Why is so much energy "lost" between trophic levels? It does not just disappear, what is it used for?

Energy decreases as it moves up trophic levels because energy is lost as metabolic heat.

Explanation:

When the organisms from one trophic level are consumed by organisms from the next level. ... A food chain can usually sustain no more than six energy transfers before all the energy is used up.

the most common energy conversion is from kinetic energy to potential energy, and then from potential energy to kinetic energy.

later on comes the heat energy, mechanical energy, and other energy conversions.

this energy conversion is so common that we can find it in our day to day lives as well.

- one of the most common energy conversions involves the changing of potential energy to kinetic energy or kinetic energy to potential energy

x would be the most and the least would be y because there are more fruit   and seeds than flock z has insects