copyright © 2007 by allyn and bacon theory of evolution i.darwin’s theory of evolution ii. cause...
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Copyright © 2007 by Allyn and Bacon
Theory of Evolution
I. Darwin’s theory of evolution
II. Cause of evolution
III. Evidence of evolution theory
Copyright © 2007 by Allyn and Bacon
Evolution – descent with modification
All species are descendants of ancestral species. Species changes.
Charles Darwin (1809-1882)
I. Darwin’s theory of evolution
Question: origin of the organisms(plants, animals, bacteria, etc.)
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Before Darwin, 18th century:
• Species were created by God
• Aristotle: species do not change
• Lamarck, 1809: species evolved
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II. Cause of evolutionDarwin: characteristics of animal and plants
suit to environment - adaptation
Beak
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What causes the fit to environment?
Lamarck: innate drive causes evolution
Darwin: natural selection causes evolution
1859: On the Origin of Species by Means of Natural Selection
Observations:1. member difference, 2. traits inherited, 3. capable of over producing, 4. competing for resources
→ individuals with traits favoring surviving and reproducing tend to leave more offspring → accumulation of favorable traits
Adaptation is caused by selection
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Mantid
Note that • Individuals do not evolve, although they may change.• Acquired characteristics do not pass to offspring.• Natural selection amplifies/diminishes Inheritable traits.
• Adaptation is caused by selection• New species develop if environment changes
or organisms migrate to new environment• Adaptation to variety of environment → diversity
of life• All species are from a common ancestor
(unity of life)
Darwinian theory of evolution
Weeks
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PatientNo. 1
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III. Evidence of evolution theory
1. From direct observationExample: virus evolution
III. Evidence of evolution theory
2. From fossil record of changes over time
Bristolia insolensBristoliabristolensis
Bristolia harringtoni
Bristolia mohavensis
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San Bernardio, CaliforniaDeposited 500 mya
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(a) Pakicetus (terrestrial)
(b) Rhodocetus (predominantly aquatic)
(c) Dorudon (fully aquatic)
Pelvis andhind limb
Pelvis andhind limb
(d) Balaena (recent whale ancestor)
III. Evidence of evolution theory
2. From fossil record of changes over
timeand origin of new
species
Cetaceans
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Fossils provide evidence of evolutionevidence for origin of new speciesevidence for chronological order
Fossils show pattern of evolution
III. Evidence of evolution theory
3. From homology of species: closely related
species are similar in structure
Mammals evolve form a common ancestor - unity of life
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human WhaleCat Bat
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Anatomical and molecular homology show characteristics from deep ancestor shared by more species;Newly evolved characteristics are shared by small group of species.
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Darwin:Species evolveCause of evolution: natural
selectionwith evidence
direct observationfossil recordhomology