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Unformatted text preview: Lecture 3 Natural Selection and Evolution A. Normal Distribution- It picks on your phenotype- If you look at any characteristic, you can come up with a normal distribution (bell-shaped curve) Could be physical (height), biochemical (missing an enzyme), behavior B. Stabilizing Selection (fig. 19.4)- The averag e phenotypes have the b est chance of surviving a nd reproducing, and bot extre m e would b e select ed a g ainst (wheth er du e to m ut ation or reco m bination du e t sexual reproduction) (check pegs not es)- Means no chang e in the species (such a s roaches, sharks)- Want to keep the av erag e ph enotype bec aus e you fit the e nvironm ent very well- C. Disruptive Selection (fig. 19.4)- Both extremes are favored and the average is selected against- Darwins finches (beaks) on the Galapagos island and there was no competition. The original beak was medium-sized, but some were different and could eat bugs or seed Because there was no competition they all survived. Because there is so many of theBecause there was no competition they all survived....
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