The two major differences between carbon and phosphorus cycle are
a) atmospheric inputs of “P” through rainfall are much smaller than carbon inputs.
b) atmospheric inputs of phosphorus through rain fall are much greater than carbon inputs.
c) gaseous exchange of phosphorus between organisms and environment is not negligible.
d) gaseous exchange of phosphorus between organisms and environment are negligible.

Unlike carbon, which enters the atmosphere through various natural and anthropogenic sources, atmospheric inputs of phosphorus are relatively small and insignificant. Phosphorus mainly enters terrestrial and aquatic ecosystems through weathering and erosion of rocks, and the dissolution of phosphorus-containing minerals in soils and sediments.

Unlike carbon, which is exchanged between organisms and the environment in gaseous form (as CO₂), phosphorus is mainly cycled in its solid and dissolved forms. Phosphorus cycles between organisms and the environment through uptake by plants, consumption by animals, and decomposition by microorganisms, but it does not exchange in gaseous form like carbon does.