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Energy is a currency common to all animals, and the suite of responses shown by insects to the environments they inhabit is dependent on the metabolism of substrates. This chapter deals largely with aerobic catabolism and gas exchange, although anaerobic metabolism, which is relatively uncommon in insects, is also discussed. Gas exchange is typically via spiracles and tracheae, with oxygen and carbon dioxide exchange being divided both spatially and temporally to varying extents. Discontinuous gas exchange is characteristic of several insect species and it is thought to have evolved either to limit water loss, prevent oxidative damage, improve gas exchange under certain conditions, or simply as the outcome of interacting feedback systems. These mechanisms have all proven controversial. Metabolic rate varies with temperature, size, activity, feeding, and time of day. Insects in flight have some of the highest metabolic rates so far measured in any animals, and the costs of transport in caterpillars are relatively high. Understanding metabolic rate variation may provide a key to understanding global patterns in diversity.

This chapter introduces the morphological characters that define the Class Amphibia and its three orders: Gymnophiona (caecilians), Caudata (salamanders), and Anura (frogs and toads). It defines the variety of morphotypes and characteristics that are related to the ecology of species, for each order. The physical principles that determine gas, solute, solvent, and energy exchange are described. Finally, an amphibian phylogeny is presented, and how it can be used to analyze and interpret physiological data.

This chapter explains the diverse ways insects manage to respire underwater. First, it reviews the basic principles of diffusion and the physical properties of gases, because this is instrumental to understanding how the various gas exchange systems function in aquatic insects. There are two main kinds of tracheal systems. In open tracheal systems, insects exchange gases in a gaseous state directly with atmospheric states or via a gas store, which they carry underwater. In closed tracheal systems, gas diffuses directly across the body surface where the integument is thin (cutaneous gas exchange). The general structure of these two systems and how gases move within them are described. Subsequent sections consider how insects with open tracheal systems have achieved independence from the atmosphere, followed by a discussion of the various morphological adaptations and behaviours insects may exploit to maximise cutaneous gas exchange. The final sections discuss what happens when environmental oxygen concentrations are very low and the use of respiratory pigments for blood-based gas exchange.

This chapter is intended to be an aide-memoire for the reader who wishes to be reminded of the normal state of the respiratory system before considering a particular symptom or condition. Descriptions refer principally to the adult lung. The basic features apply to children, but the dimensions and normal values are different. Topics discussed include ribcage, respiratory muscles, and respiratory ‘pump’; pleura, pleural space, and pleural fluid; airways; lymph; integration; airway resistance; pulmonary gas exchange; regulation of breathing; breathing during exercise; obesity; lung defence mechanisms; and lung inflammation.

Breathlessness is a basic symptom of heart failure. In spite of the importance accorded to the disease in giving insight to the severity of dyspnoea, heart failure has only been recently spoken of as a terminal disease. This chapter hence concentrates on the pathophysiology of breathlessness in heart failure and the palliative clinical management options for this symptom. Heart failure is the reduction of cardiac output and the increase in venous pressure. It is caused by several factors such as hypertension, coronary artery disease, valvular disorders, and cardiomyopathy. Among the indicators that suggest a failing heart are changes in the pulmonary haemodynamics, skeletal muscle, pulmonary function, gas exchange, and alveolar capillary structure. To counter breathlessness, palliative management approaches such as the induction of oxygen, opioids, beta-2 agonists, and benzodiazepines can be used. In addition to these pharmacological approaches, non-pharmacological methods such as introduction of exercises and improvement of the patient's morale are also crucial in the management of breathlessness in heart failure.

Respiratory discomfort or dyspnoea is the primary symptom of chronic obstructive pulmonary disorder (COPD) and is a prime contributor to the poor quality of life of patients diagnosed with this disease. This chapter examines the pathophysiology of COPD during rest and exercise to determine the origin of the symptom. It examines the relationship between dyspnoea and the ventilatory mechanisms and gas exchange in COPD, and also considers the possible neurophysiological underpinnings of this symptom.

According to the principle ‘before you can do what you want to do, you always have to do something else’, this chapter first delves into the basics of respiratory physiology. It begins with summarizing the physical gas laws and their physiological applications to the core process of respiration: diffusion. The chapter finally arrives at introducing the different gas exchange models that can be observed in the various lineages of animals and the basics of ventilatory mechanics. Equipped with this knowledge, it is hoped that the reader will better understand the functional and evolutionary discussions of the respiratory faculties in the following chapters.

This chapter introduces the ‘who has what’ in terms of respiratory organs for major water-breathing invertebrate groups. It begins with sponges and cnidarians—groups that have no recognizable respiratory faculty—and continues through the bilaterian lineage, pointing out how bits and pieces of a respiratory faculty accumulate. The most complex respiratory faculties are found in molluscs and arthropods, which consequently make up the bulk of this chapter. Aside from the ancestral aquatic respiration, this chapter furthermore explains how also within some terrestrial (air-breathing) groups such as arachnids and insects, mechanisms that allow lone—even permanent—stays under water have secondarily arisen.

Chapter 2 provides a general physiological background that will be further developed in subsequent chapters for mammals in particular. It first examines the importance of scaling effects of body mass to understand how this is inextricably linked to physiology, ecology and life history, and patterns of how animals work in their environment. Energy and thermal balance are then described, along with basic concepts for gas exchange that support the high energy lifestyle of endothermic mammals. Principles of digestion are then described, since this is the ultimate source of energy for animals; then water and solute balance are examined to complete the major physiological ‘systems’. Principles of locomotion are discussed, including lever mechanics for walking and running, and fluid dynamics for swimming and flying. The chapter concludes with a description of reproduction for egg-laying mammals (monotremes), and the differences for marsupials and placentals that have live birth.

The neural control of breathing or ventilatory movements has attracted much attention over the years because of the persistence and reliability of the underlying motor rhythm. The persistence derives from the obvious need to provide a continuous exchange of gases between the tissues of the body and the surrounding air. The drive maintaining the rhythm must thus come either from receptors that monitor the levels of carbon dioxide in the inspired gases or from some monitor of its level in the tissues. Probably both effects occur together but the receptors responsible are not well identified. Nevertheless, the ventilatory motor pattern can be recorded as readily from an isolated central nervous system as it can from an intact locust.

This chapter discusses gas exchange and other environmental responses of cacti. It focuses on net CO₂ uptake and examines the influence of three key environmental factors—temperature, soil moisture, and solar irradiation absorbed by photosynthetic pigments, i.e., the photosynthetic photon flux (PPF)—on CO₂ uptake by Opuntia ficus-indica. The response of net CO₂ uptake by Opuntia ficus-indica to these three variables is important for predicting its productivity under any environmental condition and serves as a model for assessing the net CO₂ uptake, and hence the potential biomass productivity, of other cacti.

This chapter focuses on the respiratory faculties of invertebrate air breathers. Although the partial pressure of oxygen in water is the same as in the surrounding atmosphere, the oxygen content per unit volume is around 30 times less due to its relatively low solubility in water. So it is no wonder that there is evidence for invertebrate animals on land as early as from the Palaeozoic. In spite of this apparent metabolic advantage, aside from some annelid groups, the only invertebrates to truly call dry land their home are some snails and arthropods. Among the latter, we see several independent origins of air breathing, and crustaceans present a particularly interesting study group in this regard. Arachnids and insects, on the other hand, were from the beginning terrestrial and air breathing, and insect tracheae form the most effective respiratory system going.

The Amazon, like smaller rivers, is the daughter of its drainage basin. Local climate and interactions over time with the template of topography, geology, and vegetation determine the size and flow of rivers. Likewise, the compositions of the particulate and dissolved materials carried by rivers result from initially similar rainwaters that have been uniquely imprinted by contact with almost every plant, animal, and mineral in the catchment. Rivers thus provide a continuously flowing signal, recorded by isotopes, ions and molecules, of the cumulative effects of drainage basin processes such as weathering, oxidation/reduction, gas exchange, photosynthesis, biodegradation, and partitioning. This recording is complementary to more classical methods of remote sensing based on electromagnetic radiation, but is composited over a wider range of time and space scales and includes effects of subcanopy and subsurface processes. The Amazon River is similar to other rivers in this regard, but is unusual in the size and extent of different environments its waters touch. The Amazon River is the world’s largest river and drains the world’s largest single catchment (~6,000,000 km2). It discharges an average of about 200,000 m3 of water per second to the Atlantic Ocean. This volume is about 5 times more than the Congo, the second largest river. The Amazon has 1100 major tributaries, three of which are nearly as large as the Congo. From its origins at about 5200 m in the Andes about 200 km from the Pacific Ocean, the Amazon goes through at least 10 name changes as it snakes its way 6500 km eastward to the Atlantic Ocean (Schreider and Schreider 1970). The flooded areas along the lower mainstem are important sources of greenhouse gases such as methane (Bartlett and Harriss 1993, Devol et al. 1994) and the latent heat release from convective precipitation in the basin is sufficient to influence global climate. The Amazon drainage basin contains 40% of the world’s tropical rain forest (dos Santos, 1987) and is home to countless species of plants and animals. The river itself contains some 2000 described species of fish.

Seagrasses grow by extending horizontal rhizomes which periodically grow vertical leaves and absorptive roots. Seagrass roots consolidate and stabilize the sediment. Seagrasses are limited to the depth to which light can penetrate for photosynthesis: a maximum of 200 m. Oxygen conductance through aerenchyma mitigates the problem of living in anoxic sediment. Seagrass tissues can exclude or tolerate salt. The environment is generally nutrient–poor: nutrients may be acquired through leaves as well as roots, and are efficiently utilized. Although most propagation is vegetative, seagrasses can reproduce sexually and have evolved methods of aquatic pollination.

A better understanding of what life is and how living organisms function has always been of crucial importance to humans, but ‘biology’ as a scientific discipline is quite young, the term being coined around 1800. Similarly, ‘respiratory biology’ as a discrete branch of biology is much younger and even today the term is not commonly used. However, the knowledge about life and the discovery and study of respiration as parts of other disciplines accumulated as a mosaic over the centuries. Some of the most important persons and their primary achievements in the field that we now call respiratory biology are summarized in this chapter.

Chapter 6 explores the physiological significance of gene duplication and hemoglobin isoform differentiation. Repeated rounds of gene duplication and divergence during the evolution of jawed vertebrates promoted the diversification of the subfamilies of genes that encode the different subunit chains of tetrameric hemoglobin, leading to functional differentiation between hemoglobin isoforms that are expressed during different stages of prenatal development and postnatal life. The differentiation in oxygenation properties among developmentally regulated hemoglobin isoforms has clear adaptive significance in viviparous and oviviparous vertebrates alike. In some cases, a physiological division of labor between coexpressed isoforms may also contribute to the adaptive enhancement of tissue oxygen delivery.

In the deep gravelly soils of the Bordeaux region, Seguin (1972) found vine roots at a depth of 6 m. Woody “framework roots” tend to be at least 30–35 cm be­low the surface and do not increase in number after the third year from planting (Richards 1983). Nevertheless, smaller diameter “extension roots” continue to grow horizontally and vertically from the main framework. They may extend lat­erally several meters from the trunk. These roots and finer lateral roots in the zone 10–60 cm deep provide the main absorbing surfaces for the vine. But in soils with a subsoil impediment to root growth, such as many of the duplex soils in south­east Australia (section 1.3.2.1), less than 5% of vine roots may penetrate below 60 cm (Pudney et al. 2001). Nor do vines root deeply in vineyards where irriga­tion supplies much of the vine’s water in summer. Plant roots and associated mycorrhizae (section 4.7.3.2) help to create soil structure. A desirable soil structure for vines provides optimal water and oxygen availability, which are fundamental for the growth of roots and soil organisms. The structure should be porous and not hard for roots to penetrate, allow ready exchange of gases and the flow of water, resist erosion, be workable over a range of soil water contents, allowing the seedlings of cover crops in vineyards to emerge, and be able to bear the weight of tractors and harvesting machinery with a min­imum of compaction. The quality of soil structure and its maintenance in vine­yards are discussed further in chapter 7. We might expect the soil particles described in chapter 2 simply to pack down, as happens in a heap of unconsolidated sand at a building site. However, if the sand is mixed with cement and water, and used with bricks, we can construct a building—a solid framework of floors, walls, and ceilings. This structure has in­ternal spaces of different sizes that permit all kinds of human activities. So it is with soil. Vital forces associated with the growth of plants, animals, and mi­croorganisms, and physical forces associated with the change in state of water and its movement act on loose soil particles.