Question

Natural selection that favors the one extreme in the range of variation for a phenotype is called:

Answer 1

This type of natural selection is referred to as directional selection. In this type of natural selection, either one phenotype is preferred or the other; therefore, there is no equilibrium between the populations of the phenotypes that are present.
Examples of organisms that have undergone directional selection are black bears during the ice ages, African chichlid and sockey salmon.

Answer 2

Disruptive selection is a type of natural selection that selects against the average individual in a population. This selection select types with specific advantages.
Directional selection favors a single phenotype at one of the ends of the variations (extremes) and stabilizing selection favors an average phenotype with no extreme variations.
So, natural selection that favors the one extreme in the range of variation for a phenotype is called directional selection.