s09112lect2

s09112lect2 - Evolution Chapters 2225 The Scientific Method...

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Evolution, Part 1 1 BIOL 112 Evolution Chapters 22–25 BIOL 112 The Scientific Method Two major aspects: ! Observations — Facts — What we see ! Interpretations — Theories — What it means A “good” theory does two things: " Explains what happens " 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 of 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) 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, 60 m.y. b.p. Horse Evolution Series Horse Evolution Series BIOL 112 Hyracotherium foot: 5 toes BIOL 112 Orohippus, 45 m.y. b.p.
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Evolution, Part 1 4 BIOL 112 Mesohippus, 35 m.y. b.p. Note foot: 3 toes BIOL 112 Merychippus, 26 m.y. b.p. BIOL 112 Pliohippus, 3 m.y. b.p. BIOL 112 Prezwalski’s Horse ( Equus ferus przewalskii ) Eurasian wild horse until early 1800’s; now found only in zoos BIOL 112 Modern Horse ( Equus caballus ) This breed selected for small size BIOL 112 Horse Lineage Macroevolution ! Shows general trends over past 60 million years ! Increasing body size ! Shift of toe structure from many digits to one (hoof) ! Change in diet/dentition from soft leaves to hard grasses ! Repeated branching speciation events (Adaptive Radiations) followed by selective survival
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Evolution, Part 1 5 BIOL 112 BIOL 112 Horse Evolution Showing a series of divergences and extinctions with geological ages, and marking the change in food behavior, to modern form. From: MacFadden (2005) Science 307 BIOL 112 How Old are Fossils? Dating methodologies ! Relative dating; stratigraphy Distinguishes older from younger ! Absolute dating, usually by radioactive decay Gives an estimate in years BIOL 112 BIOL 112 BIOL 112
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Evolution, Part 1 6 BIOL 112 Relative Dating ! Index fossils, common forms unique to a particular geologic period and world-wide in distribution ! Using index fossils as markers, can reconstruct a whole history of strata from different locations in the world into one sequence ! Assembled strata sequence is geologic time scale ! Need to apply dates to time scale using absolute
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This note was uploaded on 10/20/2009 for the course BIOL 112 taught by Professor Vaughn during the Spring '08 term at Texas A&M.

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s09112lect2 - Evolution Chapters 2225 The Scientific Method...

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