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4.4 Genetic diversity and mass extinctions

It is for this reason that there are now international agreements on the need to work together to retain genetic diversity in all species and, more generally, biological diversity (species and habitat diversity).

Question 10

From a
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Learning outcomes

After studying this unit you should be able to:

  • Define and use, or recognize definitions and applications of, each of the terms in bold in the text.

  • Understand the complexity of the interdependence between organisms and their environment.

  • Describe some of the consequences for health of pollution.

  • Explain why it is difficult to gain international agreements to secure biodiversity and reduce pollution.


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4 4 Renewable energy sources

Fossil and nuclear fuels are often described as non-renewable because supplies are finite and will eventually run out. Renewable fuels are those energy sources that will not run out in the future.

Most renewable energy sources originate from the sun (solar energy), while tidal energy originates from the gravitational pull of the moon, and geothermal energy results from heat trapped below the surface of our planet.

Solar energy can be used directl
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Acknowledgements

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The material acknowledged below is contained in: Ordering the International: History, Change and Transformation (eds William B
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2.2 The origins of a rights discourse

In some form, the ideas of ‘rights’ and ‘justice’ could probably be found in all societies and cultures. They are moral concepts because they are concerned with moral ideals; with how things should be rather than describing how things are. However, the notion of rights now has a prominence in political debate in a way it has not had in other times and places. In the political thought of the ancient world, for example, a key question was how individuals could best contrib
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2.3 Divisions that matter: thinking through territories

Without losing our focus on the planet as a whole, it is time now to return to what Paani Laupepa from Tuvalu refers to as the ‘front line’ of climate change: those islands that are particularly vulnerable to rising sea level and associated climatic hazards (Lynas, 2003). It has often been said that low-lying coral islands like Tuvalu or Kiribas in the Pacific Ocean, or the Maldives in the Indian Ocean, are acting as a kind of early warning system for global climate change. Sea level is e
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1.1Aim

The aim of this section is to practise the use of diagramming techniques as part of a fundamental shift in interpreting issues – from an assembly of static objects to a network of dynamic relationships.


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5.1 Why is it important to be organised?

  • 87 per cent of items that are filed into a filing cabinet are never looked at again. STANFORD UNIVERSITY

  • In 2010, the world’s digital information output was estimated to pass 1.2zettabytes – A zettabyte is a new term which equals a thousand billion gigabytes. UNIVERSITY OF CALIFORNIA (BERKELEY)

  • A new blog is created every second. TECHNORATI

  • 10 per cent of salary cos
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4.3 R is for Relevance

Relevance is an important factor to consider when you are evaluating information. It isn’t so much a property of the information itself but of the relationship it has with your question or your ‘information need’. For example, if you are writing an essay about robotics a book or website about green energy would probably not be relevant. So there are a number of ways in which a piece of information may not be relevant to your query:

  • geographical
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4.2 P is for Presentation

By presentation, we mean, the way in which the information is communicated. You might want to ask yourself:

  • Is the language clear and easy to understand?

  • Is the information clearly laid out so that it is easy to read?

  • Are the fonts large enough and clear?

  • Are the colours effective? (e.g. white or yellow on black can be difficult to read)

  • If there are graphics or photos, do they help
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2.3.4 The contract team

The contract team is brought in from outside in order to do the project work. Here, the responsibility to deliver the project rests very firmly with the project manager. The client will find such a team harder to control directly. On the other hand, it is the client who will judge the success of the project, so the project manager has to keep an eye constantly on the physical outcomes of the project. A variant of this is the so-called ‘outsourced supply team’, which simply means that the
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2.3.3 The matrix team

In a matrix team, staff report to different managers for different aspects of their work. Matrix structures are often, but not exclusively, found in projects. Staff will be responsible to the project manager for their work on the project while their functional line manager will be responsible for other aspects of their work such as appraisal, training and career development, and ‘routine’ tasks. This matrix project structure is represented in Figure 2.


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7 Summary

Polymers are long chain molecules with properties dominated by their chain behaviour and the nature of their chemical make-up or constitution. The distinction between thermoplastics and thermosets has become rather blurred with the development of new materials for more demanding environments than previously. They include high performance polymers which are more resistant to high temperatures, possess greater moduli or strengths, and can be combined with additives to enhance their intrinsic pr
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4.3.4 Ionic polymerization

Free radicals are indiscriminate in the compounds they attack, and their non-selective nature in polymerization reactions leads to problems such as chain branching and transfer which affect the structure of the polymer produced. Anionic polymerization overcomes many of these problems.

A typical commercial (but also see Box 8
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4.3.2 Propagation

Once a small number of chains have been started, propagation involves successive addition of monomer units to achieve chain growth. At each step the free radical is regenerated as it reacts with the double bond. So in the case of styrene the propagation step is

The free radical can also add on in a
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4.3.1 Initiation

Initiation is the mechanism which starts the polymerization process. Vinyl monomers are quite easily polymerized by a variety of activating methods. Styrene, for example, can be converted to solid polymer simply by heating, and ultraviolet light can have exactly the same effect. Usually, however, an activating agent is used. This is an unstable chemical which produces active species that attack the monomer. A good example is benzoyl peroxide which splits up when heated:

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4.3 Chain growth polymerization

Chain growth polymerization is basically a three-stage process, involving initiation of active molecules, their propagation and termination of the active chain ends.


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3.3.3 Higher aromatics

Benzene rings can be fused in various ways to create component parts for some of the complex aromatic repeat units shown in Table 5. One of the most important is bisphenol A, made by fusing two phenol rings with acetone:

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3.1 Primary sources of synthetic polymers

The most important primary sources of synthetic polymers are crude oil, natural gas and, to a minor extent, coal. Because all are primarily fuels rather than sources of materials, the manufacture of polymers is susceptible to changes in price or supply. However, this is also true of other materials, since fuel costs are an important component of metal, ceramic and glass manufacture where very high reaction temperatures are needed for reduction of ore to metal and/or smelting. Where polymer ma
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2.3.1 Structural isomerism

In the saturated hydrocarbons, whose structural formulae are shown in Figure 16, it is not possible to form distinct isomers with just three or less carbon atoms linked together. There is only one way in which one carbon and four hydrogen atoms can be linked together, the single compound being methane, CH4. A simila
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