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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2.1 The consequences of living in the trees

This unit contains a lot of detailed information about particular tree-dwelling mammals. You will need to take care not to get too absorbed in the fine details but to ensure that you take away the important overall messages. Those are, of course, listed as the learning outcomes at the beginning of the unit. Loo
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3 Is specialisation always advantageous?

Specialisation generally implies the possession of adaptations that make animals particularly effective or efficient in one or more aspects of their lives. In many of the examples used in other units in this series, mammals are likely to possess adaptations related to the acquisition and/or processing of food.

Que
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Introduction

In this unit, we will examine the biology of the impressive meat eaters (e.g. wolves, lions and cheetahs), focusing in part on the biological ‘equipment’ – slashing and gripping teeth, for example – and on the less obvious behavioural characteristics that have contributed to the undoubted success of these fearsome hunters. Many of the meat eaters live and hunt in groups, which raises intriguing questions about the advantages of group living and the types of social behaviour between in
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3.2 Adaptation

If you are working through the units in this series in sequence, you have already been introduced to the idea that many features of an animal's behaviour and structure are adaptations to their way of life. Unit S182_2 looked at the oily fur and the flipper-like feet of the water shrew, comparing the water shrew to the common shrew, a close relative that does not have these features and that does not chase prey under water. We also thought very carefully about the way that adaptations are desc
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2.1 Overview

In this section, you will meet some new units, the units in which energy is measured. Nowadays, there are internationally agreed units (called SI units) that are often used in combination with a prefix to show the scale of the measurement. The SI unit for energy is the joule (pronounced ‘jool’, and with the
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Learning outcomes

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

  • explain the implications of a seed/nut-eating habit;

  • suggest why rodents are a successful order of mammals;

  • describe adaptation, based on knowledge of the theory of biological evolution by natural selection;

  • explain how altruistic characteristics can be understood in terms of kin selection and inclusive fitness;

  • give examples of the fitness costs and benefits associated wit
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6.2 Opting out

This last section of the unit contains, I think, some of the most challenging science that you have met so far. Take it slowly, translating all the abbreviations in your head as you come to them (read BAT as ‘brown adipose tissue’, for example) and looking carefully at the graph in Author(s): The Open University

5.2 Body size and metabolic rate

Figure 6 is a slightly more complex graph than those used in S182_1. In particular, the masses of the mammals that are plotted on the horiz
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5.1 Introduction

If you have already worked through S182_1 Studying mammals: a winning design, you'll be aware (from Section 5) that animals break down their food for conversion into usable forms of energy; thus, breakdown of food is sometimes called (as in the commentary to the TV programme) the ‘internal fire’. Fire is a useful analogy because within the body, food is oxidised. This process is comparable to burning, but it is much, much slower and takes place in living tissue. Chemical energy rel
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3.5 Bats

There are two more activities in this section that give you more practice in writing. You will see that you are again given an approximate number of words to aim for in your answer. This number is a guide to the level of detail required – you will often find the same thing done in course assessment questions.
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6.2.3 Measurement of the angular distribution of the 3 K radiation

How are such angular distributions to be measured? One way, of course, is to take a radio telescope and swing it round the sky, taking readings in different directions. But as is clear from Figure 20(a), the atmosphere itself emits microwaves. There is therefore a grave danger, with this method, of picking up different contri
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5.2 The energy of electromagnetic waves

The energy density of an electric field E is

Although we will not prove it in this unit, a very similar result applies to magnetic fields. The energy density of a magnetic field B is

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5.1.3 Getting agreement with Faraday's law

Substituting Equation 7.21 into Faraday's law gives

This shows that a propagating electric wave is automatically accompanied by a transverse magnetic wave. The magnetic field oscillates in the y-direction, which is perpendicular to the direction of propagation and
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4.6 Postscript to Section 4

This section has considered a small number of chemical pollutants of water and has examined what is known about their harmful effects on animals, humans and the environment. You should be aware of a number of important general points that arise from what you have read. First, there is an enormous variety of chemical pollutants; you have read about only a few. Secondly, the evidence that chemical pollutants are potentially harmful is often more convincing from studies of animals than it is fro
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4.3 Mercury

Mercury is a naturally occurring metal which, in its pure form, is not particularly toxic. Under normal conditions of temperature and pressure, it is a silvery-white liquid which readily transforms into a vapour. When vaporised, it enters the atmosphere, remains there for a long time, and is circulated globally (WHO, 2005b). Through chemical reaction and precipitation it enters freshwater lakes and rivers, where it accumulates in the sediments at the bottom. Here it is transformed by bacteria
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3.6.2 Exponential increase: bacteria

Bacteria are single-celled organisms. Many different types of bacteria exist and they populate almost every environment on earth, from deep oceans to soil to human intestines. Several bacteria are beneficial to us: for instance, our gut bacteria can help to break down foodstuffs that we would otherwise find difficult to digest. However, some bacteria produce harmful toxins and if they grow in an uncontrolled way in our bodies this can have serious health consequences.

If a bacterium is
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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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2.2.2 Precision

Measuring the same sample should give the same result every time if the equipment is precise. In practice, the information displayed by a measuring device can depend on several factors (such as temperature and humidity) and can drift slightly over time. Nevertheless, during the time it takes to complete a measurement sequence, all measurements ought to remain within a specified, small margin of error, often marked on the equipment. We will see later on, in Author(s): The Open University

1.11 Addition and subtraction in practice – fluid balance

A common healthcare example that uses addition and subtraction involves calculating the fluid balance of a patient.

Fluid balance is a simple but very useful way to estimate whether a patient is either becoming dehydrated or overfilled with liquids. It is calculated, on a daily basis, by adding up the total volume of liquid that has gone into their body (drinks, oral liquid medicines, intravenous drips, transfusions), then adding up the total volume of liquid that has come out of their
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