This organism is now extinct.

This fossil is older than the mountaintop.

The mountaintop is made of metamorphic rock.

The rocks on this mountaintop were once at the bottom of an ocean.

It could also contain Fossil G.

It was formed in Periods 1, 2, and 3.

It is older than the rock layers that contain Fossil H.

It is younger than the rock layers formed in Period 4.

It is most likely an index fossil.

It is likely younger than a fossil discovered halfway up the cliff.

It is likely older than a fossil discovered in rock at the top of the cliff.

It is likely younger than a fossil discovered in rock at the top of the cliff.

The fossil record represents less than one percent of all of the species that ever lived.

Land organisms are more likely to fossilize than aquatic organisms.

It is rare for the remains of a soft-bodied organism to become a fossil.

Most fossils are found in sedimentary rock.

It gives us the exact date an organism lived.

It allows us to study the radioactive elements to determine the age.

It determines whether a fossil formed before or after another fossil.

It compares a fossil with its current living relatives and studies the differences.

Layer A contains the most recently formed fossils.

Layer B contains the second-oldest fossils.

The fossils in layer B are older than those in layer D.

The fossils in layer D are the most recently formed.

1, 3, 2, 4

2, 3, 4, 1

3, 2, 1, 4

3, 4, 1, 2

well-preserved land organisms

soft tissues of organisms preserved in great detail

fossils over 500 million years old

the remains of an ancient ocean

increasing complexity of fossils in younger rock layers

increasing diversity of fossils in rock layers following an extinction

transitional fossils

rock layers with no fossils

a sinkhole formed by a retreating glacier

sedimentary rock that formed a long time ago

a crystal formation suspended from the ceiling of a cave

remains of an organism preserved by geologic processes