1. Title page from The Origin of Species published 1859
Chapter 22 - Descent With Modification
Title page from The Origin of Species published 1859
wrote – Origin of Species by
Means of Natural Selection
Charles Darwin -
- naturalist
- sailed on the Beagle, survey ship, 22 years old
- collected specimens: plants and animals
- he found fossils different from modern species
- Darwin was influenced by Lyell’s Principles of Geology and thought that the earth was more than 6000 years old
* - He observed adaptations of plants and animals that inhabited many diverse environments

2. Figure 22.2 The historical context of Darwin’s life and ideas
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.
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.
Figure 22.2 The historical context of Darwin’s life and ideas

3. acquired characteristics
Historical Ideas
Taxonomy - Linnaeus:
Paleontology – Cuvier:
Gradualism - Hutton:
Uniformitarianism - Lyell :
Evolution - Lamark :
Populations - Malthus :
Natural Selection - Darwin :
Inheritance - Mendel :
naming and classifying the diverse forms of life “for the greater
glory of God”: kingdom, phylum, class, order, family, genus, species
paleontologist, fossils, recognized that extinctions occurred
he argued it must have been due to
catastrophism
geologist: profound change in the Earth’s features,
slow and continuous
geologist, geologic processes have not changed throughout Earth’s history rates of building and eroding same now as in past
Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of
acquired characteristics
The mechanisms he proposed are unsupported by evidence
studied populations
human suffering was due to populations
2 ideas: 1. descent with modification
2. natural selection through adaptation
parents pass traits to offspring

4. Acquired traits are not inherited
Figure 22.4 Acquired traits cannot be inherited

5. The Voyage of HMS Beagle
- discovered that most of the animal species on the Galapagos lived nowhere else
in the world
but they resemble species on the South American mainland
- Darwin studied
Finches (birds)
adaptation
In reassessing his observations, Darwin perceived to the
environment and the origin of new species as closely related processes

6. (a) Cactus-eater (c) Seed-eater (b) Insect-eater
Figure 22.6 Beak variation in Galápagos finches
(b) Insect-eater

7. In the Darwinian view, the history of life is like a tree with branches representing life’s diversity
Figure 22.7 “I think . . .”

8. 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_________________________
Darwin then described four observations of nature and from these drew two inferences
artificial selection
Observation #1: Members of a population often vary greatly in their traits
Observation #2: Traits are inherited from parents to offspring
Observation #3: All species are capable of producing more offspring than the environment can support
Observation #4: Owing to lack of food or other resources, many of these offspring do not survive
Inference #1: 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
Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations

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

10. individuals populations Adaptations edits selects selected for
Note that ______________do not evolve; ______________ evolve over time
Natural selection can only increase or decrease heritable traits in a population
________________ vary with different environments
Adaptations
edits
selects
Natural selection does not create new traits, but ________ or _________ for traits already present in the population
The local environment determines which traits will be __________________ or
_________________ in any specific population
selected for
selected against

11. (b) A stick mantid in Africa Fig. 22-12b
Figure Camouflage as an example of evolutionary adaptation
(b) A stick mantid
in Africa

12. (a) A flower mantid in Malaysia
Fig a
Observation #2: Traits are inherited from parents to offspring
Figure Camouflage as an example of evolutionary adaptation
(a) A flower mantid
in Malaysia

13. The Evolution of Drug-Resistant HIV
The use of drugs to combat HIV _______________ viruses resistant to these drugs
HIV uses the 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
selects for
reverse transcriptase
Some individual HIV viruses have a ______________ that allows them to produce DNA without errors
These viruses have a _______________________________ and increase in number relative to the susceptible viruses
The population of HIV viruses has therefore _____________________ to 3TC
The ability of bacteria and viruses to evolve rapidly poses a challenge to our society
variation
greater reproductive success
developed resistance

14. The Evolution of Drug-Resistant HIV
Fig
The Evolution of Drug-Resistant HIV
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

15. The Fossil Record provides evidence transitions
The fossil record __________________ of the extinction of species, the origin of new groups, and changes within groups over time
transitions
The Darwinian view of life predicts that evolutionary __________________ should leave signs in the fossil record
Paleontologists have discovered fossils of many such transitional forms

16. A transitional fossil linking past and present
Vestigal structures -
historical remnants of structures
that had important functions in
ancestors
ex. snakes – pelvis, leg bones

17. (a) Pakicetus (terrestrial)
Fig ab
The transition to life in the sea
(a) Pakicetus (terrestrial)
Figure The transition to life in the sea
(b) Rhodocetus (predominantly aquatic)

18. (c) Dorudon (fully aquatic)
Fig cd
Pelvis and
hind limb
(c) Dorudon (fully aquatic)
Figure The transition to life in the sea
Pelvis and
hind limb
(d) Balaena
(recent whale ancestor)

19. Homologous structures: anatomical signs of descent with modification
new species descend from
ancestral species
more evidence
for evolution
anatomical homologies
Homologous structures -
similarity in characteristics resulting from common ancestors
Homologies
– ex. forelimb: human, cat, whale, bat
- anatomical
- embryological
– ex. pharyngeal pouches in throat – all vertebrates have
- molecular
– all use same genetic material (DNA)
Analogous structures – body parts resemble one another
- evolved independently
ex. fins/body shape:
sharks, penguins, porpoise
all are adaptations for
swimming

20. Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo
Fig
Pharyngeal
pouches
Post-anal
tail
Figure Anatomical similarities in vertebrate embryos
Chick embryo (LM)
Human embryo

21. Homologies and “Tree Thinking”
The Darwinian concept of an ___________________ of life can explain homologies
Evolutionary trees are hypotheses about the __________________ among different groups
Evolutionary trees can be made using different types of data, for example,
_______________________________________________
evolutionary tree
relationships
anatomical and DNA sequence data

22. 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
Homologous
characteristic 5
Ostriches
Birds 6
Feathers
Hawks and
other birds

23. Convergent Evolution Convergent evolution analogous
_________________ is the evolution of similar, or _______________, features in distantly related groups
Analogous traits arise when groups ____________________________
to _______________________ in similar ways
Convergent evolution does not provide information about _____________
independently adapt
similar environments
ancestry

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