What Do We Know About Animals?

Animals have been on the earth from the Cambrian period of 570 to 500 million years ago. During this time life was abundant, but only in the sea. The Ordovician period 500 to 430 million years ago, the first fish came about. The period of 430 to 400 years called the Silurian period life began to move on land. Animals have lived in remote places across the earth. We cannot think of a place that animals have not lived during Earth's history. Animals live in the sea. Aquatic life refers to ani...