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4.3 Corals

Corals are especially abundant in the Wenlock Limestone.

SAQ 12

4.2 Crinoids

Figure 7 shows the fossilised remains of a type of echinoderm called a crinoid (‘cry-noyed’). Although crinoids occur today, they were far more common in the Palaeozoic and Mesozoic Eras. Most crinoids feed by bending their umbrella-like arrangement of flexible appendages (called ‘arms’) downstream so as to catch a current, rather as in an umbrella being caught in the wind. Tube feet (multipurpose tentacles) on the arms gather food particles suspended in the water, which are th
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4.1 Trilobites

As we've seen, the Cambrian explosion left the seas teeming with a huge variety of animals. In the following activity you will study some of the marine life at one particular time in the Palaeozoic Era – the middle part of the Silurian Period, 430 Ma ago. You'll look in detail at some fossils which come from a deposit in the UK called the Wenlock Limestone, famous for its many beautiful fossils. The Wenlock Limestone crops out mainly around Birmingham and the borders of Wales.

Figure
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3 The Silurian Period and the invasion of the land

Before going any further, click on 'View document' below and read pages 72–75 from Douglas Palmer's Atlas of the Prehistoric World.

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2 The Ordovician seas

Before going any further, click on 'View document' below and read pages 68–71 from Douglas Palmer's Atlas of the Prehistoric World.

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1.4 The origin of the vertebrates

Vertebrates such as ourselves are by definition animals with a backbone (or vertebral column, paired limbs, a skull and various other structures. Until recently vertebrates were thought to extend back only into late Ordovician times, some 450 million years ago. At this time fossils of strange-looking fish with bony headshields, such as Sacabambaspis (Atlas, pp. 70–71), appear in the fossil record. These jawless fish (called agnathans) are only very distantly related to the sol
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1.3 An overview of animal phyla

We have already met quite a few different animal phyla, and it's useful to get an overview of all the ones commonly found in the fossil record and their mode of life before studying some in more detail. Except for a few soft-bodied phyla with very poor fossil records, it is clear that all the animal phyla had appeared by the Ordovician Period.

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1.2 The Burgess Shale

High in the Canadian Rockies is exposed a deposit of middle Cambrian age, about 530 Ma old, called the Burgess Shale. It contains the fossils of animals that lived on a muddy sea floor, and which were suddenly transported into deeper, oxygen-poor water by submarine landslides. Their catastrophic burial has given us an exceptional view of Cambrian life. Not only have animals with hard shelly parts been preserved but entirely soft-bodied forms are also preserved as thin films on the sediment s
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1.1 A burst of evolution

One of the most important events in the history of life began about 545 million years (Ma) ago, i.e. some four billion years after the origin of the Earth, and over 3.3 billion years after the origin of life. The term ‘Cambrian explosion’ reflects a sudden burst of evolution, when a wide variety of organisms, especially those with hard, mineralised parts, first appear in the fossil record. Thus began the Phanerozoic Eon – ‘the time of visible life’ – and the Palaeozoic Era.
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Learning outcomes

After studying this unit you should be able to:

  • describe some key events in the evolution of life during the Palaeozoic Era, such as the first appearance of major groups of invertebrates and vertebrates, and the invasion of the land;

  • identify some common types of fossil organisms that were living in Palaeozoic seas, and comment on their likely environment and geological age;

  • make inferences from fossils about the biology and mode of life of some Pal
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Introduction

The Palaeozoic Era was a very important time in the history of life. Using evidence from fossils, we start by looking at the Cambrian explosion, when many forms of animal life first appeared about 545 million years ago. Then we move on to study creatures living in the Ordovician seas, including the extinct trilobites. Next, we'll investigate the invasion of land by plants and invertebrates that occurred in the Silurian Period, and look at life in Silurian seas. You'll also learn about the Dev
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Acknowledgements

The material acknowledged below is Proprietary and used under licence, not subject to Creative Commons. See Terms and Conditions.

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.

Figures

Figure 1, 3, 4, 5, 7, 12 Based on Mackay, J. and Mensah, G. (2004) The Atlas of Heart Disease and Stroke
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References

American Heart Association (2006) ‘Heart disease and stroke statistics – 2006 update: A report from the American Heart Association Statistics Committee and Stroke Statistics Subcommittee’, Circulation, 113, pp. e85–e151.
Bandolier (2005) Statins: when should you take the tablet?Author(s): The Open University

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12 Glossary

You can access the unit glossary by clicking the link below.

Open glossary now...


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11 Additional resources

Bandolier (2005) Statins: when should you take the tablet?

British Red Cross (2007) First aid guidelines in the UK

Cardiac Risk in the Young (2003) When a young person dies suddenly

Clay, R. A. (2001) Research to the heart of the matter

Department of Health (2000) National Service Framework for coronary heart disease, Chapter 4

Department of Health (2007) The coronary heart disease National Service Framework: shaping the future: progress report 2006

The Nat
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10 Test your knowledge

Question 1

Referring to Figure 6 reproduced again for
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9 Summary

Now you will be very familiar with cardiovascular diseases, their development and their diagnosis. You will also know their treatment and many of the cardiovascular disease risk factors – what they are and how they can be influenced positively to minimise cardiovascular diseases. You will understand the overall importance of a balanced diet, regular exercise and weight management (guided by adiposity measurements) throughout life, to maintain cardiac and vascular health. You will also be a
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8.5 How things change

Despite the advances made in cardiac care over the previous century, it is thought that the global epidemic of cardiovascular diseases is both increasing (see Table 5) and shifting from developed to developing countries (Mackay and Mensah, 2004). While treatments are available for some cardiovascular disease patien
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8.4 When surgery is required

For some cardiovascular disease patients, surgery may be carried out as an emergency procedure or become an inevitable progression, following on from drug therapy. There are various degrees of surgery carried out, ranging from the fairly routine and minorly invasive procedure of coronary angioplasty to the major life-saving heart (or heart and lung) transplant. While it is important to understand all of the detail of surgical procedures and how the cardiac surgical team work together, it is a
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8.3 Issues with medications

Most pharmaceutical drugs will have side effects – unwanted and sometimes unexpected effects, in addition to the medical benefits expected with the drug's use. All prescription drugs are accompanied by an information sheet outlining possible side effects. Such unwanted effects can cause problems with patient compliance: despite being prescribed certain drugs or drug combinations, patients will either not take their drugs or not take them in accordance with the suggested schedule. Sometimes
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