Question

why there is loss of energy at each step of food chain?

Answer 1

Most of the energy is consumed in one tropic level due to the running of metabolic activities. This can be explained by the "10% rule" which says that about 10% energy is transferred from one tropic level to another.

Answer 2

According to 10%law only 10% of the total energy is passed from one tropic level to another. The rest of the energy is retured back to the environment in form of heat.