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Transcript
Today’s Objectives: 10/21/02 TSW be able to write the Hardy- Weinberg equation and explain it. TSW be able to list several evolutionary mechanisms. TSW be able to list several types of speciation and discuss the rates of evolution. Hardy-Weinberg Theorem 2 p 2 q + 2pq + = 1 Studies genetic (allelic frequencies) H-W Assumptions: Large population size. Random mating. No migration. No mutations or mutational equilibrium. Ways Evolution Can Occur Genetic Drift Neutral selection – caused allelic frequencies to change based on chance Founder effect Bottleneck effect Gene Flow Changes allelic frequencies because of migration of individuals. Mutation Random events. May be beneficial, harmful or insignificant. Natural Selection Definition Selection Pressure Types of Natural Selection Directional selection Industrial melanism in Biston betularia Disruptive selection Distinct subpopulations Stabilizing selection Keeps phenotypes stable for long periods of time. Speciation Reproductive isolation must be achieved! Types of Speciation Allopatric isolation – most common type Adaptive radiation Geographic Parapatric In small, local subpopulations (demes) Sympatric Almost always in plants In same population but do not interbreed Rates of Evolution Gradualism vs. Punctuated Equilibrium Mosaic Evolution Same structure is modified for multiple uses.