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Summary

The ear is made up of the outer, middle and inner ears. The outer ear consists of the pinna, the external auditory canal and the tympanic membrane. The middle ear is air-filled and contains the middle ear ossicles. The inner ear is fluid-filled and contains the cochlea, the semicircular canals and the vestibule.

Sound in the external environment is channelled into the auditory meatus by the pinna and impinges on the tympanic membrane causing it to vibrate. These vibrations are transmitt
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3.3 The role of the basilar membrane in sound reception

So far we know that sound-induced increases and decreases in air pressure move the tympanum inwards and outwards. The movement of the tympanum displaces the malleus which is fixed to its inner surface. The motion of the malleus and hence the incus results in the stapes functioning like a piston – alternately pushing into the oval window and then retracting from it. Since the oval window communicates with the scala vestibuli, the action of the stapes pushes and pulls cyclically on the fluid
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2.5.3 The end of physics?

Suppose for the moment that quantum field theory, or string theory or M-theory, or some other theory no one has yet heard of, does turn out to be the much sought-after superunified theory. Suppose it is unique and is so wonderfully compact that it can be printed on the front of a T-shirt. What would such a theory really tell us about the world?

Looking on the positive side, the theory should indicate the fundamental entities of which the world is composed, whether they are particles, st
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5.1 Introduction

The first genetically modified organisms (GMOs) were created in the early 1970s, but for much of the 1980s biotechnology was a phenomenon confined to the laboratory. In 1988, ‘vegetarian cheese’, the first food product created using GMOs, was introduced in the UK. This cheese was produced using chymosin, an enzyme derived from genetically modified bacteria, rather than the traditional animal product (rennet). Chymosin derived from GMOs is now used to produce 90% of the hard cheeses
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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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2.2.1 Do GM crops pose unique problems?

It is perhaps overly simplistic to take the line that only ‘natural foods’ should be commended and that GM plants are unnatural. Arguably, very few of our modern foodstuffs can be termed ‘natural’, in that they are not derived from naturally evolved crops. Tremendous changes in genetic make-up have been achieved by conventional (i.e. non-GM) breeding methods. Traditional plant breeding involves selection of individuals seen as superior, and then crossing, i.e. transferring the pollen
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Learning outcomes

By the end of this unit you should be able to:

  • understand some of the social issues surrounding the development of GM crops;

  • better understand some of the social issues surrounding the development of GM crops, especially those that are ethical in nature;

  • better appreciated the disputed nature of the science that underpins GM crop development and how these relate to modern methods of assessing the safety of GM foods;

  • explain how the pu
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Learning outcomes

After studying this unit you should be able to:

  • describe and comment on the main features of a Hertzsprung-Russell diagram of stars in general, and of stars in a cluster;

  • outline a broad model of stellar evolution based on the observed properties of large numbers of stars, and describe how stars of different initial mass might evolve;

  • describe the effects of interstellar material on starlight, and outline some of the processes by which such material
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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:

Tables

Table 6 Williams et al. (2001) 'Seasonal variation in
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4.3 Cellular changes

Hibernation can result in the deposition of fat in adipose tissue. In tissues of finite size which are important sources of energy and sites for fuel metabolism, changes in cell structure (redistribution of organelles involved in energy metabolism and protein synthesis) are the most likely adaptation to a state of torpor. Liver hepatocytes of the hibernating dormouse (Muscardinus avellanarius), are visibly different from those of arousing and euthermic dormice when viewed in thin secti
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Introduction

This unit is the third in a series of three on Animals at the extreme. In order to get the most from it you should have previously studiedAnimals at the extreme: the desert environment (S324_1)andAnimals at the extreme: hibernation and torpor

This unit is from our archive and is an adapted extract from Animal physiology (S324) which is no longer taught by The Open University. If you want to study formally with us, you may wish to explore other courses we offer in <
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4.5.1 Introduction

In the UK, three-way catalysts must currently (1996) meet emission standards for a life of 50,000 miles; however, research efforts and legislation are set to double this requirement in the very near future to the current US standard of 100,000 miles. The catalysts do deactivate with use. Indeed the ability to withstand mild deactivation is built into the design of the catalyst, and into the entire emission control system in the vehicle. This is done by setting up vehicles at efficienci
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4.3.6 The role of CeO2

Figure 20 shows the effect on performance of adding CeO2 to a Pt catalyst for three-way catalytic conversion.

Figure 20
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4.4.1 Introduction

Since its development, the three-way catalyst has been exposed to the full spectrum of techniques available for the characterisation of catalytic materials. The data provided can be correlated with the results of activity tests and kinetic measurements, which provide information on the performance of the catalyst. This reveals that although the catalyst functions as a composite material, it can be divided into distinct groups of catalytic centres that provide several different types of site,
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4.1 Exhaust pollutants

The most important chemical reaction in a petrol engine – that is, the one that provides the energy to drive the vehicle – is the combustion of fuel in air. In an ‘ideal’ system, combustion would be complete so that the only exhaust products would be carbon dioxide and steam. In practice, the complete oxidation of the fuel depends on a number of factors: first, there must be sufficient oxygen present; second, there must be adequate mixing of the petrol and air; and finally, there must
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References

Blakemore, C. and Cooper, A. (1970) Development of the brain depends on visual environment, Nature, 228, pp. 477–8.
Caspi, A., McClay, J., Moffitt, T. E., Mill, J., Martin, J., Craig, I. W., Taylor, A. and Poulton, R. (2002) Role of genotype in the cycle of violence in maltreated children, Science, 297, pp. 851–4.
Caspi, A., Sugden, K., Moffitt, T. E., Taylor
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8.3 Lissencephaly

Lissencephaly, literally meaning ‘smooth brain’, is characterised by the absence of sulci and gyri, and by a four-layered cortex, instead of the usual six layers, with the majority of cortical neurons in layer four (Figure 22). Babies born with lissencephaly have a very poor prognosis; the disease proving lethal be
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8.2 Wilson's disease

The effects of a protein that is absent, or present but not doing its job, may not be evident for many years. This is called late onset, and is exemplified by Wilson's disease. Many molecules within the body require small amounts of minerals such as iron, magnesium or copper to function properly. There are mechanisms for absorbing these minerals from the diet. However, in excess, these same minerals can be toxic, as is the case with copper. So there are also mechanisms for getting rid
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10.4 Key points about minerals

  1. Certain minerals are required in the body.

  2. Some minerals form essential structural components of tissues. For example, calcium, phosphorus and magnesium compounds are major components of bones and teeth. Fluoride is also important in protecting teeth from decay.

  3. Sodium, potassium, calcium and chloride ions are important in maintaining the correct composition of cells and of the tissue fluids around them (homeostasis). These
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10.3.2 Fluid gain

In a normal diet, fluid is gained via food as well as in drinks. The amount of water in various foods is shown in Table 6. As well as plain water, most drinks, such as tea, coffee, juices and milk drinks, hydrate the body, but alcoholic drinks may not. Alcohol is a diuretic, a substance that increases the output of ur
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