Question

Explain how energy is harnessed by and then flows through ecosystems. Describe the major trophic levels. How efficient is the transfer of energy and what limits that efficiency?

Answer 1

The ultimate source of energy for all the living organism the sunlight. The only living organism which can utilise energy stored in sunlight and synthesize organic molecules is the plant and some of the photosynthetic microorganisms.

Plants undertake the process of photosynthesis which is the fixation of atmospheric carbon dioxide into glucose with the help of solar energy and chlorophyll molecules. Glucose is fixed into the biomass of plants and is the source of energy. When plants are eaten by other organisms, then glucose is transferred to those organisms which is the energy source for them.

So the flow of glucose which is the source of energy for the flow of energy is from plants to the primary consumers which are herbivorous animals and then to the secondary consumers and then tertiary consumers and so on.

The flow of energy in the ecosystem is unidirectional. It always flows from organisms present at lower trophic level to the organisms present at higher trophic level. The efficiency of transfer of energy from one trophic level to the other is defined by 10% energy law. According to this law, only 10% of the energy is transferred from one trophic level to the other. As per this statement, plants are having the maximum amount of energy and top predators are having the lowest amount of energy. This is because 90% of the energy is dissipated in the form of heat to the surroundings.

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