All elements cycle between organic and inorganic reservoirs.
of fossil fuels
In studying cycling of water, carbon, nitrogen, and phosphorus, ecologists focus on four factors:
Each chemical’s biological importance
Forms in which each chemical is available or used by organisms
Major reservoirs for each chemical
Key processes driving movement of each chemical through its cycle.
Water is essential to all organisms.
97% of the biosphere’s water is contained in the oceans, 2% is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwater.
Water moves by the processes of evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater.
Nutrient Cycles: Water Cycle
Net movement of
water vapor by wind
Carbon-based organic molecules are essential to all organisms.
Carbon reservoirs include fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, and the atmosphere.
CO2 is taken up and released through photosynthesis and respiration; additionally, volcanoes and the burning of fossil fuels contribute CO2 to the atmosphere.
Nutrient Cycles: Carbon Cycle