Pyramids of biomassSpec 4.7.4.2
In short
A pyramid of biomass represents the relative amount of biomass in each trophic level of a food chain. Trophic level 1, the producers, is at the bottom. Each bar is narrower than the one below it, because biomass decreases at each higher trophic level. To draw one, make each bar's length proportional to its biomass and centre the bars.
Pyramids of biomass can be constructed to represent the relative amount of biomass in each level of a food chain. Trophic level 1 is at the bottom of the pyramid.
Each bar is narrower than the one below it, because the biomass decreases at each higher trophic level. This gives the pyramid shape.
- Draw horizontal bars, one for each trophic level, with trophic level 1 at the bottom.
- Choose a scale so that the length of each bar is proportional to the biomass of that level.
- Centre the bars on a vertical line and label each bar with the organism or level.
Constructing a pyramid
A food chain has biomass of 400 g per m² of grass, 40 g per m² of grasshoppers and 4 g per m² of frogs. Describe how to construct the pyramid using a scale of 1 mm = 4 g.
- Grass: 400 ÷ 4 = a bar 100 mm long, at the bottom.
- Grasshoppers: 40 ÷ 4 = a bar 10 mm long, above the grass.
- Frogs: 4 ÷ 4 = a bar 1 mm long, at the top.
Answer: Three centred bars of 100 mm, 10 mm and 1 mm, with grass at the bottom and frogs at the top.
(opens full size in a new tab)Written and checked against the AQA GCSE Biology (8461) specification · Updated October 2026