Question

(b) Consider the following food chains :​ ​

(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

Solution​:

​ According to the ten percent law, with every increasing trophic level in a food chain, the amount of energy available is only 10% of the previous trophic level.​ So, a shorter food chain means that more energy is available to the highest trophic level in that food chain.​ ​ ​

• Food chain (i): Plants → Mice → Snakes → Hawks​

• Energy available at producer level (plants) is 100J.​

• As per the 10% law, energy available to the hawk will be 0.1J.​

• Food chain (ii): Plants → Mice → Hawks​

• Energy available at producer level (plants) is 100J.​

• As per the 10% law, energy available to the hawk will be 1J.​

• Hence, we can conclude that the hawk will get more energy in the food chain (ii) having three trophic levels and 1J of energy will be available to the hawk in this food chain.​