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Today we are going to discuss a little about the classes and general characters of fish whether they are fresh water or marine. The Pisces are the super class of phylum Chordata which has three sub classes, i:e i) Choanichthyes, They are jawless fish, like eel,ii) Choandricthyes, They are cartilegenous fish, like sharks and whales and iii) Osteicthyes, They are bony fish like Labeo rohita.

They have streamlined body, respire by gills, locomotion by fins and tail, with two chambered heart, cold blooded. They have well developed skull with upper and lower jaws having teeth. They also have swim bladder for buoyancy and exoskeleton of scales, They are oviparous and their fertilization is external, Female fish is the member who determines the sex which means female fish are the heterogametic . There are many other characters which distinguish fish from other classes of the phylum chordata but I don t want to prolong this topic and make you get bored.