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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
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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
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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
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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:


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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
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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
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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
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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
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4 Questions

Question 7

In what ways, if any, does the distance to a star influence its position on an H–R diagram?

Answer

The distance to a star does not influence it
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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.

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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
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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.

Question 1

Why not?


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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 (
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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).

Figure 8
Willmer, P., Stone, G. and Johnston, I. (2000) Environmental Physiology of Animals
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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:

Figures

Figure 2 Michael and Diane Porter, American Goldfinch, Ideaform Inc.;

Figure 3 Tom and Cathy Saxton, Hummingbird, Saxton.org.;

Fig
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References

Azzam, N. A., Hallenbeck, J. M. and Kachar, B. (2000) Membrane changes during hibernation. Nature, 407, 317–318.
Boutilier, R. G. and St-Pierre, J. (2002) Adaptive plasticity of skeletal muscle energetics in hibernating frogs: mitochondrial proton leak during metabolic depression. Journal of Experimental Biology, 205, 2287–2296.
Buck, C. L. an
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3.5 Arousal (continued)

Question 9

What alternatives to shivering might act as a source of heat?

Answer

BMR is maintained mainly by a number of tissues with high metabolic activity. One of
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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
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4.1 Insulation in terrestrial endotherms

For organisms of similar size and shape in a similar thermal gradient, the rate of heat loss from convection is up to 90 times as fast in water as in air, so in temperate climates, aquatic endotherms need much more efficient insulation than terrestrial species. Since seawater freezes at −1.9° C, but the temperature of the air around the Poles can fall below −50° C, the insulation requirements of aquatic and terrestrial polar animals are not very different. Nonetheless, there are impor
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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
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