Q84 · UPSC Prelims 2015 · Set A · Environment and Ecology

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

A A community of organisms interacting with one another
B That part of the Earth which is inhabited by living organisms
C A community of organisms together with the environment in which they live
D The flora and fauna of a geographical area

Correct answer: (c) A community of organisms together with the environment in which they live

Explanation

  1. A

    A community of organisms interacting with one another

    A community of organisms interacting with one another is a biotic community (or biocoenosis), not the full ecosystem, because the physical environment is missing. This option is not the key.

  2. B

    That part of the Earth which is inhabited by living organisms

    The inhabited part of the Earth is the biosphere, a planetary envelope, not a single ecosystem. This option is therefore wrong.

  3. C

    A community of organisms together with the environment in which they live

    An ecosystem is the biotic community plus the abiotic environment with which it interacts—energy flow and nutrient cycling included. That is the standard definition. This option is the official key.

  4. D

    The flora and fauna of a geographical area

    Flora and fauna of an area are only the plants and animals, without abiotic factors or the system idea. This option is not the key.

Summary. Official key is (c) a community of organisms together with the environment in which they live. Ecosystem = biotic + abiotic. Option (a) is community only; (b) is biosphere; (d) is a species list. Tansley’s term requires the physical setting. Only (c) is complete.

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