GCSE›AQA GCSE Biology›Mind mapsFood Webs and Energy TransferAQA GCSE Biology: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsFood chainsProducers (plants, algae) make biomass by photosynthesisEvery chain starts with a producerProducer → primary → secondary → tertiary consumerPredators eat prey; numbers rise and fall in cyclesTrophic levelsLevel 1: producersLevel 2: primary consumers (herbivores)Level 3: secondary consumersLevel 4: tertiary consumersApex predators have no predatorsBiomass pyramidsShow biomass at each trophic levelLevel 1 at the bottomNarrows towards the top: biomass is lostFood websand energy transferEnergy lossOnly about 10% passes to the next levelEgestion: undigested food leaves as faecesRespiration loses CO2 and waterUrine loses water and ureaGlucose used for energy, not storedConsequences1000 kg producers → 100 kg → 10 kgChains rarely exceed 4 or 5 levelsFew top predators compared with producersExam tipsBiomass pyramids are always pyramid-shaped, unlike numbersEfficiency = biomass passed on as percentage of previous level