Biogeochemical Cycles
describe the flow of essential elements from the environment through living organisms and back into the environment.
examples of biogeochemical cycles
- carbon cycle,
- nitrogen cycle,
- water cycle,
- phosphorus
- calcium,
- magnesium,
- etc…
Biogeochemical Cycle components
- Reservoir
A place where anything is kept in store - Assimilation
Absorption, the metabolic conversion of nutrients into tissue - Release
the release of chemicals in the environment
Hydrological Cycle
(water cycle)
- Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land
- Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water
- Release – plants transpire, animals breathe and expel liquid wastes
Transpiration vs Evaporation
Carbon Cycle
(carbon is required for building organic compounds)
- Reservoir – Oceans, atmosphere (as CO2), fossil fuels (oil, coal), durable organic materials (for example: cellulose).
- Assimilation – plants use CO2 in photosynthesis; animals consume plants.
- Release – plants and animals release CO2 through respiration and decomposition; CO2 is released as wood and fossil fuels are burned.
Nitrogen Cycle
(Nitrogen is required for the manufacture of
amino acids and nucleic acids)
1.Reservoir –
•atmosphere as N2
•soil
as NH4+ or ammonium, NH3 or ammonia, N02- or nitrite, N03- or nitrate
- Assimilation – plants absorb nitrogen as either ammonium or as nitrate, animals obtain nitrogen by eating plants and other animals. The stages in the assimilation of nitrogen are as follows:
—Nitrogen Fixation: N2 to ammonium by nitrogen-fixing bacteria (prokaryotes in the soil and root nodules), N2 to nitrate by lightning and UV radiation.
—Nitrification: ammonium to nitrite and nitrite to nitrate by various nitrifying bacteria.
- Release – Denitrifying bacteria convert nitrate back to N2 (denitrification); detrivorous bacteria convert organic compounds back to ammonium (ammonification); animals excrete ammonium (or ammonia) urea, or uric acid.
Phosphorus Cycle
(Phosphorus is required for the manufacture of ATP and all nucleic acids)
- Reservoir – erosion transfers phosphorus to water and soil; sediments and rocks that accumulate on ocean floors return to the surface as a result of uplifting by geological processes
- Assimilation – plants absorb inorganic PO43- (phosphate) from soils; animals obtain organic phosphorus when they plants and other animals
- Release – plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products
Biogeochemical cycles of other minerals, such as
calcium and magnesium, are similar to the phosphorus cycle.
