Early History. Principles of Evolution. The History of Evolutionary Thought. The History of Evolutionary Thought. The History of Evolutionary Thought

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1 Principles of Evolution Has become a unifying principle in Biology For >150 years, stimulated controversy mostly nonscientists Initial theory sparked controversy within science and biology Early History Preceded Darwin Ancient philosophers explained nature in terms of What they imagined to be true Not based on observation In 1500s, European philosophers began to exhibit discontent B.C. Plato B.C. Aristotle - Scala Naturae 3. Until 1700's Creationism James Ussher (17 th century, Biblical ) Sunday, October 23, 4004 BC a. Each species was created individually by God b. Earth was the center of the universe c. Man stood atop creation

2 G.L. Buffon creation provided a relatively small number of founding species that evolved through natural processes G. Cuvier theory of catastrophism L. Agassiz new creation after each catastrophe: proposed at least 50 separate catastrophes and creations J. Hutton developed uniformitarianism C. Lyell supported Hutton Lamarck inheritance of acquired characteristics Where Idea Came From? Darwin s Voyage on Beagle shaped many ideas of Biology Purpose of voyage Sail around world & survey little known coastal areas Darwin s Finches Galapagos formed from volcanoes Finch ancestors came from South America Different islands, different environments Today each island has own species

3 (a) large ground finch, beak suited to large seeds (b) small ground finch, beak suited to small seeds (c) warbler finch, beak suited to insects (d) tree finch, beak suited to leaves C. Darwin developed the theory of evolution; species evolved through natural selection and an adaptation to their ever-changing environment Darwin s Observations Populations have inherent potential to increase exponentially A. Wallace supported Darwin's theory Darwin s Observations Darwin s Observations Populations are fairly constant in size over long periods of times Natural resources are limited Competition important in limiting survival

4 Darwin s Observations Darwin s Deductions There is variation within individuals of a population & variations are inherited Only some organisms survive There is a struggle for existence among individuals in population Darwin s Deductions Individuals with favorable variations are more likely to survive and reproduce Darwin s Deductions Accumulation of variation over many generations is evolution When great enough a new species A gradual process What Exactly are Species? Distinct if they do not interbreed in nature All have differences within them Traits in population change Eventually new species arise

5 Evidence of Evolution Stages of Fossilization Fossils 1. Transitional forms are evidence of evolutionary change 2. Controversies over the interpretation of fossil data a. Dating of fossils b. Do fossils really show transitional forms? (a) (b) (c) Teeth became larger and harder, reflecting a change in diet from soft leaves and buds to more abrasive grasses. Pliohippus Selection for fast running on the open plains favored the evolution of stout, strong legs and large, hard hooves. Equus Body size increased, perhaps in response to selection by predators. Hipparion Archaeohippus Anchitherium grazing Merychippus If a modern horse had small teeth like these, the teeth would be ground away while it was still very young. Hyracotherium forefoot tooth Mesohippus Paleotheres browsing Comparative anatomy Homologous structures Evidence of evolution Comparative anatomy Evidence of evolution All mammals evolved from common ancestor

6 Evidence of evolution Comparative anatomy Analogous structures have similar form & function, but are structurally quite different Evidence of evolution Convergent evolution Unrelated organisms evolve similar adaptive characteristics Evidence of evolution Comparative anatomy: Evidence of Evolution Comparative embryology Vestigial structures These vestigial bones are similar in structure to those of the salamander but serve no function. All three animals inherited the bones from a common ancestor. salamander whale snake Fish All vertebrate embryos look similar to one another in early development, with the development of a tail and gill arches Snake Chicken Mouse Human Evidence of Evolution Evidence of Evolution Comparative biochemistry and molecular biology All cells have DNA, RNA, ribosomes, the same 20 amino acids, and use ATP as an energy carrier Comparative biochemistry and molecular biology DNA similarities

7 Evidence of Evolution Is Evolution Happening Today? Artificial selection Recent examples 1. Antibiotic resistance in bacteria 2. Pesticide resistance in insects Patterns in Evolution? Different from original Darwin model Gradualism Darwin described evolution as a slow & gradual process Evolution may occur more rapid than earlier thought Punctuated equilibrium Evolution does not always occur Patterns in Evolution? Present-day Evolution Key concepts 1. The variations upon which natural selection works are produced by chance mutations 2. Selection produces organisms that are well adapted to a particular environment

8 Present-day Evolution 3. The processes of evolution select for organisms that are best adapted to a particular environment "survival of the fittest" 4. These processes occur constantly in all the species of life on Earth