Energy flow

In ecology, energy flow (calorific flow) refers to the flow of energy through a food chain.

In following energy flow in an ecosystem, ecologists seek to quantify the relative importance of different component species and feeding relationships.

A general energy flow scenario follows:
*Solar energy is fixed by the photoautotrophs, the so called "primary producers", like green plants which fix the energy in forms such as glucose and ATP by photosynthesis.
*The primary consumers consuming these photoautotrophs are herbivores. They absorb most of the stored energy in the plant through digestion, and transform it into the form of energy they need, adenosine triphosphate, through respiration. A part of the energy received by the herbivore is converted to bodily heat (an effect of respiration), which is radiated away and lost from the system. Energy loss also occurs in the expulsion of egesta, which contains undigested energy compounds.
*Secondary Consumers then consume the primary consumers. Energy that had been used by the primary consumers for growth and storage is thus absorbed into the secondary consumers through the process of digestion. As with primary consumers, secondary consumers convert this energy into a more suitable form (ATP) during respiration. Again some energy is lost from the system, since energy which the primary consumers had used for respiration cannot be utilised by the secondary consumers.
*Tertiary consumers then consume the secondary consumers, and most of the energy is passed along, while some is again lost in the ways described above and below.
*A final link in the food chain is decomposers which break down the organic matter of the tertiary consumers (or whichever consumer is at the top of the chain) and release nutrients into the soil. Decop Saprotrophic bacteria and fungi are decomposers, and play a pivotal role in the nitrogen and carbon cycles.

The energy is passed on from trophic level to trophic level and each time some (about 90%) of the energy is lost, with some being lost as heat into the environment (an effect of respiration) and some being lost as egesta. This means the top consumer of a food chain receives the least energy, as a lot of the food chain's energy has been lost between trophic levels. This loss of energy at each level limits typical food chains to only 4-6 links.