The movement of carbon and other elements through living and nonliving parts of an ecosystem is described by which concept?

• A. Biogeochemical cycle
• B. Hydrologic cycle
• C. Fossil fuel
• D. Predation

Answer: (A)

Biogeochemical cycles describe how carbon and other elements move between living organisms and the nonliving environment, cycling through air, water, soil, and rocks. For carbon, this means moving from the atmosphere into plants during photosynthesis, passing through the food web as organisms eat each other, and returning to the air or to the earth through respiration, decomposition, and burial as sediments or fossil fuels. Some carbon is stored for long periods in soils, sediments, or rocks, making the cycle both rapid and long-term.

The hydrologic cycle, by contrast, focuses on water—evaporation, condensation, precipitation, and runoff—how water moves through the environment, rather than on most chemical elements. Fossil fuel is a geological store of carbon, not a cycle itself. Predation describes how one organism hunts another, which is an interaction within the ecosystem, not the movement of elements through biotic and abiotic parts.