Question

Assertion : Phosphorus cycle is an imperfect cycle as a sufficient amount of phosphorus combines with $A{l}^{3+},F{e}^{2+}$ and $C{a}^{2+}$ to form insoluble and unavailable salts.
Reason : Phosphate circulates in abiotic environment in lithosphere as well as in atmosphere.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (C)

Phosphorus cycle is an example of sedimentary cycle. Greatest reservoir of phosphate in the world is relatively insoluble ferric and calcium phosphate in rocks. Cyclic pool is soil for terrestrial ecosystems (lithosphere) and water for aquatic ecosystems (hydrosphere). Phosphate circulates in the abiotic environment in lithosphere as well as hydrosphere. Atmosphere or gaseous cycle is absent. Inside soil some phosphorus is lost through leaching. Similarly, a sufficient amount of phosphorus combines with calcium, iron or aluminium and becomes insoluble. It settles down at the bottom of lake or ocean as sediment. Bone and teeth may also remain undegraded. Such phosphorus becomes part of lithosphere. It is released after a very long interval when the rocks containing them are exposed to weathering agencies or are mined. Thus, phosphorus cycle is an imperfect cycle.