Which characteristic defines the Paleozoic era?(1 point)

Question

Responses

Mammals and other warm-blooded animals became dominant.
Mammals and other warm-blooded animals became dominant.

Reptiles became dominant after a mass extinction.
Reptiles became dominant after a mass extinction.

Simple, one-celled life forms were dominant.
Simple, one-celled life forms were dominant.

Animals with shells and hard parts were dominant for the first time.

Answer 1

The characteristic that defines the Paleozoic era is: Animals with shells and hard parts were dominant for the first time.