Final answer:
Sharks typically have five to seven gill slits per side, with the majority having five. These slits facilitate respiration and vary in number depending on the species and their ecological roles.
Step-by-step explanation:
Sharks exhibit a fascinating range of biological adaptations that have allowed them to thrive in various marine environments. One distinct feature of sharks is the presence of gill slits on the sides of their bodies. Gill slits are crucial for respiration, as they enable water to pass over the gills where oxygen exchange occurs.
Typically, sharks possess five to seven gill slits on each side of their body. However, the majority of sharks have five gill slits. These slits are not covered by an operculum—a bony plate found in bony fishes—given that sharks are part of the Chondrichthyes class, which includes cartilaginous fishes like rays and chimaeras. In contrast, Holocephali, like chimaeras or ratfish, have four pairs of gills covered by an operculum.
To further distinguish shark species, one may look at the number and type of fins they possess, the shape and function of their teeth, and their skin covered by placoid scales. The number of gill slits plays a role in respiratory efficiency and the particular ecological niche the shark occupies.