1. Chapter 13 Evidence of Evolution
Fossil: ©Lou Mazzatenta/National Geographic Stock
Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock
Copyright © McGraw-Hill Education.  All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

2. Clues to Evolution Lie in the Earth, Body Structures, and Molecules
Life on Earth arose 3.8 billion years ago. Changes in body structures and molecules have slowly accumulated through that time, producing the variety of organisms we see today.
Section 13.1
Figure 13.2

3. Clues to Evolution Lie in the Earth, Body Structures, and Molecules
Scientists use the geologic timescale to divide the history of the Earth into eons and eras. These periods are defined by major geological or biological events, like mass extinctions.
Section 13.1
Figure 13.2

4. Clues to Evolution Lie in the Earth, Body Structures, and Molecules
Researchers analyze fossils, anatomy, and molecular sequences to learn how species are related to one another.
Paleontology is the study of fossil remains or other clues to past life. Fossils provided the original evidence for evolution.
Ge Sun, et al. "In Search of the First Flower: A Jurassic Angiosperm, Archaefructus, from Northeast China,"
Science, Vol. 282, no. 5394, November 27, 1998, pp ©1998 AAAS. All rights reserved. Used with permission
Section 13.1

5. Clues to Evolution Lie in the Earth, Body Structures, and Molecules
Fossils are the remains of ancient organisms.
Left fossil: Ge Sun, et al. "In Search of the First Flower: A Jurassic Angiosperm, Archaefructus, from Northeast China,"
Science, Vol. 282, no. 5394, November 27, 1998, pp ©1998 AAAS. All rights reserved. Used with permission; Wood: ©PhotoLink/Getty Images RF; Embryo: ©University of the Witwatersrand/epa/Corbis; Coprolite: ©Sinclair Stammers/Science Source; Trilobite: ©Siede Preis/Getty Images RF; Fish fossil: ©Phil Degginger/Carnegie Museum/Alamy RF; Leaf fossil: ©Biophoto Associates/Science Source; Triceratops: ©Francois Gohier/Science Source
Section 13.1
Figure 13.1

6. 13.1 Mastering Concepts What is the geologic timescale?
Fossil: ©Lou Mazzatenta/National Geographic Stock
Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock

7. Fossils Record Evolution
Fossils form in many ways.
Section 13.2
Compression fossil of leaf: ©William E. Ferguson
Human skull and bone fossil: ©John Reader/Science Source
Figure 13.4

8. Fossils Record Evolution
Fossils form in many ways.
Section 13.2
Impression of dinosaur skin: ©Dr. John D. Cunningham/Visuals Unlimited
Horn coral: ©Robert Gossington/Photoshot
Figure 13.4

9. Fossils Record Evolution
Fossils form in many ways.
Section 13.2
Figure 13.4
Mosquito trapped in amber: ©Natural Visions/Alamy

10. Fossils Record Evolution
Even though fossil evidence is diverse, it is often challenging—or impossible—to find fossils of transitional forms between groups.
The fossil record is incomplete, partly because some organisms (such as those with soft bodies) fail to fossilize. Also, erosion and movement of Earth’s plates might destroy fossils.
Section 13.2
Figure 13.3
Ammonite: ©Jean-Claude Carton/Photoshot

11. Fossils Record Evolution
Dating fossils yields clues about the timeline of life’s history.
The simpler, and less precise, method of dating fossils is
relative dating, which assumes that lower rock layers
have older fossils than newer layers.
Section 13.2
Figure 12.3
Canyon: ©Terry Moore/Stocktrek Images/Getty Images RF

12. Fossils Record Evolution
Absolute dating uses chemistry to determine how long ago a fossil formed.
Radiometric dating is a type of absolute dating that uses radioactive isotopes.
Section 13.2
Figure 13.6
Woolly mammoth skeleton: ©Ethan Miller/Getty Images

13. Clicker Question #1
Which rock layer (A, B, or C) should have fossils with the most carbon-14? A B C
Flower: © Doug Sherman/Geofile/RF
Canyon: ©Terry Moore/Stocktrek Images/Getty Images RF

14. Clicker Question #1
Which rock layer (A, B, or C) should have fossils with the most carbon-14? A B C
Flower: © Doug Sherman/Geofile/RF
Canyon: ©Terry Moore/Stocktrek Images/Getty Images RF

15. Clicker Question #2
Researchers used a radioactive isotope with a 25,000-year half-life to date a fossil to 100,000 years ago. The fossil contains ____ as much of the isotope as does a living organism.
1/2
1/4
1/8
1/16
1/32
Flower: © Doug Sherman/Geofile/RF

16. Clicker Question #2
Researchers used a radioactive isotope with a 25,000-year half-life to date a fossil to 100,000 years ago. The fossil contains ____ as much of the isotope as does a living organism.
1/2
1/4
1/8
1/16
1/32
Flower: © Doug Sherman/Geofile/RF

17. 13.2 Mastering Concepts
Distinguish between relative and absolute dating of fossils.
Fossil: ©Lou Mazzatenta/National Geographic Stock
Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock

18. Biogeography Considers Species’ Geographical Locations
According to the theory of plate tectonics, Earth’s surface consists of several rigid layers, called tectonic plates, that
move in response to forces acting deep within the planet.
Section 13.3
Figure 13.7

19. Biogeography Considers Species’ Geographical Locations
Fossils help geographers piece together Earth’s continents
into Pangaea.
Section 13.3
Figure 13.8

20. Biogeography Considers Species’ Geographical Locations
Biogeography sheds light on evolutionary events.
Animals on either side of Wallace’s line have been separated for millions of years, evolving independently.
The result is a unique variety of organisms on each side of the line.
Section 13.3
Figure 13.9

21. 13.3 Mastering Concepts
How have the positions of Earth’s continents changed over the past 200 million years?
Fossil: ©Lou Mazzatenta/National Geographic Stock
Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock

22. Anatomical Relationships Reveal Common Descent
Two structures are
homologous if the similarities between them reflect common ancestry.
Section 13.4
Figure 13.10

23. Anatomical Relationships Reveal Common Descent
All of these animals, for example, have similar bones in their forelimbs.
These similarities suggests that their common ancestor had this bone configuration.
Section 13.4
Figure 13.10

24. Anatomical Relationships Reveal Common Descent
Homologous structures need not have the same function or look exactly alike.
Different selective pressures in each animal’s evolutionary line have led to small changes from their ancestor’s bone structure.
Section 13.4
Figure 13.10

25. Anatomical Relationships Reveal Common Descent
A vestigial structure has lost its function but is homologous to a functional structure in another species.
Vestigial hind limbs in some snake species and pelvises in whales are evidence of these organisms’ ancestors.
Section 13.4
Mexican-boa-constrictor: ©Pascal Goetgheluck/Science Source
Python skeleton: ©Science VU/Visuals Unlimited
Figure 13.11

26. Anatomical Relationships Reveal Common Descent
Anatomical structures are analogous if they are superficially similar but did not derive from a common ancestor.
None of these cave animals has pigment or eyes.
These similarities arose by convergent evolution, which produces similar structures in organisms that don’t share the same lineage.
Lack of pigment arose independently in each of these cave animals.
Section 13.4
Salamander: ©Francesco Tomasinelli/The Lighthouse/Visuals Unlimited
Crayfish: ©Dante Fenolio/Science Source
Figure 13.13

27. Clicker Question #3
The streamlined shapes of dolphins and sharks evolved independently. The body plan of these two animals are
homologous.
vestigial.
analogous.
a product of convergent evolution.
Both C and D are correct.
Flower: © Doug Sherman/Geofile/RF

28. Clicker Question #3
The streamlined shapes of dolphins and sharks evolved independently. The body plan of these two animals are
homologous.
vestigial.
analogous.
a product of convergent evolution.
Both C and D are correct.
Flower: © Doug Sherman/Geofile/RF

29. 13.4 Mastering Concepts What can homologies reveal about evolution?
Fossil: ©Lou Mazzatenta/National Geographic Stock
Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock

30. Embryonic Development Patterns Provide Evolutionary Clues
Anatomical similarities are often most obvious in embryos. Notice how much more similar human and chimpanzee skull structure is in fetuses compared to in adults.
Section 13.5
Figure 13.14

31. Embryonic Development Patterns Provide Evolutionary Clues
Adult fish, mice, and alligators have very different bodies.
Their evolutionary relationships are more obvious in embryos.
How do similar embryos develop into such different organisms?
Homeotic genes provide a clue.
Section 13.5
Fish: ©Dr. Richard Kessel/Visuals Unlimited; Mouse: ©Steve Gschmeissner/Science Source; Alligator: USGS/Southeast Ecological Science Center
Figure 13.15

32. Embryonic Development Patterns Provide Evolutionary Clues
Homeotic genes control an organism’s development. Small differences in gene expression might make the difference between a limbed and limbless organism.
Homeotic genes therefore help explain how a few key mutations might produce new species.
Section 13.5
Figure 13.16

33. Embryonic Development Patterns Provide Evolutionary Clues
Mutations in segments of DNA that do not encode proteins also produce new phenotypes.
Section 13.5
Figure 13.17

34. 13.5 Mastering Concepts
How does the study of embryonic development reveal clues to a shared evolutionary history?
Fossil: ©Lou Mazzatenta/National Geographic Stock
Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock

35. Molecules Reveal Relatedness
Comparing DNA and protein sequences determines evolutionary relationships in unprecedented detail.
It is highly unlikely that two unrelated species would evolve precisely the same DNA and protein sequences by chance.
It is more likely that the similarities were inherited from a common ancestor and that differences arose by mutation after the species diverged from the ancestral type.
Section 13.6

36. Molecules Reveal Relatedness
Molecular clocks assign dates to evolutionary events.
If a gene is estimated to mutate once every 25 million years, then two differences from an ancestor might arise in 50 million years.
Section 13.6
Figure 13.20

37. Molecules Reveal Relatedness
If a gene is estimated to mutate once every 25 million years, then two differences from an ancestor might arise in 50 million years.
Therefore, two species that derived from the same common ancestor 50 MYA might have four differences in the nucleotide sequence of the gene.
Section 13.6
Figure 13.20

38. Clicker Question #4
Mutations in a gene occur at a rate of one nucleotide every 10 million years. The gene sequence differs by 6 nucleotides between two related organisms. How long ago did these organisms split from a common ancestor?
about 2 million years ago
about 30 million years ago
about 60 million years ago
about 120 million years ago
None of the choices is correct.
Flower: © Doug Sherman/Geofile/RF

39. Clicker Question #4
Mutations in a gene occur at a rate of one nucleotide every 10 million years. The gene sequence differs by 6 nucleotides between two related organisms. How long ago did these organisms split from a common ancestor?
about 2 million years ago
about 30 million years ago
about 60 million years ago
about 120 million years ago
None of the choices is correct.
Flower: © Doug Sherman/Geofile/RF

40. 13.6 Mastering Concepts
How does analysis of DNA and proteins support other evidence for evolution?
Fossil: ©Lou Mazzatenta/National Geographic Stock
Protoarchaeopteryx: ©O. Louis Mazzatenta/National Geographic Stock