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LECTURE 5 THEORY OF EVOLUTION What Is Evolution? Pre-Darwinian views: - largely based on religious beliefs - world is static and young - outcome of phenomenon have to have a goal Plato (427-347BC) – philosophy of idealism Aristotle (384-322BC) – species were fixed/permanent Origins of Evolutionary Thought •1700’s: Compte de Buffon - supreme being of god that created but suggested that time modififed and changed them. •1700’s: Hutton: gradualism – earth showed changes over time, river would eat away of rocks – GRADUAL change occur •1700’s: Malthus: Essay on the Principles of Populations – poor people of London, you had overpopulation that will resolve the famine, relevant to Darwin. •1800’s: Lamarck: evolution – /change •1800’s: Lyell: Principles of Geology – world older than 1000yo, and toronado, hurricane change physical environment so organisms changed with it. World not static •1800’s: Voyage of the Beagle - darwin Jean-Baptiste de Lamarck (1744-1829) •first to use the term evolution (change) •first to provide a causal mechanism: provide mechanism how evolution occurred, many naturalists and geolists that talked about changes but none explained how changes occurred. The inheritance of acquired characters : characteristics that they needed they would aquire, lifestyle how offspring will be Evolution: Lamarck •occurred by inheritance of acquired characteristics (giraffe longer necks) – you aquire during your lifetime may be passed on to offspring. Disease not 100% pass on. Genetics, nothing known of genetics. Did not suggest genetics. Something that they did over lifetime. Ie. Dye hair green. • Individuals passed on to offspring body and behavior changes acquired during their lifetime. • Need genetic basis. Lamarack evolution produces a ladder of life bacteria spontaneously occurred, Organisms progress in complexity But if that is the case, all organisms may transform into humans, so no make sense. But what was known, Organisms progress to higher and higher levels Charles Darwin 1809-1882 initiated scientific study of evolution approach based on hypothsis testing • USED SCIENTIFIC APPROACH by measuring, using experiments. Darwin’s Voyage H.M.S. Beagle (1831-1836) Darwin: age 22, ship’s naturalist rainforests of Brazil  fossils  birds and reptiles of the Galapagos Islands Development of Darwin’s Ideas on Evolution Galapagos finches • Biodiversity of nature ( tropics) – spiders, lilies, flaura, flona, flightless cormorant birds, iguana (ability to swim, webbing between toes, flat tails to swim), tortoises, flat shell for vege, finches, mockingbirds Darwin doubts fixity of species (March, 1837) how come more species on island than mainland? – why do they resemble? – fly distance of mainland and island, cant fly back. Birds that survived that were able to adapt to the environment. Same ancestor but change occur over time. Development of Darwin’s Ideas on Evolution • Darwin reads Malthus’: Essay on the Principle of Population struggle for existence(adaptation, survival, competition) circumstances favorable variations would tend to be preserved and unfavorable ones would be destroyed.” Charles Darwin (1838) • Did not know about genes, if you have too many, not enough resources, competition. Those outcome and beta others will get shelter food etc. favorable variations will survive. Events Leading up to the Publication of The Origin of Species •June 1858: Received “On the tendency of varieties to depart indefinitely from the original type” by A.R. Wallace •First comprehensive theory of evolution Darwin and Wallace both have theory of natural selection at same time not together •Co-discoverer with A.R. Wallace of the mechanism of evolution: Natural selection • No genes theory Publication •1859: Publication of “The origin of species by means of natural selection or the preservation of favoured races in the struggle for life” Examining the Evidence for Evolution graphical representations of theory of common descent and alternative hypotheses: Figure 9.7 (a) Static model Species arise separately and do not change over time. |||| (b) Transformation Species arise separately but do change over time in order to adapt to the changing environment.// (c) Separate types Species do change over time, and new species can arise; but each group of species derives from a separate ancestor that arose independently. Y Y (d) Common descent Species do change over time, and new species can arise. All species derive from a common ancestor. W Evidence For Common Descent 1. Fossils record – concrete – compare – date - preserved but no hard skeleton( little left invertibrates) - traces of organisms that lived in the past • many fossils provide evidence for extinct species • not all fossils resemble living organisms • many extinctions – BIRD is longest lived • Darwin interpreted extinction as evidence that species are dynamic and can change Fossils and Transitional Forms • •traits that are intermediate between older and younger species ( whales – now no limbs ) • •Paleontologists have discovered extinct whales that had hind limbs • EAR BONES • Why the change? – reproduce more , gradual change as species become more adapted to live in aquatic env • Living species “succeed” fossil species in the same region. (SLOTHS) • Extinct forms are the ancestors of modern forms, and species change over time • 4 Millions of years ago horse fossils provide a clear sequence of evolutionary change HORSE W Y I 2. Classification 3. Biogeography - Biogeography – geographical distribution of organisms - •Different species of mockingbird found on Galapagos all resemble species found on the mainland - physically compare the characteristics – more similarities that are those in close proximities. Further if farther away Figure 9.13 - • species are found where they are because they evolved from ancestors that inhabited those regions - Continental drift, Australia – unique animals – south America (time isolation) 4. Anatomy Anatomy: Distinguishing Homology from Analogy HOMOLOGY : • similarity of traits due to shared ancestry – human arm, dog, seal flipper • Descent with modification over time Structural Homologies • Anatomical similarities between organisms • Forelimbs have same set of bones, humerus(wrist), radius and ulna(palm), carpal(knuckles), metacarpals(fore fingers), phalanges(fingers) • Adaptation to different environments ie turtle hand to swim, horse for speed. – to niche, similarities because common ancestors and adapt
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