Transfer of Biomass (AQA GCSE Biology): Revision Note

Biomass transfer

• When consumers consume other organisms, they digest the biomass of the organism and use the molecules to build their own biomass

  • In this way, biomass is transferred from one trophic level to the next

• Because chemical energy is stored within biomass, the transfer of biomass can be equated to the transfer of energy

• However, on a question about biomass, do not give heat or movement as ways biomass is lost – name the material that leaves the body (carbon dioxide from respiration, urea in urine, faeces)

Loss of biomass

• The transfer of biomass, and the chemical energy stored within it, is an inefficient process

• Not all biomass is transferred through an ecosystem:

  • Around 1 % of the light energy that lands on producers (mainly plants and algae) is transferred to plant biomass during photosynthesis

  • Only about 10% of the biomass of each trophic level is passed on to the next when consumers eat another organism

• This means that biomass is lost between the different trophic levels

Use this image

• Losses of biomass between trophic levels occur because:

  • some absorbed material is lost as waste:

    • During respiration glucose is used up and carbon dioxide and water are released

    • Water and urea are the waste products in urine

  • not all the biomass consumed is absorbed; some is egested as faeces

  • not all of the parts of an organism are consumed; inedible parts like fur and bones may be left to decompose

Efficiency of biomass transfers

• Because biomass is lost at every transfer (through egestion, respiration and excretion), each higher trophic level has less biomass available, so it can support fewer organisms

• Being able to calculate the efficiency of biomass transfers between trophic levels by percentages is an important skill for a biologist: