Created By Gina Wike

Fossils A fossil is evidence such as remains, imprints or traces of once living organisms preserved in rock A fossil is evidence such as remains, imprints or traces of once living organisms preserved in rock Fossils are found predominantly in sedimentary rock Fossils are found predominantly in sedimentary rock Fossils tell us when, where, & how organisms lived Fossils tell us when, where, & how organisms lived

Fossils have helped scientists: 1. Determine when life began 1. Determine when life began 2. When plants & animals 1st lived on land 2. When plants & animals 1st lived on land 3. When dinosaurs disappeared (other 3. When dinosaurs disappeared (other organisms also) organisms also)

How fossils form Body of an organism must be protected from scavengers & bacteria Body of an organism must be protected from scavengers & bacteria Body of organism must be covered by sediments (a quick burial) Body of organism must be covered by sediments (a quick burial) Needs to have hard parts such as bones & teeth Needs to have hard parts such as bones & teeth

Fossil Types Petrified Remains, Carbonaceous Film, Molds, Casts, Original Remains, Trace, & Index

Petrified Remains Hard & rocklike Hard & rocklike Some or all remains have been replaced by another mineral Some or all remains have been replaced by another mineral Example: (bone) calcium is removed and replaced with quartz Example: (bone) calcium is removed and replaced with quartz

Carbonaceous Film most living organisms contain carbon most living organisms contain carbon sometimes carbon is the only thing left sometimes carbon is the only thing left Coal is a fossil, but is more important as a fuel Coal is a fossil, but is more important as a fuel

Molds A mold is a cavity in rock that is left behind when an organism decays A mold is a cavity in rock that is left behind when an organism decays

Cast A cast is when a cavity is filled with sediments that harden into rock & take the shape of the original organism that decayed A cast is when a cavity is filled with sediments that harden into rock & take the shape of the original organism that decayed

Original Remains Actual organism remains Actual organism remains Amber (tree sap) preserves the organism Amber (tree sap) preserves the organism Ice preserves an organism Ice preserves an organism

Trace Fossils Fossilized tracks & evidence of other animal activity Fossilized tracks & evidence of other animal activity Ex. Animal tracks & worm burrows Ex. Animal tracks & worm burrows

Index Fossils Criteria to be an index fossil Criteria to be an index fossil 1. Existed on Earth for a short period of 1. Existed on Earth for a short period of time time 2. Wide spread geographically 2. Wide spread geographically 3. Abundant 3. Abundant Determine the relative (how related) age of rock layers Determine the relative (how related) age of rock layers