Which process describes the random changes in allele frequencies within small populations?

The concept you are looking at is genetic drift. This process refers to the random fluctuations in allele frequencies that can occur in small populations, primarily due to chance events. Because small populations have a limited gene pool, any random event, such as the death of individuals due to an accident or natural disaster, can significantly alter the genetic makeup of the population.

In contrast, gene flow involves the transfer of alleles between populations, which tends to make allele frequencies more similar between groups rather than causing random changes within a single population. Natural selection relies on differential survival and reproduction based on advantageous traits, leading to changes in allele frequencies that are not random, but rather dependent on environmental pressures. Mutation introduces new genetic variations into a population but does not directly cause changes in allele frequencies through random chance.

Thus, genetic drift is unique in highlighting the role of random sampling in small populations, making it the correct and most applicable process for this question.