Fish Anatomy

For about 400 million years, beginning well before reptiles or birds or mammals had even made an appearance, fish have had the same basic body plan: a streamlined bullet shape that minimizes the water’s resistance to their movement. There are exceptions, but most fish can be thought of as sheets of muscle tissue anchored with connective tissue and the backbone to a propulsive tail. The animals push water behind them, developing thrust by undulations of the whole body and flexing of the tail.