Tag: nitrogen and phosphorus cycles

Sedimentary rocks are the largest reservoir of the phosphorous .Phosphates are removed from the rocks (via weathering) and are distributed throughout both soils and water. Plants take up the phosphate ions from the soil. The phosphates then move from plants to animals when herbivores eat plants and carnivores eat plants or herbivores. The phosphates absorbed by animal tissue through consumption eventually returns to the soil through the excretion of urine and feces, as well as from the final decomposition of plants and animals after death. Hence option B is correct.

Sedimentary cycles involve the transportation of matter through the ground to water; that is from the lithosphere to the hydrosphere. Most phosphates originate as salts in ocean sediments or in rocks. Over time, geological uplift brings these sediments to the surface, and weathering releases the phosphate ions. Plants can then absorb these phosphates from the soil and use it in cellular processes. Phosphate taken up by plants may then be passed on to animals when the plant is consumed by herbivore that, in turn, may be consumed by carnivores. After death, the animal or plant decays, and the phosphates are returned to the soil by way of bacterial decomposition. Runoff from the land may carry leached phosphate back to the ocean, where it eventually enters sediments and is reincorporated into rock.

The sedimentary cycle is one of the  biogeochemical cycles that forms an important factor for the growth and development of a living organism. For the sedimentary cycle, the major reservoir is the lithosphere which releases the  elements through weathering. The mineral elements required by living organisms are obtained  from inorganic sources either from salts dissolved in water or from rocks. The sedimentary cycle is represented  by phosphorous, sulphur and iodine cycles.
Sulphur cycle is the cycle which allows the circulation of sulphur from the source to the various living organism and back to the natural resources in form of salts of sulphur.

• The term biogeochemical cycle is used for the exchange or circulation of biogenetic nutrients between living and nonliving components of the biosphere.
• The nutrient cycle can be a gaseous cycle in which the materials involved in circulation between living and nonliving components are gases or vapors, e.g., carbon, hydrogen, oxygen.
• In sedimentary cycles of matter; the materials involved in circulation between biotic and abiotic components of the biosphere are non-gaseous e.g., phosphorous, calcium, magnesium.
• The reservoir of phosphorous is phosphates present in rocks.
  
  Thus, the correct answer is option B.

Phosphorus is a critical element. In living systems, it occurs in nucleic acids, nucleotides including ATP, bones, teeth, phospholipids etc. It is obtained from the soil as orthophosphates. Organic phosphorous circulates in nature from plants to animals. Phosphate is released by decomposers back to the soil. The reservoir pool for phosphorus is phosphates in rocks from which the phosphorus is slowly transferred to cycling pool.

Phosphorus is obtained from soil as orthophosphate $(PO _{4}^{3-})$. Organic phosphorus circulates in nature from plants to animals. Phosphate is released by decomposers (Phosphatising bacteria) back to soil.

A large amount of phosphate is lost in the sea by sedimentation. This is irretrievable loss.

There are 4 layers of Earth, namely lithosphere (land), hydrosphere (water), biosphere (living), and atmosphere (air). Lithosphere of Earth includes the crust and the uppermost mantle. It makes up the hard and rigid outer layer of the Earth. It is reservoir of phosphorus. The largest reservoir of phosphorus is sediments or sedimentary rocks. Hence, phosphorous represents sedimentary type of nutrient cycle.