How did geologists decide where one division of the geologic time scale ends and the next begins?

the law of superpostion

events in the history of life on earth, like mass extinctions

they divided the time equally between eras

the placement of fossils throughout the surface layers of earth

Animal bodies (and even plant bodies for that matter) are complex enough that life couldn't exist without enzymes. enzymes are usually large, complex biological catalysts that are expensive to make. enzymes speed up the rate of chemical reactions without being used up during the reaction (they can be reused many times). they are highly specific in the reactions they regulate. knowing what enzymes are and how they function, why does this explain why complex life forms could not exist if there were no enzymes.

One gene can influence trait(s). one trait can be determined by gene(s).

Match each symbol with its description.