history of evolutionary thought
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History of Evolutionary Thought
Why is there a diversity of life?
Plato (427-347 B.C.)
• Real World Ideal• Perceived World
Imperfect via Senses
• **No need for evolution because organisms are already perfect.
Aristotle (384-322 B.C.)
• Scala Naturae All life organized on a scale, or ladder, of increasing complexity.
• Organisms are fixed at each “rung”.
• No evolution of species.
Old Testament
• Judeo-Christian culture
• Species individually designed and permanent
• No evolution of organisms
1700 A.D. Europe
• Natural Theology
• Adaptations or organisms evidence organisms were created with purpose.
• Taxonomy Reveal steps of scale of life created by God.
– Linnaeus System we use today
• K, P, C, O, F, G, S
Georges Cuvier (1769-1832)• Paleontology – study of
fossils in France.• Documented changes
in organisms present in each rock layer.
• **Catastrophism – boundary layers caused by local catastrophe and repopulated by organisms migrating in.
James Hutton (1726-1797)
• **Gradualism – geological features are cummulative products of slow, but continuous processes
• Canyons formed by rivers cutting through rocks as observed daily.
Charles Lyell (1797-1875)
• **Uniformitarianism – Geological processes, such as erosion, sediment deposition, volcanoes, earthquakes, have not changed throughout Earth’s history.
Hutton + Lyell to Biology
• 1) Geological change results from slow, continuous actions rather than sudden events and therefore, the Earth must be very old (older than 6000 years as proposed by theologians)
• 2) Very slow and subtle processes persisting over a long period of time can cause substantial change.
End of 1700’s
• Many naturalists suggested that life had evolved along with the evolution of Earth.
Jean Baptiste de Lamark(1744-1829)
• Invertebrate Collection in Paris
• Saw many lines of descent of older to younger fossils leading to modern
• Species move up the ladders to greater complexity
Lamark (cont.)
• Evolution was driven by an innate tendency toward perfection.
• Evolution responded to organisms needs.• Mechanism of Evolution:
– 1) Use and disuse – those parts used extensively to cope with environment enlarged and those not used reduced in size.
– 2) Passing on of Acquired Traits• Traits one develops in one’s lifetime – read,
music
Lamark (cont.)
• Nice theory…No evidence that Acquired Traits can be passed on.– Biceps of Blacksmith, removed tails of mice
• Deserves a lot of credit:– Evolution best explanation for both fossil
record and current diversity of life– Recognition of great age of Earth– Adaptation to Environment as product of
Evolution
Charles Darwin (1809-1882)
• 1) The occurrence of Evolution (Descent with Change) – Unity of life related by descent from some common prototype.
• 2) Mechanism is Natural Selection
Natural Selection
• 1) Species produce more offspring than can survive
• 2) Struggle for survival- limited environmental resources
• 3) Variation within a species – no two humans (except identical twins) alike.
• 4) Those best suited for the environment are selected by nature to produce more offspring.
Darwin (cont.)
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