The first law of thermodynamics states that energy can neither be created or destroyed, but can be converted from one form to another.
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Solar energy obtained from sun is the only source of energy for all the living organisms on earth.
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This solar energy is converted into chemical energy by plants through the process of photosynthesis.
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This energy captured by autotrophs does not go back into the solar system but passes from the autotrophs (green plants) to herbivores who feed on green plants.
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Producers capture only 1-5% of the photosynthetically active radiation (PAR) and remaining unutilized energy is released in the form of heat.
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A small portion of the energy captured is utilized by the producers for their respiration and only about 10% energy is used to provide food to the herbivores.
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Energy obtained by the herbivores is used in metabolism and the utilized portion is added to the detritus as faeces and liberated in the form of heat.
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The remaining portion of energy in the herbivores is utilized by carnivores or transferred to the decomposers when the herbivores die.
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In this step also, only about 10% of energy in herbivore is used by the carnivore.
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Thus, at every trophic level there is decreased in the amount of energy available for organisms of the next trophic level.
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This proves the second law of thermodynamics which states that energy is lost at every step in the ecosystem in the form of heat.
