ECU BIOL 3620 - Evolution 9-10-14 (2 pages)

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Evolution 9 10 14 Darwin recognized that evolution required an old earth Darwin argued that the earth was billions of years old This was going against Lord Kelvin s theory of the Earth s age which he predicted to be only 20 million years old Radioactive Decay Half life amount of time it takes for half the atoms to give off radiation and decay o Different isotopes have different half lives o Uses radiodating to date fossils Plate Tectonics Continetial Drift new crust is being formed and old crust is being pushed into subduction zone o In the last 400 million years continental drifts have been drastic Big Bang 16 billion years ago Earth formed 4 5 billion years ago Oldest terrestrial rocks 38 billion years ago Abundant life 3 5 billion years ago Oxygen present in the atmosphere 2 5 billion years ago Fossil record shows that earlier organisms evolved into later organisms Vast majority of species are extinct Numbers of species increase over time Earlier organisms were smaller and more simple Fossils allow us to learn about extinct species Most organisms don t fossilize o Occasionally soft tissue fossilize Burgess Shale 505 mya 65000 specimens 93 species Fossils can provide clues of development o Head body size over time morphologists take interest in this o Scanning electron microscopy provides evidence of cell structure o Cat scans help determine function of hadrosaur crest Crest connected to naval cavity sound generated by blowing air ears tuned to frequency o Biomarkers reveal traces of life Biomarker distinctive molecules only produced through biological activity Earliest life unlikely to be preserved in fossils o Oldest evidence dates back to 3 7 bya Carbon in rocks controversial How do early organisms fit into the tree of life There are three basic groups we can group organisms in bacteria archea and archaea o It s controversial to place some old organisms in these categories because it s hard to judge o Bacteria was formed about 2 6 bya Evolution 9 10 14 Origin