This book provides an accessible introduction to the biology and ecology of populations. The author assumes acquaintance with only elementary calculus and uses tutorial explanations where needed, along with real life examples and data. Emphasizing the roles of simple mathematical models in explaining the growth and behavior of populations, the book is valuable to students in population biology, population ecology, mathematical biology and mathematical ecology courses. This new edition includes more problems, as well as solutions, and more biological examples. Excel spreadsheets illustrating most of the models in the book are included on an attached CD.