Precambrian Time is the earliest and longest era. It is nicknamed “Age of Early Life.” It started 4.5 BYA (billion years ago). The era ended 543 MYA (million years ago) when complex, multicelled life forms evolved. The climate varied from warm to cold parts. The continents were formed together in a “Y” shape and were bunched up together. Half was above the equator and half was below. All of the continents were in different places than now. Glaciers formed at the equator. Rocks formed 3,950 MYA. Extinction was widespread. Oxygen levels changed. Multi-celled animals appeared 600 MYA. Ediacarans grew on seabeds and didn’t have heads, mouths, or digestive organs. Cnidarians which are sea anemones, corals, and jellyfish evolved. Sponges emerged from bacteria. Vendian Extinction happened and killed off some single-celled algae and soft-bodied animals. There was oxygen loss with the mass extinction and the sea-levels changed.