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2.5 Tree squirrels

Coevolution also underpins the relationship between many tree squirrels and the trees that house them. The creation of food caches as a ‘winter-larder’ is mutually beneficial, partly because squirrels are sufficiently profligate in their habits to ensure that many stores are overlooked. Stealing by neighbours is so common that such over-provision may be essential – it's not through forgetfulness or lack of skill; grey squirrels appear able to detect nuts buried as deep as 30 cm below th
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8.1 Introduction

You know by now that plants can synthesise all the complex molecules that make up their tissues and seeds from very simple molecules – water, carbon dioxide and minerals from the soil. Mammals, on the other hand, need to take in many complex molecules ready-made, and some foods do not contain the right amounts or the right mix of nutrients. They have evolved various strategies to overcome the shortfalls, some of which are described in this section.


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5.3 Hindgut fermenters

The odd-toed ungulates (comprising the order Perissodactyla), the horses, tapirs and rhinoceroses, are hindgut fermenters, as are elephants. Update Table 2 with this information. These animals have a relatively simple, small undivided stomach, but this time an even larger caecum and colon where the microbes are housed and whe
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4.2 Digesting cellulose

Figure 3 in this section contains a lot of information and many terms that are probably new to you. Set aside the detail for the moment, read
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4.1 A brief digression about digestion

There are many new scientific terms introduced in this unit. Are you making your own lists of them? If you were to encounter these terms in a fresh context (perhaps on a website, or during your own reading around these subjects), your aim should be not just to recognise the terms, but also to understand their m
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2 The herbivore lifestyle – living on leaves

Leaves are a much less nutritious food than most kinds of animal material, so large herbivores have to eat large quantities of plants and they have special ways to digest their food. As author David Attenborough (DA) says, ‘Leaves are extremely poor food’ [p. 89]. To find out why living on a diet of leaves is particularly difficult, we need to know something about how leaves work.


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Learning outcomes

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

  • describe the particular problems in digesting plant material;

  • give examples of the ways in which teeth are modified for a herbivorous diet;

  • explain the importance of digestive enzymes;

  • explain the importance of microbes in digesting plant material;

  • compare the main features of the digestive systems of ruminants and hindgut fermenters;

  • describe some of the way
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3.4 Competition

In plants it is particularly obvious that many more potential offspring (seeds) are produced than can survive. To a very large extent it is a matter of chance as to which are the survivors. Some are eaten, others overlooked or stored away and forgotten. Those that survive to germinate might be on unsuitable soil, too dry or too wet, so that they shrivel or rot. The successful seedling could be in poor soil, deficient in minerals, or there may be many other plants that are already established
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3.1 Introduction

How evolution proceeds is obviously of central importance when studying mammals. Of fundamental importance to the way evolution works is the notion of natural selection, and in S182_3 Studying mammals: chisellers I'll be talking about what most researchers regard as this ‘single most important idea in biology’. But before that, I want to describe some of the adaptations evident in insect eaters.

From your reading of LoM you'll appreciate that natural selection promotes the ev
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Learning outcomes

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

  • describe the characteristics of light emitted by stars, and hence the information of cosmological interest that can be deduced from it;

  • distinguish between true and false statements relevant to the distribution and motion of stars within galaxies, and of galaxies within clusters and superclusters;

  • outline the methods used for estimating the distances to stars and to galaxies;

  • explain and
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7 Unit summary

Section 2

The law of conservation of charge applies locally at each point and time, so any variation of the total charge within a closed surface must be due to charges that flow across the surface of the region. This principle leads to the equation of continuity:

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6 Appendix: a note on displacement current density

This appendix is optional reading. It is included for the sake of comparison with other texts.

The Ampère–Maxwell law,

is sometimes expressed in the form


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Introduction

This unit examines why water shortages are predicted as a result of the world's growing population and the importance of access to clean and safe drinking water in public health. It looks at the distribution of water throughout the world and problems with contamination, topics of wide general interest.

Introducing health sciences: a case study approachI (SDK125)


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3.6.1 Radioactivity and bugs!

Many natural processes involve repeated doublings or halving at regular intervals. You may have come across this already in your work, in the context of bacterial growth or radioactivity. In this section, we are going to look in more detail at bacterial growth and radioactivity and we will be using graphs to examine how the numbers of bacteria or numbers of radioactive atoms change over time.


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2.6 The surface

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

Copyright © David Rothery

Look at the Moon even with the unaided eye, and you will see that it has dark patches on a paler background (Figure 2). This simple observation picks out the two distinct types of crust on the Moon. The paler areas are the lunar highlands, and the darker areas are the lunar ‘seas’ or maria (singular: mare). Both the highla
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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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2.3 Missions to the Moon

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

Copyright © David Rothery

The Moon was the first extraterrestrial target for space missions. Probes have been directed towards it since almost the very dawn of the space age (see below), and it was the main focus of the 1960s–1970s ‘space race’ between the USA and the then Soviet Union. In the end, only NASA attempted to put people on the Moon, and the six suc
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2.1 The Moon

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

Copyright © David Rothery

In this chapter you will learn:

  • about the nearest planetary body to the Earth

  • about the long record of impact cratering on its surface, and about the ancient eruptions that flooded many low-lying areas.

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1 Observing the Moon

Activity 1

0 hours 30 minutes

Try to make out features on the surface of the Moon, even if you have no optical aid available. If you have the use of a pair of binoculars you will probably
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Learning outcomes

After studying this unit you will be able to:

  • retrieve, evaluate and interpret data and information about the Moon, so that (for example) using a close-up picture of the Moon's surface you could identify the types of feature visible and recognise the processes responsible for creating them;

  • interpret simple tables;

  • express, manipulate and compare very small numbers.


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