Question

Consider the following food chains:

(a) $Greenplants\to Mice\to Snakes\to Hawks$

(b) $Greenplants\to Mice\to Hawks$

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

Answer 1

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.
[0.5 Marks]
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:

(a) Green plants → Mice → Snakes → Hawks
100 J 10 J 1 J 0.1 J
[0.5 Marks]
(b) Green plants → Mice → Hawks
100 J 10 J 1 J
[0.5 Marks]
So, it is clear that hawks will get 10 per cent more energy in the second food chain compared with the first food chain.
[0.5 Marks]