A record of the life forms and geologic events in Earth's history.
100
Eras are divided into _______.
Periods
100
What is mass extinction?
A time when many types of living things become extinct at the same time.
200
Why do scientist use the Geologic Time scale? (rather than months, days, years)
Because the time span of Earth's past is so great, it would be difficult to show the history using months, days, years.
200
What three periods made up the Mesazoic Era?
Triassic, Jurrasic, Cretaceous.
200
What Era ended with a mass extinction of 95% of life?
Paleozoic
300
How did scientists develop the Geologic Time Scale?
By studying rock lauers and index fossils worldwide and putting them in order by relative age. Radioactive dating also geloed determine the geologic time scale.
300
The Cenezoic Era's periods are divided into _____.
Epochs
300
During which Era did Mammoths roam the Earth?
Cenozoic
400
The divisions of the geologic time scale depent on events in the _______________.
History of life on Earth.
400
What is the earliest Eon in Earth's history?
Precambrian
400
What do we call the process by which all living things change over time?
Evolution
500
How old is Earth?
Roughly 4.6 billion years.
500
What were the earliest life forms probably similar to?
Bacteria
500
During which period did the earliest dinosaurs appear?