Proterozoic Eon

The period of Earth's history that began 2.5 billion years ago and ended 543 million years ago is known as the Proterozoic.

- stable continents first appeared and began to accrete |

- took about a billion years

- the first abundant fossils of living organisms

-  mostly prokaryote bacteria

-  and Archaeans thermophilic prokaryotes

- by about 1.8 billion years ago eukaryotic cells appear as fossils

- the beginning of the Middle Proterozoic comes the first evidence of oxygen build-up in the atmosphere

- endosymbiosis of the mitochondria led to endosymbiontic evolution of the eukaryotes

 

- this global catastrophe spelled doom for many bacterial groups, but made possible the explosion of eukaryotic forms
 
 

- these include multicellular algae, and toward the end of the Proterozoic, the first multicellular  animals (animalia)