1. Darwinian Evolution Ch. 16 1

2. Darwin’s Achievement  Darwin’s Theory of Evolution is one of the greatest intellectual achievements in history of science.  Why? And how did he do it? That is the topic of this presentation. 2

3. Brief Darwin (1809 – 1882)  Darwin’s ideas formed the basis for modern evolutionary theory.  Poor student, he was a challenge for his father.  In l831, when Darwin was only 22 he signed on as the ship’s naturalist aboard the Beagle on a 5-year expedition around the world.  Darwin studied and collected many different and usual specimens which contributed to his theory. 3

4. Darwin’s Voyage to the Galapagos Islands  Some of Darwin’s most important observations were made on the Galapagos Islands.  The islands are near the equator, 1000km off the west coast of South America. 4

5. More Animals of the Galapagos Islands: 5 Blue Footed Boobies in the Galapagos

6. Assumptions at that time:  Species are fixed (do not change)  Aristotle’s Scala naturae-He believed that species were fixed creations that never changed and they were arranged from least complex to most complex-worms on the bottom and man on the top.  Earth is only a few thousand years old..6

7. Darwin’s Revolutionary Ideas: On the Origin of Species published 1859 1)Species change (they are not fixed) 2)Species changed or evolved from common ancestry over time (implying a much older Earth) 3)Natural Selection is the mechanism for change 7

8. Why species change?  Darwin observes organisms with slight differences or variations or variations  Ex: Galápagos finches with different beaks 8

9. Why Common Ancestry?  Darwin also finds fossils of organisms unlike any that live today.  Ex: giant sloth in Argentina (modern armadillos and sloths related, but MUCH smaller) 9

10. There are many Common Ancestry Implications noted by Darwin: 10

11. Why Earth had to be older than 6,000 years?  He read geology papers (Lyell’s work showed growing evidence for gradual change of landforms)  Found evidence of long extinct habitats (fossil sea shells in Andes Mountains) 11

12. How does change happen?  Ideas for selection started with interviewing pigeon breeders  artificial selection in animals and animals and plants plants 12

13. What about in nature?  What force “selects” which organisms reproduce? The Environment  What does the environment include?  Influenced by Malthus (economist) writing about competition for scarce resources.  If organisms must compete for survival, the survivors would reproduce more. 13

14. Darwin’s Natural Selection 1)Overproduction-Organisms produce more offspring than can survive because of competition for resources. 2)Variety within a population or species 3)Selection-having a particular trait can make individuals more or less likely to survive and produce offspring 4) Adaptation–over time, the traits that aid survival and reproduction become common 14

15. Darwin’s Natural Selection Summary:  Given: Too many organisms + scarce resources = fierce competition  Given: Individuals have heritable variations 15

16. Darwin’s Natural Selection  Conclusion: Individuals with beneficial variations out- reproduce others  Conclusion: Over many generations, many in the population have beneficial trait 16

17. Does natural selection occur now?  Goal – study a model organism with fast life cycle  How about bacteria? 17

18. Bacterial Evolution  Resistance to antibiotic medicines  First wide use of antibiotic penicillin in 1940s  Open books to p. 484 to figure 12 18

19. Darwin vs. Lamarck Darwinian evolution  Genetic variation  Individuals with beneficial variations reproduce more  Population evolves, NOT individuals Lamarckian evolution  Individuals change traits by use and disuse  Individuals pass acquired changes throughout life to offspring  Individuals evolve because they “want” change 19

20. Lamark’s Theory 20 “ Use and Disuse” 1.Use of structure results in Evolution 2.Does not take into account DNA or sex cell Mutations

21. Did Evolution occur in history?  Yes … transitional fossil evidence  Archaeopteryx – reptile / bird 21

22. Transitional Fossils  Tiktaalik – fish / amphibian 22

23. Homologous Structures  Homo = ?  Same evolutionary history  Different functions in different environments 23

24. Homologous DNA Most powerful evidence for a common ancestor 24

25. Homologous Development 25

26. Homologous Cell Processes  Respiration / photosynthesis pathways are similar processes in most species  Mitosis process is the same in all eukaryotes 26

27. Vestigial structures-lost over time “use it or lose it” 27

28. Vestigial Structures “use it or lose it” 28

29.  Ambulocetus natans in action. A reconstruction of an early close cousin of whales. 29 See Page 382 for Whale Evolution

30. Adaptations: Camouflage 30

31. Adaptations: Mimicry 31 Owl butterfly We think this mimicry has evolved so that potential predators, such as fish, learn more quickly that red spots are a sign that the animal has large glands of distasteful chemicals in their mantle.

32. Vestiges and Selection  Natural selection not only changes populations over time…  Selection also preserves crucial traits needed for survival  Example: The Wolf’s sense of smell. 32

33. Misconceptions  Evolution does not just add complexity, it can take it away as well  Great example: tapeworm-lacks many organ systems 33

34. Imperfections in Humans  Evolution does not “finish” with a “perfect trait”  Eye photoreceptor setup and blind spots blind spotsblind spots incoming light 34

35. Complex Changes-How?  How does random mutation lead to complex changes?  The icefish below is able to withstand the Anarctic freeze. How? 35

36. Evolution of Complexity  Organisms often “borrow” from pre existing, successful genes, which are adapted for new purposes.  Example: Icefish antifreeze protein is closely related to fish trypsinogen protein already produced by the fish. The antifreeze protein is simply modified from typsinogen. 36

37. Patterns of Evolution  Populations are not isolated, and often evolve in response to each other  Coevolution – two species are competing to “one up” each other with adaptations 37

38. Coevolution 38

39. Divergent Convergent evolutionevolution Also called Adaptive Radiation common ancestor new organisms different ancestries some similar organisms develop in similar environments in different parts of the world 39 See Page 383, Figure 8

40. Adaptive Radiation Special case of divergent evolution - when many niches are available 40

41. Patterns of Evolution  Gradualism vs. punctuated equilibrium Slow, even changeLong periods of no change with bursts of rapid change 41

42. The End 42