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Created By Gina Wike
Fossils
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A fossil is evidence such
as remains, imprints or
traces of once living
organisms preserved in
rock
Fossils are found
predominantly in
sedimentary rock
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Fossils tell us when,
where, & how
organisms lived
Fossils have helped scientists:
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1.
2.
3.
Determine when life began
When plants & animals 1st lived on land
When dinosaurs disappeared (other
organisms also)
How fossils form
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Body of an organism must be protected from
scavengers & bacteria
Body of organism must be covered by
sediments (a quick burial)
Needs to have hard parts such as bones & teeth
Fossil Types
Petrified Remains, Carbonaceous
Film, Molds, Casts, Original
Remains, Trace, & Index
Petrified Remains
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Hard & rocklike
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Some or all remains
have been replaced by
another mineral
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Example: (bone)
calcium is removed and
replaced with quartz
Carbonaceous Film
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most living organisms
contain carbon
sometimes carbon is the
only thing left
Coal is a fossil, but is
more important as a fuel
Molds
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A mold is a cavity in rock that is left behind
when an organism decays
Cast
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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
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Actual organism remains
Amber (tree sap) preserves the organism
Ice preserves an organism
Trace Fossils
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Fossilized tracks &
evidence of other
animal activity
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Ex. Animal tracks &
worm burrows
Index Fossils
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Criteria to be an index fossil
1. Existed on Earth for a short period of
time
2. Wide spread geographically
3. Abundant
Determine the relative (how related) age of
rock layers