An energy flow diagram is a good visual representation of what can happen to energy. As you can see, by the end all energy is converted into heat which is lost into the surroundings.

When matter is taken in by an organism at a trophic level it can:

• be passed onto the following trophic level when it’s consumed
• be expelled as detritus and stored until it decays and gets passed on to decomposers
• be converted into heat energy and lost into the surroundings, for example by movement friction or heat from a warm body

Energy enters a food chain as light energy. Only light absorbed by chlorophyll is converted into chemical energy in glucose. This energy has now entered the food chain. Light energy not absorbed get absorbed by other objects, like rocks or water, and is converted into heat.

Consumers get their chemical energy from the organic molecules that make up the plants or animals they consume. Biomass that isn’t eaten is passed onto decomposers. Energy is lost as heat through the consumer through a number of metabolic reactions like respiration and movement. This heat energy cannot be regained from other organisms so is ‘lost’. In large, warm-blooded animals this amounts to a lot. In fact, only between 1% and 5% is assimilated into biomass which can be consumed but the following organism in the food chain.