Q. Which one of the following is a filter feeder?

Answer: c) Oyster

Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats.
In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not all oysters are in the superfamily Ostreoidea.
Oysters are efficient filter feeders that help remove excess nitrogen from waters by incorporating it into their shells and tissue as they grow.
- Nitrogen is an essential nutrient for plants and animals, but too much nitrogen, often from fertilizer runoff and septic tanks, boosts the growth of algae, which overwhelm water bodies and ultimately reduce oxygen levels in them.
Oysters are natural filters. They capture the particles of size as small as 4 micrometers on their gills. Their gills act as filter which is self-cleaning.
- Generally, water get filtered by something which is static so that water can easily pass through them and get filtered. Pelicans, Catfish and Octopus are large organisms. Oysters are small organisms, found cemented to rocks or other hard substrates.

Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure.
Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish.