The energy of the sun is used by the primary producers i.e. autotrophs to make energy-product as glucose. The glucose or organic compound produced is consumed by the heterotrophs, the secondary or tertiary consumers. This process starts the food chain. The inference is that autotrophs from sunlight creates the biomass.
In the trophic level of food web the 90 per cent of the energy is lost only 10 per cent comes to use, also the biomass decreases with the upward direction of trophic level.
It can be explained that some of the energy consumed, is immediately lost as in process of respiration, metabolic activity and some is stored in the body. Consumers also excrete so the biomass lessen this way also.
Biomass is the total mass of the organism at the trophic level in food chain.