated wavefield and record laboratory near-field accelograms. The far field stress level is also measured using strain gages. We show that the nucleation is composed of two distinct phases, a quasi-static and an acceleration stage, followed by dynamic propagation. We propose an empirical model which describes the rupture length evolution: the quasi-static phase is described by an exponential growth while the acceleration phase is described by an inverse power law of time. The transition from quasistatic to accelerating rupture is related to the critical nucleation length, which scales inversely with normal stress in accordance with theoretical predictions, and to a critical surfacic power, which may be an intrinsic property of the interface. Finally, we discuss these results in the frame of previous studies and propose a scaling up to natural earthquake dimensions. Three spontaneously nucleated laboratory earthquakes at increasingly higher normal pre-stresses, visualized by photo-elasticity. The red curves highlight the position of rupture tips as a function of time. We propose an empirical model that describes the dynamics of rupture nucleation and discuss its scaling with the initial normal stress.

Latour, S.; Schubnel, A.; Nielsen, S. B.; Madariaga, R. I.; Vinciguerra, S.

2013-12-01

231

The Interface Theory of Perception: Natural Selection Drives True Perception To Swift Extinction  

E-print Network

The Interface Theory of Perception: Natural Selection Drives True Perception To Swift Extinction interface games, in which pithy perceptions often drive true perceptions to extinction. 1.1 Introduction

Stanford, Kyle

232

Testosterone, Endurance, and Darwinian Fitness: Natural and Sexual Selection on the Physiological  

E-print Network

Testosterone, Endurance, and Darwinian Fitness: Natural and Sexual Selection on the Physiological had higher levels of plasma testosterone (T), endurance, activity, and home range size: testosterone; territorial behavior; ESS; alternative male strategies; endurance. The presence of aggressive

Frankino, Tony

233

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

E-print Network

, Hong Kong, China; m Tibet Academy of Social Sciences, Lhasa 850000, Tibet Autonomous Region, China; n availability associated with high-altitude environments is likely to act as an agent of natural selection. We

Watkins, Joseph C.

234

Ecology of Neoschongastia americana (Hirst): laboratory life cycle, developmental period in the field and influence of selected external factors.  

E-print Network

ECOLOGY OF NEOSCHONGASTIA AMERICANA (HIRST): LABORATORY LIFE CYCLE, DEVELOPMENTAL PERIOD IN THE FIELD AND INFLUENCE OF SELECTED EXTERNAL FACTORS A Thesis by JERRY REAL CUNNINGHAM Submitted to the Graduate College of Texas A&? University... in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE August 19/4 Major Subject: Entomology ECOLOGY OF NEOSCHONGASTIA AMERICANA (HIRST): LABORATORY LIFE CYCLE, DEVELOPMENTAL PERIOD IN THE FIELD AND INFLUENCE OF SELECTED EXTERNAL...

Cunningham, Jerry Real

2012-06-07

235

On the black hole species (by means of natural selection)  

E-print Network

Recently our understanding of black holes in D-spacetime dimensions, as solutions of the Einstein equation, has advanced greatly. Besides the well established spherical black hole we have now explicitly found other species of topologies of the event horizons. Whether in asymptotically flat, AntideSitter or deSitter spaces, the different species are really non-unique when D > 4. An example of this are the black rings. Another issue in higher dimensions that is not fully understood is the struggle for existence of regular black hole solutions. However, we managed to observe a selection rule for regular solutions of thin black rings: they have to be balanced i.e. in vacuum, a neutral asymptotically flat black ring incorporates a balance between the centrifugal repulsion and the tension. The equilibrium condition seems to be equivalent to the condition to guarantee regularity on the geometry of the black ring solution. We will review the tree of species of black holes and present new results on exotic black holes with charges.

Maria J. Rodriguez

2010-03-11

236

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. PMID:4213125

Tracey, Martin L.; Ayala, Francisco J.

1974-01-01

237

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

PubMed

Populations of genetically uniform microorganisms exhibit phenotypic heterogeneity, where individual cells have varying phenotypes. Such phenotypes include fitness-determining traits. Phenotypic heterogeneity has been linked to increased population-level fitness in laboratory studies, but its adaptive significance for wild microorganisms in the natural environment is unknown. Here, we addressed this by testing heterogeneity in yeast isolates from diverse environmental sites, each polluted with a different principal contaminant, as well as from corresponding control locations. We found that cell-to-cell heterogeneity (in resistance to the appropriate principal pollutant) was prevalent in the wild yeast isolates. Moreover, isolates with the highest heterogeneity were consistently observed in the polluted environments, indicating that heterogeneity is positively related to survival in adverse conditions in the wild. This relationship with survival was stronger than for the property of mean resistance (IC(50)) of an isolate. Therefore, heterogeneity could be the major determinant of microbial survival in adverse conditions. Indeed, growth assays indicated that isolates with high heterogeneities had a significant competitive advantage during stress. Analysis of yeasts after cultivation for ??500 generations additionally showed that high heterogeneity evolved as a heritable trait during stress. The results showed that environmental stress selects for wild microorganisms with high levels of phenotypic heterogeneity. PMID:24000788

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

2014-06-01

238

The basic science and mathematics of random mutation and natural selection.  

PubMed

The mutation and natural selection phenomenon can and often does cause the failure of antimicrobial, herbicidal, pesticide and cancer treatments selection pressures. This phenomenon operates in a mathematically predictable behavior, which when understood leads to approaches to reduce and prevent the failure of the use of these selection pressures. The mathematical behavior of mutation and selection is derived using the principles given by probability theory. The derivation of the equations describing the mutation and selection phenomenon is carried out in the context of an empirical example. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25244620

Kleinman, Alan

2014-12-20

239

113 Lab Learning Objectives Week 11: Information and Natural Selection lab #6  

E-print Network

of evolution based on lab experiences. · Explain how antibiotic resistant bacteria can appear quickly in the population. · Design directed evolution process to select antibiotic resistant bacteria. #12; explanation linking genetically defined taste capacity to natural selection and evolution. · Identify possible

Campbell, A. Malcolm

240

Can natural selection favour altruism between species? G. A. K. WYATT*, S. A. WEST* & A. GARDNER*  

E-print Network

, for such could not have been produced through natural selection'. Darwin (1859, p. 201) Darwin's (1859) theory Keywords: evolutionary graph theory; Hamilton's rule; inclusive fitness; kin selection; mutualism; relatedness. Abstract Darwin suggested that the discovery of altruism between species would anni- hilate his

West, Stuart

241

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

242

Functions of courtship feeding in black-legged kittiwakes: natural and sexual selection  

Microsoft Academic Search

Various authors have proposed that courtship feeding evolved under natural selection, sexual selection or both. Using observations of 250 breeding pairs over 3 consecutive years for a total of 77000 nest-hours, we examined the functional significance of courtship feeding in a seabird, the black-legged kittiwake, Rissa tridactyla. We predicted courtship feeding would benefit males and females in different ways: males

Fabrice Helfenstein; Richard H. Wagner; Etienne Danchin; Jean-Marc Rossi

2003-01-01

243

Synonymous Codon Usage in Drosophila melanogaster: Natural Selection and Translational Accuracy  

Microsoft Academic Search

I present evidence that natural selection biases synonymous codon usage to enhance the accuracy of protein synthesis in Drosophila melanogaster. Since the fitness cost of a translational misincorporation will depend on how the amino acid substitution affects protein function, selection for translational accuracy predicts an association between codon usage in DNA and functional constraint at the protein level. The frequency

Hiroshi Akashi

1994-01-01

244

Notice of release of Prairie Harvest Germplasm common hackberry: selected class of natural germplasm  

Microsoft Academic Search

Prairie Harvest Germplasm common hackberry (Celtis occidentalis L. [Ulmaceae]) is a selected class of natural germplasm released for use in conservation plantings in the Northern Great Plains and Upper Midwest of the US. Originating from native trees located in Polk County, northwestern Minnesota, this northern selection is winter hardy with improved form and growth rates. This germplasm release is recommended

Dwight A Tober; Wayne L Duckwitz; Nancy K Jensen

2011-01-01

245

Notice of release of Prairie Harvest Germplasm common hackberry: selected class of natural germplasm  

Microsoft Academic Search

:Prairie Harvest Germplasm common hackberry (Celtis occidentalis L. [Ulmaceae]) is a selected class of natural germplasm released for use in conservation plantings in the Northern Great Plains and Upper Midwest of the US. Originating from native trees located in Polk County, northwestern Minnesota, this northern selection is winter hardy with improved form and growth rates. This germplasm release is recommended

Dwight A Tober; Wayne L Duckwitz; Nancy K Jensen

2011-01-01

246

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

PubMed

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 minnows, Phoxinus phoxinuswere exposed to Schreckstoff in small aquaria. They responded with a suite of behavioural changes that are consistent with the explanation that they perceive danger. Fish from the same population were then exposed to Schreckstoff under conditions that more closely resembled their natural habitat. Under these near-natural conditions they showed a small decrease in feeding rate and a slight increase in group size, both effects being transitory and independent of stimulus concentration. These data reveal that the ostariophysan fright reaction is context-dependent and highlight the importance of quantifying the behaviour of fish exposed to Schreckstoff under fully natural conditions. PMID:9236015

Irving; Magurran

1997-06-01

247

Animal genetic resources in Brazil: result of five centuries of natural selection  

Microsoft Academic Search

Brazil has various species of domestic animals, which developed from breeds brought by the Portuguese settlers soon after their discovery. For five centuries, these breeds have been subjected to natural selection in specific environments. Today, they present characteristics adapted to the specific Brazilian environmental conditions. These breeds developed in Brazil are known as “Crioulo,” “local,” or naturalized. From the beginning

A. da S. Mariante; A. A. Egito

2002-01-01

248

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

ERIC Educational Resources Information Center

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

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

2014-01-01

249

The paradoxical advantages and disadvantages of natural selection: the case history of Charles Darwin.  

PubMed

The biology of natural selection is an enduring mystery, as is the nature of Charles Darwin's chronic illness. Of the theories advanced to explain the latter, Oedipal conflicts and Chagas' disease are preeminent. Hypomania, however, propelled Darwin to the pinnacle of scientific achievement and good health, the depression that followed condemning him to intellectual stagnation, lethargy, impaired memory and concentration, and incapacitating gastrointestinal disorders. Examples of natural selection in humans are much sought after when, ironically, one need look no further than Darwin himself. PMID:17499450

Lieb, J

2007-01-01

250

Cambridge Companion to the Origin of Species, eds. R. Richards and M. Ruse Darwin's Theory of Natural Selection and  

E-print Network

of Natural Selection and Its Moral Purpose Robert J. Richards Thomas Henry Huxley recalled that after he--variability, struggle for existence, adaptation-- form core features of Darwin's conception of natural selection. Thus been interpreted to affirm--that the idea of natural selection was really quite simple and that when

Richards, Robert J.

251

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

252

Life-history QTLS and natural selection on flowering time in Boechera stricta, a perennial relative of Arabidopsis.  

PubMed

Plants must precisely time flowering to capitalize on favorable conditions. Although we know a great deal about the genetic basis of flowering phenology in model species under controlled conditions, the genetic architecture of this ecologically important trait is poorly understood in nonmodel organisms. Here, we evaluated the transition from vegetative growth to flowering in Boechera stricta, a perennial relative of Arabidopsis thaliana. We examined flowering time QTLs using 7920 recombinant inbred individuals, across seven laboratory and field environments differing in vernalization, temperature, and photoperiod. Genetic and environmental factors strongly influenced the transition to reproduction. We found directional selection for earlier flowering in the field. In the growth chamber experiment, longer winters accelerated flowering, whereas elevated ambient temperatures delayed flowering. Our analyses identified one large effect QTL (nFT), which influenced flowering time in the laboratory and the probability of flowering in the field. In Montana, homozygotes for the native allele at nFT showed a selective advantage of 6.6%. Nevertheless, we found relatively low correlations between flowering times in the field and the growth chambers. Additionally, we detected flowering-related QTLs in the field that were absent across the full range of laboratory conditions, thus emphasizing the need to conduct experiments in natural environments. PMID:21083662

Anderson, Jill T; Lee, Cheng-Ruei; Mitchell-Olds, Thomas

2011-03-01

253

1000 Genomes Selection Browser 1.0: a genome browser dedicated to signatures of natural selection in modern humans.  

PubMed

Searching for Darwinian selection in natural populations has been the focus of a multitude of studies over the last decades. Here we present the 1000 Genomes Selection Browser 1.0 (http://hsb.upf.edu) as a resource for signatures of recent natural selection in modern humans. We have implemented and applied a large number of neutrality tests as well as summary statistics informative for the action of selection such as Tajima's D, CLR, Fay and Wu's H, Fu and Li's F* and D*, XPEHH, ?iHH, iHS, F(ST), ?DAF and XPCLR among others to low coverage sequencing data from the 1000 genomes project (Phase 1; release April 2012). We have implemented a publicly available genome-wide browser to communicate the results from three different populations of West African, Northern European and East Asian ancestry (YRI, CEU, CHB). Information is provided in UCSC-style format to facilitate the integration with the rich UCSC browser tracks and an access page is provided with instructions and for convenient visualization. We believe that this expandable resource will facilitate the interpretation of signals of selection on different temporal, geographical and genomic scales. PMID:24275494

Pybus, Marc; Dall'Olio, Giovanni M; Luisi, Pierre; Uzkudun, Manu; Carreño-Torres, Angel; Pavlidis, Pavlos; Laayouni, Hafid; Bertranpetit, Jaume; Engelken, Johannes

2014-01-01

254

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

2012-03-01

255

2005 Nature Publishing Group Natural selection on protein-coding genes in the  

E-print Network

of the human genome. Here we analyse 11,624 genes with complementary DNA support, strong evidence of orthology , Daniel Civello4 , Mark D. Adams5 , Michele Cargill4 * & Andrew G. Clark6 * Comparisons of DNA evidence of pervasive positive selection6­9 , and others, such as the selfing weed Arabidopsis thaliana

Nielsen, Rasmus

256

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

257

Insect Choice and Floral Size Dimorphism: Sexual Selection or Natural Selection?  

Microsoft Academic Search

In considerations of sexual floral size dimorphism, there is a conflict between sexual selection theory, which predicts that\\u000a larger floral displays attract more pollinators, and optimality theory—particularly the ideal free distribution—which predict\\u000a that pollinators' visits should match nutritional rewards. As an alternate explanation of this dimorphism, Müller reported\\u000a that pollinators tend to visit larger male flowers before visiting smaller female

Joseph N. Abraham

2005-01-01

258

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

259

113 Lab Learning Objectives Week 13: Information and Natural Selection lab #8  

E-print Network

of evolution based on lab experiences. · Explain how antibiotic resistant bacteria can appear quickly in the population. · Design directed evolution process to select antibiotic resistant bacteria. · Formulate an hypothesis how antibiotic resistant bacteria evolve outside the laboratory. · Propose a mechanism that allows

Campbell, A. Malcolm

260

Evaluation of selected natural and synthetic products as house fly repellents  

Microsoft Academic Search

Twenty natural and synthetic substances, known or reported to be repellent to insects, were evaluated for repellency to adult house flies, Musca domestica L., by a new laboratory test method. Fourteen materials completely repelled the flies during a 30?min test period. The most active material was 2?phenylethanol.

Victor E. Adler; Martin Jacobson

1982-01-01

261

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

262

Nature Laboratory Permission Form Users: Any LDSA Faculty or Graduate Student may use this form to gain permission to  

E-print Network

of natural history specimens and models. These specimens and models are fragile and will break if handled carelessly. Please be extremely careful when handling the specimens and be sure to place them back be cleaned from the tables and the floor. Food and drinks are not allowed in the nature laboratory. Painting

Arnold, Jonathan

263

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

264

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

PubMed

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

Theunissen, Bert

2012-01-01

265

Natural Selection  

ERIC Educational Resources Information Center

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

Hall, Julie

2006-01-01

266

Natural Selection  

NSDL National Science Digital Library

The concept of interdependence in an ecosystem and its effect on the evolution of populations is further explored through a model of a dam. Students build a dam in the middle of the field, dividing the ecosystem in half to illustrate the affects of geographic isolation. They watch as the grass and then the rabbit populations in that region shift to one variant in the population. When students remove the dam, they observe the ecosystem slowly return to its original state.

Consortium, The C.

2011-12-11

267

164 nature physics | VOL 5 | MARCH 2009 | www.nature.com/naturephysics A quantum of natural selection  

E-print Network

selection with Mendel's genetics, was developed around the same time as quantum mechanics. Is there any with a demonstrably incorrect theory of genetics. Although Gregor Mendel's pioneering work on the genetics of pea,4 . Darwin was not the only nineteenth- century scientist to under-appreciate Mendel's work. Mendel's laws

Loss, Daniel

268

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

269

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

PubMed

Some tributaries in the Powder River Structural Basin, USA, were historically ephemeral, but now contain water year round as a result of discharge of coalbed natural gas (CBNG)-produced waters. This presented the opportunity to study field sites with 100% effluent water with elevated concentrations of sodium bicarbonate. In situ experiments, static renewal experiments performed simultaneously with in situ experiments, and static renewal experiments performed with site water in the laboratory demonstrated that CBNG-produced water reduces survival of fathead minnow (Pimephales promelas) and pallid sturgeon (Scaphirhynchus albus). Age affected survival of fathead minnow, where fish 2 d posthatch (dph) were more sensitive than 6 dph fish, but pallid sturgeon survival was adversely affected at both 4 and 6 dph. This may have implications for acute assays that allow for the use of fish up to 14 dph. The survival of early lifestage fish is reduced significantly in the field when concentrations of NaHCO(3) rise to more than 1500?mg/L (also expressed as >1245?mg HCO(3) (-) /L). Treatment with the Higgin's Loop technology and dilution of untreated water increased survival in the laboratory. The mixing zones of the 3 outfalls studied ranged from approximately 800?m to 1200?m below the confluence. These experiments addressed the acute toxicity of effluent waters but did not address issues related to the volumes of water that may be added to the watershed. PMID:24909548

Farag, Aïda M; Harper, David D; Skaar, Don

2014-09-01

270

Evidence that Natural Selection on Codon Usage in Drosophila pseudoobscura Varies Across Codons  

PubMed Central

Like other species of Drosophila, Drosophila pseudoobscura has a distinct bias toward the usage of C- and G-ending codons. Previous studies have indicated that this bias is due, at least in part, to natural selection. Codon bias clearly differs among amino acids (and other codon classes) in Drosophila, which may reflect differences in the intensity of selection on codon usage. Ongoing natural selection on synonymous codon usage should be reflected in the shapes of the site frequency spectra of derived states at polymorphic positions. Specifically, regardless of other demographic effects on the spectrum, it should be shifted toward higher values for changes from less-preferred to more-preferred codons, and toward lower values for the converse. If the intensity of natural selection is increased, shifts in the site frequency spectra should be more pronounced. A total of 33,729 synonymous polymorphic sites on Chromosome 2 in D. pseudoobscura were analyzed. Shifts in the site frequency spectra are consistent with differential intensity of natural selection on codon usage, with stronger shifts associated with higher codon bias. The shifts, in general, are greater for polymorphic synonymous sites than for polymorphic intron sites, also consistent with natural selection. However, unlike observations in D. melanogaster, codon bias is not reduced in areas of low recombination in D. pseudoobscura; the site frequency spectrum signal for selection on codon usage remains strong in these regions. However, diversity is reduced, as expected. It is possible that estimates of low recombination reflect a recent change in recombination rate. PMID:24531731

Kliman, Richard M.

2014-01-01

271

Developmental Stability of DROSOPHILA MELANOGASTER under Artificial and Natural Selection in Constant and Fluctuating Environments  

PubMed Central

Populations of Drosophila melanogaster in constant 25° and fluctuating 20/29° environments showed increases in developmental stability, indicated by decreases in bilateral asymmetry of sterno-pleural chaeta number. In both environments, rates of decrease in asymmetry were greater under natural selection (control lines) than under artificial stabilizing selection. Overall mean asymmetry was greater in the fluctuating environment.—There was no evidence that decreased asymmetry was due to heterozygosity, and the decline in asymmetry was not explained by the decline in chaeta number in the lines under only natural selection. However, the decline was consistent with changes in total phenotypic variance and environmental variance.—The divergence between lines after 39 generations of selection was seen in differences in asymmetry and also in the genotype-environment interaction expressed in cross-culturing experiments. PMID:6781983

Bradley, Brian P.

1980-01-01

272

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

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

273

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

PubMed Central

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, Jeremy; Boury, Christophe; Frigerio, Jean-Marc; Zimmermann, Niklaus E.; Kremer, Antoine

2013-01-01

274

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

PubMed

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

Kulpa, Sarah M; Leger, Elizabeth A

2013-04-01

275

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

USGS Publications Warehouse

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

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

2011-01-01

276

Alzheimer Disease Susceptibility Loci: Evidence for a Protein Network under Natural Selection  

PubMed Central

Recent genome-wide association studies have identified a number of susceptibility loci for Alzheimer disease (AD). To understand the functional consequences and potential interactions of the associated loci, we explored large-scale data sets interrogating the human genome for evidence of positive natural selection. Our findings provide significant evidence for signatures of recent positive selection acting on several haplotypes carrying AD susceptibility alleles; interestingly, the genes found in these selected haplotypes can be assembled, independently, into a molecular complex via a protein-protein interaction (PPI) network approach. These results suggest a possible coevolution of genes encoding physically-interacting proteins that underlie AD susceptibility and are coexpressed in different tissues. In particular, PICALM, BIN1, CD2AP, and EPHA1 are interconnected through multiple interacting proteins and appear to have coordinated evidence of selection in the same human population, suggesting that they may be involved in the execution of a shared molecular function. This observation may be AD-specific, as the 12 loci associated with Parkinson disease do not demonstrate excess evidence of natural selection. The context for selection is probably unrelated to AD itself; it is likely that these genes interact in another context, such as in immune cells, where we observe cis-regulatory effects at several of the selected AD loci. PMID:22482808

Raj, Towfique; Shulman, Joshua M.; Keenan, Brendan T.; Chibnik, Lori B.; Evans, Denis A.; Bennett, David A.; Stranger, Barbara E.; De Jager, Philip L.

2012-01-01

277

Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes  

PubMed Central

Identifying regions of the human genome that have been targets of natural selection will provide important insights into human evolutionary history and may facilitate the identification of complex disease genes. Although the signature that natural selection imparts on DNA sequence variation is difficult to disentangle from the effects of neutral processes such as population demographic history, selective and demographic forces can be distinguished by analyzing multiple loci dispersed throughout the genome. We studied the molecular evolution of 132 genes by comprehensively resequencing them in 24 African-Americans and 23 European-Americans. We developed a rigorous computational approach for taking into account multiple hypothesis tests and demographic history and found that while many apparent selective events can instead be explained by demography, there is also strong evidence for positive or balancing selection at eight genes in the European-American population, but none in the African-American population. Our results suggest that the migration of modern humans out of Africa into new environments was accompanied by genetic adaptations to emergent selective forces. In addition, a region containing four contiguous genes on Chromosome 7 showed striking evidence of a recent selective sweep in European-Americans. More generally, our results have important implications for mapping genes underlying complex human diseases. PMID:15361935

2004-01-01

278

Selective use of the primary literature transforms the classroom into a virtual laboratory.  

PubMed

CREATE (consider, read, elucidate hypotheses, analyze and interpret the data, and think of the next experiment) is a new method for teaching science and the nature of science through primary literature. CREATE uses a unique combination of novel pedagogical tools to guide undergraduates through analysis of journal articles, highlighting the evolution of scientific ideas by focusing on a module of four articles from the same laboratory. Students become fluent in the universal language of data analysis as they decipher the figures, interpret the findings, and propose and defend further experiments to test their own hypotheses about the system under study. At the end of the course students gain insight into the individual experiences of article authors by reading authors' responses to an e-mail questionnaire generated by CREATE students. Assessment data indicate that CREATE students gain in ability to read and critically analyze scientific data, as well as in their understanding of, and interest in, research and researchers. The CREATE approach demystifies the process of reading a scientific article and at the same time humanizes scientists. The positive response of students to this method suggests that it could make a significant contribution to retaining undergraduates as science majors. PMID:17483426

Hoskins, Sally G; Stevens, Leslie M; Nehm, Ross H

2007-07-01

279

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

280

[From alert to laboratory: a coherent network designed to deal with to naturally occurring infectious disease outbreaks and bioterrorism].  

PubMed

Public health prevention requires early detection of disease outbreaks, whether naturally occurring or due to bioterrorism. Permanent surveillance and a network of laboratories are the two main pillars of effective outbreak management. Coordination of information, training, and procedures are under the responsibility of the French public health watch institute and the scientific advisory board for the Biotox-Piratox laboratory network. Protective capacities against bioterrorism are improving but efforts must continue. PMID:18402161

Binder, Patrice; Brucker, Gilles; Josseran, Loïc

2007-06-01

281

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

PubMed Central

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

2014-01-01

282

Germination of Ocotea pulchella (Nees) Mez (Lauraceae) seeds in laboratory and natural restinga environment conditions.  

PubMed

The germination response of Ocotea pulchella (Nees) Mez seeds to light, temperature, water level and pulp presence is introduced. The laboratory assays were carried out in germination chambers and thermal-gradient apparatus, whereas the field assays were performed in environments with distinct light, temperature and soil moisture conditions within a permanent parcel of Restinga forest of the Parque Estadual da Ilha do Cardoso, Cananéia, São Paulo. The seeds do not exhibit dormancy, they are non photoblastic, and a loss of viability in dry stored seeds can be related to a decrease in water content of the seed. The presence of the pulp and the flooded substratum influenced negatively the germination of O. pulchella seeds tested in the laboratory. Otherwise, light and temperature probably are not limiting factors of the germination of O. pulchella seeds in the natural environment of Restinga. The optimum temperature range for germination of Ocotea pulchella seeds was 20 to 32 degrees C, the minimum or base temperature estimated was 11 degrees C and the maximum ranged between 33 and 42 degrees C. The isotherms exhibited a sigmoidal pattern well described by the Weibull model in the sub-optimal temperature range. The germinability of O. pulchella seeds in the understorey, both in wet and dry soil, was higher than in gaps. Germination was not affected by fluctuations in soil moisture content in the understorey environment, whereas in gaps, germination was higher in wet soils. Thus, the germination of this species involves the interaction of two or more factors and it cannot be explained by a single factor. PMID:19802455

Pires, L A; Cardoso, V J M; Joly, C A; Rodrigues, R R

2009-08-01

283

113 Lab Learning Objectives Week 14: Information and Natural Selection lab #9  

E-print Network

of evolution based on lab experiences. · Explain how antibiotic resistant bacteria can appear quickly evolution of antibiotic resistance in bacteria. · Formulate an hypothesis how antibiotic resistant bacteria explanation linking genetically defined taste capacity to natural selection and evolution. · Identify possible

Campbell, A. Malcolm

284

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

285

World-Making with Extended Gravity Black Holes for Cosmic Natural Selection in the Multiverse Scenario  

NASA Astrophysics Data System (ADS)

Physics is facing contingency. Not only in facts but also in laws (the frontier becoming extremely narrow). Cosmic natural selection is a tantalizing idea to explain the apparently highly improbable structure of our Universe. In this brief note I will study the creation of Universes by black holes in -string inspired- higher order curvature gravity.

Barrau, Aurelien

2008-09-01

286

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

287

Variation in resource limitation of plant reproduction influences natural selection on floral traits of Asclepias syriaca  

Microsoft Academic Search

The availability of both pollen and resources can influence natural selection on floral traits, but their relative importance in shaping floral evolution is unclear. We experimentally manipulated pollinator and resource (fertilizer and water) availability in the perennial wildflower Asclepias syriaca L. Nine floral traits, one male fitness component (number of pollinia removed), and two female fitness components (number of pollinia

Christina M. Caruso; Davin L. D. Remington; Kate E. Ostergren

2005-01-01

288

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

ERIC Educational Resources Information Center

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

Nehm, Ross H.; Schonfeld, Irvin Sam

2010-01-01

289

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

Microsoft Academic Search

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

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

2002-01-01

290

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

ERIC Educational Resources Information Center

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

Nola, Robert

2013-01-01

291

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

292

World-making with extended gravity black holes for cosmic natural selection in the multiverse scenario  

E-print Network

Physics is facing contingency. Not only in facts but also in laws (the frontier becoming extremely narrow). Cosmic natural selection is a tantalizing idea to explain the apparently highly improbable structure of our Universe. In this brief note I will study the creation of Universes by black holes in -string inspired- higher order curvature gravity.

A. Barrau

2006-12-07

293

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

ERIC Educational Resources Information Center

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

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

2012-01-01

294

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

ERIC Educational Resources Information Center

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

Beachly, William

2010-01-01

295

Approximating Nature's Variation: Selecting and Using Reference Information in Restoration Ecology  

Microsoft Academic Search

Restoration ecologists use reference information to define restoration goals, determine the restoration po- tential of sites, and evaluate the success of restoration efforts. Basic to the selection and use of reference in- formation is the need to understand temporal and spatial variation in nature. This is a challenging task: variation is likely to be scale dependent; ecosystems vary in complex

Peter S. White; Joan L. Walker

1997-01-01

296

Feature Selection of Facial Displays for Detection of Non Verbal Communication in Natural Conversation  

E-print Network

Feature Selection of Facial Displays for Detection of Non Verbal Communication in Natural communication has previously fo- cused on deliberately acted emotions or in structured or ar- tificial social). Another branch of emotion detection research uses a low level representation of expression, such as Facial

Bowden, Richard

297

Natural selection and sympatric divergence in the apple maggot Rhagoletis pomonella  

Microsoft Academic Search

In On the Origin of Species, Darwin proposed that natural selection had a fundamental role in speciation. But this view receded during the Modern Synthesis when allopatric (geographic) models of speciation were integrated with genetic studies of hybrid sterility and inviability. The sympatric hypothesis posits that ecological specialization after a host shift can result in speciation in the absence of

Kenneth E. Filchak; Joseph B. Roethele; Jeffrey L. Feder

2000-01-01

298

Studying the Genetics of Behavior and Evolution by Adaptation and Natural Selection.  

ERIC Educational Resources Information Center

Provides an exercise designed to give students an appreciation for the genetic basis of behavior. Employs the phenomenon of glucose aversion as an example of evolution by mutation and accelerated natural selection, thereby revealing one of the ways in which organisms adapt to human interference. (DDR)

Silverman, Jules

1998-01-01

299

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

300

Sex, death and genetic variation: natural and sexual selection on cricket song  

E-print Network

Sex, death and genetic variation: natural and sexual selection on cricket song David A. Gray1 Male ¢eld crickets, Gryllus integer, in Texas, USA, produce a trilled calling song that attracts female crickets, resulting in enhanced mating success. Gravid female parasitoid £ies, Ormia ochracea

Gray, David A.

301

Genetic Variation and Natural Selection Detection CAS-MPG Partner Institute for  

E-print Network

;· Genetic Variation is variation in alleles of genes, occurs both within and among populations. ­ MutationGenetic Variation and Natural Selection Detection CAS-MPG Partner Institute for Computational ­ Polymorphism Genetic variation #12;· Polymorphism is often defined as the presence of more than one genetically

Spang, Rainer

302

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

ERIC Educational Resources Information Center

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

Stover, Shawn K.; Mabry, Michelle L.

2007-01-01

303

UNIVERSITY OF CALGARY Population divergence and candidate signatures of natural selection in alpine and lowland  

E-print Network

and lowland ecotypes of the allotetrapoloid plant, Anemone multifida (Ranunculaceae) by Jamie R Mc of the allopolyploid plant, Anemone multifida. I found numerous signatures of divergent natural selection between evolutionary structure of the polyploid A. multifida showed complex patterns of differentiation. Overall

Rogers, Sean

304

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 with…

Nehm, Ross H.; Haertig, Hendrik

2012-01-01

305

2002 Nature Publishing Group Selective cell suicide is crucial for sculpting the embryo,  

E-print Network

© 2002 Nature Publishing Group REVIEWS Selective cell suicide is crucial for sculpting the embryo apoptosis is a crucial step in tumorigenesis. Indeed, a defective suicide programme endows nascent-being and decide whether the suicide pro- gramme should be activated? Re-evaluation of this hotly debated issue8

Gauthier, Eric

306

The realized effect of postpollination sexual selection in a natural plant population.  

PubMed Central

The ultimate importance of postpollination sexual selection has remained elusive, largely because of the difficulty of assigning paternity in the field. Here I use a powerful new molecular marker (AFLP) for paternity analysis in a natural population of the outcrossing angiosperm Persoonia mollis (Proteaceae) to assess male reproductive success following equal pollination of 15 pollen donors on each of 6310 pistils. These results were contrasted with male reproductive success of these same plants following natural mating. Following equal pollination, there was a significant departure from equal siring success, indicating a potential for postpollination sexual selection. The most successful pollen donor sired more than twice the expected number of seeds, and this was largely consistent across recipient plants. However, siring success following natural mating was significantly different from siring success following artificial pollination and showed that the reproductive gains to be made from superior pollen performance did not translate into increased reproductive success following natural mating. As the ecological context for post-pollination sexual selection is strong in P. mollis, I suggest that pollen competition may ultimately have only a weak effect on non-random male mating success under natural conditions because the realized opportunities for pollen competition within pistils are limited. PMID:11075703

Krauss, S L

2000-01-01

307

Experience-Dependent Specialization of Receptive Field Surround for Selective Coding of Natural Scenes  

PubMed Central

Summary At eye opening, neurons in primary visual cortex (V1) are selective for stimulus features, but circuits continue to refine in an experience-dependent manner for some weeks thereafter. How these changes contribute to the coding of visual features embedded in complex natural scenes remains unknown. Here we show that normal visual experience after eye opening is required for V1 neurons to develop a sensitivity for the statistical structure of natural stimuli extending beyond the boundaries of their receptive fields (RFs), which leads to improvements in coding efficiency for full-field natural scenes (increased selectivity and information rate). These improvements are mediated by an experience-dependent increase in the effectiveness of natural surround stimuli to hyperpolarize the membrane potential specifically during RF-stimulus epochs triggering action potentials. We suggest that neural circuits underlying surround modulation are shaped by the statistical structure of visual input, which leads to more selective coding of features in natural scenes. PMID:25263755

Pecka, Michael; Han, Yunyun; Sader, Elie; Mrsic-Flogel, Thomas D.

2014-01-01

308

Clay mineralogy of selected borehole sediments from the Lawrence Livermore National Laboratory and Sandia National Laboratories, Livermore, California  

SciTech Connect

Smectite, 90 to 100% interstratified illite-smectite, chlorate, and kaolinite are identified in boreholes drilled in fluvial and alluvial fan deposits of the Plio-Pleistocene Livermore Formation in the vicinity of Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratories (SNL), Livermore. X-ray diffraction, scanning electron microscopy, and electron microprobe studies indicate the clays persist through 150 ft of gravels, sands, silts, and mudstones of the vadose zone to total drilling depths of 200 ft in the saturated zone. Scanning electron microscopy indicates that true clays (layer silicate only) comprise between 2 and 15 modal percent of the Livermore Formation. Authigenic and detrital smectite, 90% interlayered illite-smectite, and chlorate persist throughout the stratigraphic section; kaolinite occurs only in the upper 100 ft of the section and is absent below. Smectite comprises between 60 to 90% of the true (layer silicate only) clay fraction. Illite and kaolinite{plus_minus}chlorite abundances fluctuate between 10 to 30% and 10 to 20% of this fraction, respectively. Authigenic smectite, illite, and chlorate crystallize together with detrital phases; the authigenic component increases with depth. The relative percentages of clay minerals define unique mineralogical intervals, which can be correlated between boreholes. Pervasive microfractures and interconnected porosity are inherent in the finer sediments; the microfractures typically are 1 mm or less in width and are variably spaced. Voids and microfractures are conspicuously lined by clays. Porosity for the argillaceous sediments ranges between 23 and 40%; Brunauer, Emmett, and Teller (BET) specific surface area decreases variably from 40 m{sup 2}/g near the surface to 15 m{sup 2}/g at the 115-ft depth. Within the pelitic matrix, iron, iron-titanium, chromium, and manganese oxides are pervasive.

Smith, D.K. [ed.; Peifer, D.W.; Rood, C.K.

1992-04-01

309

Natural selection, plasticity and the emergence of a behavioural syndrome in the wild.  

PubMed

Individuals often show consistent behavioural differences where behaviours can form integrated units across functionally different contexts. However, the factors causing and maintaining behavioural syndromes in natural populations remain poorly understood. In this study, we provide evidence for the emergence of a behavioural syndrome during the first months of life in wild brown trout (Salmo trutta). Behavioural traits of trout were scored before and after a 2-month interval covering a major survival bottleneck, whereupon the consistency and covariance of behaviours were analysed. We found that selection favoured individuals with high activity levels in an open-field context, a personality trait consistent throughout the duration of the experiment. In addition, a behavioural syndrome emerged over the 2 months in the wild, linking activity to aggressiveness and exploration tendency. These novel results suggest that behavioural syndromes can emerge rapidly in nature from interaction between natural selection and behavioural plasticity affecting single behaviours. PMID:23034098

Adriaenssens, Bart; Johnsson, Jörgen I

2013-01-01

310

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. PMID:22380592

2012-01-01

311

Unweaving misconceptions: Guided learning, simulations, and misconceptions in learning principles of natural selection  

NASA Astrophysics Data System (ADS)

College students often come to the study of evolutionary biology with many misconceptions of how the processes of natural selection and speciation occur. How to relinquish these misconceptions with learners is a question that many educators face in introductory biology courses. Constructivism as a theoretical framework has become an accepted and promoted model within the epistemology of science instruction. However, constructivism is not without its skeptics who see some problems of its application in lacking necessary guidance for novice learners. This study within a quantitative, quasi-experimental format tested whether guided online instruction in a video format of common misconceptions in evolutionary biology produced higher performance on a survey of knowledge of natural selection versus more constructivist style learning in the form of student exploration of computer simulations of the evolutionary process. Performances on surveys were also explored for a combination of constructivist and guided techniques to determine if a consolidation of approaches produced higher test scores. Out of the 94 participants 95% displayed at least one misconception of natural selection in the pre-test while the study treatments produced no statistically significant improvements in post-test scores except within the video (guided learning treatment). These overall results demonstrated the stubbornness of misconceptions involving natural selection for adult learners and the difficulty of helping them overcome them. It also bolsters the idea that some misconceptions of natural selection and evolution may be hardwired in a neurological sense and that new, more long-term teaching techniques may be warranted. Such long-term strategies may not be best implemented with constructivist techniques alone, and it is likely that some level of guidance may be necessary for novice adult learners. A more substantial, nuanced approach for undergraduates is needed that consolidates successful teaching strategies to adult students that is based on current research.

Weeks, Brian E.

312

LABORATORY PROCESS CONTROLLER USING NATURAL LANGUAGE COMMANDS FROM A PERSONAL COMPUTER  

NASA Technical Reports Server (NTRS)

The complex environment of the typical research laboratory requires flexible process control. This program provides natural language process control from an IBM PC or compatible machine. Sometimes process control schedules require changes frequently, even several times per day. These changes may include adding, deleting, and rearranging steps in a process. This program sets up a process control system that can either run without an operator, or be run by workers with limited programming skills. The software system includes three programs. Two of the programs, written in FORTRAN77, record data and control research processes. The third program, written in Pascal, generates the FORTRAN subroutines used by the other two programs to identify the user commands with the user-written device drivers. The software system also includes an input data set which allows the user to define the user commands which are to be executed by the computer. To set the system up the operator writes device driver routines for all of the controlled devices. Once set up, this system requires only an input file containing natural language command lines which tell the system what to do and when to do it. The operator can make up custom commands for operating and taking data from external research equipment at any time of the day or night without the operator in attendance. This process control system requires a personal computer operating under MS-DOS with suitable hardware interfaces to all controlled devices. The program requires a FORTRAN77 compiler and user-written device drivers. This program was developed in 1989 and has a memory requirement of about 62 Kbytes.

Will, H.

1994-01-01

313

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

ERIC Educational Resources Information Center

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

Elliott, Shannon Snyder

2007-01-01

314

An inter-laboratory evaluation of selective media for the detection and enumeration of yeasts from blue-veined cheese  

Microsoft Academic Search

Five countries representative of laboratories 1–5 evaluated 11 different selective media, designed to suppress mould and bacterial growth and support yeasts growth, for the recovery of yeast populations from blue veined cheeses. In addition, qualitative results were also incorporated. The yeast enumeration values were subjected to statistical analysis using analysis of variance (ANOVA) and the Tukey-Kramer multiple comparison test. With

B. C Viljoen; A Knox; L. R Beuchat; T Deak; M Malfeito-Ferreira; T. K Hansen; A Hugo; M Jakobsen; V Loureiro; A Lourens-Hattingh; R Vasdinnyei

2004-01-01

315

Lifetime selection on heritable life-history traits in a natural population of red squirrels.  

PubMed

Despite their importance in evolutionary biology, heritability and the strength of natural selection have rarely been estimated in wild populations of iteroparous species or have usually been limited to one particular event during an organism's lifetime. Using an animal-model restricted maximum likelihood and phenotypic selection models, we estimated quantitative genetic parameters and the strength of lifetime selection on parturition date and litter size at birth in a natural population of North American red squirrels, Tamiasciurus hudsonicus. Litter size at birth and parturition date had low heritabilities (h2 = 0.15 and 0.16, respectively). We considered potential effects of temporal environmental covariances between phenotypes and fitness and of spatial environmental heterogeneity in estimates of selection. Selection favored early breeders and females that produced litter sizes close to the population average. Stabilizing selection on litter size at birth may occur because of a trade-off between number of offspring produced per litter and offspring survival or a trade-off between a female's fecundity and her future reproductive success and survival. PMID:14628929

Réale, D; Berteaux, D; McAdam, A G; Boutin, S

2003-10-01

316

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

PubMed

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

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

2014-11-01

317

Estimating hydroxyl radical photochemical formation rates in natural waters during long-term laboratory irradiation experiments.  

PubMed

In this study it was observed that, during long-term irradiations (>1 day) of natural waters, the methods for measuring hydroxyl radical (?OH) formation rates based upon sequentially determined cumulative concentrations of photoproducts from probes significantly underestimate actual ?OH formation rates. Performing a correction using the photodegradation rates of the probe products improves the ?OH estimation for short term irradiations (<1 day), but not long term irradiations. Only the 'instantaneous' formation rates, which were obtained by adding probes to aliquots at each time point and irradiating these sub-samples for a short time (?2 h), were found appropriate for accurately estimating ?OH photochemical formation rates during long-term laboratory irradiation experiments. Our results also showed that in iron- and dissolved organic matter (DOM)-rich water samples, ?OH appears to be mainly produced from the Fenton reaction initially, but subsequently from other sources possibly from DOM photoreactions. Pathways of ?OH formation in long-term irradiations in relation to H2O2 and iron concentrations are discussed. PMID:24513701

Sun, Luni; Chen, Hongmei; Abdulla, Hussain A; Mopper, Kenneth

2014-04-01

318

The Genetic Architecture of Ecological Speciation and the Association with Signatures of Selection in Natural Lake Whitefish (Coregonus sp. Salmonidae)  

E-print Network

of the role of divergent natural selection on those traits. The lake whitefish (Coregonus clupeaformis in Natural Lake Whitefish (Coregonus sp. Salmonidae) Species Pairs S. M. Rogers1 and L. Bernatchez Que

Bernatchez, Louis

319

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. PMID:20622977

Hancock, Angela M.; Rienzo, Anna Di

2010-01-01

320

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

PubMed Central

For decades, it has been hypothesized that gene regulation has had central role in human evolution, yet much remains unknown about the genome-wide impact of regulatory mutations. Here we use whole-genome sequences and genome-wide chromatin immunoprecipitation and sequencing data to demonstrate that natural selection has profoundly influenced human transcription factor binding sites since the divergence of humans from chimpanzees 4–6 million years ago. Our analysis uses a new probabilistic method, called INSIGHT, for measuring the influence of selection on collections of short, interspersed noncoding elements. We find that, on average, transcription factor binding sites have experienced somewhat weaker selection than protein-coding genes. However, the binding sites of several transcription factors show clear evidence of adaptation. Several measures of selection are strongly correlated with predicted binding affinity. Overall, regulatory elements seem to contribute substantially to both adaptive substitutions and deleterious polymorphisms with key implications for human evolution and disease. PMID:23749186

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

2013-01-01

321

RTK/ERK Pathway under Natural Selection Associated with Prostate Cancer  

PubMed Central

Prostate cancer (PCa) is a global disease causing large numbers of deaths every year. Recent studies have indicated the RTK/ERK pathway might be a key pathway in the development of PCa. However, the exact association and evolution-based mechanism remain unclear. This study was conducted by combining genotypic and phenotypic data from the Chinese Consortium for Prostate Cancer Genetics (ChinaPCa) with related databases such as the HapMap Project and Genevar. In this analysis, expression of quantitative trait loci (eQTLs) analysis, natural selection and gene-based pathway analysis were involved. The pathway analysis confirmed the positive relationship between PCa risk and several key genes. In addition, combined with the natural selection, it seems that 4 genes (EGFR, ERBB2, PTK2, and RAF1) with five SNPs (rs11238349, rs17172438, rs984654, rs11773818, and rs17172432) especially rs17172432, might be pivotal factors in the development of PCa. The results indicate that the RTK/ERK pathway under natural selection is a key link in PCa risk. The joint effect of the genes and loci with positive selection might be one reason for the development of PCa. Dealing with all the factors simultaneously might give insight into prevention and aid in predicting the success of potential therapies for PCa. PMID:24223781

Xu, Jianfeng; Yu, Xiaoxiang; Li, Tianyu; Mo, Zengnan; Hu, Yanling

2013-01-01

322

NATURE METHODS | VOL.2 NO.12 | DECEMBER 2005 | 981 Cold Spring Harbor Laboratory Press PUBLISHED IN ASSOCIATION WITH  

E-print Network

for manipulation using genetic methods, they are simply grown and maintained in the laboratory and easily serum,for selected clones (see Step 13) HEPES buffer (20 mM,pH 7.2) Lipofectamine 2000 (Invitrogen) pCAUTION EQUIPMENT Cloning rings (6- or 8-mm outer diameter size; Fisher Scientific) Culture dishes with grid (Mat

Cai, Long

323

The Effect of Reflective Discussions following Inquiry-Based Laboratory Activities on Students' Views of Nature of Science  

ERIC Educational Resources Information Center

This research investigated the effect of reflective discussions following inquiry-based laboratory activities on students' views of the tentative, empirical, subjective, and social aspects of nature of science (NOS). Thirty-eight grade six students from a Lebanese school participated in the study. The study used a pretest-posttest control-group…

Yacoubian, Hagop A.; BouJaoude, Saouma

2010-01-01

324

Field and laboratory arsenic speciation methods and their application to natural-water analysis  

USGS Publications Warehouse

The toxic and carcinogenic properties of inorganic and organic arsenic species make their determination in natural water vitally important. Determination of individual inorganic and organic arsenic species is critical because the toxicology, mobility, and adsorptivity vary substantially. Several methods for the speciation of arsenic in groundwater, surface-water, and acid mine drainage sample matrices using field and laboratory techniques are presented. The methods provide quantitative determination of arsenite [As(III)], arsenate [As(V)], monomethylarsonate (MMA), dimethylarsinate (DMA), and roxarsone in 2-8min at detection limits of less than 1??g arsenic per liter (??g AsL-1). All the methods use anion exchange chromatography to separate the arsenic species and inductively coupled plasma-mass spectrometry as an arsenic-specific detector. Different methods were needed because some sample matrices did not have all arsenic species present or were incompatible with particular high-performance liquid chromatography (HPLC) mobile phases. The bias and variability of the methods were evaluated using total arsenic, As(III), As(V), DMA, and MMA results from more than 100 surface-water, groundwater, and acid mine drainage samples, and reference materials. Concentrations in test samples were as much as 13,000??g AsL-1 for As(III) and 3700??g AsL-1 for As(V). Methylated arsenic species were less than 100??g AsL-1 and were found only in certain surface-water samples, and roxarsone was not detected in any of the water samples tested. The distribution of inorganic arsenic species in the test samples ranged from 0% to 90% As(III). Laboratory-speciation method variability for As(III), As(V), MMA, and DMA in reagent water at 0.5??g AsL-1 was 8-13% (n=7). Field-speciation method variability for As(III) and As(V) at 1??g AsL-1 in reagent water was 3-4% (n=3). ?? 2003 Elsevier Ltd. All rights reserved.

Bednar, A.J.; Garbarino, J.R.; Burkhardt, M.R.; Ranville, J.F.; Wildeman, T.R.

2004-01-01

325

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

PubMed Central

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; Reale, Denis

2011-01-01

326

Antagonism between sexual and natural selection in experimental populations of Saccharomyces cerevisiae.  

PubMed

Trade-offs between life-history components are a central concept of evolution and ecology. Sexual and natural selection seem particularly apt to impose antagonistic selective pressures. When sex is not integrated into reproduction, as in Saccharomyces cerevisiae, natural selection can impair or even eliminate it. In this study, a genetic trade-off between the sexual and asexual phases of the yeast life cycle was suggested by sharp declines in the mating and sporulation abilities of unrelated genotypes that were propagated asexually in minimal growth medium and in mice. When sexual selection was applied to populations that had previously evolved asexually, sexual fitness increased but asexual fitness declined. No such negative correlation was observed when sexual selection was applied to an ancestral strain: sexual and asexual fitness both increased. Thus, evolutionary history affected the evolution of genetic correlations, as fitness increases in a population already well adapted to the environment were more likely to come at the expense of sexual functions. PMID:16405156

Zeyl, Clifford; Curtin, Ciara; Karnap, Kristin; Beauchamp, Elspeth

2005-10-01

327

Material selection for wellhead equipment exposed to chlorinated and natural seawater  

SciTech Connect

Corrosion resistant alloys have been used in marine environments for their corrosion resistance. However, some of these materials are prone to localized corrosion, in particular crevice and pitting corrosion, in natural seawater. Injection water normally consists of de-oxygenated seawater, but, more recently either continuously or batch chlorinated and fully oxygenated seawater has been selected for this purpose because of their cost benefits. This investigation covers testing of corrosion resistant materials to aid in the selection of materials for wellhead equipment in an oxygenated and chlorinated seawater injection environment.

Olsen, S.; Nice, P.; Strandmyr, O. [Statoil, Stavanger (Norway); Maligas, M.; Vicic, J. [FMC Corp., Houston, TX (United States). Wellhead Equipment Div.

1996-08-01

328

Kinetic Studies with Ion Selective Electrodes: Determination of Creatinine in Urine with a Picrate Ion Selective Electrode: A Laboratory Experiment.  

ERIC Educational Resources Information Center

The kinetic of the Jaffe reaction with picrate ion selective electrode (ISE) and a kinetic method for determining creatinine in urine is presented. The experiment could be used to familarize students with the application of ISE in kinetic studies and chemical analysis. (Author/JN)

Diamandis, E. P.; And Others

1983-01-01

329

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

330

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. PMID:23967097

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

2013-01-01

331

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

332

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. PMID:23966858

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

333

I'm Looking Over a White-Striped Clover A Natural Selection Case  

NSDL National Science Digital Library

This case is an exploration of the process of natural selection using white clover (Trifolium repens) as an example. In general, two forms of white clover can be found around the world in various habitats. One type is able to produce cyanide in its leaves, while the other is not. This variation within the clover species, along with the fact that cyanide production is paired with the production of a white stripe on the leaf, is used to teach the process of evolution through natural selection. Students use the scientific method to explore these concepts. As an introduction to evolutionary concepts in biology, the case would be appropriate for both high school and college biology courses.

Evarts, Susan; Krufka, Alison; Wilson, Chester

2006-01-01

334

The importance of selection at the level of the pair over 25 years in a natural population of birds  

PubMed Central

Knowledge of the pattern of selection in natural populations is fundamental for our understanding of the evolutionary process. Selection at higher levels has gained considerable theoretical support in recent years, and one possible level of selection is the breeding pair where fitness is a function of the pair and cannot be reduced to single individuals. We analyzed the importance of pair-level selection over 25 years in a natural population of the collared flycatcher. Pair-level selection was significant in five and probably in another 9 years. The relative importance of pair-level selection varied over years and can have stronger or the same strength as directional selection. This means that selection can act on the combination of the breeding pair in addition to selection on each individual separately. Overall, the conservative estimates obtained here show that this is a potentially important form of selection. PMID:24340199

Bjorklund, Mats; Gustafsson, Lars

2013-01-01

335

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

336

Darwin's Arguments in Favour of Natural Selection and Against Special Creationism  

NASA Astrophysics Data System (ADS)

In many places in The Origin of Species, Darwin compares his own theory of Natural Selection favourably with Special Creationism which comes off as a bad second best. He does this using some version of the argument form known as `Inference to the Best Explanation'. The first part of this paper is methodological. It considers Whewell's notion of consilience, that is, the way in which theories can get additional confirmation through unifying otherwise disparate and independent facts. Then it considers various forms of inference to the best explanation. The second part of the paper applies these methodological considerations to an analysis of some of the many passages in Origin where Darwin presents his case in favour of Natural Selection. This gives a far superior explanation of biological facts compared with Special Creationism which provides either an inferior explanation or no explanation at all. Contrary to the view that Creationism should not be taught, the passages from Darwin show at least that it should be understood if only to show that it offers no explanation of a wide range of obvious biological facts. As such the passages in Origin in which Darwin presents his case against Creationism can serve as a series of excellent exercises in getting students to think about Natural Selection as opposed to Creationism. For this reason alone they ought to be better known. In addition, Darwin's point in these passages can only be understood using principles of scientific method, such as inference to the best explanation, which are essential in showing that Natural Selection is to be preferred to Creationism.

Nola, Robert

2013-02-01

337

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

Microsoft Academic Search

Our study examines the efficacy of Computer Assisted Scoring (CAS) of open-response text relative to expert human scoring\\u000a within the complex domain of evolutionary biology. Specifically, we explored whether CAS can diagnose the explanatory elements\\u000a (or Key Concepts) that comprise undergraduate students’ explanatory models of natural selection with equal fidelity as expert\\u000a human scorers in a sample of >1,000 essays.

Ross H. Nehm; Hendrik Haertig

2011-01-01

338

Life history traits are affected by natural selection Affect the overall "program" of the organism  

E-print Network

45 50 Latitude (deg.N) mmd -1 (YOY = "young of the year") #12;5 1 2 3 4 5 6 7 9 (1960s) 9 (2002) 8 10 (1984) 10 (1996) 11 (1970s) 11 (1950s) 11 (1960s) 12 13 14 0 10 20 30 40 50 60 70 80 90 25 30 35 40 451 · Life history traits are affected by natural selection · Affect the overall "program

Limburg, Karin E.

339

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\\u000a among functional classes of sites in DNA. Mutational biases, biased gene conversion, and natural selection have been proposed\\u000a as causes of this variation. Here, we review patterns of base composition in Drosophila DNA. Nucleotide composition in Drosophila\\u000a melanogaster varys regionally,

Hiroshi Akashi; Richard M. Kliman; Adam Eyre-Walker

1998-01-01

340

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

341

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

PubMed Central

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 signals of selection that compares patterns of genetic variation at a candidate locus with matched random regions of the genome collected in the same way. We apply this approach to four genes that have been implicated in syndromes of impaired neurological development, comparing the pattern of variation in our re-sequencing data with a large-scale, genomic data set that provides an empirical null distribution. We confirm a previously reported signal at FOXP2, and find a novel signal of selection centered at AHI1, a gene that is involved in motor and behavior abnormalities. The locus is marked by many high frequency derived alleles in non-Africans that are of low frequency in Africans, suggesting that selection at this or a closely neighboring gene occurred in the ancestral population of non-Africans. Our study also provides a prototype for how empirical scans for ancient selection can be carried out once many genomes are sequenced. PMID:19783549

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

2009-01-01

342

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

343

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. PMID:12079531

Leigh, Egbert Giles; Vermeij, Geerat Jacobus

2002-01-01

344

Measuring Knowledge of Natural Selection: A Comparison of the CINS, an Open-Response Instrument, and an Oral Interview  

ERIC Educational Resources Information Center

Growing recognition of the central importance of fostering an in-depth understanding of natural selection has, surprisingly, failed to stimulate work on the development and rigorous evaluation of instruments that measure knowledge of it. We used three different methodological tools, the Conceptual Inventory of Natural Selection (CINS), a modified…

Nehm, Ross H.; Schonfeld, Irvin Sam

2008-01-01

345

Variation in mycorrhizal performance in the epiphytic orchid Tolumnia variegata in vitro : the potential for natural selection  

Microsoft Academic Search

Symbiotic seed germination is a critical stage in orchid life histories. Natural selection may act to favor plants that efficiently use mycorrhizal fungi. However, the necessary conditions for natural selection – variation, heritability, and differences in fitness – have not been demonstrated for either orchid or fungus. With the epiphytic orchid Tolumnia variegata as a model system, we ask the

J. Tupac Otero; Paul Bayman; James D. Ackerman

2005-01-01

346

Exploring the Development of Preservice Science Teachers' Views on the Nature of Science in Inquiry-Based Laboratory Instruction  

NASA Astrophysics Data System (ADS)

The purpose of this study was to explore the effect of the inquiry-based and explicit-reflective laboratory instruction on preservice science teachers' (PSTs) conceptions of the nature of science (NOS) aspects. This study was carried out during the Laboratory Application in Science II course. All 52 preservice elementary science teachers enrolled in the course consented to participate in the study; 37 were female and 15 were male, with a mean age of 22.8 years. All had the same science major background, and all of them were juniors. The course provided meaningful and practical inquiry-based experiences, as well as explicit and reflective instruction about NOS. Each week, a specific NOS aspect was targeted related to the inquiry-based laboratory investigation. The design of the study was qualitative and exploratory in nature. At the beginning of the study, the Views of Nature of Science Questionnaire Version B open-ended questionnaire was applied to explore PSTs' NOS views. At the end of the semester, the same questionnaire was conducted to determine the impact of the explicit-reflective and inquiry-based laboratory instruction. The results showed that many PSTs improved their views of NOS in each element, although to different degrees.

Ozgelen, Sinan; Yilmaz-Tuzun, Ozgul; Hanuscin, Deborah L.

2013-08-01

347

Footprints of divergent selection in natural populations of Castanopsis fargesii (Fagaceae).  

PubMed

Given predicted rapid climate change, an understanding of how environmental factors affect genetic diversity in natural populations is important. Future selection pressures are inherently unpredictable, so forest management policies should maintain both overall diversity and identify genetic markers associated with the environmental factors expected to change most rapidly, like temperature and rainfall. In this study, we genotyped 648 individuals in 28 populations of Castanopsis fargesii (Fagaceae) using 32 expressed sequence tag (EST)-derived microsatellite markers. After removing six loci that departed from Hardy-Weinberg equilibrium, we measured genetic variation, population structure and identified candidate loci putatively under selection by temperature and precipitation. We found that C. fargesii populations possessed high genetic diversity and moderate differentiation among them, indicating predominant outcrossing and few restrictions to gene flow. These patterns reduce the possible impact of stochastic effects or the influence of genetic isolation. Clear footprints of divergent selection at four loci were discovered. Frequencies of five alleles at these loci were strongly correlated with environmental factors, particularly extremes in precipitation. These alleles varied from being near fixation at one end of the gradient to being completely absent at the other. Our study species is an important forest tree in the subtropical regions of China and could have a major role in future management and reforestation plans. Our results demonstrate that the gene flow is widespread and abundant in natural populations, maintaining high diversity, while diversifying selection is acting on specific genomic regions. PMID:24984608

Li, C; Sun, Y; Huang, H W; Cannon, C H

2014-12-01

348

Identifying Signatures of Natural Selection in Tibetan and Andean Populations Using Dense Genome Scan Data  

PubMed Central

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.; Lopez Herraez, David; Brutsaert, Tom; Parra, Esteban J.; Moore, Lorna G.; Shriver, Mark D.

2010-01-01

349

ENVIRONMENTAL PATHWAYS OF SELECTED CHEMICALS IN FRESHWATER SYSTEMS. PART II. LABORATORY STUDIES  

EPA Science Inventory

Environmental exposure assessment models and laboratory procedures for predicting the pathways of potentially harmful chemicals in freshwater environments were described in Part I of this report (PB-274 548). Procedures were developed for measuring the rates of volatilization, ph...

350

Life history QTLs and natural selection on flowering time in Boechera stricta, a perennial relative of Arabidopsis  

PubMed Central

Plants must precisely time flowering to capitalize on favorable conditions. Although we know a great deal about the genetic basis of flowering phenology in model species under controlled conditions, the genetic architecture of this ecologically-important trait is poorly understood in non-model organisms. Here, we evaluated the transition from vegetative growth to flowering in Boechera stricta, a perennial relative of Arabidopsis thaliana. We examined flowering time QTLs using 7,920 recombinant inbred individuals, across seven lab and field environments differing in vernalization, temperature, and photoperiod. Genetic and environmental factors strongly influenced the transition to reproduction. We found directional selection for earlier flowering in the field. In the growth chamber experiment, longer winters accelerated flowering, whereas elevated ambient temperatures delayed flowering. Our analyses identified one large effect QTL (nFT), which influenced flowering time in both experiments and the probability of flowering in the field. In Montana, homozygotes for the native allele at nFT showed a selective advantage of 6.6%. Nevertheless, we found relatively low correlations between flowering times in the field and the growth chambers. Additionally, we detected flowering-related QTLs in the field which were absent across the full range of laboratory conditions, thus emphasizing the need to conduct experiments in natural environments. PMID:21083662

Anderson, Jill T.; Lee, Cheng-Ruei; Mitchell-Olds, Thomas

2011-01-01

351

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

352

Integrated data search and access to geophysical data for Geohazards Supersites and Natural Laboratories  

NASA Astrophysics Data System (ADS)

The Geohazards Supersites and Natural Laboratories (GSNL) are committed to sharing space-based and ground-based geophysical data and building collaborations to better understand Earth processes and mitigate the societal hazards related to the dynamic Earth. GSNL is global with locations in Turkey, Japan, China, Italy, Haiti the United States (e.g. Hawaii and the western U.S.) and elsewhere. The UNAVCO Data Center in Boulder, Colorado, archives and distributes geodesy data and products in the GPS/GNSS, InSAR, and LiDAR domains. UNAVCO has an open access data policy and strives to provide catalogs and data access tools for all users. In an effort to create a unified data and metadata access capability for geodesy data centers in general and for GSNL in particular, UNAVCO and our partners, have designed and implemented software for simplified access called the Geodesy Seamless Archive Centers (GSAC). GSAC is a web services based technology to facilitate data discovery and access. The GSAC technology leverages several well-accepted geodesy data and metadata formats, and identifies a relatively small set of required and recommended metadata for the basic installation. Additional optional metadata can be defined at individual data centers. The GSAC services utilize a repository layer implemented at each data center, and a service layer to identify and present the required metadata elements along with any data center-specific services and capabilities. The software for the GSAC is available through SourceForge, and any geodesy data archive can download the code and implement GSAC services for their repository; doing so will provide the data center's users with the ability to use common query and access mechanisms with other GSAC data centers. Further, optional federation of individual GSAC data centers is facilitated through the GSAC software. GSAC would significantly simplify data access and integration, while enhancing data sharing around the world. GSAC is an excellent tool for advancing the goals of GSNL and helping to make the world a safer place through simple data integration.

Rowan, L.; Baker, S.; Wier, S.; Boler, F. M.; Meertens, C. M.; Amelung, F.

2013-12-01

353

Highly Variable Recombinational Landscape Modulates Efficacy of Natural Selection in Birds  

PubMed Central

Determining the rate of protein evolution and identifying the causes of its variation across the genome are powerful ways to understand forces that are important for genome evolution. By using a multitissue transcriptome data set from great tit (Parus major), we analyzed patterns of molecular evolution between two passerine birds, great tit and zebra finch (Taeniopygia guttata), using the chicken genome (Gallus gallus) as an outgroup. We investigated whether a special feature of avian genomes, the highly variable recombinational landscape, modulates the efficacy of natural selection through the effects of Hill–Robertson interference, which predicts that selection should be more effective in removing deleterious mutations and incorporating beneficial mutations in high-recombination regions than in low-recombination regions. In agreement with these predictions, genes located in low-recombination regions tend to have a high proportion of neutrally evolving sites and relaxed selective constraint on sites subject to purifying selection, whereas genes that show strong support for past episodes of positive selection appear disproportionally in high-recombination regions. There is also evidence that genes located in high-recombination regions tend to have higher gene expression specificity than those located in low-recombination regions. Furthermore, more compact genes (i.e., those with fewer/shorter introns or shorter proteins) evolve faster than less compact ones. In sum, our results demonstrate that transcriptome sequencing is a powerful method to answer fundamental questions about genome evolution in nonmodel organisms. PMID:25062920

Gossmann, Toni I.; Santure, Anna W.; Sheldon, Ben C.; Slate, Jon; Zeng, Kai

2014-01-01

354

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

355

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

356

An inter-laboratory evaluation of selective media for the detection and enumeration of yeasts from blue-veined cheese.  

PubMed

Five countries representative of laboratories 1-5 evaluated 11 different selective media, designed to suppress mould and bacterial growth and support yeasts growth, for the recovery of yeast populations from blue veined cheeses. In addition, qualitative results were also incorporated. The yeast enumeration values were subjected to statistical analysis using analysis of variance (ANOVA) and the Tukey-Kramer multiple comparison test. With the exception of Laboratory 3, none of the other laboratories was successful in recovering yeasts on all the media. Six of the media proved inadequate for the enumeration of yeasts in the mould invested environment and were therefore omitted from statistical analysis. No significant differences in quantitative data obtained on Rose-Bengal Chloramphenicol Agar (RBCA), Dichloran Rose-Bengal Chloramphenicol Agar (DRBC), Dichloran 18% Glycerol Agar (DG18), and Malt extract agar supplemented with NaCl and oxytetracycline (MES) were detected by four of the collaborating laboratories whereas one laboratory found RBCA to be superior for yeast enumeration. DG18 and Malt Extract Agar with Biphenyl (MEB), however, were ranked superior based on qualitative results compared to the other media, attributed to distinctive individual yeast colonies and mould inhibition. RBCA, DRBC, DG18, and MES on the other hand, all proved to be adequate in supporting yeast colony development for quantitative analysis in samples obtained from blue veined cheeses. PMID:15172480

Viljoen, B C; Knox, A; Beuchat, L R; Deak, T; Malfeito-Ferreira, M; Hansen, T K; Hugo, A; Jakobsen, M; Loureiro, V; Lourens-Hattingh, A; Vasdinnyei, R

2004-07-01

357

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

358

Phenotypic variation and natural selection at catsup, a pleiotropic quantitative trait gene in Drosophila.  

PubMed

Quantitative traits are shaped by networks of pleiotropic genes . To understand the mechanisms that maintain genetic variation for quantitative traits in natural populations and to predict responses to artificial and natural selection, we must evaluate pleiotropic effects of underlying quantitative trait genes and define functional allelic variation at the level of quantitative trait nucleotides (QTNs). Catecholamines up (Catsup), which encodes a negative regulator of tyrosine hydroxylase , the rate-limiting step in the synthesis of the neurotransmitter dopamine, is a pleiotropic quantitative trait gene in Drosophila melanogaster. We used association mapping to determine whether the same or different QTNs at Catsup are associated with naturally occurring variation in multiple quantitative traits. We sequenced 169 Catsup alleles from a single population and detected 33 polymorphisms with little linkage disequilibrium (LD). Different molecular polymorphisms in Catsup are independently associated with variation in longevity, locomotor behavior, and sensory bristle number. Most of these polymorphisms are potentially functional variants in protein coding regions, have large effects, and are not common. Thus, Catsup is a pleiotropic quantitative trait gene, but individual QTNs do not have pleiotropic effects. Molecular population genetic analyses of Catsup sequences are consistent with balancing selection maintaining multiple functional polymorphisms. PMID:16682353

Carbone, Mary Anna; Jordan, Katherine W; Lyman, Richard F; Harbison, Susan T; Leips, Jeff; Morgan, Theodore J; DeLuca, Maria; Awadalla, Philip; Mackay, Trudy F C

2006-05-01

359

Culture and maintenance of selected invertebrates in the laboratory and classroom.  

PubMed

Invertebrate species have been used for many years in the laboratory and teaching environment. We discuss some of the most commonly maintained invertebrates--the nematode (Caenorhabditis elegans), the California sea hare (Aplysia californica), the fruit fly (Drosophila melanogaster), terrestrial hermit crabs, the horseshoe crab (Limulus polyphemus), and cephalopods--and briefly describe general techniques for culturing them in captivity. The aim of this article is to give potential users an idea of the materials, methods, and effort required to maintain each type of organism in a laboratory or classroom setting. PMID:21709308

Smith, Stephen A; Scimeca, Joseph M; Mainous, Mary E

2011-01-01

360

Select Agent and Toxin Regulations: Beyond the Eighth Edition of the Guide for the Care and Use of Laboratory Animals  

PubMed Central

In the interval between the publication of the seventh and eighth editions of the Guide for the Care and Use of Laboratory Animals (Guide), much has changed with regard to the regulation and funding of highly pathogenic biologic agents and toxins (Select Agents). Funding of research involving highly pathogenic agents has increased dramatically during this time, thus increasing the demand for facilities capable of supporting this work. The eighth edition of the Guide briefly mentions Select Agents and provides a limited set of references. Here we provide some background information regarding the relevant laws and regulations, as well as an overview of the programmatic requirements pertaining to the use of Select Agents, with a focus on use in animals. PMID:22776191

Kastenmayer, Robin J; Moore, Rashida M; Bright, Allison L; Torres-Cruz, Rafael; Elkins, William R

2012-01-01

361

Aggression and feeding of hatchery-reared and naturally reared steelhead (Oncorhynchus mykiss) fry in a laboratory flume and a comparison with observations in natural streams  

USGS Publications Warehouse

We quantified the aggression and feeding of naturally reared steelhead (Oncorhynchus mykiss) fry stocked into a laboratory flume with naturally reared fry or hatchery-reared fry from conventional and enriched rearing environments at three densities in the presence and absence of predators, and compared the aggression and feeding observed in the flume to that observed in two streams. Steelhead fry attack rate increased with density and was reduced in the presence of predators, but was not affected by rearing treatment. Threat rate appeared to increase with density and was significantly affected by rearing treatment combination, but was not significantly affected by predator presence. Feeding rate was not affected by density or rearing treatment, but was reduced in the presence of predators. The rate of aggression by steelhead fry in two streams was lower than that observed in the laboratory and did not increase with density. Rates of aggression and feeding of hatchery-reared and wild steelhead fry were not significantly different in the streams. Overall, we found no evidence that hatchery rearing environments caused higher aggression in steelhead fry. Laboratory observations of salmonid aggression, particularly at high density, may not reflect aggression levels in the wild. ?? 2005 NRC.

Riley, S. C.; Tatara, C. P.; Scheurer, J. A.

2005-01-01

362

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 ...

363

Interaction-based evolution: how natural selection and nonrandom mutation work together  

PubMed Central

Background The modern evolutionary synthesis leaves unresolved some of the most fundamental, long-standing questions in evolutionary biology: What is the role of sex in evolution? How does complex adaptation evolve? How can selection operate effectively on genetic interactions? More recently, the molecular biology and genomics revolutions have raised a host of critical new questions, through empirical findings that the modern synthesis fails to explain: for example, the discovery of de novo genes; the immense constructive role of transposable elements in evolution; genetic variance and biochemical activity that go far beyond what traditional natural selection can maintain; perplexing cases of molecular parallelism; and more. Presentation of the hypothesis Here I address these questions from a unified perspective, by means of a new mechanistic view of evolution that offers a novel connection between selection on the phenotype and genetic evolutionary change (while relying, like the traditional theory, on natural selection as the only source of feedback on the fit between an organism and its environment). I hypothesize that the mutation that is of relevance for the evolution of complex adaptation—while not Lamarckian, or “directed” to increase fitness—is not random, but is instead the outcome of a complex and continually evolving biological process that combines information from multiple loci into one. This allows selection on a fleeting combination of interacting alleles at different loci to have a hereditary effect according to the combination’s fitness. Testing and implications of the hypothesis This proposed mechanism addresses the problem of how beneficial genetic interactions can evolve under selection, and also offers an intuitive explanation for the role of sex in evolution, which focuses on sex as the generator of genetic combinations. Importantly, it also implies that genetic variation that has appeared neutral through the lens of traditional theory can actually experience selection on interactions and thus has a much greater adaptive potential than previously considered. Empirical evidence for the proposed mechanism from both molecular evolution and evolution at the organismal level is discussed, and multiple predictions are offered by which it may be tested. Reviewers This article was reviewed by Nigel Goldenfeld (nominated by Eugene V. Koonin), Jürgen Brosius and W. Ford Doolittle. PMID:24139515

2013-01-01

364

Laboratory lore and research practices in the experimental analysis of human behavior: Subject selection  

E-print Network

Discusses data on S selection processes obtained from a literature survey and 52 members of the Association for Behavior Analysis. Choice of S samples is discussed in terms of marker variables, including age, gender, and ...

Morris, Edward K.; Johnson, Lisa M.; Todd, James T.; Higgins, Stephen T.

1988-01-01

365

Animal genetic resources in Brazil: result of five centuries of natural selection.  

PubMed

Brazil has various species of domestic animals, which developed from breeds brought by the Portuguese settlers soon after their discovery. For five centuries, these breeds have been subjected to natural selection in specific environments. Today, they present characteristics adapted to the specific Brazilian environmental conditions. These breeds developed in Brazil are known as "Crioulo," "local," or naturalized. From the beginning of the 20th century, some exotic breeds, selected in temperate regions, have begun to be imported. Although more productive, these breeds do not have adaptive traits, such as resistance to disease and parasites found in breeds considered to be "native." Even so, little by little, they replaced the native breeds, to such an extent that the latter are in danger of extinction. In 1983, to avoid the loss of this important genetic material, the National Research Center for Genetic Resources and Biotechnology (Cenargen) of the Brazilian Agricultural Research Corporation (Embrapa) decided to include conservation of animal genetic resources in its research program Conservation and Utilization of Genetic Resources. Until this time, they were only concerned with conservation of native plants. Conservation has been carried out by various research centers of Embrapa, universities, state research corporations, and private farmers, with a single coordinator at the national level, Cenargen. Specifically, conservation is being carried out by conservation nuclei, which are specific herds in which the animals are being conserved, situated in the habitats where the animals have been subjected to natural selection. This involves storage of semen and embryos from cattle, horses, buffaloes, donkeys, goats, sheep, and pigs. The Brazilian Animal Germplasm Bank is kept at Cenargen, which is responsible for the storage of semen and embryos of various breeds of domestic animals threatened with extinction, where almost 45,000 doses of semen and more than 200 embryos exist presently. An important challenge for this program is to make the different segments of society realize the importance of the conservation of animal genetic resources. PMID:11775972

Mariante, A da S; Egito, A A

2002-01-01

366

Natural selection on individual variation in tolerance of gastrointestinal nematode infection.  

PubMed

Hosts may mitigate the impact of parasites by two broad strategies: resistance, which limits parasite burden, and tolerance, which limits the fitness or health cost of increasing parasite burden. The degree and causes of variation in both resistance and tolerance are expected to influence host-parasite evolutionary and epidemiological dynamics and inform disease management, yet very little empirical work has addressed tolerance in wild vertebrates. Here, we applied random regression models to longitudinal data from an unmanaged population of Soay sheep to estimate individual tolerance, defined as the rate of decline in body weight with increasing burden of highly prevalent gastrointestinal nematode parasites. On average, individuals lost weight as parasite burden increased, but whereas some lost weight slowly as burden increased (exhibiting high tolerance), other individuals lost weight significantly more rapidly (exhibiting low tolerance). We then investigated associations between tolerance and fitness using selection gradients that accounted for selection on correlated traits, including body weight. We found evidence for positive phenotypic selection on tolerance: on average, individuals who lost weight more slowly with increasing parasite burden had higher lifetime breeding success. This variation did not have an additive genetic basis. These results reveal that selection on tolerance operates under natural conditions. They also support theoretical predictions for the erosion of additive genetic variance of traits under strong directional selection and fixation of genes conferring tolerance. Our findings provide the first evidence of selection on individual tolerance of infection in animals and suggest practical applications in animal and human disease management in the face of highly prevalent parasites. PMID:25072883

Hayward, Adam D; Nussey, Daniel H; Wilson, Alastair J; Berenos, Camillo; Pilkington, Jill G; Watt, Kathryn A; Pemberton, Josephine M; Graham, Andrea L

2014-07-01

367

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

PubMed

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. PMID:22957168

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

2012-07-01

368

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. PMID:22957168

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

2012-01-01

369

Environmental cost-effectiveness analysis in intertemporal natural resource policy: evaluation of selective fishing gear.  

PubMed

In most decision-making involving natural resources, the achievements of a given policy (e.g., improved ecosystem or biodiversity) are rather difficult to measure in monetary units. To address this problem, the current paper develops an environmental cost-effectiveness analysis (ECEA) to include intangible benefits in intertemporal natural resource problems. This approach can assist managers in prioritizing management actions as least cost solutions to achieve quantitative policy targets. The ECEA framework is applied to a selective gear policy case in Danish mixed trawl fisheries in Kattegat and Skagerrak. The empirical analysis demonstrates how a policy with large negative net benefits might be justified if the intangible benefits are included. PMID:24184529

Kronbak, Lone Grønbæk; Vestergaard, Niels

2013-12-15

370

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

371

Vegetation-derived cues for the selection of oviposition substrates by Anopheles albimanus under laboratory conditions.  

PubMed

Oviposition response of gravid Anopheles albimanus Wiedemman (Diptera: Culicidae) females to water containing Brachiaria mutica, Cynodon dactylon, Jouvea straminea, Fimbristylis spadicea, and Ceratophyllum demersum was investigated. Gravid An. albimanus females deposited similar egg numbers in cups containing natural plants in water from natural breeding sites and in cups containing natural plants in distilled water. Gravid mosquitoes deposited significantly more eggs in cups containing natural plants in water from natural breeding sites than in cups containing artificial plants in water from the corresponding natural breeding sites. These results were confirmed in experiments conducted in a wind tunnel, indicating that female response is mediated by chemical cues from plants. Bioassays with organic extracts of all 5 plant species indicated that these extracts at 100%, 10%, and 1% concentrations had an oviposition repellent effect, while attractiveness was observed at 0.1%, 0.01%, and 0.001%. Gas chromatography and mass spectrometry analysis of the organic extracts found in all 5 plants showed a mixture of terpenoid and alcohol compounds, among them: guaiacol, phenol, isoeugenol, longifolene, caryophyllene, phenyl ethyl alcohol, and p-cresol. These results suggest that middle-range volatiles from plants may function as chemical cues for the female's oviposition response in this mosquito species. PMID:16506557

Torres-Estrada, José Luis; Meza-Alvarez, R Amanda; Cibrián-Tovar, Juan; Rodríguez-López, Mario H; Arredondo-Jiménez, Juan I; Cruz-López, Leopoldo; Rojas-Leon, Julio C

2005-12-01

372

Natural selection on floral traits of female Silene dioica by a sexually transmitted disease.  

PubMed

Floral traits endowing high reproductive fitness can also affect the probability of plants contracting sexually transmitted diseases. We explore how variations in floral traits influence the fitness of Silene dioica females in their interactions with pollinators carrying pollen or spores of the sterilizing anther-smut fungus Microbotryum violaceum. We collected healthy and infected plants in a highly diseased population and grew them under conditions that 'cure' infected individuals, and used standard regression methods to detect natural selection on floral traits. Narrow-sense heritabilities, coefficients of additive genetic variation (CV(A)) and genetic correlations among traits were estimated from paternal half-sib groups. Pollinator preferences imposed strong direct and directional selection on traits affecting female attractiveness and pollen-/spore-capturing abilities. Levels of additive genetic variance were high in these traits, suggesting that rapid responses to selection are possible. By considering our results in the light of spatial and temporal heterogeneity resulting from the colonization dynamics typical for this species, we suggest that the conflicting selective effects of pollen/spore loads lead to the maintenance of genetic variation in these traits. PMID:16441754

Giles, Barbara E; Pettersson, Tor Mikael; Carlsson-Granér, Ulla; Ingvarsson, Pär K

2006-01-01

373

Seasonal and diel habitat selection by bluegills in a shallow natural lake  

USGS Publications Warehouse

Habitat use by bluegill Lepomis macrochirus may be dictated by the avoidance of predators and the availability of prey. Previous work suggests that bluegills large enough to avoid predators will select habitats based on foraging profitability. However, these studies focused on smaller fish (200 mm total length [TL]) bluegills in a shallow (mean depth = 1.2 m), 332-ha, natural lake (Pelican Lake, Nebraska) with both emergent and submergent vegetation distributed throughout. A total of 78 bluegills (200-273 mm TL) were implanted with radio transmitters and relocated daily for 6 d per month (April-September); up to 20 of the tagged fish were relocated every 2 h for a 24-h period once each month. Regardless of diel period, bluegills used open-water, emergent vegetation, submergent vegetation, and mixed emergent - submergent vegetation habitat types in similar proportions. During April, June, and July, male bluegills positively selected emergent vegetation, whereas female bluegills showed no vegetation selection preference during any month. Throughout the study period, bluegills never avoided open-water habitats, suggesting that larger individuals may continue to use open-water habitats in proportion to their availability. In addition, emergent vegetation appeared to be important, particularly for male bluegills. Although the mechanism for the positive selection of emergent vegetation by males was unclear, the protection or enhancement of such habitats may facilitate the preservation of quality bluegill populations in shallow lakes.

Paukert, C. P.; Willis, D. W.

2002-01-01

374

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

375

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. PMID:22973246

Weigelt, Matthias; Memmert, Daniel

2012-01-01

376

Path analysis of natural selection via survival and fecundity across contrasting environments in Avena barbata.  

PubMed

We employed path analysis to analyse natural selection through two major fitness components in each of three contrasting environments. Using a randomized block design, 188 Recombinant Inbred Lines (RILs) derived from a cross between contrasting ecotypes of Avena barbata were planted in common gardens in the greenhouse, and in two field sites typical of each ecotype's native habitat. Individuals were monitored for germination phenology, early growth, survival, final size, flowering phenology, reproductive allocation, fecundity and lifetime reproductive success. The variance/covariance matrix of the RIL (genotype) means was fit to a path model in which total fitness was made up of survival and fecundity (of survivors) components. In the greenhouse, all fitness variation was determined by fecundity variation (with no mortality), which was itself primarily determined by reproductive allocation mediated by date of first flowering. By contrast, in the field, early growth was the major determinant of survival, and final size was the major determinant of fecundity. Both components of fitness affected lifetime reproductive success equally in the field. Thus the major difference between greenhouse and field seems to be a shift from selection on allocation patterns in adults, to selection on resource acquisition, especially at earlier life stages. The pattern of selection was similar in the two field sites, despite the contrasting environments. PMID:19824926

Latta, R G; McCain, C

2009-12-01

377

Conceptual Knowledge of Evolution and Natural Selection: How Culture Affects Knowledge Aquisition  

E-print Network

Conceptual Knowledge of Evolution and Natural Selection: How Culture Affects Knowledge Acquisition. (December 2009) Mar?a del Refugio Guti?rrez, B.A., Southwest Texas State University; B.A., Southwest Texas State University; M.A.G., Southwest Texas... would like to thank John J. Gonzalez M.D. and his staff for always accommodating my short notice medical appointments. In addition, I also would like to thank Russell B. Bacak, M.D. for his willingness to address and eventually resolve my thyroid...

Gutierrez, Maria Del Refugio

2011-02-22

378

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

379

Soil organic carbon content estimation with laboratory-based visible-near-infrared reflectance spectroscopy: feature selection.  

PubMed

This study, with Yixing (Jiangsu Province, China) and Honghu (Hubei Province, China) as study areas, aimed to compare the successive projection algorithm (SPA) and the genetic algorithm (GA) in spectral feature selection for estimating soil organic carbon (SOC) contents with visible-near-infrared (Vis-NIR) reflectance spectroscopy and further to assess whether the spectral features selected from one site could be applied to another site. The SOC content and Vis-NIR reflectance spectra of soil samples were measured in the laboratory. Savitzky-Golay smoothing and log10(1/R) (R is reflectance) were used for spectral preprocessing. The reflectance spectra were resampled using different spacing intervals ranging from 2 to 10 nm. Then, SPA and GA were conducted for selecting the spectral features of SOC. Partial least square regression (PLSR) with full-spectrum PLSR and the spectral features selected by SPA (SPA-PLSR) and GA (GA-PLSR) were calibrated and validated using independent datasets, respectively. Moreover, the spectral features selected from one study area were applied to another area. Study results showed that, for the two study areas, the SPA-PLSR and GA-PLSR improved estimation accuracies and reduced spectral variables compared with the full spectrum PLSR in estimating SOC contents; GA-PLSR obtained better estimation results than SPA-PLSR, whereas SPA was simpler than GA, and the spectral features selected from Yixing could be well applied to Honghu, but not the reverse. These results indicated that the SPA and GA could reduce the spectral variables and improve the performance of PLSR model and that GA performed better than SPA in estimating SOC contents. However, SPA is simpler and time-saving compared with GA in selecting the spectral features of SOC. The spectral features selected from one dataset could be applied to a target dataset when the dataset contains sufficient information adequately describing the variability of samples of the target dataset. PMID:25061784

Shi, Tiezhu; Chen, Yiyun; Liu, Huizeng; Wang, Junjie; Wu, Guofeng

2014-08-01

380

PROJECTS IN IMAGINATIVE NATURE EDUCATION, SURVEY REPORT AND OUTDOOR LABORATORY PLAN.  

ERIC Educational Resources Information Center

THIS PLAN SUGGESTS HOW THE MID HUDSON-CATSKILLS MUSEUM CAN WORK CREATIVELY WITH COOPERATING SCHOOL DISTRICTS TO STRENGTHEN THEIR CURRICULUMS THROUGH OUTDOOR EDUCATION. THE RESULT OF THIS COOPERATIVE ENDEAVOR IS TO BE AN OUTDOOR LABORATORY CALLED "GATEWAY CENTER" LOCATED NEAR NEW PALTZ, NEW YORK. PART 1 CONTAINS (1) BACKGROUND INFORMATION, (2)…

National Audubon Society, New York, NY.

381

Cold Spring Harbor Laboratory Press NATURE METHODS | VOL.3 NO.1 | JANUARY 2006 | 67 CLASSIC PROTOCOL  

E-print Network

by electroporation Pulsed electrical fields can be used to introduce DNA into a wide variety of animal cells1 and to allow colonies of resistant cells to grow. Thereafter, clone individual colonies and propagate Cloning: A Laboratory Manual (eds. Sambrook, J. & Russell, D.W.) 16.33­16.36 (Cold Spring Harbor

Cai, Long

382

Role of the Special Librarian in a Federal Natural Resources Research Laboratory.  

ERIC Educational Resources Information Center

The function of a Federal research library reflects the purpose of the laboratory it serves and the philosophy of the librarian. Libraries at the Fish and Wildlife Service research centers must rely on small specialized collections, supplemented by a large amount of cooperation among agency libraries and other subject-related collections. Due to…

Eaton, Deborah A.

383

OTEC biofouling and corrosion study at the Natural Energy Laboratory of Hawaii, 1983--1987  

Microsoft Academic Search

Long-term research on fouling and corrosion has been conducted as a part of the effort to develop heat exchangers for the US Department of Energy's Ocean Energy Technology program. After obtaining initial experimental data from various sites, including Puerto Rico, the Gulf of Mexico, open ocean (a buoy) in Hawaii, and Wrightsville Beach in North Carolina, Argonne National Laboratory carried

C. Panchal; H. Stevens; L. Genens; A. Thomas; C. Clark; F. Yaggee; J. Darby; D. Sasscer; J. Larsen-Basse; B. Liebert; L. Berger; A. Bhargava; B. Lee

1990-01-01

384

To Spin or Not to Spin? Natural and Laboratory Experiments from The Price is Right  

Microsoft Academic Search

The Wheel is a sequential game of perfect information played twice during each taping of the television game show The Price is Right. This game has simple rules and the stakes are high. We derive the unique subgame perfect Nash equilibrium (USPNE) for The Wheel and test its predictive ability using data from both the television show and laboratory plays

Rafael Tenorio; Timothy N

2002-01-01

385

Scaffolding Preservice Science Teachers' Evidence-Based Arguments During an Investigation of Natural Selection  

NASA Astrophysics Data System (ADS)

In this qualitative case study, preservice science teachers (PSTs) enrolled in their advanced methods course participated in a complex, data-rich investigation based on an adapted version of the Struggle for Survival curriculum. Fundamental to the investigation was the use of the Galapagos Finches software and an emphasis on giving priority to evidence and constructing evidence-based arguments. The questions that guided the research were: (1) What is the nature of the scientific arguments developed by PSTs? (2) How do PSTs go about constructing scientific arguments (emphasis on processes and strategies)? (3) In what ways do the scaffolds embedded in the Galapagos Finches software influence the development of PSTs arguments? Two pairs of PSTs were selected for in-depth examination. The primary sources of data were the electronic artifacts generated in the Galapagos Finches software environment and the videotaped interactions of both pairs as they investigated the data set, constructed and revised their arguments, engaged in peer review sessions, and presented their arguments to the class at the end of the unit. Four major patterns emerged through analysis of the data. First, using the software, PSTs consistently constructed claims that were linked to evidence from the investigation. Second, although PSTs consistently grounded their arguments in evidence, they still exhibited a number of limitations reported in the literature. Third, the software served as a powerful vehicle for revealing PSTs knowledge of evolution and natural selection. Finally, the PSTs approach to the task had a strong influence on the way they used the software.

Zembal-Saul, Carla; Munford, Danusa; Crawford, Barbara; et al.

2002-08-01

386

RESPONSES OF ZOOPLANKTON AND CHAOBORUS TO TEMEPHOS IN A NATURAL POND AND IN THE LABORATORY  

EPA Science Inventory

Application of the organophosphorus insecticide temephos to a natural pond in central Minnesota was followed by reduction within 24 hr in all cladocerans, in Diaptomus leptopus and in Chaoborus americanus, and increases in cyclopoid copepods, copepod nauplii and rotifer Keratella...

387

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.

388

Geospatial Toolkits and Resource Maps for Selected Countries from the National Renewable Energy Laboratory (NREL)  

DOE Data Explorer

NREL also has developed high-resolution resource maps and data products for selected, individual countries using its Geospatial Toolkit. Countries with both a GsT product and related maps and data products are Afghanistan, Bhutan, Northwest India, and Pakistan. [Taken and edited from http://www.nrel.gov/international/geospatial_toolkits.html

389

Allergic reactions to glove materials Gloves are common in research laboratories. The selection  

E-print Network

-immune reaction affecting the skin, and should not be confused with an allergy. Exposure to glove materials can to natural rubber latex proteins and/or synthetic chemicals in the glove material. Latex allergy is an Ig a protein. Latex products can cause Type I allergy as well as Type IV allergy. Type I allergy to latex

Shull, Kenneth R.

390

Multi-modal hard x-ray imaging with a laboratory source using selective reflection from a mirror  

PubMed Central

Multi-modal hard x-ray imaging sensitive to absorption, refraction, phase and scattering contrast is demonstrated using a simple setup implemented with a laboratory source. The method is based on selective reflection at the edge of a mirror, aligned to partially reflect a pencil x-ray beam after its interaction with a sample. Quantitative scattering contrast from a test sample is experimentally demonstrated using this method. Multi-modal imaging of a house fly (Musca domestica) is shown as proof of principle of the technique for biological samples. PMID:24761297

Pelliccia, Daniele; Paganin, David M.

2014-01-01

391

Negative frequency-dependent selection or alternative reproductive tactics: maintenance of female polymorphism in natural populations  

PubMed Central

Background Sex-limited polymorphisms have long intrigued evolutionary biologists and have been the subject of long-standing debates. The coexistence of multiple male and/or female morphs is widely believed to be maintained through negative frequency-dependent selection imposed by social interactions. However, remarkably few empirical studies have evaluated how social interactions, morph frequencies and fitness parameters relate to one another under natural conditions. Here, we test two hypotheses proposed to explain the maintenance of a female polymorphism in a species with extreme geographical variation in morph frequencies. We first elucidate how fecundity traits of the morphs vary in relation to the frequencies and densities of males and female morphs in multiple sites over multiple years. Second, we evaluate whether the two female morphs differ in resource allocation among fecundity traits, indicating alternative tactics to maximize reproductive output. Results We present some of the first empirical evidence collected under natural conditions that egg number and clutch mass was higher in the rarer female morph. This morph-specific fecundity advantage gradually switched with the population morph frequency. Our results further indicate that all investigated fecundity traits are negatively affected by relative male density (i.e. operational sex ratio), which confirms male harassment as selective agent. Finally, we show a clear trade-off between qualitative (egg mass) and quantitative (egg number) fecundity traits. This trade-off, however, is not morph-specific. Conclusion Our reported frequency- and density-dependent fecundity patterns are consistent with the hypothesis that the polymorphism is driven by a conflict between sexes over optimal mating rate, with costly male sexual harassment driving negative frequency-dependent selection on morph fecundity. PMID:23822745

2013-01-01

392

Winter habitat selection of mule deer before and during development of a natural gas field  

USGS Publications Warehouse

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 deer before and during the first 3 years of development in a natural gas field in western Wyoming. We used global positioning system (GPS) locations collected from a sample of adult female mule deer to model relative frequency or probability of use as a function of habitat variables. Model coefficients and predictive maps suggested mule deer were less likely to occupy areas in close proximity to well pads than those farther away. Changes in habitat selection appeared to be immediate (i.e., year 1 of development), and no evidence of well-pad acclimation occurred through the course of the study; rather, mule deer selected areas farther from well pads as development progressed. Lower predicted probabilities of use within 2.7 to 3.7 km of well pads suggested indirect habitat losses may be substantially larger than direct habitat losses. Additionally, some areas classified as high probability of use by mule deer before gas field development changed to areas of low use following development, and others originally classified as low probability of use were used more frequently as the field developed. If areas with high probability of use before development were those preferred by the deer, observed shifts in their distribution as development progressed were toward less-preferred and presumably less-suitable habitats.

Sawyer, H.; Nielson, R. M.; Lindzey, F.; McDonald, L. L.

2006-01-01

393

Copy number variants and selective sweeps in natural populations of the house mouse (Mus musculus domesticus)  

PubMed Central

Copy–number variants (CNVs) may play an important role in early adaptations, potentially facilitating rapid divergence of populations. We describe an approach to study this question by investigating CNVs present in natural populations of mice in the early stages of divergence and their involvement in selective sweeps. We have analyzed individuals from two recently diverged natural populations of the house mouse (Mus musculus domesticus) from Germany and France using custom, high–density, comparative genome hybridization arrays (CGH) that covered almost 164 Mb and 2444 genes. One thousand eight hundred and sixty one of those genes we previously identified as differentially expressed between these populations, while the expression of the remaining genes was invariant. In total, we identified 1868 CNVs across all 10 samples, 200 bp to 600 kb in size and affecting 424 genic regions. Roughly two thirds of all CNVs found were deletions. We found no enrichment of CNVs among the differentially expressed genes between the populations compared to the invariant ones, nor any meaningful correlation between CNVs and gene expression changes. Among the CNV genes, we found cellular component gene ontology categories of the synapse overrepresented among all the 2444 genes tested. To investigate potential adaptive significance of the CNV regions, we selected six that showed large differences in frequency of CNVs between the two populations and analyzed variation in at least two microsatellites surrounding the loci in a sample of 46 unrelated animals from the same populations collected in field trappings. We identified two loci with large differences in microsatellite heterozygosity (Sfi1 and Glo1/Dnahc8 regions) and one locus with low variation across the populations (Cmah), thus suggesting that these genomic regions might have recently undergone selective sweeps. Interestingly, the Glo1 CNV has previously been implicated in anxiety–like behavior in mice, suggesting a differential evolution of a behavioral trait. PMID:24917877

Bryk, Jaroslaw; Tautz, Diethard

2014-01-01

394

Learning Natural Selection in 4th Grade with Multi-Agent-Based Computational Models  

NASA Astrophysics Data System (ADS)

In this paper, we investigate how elementary school students develop multi-level explanations of population dynamics in a simple predator-prey ecosystem, through scaffolded interactions with a multi-agent-based computational model (MABM). The term "agent" in an MABM indicates individual computational objects or actors (e.g., cars), and these agents obey simple rules assigned or manipulated by the user (e.g., speeding up, slowing down, etc.). It is the interactions between these agents, based on the rules assigned by the user, that give rise to emergent, aggregate-level behavior (e.g., formation and movement of the traffic jam). Natural selection is such an emergent phenomenon, which has been shown to be challenging for novices (K16 students) to understand. Whereas prior research on learning evolutionary phenomena with MABMs has typically focused on high school students and beyond, we investigate how elementary students (4th graders) develop multi-level explanations of some introductory aspects of natural selection—species differentiation and population change—through scaffolded interactions with an MABM that simulates predator-prey dynamics in a simple birds-butterflies ecosystem. We conducted a semi-clinical interview based study with ten participants, in which we focused on the following: a) identifying the nature of learners' initial interpretations of salient events or elements of the represented phenomena, b) identifying the roles these interpretations play in the development of their multi-level explanations, and c) how attending to different levels of the relevant phenomena can make explicit different mechanisms to the learners. In addition, our analysis also shows that although there were differences between high- and low-performing students (in terms of being able to explain population-level behaviors) in the pre-test, these differences disappeared in the post-test.

Dickes, Amanda Catherine; Sengupta, Pratim

2013-06-01

395

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

396

Artificial natural selection: can supplemental feeding domesticate mosquitoes and control mosquito-borne diseases?  

PubMed

A new method is proposed for controlling mosquito-borne diseases. In particular, instead of trying to kill mosquitoes, we suggest provisioning them with food from artificial feeders. Because mosquito populations are frequently limited by ecological factors other than blood meals, such as the availability of egg-laying sites, feeding mosquitoes would not necessarily increase the total number of mosquitoes, but could reduce the number of human-drawn mosquito meals. Like mosquito traps, feeders could divert biting mosquitoes away from people by means of lures, but, after diversion, prevent subsequent human bites by satiating the mosquitoes instead of killing them. Mosquito feeders might reduce the problem of the evolution of resistance to control: in an ecology with mosquito feeders, which provide safe and abundant calories for adult female mosquitoes, there could be selection for preferring (rather than avoiding) feeders, which could eventually lead to a population of feeder-preferring mosquitoes. Artificial feeders also offer the chance to introduce novel elements into the mosquito diet, such as anti- malarial or other anti-parasitic agents. Feeders might directly reduce human bites and harnesses the power of natural selection by selectively favoring feeder-preferring (rather than trap-resistant) mosquitoes. PMID:22947681

Egeth, Marc; Kurzban, Robert

2012-01-01

397

Reduced Efficacy of Natural Selection on Codon Usage Bias in Selfing Arabidopsis and Capsella Species  

PubMed Central

Population genetic theory predicts that the efficacy of natural selection in a self-fertilizing species should be lower than its outcrossing relatives because of the reduction in the effective population size (Ne) in the former brought about by inbreeding. However, previous analyses comparing Arabidopsis thaliana (selfer) with A. lyrata (outcrosser) have not found conclusive support for this prediction. In this study, we addressed this issue by examining silent site polymorphisms (synonymous and intronic), which are expected to be informative about changes in Ne. Two comparisons were made: A. thaliana versus A. lyrata and Capsella rubella (selfer) versus C. grandiflora (outcrosser). Extensive polymorphism data sets were obtained by compiling published data from the literature and by sequencing 354 exon loci in C. rubella and 89 additional loci in C. grandiflora. To extract information from the data effectively for studying these questions, we extended two recently developed models in order to investigate detailed selective differences between synonymous codons, mutational biases, and biased gene conversion (BGC), taking into account the effects of recent changes in population size. We found evidence that selection on synonymous codons is significantly weaker in the selfers compared with the outcrossers and that this difference cannot be fully accounted for by mutational biases or BGC. PMID:21856647

Qiu, Suo; Zeng, Kai; Slotte, Tanja; Wright, Stephen; Charlesworth, Deborah

2011-01-01

398

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. PMID:15209099

Knight, Mairi E.; Turner, George F.

2004-01-01

399

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

400

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

401

The Nature of Pre-service Science Teachers’ Argumentation in Inquiry-oriented Laboratory Context  

Microsoft Academic Search

The aim of this study was to investigate the kinds of argumentation schemes generated by pre-service elementary science teachers (PSTs) as they perform inquiry-oriented laboratory tasks, and to explore how argumentation schemes vary by task as well as by experimentation and discussion sessions. The model of argumentative and scienti?c inquiry was used as a design framework in the present study.

Yasemin Ozdem; Hamide Ertepinar; Jale Cakiroglu; Sibel Erduran

2011-01-01

402

Laboratory and field evaluation of selective media for isolation of group B streptococci.  

PubMed Central

Problems encountered with currently recommended selective media for group B streptococci (GBS) (selective broth medium and CNA agar) prompted a searach for alternative culture methods in ongoing epidemiological studies. Previously recommended inhibitory agents were tested in vitro. Gentamicin, alone or in combination with nalidixic acid, proved inhibitory for many GBS strains. Among other agents tested, polymyxin was most complementary to the gram-negative spectrum of nalidixic acid, without compromising GBS growth. Crystal violet provided the simplest, most economical staphylococcal inhibitor. Broth and agar media, constituted with these three agents and designated NPC, were evaluated in vitro and in field studies. This investigation represents the first direct comparison of broth media containing inhibitory agents for the preferential isolation of GBS. In maternal colonization studies, NPC broth proved superior to Todd-Hewitt broth containing nalidixic acid and gentamicin at concentrations employed in the previously described selective broth medium (95% versus 59% recovery). Our comparisons were done without added sheep blood since GBS grow well in Todd-Hewitt broth. NPC broth proved more sensitive than NPC agar for detecting GBS colonization in newborns. The NPC agar medium was useful for further purification of broth cultures and quantitative culture techniques. PMID:379037

Gray, B M; Pass, M A; Dillon, H C

1979-01-01

403

The modeling of a laboratory natural gas-fired furnace with a higher-order projection method for unsteady combustion  

SciTech Connect

A higher-order, embedded boundary projection method for axisymmetric, unsteady, low-Mach number combustion is used to model a natural gas flame from a 300 kW IFRF burner in the Burner Engineering Research Laboratory (BERL) at Sandia National Laboratory under hot wall conditions. The numerical predictions presented are the late simulated-time results of a computation of unsteady flow in the furnace. The predictions are compared both with measurements completed in the BERL as part of the GRI SCALING 400 Project and with results from a steady-state axisymmetric reacting flow code in order to evaluate the combustion model and the numerical method. The results compare favorably with the experimental data.

Pember, R.B.; Colella, P.; Howell, L.H.; Almgren, A.S. [and others

1996-02-01

404

Natural Selection on Female Life-History Traits in Relation to Socio-Economic Class in Pre-Industrial  

E-print Network

-history traits. In species where the inherited structure of social class may lead to consistent resourceNatural Selection on Female Life-History Traits in Relation to Socio-Economic Class in Pre selection and quantitative genetics of life-history trait variation in relation to individual lifetime

Lummaa, Virpi

405

Notice of release of Majestic Germplasm and Spectrum Germplasm western prairie clover: selected class of natural germplasm  

Microsoft Academic Search

:Two natural-track selected germplasms of western prairie clover (Dalea ornata (Douglas ex Hook.) Eaton & J. Wright [Fabaceae]) have been released for use in revegetation of semiarid rangelands in the western US. Western prairie clover is a perennial leguminous forb that occurs naturally in Idaho, Washington, Oregon, California, and Nevada. Majestic Germplasm western prairie clover originates from seed collected from

Douglas A Johnson; B Shaun Bushman; Kishor Bhattarai; Kevin J Connors

2011-01-01

406

Notice of release of Majestic Germplasm and Spectrum Germplasm western prairie clover: selected class of natural germplasm  

Microsoft Academic Search

Two natural-track selected germplasms of western prairie clover (Dalea ornata (Douglas ex Hook.) Eaton & J. Wright [Fabaceae]) have been released for use in revegetation of semiarid rangelands in the western US. Western prairie clover is a perennial leguminous forb that occurs naturally in Idaho, Washington, Oregon, California, and Nevada. Majestic Germplasm western prairie clover originates from seed collected from

Douglas A Johnson; B Shaun Bushman; Kishor Bhattarai; Kevin J Connors

2011-01-01

407

Laboratory studies using naturally occurring “green rust” to aid metal mine water remediation  

Microsoft Academic Search

Green rust, an Fe (II) and (III) oxyhydroxy salt, can alter the aqueous oxidation state, mobility and toxicity, of inorganic contaminants and thus could have applications in water treatment. This paper discusses a series of stirred, open batch experiments designed to evaluate green rust, and its oxidised equivalent in this context comparing it to a ferrihydrite\\/goethite ‘ochre’. Natural green rust

Jenny M. Bearcock; William T. Perkins; Nicholas J. G. Pearce

2011-01-01

408

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

409

I. ASCRC General Education Form Group Group XI Natural Science (non laboratory)  

E-print Network

method is used within the discipline to draw scientific conclusions. This course explores the field to a hypothesis and then to a validated scientific theory. The scientific method as it is applied in physical://www.umt.edu/facultysenate/ASCRCx/Adocuments/GE_Criteria5-1-08.htm Courses explore a discipline in the natural sciences and demonstrate how the scientific

Vonessen, Nikolaus

410

Are laboratory-based antibiograms reliable to guide the selection of empirical antimicrobial treatment in patients with hospital-acquired infections?  

Microsoft Academic Search

Objectives: Antibiograms are often taken into account to define a rational selection of an empirical antimicrobial therapy for treating patients with hospital-acquired infections. In this study, we performed a paired comparison between the antibiogram constructed with laboratory-based data and that formed with data subjected to prior clinical validation. Methods: Between 2003 and 2005, the laboratory of microbiology printed in duplicate

Carlos Bantar; Gabriela Alcazar; Diego Franco; Francisco Salamone; Eduardo Vesco; Teodoro Stieben; Florencia Obaid; Alejandro Fiorillo; Mariano Izaguirre; Maria Eugenia Oliva

2007-01-01

411

Natural scene logo recognition by joint boosting feature selection in salient regions  

NASA Astrophysics Data System (ADS)

Logos are considered valuable intellectual properties and a key component of the goodwill of a business. In this paper, we propose a natural scene logo recognition method which is segmentation-free and capable of processing images extremely rapidly and achieving high recognition rates. The classifiers for each logo are trained jointly, rather than independently. In this way, common features can be shared across multiple classes for better generalization. To deal with large range of aspect ratio of different logos, a set of salient regions of interest (ROI) are extracted to describe each class. We ensure the selected ROIs to be both individually informative and two-by-two weakly dependant by a Class Conditional Entropy Maximization criteria. Experimental results on a large logo database demonstrate the effectiveness and efficiency of our proposed method.

Fan, Wei; Sun, Jun; Naoi, Satoshi; Minagawa, Akihiro; Hotta, Yoshinobu

2011-01-01

412

Selective reduction of diphenyldisulfides catalyzed by sulfides-influence of the nature of the catalyst  

SciTech Connect

The catalytic activities of a series of sulfide catalysts have been examined for the reduction of diphenyldisulfide into benzenethiol. This reaction was studied in a gas-liquid-solid batch reactor. The first step of this study was devoted to the hydrodynamic of the reactor in order to ensure that the reaction proceeds under chemical control. The catalytic activities of the various catalysts vary in a wide range, the most efficient being one of the industrial hydrotreating catalyst tested, i.e., a NiMo/Al[sub 2]O[sub 3]. Whatever the nature of the active phase, the reaction was 100% selective toward the formation of benzenethiol. The effects of reducing pretreatments on the catalytic activities as well as the results of TPR and TPD studies suggest a reaction mechanism in which M-H (M - transition metal ion) and SH groups intervene simultaneously. 55 refs., 11 figs., 5 tabs.

Calais, C.; Lacroix, M.; Geantet, C.; Breysse, M. (Institut de Recherches sur la Catalyse, Villeurbanne (France))

1993-11-01

413

The Formulation of Explanations: An Invitation to Inquiry on Natural Selection  

NSDL National Science Digital Library

This activity uses the concept of natural selection to introduce the idea of formulating and testing scientific hypotheses. Through a focused discussion approach, the teacher provides information and allows students time to think, interact with peers, and propose explanations for observations described by the teacher. While working on this activity, students will be able to: identify questions that can be answered through scientific investigations, design and conduct a scientific investigation, and use appropriate tools and techniques to gather, analyze, and interpret data. They will also have an opportunity to develop descriptions, explanations, predictions, and models using evidence and think critically and logically to make relationships between evidence and explanations. This site contains all information and instructions to complete the activity.

414

Salience: the key to the selection problem in natural language generation  

SciTech Connect

The authors argue that in domains where a strong notion of salience can be defined, it can be used to provide: (1) an elegant solution to the selection problem, i.e. the problem of how to decide whether a given fact should or should not be mentioned in the text; and (2) a simple and direct control framework for the entire deep generation process, coordinating proposing, planning, and realization. (Deep generation involves reasoning about conceptual and rhetorical facts, as opposed to the narrowly linguistic reasoning that takes place during realization.) The authors report on an empirical study of salience in pictures of natural scenes, and its use in a computer program that generates descriptive paragraphs comparable to those produced by people. 13 references.

Conklin, E.J.; McDonald, D.D.

1982-01-01

415

Genome-wide SNP genotyping highlights the role of natural selection in Plasmodium falciparum population divergence  

PubMed Central

Background The malaria parasite Plasmodium falciparum exhibits abundant genetic diversity, and this diversity is key to its success as a pathogen. Previous efforts to study genetic diversity in P. falciparum have begun to elucidate the demographic history of the species, as well as patterns of population structure and patterns of linkage disequilibrium within its genome. Such studies will be greatly enhanced by new genomic tools and recent large-scale efforts to map genomic variation. To that end, we have developed a high throughput single nucleotide polymorphism (SNP) genotyping platform for P. falciparum. Results Using an Affymetrix 3,000 SNP assay array, we found roughly half the assays (1,638) yielded high quality, 100% accurate genotyping calls for both major and minor SNP alleles. Genotype data from 76 global isolates confirm significant genetic differentiation among continental populations and varying levels of SNP diversity and linkage disequilibrium according to geographic location and local epidemiological factors. We further discovered that nonsynonymous and silent (synonymous or noncoding) SNPs differ with respect to within-population diversity, inter-population differentiation, and the degree to which allele frequencies are correlated between populations. Conclusions The distinct population profile of nonsynonymous variants indicates that natural selection has a significant influence on genomic diversity in P. falciparum, and that many of these changes may reflect functional variants deserving of follow-up study. Our analysis demonstrates the potential for new high-throughput genotyping technologies to enhance studies of population structure, natural selection, and ultimately enable genome-wide association studies in P. falciparum to find genes underlying key phenotypic traits. PMID:19077304

Neafsey, Daniel E; Schaffner, Stephen F; Volkman, Sarah K; Park, Daniel; Montgomery, Philip; Milner, Danny A; Lukens, Amanda; Rosen, David; Daniels, Rachel; Houde, Nathan; Cortese, Joseph F; Tyndall, Erin; Gates, Casey; Stange-Thomann, Nicole; Sarr, Ousmane; Ndiaye, Daouda; Ndir, Omar; Mboup, Soulyemane; Ferreira, Marcelo U; Moraes, Sandra do Lago; Dash, Aditya P; Chitnis, Chetan E; Wiegand, Roger C; Hartl, Daniel L; Birren, Bruce W; Lander, Eric S; Sabeti, Pardis C; Wirth, Dyann F

2008-01-01

416

THE zCOSMOS-SINFONI PROJECT. I. SAMPLE SELECTION AND NATURAL-SEEING OBSERVATIONS  

SciTech Connect

The zCOSMOS-SINFONI project is aimed at studying the physical and kinematical properties of a sample of massive z {approx} 1.4-2.5 star-forming galaxies, through SINFONI near-infrared integral field spectroscopy (IFS), combined with the multiwavelength information from the zCOSMOS (COSMOS) survey. The project is based on one hour of natural-seeing observations per target, and adaptive optics (AO) follow-up for a major part of the sample, which includes 30 galaxies selected from the zCOSMOS/VIMOS spectroscopic survey. This first paper presents the sample selection, and the global physical characterization of the target galaxies from multicolor photometry, i.e., star formation rate (SFR), stellar mass, age, etc. The H{alpha} integrated properties, such as, flux, velocity dispersion, and size, are derived from the natural-seeing observations, while the follow-up AO observations will be presented in the next paper of this series. Our sample appears to be well representative of star-forming galaxies at z {approx} 2, covering a wide range in mass and SFR. The H{alpha} integrated properties of the 25 H{alpha} detected galaxies are similar to those of other IFS samples at the same redshifts. Good agreement is found among the SFRs derived from H{alpha} luminosity and other diagnostic methods, provided the extinction affecting the H{alpha} luminosity is about twice that affecting the continuum. A preliminary kinematic analysis, based on the maximum observed velocity difference across the source and on the integrated velocity dispersion, indicates that the sample splits nearly 50-50 into rotation-dominated and velocity-dispersion-dominated galaxies, in good agreement with previous surveys.

Mancini, C.; Renzini, A. [INAF-OAPD, Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, I-35122 Padova (Italy); Foerster Schreiber, N. M.; Hicks, E. K. S.; Genzel, R.; Tacconi, L.; Davies, R. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Cresci, G. [Osservatorio Astrofisico di Arcetri (OAF), INAF-Firenze, Largo E. Fermi 5, I-50125 Firenze (Italy); Peng, Y.; Lilly, S.; Carollo, M.; Oesch, P. [Institute of Astronomy, Department of Physics, Eidgenossische Technische Hochschule, ETH Zurich CH-8093 (Switzerland); Vergani, D.; Pozzetti, L.; Zamorani, G. [INAF-Bologna, Via Ranzani, I-40127 Bologna (Italy); Daddi, E. [CEA-Saclay, DSM/DAPNIA/Service d'Astrophysique, F-91191 Gif-Sur Yvette Cedex (France); Maraston, C. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, PO1 3HE Portsmouth (United Kingdom); McCracken, H. J. [IAP, 98bis bd Arago, F-75014 Paris (France); Bouche, N. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Shapiro, K. [Aerospace Research Laboratories, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States); and others

2011-12-10

417

OTEC biofouling and corrosion study at the Natural Energy Laboratory of Hawaii, 1983--1987  

SciTech Connect

Long-term research on fouling and corrosion has been conducted as a part of the effort to develop heat exchangers for the US Department of Energy's Ocean Energy Technology program. After obtaining initial experimental data from various sites, including Puerto Rico, the Gulf of Mexico, open ocean (a buoy) in Hawaii, and Wrightsville Beach in North Carolina, Argonne National Laboratory carried out a six-year research program at the National Energy Laboratory of Hawaii. In the Phase 1 experimental program, a data base was developed for characterization of biofouling of corrosion-resistant material exposed to two types of seawater -- surface (warm) and deep-ocean (cold). The major objective was to determine optimal biofouling-control methods. The results of the Phase 1 research were published in a report in 1985. The major objective of the Phase 2 research has been to develop a technical data base for the qualification of aluminum alloys for ocean thermal energy conversion (OTEC) heat-exchanger applications. Aluminum alloys have many desirable mechanical properties that can be utilized for the development of low-cost, compact heat exchangers that can be designed on a modular basis. The research program for aluminum alloys has included biofouling, corrosion fouling, uniform corrosion, localized corrosion, and evaluation of brazed joint and epoxy-bonded joints. Conclusions derived in this report represent a major milestone in OTEC materials and fouling research. 70 refs., 109 figs., 18 tabs.

Panchal, C.; Stevens, H.; Genens, L.; Thomas, A.; Clark, C.; Yaggee, F.; Darby, J. (Argonne National Lab., IL (USA)); Sasscer, D. (Argonne National Lab., IL (USA) Northwestern Univ., Evanston, IL (USA)); Larsen-Basse, J.; Liebert, B.; Berger, L. (Argonne National Lab., IL (USA) Hawaii Univ., Honolulu, HI (USA)); Bhargava, A.; Lee, B. (Argonne National Lab., IL (USA) Hawaii Natural Energy Inst., Honolulu,

1990-10-01

418

Laboratory process control using natural language commands from a personal computer  

NASA Technical Reports Server (NTRS)

PC software is described which provides flexible natural language process control capability with an IBM PC or compatible machine. Hardware requirements include the PC, and suitable hardware interfaces to all controlled devices. Software required includes the Microsoft Disk Operating System (MS-DOS) operating system, a PC-based FORTRAN-77 compiler, and user-written device drivers. Instructions for use of the software are given as well as a description of an application of the system.

Will, Herbert A.; Mackin, Michael A.

1989-01-01

419

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

420

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

421

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. PMID:24187584

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

2013-01-01

422

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

SciTech Connect

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 monitoring of habitat characteristics and benthic aquatic macroinvertebrate communities at six key sites in Los Alamos, Sandia, Water, Pajarito, and Starmer's Gulch Canyons. Data were collected on aquatic habitat characteristics, channel substrate, and macroinvertebrate communities during 2001 and 2002. Aquatic habitat scores were stable between 2001 and 2002 at all locations except Starmer's Gulch and Pajarito Canyon, which had lower scores in 2002 due to low flow conditions. Channel substrate changes were most evident at the upper Los Alamos and Pajarito study reaches. The macroinvertebrate Stream Condition Index (SCI) indicated moderate to severe impairment at upper Los Alamos Canyon, slight to moderate impairment at upper Sandia Canyon, and little or no impairment at lower Sandia Canyon, Starmer's Gulch, and Pajarito Canyon. Habitat, substrate, and macroinvertebrate data from the site in upper Los Alamos Canyon indicated severe impacts from the Cerro Grande Fire of 2000. Impairment in the macroinvertebrate community at upper Sandia Canyon was probably due to effluent-dominated flow at that site. The minimal impairment SCI scores for the lower Sandia site indicated that water quality improved with distance downstream from the outfall at upper Sandia Canyon.

L.J. Henne; K.J. Buckley

2005-08-12

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

Natural selection canalizes expression variation of environmentally induced plasticity-enabling genes.  

PubMed

Many organisms survive fluctuating and extreme environmental conditions by manifesting multiple distinct phenotypes during adulthood by means of developmental processes that enable phenotypic plasticity. We report on the discovery of putative plasticity-enabling genes that are involved in transforming the gill of the euryhaline teleost fish, Fundulus heteroclitus, from its freshwater to its seawater gill-type, a process that alters both morphology and function. Gene expression that normally enables osmotic plasticity is inhibited by arsenic. Gene sets defined by antagonistic interactions between arsenic and salinity show reduced transcriptional variation among individual fish, suggesting unusually accurate and precise regulatory control of these genes, consistent with the hypothesis that they participate in a canalized developmental response. We observe that natural selection acts to preserve canalized gene expression in populations of killifish that are most tolerant to abrupt salinity change and that these populations show the least variability in their transcription of genes enabling plasticity of the gill. We found that genes participating in this highly canalized and conserved plasticity-enabling response had significantly fewer and less complex associations with transcriptional regulators than genes that respond only to arsenic or salinity. Collectively these findings, which are drawn from the relationships between environmental challenge, plasticity, and canalization among populations, suggest that the selective processes that facilitate phenotypic plasticity do so by targeting the regulatory networks that gives rise to the response. These findings also provide a generalized, conceptual framework of how genes might interact with the environment and evolve toward the development of plastic traits. PMID:25158801

Shaw, Joseph R; Hampton, Thomas H; King, Benjamin L; Whitehead, Andrew; Galvez, Fernando; Gross, Robert H; Keith, Nathan; Notch, Emily; Jung, Dawoon; Glaholt, Stephen P; Chen, Celia Y; Colbourne, John K; Stanton, Bruce A

2014-11-01

425

Effects of Novel Isoform-Selective Phosphoinositide 3-Kinase Inhibitors on Natural Killer Cell Function  

PubMed Central

Phosphoinositide 3-kinases (PI3Ks) are promising targets for therapeutic development in cancer. The class I PI3K isoform p110? has received considerable attention in oncology because the gene encoding p110? (PIK3CA) is frequently mutated in human cancer. However, little is known about the function of p110? in lymphocyte populations that modulate tumorigenesis. We used recently developed investigational inhibitors to compare the function of p110? and other isoforms in natural killer (NK) cells, a key cell type for immunosurveillance and tumor immunotherapy. Inhibitors of all class I isoforms (pan-PI3K) significantly impaired NK cell-mediated cytotoxicity and antibody-dependent cellular cytotoxicity against tumor cells, whereas p110?-selective inhibitors had no effect. In NK cells stimulated through NKG2D, p110? inhibition modestly reduced PI3K signaling output as measured by AKT phosphorylation. Production of IFN-? and NK cell-derived chemokines was blocked by a pan-PI3K inhibitor and partially reduced by a p110?inhibitor, with lesser effects of p110? inhibitors. Oral administration of mice with MLN1117, a p110? inhibitor in oncology clinical trials, had negligible effects on NK subset maturation or terminal subset commitment. Collectively, these results support the targeting of PIK3CA mutant tumors with selective p110? inhibitors to preserve NK cell function. PMID:24915189

Yea, Sung Su; So, Lomon; Mallya, Sharmila; Lee, Jongdae; Rajasekaran, Kamalakannan; Malarkannan, Subramaniam; Fruman, David A.

2014-01-01

426

Characterizing selection on phenotypic plasticity in response to natural environmental heterogeneity.  

PubMed

Adaptive genetic differentiation and adaptive phenotypic plasticity can increase the fitness of plant lineages in heterogeneous environments. We examine the relative importance of genetic differentiation and plasticity in determining the fitness of the annual plant, Erodium cicutarium, in a serpentine grassland in California. Previous work demonstrated that the serpentine sites within this mosaic display stronger dispersal-scale heterogeneity than nonserpentine sites. We conducted a reciprocal transplant experiment among six sites to characterize selection on plasticity expressed by 180 full-sibling families in response to natural environmental heterogeneity across these sites. Multivariate axes of environmental variation were constructed using a principal components analysis of soil chemistry data collected at every experimental block. Simple linear regressions were used to characterize the intercept, and slope (linear and curvilinear) of reaction norms for each full-sibling family in response to each axis of environmental variation. Multiple linear regression analyses revealed significant selection on trait means and slopes of reaction norms. Multivariate analyses of variance demonstrated genetic differentiation between serpentine and nonserpentine lineages in the expression of plasticity in response to three of the five axes of environmental variation considered. In all but one case, serpentine genotypes expressed a stronger adaptive plastic response than nonserpentine genotypes. PMID:20649815

Baythavong, Brooke S; Stanton, Maureen L

2010-10-01

427

Selective removal of copper (II) from natural waters by nanoporous sorbents functionalized with chelating diamines  

PubMed Central

Copper has been identified as a pollutant of concern by the Environmental Protection Agency (EPA) because of its widespread occurrence and toxic impact in the environment. Three nanoporous sorbents containing chelating diamine functionalities were evaluated for Cu2+ adsorption from natural waters -- ethylenediamine functionalized self-assembled monolayers on mesoporous supports (EDA-SAMMS®), ethylenediamine functionalized activated carbon (AC-CH2-EDA), and 1,10-Phenanthroline functionalized mesoporous carbon (Phen-FMC). The pH dependence of Cu2+ sorption, Cu2+ sorption capacities, rates, and selectivity of the sorbents were determined and compared with those of commercial sorbents (Chelex-100 ion exchange resin and Darco KB-B activated carbon). All three chelating diamine sorbents showed excellent Cu2+ removal (~95–99%) from river water and sea water over the pH range of 6.0–8.0. EDA-SAMMS and AC-CH2-EDA demonstrated rapid Cu2+ sorption kinetics (minutes) and good sorption capacities (26 and 17 mg Cu/g sorbent, respectively) in sea water, while Phen-FMC had excellent selectivity for Cu2+ over other metal ions (e.g. Ca2+, Fe2+, Ni2+, and Zn2+) and was able to achieve Cu levels below the EPA standards for river and sea waters. PMID:20608701

Chouyyok, Wilaiwan; Shin, Yongsoon; Davidson, Joseph; Samuels, William D.; LaFemina, Nikki H.; Rutledge, Ryan D.; Fryxell, Glen E.; Sangvanich, Thanapon; Yantasee, Wassana

2010-01-01

428

Rhythmic natural selection over intertidal and brackish water genotypes: simple formulations for testing hypothesis.  

PubMed

Tidal cycles at benthic habitats induce a set of periodic environmental changes in variables like salinity, temperature and sediment water content which are able to stress benthic organisms. Consequently, a natural selection temporally correlated with tides affects the fitness of genotypes (wi) depending on their adaptation degree. Classic population genetics demonstrate that (1) rhythmic wi is more restrictive than equivalent spatial variations to preserve genetic variance, and (2) mean fitness of the population (w¯) does not have to be enhanced by genetic variance (?(2)w). The present study develops a simple replicator dynamics-based model of continuous selection, where wi of multiple asexual genotypes fluctuates as a sinusoid. The amplitude of w was set as 0.5 (1-wmin), whereas the ratio of tide period to generation time (h) was defined. Overall, the model shows that if h>1, then the success of an advantageous genotype is exposed to randomness, and w¯ may decrease over generations. In contrast, if h<1 the success is deterministic, is limiting co-dominance, and only depends on wmin. The amount of different genotypes buffers the decay of ?(2)w and hence increases cohesiveness. Finally, the reliability of the model is analyzed for a set of target intertidal and brackish water organisms. PMID:24412494

Lara, M; Binder, P M; Figueredo-Fernández, M A

2014-04-01

429

Natural Selection Canalizes Expression Variation of Environmentally Induced Plasticity-Enabling Genes  

PubMed Central

Many organisms survive fluctuating and extreme environmental conditions by manifesting multiple distinct phenotypes during adulthood by means of developmental processes that enable phenotypic plasticity. We report on the discovery of putative plasticity-enabling genes that are involved in transforming the gill of the euryhaline teleost fish, Fundulus heteroclitus, from its freshwater to its seawater gill-type, a process that alters both morphology and function. Gene expression that normally enables osmotic plasticity is inhibited by arsenic. Gene sets defined by antagonistic interactions between arsenic and salinity show reduced transcriptional variation among individual fish, suggesting unusually accurate and precise regulatory control of these genes, consistent with the hypothesis that they participate in a canalized developmental response. We observe that natural selection acts to preserve canalized gene expression in populations of killifish that are most tolerant to abrupt salinity change and that these populations show the least variability in their transcription of genes enabling plasticity of the gill. We found that genes participating in this highly canalized and conserved plasticity-enabling response had significantly fewer and less complex associations with transcriptional regulators than genes that respond only to arsenic or salinity. Collectively these findings, which are drawn from the relationships between environmental challenge, plasticity, and canalization among populations, suggest that the selective processes that facilitate phenotypic plasticity do so by targeting the regulatory networks that gives rise to the response. These findings also provide a generalized, conceptual framework of how genes might interact with the environment and evolve toward the development of plastic traits. PMID:25158801

Shaw, Joseph R.; Hampton, Thomas H.; King, Benjamin L.; Whitehead, Andrew; Galvez, Fernando; Gross, Robert H.; Keith, Nathan; Notch, Emily; Jung, Dawoon; Glaholt, Stephen P.; Chen, Celia Y.; Colbourne, John K.; Stanton, Bruce A.

2014-01-01

430

Natural and bioremediated selective degradation of polycyclic aromatic alkyl isomers in oil-contaminated soils  

SciTech Connect

In studies where 2- to 6-ring polycyclic aromatic hydrocarbons (PAHs) are determined as part of characterizing released oil constituents in environmental samples, the changes in composition of PAHs from weathering (e.g., evaporation, dissolution) and biodegradation are most often represented by PAH alkyl homologue distributions. Concentrations of PAH alkyl groups are the sum of individual PAH isomers of similar carbon number; such as for C2-naphthalenes, the C2 alkyl group consists of dimethyl and ethyl substitutions on the parent naphthalene. In weathering and degradation studies, the changes in relative concentration of the individual isomers within an alkyl group are rarely reported. In a field study of oiled soils, the authors looked at the selective losses, for a period of a year, of individual PAH alkyl isomers that occur both naturally by weathering processes and through the use of bioremediation technology. Results showed that decreases in alkyl group concentrations were not always represented by similar losses of each isomer in the alkyl group, but were often due to the preferential or selective loss of certain isomers in the group.

Sauer, T.C.; McCarthy, K.; Uhler, A. [Battelle, Duxbury, MA (United States); Porta, A. [Battelle, Geneva (Switzerland)

1995-12-31

431

Reduced disease in black abalone following mass mortality: phage therapy and natural selection.  

PubMed

Black abalone, Haliotis cracherodii, populations along the NE Pacific ocean have declined due to the rickettsial disease withering syndrome (WS). Natural recovery on San Nicolas Island (SNI) of Southern California suggested the development of resistance in island populations. Experimental challenges in one treatment demonstrated that progeny of disease-selected black abalone from SNI survived better than did those from naïve black abalone from Carmel Point in mainland coastal central California. Unexpectedly, the presence of a newly observed bacteriophage infecting the WS rickettsia (WS-RLO) had strong effects on the survival of infected abalone. Specifically, presence of phage-infected RLO (RLOv) reduced the host response to infection, RLO infection loads, and associated mortality. These data suggest that the black abalone: WS-RLO relationship is evolving through dual host mechanisms of resistance to RLO infection in the digestive gland via tolerance to infection in the primary target tissue (the post-esophagus) coupled with reduced pathogenicity of the WS-RLO by phage infection, which effectively reduces the infection load in the primary target tissue by half. Sea surface temperature patterns off southern California, associated with a recent hiatus in global-scale ocean warming, do not appear to be a sufficient explanation for survival patterns in SNI black abalone. These data highlight the potential for natural recovery of abalone populations over time and that further understanding of mechanisms governing host-parasite relationships will better enable us to manage declining populations. PMID:24672512

Friedman, Carolyn S; Wight, Nathan; Crosson, Lisa M; Vanblaricom, Glenn R; Lafferty, Kevin D

2014-01-01

432

Periodic Table of Virus Capsids: Implications for Natural Selection and Design  

PubMed Central

Background For survival, most natural viruses depend upon the existence of spherical capsids: protective shells of various sizes composed of protein subunits. So far, general evolutionary pressures shaping capsid design have remained elusive, even though an understanding of such properties may help in rationally impeding the virus life cycle and designing efficient nano-assemblies. Principal Findings This report uncovers an unprecedented and species-independent evolutionary pressure on virus capsids, based on the the notion that the simplest capsid designs (or those capsids with the lowest “hexamer complexity”, ) are the fittest, which was shown to be true for all available virus capsids. The theories result in a physically meaningful periodic table of virus capsids that uncovers strong and overarching evolutionary pressures, while also offering geometric explanations to other capsid properties (rigidity, pleomorphy, auxiliary requirements, etc.) that were previously considered to be unrelatable properties of the individual virus. Significance Apart from describing a universal rule for virus capsid evolution, our work (especially the periodic table) provides a language with which highly diverse virus capsids, unified only by geometry, may be described and related to each other. Finally, the available virus structure databases and other published data reiterate the predicted geometry-derived rules, reinforcing the role of geometry in the natural