 Changes in the frequency of an allele in a population are mainly influenced by natural selection, where a given allele provides a selective or reproductive advantage to the organism, as well as other factors such as mutation, genetic drift, genetic hitchhiking, artificial selection and migration.Over many generations, the genomes of organisms can change significantly, resulting in evolution.In the process called adaptation, selection for beneficial mutations can cause a species to evolve into forms better able to survive in their environment.