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The Evidence for Evolution

The Evidence for Evolution. Darwin’s Voyage – BBC 2009. http://www.sciencechannel.com/tv-shows/greatest-discoveries/videos/evolution.htm. Evidence for Evolution. Types of evidence Darwin used to support his theory: 1. Biogeography 2. Homologous and Analogous features

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The Evidence for Evolution

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  1. The Evidence for Evolution

  2. Darwin’s Voyage – BBC 2009 • http://www.sciencechannel.com/tv-shows/greatest-discoveries/videos/evolution.htm

  3. Evidence for Evolution • Types of evidence Darwin used to support his theory: • 1. Biogeography • 2. Homologous and Analogous features • 3. Vestigial features • 4. Competition within populations

  4. 1. Biogeography + Darwin’s Observations

  5. Reptiles, Birds, but No Mammals or Amphibians?

  6. Key Observation from Galapagos Islands

  7. Testing Darwin’s Hypotheses:Hawaiian Islands

  8. Testing Darwin’s Hypotheses • When non-native mammals and amphibians introduced to islands, they have been able to thrive. This eliminates the possibility that they can’t survive on remote islands. Dodo Bird Extinction within 175 years – Mauritius Islands (Indian Ocean)

  9. 2. Homologous Features • Structures with common evolutionary features which serve different functions in modern species . Example of Divergent Evolution • Video on homology: http://www.youtube.com/watch?v=XgXT9sU6y18&feature=related http://www.xspore.com/community/drama/6876-evolution-vs-religion-4.html

  10. Homology: Similar structures for different functions

  11. How many bones in the Human Neck?

  12. How many bones in a Giraffe’s neck?

  13. Embryological Homology

  14. 2. Analogous Features • Structures that perform same function in two species but are not similar in origin or anatomy Convergent Evolution

  15. Analogous: Same function, different structure

  16. 3. Vestigial Features • Features that no longer serve the function they do in similar species http://paxarcana.wordpress.com/2009/08/25/your-appendix-may-actually-do-something/ http://www.youtube.com/watch?v=lBkiT0zyYm0 http://rebeccamcc.blogspot.com/

  17. 4. Competition Within Populations • Thomas Malthus (Principle of Population) showed that all population are limited in size by the environment (food supply) Darwin’s thoughts: • All species produce more offspring than can survive to reproduce • This results in competition for resources between members of the same species • Environment might be favouring certain individuals

  18. Evidence of Natural Selection • J.W. Tutt hypothesized that light-colored moths declined because of predation • Light moths were easily seen by birds on darkened (sooty) trees

  19. http://www.techapps.net/interactives/peppermoths.htm

  20. Evidence of Natural Selection • Bernard Kettlewell tested the hypothesis • Dark tree trunks = more dark-colored moths survived • Light tree trunks = more light-colored moths survived • When environmental conditions reverse, so does selection pressure

  21. Evidence of Natural Selection • Industrial melanism: phenomenon in which darker individuals come to predominate over lighter ones • Pollution controlresulted in lichen growing on trees and bark color being lighter again • Light-colored peppered moths now are dominant in the population

  22. Evidence of Natural Selection • The agent of selection may be difficult to pin down • Could poisoning by pollution be the agent of natural selection? Selection against melanism

  23. Homework  • Page 303 # 1,2,4-7

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