Fifth Grade
Worksheets
Life During the Paleozoic Era
The Earth had cooled. Clouds had formed. Rain had fallen. Organisms were already living on Earth at the beginning of the Paleozoic Era. During this time, life became more complex.
Shallow seas covered some of the land. This was a perfect place for life to grow. Early in the era, most organisms were invertebrates. These are animals without backbones. Trilobites were plentiful. They were arthropods that lived in shallow water. There were also many brachiopods. These animals looked like clams. Soft-bodied animals like sponges also lived at this time.
Coral was very plentiful during this time. Scientists have learned much about the Earth during the Paleozoic Era by studying coral. Coral adds new material to its shell each day. This forms growth lines. Fossils of coral that lived during this era showed these growth lines. Scientists have studied them. Based on the spacing of coral growth lines, scientists believed that days were shorter then. This means that the Earth rotated on its axis faster. There were also about four hundred days in a year. This means that the Earth took longer to revolve around the sun.
