In population genetics, directional selection, or positive selection is a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype.

What is an example of directional selection?

An example of directional selection is fossil records that show that the size of the black bears in Europe decreased during interglacial periods of the ice ages, but increased during each glacial period. Another example is the beak size in a population of finches.

What is meant by directional selection?

Directional selection occurs when individuals with traits on one side of the mean in their population survive better or reproduce more than those on the other.