The functional designs of gas exchangers

Inaugural lecture--Dept.of Zoology, University of Johannesburg, 13 July 2011@@I have extensively researched the area of comparative respiratory structural, functional and developmental biology. Animals at different evolutionary and developmental levels, those that pursue different behaviours and lifestyles, and those that inhabit diverse ecological environments and habitats, especially the extreme (challenging) ones, have been investigated. The following questions have directed my research inquiry: When? Why? and How? have gas exchangers (respiratory organs/structures) adaptively and developmentally evolved to afford the required demands for molecular oxygen? To obtain the most robust answers to the research question(s) and therefore more satisfactorily explain the structural and functional fidelities of modern gas exchangers, microscopic, stereological, molecular, mathematical and computational modelling and three-dimensional reconstruction techniques have been applied. The following points that will be highlighted are: a). During the time that life has evolved on Earth, dramatic shifts in the levels of oxygen (O2) and carbon dioxide (CO2) have occurred in the biosphere. b). The physicochemical laws that govern the flow and behaviour of the respiratory fluid media (fluids/gases), the environment occupied, the respiratory medium utilized and the lifestyles pursued have determined the functional designs of the gas exchangers. c). The differences and the similarities that exist in the designs of the gas exchangers display the different evolutionary strategies and solutions for acquisition of O2. d). The efficiencies of gas exchangers closely correlate with the metabolic demands of organisms/animals. e). For the reason that interplay between different factors prescribes the structural and functional designs, it is difficult, if not impossible, to extrapolate these attributes to adequately explain the evolutionary basis of the modern gas exchangers. f). Since the most evolutionary advanced animals do not of necessity have the most complex and efficient gas exchangers, our studies show that the designs of gas exchangers stem from need.