Transfer of biomass

The arrows in a food chain show the transfer of biomass from one organism to another. An example of a food chain is:

maize → locust → lizard → snake

Some of the energy from the Sun absorbed by maize when it photosynthesises is transferred to the locusts when they eat the plant. So biomass is transferred. Then some of the biomass in the locust is transferred to the lizards when they are eaten and so on.

Lowest (fourth) tier of pyramid of biomass showing the producers, for example oak tree, flowers. They produce 25 MJ per meter squared per year.

Energy transfer

A pyramid of biomass

Not all of the biomass is passed from the maize plants to the locusts. In fact, only about ten per cent of the biomass is transferred from each trophic level to the next. The remaining 90 per cent is used by the trophic level to complete life processes. Biomass can be lost between stages because not all of the matter eaten by an organism is digested. Some of it is excreted as waste such as solid faeces, carbon dioxide and water in respiration and water and urea in urine.

Because only around 10% of the biomass at each trophic level is passed to the next, the total amount becomes very small after only a few levels. So food chains are rarely longer than six trophic levels.

curriculum-key-fact
We do not put the Sun at the bottom of a food chain even though the producing plants or algae transfer energy from the Sun during photosynthesis. This is because the Sun is not a living organism.

In fact, only about one percent of the energy from the Sun that reaches the plant's leaves is used by the plant during photosynthesis. This sounds small but is still enough to power almost all food chains on our planet.