Final answer:
Energy is transferred through trophic levels in a food web with about 10 percent efficiency each time. Approximately 90 percent of energy is used up or lost as heat due to metabolic processes, explaining the limited number of trophic levels in most ecosystems.
Step-by-step explanation:
Energy Transfer Through Trophic Levels
Organisms acquire energy within an ecosystem via food webs and food chains. When an organism eats another, it gains energy that the prey organism had stored. However, not all of the energy is transferred to the next level. Ecological pyramids are models that show the distribution of energy among trophic levels, illustrating the decreasing energy available at each higher level.
Efficiency of Energy Transfer
The efficiency with which energy is transferred from one trophic level to the next is roughly 10 percent. About 90 percent of the energy at any given level is used for metabolic processes, such as growth and repair, or lost as heat. This loss is described by the second law of thermodynamics, which introduces the concept of entropy. Due to this low efficiency, ecosystems typically have a limited number of trophic levels, often no more than four. Beyond that, there usually isn't enough energy left to sustain an additional level.
Trophic Level Transfer Efficiency
The trophic level transfer efficiency (TLTE) quantifies the percentage of energy passed from one trophic level to the next and is calculated using this formula: production at present trophic level x 100/production at previous trophic level. For example, if a primary consumer level produces 1,103 kcal/m²/yr from the 7,618 kcal/m²/yr of energy it received from primary producers, we can deduce the TLTE for this scenario.