Evolutionary Origins: Descent with Modification

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

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

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

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

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

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

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

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

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

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. Original Cultivars Ex - Mustard Plant

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.