What is the term for random changes in allele frequencies in small populations?

The term that describes random changes in allele frequencies in small populations is genetic drift. This phenomenon occurs due to random sampling effects, where certain alleles may become more or less common in a population purely by chance rather than through natural selection or other evolutionary forces. In small populations, even minor changes can have significant effects on the genetic makeup over generations, leading to the fixation or loss of alleles.

Genetic drift contrasts with processes like natural selection, where specific traits have a direct advantage, or gene migration, which involves the movement of alleles between populations. A Mendelian population is a theoretical concept that describes a population where mating is random concerning the alleles under consideration, while a gene pool refers to the total collection of genes and their alleles present within a population. Understanding genetic drift is crucial as it highlights the role of chance events in shaping genetic diversity, especially in small populations that are more susceptible to such fluctuations.