Our aim in writing this book is to provide students and teachers with a simple introductory text which deals with practical aspects of ecology, environmen­ tal biology and biogeography, emphasizing actual field and classroom investigations. Basic concepts and methods of survey, mapping and aerial photography, data collection and data analysis are described and discussed, in order to encourage students to identify and tackle worthwhile projects. The level at which this text is appropriate depends very much upon particular circumstances. The greater part lies within the scope of the sixth form and the first and second years of college, polytechnic and university courses in the British Isles and their equivalents overseas. All students inevitably meet difficulties in the identification of plant and animal species, particularly when they venture into unfamiliar habitats and regions. This is often the cause of unnecessary alarm. Many ecological principles or problems may be illustrated by reference to familiar species and habitats, such as are found in urban environments, as well as those areas of semi-natural vegetation favoured for field courses.