Types of Fossils

Types of fossils

2. What is afossil?
•A fossil is the preserved remains of a once-
living organism (at least 10,000 yrs.old).
•Latin: fossilis (something dugup)
What do fossils tellus?
•Fossils give clues about organisms that lived
long ago. They help to show that evolution
hasoccurred.
•They also provide evidence about how
Earth’s surface has changed over time.
•Fossils help scientists understand what past
environments may have beenlike.

3. The FossilRecord
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All of the fossils that exist are part of the
FossilRecord
•Includes fossils that have yet to be
discovered
•Paleontologists-study life in thepast

4. Questions
4
1.What types of organisms existed in the
past?
2.What did the oceans look like over
different timeperiods?
3.What did the land look like over
different timeperiods?
4.How did organisms moveabout?
5.How did behaviors, such asflight,
evolve?

5. HOW IS A FOSSILFORMED?
1.Sediment
An animal is buried by
sediment, such as
volcanic ash or silt,
shortly after it dies. Its
bones are protected
from rotting by the
layer ofsediment.
2.Layers
More sediment layers
accumulate above the
animal’s remains, and
minerals, such as
silica (a compound of
silicon and oxygen),
slowly replace the
calcium phosphate in
thebones.
3.Movement 4. Erosion
Movement oftectonicErosion from rain,
plates, or giantrock rivers, and windwears
slabs that makeup away theremaining
Earth’s surface,liftsrock layers.Eventually,
up the sedimentsanderosion orpeople
pushes thefossil digging for fossils will
closer to thesurface.expose thepreserved
remains.

6. FIVE MAIN TYPES OFFOSSILS
Petrified
Fossils
Moldsand
Casts
Carbon
Films
Trace
Fossils
Preserved
Remains

7. •
•
•Theword“petrified”means
“turningintostone.”
Petrifiedfossilsformwhen
mineralsreplaceallorpart
ofanorganism.
Water is full of dissolved
minerals. It seeps through
the layers of sediment to
reach the dead organism.
When the water evaporates,
only the hardened minerals
are leftbehind.
PETRIFIEDFOSSILS
PETRIFIEDFOSSIL
The Field Museum inChicago
displays a fossil of a
Tyrannosaurusrex.

8. MOLDS ANDCASTS
•
MOLDFOSSIL
This mold, or imprint, isof
an extinct mollusk called
anammonite.
•
•
•
•
•A mold forms when hard parts ofan
organism are buried in sediment,
such as sand, silt, orclay.
The hard parts completely dissolve
over time, leaving behind a hollow
area with the organism’sshape.
A cast forms as the result of amold.
Water with dissolved mineralsand
sediment fills the mold’s empty
spaces.
Minerals and sediment that are left
in the mold make acast.
A cast is the opposite of itsmold.
CASTFOSSIL
This ammonite cast was
discovered in theUnited
Kingdom.

9. •All living things contain an
element called carbon.
•When an organism dies
and is buried in sediment,
the materials that make up
the organism breakdown.
•Eventually, onlycarbon
remains.
•The thin layer of carbon
left behind can show an
organism’s delicate parts,
like leaves on aplant.
CARBONFILMS
FERNFOSSIL
This carbon-film fossil ofa
fern is morethan
300 million yearsold.

10. TRACEFOSSILS
•Trace fossils show the
activities oforganisms.
•An animal makes a footprint
when it steps in sand ormud.
•Over time the footprint is
buried in layers of sediment.
Then, the sediment becomes
solid rock.FANCYFOOTWORK
This dinosaur footprint was
found in Namibia,Africa.

11. PRESERVEDREMAINS
Some organisms get preserved in or close to their
original states. Here are some ways that can happen.
Amber
An organism,
such as an insect,
is trapped in a
tree’s sticky resin
and dies. More
resin covers it,
sealing the insect
inside. It hardens
intoamber.
Tar
An organism,
such as a
mammoth, is
trapped in a tarpit
and dies. The tar
soaks into its
bones and stops
the bones from
decaying.
Ice
An organism,
such as a woolly
mammoth, dies in
a very coldregion.
Its body is frozen
in ice, which
preserves the
organism—even
itshair!

12. Earth SystemsScience
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Most fossils form when organisms are
buried insediment
NaturalCycle:The RockCycle
•Abiotic factors such as wind, rain, ice,
and sun weatherrocks
•Form sediments that are erodedby
water, landslides, orwind
•Depositedand accumulate over time to
cover the remains oforganisms/traces

13. Burial
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•Quick burial isimportant!
•Abiotic (non-living)and biotic (living)
factors destroy most bodies beforethey
becomefossils.
•Macroscopic and microscopic
scavengers, predators,decomposers,

14. Which OrganismsBecome
Part of the FossilRecord?
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•Soft BodyParts:skin,muscle
•Hard Body Parts: bone, teeth,shells,
andwood.
•Oldest bodyfossils?
•Phanerozoic Eon, Cambrian Period
(Trilobites)

15. Review Pre-CambrianLife
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•Hadean Eon:nofossils
•Archean Eon: only trace fossils of
prokaryotic organisms (no true nucleus,
otherorganelles)Stromatolites
•Proterozoic Eon: first eukaryotic
organisms, Stromatolites reach greatest
abundance, still no bodyfossils

16. Inorganic vs.Organic
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•Inorganic exoskeletons very resistant to
destruction
•Calcium
•Some inorganic exoskeletons
connected with organic material.
Unlikely to find these species in one
“piece” ie. seaurchin

17. Location, Location,Location…
17
•Underwater
•Close to run-off carryingsediment
•Stillwater
Nice neighborhoods:
•Lakes, ocean, rivers, swamps,deltas,
lagoons
Bad neighborhoods:
•Intertidal zone,Rainforests

18. The FossilRecord
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The Fossil Record is NOTcomplete
•Organisms live and die in different
environments
•Only some remains resistdestruction
•Of those only some willfossilize
Fewer than 10% of the organisms alive
today will becomefossils.