Aquatic ecology and Biodiversity

Unit 2- Ecosystem ecology

2.2.4. Energy and matter transfer in ecosystem
The transfer of energy from one trophic level to another is called energy flow. This flow of energy is always unidirectional and never returns back, like nutrients, which cycles in the ecosystem. So, energy can be utilized once in the ecosystem and otherwise it will go as waste heat.Through these series of steps of eating and being eaten, energy flows from one trophic level to another. Green plants or other photosynthesizing organisms use light energy from the sun to manufacture carbohydrates for their own needs. Most of this chemical energy is processed in metabolism and dissipated as heat in respiration. Plants convert the remaining energy to biomass. Ultimately, this material, which is stored energy, is transferred to the second trophic level, which comprises grazing herbivores, decomposers and detrital feeders.
Most of the energy assimilated at the second trophic level is again lost as heat in respiration; a fraction becomes new biomass. Organisms in each trophic level pass on as biomass with much less energy than they receive. Thus, the more steps between producer and final consumer, the less energy remains available. Seldom are there more than four links, or five levels, in a food web. Eventually, all energy flowing through the trophic levels is dissipated as heat. The process whereby energy loses its capacity to do work is called entropy.
The energy transfer between producers and herbivores is only 10% remain 90% is lost through faces, respiration and unused energy or heat. A large amount of energy is lost at each tropic level i.e. 90%. Hence, the amount of energy available decreases from trophic level to another trophic level. When the food chain is short the final consumers will get a large amount of energy. But when the food chain is long final consumer will get a lesser amount of energy.