In energy transfer through trophic levels, what percentage of energy is typically lost?

In ecosystems, energy transfer through trophic levels is governed by the concept known as the 10% rule. This rule states that, on average, only about 10% of the energy from one trophic level is passed on to the next level. The remaining energy is lost primarily through metabolic processes—such as respiration, growth, reproduction—and as heat. This loss is a natural part of energy flow in biological systems and impacts the structure of food webs.

The reason why the correct answer is 10% is rooted in the efficiencies of energy transfer across different levels of life forms, starting from producers (like plants) to various levels of consumers (herbivores, carnivores, etc.). For instance, if a plant harnesses 1,000 joules of solar energy through photosynthesis, approximately 100 joules would be available to herbivores that consume the plant, and around 10 joules would then be available to primary carnivores that eat the herbivores, and so on. This illustrates how energy diminishes at each level, illustrating the importance of productivity and energy flow in ecosystems.