Students should be able to describe pyramids of biomass and explain how biomass is lost between the different trophic levels. • Producers are mostly plants and algae which transfer about 1% of the incident energy from light for photosynthesis. • Only approximately 10% of the biomass from each trophic level is transferred to the level above it. Losses of biomass are due to: not all the ingested material is absorbed, some is egested as faeces; some absorbed material is lost as waste, such as carbon dioxide and water in respiration and water and urea in urine. Large amounts of glucose are used in respiration. • Students should be able to calculate the efficiency of biomass transfers between trophic levels by percentages or fractions of mass. Students should be able to explain how this affects the number of organisms at each trophic level.