Descent with Modification A Darwinian View of Life

1. Descent with Modification � A Darwinian View of Life Chapter 22 A.P. Biology Liberty Senior High School Rick L. Knowles

3. Theodosius Dobzhansky �Nothing in biology makes sense except in the light of evolution.� The American Biology Teacher (1973)

4. Overview: Darwin Introduces a Revolutionary Theory A new era of biology began on November 24, 1859 The day Charles Darwin published On the Origin of Species by Means of Natural Selection

5. Concept 22.1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species In order to understand why Darwin�s ideas were revolutionary We need to examine his views in the context of other Western ideas about Earth and its life

6. The historical context of Darwin�s life and ideas

7. The Scale of Nature and Classification of Species The Greek philosopher Aristotle Viewed species as fixed and unchanging The Old Testament of the Bible Holds that species were individually designed by God and therefore perfect �Intelligent Design�

8. Carolus Linnaeus Interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose Was a founder of taxonomy, classifying life�s diversity �for the greater glory of God� Viewed species similarities not as evolutionary relationship, but as patterns of creation.

9. Fossils, Cuvier, and Catastrophism The study of fossils Helped to lay the groundwork for Darwin�s ideas Fossils are remains or traces of organisms from the past Usually found in sedimentary rock, which appears in layers or strata

10. Paleontology, the study of fossils Was largely developed by French scientist Georges Cuvier Observed that upper strata were younger and lower strata were older Noticed that new species would appear in an older strata and then disappear in a newer strata. Cuvier opposed the idea of gradual evolutionary change And instead advocated catastrophism, speculating that each boundary between strata represents a catastrophe (flood or drought).

11. Theories of Gradualism Gradualism Is the idea that profound change can take place through the cumulative effect of slow but continuous processes. 1795, James Hutton proposed that Earth�s geologic features could be explained by gradual mechanisms currently operating (ex. valleys are created by rivers)

12. Geologists Hutton and Charles Lyell Perceived that changes in Earth�s surface can result from slow continuous actions still operating today Lyell proposed uniformitarianism � same geologic processes are operating today as in the past and at the same rate. Exerted a strong influence on Darwin�s thinking

13. One of the First �Ideas� of Evolution Lamarck compared species today with the fossil record. 1809, hypothesized that species evolve through use and disuse and the inheritance of acquired traits. Organisms have an innate drive to become more complex. But the mechanisms he proposed are unsupported by evidence

15. Darwin and the HMS Beagle During his travels Darwin observed and collected many specimens of South American plants and animals Darwin observed various adaptations of plants and animals That inhabited many diverse environments

17. Name Two (2) Observations that Darwin Made Leading to His Theory.Name One (1) Observation We�ve Since Made About the Natural World.

18. Darwin�s Observations about Evolution 1. Fossil Record: noticed that the fossils of South America resembled living species of that continent. Example: Glyptodon related to modern armadillo?

19. Glyptodon

20. Darwin�s Observations of Evolution 2. Biogeography � plants and animals in temperate regions of South America resemble tropical species in South America than the temperate species in Europe. The distribution of life across similar climates is not always the same; (climate alone is not causing diversity). Closely related species are found in same geographic region.

21. Different geographic regions, different mammalian �brands� Have evolved independently from different ancestors

22. Charles Darwin, 1835, Galapagos

23. What�s so special about a bunch of islands?National Geographic SeriesGalapagos, Tape #254

25. Darwin�s Finches

26. The Galapagos Archipelago

27. Bartoloma Island

28. Isabela Island

29. Darwin proposed that natural selection Could enable an ancestral species to �split� into two or more descendant species, resulting in a �tree of life�

31. Seen one tortoise, you�ve seen them all?

32. Galapagos Tortoise Distribution

33. Galapagos Tortoise-Env. Club 2008, Omaha Zoo

34. Darwin�s Focus on Adaptation Years later, Darwin reassessed all that he had observed during the voyage of the Beagle He began to perceive adaptation to the environment and the origin of new species as closely related processes

35. Alfred Russel Wallace, 1823-1913

39. Other Observations about Evolution 3. Artificial Selection - humans have modified other species over many generations by selecting and breeding individuals that possess desired traits

40. The Origin of Species articulated two main points� Descent with modification Natural selection

41. Natural Selection Darwin proposed natural selection As the mechanism for evolutionary adaptation of populations to their environments

42. Natural selection is the evolutionary process that occurs� When a population�s heritable variations are exposed to environmental factors that favor the reproductive success of some individuals over others.

43. The Origin of Species Darwin developed two main ideas Evolution explains life�s unity and diversity Natural selection is a cause of adaptive evolution The phrase descent with modification Summarized Darwin�s perception of the unity of life States that all organisms are related through descent from an ancestor that lived in the remote past

44. Elephant Phylogeny

45. Summary of Natural Selection Natural selection is differential success in reproduction That results from the interaction between individuals that vary in heritable traits and their environment If an environment changes over time Natural selection may result in adaptation to these new conditions

46. Over time natural selection can produce an increase In the adaptation of organisms to their environment

47. Concept 22.3: Darwin�s theory explains a wide range of observations Darwin�s theory of evolution Continues to be tested by how effectively it can account for additional observations and experimental outcomes Natural Selection in Action � Evolution continues today! Guppies HIV Humans

48. Differential Predation in Guppy Populations Researchers have observed natural selection Leading to adaptive evolution in guppy populations

50. The Evolution of Drug-Resistant HIV In humans, the use of drugs Selects for pathogens that through chance mutations are resistant to the drugs� effects Natural selection is a cause of adaptive evolution

51. Anatomy of HIV

52. Inside HIV

53. Researchers have developed numerous drugs to combat HIV But using these medications selects for viruses resistant to the drugs

54. New Evidence that Darwin Did Not Have How old did most 19th Century people believe the Earth was? About 6,000 years old (Cuvier�s young Earth) 1. Age of the Earth- 4.5 billion year old. Better dating techniques than in Darwin�s time; more complete fossil record.

55. 2. Transitional Species Have intermediate characteristics of two groups of animals � may represent a link in evolution (missing link?). Changes in structures may be small � difficult to identify in fossils. Species replaced quickly � not common in fossil record.

56. Archaeopteryx (150 million years ago)

57. Archaeopteryx

58. Archaeopteryx at the KU Natural History Museum

59. Evolution Happens in Small Steps Show me the frogs! Discover- Weird Nature: Marvelous Motion, tape #55

60. Other Transitional Examples?

61. A Walking Whale?

62. Transitional Skulls

63. Rodhocetus Foot

64. Transitional Diatoms in Yellowstone

65. 3. Vestigial Structures Existing structures that have no apparent function, but resemble structures of presumed ancestors. Examples: human appendix; muscle set in humans for moving ears;

66. The �Pelvis� of a Whale

67. Evidence of Transitional Species Today! Vestigial Structure- blue whales with femurs? Life of Mammals-Return to the Water video, tape #110

68. Vestigial Organs in Humans? Structures of little or no use but may represent historical remnants of structures that had important functions in ancestors.

69. Vermiform Appendix

70. Goosebumps?

71. Vomeronasal or Jacobson�s Organ

72. �Junk�DNA; L-gulonolactone oxidase gene

73. Extra Ear Muscles � auriculares muscles

74. Plantaris Muscle � 9% don�t have it

75. Wisdom Teeth � mandible becoming smaller

76. Third Eyelid � Plica semilunaris

77. Darwin�s (Auricular) Tubercle � only 10.4% have it.

78. Coccyx

79. Four-Finned Dolphin; Oct, 2006

80. Four-Finned Dolphin; Oct, 2006

81. Show me more vestigial structures! Do snakes have �feet�? The story of boas and pythons.

82. 4. Anatomical Homologies Homologous structures between organisms Are anatomical resemblances that represent variations on a structural theme that was present in a common ancestor

83. Homology Homologous Structures � structures in different species that are similar because of commons ancestry.

84. Sophie and a Mosasaur

85. Analogous Structures � similarity in structures due to adaptations from similar evolutionary pressures (convergent evolution) and not a common ancestor. Analogy

86. The products of natural selection Are often exquisite adaptations of organisms to the special circumstances of their way of life and their environment

87. 5. Comparative Embryology Reveals additional anatomical homologies not visible in adult organisms

88. Show me an example of homologous structures! Compare a human hand and bat wing. Life of Mammals- Life in the Trees video, tape #110

89. 6. Molecular Homologies Biologists observe homologies among organisms at the molecular level Genes and proteins that are shared among organisms inherited from a common ancestor.

90. Darwin�s Theory of Evolution Natural selection is the driving force of changes within species populations.

91. Can we see evolution? Weiner, J. 1994. The Beak of the Finch. Knopf, New York. The video �What Darwin Never Saw�

92. I want to see evolution in action! Scientific American Frontiers-Voyage to the Galapagos, 2000, VT 551.4 SCI