Question

the flow of energy in unidirectional . Explain how!

Answer 1

The Flow Of Energy Is Unidirectional Because It Can Flow From Any Object To Any Object Unlike Temperature Which Flows From High To Low.
Flow Of Energy Doesnt Depends on anything 

Answer 2

because once the energy is absorbed by autotrophs it cannot be given back to the solar input(sun) similarly as it reaches the herbivores it can't reverse itself and reach autotrophs so as it moves in one direction and cannot reverse itself ,it proves it to be unidirectional .