Answer:
Energy is transferred between trophic levels when one organism eats another and gets the energy-rich molecules from its prey's body.
Explanation:
The flow of energy in an ecosystem is always linear ie uni direction. At each energy step in food chain, the energy received by the organisms is used for its own metabolism and maintenance. The left over energy is passed to next higher trophic level. Thus the energy flow decreases with successive trophic level.