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1.6.2 Metamorphic recrystallisation

To consider metamorphic recrystallisation at its simplest, let's begin by imagining a sedimentary rock composed entirely of quartz grains – a quartz sandstone. Sandstone is a sedimentary rock and so has a fragmental texture (see Figure 7b). When it is subjected to high temperature and high pressure n
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1.6.1 Causes of metamorphism

What natural process could cause a rock to be heated?

Answer

Heating can be caused when hot magma is intruded into a cool rock.

On the o
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1.5.5 Fossils and ancient environments

An essential component of any environment is the plant and animal life that is adapted to the prevailing conditions. Fossil plants and animals are therefore wonderful sources of information about ancient environments. Plants can leave behind remains ranging from roots, leaves and twigs to seeds and pollen. Leaves and twigs are relatively fragile, and require a comparatively low energy environment (e.g. the mudflats of an estuary) for their preservation. Seeds, pollen and spores are surprising
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1.5.2 Sedimentary processes

Sedimentary grains are formed when the rocks at the Earth's surface are slowly broken up physically by exposure to wind and frost, and decomposed (chemically) by rainwater or biological action. These processes are collectively termed weathering. Once a rock has been broken up by weathering, the small rock fragments and individual mineral grains can be eroded from their place of origin by water, wind or glaciers and transported to be deposited elsewhere as roughly horizontal layers of sediment
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1.4 The formation of igneous rocks

Igneous rocks are defined as having solidified from a molten state, either inside the Earth or on the surface at volcanoes.


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1.3.2 Rocks

Any naturally formed solid assemblage of mineral grains can be described as a rock. The mineral grains may be fragments of crystals or intact crystals and their size can range from a few micrometres (1 micrometre = 10−6m) to a few centimetres. A rock may consist of one type of mineral but more usually it consists of several minerals. Rocks can be classified according to the way in which the grains are arranged, although the identity of the minerals present (for example, the rock
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1.3 Minerals and rocks

To begin with, it is necessary to explain the meanings of the two terms ‘minerals’ and ‘rocks’.


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1.1 About this unit

Science is all about knowledge, what we know about the material world and the Universe in which our world is just a microscopic speck. The aim of scientists is to extend the frontiers of this knowledge so that we can understand more about the physical Universe and the life within it.

Scientists acquire knowledge by engaging in four fundamentally important and connected tasks. The first is observation: they observe the natural world and the space beyond it, and both describe and r
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Learning outcomes

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

  • explain the difference between a mineral and a rock;

  • describe the textural differences between igneous, sedimentary and metamorphic rocks;

  • account for these differences in terms of the processes that produce these rocks;

  • classify igneous rocks according to their grain size and mineralogical composition;

  • recognise the difference between a body fossil and a trace fossil;

    <
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References

N. Carlson (2007) ‘Physiology of Behaviour’ 9th International Edition. Boston: Allyn and Bacon.

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8 Websites for further information:

Primers on drug addiction:

For general in
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5.3.2 Conclusion after reading this article:

The paper suggests that the factors that had long been considered responsible for neurodegenerative disease are also important for normal neuronal function. For example, they exert a physiological homeostatic effect by reducing excitatory transmission in Author(s): The Open University

5.2 Neural ageing: article 2

In the article presented here by Esteban (2004) entitled ‘Living with the enemy: a physiological role for theβ-amyloid peptide’, Trends in Neurosciences, 27, pp. 1–3, the author introduces us to a very important molecule implicated in the aetiology of Alzheimer's disease. However, the β-am
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5.2.2 Calorie restriction

Since the publication of Osborne, Mendel and Ferry's paper (Science, 1917, Vol 45, pp. 294–5) calorie restriction has been the most reliable method of extending the lifespan of laboratory animals. These results have been confirmed by many researchers and have been extended to a variety of verteb
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5.2 Neural ageing: article 1

Now read Neural Ageing Article 1: Concar, D. (2001) ‘Forever young’, New Scientist, 171, pp. 26–27.

Click to view 'Concar article'

4.7 Ageing brains: hope for the future

Due to the enormous progress in the field of molecular and cell biology, new avenues in brain research have opened up.
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4.6 Consequences of neural ageing

While we are beginning to understand the underlying molecular and cellular changes that take place in the ageing brain, the consequences of these changes are all too familiar. As people age, their mental competence may change and their ability to cope with the demands of everyday life may alter. A decline in
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4.2 Definitions of ageing

The term ‘ageing’ carries a number of different meanings. It encompasses changes that occur at many levels, from the population down to the molecular. Even at a single level, ageing does not represent a single process, but many processes, which may operate independently. Therefore, the challenge of defining ageing is more complex than it might first
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