2Fossils Preserved remains or traces of ancient organisms Ex. Shells, teeth, imprints, boneItems are found in sedimentary rock and amber.Paleontologists study fossils to learn about:Structure of ancient organisms, their environment and the ways in which they lived
3How do we date fossils?Relative dating: allows paleontologist to determine whether a fossil is older or younger than other fossils.Index fossils – distinctive fossils used to establish and compare the relative ages of rock layers and their fossils.
4Dating fossilsRadiometric Dating – using radioactive isotopes, which decay into stable isotopes at a steady rate ex. – potassium-40, carbon-14Half life – time required for half of the radioactive atoms in a sample to decay.
5Geological Time Scale Time line of Earth’s History Based on relative and absolute dating.Broken into eons, eras, and periods.
6Life on a changing planet Physical forces – climate and geological forcesBuilding mountains, opening coastlines, changing climates and geological forces have altered habitats of living organisms repeatedly throughout Earth’s history.Continental Drift/plate tectonics – PanageaBiological forces – the actions of living organisms over time have changed conditions in the land, water and atmosphere of planet earth.