Question

If an ecosystem is composed of only three trophic levels, then how much energy will be conserved at the III trophic level?
A. 30%
B. 20%
C. 10%
D. 1%

Answer 1

Hint: All living organisms are a part of a systematic system of energy and nutrient flow in ecosystems called food chains. The organisms at lowest levels have a certain amount of energy and nutrients which gets passed on to the next level to other organisms who feed on them and the chain continues.


Complete step by step solution:
Energy flow in a food chain is based on a law that says total transmission of energy from one trophic level to another never occurs. There's some amount of energy lost in between. The energy is usually lost in the metabolic processes of organisms in the form of heat. These processes might involve digestion or respiration etc.

Thus, only 10% of the total energy from one trophic level goes to the next level. This implies that organisms at higher levels tend to have low energy levels and fewer nutrients. Producers are said to have the highest amount of energy because they are autotrophs and synthesise their own food so they have high amounts of nutrition and energy for themselves and for others who feed on them.

These producers are consumed by primary consumers who are herbivores and get 10% to the total energy that was there in the lower trophic level. Similarly, when these primary consumers are consumed by secondary consumers in the next trophic level then only 1% of the total energy is obtained.

Thus, any ecosystem which is composed of only 3 trophic levels will have only 1% of energy at the III trophic level. So the correct option is A.


Note: Consumption of energy varies for each and every organism for example the ground dwellers of lower species such as an earthworm will require less amount of energy while a ground dweller of a higher species such as humans or cattle will need more energy. But the energy distribution is such that only 10% of the nutrients transfer from one level to another.