Biology 30 – Populations Practice Test

Genetic drift describes random fluctuations in allele frequencies from one generation to the next, driven by chance sampling effects in small populations. When only a small number of individuals contribute genes to the next generation, the alleles that get passed on may not represent the entire parental gene pool. These random shifts can cause certain alleles to become more common or disappear entirely over time, sometimes leading to fixation of an allele independent of its fitness. This contrasts with natural selection, which changes frequencies based on differential survival and reproduction, and with gene flow, which moves alleles between populations. Mutation introduces new alleles but does not describe the random sampling changes in existing allele frequencies typical of drift.