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Download 1/23/02 Lecture Highlights – Evolution
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1/23/02 Lecture Highlights – Evolution In general sense: evolution is “change through time” Outline • Evolution of evolutionary thinking (history) • Darwin’s theories of evolution • Evidence for evolution “The great chain of being” • Aristotle’s “Scala Naturae” • Species “fixed” – do not evolve • Supernatural force • Organized forms – lower to higher (e.g., jellyfish to humans) Erasmus Darwin – Charles’ grandfather • One of earliest evolutionary thinkers • Life came from “one living filament” (common ancestor) • Temple of Nature (1802) (famous poem) John Baptiste Lamarck • Organisms change over time (evolve) • Mechanism: principle of use/disuse • Inheritance of acquired characters Example – Giraffe • As a species, giraffe was “created” • Within a generation, stretched necks to reach juciest leaves • Parents that stretched necks->offspring w/long necks • Across generations – longer & longer necks Charles Darwin – Voyage of the Beagle (5 year trip around earth) • Galapagos finches – • 13 species – Some unique to individual islands – Beaks for feeding on specialized foods – Resembled mainland ancestor Darwin’s theoriesOrganisms evolve over time- descent with modification (macroevolution) – accepted The primary mechanism of evolutionary change is natural selection (microevolution) – not readily accepted So, Darwinean evolution is “descent with modification”; change in populations through time “descent with modification” Predictions: • Relatedness of life forms • Homology - similarities that link dissimilar life forms together – common descent (e.g,. bat wing, human arm) • Hierarchy: current (extant) forms can be grouped by decreasing similarity • Change through time • Direct Observation: change observed in natural populations • Example: Peppered Moth in Great Britain • Frequencies of light and dark moths changed with industrial revolution • 20th Century – clean air standards -> less soot -> trend reversed • We saw evolution happen! • • Fossil Record: documents abundant change! • Extinction • Many, many, many fossils represent extinct organisms • Transitional forms (e.g., Archeopteryx) • Whale pelvis – vestigial trait: rudimentary (functionless) traits homologous to fully functional traits in closely related species / whale fossils also represent transition • NYTimes 1-22-02 – Fish fossils used to date continental shifts – S America from Antarctica ~20 MYA • Succession • Example: Horse • Life on earth is old • Fossil dating • Geological processes (e.g., erosion)