Inside the Restless Earth
Chapter 3 Section 4
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A fossil of a preserved remains of once living
organisms.
Fossils give clues about organisms that lived long
ago. They help to show that evolution has
occurred.
They also provide evidence about how Earth’s
surface has changed over time.
Fossils help scientists understand what past
environments may have been like.
 A:Fossils
are the remains of
organisms that are preserved.
◦Hard parts (bones, shells) get
buried in sediment
◦Soft parts of the organism
decays
 A:Petrifaction
is the process in
which minerals replace an
organisms tissues.
◦ Replacement-organism’s tissues are
completely replaced by minerals
◦ Permineralization-minerals fill
spaces
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A: An organism gets stuck in soft,
sticky tree sap and then gets covered
in more sap. The sap then hardens.
◦ Hardened tree sap is called amber.
◦ Insects, frogs, lizards have been found in
amber.
◦ Organism land on sap
◦ Gets stuck
◦ Gets covered in more sap
◦ Sap hardens
 A:
Frozen fossils are the
remains of organisms that
have been preserved in ice.
Usually during the ice age.
◦ Cold temperatures slow down
decay
◦ Organism falls-freezes
◦ Makes good fossils
 A:
Fossils are in asphalt
because organisms got stuck
in the thick, sticky substance.
◦ La Brea asphalt/tar pits in
California are over 38,000 years
old.
◦ Scientists learned a lot about the
past environment in California.
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La Brea Tar Pits
 A:
These form when animal
footprints, burrow, or coprolite
are filled in with sediment and are
preserved in rock.
◦ Tell how big the animal was
◦ How fast the animal moved
◦ Borrows that animals made are an
example
◦ Coprolite is preserved animal dung
 A:
A mold is a cavity (hole-space)
where a plant or animal was
buried.
 A: A cast is an object created
when sediment fills a mold and
becomes a rock.
◦ Mold-impression in ground or rock
◦ Cast—sediment filled mold
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Internal and External mold
 A:
The fossil record provides
evidence about the past.
◦ We know more about organisms with
hard parts (ex. Shells)
◦ The fossil record is incomplete.
◦ Many organisms never become
fossils
◦ Many fossil haven’t been discovered
 A:
Fossil records provide
evidence of changes in the
environment.
◦ Marine fossils were found on a
mountain top. This suggests that
the mountain top was once the
ocean floor.
◦ Fossils show evidence of climate
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A: Fossils show how organisms have
changed over time. Scientists study
the relationship between fossils.
◦ Fossils in different rock layers suggest
that fossils can be younger or older
depending on the layer they are found in.
◦ Only a fraction of organisms in history
have been fossilized = incomplete fossil
record
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A: Fossils are used to date rocks
because certain types of fossils can be
used to estimate the absolute (exact)
age of the sedimentary rock they are
found in.
• An index fossil is a fossil used to estimate
the absolute age of rock layers.
• An index fossil lived for a short period of
time.
• Ammonites and Trilobites (index fossils)
 A:Mummification
is the
preservation of a body, either
animal or human.
◦ Some mummies are preserved wet,
some are frozen, and some are dried.
◦ It can be a natural process or it may
be deliberately achieved.
◦ Eliminate moisture