UPSC CSE Prelims
Biomes Previous Year Questions (PYQs)
Practice solved questions for Biomes with detailed step-by-step solutions, key insights, and trend analysis for UPSC CSE PRELIMS.
Solved Previous Year Questions
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“Leaf litter decomposes faster than in any other biome and as a result the soil surface is often almost bare. Apart from trees, the vegetation is largely composed of plant forms that reach up into the canopy vicariously, by climbing the trees or growing as epiphytes, rooted on the upper branches of trees”. This is the most likely description of
Detailed Explanation:
Answer: Option 4 — tropical rain forest
The description perfectly characterizes tropical rain forests, where high temperature and humidity year-round create optimal conditions for rapid microbial decomposition of leaf litter, leaving the soil surface almost bare. The dense multi-layered canopy blocks sunlight to the forest floor, forcing many plants to adapt by climbing trees (lianas) or growing as epiphytes on upper branches to access light. These unique features—rapid nutrient cycling, bare soil surface, and abundant epiphytes—are hallmarks of tropical rain forests, distinguishing them from coniferous, deciduous, or mangrove ecosystems.
📝 Short Notes: Forest Biomes - Comparative Features
| Forest Type | Decomposition Rate | Soil Surface | Vegetation Characteristics | Climate |
|---|---|---|---|---|
| Tropical Rain Forest | Very rapid (fastest of all biomes) | Almost bare due to quick nutrient recycling | Dense canopy; abundant lianas, epiphytes (orchids, ferns); multi-layered structure | High temperature, high rainfall (>200 cm), high humidity year-round |
| Coniferous Forest | Very slow (cold climate inhibits decomposition) | Thick layer of undecomposed needles | Cone-bearing trees (pine, fir, spruce); needle-like leaves; limited undergrowth | Cold, long winters; moderate rainfall |
| Dry Deciduous Forest | Moderate (seasonal) | Leaf litter accumulates in dry season | Trees shed leaves in dry season; open canopy; less dense undergrowth | Distinct wet and dry seasons; 100-200 cm rainfall |
| Mangrove Forest | Slow to moderate (waterlogged, saline conditions) | Waterlogged, muddy, saline | Stilt/prop roots; pneumatophores; salt-tolerant species; sparse canopy | Coastal tropical/subtropical; tidal influence |
- Epiphytes in Tropical Rain Forests: Non-parasitic plants (orchids, bromeliads, ferns) that grow on tree branches to access sunlight without competing for soil nutrients.
- Rapid Nutrient Cycling: Despite lush vegetation, tropical rain forest soils are often nutrient-poor because nutrients are quickly absorbed by plants rather than accumulating in soil.
- Indian Distribution: Tropical rain forests in India are found in Western Ghats, Northeast states (Assam, Arunachal Pradesh), and Andaman & Nicobar Islands.
- Key Species: Mahogany, Rosewood, Ebony, Rubber, Cinchona in tropical rain forests.
“Climate is extreme, rainfall is scanty and the people used to be nomadic herders.” The above statement best describes which of the following regions?
Detailed Explanation:
Central Asian Steppe is characterized by extreme continental climate with summer temperatures up to 45°C and winter temperatures down to -50°C, scanty rainfall (250-500 mm annually), and was historically inhabited by nomadic herders like the Mongols and Kazakhs.
African Savannah has moderate tropical climate with 500-1500 mm rainfall; North American Prairie receives higher rainfall (500-900 mm) with less extreme temperatures; Siberian Tundra has permafrost and extremely cold climate unsuitable for extensive grazing and nomadic pastoralism.
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