Question

why the energy flow in the biosphere is undirectional

Answer 1

We say that it is unidirectional because the energy once passed by a trophic level cannot be reverted back.

Answer 2

Answer:

The energy flow through different steps in the food chain is unidirectional. This means that energy captured by autotrophs does not revert back to the solar input and it passes to the herbivores, i.e. it moves progressively through various trophic levels. Thus, energy flow from the sun through producers to consumers is in single direction only.

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