A farmer wants apples that are crisper and more resistant to bruising. The farmer breeds apples with these target traits. After several generations, the farmer's orchards are producing apple crops with these traits. Which evolutionary mechanism is responsible for the changes in the gene pool of the farmer's crops?

Genetic drift refers to random changes in allele frequencies within a population, often occurring in small populations due to chance events. This mechanism does not involve selection based on specific traits and is unrelated to the intentional breeding efforts made by the farmer to enhance certain apple qualities.

Sexual selection involves preferences for certain traits in mate choice, influencing reproductive success. While it can lead to changes in traits within a population, it does not apply to the farmer's breeding of apples, which focuses on agricultural traits rather than traits that enhance mating success.

Gene flow is the transfer of genetic material between populations through migration or reproduction. This mechanism can introduce new genetic variations but does not account for the targeted breeding practices employed by the farmer to develop specific apple traits, which is a controlled process rather than a natural exchange.