Disruptive selection occurs when:

Disruptive selection occurs when both extremes of a trait are favored over intermediate phenotypes within a population. This means individuals with traits at either end of the spectrum have a higher reproductive success compared to those with average traits. In environments where resources or conditions favor traits that are markedly different from the norm, such as those that may benefit from specialized adaptations, disruptive selection can lead to increased diversity within a population.

For instance, consider a situation where a population of birds has varying beak sizes. If very large and very small beaks are more advantageous for accessing food resources than medium-sized beaks, birds with the extreme trait values will thrive more effectively, leading to disruptive selection. This kind of selection can eventually contribute to speciation, as populations may diverge from their original form over time.