Production, storage, and optimal use of energy are important processes for supporting the activities that sustain life. Solar energy is captured by plants and conserved in chemical bonds of compounds such as glucose, fatty acids, starch, and glycogen. Animals are conduits of energy in the immensity of the Universe. The designs of the respiratory and the cardiovascular systems are fundamental to the wholesomeness of vertebrate life. The fundamental structural features of a respiratory organ include: an extensive respiratory surface area, a thin water/air-blood barrier, and a large volume of capillary blood. Factors that have profoundly shaped the structure and function of vertebrate respiratory organs are: body mass, respiratory medium utilized, phylogenetic level of development, lifestyle, and habitat. The presentation and exposure of the respiratory media, features determined by the geometry and arrangement of the structural components, contribute highly to respiratory efficiency.