UPSC Prelims 2023 Q18: Environment & Ecology – Climate Change & Greenhouse Gases
- (a) Only one
- (b) Only two
- (c) All three
- (d) None
Answer: (c) All three
Explanation
Microorganisms in Extreme Environments (Extremophiles)
| Statement | Environment | Verdict | Examples |
|---|---|---|---|
| 1 | Microorganisms can grow above 100°C (boiling point) | TRUE | Hyperthermophiles grow at 80–121°C. *Pyrolobus fumarii* grows at 121°C in deep-sea hydrothermal vents. These are archaea (not bacteria). |
| 2 | Microorganisms can grow below 0°C (freezing point) | TRUE | Psychrophiles grow at -20°C to +10°C. Found in Arctic/Antarctic ice, permafrost. Examples: *Psychrobacter*, certain snow algae. |
| 3 | Microorganisms can grow at pH below 3 (highly acidic) | TRUE | Acidophiles thrive at pH 1–3. *Acidithiobacillus ferrooxidans* grows at pH 1. Found in acid mine drainage, volcanic hot springs. |
All three statements are correct.
Answer: (c) All three.
Why each option is right or wrong
- (a) Incorrect. 'Only one' — all three categories of extremophiles (hyperthermophiles, psychrophiles, acidophiles) are scientifically documented.
- (b) Incorrect. 'Only two' — psychrophiles living below freezing are well-documented in Antarctic and Arctic environments.
- (c) CORRECT. All three environments support microbial life: hyperthermophiles (>100°C), psychrophiles (<0°C), and acidophiles (pH<3).
- (d) Incorrect. 'None' — extremophile biology is a well-established scientific field with commercial applications (Taq polymerase from thermophiles, for example).
Key point
Extremophiles: Hyperthermophiles (>100°C, deep sea vents), Psychrophiles (<0°C, Antarctic ice), Acidophiles (pH<3, volcanic springs). All three types exist — life adapts to seemingly impossible conditions.
Remember
Extremophiles include hyperthermophiles (>100°C in hydrothermal vents), psychrophiles (<0°C in Antarctic ice), and acidophiles (pH<3 in volcanic springs). All three microorganism types exist — all three statements are correct.
Common mistakes
- Assuming boiling water kills all life — hyperthermophilic archaea at deep-sea hydrothermal vents survive well above 100°C under pressure.
- Not knowing psychrophiles — Antarctic and Arctic environments host thriving microbial communities at sub-zero temperatures.
- Underestimating acid tolerance — some bacteria live in acid mine drainage at pH < 1.
Exam tip
Extremophile categories: Thermophile (heat), Psychrophile (cold), Halophile (salt), Acidophile (acid), Alkaliphile (base), Barophile (pressure). All three in this question are real. Taq polymerase (DNA tech) comes from *Thermus aquaticus* — thermophile connection to biotechnology.
Sources
- NCERT Biology Class 11 — Chapter 2: Biological Classification (Archaea/Extremophiles)
- Astrobiology — Extremophiles as models for life on other planets