Final answer:
Energy within each trophic level of a food chain is measured in kilocalories per square meter per year (kcal/m²/yr). Only about 10% of energy is transferred between trophic levels, with the rest lost as heat, which restricts the amount of energy available for higher levels and thus the number of trophic levels in an ecosystem.
Step-by-step explanation:
Understanding Energy Transfer in Trophic Levels
The unit used for communicating the energy in each trophic level of a food chain is typically measured in kilocalories per square meter per year (kcal/m²/yr).
Energy is passed up a food chain or web from lower trophic levels to higher ones. However, only about 10 percent of the energy at one level is available to the next level because the rest is used for metabolic processes or given off as heat.
This loss of energy explains why ecosystems rarely have more than four trophic levels, as the energy that remains is generally insufficient to support organisms at additional levels.
The second law of thermodynamics highlights that energy conversions are inherently inefficient, with a significant portion lost as heat.
This is a central reason energy losses between trophic levels restrict the length of food chains and the resultant biomass of higher trophic levels.
The reduced energy availability constrains the number of possible trophic energy transfers within an ecosystem, limiting the sustainable number of trophic levels.