SAT Subject Biology Practice Question 38: Answer and Explanation

Next steps

Question: 38

2. The graph shows the distribution of fur color in a population of rodents. Over time, the environment changes so that it includes only light and dark rocks, with little vegetation. How will natural selection affect the distribution of phenotypes in this population?

A. The mean will shift toward the right, and the center of the curve will be higher.
B. The mean will shift toward the left, and the center of the curve will be higher.
C. The mean will shift toward the right, and the center of the curve will be lower.
D. The mean will remain the same, and the center of the curve will be higher.
E. The mean will remain the same, and the center of the curve will be lower.

Correct Answer: E

Explanation:

Because of the changing environment, rodents at both ends of the curve have greater fitness. Therefore, the frequency curve will become higher at the tips and lower near the current mean. However, the mean will not shift because the average phenotype will still be intermediate in color.

Previous       Next