Which one of the following is a filter feeder?
- (a) Catfish
- (b) Octopus
- (c) Oyster ✓ UPSC's answer
- (d) Pelican
Why the answer is (c)
• Filter feeders strain suspended food particles from water. Oysters draw water over their gills and trap plankton and organic matter — option (c).
• Catfish (a) are bottom-feeding predators/scavengers; octopuses (b) actively hunt crabs and molluscs; pelicans (d) scoop fish with their pouch — none filter water.
• Because they filter up to 50 gallons a day, oysters improve water quality, which is why oyster reefs are valued in coastal restoration.
• Hence option (c).
Why the other options are wrong
- (a) Catfish
- Catfish are bottom feeders, not filter feeders.
- (b) Octopus
- Octopuses are active predators.
- (d) Pelican
- Pelicans scoop fish; they do not filter water.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2021, held on 10 October 2021. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.