The Cambrian Period

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The Cambrian Period
542-488 MYA
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Cambrian Period Facts

• The Cambrian Period started 542 million years ago
  and lasted about 54 million years
• It was a very slow evolving period
• Animals evolved the ability to swim and crawl,
  and also developed more acute senses of smell and
  taste
• The sense of sight appeared with small changes in
  light
• Sight became so useful in detecting a swimming
  predator moving over head. Sight helped the
  evolution of many different organisms

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Stages of the Cambrian Period

• The Early Cambrian Epoch (542-513 MYA)
• The Middle Cambrian Epoch (513-501 MYA)
• The Furongian Epoch (501-488 MYA)

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Earths Development

• The continents were concentrated in the Southern
  Hemisphere near the equator
• The land masses were fragmented from the super
  continent, Rodinia
• Continental plate movement and collisions
  generated pressure and heat that led to the
  formation of large mountain ranges

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Climactic Changes

• The Cambrian Period was between two Ice Ages
• Global Climate was warmer and more uniform (near
  the equator)
• Sea level rose at the beginning from ice melting
• Much of the world was covered by sea
• This allowed new habitats where marine life could
  flourish

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Evidence of Cambrian Explosion
The Cambrian Explosion was a sudden appearance
of a large diversity of animals in a short
geological amount of time

• Pre Cambrian fossils are simple and
  two-dimensional
• Cambrian fossils are very diverse with many new
  traces

• Fossil Records were found to explain this period
• The Burgess Shale of Canada
• Chengjiang, in Yunnan Province of China
• The Wheeler and Marjum Formations of Utah

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Dominant Species

• Bacteria and Protists were in the worlds shallow
  seas
• Plants had not evolved yet, so no vegetation on
  the land
• Oxygen mixed into the worlds oceans and was
  available to many kinds of animals causing the
  Cambrian Explosion
• Most of the organisms that lived then were hard
  shelled animals according to the fossil record

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Dominant Species

• The Trilobites were the most characteristic
  animal. They had highly developed eyes.

Other groups that appeared were sponges and
modern day starfish (echinoderms).
There were also soft-bodied echiurians which were
worm-like creatures that were carnivores.
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Dominant Species
Marine Snails and Molluscs appeared during this
time.
The first chordates or vertebrates (foraminifers)
and shelled amoebas appeared also.
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The Early Cambrian Epoch
542-513 MYA

• Simple worm traces
• Much more diverse shelly animals and molluscs
• All of the modern phyla had evolved
• The seas rose continuously throughout
• Shallow waters allowed for more species

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The Middle Cambrian Epoch
513-501 MYA

• Low Magnesium concentrations occurred in the
  seawater making calcium precipitate as calcite
• Because of the calcite building up in the sea and
  the shallow waters, life could no longer survive
• Now the bigger and more mobile organisms could
  take advantage of the sea bottom (the first
  really large carnivores)

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The Middle Cambrian Epoch
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The Furongian Epoch
501-488 MYA

• Metazoans chewed holes in the sea floor to loosen
  it up
• Many species flourished
• More molluscs diversified
• Donodonts first appeared (they had eel like
  bodies and could swim very fast in deeper water)
• Because of environmental changes, natural
  selection wiped out species and they were
  replaced by similar organisms

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Mass extinctions

• The Cambrian Period was between two Ice Ages
• There are two hypothesis for the Cambrian
  extinction
• The Glacial Cooling Hypothesis continental
  glaciation caused a decline in temperature with
  mass extinction of warm water species
• Oxygen Depletion Hypothesis cooling and
  depletion of water eliminated organisms not able
  to tolerate the cold or decrease in oxygen