Acknowledgements Grateful acknowledgement is made to the following sources for permission to reproduce material in this unit: The material acknowledged below is Proprietary and used under licence (not subject to Creative Commons Licence). See Terms and Conditions.
Acknowledgements
4.1 Natural stores of carbon The major natural stores of carbon (called ‘reservoirs’) are shown below in Figure 1.9. 4 Fossil fuels Part of the incoming solar energy becomes stored in fossil fuels (oil, gas and coal: 2.3 Global power demand In Section 2.2 we calculated a value of 14.3 TW for the average global requirement for primary power in 2002 1 Energy use Until about 8000 years ago humans relied on hunting and gathering for food, and burning wood to keep warm. Their exact energy demands can at best only be estimated but to survive they probably needed about as much Author(s): 7.6 Questions Suppose that a galaxy has emission lines in its optical spectrum. A line of wavelength 654.3 nm is broadened by 2.0 nm. Estimate the velocity dispersion of the gas giving rise to the broadened spectral line. Is it likely to 7.1 The spectra of galaxies The spectrum of a galaxy is the composite spectrum of the objects of which it is composed. The optical spectrum of a normal galaxy contains contributions from stars and HII regions. An elliptical galaxy has no HII regions and has an optical spectrum that looks somewhat like a stellar spectrum but with rather fainter absorption lines. A spiral galaxy has both stars and star-forming regions, and its optical spectrum is the composite of its st 6.2 Do supermassive black holes really exist? One outstanding feature of the black-hole model is that the black hole must be supermassive. Can one at least detect the presence of a massive central object? How might a massive central object be detected using information from galactic rotation curves? By measuring rotation speeds near the nucleus of the galaxy. The faster the rotation speeds, the greater the enclosed mass. So the answer is yes. In NGC 4151 Radio-loud AGNs The second model (Figure 36b) is similar to the first, but now the engine is producing a pair of jets that will eventually end in a pair of lobes, as seen in radio galaxies and some quasars. Looking at the model from the side, one expects to see narrow lines in the spectrum (but not broad lines) and two 3.4 Radio galaxies Radio galaxies were discovered accidentally by wartime radar engineers in the 1940s, although it took another decade for them to be properly studied by the new science of radio astronomy. Radio galaxies dominate the sky at radio wavelengths. They show enormous regions of radio emission outside the visible extent of the host galaxy – usually these radio lobes occur in pairs. The first radio galaxy to be discovered, and still the brightest, is called Cygnus A (Author(s): Active galaxies
Figure 10 shows the spectral energy distribution of an active galaxy. 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 Introduction There are a wide range of different interactions between ‘science and the public’. Examples range from visiting a museum, or indulging in a science-related hobby, to reading a newspaper article about a breakthrough in the technique of therapeutic cloning, to attending a protest meeting about plans to build a waste disposal unit near to a residential area. Some such interactions are largely one-way; being a member of the audience for a ‘go-hear’ lecture, visiting a museum or‘‘liste 4.4 The ongoing story At the time of writing (2006), the Golden Rice tale is an unfinished story. Some of the developments of the last five years are summarised here. One area of ongoing scientific dispute is the question of whether the enriched rice can contribute significantly to the alleviation of vitamin A deficiency. We have seen that Shiva estimated that at best 100 g of rice a day would provide 4.4% of the recommended daily allowance. More sophisticated theoretical models, published since that time, h 4.3 Golden Rice in the public domain In January 2000, the successful experiments were announced in a paper published in the American journal Science. This, in itself, is significant. Generally, work on genetic manipulation would be published in one of a number of more specialist journals. Publication in a journal like Science indicates that this was important work, likely to be of interest to a wider audience. In its ‘Notes for Authors’, the journal states that ‘Priority is given to papers that reveal novel c A strategy for ridding the world of VAD? In July 2000, Time magazine announced that a potential solution to VAD had been found – ‘Golden Rice’ (Figure 8). This was a variety of rice that had been genetically modified to introduce β-carotene into the endosperm (part of the grain of the rice). The name arises from the fact that the otherwise white grains of rice are given a golden colour by the presence of carotenoid compounds. The announcement came at the height of the global controversy over genetically modified 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. Preamble Your answers to Activity 1 will have revealed that the initial development of commercial GM crops has focused on the introduction of two traits: herbicide tolerance and insect resistance. However, many other traits have been introduced into crops that have yet to be grown commercially on any scale. These traits include characteristics such as resistance to viral, bacterial and fungal infections, stress tolerance (for example to high levels of salt in the soil), changes to flower pigmentation, 1 Genetic manipulation of plants and GM crops: an introduction In this unit we will consider the genetic manipulation of plants, and the production of GM crops. A great deal has been written about the science of GM crops and the controversial issues surrounding their introduction around the world. In the study time available, we will focus on a small number of selected issues. In this unit you'll have the opportunity to learn more about the science that has been used to engineer a range of GM crops, and examine both the science and social concerns Learning outcomes By the end of this unit you should be able to: understand more about the science that underlies the development of genetically modified organisms and in particular how gene transfer is brought about; know something of the potential benefits and uncertainties associated with gene transfer and the high levels of technical ingenuity involved; be better able to understand the science that underpins the development of Golden Rice and understand why the u
Question 15
Author(s): 