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Environment & ecology

Prelims · Environment & ecology · 27 questions

Ecology & ecosystems

Every UPSC Prelims question on this topic, 2016–2026, newest first. Tap an option to check yourself; the answer and explanation open below it.

Ecology & ecosystems questions per year: 2016: 0, 2017: 1, 2018: 0, 2019: 0, 2020: 0, 2021: 7, 2022: 3, 2023: 0, 2024: 2, 2025: 1, 2026: 1 Asked in 6 of 11 years · most in 2021 (7)

UPSC syllabus: “General issues on Environmental ecology, Bio-diversity and Climate Change - that do not require subject specialization.” See the full syllabus →

Consider the following statements:

  1. Statement-I: The soil in tropical rain forests is rich in nutrients.
  2. Statement-II: The high temperature and moisture of tropical rain forests cause dead organic matter in the soil to decompose quickly.

Which one of the following is correct in respect of the above statements?

Answer & explanation

Answer: (d) Statement-I is incorrect but Statement-II is correct

The soil of a tropical rain forest is poor, not rich, in nutrients. Heat and moisture make bacterial action intense, so dead plant matter is oxidised quickly and very little humus builds up in the soil; heavy rain also leaches nutrients out of tropical soils.

  • ✗ Statement-I Fast decay leaves the soil with very low humus content, and heavy rain leaches away nutrients; lateritic soils of heavy-rain tropical areas are generally deficient in plant nutrients.
  • ✓ Statement-II In humid tropical and equatorial climates bacterial growth and action is intense, so dead vegetation is rapidly oxidised. This is the reason the humus content of the soil stays low, not a sign of richness.

Remember · Fast decay plus heavy rain leave tropical rain forest soil low in humus and nutrients; in cold climates decay is slow, so humus and peat accumulate.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 5 (practise this chapter) · Class 10 Contemporary India – II, Ch 1 (practise this chapter)

Sources

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). Permalink ·

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