This deep dive covers Pyramids of Biomass within Ecosystems Communities for GCSE Biology. Topic 1: Ecosystems Communities It is section 8 of 15 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 8 of 15
Practice
15 questions
Recall
20 flashcards
📊 Pyramids of Biomass
A pyramid of biomass shows the total mass of living material at each trophic level in a food chain. Each bar represents the biomass (dry mass) of all organisms at that level.
Why Is It Pyramid-Shaped?
At each trophic level, energy is lost through:
- Respiration — organisms use energy for movement, growth, and keeping warm
- Waste products — not all food is digested (faeces, urine)
- Heat — energy transferred to the surroundings
Only about 10% of the biomass at one level is passed to the next. This means there is always less biomass at higher trophic levels — which is why the diagram forms a pyramid shape.
Pyramids of Biomass vs Pyramids of Numbers
Pyramids of numbers can sometimes look inverted (e.g. one oak tree → thousands of caterpillars), but pyramids of biomass are almost always pyramid-shaped because biomass accounts for the size of organisms, not just how many there are.
Exam tip: If asked why biomass decreases at each trophic level, always mention respiration and waste/egestion — these are the two mark points examiners look for.