In case of which one of the following biogeochemical cycles, the weathering of rocks is the main source of release of nutrient to enter the cycle?
Detailed Explanation:
Answer: Option 3 — Phosphorus Cycle
The Phosphorus Cycle is unique among biogeochemical cycles as it lacks a gaseous phase and primarily relies on the weathering of phosphate-rich rocks as its main source. Geological weathering processes break down these rocks over time, releasing phosphate ions (PO₄³⁻) into the soil and water, which are then absorbed by plants and move through the food chain.
Why other options are incorrect:
• Carbon Cycle: Primarily driven by atmospheric CO₂ from respiration, combustion, and volcanic activity, not rock weathering.
• Nitrogen Cycle: Relies on atmospheric nitrogen with fixation by bacteria as the key process, not weathering of rocks.
• Sulphur Cycle: Main sources include volcanic eruptions, decaying organic matter, and fossil fuel combustion, not primarily rock weathering.
📝 Short Notes: Biogeochemical Cycles
| Cycle | Main Source of Nutrient | Key Features |
|---|---|---|
| Phosphorus Cycle | Weathering of phosphate rocks | No gaseous phase; slowest cycle; limiting nutrient in aquatic ecosystems |
| Carbon Cycle | Atmospheric CO₂ | Involves photosynthesis, respiration, combustion; has gaseous phase |
| Nitrogen Cycle | Atmospheric N₂ | Nitrogen fixation by bacteria; involves nitrification, denitrification |
| Sulphur Cycle | Volcanic activity, fossil fuels | Involves atmospheric SO₂; acid rain formation |
| Water Cycle | Oceans, water bodies | Evaporation, condensation, precipitation processes |
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