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10 Clues to Earth’s Past

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Lesson Outline

FossilsA. Evidence of the Distant Past

1. provide clues to Earth’s past. Some of the most obvious

clues that are present in rocks are , the preserved remains or evidence of ancient living organisms.

2. Some early scientists thought that fossils formed from the remains of organisms

killed in .

3. is the idea that conditions and creatures on Earth change because of quick, violent events.

4. Based on his observations, proposed that changes on Earth take place very slowly.

5. Hutton developed the principle of . According to this

principle, the same processes that occur today occurred in the past.

a. This principle says that most changes on Earth’s surface occur in slow,

continuous .

b. In addition to the changes explained by uniformitarianism, sometimes

events quickly change Earth’s surface.

B. Formation of Fossils

1. An organism is more likely to become a fossil if it contains

parts such as teeth or bones.

2. Fossils are more likely to form if an organism is quickly after it dies.

3. Tiny fossils are called .

C. Types of Preservation

1. If the actual organism becomes a fossil, it was completely

over a long period of time to keep it away from air and bacteria.

2. Some fossils are , which form when pressure drives off the gases and liquids from an organism’s tissues, leaving only the carbon behind.

LESSON 1

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Clues to Earth’s Past 11

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Lesson Outline continued

3. Fossils also form when in groundwater replace the tissues of dead organisms.

4. Some fossils are , which is the impression in a rock left by an ancient organism.

5. When a mold fills with sediment or mineral deposits, it forms a fossil called

a(n) .

6. show evidence of the activity of ancient organisms, such as tracks or nests.

D. Ancient Environments

1. are scientists who study fossils.

2. Paleontologists compare fossils of with organisms that live today.

a. Paleontologists use to learn about the environments of ancient organisms.

b. If a fossil of an ancient organism is similar to an organism that lives today, these

two organisms might have lived in a similar .

3. Fossils show that Earth’s climate has many times in the past.

4. Fossils of plants such as indicate that much of Earth was warm and humid 200 million years ago.

5. Fossils of organisms such as the woolly mammoth help scientists learn about times

that the climate of Earth was .



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FossilsDirections: Label this diagram by writing a term and its matching clue in each space provided.

LESSON 1Content Practice A

Termcarbon filmcastmineral replacementmoldspreserved remainstrace fossils

Cluea mold that fills with sedimentactual remains of the organismimpressions of the organismcopy of an organism made by mineral replacement evidence of ancient organism activitycarbon outline of the organism

Types of Preservation

1.

4.

6. 2.

5. 3.



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FossilsDirections: Respond to each statement in the space provided.

LESSON 1Content Practice B

Describe two principles that explain how fossils form.

8.

5.

Describe the types of fossils that form.

Describe the conditions needed for fossil formation.

2.

3. 4.

1.

10.

7.

9.

6.



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FossilsKey Concept What are fossils, and how do they form?

Directions: Use these terms and the clues listed below to complete the puzzle.

carbon films catastrophism microfossils mineral replacement

paleontologist preserved remains trace fossils uniformitarianism

Key Concept Builder LESSON 1

Across 4. copies of organisms made when

groundwater fills pore spaces

5. evidence of the activity of an ancient organism

6. tiny fossils about the size of a speck of dust

7. actual remains of organisms

8. a carbon outline of an organism left after gases and liquids are driven off

CluesDown 1. a scientist who studies fossils

2. the idea that geologic processes occurring today are similar to those that have occurred in the past

3. the idea that conditions and creatures on Earth change in quick, violent events

1

4

5

3

7

8

6

2

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Directions: Use the diagram to answer each question.

1. What does the second drawing show about how a fish fossil forms?

2. What does the third drawing show about how a fish fossil is discovered?

3. How does catastrophism explain how the fossil formed?

4. How does uniformitarianism explain how the fossil formed?

A dead fish falls to a river bottom during a flood. Its body is rapidly buried by mud, sand, or other sediment.1

Over time the body decomposes, and its hard parts are changed into rock.2

As rocks are uplifted and eroded, the fossil is exposed.3

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Directions: Respond to each statement in the space provided.

Preserved Remains

Type of Preservation Describe each type of preservation. Describe how each fossil forms.

Preserved remains

1. 2.

Carbon films 3. 4.

Mineral replacement

5. 6.

Molds 7. 8.

Casts 9. 10.

Trace fossils 11. 12.



fossils - voorhees township public schools...fossils show that earth’s climate has many times in...

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