Final answer:
Metazoans in the Paleozoic era exhibited a planktonic mode of life, where they lived freely floating or swimming in the water column. The Paleozoic marine environments also saw significant evolutionary changes, leading to increased diversity and eventual adaptation towards a terrestrial lifestyle.
Step-by-step explanation:
During the Paleozoic Era, metazoans exhibited diverse life modes. The term 'metazoan' refers to multi-celled organisms that form the animal kingdom, excluding the sponges and some other simpler animals. In the Paleozoic marine environments, metazoans could be found in different modes of life including sessile, motile, benthic, and planktonic. The planktonic mode of life refers to organisms that floated or swam in the water column, rather than living at the bottom of the sea. Planktonic metazoans would have been part of the pelagic ecosystem, drifting or swimming in the ocean currents, and could include a variety of Paleozoic organisms from different phyla.
Life during the Paleozoic was marked by the Cambrian explosion, a significant event where there was an abundance of new life forms, and significant diversification including primitive animals such as sponges and trilobites. The era was also marked by major extinction events that drastically impacted metazoan life and their evolution. However, some species survived these events, leading to the wide variety of species present today.
Over the course of the Paleozoic Era, organisms evolved and increasingly moved towards terrestrial living. This adaptation from marine to terrestrial life was accompanied by the growth of complex ecosystems and the movement of vertebrates from water to land. The evolutionary transition from water to land was facilitated by changes in the anatomy and behavior of aquatic animals, with certain developments, such as the use of fins to maneuver through vegetation, acting as precursors to the development of limbs suited for life on land.