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Learning outcomes

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

  • explain how and why the optical spectrum of an active or starburst galaxy differs from that of a normal galaxy;

  • explain how and why the broadband spectrum of an active or starburst galaxy differs from that of a normal galaxy;

  • describe briefly the observed features of starburst galaxies and the four main classes of active galaxies (quasars, radio galaxies, Seyfert galaxies and blazars);


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References

References and further reading
Bodmer, W. (1985) The Public Understanding of Science, London, Royal Society.
Bown, W. (2005) Time to disengage. Editorial. Research Fortnight, 14 September 2005.
Council for Science and Technology (2005) Policy through dialogue: informing policies based on science and technology
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6.2 How DEMOCS works

DEMOCS games involve groups of around six to eight participants and take a couple of hours to play. They come as self-contained kits, which can be downloaded from nef's website. To register and log in for access to DEMOCS games, see http://www.neweconomics.org/gen/z_sys_DemocsRegister.aspx?destination=/gen/democsdownload.aspx, accessed 13 March 2007. Topics covered so far include stem cell research, over-the-counter genetic testing kits, xenotransplantation, pre-implantation genetic diagnosis
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6.1 Introduction

Reading 5 ends with a call for a move towards a more ‘deliberative democracy’ in which public engagement takes place in parallel with the development of new technologies, so that opportunities are provided for ongoing dialogue and influence between the two. To help to achieve this, the authors argue, ‘… now is the right time to start experi
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4 The GM Nation? debate

The UK's GM Nation? debate took place in the summer of 2003 – a time when both the political mood and scientific innovation had moved on a good deal in the eight years since the first UKNCC. Despite the relatively non-controversial introduction of the first GM products (notably a GM tomato paste and GM cheese) in the shops in the mid-1990s, public concerns grew in subsequent years. One particularly influential event was the arrival in the late 1990s of US and Canadian soya beans in Europe,
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9.2 Other hazards

9.2.1 Stumbles, falls, etc.

Such minor accidents are always possible, especially on rough or uneven terrain. It is recommended, therefore, that boots should be worn to protect the feet and ankles, and that outer clothing should be of a suitable nature to minimise the chance of cuts, scratches, and abrasions being sustained. Wearing gloves will minimise damage to hands.


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8.1 Syringes and sharps

  • Observe good laboratory practice by wearing gloves; latex or nitrile gloves are best.

  • Do not re-sheath needles or sharps unless unavoidable due to the nature of the work.

  • Remove scalpel blades with a specific scalpel-blade-removing tool.

  • Dispose of all syringes and sharps in designated containers (labelled ‘sharps’); when these are full they should be taken for commercial disposal
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3.1 Insect resistance

We will now look briefly at the science underlying the traits introduced into commercial crops, which you explored in Activity 1; a useful place to start is by considering how the property of resistance to insects is acquired by crops.

Insect damage causes huge losses of agricultural crops each year. For example, without co
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2.2 Using A. tumefaciens to genetically modify plant cells

Genetic engineers have capitalised on the fact that part of the DNA from the Ti plasmid of A. tumefaciens is integrated into the plant genome during the infection process. Ti plasmids can be isolated and a foreign gene spliced in at an appropriate point, making it possible to transfer the novel gene into the plant.

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Introduction

In recent years, scientists have made huge gains in their understanding of how genes can be altered and transferred from one organism to another – but that knowledge has been acquired amidst controversy and concern. The deep ethical concerns that have resulted from the emergence of genetic manipulation are explored in this unit. We begin with an examination of the basic structure and function of genes. A number of pioneering examples and techniques are explored, helping to explain why our p
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5 Summary of unit

We have seen in this unit that, despite having a high natural abundance, iron is in very short supply because of the insolubility of its oxides and hydroxides. A result of this is that organisms have developed methods for the uptake, transport and storage of iron. Bacteria, in particular, secrete very powerful iron chelators known as siderophores. Of all the iron–siderophore complexes, the iron(III)–enterobactin complex has the exceptionally high stability constant of 1049 mol<
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4.2 Iron transport

It is obvious that iron must be transported around the human body. Firstly, it must be transported from the food in the gut to the places where it is required. Mostly, iron is required in the bone marrow, where red blood cells are formed. Red blood cells have a finite lifetime of about only four months, and old cells are destroyed, usually in the spleen. Iron from the destruction of these cells is then transported from the spleen back to the bone marrow to be recycled.

Iron cannot be tr
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2.1 The problems of iron uptake

Iron has a high natural abundance. It is the second most abundant metallic element by mass in the Earth's crust (7.1 per cent).

Activity 1

What are the main oxidation states of iron?


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3.6.2 Experiencing the pregnancy

If a woman does find herself pregnant, what can she expect? Pregnancy is a time of enormous physical and emotional changes, and these are often difficult to cope with. To begin with, the physical effects of early pregnancy can be extremely unpleasant. The nausea and vomiting of morning sickness can be very severe, and although in many women the symptoms abate after a while, in others they persist right through the pregnancy. Sickness is thought to be due to the high levels of progestogen circ
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3.4.2 Compaction and adhesion

Around the time of the 8- to 16-cell division, the conceptus undergoes a morphological (shape) change, called compaction, in which the cells fatten on each other, and the outlines of individual cells become hard to distinguish. This stage, sometimes referred to as a morula, from the Greek word for mulberry, is shown in Figure 17i. At this stage it is hard to see individual cells; in fact, unless the cells are separated by various laboratory treatments, it is not possible to see the two
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2 Summary of Section 4

  1. Gametes are special cells because they contain only one set of chromosomes instead of the more usual two sets.

  2. The chromosome number is halved by meiosis.

  3. The crossing over and random assortment of chromosomes in meiosis produces a unique set of genes in every gamete, and thus in every individual (except for identical twins, who are derived from the same conceptus).

  4. Sperm production involves many rounds of
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4.6 Hormonal control of egg production

As you can see from the preceeding section, hormones play a crucial role in the maturation of the oocyte. Figure 3 showed you how levels of oestogen and progestogen vary throughout the menstrual cycle, and suggested that hormone balance is important for a woman's fertility, but you can now see how subtle the control really is. Cells have to develop sensitivity to hormones at the times when the hormones are likely to be present, otherwise the entire operation will fail.

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4 Summary

  1. Many rivers are fed by springs, which occur at points where groundwater reaches the surface. Springs can occur in different geological settings, forming valley springs, stratum springs or solution channel springs.

  2. The water in a river originates from overland flow, from interflow and from baseflow. Baseflow forms a higher proportion of river water in summer than in winter, and in rivers flowing over good aquifers.

  3. River discharg
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3.4.4 Sediment filling

The lifetime of reservoirs can vary greatly. Many reservoirs have lasted for over a hundred years, but some may be useful for only a much shorter period—fifty years or so — not because of the general deterioration of the dam as it gets older, but because sediment accumulates in the reservoir. Rivers carry large amounts of mud, silt and sand in suspension, particularly during floods, and when a river enters a reservoir it slows down and the sediment carried in suspension is deposited on th
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