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Tuesday, October 27 2009

Tuesday, October 27 2009. Pre-test Discussion of writing assignment & student questions Video Activity on the reading. Biological evolution: Overview. Darwin and his theory Diversity of life Mendel and genetics Human evolution Societal implications. Image from Wikipedia.

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Tuesday, October 27 2009

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  1. Tuesday, October 27 2009 • Pre-test • Discussion of writing assignment & student questions • Video • Activity on the reading

  2. Biological evolution: Overview • Darwin and his theory • Diversity of life • Mendel and genetics • Human evolution • Societal implications Image from Wikipedia Author: Jose Braga Source :National Human Genome Research Institution

  3. Source: Stefan Laube Source: Derek Ramsey Emerald boa, one of many tropical snakes. A tree sloth, who spends most of each day hanging as you see here. Image from US Fish & Wildlife Service Jaguar Source: Richard Bartz A colorful butterfly.

  4. Why is it important to understand evolutionary theory? • It changed the way humans viewed their place in the universe (philosophical) • It is an rich example of the changing nature of scientific knowledge • It has enormous predictive power and is supported by an large body of evidence (it is consistent with data) • It is the force that explains the diversity of life on earth, allowing us to make sense of the biological world • It has major implications for human welfare (microbial resistance)

  5. Writing assignment on podcast • What were the main points that Elliott Sober made about the development of Darwin’s idea? • What was surprising to you? • What questions did you have about evolution?

  6. Student questions • Fell into roughly four main categories: • Questions about the science • Questions about the cultural context • Questions about human evolution • Questions about science and religion

  7. Student questions • In groups, identify 2-3 questions on the list that are interesting to your group • Be prepared to share: • Why you found the question interesting • Summary of discussion and possible answers • What is the nature of the evidence required to answer the question? • How you might go about finding out more? • What are the scientific certainties and uncertainties?

  8. How do we know evolution happens? Video clip from PBS program, Evolution • http://www.pbs.org/wgbh/evolution/library/11/2/e_s_1.html Video clip from Evolution: Darwin’s Dangerous Idea • http://www.pbs.org/wgbh/evolution/library/01/1/l_011_20.html

  9. Scientific theory Video clip from AMNH on theories http://www.amnh.org/exhibitions/darwin/evolution/theory.php Video clip from PBS’s Evolution, “Is evolution just a theory?” http://www.pbs.org/wgbh/evolution/library/11/2/e_s_1.html

  10. Evolution is a theory that unites many areas of research: Classification Behavior Morphology Physiology Genetics Biogeography Paleontology

  11. Evolutionary relationships and the diversity of life • How do we classify life on Earth? • How do we determine the patterns of relatedness between species? • What evidence is used to determine these patterns? • Where do we see uncertainty in the data?

  12. Common ancestor of birds and dinosaurs Common ancestor of humans and dinosaurs

  13. offspring parents Consider four butterflies connected to their parents

  14. future Individuals past Population

  15. Population Lineage/ Species What happened here? Lineage-branching Speciation Phylogeny

  16. Most speciation (the production of new species) is due to geographical barriers

  17. Representation of phylogenies A B C A B C A simplified representation The True History

  18. When reading a phylogeny: 1) It is tree-like, not ladder like 2) There is no “advancement”

  19. 3) For any speciation event on a phylogeny, the choice of which lineage goes left and which goes right is arbitrary:

  20. Humans didn’t evolve from chimps, they share a common ancestor that was neither chimp nor human

  21. Relatedness = How recent is the common ancestry • You are more closely related to your first cousins than to your second cousins because you share a more recent common ancestor • grandparents vs. great-grandparents • You are more closely related to a chimpanzee than to a worm because you share a more recent common ancestor ≈ 6 Million years ago vs. ≈ 600 Mill. years ago

  22. Fish Newt Lizard Mouse Human Is a newt more closely related to a fish or a human?

  23. Why might you go wrong?If you look “along” the top Fish Newt Lizard Mouse Human Is a newt more closely related to a fish or a human?

  24. Human Fish Newt Lizard Mouse • But this is not how evolution happened • All these species are alive today: A living fish is not an ancestor of a newt • The order “along the top” can change without changing the content of the tree

  25. Which of the following is different? A B C D E A B D E C A B D E C A B E D C A B C D

  26. Why are phylogenies useful? • They provide the basis for biological classification • They allow us to infer the evolutionary history of traits (when, where, and why they evolved)

  27. Suggests one change from yellow to red How can we use a tree to make inferences about character evolution? Parsimony: pick the mapping that involves fewest changes

  28. By parsimony, where did flower color change? D B E C A

  29. Sometimes more than one change must have taken place Suggests that red-flower in the two groups are not really the “same” or homologous

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