FOSSILS

Fossils Is any preserved evidence of an organism Plants, animals, and even bacteria can form fossils Not all organisms fossilize. Most organisms decompose before they have a chance to become fossilized.

6 Types of fossils Trace fossil Molds and casts Replacement Petrified or Permineralized Amber Original material

1) Trace Fossils Indirect evidence left by an organism Examples: Footprints and Burrows

2) Molds and casts A mold is an impression of an organism A cast is a mold filled with sediment

3) Replacement Original material of an organism is replaced with mineral crystals

4) Petrified or permineralized Empty pore spaces are filled in by minerals, such as in petrified wood

5) Amber Preserved tree sap traps an entire organism

6) Original material Mummification or freezing preserves original organisms

Paleontologist People who study fossils He or she attempts to read the record of life in rocks.

Fossils tell us: Organisms before have evolved from earlier organisms When species have become extinct What structures are similar among species (Homologous structures) Date of when organism/fossil existed

Geological Time Scale A model that expresses the major geological and biological events in Earth’s history

What makes a geological time period? Periods are divisions in an Era At the end of each time period, an event occurred leading to large percentage of living things becoming extinct This event is known as Mass Extinction http://youtu.be/FlUes_NPa6M

Mass Extinctions The last mass extinction occurred about 65 million years ago when the last surviving dinosaurs became extinct