2.2 How animals interact with the environment is affected by their body size Willmer et al. (2000) classify desert animals in terms of the range of body sizes and the rate of evaporation (Figure 8). 2.4 Summary Adaptive hypothermia occurs widely in both mammals and birds, but the ability is scattered throughout different families: even within single families, some species show torpor and some do not, suggesting that the ability may have evolved independently many times. Whereas a number of small birds show a daily, shallow torpor, so far only the poor will has been described as showing extended bouts of torpor comparable to those seen in mammals. Species of birds and mammals that hibernate (Figures 2.1 Degrees of torpor Adaptive hypothermia occurs in at least six distantly related mammalian orders (Table 1) and in several orders of birds. There is a spectrum running from those species which can tolerate a drop in T
b by 2° C for a few hours, to the seasonal deep hibernators which maintain a T
b as low as 4° C for weeks on end. Learning outcomes By the end of this unit you should be able to: define and use, or recognize definitions and applications of, each of the bold terms; give definitions of the terms ‘hibernation’, ‘torpor’ and ‘adaptive hypothermia’, and the three physiological processes that underlie them; give examples of the diversity of the major groups of mammals and birds that contain hibernating species; describe the physiological changes occur 3.5 The structure of adipose tissue Since food is only available seasonally or intermittently at high latitudes, many arctic birds and mammals, including polar bears, Svalbard reindeer, arctic foxes, seals and walruses, naturally accumulate large stores of fat. The quantity of energy stored and the metabolic control of its use are finely adjusted to the habits and habitat of the species. This section is concerned with the cellular structure and anatomical organization of adipose tissue in such naturally obese species. Most labo 4.5.6 Catalyst deterioration: summary An ability to withstand mild deactivation is built into the design of the catalytic converter. However, severe deactivation could prevent the system from meeting emissions legislation. The major causes of deactivation are thermal damage and poisoning. High temperatures may cause sintering of the metals and/or the support; this can be prevented to some extent by the addition of ceria as a structural promoter. Damaging interaction 4.5.4 Phosphorus Phosphorus is recognised as a potential poison for automotive catalysts. The phosphorus level in fuel is generally very low (2×10−5 g l−1), but it is present in higher concentrations in engine oils (1.2 g l−1). Phosphorus derived from the engine oil is believed to react with the alumina support, and also to reduce the activity of the noble metal component. This deactivation is particularly important for Pd, with which phosphorus may form an all Introduction Ensuring good quality air is essential for the protection of public health. Governments worldwide have adopted a range of increasingly demanding measures to curb air pollution with a particular focus on the emissions from motor vehicles. An important part of this strategy has been the development of the three-way catalytic converter to remove exhaust pollutants such as carbon monoxide, unburnt hydrocarbons and nitrogen oxides. This unit takes an in-depth look at the construction of this conve 9.1 The psychological arena The examples in the previous section followed the traditional medical approach, namely that there is a disease, it can be diagnosed (identified), and the cause of the disease, be it viruses, bacteria, pathogens, genes or poisons, can be sought. This section moves away from the medical arena and into the psychological arena, where the symptoms are behavioural. In this case, the symptoms are socially unacceptable behaviour and to the list of causes just mentioned is added family circumstances a 7.8 Summary of Section 7 This section has sought to illustrate the formation of connections between neurons and their targets by exploring a few examples. The picture that emerges is one of cells at different stages of development subjected to a vast array of signals. These signals are the medium through which environmental factors exert their effects. To some of these signals, some cells respond; to other signals, other cells respond. What a cell, a neuroblast, a growth cone actually does is dependent on the combina 6.5 Summary of Section 6 Growth cones respond to proximal and distal cues. The proximal cues in the extracellular matrix or other cells affect adhesion and result in chemotactic guidance. Distal cues are also in the extracellular matrix but they diffuse through it and result in the growth cone either moving towards the source (attractants) or away from it (repellants). These distal cues are chemotropic cues and can have different effects on different growth cones; what may be an attractant to one growth cone may be r 4.4 Summary of Section 4 Two important points emerge from this section. The first is the powerful effect of maternal contact on the development and later behaviour of their charges. In the Feldman study the disadvantages of prematurity were essentially overcome by early maternal contact. The second point is that some behavioural traits really do run in families, without being genetic. The Francis study clearly showed that some aspects of Open Field behaviour were the result of nursing care. Learning outcomes After studying this unit you should be able to: recognise definitions and applications of each of the terms printed in bold in the text; critically evaluate statements about the influence of the genome on behaviour; explain the ways in which genetic and environmental factors influence the development of the nervous system; provide examples of the influence of genetic and environmental factors on the development of the nervous s 4.1 Introduction to minerals and why we need them Both vitamins and minerals are essential in the diet in small quantities and so they are often grouped together as micronutrients. Which items in the diet are classified as macronutrients? 3.5 Vitamin K Like vitamin E, vitamin K is fat-soluble and composed of a series of related compounds. Vitamin K is widely distributed in the diet (see Table 1) and it is absorbed from the small intestine with the assistance of bile acids. Vitamin K is also manufactured by the bacteria that inhabit the human large intestine and appears to be absorbed there too. The main role of vitamin K is in blood clotting. This process requires the presence of a number of different chemicals, called clotting factors, in 1.8 Enter aspirin! Aspirin is able to release part of its ester group (Figure 15) in a hydrolysis reaction. Look again at the structure of aspirin, 2.8, and identify this group on the molecule. It is known as an acetyl group and accounts for aspirin also being called acetylsalicylic acid. The acetyl group on aspirin is fairly easily removed and can be available for forming another ester with an —OH group on another molecule; in this case, part of the structure that makes up the inside of the cavi Learning outcomes After studying this unit you should understand: that genes are the units of inheritance for individual characteristics and also may contribute to susceptibility to certain diseases; the number of chromosomes that make up the human genome and where they are located within the cell; something of the immense scale of the human genome project; how gametes are produced by the process of meiosis and how the full complement of 46 chromosomes 5 Where does transcription occur in the cell? Up to now we have described the processes of transcription without considering where each occurs within the cell. Given that transcription — the production of mRNA — requires a DNA template, where do you think this process occur 5 Summary Section 1 Superconductivity was discovered in 1911, and in the century since then there have been many developments in knowledge of the properties of superconductors and the materials that become superconducting, in the theoretical understanding of superconductivity, and in the applications of superconductors. Section 2 A superconductor has zero resistance to flow of electric current, and can sustain a current indefinitely. The magnetic flux remains constant in a completel 2.3 The Meissner effect The second defining characteristic of a superconducting material is much less obvious than its zero electrical resistance. It was over 20 years after the discovery of superconductivity that Meissner and Ochsenfeld published a paper describing this second characteristic. They discovered that when a magnetic field is applied to a sample of tin, say, in the superconducting state, the applied field is excluded, so that B = 0 throughout its interior. This property of the superconducting s
Table 1 Groups o
Activity 24
SAQ 5
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Willmer, P., Stone, G. and Johnston, I. (2000) Environmental Physiology of Animals
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