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The Evolution of Galapagos Finches: A Tale of Survival and Change

Explore the fascinating story of Galapagos finches' evolution as documented by researchers. Witness natural selection in action as finch populations adapt to changing environmental conditions over time. Discover the impact of fluctuating rainfall on these iconic birds.

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The Evolution of Galapagos Finches: A Tale of Survival and Change

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  1. Epilogue • A few years later, 1359mm of rain fell on the Islands: • The finches went crazy — the finch population increased by 400%! • Lisle Gibbs, a graduate student of the Grants, was there and she measured every finch carefully.

  2. Epilogue continued… • When Gibbs returned to Princeton and analyzed his data, he was stunned: • Natural selection had reversed course. • Large finches were dying: • Small seeds were everywhere, but it took too many of them to satiate a large finch with a beak built for big seeds. • Small finches were reproducing like crazy.

  3. CQ10: If small birds are selected against in one year and selected for in another, is evolution still taking place? A: Yes. B: No. C: Maybe. D: I don’t know.

  4. Epilogue continued… • The cycles weren’t over yet: • A year after the heavy rains, 53mm of rain fell. • The year after that, the grand total: 4mm. • Galapagos weather patterns are cyclical. • Let’s look at the finches over a longer time scale…

  5. The graphs on this and the following slides are details from Figure 1 in "Unpredictable Evolution in a 30-Year Study of Darwin's Finches” by Peter R. Grant and B. Rosemary Grant, Science, 26 April 2002, vol. 296, no. 5568, pp. 707–711. Used with permission from AAAS.

  6. CQ11: How has the average body size of these finches changed 1973-2001? A: They are much larger. B: They are a little larger. C: They didn’t change. D: They are a little smaller. E: They are a lot smaller.

  7. CQ12: How has the average beak size of these finches changed? A: They are much larger. B: They are a little larger. C: They didn’t change. D: They are a little smaller. E: They are a lot smaller.

  8. CQ13: How has the beak shape changed? A: They are a lot more pointed. B: They are a little more pointed. C: They didn’t change. D: They are a little more blunt. E: They are a lot more blunt.

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