What Is a Fish?

All types of fish live in water, and almost all of them breathe through gills. Most of them also have scales and fish. The Entire fish family is classified into three categories: jawless, cartilaginous, and bony.

Jawless

Jawless fish are the most ancient type of fish living today. A good example of jawless fish is the lamprey. Lampreys look a lot like eels, except for their jawless, sucking mouths which have sharp teeth.

Cartilaginous

Cartilaginous fish, as their name suggests, have bones made of cartilage, a tough, flexible connective tissue. Good examples of this type of fish include sharks, skates and rays.

Bony

The largest groups of the three, bony fish are distinguished by the bone-laden structure of their bodies. Their scales are made of fine bony platelets that overlap each other. Also, a bony jacket covers their gills, and their skeletal structure is composed entirely of bone. A good example of bony fish is the trout.

This is a very basic grouping of types of fish. With over 450 million years of evolution, the fish family is one of the most varied families in the animal kingdom, thus allowing it to be classified in many ways.