In evolutionary biology, which statement best describes the difference between genetic drift and natural selection?

• A. Genetic drift occurs only when mutations create new alleles, whereas natural selection occurs only when migration introduces alleles.
• B. Genetic drift always increases adaptation to the environment, whereas natural selection is random with respect to fitness.
• C. Genetic drift is random change in allele frequencies due to chance (especially in small populations), whereas natural selection is nonrandom change driven by heritable differences in fitness.
• D. Genetic drift affects only recessive alleles, whereas natural selection affects only dominant alleles.

Answer: (C)

Verified step by step guidance

1. Identify the key concepts involved: genetic drift and natural selection, both mechanisms that cause changes in allele frequencies within populations.
2. Understand genetic drift as a random process where allele frequencies change due to chance events, especially significant in small populations, without regard to the alleles' effects on fitness.
3. Recognize natural selection as a nonrandom process where alleles that confer higher fitness tend to increase in frequency because individuals with those alleles are more likely to survive and reproduce.
4. Compare the two by noting that genetic drift is random and can lead to allele frequency changes regardless of fitness, while natural selection is directed by differences in fitness and adaptation to the environment.
5. Conclude that the best description differentiates genetic drift as random changes due to chance and natural selection as nonrandom changes driven by heritable fitness differences.