Question

Which characteristic defines the paleozoic era?

a) animals with shells and hard parts were dominant for the first time. animals with shells and hard parts were dominant for the first time.
b) mammals and other warm-blooded animals became dominant. mammals and other warm-blooded animals became dominant.
c) reptiles became dominant after a mass extinction. reptiles became dominant after a mass extinction.
d) simple, one-celled life forms were dominant.

Answer 1

The Paleozoic Era is characterized by the emergence and dominance of animals with shells and hard parts, marking a period of significant diversification and evolution of life forms.

Step-by-step explanation:

The characteristic that defines the Paleozoic era is that a) animals with shells and hard parts were dominant for the first time. During the Paleozoic Era, which began with the Cambrian explosion and lasted until the Permian extinction, there was a significant diversification of life. The Cambrian explosion saw the emergence of many animal phyla, such as ocean invertebrates like trilobites, which became abundant during this period. As the era progressed, vertebrates moved from water to land, leading to further evolution and diversification.

By the end of the Paleozoic, complex ecosystems had formed and vertebrates had diversified, with the appearance of two different lines. One led to synapsids and mammals, and the other to reptiles, dinosaurs, and birds. Life during the Paleozoic was marked by both spectacular evolutionary advances and significant mass extinctions, which reshaped the course of life on Earth.