550 million years ago, came the Paleozoic era.
This era is subdivided into Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and permian periods. In the Cambrian period, defferent types of Organisms lived in the sea.
land plants appeared in the Ordovician period. This fact can be proved with the help of fossils. The Mesozoic Or the'medieval age of the Earth', which is Clssified into the trassic, Jurassic, and Cretaceous periods, began around 250million years ago. The first mammals, as well as the dinosaurs, first appeared in the trissic period. At the end of the Cretaceous period, the dinosaurs became extinct. Man evolved in the late Cenozoic period, which started about 65million years ago
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