Question

In northern Canada a population of rabbits was predominantly white in color. The allele for white color is recessive while the allele for gray color is dominant. Over the last several decades, the average annual temperature of this area has increased and the long-term deposits of ice and snow have become scarce. This is an example of directional selection which tends to
Responses
A decrease genetic diversity.decrease genetic diversity.
B increase the frequency of a previously scarce allele.increase the frequency of a previously scarce allele.
C decrease the frequency of a previously scarce allele.decrease the frequency of a previously scarce allele.
D increase the frequency of two previously rare alleles.

Answer 1

B — increase the frequency of a previously scarce allele.

Explanation: As the environment warms and snow cover declines, gray rabbits (carrying the dominant gray allele) are favored. Directional selection shifts allele frequencies toward that favored extreme, increasing the frequency of the previously rare gray allele (and typically reducing genetic variation for that trait).