Which one of the following is a filter feeder?
Answer & explanation
Answer: (c) Oyster
A filter feeder draws in water and strains out tiny food particles such as plankton and algae. The oyster, a bivalve mollusc fixed to one spot, feeds exactly this way, pumping water through its gills; the others actively hunt or scavenge.
- ✓ (c) Oysters feed by filtering algae out of the water; one oyster can filter up to about 50 gallons (roughly 190 litres) a day, which also cleans estuary water.
- ✗ (b) The octopus is an active predator that catches crabs, shellfish and fish with its arms.
- ✗ (d) Pelicans scoop up fish in their throat pouch and drain the water out; they are fish-eaters, not strainers of plankton.
Remember · Filter feeders strain food from water: oysters, mussels, clams, sponges, krill, baleen whales, whale sharks, flamingos. Oyster reefs clean estuary water.
Sources
- NOAA Fisheries (US National Oceanic and Atmospheric Administration), Oyster Reef Habitat ↗ “Because oysters feed by filtering algae from the water, they function as a natural filter and improve water overloaded with nutrients. Under certain conditions, a single oyster can filter up to 50 gallons of water per day.”
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). ·