biology

1. Chapter 16
Evidence of Evolution
Section 16.1

2. © Cengage Learning 2015
16.1 How Did Observations of Nature
Change Our Thinking in the 19th Century?
• Expeditions by 19th century naturalists
– Yielded increasingly detailed observations of nature
– Collected thousands of plants and animals from around the
world
– Catalogued and described newly discovered species

3. © Cengage Learning 2015
How Did Observations of Nature Change
Our Thinking in the 19th Century? (cont’d.)
• 19th century naturalists (cont’d.)
– Pioneered the field of biogeography
• The study of patterns in the geographic distribution of species
– What are some patterns that emerged?

4. © Cengage Learning 2015
How Did Observations of Nature Change
Our Thinking in the 19th Century? (cont’d.)
A
B
C
Figure 16.1 A. Emu, native to Australia. B. Rhea,
native to South America. C. Ostrich, native to
Africa. Similar-looking, related species native to
distant geographic realms. These birds are unlike
most others in several unusual features,
including long, muscular legs and an inability to
fly. All are native to open grassland regions
about the same distance from the equator

5. © Cengage Learning 2015
How Did Observations of Nature Change
Our Thinking in the 19th Century? (cont’d.)
• Comparative morphology
– Study of anatomical patterns
– The only way to distinguish differences in species at that time
– Problematic in classifying organisms that are outwardly very
similar, but quite different internally

6. © Cengage Learning 2015
How Did Observations of Nature Change
Our Thinking in the 19th Century? (cont’d.)
• Example: the American spiny cactus and African spiny
spurge
– Live in similar environments
– Native to different continents
– Reproductive parts are very different, so they can’t be as
closely related they appear

7. © Cengage Learning 2015
How Did Observations of Nature Change
Our Thinking in the 19th Century? (cont’d.)
Figure 16.2 Similar-looking, unrelated
species. On the left, an African milk barrel
cactus (Euphorbia horrida), native to the
Great Karoo desert of South Africa. On the
right , saguaro cactus (Carnegiea
gigantea), native to the Sonoran Desert of
Arizona

8. © Cengage Learning 2015
How Did Observations of Nature Change
Our Thinking in the 19th Century? (cont’d.)
• Vestigial structures
– 19th century naturalists had difficulty explaining
– Body parts that have no apparent function
– Leg bones in snakes and tail bones in humans

9. © Cengage Learning 2015
How Did Observations of Nature Change
Our Thinking in the 19th Century? (cont’d.)
coccyx
(tailbones)
Figure 16.3 A vestigial structure:
human tailbones. Nineteenth-
century naturalists were well aware
of—but had trouble explaining—
body structures such as human
tailbones that had apparently lost
most or all function.

10. © Cengage Learning 2015
How Did Observations of Nature Change
Our Thinking in the 19th Century? (cont’d.)
• Fossils
– Physical evidence of an organism that lived in ancient past
– Proved puzzling
• Deeper layers held fossils of simple marine life
• Layers above held similar but more complex fossils

11. © Cengage Learning 2015
How Did Observations of Nature Change
Our Thinking in the 19th Century? (cont’d.)
58 million
years old
64.5 million
years old
Figure 16.4 Sequence of ten fossil foraminifera