the Hardy-Weinberg principle states that allele frequencies in a population remain stable and constant from generation to generation unless disturbed . Factors that can disrupt this equilibrium include gene migration, genetic drift, mutation, genetic recombination, and natural selection . Genetic drift (or random drift) is specifically defined as a change in allele frequency that occurs by chance . Because these changes are caused by random events rather than selective pressures, the resulting change in gene frequency is non-directional. In contrast, natural selection can lead to directional changes , and while mutations are described as random and directionless , 'random drift' is the standard biological term for chance-driven frequency fluctuations in a population.