The Fossil Record

Fossils Preserved remains or traces of ancient organisms Ex. Shells, teeth, imprints, bone Items 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

How 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.

Dating fossils Radiometric Dating – using radioactive isotopes, which decay into stable isotopes at a steady rate ex. – potassium-40, carbon-14 Half life – time required for half of the radioactive atoms in a sample to decay.

Geological Time Scale Time line of Earth’s History Based on relative and absolute dating. Broken into eons, eras, and periods.

Life on a changing planet Physical forces – climate and geological forces Building mountains, opening coastlines, changing climates and geological forces have altered habitats of living organisms repeatedly throughout Earth’s history. Continental Drift/plate tectonics – Panagea Biological forces – the actions of living organisms over time have changed conditions in the land, water and atmosphere of planet earth.