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Topic Ocean acidification
Asked 3 times across 3 UPSC exams over 13 years (2012–2025), peaking in 2012.
Key insights
- Most tested in CSE — 1 of 3 PYQs
- Most asked in 2012
- Recurs across 3 years (2012–2025)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
CSE 2012 → CAPF 2015 → GEO 2025
How the concept evolved
Long-running — most appearances (2 of 3) predate 2016, and it still returns.
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.
GEO2025
The ability of corals to make their skeletons primarily depends on which one of the following factors?
- A Temperature
- B pH
- C CO₂ concentration ✓
- D Salt concentration
✓ Correct answer: (C)
Environment & Ecology › Climate Change
CAPF2015
It is reported that there is a ongoing decrease in the pH value of ocean water because of global warming. It happens due to :
- A larger uptake of CO2 by ocean water ✓
- B lesser uptake of CO2 by ocean water
- C larger uptake of atmospheric nitrogen by ocean water
- D lesser uptake of atmospheric nitrogen by ocean water
✓ Correct answer: (A)
Environment & Ecology › Climate Change
CSE2012
The acidification of oceans is increasing. Why is this phenomenon a cause of concern?
- The growth and survival of calcareous phytoplankton will be adversely affected
- The growth and survival of coral reefs will be adversely affected
- The survival of some animals that have phytoplanktonic larvae will be adversely affected
- The cloud seeding and formation of clouds will be adversely affected
Which of the statements given above is/are correct?
- A 1, 2 and 3 only ✓
- B 2 only
- C 1 and 3 only
- D 1, 2, 3 and 4
✓ Correct answer: (A)
Environment & Ecology › Climate Change
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