As a rule of thumb, how much of the food energy taken in by an herbivore is passed on to a carnivore (primary consumer)? Multiple Choice 90% 50% 1% 5% 10%
The Correct Answer and Explanation is:
The correct answer is 10%.
In an ecological food chain, energy transfer between trophic levels is governed by the 10% Rule, which states that only about 10% of the energy from one trophic level is passed on to the next level. This rule applies because energy is lost at each stage due to metabolic processes, heat loss, and inefficiencies in digestion and assimilation.
For example, when a primary consumer (such as a herbivore) consumes plants, only about 10% of the energy stored in the plants is converted into body mass. The herbivore then becomes food for a secondary consumer, such as a carnivore. However, only about 10% of the herbivore’s energy (which has already been reduced) is transferred to the carnivore. The rest is lost as heat, used for the herbivore’s metabolic functions, or excreted as waste.
This energy transfer efficiency leads to a pyramid shape in ecosystems, where producers (plants) form the base, and each subsequent level in the food chain has less energy available. The higher up the food chain you go, the less energy is available to support each successive trophic level, which is why carnivores, such as apex predators, require large amounts of herbivores or smaller carnivores to meet their energy needs.
In summary, due to the inefficiency of energy transfer, approximately 10% of the energy originally obtained by herbivores from plants is passed on to carnivores in an ecosystem. This is why ecosystems can support fewer carnivores than herbivores or producers.
