MYP Biology: Ecosystems & Food Webs FAQ

A food chain shows one straight-line feeding sequence — grass to grasshopper to frog to snake — while a food web links several chains together to show the real feeding relationships in an ecosystem, since most organisms eat more than one thing. MYP Biology expects you to build and interpret webs, not just chains, from Year 4 onward.

Only around 10% of the energy stored at one trophic level passes to the next; the rest is lost as heat through respiration, movement and undigested waste. To find energy available at the next level, multiply the current level's energy by 0.1 — which is exactly why food chains rarely extend past four or five links.

You need producer, consumer (primary/secondary/tertiary), decomposer, trophic level, biomass, biotic and abiotic factor, habitat, niche and carrying capacity — fluently enough to apply them, not just define them. Criterion A tasks often drop these terms into an unfamiliar ecosystem you've never studied, so rote definitions alone won't get you into the top band.

A population is every member of one species living in the same area at the same time. A community is all the different populations interacting together in that area. An ecosystem adds the abiotic environment — soil, water, temperature, light — to that community. Blurring these three costs marks in Criterion A far more often than students expect.

Ecosystems and food webs get assessed the same way as any MYP Biology unit — through tasks mapped to the four Sciences criteria (A–D), each marked out of 8. Expect a Criterion A test on concepts like trophic levels and energy flow, alongside a Criterion B/C investigation such as a pond or quadrat study, plus a Criterion D task on human impact.

All four MYP Sciences criteria can apply to this topic. Criterion A tests recall and application of ecosystem concepts; Criterion B covers planning an ecosystem investigation; Criterion C covers analysing data such as population counts; Criterion D covers evaluating issues like habitat loss or invasive species and their scientific and social impact.

Command terms set the depth expected in your answer. "Identify" or "state" wants a short, precise fact — name the producer. "Describe" wants detail without reasons. "Explain" wants mechanisms and reasoning, such as why energy decreases up trophic levels. "Evaluate" wants strengths and weaknesses — useful when judging a sampling method's reliability.

A 7 or 8 in Criterion A means applying ecosystem concepts to an unfamiliar context with sophisticated, accurate scientific language — not just recalling definitions. In years of marking these tasks, the students who reach the top band always link cause and effect, explaining why removing one predator reshapes the whole food web rather than describing it in isolation.

The most common mistake is drawing a pyramid of numbers instead of a pyramid of biomass or energy, which can invert — one tree can host thousands of aphids. The second is treating decomposers as a trophic level on the pyramid; they aren't one at all, since they recycle nutrients across every level, not just the top or bottom.

A strong Criterion B ecosystem investigation starts with a testable research question — does light intensity affect plant species distribution? — backed by a hypothesis with scientific reasoning, and a method detailed enough for someone else to repeat exactly, including how you'll control variables like quadrat size, sampling points and time of day.

Yes — MYP ecosystems work is the direct foundation for DP Biology's Ecology and conservation topic, first examined under the current DP Biology guide in 2025. Students who understand energy flow, trophic levels and carrying capacity at MYP level find the DP topic — with its added maths, like the Lincoln index — noticeably easier to pick up.

Most schools timetable ecosystems and food webs as one full unit across several weeks in Year 4 or Year 5, though exact hours vary by school since the IB doesn't prescribe fixed teaching hours for MYP units — only the four assessment criteria are mandated. Check your school's unit planner for the exact sequencing at your school.

MYP Biology assesses ecosystems through criterion-based tasks graded 1-8 across four skills — knowing, inquiring, processing and reflecting — with no single terminal ecosystems exam. IGCSE Biology tests ecology mostly through timed written papers marked against grade boundaries. Both cover food chains, food webs and nutrient cycles, but MYP weighs your child's own investigation and reflection skills far more heavily.

Past school unit tests, criterion-specific practice questions, and clear topic summaries covering trophic levels, energy pyramids and nutrient cycles all help. On RevisionPrep, MYP Biology Revision Notes and Topical Worksheets cover ecosystems & food webs criterion-by-criterion, so your child can practise the exact skills — knowing, inquiring, processing, reflecting — their teacher will actually be grading.