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Mechanisms of Evolution

This article explores the definition of a species and mechanisms of evolution including natural selection, artificial selection, stabilizing selection, directional selection, disruptive selection, and sexual selection. It clarifies species interbreeding capabilities, illustrated with examples like dogs, horses, and mules. Furthermore, it discusses reproductive isolation, both prezygotic and postzygotic. The insights provided help comprehend how species differentiate and evolve through various evolutionary pressures and environmental influences.

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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

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