Question

the size of a food chain can vary, but the number of levels that a food chain can reach is limited. why does this limit exist?
plants are not infinite in number.
producers are limited by consumers.
carnivores are too large to be eaten.
energy is lost at each trophic level.

Explanation:

Energy transfer in a food - chain is not 100% efficient. Only about 10 - 20% of energy is passed on from one trophic level to the next. As a result, after a few levels, there is not enough energy available to support a higher - level consumer, thus limiting the number of levels in a food chain.

Answer:

Energy is lost at each trophic level.