BIOGEOCHEMICAL CYCLES

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BIOGEOCHEMICAL CYCLES
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• The flow of energy in the biosphere is in one
  direction only from the sun, through living
  organisms, into the environment, and out into
  space.
• Matter cycles constantly from organism to
  organism as well as to and from the environment,
  which acts as a reservoir.

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• The cyclic pathways taken by various elements in
  passing through living organisms (biotic) and the
  earth, its atmosphere and its bodies of water
  (abiotic) are generally called biogeochemical
  cycles.
• The NITROGEN CYCLE is one of the most important.

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• Proteins and nucleic acids are essential to life.
  In order to make them, living things must obtain
  nitrogen in a useable form.
• Nitrogen in the air is diatomic (2-atom)
  molecules N2, and no animal or plant can separate
  them to use them.
• To be useful the nitrogen must be fixedbe
  attached to atoms of some other elements to form
  a compound.

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Nitrogen fixation..

• Can occur by
• Passage of UV light and lightning through the air
  NO3- (nitrate ions) formed
• Volcanoes, combustion of fossil fuels (coal, oil,
  natural gas) and forest fires nitrate and NH3
  (ammonia)
• Rain brings the fixed nitrogen to the soil as
  NH4- (ammonium ion)

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• The bulk of this is carried out by
  nitrogen-fixing bacteria in soil and by
  cyanophytes (blue-green bacteria).
• The most efficient nitrogen fixers are bacteria
  found in nodules on the roots of certain plants,
  notably the legumes (alfalfa, beans, peas,
  lentils, clover).
• Fertilizers also add nitrogen to the soil

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• Animals must consume Nitrogen in the form of
  already formed amino acids in their food.
• Excretions of animals and the dead bodies of all
  organisms are broken down in the soil by
  decomposers in the process of ammonification ,
  which produces ammonia.

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• Nitrifying bacteria convert the ammonia to NO2-
  (nitrite ion), then another group of nitrifying
  bacteria convert the nitrite ion to NO3- (nitrate
  ion). This is know as nitrification.
• Nitrate is readily taken up by
• roots of plants and utilized.

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• Denitrifying bacteria convert nitrate to N2O
  (nitrous oxide) or N2 (nitrogen gas), which is
  then lost to the atmosphere.
• Nitrogen is lost from soil by erosion and carried
  into streams, rivers, and ultimately the ocean.
• It then cycles through aquatic organisms.
• Eventually, some nitrogen is lost to sediments at
  the bottoms of oceans or lakes.

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http//www.biology.ualberta.ca/facilities/multimed
ia/uploads/intro-biology/ncycle.swf
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• Assignment
• 1)Diagram and label one of the Biogeochemical
  Cycles. (pg371-374)
• 2)Provide a caption under it explaining what is
  occurring.
• 3)Answer Section 4 Review (questions 1-8) on pg.
  374.(due by end of class on Wed.. 9/8)
• Finish your Energy Pyramid model first

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