Life: The Science of Biology
11th Edition
ISBN: 9781319010164
Author: David E. Sadava, David M. Hillis, H. Craig Heller, Sally D. Hacker
Publisher: W. H. Freeman
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Chapter 20.4, Problem 3R
Summary Introduction
To review:
The examples of extreme
Introduction:
The directional selection is the type of natural selection in which an extreme phenotypic character or trait is promoted due to the changes in the environment. This causes the changes in the allele frequency and the shifting of the phenotype in a fixed direction.
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Life: The Science of Biology
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- How does the concept of artificial selection is applied in the creation and domestication of chihuahuas out of wolves? Explain in an explicit way.arrow_forwardExplain how natural selection might be responsible for the PTC taster polymorphism.Why might some populations have a higher frequency of the taster allele than others?arrow_forwardThe effect(s) of the environment on the variation seen in phenotypes include: influencing the heritability of the phenotype influencing the phenotype's response to selection allowing continuous phenotypic variance from a discrete genetic basis all of the above a) and b) only O a) and c) only b) and c) onlyarrow_forward
- Let’s suppose that pigmentation in a species of insect is controlledby a single gene that exists as two alleles, D for dark and d for light.The heterozygote, Dd, is intermediate in color. In a heterogeneousenvironment, the allele frequencies are D = 0.7 and d = 0.3. Thispolymorphism is maintained because the environment has somedimly lit forested areas and some sunny fields. During a hurricane,a group of 1000 insects is blown to a completely sunny area. In thisenvironment, the relative fitness values are DD = 0.3, Dd = 0.7, anddd = 1.0. What are the predicted allele frequencies in thenext generation?arrow_forwardWhat are considered significant factors in maintaining the surprisinglyhigh levels of genetic variation in natural populations ?arrow_forwardWhich microevolutionary force typically changes genotype frequencies without changing allele frequencies? Explain.arrow_forward
- The forward mutation rate for piebald spotting in guinea pigs is 8 × 10-5;the reverse mutation rate is 2 × 10-6. If no other evolutionary forces areassumed to be acting, what is the expected frequency of the allele forpiebald spotting in a population that is in mutational equilibrium?arrow_forwardConsider the first copy of an allele for insecticideresistance that arises by mutation in a populationof insects exposed to an insecticide. Is this mutation an adaptation? If, after some generations,we find that most of the population is resistant,is the resistance an adaptation? If we discovergenetic variation for insecticide resistance in apopulation that has had no experience of insecticides, is the variation an adaptation? If an insectpopulation is polymorphic for two alleles, eachof which confers resistance against one of twopesticides that are alternately applied, is thevariation an adaptation? Or is each of the tworesistance traits an adaptation?arrow_forwardIn New Zealand you begin to study the relationship between snails and their trematode parasites. You found that the parasites cause cyclical patterns of selection on the snail populations, and vice a versa, such that snails with rare genotypes typically survive better compared to those that have more common genotypes. In the ten years you’ve been sampling, you notice that the two alleles cycle between being rare and common from year to year. What pattern of selection did you observe? a. selection against the dominant allele b. selection against the recessive allele c. frequency-dependent selection d. overdominancearrow_forward
- Which of the following statements does NOT apply to the Hardy-Weinberg expression: p2 + 2pq + q2? Group of answer choices p2 is the frequency of individuals with the homozygous recessive genotype. 2pq is the frequency of individuals with the heterozygous genotype. It can be used to determine the genotype and allele frequencies of the previous and the next generations. Knowing either p2 or q2, you can calculate all the other frequenciesarrow_forwardIn a population of 10,000 individuals, where 3600 are MM, 1600 are Mm, and 4800 are mm, what are the frequencies of the M alleles and the m alleles? M= 0.7; m = 0.3 M= 0.6; m = 0.4 М-0.8; т %3D 0.2 M= 0.9; m = 0.1 M= 0.5; m = 0.5arrow_forwardIn a certain breeding population , it is known for certain that only 7.8% of the individuals are "true breeding" for the dominant phenotype. What would be the predicted frequency of individuals that are "true-breeding" for the recessive phenotype?arrow_forward
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