The most primitive groups of vertebrates are fish. All fish live in water.
CHARACTERISTICS OF FISH
- Their body is elongated and pointed at the ends. It is very well adapted to living in water.
Fish have fins to move. The tail fins move the fish forward. The other fins( pectoral , pelvic, anal and dorsal) help maintain the fish’s balance and control its direction.
- The skin of fish is slippery. Thin, bony scales protect their bodies.
- Fish breathe using gills. The gills are thin red filaments at the back of the mouth. Fish breathe by absorbing oxygen dissolved in water through their gills.
- Fish reproduce by laying small eggs in the water. Baby fish are called fry. Females lay lots of eggs but only a few live
- Fish have a special sensory organ on the side of their bodies that other vertebrates do not have. It is called the lateral line and allows the fish to detect movement in the water.