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Question
Assertion : The number of trophic levels in the grazing food chain is restricted.
Reason : Energy decreases when it get transferred from lower trophic level to the higher trophic level.
Assertion : The number of trophic levels in the grazing food chain is restricted.
Reason : Energy decreases when it get transferred from lower trophic level to the higher trophic level.
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Solution
The correct option is A Both the assertion and reason are true and the reason is the correct explanation of the assertion
A food chain refers to the sequence of organisms where one living organism eats another, and later that organism is consumed by larger organisms. Different organisms occupy different levels in the food chain and each level is referred to as trophic levels.
Energy transfer between trophic levels follows 10 percent law in a food chain. The law states that only 10 percent of the energy is transferred to each trophic level from the lower trophic level.
In any kind of food chain, detritus (begins with dead and decaying matter) or grazing (begins with producers like green plants), the number of trophic levels is limited to 4 - 5 because of the above reason.
For example, in a grazing food chain, when a herbivore (rat) eats plants (producers), only a fraction of the energy that it gets from the plants becomes new body mass. The rest of the energy is lost as waste or used up by the herbivore to carry out its life processes (e.g. movement, digestion, reproduction).
Therefore, when the herbivore is eaten by a carnivore (bird), it passes only a small amount of total energy to the carnivore. Of the energy transferred from the herbivore to the carnivore, some energy will be 'wasted' or 'used up' by the carnivore. The carnivore then has to eat many herbivores to get enough energy to grow.
For example, if plants receive 20000 kJ from sun, 10% of it will be transferred to rodents i.e 2000 kJ and fox receive 200kJ. Hence both the assertion and reason are true and the reason is the correct explanation of the assertion.
Figure : Energy transfer in food chain
A food chain refers to the sequence of organisms where one living organism eats another, and later that organism is consumed by larger organisms. Different organisms occupy different levels in the food chain and each level is referred to as trophic levels.
Energy transfer between trophic levels follows 10 percent law in a food chain. The law states that only 10 percent of the energy is transferred to each trophic level from the lower trophic level.
In any kind of food chain, detritus (begins with dead and decaying matter) or grazing (begins with producers like green plants), the number of trophic levels is limited to 4 - 5 because of the above reason.
For example, in a grazing food chain, when a herbivore (rat) eats plants (producers), only a fraction of the energy that it gets from the plants becomes new body mass. The rest of the energy is lost as waste or used up by the herbivore to carry out its life processes (e.g. movement, digestion, reproduction).
Therefore, when the herbivore is eaten by a carnivore (bird), it passes only a small amount of total energy to the carnivore. Of the energy transferred from the herbivore to the carnivore, some energy will be 'wasted' or 'used up' by the carnivore. The carnivore then has to eat many herbivores to get enough energy to grow.
For example, if plants receive 20000 kJ from sun, 10% of it will be transferred to rodents i.e 2000 kJ and fox receive 200kJ. Hence both the assertion and reason are true and the reason is the correct explanation of the assertion.
Figure : Energy transfer in food chainSuggest Corrections
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