Question

give scientific reason : 1) energy flow through an ecosystem is one way .

Answer 1

The best example to understand that energy flow through an ecosystem is one way is through the simple food chain.

The primary source of energy for the ecosystem is from the sun. Producers transform the sunlight into either food or chemical energy. The food is in turn eaten by consumers to gain energy. At no point of time, does this cycle happen in reverse.

This is the reason why the energy flow through an ecosystem is always one way. 

Answer 2

Energy flow through an ecosystem is one way, because when the energy enters the plants (from the sun) during photosynthesis.This energy is then passed on from one organism to another in a food chain but it does not come back. Thus energy flow in an ecosystem is unindirectional.