Assertion (A) : An ecosystem is a natural resource system.
Reason (R) : An ecosystem is a single concept in which the physical environment (Physical or Inorganic Factors) and biotic factors (Humans, a

Question

Assertion (A) : An ecosystem is a natural resource system.
Reason (R) : An ecosystem is a single concept in which the physical environment (Physical or Inorganic Factors) and biotic factors (Humans, animals, microorganisms and plants) live together in a single framework.
Which one of the following is correct ?

UnlockIAS · Accepted Answer

Correct — option (1), both statements are true and the Reason is the correct explanation of the Assertion. An assertion-reason question demands three separate judgements, and they must be made in order. First, is the Assertion true? An ecosystem is indeed treated as a natural resource system: it is the working unit within which soil, water, air, sunlight, minerals and living organisms are held together, and every natural resource a society draws on — food, fodder, fuel, fibre, timber, fish, fresh water — is produced by, or stored within, some ecosystem. This is why natural resource management is organised ecosystem by ecosystem: forest, grassland, wetland, coastal, agro-ecosystem. The Assertion is true. Second, is the Reason true? It states the standard definition of an ecosystem as a single unit in which the physical or abiotic environment and the biotic components exist within one framework. That is precisely what A.G. Tansley meant when he introduced the term in 1935 — a system comprising not only the organisms but the whole complex of physical factors with which they form one physical system. The Reason is true. Third, and this is the step candidates skip, does the Reason explain the Assertion? It does, and directly. The Assertion claims that an ecosystem is a resource system; the Reason supplies the ground for that claim by pointing out that the ecosystem unites the inorganic stock — the soil, water, air and minerals that are themselves resources — with the living components that capture energy and convert that stock into usable form. It is the integration of the two, in one functioning framework through which energy flows and nutrients cycle, that makes an ecosystem a resource-producing system rather than a mere inventory of separate resources. Remove either half and the claim collapses: abiotic material alone yields nothing, and organisms cannot exist without the physical environment. The Reason therefore states the very fact from which the Assertion follows, and option (1) is the answer.

Why the other options are wrong — (b) This is the default landing place for a candidate who verifies both statements and then declines to test the link between them. Here the link is unusually tight: the Reason is the definition of the thing the Assertion makes a claim about, and the claim follows from the definition. Because an ecosystem unites abiotic stock with living components in one functioning framework, it produces and holds resources — which is exactly what the Assertion says. Option (2) is correct only where two independently true statements have no explanatory relation, and that is not the case here.  (c) Declares the standard definition of an ecosystem to be false. The Reason describes the ecosystem as one framework containing both the physical or inorganic environment and the biotic components — plants, animals, microorganisms and humans — which is the definition given in every textbook treatment since Tansley coined the term in 1935 and which Eugene Odum's work made the organising idea of modern ecology. There is nothing in it to reject, and a candidate choosing this option has almost certainly misread 'single concept' or 'single framework' as an overstatement rather than as the ordinary meaning of a system.  (d) Rejects the Assertion, which would mean denying that an ecosystem is a natural resource system. That denial cannot be sustained: natural resources do not exist independently of the ecosystems that generate and hold them, and the whole practice of natural resource management — of forests, grasslands, wetlands, fisheries and agro-ecosystems — is built on treating the ecosystem as the unit of the resource. A candidate may arrive here by reading 'natural resource' narrowly as mineral wealth, but even on that reading the soil and water components of the definition would keep the Assertion standing.

Concept: An ecosystem is a community of living organisms together with the non-living components of their environment, interacting as one functional unit. Its structure has two halves. The abiotic half consists of the physical and chemical factors — sunlight, temperature, rainfall, wind, soil, water, air and inorganic nutrients. The biotic half consists of producers or autotrophs, which capture solar energy through photosynthesis; consumers or heterotrophs, arranged as herbivores, carnivores and omnivores across trophic levels; and decomposers or saprotrophs, the bacteria and fungi that break dead organic matter back down into inorganic nutrients. Its functioning rests on two processes that behave quite differently. Energy flows through the system in one direction only — entering as sunlight, passing up the food chain with heavy losses at each step, and leaving as heat — so an ecosystem needs a continuous external energy supply. Nutrients, by contrast, cycle: carbon, nitrogen, phosphorus and water move between the abiotic pool and living tissue and back again, so the same atoms are used repeatedly. That combination of one-way energy flow and closed nutrient cycling is what makes the ecosystem self-sustaining, and therefore what makes it a resource system rather than a stock that is simply drawn down.

State PCS 2026 Q32 — Environment & Ecology PYQ with Answer

State PCS 2026 Q32 — Environment & Ecology PYQ with Answer