BIOL208 Lecture Notes - Lecture 22: Nutrient Cycle, Nitrogen Fixation, Nitrogen Cycle
1 May 2018
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Nutrient Cycling
• Where energy flows through ecosystems, nutrient cycle
o FLOW = one way trip
o CYCLE = continuously recycled
• Nutrients and Water Cycle
o Transformation
o Use
o Movement & reuse
• Reservoirs
o Stores of water or nutrients in a cycle
• Nutrients: Elements are required for the development, maintenance, and reproduction
of organisms
o Macronutrients: Essential elements required in large concentrations in an
organism
o Micronutrients: Essential elements required only in small concentrations in an
organism
Phosphorus Cycle
• Cycles via phosphate ion
• Most phosphorus is tied up in mineral deposits and marine sediments
• Phosphorus is usually released to ecosystems through weathering of rock
• Plants take up phosphate ions from soil or water and incorporate them directly in tissue
• Animals gain phosphate by eating these tissues or from the tissues of other organisms
• Animals eliminate excess phosphorus through urine
• Phosphate in water can sometimes precipitate into the sediment under the right
conditions
o High O2 = calcium, iron
o Low O2 = sulfur
Nitrogen Cycle
• Ammonia, ammonium, nitrite, nitrate, nitrogen gas, nitric oxide
• Nitrogen fixation: Process of converting N2 into forms primary producers can use
• Immobilization: Conversion of mineral forms of N2 (ex. Ammonia and nitrate) into
organic forms (ex. Proteins)
• Mineralization: Conversion of organic forms of N2 into mineral forms
• Nitrification: Conversion of ammonium to nitrite and nitrite to nitrate
• Denitrification: Process of converting nitrate into nitrogen gas
• Biggest reservoir of N is the atmosphere
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