Correct Response: B. Phytoplankton in the oceans remove carbon dioxide from the atmosphere during photosynthesis. Much of the carbon gets incorporated into the phytoplankton in the form of calcium carbonate. When the organisms die, their bodies sink to the ocean floor and become part of the ocean sediment, taking the calcium carbonate with them. All living organisms, including decomposers and other heterotrophs release carbon dioxide into the atmosphere during respiration, rather than absorb it (A). Consumers from the higher trophic levels represent such a small percentage of all organisms that their contribution of carbon dioxide is relatively small (C) and could not be considered a main source of carbon dioxide returning to the atmosphere. The amount of carbon dioxide released by an acre of burning trees represents many, not just one, years' worth of carbon dioxide absorbed during photosynthesis by those same trees (D).
