Question 73 from UPSC CSE 2014 - Science and Technology

Question

Which one of the following is the correct sequence of a food chain?

IASCODEX · Accepted Answer

Correct Option: A. Diatoms-Crustaceans-Herrings

Strategy: Focus on the ecological roles: diatoms are known as phytoplankton and producers, crustaceans as small zooplankton consumers, and herrings are small fish higher up. The sequence must start with diatoms, followed by crustaceans that feed on them, then herrings feeding on crustaceans, making option A the only logically correct order.

Key Info: A food chain represents the linear transfer of energy through different organisms in an ecosystem. In marine ecosystems:

- Diatoms are single-celled algae, classified as phytoplankton, and serve as the primary producers. They form the base of the aquatic food web through photosynthesis.
- Crustaceans such as copepods and small shrimps act as primary consumers (zooplankton), feeding on phytoplankton like diatoms.
- Herrings are small pelagic fish and serve as secondary consumers, feeding predominantly on zooplankton including crustaceans.

Thus, the correct food chain is: Diatoms (Producer) → Crustaceans (Primary Consumer) → Herrings (Secondary Consumer). This exemplifies the transfer of energy and nutrients from producers up to higher trophic levels within marine ecosystems.

IASCODEX · Answer

Option B: Crustaceans-Diatoms-Herrings

IASCODEX · Answer

Option C: Diatoms-Herrings-Crustaceans

IASCODEX · Answer

Option D: Crustaceans-Herrings-Diatoms