Introduction

Active galaxies provide a prime example of high-energy processes operating in the Universe. This unit introduces the evidence for activity from the spectra of some galaxies, and the concept of a compact active galactic nucleus as a unifying model for the observed features of several types of active galaxy. It also develops the key skill of applying arithmetic and simple algebra to solving scientific problems.

This course is an adapted extract fromt he course Author(s): The Open University

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Readings

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Reading 1: Miller, S. (2001) ‘Publ
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3.1 Introduction

On an autumnal morning in November 1994, a group of people gathered at Regent's College, London, conscious that they were making history. The purpose of the meeting was to discuss an important issue: plant biotechnology and how it should be regulated in the UK. At the time, the genetic engineering of plants was emerging as a technology of great potential for the development of new pest-resistant, higher yield crops, although the technique hadn't attracted the degree of media attention and pub
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Acknowledgements

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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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3.1 Introduction

The simplest and oldest way of storing surface water is in reservoirs and this has been done for thousands of years. Most reservoirs are still built to increase water supplies, but some are also built for other purposes, especially for generating hydroelectric power and for protection against floods. The Tennessee River in the United States, for example, has reservoirs to trap and store water that would otherwise cause floods, the water being released when the height of the river falls to saf
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6 Direct heating using geothermal energy

In the same way that waste heat from conventional power stations can be used for direct heating of buildings, and in industrial production and horticulture, low-grade geothermal energy has considerable potential. Many existing developments, such as those in Iceland, use spent fluids from geothermal electricity generation. Areas of natural hot springs are an obvious target, but it is also relatively simple to exploit normal heat flow using either natural groundwater or a variety of heat-exchan
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4 Locating high-enthalpy geothermal fields

The search for potentially useful geothermal fields focuses initially on locating rocks that have been chemically altered by natural geothermal fluids, as well as looking for obvious surface features of geothermal activity such as geysers and hot springs. Measurements of fluid flow through the field allow estimation of its likely economic potential.

When a promising resource has been located exploration wells are drilled. However, given the high pressures and temperatures typical of a g
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2.7 Summary

  1. Eukaryotic cells contain numerous distinct types of membrane-bound compartment. Transport vesicles move proteins and other molecules between the compartments.

  2. Proteins contain signalling sequences or patches that specify their destination compartment.

  3. Proteins destined for lysosomes, secretion or the plasma membrane are synthesised in the ER, transported to the cis Golgi, modified in the Golgi apparatus, and sorted and pa
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6.2 Catalytic mechanisms

In general terms, the following mechanisms operate at the active site of an enzyme to bring about the conversion of substrate to product:

  1. Charged groups at the enzyme active site alter the distribution of electrons in the substrate. By affecting the electron distributions in key atoms in the substrate, the enzyme can destabilise existing bonds and favour the formation of new bonds. This principle is illustrated below, using as an example the hydrolysis
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6.1 Introduction

Among those proteins of known function, the majority are enzymes. Enzymes act as catalysts, i.e. they increase the rates of reactions, making and breaking bonds, without themselves undergoing any permanent change. They are highly specific for particular reactions and are excellent examples of how a protein's function is entirely dependent on its structure.

First of all, a protein must bind its substrate (or substrates) in a specific fashion; it must then convert the substrate(s) into th
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1.1 So what's it all about?

iSpot is a website aimed at helping anyone identify anything in nature. Once you've registered, you can add an observation to the website and suggest an identification yourself or see if anyone else can identify it for you. You can also help others by adding an identification to an existing observation, which you may like to do as your knowledge grows. Your reputation on the site will grow as people agree with you identifications. You may also like to visit our forums which offer lively debat
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4.2 Social dynamics

Yet another type of diagram is given in this section. Take a preliminary look at Figure 7, which is a way of illustrating the relationship
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2.2 Size and shape

The shape of the head is determined mainly by the relative sizes of the jaws and the nose and the back of the skull containing the brain, eyes, ears and, in artiodactyls, the horns or antlers. All these structures may differ greatly between otherwise similar species.

SAQ 7


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5.3.3 Ring-tailed lemurs

LoM p. 239 describes the life and habits of the ring-tailed lemur, drawing attention to what are commonly called their ‘stink-fights’ – a further example of the importance of smell in lemur society. But here the habit is prevalent in a species that is active by day and can spend as much as 40 per cent of its waking time on the ground. In fact, these animals seem equally at home on the ground and in the trees. Over time, some populations in Madagascar have become more ground-based than o
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7 The threat of extinction

DA ends his book by writing eloquently of the dangers of extinction faced by mammals, from habitat loss as we exploit our environment to produce more and more food, for our growing population. However bleak the picture, there is still time and opportunity to save mammal species from extinction. Although bison in the USA and Canada were reduced to barely 1000 individuals in 1900, their numbers have now risen to well over 150 000 thanks to the efforts of First Nation indigenous peoples, and ran
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Introduction

In this unit, we will explore the fascinating question of who our ancestors were. I'll be looking at living species of apes in order to pick up clues about social structure and lifestyle in our ancestors and gain some understanding about why we humans behave as we do. I'll discuss tool use and culture in both ape and human societies, and look at two ancient species known only from their fossils – an australopithecine and Homo erectus.

This is the tenth in a series of units abou
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4.1 The advantages

On the basis of LoM and the TV programme, and hearing so much about African hunting dogs and lions, you might be tempted to believe that carnivores generally live in groups.

Question: Do you think this generalisation is true? Can you think of
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2.1 Introducing the Carnivora

Table 1 in this section lists the scientific names of the families of the Carnivora, as well as their common names. You are not expected to recall
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