2.1 Structure and function of the outer and middle ear Figure 1 is a diagram of the human ear. The outer ear consists of the visible part of the ear or pinna, the external auditory canal (meatus), and the tympanic membrane (tympanum) or eardrum. The human pinna is formed primarily of cartilage and is attached to the head by muscles and ligaments. The deep central portion of the
1 Sound reception: the ear In order to hear a sound, the auditory system must accomplish three basic tasks. First it must deliver the acoustic stimulus to the receptors; second, it must transduce the stimulus from pressure changes into electrical signals; and third, it must process these electrical signals so that they can efficiently indicate the qualities of the sound source such as pitch, loudness and location. How the auditory system accomplishes these tasks is the subject of much of the rest of this block. We will
2.6.2 End-of-unit questions Express the following numbers using scientific (powers of ten) notation: (a) 2.1 million (b) 36 000 (c) 1/10 (d) 0.00005 2.3.1 Thermodynamics and entropy The first half of the nineteenth century was a period of great economic and industrial growth. The steam engine, invented in the previous century, was becoming increasingly common in locomotives, mines and factories; power was becoming available on demand. A major priority for engineers was to produce more efficient engines, in order to deliver more useful power for less expenditure on fuel. Thermodynamics emerged as a study of the basic principles determining energy flows and the effi 5.3 GM Nation? The public debate The key objective of the national dialogue on GM was to allow the exchange of views and information – members of the public would presumably learn more about the issues; experts and policy makers would learn more of the reasoning behind the public's concerns. 4.7 Safety assessment today At the time of writing (2006), the descriptions of safety assessment for GM crops and derived products are far more rigorous than the vague prescriptions offered in the early 1990s (see Figure 2). This might be seen as an inevitable development as scientific knowledge increases and technology improves. However, that would only be part of the story. A fully rounded appraisal of the evolution of safety assessment in this field would have to acknowledge the huge part that both the direct critici 4.2 Scientific risk analysis In the context of national and international legislation on the safety of food and animal feed, much of the thinking about assessing risk has come from the experience of developing legislation to cover potentially toxic chemicals. In this regard, the terms ‘risk’ and ‘hazard’ are particularly important. ENTRANSFOOD (European network safety assessment of genetically modified food crops) has defined the terms as follows: 4.1 Introduction Pusztai and his team were attempting to develop suitable tests to assess the safety of GM potatoes. Typically, testing the safety of GM food involves comparing its composition and/or its effects with that of the conventionally produced food it most closely resembles. We have seen that such comparisons were at the heart of Pusztai's work. The comparison of GM and conventional crops and food has led to the so-called principle of substantial equivalence, which has been used extensiv 3.2 Communicating Pusztai's findings In mid-1998, the Rowett Institute released a succession of press releases describing Pusztai's findings. The safety, or otherwise, of GM foods was a hot issue at the time and his preliminary findings gained widespread publicity. Pusztai gave an extended interview to the World in Action TV programme ‘Eat up your genes’, broadcast in August 1998. He described some of his experiments and outlined his interpretations in ways that helped shape the general tone of the programme, which was highl 2.4.1 The second generation of GM crops Much of the present-day debate about GM plants centres around the existing range of GM crops, most of which have been engineered for herbicide tolerance or insect resistance (covered in unit S250_1 Gene manipulation in plants). One of the implications of this narrow commercial focus is that the benefit that such crops would bring, other than to those multinational companies that produce them, is by no means clear. Weighing up their value on some form of ethical scales might be unlikely 2.4 Can GM crops feed the world? The issue of global food security is at the heart of many of the ethical issues related to GM technology. United Nations population scientists estimate that the world's population will increase by 2 billion over the next 30 years, posing huge challenges for global food production. More than 842 million people are currently chronically hungry. Proponents of GM crops argue that further development of this technology is vital to meet this challenge. However, a more equal distribution of ex Introduction This unit is an adapted extract from the course Science in context
(S250) In recent years, scientists have made huge gains in their understanding of how genes can be altered and transferred from one organism to another – but that knowledge has been acquired amidst controversy and concern. The deep ethical concerns that have resulted from the emergence of genetic manipulation are explor 4 Questions In what ways, if any, does the distance to a star influence its position on an H–R diagram? The distance to a star does not influence it 1.5 Star clusters and stellar evolution Detailed observations of star clusters suggest that they occur because the stars in them form at about the same time. Moreover, the compositions of the stars are similar. Isolated stars (including isolated binary stars) result from the later partial or complete dispersal of a cluster. The crucial points for us here are that all the stars in a cluster formed at about the same time, and all have similar compositions. 1.3 How can we explain the distribution of stars on the H–R diagram? Here is a possible explanation for the concentration of stars into certain regions on the H–R diagram. It is based on the reasonable assumptions that: Any particular star is luminous for only a finite time; There are distinct stages between the star's cradle and grave, each stage being characterized by some range of temperature and luminosity; the star thus moves around the H–R diagram as it evolves; The stars we 1.1 Constructing the H–R diagram Three properties which are suitable for comparing stars are temperature, luminosity and radius. However, we don't need all three. Why not? 7 Conclusion In this unit we have studied animals in the context of their own habitat rather than using the traditional comparative physiology approach of comparing organ systems in different species. Although we have looked at extreme habitats, specifically deserts, it has become clear that, for many species, extreme physiological adaptations are not present and that even endotherms, birds and mammals rely on behavioural strategies, thereby reducing the need for physiological strategies that are costly i 3.4 Integration of anatomical features and biochemical and physiological strategies in endurers The endurers, large animals with a relatively low surface area: volume ratio, have problems in losing heat from the body when exposed to high T
a. Certain large lizard species behave like endurers, but they are evaders and evaporators too, a salutary reminder that we should not apply classification criteria too rigidly.
Dipsosaurus dorsalis, the desert iguana, lives in the Sonoran desert and is found most commonly in dry sandy areas where creosote bushes grow ( 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). Acknowledgements The content acknowledged below is Proprietary (see terms and conditions) and is used under licence. Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit: Figure 2 Michael and Diane Porter, American Goldfinch, Ideaform Inc.; Figure 3 Tom and Cathy Saxton, Hummingbird, Saxton.org.; Fig
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