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FIGURE 7.9 Types of Selection-Stabilizing, Directional, and Disruptive
The bell-shaped curve represents the distribution of a character in a population. The shading indicates where in that variation selection acts to eliminate individuals. (a) In stabilizing selection, extremes are eliminated, leading to a narrowing of the variation. (b) In directional selection, one extreme is eliminated, shifting the curve. (c) In disruptive selection, individuals with intermediate variation are eliminated, producing two bell-shaped curves at the extremes.