Which characteristic defines the Paleozoic era?(1 point) Responses Mammals and other warm-blooded animals became dominant. Mammals and other warm-blooded animals became dominant. Simple, one-celled life forms were dominant. Simple, one-celled life forms were dominant. Reptiles became dominant after a mass extinction. Reptiles became dominant after a mass extinction. 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 emergence and diversification of various marine life forms, including those with hard shells, and it saw significant evolutionary developments leading up to more complex land-dwelling organisms.