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17.1 Fossils Paleontologists- study fossils Fossil Record evidence for hist. of life and how species have changed over time Extinct- some species have died out Fossils Fossils Form buried in rock (sand/silt/clay) hardens around organism preserves an imprint of specimin dating Relative dating age of a fossil is compared to other fossils in other layers of rocks Index fossils easily recognized organism that only existed for a short period of time dating Radioactive dating C-14 dating fossils younger than 60,000 years Potassium-40 dating fossils billions of years old Time Geological Time represents evolutionary time line of earth Time is divided into eras Eras is divided into periods