Question

Consider the following statement about the food chain.
(I) Removal of most carnivores resulted in increased deer population
(II) If 80% of top consumers are removed from an area, vegetation growth increases
(III) The length of food chain is limited to few trophic levels due to energy restriction
(IV) The trophic levels in a food chain can vary from 2-8

Choose the option which mentions the correct statements:

• A. I and II
• B. II and III
• C. II and IV
• D. I and III

Answer 1

The correct option is D I and III

The sequence of species through which the organic molecules passes in a community is called food chain. In the natural surroundings, organisms occupy a place according to their feeding relationship with other organisms, thus occupying a specific place in the food chain that is known as their trophic level. Producers belong to the first trophic level, herbivores (primary consumers) to the second and carnivores (secondary consumers) to the third and top consumers (tertiary consumers) to the fourth trophic level.

Removal of most carnivores resulted in increased deer population because carnivores are directly dependent on herbivores for their food which is the ultimate source of energy which flows from one trophic level to another in an ecosystem. So statement I is true.

If 80% of top consumers are removed from an area, vegetation growth decreases because in the absence of any predator, herbivore population increases, which ultimately decreases the vegetation. So statement II is incorrect.

The length of the food chain is limited to a few trophic levels due to energy restriction as only 10% of the energy available at any given trophic level is transferred to the next trophic level, thus supporting a maximum of 2-5 trophic levels in food chains. So statement III is true while IV is not.