Define ecological efficiency, including ranges of ecological efficiencies in nature.
a. The proportion of energy in the biomass of the primary producers of an ecosystem, ranging from 50-80%.
b. The percent transfer of energy from the top of the food web to the bottom, ranging from 1-3\%.
c. The percentage of energy in the biomass of herivores transferred to decomposers, ranging from 20-50%.
d. The percentage of energy in the biomass at a lower trophic level that is transferred to the next higher trophic level, ranging from 5 to 20%.
The Correct Answer and Explanation is:
Correct Answer: d. The percentage of energy in the biomass at a lower trophic level that is transferred to the next higher trophic level, ranging from 5 to 20%.
Explanation
Ecological efficiency refers to the efficiency with which energy is transferred from one trophic level to the next in an ecosystem. Organisms at each trophic level consume biomass from the level below them, but not all the energy contained in that biomass is passed on. Ecological efficiency quantifies the proportion of that energy that is actually assimilated and used for growth and reproduction by consumers at the next level.
In most ecosystems, ecological efficiency tends to range between 5% and 20%, with an average close to 10%. This means that only about 10% of the energy stored in the biomass of a trophic level is converted into biomass at the next higher level. The remaining energy is lost as heat through metabolic processes such as respiration, or it is left unconsumed or unassimilated due to indigestible materials.
For example, when herbivores (primary consumers) eat plants (primary producers), they do not use all the plant material effectively. A large portion of the energy in the plant matter is either not eaten or is lost during digestion and cellular respiration. The same pattern holds true as energy moves up the food chain from herbivores to carnivores (secondary consumers) and so on.
This inefficiency in energy transfer has important ecological implications. It limits the number of trophic levels in an ecosystem—typically no more than four or five—because there is progressively less energy available at higher levels. This also explains why biomass pyramids typically narrow toward the top.
Understanding ecological efficiency helps scientists predict population sizes, energy needs, and the sustainability of ecosystems. It is a key concept in ecological modeling, conservation biology, and resource management.
