This is the leading textbook of population ecology worldwide. Written primarily for students, it describes the present state of population ecology in terms which can be readily understood by undergraduates with little or no background in the subject. Carefully chosen experimental examples illustrate each topic. Studies of plants and animals are combined to show how fundamental principles that apply to both groups can be derived. Throughout the book, complex mathematics is avoided, and the maths that is necessary is dealt with by examining real experimental data rather than dull theory.