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Bell Curves

Bell Curves. Bell Curves. Parabolic shape—most organisms fall into the “medium” phenotype Shows frequency of a specific phenotype. Stabilizing Selection. “Goldie Locks” phenotype is selected for Extreme phenotypes do not survive. Directional Selection. One extreme phenotype is selected for

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Bell Curves

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  1. Bell Curves

  2. Bell Curves • Parabolic shape—most organisms fall into the “medium” phenotype • Shows frequency of a specific phenotype

  3. Stabilizing Selection • “Goldie Locks” phenotype is selected for • Extreme phenotypes do not survive

  4. Directional Selection • One extreme phenotype is selected for • Middle and other extreme are selected against

  5. Leaf mantid

  6. Disruptive Selection • BOTH extreme phenotypes are favored • Middle phenotype is selected against • Two-peaked curve • New species?

  7. African seedcracker finch Anolis lizard

  8. Sexual dimorphism • When the two sexes of the species look different • One sex will chose mates based on the phenotypes of the other sex

  9. Adaptations • A trait that is important for an organism to survive and/or reproduce • Can you think of any specific examples?

  10. Industrial melanism • Proof that actions of humans have impacts on their environment!

  11. Industrial melanism • Peppered moths were often light-colored pre-industrial revolution England. • Main habitat: light-barked trees covered with lichens (also light in color) • What kind of selection is • this?

  12. Enter the Industrial Revolution: Lots of factories, producing lots and lots of air pollution • Pollution kills lichens, covers trees in soot • Now which type is most fit for their environment?

  13. Now: More laws and sanctions against companies that pollute air and water • Less soot in the air, lichens grow back • Habitats are now lighter

  14. Some numbers

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