Through their studies, paleontologists can learn about ________.

The history of life as documented by the remains or imprints of organisms from earlier geologic periods preserved in rock is called the _______________.

The fossil record shows that life on Earth ___________________.

Fossils have been arranged in the order in which they lived.

More than 99% of all species that have ever lived on Earth have become extinct.

The earth is ________________ years old.

Most fossils form in ___________ rock.

The formation of any fossil depends on a precise combination of conditions.

During fossilization, compression and chemical activity turns the remains of an organism into _____________.

To make sense of the fossil record, the age of the fossil is not important.

Paleontologists determine the age of fossils using two techniques:

Relative dating allows paleontologists to estimate a fossil's ________ compared with that of other fossils.

The _______________ of the fossils in layers of rock is used in relative dating.

A half-life is the length of time required for half of the radioactive atoms in a sample to _______________.

In radioactive dating, scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains.