As Ecology teachers ourselves we have become increasingly aware of the lack of a single comprehensive textbook of Ecvlogy which we can recommend unreservedly to our students. While general, review texts are readily available in other fields, recent publications in Ecology have tended for the most part to be small, specialised works on single aspects of the subject. Such general texts as are available are often rather too detailed and, in addition, tend to be somewhat biased towards one aspect of the discipline or another and are thus not truly balanced syntheses of current knowledge. Ecology is, in addition, a rapidly developing subject: new information is being gathered all the time on a variety of key questions; new approaches and techniques open up whole new areas of research and establish new principles. Already things have changed radically since the early '70s and we feel there is a need for an up to date student text that will include some of this newer material. We have tried, therefore, to create a text that will review all the major principles and tenets within the whole field of Ecology, presenting the generally accepted theories and fundamentals and reviewing carefully the evidence on which such principles have been founded. While recent developments in ecological thought are emphasised, we hope that these will not dominate the material to the extent where the older-established principles are ignored or overlooked