Fossil Record

radioactive dating

Technique used to determine how old a rock is by analyzing the amounts of a radioactive isotope and its decay products in the rock.

relative age

The age of a rock compared to the ages of rock layers

absolute age

The age of a rock given as the number of years since the rock formed.

index fossil

distinctive fossil used to compare the relative ages of fossils

mass extinction

event in which many types of living things become extinct at the same time

law of superposition

states that younger layers of rock are deposited on top of older layers

chronological order

the order in which events happen in time

extinction

A term that typically describes a species that no longer has any known living individuals.

fossil record

The mineralized remains of organisms and the rock layers in which they are found, showing when and where long -dead organisms lived and how their bodies were structured.

fossils

The preserved remains or traces of organisms that once lived on Earth.

diversity

The quality or state of having many different forms, types, ideas, etc.

half life

The time it takes for half of the radioactive atoms to decay

common ancestry

When Organisms are descended from a single ancestor

paleontologist

a scientist who studies fossils to learn about organisms that lived long ago