Extreme levels of hypoxia (lack of oxygen) are referred to as anoxia. This book analyzes how chronic oxygen deprivation influences biological systems - from the molecular to the ecological level - through the contributions from authors from diverse regions of the world, which shows the concern in the academic analysis of oxygen deprivation. Throughout the book, the variety in the experimental approach scientists take, for understanding the impact oxygen deprivation has on living systems has been presented using diverse ideas. For instance, one of these ideas deals with the exploration and analysis of the physiological, cellular and genetic features of killifish embryos and nematodes exposed to anoxia. The book also comprises of content on the mechanisms managing hypoxia and anoxia tolerance and their implications on human health issues along with new methodologies to analyze oxygen deprivation and the effect of human-related activities on oxygen level, within essential ecological systems such as Lake Victoria, since the oxygen molecule is undoubtedly, central to every stratum of biological systems.