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Q47 (IAS/2021) Environment & Ecology › Ecology & Ecosystem Basics › Biogeochemical cycles Official Key

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?

Result
Your answer: —  ·  Correct: C
Explanation

The correct answer is Option 3.

Biogeochemical cycles are categorized into gaseous and sedimentary types. The Phosphorus cycle is a prime example of a sedimentary cycle. Unlike carbon or nitrogen, phosphorus does not exist in a gaseous phase in the atmosphere. Instead, its primary reservoir is the Earth's crust, specifically in the form of phosphate rocks.

  • Phosphorus Cycle: Phosphorus is released into the soil and water through the weathering of rocks (chemical and physical erosion). This is the fundamental mechanism that introduces phosphorus into the biological food chain.
  • Carbon and Nitrogen Cycles: These are primarily gaseous cycles where the atmosphere or hydrosphere serves as the main reservoir.
  • Sulphur Cycle: While it has a sedimentary component, it also has a significant gaseous phase (SO2, H2S), making phosphorus the most direct answer for rock weathering as the primary source.

Therefore, because phosphorus is almost exclusively mineral-based, rock weathering is the critical step for its entry into the cycle.

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Q. In case of which one of the following biogeochemical cycles, the weathering of rocks is the main source of release of nutrient to enter t…
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Origin: Books + Current Affairs Fairness: Low / Borderline fairness Books / CA: 2.5/10 · 2.5/10
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This is a textbook 'Sitter' found directly in standard sources like Shankar IAS (Chapter 2) and Majid Hussain. The core concept tested is the fundamental classification of biogeochemical cycles into 'Gaseous' (Atmosphere-based) vs. 'Sedimentary' (Lithosphere-based). If you missed this, you are skimming headings rather than understanding the basic mechanics of nutrient reservoirs.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Is weathering of rocks the main source of nutrient release into the phosphorus biogeochemical cycle?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > a) Phosphorus Cycle > p. 20
Presence: 5/5
“(a) Phosphorus Cycle Phosphorus plays a central role in aquatic ecosystems and water quality. Unlike carbon ancl nitrogcn, which conre primarily from the atmosphere, phosphorus occurs in large amounts as a mincral in phospharc rocks and enters the cycle from erosion and n'rining activities. This is the nutrieut r:onsidered to be the main cause of excessive growth of rooted and i'ccfloating microscopic plants in lakes. The main storage for phosphorus is in the earth's crust. On land, phosphorus is usually found in the form ofphosphates. By the process ofweathering and erosirin phosphates enter rivers and streams that transport them to the ocean.”
Why this source?
  • Explicitly identifies phosphorus as occurring mainly as mineral in phosphate rocks.
  • States that phosphates enter the cycle from erosion, mining and by weathering into rivers and streams.
Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > Phosphorus Cycle > p. 27
Presence: 5/5
“Te depletion of phosphorus from exchange pool is compensated very slowly by the release of the element from the phosphate rocks of the reservoir pool. Tis occurs by the process of erosion and weathering. Te phosphorus cycle can be easily disrupted by the use of phosphate fertilizers in modern agriculture. Most of the manufactured phosphate fertilizers are produced from phosphate rocks, but are rapidly lost from the exchange pool to marine deposits as they are easily leached from the soil. Tis could lead to serious defciencies in available phosphorus for agriculture in the future.”
Why this source?
  • Says depletion of the exchange pool is slowly compensated by release from phosphate rocks.
  • Specifies that erosion and weathering of phosphate rocks release phosphorus into the cycle; links to fertilizer production from these rocks.
Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > FUNCTIONS OF AN ECOSYSTEM > p. 21
Presence: 4/5
“In the ocean, once the phosphorus accumulates on continental shelves in the form of insoluble deposits. After millions of years, the crustal plates rise from the sea floor and expose the phosphates on land. After more time, weathering will release them from rock and the cycle's geochemical phase begins again.”
Why this source?
  • Describes geological recycling where phosphates exposed by uplift are released by weathering from rock.
  • Connects long-term geochemical phase of the cycle to weathering as the mechanism releasing phosphates back into the system.
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SIMILAR QUESTIONS

NDA-II · 2011 · Q58 Relevance score: -3.96

Which one of the following processes of weathering belongs to both mechanical and chemical weathering ?

CAPF · 2011 · Q92 Relevance score: -4.09

Which one among the following phenomena includes processes, such as production, predation, nutrient transformation, and the influx and efflux of energy and materials ?

NDA-I · 2022 · Q89 Relevance score: -4.13

Weathering, mass wasting, erosion and transportation are indicators of which one of the following processes?

NDA-I · 2018 · Q50 Relevance score: -4.18

Chemical weathering of rocks is much greater in a place with

CDS-II · 2024 · Q101 Relevance score: -5.29

Which one of the following is not an example of chemical weathering?