Biology · Ecosystems · NEET
| Nature | Non-living, physical/chemical | Living organisms |
| Examples | Soil, water, air, sunlight, temperature, nutrients | Plants, animals, fungi, bacteria |
| Sub-groups | Edaphic (soil), climatic (light, temp), inorganic nutrients | Producers, consumers, decomposers |
| Role | Provides energy source, minerals and physical conditions | Capture energy, transfer it, recycle nutrients |
| In a pond | Water, dissolved substances, bottom soil, solar input | Phytoplankton, zooplankton, fungi and bacteria |
Every ecosystem is made of two components. (1) Abiotic component: the non-living physical and chemical part such as soil, water, air, sunlight, temperature and dissolved nutrients (like nitrogen, phosphorus). (2) Biotic component: all the living organisms, grouped as producers, consumers and decomposers. NCERT says a physical structure forms from the interaction of these biotic and abiotic components, and this structure is different for each type of ecosystem.
Soil is an abiotic (non-living) component. In the NCERT pond example, the abiotic component is described as the water with all the dissolved inorganic and organic substances plus the rich soil at the bottom of the pond. Soil supplies minerals and a surface, but it is not a living organism, so it is abiotic. Note: the living microbes inside the soil are biotic, but the soil itself is abiotic.
Decomposers are biotic (living). They are fungi, bacteria and flagellates that break down dead matter. Students often confuse them because they act on non-living dead material, but the decomposers themselves are living organisms, so they belong to the biotic component along with producers and consumers.
Sunlight is abiotic. NCERT lists solar input, temperature, day-length and other climatic conditions as the abiotic factors that regulate the rate of function of the whole ecosystem. Sunlight is the energy source for producers, but it is non-living, so it is an abiotic factor.
The biotic component has three groups by their role: (1) Producers or autotrophs (green plants, phytoplankton, algae) that make food using sunlight; (2) Consumers or heterotrophs (herbivores and carnivores like zooplankton and fish) that eat other organisms; (3) Decomposers (fungi and bacteria) that break down dead matter and return nutrients to the soil. All three are living, so all are biotic.
Stratification is the vertical distribution of different species at different levels. NCERT example: in a forest, trees occupy the top layer, shrubs the second layer, and herbs and grasses the bottom layer. Stratification is part of the physical structure that results when biotic and abiotic components interact. This is a common one-line NEET fact.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Abiotic (non-living: soil, water, air, sunlight, temperature, nutrients) and biotic (living: producers, consumers, decomposers).
Water, soil, sunlight (solar input), temperature, day-length, air and dissolved inorganic nutrients like nitrogen and phosphorus are abiotic components.
In NCERT's pond example: producers are phytoplankton, algae and floating, submerged and marginal plants; consumers are zooplankton and free-swimming and bottom-dwelling forms; decomposers are fungi, bacteria and flagellates at the bottom.
The Ecosystem chapter is a scoring unit. Questions on structure, the pond example, stratification and the roles of producers, consumers and decomposers are directly asked, so clear biotic vs abiotic sorting saves easy marks.
Species composition is the identification and enumeration (counting) of the plant and animal species present in an ecosystem. It describes which species live there and in what numbers.
