Question

When does directional selection occur?

Answer 1

Directional Selection:

1. Directional selection happens when a certain mutation or change in the actual phenotype is more suitable/adaptable to the environment.
2. Thus, the evolutionary advantage of a mutation causes its selection and is favored by natural selection.
3. This causes the mutational trait to become dominant over the pure trait and is hence passed on in the generations.
4. An example of directional selection was the mutation that led to the blackening of the moth, Biston betularia to form a new species called Biston carbonaria.
5. The original moth was white and easily identifiable by predators.
6. The mutated moth was black in colour with pepper-colored wings. As a result, it was able to camouflage with the bark of the trees and save itself from predators.
7. This allowed the survival of Biston carbonaria, and resulted in a directional selection of the trait while Biston betularia became extinct.