Energy is transferred along food chains from one trophic level to the next. However, the amount of available energy decreases from one trophic level to the next.

In a food chain only around 10% of the energy is passed on to the next trophic level. The rest of the energy passes out of the food chain in a number of ways:

• it is used as heat energy
• it is used for life processes (eg movement)
• faeces and remains are passed to decomposers

Less energy is transferred at each level of the food chain so the biomass gets smaller. As a result, there are usually fewer than five trophic levels in food chains.