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Bell Work 3/2/12 . Write the green part today. Study the population of dots below. What do you think might have happened?. Have flash cards out Compare pg.121. Before. After. Theory of Natural Selection. British naturalist Lived February, 12 1809 –April 19, 1882

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bell work 3 2 12
Bell Work 3/2/12

Write the green part today.

  • Study the population of dots below. What do you think might have happened?
  • Have flash cards out
  • Compare pg.121



theory of natural selection
Theory of Natural Selection
  • British naturalist
  • Lived February, 12 1809 –April 19, 1882
  • Traveled around the world for 5 years on the HMS Beagle

Charles Darwin

how s it work
How’s it work?
  • There is competition in living things
    • More are born than survive and reproduce
  • Reproduction has genetic variation
how s it work1
How’s it work?
  • Selection determines which organisms will become adults.
    • This selection is done by the environment
    • The organisms that are best suited for the environment reproduce and pass on traits to offspring (kids).
    • They pass these well suited characteristics on to their young
how s it work2
How’s it work?
  • REPRODUCTION is the key, not merely survival.
  • If you survive to be 128 but have no kids, you are not doing as well as someone else who has reproduced.
  • Assuming the traits that made the second person

successful will help his children, then he is more “fit” NOW than the 128 year old guy.

how s it work3
How’s it work?
  • The traits that help an organism survive in a particular environment are “selected” for in natural selection.
  • The traits that make it more likely that an organism will not survive are “selected” against in natural selection.
how s it work4
How’s it work?
  • Over time, natural selection results in changes in the inherited characteristics of a population.
  • These changes increase a species fitness (survival rate)
summary of darwin s theory
Summary of Darwin’s Theory

1. Populations have variations.

2. Some variations are favorable.

3. Organisms produce more offspring than survive.

4. Organisms with advantages survive to pass those advantages to their children

5. A population will change over time.