Britannica Educational Publishing - Conservation and Ecology

CONSERVATION AND ECOLOGY

THE
LIVING EARTH

EDITED BY JOHN P. RAFFERTY, ASSOCIATE EDITOR, EARTH AND LIFE SCIENCES

Published in 2011 by Britannica Educational Publishing
(a trademark of Encyclopdia Britannica, Inc.)
in association with Rosen Educational Services, LLC
29 East 21st Street, New York, NY 10010.

Copyright 2011 Encyclopdia Britannica, Inc. Britannica, Encyclopdia Britannica, and the Thistle logo are registered trademarks of Encyclopdia Britannica, Inc. All rights reserved.

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First Edition

Britannica Educational Publishing
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John P. Rafferty: Associate Editor, Earth and Life Sciences

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Introduction by Linda George

Library of Congress Cataloging-in-Publication Data

Conservation and ecology / edited by John P. Rafferty.
p. cm. (The living earth)
In association with Britannica Educational Publishing, Rosen Educational Services.
Includes bibliographical references and index.
ISBN 978-1-61530-390-8 (eBook)
1. Ecology. 2. Biodiversity conservation. 3. Nature conservation. I. Rafferty, John P.
QH541.C653 2011
333.9516dc22

2010017133

On the cover: Across the planet, only isolated sections in Chinas mountains remain habitable for giant pandas. Perhaps fewer than 2,500 survive in the wild. Shutterstock.com

On page : El Capitan and the Merced River in Yosemite National Park, California. Jeremy Woodhouse/Getty Images

On pages : Giant panda (Ailuropoda melanoleuca). Mike Clarke/AFP/Getty Images

C onservation and ecology cover a vast array of topics related to the preservation of Earths biosphere: the atmosphere, landmasses, and oceans where organisms, plants, and animals live. Species interact with one another within food chains and food webs as well as through other close relationships. These interactions can be disrupted by natural forces, such as climate changes, fire, and floods, as well as through the activities of human beings. Several challenges have focused the worlds attention on Earths environment and the conservation of natural resources. This book addresses those topics and how they relate to Earths future as a living planet.

Although Earths biosphere is primarily located on the planets surface, it also extends some distance upward into the planets atmosphere and downward into the planets lithosphere. Ecology is the study of the relationships between living things and the environments they inhabit. The study of ecology includes the study of all forms of life, from the smallest bacteria to the largest animals and fungi. Ecology also considers the effects an organisms surroundings have on its survival and success.

Interacting species form biological communities. For example, a typical North American desert community is made up of coyotes, snakes, rabbits, birds, mice, various forms of cactus, creosote bushes, along with several species of insects, fungi, and other organisms. Communities of species interact with one another within an ecosystem, an ecological unit that includes the biological community along with its non-living surroundings. All species within a given ecosystem must contend with the demands made by the ecosystems climate and topography. Different parts of an ecosystem are involved in nutrient cycling, which provides sustenance to the species that live there. Taken together, all ecosystems on the planet make up Earths biosphere. To preserve the delicate balance inherent in ecosystems, biological communities, and populations of species, it is necessary to understand how organisms interact with one another.

Ecosystem function largely relies on the maintenance of nutrient cycles. Nutrients move through ecosystems driven by the actions of wind, water, and other physical forces, but they are also cycled through the organisms themselves through food chains and food webs. Food chains and food webs are structures that typically begin with plants. Energy from the sun is converted through a process called photosynthesis into plant tissues. Plant tissues (leaves, stems, roots, etc.) are consumed by animals called herbivores, which are, in turn, eaten by other animals called carnivores. Thus, energy passes through a chain of living players as food. Because most animals eat more than one plant or animal, however, a more complex structure called a food web emerges. Whenever a food chain or web is interrupted, through the sudden extinction of a species forming a link in the chain, the entire ecosystem may be changed. The degree of this alteration depends on how important the missing species is. In some cases, other species easily assume the role, or ecological niche, of the missing species. In others, where the species is an important food source or important predator, other species dependent on the missing species or its activities could become extinct as well.

Species also co-exist with one another symbiotically (that is, in close association). The interaction of two or more species can benefit each of the species involved (mutualism), harm both of the species involved (competition), benefit one species without benefiting or harming the other (commensalism), harm one species without benefiting or harming the other (ammensalism), or benefit one species while harming the other (predation or parasitism). Such close relationships are prevalent in ecosystems. In other situations when one species disappears from an ecosystem, the remaining species may adjust to its absence over time. However, the loss of an important species or the loss of multiple species over a short period of time can throw many of these relationships out of balance, possibly bringing about the extinction of other species in the ecosystem.

Organisms also face threats from the physical environment. Such threats range from everyday temperature and moisture conditions to sudden and catastrophic events such as volcanic eruptions and floods. In many ecosystems, seasonal changes bring about life-threatening conditions. In response, some species have developed unique adaptations to overcome acute periods of environmental stress or competition.

During parts of the year when food is scarce or environmental conditions are not conducive to life as usual, one adaptation certain animals make in response to changes in their habitat is dormancy, which includes hibernation and estivation (also spelled aestivation). Dormancy involves the slowing of life processes that, for animals, results in a lowering of body temperature, reduction of movement, and conservation of energy over a period of time that can range from weeks to months.