1. Fossils
Ex-Life

2. What are Fossils? Remains of past life Two types: Altered remains
Unaltered remains

3. Unaltered Remains Remains that haven’t changed over the years.
“hard parts”
Examples:
Teeth
Bones
Shells
Whole organisms (under special circumstances)

4. Petrification Altered Organism turns into stone
Often with trees (cells replaced with silica by water)
Creates an exact replica

5. Molds and Casts Altered Mold: indent Cast: raised
Mold holds the shape of the object and the cast is the reverse

6. Carbonization Altered Only happens in fine sediment
Organism is pressed and liquids and gases are squeezed out
Only a thin film of carbon is left
Lots of details!

7. Amber Fossilized tree sap Flows over organism and hardens
Protects delicate organisms
DOESN’T ALTER ORGANISM (unaltered remains)

8. Indirect Evidence AKA trace fossil
Any evidence of past life that is not an actual life form
Examples:
Footprints and tracks
Burrows
Gastroliths
Coprolites

9. Fossil Preservation 2 conditions are necessary: William Smith
Rapid burial
Decomposition
Scavengers
Hard parts
More resilient
William Smith
Fossils can be used in geology
Why?

10. Fossil Succession Fossils are found in a specific order
Any period of time can be identified by its fossils
Order:
Age of Trilobites
Age of Fishes
Age of Coal Swamps
Age of Reptiles
Age of Mammals

11. Index Fossils Requirements: Widespread geographically
Short period of time (geologically)
Large numbers