The Phanerozoic Eon

 The Phanerozoic Eon is the current geologic eon, which began about 541 million years ago and continues to the present day. It is divided into three eras: the Paleozoic, Mesozoic, and Cenozoic. The Phanerozoic Eon is characterized by the evolution and diversification of life, with the first appearance of many major groups of organisms, including fish, plants, insects, reptiles, birds, and mammals.

During the Paleozoic Era, which lasted from about 541 to 252 million years ago, life on Earth underwent rapid diversification, with the development of many new forms of marine life, such as trilobites, brachiopods, and corals. Land plants also appeared during this time, along with the first terrestrial animals, such as insects, spiders, and millipedes. The Paleozoic Era also saw the emergence of the first amphibians, reptiles, and primitive mammals.

The Mesozoic Era, which lasted from about 252 to 66 million years ago, is known as the "Age of Reptiles" because it saw the rise of the dinosaurs, which dominated the Earth for over 150 million years. During this time, the first birds and mammals also appeared, and flowering plants began to diversify.

The Cenozoic Era, which began about 66 million years ago and continues to the present day, is known as the "Age of Mammals." During this time, the dinosaurs went extinct, and mammals diversified and evolved to occupy many ecological niches. Humans also evolved during the Cenozoic Era, with the emergence of the first primates about 60 million years ago and the evolution of modern humans about 300,000 years ago.