Question

Pharyngeal gill slits are found in
(a) Shark
(b) Crayfish
(c) Cuttlefish
(d) Starfish

Answer 1

Hint: A third chordate purpose is pharyngeal slits; these are openings between the pharynx, or throat, and the outside. These slits are used for filtering food particles out of the water in primitive chordates. The slits hold gills and are used for gas exchange in fishes and some amphibians.

Complete answer:
The arthropod is a crayfish. A mollusc is a cuttlefish. The starfish is an animal of the Echinoderm. Chordates are sharks. They've got gill pharyngeal slits. One of the principal characters of chordates is pharyngeal gill slits. They have a single dorsal fin, a simple vertebral column, a sub-terminal mouth, and gill slits of more than 5 pairs.

There are five pairs of gill slits in the majority of sharks and rays, but a few species have 6 or 7 pairs. Shark gill slits lie behind the head in a row. A gill slit's anterior edge is motile, moving outward to allow the escape of water, but closing to prevent reverse flow. Just behind the eye lies a modified slit, called a spiracle, which allows the shark to take in water during respiration and plays a major role in bottom-dwelling sharks. In active pelagic sharks, the spiracles are reduced or absent. When the shark runs, in a process known as "ram breathing," water goes through the mouth and over the gills. When at rest, to maintain a continuous supply of oxygenated water, most sharks pump water over their gills. The ability to filter water through their gills has been lost to a limited number of organisms and they must swim without rest.

Additional information: The gills are found in a space between the body wall and the carapace on the outside of the body cavity. To show them, cut a part of the carapace on one side of the crayfish.
Cuttlefish are some of the smartest invertebrates in the world. Like many marine mollusks, they have gills. Water is taken into the gills by the mantle of the cuttlefish, where the oxygen is taken from the water and into the bloodstream. Via the gills, waste gases are also removed.
No gills or lungs are used by sea stars to breathe. In their bodies, they rely on diffusion through surfaces. For instance, most oxygen is extracted from water that passes through the feet of their tubes and papules or skin gills. Skin gills, typically on the topside, are tiny projections at the base of the spines.
So, the correct answer is ‘(a) Shark’.

Note: The pharyngeal slits grow into gill arches in vertebrate fishes, supported by bony or cartilaginous gills. Pharyngeal slits are present only during embryonic development in most terrestrial species, including mammals and birds. The pharyngeal slits in these animals grow into the bones of the jaw and inner ear.