Question

(a) How is energy introduced into the ecosystem?
(b) Consider the following food chain :
(i) Plants → Mice → Snakes → Hawks
(ii) 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.

Answer 1

(a) Plants trap solar energy to make their food. In this way, energy is introduced into the ecosystem by the sun.

(b) According to the 10 per cent law, only 10 per cent of the energy entering a particular trophic level of organisms is available for the next higher trophic level. If the energy at the producer level is 100 J, the energy at the hawk level in both the food chains can be calculated as under.
(i) Plants $\to$ Mice $\to$ Snakes $\to$ Hawks
100 J $\to$ 10 J $\to$ 1 J $\to$ 0.1 J

(ii) Plants $\to$ Mice $\to$ Hawks
100 J $\to$ 10 J $\to$ 1 J

So, it is clear that hawks will get 10 per cent more energy in the second food chain compared with the first food chain.