Energy is transferred along food chains from one stage to the next. But not all of the energy available to organisms at one stage can be absorbed by organisms at the next one. The amount of available energy decreases from one stage to the next.
Some of the available energy goes into growth and the production of offspring. This energy becomes available to the next stage, but most of the available energy is used up in other ways:
energy released by respiration is used for movement and other life processes, and is eventually lost as heat to the surroundings
energy is lost in waste materials, such as faeces
All of the energy used in these ways returns to the environment, and is not available to the next stage. The animation shows how the level of available energy goes down as it is transferred through a temperate forest food chain.