Stabilizing selection is a type of natural selection that favors the intermediate variants of a trait over extreme values. This means that individuals with traits that are close to the average are more likely to survive and reproduce than those with traits that are at either end of the spectrum.
Here are some key features of stabilizing selection:
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Reduction of Variation: Stabilizing selection tends to reduce genetic variation in a specific trait within a population. Over time, this can lead to a population that has a narrower range of traits.
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Common Examples: A classic example is human birth weight. Babies who are born at average weights have better survival rates compared to those who are underweight or overweight. Very small babies may be more likely to face health complications, while very large babies may have difficulties during birth.
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Adaptive Nature: Stabilizing selection often occurs in stable environments where extreme variations in traits do not provide a survival advantage. It is adaptive because it maintains traits that are well-suited to the environment.
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Comparisons with Other Selection Types: This form of selection can be contrasted with directional selection (which favors one extreme) and disruptive selection (which favors both extremes over intermediate traits).
Overall, stabilizing selection plays a crucial role in evolutionary biology by helping to conserve beneficial traits within a population while maintaining its overall stability.