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Origins of Biological Diversity Chapter 15 Fossil Record • Found in sedimentary rock • Show clear relationship for many species over time example: horse • Two methods of dating: 1. Relative Dating 2. Radioactive Dating Relative Dating • Determine age of fossils relative to other fossils in different layers of rock • Rock superpositionyounger rock on top of older rock • Index fossils- fossils which we know when they lived *determines relative age Radioactive Dating • Elements such as 14C decay/breakdown at steady rate into another element • half life- length of time for half the radioactive atoms in sample to decay • # of radioactive atoms in bodies constant through time • Example carbon-14 decays to nitrogen-14, half life 5,730 years • Uranium-238 decays into Lead-206, 4.5 billion years * Determine actual age Geologic Time Scale • Based on relative and radioactive dating • Displays evolution of life and geologic events • Divided into eras: Precambrian Paleozoic Mesozoic Cenozoic • Eras divided into periods, periods into epochs Precambrian Era • ~4.6 bya to 580 mya • 1st prokaryotic cell • Stromatolites- mats of photosynthetic bacteria • 1st eukaryotic cell • 87% of Earth’s history Paleozoic Era • 579 mya to 245 mya • Age of the Invertebrates (marine) • Jawless Fish then Jawed (1st vertebrates) • First forests (coal forming) • Amphibians and reptiles • Pangea exists Agnaths Mesozoic Era • 244 mya to 65 mya • Triassic- Age of the Reptiles, mammal appear • Jurassic- dinosaurs flourish • Cretaceous- first flowering plants, mass extinction; climate change • 135 mya Pangea splits into Laurasia and Gondwana Cenzoic Era • • • • 64 mya to present Age of the Mammals Primates evolve Modern humans 200,000 years ago • Plate tectonics, present day positions Comparative Embryology • Similar developmental stages in vertebrate embryos • Example, gill pouches and bony tails Comparative Anatomy VESTIGIAL STRUCTURES HOMOLOGOUS STRUCTURES Comparative Biochemistry • Same four bases in DNA • Same 20 amino acids • Produce similar proteins (order of amino acids) • Example, human’s DNA 98.2% similar to chimpanzee • Example, Cytachrome C 104 aa’s, same in human and chimp, dog 13 differences, rattlesnakes 20 • Populations evolve, individuals do not