Paleozoic era → Fishes (485 MA)

The evolution of fishes began about 485 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. 

Fishes are cold-blooded animals that live in the water. They have backbones, fins, and gills. There are 32.000 different species of fish. There are three major types or classes of fishes including jawless, cartilaginous, and bony fish. An example of a jawless fish is the lamprey eel. Sharks are cartilaginous fish and the blue marlin is a bony fish. Fish vary in all sorts of colors and sizes. Fish can be as large 40 ft long to 1/2 inch long. There are some animals that live in the water and we may think of as fish, but really aren't classified by scientists as fish. These include whales, dolphins, octopus, and jellyfish.

All fishes;

• Are vertebrates (which means they have a backbone).

• Live in water.

• Breathe using gills. They absorb oxygen through the gills.

• Almost all fishes are cold-blooded. Two of the exceptions are the tuna and the Pacific salmon shark, which can raise their body temperature to some degree.

• Some fishes have scales.