Precambrian and Devonian Periods

							Precambrian and
Devonian Periods
Doug Chiki, Daniel Rankin,
      Cora Wilen
       Precambrian Time Period
• From the 4.5 billion years ago to 542 million years ago
• Named after Adam Sedgwick use of the term “cambrian” for the
  oldest sedimentary strata. It means “before the cambrian” meaning
  the underlying rocks.
• Marked by the formation of earth in the beginning and in the end the
  Cambrian Explosion from simple microbes to multicellular organisms
  and hard-shelled fossils
• Little is known about the climate and atmosphere of the
  Precambrian time period, however, there was little oxygen.
• Series of glacial periods are scattered throughout this period
Geography
     • 1100 to 1200 MYA
       land mass called
       Rodinia
     • 900 MYA Rodinia
       begins fracturing into
       present day
       continents
                      Life
• Bacteria
• Ediacara biota: group
  of soft bodied
  organisms
• Small shelly fauna
• Plankton
         Devonian Time Period
• Began 408 million years ago/Ended 360 million years
  ago.
• The beginning of the Devonian is marked by the
  appearance of the fossil Monograptus Parultimus, as
  well as two new species of marine plankton.
• The end of the Devonian is marked by the Frasnian-
  Famennian mass extinction. Possible causes for the
  extinction were the formation of glaciers and lowering of
  global sea levels. Meteorite impacts and alterations in
  atmospheric carbon dioxide may also have affected the
  extinction. Warm water species were thought to have
  been most affected by this.
         Climate & Naming
The climate was fairly   The Devonian period was named
warm and humid until     after Devon, England, where rocks
                         from the period were initially
a drastic drop in        studied. It is also referred to as the
                         “Age of Fishes” because of the
temperatures             drastic evolution that fish
occurred at the end of   underwent during this time. Lastly,
                         it has wrongly been called the
the period.              Greenhouse Age because the first
                         discoveries from the period were
                         found in western Europe and
                         eastern North America and
                         indicated tropical temperatures,
                         but these land masses straddled
                         the Equator during the Devonian
                         and were therefore warmer than
                         the rest of the globe.
Geography
      Land during the period
      existed in two
      supercontinents,
      Gondwana and
      Euramerica. These were
      located mainly in a single
      hemisphere, while the
      rest of the Earth was
      covered by ocean. These
      would later collide and
      form one continent,
      Pangaea.
                  Plate Tectonics
• Gondwana and Euramerica
  were surrounded by
  subduction zones- places
  where one tectonic plate slides
  beneath another into the
  earth’s mantle. These zones
  set in motion the collision
  between the two continents
  that would form Pangaea. Also
  during this period, present-day
  North America and Europe
  collided to form the
  Appalachian Mountains.
                            Flora
By the beginning of the period,
vegetation had begun to spread to
land. These plants were not like
those we see today, however:
they had no roots or leaves, and
many had no vascular tissue at all
but spread only by vegetative
growth. By the late Devonian,
other plants that more closely
resemble those of today had
evolved, such as ferns and the
world’s first seed plants.
Archaeopteris, the world’s first
tree which formed the earliest
forests, also began to appear. The
sudden appearance of so many
flora is known as the Devonian
Explosion.
Fauna
    •   Oceans were dominated by
        brachiopods (small two-shelled
        marine animals) and corals.
    •   The first jawed fish evolved during
        the middle of the period, and the
        first shark, the four-foot-long
        Cladoselache, appeared not long
        after. These fish became
        fearsome predators.
    •   The first fish grew legs and began
        walking on land as tetrapods, or
        four-legged vertebrates. Insects
        and arthropods first appeared.
    •   The first ammonite mollusks
        evolved and trilobites were still
        common.
                               Sources
•   Info:
     – http://www.palaeos.com/Timescale/Precambrian.htm
     – http://en.wikipedia.org/wiki/Precambrian
     – http://www.palaeos.com/Paleozoic/Devonian/Devonian.htm
     – http://www.palaeos.com/Paleozoic/Devonian/Devonian.2.htm
     – http://www.science501.com/PTDevonian.html
     – http://en.wikipedia.org/wiki/Devonian
     – http://www.ucmp.berkeley.edu/devonian/devonian.html
     – http://www.ucmp.berkeley.edu/silurian/silustrat.html
•   Images:
     – http://www.palaeos.com/Proterozoic/Proterozoic.htm
     – http://www3.interscience.wiley.com:8100/legacy/college/levin/0470000201/chap_
       tutorial/ch09/images/le08_01devon.jpg
     – http://www.ucmp.berkeley.edu/seedplants/archaeopteris.gif
     – http://www.elasmo-research.org/education/evolution/ancient.htm
     – http://www.sharkfriends.com/fossilD.jpg