1. The Fossil Record Ch. 6, section 3

2. HOW DO FOSSILS FORM MOST FOSSILS FORM WHEN ORGANISMS THAT DIE BECOME BURIED IN SEDIMENTS. USUALLY BONES OR SHELLS OF ANIMALS FORM FOSSILS

3. Petrified Fossils Fossils that are buried in sediment and turned to rock.

4. Molds and Casts Shells or other hard parts buried gradually dissolve and leave a blank space called a mold. (footprint) When minerals fill the space that was left a casts is formed.

5. Preserved remains Animals that have been found in ice and have not changed since the day they died.

6. Relative Dating Scientists look at the layers of sediment and rock to determine how old a fossil is. If a fossil is found closer to the surface it is usually younger. If it is found in an older layer (deeper) it is usually older.

7. Radioactive Dating Scientists can compare the amount of a radioactive element in a sample to the amount of the element into which it breaks down. Which can be used to determine the actual age of the fossil.

8. Precambrian Time 4.6 billion - 544 million years ago. Formation of Earth Bacteria forms (1st living thing) Animals first appeared 600 million years ago.

9. Paleozoic Era 544 million - 245 million years ago Sponges, jawless fish, jawed fish, sharks, and amphibians lived during this time.

10. Mesozoic Era 245 - 66 million years ago. Dinosaurs, mammals, birds appeared. Mass extinction happened during this time.

11. Cenozoic Era 66 millions years ago - present Large mammals (mammoths, saber- tooth tigers, etc) Humans appeared

12. Unanswered Qestions How did animals become extinct? Climate change- asteroid or volcanoes. We are exactly sure.