1. Terminal
bud
Lateral
buds
Cabbage
Brussels sprouts
Flower
clusters
Evolution Chapter 22
Leaves
Kale
Cauliflower
22.2: Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life
Stem
Wild mustard
Flowers
and stems
Broccoli
Kohlrabi

4. Overview: Endless Forms Most Beautiful
A new era of biology began in 1859 when Charles Darwin published The Origin of Species
The Origin of Species focused biologists’ attention on the great diversity of organisms
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5. Darwin noted that current species are descendants of ancestral species
Evolution can be defined by Darwin’s phrase descent with modification
Evolution can be viewed as both a pattern and a process
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6. Fig. 22-2
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.

7. Concept 22.2: Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life
As the 19th century dawned, it was generally believed that species had remained unchanged since their creation
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8. The Voyage of the Beagle
During his travels on the Beagle, Darwin collected specimens of South American plants and animals
He observed adaptations of plants and animals that inhabited many diverse environments
Darwin was influenced by Lyell’s Principles of Geology and thought that the earth was more than 6000 years old
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

9. Fig. 22-5
Darwin’s interest in geographic distribution of species was kindled by a stop at the Galápagos Islands near the equator west of South America
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
Santa
Cruz
Andes
Cape of
Good Hope
Figure 22.5 The voyage of HMS Beagle
For the Discovery Video Charles Darwin, go to Animation and Video Files.
Santa Fe
San
Cristobal
Tasmania
Florenza
Española
Cape Horn
New
Zealand
Tierra del Fuego

10. (a) Cactus-eater (c) Seed-eater (b) Insect-eater
Fig. 22-6
(a) Cactus-eater
(c) Seed-eater
In reassessing his observations, Darwin perceived adaptation to the environment and the origin of new species as closely related processes
Figure 22.6 Beak variation in Galápagos finches
(b) Insect-eater

11. In 1844, Darwin wrote an essay on the origin of species and natural selection but did not introduce his theory publicly, anticipating an uproar
In June 1858, Darwin received a manuscript from Alfred Russell Wallace, who had developed a theory of natural selection similar to Darwin’s
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

12. The Origin of Species Darwin developed two main ideas:
Descent with modification explains life’s unity and diversity
Natural selection is a cause of adaptive evolution
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13. Descent with Modification
Darwin never used the word evolution in the first edition of The Origin of Species
Instead he used the phrase “descent with modification”: all organisms are related through descent from an ancestor that lived in the remote past
In the Darwinian view, the history of life is like a tree with branches representing life’s diversity
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

15. Fig. 22-8 Figure 22.8 Descent with modification Millions of years ago
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

16. Artificial Selection, Natural Selection, and Adaptation
Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called artificial selection
4 Observations he made:
Members of a population often vary greatly in their traits
Traits are inherited from parents to offspring
All species are capable of producing more offspring than the environment can support
Owing to lack of food or other resources, many of these offspring do not survive
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17. #1: Members of a population often vary greatly in their traits
Fig. 22-9
#1: Members of a population often vary greatly in their traits
Terminal
bud
Lateral
buds
Cabbage
Brussels sprouts
Flower
clusters
Leaves
Kale
Cauliflower
Figure 22.9 Artificial selection
Stem
Wild mustard
Flowers
and stems
Broccoli
Kohlrabi

18. #2: Traits are inherited from parents to offspring
Fig
#2: Traits are inherited from parents to offspring
Figure Variation in a population

19. Fig
#3:
All species are capable of producing more offspring than the environment can support
Spore
cloud
#4:
Owing to lack of food or other resources, many of these offspring do not survive
Figure Overproduction of offspring

20. Darwin made 2 inferences:
Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals (differential reproductive success)
This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations
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21. Natural Selection: A Summary
(a) A flower mantid
in Malaysia
Individuals with certain heritable characteristics survive and reproduce at a higher rate than other individuals
Natural selection increases the adaptation of organisms to their environment over time
If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species
(b) A stick mantid
in Africa
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22. Individuals do not evolve; populations evolve over time
Natural selection can only increase or decrease heritable traits in a population
Adaptations vary with different environments
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24. Evolution Chapter 22
22.3: Evolution is supported by an overwhelming amount of scientific evidence

25. Evidence for evolution: Direct Observations of Evolutionary Change
Biogeography
Vestigial Organs
Comparative Embyology
Homologies
Comparative Biochemistry
Molecular Biology
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26. Predation and Coloration in Guppies : Scientific Inquiry
John Endler has studied the effects of predators on wild guppy populations
Brightly colored males are more attractive to females
However, brightly colored males are more vulnerable to predation
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27. Fig. 22-13 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?
Guppy populations in pools with fewer predators had more brightly colored males
Endler transferred brightly colored guppies (with few predators) to a pool with many predators
As predicted, over time the population became less brightly colored
Endler also transferred drab colored guppies (with many predators) to a pool with few predators
As predicted, over time the population became more brightly colored 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

28. The Evolution of Drug-Resistant HIV
The use of drugs to combat HIV selects for viruses resistant to these drugs
HIV uses an enzyme to make a DNA version of its own RNA genome
The drug 3TC is designed to interfere and cause errors in the manufacture of DNA from the virus
Some individual HIV viruses have a variation that allows them to produce DNA without errors
greater reproductive success
increase in number relative to the susceptible viruses
The population of HIV viruses has become resistance to 3TC
Rapid evolution
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

29. Fig
100
Patient
No. 1
Patient No. 2 75
Percent of HIV resistant to 3TC 50
Patient No. 3
Figure Evolution of drug resistance in HIV 25 2 4 6 8 10 12
Weeks

30. Natural selection does not create new traits, but edits or selects for traits already present in the population
The traits that will be selected for or selected against in any specific population is determined by the environment!
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

31. Fig
The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time 2 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

32. Fig
The Darwinian view of life predicts that evolutionary transitions should leave signs in the fossil record
(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)

33. Fig
Homology: characteristics in related species that have an underlying similarity even though they have different functions
Humerus
Radius
Ulna
Carpals
Metacarpals
Figure Mammalian forelimbs: homologous structures
Phalanges
Human
Cat
Whale
Bat
Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor

34. Fig
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

35. Vestigial structures are remnants of features that served important functions in the organism’s ancestors
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36. Homologous characteristic
Fig
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
The Darwinian concept of an evolutionary tree of life can explain homologies and show relationships between different groups
Evolutionary trees can be made using different types of data, for example, anatomical and DNA sequence data
Homologous
characteristic 5
Ostriches
Birds 6
Feathers
Hawks and
other birds

37. Convergent Evolution
Convergent evolution is the evolution of similar/analogous, features in distantly related groups
Analogous traits arise when groups independently adapt to similar environments in similar ways
Convergent evolution does not provide information about ancestry
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

38. Fig
NORTH
AMERICA
Sugar
glider
AUSTRALIA
Figure Convergent evolution
Convergent evolution is the evolution of similar/analogous, features in distantly related groups
Flying
squirrel

39. Biogeography
Biogeography: the geographic distribution of species, formed an important part of his theory of evolution
Islands have many endemic species that are often closely related to species on the nearest mainland or island
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40. The splitting of the supercontinent Pangaea, by continental drift, explains the modern distribution of species.
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41. What Is Theoretical About Darwin’s View of Life?
In science, a theory accounts for many observations and data and attempts to explain and integrate a great variety of phenomena
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43. Individuals in a population vary in their heritable characteristics.
Fig. 22-UN1
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.