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Occurrence of evolution was debated. Georges Cuvier (early 1800’s) – paleontologist & comparative anatomist - established extinction as fact: described large mammal fossils with no living members of the species recent fossils resembled extant species more than ancient fossils do

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Occurrence of evolution was debated

  • Georges Cuvier (early 1800’s) – paleontologist & comparative anatomist

  • - established extinction as fact:

  • described large

  • mammal fossils

  • with no living members

  • of the species

  • recent fossils resembled extant species more than ancient fossils do

  • suggested that extinctions were caused by periodic global catastrophes

  • - did not think evolution could occur:

  • believed that function dictates form, and similarity in form

  • reveals similarity in function, not common ancestry

“Irish elk”

mastodon


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similarity in form can reveal similarity in function

convergence – trait adapted to similar function but

with a different origin


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similarity in form can reveal similarity in function

convergence – trait adapted to similar function but

with a different origin


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Occurrence of evolution was debated

  • Étienne Geoffroy-St. Hilaire (early 1800’s) – vertebrate morphologist

  • believed that form dictates function: similarity due to shared “archetype”

  • evidence:homologous structures,

  • vestigial traits

  • evidence:embryonic changes

  • thought that form could be changed

  • by the environment and inherited

  • thought that morphological change

  • did not have to be gradual


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three-toed sloth

giant ground sloth

Charles Darwin ends the debate

Charles Darwin

- medical school dropout; earned a theology degree

- botany professor nominated him to be a naturalist on a

voyage to South American (1831-1836), HMS Beagle

encountered more evidence for evolution: biogeography

- fossils similar to extant species in South American, but not elsewhere


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Charles Darwin ends the debate

Charles Darwin

- medical school dropout; earned a theology degree

- botany professor nominated him to be a naturalist on a

voyage to South American (1831-1836), HMS Beagle

encountered more evidence for evolution: biogeography

- new species in Galápagos that were

similar to mainland species

- differences in species among

islands on the Galápagos


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Charles Darwin ends the debate

Charles Darwin

- medical school dropout; earned a theology degree

- botany professor nominated him to be a naturalist on a

voyage to South American (1831-1836), HMS Beagle

encountered more evidence for evolution: biogeography

- 14 species of finches, adapted

to different niches (different

food sources)


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Charles Darwin ends the debate

Charles Darwin

- medical school dropout; earned a theology degree

- botany professor nominated him to be a naturalist on a

voyage to South American (1831-1836), HMS Beagle

encountered more evidence for evolution: biogeography

- Australian marsupials outwardly similar and with similar niches to

placental species elsewhere

Australian sugar glider

North American flying squirrel


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Charles Darwin ends the debate

Charles Darwin

- medical school dropout; earned a theology degree

- botany professor nominated him to be a naturalist on a

voyage to South American (1831-1836), HMS Beagle

encountered more evidence for evolution: biogeography

- fossils similar to extant species in South American, but not elsewhere

- new species in Galápagos that were similar to mainland species

- differences in species among islands on the Galápagos

- 14 species of finches, adapted to different niches (food source)

- Australian marsupials outwardly similar and with similar niches to

placental species elsewhere


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common ancestry

- homology

- related species

- biogeography

change over time

- vestigial traits

- selective breeding

- direct observation

- fossil record

History of “evolutionary thought” & evidence for evolution

Charles Darwin

- not the first to suggest that evolution has occurred

- amassed the evidence for “descent with modification”

- suggested natural selection as a mechanism

Evidence for “descent with modification”


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Structural homology

Homology – similarities across species

especially when similar form is modified for different function


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Developmental homology

Homology – similarities across species

especially when similar form is modified for different function


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Biochemical homology

Homology – similarities across species

especially when similar form is modified for different function

also commonality of genetic code, amino acids


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Related species & biogeography

Adaptive radiation of honeycreepers on Hawaiian islands


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Vestigial traits – no longer in use, but present in reduced form


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Selective breeding & direct observation

experimental evolution; rapid evolution in nature

Teosinte


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Selective breeding & direct observation

experimental evolution; rapid evolution in nature


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