7.12 Pyramids of Biomass

Shows the biomass of each trophic level in a food chain

Biomass - mass of living organisms

Bars get smaller as you go up trophic levels

• Total mass of organisms in each level is decreasing

• Most of biomass & energy is either lost or used

  • only around 10% of biomass & energy gets passed on

3 reasons why only 10% is passed on

1. Organisms don’t normally eat every part of organisms they are consuming

2. Parts that are eaten may not be absorbed if they can’t be broken down properly (egested as faeces)

3. Most nutrients that animals absorb are used to release energy through respiration

   • so biomass gets released as waste products (CO2 & urea)

   • When organism is eaten, it doesn’t pass on all biomass consumed throughout its life

Calculating efficiency of biomass transfer

Efficiency = (biomass transferred to next level / biomass available at previous level) x 100