3-5 Time Marches On Flashcards
The standard method used to divide the Earth’s long natural history into manageable parts
Geologic Time Scale
The largest division of geologic time
Eons
A unit of geologic time that includes two or more periods
Eras
A unit of geologic time into which eras divided
Periods
A subdivision of a geologic period
Epochs
One of numerous marine organisms to make its appearance during the early Cambrian period
Hallucigenia
The death of every member of a species
Extinction
In the Mesozoic Era; reptiles, such as dinosaurs, inhabited the land and were the dominant animal; ended in a mass extinction
Age of Reptiles
In the Cenozoic Era; mammals inhabited the land and were the dominant animal; we live in this era
Age of Mammals
Earth’s age
About 4.6 billion
The rock and fossils record mainly represents this eon, which is the eon in which we live
Phanerozoic Eon
The first organisms with well developed cells appeared during this eon
Proterozoic Eon
The earliest known rocks on Earth formed during this eon
Archean Eon
The only rocks that scientists have found from this eon are meteorites and rocks from the moon
Hadean eon
The largest mass extinction occurred in this era, marine life flourished and their were few land organisms
Paleozioc Era
