Question

most of the individuals in a small, isolated population of alpine plants are killed in a landslide. in the next generation the frequency of a particular allele is lower than it was before the landslide. what has occurred?

○ evolution, genetic drift and a genetic bottleneck
○ a genetic bottleneck only
○ genetic drift only
○ evolution only
○ evolution and genetic drift only

Explanation:

• Evolution: Evolution is defined as a change in the genetic composition (allele frequencies) of a population over time. Since the allele frequency has changed from one generation to the next, evolution has occurred.
• Genetic drift: Genetic drift is a mechanism of evolution that refers to random changes in allele frequencies in a population. In small populations, chance events (like a landslide killing most of the population) can have a large impact on allele frequencies. Here, the landslide (a random event) led to a change in allele frequency, so genetic drift has occurred.
• Genetic bottleneck: A genetic bottleneck is a type of genetic drift where a population’s size is drastically reduced (in this case, by the landslide). This reduction in population size can lead to a change in allele frequencies. So, a genetic bottleneck (which is a specific case of genetic drift) has also occurred.

Answer:

evolution, genetic drift and a genetic bottleneck