The Paleozoic era

540-250 MYA


The Paleozoic era was an era that started approximately 540 million years ago and deceased 250 million years ago. So much went on during this period that it was broken up into 6 different periods. These periods were named the Cambrian period, Ordovician period, the Silurian period, the Devonian period, the Carboniferous period, and the Permian period.

The Cambrian period

The Cambrian Period (542 to 488 million years ago) was the time when most of the major groups of animals first appeared in the fossil record. This event is sometimes called the "Cambrian explosion," because of the relatively short time over which this diversity of forms appeared.

The Ordovician period

The Ordovician Period (488 to 444 million years ago) is best known for its diverse marine invertebrates, including graptolites, trilobites, brachiopods, and the conodonts (early vertebrates).The end of the Ordovician Period was marked by a mass extinction in which 60% of all marine invertebrate genera and 25% of all families went extinct.

The Silurian period

The Silurian Period (444 to 416 million years ago) was a time of reef expansion in the oceans, as well as the period when vascular plants first gained a foothold on land. In the oceans, fish diversified dramatically.

The Devonian period

The Devonian Period (416 to 359 million years ago) was a time of major diversification of plant life on the land. By the end of the period, ferns, horsetails, and seed plants had all appeared, producing the first trees and forests. Two major groups of terrestrial animals—tetrapods, the first land-living vertebrates, and insects—appeared during this period.

The Carboniferous period

The Carboniferous Period (359 to 299 million years ago) is notable for having some of the highest atmospheric concentrations of oxygen in Earth history, which may have contributed to the development of large insects. The term "Carboniferous" comes from the rich deposits of coal that are found around the world that date to this period.

The Permian period

The end of the Permian Period (299 to 252 million years ago) is marked by the largest mass extinction recorded in the history of life on Earth. It affected many groups of organisms in diverse environments, with marine communities being especially devastated. On land, many diapsid (ancestors of dinosaurs and many other reptiles) and synapsid (mammal-like reptiles) vertebrates became extinct, clearing the way for new forms to dominate. What followed has been called the "Age of the Dinosaurs."
Physical Geography: Life During the Paleozoic Era


1. How old is the oldest fossil ever found?

2. How many periods are in the Paleozoic era?

3. In which period did animal life first appear on the earth?


1. 3.5 billion years old

2. 6 periods

3. The Carboniferous period