Question

questions 1 through 6 refer to the following. researchers have undertaken a long-term study of populations of rock pocket mice, chaetodipus intermedius, in arizona and new mexico. rock pocket mouse fur is either dark or light in color. most of the populations studied live in areas with light-colored granite rocks; however, some areas are dominated by dark-colored rocks from ancient lava flows. researchers collected mice from six sites in arizona and recorded their coat colors. figure 1 shows the study sites, the rock colors, and the distribution of coat colors. the researchers built an enclosure to prevent migration into and out of the o’neill rock pocket mouse population for a period of two years. which of the following best predicts the effect of the enclosure on the o’neill population? a) the o’neill population will rapidly evolve into a separate species. b) the o’neill population will become less diverse due to the bottleneck effect. c) the frequency of the mc1r d allele will decline due to natural selection. d) one of the alleles for the mc1r gene will become fixed due to genetic drift.

Explanation:

1. Analyze Option A: Speciation (forming a new species) requires reproductive isolation over a long time, not just a 2 - year enclosure. So A is incorrect.
2. Analyze Option B: The bottleneck effect is due to a drastic population reduction. The enclosure just prevents migration, not a population crash. So B is incorrect.
3. Analyze Option C: The O'Neill rock color is light (from the table: Rock Color for O'Neill is light - colored as per the image). The \(MC1R D\) allele is associated with dark fur. In a light - rock environment, dark - furred mice (with \(MC1R D\) allele) would be more visible to predators, so natural selection would act against the \(MC1R D\) allele, causing its frequency to decline. This makes C a valid prediction.
4. Analyze Option D: Genetic drift (like fixation) is more likely in small populations or with random events. The enclosure prevents migration but doesn't imply strong genetic drift - inducing conditions (like a small population size change here). Also, natural selection (as in Option C) is a stronger force here due to the environmental - fur color match. So D is less likely.

Answer:

C. The frequency of the \(MC1R D\) allele will decline due to natural selection.