Download Notes 1 Ch 22 - MacWilliams AP Biology

Chapter 22
Descent with Modification: A
Darwinian View of Life
Mrs. MacWilliams
AP Biology
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
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mechanism for this
evolutionary process was
natural selection…
the result of natural selection
is evolutionary adaptation
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The Darwinian view challenged
traditional views
What did these people contribute/believe
NOT EVOLUTION!
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Aristotle
 scala naturae
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Carolus Linnaeus
 binomial naming of species
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Georges Cuvier
 catastrophism
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Old Testament
 species designed by God
The two geologists:
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James Hutton
 changes in Earth’s surface can result from slow
continuous actions still operating today
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Charles Lyell
 uniformitarianism (change over time is constant)
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What did these people contribute/believe
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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
Lamarck’s Giraffes
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According to Lamarck’s theory of inheritance of acquired
characteristics
–ancestral shortnecked giraffes
stretched their
necks to reach
leaves high on
trees. Their
offspring were
born with longer
necks
– Incorrect!!!!
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
Darwin’ Research
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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
The Origin of Species

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Evolution explains life’s unity and diversity
Natural selection is a cause of adaptive evolution
Descent With Modification “evolution”
Artificial Selection…Selective Breeding
Darwin’s 4 Observations and 2 Inferences
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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
OBSERVATION #1
Spore
cloud
Observations
2, 3, and 4
Darwin’s 4 Observations and 2 Inferences
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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.
Summary of Natural Selection
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Differential Reproductive success
Increase the adaptation to a environment
New species may arise
Can amplify or diminish heritable traits
POPULATIONS evolve…individuals don’t!!!!
Why don’t individuals evolve??
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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.
Fig. 22-12
(a) A flower mantid
in Malaysia
(b) A stick mantid
in Africa
4 Lines of Evidence for Evolutionary Change
1.
Direct Observations
Example: Predation and Coloration in Guppies
Example: Evolution of Drug Resistant HIV
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
Example: Natural Selection in Action
HIV resistant to 3TC Drug
Natural selection
“edits”…it doesn’t
create
Natural selection favors
characteristics
that increase
“fitness”
2. The Fossil Record
3. Homology
similarity resulting from common ancestry
**Prefix “HOMO” means SAME
Homology/Embryology
anatomical
homologies not
visible in adult
organisms
Fig. 22-18
Homology/Embryology
Pharyngeal
pouches
Post-anal
tail
Chick embryo (LM)
Human embryo
Homology
Vestigial structures
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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)
Homology/Molecular
Homology/Convergent Evolution
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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
Homology/Convergent Evolution
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Convergent evolution
4. Biogeography
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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.
You should now be able to:
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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
You should now be able to:
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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)
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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