1. Chapter 22: Descent with Modification: A Darwinian View of Life

2. Question? How did the diversity of life originate? Through the process of Evolution.

3. Evolution The processes that have transformed life on earth from its beginnings to today's diversity. Evolution is the most pervasive principle in biology.

4. Teaching Philosophy on Evolution

5. Evolution Has itself "evolved" or changed over time. Illustrates “Science as a Process”.

6. Pre-Darwinian Views 1. Greeks 2. Fixed Species 3. Catastophism 4. Hutton and Lyell 5. Lamarck

7. Greek Philosophers 1. Plato - Organisms are already perfectly adapted to their environments. 2. Aristotle - Organisms arranged on a “scale of life” from simple to complex.

8. Result No evolution. Life is already perfect and doesn’t need to change. All the rungs on life's "ladder" are already occupied.

9. Fixed Species Concept The creator had designed each and every species for a particular purpose.

10. Result No evolution. Created the viewpoint that all species could be identified and named (Taxonomy). A major factor in the Linnaeus classification system.

11. Catastrophism Georges Cuvier (1769- 1832). Attempted to relate fossils to current life.

12. Theory Fossils were the remains of species lost due to catastrophe. No new species originated; species could only be lost over time. Result - No evolution.

13. James Hutton 1795 - Gradualism Profound change is the cumulative product of slow, but continuous processes.

14. Result Changes on the earth were gradual, not catastrophic.

15. Charles Lyell 1797 - 1875. Incorporated Hutton’s gradualism into a theory called Uniformitarianism.

16. Uniformitarianism Geological processes have operated at the same rate over the Earth’s history.

18. Result The Earth must be VERY old. (much older than 6000 years of the fixed species concept). Idea that slow and subtle processes can cause substantial change.

19. Jean Baptiste Lamarck Published theory in 1809. Theory - Life changed from simple to complex over time.

20. Lamark Fossils were the remains of past life forms. Evolution did occur.

21. Mechanisms 1. Use and Disuse -  Body parts used to survive become larger and stronger.  Body parts not used to survive deteriorate.

22. Mechanisms 2. Acquired Characteristics  Modifications acquired by use/disuse were passed on to offspring.

23. Problem No knowledge of genetics. Acquired traits are not transmitted offspring.

24. Lamarck’s Credits Did suggest correctly the role of fossils in evolution. Did suggest that adaptation to the environment is a primary product of evolution.

25. Charles Darwin Father of the modern theory of evolution. Theory - Descent with Modification.

26. Darwin's Background Trained as a Naturalist (after trying religion and medicine).

27. Voyage of the Beagle

28. Result Darwin's training and travel opportunities allowed him to formulate and support his ideas on Natural Selection.

29. Galapagos Finches

31. http://www.galapagosislands.com/html/ wildlife_gallery.html Marine Iquana Tortise

32. Alfred Wallace - 1858 Paper on Natural Selection identical to Darwin's ideas.

33. Result - July 1, 1858 Dual presentation of the Wallace-Darwin ideas to the Linnaean Society of London.

34. Darwin - 1859 Publication of "The Origin of Species”

35. Comment Darwin best remembered for the theory because of his overwhelming evidence and because he published.

36. Darwinian View History of life is like a tree with branches over time from a common source. Current diversity of life is caused by the forks from common ancestors.

37. Example

38. “The Origin of Species” Documented the occurrence of evolution. Suggested that the mechanism for evolution was Natural Selection.

39. The Facts: Fact 1 - All species reproduce themselves exponentially. Fact 2 - Most populations are normally stable in size. Fact 3 - Natural Resources are limited (finite).

40. More Facts Fact 4 - No two individuals in a population are exactly alike. Fact 5 - Variation is inheritable.

41. Inference 1 The large number of offspring must compete for the finite resources. Result - Most offspring die.

42. Inference 2 Those individuals whose inherited characteristics fit them best to their environment survive and reproduce. Offspring inherit the favorable characteristics. Populations shift over time as the favorable characteristics accumulate.

43. Nature Determines which characteristics are favorable. Determines who survives. Result - “Natural Selection”

44. Natural Selection in action

45. Artificial Selection When man determines the characteristics that survive and reproduce. Result - the various breeds of animals and plants we’ve developed.

46. Ex - Mustard Plant Original Cultivars

48. Evolution Success Measured By Survival Reproduction Whoever lives long enough and has kids is the “winner” in evolution.

49. Requirements In order for Natural Selection to work, you must have:  Long periods of time.  Variations within a population.

50. Subtleties of Natural Selection 1. Populations are the units of Evolution. 2. Only inherited characteristics can evolve.

51. Comment Acquired characteristics may allow a species to evolve "outside" of Natural Selection. Ex: culture, learning

52. Additional Signs 1. Biogeography 2. Fossils 3. Taxonomy 4. Comparative Anatomy 5. Comparative Embryology 6. Molecular Biology

53. Biogeography The geographical distribution of species. Problem:  Species mixtures on islands  Marsupials in Australia

56. Evolution Viewpoint Biogeographical patterns reflect descent from the ancestors that colonized that area.

57. Fossils Relics or impressions of organisms from the past. Problem:  Show changes over time from simple to complex.  Many fossils don't have descendants.

58. Evolution Viewpoint Life has changed over time. Many species failed to survive and became extinct.

59. Comments 1. Fossilization is a rare event. 2. Only hard parts fossilize well. 3. Problem in finding fossils. 4. Interpretation. 5. Missing Links.

60. Taxonomy Science of Classification.

61. Main Categories Kingdom Phylum or Division Class Order Family Genus Species

62. Problem - Why can life be grouped this way? Evolution Viewpoint -Hierarchy reflects the branching genealogy of the tree of life.

63. Comparative Anatomy Problems 1. Homologous Structures - Common "building plan” with divergent functions. Mammal forelimbs

64. Comparative Anatomy Problems 2. Vestigial Organs - Rudimentary structures of marginal, if any, use. Whale Legs

65. Human Example

66. Evolution Viewpoint Remodeling of ancestral structures as their functions or adaptations changed.

67. Comparative Embryology Problem - closely related organisms go through similar stages in their embryonic development. Ex: Gill pouches in vertebrates

68. Evolution Viewpoint Ontogeny is a replay of Phylogeny. (Development reflects descent)

69. Molecular Biology Study of Evolution at the DNA or protein levels. Problem - related species have similar DNA sequences.

71. Evolution Viewpoint Related species share a common ancestrial DNA. The closer the relationship, the more similar the DNA sequences should be.

72. Summary Darwin's ideas now a "Theory”. Predictions of a Theory are tested by experiments and observations. Be familiar with the pre-Darwin views of evolution.

73. Summary Know Darwin’s “facts” and “inferences”. Be able to discuss the various evidences of Darwinian evolution.