A pyramid of biomass is a visual representation of the amount of biomass being passed from one stage to the next. The larger the bar the more biomass there is at that stage. As you reach the top of a biomass pyramid you can notice that the bar becomes smaller in size.

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Energy and biomass in food chains Energy flow

Energy flows in one direction: from the food to the consumer.

Grass ? Grasshopper ? Toad ? Snake ? Hawk

The transfer of energy

Energy is transferred from one part of a food chain to the next. However, the biomass decreases as the chain progresses.

There are a number of reasons for this:

• a certain amount of material and energy is lost by an organism though waste materials like faeces
• energy, released by respiration for movement and other processes, is lost to the surroundings as heat

Any energy lost to the environment cannot be passed onto the next organism. In general a food chain is only up to four stages simply because too much energy is lost at each stage, as you can see below.

Humans (secondary consumers)

67 kcal/m2/yr

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Cows (primary consumers)

1478 kcal/m2/yr

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Grass (producers)

8863 kilocalories per square metre per year (kcal/m2/yr)