2. Earths History __________________ - a timeline that organizes the events in Earths history Like a calendar extending from Earths formation to the present Divided into eons, eras, periods, and epochs Earths History

3. www.fas.org

4. ________-the largest group; divided by the Cambrian boundary (about 550 million years ago) when the variety of life forms explodes; billions of years long ____________: mass extinctions mark the boundaries between the eras; hundreds of millions years long _______________: blocks of time when a unique rock series was laid down; tens of millions of years long ________________: divisions of the most recent periods; several million years long

5. ____________________________________________ Typically form in ______________________, however: May form in rocks Amber Petrification Asphalt Frozen Fossils

6. ______________________ - any naturally preserved evidence of animal activity __________-a cavity in rock where a plant or animal was buried ___________-created when sediment fills in a mold and becomes rock History of Change The fossil record reveals a history of environmental change. Why? Studying the relationship between older and younger fossils

7. Fossils of organisms that lived during a relatively short, well-defined geologic time span Found in rock layers throughout the world Ammonites 230-208 MYA louisvillefossils.blogspot.com/2010/01/remark... brianlean.wordpress.com/2008/08/ Trilobite ~400 MYA _____________________________________________________________