Question

Filter feeding seems to be a very common strategy in aquatic animals. Describe how filter feeding accomplished by animals in different lineages (i.e. phyla). What other functions can filter feeding structures perform for some animals?

Answer 1

Filter feeders are aquatic animals that feed by filtering out plankton or nutrients suspended in water by passing water over over a specialised filtering structure.
IN different PHYLA
a)SPONGES (PORIFERA)
They don't have any circulatory system so, they create a water current which is used for circulation. Dissolved gases are brought to cells and enter the cells via simple diffusion. Metabolic wastes are also transferred to the water through diffusion.Particles that are too big to enter through the pores of the surface may be phagocytized by the cells of the epithelium. in highly developed sponges a large part of the particles are phagocytized by the walls of the incurrent canals before they reach the flagellated chambers.In some primitive sponges through choanocytes.
b)CNIDARIANS
The jellyfish has a grid of fibres which are slowly pulled through the water. It is slow and prey can't sense it . More examples are:Sea pen . Sea fan etc.
c)ARTHROPODA
1.Crustaceans
mall crustaceans that live close to shore and hover above the sea floor, constantly collecting particles with their filter basket. Antarctic krill manages to directly utilize the minute phytoplankton cells, which no other higher animal of krill size can do. This is accomplished through filter feeding, using the krill's developed front legs, providing for a very efficient filtering apparatus.  Porcelain crabs have feeding appendages covered with setae to filter food particles from the flowing water
2.Copepods
In suspension‐feeding copepods a filter chamber is enclosed between the ventral body wall and the maxillae which project ventroanteriorly. The maxillae carry long plumose setae extending antero‐medially towards the mouth and forming the lateral walls of the filter chamber. The feeding currents are produced chiefly by rapid vibratory movements of the antennae.
d) MOLLUSCA
1.Bivalves
Buried bivalves feed by extending a siphon to the surface. For example, oysters draw water in over their gills through the beating of cilia. Suspended food (phytoplankton, zooplankton, algae etc.) are trapped in the mucus of a gill, and from there are transported to the mouth, where they are eaten, digested and expelled as feces.
2.Gastropods
it is generally the cleansing mechanisms of the unmodified gill and of the mantle cavity that have been developed into food‐collecting mechanisms.
e)PISCES
few fishes(mainly cartilegenous) sucks in a mouthful of water, closes its mouth and expels the water through its gills. During the slight delay between closing the mouth and opening the gill flaps, plankton is trapped against the dermal denticles which line its gill plates and pharynx.
Other functions may include, Removal of waste from body as in sponges or sometimes even in respiration.