Ecosystems & Biodiversity

What you'll learn

Learn how ecosystems work — producers to decomposers, the 10% energy law, ecological pyramids, and biodiversity levels, hotspots, and conservation for UPSC Prelims.

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Ecosystems & Biodiversity — solved practice questions

8 UPSC Environment & Ecology questions with step-by-step solutions. Attempt each, then reveal the answer.

1. Q1medium

   Which ecological pyramid is always upright, irrespective of the type of ecosystem?

   • APyramid of numbers
   • BPyramid of biomass
   • CPyramid of energy
   • DAll three pyramids are always upright
   Show answer & solution

   Correct answer: (C) Pyramid of energy

   The pyramid of energy is always upright because energy is lost mainly as metabolic heat at each transfer (only about 10% passes up), so a lower trophic level always holds more energy than the one above it. Pyramids of number and of biomass can be inverted.

2. Q2medium

   According to Lindeman's ten per cent law, approximately how much of the energy stored at one trophic level is transferred to the next higher level?

   • AAbout 10%
   • BAbout 1%
   • CAbout 50%
   • DAbout 90%
   Show answer & solution

   Correct answer: (A) About 10%

   Only about 10% of the energy available at a trophic level is passed on to the next; the remainder is lost largely as respiratory heat. This steep loss limits the number of trophic levels a food chain can support.

3. Q3hard

   With reference to the criteria for identifying a biodiversity hotspot, consider the following statements: 1. The region must contain at least 1,500 species of endemic vascular plants. 2. The region must have lost at least 70% of its original (primary) natural vegetation. Which of the statements given above is/are correct?

   • A1 only
   • B2 only
   • CBoth 1 and 2
   • DNeither 1 nor 2
   Show answer & solution

   Correct answer: (C) Both 1 and 2

   A region qualifies as a biodiversity hotspot only if it satisfies both conditions: at least 1,500 endemic vascular plant species and the loss of 70% or more of its primary vegetation.

4. Q4hard

   Consider the following biodiversity hotspots: 1. Himalaya 2. Indo-Burma 3. Western Ghats and Sri Lanka 4. Sundaland Which of the above extend into Indian territory?

   • AHimalaya and Western Ghats-Sri Lanka only
   • BHimalaya, Indo-Burma and Western Ghats-Sri Lanka only
   • CIndo-Burma, Western Ghats-Sri Lanka and Sundaland only
   • DHimalaya, Indo-Burma, Western Ghats-Sri Lanka and Sundaland
   Show answer & solution

   Correct answer: (D) Himalaya, Indo-Burma, Western Ghats-Sri Lanka and Sundaland

   All four hotspots have portions within India — the Himalaya, Indo-Burma, the Western Ghats & Sri Lanka, and Sundaland, the last of which includes the Nicobar group of islands.

5. Q5medium

   A 'keystone species' in an ecosystem is best described as one that:

   • AHas an effect on its ecosystem disproportionately large relative to its abundance
   • BIs the most abundant species in the community
   • CAlways occupies the highest trophic level
   • DIs restricted to a single geographic region
   Show answer & solution

   Correct answer: (A) Has an effect on its ecosystem disproportionately large relative to its abundance

   A keystone species has an effect on community structure far greater than its numerical abundance would suggest; its removal can trigger disproportionate, cascading changes in the ecosystem.

6. Q6medium

   Which of the following is an example of ex situ conservation of biodiversity?

   • ABiosphere reserve
   • BSeed or gene bank
   • CNational park
   • DWildlife sanctuary
   Show answer & solution

   Correct answer: (B) Seed or gene bank

   Ex situ conservation protects species outside their natural habitat, as in gene/seed banks, zoos and botanical gardens. Biosphere reserves, national parks and wildlife sanctuaries are forms of in situ conservation.

7. Q7hard

   The diversity of species found within a single community or habitat is referred to as:

   • AAlpha diversity
   • BBeta diversity
   • CGamma diversity
   • DGenetic diversity
   Show answer & solution

   Correct answer: (A) Alpha diversity

   Alpha diversity is the species diversity within one community. Beta diversity measures the change in composition between communities, while gamma diversity is the overall diversity across a large landscape or region.

8. Q8medium

   During primary ecological succession on a bare rock surface, the usual pioneer community consists of:

   • AGrasses
   • BShrubs
   • CLichens
   • DAnnual herbs
   Show answer & solution

   Correct answer: (C) Lichens

   Lichens are typically the pioneers on bare rock; the acids they secrete weather the rock and help form soil, enabling mosses and higher plants to colonise in later seral stages.

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