Earth Science: Paleontology: Reading the Fossil Record Worksheet

Question 1

A fossil shell is found in a rock layer on top of a mountain. What does this fossil suggest about the environment where the rock originally formed?

Accepted Answer

The fossil shell suggests that the rock originally formed in a marine or ocean environment. The area may have been underwater in the past and later uplifted to form part of a mountain.

Question 2

Explain the law of superposition and how it helps paleontologists read the fossil record.

Accepted Answer

The law of superposition states that in an undisturbed sequence of sedimentary rock layers, the oldest layers are at the bottom and the youngest layers are at the top. Paleontologists use this rule to determine the relative ages of fossils found in different layers.

Question 3

A student finds three fossils in different rock layers. Fossil A is in the lowest layer, Fossil B is in the middle layer, and Fossil C is in the top layer. Which fossil is probably the oldest, and why?

Accepted Answer

Fossil A is probably the oldest because it is found in the lowest rock layer. In undisturbed sedimentary rocks, lower layers are usually older than layers above them.

Question 4

A fossil of a fern is found in an area that is now a dry desert. What can scientists infer about the past environment of that area?

Accepted Answer

Scientists can infer that the area may have been wetter in the past because ferns usually need moist conditions to grow. The fossil is evidence that the environment changed over time.

Question 5

What is an index fossil, and why is it useful for comparing the ages of rock layers in different places?

Accepted Answer

An index fossil is a fossil from an organism that was widespread but lived during a relatively short time period. It is useful because rock layers containing the same index fossil are likely to be similar in age.

Question 6

Two rock layers in different states both contain the same index fossil. What conclusion can geologists reasonably make about these two layers?

Accepted Answer

Geologists can reasonably conclude that the two rock layers formed during about the same time period. The matching index fossil helps correlate the layers across different locations.

Question 7

A fossilized footprint is found in sandstone. Is the footprint a body fossil or a trace fossil? Explain your answer.

Accepted Answer

The fossilized footprint is a trace fossil because it records evidence of an organism's activity rather than the preserved body of the organism. It shows that an animal walked through the area.

Question 8

List two examples of body fossils and two examples of trace fossils.

Accepted Answer

Two examples of body fossils are fossil bones and fossil shells. Two examples of trace fossils are footprints and burrows because they show activity rather than body parts.

Question 9

A rock layer contains fossil fish, fossil coral, and ripple marks. What type of environment did this layer most likely form in? Use evidence to support your answer.

Accepted Answer

This layer most likely formed in a shallow water environment such as a sea or ocean. Fossil fish and coral are marine life, and ripple marks can form when moving water shapes sediment.

Question 10

Why is the fossil record incomplete?

Accepted Answer

The fossil record is incomplete because not all organisms become fossils. Many organisms decay, are eaten, or are destroyed before fossilization, and some fossils are later changed or destroyed by erosion, heat, pressure, or tectonic activity.

Question 11

In one rock sequence, a certain fossil species appears in older layers, becomes common in middle layers, and then disappears from younger layers. What might this pattern suggest?

Accepted Answer

This pattern might suggest that the species lived for a period of time, became more successful or widespread, and then went extinct or moved away from the area. The fossil record can show changes in populations over time.

Question 12

How can fossils provide evidence that Earth's environments and life forms have changed over time?

Accepted Answer

Fossils show what organisms lived in the past and where they lived. When fossils in older layers differ from fossils in younger layers, or when fossils show past environments unlike today's environment, they provide evidence that life and Earth's environments have changed over time.

Earth Science: Paleontology: Reading the Fossil Record

More Earth Science Worksheets

More Grade 6-8 Worksheets