Biology A
Nutrient Cycling
Background: In biogeochemical cycles (including carbon, water and nitrogen cycles), chemical elements
are transported between the atmosphere, biosphere (living things), hydrosphere (water), and geosphere
(rocks, minerals, and soils). These cycles help us remember that Earth is a complex system and identify the
processes that link the living (biotic) and nonliving (abiotic) worlds.
Abiotic Factors:
Examples:
Biotic Factors:
Examples:

How might abiotic and biotic factors interact?
Energy – all life processes rely on sunlight for energy!

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Sunlight is captured by _______________________ doing _____________________ to store
energy as ________________________.
Energy gets transferred through an ecosystem by
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Energy transfer is not efficient! With each transfer, about 90% of the stored energy either gets used
to power life activities or is wasted as ______________.

Producers can only store energy from light. Heat energy is just wasted.
Nutrients can cycle through an ecosystem and be recaptured, but energy flows through and it lost.
Water Cycle:
1. Why is water important to life?
2. In what form does water exist in the atmosphere?
3. How does water return to the earth’s surface?
4. How does water become part of the biotic world?
5. How does water move from one organism to another?
6. Describe three ways that water enters the atmosphere.
Carbon Cycle:
1. Why is carbon important to life?
2. In what form does carbon exist in the atmosphere?
3. How does carbon become part of the biotic world?
4. How does carbon move from one organism to another?
5. Describe three ways that carbon enters the atmosphere.
6. How are the oceans involved in the carbon cycle?
7. What role do rocks have within the carbon cycle?
Nitrogen Cycle:
1. Why is nitrogen important in living organisms?
2. In what form does nitrogen exist in the atmosphere?
3. Can most organisms get nitrogen directly from the air?
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4. What types of organisms are responsible for “nitrogen fixation?” Where can they be found?
5. What two forms of nitrogen can plants utilize from the soil?
6. Unlike plants, animals cannot get their nitrogen from the soil (they don’t have roots!) How do
animals get their nitrogen?????
7. What types of organisms are responsible for decomposition? Why is this process important for a
healthy ecosystem?
7. How is nitrogen returned to the atmosphere?
8. Every spring, farmers actually spray large amounts of liquefied cow manure on their fields before
planting any crops (such as corn.) While this is not a pleasant experience to witness, how does this
help the crops in the future?
Other element cycles to keep in mind
Oxygen  closely linked to carbon cycle. Important as a reactant in cellular respiration (releasing
energy in cells!)
Sulfur  found in many proteins, hormones and vitamins. It is what you smell when a dead animal
is rotting as well as the main contributor to odor in flatulence.
Phosphorus  found in DNA and the energy molecule of life ATP. Cycles between inorganic
abiotic regions such as rocks and soil to the organic tissues of organisms.
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