Trophic Levels and Energy Flow Explained

The levels of a food chain (food pyramid) are called Trophic levels.
The various steps in a food chain at which the transfer of food (or energy) takes place are called trophic levels.
In a food chain, each step representing an organism forms a trophic level.
The plants are producers (or autotrophs) and constitute the first trophic level.
They fix up the sun’s energy and make it available for consumers (or heterotrophs).
Herbivores (which feed on plants) constitute the second trophic level.
Carnivores (that feed on herbivores) constitute the third trophic level.
Large carnivores or Top carnivores (which feed upon small carnivores), constitute the fourth trophic level

When any organism dies, detritivores (like vultures, worms and crabs) eat them up.
The rest are broken down by decomposers (mostly bacteria and fungi), and the exchange of energy continues.
Decomposers start the cycle again.

Ecosystem energy processes conform to the thermodynamic laws.
Energy cannot be made or destroyed.
Energy transformations are not perfect and energy is lost in each transformation in the form of heat.
The flow of energy in the ecosystem is unidirectional.
The energy enters the plants (from the sun) through photosynthesis during the making of food. This energy is then passed on from one organism to another in a food chain.
Energy given out by the organisms as heat is lost to t used by the plants again.
This makes the flow of energy in the ecosystem ‘unidirectional’.
Thus the flow of energy in the ecosystem is said to be unidirectional because the energy lost as heat from the living organisms of a food chain cannot be reused by plants in photosynthesis.
During the transfer of energy through successive trophic levels in an ecosystem, there is a loss of energy all along the path.
No transfer of energy is 100 percent.

The energy available at each successive trophic level is 10 per cent of the previous level.

Thus, there is a progressive decline gradual reduction) in the amount of energy available as we go from producer level to the higher trophic levels of organisms.