Chapter 9

A time line of earths history

An eon divided into smaller units of time

Eras divided into smaller units of time

a period divided into a smaller unit of time

the gradual development of new organisms from preexisting organisms

the time interval that began with the formation of earth and ended about 542 million years ago

the geological era that began about 542 million years ago and ended about 251 million years ago

an enormous number of species dead

the geologic era that began about 251 million years ago and ended 65 million years ago

the division of geological time that began about 65 million years ago and that includes the present period