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3.1 Introduction

The inner ear (Figure 3) can be divided into three parts: the semicircular canals, the vestibule and the cochlea, all of which are located in the temporal bone. The semicircular canals and the vestibule affect the sense of balance and are not concerned with hearing. However, the cochlea, and what goes on inside it, provides
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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
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Learning outcomes

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

  • distinguish between the major anatomical components of the outer, middle and inner ear;

  • describe the function of the outer, middle and inner ear;

  • describe the structure of the cochlea;

  • describe the structural arrangements of the organ of Corti and the function of the basilar membrane;

  • explain the difference between the four coding mechanisms used in order to transmit inform
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2.5 The uncertain Universe

Despite the impact of relativity, the greatest source of change in the scientific world-view in the twentieth century has undoubtedly been the development of quantum physics. This is the branch of physics that is mainly concerned with microscopic entities such as atoms and molecules, and their constituents. It is by far the most quantitatively accurate part of science, routinely providing predictions that are correct to just a few parts in a million. Quantum physics is also of enormous
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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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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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4.3 Assessing GM foods: substantial equivalence is introduced

In the early 1990s, biotechnology companies were preparing to market the first food products derived from GM crops. This provided a challenge to legislators. There were no precedents to guide them as to how to approve or ban novel food products. The methods used to approve pharmaceuticals, summarised above (Section 3.1), did not seem to transfer easily to whole food products.

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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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2.1 Introduction

There are at least three broad and overlapping areas of concern about GM crops. First, there is a concern that GM products might be detrimental to human health. These include concerns that:

  • The use of antibiotic marker genes might increase bacterial resistance to antibiotics. These concerns have led to the development of alternative selectable marker genes.

  • New proteins manufactured in GM crops might provoke unwanted allergic response
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2.4 The effect of interstellar dust

Let's now consider the dust. Photoexcitation (by absorption of photons) and collisional excitation (by atoms/molecules) occur in the atoms and molecules that constitute the surface of a dust grain. Much of this energy is shared throughout the grain, raising its temperature until thermal radiation from the grain balances the energy absorbed. An alternative fate for an incident photon is to be scattered (Figure 15), a process that is very efficient at certain wavelengths. Figure 20 illustrates
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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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5 Integrating across species

Populations of related species occupy similar niches in different environments. A big question for environmental physiologists is whether differences in biochemistry and physiology between related species living in different environments derive from physiological acclimatisation (sometimes referred to as phenotypic flexibility), phenotypic plasticity or evolutionary adaptation.

Recall from Section 3.3 how hoopoe larks, wild-captured from the Arabian desert and kept at T a
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3.1 Introduction

In mammals and birds, homeostasis, the provision of a stable internal environment, includes keeping certain physiological variables, T b, cellular and extracellular water and blood glucose at near constant levels. T b of reptiles varies with T a, but reptiles can only function over a limited range of T b. Nevertheless, vertebrate species live successfully in deserts, which are arid, have low productivity and extremes of <
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2.1 Introduction

The unique climate and topography of each desert links to the unique and characteristic flora and fauna found there. From the brief description of deserts provided in Section 1, you can appreciate that a desert provides a variety of niches for animals and plants. The term ‘niche’ applied to animals describes its role in a particular environment, and includes a number of characteristics such as habitat range, how the animal feeds, its diet, its environmental requirements and also its preda
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2.3 Hibernators as eutherms

Hibernating endotherms are not the easiest animals to study. Thus, until the late 1960s many biologists believed that mammalian hibernation was a process in which thermoregulation was simply ‘switched off’, following the receipt of a set of ‘cues’. These cues included a declining T a, a shortening daylength, the extent of body fat and a lack of food etc. With this model, the hibernator essentially becomes an ectotherm whose T b follows the T
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1 Hibernation and torpor: An introduction

This unit examines hibernation, a special form of adaptation that animals can make to the ecological demands of remaining in a chosen habitat in winter. Hibernation is a state which enables energy-efficient survival when ambient temperatures are so low that foraging or simply maintaining normal core body temperature and basal metabolic rate are either energetically too costly or impossible.

Polar endotherms can maintain a high T b even when living actively at sub-zero
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Introduction

This is the second in a series of three units on Animals at the extremes. In order to get the most from it, you should have previously studied Animals at the extremes: The desert environment (S324_1). After completing this unit you might like to complete the series by studying Author(s): The Open University

3.3.1 Dormancy in black and brown bears

The dormant state of bears differs from true hibernation in that the body temperature does not fall below 31–35° C and a major disturbance (such as an intruding biologist) can arouse them to full activity in a few minutes. Dormant bears do not eat, drink, urinate or defaecate, the heart rate drops from 50–60 beats min−1 to 8–12 beats min−1, and oxygen consumption is only 32% of that of actively foraging bears. Nonetheless, the rate of protein turnover, as mea
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4.5.5 Sulfur

Deactivation

The presence of sulfur in the exhaust gas mixture causes a reduction in the activity of the three-way catalyst, particularly for the water-gas shift and steam reforming reactions – processes that are important mechanisms for the removal of CO and hydrocarbons under fuel-rich conditions. Sulfur also decreases the efficiency of NOx removal. The deleterious effect of exposure to SO2 on the catalytic activity of a commercial monolithic cata
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4.5.3 The effect of poisons

The use of catalytic converters was one of the major contributors to the phasing-in of unleaded petrol. Lead in petrol is a severe poison for the catalyst, and there have been many stories, particularly in the early days of the converter, of people disabling the catalyst by misfuelling. Figure 25 shows how the activity
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