1.5 - Energy & 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.

Candidates should use their skills, knowledge and understanding to:

• interpret pyramids of biomass and construct them from appropriate information.

B1.5.1 Energy in biomass

a) Radiation from the Sun is the source of energy for most communities of living organisms. Green plantsand algae absorb a small amount of the light that reaches them. The transfer from light energy to chemical energy occurs during photosynthesis. This energy is stored in the substances that make up the cells of the plants.

b) The mass of living material (biomass) at each stage in a food chain is less than it was at the previous stage. The biomass at each stage can be drawn to scale and shown as a pyramid of biomass.

c) The amounts of material and energy contained in the biomass of organisms are 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 transferred to the surroundings.