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Mechanisms of Evolution

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  1. Mechanisms of Evolution

  2. Species • What is a species? A species is defined as a group of organism that can interbreed and create fertile offspring. Are a Dotson and a Chiwawa the same species? What about a wolf and a Chiwawa? A zebra and a horse? A Mule and a Donkey?

  3. Other Mechanisms • Artificial selection • Humans choosing traits we want and selectively breeding them into a species • Natural Selection (modern) • Stabilizing Selection • Eliminates Extreme expressions of a trait when the average leads to higher “fitness” • Example: Human Birth Weight

  4. Directional Selection Extreme selection favored. • Example: Peppered Moth

  5. More Mechanisms • Disruptive Selection • Splits populations into 2 groups, removing average.

  6. Sexual Selection • Exists when males and females differ greatly • Example - Peacocks

  7. Reproductive Isolation • Prezygotic Isolation • Pre Fertilization • Geographical, ecological, behavioral • Eastern/Western Meadowlarks • Orchids • PostzygoticIsolation • After Fertilization • Prevent survival or infertility • Mule, Liger, Zorse