2 SEM ACC W/RAVEN CARDED
12th Edition
ISBN: 9781264439218
Author: Raven
Publisher: MCGRAW-HILL HIGHER 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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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?
Some genetic disorders are caused by autosomal recessive alleles. Many such alleles are recessive lethals, causing lethality very early in life (say, before the age of 20 yrs). Intuitively one might suggest that selection working on human population should completely remove such alleles from the population. Yet, there are many examples of such lethal genetic disorders occurring in low frequency in several human populations. Why is it almost impossible to completely remove these seemingly fitness-detrimental alleles from the population? Under what condition, extinction of such an allele from a population can be achieved?
Fitness is, most correctly, a technical term. What does it mean? What two things do you suppose govern the rate of evolution by natural selection? Explain how Darwinian evolution can decrease and increase the frequency of an allele (or a more complex heritable trait, for that matter)
Chapter 20 Solutions
2 SEM ACC W/RAVEN CARDED
Ch. 20.1 - Define evolution and population genetics.Ch. 20.1 - Prob. 2LOCh. 20.2 - Explain the HardyWeinberg principle.Ch. 20.2 - Describe the characteristics of a population that...Ch. 20.2 - Prob. 3LOCh. 20.3 - Define the five processes that can cause...Ch. 20.3 - Prob. 2LOCh. 20.4 - Prob. 1LOCh. 20.4 - Prob. 2LOCh. 20.4 - Demonstrate how the success of different...
Ch. 20.5 - Prob. 1LOCh. 20.5 - Prob. 2LOCh. 20.5 - Prob. 3LOCh. 20.6 - Define frequency-dependent selection, oscillating...Ch. 20.6 - Prob. 2LOCh. 20.7 - Define and contrast disruptive, directional, and...Ch. 20.7 - Prob. 2LOCh. 20.8 - Explain how experiments can be used to test...Ch. 20.9 - Prob. 1LOCh. 20.9 - Prob. 2LOCh. 20.10 - Prob. 2LOCh. 20 - If all white cats died, what proportion of the...Ch. 20 - Assuming that the values on the x-axis represent...Ch. 20 - Prob. 3DACh. 20 - Prob. 4DACh. 20 - Examine the index of copper tolerance on nonmine...Ch. 20 - Prob. 6DACh. 20 - Why are rare alleles particularly likely to be...Ch. 20 - Prob. 2IQCh. 20 - Prob. 3IQCh. 20 - Prob. 4IQCh. 20 - Prob. 5IQCh. 20 - Prob. 6IQCh. 20 - Prob. 7IQCh. 20 - Prob. 8IQCh. 20 - Prob. 9IQCh. 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 - Prob. 8UCh. 20 - In a population of red (dominant allele) or white...Ch. 20 - Genetic drift and natural selection can both lead...Ch. 20 - Prob. 3ACh. 20 - Prob. 4ACh. 20 - In Trinidadian guppies a combination of elegant...Ch. 20 - On large, black lava flows in the deserts of the...Ch. 20 - Based on a consideration of how strong artificial...
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- PINE TREE NEEDLES Variation among members of a population can lead to natural selection, but only if two conditions are met: First, the trait must be relevant to an individual's survival and/or reproductive rate. Second, variation in this trait must be heritable, that is, at least partly controlled by genes. a. How might you design an experiment to determine the importance of needle length in determining survival and reproduction? b. How might you test the extent to which needle length is heritable?arrow_forwardwhat is the meaning of fitness ?what two things do you suppose govern the rate of evolution by natural selection?arrow_forwardArtificial selection is when people selectively choose individuals with a certain desired trait to use as parents of the next generation. It is done to domesticated (or semi-domesticated) organisms. It has produced such monstrosities as bubble-eyed goldfish, revealing the potential for selection acting on heritable variation to produce varieties appearing very different than their ancestors. How is that different from natural selection? (Select all that apply) A- In artificial selection, humans directly cause new mutations to occur, whereas natural selection relies on mutations that occur randomly over time. B- Artificial selection can lead to organisms that would be unfit to survive in the wild, whereas natural selection usually makes the population better adapted. C- Artificial selection is directed ahead of time towards an intentional goal; not so with natural selection. D- Really, they are exactly the same process. Both cause what seems to be design without a designer. E-…arrow_forward
- What are considered significant factors in maintaining the surprisinglyhigh levels of genetic variation in natural populations ?arrow_forwardIf both mutation and drift are acting simultaneously, predict how this will influence variation in that population. Will variation increase, decrease, or be maintained at some equilibrium, etc.? (note: consider how mutation and drift each affect variation within a population).arrow_forwardNatural 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_forward
- You are studying two genetic loci that are on the same chromosome. One of the loci is a gene that produces darker feathers in dark environments in birds. The second locus is a gene associated with metabolism. In your research you find that the second locus is not under selection, but the first locus is undergoing positive selection. The positive selection at the first locus is increasing a specific allele at the second locus. This discovery of yours is best described as which of the following? a. Recombinaton b. Linkage equilibrium c. Genetic hitchhiking d. Chromosome inversionarrow_forwardAn allele A is present in a population at a frequency of 0.29, and there is only one other allele at the same locus. Fitness is associated with variation at the locus carrying the A allele such that there is a selection coefficient s equal to 0.03. What would you expect the frequency of the A allele to be after one generation of natural selection. Compute your result up to four decimal places.arrow_forwardThe Galapagos Islands are home to a unique iguana species that dives for extended periods of time to feed on algae from the sea floor. This makes them the world's only marine lizard. Assume the scales of these iguanas exhibit two phenotypes controlled by a single gene with two alleles: dominant, brown (G) and recessive, green (g). After studying the population for many years, a group of scientists concluded that a mess of 10,000 iguanas was not evolving, and that this mess contained 30% brown alleles and 70% green alleles. a) What is the expected frequency of each genotype for scale color? b) What is the expected number of individuals with each phenotype? Much to the researchers' dismay, one year during an EI Niño cycle, food became scarce and the mess of iguanas was randomly reduced to 100 individuals: 75 brown and 25 green. The researchers then conducted a genetic study on these individuals and found that of the 75 brown individuals, 30 were heterozygous. c) What is the actual…arrow_forward
- A dominant allele that arises from recurrent mutation is mildly deleterious. The fitness of heterozygotes is 99% of normal. The phenotype appears in about 1 out of every 10,000 newborns. What is the allele frequency? Assuming that there is a mutation/selection balance, estimate the mutation rate. (this is all the information given on the questionarrow_forwardFitness is, most correctly, a technical term. What does it mean? What two things do you suppose govern the rate of evolution by natural selection? Explain how Darwinian evolution can decrease and increase the frequency of an allele (or a more complex heritable trait, for that matter). Write it in an essay formarrow_forwardThe agouti gene determines coat colour in mice. Heterozygous mice have yellow coats, while homozygous dominant mice have black coats. However, having two copies of the recessive alleles is lethal. In a population of 2 000 mice, 1 082 mice have black coats. a) Calculate the frequency of each allele. Show all your work and express your answer as a value between 0 and 1 rounded to two decimal places. b) What percentage of the mouse population is expected to be carriers of the lethal allele? Show all your work and express your answer rounded to one decimal place. c) How many mice will die during fetal development? Show all your work and round your answer to the closest whole number.arrow_forward
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