1. What do fossils tell us about Earth? What do fossils tell us about life in the past?

2. Scientists measure the amounts of radioactive atoms in a rock sample to determine how old the rock is.

3.  Sedimentary rock forms in layers.  Older layers will be on the bottom because it was deposited first.  Younger layers will be on top as they were deposited last.

4.  Scientists use the fossils found in the layers to help determine the age of the rock.

5.  Fossils of an organism that lived during a relatively short time span.  They are common and are found in many places on Earth.  A fossil that is rare or only found in one place is NOT useful as an index fossil.

6.  The age of the rock layer.  Provide clues about how Earth’s surface has changed (ex: finding fish in mountains)

7.  Fossils of plants and reptiles have been found in Antarctica.  These organisms could not have lived in extremely cold climate so that means Antarctica was once closer to the equator.

8.  The same type of fossil found across large oceans means that the land masses were once joined together.

9.  Ecosystems have undergone major changes throughout Earth’s history.  Scientists study fossils to figure out what the environment was like millions of years ago.

10.  Is a period in which a large number of species become extinct relatively quickly.