What is an example of genetic drift?

Genetic drift refers to the random fluctuations in allele frequencies within a population over time, particularly in small populations. It can lead to significant changes in a population's genetic makeup simply due to chance events rather than natural selection.

Geographic isolation serves as an example of genetic drift because it can lead to populations becoming separated and evolving independently. When a population is geographically isolated — for example, when a group of organisms is separated by a mountain range or river — the gene flow between the isolated population and its original population ceases. This isolation can result in genetic drift, as the separate populations may experience different random events that affect allele frequencies. Over generations, this can lead to distinct genetic differences between the isolated population and the original one, illustrating the concept of genetic drift.

While the other choices involve concepts relevant to evolution and population biology, they do not exemplify genetic drift in the same way. Directional selection pertains to the process where specific traits become more common due to their advantageous nature. A polymorphic population refers to a population that has multiple alleles for a trait, which is not inherently linked to genetic drift. Habitat loss describes an environmental change that can impact populations but does not necessarily illustrate the random nature of genetic drift.