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Natural Selection

Natural Selection. and Evolution!. Why two types of clover?. What advantages does the striped clover have? The plain? How does cyanide help/hurt these plants in different habitats?. Organisms have variation. Same species ( Trifolium repens ), different characteristics

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Natural Selection

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  1. Natural Selection • and Evolution!

  2. Why two types of clover? • What advantages does the striped clover have? The plain? • How does cyanide help/hurt these plants in different habitats?

  3. Organisms have variation • Same species (Trifolium repens), different characteristics • Variation = differences among individuals of one species; different forms of same trait (ex: eye colors)

  4. Variation helps organisms adapt • Adaptation = inherited characteristic, increases an organism’s chance for survival • Fitness = ability of an individual to survive and reproduce in its environment • Which clover is more “fit?” Why?

  5. Variation allows for Selection • Humans and nature “choose” which organisms win and get to procreate • Artificial selection = human select most useful variations, allow those to reproduce • ex: race horses - what trait would be selected for? • ex: broccoli and other veggie friends

  6. The struggle for existence • Resources are limited, so only some can survive • Natural Selection = individuals better adapted to their environment survive, reproduce, and pass on their genes • AKA “survival of the fittest” • leads to change over time (EVOLUTION!)

  7. Natural Selection - Ex: Darwin’s Finches Beak size and shape vary - all descended from common ancestor but changed over time

  8. Evolution by Natural Selection • Descent with modification = over time, natural selection produces organisms with differences from their ancestors • Different food sources, habitats, body parts, behaviors • Implies that living things are all related, have a common ancestor (common descent)

  9. Common Descent - one ancestor in the past Phylogenetic tree - distance between organisms is directly related to differences in genes (short distance = few differences, long = many)

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