Question 47 from UPSC CSE 2021 - Environment

Question

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?

IASCODEX · Accepted Answer

Correct Option: B. 2 and 3

Strategy: Identify the core function of a primary producer (photosynthesis or chemosynthesis). Evaluate each organism based on this function: Copepods and Foraminifera are consumers, while Cyanobacteria and Diatoms are photosynthetic. Select the photosynthetic organisms as the correct answer.

Key Info: Primary producers are autotrophic organisms capable of photosynthesis or chemosynthesis, forming the base of aquatic food chains.

**Organism Profiles**
- **Copepods**: These are small crustaceans found as zooplankton. They feed on phytoplankton and do not photosynthesize, making them primary consumers, not primary producers.
- **Cyanobacteria**: Also known as blue-green algae, these are photosynthetic bacteria. They are critical to marine and freshwater ecosystems, converting sunlight to energy, producing oxygen, and fixing nitrogen. They are a major component of phytoplankton and key oceanic primary producers.
- **Diatoms**: These unicellular algae have silica-based cell walls and are vital oceanic primary producers. Through photosynthesis, they contribute significantly to global oxygen and carbon fixation, responsible for about 20% of the world's annual photosynthetic activity.
- **Foraminifera**: These are single-celled heterotrophic organisms with calcareous shells. They consume smaller microorganisms, including phytoplankton, and do not photosynthesize. They are not primary producers.

Phytoplankton such as diatoms and cyanobacteria form the foundation of marine food webs, unlike heterotrophic zooplankton like copepods or protists like foraminifera.

IASCODEX · Answer

Option A: 1 and 2

IASCODEX · Answer

Option C: 3 and 4

IASCODEX · Answer

Option D: 1 and 4

Consider the following kinds of organisms: Copepods Cyanobacteria Diatoms Foraminifera Which of the above are primary producers in the food chains of oceans?

Consider the following kinds of organisms:

Copepods

Cyanobacteria

Diatoms

Foraminifera
Which of the above are primary producers in the food chains of oceans?