Energy Losses between Trophic Levels
- When a consumer ingests another organism not all the chemical energy in the consumer’s food is transferred to the consumer's tissues
- Only around 10 % of the energy is available to the consumer to store in their tissues
- This is because around 90 % of the energy is lost to the environment
- Around 90 % of the energy is lost to the environment because
- Not every part of the food organism is eaten
- E.g. the roots and woody parts of plants or the bones of animals, meaning that the chemical energy these uneaten tissues contain is lost to the environment
- Consumers are not able to digest all of the food they ingest
- E.g. cellulose in plants, or the fur of animals, so some is egested as faeces; the chemical energy in this undigested food is also lost to the environment
- Energy is lost to the environment in the form of heat when consumers respire
- Energy is lost to the environment when organisms excrete the waste products of metabolism
- E.g. urea in urine
- Not all individual organisms are consumed; some die without being consumed, and their bodies decompose
- Not every part of the food organism is eaten
- The energy that is left after these losses is available to the consumer to fuel their life functions, including being stored in carbon compounds in their tissues during growth
Energy losses diagram
Energy is lost from the food chain as heat during respiration, due to incomplete digestion, and through excretion of the waste products of metabolism. Remaining energy fuels the organism’s life processes or is stored in carbon compounds in the tissues.
The role of decay organisms in energy loss
- Note that while detritivores and saprotrophs are not considered to be part of a food chain, they have a role to play in the loss of energy from food chains:
- They decompose the parts of organisms that are not eaten, e.g. the bones and teeth of dead prey animals
- They break down undigested waste material
- They decompose the bodies of any organisms that die and are not consumed