ABSTRACT
A basic understanding of the diversity of ‘shes will be very useful in understanding their place in the structure and function of nature. The following three chapters explore the evolution of major ‘sh groups of interest as an aid in understanding ‘sh adaptation. The purpose of this section is to acquaint the reader on how nature has shaped the evolution of ‘shes and to know how major groups of ‘shes differ. As each major ecosystem is described later, these ‘shes will become more familiar. Much of the information about ‘sh and the identi‘cation of extant ‘shes also is presented in an exercise given in the Appendix to this book.
