-Time since Earth formed is split into units called eras, which are in split into periods. Some periods split into epochs. These units relate to the formation of rock layers.
-The Precambrian Era ran from 4600-542 million years ago(mya). It saw the beginning of sea life. In the Cambrian Period(542-490mya) vertebrates appeared.
-In the Ordovician Period(490-435mya) plants spread to land. In the Silurian Period(435-410mya) the first jawed fish appeared. Upright plants grew on land.
-The Domain Period(410-355mya) saw the arrival of bony fish. Trees and insects appeared on land.
-The Carboniferous Period(355-298mya) was the time of great tropical forests and the first land vertebrates.
-Reptiles rule land in the Permian Period(298-250mya).
-The Triassic Period(250-208mya) saw the rise of the dinosaurs and the first mammals. In the Jurassic Period(208-144mya) reptiles rule land, sea and sky.
-In the Cretaceous Period(144-65mya) flowering plants appeared. The dinosaur died out.
-The Tertiary Period(65-1.6mya) saw the rise of mammals. Temperatures cooled.
-The Quaternary Period(1.6mya-present) has seen the most recent ice ages and the rise of humans.
