VI. Cycles in the Environment

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VI. Cycles in the Environment
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A. Carbon Cycle

• 1. Cycles the organic matter necessary for all
  life
• 2. Bulk is preformed by life through
  photosynthesis and respiration
• a. 6CO2 6H2O Energy ? C6H12O6 6O2
• b. Most carbon is locked in life because of
  this

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• 3. As death and sedimentation occur,
  atmospheric carbon gets trapped as rock and
  fossil fuels.
• 4. Oceans also absorb CO2 from the air and
  volcanic eruptions
• a. This can combine with Ca to form CaCO3
  which makes shells of aquatic life

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• 5. CO2s atmospheric concentration is
  increasing
• a. Burning of fossil fuels
• b. Loss of plants that cycle
• c. There is an undiscovered sink though

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B. Phosphorus Cycle

• 1. Key to production of membranes, DNA, RNA,
  and ATP
• 2. Very small amount present in life and
  negligible in the atmosphere
• 3. Vast majority locked in rock sand released
  slowly by weathering

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• a. Dissolves in water which can
• 1. precipitate back out to form rocks
• 2. be absorbed by plants and incorporated
  into the food web
• a. This is the limiting element in plant
  growth

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• 4. Because amount limits growth, it is a main
  component of fertilizers
• a. Excess runs off, removing limitation from
  plants and algae
• 1. these overgrow, using up resources such
  as oxygen killing themselves and other
  organisms

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C. Nitrogen Cycle

• 1. N2 makes up 78 of atmosphere but is
  inaccessible to most life.
• 2. Must be made biologically active by nitrogen
  fixation
• 3. Several steps
• a. Specially adapted nitrogen-fixing bacteria
  combine it with H2 to make ammonia (NH3)
• 1. live in the root nodules of legumes

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• b. Ionized by water, NH4 (ammonium) can be
  used by few plants
• c. Other bacteria use nitrification to
  convert ammonium in to more readily usable NO2-
  (nitrite) and NO3- (nitrate)
• 1. also what is in fertilizers
• d. Plants then pass N up the food web
• e. Process can also by-pass N fixing bacteria
  as lightning can produce ammonia as well

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• 4. As organisms decay, bacteria release N2 back
  into air to start over
• 5. Along with phosphates, nitrates in
  fertilizers have created dead spots in several
  waterways.

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