Ohio Assessment for Educators (OAE) Integrated Science (024) Practice Exam

What is disruptive selection?

1. Selection favoring extreme phenotypes

2. Selection favoring intermediate phenotypes

3. Selection with no effect on traits

4. Selection causing extinction

The correct answer is: Selection favoring extreme phenotypes

Disruptive selection is characterized by the phenomenon where selection favors extreme phenotypes over intermediate phenotypes within a population. This form of natural selection drives the divergence of traits, as those individuals exhibiting the most pronounced traits on either end of the phenotypic spectrum have a higher fitness compared to those with average traits. As a result, disruptive selection can lead to increased variability in a population and can promote the emergence of two distinct groups over time. For instance, in a population of birds that primarily feed on seeds, if there are two extreme seed sizes—small and large—the birds with beaks that can specialize in either small or large seeds may have a survival advantage compared to those with beaks that are intermediate in size, which may not be as efficient in either feeding niche. This selection process can eventually lead to speciation, where new species arise from the population as the extremes become more favored. The other choices describe different forms of selection or effects that do not accurately represent disruptive selection. For example, favoring intermediate phenotypes is characteristic of stabilizing selection, while having no effect on traits does not signify a form of selection at all. Similarly, selection causing extinction would imply negative selection that drives a species to become extinct, which differs from the