1. Do Now: Put in order from oldest to most recent What did each person contribute to science?
Gregor Mendel
James Watson
Charles Darwin

2. How are they linked??? Charles Darwin 1859
Gregor Mendel 1865 (significance recognized 1900)
James Watson

3. Descent with Modification: A Darwinian View of Life
Chapter 22
Descent with Modification:
A Darwinian View of Life

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. Concept 22.1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species
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7. Scala Naturae and Classification of Species
The Greek philosopher Aristotle viewed species as fixed and arranged them on a scala naturae
The Old Testament holds that species were individually designed by God and therefore perfect
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8. Carolus Linnaeus interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose
Linnaeus was the founder of taxonomy, the branch of biology concerned with classifying organisms
He developed the binomial format for naming species (for example, Homo sapiens)
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9. Figure 22.2
1809
Lamarck publishes his
hypothesis of evolution.
1798
Malthus publishes
“Essay on the Principle
of Population.”
1812
1858
Cuvier publishes his extensive studies of vertebrate fossils.
1795
While studying species in the Malay Archipelago, Wallace (shown in 1848) sends Darwin his hypothesis of natural selection.
Hutton proposes
his principle of
gradualism.
1830
Lyell publishes
Principles of Geology.
1790
1870
1809
183136
1859
Charles Darwin
is born.
Darwin travels around the world on HMS Beagle.
On the Origin of Species is published.
Figure 22.2 The intellectual context of Darwin’s ideas.
1844
Darwin writes his essay on descent with modification.
The Galápagos Islands

10. Video: Grand Canyon
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11. Sedimentary rock layers (strata) Younger stratum with more recent
Figure 22.3
Sedimentary rock
layers (strata)
Figure 22.3 Formation of sedimentary strata with fossils.
Younger stratum
with more recent
fossils
Older stratum
with older fossils

12. Great Britain EUROPE NORTH AMERICA ATLANTIC OCEAN The Galápagos
Figure 22.5a
Great
Britain
EUROPE
NORTH
AMERICA
ATLANTIC
OCEAN
The
Galápagos
Islands
AFRICA
Equator
Malay Archipelago
SOUTH
AMERICA
PACIFIC
OCEAN
Chile
Brazil
AUSTRALIA
PACIFIC
OCEAN
Figure 22.5 The voyage of HMS Beagle.
Andes Mtns.
Cape of
Good Hope
Argentina
Tasmania
Cape Horn
New
Zealand

13. Darwin in 1840, after his return from the voyage
Figure 22.5b
Figure 22.5 The voyage of HMS Beagle.
Darwin in 1840, after his return from the voyage

14. The Galápagos Islands Equator PACIFIC OCEAN Pinta Genovesa Marchena
Figure 22.5c
The
Galápagos
Islands
PACIFIC
OCEAN
Pinta
Genovesa
Marchena
Equator
Santiago
Daphne
Islands
Pinzón
Fernandina
Isabela
Santa
Cruz
Figure 22.5 The voyage of HMS Beagle.
Santa Fe
San
Cristobal 20 40
Florenza
Española
Kilometers

15. Figure 22.5d
Figure 22.5 The voyage of HMS Beagle.
HMS Beagle in port

16. Video: Galápagos Islands Overview
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17. Video: Albatross Courtship Ritual
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18. Video: Galápagos Sea Lion
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19. Video: Galápagos Tortoises
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20. Darwin’s Focus on Adaptation
Darwin perceived adaptation to the environment and the origin of new species as closely related
From studies made years after Darwin’s voyage, biologists have concluded that this is what happened to the Galápagos finches
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21. (a) Cactus-eater (b) Insect-eater (c) Seed-eater Figure 22.6
Figure 22.6 Three examples of beak variation in Galápagos finches.
(c) Seed-eater

22. The Origin of Species Darwin explained three broad observations:
The unity of life
The diversity of life
The match between organisms and their environment
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23. Descent with Modification
Darwin never used the word evolution in the first edition of The Origin of Species
The phrase descent with modification summarized Darwin’s perception of the unity of life
The phrase refers to the view that all organisms are related through descent from an ancestor that lived in the remote past
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24. Darwin’s theory meshed well with the hierarchy of Linnaeus
In the Darwinian view, the history of life is like a tree with branches representing life’s diversity
Darwin’s theory meshed well with the hierarchy of Linnaeus
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25. Figure 22.7
Figure 22.7 “I think. . .”

26. Figure 22.8 Descent with modification. Elephas maximus (Asia)
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) 60 34 24
5.5 2
104
Millions of years ago
Years ago

27. 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
Darwin drew two inferences from two observations
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28. Cabbage Brussels sprouts Broccoli Kale Wild mustard Kohlrabi
Figure 22.9
Cabbage
Selection for apical (tip) bud
Brussels
sprouts
Selection for axillary (side) buds
Broccoli
Selection for flowers and stems
Figure 22.9 Artificial selection.
Selection for stems
Selection for leaves
Kale
Wild mustard
Kohlrabi

29. Observation #1: Members of a population often vary in their inherited traits
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30. Figure 22.10
Figure Variation in a population.

31. Observation #2: All species can produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce
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32. Figure 22.11
Spore
cloud
Figure Overproduction of offspring.

33. Inference #1: Individuals whose inherited traits give them a higher probability of surviving (Darwinian Fitness) and reproducing in a given environment tend to leave more offspring than other individuals
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34. Inference #2: 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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35. Video: Seahorse Camouflage
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36. (a) A flower mantid in Malaysia (b) A leaf mantid in Borneo
Figure 22.12
Figure Camouflage as an example of evolutionary adaptation.
(a) A flower mantid in Malaysia
(b) A leaf mantid in Borneo

37. Populations evolve (NOT individuals)
Natural selection alters allele frequencies, doesn’t make new traits
Adaptations vary with different environments
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38. Concept 22.3: Evolution is supported by an overwhelming amount of scientific evidence
New discoveries continue to fill the gaps identified by Darwin in The Origin of Species
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39. Direct Observations of Evolutionary Change
Two examples provide evidence for natural selection: natural selection in response to introduced plant species, and the evolution of drug-resistant bacteria
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40. Natural Selection in Response to Introduced Plant Species
Soapberry bugs use their “beak” to feed on seeds within fruits
In southern Florida soapberry bugs feed on balloon vine with larger fruit; they have longer beaks
In central Florida they feed on goldenrain tree with smaller fruit; they have shorter beaks
Correlation between fruit size and beak size has also been observed in Louisiana, Oklahoma, and Australia
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41. These cases are examples of evolution by natural selection
In all cases, beak size has evolved in populations that feed on introduced plants with fruits that are smaller or larger than the native fruits
These cases are examples of evolution by natural selection
In Florida this evolution in beak size occurred in less than 35 years
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42. Soapberry bug with beak inserted in balloon vine fruit
Figure 22.13a
FIELD STUDY
Figure Inquiry: Can a change in a population’s food source result in evolution by natural selection?
Soapberry bug with beak inserted in balloon vine fruit

43. On native species, southern Florida
Figure 22.13b
RESULTS
Beak 10
On native species, southern Florida 8 6 4 2
Number of individuals
Museum-specimen average 10 8
On introduced species, central Florida
Figure Inquiry: Can a change in a population’s food source result in evolution by natural selection? 6 4 2 6 7 8 9 10 11
Beak length (mm)

44. The Evolution of Drug-Resistant Bacteria
The bacterium Staphylococcus aureus is commonly found on people
One strain, methicillin-resistant S. aureus (MRSA) is a dangerous pathogen
S. aureus became resistant to penicillin in 1945, two years after it was first widely used
S. aureus became resistant to methicillin in 1961, two years after it was first widely used
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45. MRSA bacteria use a different protein in their cell walls
Methicillin works by inhibiting a protein used by bacteria in their cell walls
MRSA bacteria use a different protein in their cell walls
When exposed to methicillin, MRSA strains are more likely to survive and reproduce than nonresistant S. aureus strains
MRSA strains are now resistant to many antibiotics
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46. Chromosome map of S. aureus clone USA300
Figure 22.14 1
2,750,000
250,000 base pairs
2,500,000
Chromosome map of S. aureus clone USA300
500,000
2,250,000
Key to adaptations
Methicillin resistance
Ability to colonize hosts
750,000
Increased disease severity
2,000,000
Increased gene exchange (within species) and toxin production
Figure Impact: The Rise of MRSA
1,000,000
1,750,000
1,250,000
1,500,000

47. Natural selection does not create new traits, but edits or selects for traits already present in the population
The local environment determines which traits will be selected for or selected against in any specific population
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48. Homology Homology is similarity resulting from common ancestry
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49. Anatomical and Molecular Homologies
Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor
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50. Humerus Radius Ulna Carpals Metacarpals Phalanges Human Cat Whale Bat
Figure 22.15
Humerus
Radius
Ulna
Carpals
Metacarpals
Figure Mammalian forelimbs: homologous structures.
Phalanges
Human
Cat
Whale
Bat

51. Comparative embryology reveals anatomical homologies not visible in adult organisms
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52. Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo
Figure 22.16
Pharyngeal pouches
Post-anal tail
Figure Anatomical similarities in vertebrate embryos.
Chick embryo (LM)
Human embryo

53. Pharyngeal pouches Post-anal tail Chick embryo (LM) Figure 22.16a
Figure Anatomical similarities in vertebrate embryos.
Chick embryo (LM)

54. Pharyngeal pouches Post-anal tail Human embryo Figure 22.16b
Figure Anatomical similarities in vertebrate embryos.
Human embryo

55. Vestigial structures are remnants of features that served important functions in the organism’s ancestors
Examples of homologies at the molecular level are genes shared among organisms inherited from a common ancestor
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56. Homologies and “Tree Thinking”
Evolutionary trees are hypotheses about the relationships among different groups
Homologies form nested patterns in evolutionary trees
Evolutionary trees can be made using different types of data, for example, anatomical and DNA sequence data
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57. Homologous characteristic
Figure 22.17
Branch point
Lungfishes
Amphibians 1
Tetrapods 2
Mammals
Digit- bearing
limbs
Amniotes 3
Lizards and snakes
Amnion 4
Crocodiles
Homologous characteristic
Figure Tree thinking: information provided in an evolutionary tree. 5
Ostriches 6
Birds
Feathers
Hawks and other birds

58. A Different Cause of Resemblance: Convergent Evolution
Convergent evolution is the evolution of similar, or 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
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59. Sugar glider Flying squirrel NORTH AMERICA AUSTRALIA Figure 22.18
Figure Convergent evolution.
Flying squirrel

60. The Fossil Record
The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time
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61. Cetaceans and even-toed ungulates
Figure 22.19
Most mammals
Cetaceans and even-toed ungulates
Figure Ankle bones: one piece of the puzzle.
(a) Canis (dog)
(b) Pakicetus
(c) Sus (pig)
(d) Odocoileus (deer)

62. Figure 22.UN01
Figure 22.UN01 In-text figure, p. 465

63. Fossils can document important transitions
For example, the transition from land to sea in the ancestors of cetaceans
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64. Other even-toed ungulates
Figure 22.20
Other even-toed ungulates
Hippopotamuses
†Pakicetus
†Rodhocetus
Common ancestor of cetaceans
†Dorudon
Figure The transition to life in the sea.
Living cetaceans 70 60 50 40 30 20 10
Key
Pelvis
Tibia
Millions of years ago
Femur
Foot

65. Biogeography
Biogeography, the geographic distribution of species, provides evidence of evolution
Earth’s continents were formerly united in a single large continent called Pangaea, but have since separated by continental drift
An understanding of continent movement and modern distribution of species allows us to predict when and where different groups evolved
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66. NORTH AMERICA AUSTRALIA Figure 22.18
Figure Convergent evolution.
AUSTRALIA

67. Endemic species are species that are not found anywhere else in the world
Islands have many endemic species that are often closely related to species on the nearest mainland or island
Darwin explained that species on islands gave rise to new species as they adapted to new environments
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68. 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
Darwin’s theory of evolution by natural selection integrates diverse areas of biological study and stimulates many new research questions
Ongoing research adds to our understanding of evolution
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69. Individuals in a population vary in their heritable characteristics.
Figure 22.UN02
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.
Figure 22.UN02 Summary figure, Concept 22.2
and
Over time, favorable traits accumulate in the population.

70. Figure 22.UN03
Figure 22.UN03 Test Your Understanding, question 7

71. Figure 22.UN04
Figure 22.UN04 Appendix A: answer to Test Your Understanding, question 7