For the most part in this website we have based our approach to ecology on the analysis of units of the landscape as ecological systems. Principles and common denominators that apply to any and all situations, whether aquatic or terrestrial, natural or man – made, have been emphasized. The importance of the driving force of energy has been stressed. In this post useful approach was introduced, that of concentrating study on population units which are the vehicles for evolutionary change. Still another useful approach is geographical – involving the study of the pattern of earth forms, climates, and biotic communities that make up the biosphere. In this post we shall list and briefly characterize the major ecological formations, or easily recognized ecosystem types, with emphasis on geographical and biological differences that underlie the remarkable diversity of life on earth. In this manner we hope to establish a global frame of reference for the next and this post, which deals with mankind’s new challenge to attack his problems on a large scale.

       We would do well to start our world tour with the seas, the largest and most stable ecosystem. The sea, presumably, was the first ecosystem, for life is now thought to have originated in the saltwater nileu.