2.4 The atmosphere and polar ice

David A. Rothery Teach Yourself Planets, Chapter 6, pp. 66–75, Hodder Education, 2000, 2003.

Copyright © David Rothery

The Moon's atmosphere is almost as insubstantial as Mercury's, and probably has much the same origin. The Clementine mission returned our first clear views of the lunar poles, showing sites in particular near the south pole that are permanently in shadow, and which could therefore be places where ice might accumulate (Figure 1). Clementine'
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7 Ions and ionic bonding

This section returns to bonding – the way in which atoms are joined to each other. You have already met one type of bonding involving covalent bonds, which is found in molecules. However, this is not the only bonding found in compounds. In this section you will look at ionic bonding and the ionic compounds that contain such bonding. What is the main difference between the covalent compounds you met in Author(s): The Open University

3 What are compounds?

Activity 1: Elements and compounds

0 hours 10 minutes

Click on the video clip to watch Elements and Compounds, which focuses on water and its constituent elements.

Click below to v
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2 Britain's oldest rocks: remnants of Archaean crust

The document attached below includes the second section of Mountain building in Scotland. In this section, you will find the following subsections:

  • 2.1 Introduction

  • 2.2 The Lewisian Complex

    • 2.2.1 The nature, age and origin of the gneiss protoliths

    • 2.2.2 Deformation and high-grade metamorphism

  • 2.3 Basement inliers in the Moine Supergroup


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References

Barrow, J (1988) The World Within the World, Oxford.
Berkson, W. (1974) Fields of Force, RKP.
Cassidy, D.C., (1992) Uncertainty, New York.
Cohen, I.B., (1987) The Birth of a New Physics, Penguin.
Einstein, A et al. (1952) The Principle of Relativity, New Y
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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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1 The desert climate: An introduction

If you have visited a desert you will have noticed the sparse plant cover, or in certain sandy deserts, the almost complete absence of plant life. The low productivity of deserts derives from their defining feature, which is aridity. Scarcity of water restricts the diversity and amount of plant cover, and in turn the diversity and abundance of animals. However, if you were visiting one of the American deserts after rains, you would be rewarded by the sight of the desert ‘in bloom’, as vas
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6.4 Rapid-response genes and rhythmic neuronal activity

Reactive changes in the brain are usually marked by changes in neuronal electrical activity. If these changes are to be of long duration, adjustments in neuronal electrical behaviour may be made through changes in gene expression. Rapid-response genes (sometimes called ‘immediate-early’ genes) are activated within minutes of the onset of such sustained electrical activity. These genes are master controls, acting as a gateway to a series of linked events: alteration of electrical firing pa
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6.1 Introduction

Measurements of thermoregulation, respiration and metabolic depression in the edible dormouse (Myoxus glis) during the early stages of torpor, hibernation and aestivation, indicate remarkable similarities in the profile of physiological changes for all three adaptive phenomena, suggesting that they are controlled by essentially the same mechanism. The capacity for adaptive hypothermia in animals is clearly determined genetically and is manifested in cells from many different tissues. N
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5.4 Inspiratory drive

The supply of oxygen to tissues such as the heart, liver and WAT is, under euthermic conditions, invariably linked to and dependent upon local blood flow and pulmonary function. However, as we have already seen, under conditions in which blood flow is reduced to a trickle, the control of energy supply switches to local adaptations in the capillaries and tissue cells, including the oxygen affinity of erythrocyte haemoglobin, the supply and metabolism of respiratory fuels and the rate of protei
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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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4.1 Scientific approaches

Even after many years of research, the phenomenon of hibernation continues to be a mystery to scientists. Despite coming nearer to an understanding of how and why it happens, some fundamental questions remain unanswered. Is there a genetic basis underlying the evolutionary predisposition of animals to hibernate, given its occurrence in many groups of vertebrates and invertebrates? Is the problem of metabolic adaptation in cells separate from thermal regulation which occurs throughout the orga
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3.5.1 Final arousal

Emergence can be viewed as the final step in the series of periodic arousals. Instead of re-entering hibernation, the animal maintains the euthermic condition. The cue for maintaining this final arousal is probably not temperature, as some species emerge when T a is well below zero. It is also difficult to see how arousal could be affected by daylength, since the hibernating animal is usually underground in a cavity or a burrow. Perhaps fat or food stores reach a minimum lev
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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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2.2 Species showing torpor or deep hibernation

Among the birds, torpor occurs in a number of species in the orders Apodiformes (hummingbirds and swifts), Caprimulgiformes (nightjars, nighthawks, goatsuckers and poor wills) and Coliiformes (mousebirds). In all of the hummingbirds (family Trochilidae) studied to date, torpor, if it occurs, takes place on a daily (or more usually nightly) basis. They are able to re-warm themselves independently of T a and show an increased thermogenesis if T a falls below
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2.1 Degrees of torpor

Adaptive hypothermia occurs in at least six distantly related mammalian orders (Table 1) and in several orders of birds. There is a spectrum running from those species which can tolerate a drop in T b by 2° C for a few hours, to the seasonal deep hibernators which maintain a T b as low as 4° C for weeks on end.

Table 1 Groups o
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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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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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2.1 Nutrient budgeting

All plants and animals respond to environmental changes such as the light–dark cycle and temperature, but the impact of the environment on essential physiological processes such as eating, fattening and breeding is more evident and often more finely controlled in polar species than in those that are native to warmer and more equable habitats. Large effects are nearly always easier to quantify and to investigate experimentally, so arctic species offer an excellent opportunity to study the su
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4.2.1 Composition

The current three-way catalyst, shown schematically in Figure 1, is generally a multicomponent material, containing the precious metals rhodium, platinum and (to a lesser extent) palladium, ceria (CeO2), γ-alumina (Al2O3), and other metal oxides. It typically consists of a ceramic mono
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