Why is the flow of energy unidirectional?
The energy enters the plants from the sun through the photosynthesis process. This energy is then passed on from one organism to another in a food chain. The flow of energy in the ecosystem is 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.