Which one of the following is a filter feeder?

Explicitly labels catfish as 'bottom feeders', a feeding category that typically consumes benthic material and detritus rather than filtering plankton from the water column.

A student could use this rule to contrast 'bottom feeder' diets with known filter-feeding mechanisms and ask whether catfish species commonly show filter-feeding anatomy/behaviour.

Describes zooplankton as the link between primary producers and many pelagic fish that feed directly on plankton (examples: mackerel, sardines, herring), illustrating what kinds of fishes are typical plankton/ filter feeders.

Compare anatomical/behavioral traits of those pelagic plankton feeders with catfish to judge whether catfish are likely to be filter feeders.

Lists catfish among many commercially farmed species, implying catfish is a broad group with varied ecology and importance in aquaculture.

Use this to consider species diversity within 'catfish'—a student could check whether some farmed catfish species are raised on particulate diets (suggesting non-filter feeding) or on plankton-based diets.

Explains environmental 'filter' functions (seagrass beds filtering sediments/nutrients), offering a clear notion of what 'filtering' means in aquatic contexts.

Apply this concept of filtering (removing suspended particles/nutrients) to animal feeding modes and ask whether catfish morphology/behaviour matches that function.

Lists mollusks together (oyster, mussel, clam — known filter feeders — alongside squid and octopus), showing the phylum contains species with very different feeding modes.

A student could note that because some mollusks are filter feeders while others (squid, octopus) are different types, octopus may belong to a different feeding category and so should be checked against cephalopod feeding habits.

Describes marine trophic roles (zooplankton as primary consumers, demersal fauna that feed on plants, and other links), outlining that marine animals occupy diverse feeding niches.

Use this pattern (distinct trophic roles) plus knowledge that octopus are cephalopods to infer they might occupy a predatory trophic role rather than passive filter feeding.

Notes benthos animals include carnivorous crustaceans that actively hunt, illustrating benthic predators exist among invertebrates.

Combine this example of active benthic predation with the grouping of octopus as a marine invertebrate to hypothesize octopus could be an active predator rather than a filter feeder.

Defines other consumer categories (detritivores, saprotrophs), showing multiple alternative feeding modes among organisms besides filter feeding.

A student can use this list of alternate feeding strategies to rule out filter feeding as the only possibility for a given mollusk like the octopus and seek specific evidence about octopus diet.

States seagrass beds provide habitat for marine invertebrates and fishes, implying ecological niches and specialized feeding strategies within habitats.

Use habitat–niche reasoning: since habitats support specialized feeders, check whether octopus occupy niches typical of predators/scavengers rather than niches typical of stationary filter feeders.

Explicitly places pelicans in an aquatic food chain as consumers that eat fish, indicating piscivorous feeding in watery habitats.

A student could combine this with basic anatomy knowledge (large bill and throat pouch) to investigate whether pelicans capture fish by scooping vs. filtering small prey.

Lists pelicans among species that inhabit estuaries — environments where suspension feeding and filter-feeding strategies are common.

Knowing pelicans occur in estuaries, a student could look for behavioral/feeding observations in such habitats (scooping in shallow water vs. true filtration of plankton).

Describes aquatic food-web roles of zooplankton and mentions surface pelagic fishes and large filter feeders (e.g., basking shark) that feed on plankton, providing a model of what 'filter feeding' looks like in aquatic systems.

A student could use this example of known filter feeders (basking shark) as a comparison to judge whether pelican feeding mechanics match plankton-filtering or are different (fish-scooping).

Notes large freshwater wetlands (Kolleru Lake) as important pelican habitat, implying pelicans forage in shallow, food-rich waters where both small fish and planktonic prey occur.

With this habitat context, a student could infer likely feeding methods used in shallow lakes (scooping schooling fish vs. straining small organisms) and seek behavioral descriptions to distinguish them.