Keystone Biology Practice Exam 2025 - Free Biology Exam Practice Questions and Study Guide

Disruptive selection is the correct answer because it specifically favors individuals at both extremes of a trait continuum rather than individuals with intermediate traits. In this type of selection, the environment favors two or more contrasting phenotypes within a population, which can lead to increased biodiversity and potentially the formation of new species over time.

For example, consider a species of birds where the individuals have varying beak sizes. If the environment provides food sources that are only accessible to birds with either very large or very small beaks, then those birds with intermediate-sized beaks may not thrive as well. As a result, over time, the population could evolve to have more individuals with either very large or very small beaks, illustrating how disruptive selection can shape the evolution of traits.

Direction selection, in contrast, favors individuals at one extreme of a trait, while stabilizing selection favors the average or intermediate traits, reducing variation. Sexual selection focuses on traits that improve mating success rather than survival. Therefore, the characteristics of disruptive selection emphasize the survival advantage and reproductive success of both extreme phenotypes within a trait continuum.