1. Evidence of Evolution Chapter 16
Biology Concepts and Applications, Eight Edition, by Starr, Evers, Starr. Brooks/Cole, Cengage Learning 2011.

2. 16.1 Early Discoveries
By the 19th century, advances in geology, biogeography, and comparative morphology resulted in awareness of change in lines of descent of species

3. Geological Evidence Asteroids: small planets size 1-1,500 kilometers
Mile wide Barringer Crater in Arizona 300,000 ton asteroid, 50,000 years ago. Impact 150x greater than Hiroshima bomb

4. Geological Evidence Mass extinction Inferred from evidence 
Permanent loss of major groups of organisms
Occurred 65.5 million years ago
Event marked by unusual, worldwide layer of rock called the K-T boundary layer
Below layer  Dinosaur fossils
Above layer  no Dinosaur fossils
Impact crater off the coast of the Yucatan Peninsula dates about 65.5 million years ago
Inferred from evidence 
20 km or 12 mile wide asteroid wiped out the dinosaurs

5. 16.2 Early Beliefs, Confounding Discoveries
Aristotle  Naturalist
Person who observes life from a scientific perspective
Viewed nature as a continuum of organization, from lifeless matter through complex plants and animals
“Great chain of being”
From the lowest form (snakes) to humans and even spiritual beings
Chain links = a species
Each new species discovered was another link in the chain of being
Chain = complete and continuous
Once chain is complete  meaning of life would be revealed

6. Early Beliefs, Confounding Discoveries
Alfred Wallace  Biogeography
Study of patterns in the geographic distribution of species and communities
Looked at the natural forces that shape life
Raised ?
Isolated species look suspiciously similar to species living across vast expansions of open ocean, or on the other side of mountain ranges

7. Early Beliefs, Confounding Discoveries
Rhea
South America
Ostrich
Africa
All flightless birds.
Long, muscular legs.
Inhabit flat, open grasslands
about the same distance from
the equator.*Common Ancestors!
Emu
Australia

8. Comparative Morphological Evidence
Comparative Morphology
Study of body parts and structures among groups of organisms
Organisms outwardly similar but different internally
Fish and porpoises  Very different
Outwardly different but similar internally
Human arm and porpoise flipper
Elephant leg and bat wing
Useless parts 
leg bones in snakes or vestiges of tail in humans

9. Comparative Morphological Evidence

10. Fossil Evidence Fossil  physical evidence Of an organism that lived
In the ancient past
Mapping rock formation:
Deeper layers hold
Fossils of simple marine
Life. Layers above held
Similar but more intricate
Fossils. Higher layers,
Similar that belong to
Modern species.

11. 16.3 Evolution: Development of New Theories
Change that occurs in a line of descent (lineage)
19th-century naturalists tried to reconcile traditional beliefs with evidence of evolution
Georges Cuvier’s theory of catastrophism
Now abandoned hypothesis that catastrophic geologic forces unlike those of the present day shaped Earth’s surface
Lamarck’s theory of inheritance of acquired characteristics due to environmental factors
Species gradually improved over generations to drive to perfection. Ex. Giraffe  long neck

12. Voyage of the Beagle
Charles Darwin’s observations on a voyage around the world led to new ideas about species
Theory of uniformity (gradual, repetitive change)
Idea that gradual repetitive
processes occurring over
long time spans shaped
Earth’s surface
Theory challenged idea that
Earth was 6,000 yrs old
**However, must have taken
longer to sculpt Earth’s surface

13. Voyage of the Beagle

14. Key Concepts: EMERGENCE OF EVOLUTIONARY THOUGHT
Long ago, Western scientists started to catalog previously unknown species and think about their global distribution
They discovered similarities and differences among major groups, including those represented as fossils in layers of sedimentary rock

15. 16.4 Descent with Modification
Darwin compared the modern armadillo with the extinct glyptodont
Glyptodont – Argentina
Extinct but similar to Armadillo
Armadillo – live only in
Places the Glyptodont once lived

16. Variations in Traits
Darwin observed that variations in traits influence an individual’s ability to secure resources – to survive and reproduce

17. A Key Insight – Variation in Traits
Adaptation (adaptive trait)
A heritable trait the enhances an individual’s fitness
Artificial selection
Selective breeding of animals by humans

18. Darwin, Wallace, and Natural Selection
In 1858, Charles Darwin and Alfred Wallace independently proposed a new theory, that natural selection can bring about evolution

19. Theory of Natural Selection
Process in which environmental pressures result in the differential survival and reproduction of individuals of a population who vary in the details of shared, heritable traits
Can lead to increased fitness
Fitness
Degree of adaptation to an environment, as measured by an individual’s relative genetic contribution to future generations.

20. Main Premises of the Theory of Natural Selection
1. A population tends to grow until it begins to exhaust the resources of its environment
2. Individuals must then compete for resources such as food and shelter from predators
3. Individuals with forms of traits that make them more competitive tend to produce more offspring

21. Inferences of the Theory of Natural Selection
Environmental factors acting on a range of traits in a population influence differential survival and reproduction of individuals (natural selection)
Forms of heritable traits that impart greater fitness to an individual become more common in a population over generations

22. Key Concepts: A THEORY TAKES FORM
Evidence of evolution, or changes in lines of descent, gradually accumulated
Charles Darwin and Alfred Wallace independently developed a theory of natural selection to explain how heritable traits that define each species evolve

23. 16.5 Fossil Evidence Fossils
Physical evidence of life in the distant past
Found in stacked layers of sedimentary rock
Younger fossils in more recently deposited layers
Older fossils underneath, in older layers

24. Fossilization

25. Fossilization
Begins when organisms become covered by sediments or volcanic ash.
Water seeps into the remains, and metal ions and other organic compounds dissolved in water replace the minerals in the bones and hard tissues.
Pressure and mineralization process transforms the remains into rock

26. Stratification
Layers of sedimentary rock made from river silt, sand, volcanic ash, and other materials from land to sea

27. Interpreting the Fossil Record
The fossil record is incomplete
Have fossils for 250,000 known species
Most times, remains are obliterated by decay because organic materials decompose in the presence of oxygen
Material remains IF encased in air-excluding materials (sap, tar, ice, or mud)
Favors species with hard parts, dense populations with wide distribution, and that persisted a long time

28. Dating Fossils Geologic time scale  Chronology of Earth’s History
Boundaries for major intervals determined by transitions in the fossil record
Correlated with macroevolutionary events
Includes dates obtained by radiometric dating

29. Geologic Time Scale

30. Macroevolution
Major patterns, trends, and rates of change among lineages (Geologic time scale)

31. Radiometric Dating: Half-Life
Characteristic time it takes for half of a quantity of a radioisotope to decay
Ex. Uranium 238  thorium 234   lead 206 (takes 4.5 billion yrs)
Predictable radioactive decay can be used to find the age of a volcanic rock

32. Radiometric Dating: Half-Life
Radioactive dating
Method of estimating the age of a rock or fossil by measuring the content and proportions of a radioisotope and its daughter elements
Oldest terrestrial rock (tiny zircon crystal) in Australia
4.404 billion years old
Recent fossils that still contain carbon can by dated by measuring their carbon 14 content
Complete decay of 14C occurs in 60,000 years

33. Parent isotope remaining (%)
parent isotope in
newly formed rock
100 75
after one half-life
Parent isotope remaining (%) 50
after two half-lives 25 1 2 3 4
Time (half-life) for any radioisotope
a A simple way to think about the decay of a radioisotope to a more
stable isotope, as plotted against time.
Fig a, p.248

34. Fig b-d, p.248

35. Key Concepts: EVIDENCE FROM FOSSILS
The fossil record offers physical evidence of past changes in lines of descent

36. 16.7 Plate Tectonics Theory
Movements of Earth’s tectonic plates rafted land masses to new positions
Pangea: First ancient supercontinent that formed about 237 million years ago and broke up about 152 million years ago
Gondwana  supercontinent that existed before Pangae, more than 500 million years ago
Include Southern Hemisphere and India and Arabia
Most modern species live only in places that were once part of Gondwana

37. 16.7 Plate Tectonics Theory
Plate Tectonics OR Continental drift
Theory that Earth’s outer layer of rock is cracked into plates
Slow movement of which rafts continents to new locations over geologic time
Movements had profound impacts on the directions of life’s evolution
Evidence of at least 5x since Earth’s outer layer solidified 4.55 billion years ago, a single supercontinent with one ocean lapping the coast line formed and then split up.
14 million years ago, that Earth and it’s continents mirror today

38. Evidence of Drifting Continents
Evidence for plate tectonics theory
Distribution of global land masses
Global fossil distribution
Magnetic rocks
Seafloor spreading from mid-oceanic ridges
In faults (fault lines)
Volcanic island chains  form as a plate moves across an undersea hot spot (place where a narrow plume of molten rock wells up from deep inside Earth and ruptures a plate

39. Forces of Plate Tectonics

40. (solid layer of mantle) hot spot asthenosphere
island arc
oceanic crust
oceanic ridge
trench
continental crust
lithosphere
(solid layer of mantle)
hot
spot
asthenosphere
(plastic layer of mantle)
subducting
plate
Fig b, p.250

41. Drifting Continents

42. a 420 mya
b 237 mya
c 152 mya
d 66 mya
e 14 mya
Fig , p.251

43. Key Concepts: EVIDENCE FROM BIOGEOGRAPHY
Correlating evolutionary theories with geologic history helps explain the distribution of species, past and present

44. 16.8 Comparative Morphology
Comparisons of body form and structure of major groups of organisms
Reveals evolutionary connections among lineages

45. Morphological Divergence
Homologous structures:
Similar body parts that became modified differently in different lineages
Evidence of descent from a common ancestor
Morphological divergence
Evolutionary pattern in which a body part of an ancestor changes in its descendants

46. Homologous Structures
Morphological
Divergence

47. 1 2 3 4
stem reptile 5
Fig a, p.252

48. 1 2 3
pterosaur 4
Fig b, p.252

49. 1 2
chicken 3
Fig c, p.252

50. 2 3
penguin
Fig d, p.252

51. 1
porpoise 4 2 5 3
Fig e, p.252

52. 1 2
bat 3 4 5
Fig f, p.252

53. 1 2 3 4 5
human
Fig g, p.252

54. 1 2 3 4
elephant 5
Fig h, p.252

55. Morphological Convergence
Analogous structures:
Body parts in different lineages that look alike, but evolved separately after the lineages diverged
Did not evolve in a common ancestor
Morphological convergence
Evolutionary pattern in which similar body parts evolve separately in different lineages

56. Analogous Structures

57. Morphological convergence
Insects
Bats
Humans
Crocodiles
Birds
wings
wings
wings
limbs with
5 digits
Fig d, p.253

58. 16.9 Changes in Patterns of Development
Similarities in patterns of embryonic development suggest shared ancestry
Mutations in genes that affect development may cause morphological shifts in a lineage
Gene duplications account for some differences between closely related lineages

59. Comparative Embryology: Vertebrate Relationships
Human
Mouse
Bat
Chicken
Alligator
All vertebrate embryos have similar stages:
- Stage with 4 limb buds, a tail, and divisions called somites
along their back

60. Chimps and Humans: Genes That Control Growth Rate

61. Key Concepts: EVIDENCE FROM COMPARATIVE MORPHOLOGY
Species of different lineages often have similar body parts that may be evidence of descent from a shared ancestor

62. DNA, RNA, and Proteins
Comparisons of DNA, RNA, and proteins reveal and clarify evolutionary relationships

63. Molecular Clock
Neutral mutations accumulate in DNA at a predictable rate
Help estimate when two lineages diverged
Mitochondrial DNA (mtDNA) is inherited intact
Closely related species share more nucleotide or amino acid sequences than less related ones

64. Key Concepts: EVIDENCE FROM COMPARATIVE BIOCHEMISTRY
Molecular comparisons help us discover and confirm relationships among species and lineages

65. Constructing a Cladogram
All organisms are related by descent
Representing life’s history as a tree with branchings from ancestral stems clarifies relationships

66. Constructing a Cladogram

67. Fig a, p.260

68. Fig c, p.260

69. Fig d, p.260

70. Life’s Evolutionary History

71. Key Concepts: ORGANIZING THE EVIDENCE
Evolutionary tree diagrams are based on the premise that all species interconnect through shared ancestors—some remote, others recent

72. Animation: Comparative pelvic anatomy

73. Animation: Evolutionary tree diagrams

74. Animation: Finches of the Galapagos

75. Animation: Geologic forces

76. Animation: Interpreting a cladogram

77. Animation: Morphological divergence

78. Animation: Mutation and proportional changes

79. Animation: Plate margins

80. Animation: Radioisotope decay

81. Animation: Radiometric dating

82. Animation: The Galapagos Islands