A record of the life forms and geologic events in Earth's history.
100
Geologic time begins with a long span of time called ____________ Time.
Precambrian
100
Eras are divided into _______.
Periods
100
What Era did not have any sign of life?
Hayden
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
After Precambrian time, time is divied into three long units of time called _______.
Bonus: The __________ _______ is known as the Age of Mammals.
Eras
bonus: Cenozoic Era
200
What three periods made up the Mesazoic Era?
Triassic, Jurrasic, Cretaceous.
200
Describe reptiles.
Organisms with scaly skin that lay eggs with rough, leathery shells.
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
Name the three eras of the geologic time scale.
Cenozoic, Mesozoic, Paleozoic.
300
The Cenezoic Era's periods are divided into _____.
Epochs
300
What is an amphibian?
An animal that lives part of its life on land and part in water.
300
What Era is known as the Age of Reptiles?
Mesozoic
400
The divisions of the geologic time scale depent on events in the _______________.
History of life on Earth.
400
Invertebrates were animals that lived mostly during the ________ era.
Bonus: define invertebrate.
Paleozoic.
bonus: animals without backbones
400
During which time period did Earth form?
Hadean
400
How can scientists tell that Earth has changed over time by looking at fossils?
Fossils show that organisms were much simpler in the past.
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
During this era, the dinasours lived and mammals began to evolve.
Mesozoic
500
What were the earliest life forms probably similar to?
Bacteria
500
What was the Cambrian Explosion?
A time at the beginning of the Paleozoic Era when many different kinds of organisms evolved.