Question
Draw a food chain in a grassland ecosystem with at least 4 trophic levels. Identify the producers, primary consumers, secondary consumers, and tertiary consumers. Also mention where decomposers fit in.
Solution — Step by Step
In any food chain, we always begin with the organism that makes its own food — the autotroph.
In a grassland, that’s grass. Grass captures sunlight and converts it into chemical energy via photosynthesis. Everything above it depends on this energy.
The first animal in the chain eats the producer directly. In a grassland, grasshoppers feed on grass.
Grasshoppers are herbivores — they occupy Trophic Level 2 (TL-2). Energy flows from grass → grasshopper, but only about 10% is transferred (the rest is lost as heat).
Now we need a carnivore that eats the grasshopper. Frogs hunt grasshoppers in grassland ecosystems.
Frogs are at TL-3 — secondary consumers. This is where the chain starts to get “interesting” from NEET’s perspective because questions often ask whether frogs are secondary or tertiary consumers. Here, they’re secondary.
Snakes eat frogs. Snakes sit at TL-4.
This is the tertiary consumer level — they eat secondary consumers. Many food chains in NCERT examples end here, but we can go one step further.
Eagles eat snakes, placing them at TL-5 — the apex predator of this chain.
The complete food chain:
Decomposers (bacteria, fungi) don’t appear in the chain itself — they work at every level, breaking down dead organisms from all trophic levels and returning nutrients to the soil.
Why This Works
A food chain shows the unidirectional flow of energy from one trophic level to the next. Each arrow means “is eaten by” — energy moves in that direction. This is the core concept NCERT Chapter 14 (Ecosystem) tests.
The reason food chains rarely exceed 4–5 levels is the 10% law (Lindemann’s Law). Only 10% of energy at one trophic level passes to the next. By TL-5, so little energy remains that supporting a higher consumer becomes impossible. An eagle eating snakes is at the edge of what the ecosystem can sustain.
Decomposers are often called a separate trophic level by some textbooks, but NCERT treats them as organisms that feed on all levels simultaneously. Keep this distinction clear for CBSE board papers — they sometimes ask why decomposers are not placed within the food chain.
Alternative Method — Drawing as a Table
If a question says “draw and label,” use this table format in your answer sheet:
| Trophic Level | Organism | Role |
|---|---|---|
| TL-1 | Grass | Producer |
| TL-2 | Grasshopper | Primary Consumer (Herbivore) |
| TL-3 | Frog | Secondary Consumer (Carnivore) |
| TL-4 | Snake | Tertiary Consumer (Carnivore) |
| TL-5 | Eagle | Quaternary Consumer / Apex Predator |
| — | Bacteria/Fungi | Decomposers |
NEET 2-mark questions often ask you to both draw the chain and state the trophic level of a specific organism. Writing it as a table ensures you hit both requirements without missing marks.
NEET 2022 and CBSE 2023 both had questions asking “At which trophic level does maximum energy loss occur?” — the answer is always at the first transfer (TL-1 to TL-2), because that’s where the largest absolute amount of energy exists to begin with. 10% of 1000 units is a bigger loss than 10% of 10 units.
Common Mistake
Students often write “Decomposers are at TL-6” or place them at the end of the chain with an arrow from the eagle. This is wrong. Decomposers don’t receive energy from the last consumer only — they break down organisms at every trophic level simultaneously. They’re not part of the chain; they’re parallel to it. Drawing an arrow from only the eagle to decomposers will cost you marks in a 3-mark CBSE question.