1. Intellectuals / Ideas in Darwin’s Era
Linnaeus (classification)
Hutton (gradual geologic change)
Lamarck (species can change)
Malthus (population limits)
Cuvier (fossils, extinction)
Lyell (modern geology)
Darwin (evolution, natural selection)
Wallace (evolution, natural selection)
American Revolution
French Revolution
U.S. Civil War
1750
1800
1850
1900
1795
Hutton proposes his theory of gradualism.
1798
Malthus publishes “Essay on the Principle of Population.”
1809
Lamarck publishes his hypothesis of evolution.
1830
Lyell publishes Principles of Geology.
Figure 22.2 The historical context of Darwin’s life and ideas
1831–1836
Darwin travels around the world on HMS Beagle.
1837
1837
Darwin begins his notebooks.
1844
Darwin writes essay on descent with modification.
1858
Wallace sends his hypothesis to Darwin.
1859
The Origin of Species is published.

2. Layers of deposited sediment Younger stratum with more recent fossils
Figure 22.3 Formation of sedimentary strata with fossils
Older stratum
with older fossils

3. Darwin’s Voyage on the Beagle
GREAT
BRITAIN
EUROPE
NORTH
AMERICA
ATLANTIC
OCEAN
The
Galápagos
Islands
AFRICA
Pinta
Genovesa
Marchena
Equator
SOUTH
AMERICA
Santiago
Daphne
Islands
Pinzón
AUSTRALIA
Fernandina
PACIFIC
OCEAN
Isabela
Figure 22.5 The voyage of HMS Beagle
For the Discovery Video Charles Darwin, go to Animation and Video Files.
Santa
Cruz
Andes
Cape of
Good Hope
Santa Fe
San
Cristobal
Tasmania
Florenza
Española
Cape Horn
New
Zealand
Tierra del Fuego

4. Speciation of Galapagos Finches
(a) Cactus-eater
(c) Seed-eater
Figure 22.6 Beak variation in Galápagos finches
(b) Insect-eater

5. (a) Cactus-eater Fig. 22-6a
Figure 22.6 Beak variation in Galápagos finches
(a) Cactus-eater

6. (b) Insect-eater Fig. 22-6b
Figure 22.6 Beak variation in Galápagos finches
(b) Insect-eater

7. Fig. 22-6c
Figure 22.6 Beak variation in Galápagos finches
(c) Seed-eater

8. Descent With Modification
Hyracoidea
(Hyraxes)
Sirenia
(Manatees
and relatives)
Moeritherium
Barytherium
Deinotherium
Mammut
Platybelodon
Stegodon
Mammuthus
Figure 22.8 Descent with modification
Elephas maximus
(Asia)
Loxodonta
africana
(Africa)
Loxodonta cyclotis
(Africa) 34 24
5.5 2
104
Millions of years ago
Years ago

9. Observation #1: Members of a population often vary greatly in their traits.
Figure Variation in a population

10. Natural Selection EXPERIMENT RESULTS 12 12 10 10 8 8 Area of colored
Predator: Killifish; preys
mainly on juvenile
guppies (which do not
express the color genes)
Experimental
transplant of
guppies
Pools with
killifish,
but no
guppies prior
to transplant
Guppies: Adult males have
brighter colors than those
in “pike-cichlid pools”
Predator: Pike-cichlid; preys mainly on adult guppies
Guppies: Adult males are more drab in color
than those in “killifish pools”
RESULTS 12 12
Figure Can predation result in natural selection for color patterns in guppies? 10 10 8 8
Area of colored
spots (mm2)
colored spots
Number of 6 6 4 4 2 2
Source
population
Transplanted
population
Source
population
Transplanted
population

11. Fossil Evidence of Change Over Time2 4 4 6 4
Bristolia insolens 8 3
Bristolia bristolensis 10 12 3
Depth (meters) 2
Bristolia harringtoni 14 16 18 1
Bristolia mohavensis 3
Figure Fossil evidence of evolution in a group of trilobites 2 1
Latham Shale dig site, San
Bernardino County, California

12. Paleontologists study fossils of possible transitional forms: Whale Ancestors
(a) Pakicetus (terrestrial)
(b) Rhodocetus (predominantly aquatic)
Figure The transition to life in the sea
Pelvis and
hind limb
(c) Dorudon (fully aquatic)
Pelvis and
hind limb
(d) Balaena
(recent whale ancestor)

13. Homologous Structures
Humerus
Radius
Ulna
Carpals
Metacarpals
Figure Mammalian forelimbs: homologous structures
Phalanges
Human
Cat
Whale
Bat

14. Comparative embryology reveals anatomical homologies not visible in adult organisms:
Pharyngeal
pouches
Post-anal
tail
Figure Anatomical similarities in vertebrate embryos
Chick embryo (LM)
Human embryo

15. Homologies and “Evolutionary Tree”
Branch point
(common ancestor)
Lungfishes 1
Amphibians
Tetrapods 2
Mammals
Tetrapod limbs
Amniotes 3
Lizards
and snakes
Amnion 4
Crocodiles
Figure Tree thinking: information provided in an evolutionary tree
Homologous
characteristic 5
Ostriches
Birds 6
Feathers
Hawks and
other birds

16. NORTH AMERICA Sugar glider AUSTRALIA Flying squirrel Fig. 22-20
Figure Convergent evolution
Flying
squirrel

17. Darwin : Natural Selection
Observations
Individuals in a population
vary in their heritable
characteristics.
Organisms produce more
offspring than the
environment can support.
Inferences
Individuals that are well suited
to their environment tend to leave
more offspring than other individuals
and
Over time, favorable traits
accumulate in the population.

18. Mutation = Resistance to DDT
Mutation = Resistance to DDT. Natural Selection Favors this Resistance --> Number of Resistant Individuals Increases Over Time.

19. You should now be able to:
Describe the contributions to evolutionary theory made by Linnaeus, Cuvier, Lyell, Lamarck, Malthus, and Wallace.
Describe Lamarck’s theories, and explain why they have been rejected.
Explain what Darwin meant by “descent with modification.”
Explain Darwin’s observations and inferences.
Explain why an individual organism cannot evolve.
Describe evidence for evolution by natural selection.