2020 Unit 1 Review: Analyzing the Fossil Record

Unit 1 Review

Let's study!!!

Observations and Inferences

• First, scientists observe carefully and accurately, and collect all of the evidence.

• Second, scientists can make inferences about what might have happened in the past!

Multiple Choice

What EVIDENCE best helps us infer our fish was a violent predator that ate other animals?

• we observe the fossil is large

• we observe the fossil is in the desert

• we observe the fossil has jaws with sharp teeth

• we observe the fossil has bones

Multiple Choice

What is the BEST inference we can make from this evidence (our mushroom rocks)?

• Nowhere else on Earth has these rocks.

• Storms caused weathering and erosion here.

• These rocks were here before the dinosaurs.

• Ancient humans carved these rocks.

We can do this with OTHER fossils, too!

Look at the evidence. Make an inference!

Multiple Choice

What can we infer from this trilobite fossil?

• it was also a predator that ate other animals

• it rolled up to defend itself from predators

• it ate grass and seaweed

• it lived millions and millions of years ago

Evidence and Inference

• Remember, you can only make inferences that you have the evidence for!

• We can observe the fossil is rolled up like a ball.

• Therefore, we can infer that maybe the fossil liked to roll up for protection!

Evidence of Environmental Change

• We can also look for evidence that says the environment has changed over time.

• Let's take a look!

Multiple Choice

When we observe all of these fossils, what can we infer about the past environment?

• it used to be a forest

• it has always been a desert

• it used to be watery, like an ocean

• it used to be a forest

Weird Rocks

• Next, we observed some strange rocks in the Egyptian desert.

• What did this mean might have happened in the past?

Multiple Choice

What is the BEST inference we can make from this evidence (our mushroom rocks)?

• Nowhere else on Earth has these rocks.

• Storms caused weathering and erosion here.

• These rocks were here before the dinosaurs.

• Ancient humans carved these rocks.

Weathering and Erosion

• Weathering breaks down rock.

• Erosion carries rock new places.

• The holes on top and smooth sides of our mushroom rock tell us strong storms might have been here!

• But not just here ...

Multiple Choice

Which of these pictures best shows weathering and erosion?

Weathering and Erosion

• The river breaks down rock (weathering)

• and then carries it away (erosion)

• creating this river canyon!

Deposit

• Here, we don't see weathering and erosion.

• (although they probably helped make this)

• We just see layers of sediment DEPOSITED.

• Speaking of which ...

Multiple Choice

How can we infer our fish fossil was made?

• Our fish was frozen in ice, and saved for a long time.

• Sediment is deposited on top, and then hardened into rock.

• The fossil was stuck in the ocean, and washed up recently.

• It's fake. Mr. Adler put it there to mess with us.

How to Make Fossils

• First, my fishy dies :(

• Sediment is deposited, or put down, on top.

• The sediment hardens into rock over thousands of years.

• A fossil is made!

Layers of Fossils!

• Sometimes, we find fossils in layers of rock, like these!

• What can we learn from this evidence?

Multiple Choice

How old is our fish here?

• Oldest

• Second Oldest

• Youngest

• Second Youngest

Evidence and Reasoning

• YES, it's second-youngest!

• Evidence: It's second from the top.

• But so what? Why is that important?

Multiple Choice

Give the reasoning!

• This means the fish fossil was deposited first, and is oldest.

• This means the fish is about 50 million years old.

• This means the fish layer W was deposited after all but layer V.

• This means the fish fossil is in the second layer.

Evidence and Reasoning

• Evidence: It's second from the top.

• Reasoning: This means the fish layer W was deposited after almost everything, except Layer V!

• Remember, Deposit = PUT DOWN!

Multiple Choice

On to index fossils! What do they let you do?

• tell you what's oldest

• tell you what's youngest

• tell you what lived a loooong time

• tell you what layers are the same age

Index Fossils

• Index fossils let you match layers of rock in different places that are about the same age!

• Match the Layers, Same Age!

• Here it's the fern. Why?

Multiple Choice

What makes the fern our index fossil?

• it's widespread (in both dig sites)

• it's short-lived (only lives in one layer each time)

• it's widespread AND short-lived

• actually, it's not an index fossil at all!

Index Fossils

• To be a good index fossil, you must be:

• Widespread: Found Everywhere

• Short-Lived: Only live in one layer in each place, so it's easy to match the layers!

Multiple Choice

So what's the index fossil here?

• dinosaur

• human

• plant

• none of them are index fossils

Multiple Choice

The dinosaur is the index fossil! So what layers are about the same age?

• 1, 5, 8

• 2, 6, 9

• 3, 6, 10

• 4, 7, 10

Index Fossils!

• The dino is the index fossil because it's widespread (in all three places) and short-lived (always in just one layer).

• Because 4, 7, and 10 have the index fossil, those three layers must be about the same age!

Multiple Choice

So if the dino is the index fossil, what must be the OLDEST layer here?

• 1

• 4

• 7

• 11

HULK SMASH!

• Because the index fossils are about the same age, we can pretend they all line up!

• When we do this, we see Layer 11 is below the other layers.

• That means it was deposited before them, and is older!

Multiple Choice

EVIDENCE: Below the line, lots of fossils. Above, not many fossils. INFER: What happened here?

• rain caused lots of weathering and erosion

• the layers were deposited in a strange shape

• a mass extinction event killed many animals

• the ocean dried up and all the sea-creatures drowned

Extinction!

• A species goes extinct when all of them are dead and gone.

• Extinct = All Dead = Todos Muertos

• Since LOTS of fossils disappear all at once, we can infer something BIG happened to make them go extinct.

• But what could do that?!?

Multiple Choice

What could cause a mass extinction?

• asteroid impact

• human activity

• tectonic plate movement and earthquakes

• all of the above!

Extinction!

• Thanks to Luis and Walter Alvarez, and the iridium they found, we know an asteroid probably killed the dinosaurs.

• But our fish was killed by tectonic activity.

• Some species die because of volcanic activity.

• And many today die because of humans destroying their habitats.

Multiple Choice

What happened LAST here?

• Layer A was deposited.

• Layer C was deposited.

• a Volcanic Eruption

• an Earthquake at Fault E

Cross-Cutting Relationships!

• We know that whatever cuts through layers of rock came AFTER.

• That makes sense ... otherwise there would be nothing to cut through.

• The Fault E cuts through EVERYTHING, so it happened last!

Multiple Choice

What happened last here?

• an earthquake at Fault I

• a volcano at magma G

• Layer F was deposited

• Layer I was deposited

Cross-Cutting Relationships!

• See how NOTHING cuts through I, on the top?

• That means it was deposited after the earthquake and volcano happened!

Multiple Choice

What probably killed the shell fossil?

• an asteroid impact

• an earthquake at a fault

• a volcano

• humans

Layers = TIME

• See how the fault H stops right at the layer where our fossil is?

• That means it happened RIGHT after the shell was alive!

• The earthquake and tectonic activity at Fault H killed the shell!!!

• But what about the volcano?

Multiple Choice

How do we know the volcano didn't kill the shell fossil?

• the eruption is too small

• the eruption is just at the right side of the picture

• the eruption cuts through too many more layers

• we do not observe a volcano

Layers = TIME

• See how the magma cuts through Layers M, D, and J?

• Layers = TIME

• Each layer took millions of years for sediment to harden into rock.

• So volcanic activity happened wayyyy after the shell was alive.

Multiple Select

Final Question: Why do we study the fossil evidence we can find on Earth? Pick more than one answer.

• When we examine fossils, we can make good inferences (guesses) about the past.

• Everyone needs to find evidence before we can make a good inference, or we won't be believed.

• More people - including the police - should use evidence, like scientists.

The Key Point!

• Scientists can use evidence to make lots of good inferences about the past.

• WE need to observe and collect evidence if we’re going to make good inferences and arguments.

• EVERYONE needs to do this - including the police.

Open Ended

What have you learned during Unit 1? Write a paragraph of least four sentences.