Which characteristic defines the Paleozoic era?(1 point)
Responses
Animals with shells and hard parts were dominant for the first time.
Animals with shells and hard parts were dominant for the first time.
Simple, one-celled life forms were dominant.
Simple, one-celled life forms were dominant.
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.