5.2.1 The GM Science Review

The review was undertaken by the GM Science Review Panel, chaired by the Government's Chief Scientific Adviser, Sir David King. Its role was to assess the evidence available in the peer-reviewed scientific literature. The panel produced two reports, the first in July 2003 and the second in January 2004. The main conclusions of these reports are listed below.

  • The risk to human health is very low.

  • There is little likelihood of such plan
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2.3 The effect of interstellar gas

You have seen that the ISM has been studied through the radiation that the gas and dust absorb, emit and scatter. Figure 15 summarizes the differences between these three phenomena.

Let's first consider the three phenomena in relation to the gas. The gas scatters very little light and so we need only consider absorption and emission of radiation. You have already met absorption and emission of photons by atoms (which we shall call photoexcitation and photoemissio
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2.2 Interstellar space is not empty

The difference between the apparent brightness of a star (as measured by its apparent magnitude), and its luminosity (represented by its absolute magnitude) is defined by the distance of the star. We can explicitly state this relationship as in Equations B and C:

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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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1.2 The main classes of stars

The main classes of stars are shown in Figure 5.

The main sequence is ‘main’ in the sense that about 90% of stars fall into this class, and ‘sequence’ in the sense that it is a long, thin region that trails across the H–R diagram, covering a very wide range of temperatures and luminosities. The Sun i
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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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Introduction

We can study the individual properties of individual stars, such as photospheric temperature, luminosity, radius, composition and mass. If we wish to understand more about stars and obtain some insight into their evolution, we need to look at the overall distribution of stellar properties. We would like to know the answers to such questions as ‘Can stars have any combination of these properties?’ and ‘How many stars are there of each type?’ We can potentially learn a lot more about th
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References

Bozinovic, F., Gallardo, P. A., Visser, G. H., Ortes, A. (2003) Seasonal acclimatization in water flux rate, urine osmolality and kidney water channels in free-living degus: molecular mechanisms, physiological processes and ecological implications. Journal of Experimental Biology, 206, 2959–2966.
Bulova, S. (2002) How temperature, humidity, and burrow selection affect evaporative water loss in desert t
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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
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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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2.5.1 Summary of Section 2

Desert animals are classified in terms of their body size and physiology into three groups: evaders, evaporators and endurers. The logic for this classification is that the smaller the animal, the larger its surface area to volume ratio. Small animals therefore gain and lose heat faster than large animals, warming rapidly when exposed to intense solar radiation, and cooling rapidly at night. Small endothermic evaders, e.g. kangaroo rats, rest in cool microenvironments, e.g. shade or burrows,
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2.5 Behavioural strategies of endurers

Endurers are defined as large desert mammals such as oryx and camel, and large desert birds, ostrich and emu. The term ‘endurers’ suggests that these animals are forced to endure the extreme conditions of the desert climate because they cannot shelter from high T a and intense solar radiation during the day or low T a at night, as they are too large to hide in burrows or dens. Nevertheless, in spite of their size, endurers do take advantage of aspects o
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2.4 Behavioural strategies of evaporators

Willmer (2000) defines evaporators as animals that depend on sufficient water intake to enable them to cool T b by evaporation. Few of these species can survive in deserts, and those that do either live on the edges of deserts where they can access water, or have behavioural and physiological adaptations that reduce reliance on evaporative cooling. So for evaporators, evasion may be an important part of their thermoregulatory strategy. Evaporators include medium-sized mammal
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2.3 Behavioural strategies of evaders

Small animals, classified as evaders, include desert amphibians and reptiles, and also mammals, rodents and insectivores. The term ‘evaders’ refers to the animals’ behaviour, which helps to prevent overheating of the body on hot sunny days, and avoids the need for cooling by evaporative water loss, which is not feasible for small animals living in an arid habitat. Evaders make use of microenvironments such as shady rock crevices, underground burrows and shade cast by plants, for behavio
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Learning outcomes

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

  • define and use, or recognise definitions and applications of, each of the bold terms;

  • provide examples that show there is a continuum of desert climates and environments that link to diversity of flora and fauna;

  • explain, with examples, the thermoregulatory strategies of evaders, evaporators and endurers, and interpret relevant data;

  • describe the importance of integration of behavi
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Introduction

This unit is the first in a series of three on Animals at the extreme. It is concerned with the integration of behaviour anatomy, physiology and biochemistry in diverse vertebrates that live in deserts. Once you have completed this unit, you will be all the more able to appreciate the linked units that follow, Animals at the extreme: hibernation and torpor and Animals at the extreme: the polar environment. These units build on and develop some of the science you will stud
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6.7 Sleep, the brain and hibernation

There has been a popular misconception that hibernating animals are asleep when dormant, and that arousal during or at the end of hibernation involves waking analogous to that following deep sleep. Sleep in homeothermic animals can be divided into several phases, each with distinct patterns of electrical activity in the brain, as measured by an electroencephalogram (EEG). The passage into sleep is a transition from wakefulness into the stage called slow-wave sleep (SWS). SWS, and its c
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6.3 Metabolic regulation and the midbrain

As you found in the last section, the physiological evidence points to the likelihood that different components of regulation may be regulated separately. The hypothalamus, which appears to be central to the depression and recovery of body temperature during entry to torpor and arousal, is not the only player in the control of metabolic processes underlying non-behavioural thermogenesis. In many respects, the initiation of thermogenesis is the prime event in the reactivation of a cold body: t
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4.2 Arresting protein synthesis

The regulation of T b in hibernators has traditionally been viewed as the fundamental physiological process in hibernation. But recently, questions have been raised about whether thermal changes initiate or simply accompany metabolic depression. Is the metabolic inactivity of animal tissues during bouts of torpor or in hibernation, the cause or the result of hypothermia? A common-sense view is that temperature directly influences metabolism by regulating enzyme activity. Evi
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