An unexpected freeze that kills a population of chipmunks is an example of:

• A. gene flow
• B. genetic drift
• C. directional selection
• D. sexual selection

Answer: (B)

Verified step by step guidance

1. Understand the key terms in the problem: 'gene flow,' 'genetic drift,' 'directional selection,' and 'sexual selection.' Each term represents a different evolutionary mechanism. For example, genetic drift refers to random changes in allele frequencies within a population due to chance events.
2. Analyze the scenario: An unexpected freeze is a random environmental event that impacts the population of chipmunks. This suggests that the event is not related to traits or behaviors that would influence survival or reproduction.
3. Eliminate options that do not fit: 'Gene flow' involves the movement of alleles between populations, which is not described in this scenario. 'Directional selection' involves a consistent advantage for a specific trait, which is not relevant here. 'Sexual selection' involves traits that increase mating success, which is also unrelated to the freeze.
4. Focus on 'genetic drift': Since the freeze is a random event that affects the population without regard to specific traits, it aligns with the concept of genetic drift, where chance events cause changes in allele frequencies.
5. Conclude that the correct answer is 'genetic drift,' as it best describes the impact of a random environmental event like an unexpected freeze on the chipmunk population.