Consider the following kinds of organisms:
- 1.Copepods
- 2.Cyanobacteria
- 3.Diatoms
- 4.Foraminifera
Which of the above are primary producers in the food chains of oceans?
Answer & explanation
Answer: (b) 2 and 3
Primary producers make their own food by photosynthesis. In the sea these are the phytoplankton, which include cyanobacteria and diatoms. Copepods are tiny crustaceans and foraminifera are shelled protists; both eat other organisms, so they are consumers.
- ✗ 1. Copepods are small crustaceans; they graze on phytoplankton or live as parasites on fish, so they are consumers, not producers.
- ✓ 2. Cyanobacteria (blue-green algae) are photosynthetic bacteria and form part of the ocean's phytoplankton.
- ✓ 3. Diatoms are single-celled, silica-walled algae that make their own food using sunlight; they are among the most important phytoplankton.
- ✗ 4. Foraminifera are single-celled protists with shells that capture food such as bacteria, diatoms and even copepods; they are consumers, even though some species harbour algae inside.
Remember · Ocean food chains start with phytoplankton (cyanobacteria, diatoms, dinoflagellates, coccolithophores). Zooplankton such as copepods and foraminifera are consumers.
📘 Read it in NCERT: Class 8 Curiosity, Ch 2 (practise this chapter) · Class 12 Biology, Ch 11 (practise this chapter)
Sources
- NASA Earth Observatory, What are Phytoplankton? ↗ “Among the common kinds are cyanobacteria, silica-encased diatoms, dinoflagellates, green algae, and chalk-coated coccolithophores. … Phytoplankton are the foundation of the aquatic food web, the primary producers, feeding everything from microscopic, animal-like zooplankton to multi-ton whales.”
- NCERT Class 8 · Curiosity, Chapter 2 “Microalgae are microscopic plant-like organisms that live in water, soil, air, and even on trees. They make their own food using sunlight.”
- NCERT Class 12 · Biology, Chapter 11 “Many marine fish are infested with ectoparasitic copepods.”
- University of California Museum of Paleontology, Introduction to the Foraminifera ↗ · reference work “Other species eat foods ranging from dissolved organic molecules, bacteria , diatoms and other single celled phytoplankton, to small animals such as copepods.”
Question and answer: UPSC's official GS Paper I (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·