PRE-CAMBRIAN ERA: ...the time before the first complex organisms
appear.
Precambrian time, All geologic time before the beginning of the Paleozoic
era. This includes about 90% of all geologic time and is from about 544
million years ago to about 4.5 billion years ago at the beginning of
earth. Precambrian means "before Cambrian."
- The Proterozoic Eon
- Its name means "early life." The most recent era of the Precambrian, the
time between 544 million years ago and 2.5 billion years ago Fossils of
primitive single celled and multicellular life begin to show up a lot in
rocks from this era.
- Simple Life
- Algae Photosynthetic, almost exclusively aquatic, nonvascular plants that
range in size from simple unicellular forms to giant kelps several feet first
appeared in the Precambrian.
- Archaean
- Its name means "ancient." The middle era of Precambrian time, the period
between 2.5 billion years ago and 3.8 billion years ago and . Life arose on
Earth during the early Archaean, as shown by fossils of microscopic plants
and bacteria found in rocks thought to be about 3.5 billion years old. That
was before my time and I only heard about it.
- Hadean
- The oldest (earliest) subdivision of the Precambrian, covering the time
between the formation of the Earth, about 4.5 billion years ago, and the
start of the Archaean era, 3.8 billion years ago. This interval is before
true geologic time since no rocks of this age are known on Earth except a few
meteorites and stuff like that.
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