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3/22/12

3/22/12. Objective: Explain case studies of natural selection Warm-Up: What kind of evidence would you look for in order to determine that natural selection had occurred?. Natural selection. What is Natural Selection?.

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3/22/12

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  1. 3/22/12 • Objective: Explain case studies of natural selection • Warm-Up: What kind of evidence would you look for in order to determine that natural selection had occurred?

  2. Natural selection

  3. What is Natural Selection? • In a population of organisms, individuals who are best adapted to their environment will survive and reproduce more successfully than others • This leads to a change in a population over time • Traits that are advantageous—that help individuals survive in an environment—will become more common in a population over time

  4. Conditions for Natural Selection • There is variation in a population • Individuals are different from one another • Variation is heritable • Parents pass on traits to offspring • This variation causes some individuals to survive and reproduce better than others

  5. Your Task • You will be given data describing a population and a set of questions to answer • Tomorrow, your group will present its findings to the rest of the class • 10 pts, the group with the “most scientific” presentation will earn an additional 3 bonus pts • Your group will have to respond to questions from the audience • If no one asks any questions, then the group presenting will automatically receive the bonus points

  6. Your Task (continued) • There are different data sets, but the questions you are responsible for are similar for each set • Types of questions to ask presenters: • What evidence do you have for that claim? • What do those data mean? • How do you know that you’re right? • Questions that are irrelevant, rude, or disrespectful will cost you participation points. • The winner will be determined by a class vote. No one may vote for their own group.

  7. Sunflower Questions • Is this sunflower population experiencing natural selection? • What patterns are there in this data? • What factors, if any, affect the sunflower population? • What do you predict would happen to the sunflower population if more falcons were introduced into the meadow?

  8. Finch Questions • Is this finch population experiencing natural selection? • What patterns are there in this data? • What, if anything, affects finch beak size? • What do you predict would happen to the beak sizes if humans cut down many of the trees on the island?

  9. Guppy Questions • Is this guppy population experiencing natural selection? • What patterns are there in this data? • What, if anything, affects guppy body size? • What do you predict would happen to the guppy sizes if the pike were removed?

  10. Sunflower Seed Size, 2000-2005

  11. Sunflower Seed Size, 2006-2010

  12. Relationship between Parent Seed Size and Offspring Seed Size

  13. Finch Beak Sizes, 1996

  14. Finch Beak Sizes, 2006

  15. Relationship between Parent Beak Size and Offspring Beak Size

  16. Guppy Body Size, 2000

  17. Guppy Body Size, 2010

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