4. What is an energy pyramid? Why is there a loss of energy at each level
moving up?

#1 An ecological pyramid is a graphical representation designed to show the biomass or bioproductivity at each trophic level in a given ecosystem.  And #2 Most of the food energy that enters a trophic level is "lost" as heat when it is used by organisms to power the normal activities of life. Thus, the higher the trophic level on the pyramid, the lower the amount of available energy.

Explanation:

there's the proffessional site that will you.