1. Evidence of Evolution
Chapter 11

2. 11.1 Impacts/Issues Reflections of a Distant Past
Events of the ancient past can be explained by the same physical, chemical, and biological processes that operate in today’s world

3. From Evidence to Inference
Scientists infer from evidence such as the K-T boundary layer that an asteroid impact near the Yucatán 65 million years ago caused the mass extinction of dinosaurs
Mass extinction
Simultaneous loss of many lineages from Earth

4. From Evidence to Inference
Barringer crater, Arizona

5. Video: Measuring time

6. Video: ABC News: Asteroid menace

7. Video: ABC News: Creation vs. evolution

8. 11.2 Early Beliefs, Confusing Discoveries
By the 19th century, naturalists were returning from globe-spanning survey expeditions with increasingly detailed observations of nature
Naturalist
Person who observes life from a scientific perspective

9. Pioneers of Biogeography
Late 1800s: Alfred Wallace and other naturalists observed patterns in where species live, how they might be related, and how natural forces might shape life
Biogeography
Study of patterns in the geographic distribution of species and communities

10. Biogeography
Wallace thought similarities in birds on different continents might indicate a common ancestor

11. Biogeography
Some plants that lived in similar climates on different continents had similar features, but were not closely related

12. Comparative Morphology
Naturalists studying body plans were confused by vestigial body parts with no apparent function
Comparative morphology
Scientific study of body plans and structures among groups of organisms

13. Vestigial Body Parts

14. coccyx leg bones Figure 11.3
Vestigial body parts. (A) Pythons and boa constrictors have tiny leg bones, but snakes do not walk. (B) We humans use our legs, but not our coccyx (tail) bones.
leg bones
Fig. 11-3, p. 198

15. Geology
Identical rock layers in different parts of the world, sequences of similar fossils, and fossils of giant animals with no living representatives also puzzled early naturalists

16. Confusing Discoveries
Taken as a whole, findings from biogeography, comparative morphology, and geology did not fit with prevailing beliefs of the 19th century
Increasingly extensive observations of nature led to new ways of thinking about the natural world

17. Animation: Comparative pelvic anatomy

18. 11.3 A Flurry of New Theories
Nineteenth-century naturalists tried to explain the accumulating evidence of evolution
Georges Cuvier proposed that catastrophic geologic forces unlike those of the present day shaped Earth’s surface (catastrophism)
Jean-Baptiste Lamarck proposed that changes in an animal over its lifetime were inherited

19. Evolution
Naturalists suspected that environmental factors affected affect a species’ traits over time, causing changes in a line of descent
Evolution
Change in a line of descent (in a line from an ancestor)

20. Voyage of the Beagle
1831: Charles Darwin set out as a naturalist on a five-year voyage aboard the Beagle
He found many unusual fossils and observed animals living in many different environments

21. Darwin and the Voyage of the Beagle

22. Lyell’s Theory of Uniformity
Darwin was influenced by Charles Lyell’s Principles of Geology, which set forth the theory of uniformity – in contrast to catastrophism
Theory of uniformity
Idea that gradual repetitive processes occurring over long time spans shaped Earth’s surface

23. Shared Traits
Darwin collected fossils of extinct glyptodons, which shared traits with modern armadillos

24. Limited Resources Thomas Malthus observed that:
A population tends to grow until it begins to exhaust environmental resources—food, shelter from predators, etc
When resources become scarce, individuals must compete for them
Darwin applied these ideas to the species he had observed on his voyage

25. Fitness
Darwin realized that in any population, some individuals have traits that make them better suited to the environment than others, and therefore more likely to survive and reproduce
Fitness
The degree of adaptation to an environment, as measured by an individual’s relative genetic contribution to future generations

26. Adaptation
Adaptive traits that impart greater fitness to an individual become more common in a population over generations, compared with less competitive forms
Adaptation (adaptive trait)
A heritable trait that enhances an individual’s fitness

27. Natural Selection
Darwin concluded that the process of natural selection, through variations in fitness and adaptation, is a driving force of evolution
Natural selection
Differential survival and reproduction of individuals of a population that vary in the details of shared, heritable traits

28. Great Minds Think Alike
Alfred Wallace, the “father of biogeography”, proposed the theory of natural selection in 1858, at the same time as Darwin
Darwin published On the Origin of Species the following year, in which he described descent with modification, or evolution

29. Alfred Wallace
The codiscoverer of natural selection

30. Principles of Natural Selection

31. Animation: The Galapagos Islands

32. 11.4 About Fossils
Fossils
Physical evidence of organisms from the past
Hard fossils include mineralized bones, teeth, shells, spores and other hard body parts
Trace fossils include footprints, nests, trails, feces and other evidence of activities

33. Process of Fossilization
Layers of sediment cover an organism or its traces – pressure and mineralization change remains to rock
Younger fossils usually occur in more recently deposited layers of sedimentary rock, on top of older fossils in older layers

34. The Fossil Record
Fossils are relatively scarce, so the fossil record will always be incomplete
The fossil record helps us reconstruct the lineage of some species, such as whales
Lineage
Line of descent from a common ancestor

35. Fossil Links Ancient Artiodactyl to Modern Whale Lineage

36. Figure 11.7
New links in the ancient lineage of whales. With their artiodactyl-like ankle bones, Rodhocetus and Dorudon were probably offshoots of the ancient artiodactyl-to-modern-whale lineage as it transitioned back to life in water. Modern cetaceans do not have even a remnant of an ankle bone.
A A 30-million-year-old fossil of Elomeryx. This small terrestrial mammal was a member of the same artiodactyl group that gave rise to hippopotamuses, pigs, deer, sheep, cows, and whales.
Fig. 11-7a, p. 202

37. Figure 11.7
New links in the ancient lineage of whales. With their artiodactyl-like ankle bones, Rodhocetus and Dorudon were probably offshoots of the ancient artiodactyl-to-modern-whale lineage as it transitioned back to life in water. Modern cetaceans do not have even a remnant of an ankle bone.
Fig. 11-7b, p. 202

38. B Rodhocetus, an ancient whale, lived about 47 million years ago
B Rodhocetus, an ancient whale, lived about 47 million years ago. Its distinctive ankle bones point to
a close evolutionary connection to artiodactyls. Inset: compare a Rodhocetus ankle bone (left) with that of a modern artiodactyl, a pronghorn antelope (right).
Figure 11.7
New links in the ancient lineage of whales. With their artiodactyl-like ankle bones, Rodhocetus and Dorudon were probably offshoots of the ancient artiodactyl-to-modern-whale lineage as it transitioned back to life in water. Modern cetaceans do not have even a remnant of an ankle bone.
Fig. 11-7b, p. 202

39. Figure 11.7
New links in the ancient lineage of whales. With their artiodactyl-like ankle bones, Rodhocetus and Dorudon were probably offshoots of the ancient artiodactyl-to-modern-whale lineage as it transitioned back to life in water. Modern cetaceans do not have even a remnant of an ankle bone.
Fig. 11-7b (1), p. 202

40. Figure 11.7
New links in the ancient lineage of whales. With their artiodactyl-like ankle bones, Rodhocetus and Dorudon were probably offshoots of the ancient artiodactyl-to-modern-whale lineage as it transitioned back to life in water. Modern cetaceans do not have even a remnant of an ankle bone.
Fig. 11-7b (2), p. 202

41. Figure 11.7
New links in the ancient lineage of whales. With their artiodactyl-like ankle bones, Rodhocetus and Dorudon were probably offshoots of the ancient artiodactyl-to-modern-whale lineage as it transitioned back to life in water. Modern cetaceans do not have even a remnant of an ankle bone.
Fig. 11-7b (3), p. 202

42. Figure 11.7
New links in the ancient lineage of whales. With their artiodactyl-like ankle bones, Rodhocetus and Dorudon were probably offshoots of the ancient artiodactyl-to-modern-whale lineage as it transitioned back to life in water. Modern cetaceans do not have even a remnant of an ankle bone.
Fig. 11-7c, p. 202

43. Figure 11.7
New links in the ancient lineage of whales. With their artiodactyl-like ankle bones, Rodhocetus and Dorudon were probably offshoots of the ancient artiodactyl-to-modern-whale lineage as it transitioned back to life in water. Modern cetaceans do not have even a remnant of an ankle bone.
C Dorudonatrox, an ancient whale that lived about 37 million years ago. Its artiodactyl-like ankle bones (left) were much too small to have supported the weight of its huge body on land, so this mammal had to be fully aquatic.
Fig. 11-7c, p. 202

44. Figure 11.7
New links in the ancient lineage of whales. With their artiodactyl-like ankle bones, Rodhocetus and Dorudon were probably offshoots of the ancient artiodactyl-to-modern-whale lineage as it transitioned back to life in water. Modern cetaceans do not have even a remnant of an ankle bone.
Fig. 11-7c (1), p. 202

45. Figure 11.7
New links in the ancient lineage of whales. With their artiodactyl-like ankle bones, Rodhocetus and Dorudon were probably offshoots of the ancient artiodactyl-to-modern-whale lineage as it transitioned back to life in water. Modern cetaceans do not have even a remnant of an ankle bone.
Fig. 11-7c (2), p. 202

46. Figure 11.7
New links in the ancient lineage of whales. With their artiodactyl-like ankle bones, Rodhocetus and Dorudon were probably offshoots of the ancient artiodactyl-to-modern-whale lineage as it transitioned back to life in water. Modern cetaceans do not have even a remnant of an ankle bone.
Fig. 11-7c (3), p. 202

47. Radiometric Dating
The age of rocks and fossils can be determined using radiometric dating
Half-life
Characteristic time it takes for half of a quantity of a radioisotope to decay into daughter elements
Radiometric dating
Estimates age of a rock or fossil by measuring the ratio of a radioisotope and daughter elements

48. Half-Life and Radiometric Dating

49. Animation: Radioisotope decay

50. Animation: Radiometric dating

51. 11.5 Putting Time Into Perspective
Transitions in the fossil record, found in characteristic layers of sedimentary rock, became boundaries for great intervals of the geologic time scale
Geologic time scale
Chronology of Earth history
Correlates with evolutionary events

52. The Geologic Time Scale

53. The Geologic Time Scale

54. Animation: Geologic time scale

55. Drifting Continents, Changing Seas
Theory of continental drift
Earth’s continents were once part of a single supercontinent that split up and drifted apart
Explains how the same types of fossils can occur on both sides of an ocean
Pangea
Supercontinent that formed about 237 million years ago and broke up about 152 million year ago

56. Plate Tectonics: A Mechanism of Continental Drift
Theory of plate tectonics
Earth’s outer layer of rock is cracked into plates
Slow movement rafts continents to new positions over geologic time
Where plates spread apart, molten rock wells up from deep inside the Earth and solidifies
Where plates collide, one slides under the other and is destroyed

57. Plate Tectonics

58. trench hot spot ridge 4 trench rift 1 2 3 Figure 11.10
Plate tectonics. Huge pieces of Earth’s outer layer of rock slowly drift apart and collide. As the plates move, they raft continents around the globe. (1) At oceanic ridges, huge plumes of molten rock welling up from Earth’s interior drive the movement of tectonic plates. New crust spreads outward as it forms on the surface, forcing adjacent tectonic plates away from the ridge and into trenches elsewhere. (2) At trenches, the advancing edge of one plate plows under an adjacent plate and buckles it. (3) Faults are ruptures in Earth’s crust where plates meet. Plates move apart at rifts. The aerial photo in (B) shows about 4.2 kilometers (2.6 miles) of the San Andreas Fault, which extends 1,300 km (800 miles) through California. This fault is a boundary between two tectonic plates slipping by one another. (4) Plumes of molten rock rupture a tectonic plate at what are called “hot spots.” The Hawaiian Islands have been forming this way.
Fig a, p. 206

59. Gondwana
Certain fossils of ferns and reptiles that predate Pangea are found in similar rock layers in Africa, India, South America, and Australia – evidence of an even earlier supercontinent
Gondwana
Supercontinent that formed more than 500 million years ago

60. Gondwana and Pangea

61. A 420 mya B 237 mya C 152 mya D 65.5 mya E 14 mya
Figure 11.11: Animated!
A series of reconstructions of the drifting continents. (A) The supercontinent Gondwana (yellow) had begun to break up by the Silurian. (B) The supercontinent Pangea formed during the Triassic, then (C) began to break up in the Jurassic. (D) K–T boundary. (E) The continents reached their modern configuration in the Miocene.
Fig , p. 207

62. Animation: Continental drift

63. Impacts on Evolution
Evidence suggests that supercontinents have formed and broken up at least five times
The resulting changes in the Earth’s surface, atmosphere, waters and climates have had profound impacts on evolution

64. Animation: Plate margins

65. Animation: Five major extinctions

66. Animation: Geologic forces

67. Video: ABC News: Indonesian earthquake

68. 11.6 Similarities in Body Form and Function
Similarities in structure of body parts are often evidence of a common ancestor
Homologous structures
Similar body parts that reflect shared ancestry
May be used for different purposes in different groups, but the same genes direct their development

69. Morphological Divergence
A body part that appears very different in appearance may be quite similar in underlying aspects of form – evidence of shared ancestry
Morphological divergence
Evolutionary pattern in which a body part of an ancestor changes in its descendants (homologous structures)

70. Morphological Divergence Among Vertebrate Forelimbs

71. pterosaur chicken penguin stem reptile porpoise bat human elephant
Figure 11.12
Morphological divergence among vertebrate forelimbs, starting with the bones of a stem reptile. The number and position of many skeletal elements were preserved when these diverse forms evolved; notice the bones of the forearms. Certain bones were lost over time in some of the lineages (compare the digits numbered 1 through 5). The drawings are not to the same scale.
bat
human
elephant
Fig , p. 208

72. Morphological Convergence
Some body parts look alike in different lineages, but did not evolve in a common ancestor
Analogous structures
Similar structures that evolved separately in different lineages
Morphological convergence
Evolutionary pattern in which similar body parts evolve separately in different lineage

73. Morphological Convergence

74. Figure 11.13
Morphological convergence. The flight surfaces of a bat wing (A), a bird wing (B), and an insect wing (C) are analogous structures. (D) The independent evolution of wings in the three separate lineages that led to bats, birds, and insects. You will read more about diagrams that show evolutionary relationships in Section 12.7.
Fig a, p. 209

75. Figure 11.13
Morphological convergence. The flight surfaces of a bat wing (A), a bird wing (B), and an insect wing (C) are analogous structures. (D) The independent evolution of wings in the three separate lineages that led to bats, birds, and insects. You will read more about diagrams that show evolutionary relationships in Section 12.7.
Fig b, p. 209

76. Figure 11.13
Morphological convergence. The flight surfaces of a bat wing (A), a bird wing (B), and an insect wing (C) are analogous structures. (D) The independent evolution of wings in the three separate lineages that led to bats, birds, and insects. You will read more about diagrams that show evolutionary relationships in Section 12.7.
Fig c, p. 209

77. Figure 11.13
Morphological convergence. The flight surfaces of a bat wing (A), a bird wing (B), and an insect wing (C) are analogous structures. (D) The independent evolution of wings in the three separate lineages that led to bats, birds, and insects. You will read more about diagrams that show evolutionary relationships in Section 12.7.
Fig d, p. 209

78. Insects Bats Humans Crocodiles Birds wings wings wings
Figure 11.13
Morphological convergence. The flight surfaces of a bat wing (A), a bird wing (B), and an insect wing (C) are analogous structures. (D) The independent evolution of wings in the three separate lineages that led to bats, birds, and insects. You will read more about diagrams that show evolutionary relationships in Section 12.7.
limbs with 5 digits
Fig d, p. 209

79. Comparative Embryology
Embryos of related species tend to develop in similar ways
Similarities in patterns of embryonic development are the result of master genes (homeotic genes) that have been conserved over evolutionary time

80. Comparative Embryology

81. Figure 11.14
Comparative embryology. All vertebrates go through an embryonic stage in which they have four limb buds and a tail. From top to bottom: human, mouse, bat, chicken, and alligator embryos.
Fig a, p. 210

82. Figure 11.14
Comparative embryology. All vertebrates go through an embryonic stage in which they have four limb buds and a tail. From top to bottom: human, mouse, bat, chicken, and alligator embryos.
Fig b, p. 210

83. Figure 11.14
Comparative embryology. All vertebrates go through an embryonic stage in which they have four limb buds and a tail. From top to bottom: human, mouse, bat, chicken, and alligator embryos.
Fig c, p. 210

84. Figure 11.14
Comparative embryology. All vertebrates go through an embryonic stage in which they have four limb buds and a tail. From top to bottom: human, mouse, bat, chicken, and alligator embryos.
Fig d, p. 210

85. Figure 11.14
Comparative embryology. All vertebrates go through an embryonic stage in which they have four limb buds and a tail. From top to bottom: human, mouse, bat, chicken, and alligator embryos.
Fig e, p. 210

86. Animation: Morphological divergence

87. Animation: Mutation and proportional changes

88. 11.7 Biochemical Similarities
Each lineage has unique characters that are a mixture of ancestral and novel traits, including biochemical features such as the nucleotide sequence of DNA
We can discover and clarify evolutionary relationships through comparisons of nucleic acid and protein sequences

89. Mutations and Speciation
Genes for essential proteins (such as cytochrome b) are highly conserved across diverse species
Neutral mutations tend to accumulate in DNA at a predictable rate
Lineages that diverged recently have more nucleotide or amino acid sequences in common than ones that diverged long ago

90. Comparing Amino Acids in Cytochrome b

91. Animation: Cytochrome C comparison

92. 11.8 Impacts/Issues Revisited
The K-T boundary layer (formed 65 million years ago at a time of mass extinction) is made up of clay rich in iridium – rare on Earth but common in asteroids

93. Digging Into Data: Abundance of Iridium in the K-T Boundary Layer