Why is it that oniy part of the energy stored in one trophic level is passed on to the next level?

Entropy, the second law of thermodynamics, states that everything naturally descends from a higher order of complexity to a lower order of complexity and from a higher level of energy to a lower level of energy. In order to counteract and reverse entropy, organisms must expend energy through metabolic reactions; approximately 90% of the energy that an organism absorbs is used in the metabolic processes necessary to sustain life.

There is very little energy left over to be transferred to the next tropic level because the metabolic process uses up all but 10% of the energy stored in the lower tropic level.

Only a portion of the energy stored in one trophic level is passed on to the next level due to inefficiencies in energy transfer, such as metabolic processes, heat loss, and incomplete digestion. Additionally, organisms at higher trophic levels expend energy on activities like movement and reproduction, further reducing the amount of energy available for consumption by the next trophic level.