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

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

Aristotle ( 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 ( ) 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 ( ) **Gradualism – geological features are cummulative products of slow, but continuous processes Canyons formed by rivers cutting through rocks as observed daily.

Charles Lyell ( ) **Uniformitarianism – Geological processes 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 ( ) 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 explaination for both fossil record and current diversity of life –Recognition of great age of Earth –Adaptation to Environment as product of Evolution

Charles Darwin ( ) 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.)