Which term describes natural selection that selects against the average individuals in a population?

The term that describes natural selection selecting against the average individuals in a population is indeed disruptive selection. This type of selection operates when extreme phenotypes are favored over intermediate ones, leading to a gradual increase in the diversity of traits within a population. In disruptive selection, individuals at both extremes of the phenotype spectrum have a fitness advantage, while those with average traits face selection pressures that reduce their survival and reproductive success.

Disruptive selection often occurs in heterogeneous environments where the average trait does not confer the best advantage. For example, in a population of birds with diverse beak sizes, some birds with very small beaks might be better suited to access small seeds, while those with very large beaks might excel at cracking larger seeds. The average-sized beaks, which may be less efficient at either task, are therefore less favored.

In contrast, stabilizing selection would favor average individuals and reduce variation, while directional selection would favor one extreme phenotype over another, shifting the population's traits in one direction. Sexual selection relates specifically to mate choice and does not focus on the survival of individuals based on their traits as directly as the other forms of selection. This distinction highlights why disruptive selection is the correct choice in this scenario.