Eras, like the Paleozoic, Mesozoic, and Cenozoic periods are separated into periods by which marker?
Question 4 options:


Changes in rock layers


Species extinction


100 million year chunks


The types of living organisms that were present

Respuesta :

Eras are divided according to mass extinction. More specifically, when a type of species was most prominent on land. For example, we are living in a mammal dominated era -  the cenozoic.