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Topic Keystone species
Asked 3 times across 2 UPSC exams over 26 years (2000–2026), peaking in 2000.
Key insights
- Most tested in GEO — 2 of 3 PYQs
- Most asked in 2000
- Recurs across 3 years (2000–2026)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
CSE 2000 → GEO 2025
How the concept evolved
Rising — more than half its appearances (2 of 3) are since 2016.
Sample questions
You've seen the pattern — here are a few of the actual PYQs.
GEO2026
Consider the following statements
- Keystone species is an organism that has a disproportionately large effect on its environment relative to its abundance
- Sentinel species gives us an early warning of problems that could potentially affect other species
Which of the statements given above is/are correct?
- A I only
- B II only
- C Both I and II
- D Neither I nor II
Answer key not yet available (pending official release)
Environment & Ecology › Ecology & Ecosystems
GEO2025
Which one of the following species disproportionately affects ecosystem dynamics?
- A Umbrella species
- B Flagship species
- C Priority species
- D Keystone species ✓
✓ Correct answer: (D)
Environment & Ecology › Ecology & Ecosystems
CSE2000
Within biological communities, some species are important in determining the ability of a large number of other species to persist in the community. Such species are called (2000)
- A Keystone species ✓
- B Allopatric species
- C Sympatric species
- D Threatened species
✓ Correct answer: (A)
Environment & Ecology › Ecology & Ecosystems
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