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Why can carbon and nitrogen atoms be reused in the biosphere?
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Biosphere
Earth's environment includes the atmosphere, the hydrosphere, the lithosphere, and the biosphere.
Carbon and nitrogen atoms can be reused in the biosphere because, unlike energy—which flows through an ecosystem and cannot be recycled—chemical elements are continuously circulated through biogeochemical cycles.12
These elements alternate between inorganic and organic states as they move between the biotic (living) and abiotic (nonliving) components of the environment. The process functions as follows:13
- Capture and Concentration: Organisms take up these elements from their surroundings to build essential biological structures, such as proteins and nucleic acids.14
- Release: Through metabolism, respiration, and the death of organisms, these elements are released back into the environment.15
- Decomposition: Decomposers—including bacteria, fungi, and various soil organisms—break down complex organic matter, converting it back into simpler inorganic forms like carbon dioxide, ammonia, or nitrates.463
Once returned to the soil, water, or atmosphere, these atoms become available for uptake by other organisms, allowing them to move repeatedly through the biosphere over vast periods of time.12