Comparative Biochemistry: A Comprehensive Treatise, Volume I: Sources of Free Energy focuses on the desire to provide a sound, critical, and provocative summary of knowledge in comparative biochemistry, including thermodynamics, biological systems, oxidation, visual systems, and aerobic and anaerobic reactions of inorganic substances. The selection first offers information on the introduction to comparative biochemistry and thermodynamics of living systems. Discussions focus on comparative point of views in biology and biochemistry, classical thermodynamics, reaction rates in chemical and biological systems, and thermodynamics of open systems. The text then ponders on comparative mechanisms for fatty acid oxidation; phosphoric acid anhydrides and other energy-rich compounds; and onium compounds and their biological significance. The publication examines phototropism and phototaxis and distribution and evolution of visual systems. Topics include phototropism in plants, analysis of phototropic reaction, nature of photoreceptors, role of auxin in phototropism of plants, visual systems of vertebrates, and habitat relations. The book also tackles aerobic and anaerobic reactions of inorganic substances and comparative biochemistry of glycolysis. The selection is a dependable source of data for readers interested in the sources of free energy.