Question

Phosphorus remain outside the natural cycle for a long time

• A. Because bones and teeth take a long time to decompose
• B. When the bodies of the organisms excrete and decompose
• C. Both a and b
• D. None of the above

Answer 1

The correct option is A Because bones and teeth take a long time to decompose

On land, phosphorus gets distributed in the soil from the weathering of rocks, which is taken up by plants from the soil as phosphate ions, an inorganic form of phosphate. Herbivores eat the plants and carnivores eat the herbivores and the journey of phosphate continues in the food chain. In the animal bodies phosphate gets incorporated into organic molecules such as DNA and when the animal dies organic phosphate is returned to the soil. Within soil, organic phosphates are made available to plants by bacteria that break down organic matter to inorganic forms of phosphorus in a process called mineralisation. Phosphorus in molecules like DNA, RNA and other molecules can be easily decomposed by the soil decomposers within two weeks to months. But in humans and animals 80% of the phosphorus is found in bones and teeth. It takes a very long time for it to decompose as microbial activity on teeth and bones is comparatively very slow and hence phosphorus remains outside the natural cycle of decomposition for a longer time.