AP BIOLOGY

Detailed explanation-1: -Later Paleozoic seas were dominated by echinoderms (such as sand dollars, star fish, and sea anemones), more advanced kinds of brachiopods, and corals. The principal hallmark of the Ordovician Period was the colonization of the land by arthropods and primitive land plants.

Detailed explanation-2: -Two major groups of fishes were present by the middle Paleozoic, the Jawless Fish and the Jawed Fish. 1. Jawless fish (also known as agnaths) first appeared during the Late Cambrian and continued to be abundant in the Middle Paleozoic. They are survived today by their descendents, the Hagfishes and Lampreys.

Detailed explanation-3: -So, the correct answer is “Reptiles".

Detailed explanation-4: -The Devonian, part of the Paleozoic era, is otherwise known as the Age of Fishes, as it spawned a remarkable variety of fish. The most formidable of them were the armored placoderms, a group that first appeared during the Silurian with powerful jaws lined with bladelike plates that acted as teeth.

Detailed explanation-5: -During the Paleozoic Era, which lasted 289 million years, plants and reptiles began moving from the sea to the land. The era has been divided into six periods: Permian, Carboniferous, Devonian, Silurian, Ordovician, and Cambrian.