Which type of selection increases the variation in a trait by favoring both extremes?

Study for the DAT Quantitative Reasoning Test with multiple choice questions and detailed explanations. Hone your skills and get ready for your exam!

Disruptive selection is a form of natural selection that acts on a trait by favoring individuals at both extremes of the trait’s distribution. In this process, individuals who exhibit characteristics at the extremes, whether high or low, have a higher chance of survival and reproduction compared to those with average traits. This differential survival leads to an increase in variation within the trait since it encourages the presence of both extremes in a population.

For example, consider a population of birds with beak sizes. If very small and very large beaked birds are better able to access food resources than those with intermediate beak sizes, over time, the population can become increasingly bimodal in distribution, with fewer individuals exhibiting average-sized beaks.

In contrast, stabilizing selection tends to reduce variation by favoring intermediate traits, while directional selection favors one extreme over the other, leading to a shift in the trait's average value. Balanced selection involves maintaining genetic diversity, which does not directly correspond to favoring extreme traits on both ends. Thus, the process described clearly aligns with the characteristics of disruptive selection.

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