1. Introduction to Darwinian Evolution
Chapter 18

2. Learning Objective 1
What is evolution?

3. Evolution
Accumulation of inherited changes within a population over time
Unifying concept of biology
links all fields of life sciences into a unified body of knowledge

4. Learning Objective 2
Discuss the historical development of the theory of evolution

5. Jean Baptiste de Lamarck
Proposed that organisms
change over time by natural phenomena, not divine intervention
had vital force that changed them toward greater complexity over time
could pass traits acquired during lifetime to offspring

6. Charles Darwin Theory of evolution
Based on observations during voyage of HMS Beagle
Found similarities between organisms
on arid Galápagos Islands
on humid South American mainland

7. Voyage of HMS Beagle

8. Darwin Influenced by artificial selection
variety of domesticated plants and animals
Applied Thomas Malthus’s ideas
on human populations to natural populations
Influenced by geologists (Charles Lyell)
idea that Earth was extremely old

9. Genetic Variation
Artificial selection
Natural Variation

10. KEY CONCEPTS
Ideas about evolution originated long before Darwin’s time

11. Learning Objective 3
What are the four premises of evolution by natural selection as proposed by Charles Darwin?

12. 4 Premises of Evolution by Natural Selection
1. Genetic variation
exists among individuals in population
2. Reproductive ability of each species
causes populations to geometrically increase over time

13. 4 Premises of Evolution 3. Organisms compete with one another
for resources: food, living space, water, light
4. Offspring with most favorable characteristics
most likely to survive and reproduce
pass genetic characteristics to next generation

14. Natural Selection Results in adaptations Over time
evolutionary modifications
improve chances of survival and reproductive success in a particular environment
Over time
accumulated changes in geographically separated populations produce new species

15. KEY CONCEPTS
Darwin’s voyage on the Beagle provided the basis for his theory of evolution by natural selection

16. Galapagos Finches

17. Fig. 18-4a, p. 395 Figure 18.4: Three species of Galápagos finches.
Darwin inferred that these birds are derived from a common ancestral population of seed-eating birds from South America. Variation in their beaks is the result of adaptation to different kinds of food.
Fig. 18-4a, p. 395

18. Fig. 18-4b, p. 395 Figure 18.4: Three species of Galápagos finches.
Darwin inferred that these birds are derived from a common ancestral population of seed-eating birds from South America. Variation in their beaks is the result of adaptation to different kinds of food.
Fig. 18-4b, p. 395

19. Fig. 18-4c, p. 395 Figure 18.4: Three species of Galápagos finches.
Darwin inferred that these birds are derived from a common ancestral population of seed-eating birds from South America. Variation in their beaks is the result of adaptation to different kinds of food.
Fig. 18-4c, p. 395

20. Animation: The Galapagos Islands
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21. KEY CONCEPTS
Natural selection occurs because individuals with traits that make them better adapted to local conditions are more likely to survive and produce offspring than are individuals that are not as well adapted

22. Learning Objective 4
What is the difference between the modern synthesis and Darwin’s original theory of evolution?

23. Modern Synthesis Or synthetic theory of evolution Explains
combines Darwin’s theory of evolution by natural selection with modern genetics
Explains
why individuals in a population vary
how species adapt to their environment

24. Mutation Provides genetic variability
that natural selection acts on during evolution

25. KEY CONCEPTS
The modern synthesis combines Darwin’s theory with genetics

26. Learning Objective 5
What evidence for evolution can be obtained from the fossil record?

27. Fossil Record Fossils remains or traces of ancient organisms
provide direct evidence of evolution

28. Fossil Record Sedimentary rock Index fossils Radioisotopes
layers occur in sequence of deposition
recent layers on top of older ones
Index fossils
characterize specific layer
Radioisotopes
in rock accurately measure rock’s age

29. Sedimentary Rock

30. Fossils

31. Whale Evolution

32. Figure 18.8: Fossil intermediates in whale evolution.
Figures are not drawn to scale. (a–d: Adapted with permission from D. J. Futuyma, Science on Trial: The Case for Evolution, Fig. 2, pp. 260–61, Sinauer Associates, Sunderland, MA, 1995.)
Mesonychid
Fig. 18-8a, p. 399

33. Ambulocetus natans Fig. 18-8b, p. 399
Figure 18.8: Fossil intermediates in whale evolution.
Figures are not drawn to scale. (a–d: Adapted with permission from D. J. Futuyma, Science on Trial: The Case for Evolution, Fig. 2, pp. 260–61, Sinauer Associates, Sunderland, MA, 1995.)
Ambulocetus natans
Fig. 18-8b, p. 399

34. Figure 18.8: Fossil intermediates in whale evolution.
Figures are not drawn to scale. (a–d: Adapted with permission from D. J. Futuyma, Science on Trial: The Case for Evolution, Fig. 2, pp. 260–61, Sinauer Associates, Sunderland, MA, 1995.)
Rodhocetus
Fig. 18-8c, p. 399

35. Figure 18.8: Fossil intermediates in whale evolution.
Figures are not drawn to scale. (a–d: Adapted with permission from D. J. Futuyma, Science on Trial: The Case for Evolution, Fig. 2, pp. 260–61, Sinauer Associates, Sunderland, MA, 1995.)
Basilosaurus
Fig. 18-8d, p. 399

36. Figure 18.8: Fossil intermediates in whale evolution.
Figures are not drawn to scale. (a–d: Adapted with permission from D. J. Futuyma, Science on Trial: The Case for Evolution, Fig. 2, pp. 260–61, Sinauer Associates, Sunderland, MA, 1995.)
Balaenoptera
Fig. 18-8e, p. 399

37. Radioisotope Decay

38. Learning Objective 6
What evidence for evolution is derived from comparative anatomy?

39. Homologous Features Basic structural similarities
structures may be used in different ways
Derived from same structure
in common ancestor
Indicate organism’s evolutionary affinities

40. Homology in Animals

41. HUMAN CAT WHALE BAT Humerus Radius Ulna Humerus Carpal Radius 5 Ulna 4
Metacarpal
Ulna 4
Carpal 1
Radius
Ulna 1 5
Figure 18.10: Homology in animals.
The human arm, cat forelimb, whale flipper, and bat wing have a basic underlying similarity of structure because they are derived from a common ancestor. The five digits are numbered in each drawing.
Carpal
Metacarpal 1 3 2
Phalanges 4 1 2 2 3 4
Phalanges 5 3 5 2 4 3
Fig , p. 401

42. HUMAN CAT WHALE BAT Humerus Radius Ulna Carpal 5 4 1 3 2 Phalanges
Metacarpal
Figure 18.10: Homology in animals.
The human arm, cat forelimb, whale flipper, and bat wing have a basic underlying similarity of structure because they are derived from a common ancestor. The five digits are numbered in each drawing.
Stepped Art
Fig , p. 401

43. Homology in Plants

44. Spine Fig. 18-11a, p. 401 Figure 18.11: Homology in plants.
(a) The spines of the fishhook cactus (Ferocactus wislizenii) are modified leaves, as are (b) the tendrils of the garden pea (Pisum sativum). Leaves of the garden pea are compound, and the terminal leaflets are modified into tendrils that are frequently branched.
Fig a, p. 401

45. Tendril Leaflet Leaf petiole Stipule Stem Fig. 18-11b, p. 401
Figure 18.11: Homology in plants.
(a) The spines of the fishhook cactus (Ferocactus wislizenii) are modified leaves, as are (b) the tendrils of the garden pea (Pisum sativum). Leaves of the garden pea are compound, and the terminal leaflets are modified into tendrils that are frequently branched.
Stipule
Stem
Fig b, p. 401

46. Homoplastic Features Evolved independently
similar functions in distantly related organisms
Demonstrate convergent evolution
organisms with separate ancestries adapt similarly to comparable environments

47. Aardvark (Orycteropus afer)
Figure 18.12: Convergent evolution.
Three distantly related mammals adapted independently to eat ants and termites in similar grassland/forest environments in different parts of the world.
Aardvark (Orycteropus afer)
Fig a, p. 402

48. Giant anteater (Myrmecophaga tridactyla)
Figure 18.12: Convergent evolution.
Three distantly related mammals adapted independently to eat ants and termites in similar grassland/forest environments in different parts of the world.
Giant anteater (Myrmecophaga tridactyla)
Fig b, p. 402

49. Pangolin (Manis crassicaudata)
Figure 18.12: Convergent evolution.
Three distantly related mammals adapted independently to eat ants and termites in similar grassland/forest environments in different parts of the world.
Pangolin (Manis crassicaudata)
Fig c, p. 402

50. Homoplasy

51. Shoot (develops from axillary bud)
Spine (midrib of leaf)
Leaf scar
Figure 18.13: Homoplasy in plants.
A spine of Japanese barberry (Berberis thunbergii) is a modified leaf. (In this example, the spine is actually the midrib of the original leaf, which has been shed.)
Fig a, p. 403

52. Thorn (develops from axillary bud)
Figure 18.13: Homoplasy in plants.
Thorns of downy hawthorn (Crataegus mollis) are modified stems that develop from auxillary buds
Fig b, p. 403

53. Vestigial Structures Nonfunctional or degenerate remnants
of structures functional in ancestral organisms
Structures occasionally become vestigial
as species adapt to different modes of life

54. Vestigial Structures

55. Learning Objective 7 What is biogeography?
How does distribution of organisms support evolution?

56. Biogeography Geographic distribution of organisms
affects evolution
Areas separated from the rest of the world
contain organisms evolved in isolation
unique to those areas

57. Continental Drift
At one time, continents were joined to form a supercontinent
Continental drift
caused landmasses to separate
played major role in evolution

58. Continental Drift

59. Pangaea Fig. 18-15a, p. 404 Figure 18.15: Continental drift.
Geologists hypothesize that the breakup of Pangaea is only the latest in a series of continental breakups and collisions that have taken place since early in Earth’s history.
Fig a, p. 404

60. Laurasia Gondwana Fig. 18-15b, p. 404 Figure 18.15: Continental drift.
Geologists hypothesize that the breakup of Pangaea is only the latest in a series of continental breakups and collisions that have taken place since early in Earth’s history.
Fig b, p. 404

61. Asia N. America Europe Africa S. America India Australia Antarctica
Figure 18.15: Continental drift.
Geologists hypothesize that the breakup of Pangaea is only the latest in a series of continental breakups and collisions that have taken place since early in Earth’s history.
Australia
Antarctica
Fig c, p. 404

62. Eurasia Africa S. America Australia Antarctica
N. America
Eurasia
Africa S.
America
Australia
Figure 18.15: Continental drift.
Geologists hypothesize that the breakup of Pangaea is only the latest in a series of continental breakups and collisions that have taken place since early in Earth’s history.
Antarctica
Fig d, p. 404

63. Fossil Distribution

64. Cynognathus Lystrosaurus (a) (b) Africa India South America Antarctica
Australia
Antarctica
Figure 18.16: Distribution of fossils on continents that were joined during the Permian and Triassic periods (286 mya to 213 mya).
(a) Cynognathus was a carnivorous reptile found in Triassic rocks in South America and Africa. (b) Lystrosaurus was a large, herbivorous reptile with beaklike jaws that lived during the Triassic period. Fossils of Lystrosaurus have been found in Africa, India, and Antarctica. (c) Mesosaurus was a small freshwater reptile found in Permian rocks in South America and Africa. (d) Glossopteris was a seed-bearing tree dating from the Permian period. Glossopteris fossils have been found in South America, Africa, India, Antarctica, and Australia. (Adapted from E. H. Colbert, Wandering Lands and Animals, Hutchinson, London, 1973.)
(c)
Mesosaurus
(d)
Glossopteris
Fig , p. 405

65. Learning Objective 8
How do developmental biology and molecular biology provide insights into the evolutionary process?

66. Evolutionary Changes
Often result of gene mutations that affect events in development
Development in different animals
controlled by same kinds of genes
indicates shared evolutionary history

67. Genetic Changes Accumulation of genetic changes
since organisms diverged
modified development patterns in more complex vertebrate embryos

68. Divergence in Whales

69. Ruminants (cow, sheep, giraffe) Cetaceans (whale, dolphin)
Artiodactyls
Ruminants (cow, sheep, giraffe)
Cetaceans (whale, dolphin)
Hippopotamus
Camel
Pig
Common ancestor of hippos and whales
Figure 18.17: Phylogenetic tree of whales and their closest living relatives.
This branching diagram, called a cladogram, shows hypothetical evolutionary relationships. Based on DNA sequence differences among selected mammals, it suggests that artiodactyls are the close relatives of whales, that the hippopotamus is the closest living artiodactyl relative of whales, and that artiodactyls and whales share a common ancestor in the distant past. The nodes (circles) represent branch points where a species splits into two or more lineages. (Ruminants are artiodactyls that have a multichambered stomach and chew regurgitated plant material to make it more digestible.) (Adapted from M. Nikaido et al., “Phylogenetic Relationships among Cetartiodactyls Based on Insertions of Short and Long Interspersed Elements: Hippopotamuses Are the Closest Extant Relatives of Whales,” Proceedings of the National Academy of Sciences, Vol. 96, Aug. 31, 1999.)
Common ancestor of artiodactyls and cetaceans
Fig , p. 407

70. Molecular Evidence for Evolution
Universal genetic code
Conserved sequences
of amino acids in proteins
of nucleotides in DNA

71. Molecular Clock

72. Learning Objective 9
How are evolutionary hypotheses tested experimentally?

73. Reznick and Endler Studied effects of predation intensity
on evolution of guppy populations in laboratory and nature
Tested underlying processes of natural selection

74. Reznick Experiment

75. KEY CONCEPTS
The evidence that evolution has taken place and is still occurring is overwhelming

76. Animation: Radiometric Dating
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77. Animation: Morphological Divergence
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78. Animation: Radioisotope Decay
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79. Video: Creation vs. Evolution
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From ABC News, Environmental Science in the Headlines, 2005 DVD.

80. Video: Dinosaur Discovery
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From ABC News, Environmental Science in the Headlines, 2005 DVD.