Chapter 21 Quiz, Evolution of Population

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this allele? 9.0 0.9 0.49 0.09

0.09

In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population? 0.80 0.64 0.36 0.75

0.80

If, on average, 46% of the loci in a species' gene pool are heterozygous, then the average homozygosity of the species should be 54%. 46%. 23%.

54%

Which of the following is correct about genetic variation? It tends to be reduced when diploid organisms produce gametes and reproduce. It must be present in a population before natural selection can act upon the population. It arises in response to changes in the environment. It is created by the direct action of natural selection. A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity.

It must be present in a population before natural selection can act upon the population.

Why don't similar genotypes always produce the same phenotype? Animals display different phenotypes dependent on diet, not genotype. Phenotypes can vary depending upon environment Parents alter their phenotypes and pass on this phenotype to progeny. Genetic variants of ADH enzyme produce the same phenotype.

Phenotypes can vary depending upon environment

Mountains also have an unmatched power to drive human evolution. Starting tens of thousands of years ago, people moved to high altitudes, and there they experienced natural selection that has reworked their biology. In Tibet, for example, people have broader arteries and capillaries. In the Andes, they can dissolve more oxygen into their blood. These different traits of people who live in high altitudes illustrate stabilizing evolution. adaptive evolution. acclimatization. sexual selection.

adaptive evolution.

In a very large population, a quantitative trait has the distribution pattern shown in Figure 21.3. If the curve in Figure 21.3 shifts to the left or to the right, there is no gene flow, and the population size consequently increases over successive generations. Which of the following is (are) probably occurring? immigration or emigration only directional selection and adaptation genetic drift only immigration or emigration, directional selection, and adaptation genetic drift and disruptive selection

directional selection and adaptation

Examining the figure, which type of selection has two peaks of frequency of individuals? directional selection stabilizing selection natural selection disruptive selection

disruptive selection

Which of the following describes a mechanism for generating more genes? meiosis gametogenesis duplication translocation

duplication

Soon after the island of Hawaii rose above the sea surface (somewhat less than 1 million years ago), the evolution of life on this new island should have been most strongly influenced by sexual selection. founder effect. habitat differentiation. genetic bottleneck.

founder effect.

Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing gene flow. genetic drift. nonrandom mating. geographic isolation

gene flow.

In evolution, which driving factor most consistently requires a small population as a precondition for its occurrence? genetic drift mutation natural selection nonrandom mating

genetic drift

The Hardy-Weinberg equation p2 + 2pq + q2 = 1 allows you to calculate genome frequencies. population declines. genotype frequencies. population abundance and mating patterns.

genotype frequencies.

In the formula for determining a population's genotype frequencies, the 2 in the term 2pq is necessary because heterozygotes can come about in two ways based upon parental gametes. heterozygotes have two alleles. the population is doubling in number. the population is diploid.

heterozygotes can come about in two ways based upon parental gametes.

In the formula for determining a population's genotype frequencies, the pq in the term 2pq is necessary because heterozygotes can come about in two ways. heterozygotes have two alleles. the population is diploid. the population is doubling in number.

heterozygotes have two alleles

Which of the following consistently improves the degree to which organisms are well suited for life in their environment? natural selection gene flow genetic drift adaptation

natural selection

When using the Hardy-Weinberg equilibrium model, we assume that natural selection is not occurring. the population under study has experienced gene flow. the population has passed through a bottleneck. the population is infinitely large.

natural selection is not occurring.

Adult male humans generally have deeper voices than do adult female humans, which is the direct result of higher levels of testosterone causing growth of the larynx. If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females and increasing larynx size in adult males, then sexual dimorphism was developing over time in these species. stabilizing selection was occurring in these species concerning larynx size. selection was acting more directly upon genotype than upon phenotype. intrasexual selection seems to have occurred.

sexual dimorphism was developing over time in these species.

A mutation that is neither harmful nor beneficial is termed a deleterious mutation. point mutation. heterozygote advantage. silent mutation.

silent mutation.

Examining the figure, which type of selection eliminates extreme frequency of individuals' phenotype? natural selection disruptive selection directional selection stabilizing selection

stabilizing selection