From the energy flow diagram, two inferences can be drawn. 1. Firstly, the flow of energy is unidirectional. Sun is the ultimate source of energy. The energy that is captured by the autotrophs does not revert back to the solar input and the energy which passes to the herbivores does not come back to autotrophs. As it moves progressively through the various trophic levels it is no longer available to the previous level.2. Secondly, the energy available at each trophic level gets diminished progressively due to loss of energy at each level. Every food chain starts with producers.