Question map
Which one of the following is the best description of the term 'ecosystem'?
Explanation
An ecosystem is a self-regulating association of living organisms such as plants, animals, and microorganisms, together with their non-living environment such as physical and chemical [1]components. It is defined as a structural and functional unit of the biosphere consisting of a community of living things and the physical environment, both interacting and exchanging materials between them.[2]
Option C correctly captures both essential components of an ecosystem: the community of organisms AND the environment in which they live, along with their interactions. Option A is incomplete as it only mentions organisms interacting with each other, ignoring the crucial abiotic (non-living) components. Option B describes the biosphere, not an ecosystem. Option D merely lists biological components without acknowledging the environmental elements or the interactions that define an ecosystem.
An ecosystem consists of both biotic (living) and abiotic (non-living) components[3], making option C the most comprehensive and accurate description.
Sources- [1] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > Ecosystem > p. 11
- [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 1: Ecology > r.3.4. Ecosystem > p. 5
- [3] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > COMPONENTS OF AN ECOSySTEM. > p. 16
PROVENANCE & STUDY PATTERN
Full viewThis is a 'Gatekeeper Question'—a fundamental definition found in the first chapter of every Ecology textbook. Missing this indicates a lack of basic reading. It requires zero current affairs, just conceptual clarity on the hierarchy of ecological organization.
This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.
- Provides an explicit definition: an association of living organisms with their non-living environment described as an ecosystem.
- Specifies constituent groups (plants, animals, microorganisms and physical/chemical environment) supporting the definition.
- Mentions historical origin (Tansley, 1935), indicating this is a canonical definition used in texts.
- Defines ecosystem as a structural and functional unit of the biosphere, emphasising both structure and function.
- Stresses interaction and exchange of materials between community (living things) and the physical environment — core to the definition.
- Lists typical components (plants, animals, microorganisms, water, soil, people), reinforcing the concept scope.
- Gives a concise statement: ecosystem = group of organisms + the environment with which they interact.
- Explicitly categorises components as biotic (living) and abiotic (non-living), clarifying the two-part composition.
- [THE VERDICT]: Sitter. Direct lift from NCERT Class 12 Biology (Chapter 13) or Shankar IAS Chapter 1.
- [THE CONCEPTUAL TRIGGER]: Levels of Ecological Organization: Organism → Population → Community → Ecosystem → Biome → Biosphere.
- [THE HORIZONTAL EXPANSION]: Memorize the distinctions: 1. Population (Same species, same area) 2. Community (Different populations, biotic only) 3. Ecosystem (Community + Abiotic Environment) 4. Biome (Large ecosystem defined by climate/vegetation) 5. Biosphere (Global sum of all ecosystems).
- [THE STRATEGIC METACOGNITION]: UPSC tests definitions by offering 'partial truths' as distractors. Option A describes a 'Community'. Option B describes the 'Biosphere'. You must study definitions by identifying the *missing component* in the wrong options.
The definition of ecosystem repeatedly emphasises living (biotic) and non-living (abiotic) parts and their interactions.
High-yield for UPSC: questions often ask to distinguish or list ecosystem components and explain dependencies. It links to topics like nutrient cycles, habitat, and conservation. Master by memorising component categories and practising short explanatory answers and diagrams.
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > COMPONENTS OF AN ECOSySTEM. > p. 16
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > Ecosystem > p. 11
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 1: Ecology > r.3.4. Ecosystem > p. 5
Sources describe ecosystem not just as a collection but as a structural and functional unit with material exchange and processes.
Important for conceptual answers on ecosystem processes (energy flow, nutrient cycling, succession) and for higher-level questions on ecosystem services and sustainability. Prepare by mapping functions to components and revising examples of energy/nutrient flows.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 1: Ecology > r.3.4. Ecosystem > p. 5
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > FUNCTIONS OF AN ECOSYSTEM > p. 11
References note examples (gardens, ponds, forests) and mention difficulty in demarcating ecosystem boundaries and overlapping systems.
Useful for case-based and analytical UPSC questions comparing natural vs artificial ecosystems, or discussing ecosystem diversity and conservation. Study by classifying ecosystem types, noting examples, and practising answers on scale and boundary issues.
- Science , class X (NCERT 2025 ed.) > Chapter 13: Our Environment > 13.1 ECO13.1 ECO 13.1 ECO-SYSTEM — WHAT ARE ITS COMPONENTS? > p. 208
- FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 14: Biodiversity and Conservation > Ecosystem Diversity > p. 116
- Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 12: How Nature Works in Harmony > Criterion 3 > p. 197
Standing Crop vs. Standing State. Found on the same pages as Ecosystem structure. 'Standing Crop' is the mass of living material (biomass) at a particular time. 'Standing State' is the amount of nutrients (N, P, Ca) present in the soil at a given time. UPSC will likely swap these definitions in a future statement.
Etymological Breakdown: 'Eco' implies Oikos (Home/Environment) and 'System' implies functional interaction.
Option A has interaction but no 'home' (abiotic).
Option B is just the 'home' (location).
Option D is just a list of items.
Only Option C combines the 'actors' (organisms) with the 'stage' (environment) to form a 'system'.
Mains GS-3 (Environment & Economy): Link 'Ecosystem' to 'Ecosystem Services'. The definition implies functional exchange. This is the basis for 'Natural Capital Accounting' and 'Payment for Ecosystem Services (PES)'—where we put a price tag on the abiotic-biotic interaction (e.g., carbon sequestration).