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History of Evolutionary Thought

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.).

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History of Evolutionary Thought

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  1. History of Evolutionary Thought Why is there a diversity of life?

  2. Plato(427-347 B.C.) • Real World  Ideal • Perceived World  Imperfect via Senses • **No need for evolution because organisms are already perfect.

  3. 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.

  4. Old Testament • Judeo-Christian culture • Species individually designed and permanent • No evolution of organisms

  5. 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

  6. 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.

  7. 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.

  8. Charles Lyell (1797-1875) • **Uniformitarianism – Geological processes, such as erosion, sediment deposition, volcanoes, earthquakes, have not changed throughout Earth’s history.

  9. 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.

  10. End of 1700’s • Many naturalists suggested that life had evolved along with the evolution of Earth.

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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.

  16. Darwin (cont.)

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