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4.1 Introduction

Domestication of dogs and of most other livestock took place so long ago that reconstructing the course of events is extremely difficult. Written records and illustrations describing the origins of many modern breeds are also sparse until the 19th century. We can only guess at what the domesticators were aiming to produce and how and when domesticated traits appeared in the species subjected to artificial selection. However, a little-known experiment on the domestication of red foxes (Vulp
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3.1 The origins of domesticated dogs

Archaeologists and biologists agree that dogs (Canis familiaris) were the first species to become domesticated. Francis Galton, Darwin's younger cousin, suggested at the end of the 19th century that domestication began when humans captured and raised wolf puppies. The resulting adults ate scraps of human food, assisted in hunting and acted as guard dogs around camps. Among the evidence in support of this hypothesis is the observation that tribal people all over the world take wild anim
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2.3 Skin pigmentation and pattern

Most domesticated livestock differ from their wild ancestors in the colour and pattern of the skin, hair or feathers.

SAQ 10

  • What gene-associated
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Learning outcomes

When you have completed this unit you should be able to:

  • define the terms ‘artificial selection’ and ‘domestication’ and explain the relationship between artificial and natural selection;

  • describe some forms of dwarfism in modern breeds of dogs and explain their relationship to dwarfism in humans and in modern and extinct wild mammals;

  • describe some features of the skin, fur, feathers and the shape of the head frequently observed in domestic
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3.2 Angular size, actual size and distance

The angular size of an object is determined uniquely by its actual size and its distance from the observer. For an object of fixed size, the larger the distance, the smaller the angular size. For objects at a fixed distance, the larger the actual size of an object, the larger its angular size. For objects with small angular sizes, such as typical astronomical objects, the precise relationship between angular size, actual size and distance is well approximated by th
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3 Measuring the Sun

Section 2 referred to observations that can only be made using sophisticated telescopes, but this section turns to an observation you can do yourself. There are two reasons for this: one is to give you experience in scientific measuring and the other is to introduce some terminology that astronomers use frequently.


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1.3 Beyond visible light

During the twentieth century, astronomers extended their capabilities by developing telescopes and detectors that were sensitive to radio waves, microwaves, infrared and ultraviolet radiation, X-rays and gamma rays. All these forms of electromagnetic radiation, along with visible light, are emitted by the Sun.

Figure 6</span><br><span class=Author(s): The Open University

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1.1 The Sun at visible wavelengths

The Sun is seen as a blindingly bright, yellow object in the sky. The part of the Sun that you normally see is called the photosphere (meaning ‘sphere of light’); this is best thought of as the ‘surface’ of the Sun, although it is very different from the surface of a planet such as Earth. Its diameter is about 1.4 million kilometres, making the Sun's volume roughly one million times that of the Earth. The photosphere is not solid. Rather, it is a thin layer of hot gaseous mater
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1 Observing the Sun

Safety warning

Never look directly at the Sun, either with the unaided eye or through spectacles, binoculars or a telescope. You risk permanently damaging your eyes if you do so.


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Learning outcomes

At the end of this unit you should:

  • know about the electromagnetic spectrum and how it is used to infer properties of sources of radiation;

  • know about the range of sizes, distances and motions of objects in the Universe and how they can be measured;

  • know about the structure of, and the main processes operating in, the Sun;

  • comprehend concepts lying well outside everyday experience, including those that involve very large and very smal
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Acknowledgements

The content acknowledged below is Proprietary (see terms and conditions) and is used under licence.

Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit:

The content acknowledged below is Proprietary and is used under licence.

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5.3.4 Aye-ayes

Perhaps with good reason, the aye-aye has been dubbed by some ‘the strangest of all primates’ and LoM provides some of the reasons [p. 243]. Little wonder that, as DA points out, the species was first classified as a rodent like them, it has powerful incisor teeth that grow continuously.

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5.5.2 Indris and sifakas

Both indris and sifakas are unusual amongst lemurs in that they are active largely by day. Leaves are their primary food. They have a specialised form of locomotion, best described as ‘vertical clinging and leaping’ and the leaps they can take, using their powerful legs, can be up to 10 m. DA describes the bounding movement of sifakas when they are compelled to come to ground. (If you go back to the previous video sequence that shows this strikingly white species – the so-called silky s
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5.2 Madagascan diversity

Activity 7

Watch the video sequence below, which focuses on just three lemur species – the ring-tailed (in a very brief sequence, leaping from one tree to another), the golden bamboo lemur, already mentioned, and the sifaka, plus the
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4 Galagos, lorises and pottos

Activity 6 is divided into several parts, on successive pages, and asks you to answer a number of questions. Look ahead to this activity now and highlight, or list, the different ‘process’ words, which tell you what you need to do with the content You should have found ‘describe’, ‘contrast’, ‘eva
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2.3 The colugo

In LoM, DA vividly describes one particular evolutionary development associated with tree dwelling – taking to the air [pp. 221–227]. The gliding habit evolved independently in different mammalian lineages and yet the anatomical modifications that allow it are similar in, for example, flying squirrels and the unrelated colugo. In particular, the ‘sail of skin’ [p. 221], technically termed a patagium, stretches between the limbs – and a good deal further in the colugo, acting as an e
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2.2 The kinkajou

LoM describes this tree dweller as a relative of the raccoon. It belongs to the order Carnivora and is one member of a family generally referred to as procyonids [p. 170], or more commonly the raccoon family. You'll be aware that some members of this family – for example, coatis [p. 174] – are omnivores. As you'll see in the video sequence below, coatis are more typically found in the undergrowth and leaf litter, rather than high up in the trees. (If you need to remind yourself of the lif
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Introduction

This unit will introduce you to the wide-ranging types of mammals that live in the trees. You will learn how they thrive in this demanding environment, with the help of a range of intriguing adaptations related to their unusual life-styles.

This is the eighth in a series of units about studying mammals. To get the most from these units, you will need access to a copy of The Life of Mammals (2002) by David Attenborough, BBC Books (ISBN 0563534230), and The Life of Mammals (
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7 The threat of extinction

DA ends his book by writing eloquently of the dangers of extinction faced by mammals, from habitat loss as we exploit our environment to produce more and more food, for our growing population. However bleak the picture, there is still time and opportunity to save mammal species from extinction. Although bison in the USA and Canada were reduced to barely 1000 individuals in 1900, their numbers have now risen to well over 150 000 thanks to the efforts of First Nation indigenous peoples, and ran
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