Question 31: Indicate the flow of energy in an ecosystem. Why is it unidirectional? Justify.
Answer:
An ecosystem does not have its own source of energy so they receive the energy from the sun. Total incoming solar radiations trapped by the producers (green plants) and change this energy into the chemical energy in the synthesis of food. When the green plants are eaten by the herbivores with the efficiency of energy capture 1% of sunlight, a lot of energy is lost as heat or consumed in the metabolic reactions for their growth and the rest is used for the development or reproduction. When the primary consumers are the herbivores 10% (10% law) of the amount of energy of herbivores is transferred to the primary consumers level and the same process repeats for the next trophic level with the sharing of 10% energy from the previous level. There can be only 4-5 trophic levels. Thus when the energy is transferred at each level, less amount of usable energy is available for the last trophic level. Flow of energy is always unidirectional and shows an upright pyramid.
Flow of energy is unidirectional because energy captured by the producers or the green plants does not revert back to the solar input but it passes to the herbivores for their metabolic reactions. And, when the energy is passed to the herbivores it does not go back to the producers but passes to the primary consumers or the carnivores. At each trophic level there would be a progressive decrease in the energy due to the energy being lost as heat in respiration, development and reproduction.
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