Question

6. The first vertebrates appeared during

a. Precambrian time
b. the Paleozoic Era
C. the Mesozoic Era
d. The Cenozoic Era

Answer 1

b. the Paleozoic Era

Step-by-step explanation:

The first vertebrates to appear are primitive fish in the Cambrian Period, but bony fishes with actual bony vertebratae didn't appear for another 100 million years. The Cambrian Period is the first of three periods in the Paleozoic Era. The Cambrian explosion was an event when practically all major animal phyla started appearing in the fossil record.