How is the Earth’s time broken up?

 

                         Scientists break up the earliest history of the Earth in several ways, according to the forms of life that existed. The time we consider in this book is split into the Palaeozoic Era, when most modern life forms developed, and the Mesozoic Era. During this period, many life forms evolved further and mammals and birds gradually began to appear. Dinosaurs also evolved during the Mesozoic Era and lived throughout three distinct periods, called the Triassic, Jurassic and Cretaceous Periods.

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