What does genetic drift refer to in a population?

Genetic drift refers to the random fluctuations in the frequencies of alleles (gene variants) within a population over time, particularly in small populations. This phenomenon can occur from one generation to the next due to random sampling of organisms during reproduction. It can lead to significant changes in the genetic makeup of a population, independent of natural selection or adaptation.

When we consider the idea of change of gene frequency in the same generation, this aspect accurately captures the essence of genetic drift. Allele frequencies can differ between populations purely by chance, as some alleles may become more common while others may diminish or even disappear, regardless of their adaptive advantages. This randomness contributes to the genetic diversity and evolution of the population under study.

The other options address different concepts in population genetics and evolution. Changes in population size refer to demographic shifts rather than genetic changes, mutation rates over time focus on the introduction of new genetic variations rather than changes in existing frequencies, and natural selection effects involve differential survival and reproduction based on advantageous traits, which is a distinct mechanism of evolution compared to the random nature of genetic drift.