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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. p 2 + 2pq + q 2 = 1
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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 p2 + 2pq + q2 = 1 Studies genetic (allelic frequencies)
H-W Assumptions: • Large population size. • Random mating. • No migration. • No mutations or mutational equilibrium.
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 • Geographic isolation – most common type • Adaptive radiation • 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.