Chapter 22 Descent with Modification: A Darwinian View of Life

1. Chapter 22Descent 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. Theory Hypothesis supported repeatedly by data Makes testable predictions theory Layman’s and TV use of the word Confused with hypothesis in Science Theory vs theory

5. Examples of Theory • Cell Theory • Big Bang Theory • Atomic Theory • Theory of Gravity • Theory of Evolution

6. Teaching Philosophy on Evolution as a Theory

7. Evolution • Has itself "evolved" or changed over time. • Illustrates “Science as a Process”. • Students should be able to give the main points of several views.

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

9. 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.

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

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

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

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

14. 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.

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

16. Result • Changes on the earth were gradual, not catastrophic.

17. 1797 - 1875. Incorporated Hutton’s gradualism into a theory called Uniformitarianism. Charles Lyell

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

20. 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.

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

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

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

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

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

26. 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.

27. Thomas Malthus • Essay on human population growth in 1798. • Disease, famine, homelessness, and war are inescapable because human populations grow faster than food supplies. • Darwin read Malthus.

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

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

30. Voyage of the Beagle

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

32. Galapagos Finches

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

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

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

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

37. 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.

39. Example

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

41. Observations: Observation 1 – Members of a population often vary greatly in their traits. .

42. Observation 2 • Traits are inherited from parents to offspring.

43. All species are capable of producing more offspring than their environment can support. Observation 3

44. Observation 4 • Owing to lack of food or other resources, many of these offspring do not survive.

45. Inference 1 • Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals.

46. Inference 2 • This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations.

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

48. Natural Selection in action

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

50. Original Cultivars Ex - Mustard Plant