BIOLOGY VOL. II
16th Edition
ISBN: 9781308795317
Author: Raven
Publisher: Mcgraw-Hill/Create
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Textbook Question
Chapter 20, Problem 4U
Stabilizing selection differs from directional selection because
a. in the former, phenotypic variation is reduced but the average phenotype stays the same, whereas in the latter both the variation and the mean phenotype change.
b. the former requires
c. intermediate
d. None of the choices is correct.
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Which of the following is an example of stabilizing selection?a. Over time, Equus developed strength, intelligence, speed,and durable grinding teeth.b. British land snails mainly have two different phenotypes.c. Swiss starlings usually lay four or five eggs, therebyincreasing their chances of more offspring.d. Drug resistance increases with each generation; theresistant bacteria survive, and the nonresistant bacteriaget killed off.e. All of these are correct
A gene exists in two alleles, and the heterozygote has the highest fitness. This situation is likely to result in
a. directional selection. c. disruptive selection.
b. stabilizing selection. d. balancing selection.
You are examining the gene in your snail population that confers resistance to a parasite. There are multiple alleles at this locus. Identify the characteristics that would result in the greatest increase in allele frequency (not necessarily the greatest allele frequency) in one single generation of the resistant allele.
Answer
Resistant allele acts…
Initial resistant allele frequency…
Selection strength is…
a.
dominantly
high
weak
b.
recessively
low
strong
c.
dominantly
low
strong
d.
recessively
high
weak
a.
Answer a.
b.
Answer b.
c.
Answer c.
d.
Answer d.
Chapter 20 Solutions
BIOLOGY VOL. II
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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- Which of the following is the MOST important characteristic of a trait for it to undergo descent with modification? A. It must be heritable. B. It must exhibit variation. C. It must exhibit phenotypic plasticity. D. Variation in the trait must be accompanied by variation in fitness.arrow_forwardYou are examining the gene in your snail population that confers resistance to a parasite. There are multiple alleles at this locus. Identify the characteristics that would result in the greatest increase resistant allele. allele frequency (not necessarily the greatest allele frequency) in one single generation of the Answer Resistant allele acts.. Initial resistant allele frequency... Selection strength is... dominantly high weak la. b. recessively low strong dominantly low strong С. d. recessively high weak O a. Answer a. O b. Answer b. O c. Answer C. O d. Answer d.arrow_forwardIn the movie on rock pocket mice, what did the team discover about black colouration? Select the ONE BEST answer. a. Fur colouration is the result of a new adaptive behaviour where pocket mice rolled in lava dust to camouflage themselves. b. It is the result of the same, single mutation in all populations. C. Different mutations cause similar dark colouration in different populations. d. One specific mutation causes black or white fur depending on the population. e. Fur colouration is the result of dietary changes in different environments, not natural selection.arrow_forward
- You are studying a genetically modified mouse that produces electric blue fur, which is not a fur color observed in nature. You notice that females prefer males that have the blue fur when given a choice test for mates. This result supports which of the following models of sexual selection? a. Sexual selection for indirect benefits b. Sexual selection for direct benefits c. Sexual selection for arbitrary traits d. None of the abovearrow_forwardWhich of the following is false? a. The color of a fruit fly's eyes is a trait. b. The instructions for producing a trait are found in a gene that controls the physical expression of that trait. c. A gene can have different alleles that can specify different traits, such as red or brown eye color. d. The trait is influenced by the gene, independent of the environment. e. By studying the patterns of traits over generations of an organism, the genetic composition of an organism can be deduced.arrow_forwardThe good genes hypothesis is a theory that explains what? a. why more fit individuals are more likely to have more offspring b. why alleles that confer beneficial traits or behaviors are selected for by natural selection c. why some deleterious mutations are maintained in the population d. why individuals of one sex develop impressive ornamental traitsarrow_forward
- Selection that causes one extreme phenotype to be more frequent in a population is an example ofa. disruptive selection.b. stabilizing selection.c. directional selection.d. equivalent selection.arrow_forwardThe relative fitnesses of A1A1, A1A2, and A2A2 are 0.5,0.8 and 1 respectively. What is the expected result of natural selection in this selection? a.) A1 will increase and A2 will decrease. b.) A2 will increase and A1 will decrease. c. Both alleles will decrease in frequency d.) A stable equilibrium will be achieved in which both alleles are maintained e.) An unstable equilibrium will exist and the outcome depends on the allele frequencies.arrow_forwardA population occupies heterogeneous environments in which the fitness of some genotypes is higher in one environment and the fitness of other individuals is higher in another environment. This situation is likely to result in a. directional selection. b. stabilizing selection. c. disruptive selection. d. balancing selection.arrow_forward
- Consider a gene with two alleles, C and M. The table below describes fitness for different genotypes in two populations. Fitness CC CM MM Population 1 1.0 1.0 0.6 Population 2 0.9 0.9 1.0 Which of the following is true based on this table? A.) C is recessive and M is dominant B.) M is recessive and C is dominant C.) Neither allele is dominant D.) C is dominant in population 1 and M is dominant in population 2arrow_forwardWhat is the difference between artificial selection (e.g., greyhounds that are bred for speed) and natural selection? a. In artificial selection, the genetic variation introduced into the population is limited, but in natural selection, it is not b. In artificial selection, the environment is the selective force, while in natural selection, humans are the selective force c. In natural selection, the environment is the selective force, while in artificial selection, humans are the selective force d. Unlike other species, dogs are not subject to natural selection e. Both A & Carrow_forwardC28. Do the following examples describe directional, disruptive, balancing, or stabilizing selection? A. Polymorphisms in snail color and banding pattern as described in Figure 24.13 B. Thick fur among mammals exposed to cold climates C. Birth weight in humans D. Sturdy stems and leaves among plants exposed to windy climatesarrow_forward
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