We introduce the most common quantitative approaches to population dynamics and ecology, emphasizing the different theoretical foundations and assumptions. These populations can be aggregates of cells, simple unicellular organisms, plants or animals. The basic types of biological interactions are analysed: Consumer-Resource, Prey-Predation, competition and mutualism. Some of the modern
... [Show full abstract] developments associated with the concepts of chaos, Quasi-Periodicity, and structural stability are discussed. To describe Short-And Long-Range population dispersal, the integral equation approach is derived, and some of its consequences are analysed. We derive the standard McKendrick Age-Structured density dependent model, and a particular solution of the McKendrick equation is obtained by elementary methods. The existence of demography growth cycles is discussed, and the differences between mitotic and sexual reproduction types are analysed. © 2006 by World Scientific Publishing Co. Pte. Ltd. All rights reserved.