In a population of beetles, there are green and brown colorations that occur with equal frequency. After a forest fire, only 20 beetles remain. 18 of them are green and 2 of them are brown. What describes this change in frequencies?

The answer is C / A population bottleneck occurred, altering the resulting allele frequencies.

Explanation:

A population bottleneck occurred, altering the resulting allele frequencies. Since a catastrophic fire affected the original population, many of the beetles were killed off. The resulting population that is left to reproduce has a different allele frequency. This is known as the bottleneck effect, and is a type of genetic drift. Allele frequency and phenotype frequency changes are random and are not due to selective pressures.

A population bottleneck occurred, altering the resulting allele frequencies.

Explanation:

A population bottleneck occurs when the size of a population is reduced by at least a generation. In this case, genetic drift acts more quickly to reduce genetic variation in small populations, but going through a "bottleneck" can greatly reduce variation, even if the bottleneck does not last for many generations. This effect called a bottleneck usually happens when a major disaster occurs in the population's habitat, changing the allelic frequencies and even the genetic variability of the population.

The population bottleneck can be seen in the question above, where after a forest fire, only 20 beetles remain in a population of beetles. 18 of them are green and 2 of them are brown.