Genetic diversity is most likely to be lost in a small population when which of the following occurs?

• A. A population bottleneck occurs, and random sampling causes some alleles to be lost entirely
• B. Balancing selection maintains multiple alleles because heterozygotes have the highest fitness
• C. High gene flow from neighboring populations introduces new alleles each generation
• D. Strong directional natural selection consistently favors the same allele due to its adaptive advantage

Answer: (A)

Verified step by step guidance

1. Understand that genetic diversity refers to the variety of alleles (different versions of a gene) present in a population.
2. Recognize that small populations are more vulnerable to losing genetic diversity because random events can have a larger impact on allele frequencies.
3. Identify that a population bottleneck is an event where a population's size is drastically reduced for at least one generation, causing random sampling of alleles.
4. Know that during a bottleneck, some alleles may be lost entirely simply by chance, reducing genetic diversity significantly.
5. Compare this with other scenarios: balancing selection maintains diversity, gene flow introduces new alleles, and directional selection favors certain alleles but does not necessarily cause loss due to random sampling.