BIOL 1104 Lecture Notes - Lecture 11: Directional Selection, Disruptive Selection, Stabilizing Selection
20 Apr 2020
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In a histogram you always have a continuous variable in x variable and in y variable you have a frequency or count. Because the environment can change, adaptive evolution is a continuous process. The beak size of medium ground finches on the galapagos islands fluctuates over time as the environment changes. Variation phenotypic + heritability ex: molecular method or mendelian + non random survival and reproduction finches: who survives and who doesn"t = evolution. Both case studies are examples of directional selection both mice and finches were examples of directional selection. Directional selection : you have 2 extremes/ distributions and one side of the distribution does better than the other (produce more surviving offspring) and this would cause a directional shift towards that side. It doesn"t mean bigger is better, it means the selection favours the extreme of that distribution . (modes of selection) But selection can affect phenotypic variation in different ways.
