(a) carbon cycle
(b) Nitrogen cycle
(c) Phosphorus Cycle
(d) Sulphur Cycle
14. Ans: c
Explanation:
Phosphorus is a major constituent of biological membranes, nucleic acids and cellular energy transfer systems. Many animals also need large quantities of this element to make shells, bones and teeth. P is the eleventh most abundant element in the Earth’s crust.
The Phosphorus Cycle
- It is the biogeochemical cycle that describes the transformation and translocation of phosphorus in soil, water, and living and dead organic material.
- Phosphorus additions to soil occur due to additions of inorganic and organic (manure) fertilizer and the degradation and decomposition of organic (plant and animal) material.
- The natural reservoir of phosphorus lies in the rocks, fossils, etc. which contains phosphorus in the form of phosphates.which is excavated by manfor using it as Fertiliser.
- Export of P from soil occurs mainly through plant uptake. When rocks are weathered, minute amounts of these phosphates dissolve in soil solution and are absorbed by the roots of the plants. Herbivores and other animals obtain this element from plants.
- Phosphorus may also be exported from soil via surface runoff and erosion or subsurface loss through leaching. A good proportion of phosphates moving with surface run-off reaches the oceans and are lost into the dep sediments.
- Sea birds also play an important role in phosphorus cycling. They eat sea fishes which phosphorus rich and the droppings or excreta of the birds return the phosphorus on land. The Guano deposits on the coast of Peru are very rich sources of phosphorus.
- The waste products and the dead organisms are decomposed by phosphate-solubilising bacteria releasing phosphorus back into the soil.
- Unlike carbon cycle, there is no respiratory release of phosphorus into atmosphere.
In the Sulphur cycle, the ocean represents a major reservoir of sulfur on Earth, with large quantities in the form of dissolved sulfate and sedimentary minerals (e.g., gypsum and pyrite).
Hence, option c is correct.
Read: Previous Year UPSC Environment Questions (PYQs) With Explanation 2021