1. Fossil Evidence of Change Main Idea: Fossils provide evidence of the change in organisms

2. Objective Compare techniques for dating fossils. Identify and describe major events using the geologic time scale. What life form could the atmosphere of the Earth have supported? Why?

3. Early Earth History Land environments: a molten body of elements—4.6 billion years ago. Denser elements pull to the center by gravity. Volcanic features—the cooling interior radiated heat to the surface.

4. Atmosphere Gravitational field enabled Earth to maintain an atmosphere. Gases expelled by volcanoes included water vapor, carbon dioxide CO 2, sulfur dioxide, carbon monoxide, hydrogen sulfide H 2 S, hydrogen cyanide, nitrogen, and hydrogen. Little or no oxygen.

5. Categories of Fossils 393, table 14-1, trace fossils, molds and casts, replacements, petrified or permineralized, amber, original materials. Fossil formation—certain condition—none found in igneous rocks.

6. Dating Fossils Relative dating—-based on law of superposition. Comparing rock layers Radiometric dating—uses the decay of radioactive isotopes—half-life Uranium 238 (U) decays to Lead (Pb) 206 With a half-life of 4510 million years found in igneous and metamorphic rocks. Carbon-14 half-life of 5730 years.

7. Geologic time scale Eon, era, periods—time scale on pp. 397. Precambrian Paleozoic era—Cambrian explosion Mesozoic era---K-T boundary Cenozoic era Plate tectonics describes land movements