The Archaeozoic and Proterozoic eras are commonly referred to as precambrian time. The Archaeozoic era begins about 4,560 million years ago, followed by the Proterozoic era from 3,800 million years ago to 610 million years ago.
4,600 million years back the earth formed into a solid object. 4,300 million years ago the Earth was warmed by gravitational action and radioactivity. The inner core collected heavy atoms and the layers stratified. Water, methane, ammonia, hydrogen, nitrogen and carbon dioxide began to form an atmosphere.
By 4,000 million years back the Earth was no longer under constant bombardment by debri floating around our solar system. By 3,800 million years ago a crust had formed on the surface and the water in the atmosphere had condensed into oceans.
3,500 million years ago single celled organisms first appeared. Cyanobacteria forms during this time and finds a way to synthesize sunlight into food. This blue-green algae absorbed carbon-dioxide, and released oxygen into the atmosphere which strengthened the ozone layer which protects the earth from some of the radiation from the sun. The cyanobacteria thrived on the surfaces of the planet’s oceans forming stromatolites, or communities of cells of cyanobacteria. The cyanobacteria cells each gave off a sticky film which trapped sediments. Sediments got stuck together and the cells climbed on top of the sediment to get closer to the sunlight. More sediment got trapped, more cells climbed up and you ended up with a mushroomed shaped collection of cyanobacteria floating through the ocean. Stromolite communities of blue-green algae can still be found today in warmer, shallow oceans today. Cyanobacteria frequently makes its appearance today in aquariums and home ponds, much to the dismay of the caretakers.
Around 1,500 million years ago prokaryotes ( cells with walls ) begin to capture other cells. In time the captured cells become the nucleus, organelles and chloroplasts of cells and eurkaryotes emerge. The captured cyanobacteria becomes chloroplast. Chloroplasts are orgenlles inside a cell and they are what convert sunlight into energy. All the green parts of your plant are made up of cells containing chloroplasts. About 500,000 chloroplasts are in a square millimeter of leaf surface.
This era we also brings us thermophiles. These bacteria live at the bottom of the ocean near volcanic vents. They thrive in boiling water. They need no sun, nor CO2. They too have survived all the upheavals and can be found today inside hot water springs and geysers.
Near the end of this era most of the land is locked into one continent, Rodinia. The United States is down by the south pole and mostly covered in a sheet of ice. This is a cold time in the planet’s history.