Question

5 multiple choice 16.6 points dok 2: in a small, isolated fish population, a severe thunderstorm washes a large portion of the stream bank into the water, eliminating many fish indiscriminately. the surviving population exhibits different allele frequencies than the original. this is a clear demonstration of: gene flow, due to the mixing of water which will reduce the population size and therefore cause a founder effect. mutation pressure, resulting from the environmental stress and causing mutation proportions to rise dramatically. directional selection, because the environment changed and organisms with an extreme variation were the only ones to survive. the bottleneck effect, because the population size was sharply reduced by a random event.

Explanation:

• Gene flow: Involves movement of genes between populations. Here, it's a reduction within a single population due to a random event (thunderstorm), not gene - flow.
• Mutation pressure: Deals with new mutations. The problem is about allele frequency change due to population size reduction (not new mutations).
• Directional selection: Selects for an extreme phenotype. The fish were eliminated indiscriminately (not based on a particular trait).
• Bottleneck Effect: Occurs when a population's size is drastically reduced by a random event (like the thunderstorm here), leading to different allele frequencies.

Answer:

The Bottleneck Effect, because the population size was sharply reduced by a random event.