FOSSILSFOSSILSChapter 9, Section 1Chapter 9, Section 1

Think About It . . . Think About It . . . Can you name any Can you name any

dinosaurs?dinosaurs? Do you know what Do you know what

they looked like or they looked like or how they moved?how they moved?

Scientists have been Scientists have been able to tell us many able to tell us many things about things about organisms (such as organisms (such as dinosaurs) that lived dinosaurs) that lived millions of years ago.millions of years ago.

How do scientists How do scientists learn about these learn about these organisms if they’ve organisms if they’ve never seen them?never seen them?

Fossils!Fossils! Fossils = the remains or imprints of an Fossils = the remains or imprints of an

organism that lived long ago. organism that lived long ago. Fossils can be formed in five different Fossils can be formed in five different

ways. . .ways. . .

1) Fossils in Rocks1) Fossils in Rocks

Usually when an organism dies, Usually when an organism dies, it begins to decay right away. it begins to decay right away.

But sometimes organisms are But sometimes organisms are buried by sediment when they die. buried by sediment when they die.

Sediment can preserve the organism.Sediment can preserve the organism. Hard parts (shells, teeth, bones) are preserved more Hard parts (shells, teeth, bones) are preserved more

often than soft parts (skin, organs).often than soft parts (skin, organs). These parts become fossils when the sediment hardens to These parts become fossils when the sediment hardens to

form a sedimentary rock.form a sedimentary rock.

2) Fossils in Amber2) Fossils in Amber Sometimes organisms (such as insects, frogs, Sometimes organisms (such as insects, frogs,

and lizards) are caught in sticky tree sap.and lizards) are caught in sticky tree sap. If the sap hardens around the insect, a fossil is If the sap hardens around the insect, a fossil is

created.created. Hardened tree sap is Hardened tree sap is

called “amber.” called “amber.”

3) Frozen Fossils3) Frozen Fossils Ice and cold temperatures slow down decay.Ice and cold temperatures slow down decay. Fossils can be preserved in blocks of ice.Fossils can be preserved in blocks of ice. Fossils of woolly mammoths, relatives of Fossils of woolly mammoths, relatives of

elephants that went extinct 10,000 years elephants that went extinct 10,000 years ago, have been found in ice.ago, have been found in ice.

4) Petrification4) Petrification Minerals can replace Minerals can replace

tissues (organs, muscles, tissues (organs, muscles, skin)skin)

In animals, minerals fill the In animals, minerals fill the tiny spaces in the hard tiny spaces in the hard tissues (like bone)tissues (like bone)

In trees, minerals replace In trees, minerals replace the wood, so the wood the wood, so the wood becomes rock.becomes rock.

5) Fossils in Asphalt/Tar5) Fossils in Asphalt/Tar In some places, asphalt In some places, asphalt

can bubble and form sticky can bubble and form sticky pools of tar.pools of tar.

The La Brea Tar Pits in L.A. The La Brea Tar Pits in L.A. are at least 38,000 years are at least 38,000 years old.old.

These pools have trapped These pools have trapped and preserved many and preserved many different organisms, like different organisms, like the saber-toothed cats & the saber-toothed cats & dire wolves.dire wolves.

From these fossils From these fossils scientists have learned scientists have learned about what California was about what California was like 10,000 to 40,000 years like 10,000 to 40,000 years ago.ago.

Trace FossilsTrace Fossils Organisms can leave Organisms can leave

behind clues about their behind clues about their lives that are also fossils.lives that are also fossils.

These clues were made These clues were made by an organism, but they by an organism, but they do not include parts of do not include parts of the organism’s body.the organism’s body.

This is called a trace This is called a trace fossil.fossil.

For example, fossils of For example, fossils of footprints / tracks tell footprints / tracks tell scientists how big the scientists how big the animals was and how fast animals was and how fast it moved.it moved.

Other Examples of Trace Other Examples of Trace FossilsFossils

Burrows (shelters made by animals that Burrows (shelters made by animals that bury themselves in the sediment) may be bury themselves in the sediment) may be filled with sediment and preserved.filled with sediment and preserved.

““Caprolites” = dung (“poop”) that is Caprolites” = dung (“poop”) that is fossilized.fossilized.

Molds & CastsMolds & Casts Mold = the print/impression left in Mold = the print/impression left in

sediment/rock where the plant/animal was sediment/rock where the plant/animal was buried.buried.

Cast = forms when sediment fills a mold and Cast = forms when sediment fills a mold and becomes rock.becomes rock.

Both can show what the inside or outside of Both can show what the inside or outside of an organism looked like.an organism looked like.

What Can Fossils Tell Us?What Can Fossils Tell Us? Fossils can show scientists 3 main things:Fossils can show scientists 3 main things:

1)1) The kind of organism that lived in the pastThe kind of organism that lived in the past

2)2) How the environment has changed (ex: How the environment has changed (ex: forest fossils found in Antarctica show the forest fossils found in Antarctica show the climate was much warmer in the past)climate was much warmer in the past)

3)3) How organisms have changedHow organisms have changed

How Old Is It?How Old Is It? To understand the To understand the

history of the history of the Earth, scientists Earth, scientists have put fossils in have put fossils in order based on order based on their ages.their ages.

They use relative They use relative dating and dating and absolute dating absolute dating methods methods

Index FossilsIndex Fossils Fossils of certain types of Fossils of certain types of

organisms can be found all over organisms can be found all over the world.the world.

But these fossils are found only But these fossils are found only in rock layers of a certain age.in rock layers of a certain age.

These are called index fossils.These are called index fossils. When scientists see a specific When scientists see a specific

index fossil, they know right index fossil, they know right away how old it is away how old it is

Ex: When scientists find Ex: When scientists find PhacopsPhacops in a rock layer, they in a rock layer, they know the rock layer is 400 know the rock layer is 400 million yrs old.million yrs old.

Pop QuizPop Quiz What is a fossil?What is a fossil?

The remains or imprints of an organism that The remains or imprints of an organism that lived long ago.lived long ago.

What are 5 different ways fossils can form?What are 5 different ways fossils can form? In rock, amber, ice, asphalt, or by In rock, amber, ice, asphalt, or by

petrificationpetrification What 3 things can fossils tell us?What 3 things can fossils tell us?

1)1) The kind of organism that lived in the pastThe kind of organism that lived in the past2)2) How the environment has changed How the environment has changed 3)3) How organisms have changedHow organisms have changed

Who loves fossilized poop (caprolites)?Who loves fossilized poop (caprolites)? We all do!We all do!