What are 3 major eras of earths history?

The three major eras of Earth's history are the Paleozoic, Mesozoic, and Cenozoic eras. The Paleozoic era, spanning from about 541 to 252 million years ago, is characterized by the emergence of diverse marine life and the first land animals. The Mesozoic era, known as the "Age of Reptiles," lasted from approximately 252 to 66 million years ago and is marked by the dominance of dinosaurs. The Cenozoic era, beginning around 66 million years ago and continuing to the present, is marked by the rise of mammals and birds, as well as significant climate changes.