Final answer:
About 90% of energy in a food chain is lost as heat, while roughly 10% is assimilated into the next trophic level. This limitation in energy transfer results in typically no more than four trophic levels in a food chain.
Step-by-step explanation:
When moving up the food chain, approximately 90% of energy is lost as heat at each trophic level, while only about 10% of energy is assimilated into the biomass of the organisms at the next level. This loss of energy as heat is due to metabolic processes, which include activities such as growth, repair, and movement. Energy is also lost in forms such as incompletely digested food. As a result, food chains rarely have more than four trophic levels because there isn't enough energy available to sustain additional levels. The assimilation of energy refers to the incorporation of this 10% into the body tissues of organisms and is critical for their growth and reproduction.