Fish are the largest group of vertebrates found in fresh and salt water. Over 25,000 species of fish comprise about 50% of the vertebrate population. Part of the reason for the large number of fish is due to how they are well adapted to life in an aquatic environment. Students from grade 10 dissected a typical boney fish during their laboratory time to observe the external and internal structures of the fish. Students saw how its structures make the fish ideally suited to living in an aquatic environment.