1. Chapter 22 Descent with Modification: A Darwinian View of Life
Mrs. MacWilliams
AP Biology

2. Darwin Introduces a Revolutionary Theory
the many species of organisms presently inhabiting Earth are descendants of ancestral species that were different from the modern species
mechanism for this
evolutionary process was
natural selection…
the result of natural selection
is evolutionary adaptation

3. The Darwinian view challenged traditional views

4. What did these people contribute/believe
NOT EVOLUTION!
Aristotle
scala naturae
Carolus Linnaeus
binomial naming of species
Georges Cuvier
catastrophism
Old Testament
species designed by God
The two geologists:
James Hutton
changes in Earth’s surface can result from slow continuous actions still operating today
Charles Lyell
uniformitarianism (change over time is constant)

5. What did these people contribute/believe
Thomas Malthus
potential for human population to increase faster than food supplies and other resources (influenced Darwin)
Alfred Wallace
Published his paper on natural selection at the same time Darwin did
Jean-Baptiste de Lamarck
species evolve through use and disuse of body parts and the inheritance of acquired characteristics
Unsupported by evidence

6. Lamarck’s Giraffes
According to Lamarck’s theory of inheritance of acquired characteristics
ancestral short-necked giraffes stretched their necks to reach leaves high on trees. Their offspring were born with longer necks
Incorrect!!!!

7. What did these people contribute/believe
Charles Darwin
Descent with modification explains life’s unity and diversity
Natural selection is a cause of adaptive evolution
Wrote On the Origin of Species by Means of Natural Selection
aka The Origin of Species

8. Darwin’ Research
Observed adaptations of plants and animals in diverse environments
Species resembled other species of the same climate
Fossils and geologic observations pointed to the fact that Earth has been changing
Galapagos Islands inhabited by species from South America then diversified…ADAPTATIONS!!!
Natural selection is the mechanism of evolution….biological diversity is the product of evolution

9. The Origin of Species Evolution explains life’s unity and diversity
Natural selection is a cause of adaptive evolution

10. Descent With Modification “evolution”

11. Artificial Selection…Selective Breeding

12. Darwin’s 4 Observations and 2 Inferences
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 their environment can support
Observation #4: Owing to lack of food or other resources, many of these offspring do not survive

13. OBSERVATION #1
Figure Variation in a population

14. Observations 2, 3, and 4 Spore cloud
Figure Overproduction of offspring

15. Darwin’s 4 Observations and 2 Inferences
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.

16. Summary of Natural Selection
Differential Reproductive success
Increase the adaptation to a environment
New species may arise
Can amplify or diminish heritable traits
POPULATIONS evolve…individuals don’t!!!!

17. Why don’t individuals evolve??
The word 'evolution' in biology is reserved for *species*, not individual organisms.
Genetically, every individual organism does not change, but a *population* changes over time.
Darwin explained of how species change (evolve). Even though each individual dies with the same genes it is born with, some individuals will survive better than others, and reproduce more. Those individuals with traits that give them a slight edge in this competition for survival and reproduction, will ON AVERAGE produce more offspring. And *THAT* is why the population changes (evolves) over time.

18. (a) A flower mantid in Malaysia (b) A stick mantid in Africa
Fig
(a) A flower mantid
in Malaysia
(b) A stick mantid
in Africa
Figure Camouflage as an example of evolutionary adaptation

19. 4 Lines of Evidence for Evolutionary Change
Direct Observations
Example: Predation and Coloration in Guppies
Example: Evolution of Drug Resistant HIV

20. Example: Natural Selection in Action
Can predation
pressure select
for size & age
at maturity in
guppies?
Change in predator
resulted in different
variations in the
population being
favored

21. Example: Natural Selection in Action HIV resistant to 3TC Drug
Natural selection “edits”…it doesn’t create
Natural selection favors characteristics that increase “fitness”

22. 2. The Fossil Record

23. 3. Homology similarity resulting from common ancestry
**Prefix “HOMO” means SAME

24. Homology/Embryology
anatomical homologies not visible in adult organisms

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

26. Homology Vestigial structures
Remnants of features that served important functions in the organism’s ancestors
Examples in humans: coccyx, wisdom teeth, appendix (?), “goosebumps”, external ear muscles, etc. (see Human Vestigial PPT if time)

27. Homology/Molecular

28. Homology/Convergent Evolution
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

29. Homology/Convergent Evolution

30. 4. Biogeography Geographic distribution of species
Influenced by continental drift from the large continent of Pangea over 200 million years ago
Example: Horses originated on North America when South America was not yet connected. Earliest horse fossils will be found only on North America.
ENDEMIC- species of plants and animals found only in one place and nowhere else on earth.

31. You should now be able to:
Explain that, prior to Darwin, it was believed that species do not change and the Earth was very young (a few thousand years old).
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 *Lemarck’s giraffes
Explain what Darwin meant by “descent with modification”
Describe how Darwin was the first person to propose evidence for Natural Selection
Explain Darwin’s 4 Observations and 2 Inferences

32. You should now be able to:
Explain why an individual organism cannot evolve
Describe at least four lines of evidence for evolution by natural selection
**Strongest evidence: all organisms share essentially the same genetic code (DNA with A, T, G, and C)
7. Describe the two examples of direct observation of evolution (“Predation and Coloration in Guppies” and “Drug Resistant HIV”)
8. Define Homologous/Analogous and Vestigial structures
9. Describe convergent evolution with examples (flying squirrel/sugar glider)
9. Explain artificial selection using the wild mustard plant as an example