Transcript p p t fossils 91897

FOSSILS
Chapter 9, Section 1
Think About It . . .
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Can you name any
dinosaurs?
Do you know what they
looked like or how they
moved?
Scientists have been able
to tell us many things
about organisms (such as
dinosaurs) that lived
millions of years ago.
How do scientists learn
about these organisms if
they’ve never seen
them?
Fossils!
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Fossils = the remains or imprints of an organism
that lived long ago.
Fossils can be formed in five different ways. . .
1) Fossils in Rocks
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Usually when an organism dies,
it begins to decay right away.
But sometimes organisms are
buried by sediment when they die.
Sediment can preserve the organism.
Hard parts (shells, teeth, bones) are preserved
more often than soft parts (skin, organs).
These parts become fossils when the sediment
hardens to form a sedimentary rock.
2) Fossils in Amber
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Sometimes organisms (such as insects, frogs, and
lizards) are caught in sticky tree sap.
If the sap hardens around the insect, a fossil is
created.
Hardened tree sap is
called “amber.”
3) Frozen Fossils
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Ice and cold temperatures slow down decay.
Fossils can be preserved in blocks of ice.
Fossils of woolly mammoths, relatives of elephants
that went extinct 10,000 years ago, have been
found in ice.
4) Petrification
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Minerals can replace tissues
(organs, muscles, skin)
In animals, minerals fill the
tiny spaces in the hard tissues
(like bone)
In trees, minerals replace the
wood, so the wood becomes
rock.
5) Fossils in Asphalt/Tar
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In some places, asphalt
can bubble and form sticky
pools of tar.
The La Brea Tar Pits in L.A.
are at least 38,000 years
old.
These pools have trapped
and preserved many
different organisms, like the
saber-toothed cats & dire
wolves.
From these fossils scientists
have learned about what
California was like 10,000 to
40,000 years ago.
Trace Fossils
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Organisms can leave behind
clues about their lives that
are also fossils.
These clues were made by
an organism, but they do not
include parts of the
organism’s body.
This is called a trace fossil.
For example, fossils of
footprints / tracks tell
scientists how big the
animals was and how fast it
moved.
Other Examples of Trace Fossils
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Burrows (shelters made by animals that bury
themselves in the sediment) may be filled with
sediment and preserved.
“Caprolites” = dung (“poop”) that is fossilized.
Molds & Casts
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Mold = the print/impression left in sediment/rock
where the plant/animal was buried.
Cast = forms when sediment fills a mold and
becomes rock.
Both can show what the inside or outside of an
organism looked like.
What Can Fossils Tell Us?
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Fossils can show scientists 3 main things:
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The kind of organism that lived in the past
How the environment has changed (ex: forest
fossils found in Antarctica show the climate was
much warmer in the past)
How organisms have changed
How Old Is It?
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To understand the
history of the Earth,
scientists have put
fossils in order based
on their ages.
They use relative
dating and absolute
dating methods
Index Fossils
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Fossils of certain types of
organisms can be found all over
the world.
But these fossils are found only in
rock layers of a certain age.
These are called index fossils.
When scientists see a specific
index fossil, they know right
away how old it is
Ex: When scientists find Phacops
in a rock layer, they know the
rock layer is 400 million yrs old.
Pop Quiz
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What is a fossil?
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What are 5 different ways fossils can form?
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In rock, amber, ice, asphalt, or by petrification
What 3 things can fossils tell us?
1)
2)
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The remains or imprints of an organism that
lived long ago.
The kind of organism that lived in the past
How the environment has changed
How organisms have changed
Who loves fossilized poop (caprolites)?
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We all do!