What does "genetic drift" refer to?

Genetic drift refers to the changes in allele frequencies within a population that occur due to random sampling effects. This phenomenon is particularly significant in small populations where chance events can lead to large fluctuations in allele frequencies from one generation to the next, independent of natural selection.

For example, if a few individuals in a small population happen to carry certain alleles, and they reproduce, those alleles may become more common simply by chance. Conversely, alleles that are present in individuals who do not reproduce may disappear from the population entirely, also due to random chance rather than any influence of advantageous traits.

This contrasts with the systematic change in allele frequencies driven by natural selection (which involves favorable traits being passed on more frequently). Additionally, environmental changes may influence survival and reproduction but are not synonymous with genetic drift. Furthermore, the selection of specific traits based on fitness does not encapsulate the random nature of genetic drift, which operates independently of the adaptive value of traits.