Water, Nitrogen, and Carbon Cycles

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Water, Nitrogen, and Carbon Cycles

• Bio CC

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Outline

• Water Cycle
• Nitrogen Cycle
• Carbon Cycle

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Water Cycle

• From the oceans, water evaporates into the
  atmosphere.
• From land, 90 of water reaching the atmosphere
  transpires from plants.
• Only about 2 of all water on earth is captured
  in any form.
• The rest is free water circulating between the
  atmosphere and the oceans.

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Carbon cycle

• Carbon is taken from the atmosphere by
  photosynthesis
• used to make organic molecules
• returned to the atmosphere by cellular
  respiration, decomposers

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The nitrogen cycle relies heavily on bacteria

• Nitrogen is plentiful in the atmosphere as N2
• But plants and animals cannot use N2
• Some bacteria in soil and legume root nodules
  convert N2 to compounds that plants can use
• ammonium (NH4) and nitrate (NO3)

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Human impact on chemical cycles
76 naturally occurring
24 naturally occurring
24 human- caused
58 human- caused
46 available
54 used
Atmospheric CO2 concentration
Terrestrial nitrogen fixation
Accessible surface water
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• Environmental changes caused by humans can
  unbalance nutrient cycling over the long term

• Example acid rain