Precambrian

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Precambrian

• ByAmanda Hoeschle
• Kim Osman

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Time Period

• The Precambrian time period is the largest time
  period yet. It started with the earths creation
  about 4.5 billion years ago. The Precambrian time
  accounts for about 90 geologic time! The
  Precambrian is the earliest of the geologic ages,
  these rocks were laid down millions of years so
  they contain records of the earths past. These
  records include fossils of plants and animals
  remains from billion of years ago.

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Major Events

• 1. The formation of the Sun and light.
• 2. The creation of the Earth.
• 3. The creation of the atmosphere through
  volcanic out-gassing.
• 4. The creation of the oceans. 
• 5. The creation of life.  This actual process
  remains open to debate as to how it all took
  place.
• 6. Tectonic plates were formed and began to move
• 7.Eukaryotic cells evolved,
• 8.The atmosphere became enriched in oxygen
• 9. Complex multi cellular organisms, including
  the first animals

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Landforms

• Very little is known about the positions of the
  continents during the Precambrian time period. We
  know that there was a large landmass called
  Laurasia, which began to form near the equator.
  And another landmass formed near the south pole.

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Atmosphere

• The atmosphere is poorly known, but it is
  thought to have been covered in reducing gases,
  containing small amounts of free oxygen. The
  young planets had a reddish tint, the seas were
  thought to be olive green.

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Climate

• It is very empty and only single-celled
  organisms were present in the Precambrian era. No
  animals were living on land because of the
  poisonous gas in the air. By at least the late
  Pre-Cambrian, the climate was cold enough to have
  glaciers. As well the greenhouse gases may have
  been lower. The reason for this was that plants
  were photosynthesizing and using the greenhouse
  gas. This lowered the amount of greenhouse gas in
  the atmosphere and promoted a colder climate
  condition, even near the equator. It also wasnt
  very hot because the sun would have emitted less
  solar radiation 4 billion years ago and has
  increased ever since.

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Animal

• The earliest animals that survived in the
  Precambrian time were sponges lacking organs or a
  nervous system. The second group was the
  Cnidarians which was made up of anemones, corals,
  and jellyfish. The third group was the annelids
  which is basically made up of flatworms.

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Plant

• The earliest organisms were microscopic
  bacteria about 3.4 billion years ago. As their
  numbers multiplied and supplies of their chemical
  fuel were disappearing the bacteria found another
  source. Photosynthesis began to take place which
  lead to simple plants being formed, and opening
  the planet up to animal life.

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Extinction

• The first extinction of the Precambrian time
  was because of a large glaciations event that
  occurred about 600 million years ago. This event
  was of such severity that almost all
  micro-organisms were completely wiped out. The
  Vendian extinction, occurring near the close of
  the Vendian period, is currently under debate as
  to whether an extinction event occurred or not.
  Under later dicussion, the Vendian fauna is
  believed to have an undergone an extinction,
  after which the Cambrian fauna evolved.

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Bibliography

• 1.http//science.nationalgeographic.com/science/pr
  ehistoric-world/precambrian.html
• 2. http//en.wikipedia.org/wiki/Precambrian
• 3. http//en.wikipedia.org/wiki/Precambrian
• 4.http//www.encyclopedia.com/topic/Precambrian_er
  a.aspx