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III. A Closer Look at Natural Selection

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Presentation on theme: "III. A Closer Look at Natural Selection"— Presentation transcript:

1 III. A Closer Look at Natural Selection
A. Natural selection, adaptation, and evolution B. Patterns of natural selection 1. Directional selection 2. Stabilizing selection 3. Diversifying selection C. Effects of selection on the distribution of phenotypes

2 Non-random mating affects the frequency of genotypes in a
population, but does not change allele frequency Positive assortative mating Negative assortative mating AA aa aa aa X X All offspring heterozygous All offspring homozygous

3 Biston betularia - the peppered moth
Dark morph on sooty tree Each morph on the “wrong” tree Grey moth on lichen

4 Industrial Melanism in the peppered moth
Released in rural woodland grey melanic # released # recaptured % recaptured Released in industrial region # released # recaptured % recaptured

5 Fig


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