Consider the following statements:
- 1.Some microorganisms can grow in environments with temperature above the boiling point of water.
- 2.Some microorganisms can grow in environments with temperature below the freezing point of water.
- 3.Some microorganisms can grow in highly acidic environment with a pH below 3.
How many of the above statements are correct?
Answer & explanation
Answer: (c) All three
Microbes live in places no other life can: hot vents, snow and ice, and strongly acidic sites. Such extremophiles (thermophiles, psychrophiles, acidophiles) make all three statements true.
- ✓ 1. Hyperthermophiles thrive in hydrothermal vents. Under high pressure, the methanogen Methanopyrus kandleri strain 116 has multiplied at 122 °C in the laboratory, above water's normal boiling point of 100 °C.
- ✓ 2. Cold-loving microbes (psychrophiles) live in permafrost, sea ice and under thick snow, where they stay active below 0 °C in films of salty, unfrozen water.
- ✓ 3. Acidophiles grow in highly acidic places such as acid mine drainage and acidic hot springs; some archaea grow best at a pH below 1.
Remember · Extremophiles: thermophiles (up to 122 °C under pressure), psychrophiles (below 0 °C), acidophiles (pH < 3), halophiles (salt).
📘 Read it in NCERT: Class 12 Biology, Ch 8 (practise this chapter)
Sources
- NCERT Class 12 · Biology, Chapter 8 “sites such as deep inside the geysers (thermal vents) where the temperature may be as high as 1000C, deep in the soil, under the layers of snow several metres thick, and in highly acidic environments.”
- Takai et al. (2008), Cell proliferation at 122°C by a hyperthermophilic methanogen, PNAS 105(31) (PMC) ↗ “Elevated hydrostatic pressures extend the temperature maximum for possible cell proliferation from 116°C at 0.4 MPa to 122°C at 20 MPa, providing the potential for growth even at 122°C under an in situ high pressure.”
Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·