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Topic Nitrogen cycle
Asked 7 times across 2 UPSC exams over 39 years (1987–2026), peaking in 2013.
Key insights
- Most tested in CSE — 4 of 7 PYQs
- Most asked in 2013
- Recurs across 7 years (1987–2026)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
CSE 1987 → GEO 2022
How the concept evolved
Rising — more than half its appearances (5 of 7) are since 2016.
Related concepts
Ideas UPSC tests alongside this one — keep exploring.
Sample questions
You've seen the pattern — here are a few of the actual PYQs.
GEO2026
The conversion of nitrogen to ammonium by bacteria and cynobacteria is called
- A nitrification
- B denitrification
- C ammonification
- D None of the above
Answer key not yet available (pending official release)
Environment & Ecology › Ecology & Ecosystems
GEO2024
Nitrogen cycle is one of the most important microorganisms-mediated chemical reactions in aquatic and soil environments. In this context consider the following statements
- Nitrogen fixation is the process of oxidising NH3 to NO3^-
- Nitrification process causes reduction of NO3 and NO2^- to NO2^-, followed by recycling of N2 to the atmosphere
- Denitrification converts molecular N2 into a fixed form as an organic nitrogen
How many of the statements given above is/are correct ?
- A 1
- B 2
- C 3
- D None ✓
✓ Correct answer: (D)
Environment & Ecology › Ecology & Ecosystems
CSE2023
With reference to the role of biofilters in Recirculating Aquaculture System, consider the following statements
- Biofilters provide waste treatment by removing uneaten fish feed
- Biofilters convert ammonia present in fish waste to nitrate
- Biofilters increase phosphorus as nutrient for fish in water
How many of the statements given above are correct?
- A Only one
- B Only two ✓
- C All three
- D None
✓ Correct answer: (B)
Environment & Ecology › Ecology & Ecosystems
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