Why isn't 100% of energy passed from one trophic level to the next

Energy decreases as it moves up trophic levels because energy is lost as metabolic heat when the organisms from one trophic level are consumed by organisms from the next level.

Explanation:

{ why is it that only part of the energy stored in one trophic level is passed on to the next level? :  This is because organisms use much of the energy that they consume for life processes, such as respiration, movement, and reproduction. Some of the remaining energy is released into the environment as heat.}