Final answer:
An energy pyramid displays the amount of energy available at each trophic level in an ecosystem, with primary consumers typically receiving about 10 percent of the energy from the level below, which are the producers.
Step-by-step explanation:
An energy pyramid shows the amount of energy available at each feeding level in an ecosystem. Therefore, the correct answer to the question is C) Energy. Energy pyramids are graphical representations that show the flow of energy through trophic levels.
Producers, such as plants, are at the base of the pyramid and have the highest amount of energy. In a typical ecosystem, producers might start with 1,000,000 kilocalories of energy. Primary consumers, which are herbivores that eat the producers, receive approximately 10 percent of this energy, because much of the energy is lost as heat or used for metabolic processes at the lower level. Therefore, primary consumers would have about 100,000 kilocalories of energy available to them. Predators, or higher trophic levels, have even less energy available because of this energy loss at each step.
This efficiency of energy transfer is what makes energy pyramids always appear upright, unlike biomass or numbers pyramids, which can take various shapes depending on the ecosystem.