Consider the following kinds of organisms:
- Copepods
- Cyanobacteria
- Diatoms
- Foraminifera
Which of the above are primary producers in the food chains of oceans?
[UPSC Civil Services Exam – 2021 Prelims]
(a) 1 and 2 only
(b) 2 and 3 only
(c) 3 and 4 only
(d) 1 and 4 only
Answer: (b)
Explanation:
Copepods:
- These are any member of the widely distributed crustacean subclass Copepoda.
- Free-living copepods form a crucial link in the food chain and are often assigned the role of “primary consumers”. Hence statement 1 is incorrect.
- Copepods are of great ecological importance, providing food for many species of fish.
Cyanobacteria:
- Cyanobacteria, also called blue-green algae, are microscopic organisms found naturally in all types of water.
- These single-celled organisms live in fresh, brackish (combined salt and fresh water), and marine water.
- These organisms use sunlight to make their own food. Hence statement 2 is correct.
Diatoms:
- Diatoms are photosynthesizing algae, they have a siliceous skeleton (frustule) and are found in almost every aquatic environment including fresh and marine waters, soils, in fact almost anywhere moist. Hence statement 3 is correct.
- They are non-motile, or capable of only limited movement along a substrate by secretion of mucilaginous material along a slit-like groove or channel called a raphe.
- Being autotrophic they are restricted to the photic zone (water depths down to about 200m depending on clarity).
Foraminifera:
- These are any unicellular organism of the rhizopodan order Foraminiferida (formerly Foraminifera), characterized by long, fine pseudopodia that extend from a uninucleated or multinucleated cytoplasmic body encased within a test, or shell.
- Foraminifera are found in all marine environments, they may be planktic or benthic in their mode of life.
- Foraminifera are recorded as feeding chiefly upon bacteria, small diatoms, and nannoplankton in a wide variety of marine environments. Hence statement 4 is incorrect.
