Environmental Science

Carbon Cycle--Review of Some Basic Reservoirs and Pathways

General: At any given time, carbon can be found (i.e., it is stored) in different reservoirs in the HYDROSPHERE, ATMOSPHERE, BIOSPHERE, and LITHOSPHERE.  It is stored in both organic forms and inorganic (CO2) forms.  The carbon is cycled and recycled between and among the different reservoirs via many different pathways.

Directions: Review the processes and pathways described below and draw your own diagram of the carbon cycle.


  1. Inorganic carbon (in the form of CO2 gas ) moves between the oceans (HYDROSPHERE) and the ATMOSPHERE.Some CO2 is dissolved in the ocean from the air and some CO2 enters the air from the ocean.
  2. Carbon moves from the ATMOSPHERE to the BIOSPHERE via fixation ofinorganic CO2 gas to organic carbon by plants, algae, and certain bacteria (i.e., producers).
  3. Organic carbon moves within the BIOSPHERE via the food web (i.e.,consumers eat the producers).
  4. Producers and consumers die and their remains end up as organic matter(part of the BIOSPHERE and LITHOSPHERE).
  5. Organic carbon in organic matter gets transformed into inorganic CO2 gas via the respiration of decomposers(e.g., fungi and certain kinds of bacteria) that eat the remains of dead organisms.  This gas returns to the ATMOSPHERE.
  6. Organic carbon also gets transformed into CO2 gas via the respiration of living producers and consumers (i.e., through their metabolic processes).  (As above, this gas moves to the ATMOSPHERE).
  7. Some organic matter does not get transformed by decomposers and insteadstays in the LITHOSPHERE.  It gets stored in soil, rocks, and fossil fuels.  Eventually it can be transformed into CO2 gas by the burning of fossil fuels or the respiration of decomposers (and is returned to the ATMOSPHERE).