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All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs, and Patents Act , without the prior permission of the publisher First edition published by Blackwell Publishing Ltd Second edition published Third edition published Fourth edition published 1 Library of Congress Cataloging-in-Publication Data Begon, Michael.
Townsend, John L. Includes bibliographical references and index. ISBN hard cover : alk. Townsend, Colin R. Harper, John L. B —dc22 A catalogue record for this title is available from the British Library. Set in 9. Furthermore, the publisher ensures that the text paper and cover board used have met acceptable environmental accreditation standards. For further information on Blackwell Publishing, visit our website: www. A science for everybody — but not an easy science This book is about the distribution and abundance of different types of organism, and about the physical, chemical but especially the biological features and interactions that determine these distributions and abundances.
Unlike some other sciences, the subject matter of ecology is apparent to everybody: most people have observed and pondered nature, and in this sense most people are ecologists of sorts. But ecology is not an easy science. It feeds on advances in our knowledge of biochemistry, behavior, climatology, plate tectonics and so on, but it feeds back to our understanding of vast areas of biology too.
If, as T. Ecology has the distinction of being peculiarly confronted with uniqueness: millions of different species, countless billions of genetically distinct individuals, all living and interacting in a varied and ever-changing world. The challenge of ecology is to develop an understanding of very basic and apparent problems, in a way that recognizes this uniqueness and complexity, but seeks patterns and predictions within this complexity rather than being swamped by it.
Much has changed — in ecology, in the world around us, and even strange to report! Nineteen years on, we have tried to capture in our cover design both how much and how little has changed. As a species, we are still driven to broadcast our feelings graphically and publicly for others to see. But simple, factual depictions have given way to urgent statements of frustration and aggression. The human subjects are no longer mere participants but either perpetrators or victims.
Now, we must accept the immediacy of the environmental problems that threaten us and the responsibility of ecologists to come in from the sidelines and play their full part in addressing these problems.
But we remain wedded to the belief that environmental action can only ever be as sound as the ecological principles on which it is based. Hence, while the remaining chapters are still largely about the principles themselves rather than their application, we believe that the whole of this book is aimed at improving preparedness for addressing the environmental problems of the new millennium.
To this end, the results from around studies have been newly incorporated into the text, most of them published since the third edition. We have also consciously attempted, while including so much modern work, to avoid bandwagons that seem likely to have run into the buffers by the time many will be using the book. Having said this, we hope, still, that this edition will be of value to all those whose degree program includes ecology and all who are, in some way, practicing ecologists.
We believe that all ecologists should to some extent try to combine all these facets. Technical and pedagogical features One technical feature we have retained in the book is the incor- poration of marginal es as signposts throughout the text. These, we hope, will serve a number of purposes. However, because they are numerous and often informative in their own right, they can also be read in sequence along with the conventional subheadings, as an outline of each chapter.
They should act too as a revision aid for students — indeed, they are similar to the annotations that students themselves often add to their textbooks. Finally, because the marginal notes generally summarize the take-home message of the paragraph or paragraphs that they accompany, they can act as a continuous assessment of comprehension: if you can see that the signpost is the take-home message of what you have just read, then you have understood.
For this edition, though, we have also added a brief summary to each chapter, that, we hope, may allow readers to either orient and prepare themselves before they embark on the chapter or to remind themselves where they have just been. Acknowledgements Finally, perhaps the most profound alteration to the construction of this book in its fourth edition is that the revision has been the work of two rather than three of us.
John Harper has very rea- sonably decided that the attractions of retirement and grand- fatherhood outweigh those of textbook co-authorship. We cannot promise to have absorbed or, to be frank, to have accepted, every one of his views; and we hope in particular, in this fourth edition, that we have not strayed too far from the paths through which he has guided us.
In previous editions we thanked the great many friends and colleagues who helped us by commenting on various drafts of the text. The effects of their contributions are still strongly evident in the present edition. This fourth edition was also read by a series of reviewers, to whom we are deeply grateful.
Mike Begon Colin Townsend 9. The environment therefore retains the central position that Haeckel gave it. But we need to expand it.
The living world can be viewed as a biological hierarchy that starts with subcellular particles, and continues up through cells, tissues and organs. Ecology deals with the next three levels: the individual organism, the population consisting of individuals of the same species and the community consisting of a greater or lesser number of species populations.
At the level of the organism, ecology deals with how individuals are affected by and how they affect their environment. Community ecology then deals with the composition and organization of ecological communities.
Ecologists also focus on the pathways followed by energy and matter as these move among living and nonliving elements of a further category of organization: the ecosystem, comprising the community together with its physical environment. There are two broad approaches that ecologists can take at each level of ecological organization. First, much can be gained by building from properties at the level below: physiology when studying organismal ecology; individual clutch size and survival probabilities when investigating the dynamics of individual species populations; food consumption rates when dealing with inter- actions between predator and prey populations; limits to the similarity of coexisting species when researching communities, and so on.
An alternative approach deals directly with properties of the level of interest — for example, niche breadth at the organis- mal level; relative importance of density-dependent processes at the population level; species diversity at the level of community; rate of biomass production at the ecosystem level — and tries to relate these to abiotic or biotic aspects of the environment. Both approaches have their uses, and both will be used in each of the three parts of this book: Organisms; Species Interactions; and Communities and Ecosystems.
Introduction: Ecology and its Domain This, too, adds to our knowledge of the living world. All descriptions are selective: but undirected description, carried out for its own sake, is often found afterwards to have selected the wrong things. Ecologists also often try to predict what will happen to an organism, a population, a community or an ecosystem under a particular set of circumstances: and on the basis of these predic- tions we try to control the situation.
We try to minimize the effects of locust plagues by predicting when they are likely to occur and taking appropriate action. We try to protect crops by predicting when conditions will be favorable to the crop and unfavorable to its enemies. We try to maintain endangered species by predicting the conservation policy that will enable them to persist. Some prediction and control can be carried out without explanation or understanding. Mathematical modeling has played, and will continue to play, a crucial role in the development of ecology, particularly in our ability to predict outcomes.
But it is the real world we are interested in, and the worth of models must always be judged in terms of the light they shed on the working of natural systems. It is important to realize that there are two different classes of explanation in biology: proximal and ultimate explanations. This is a proximal explanation.
However, we may also ask how this species of bird comes to have these properties that now appear to govern its life. This question has to be answered by an explanation in evolutionary terms.
The ultimate explanation of the present distribution and abundance of this bird lies in the ecological experiences of its ancestors. These problems are as much part of modern ecology as are the prevention of plagues, the protection of crops and the preservation of rare species. Our ability to control and exploit ecosystems cannot fail to be improved by an ability to explain and understand.
Ecologia de Individuos a Ecossistemas - 4 Ed. (Begon, Townsed, Harper, 2007)
Ecologia: De Individuos a Ecossistemas