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1.1 Popular conceptions about addiction and neural ageing

First of all, consider the following statements found in popular information media:

  • Some addictions are in the mind, like that to shopping, gambling or the internet, whereas others are in the body, like an addiction to heroin, alcohol or food.

  • Once you have tried cannabis, you are hooked for life. The craving for cannabis will never go away.

  • The thinking patterns of an addicted brain can never be changed.

  • Sm
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Introduction

The material presented in this unit is taken from SD805 ‘Issues in Brain and Behaviour’ – a 60-point postgraduate course within the Frontiers in Medical Science strand of The Open University's M.Sc in Science Programme. SD805 consists of two topics that are of immense worldwide social, economic, ethical, and political importance – ‘Addiction’ and ‘Author(s): The Open University

2.5 Summary of Section 2 and questions

  • In an astronomical spectrograph light may be dispersed using either a prism, a reflective diffraction grating or a volume phase holographic diffraction grating.

  • The grating equation quantifies the amount by which light of different wavelengths is dispersed by a grating having a particular groove spacing.

  • In a spectrograph, light is first collimated before passing through the dispersive element, and then focused by a secon
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2.1.3 Reflective diffraction gratings

Although the above description of diffraction has been in terms of light passing through a series of slits in a (transmission) diffraction grating, the type of grating which is currently most common in astronomy is a reflective diffraction grating or reflection grating. This again exploits the wave properties of light, in this case by making adjacent sections of a wavefront travel extra distances as it is reflected off a non-uniform surface. The non-uniform surface is actually a
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1.7 Summary of Section 1 and questions

  • Converging lenses or mirrors cause parallel beams of light to be brought to a focus at the focal point, situated at a distance of one focal length beyond the lens or one focal length in front of the mirror. Diverging lenses or mirrors cause parallel beams of light to diverge as if emanating from the focal point of the lens or mirror. Light paths are reversible, so a converging lens or mirror may also act as a collimator and
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1.5.5 Point spread function and angular resolution

The image of a point-like source of light (such as a distant star) obtained using a telescope will never be a purely point-like image. Even in the absence of aberrations and atmospheric turbulence to distort the image, the image of a point-like object will be extended due to diffraction of light by the telescope aperture. The bigger the aperture, the smaller is the effect, but it is still present nonetheless. The intensity of the image of a point-like object will take the form shown in
Author(s): The Open University

1.4 Reflecting telescopes

A lens is not the only object that can collect and focus light and thus produce visual images. People have known about and used mirrors for much of recorded history, but it took no less a genius than Isaac Newton to realise how a curved mirror could be used to construct an optical telescope, and that this would overcome some of the most important shortcomings of refracting telescopes.

As noted earlier, a concave spherical mirror will reflect parallel rays approaching along its ax
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Learning outcomes

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

  • understand the application of basic principles in geometrical optics;

  • appreciate the phenomena relating to the wave nature of light.


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2 SAQs

Question 1.1

Read the following account and then state which strategy from Table 1.1 it best fits.

While freezing is lethal for most organisms, one group of organisms is unaffected by it. Water-bears or tardigrades (phylum Tardigrada)
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1.5.3 Summary of Section 1.5

  1. Some annual plants and insects can spend the winter at juvenile stages, such as seed, egg, larva or pupa. Butterflies in Britain display a variety of juvenile overwintering strategies.

  2. Migration often results in high mortality, but completion of the journey results in higher breeding success, due to increased availability of food and fewer competitors.

  3. Birds increase their body mass, sometimes by up to 50%, prior to migration. T
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1.5.2 Strategy 4: migration (‘go away’)

About 40% of the bird species that breed in Britain do not spend the winter there but migrate south, some to southern Europe, others much further afield. The swallow (Hirundo rustica), for example, may migrate as far as the Cape of southern Africa. From one perspective, migrants are European species that avoid the northern winter by migrating to a less severe environment. On the other hand, the swallow can also be regarded as an African bird that migrates to northern latitudes to breed
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1.5.1 Juvenile survival

For organisms that are able to complete their life cycles within a year there is the possibility of spending the winter in various juvenile stages. We have already considered annual plants, the adults of which may die before the onset of winter, with seed not germinating until the spring. Surviving the winter as seeds has the advantages that the seeds are robust, and because they have a low water content they are less affected by freezing temperatures. Disadvantages of this strategy include t
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1.4.5 Summary of Section 1.4

  1. Deciduous trees avoid the problems of winter by shedding their leaves.

  2. Plants can store nutrients over winter in a variety of structures.

  3. Amphibians have evolved behavioural responses (e.g. burying themselves) and physiological responses (e.g. different types of antifreeze in the body fluids) to winter.

  4. Hibernation occurs only in certain small mammal species and one species of bird and is accompanied by marked phy
    Author(s): The Open University

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1.4.4 Hibernation in mammals

Many animals become inactive for periods of varying duration during the winter and there is a diversity of terms used to describe this state, including: sleep, torpor, dormancy, lethargy and hibernation. The word hibernation is often used loosely to refer to general inactivity but, in biology, it refers to a specific phenomenon, sometimes called ‘true hibernation’. Hibernation is defined as the condition of passing the winter in a resting state of deep sleep, during which metabolic
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1.4.3 Freeze tolerance in ectothermic vertebrates

In Britain, the vertebrate class Amphibia is represented by frogs, toads and newts. Amphibians are ectotherms, meaning that they are unable to generate large quantities of heat within their bodies, so their body temperature is close to that of their surroundings. The majority of amphibian species avoid the lethal consequences of being frozen, by digging their way under a large object, such as a rock, or deep into the soil, below the level that is penetrated by frost. There are some species, h
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1.4.2 Winter storage in plants

Many plants that survive winter in a dormant state form storage organs below the ground which store nutrients during the winter, the rest of the plant withering away. Storage organs come in a variety of forms, including tap roots, bulbs, corms, rhizomes, root tubers and stem tubers (Figure 13). In the carrot, the root is greatly enlarged into a fleshy tap root; the bulbs of onions are modified leaves; crocus corms, iris rhizomes and dahlia tubers are modified stems, and the tubers of potatoes
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1.4.1 Deciduous trees

During the winter months, a combination of factors, including lower temperatures, reduced light intensity and shorter days, means that plants can only photosynthesise at a slow rate and for restricted periods. As a result, photosynthesis cannot produce energy as fast as respiration expends it. In addition, water is often in short supply because of freezing, and so plants that do not have adaptations to conserve water, as conifers do, would lose water. Deciduous trees avoid these problems in w
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1.2.5 Summary of Sections 1.1 and 1.2

  1. The majority of organisms are exposed to environmental fluctuations, including seasonal change in climate. In this unit, we focus on the effects of winter.

  2. Organisms have evolved a range of strategies to cope with winter. Thus this common environmental variable has led to a diversity of responses.

  3. The strategies for coping with winter can be considered with respect to different levels and types of explanation.

  4. Mol
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1.2.4 The evolutionary level

Life histories and trade-offs

In this section, the emphasis switches from proximate (molecular, cellular, physiological and behavioural) types of explanation to ultimate types of explanation. In order to proceed, we need to understand two key concepts: life history and trade-off. Both of these concepts are important tools in organising thoughts about why organisms are so diverse. An organism's life history is the set of key biological events in its life, including b
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Cover of Suffragette pamphlet

The National Archives UK posted a photo:

Cover of Suffragette pamphlet

Women's Movements. Women's Labour League, Suffrage; various material on women workers


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