BIO120H1 Lecture Notes - Lecture 19: Disruptive Selection, Stabilizing Selection, Directional Selection
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BIO120H1 Full Course Notes
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Orchid from madagascar w/ long floral tube pollinated by night-flying moth w/ exceptionally long proboscis: darwin predicted existence of moth w/ proboscis long enough to get to the nectar, a century later it was discovered. Fitness: relative genetic contribution of individuals to next generation as a result of differences in viability and fertility (= darwinian fitness) Selection by humans: has a purpose or goal, natural selection, all organisms. Selection by abiotic & biotic environment: no purpose or goal; simply a blind mechanistic process w/ no foresight, blind, mechanistic process that will always occur in organisms in an environment. Stabilizing selection: mean is the fittest type but variants change, over time distribution shrinks, directional selection. Individuals at one end of distribution are most fit. Individuals in middle are middle: over time, distribution shifts, disruptive selection. Seed abundance decreases, population fell, so selection favoured beak size: beak size changed in directional fashion, over time, different populations will become adapted to different resources.
