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The Precambrian makes up the largest proportion of geologic time.

The last of the three Cordilleran Orogenies began in the Cretaceous and extended into the Cenozoic. This orogenic event was the:

Oxygen levels in the atmosphere increased throughout the Proterozoic.

Periods are the largest subdivision of geologic time.

A period of time missing from the geologic record is called a(n):

The first major transgression onto the North American continent is represented by the Kaskaskia Sequence.

If a small population of a species becomes separated from its parent population and evolves into a new species, that is called:

Most traits or features of living things are controlled by:

A marine transgression is a period of lower sea level.​

Microevolution results from the cumulative effects of macroevolution.​