What mechanism of evolution is described by random changes in allele frequencies?

Genetic drift refers to the process by which allele frequencies within a population change randomly over time, primarily due to chance events. This mechanism is particularly significant in small populations, where random events can have a disproportionately large impact on the genetic makeup of the population. For instance, if a particular allele becomes more common or less common purely by random chance rather than due to advantageous traits or environmental pressures, this is a clear demonstration of genetic drift.

In contrast, natural selection is a process that leads to changes in allele frequencies based on the differential survival and reproduction of individuals with certain traits that provide a survival advantage. Gene flow involves the transfer of alleles between populations through migration, leading to changes in allele frequencies as individuals from different populations interbreed. Mutation is the origin of new alleles in a population but does not directly pertain to the random changes in existing allele frequencies that characterize genetic drift.