Which type of selection occurs when individuals at both extremes of a trait distribution are favored?

Disruptive selection is a type of natural selection that favors individuals at both extremes of a trait distribution while selecting against those with intermediate traits. This process occurs in environments where the extremes confer a survival advantage, leading to a greater probability of these traits being passed on to successive generations. For example, in a hypothetical situation involving a species of bird that feeds on seeds, if very large and very small beaks are advantageous for accessing different types of seeds while those with medium-sized beaks are less efficient at feeding, then the population may evolve toward these two extremes over time. This can result in increased diversity within the population as it may split into two distinct phenotypes adapted to different niches in the environment.

In contrast, directional selection favors individuals at one extreme of a trait distribution, leading to a shift in the population toward that particular trait. Stabilizing selection promotes the intermediate form of a trait, reducing variation and favoring average individuals. Balancing selection maintains multiple phenotypes within a population, generally in fluctuating environments, without strongly favoring one over the others. Therefore, the correct identification of disruptive selection highlights its unique role in promoting extremes and enhancing diversity within a population.