Our Environment — Science STD 10 — Question

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 the environment, it does not return to be used by the plants again. This makes the flow of energy in 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.
The flow of energy is generally from
Sun --> Producer → Primary Consumer → Secondary Consumer → Tertiary Consumer.
since the flow of energy is progressiely from one trophic level to another and does not revert back, it is siad to be unidirectional. Further, the available energy decreases in the higher trophic levels making it impossible for energy to flow in the reverse direction.