Exam 23: Microevolution

Harmful mutations occur in both diploid and haploid organisms. Which of the following statements about the abundance of harmful mutations in diploid and haploid organisms is accurate?

In a very large population, a measurable trait has the distribution pattern shown in the diagram. Assume the trait is genetically determined. If there is no gene flow and the curve shifts to the left or to the right, which of the following processes is most likely occurring?

Which of the following comparisons illustrates differences in phenotypes caused by the environment?

A population of dark-eyed junco birds became established near the California coastline, many miles from the junco's normal habitat in the mixed-coniferous temperate forests in the mountains. Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays. Males with more white in their tail are more likely to win aggressive interactions, and females prefer to mate with males with more white in their tails. The coastal male junco population tails were, on average, 36% white; whereas the tails of males from the mountain populations averaged 40-45% white. Which of the following factors is the most likely original cause of the difference between the populations if the trait is inherited?

Two researchers measured the snout-to-vent (anus) length of Galápagos marine iguanas (lizards) and observed the percent survival of different-sized animals, all of the same age. The graph shows the log snout-vent length (SVL, a measure of overall body size) plotted against the percent survival of these different size classes for males and females. (Data from M. Wikelski and L. Michael Romero. Body size, performance and fitness in Galapagos marine iguanas. Integrative and Comparative Biology 43:376-386 [2003].) Based on the data in the figure, what type of selection for body size appears to be occurring in these marine iguanas?

A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (A2A2), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants. What is the estimated frequency of allele A1 in the gene pool?

A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. Which of the following statements best explains why the actual forelimbs of these mammals do not seem to be optimally arranged?

A species of moth lays eggs on oak trees in spring and summer. Spring caterpillars eat oak flowers and look like oak flowers. Summer caterpillars eat oak leaves and look like twigs. To investigate how the same population of moths can produce such variable caterpillars, a researcher collected eggs from a population of moths and allowed them to hatch and grow under the conditions shown in the table below. Which of the following statements is NOT a testable hypothesis in the described experiment?

If individuals tend to mate within a subset of the population, there is ________.

Imagine a human population with an extremely low frequency of sickle cell alleles. Which of the following changes is most likely in the human population 15 generations after introducing a mosquito population that carries the malaria parasite?

In peas, a gene controls flower color such that R1 = purple and R2 = white. The purple allele is dominant to the white allele. 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?

The effect of which Hardy-Weinberg condition is affected by population size?

The idea of relative fitness is best exemplified in which of the following statements?

Two scientists measured the snout-to-vent (anus) length of Galápagos marine iguanas (lizards) and observed the percent survival of different-sized animals, all of the same age. The graph shows the log snout-vent length (SVL, a measure of overall body size) plotted against the percent survival of these different size classes for males and females. (Data from M. Wikelski and L. Michael Romero. Body size, performance and fitness in Galapagos marine iguanas. Integrative and Comparative Biology 43:376-386 [2003].) Currently, the only predators of Galápagos marine iguanas are Galápagos hawks. Although small iguanas can sprint faster than large iguanas, iguana body size is not correlated with risk of hawk predation. If predators (for example, cats) that preferentially catch and eat slower iguanas are introduced to the island, iguana body size is likely to ________ in the absence of other factors; the iguanas would then be under ________ selection.

The higher the proportion of loci that are "fixed" in a population, the lower is that population's ________.

In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool. In the United States, the parasite that causes malaria is not present, but the sickle cell allele is present in many African-Americans whose ancestors were from equatorial Africa. Which of the following processes are most likely acting on the sickle-cell allele in the United States, and in equatorial Africa?

Which of the following situations leads to microevolution?

In a Hardy-Weinberg population with two alleles A1 and A2 that are in equilibrium, the frequency of allele A2 is 0.1. What is the frequency of individuals with A1A1 genotype?

Suppose 64% of the individuals in a remote mountain village can taste phenylthiocarbamide (PTC) and must, therefore, have at least one copy of the dominant PTC taster allele. If this population conforms to Hardy-Weinberg equilibrium for this gene, what percent of the population must be heterozygous for this trait?

Adult male humans generally have deeper voices than do adult female humans. Which of the following processes was most likely occurring given that 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?