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  • http://www.youtube.com/watch?v=zj8istSAMoYhttp://www.youtube.com/watch?v=7l79rgG9bDk

Transcript

  • 1. Types of Natural Selection
  • 2. Think. Pair. Share. What are the driving factors for the evolution of a beetle from small and brown to larger, red, and spotted?
  • 3. Types of Natural Selection
  • 4. Types of Natural Selection
  • 5. Types of Natural Selection
  • 6. Types of Natural Selection
  • 7. Types of Natural Selection
  • 8. Types of Natural Selection
  • 9. Types of Natural Selection In some environments, a species may face one or many selective pressures.
  • 10. Types of Natural Selection A selective pressure may increase or decrease the survival and reproduction rate of certain traits. Weed killer is a selective pressure.
  • 11. Types of Natural Selection New population Why do they not die?
  • 12. Types of Natural Selection Evolution
  • 13. Types of Natural Selection Examples include climate, food availability, and predators.
  • 14. Types of Natural Selection There are 4 types of Natural Selection: 1) Directional Selection 2) Stabilizing Selection 3) Disruptive Selection 4) Sexual Selection
  • 15. Types of Natural Selection Suppose a certain mouse population has a range of fur colours, from light brown to dark brown.
  • 16. Directional Selection 1) Directional selection occurs when a selective pressure favours an extreme variation of a trait.
  • 17. Directional Selection For example, the surrounding woody environment may provide better camouflage for darker mice, thus most of the lighter colour mice may be easily hunted.
  • 18. Stabilizing Selection 2) Stabilizing selection occurs when a selective pressure favours the average phenotype.
  • 19. Stabilizing Selection For example, a new predator may only be able to see vivid colours (like white and dark brown), allowing the dull brown mouse to avoid detection and escape.
  • 20. Disruptive Selection 3) Disruptive selection favours extreme traits for survival while the average phenotype declines.
  • 21. Disruptive Selection For example, predators may not eat the vividly coloured mice in the area because the other white and dark brown creatures in the area are toxic.
  • 22. Sexual Selection 4) Sexual selection favours traits that increase the success for an organism to find a mate and reproduce.
  • 23. Sexual Selection Usually involves (female) mate choice or (male versus male) competition. Examples: Peacock Satyr tragopan (video) Bighorn rams (video)
  • 24. Sexual Selection Sexual Dimorphism is the difference of phenotypes between males and females of the same species. These are the traits often used in sexual selection. Examples include: - Colour - Height - Size of a particular feature (such as horns or tusks)
  • 25. Sexual Selection The satyr tragopan displays its blue horns and wattle to attract females.