SCI/230
March 8, 2013

Fish Evolution and Physiology
The organism that I decided to write about is fish. There are so many different types of fish in the world that I narrowed it down to freshwater Perch. A perch is a snub-nosed bony freshwater fish with an oval body and spiny dorsal fin. The flesh of perch fish is highly valued. Perch fish are in the bony fish category also classified as ostieithyes. These fish are the largest section of the vertebrates. As well as being the largest, the way that they have evolved are much different than animals on land.
Perch are called bony fish because their skeletons are calcified. This makes them harder than cartilage bones which are found in other fish. Bony fish have great maneuverability and speed, mouths with protrusible jaws, (jaw that enables the animal to extend the mouth at will. When fully protruded, the cavity of the mouth is enlarged to form a funnel-like space facilitating the uptake of food.) (http://www.encyclopedia.com/doc/1O8-protrusiblemouth.html). Fish also have a swimming bladder to control buoyancy. The skull is the stable part of the fish. The vertebral column acts as a lever to operate the movement of the fish. Muscles provide the power for swimming. Muscles are arranged in multiple directions which allow fish to move in any direction. Fins provide a platform to exert the thrust from the muscles onto the water. Fish are cold-blooded. They derive their body heat from their environment and conform to its