Correct Answer:
B. 10%
In an ecological food chain, only about 10% of the energy from one trophic level is typically transferred to the next trophic level. This fundamental principle is widely known as the "10% rule" in ecology. The vast majority of the remaining energy, approximately 90%, is lost at each step. This energy is primarily used by the organisms for their own metabolic processes, such as respiration, movement, growth, and reproduction, or is lost as heat. A significant portion also remains unconsumed or undigested. This considerable energy loss explains why food chains rarely extend beyond four or five trophic levels, as there isn't enough energy to support higher levels.
- 90%: This percentage largely represents the amount of energy that is lost or utilized by the organisms at a given trophic level for their own life processes, rather than the amount transferred to the next level.
- 50%: This is an overly optimistic estimate of energy transfer. If 50% of energy were transferred, food chains would be much longer and more complex, and ecosystems would be capable of supporting much larger biomasses at higher trophic levels than observed in reality.
- 100%: A 100% energy transfer is thermodynamically impossible. According to the second law of thermodynamics, energy transformations are never 100% efficient; some energy is always converted into unusable forms, typically heat, during any transfer or conversion process.