B1.5 Energy and biomass in food chains

B1.5 Energy and biomass in food chains


By observing the numbers and sizes of the organisms in food chains we can find out what happens to energy and biomass as it passes along the food chain.


Energy transfer

  • Radiation from the Sun is the source of energy for most communities of living organisms.
  • Green plants and algae capture a small part of the solar energy which reaches them.
  • This energy is stored in the substances which make up the cells of the plants.
  • Food chain = diagram to represent feeding relationships between organisms, showing direction of energy flow.
  • At each stage in a food chain, less material and less energy are contained in the biomass of the organisms.
  • The amounts of material and energy contained in the biomass of organisms is reduced at each successive stage in a food chain because:
    • some materials and energy are always lost in the organisms’ waste materials
    • respiration supplies all the energy needs for living processes, including movement.
  • Much of this energy is eventually lost as heat to the surroundings


Pyramids of biomass

  • The biomass at each stage can be drawn to scale and shown as a pyramid of biomass.
  • Biomass = mass of living material

  • All pyramids of biomass are pyramid shaped
  • The mass of living material (biomass) at each stage in a food chain is less than it was at the previous stage.