Ch. 21-25 Evolution

Ch. 21-25 Evolution - Evolution Chapters 21–25 BIOL 112...

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Evolution, Part 1 1 BIOL 112 Evolution Chapters 21–25 BIOL 112 The Scientific Method Two major aspects: ± Observations — Facts — What we see ± Interpretations — Theories — What it means A “good” theory does two things: ² Explains what happens ² Predicts what will happen, if certain conditions are established. (Not fortune-telling, but expected data from specified situation: experiment) BIOL 112 Evolution: Major Biological Paradigm Evolution: a change in population of organisms over long period of time Basis of change — change in genetic composition of population. Genetic changes produce: ± Change in biochemistry ± Change in morphology ± Change in behavior ± Any other aspects of organisms under genetic control BIOL 112 Observations Significant to Evolution ± Fossil Record ± Anatomical Homologies ± Vestigial Organs ± Embryological Development ± Molecular (Sequence) Homologies BIOL 112 Fossils ± From the Greek: “dug up” ± Preserved parts of plants or animals that were once alive ± Hard parts have highest chance of being preserved: bones, teeth, wood, shells* ± Soft parts found less frequently: skin, feathers, leaves, flowers; rarely, even cell structures are found ± Organic materials usually replaced by inorganic materials (stone) * Taphonomy — the science of decaying organisms over time and how this relates to fossilization. BIOL 112
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Evolution, Part 1 2 BIOL 112 BIOL 112 BIOL 112 BIOL 112 BIOL 112 BIOL 112
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Evolution, Part 1 3 BIOL 112 BIOL 112 BIOL 112 BIOL 112 Hyracotherium (“Eohippus”) Skull, 55 m.y. b.p. Horse Evolution Series Horse Evolution Series BIOL 112 Hyracotherium foot: 4 toes BIOL 112 Orohippus, 50 m.y. b.p.
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Evolution, Part 1 4 BIOL 112 Mesohippus, 40 m.y. b.p. Note foot: 3 toes BIOL 112 Merychippus, 17 m.y. b.p. BIOL 112 Pliohippus, 15 m.y. b.p. BIOL 112 Prezwalski’s Horse ( Equus ferus przewalskii ) Eurasian wild horse until early 1800’s; now found only in zoos Equus appears about 4 m. y. b. p. BIOL 112 Modern Horse ( Equus caballus ) The horse in the picture is an adult, not a colt. This particular breed selected for small size BIOL 112 Horse Lineage Macroevolution ± Shows general trends over past 60 million years: ± Increasing body size; change in proportions ± Shift of toe structure from many digits to one (hoof) ± Change in diet/dentition from soft leaves to hard grasses ± Macroevolutionary sequence ± Repeated branching speciation events ( Adaptive Radiations ) followed by selective survival and extinctions
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Evolution, Part 1 5 BIOL 112 BIOL 112 Horse Evolution Showing a series of adaptive radiations and extinctions with geological ages, and marking the change in food behavior, to modern form. From: MacFadden (2005) Science 307
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This note was uploaded on 04/28/2010 for the course BIOL 102 taught by Professor Aufderheide during the Spring '10 term at Texas A&M.

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Ch. 21-25 Evolution - Evolution Chapters 21–25 BIOL 112...

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