Bio1_22_EvolutionII - 1 2 3 4 1 2 5 6 7 8 9 10 1 2...

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1 Self-Quiz 3. Describe a population in equilibrium. Compare it to an evolving population. 4. Where does pesticide resistance in an insect originate? 5. When is genetic drift likely? Why? Overview • Ch. 16: How Populations Evolve – Natural selection •Change phenotype frequencies •Sexual selection – Maintaining genetic diversity • Ch. 17: Speciation – What is a species? – Reproductive isolation – Modes of speciation Natural Selection • If variant trait survival, members with trait in the population, affecting future populations – Overproduction b Competition – Survival & reproduction b Inheritance • A population is evolving when heritable traits are changing through successive generations Natural Selection • Stabilizing selection • Directional selection • Disruptive selection Stabilizing Selection • Both extreme phenotypes are selected against • Intermediate phenotype favored, distribution narrows Directional Selection • An extreme phenotype is selected against • Distribution curve shifts towards favorable extreme Disruptive Selection • Intermediate phenotype is selected against • Extreme phenotypes favored Assignment 1 • Think, Pair, Share • Topic: Does the graph below of human birth weights represent directional, stabilizing, or disruptive selection? Assignment 2
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Bio1_22_EvolutionII - 1 2 3 4 1 2 5 6 7 8 9 10 1 2...

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