Question

Which of the following is least likely to change the gene pool of a population of chipmunks?
A pesticide poisons and kills a large number of chipmunks.
A group of chipmunks moves to a new habitat.
A number of chipmunks die due to old age.
A genetic mutation causes some of the chipmunks to have larger eyes.

Answer 1

"A number of chipmunks die due to old age."

Reason: Age-related death is a neutral, nonselective removal of individuals and typically does not change allele frequencies in the population. The other events (pesticide killing, migration, and mutation) directly alter allele frequencies via selection, gene flow, or introduction of new alleles.