UPSC Prelims 2015 · Question 84 of 98

UPSC Prelims 2015 question on Ecosystem Definition

Which one of the following is the best description of the term 'ecosystem'?

  1. a community of organisms interacting with one another
  2. that part of the Earth which is inhabited by living organisms
  3. a community of organisms together with the environment in which they live
  4. the flora and fauna of a geographical area
Show answer

Answer: C. a community of organisms together with the environment in which they live

Verdict

The answer is a community of organisms together with the environment in which they live. That is the standard definition of an ecosystem.

Analysis

An ecosystem comprises all the living things in a given area interacting with one another and also with their non living surroundings, that is weather, soil, water, sunlight and atmosphere. The first option describes only the biotic component and therefore defines a community rather than an ecosystem. The fourth option, the flora and fauna of a geographical area, likewise omits the abiotic environment. The second option, the part of the Earth inhabited by living organisms, is the definition of the biosphere, which is a much larger unit.

Source

NCERT Class XII Biology, page 241.

How to crack it

Best description questions are answered by finding the option that is complete rather than merely true, since several options will be partially correct. Here the test is a single word: does the option include the non living environment. Only one does. Hold the nested hierarchy of organism, population, community, ecosystem, biome and biosphere in order, and any definitional question in ecology reduces to identifying which level the option describes.

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