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# How is energy introduced into the ecosystem? (b) Consider the following food chains: Plants → Mice → Snakes →Hawks Plants → Mice → Hawks If energy available at the producer level in both the food chains is 100 J

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(a) How is energy introduced into the ecosystem?

(b) Consider the following food chains:

Plants → Mice → Snakes →Hawks

Plants → Mice → Hawks

If energy available at the producer level in both the food chains is 100 J, in which case will hawks get more energy as food and by how much? Justify your answer.

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(a) The energy enters the living components of the ecosystem through the process of photosynthesis.

(b) (i) The producer level in the food chain are plants, so 100 J of energy is available in plants as food.

Applying the 10% law to the above food chain:

(a) According to the 10% law, 10% of energy of plants will be available as food in mice. Thus, the energy available to mice will be 10% of 100 J, which is 10 J.

(b) The energy available to snakes will be 10% of 10 J, which is 1 J.

(c) The energy available to hawks will be 10% of 1 J, which is 0.1 J.

Plants + 10% → Mice + 10% → Snakes + 10% → Hawks

100J                  10J                   1J                      0.1J

(ii) The producer level in the food chain is plants, so 100 J of energy is available in plants as food.

Applying the 10% law to the above food chain:

(a) According to the 10% law, 10% of energy of plants will be available as food in mice. Thus, the energy available to mice will be 10% of 100 J, which is 10 J.

(b) The energy available to hawks will be 10% of 10 J, which is 1J.

Plants + 10% → Mice + 10% → Hawks

100J                  10J                 1J

Hawks will get more energy in food chain

(a) because in this food chain there are three trophic levels so the energy available will be more as compared to food chain

(b) which has four trophic levels.

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