MYP Biology: Food Chains & Trophic Levels FAQ

A food chain is a single line showing energy flow from one organism to the next, always starting with a producer and drawn with arrows pointing towards the organism receiving energy. A food web links several overlapping food chains together, showing that most organisms eat — and are eaten by — more than one species.

A trophic level is a feeding position in a food chain — producers occupy the first level, primary consumers (herbivores) the second, secondary consumers the third, and so on. Each level represents one step of energy transfer, and organisms are classified by what they eat, not by species alone.

Producers make their own food through photosynthesis (plants, algae), consumers obtain energy by eating other organisms, and decomposers break down dead organic matter and waste, releasing nutrients back into the ecosystem. Decomposers — fungi and bacteria mostly — don't sit neatly in the food chain arrow sequence; they recycle at every level.

Roughly 10% of energy passes to the next trophic level because most energy at each stage is lost as heat through respiration, used for movement and growth, or lost in waste and undigested material. This is why food chains rarely extend beyond four or five levels — there simply isn't enough energy left to support another one.

This topic is mostly assessed under MYP Sciences Criterion A (Knowing and understanding) and Criterion C (Processing and evaluating), through questions asking you to construct food chains, label trophic levels, interpret pyramids of biomass or energy, and explain energy loss between levels using command terms like 'construct', 'explain' and 'analyse'.

The most common command terms are 'construct' (build a food chain or pyramid from data), 'label' (identify trophic levels or organisms), 'explain' (give reasons using biological ideas, e.g. energy loss), and 'suggest' (propose an idea using evidence, common when a novel ecosystem is given). Each demands a different depth of response.

Draw the pyramid with producers as the widest bar at the bottom and each subsequent trophic level narrower above it, always to scale where data is given. Label each bar with the trophic level name and its biomass or energy value, and title the diagram clearly as either a pyramid of biomass or pyramid of energy — they aren't interchangeable.

Top-level responses (7-8 in Criterion A/C) don't just label a diagram correctly — they explain the biology behind it, using terms like 'energy transfer', 'respiratory heat loss' and 'biomass' precisely, and they link the pattern to a real consequence, such as why apex predators need large territories.

The three most common errors are: drawing arrows backwards (pointing towards the organism doing the eating rather than the energy's destination), confusing a food chain with a food web when the question asks for one specifically, and stating 'energy is lost' without explaining how — through respiration, movement, or waste.

Command terms tell you exactly how much detail is expected — 'identify' wants a short, direct answer (like naming the producer), while 'discuss' or 'explain' expects a developed response linking cause and effect, such as why energy transfer efficiency limits food chain length. Matching your answer's depth to the command term is often worth more than extra content.

MYP food chains and trophic levels build the foundation for DP Biology's ecology topic, where students calculate energy transfer efficiency with formulas, analyse real ecosystem data sets, and discuss nutrient cycling in far more mathematical detail. According to the IB, the current DP Biology guide had first exams in 2025, and its ecology strand assumes the MYP-level vocabulary is already secure.

Not inherently — most students find food chains more accessible than genetics or cell biology because it's visual and logical rather than abstract. Where students genuinely struggle is with the maths (percentage energy calculations) and with precise scientific writing, not with understanding the ecological concept itself.

The most effective revision combines labelled diagram practice, short-answer questions using command terms, and past-style questions that require calculating energy transfer percentages — not just re-reading notes. On RevisionPrep, students can work through topical worksheets and revision notes built specifically around MYP Sciences criteria to practise exactly this kind of question.