Biology
11th Edition
ISBN: 9781259188138
Author: Peter H Raven, George B Johnson Professor, Kenneth A. Mason Dr. Ph.D., Jonathan Losos Dr., Susan Singer
Publisher: McGraw-Hill Education
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Chapter 20, Problem 3S
Based on a consideration of how strong artificial selection has helped eliminate
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Why is population level genetic variation important for evolution and what causes genetic variation ? How do we detect if evolution is occurring ?
If gene A/a is not in Hardy-Weinberg equilibrium due to natural selection such that individuals with the genotype AA have a fitness value of 1.0, heterozygotes have only slightly reduced fitness at 0.9, and individuals with the genotype aa have a fitness value of 0.6, what kind of change in allele frequency would you expect to see over time assuming you start with equal frequencies of the 2 alleles?
Is evolution by natural selection based on the desires of individuals within the evolving population? In other words, are individuals able to control natural selection to obtain a certain outcome? Explain.
Chapter 20 Solutions
Biology
Ch. 20 - Assortative mating a. affects genotype frequencies...Ch. 20 - When the environment changes from year to year and...Ch. 20 - Many factors can limit the ability of natural...Ch. 20 - Stabilizing selection differs from directional...Ch. 20 - Founder effects and bottlenecks are a. expected...Ch. 20 - Relative fitness a. refers to the survival rate of...Ch. 20 - For natural selection to result in evolutionary...Ch. 20 - In a population of red (dominant allele) or white...Ch. 20 - Genetic drift and natural selection can both lead...Ch. 20 - Prob. 3A
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- What is the intuitive meaning of the mean fitness of a population? How does its value change in response to natural selection?arrow_forwardin general, will natural selection result in an increase or decrease in variation? Why does this happen and how, in theory, will it affect evolution in the futurearrow_forwardApply the VIDA table to the evolution of sickle cell disease to justify whether it is an instance of evolution by natural selection. Answer the following questions. Is there variation in this trait in the population? How exactly does it vary? Is the trait at least partly inherited? Is there selection for this trait in a particular environment? (What is the selective pressure? And how does a trait give an advantage or disadvantage in that environment?) What is the evidence that this trait makes organisms better adapted to their environment?arrow_forward
- Natural selection occurs only if there is both (1) variation in the genetic information between organisms in a population and (2) variation in the expression of that genetic information—that is, trait variation—that leads to differences in performance among individuals. What kind of variation might exist in bioluminescing organisms, and what differences in performance might result? (Remember, evolution is a consequence of the interaction of four factors: (1) the potential for a species to increase in number, (2) the genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for an environment’s limited supply of the resources that individuals need in order to survive and reproduce, and (4) the ensuing proliferation of those organisms that are better able to survive and reproduce in that environment.)arrow_forwardwhat is the meaning of fitness ?what two things do you suppose govern the rate of evolution by natural selection?arrow_forwardThe trait that natural selection “selects for” is lifetime Darwinian fitness. If relative matching of the moths to the background is determining fitness differences, is there any difference in other fitness components in the color morphs of Biston betularia that is influencing the direction of evolution in the three populations shown in the graph? Give a reason for your answer.arrow_forward
- Is it likely that the selection coefficient (s) is similar in value for the three populations shown? Is it important to know if the amount of genetic variation for the trait under selection is approximately equal in all three populations in the graph? Why or why not?arrow_forwardWhen discussing natural selection and behaviour, we often say that members of a species have certain behavioural traits because those traits are adaptive, in the sense that they increase inclusive fitness relative to alternative forms of those traits that have existed in the past. Instead of emphasizing the adaptiveness of behavioural traits, some biologists describe natural selection as a process that operates on nervous system traits, increasing the prevalence within a population of particular patterns of neural circuitry and neurobiological mechanisms. As an alternative to emphasizing either the behaviour or the nervous system, some biologists describe natural selection as a process that operates on genes; according to this perspective, certain forms of certain genes (ie., particular alleles) increase in prevalence within a population relative to alternative forms of those genes. Which, if any, of these three perspectives on natural selection and behaviour do you think is the most…arrow_forwardWhat are two reasons why a selection limit is reached in which artificial selection no longer has an effect?arrow_forward
- Regardless of the rate of evolutionary change, the product of genetic alterations is ultimately tested by Natural Selection. Gradualism accounts for the constant yet slow linear modification of a population while punctuated equilibrium accounts for long periods of stasis followed by rapid divergence (multiple forms emerging). -First, in no more than two sentences, explain Natural Selection (use your own words).-Second, explain the dynamics of selection. If natural selection acts on individuals, how might itshift allele frequencies in a population?-Third, explain gradualism and punctuated equilibrium in terms of selection. When discussingpunctuated equilibrium, remember that selection is still active in times of stasisarrow_forwardIn what way is diversity intrinsically valuable to a population? How is genotypic or phenotypic diversity maintained if natural selection reduces variation?arrow_forwardWhich evolutionary forces a. cause an increase in genetic variation both within and between populations? b. cause a decrease in genetic variation both within and between populations? c. cause an increase in genetic variation within populations but cause a decrease in genetic variation between populations?arrow_forward
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