The history of biology is replete with examples of how comparative biology helped clarify the meaning of structure and function in complex animals. Indeed, without the comparative approach to biology, the birth of physiology would have been delayed. Fishman (1979) Comparative morphologists are challenged to discern the changes that have occurred in evolution and development of the forms and states of organisms as well as to explain the factors that compelled them (e.g. Dullemeijer 1974). The main objective of this contribution is to present what I deem to be some of the fundamental structural aspects in the design of respiratory or gans while debating and speculating on when, how and why these states were founded. My main thesis is that the modern gas exchangers are products of protracted processes that have en tailed adaptation to specific environments and lifestyles. Only those feasible designs that have proven adequately competent in meeting demands for molecular oxygen have been preserved. Unfortunately, August Krogh's (Krogh 1941) and Pierre Dejours' (Dejours 1975) seminal works on the comparative physiology of the respiratory organs have not been paralleled by equally exten sive and detailed morphological work. Our approach has been to look into the limiting functional properties as regards the respi ratory capacities of gas exchangers while finding out the specific structural adaptations that have evolved to meet the metabolic needs or to look into form and to discern how it limits function. This has allowed a deduction of structure-function correlation.

The history of biology is replete with examples of how comparative biology helped clarify the meaning of structure and function in complex animals. Indeed, without the comparative approach to biology, the birth of physiology would have been delayed. Fishman (1979) Comparative morphologists are challenged to discern the changes that have occurred in evolution and development of the forms and states of organisms as well as to explain the factors that compelled them (e.g. Dullemeijer 1974). The main objective of this contribution is to present what I deem to be some of the fundamental structural aspects in the design of respiratory or gans while debating and speculating on when, how and why these states were founded. My main thesis is that the modern gas exchangers are products of protracted processes that have en tailed adaptation to specific environments and lifestyles. Only those feasible designs that have proven adequately competent in meeting demands for molecular oxygen have been preserved. Unfortunately, August Krogh's (Krogh 1941) and Pierre Dejours' (Dejours 1975) seminal works on the comparative physiology of the respiratory organs have not been paralleled by equally exten sive and detailed morphological work. Our approach has been to look into the limiting functional properties as regards the respi ratory capacities of gas exchangers while finding out the specific structural adaptations that have evolved to meet the metabolic needs or to look into form and to discern how it limits function. This has allowed a deduction of structure-function correlation.

Birds have and continue to fascinate scientists and the general public. While the avian respiratory system has unremittingly been investigated for nearly five centuries, important aspects on its biology remain cryptic and controversial. In this book, resolving some of the contentious issues, developmental-, structural- and functional aspects of the avian lung-air sac system are particularized: it endeavors to answer following fundamental questions on the biology of birds: how, when and why did birds become what they are? Flight is a unique form of locomotion. It considerably shaped the form and the essence of birds as animals. An exceptionally efficient respiratory system capacitated birds to procure the exceptionally large quantities of oxygen needed for powered (active) flight. Among the extant air-breathing vertebrates, comprising ~11,000 species, birds are the most species-rich-, numerically abundant- and extensively distributed animal taxon. After realizing volancy, they easily overcame geographical obstacles and extensively dispersed into various ecological niches where they underwent remarkable adaptive radiation. While the external morphology of birds is inconceivably uniform for such a considerably speciose taxon, contingent on among other attributes, lifestyle, habitat and phylogenetic level of development have foremost determined the novelties that are displayed by diverse species of birds. Here, critical synthesizes of the most recent findings with the historical ones, evolution and behavior and development, structure and function of the exceptionally elaborate respiratory system of birds are detailed. The prominence of modern birds as a taxon in the Animal Kingdom is underscored. The book should appeal to researchers who are interested in evolutionary processes and how adaptive specializations correlate with biological physiognomies and exigencies, comparative biologists who focus on how various animals have solved respiratory pressures, people who study respiration in birds and other animals and ornithologists who love and enjoy birds for what they are – profoundly interesting animals.

The idea of this book is to attempt to provide an appropriate ground for the discussion of modern PTHrP-related issues, and for the consideration of attentive speculation and comments on current work. It is designed to intersect all the usual lines of disciplines, providing a site for presenting pertinent investigations and for discussing critical questions relevant to the entire field, thus seeking to develop a new focus and new perspectives for all those concerned with PTHrP and its pathobiology.

There has been no mechanistic explanation for evolutionary change consistent with phylogeny in the 150 years since the publication of ‘Origins’. As a result, progress in the field of evolutionary biology has stagnated, relying on descriptive observations and genetic associations rather testable scientific measures. This book illuminates the need for a larger evolutionary-based platform for biology. Like physics and chemistry, biology needs a central theory in order to frame the questions that arise, the way hypotheses are tested, and how to interpret the data in the context of a continuum.The reduction of biology to its self-referential, self-organized properties provides the opportunity to recognize the continuum from the Singularity/Big Bang to Consciousness based on cell-cell communication for homeostasis.

This book provides a comprehensive and up-to-date account of the information available on the morphological, physiological and evolutionary aspects of specialized cells distributed within the epithelia of the airways in the vertebrates. A lot of work has been done on the cell and molecular biology of these cells which are regarded as as oxygen receptor neuroepithelial cells. These chemoreceptors which were conserved throughout evolution have neuroendocrine functions carrying their signals to the central nervous system. The chemoreceptor cells are sensors which detect the signal changes in the external and internal environments, and play a key role in the survival of various species. Studies addressed to the chemoreceptor cell systems in the airways are of great importance for investigating their response to changes in the oxygen and carbon dioxide concentrations in the environment since the future of the planet earth is being threatened by global warming and climate change. Praise for the book: ...This volume would be of special interest to researchers who are curious about the evolution of vertebrate respiratory control in general and the regulation of ventilation in nonmammalian vertebrates in particular. -Wayne L. Silver, Wake Forest University, in The Quarterly Review of Biology, Volume 85, Number 2

Gives an account of the morphologies of vertebrate respiratory organs and attempts to explicate the basis of the common and different structural and functional designs and stratagems that have evolved for acquisition of molecular oxygen. The book has been written with a broad readership in mind: students of biology as well as experts in the discipl