Question

Question: (a) Which region of Earth’s crust is not involved in the phosphorus cycle? (b) Name two roles organisms play in the cycle.

Short answer

(a) There are no gaseous components in the phosphorus cycle. So atmosphere is not involved in phosphorus cycle.

(b) Dihydrogen phosphate is absorbed by plants from the soil. Animals eat these plants, and phosphorus is released into the soil, rivers, and oceans through animal faces and the decay of dead organisms (animals and plants). Photosynthetic algae can also synthesis biomolecules using phosphorus.

Step-by-step solution

Atmosphere

The gases that surround a star or planetary body are held in place by gravity and are referred to as the atmosphere. If gravity is high and the temperature of the atmosphere is low, a body is more likely to keep an atmosphere over time.

Subpart (a)

(a). Since this phosphorus cycle has no gaseous component, it does not involve the atmosphere. Phosphorus in the Earth's crust cycles through three biological cycles: land-based, water-based, and inorganic, all of which interact through erosion and organism growth and decay.

Therefore, no gaseous component in phosphorus cycle.

Subpart (b)

(b) Organisms are critical players in the phosphorus cycle.

1. The incorporation of phosphate into organisms (bones, teeth, proteins, etc.) and the release of phosphate through excretion and decay are both part of the land-based biological cycle. In an aqueous environment, phosphorus is frequently found in the cycle as a phosphate oxo anion, which exists in equilibrium: ${\mathrm{H}}_2{\mathrm{PO}}_4^{-}\rightleftharpoons {\mathrm{HPO}}_4^{2-}+{\mathrm{H}}^{+}\rightleftharpoons {\mathrm{PO}}_4^{3-}+2{\mathrm{H}}^{+}$. As plants can only absorb the water-soluble dihydrogen phosphate, phosphates create insoluble complexes with ${\mathrm{Ca}}^2+,{\mathrm{Fe}}^3+,{\mathrm{Al}}^3$. As a result, plants have acquired the ability to produce acids near their roots. Animals consume phosphates while eating vegetation. Phosphates are released into rivers and oceans by the decay, death, and excretion of waste by animals and plants.

2. The work of photosynthetic algae, which utilize phosphate produced by animal and plant excretion or decay to synthesize their macromolecules, is part of the water-based biological cycle. Other aquatic creatures utilize part of the released phosphate, while others precipitate with calcium ions, sink to the seabed, and return to the inorganic cycle's long-term phosphorus reserves. Therefore, phosphates are consumed by plants, animals and algae.