Question

A series of forest fires burned through the valleys, and most of the established population of butterflies were destroyed. The butterflies had been mostly cream colored with black spots. Some members of the population were cream colored with brown spots. After a few years, the population had returned to its previous level, but now most of the butterflies are cream with brown spots.

A. Gene Flow
B. Genetic Drift

Answer 1

The change in butterfly population from mostly cream with black spots to cream with brown spots after a forest fire is an example of Genetic Drift, a random event causing a shift in allele frequency within a population. This illustrates how a species' response to environmental changes, such as predator behavior, can affect natural selection and lead to evolutionary changes.

Step-by-step explanation:

The situation described suggests that the change in the butterfly population is due to Genetic Drift rather than Gene Flow. Genetic Drift happens due to random events that reduce the genetic variation within a population, in this case, a forest fire that destroyed most of the cream-colored butterflies with black spots, leaving those with brown spots to reproduce.

Such stochastic events can cause certain alleles to become more or less common in the population purely by chance. The butterfly population data support the concept that a species' response to the environment can influence natural selection. Predators, like the yellow buntings, show different responses based on the appearance of their prey, which can confer a selective advantage or disadvantage to the butterflies, potentially affecting their survival and, consequently, the frequency of their traits in the population over time. This reflects directional selection, emphasizing how species interactions can shape the evolution of traits within a population.