Which evolutionary mechanism causes random changes in allele frequencies that are not the result of natural selection, particularly affecting small populations?

Which evolutionary mechanism causes random changes in allele frequencies that are not the result of natural selection, particularly affecting small populations?

• A. Gene Flow
• B. Genetic Drift
• C. Natural Selection
• D. Mutation

Answer: (B)

Genetic drift is the random fluctuation of allele frequencies from one generation to the next due to chance events, and it has a stronger effect in small populations. Because only a small number of individuals contribute to the next generation, random sampling can cause certain alleles to be overrepresented or underrepresented by luck alone, regardless of any fitness advantage or disadvantage. Over time, drift can even fix or lose alleles purely by chance, reducing genetic variation. This differs from gene flow, which changes frequencies through the movement of alleles between populations and tends to make populations more similar; natural selection, which shifts frequencies because some alleles confer a reproductive advantage; and mutation, which introduces new alleles but does so at a slow rate and is not about random shifts in the frequencies of existing alleles.

Genetic drift is the random fluctuation of allele frequencies from one generation to the next due to chance events, and it has a stronger effect in small populations. Because only a small number of individuals contribute to the next generation, random sampling can cause certain alleles to be overrepresented or underrepresented by luck alone, regardless of any fitness advantage or disadvantage. Over time, drift can even fix or lose alleles purely by chance, reducing genetic variation.

This differs from gene flow, which changes frequencies through the movement of alleles between populations and tends to make populations more similar; natural selection, which shifts frequencies because some alleles confer a reproductive advantage; and mutation, which introduces new alleles but does so at a slow rate and is not about random shifts in the frequencies of existing alleles.