Which characteristic defines the Paleozoic era?(1 point)
Responses
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.
Reptiles became dominant after a mass extinction.
Reptiles became dominant after a mass extinction.
Mammals and other warm-blooded animals became dominant.