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Published byAbigayle Boner Modified over 9 years ago
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Arguments & evidence
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How incredibly stupid not to have thought of that Thomas Huxley
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Arguments Blending inheritance Variability Isolation Age of the earth
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Arguments Blending inheritance -new adaptations diluted with each generation Darwin’s reply: Favorable traits maintained if popln isolated Some traits ‘preponent’ Adaptive traits arise often Enhanced reproduction of favorable traits
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Arguments Variability -Darwin confined natural selection to small, continuous variation How could new spp arise from small variations? -successive change through time How could small variations confer an advantage? -Darwin could not answer, later demonstrated How could selection act on a nonexistent trait? -preadaptation - new organ modified from another
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1% per generation change in anatomy <500000 yrs
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Arguments Isolation -how could a new spp evolve in close proximity to its parents Darwin did not emphasize isolation as a primary cause for evolution
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Arguments Age of the earth -earth was not old enough to allow time for evolution 5,000 50,000 75,000 100,000,000 Biblical Newton Buffon Kelvin 4,500,000,000present
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Arguments Blending inheritance Variability Isolation Age of the earth
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Evidence Systematics Geographic distribution Comparative anatomy Embryology Fossils Artificial selection Direct observation
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Evidence Systematics -gradation of species easily understood by evolutionary relationships
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Evidence Geographic distribution -evolutionarily related organisms geographically connected
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Evidence Geographic distribution -evolutionarily related organisms geographically connected marsupial radiation
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Evidence Comparative anatomy homologous/analogous organs
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Evidence Comparative anatomy homologous/analogous organs Darwin’s interpretation of homology has become the definition: similarity due to common ancestry
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Evidence Comparative anatomy homologous/analogous organs
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Organisms show curious similarities in structure and development unrelated to function
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Evidence Comparative anatomy convergent evolution
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Evidence Comparative anatomy vestigial organs
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Evidence Comparative anatomy vestigial organs femur whale ancestor modern whale
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Organisms have vestigial structural, developmental and molecular traits Vestigial structures are a manifestation of change through time
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Evidence Embryology -remarkable similarity among diverse vertebrates
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Evidence Fossils -vast majority of fossil forms differ from extant spp extinction succession transitional forms environmental changes
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Evidence Fossils -vast majority of fossil forms differ from extant spp extinction The fact that many species have gone extinct suggests that Earth’s flora and fauna have changed over time
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Evidence Fossils -vast majority of fossil forms differ from extant spp transitional forms
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Evidence Fossils -vast majority of fossil forms differ from extant spp “living fossils”
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Evidence Fossils -vast majority of fossil forms differ from extant spp extinction succession transitional forms environmental changes
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Evidence Artificial selection -accelerated evolution based on human-favored traits
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Evidence Artificial selection -accelerated evolution based on human-favored traits
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Evidence Direct observation -natural selection can be observed in real time Observations on living organisms show that populations and species change over time
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