A Brief Overview of the Paleozoic Era for Middle School Science Classes

Dec 4, 2024

4 min read

Earth history is a fascinating topic! It is also a massive topic! The reading passage below will teach you all about the Paleozoic Era. If you want to learn more (and why wouldn't you?!), you can check out my Earth History page. I also have all of my passages available at Teachers Pay Teachers. They come with so many extras to get your students thinking about the content! I also recommend scrolling to the bottom of the page to check out my digital picture book on the Paleozoic Era!

Cambrian Explosion

The Paleozoic era began with the Cambrian explosion. This was a sudden — over just a few million years — appearance of new life. Almost every animal phyla that exists today evolved during the Cambrian explosion.

At the beginning of the Paleozoic era, life was still confined to the seas. Trilobites, brachiopods, mollusks, and hyolithids were just a few of the species making their homes in the water.

Plants

During the Ordovician period, the first plants spread to land. These early plants were similar to mosses. They had no vascular tissue and only shallow roots. Invertebrates quickly followed the plants onto the land. By the Devonian period, these early land plants had diversified and evolved into giant forests of trees such as the Archaeopteris.

Fish

In the oceans, fish evolved from primitive jawless fish into modern fish during the Silurian period. Fish were such an important part of the period that it is known as the “age of fish.” Corals also appeared during the Silurian period. The coral reefs built became a new habitat for many marine animals.

Vertebrates

Vertebrates spread to the land during the Devonian period. The first vertebrates to move to the land were tetrapods. They lived in swamps and marshes. They spent most of their lives in the water but could escape to land if they were in danger. Amphibians evolved from the tetrapods.

Insects

Insects also evolved during the Devonian period. Late in the period, some insects developed wings and were able to fly. Increased oxygen in the atmosphere meant these insects grew much larger than they do today. During the Carboniferous period, an early dragonfly had a wingspan of twenty-eight inches.

Amphibians and Reptiles

Amphibians were also changing during the Carboniferous period. Some of them developed thicker skin, which allowed them to stay out of the water for longer periods of time. Their eggs also grew a tough shell, so they didn’t have to lay their eggs in water. These eggs are called amniotic eggs. Over time, these amphibians evolved into the first reptiles. With their new adaptations, reptiles moved into habitats outside of the coastline. Near the end of the Permian period, some reptiles evolved into archosaurs, the ancestors of the dinosaurs of the Triassic period.

Continental Drift

While life was evolving on Earth, the continents were changing too. While life was evolving on Earth, the continents were changing too. At the beginning of the Paleozoic era, there were small continents scattered around the globe. The continents moved together throughout the era. By the end of the era, the continents would form a supercontinent called Pangaea.

Climate

The climate during the Paleozoic era was similar to our climate today. It was warmer at the beginning of the era, but the climate cooled during the Silurian period when a large continent called Gondwana moved over the South Pole. The climate recovered to normal levels during the Devonian periods. The large amounts of oxygen in the atmosphere during the Carboniferous period most likely led to more ice ages. When Pangaea formed during the Permian period, the land became much cooler and drier than before. This would change when Pangaea broke up during the Mesozoic era.

Permian Extinction

The Paleozoic era ended with the largest mass extinction in Earth’s history. Ninety-six percent of life in the oceans and seventy percent of the life on land was wiped out over fifteen million years. Scientists believe the extinction event may have been caused by a large number of volcanic eruptions. The eruptions spewed carbon dioxide into the atmosphere. As a result, the carbon dioxide temporarily increased the temperatures on Earth. When the carbon dioxide dissolved in the oceans, it turned the water acidic. This may explain why marine life was affected more than terrestrial life.

The Permian extinction opened opportunities for new life to emerge. Before the extinction, Earth’s habitats were full of plants and animals. There wasn’t room for new life. After the extinction, the habitats were empty, so new animals could evolve. The dinosaurs of the Mesozoic might never have existed without the Permian extinction that ended the Paleozoic era.

Paleozoic Era Picture Book

Looking for another way to learn about the Paleozoic Era? Check out this picture book version. The pages are a part of my Earth History bundle on Teachers Pay Teachers.