Which type of natural selection acts against extreme phenotypes?

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Stabilizing selection is the type of natural selection that acts against extreme phenotypes, favoring the average or intermediate traits within a population. This form of selection typically occurs in stable environments where certain traits provide a survival advantage over extremes. For instance, consider a scenario involving a species of birds with varying beak sizes; those with very small or very large beaks may struggle to access food efficiently, while those with medium-sized beaks are better suited to a wider variety of food sources. By favoring the individuals that possess these average traits, stabilizing selection reduces the occurrence of extreme variations, leading to a decrease in genetic diversity for those specific traits over time. This mechanism helps maintain the status quo in a population, ensuring the survival of well-adapted individuals while limiting the representation of less favorable adaptations.