Chapter 8: Evolution and Natural Selection

1. Chapter 8: Evolution and Natural Selection Darwin’s dangerous idea: evolution by natural selection Lectures by Mark Manteuffel, St. Louis Community College ; Clicker Questions by Kristen Curran, University of Wisconsin-Whitewater

3. Evolution in Action We can see evolution occur right before us.

4. Could you breed fruit flies who could live longer than 20 hours on average?

6. When these eggs hatch, do you think the flies in this new generation will live longer than 20 hours without food?

7. A population of fruit flies was starved until 80% of the flies were dead. The remaining flies were fed and offspring were produced.

9. After 60 generations the average starvation resistance of fruit flies was 160 hours They are genetically identical to the original population. They are genetically different from the original population.

10. What happened? • Evolution • Natural selection

11. Experiments in Evolution Dogs? Rabbits?

12. Evolution • How does evolution occur? • What types of changes can evolution cause in a population? • Five primary lines of evidence • Evolution by natural selection

13. It is indeed remarkable that this theory [evolution] has been progressively accepted by researchers, following a series of discoveries in various fields of knowledge. The convergence, neither sought nor fabricated, of the results of work that was conducted independently is in itself a significant argument in favor of this theory. —Pope John Paul II, 1996

14. Natural Changes • The characteristics of individuals in a population can change over time. • We can observe such change in nature and can even cause such change to occur.

18. Darwin’s Journey to an Idea A job on a ’round-the-world survey ship allowed Darwin to indulge and advance his love of nature.

19. A job on a ‘round-the-world survey ship allowed Darwin to indulge and advance his love of nature. • Age 16, University of Edinburgh, medical studies • Studied theology at Cambridge University • His real love: study of nature

20. Darwin’s Journey to an Idea Before Darwin, most people believed that all species had been created separately and were unchanging.

23. Jean-Baptiste Lamarck • Biologist, early 1800s • Living species might change over time. • If we need to jump higher we will learn to jump higher.

24. Charles Lyell & James Hutton • Geologist • 1830 book Principles of Geology • Geological forces had shaped the earth and were continuing to do so. • Gradual but constant change • Darwin had this book with him on the Beagle

25. Emerging Beliefs • People used to think that the earth was 6,000 years old and that species were unchanging. • In the 18th and 19th centuries, scientists began to change their beliefs. • These changes helped shape Darwin’s thinking.

27. Darwin’s 5-year Journey http://www.nhm.ac.uk/nature-online/science-of-natural-history/expeditions-collecting/beagle-voyage/

28. Different Influences on Darwin’s Ideas Observing geographic similarities and differences among fossils and living plants and animals, Darwin developed a theory of evolution.

30. Two important and unexpected patterns:1. Things that look alike are not the same species.

31. 1. Things that look alike are not the same species. • 13 Different Finch Species

32. 2. the fossils of extinct species and the living species in that same area resemble each other. • Glyptodonts and armadillos

33. 2. the fossils of extinct species and the living species in that same area resemble each other. • If no giants exist today, then living things must change.

34. Darwin’s Fossils The slides were made by slicing and polishing the fossils into translucent sheets and then placing them between two glass plates so they could be studied under a microscope.

35. Darwin’s Fossils

36. Darwin’s Fossils These images were made available by the Royal Holloway, University of London on Jan. 17, 2012 . and were collected by Charles Darwin during the course of his famous "Voyage of the Beagle." (University of London, Kevin D'SouzaHo,AP Photo/Royal Holloway)

37. Thomas Malthus • Economist • Essay on the Principle of Population • - populations can grow much faster than the food supply. We will eat ourselves out of existence in the foreseeable future.

38. The Book that Would “Rock the World” • 1842 first draft • 14 years in a drawer

39. Darwin’s Journey to an Idea In 1858, Darwin published his thoughts on natural selection after decades of percolating and procrastinating

41. Historical Progress • After putting off publishing his thoughts on natural selection for more than 15 years, Darwin did so only after Alfred Russel Wallace independently came up with the same idea. • They published a joint presentation on their ideas in 1858 and Darwin published a much more detailed treatment in The Origin of Species in 1859, sparking wide debate and discussion of natural selection.

42. the observations Darwin made during his trip on the HMS Beagle? The earth is shaped by gradual forces. (Lyell) The earth is older than 6,000 years. (Buffon) Populations could grow beyond the ability of the environment to support them. (Malthus) Malthus thesis was that the population of England would soon reach a point that was impossible to feed with the island’s resources.

44. Allele frequencies in a population change. Four mechanisms can give rise to evolution.

46. Allele Frequencies Increase the white phenotype through breeding. As the generations go by - Higher proportion of white tigers Evolution = change in allele frequencies of the population

47. Individuals do NOT evolve. Populations evolve – get better with the resources they have Allele frequencies – dark colored moths on dark tree trunks

48. 4 Mechanisms of Evolutionary Change Mutation Genetic drift Migration Natural selection Evolution is genetic change in a population.

49. 1. Mutation—a direct change in the DNA of an individual—the ultimate source of all genetic variation. Four mechanisms of evolutionary Change

50. Mutation An alteration of the base-pair sequence of an individual’s DNA When this alteration occurs in a gene, the change in the DNA sequence may change the allele.