Transfer of Biomass (AQA GCSE Biology): Revision Note

Biomass transfer

• When primary consumers consume (eat) producers, they break down the biomass of the producer (digestion) and use the chemical energy to increase or sustain their own biomass

• When secondary consumers consume (eat) primary consumers, they break down the biomass of the primary consumer (digestion) and use the chemical energy to increase or sustain their own biomass, and so on

• In this way, as chemical energy is transferred from one trophic level to the next, biomass is also transferred

Loss of biomass

• Not all biomass is transferred from one trophic level to the next

• Only about 10% of the biomass of each trophic level is passed on to the next

• This is why food chains are rarely made up of more than six trophic levels – the total amount of biomass available eventually becomes too small to support another trophic level

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• Losses of biomass are due to:

  • organisms rarely eat every part of the organism they are consuming – some of the biological material of plants and animals may be inedible (e.g. many predators do not consume the bones of their prey)

  • not all the ingested material is digested and absorbed, some is egested as faeces

  • some absorbed material is lost as waste.

    • Carbon dioxide and water are waste products of respiration (when glucose is used by an organism to provide energy for moving and keeping warm, rather than to produce more biomass)

    • Water and urea are the waste products in urine, which is produced when proteins are broken down

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Efficiency of biomass transfers

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