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Precambrian time covers a bulk of Earth's history. Precambrian started off when the world was
formed 4.5 billion years ago. Precambrian time started when the Earth cooled down from it’s original molten state. The first period of the Precambrian time was the Azoic period. The Azoic period was the forming of Earth's oceans. It was also the forming of Earth’s atmosphere. It was a very hot molten like environment. The Earth then became very rocky when the Earth started to cool.
Life started to appear during the Archeozoic period during the Precambrian time area. The first life forms during this area were very simple. Simple such as bacteria, algae and other kinds of single celled organism. At the end of Precambrian time Earth started to have organisms such as jellyfish and sea worms. The environment was a very hot oceanic environment when there live organisms living on Earth.
The Precambrian time area ended 540 million years ago. The Precambrian area ended with an ice age. The ice age might have led to a series of extinctions. The Precambrian time lasted for most of Earth's existence. Precambrian time lasted 90% of Earth’s existence.
http://www.kinderscience.com/precambrian_era.htm
http://www.geo.msu.edu/geogmich/Precambrian.html
http://geology.about.com/od/geotime_dating/a/Geologic-Time-Scale-Precambrian.htm