The Gas Exchangers

1 Perspectives on Life and Respiration: How, When, and Wherefore.- 1.1 Life: Diversity, Complexity, and Uniformity Fabricated on Simplicity.- 1.2 The Earth: a Highly Dynamic Planet.- 1.3 Factors that Encouraged the Evolution of Life on Earth.- 1.4 Oxygen: a Vital Molecular Resource for Life.- 1.5 Anaerobic Metabolism and Adaptive Success in Animals.- 1.6 Evolved Mechanisms and Strategies of Procuring Molecular O­2.- 1.7 Explicating the Process of Evolution of Respiration: Limitations.- 1.8 Plans and Performance Measures of the Gas Exchangers.- 1.9 The Early Anoxic Earth and the Evolution of Life.- 1.10 Abundance of Molecular O2 in the Earth’s Biosphere.- 1.11 Shift from Anaerobiotic to Aerobiotic State in the Early Earth.- 1.12 Accretion of Molecular O2.- 1.13 CO2 Pulses in the Biosphere.- 1.14 The Overt and Covert Roles of O2 in Colonization and Extinctions of Biota.- 1.15 Oxygen: a Paradoxical Molecule.- 1.16 The Rise of the Level of Molecular O2: a Curse or a Blessing?.- 1.16.1 The Deleterious Reactive Radicals of Molecular O2.- 1.16.2 Senescence: the Effects Molecular O2.- 1.16.3 Biological Defenses Against O2 Toxicity.- 1.17 The Evolution of Complex Metabolic Processes.- 1.18 Oxygen and CO2 as Biochemical Factors in Respiration.- 1.19 Homeostasis: the Role of Respiration.- 2 Essence of the Designs of Gas Exchangers - the Imperative Concepts.- 2.1 Innovations and Maximization of Respiratory Efficiency.- 2.2 Safety Factors and Margins of Operation of Gas Exchangers.- 2.3 Engineering Principles in the Design of the Gas Exchangers.- 2.4 Scopes and Limitations in the Design and Refinement of the Gas Exchangers.- 2.5 Optimal Designs in Biology and Gas Exchangers in Particular.- 2.5.1 Symmorphosis: the Debate.- 2.5.2 The Operative Strategies for Optimization in the Gas Exchangers.- 2.5.3 Symmorphosis and Optimization: are they Logical Outcomes of Evolution?.- 2.6 Fractal Geometry: a Novel Approach for Discerning Biological Form.- 2.7 From Diffusion, Perfusion, and Ventilation to Respiratory Pigments.- 2.7.1 Diffusion.- 2.7.2 Convective Flows.- 2.8 Blood and the Respiratory Pigments.- 2.8.1 Hemoglobinless Fish.- 2.9 Energetic Cost and Efficiency of Respiration.- 2.9.1 The Requisites for Efficient Gas Exchange.- 2.9.2 Efficient vs. Inefficient - Primitive vs. Advanced Gas Exchangers: the Contention.- 2.10 Modeling: Utility in Study of Integrative Construction of the Gas Exchangers.- 2.10.1 Evaluation of the Functional Efficiency of the Gas Exchangers.- 2.10.2 Modeling the Gas Exchangers.- 3 Gas Exchange Media, Respiratory States, and Environments.- 3.1 Water and Air as Respiratory Media: General Considerations.- 3.2 Physical Charateristics of Water and Air.- 3.3 The Distribution of Water and Air on Earth.- 3.4 Water: a Respirable Medium and an Integral Molecule for Life.- 3.4.1 Oxygen and CO2 Content in Water: Effect on Respiration.- 3.4.2 Density and Viscosity of Water.- 3.4.3 Thermal Capacity and Conductivity of Water.- 3.4.4 Derelict Waters: Respiratory Stress from Hypercapnia and Hypoxia.- 3.5 Terrestrial Habitation and Utilization of Atmospheric O2.- 3.6 Hydrogen Sulfide Habitats. Tolerance and Utilization.- 3.7 The Porosphere and Fossorial Respiration.- 3.7.1 Gaseous Composition in Burrows.- 3.7.2 Burrowing Aquatic Annelids, Crustaceans, and Fish.- 3.8 Living at High Altitude: Coping with Hypoxia and Hypobaria.- 3.8.1 Tolerance of Arterial Hypocapnia in Birds.- 3.8.2 Flying over Mt. Everest: the Bar Headed Goose, Anser indicus.- 3.9 Gravity: Effects on Respiratory Form and Function.- 4 Water Breathing: the Inaugural Respiratory Process.- 4.1 The Design of the Gills.- 4.2 Adaptive Diversity and Heterogeneity of Gill Form.- 4.3 The Functional Innovations of the Gills for Aquatic Respiration.- 4.4 The Simple Gills.- 4.4.1 Morphological Characteristics.- 4.4.2 Ventilation and Functional Capacities.- 4.4.3 Gas Exchange Pathways and Mechanisms.- 4.5 The Complex Gills.- 4.5.1 Structure and Architectural Plans.- 4.6 The Water Lungs

The factors which set the metabolic potentials of animals - the physicochemistry of the respiratory medium utilized, the phylogenetic level of development, the habitat occupied, and the life-style pursued -, have been the most decisive determinants of the constructions of the gas exchangers. After molding the most appropriate respiratory devices and adjusting them in accord with the individual needs for molecular oxygen, animals occupy different ecological niches and even share common environments. From the perspective of respiration, they have very few choices: there are only two fluid respiratory media and essentially two habitable spaces - water and air. They must adapt to either and in rarer cases to both.