Biomass is the mass of living material in an organism or a trophic level. It represents the chemical energy stored in organic compounds, so biomass transfer is also energy transfer.Biomass is measured as dry mass, because the water content of living tissue varies. Organisms are dried at about 80 °C until their mass stops changing. This destroys them, so usually only a small sample is dried and the result scaled up. Biomass is given per unit area, for example g m−2, or per unit volume in water (g m−3). Measured over time, it becomes a rate, such as g m−2 yr−1. Energy can be found by burning a sample in a calorimeter (kJ m−2 yr−1).Why only some biomass is transferred
• Not all of an organism is eaten, for example roots, woody stems, bones and fur.
• Not all that is eaten is digested and absorbed. Some is lost in faeces, especially in herbivores, because cellulose is hard to digest.
• Some is lost in excretory products such as urea in urine.
• Much of the absorbed energy is used in respiration and lost as heat, so it cannot be passed on.Only what remains, added to the consumer's body as new tissue, is available to the next trophic level.
Pyramids of biomass show the dry mass at each trophic level. They are almost always pyramid-shaped, because biomass decreases at each level. Losses at the dead parts, faeces and urine are not wasted: they pass to decomposers.
• Not all of an organism is eaten, for example roots, woody stems, bones and fur.
• Not all that is eaten is digested and absorbed. Some is lost in faeces, especially in herbivores, because cellulose is hard to digest.
• Some is lost in excretory products such as urea in urine.
• Much of the absorbed energy is used in respiration and lost as heat, so it cannot be passed on.Only what remains, added to the consumer's body as new tissue, is available to the next trophic level.
Pyramids of biomass show the dry mass at each trophic level. They are almost always pyramid-shaped, because biomass decreases at each level. Losses at the dead parts, faeces and urine are not wasted: they pass to decomposers.