Which type of natural selection operates when environmental pressure favors intermediate phenotypic variants, eliminating individuals with extreme traits and narrowing the phenotypic bell curve?
Answer and explanation
Correct answer: B. Stabilizing selection
- Step 1: Natural selection affects population curves in three distinct ways: stabilizing, directional, or disruptive.
- Step 2: In stabilizing selection, the mean phenotype is favored while both phenotypic extremes are culled (e.g., human birth weight, where very low and very high birth weights have higher mortality).
- Step 3: Over generations, the peak of the bell curve becomes taller and narrower with reduced variance.
Answer
Stabilizing selection.
Why not the others: Directional selection shifts the peak toward one phenotypic extreme; Disruptive selection favors both extremes simultaneously, forming two distinct peaks; Sexual selection is selection based on mate choice and competition.
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