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Anatomy

The study of the structure of an organism

Epoch

A medium sized division in the geologic time scale (tens of millions of years)

Era

A big division in the geologic time scale (several hundred years) made up of periods

Period (Geological)

A small division in the geologic time scale (made up of epochs)

Theory

A proposed explanation of a scientific event

Variation

Difference in members of the same species

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