UPSC Prelims 2015— Question 84

Correct answer: Option C. An ecosystem consists of a community of organisms together with the physical and chemical environment with which they interact. It includes both biotic components, such as plants, animals and microorganisms, and abiotic components, such as soil, water, air, light and nutrients. Thus option C gives the most complete description. Option-wise analysis: Option A: “A community of organisms interacting with one another” is incorrect. It does not match the specific fact, definition, institutional role, geographical association, or constitutional/economic principle required here. The key distinction is the one identified in the core explanation, so this option can be eliminated. Option B: “That part of the Earth which is inhabited by living organisms” is incorrect. It does not match the specific fact, definition, institutional role, geographical association, or constitutional/economic principle required here. The key distinction is the one identified in the core explanation, so this option can be eliminated. Option C: “A community of organisms together with the environment in which they live” is correct. It directly matches the factual or conceptual requirement tested by the question and is supported by the principle explained above. Option D: “The flora and fauna of a geographical area” is incorrect. It does not match the specific fact, definition, institutional role, geographical association, or constitutional/economic principle required here. The key distinction is the one identified in the core explanation, so this option can be eliminated. Prelims takeaway: Focus on the precise institutional role, constitutional provision, geographical association, or technical definition being tested. UPSC questions often place a broadly familiar fact beside a narrowly incorrect qualifier; identifying that qualifier is essential for elimination.