Transcript Fossils - SharpSchool

Fossils
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Remains or traces of once living organisms
Most organisms decay and don’t become
fossils
Help approximate:
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When life began
How animals and plants lived
Extinction of species
Fossils
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Fossils are more likely to form if:
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Quick burial occurs
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Protected from predators and the elements
Organisms body has hard body parts (bones,
teeth, shells)
Types of Fossils
1. Petrified Fossils
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Soft tissue inside hard bones or teeth
decay
Minerals are deposited in spaces
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Examples = Petrified wood, dinosaur bones,
shells
2. Carbon Films
Fossil are buried
 Sediments pile up on fossil,
causes pressure and heat
 Gases and liquids are forced out leaving a
carbon silhouette of the original organism
(coal forms when ancient plants
become completely carbonized)
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3. Molds
A shell or organisms falls into
soft sediment and leaves an impression
 Sediment turns into rock
 Air somehow gets in and the shell or
organism decays
 What is left behind is the impression of
what the organism looked like
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4. Cast
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Sediment moves into the mold, hardens
into rock and produces a copy of the
organism
5. Preserved
Remains
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Entire body, including soft parts of
organisms have been preserved in some
way
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Mosquito trapped in tree resin
Frozen mammoth in Siberia
Found in tar pits of La Brea in California
6. Trace Fossils
Fossilized evidence of the
activity of organisms
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Fossilized tracks
Trails and burrows
7. Index Fossils
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Remains of organisms that were on Earth
for short periods of time
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Give information about the ages of rock layers
they are found in (trilobites, dinosaurs)