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.
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.

This era is known for the appearance and diversification of many types of marine life, particularly those with hard shells, during the Cambrian period and beyond.