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Campbell Biology in Focus PDF Free Download Download for free: http://bit.ly/CampBFocPDFFree Additional tags: biology in focus biology in focus campbell biology in focus pdf biology textbook pdf campbell biology book campbell biology in focus 1st edition campbell biology in focus pdf campbell biology pdf campbell biology textbook campbell biology textbook pdf campbell reece biology campbell textbook

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CAMPBELL BIOLOGY IN FOCUS Lisa A. Urry Mills College Oakland California Michael L. Cain Bowdoin College Brunswick Maine Steven A. Wasserman University of California San Diego Peter V. Minorsky Mercy College Dobbs Ferry New York Robert B. Jackson Duke University Durham North Carolina Jane B. Reece Berkeley California Boston Columbus Indianapolis New York San Francisco Upper Saddle River Amsterdam Cape Town Dubai London Madrid Milan Munich Paris Montréal Toronto Delhi Mexico City São Paulo Sydney Hong Kong Seoul Singagore Taipei Tokyo

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Editor-in-Chief: Beth Wilbur Executive Director of Development: Deborah Gale Senior Acquisitions Editor: Josh Frost Senior Editorial Manager: Ginnie Simione Jutson Supervising Editors: Beth N. Winickoff and Pat Burner Senior Developmental Editors: Matt Lee and Mary Ann Murray Developmental Artist: Andrew Recher Precision Graphics Senior Supplements Project Editor: Susan Berge Project Editor: Brady Golden Assistant Editor: Katherine Harrison-Adcock Director of Production: Erin Gregg Managing Editor: Michael Early Assistant Managing Editor: Shannon Tozier Production Management and Composition: S4Carlisle Publishing Services Illustrations: Precision Graphics Design Manager: Marilyn Perry Text Design: Hespenheide Design Cover Design: Riezebos Holzbaur Design Senior Photo Editor: Donna Kalal Photo Researcher: Maureen Spuhler Manager Text Permissions: Tim Nicholls Project Manager Text Permissions: Joseph Croscup Permissions Specialists: James W. Toftness and Lara Levitan Creative Compliance LLC Director of Content Development MasteringBiology®: Natania Mlawer Senior Developmental Editor MasteringBiology®: Sarah Jensen Senior Media Producer: Jonathan Ballard Assistant Mastering® Media Producer: Caroline Ross Director of Marketing: Christy Lesko Executive Marketing Manager: Lauren Harp Manufacturing Buyer: Michael Penne Text Printer: Courier Kendallville Cover Printer: Moore Langen Printer Cover Photo Credit: Chris Hellier/Photo Researchers Inc. Credits and acknowledgments for materials borrowed from other sources and reproduced with permission in this textbook appear starting on p. CR-1. Copyright © 2014 Pearson Education Inc. All rights reserved. Manufactured in the United States of America. This publication is protected by Copyright and permission should be obtained from the publisher prior to any prohibited reproduction storage in a retrieval system or transmission in any form or by any means electronic mechanical photocopying recording or likewise. To obtain permissions to use material from this work please submit a written request to Pearson Education Inc. Permissions Department 1900 E. Lake Ave. Glenview IL 60025. For information regarding permissions call 847 486-2635. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book and the publisher was aware of a trademark claim the designations have been printed in initial caps or all caps. MasteringBiology ® and BioFlix ® are registered trademarks in the U.S. and/or other countries of Pearson Education Inc. or its affliates. Library of Congress Cataloging-in-Publication Data Campbell biology in focus / Lisa A. Urry . . . et al.. p. cm. ISBN-13: 978-0-321-81380-0 ISBN-10: 0-321-81380-4 1. Biology. I. Urry Lisa A. II. Title: Biology in focus. QH308.2C347 2014 570--dc23 2012017759 ISBN-10: 0-321-81380-4 ISBN-13: 978-0-321-81380-0 Student Edition ISBN-10: 0-321-83323-6 ISBN-13: 978-0-321-83323-5 Instructor Review Copy 1 2 3 4 5 6 7 8 9 10—CRK—16 15 14 13 12 www.pearsonhighered.com Proudly sourced and uploaded by StormRG Kickass Torrents | TPB | ET | h33t

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▼ Figure 1.1 What can this beach mouse teach us about biology OVERVIEW Inquiring About Life T he brilliant white sand dunes and sparse clumps of beach grass along the Florida seashore afford little cover for the beach mice that live there. However a beach mouse’s light dappled fur acts as camouflage allowing the mouse to blend into its surroundings Figure 1.1. Although mice of the same species oldfield mice Peromyscus polionotus also inhabit nearby inland areas the inland mice are much darker in color matching the darker soil and vegetation where they live Figure 1.2. Tis close match of each mouse to its environment is vital for survival since hawks herons and other sharp-eyed predators periodically scan the landscape for food. How has the color of each mouse come to be so well matched or adapted to the local background An organism’s adaptations to its environment such as camouflage that helps protect it from predators are the result of evolution the process of change that has transformed life from its beginnings to the astounding array of organisms today. Evolution is the fundamental principle of biology and the core theme of this book. Although biologists know a great deal about life on Earth many mysteries remain. Te question of how the mice’s coats have come to match the colors of their habitats is just one example. Posing questions about the living world and seeking answers through scientific inquiry are the central activities of biology the scien- tific study of life. Biologists’ questions can be ambi- tious. Tey may ask how a single tiny cell becomes a tree or a dog how the human mind works or how the different forms of life in a forest interact. When questions occur to you as you observe the liv- ing world you are already thinking like a biologist. How do biologists make sense of life’s diversity and complexity Tis open- ing chapter sets up a framework for answering this question. Te first part of the chapter provides a panoramic view of the biological “landscape ” organized around a set of unifying themes. We’ll then focus on biology’s core theme evolution. Finally we’ll examine the process of scientific inquiry—how scientists ask and attempt to answer questions about the natural world. 1 KEY CONCEPTS 1.1 Studying the diverse forms of life reveals common themes 1.2 The Core Theme: Evolution accounts for the unity and diversity of life 1.3 Biological inquiry entails forming and testing hypotheses based on observations of nature Introduction: Evolution and the Foundations of Biology ▶ Figure 1.2 An “inland” oldfield mouse Peromyscus polionotus. This mouse has a much darker back side and face than mice of the same species that inhabit sand dunes.

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The array of organisms inhabiting a particular ecosystem is called a biological community. The community in our forest ecosystem includes many kinds of trees and other plants various animals mushrooms and other fungi and enormous numbers of diverse microorganisms which are living forms such as bacteria that are too small to see without a microscope. Each of these forms of life is called a species. ◀ 1 The Biosphere Even from space we can see signs of Earth’s life—in the green mosaic of the forests for example. We can also see the scale of the entire biosphere which consists of all life on Earth and all the places where life exists: most regions of land most bodies of water the atmosphere to an altitude of several kilometers and even sediments far below the ocean foor. ◀ 2 Ecosystems Our frst scale change brings us to a North American forest with many deciduous trees trees that lose their leaves and grow new ones each year. A deciduous forest is an example of an ecosystem as are grasslands deserts and coral reefs. An ecosystem consists of all the living things in a particular area along with all the nonliving components of the environment with which life interacts such as soil water atmospheric gases and light. ▶ 4 Populations A population consists of all the individuals of a species living within the bounds of a specifed area. For example our forest includes a population of sugar maple trees and a population of white-tailed deer. A community is therefore the set of populations that inhabit a particular area. ▲ 5 Organisms Individual living things are called organisms. Each of the maple trees and other plants in the forest is an organism and so is each deer frog beetle and other forest animals. The soil teems with microorganisms such as bacteria. ▶ 3 Communities CONCEPT 1.1 Studying the diverse forms of life reveals common themes Biology is a subject of enormous scope and exciting new bio- logical discoveries are being made every day. How can you organize and make sense of all the information you’ll encoun- ter as you study biology Focusing on a few big ideas—ways of thinking about life that will still hold true decades from now— will help. Here we’ll describe five unifying themes to serve as touchstones as you proceed through this book. Theme: New Properties Emerge at Successive Levels of Biological Organization ORGANIZATION Te study of life extends from the micro- scopic scale of the molecules and cells that make up organisms to the global scale of the entire living planet. As biologists we can divide this enormous range into different levels of biologi- cal organization. Imagine zooming in from space to take a closer and closer look at life on Earth. It is spring in Ontario Canada and our destination is a local forest where we will eventually narrow our focus down to the molecules that make up a maple leaf. Figure 1.3 narrates this journey into life as the numbers guide ▼ Figure 1.3 Exploring Levels of Biological Organization 2

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50μm 10μm 1μm Atoms Chloroplast Chlorophyll molecule Cell ▶ 9 Organelles ▼ 6 Organs and Organ Systems The structural hierarchy of life continues to unfold as we explore the architecture of more complex organisms. A maple leaf is an example of an organ a body part that carries out a particular function in the body. Stems and roots are the other major organs of plants. The organs of complex animals and plants are organized into organ systems each a team of organs that cooperate in a larger function. Organs consist of multiple tissues. ◀ 7 Tissues To see the tissues of a leaf requires a microscope. Each tissue is a group of cells that work together performing a specialized function. The leaf shown here has been cut on an angle. The honeycombed tissue in the interior of the leaf left side of photo is the main location of photosynthesis the process that converts light energy to the chemical energy of sugar. The jigsaw puzzle–like “skin” on the surface of the leaf is a tissue called epidermis right side of photo. The pores through the epidermis allow entry of the gas CO 2 a raw material for sugar production. ▲ 8 Cells The cell is life’s fundamental unit of structure and function. Some organisms are single cells while others are multicellular. A single cell performs all the functions of life while a multicellular organism has a division of labor among specialized cells. Here we see a magnifed view of cells in a leaf tissue. One cell is about 40 micrometers μm across— about 500 of them would reach across a small coin. As tiny as these cells are you can see that each contains numerous green structures called chloroplasts which are responsible for photosynthesis. Chloroplasts are examples of organelles the various functional components present in cells. This image taken by a powerful microscope shows a single chloroplast. Our last scale change drops us into a chloroplast for a view of life at the molecular level. A molecule is a chemical structure consisting of two or more units called atoms represented as balls in this computer graphic of a chlorophyll molecule. Chlorophyll is the pigment molecule that makes a maple leaf green and it absorbs sunlight during photosynthesis. Within each chloroplast millions of chlorophyll molecules are organized into systems that convert light energy to the chemical energy of food. ▶ 10 Molecules Emergent Properties Let’s reexamine Figure 1.3 beginning this time at the molecu- lar level and then zooming out. Viewed this way we see that at each level novel properties emerge that are absent from the preceding one. Tese emergent properties are due to the ar- rangement and interactions of parts as complexity increases. For example although photosynthesis occurs in an intact chloroplast it will not take place in a disorganized test-tube mixture of chlorophyll and other chloroplast molecules. Te coordinated processes of photosynthesis require a specific organization of these molecules in the chloroplast. Isolated components of living systems acting as the objects of study in you through photographs illustrating the hierarchy of biologi- cal organization. Zooming in at ever-finer resolution illustrates the principle of reductionism—the approach of reducing complex systems to simpler components that are more manageable to study. Reductionism is a powerful strategy in biology. For example by studying the molecular structure of DNA that had been extracted from cells James Watson and Francis Crick inferred the chemical basis of biological inheritance. However although it has propelled many major discoveries reductionism pro- vides a necessarily incomplete view of life on Earth as we’ll discuss next. 3

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4 CHAPTER 1 INTRODUCTION: EVOLUTION AND THE FOUNDATIONS OF BIOLOGY ▲ Figure 1.4 Form fits function in a hummingbird’s body. The unusual bone structure of a hummingbird’s wing allows the bird to rotate its wings in all directions enabling it to fly backward and to hover while it feeds. What other examples of form fitting function do you observe in this photograph Eukaryotic cell Prokaryotic cell Membrane DNA no nucleus Membrane Membrane- enclosed organelles DNA throughout nucleus Nucleus membrane- enclosed Cytoplasm 1μm ▲ Figure 1.5 Contrasting eukaryotic and prokaryotic cells in size and complexity. a reductionist approach to biology typically lack some of the properties that emerge at higher levels of organization. Emergent properties are not unique to life. A box of bicycle parts won’t transport you anywhere but if they are arranged in a certain way you can pedal to your chosen destination. Compared to such nonliving examples however the unrivaled complexity of biological systems makes the emergent proper- ties of life especially challenging to study. T o fully explore emergent properties biologists today complement reductionism with systems biology the explora- tion of a biological system by analyzing the interactions among its parts. A single leaf cell can be considered a system as can a frog an ant colony or a desert ecosystem. By examining and modeling the dynamic behavior of an integrated network of components systems biology enables us to pose new kinds of questions. For example how does a drug that lowers blood pressure affect the functioning of organs throughout the body At a larger scale how does a gradual increase in atmospheric carbon dioxide alter ecosystems and the entire biosphere Sys- tems biology can be used to study life at all levels. Structure and Function At each level of the biological hierarchy we find a correlation of structure and function. Consider the leaf in Figure 1.3: Its thin flat shape maximizes the capture of sunlight by chloro- plasts. More generally analyzing a biological structure gives us clues about what it does and how it works. Conversely knowing the function of something provides insight into its structure and organization. Many examples from the animal kingdom show a correlation between structure and function including the hummingbird Figure 1.4. Te humming- bird’s anatomy allows the wings to rotate at the shoulder so hummingbirds have the ability unique among birds to fly backward or hover in place. Hovering the birds can extend their long slender beaks into flowers and feed on nectar. Te elegant match of form and function in the structures of life is explained by natural selection as we’ll explore shortly. The Cell: An Organism’s Basic Unit of Structure and Function In life’s structural hierarchy the cell is the smallest unit of organization that can perform all required activities. In fact the activities of organisms are all based on the activities of cells. For instance the movement of your eyes as you read this sentence results from the activities of muscle and nerve cells. Even a process that occurs on a global scale such as the recycling of carbon atoms is the cumulative product of cellular functions including the photosynthetic activity of chloroplasts in leaf cells. All cells share certain characteristics. For instance every cell is enclosed by a membrane that regulates the passage of materi- als between the cell and its surroundings. Nevertheless we rec- ognize two main forms of cells: prokaryotic and eukaryotic. Te cells of two groups of single-celled microorganisms—bacteria singular bacterium and archaea singular archaean—are prokaryotic. All other forms of life including plants and ani- mals are composed of eukaryotic cells. A eukaryotic cell contains membrane-enclosed organelles Figure 1.5. Some organelles such as the DNA-containing nucleus are found in the cells of all eukaryotes other organ- elles are specific to particular cell types. For example the chlo- roplast in Figure 1.3 is an organelle found only in eukaryotic cells that carry out photosynthesis. In contrast to eukaryotic cells a prokaryotic cell lacks a nucleus or other membrane- enclosed organelles. Furthermore prokaryotic cells are gener- ally smaller than eukaryotic cells as shown in Figure 1.5.

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chapter 1 Introduct Ion: Evolut Ion and th E foundat Ions of b Iology 5 10 µm ▲ Figure 1.6 A lung cell from a newt divides into two smaller cells that will grow and divide again. Egg cell Sperm cell Nuclei containing DNA Fertilization Fertilized egg with DNA from both parents Embyro’s cells with copies of inherited DNA Offspring with traits inherited from both parents ▲ Figure 1.7 Inherited DNA directs development of an organism. a A A T A T A T A T C C C G G DNA double helix. This model shows each atom in a segment of DNA. Made up of two long chains of building blocks called nucleotides a DNA molecule takes the three-dimensional form of a double helix. Single strand of DNA. These geometric shapes and letters are simple symbols for the nucleo- tides in a small section of one chain of a DNA molecule. Genetic information is encoded in specific sequences of the four types of nucleotides. Their names are abbreviated A T C and G. b Nucleotide Nucleus Cell DNA ▲ Figure 1.8 DNA: The genetic material. DNA Structure and Function Each time a cell divides the DNA is frst replicated or copied and each of the two cellular ofspring inherits a complete set of chromosomes identical to that of the parent cell. Each chro- mosome contains one very long DNA molecule with hundreds or thousands of genes each a stretch of DNA arranged along the chromosome. Transmitted from parents to ofspring genes are the units of inheritance. Tey encode the information nec- essary to build all of the molecules synthesized within a cell which in turn establish that cell’s identity and function. Each of us began as a single cell stocked with DNA inherited from our parents. Te replication of that DNA during each round of cell division transmitted copies of the DNA to what eventually be- came the trillions of cells of the human body. As the cells grew and divided the genetic information encoded by the DNA di- rected our development Figure 1.7. Te molecular structure of DNA accounts for its ability to store information. A DNA molecule is made up of two long chains called strands arranged in a double helix. Each chain is made up of four kinds of chemical building blocks called nucleotides abbreviated A T C and G Figure 1.8. Te way DNA encodes information is analogous to how we arrange the letters of the alphabet into words and phrases with specifc meanings. Te word rat for example evokes a rodent the words tar and art which contain the same letters mean very diferent things. We can think of nucleotides as a four-letter alphabet. Specifc sequences of these four nucleotides encode the information in genes. DNA provides the blueprints for making proteins which are the major players in building and maintaining the cell and t heme: Life’s processes Involve the expression and transmission of Genetic Information Informat Ion Within cells structures called chromosomes contain genetic material in the form of DNA deoxyribonu- cleic acid. In cells that are preparing to divide the chromo- somes may be made visible using a dye that appears blue when bound to the DNA Figure 1.6.

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882 OVERVIEW Psychedelic Treasure S currying across a rocky outcrop a lizard stops abruptly in a patch of sunlight. A conservation biologist senses the motion and turns to find a gecko splashed with rainbow colors its bright orange legs and tail blend- ing into a striking blue body its head splotched with yellow and green. Te psy- chedelic rock gecko Cnemaspis psychedelica was discovered in 2010 during an expedition to the Greater Mekong region of southeast Asia Figure 43.1. Its known habitat is restricted to Hon Khoai an island occupying just 8 km 2 3 square miles in southern Vietnam. Other new species found during the same series of expeditions include the Elvis monkey which sports a hairdo like that of a certain legendary musician. Between 2000 and 2010 biologists identified more than a thousand new spe- cies in the Greater Mekong region alone. To date scientists have described and named about 1.8 million species of organisms. Some biologists think that about 10 million more species currently exist oth- ers estimate the number to be as high as 100 million. Te greatest concentrations of species are found in the tropics. Unfortunately tropical forests are being cleared at an alarming rate to support a burgeoning human population. In Vietnam rates of deforestation are among the very highest in the world Figure 43.2. What will become of the psychedelic rock gecko and other newly discovered species if such activities con- tinue unchecked Troughout the biosphere human activities are altering trophic structures energy flow chemical cy- cling and natural disturbance—ecosystem processes on which we and all other species depend see Chapter 42. We have physically altered nearly half of Earth’s land surface and we use over half of all accessible surface fresh water. In the oceans stocks of most major fisheries are shrinking because of overharvesting. By some estimates we may be pushing more species toward extinction than the large asteroid that triggered the mass extinctions at the close of the Cretaceous period 65.5 million years ago see Figure 23.10. In this chapter we apply a global perspective to the changes happening across Earth focusing on a discipline that seeks to preserve life: Conservation biology integrates ecology evolutionary biology molecular biology genetics 43 Global Ecology and Conservation Biology KEY CONCEPTS 43.1 Human activities threaten Earth’s biodiversity 43.2 Population conservation focuses on population size genetic diversity and critical habitat 43.3 Landscape and regional conservation help sustain biodiversity 43.4 Earth is changing rapidly as a result of human actions 43.5 The human population is no longer growing exponentially but is still increasing rapidly 43.6 Sustainable development can improve human lives while conserving biodiversity ▼ Figure 43.1 What will be the fate of this newly described lizard species

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CHAPTER 43 GLOBAL ECOLOGY AND CONSERVATION BIOLOGY 883 and physiology to conserve biological diversity at all levels. Ef- forts to sustain ecosystem processes and stem the loss of bio- diversity also connect the life sciences with the social sciences economics and humanities. We’ll begin by taking a closer look at the biodiversity crisis and examining some of the conservation strategies being adopted to slow the rate of species loss. We’ll also examine how human activities are altering the environment through climate change and other global processes and we’ll investi- gate the link between these alterations and the growing human population. Finally we’ll consider how decisions about long- term conservation priorities could affect life on Earth. CONCEPT 43.1 Human activities threaten Earth’s biodiversity Extinction is a natural phenomenon that has been occurring since life first evolved it is the high rate of extinction that is responsible for today’s biodiversity crisis see Chapter 23. Because we can only estimate the number of species cur- rently existing we cannot determine the exact rate of species loss. However we do know that human activities threaten Earth’s biodiversity at all levels. Three Levels of Biodiversity Biodiversity—short for biological diversity—can be considered at three main levels: genetic diversity species diversity and ecosystem diversity Figure 43.3. Genetic Diversity Genetic diversity comprises not only the individual genetic variation within a population but also the genetic variation between populations that is often associated with adapta- tions to local conditions see Chapter 21. If one population becomes extinct then a species may have lost some of the ▲ Figure 43.2 Tropical deforestation in Vietnam. genetic diversity that makes microevolution possible. Tis erosion of genetic diversity in turn reduces the adaptive po- tential of the species. Species Diversity Public awareness of the biodiversity crisis centers on species diversity—the variety of species in an ecosystem or across the biosphere see Chapter 41. As more species are lost to extinc- tion species diversity decreases. Te U.S. Endangered Species Act defines an endangered species as one that is “in danger of extinction throughout all or a significant portion of its range. ” Treatened species are those considered likely to become endangered in the near future. Te following are just a few sta- tistics that illustrate the problem of species loss: • According to the International Union for Conservation of Nature and Natural Resources IUCN 12 of the 10000 known species of birds and 21 of the 5500 known species of mammals are threatened. Genetic diversity in a vole population Species diversity in a coastal redwood ecosystem Community and ecosystem diversity across the landscape of an entire region ▲ Figure 43.3 Three levels of biodiversity. The oversized chromosomes in the top diagram symbolize the genetic variation within the population.

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884 UNIT SEVEN ECOLOGY • A survey by the Center for Plant Conservation showed that of the nearly 20000 known plant species in the United States 200 have become extinct since such records have been kept and 730 are endangered or threatened. • In North America at least 123 freshwater animal species have become extinct since 1900 and hundreds more spe- cies are threatened. Te extinction rate for North American freshwater fauna is about five times as high as that for ter- restrial animals. Extinction of species may also be local for example a species may be lost in one river system but survive in an adjacent one. Global extinction of a species means that it is lost from all the ecosystems in which it lived leaving them permanently impov- erished Figure 43.4. Ecosystem Diversity Te variety of the biosphere’s ecosystems is a third level of biological diversity. Because of the many interactions between populations of different species in an ecosystem the local extinction of one species can have a negative impact on other species in the ecosystem see Figure 41.15. For instance bats called “flying foxes” are important pollinators and seed dispers- ers in the Pacific Islands where they are increasingly hunted as a luxury food Figure 43.5. Conservation biologists fear that the extinction of flying foxes would also harm the native plants of the Samoan Islands where four-fifths of the tree species de- pend on flying foxes for pollination or seed dispersal. Some ecosystems have already been heavily affected by humans and others are being altered at a rapid pace. Since European colonization more than half of the wetlands in the contiguous United States have been drained and converted to agricultural and other uses. In California Arizona and New Mexico roughly 90 of native riparian streamside com- munities have been affected by overgrazing flood control water diversions lowering of water tables and invasion by non-native plants. Biodiversity and Human Welfare Why should we care about the loss of biodiversity One rea- son is what Harvard biologist E. O. Wilson calls biophilia our sense of connection to nature and all life. Te belief that other species are entitled to life is a pervasive theme of many reli- gions and the basis of a moral argument that we should protect biodiversity. Tere is also a concern for future human genera- tions. Paraphrasing an old proverb G. H. Brundtland a former prime minister of Norway said: “We must consider our planet to be on loan from our children rather than being a gift from our ancestors. ” In addition to such philosophical and moral justifications species and genetic diversity bring us many prac- tical benefits. Benefits of Species and Genetic Diversity Many species that are threatened could potentially provide medicines food and fibers for human use making biodiversity a crucial natural resource. Products from aspirin to antibiotics were originally derived from natural sources. In food produc- tion if we lose wild populations of plants closely related to agricultural species we lose genetic resources that could be used to improve crop qualities such as disease resistance. For instance plant breeders responded to devastating outbreaks of the grassy stunt virus in rice Oryza sativa by screening 7000 populations of this species and its close relatives for Philippine eagle Yangtze River dolphin ▲ Figure 43.4 A hundred heartbeats from extinction. These are two members of what E. O. Wilson calls the Hundred Heartbeat Club species with fewer than 100 individuals remaining on Earth. The Yangtze River dolphin was even thought to be extinct but a few individuals were reportedly sighted in 2007. To document that a species has actually become extinct what factors would you need to consider ▲ Figure 43.5 The endangered Marianas “flying fox” bat Pteropus mariannus an important pollinator.

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CHAPTER 43 GLOBAL ECOLOGY AND CONSERVATION BIOLOGY 885 ecosystem services to purify its water naturally the city saved 8 billion it would have otherwise spent to build a new water treatment plant and 300 million a year to run the plant. Tere is growing evidence that the functioning of ecosys- tems and hence their capacity to perform services is linked to biodiversity. As human activities reduce biodiversity we are reducing the capacity of the planet’s ecosystems to perform processes critical to our own survival. Threats to Biodiversity Many different human activities threaten biodiversity on local regional and global scales. Te threats posed by these activi- ties are of four major types: habitat loss introduced species overharvesting and global change. Habitat Loss Human alteration of habitat is the single greatest threat to biodi- versity throughout the biosphere. Habitat loss has been brought about by agriculture urban development forestry mining and pollution. As discussed later in this chapter global climate change is already altering habitats today and will have an even larger effect later this century. When no alternative habitat is available or a species is unable to move habitat loss may mean extinction. Te IUCN implicates destruction of physical habitat for 73 of the species that have become extinct endangered vulnerable or rare in the last few hundred years. Habitat loss and fragmentation may occur over large re- gions. Approximately 98 of the tropical dry forests of Central America and Mexico have been cut down. Te clearing of tropical rain forest in the state of Veracruz Mexico mostly for cattle ranching has resulted in the loss of more than 90 of the original forest leaving relatively small isolated patches of forest. Other natural habitats have also been fragmented by human activities Figure 43.6. resistance to the virus. One population of a single relative In- dian rice Oryza nivara was found to be resistant to the virus and scientists succeeded in breeding the resistance trait into commercial rice varieties. T oday the original disease-resistant population has apparently become extinct in the wild. In the United States about 25 of the prescriptions dispensed from pharmacies contain substances originally derived from plants. In the 1970s researchers discov- ered that the rosy periwinkle Catharanthus roseus which grows on the island of Mada- gascar off the coast of Africa contains alkaloids that inhibit cancer cell growth. Tis discovery led to treatments for two deadly forms of cancer Hodgkin’s lymphoma and childhood leukemia resulting in remission in most cases. Each loss of a species means the loss of unique genes some of which may code for enormously useful proteins. Te en- zyme Taq polymerase was first extracted from a bacterium Termus aquaticus found in hot springs at Yellowstone Na- tional Park. Tis enzyme is essential for the polymerase chain reaction PCR because it is stable at the high temperatures required for automated PCR see Figure 13.25. However because millions of species may become extinct before we dis- cover them we stand to lose the valuable genetic potential held in their unique libraries of genes. Ecosystem Services Te benefits that individual species provide to humans are substantial but saving individual species is only part of the reason for preserving ecosystems. We humans evolved in Earth’s ecosystems and we rely on these systems and their in- habitants for our survival. Ecosystem services encompass all the processes through which natural ecosystems help sustain human life. Ecosystems purify our air and water. Tey detoxify and decompose our wastes and reduce the impacts of extreme weather and flooding. Te organisms in ecosystems pollinate our crops control pests and create and preserve our soils. Moreover these diverse services are provided for free. Perhaps because we don’t attach a monetary value to the services of natural ecosystems we generally undervalue them. In 1997 ecologist Robert Costanza and his colleagues esti- mated the value of Earth’s ecosystem services at 33 trillion per year nearly twice the gross national product of all the countries on Earth at the time 18 trillion. It may be more realistic to do the accounting on a smaller scale. In 1996 New York City invested more than 1 billion to buy land and restore habitat in the Catskill Mountains the source of much of the city’s fresh water. Tis investment was spurred by increasing pollution of the water by sewage pesticides and fertilizers. By harnessing Rosy periwinkle ▲ Figure 43.6 Habitat fragmentation in the foothills of Los Angeles. Development in the valleys may confine the organisms that inhabit the narrow strips of hillside.

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886 UNIT SEVEN ECOLOGY Introduced species are a worldwide problem contributing to approximately 40 of the extinctions recorded since 1750 and costing billions of dollars each year in damage and control efforts. Tere are more than 50000 introduced species in the United States alone. Overharvesting Te term overharvesting refers generally to the harvesting of wild organisms at rates exceeding the ability of their popula- tions to rebound. Species with restricted habitats such as small islands are particularly vulnerable to overharvesting. One such species was the great auk a large flightless seabird found on islands in the North Atlantic Ocean. By the 1840s the great auk had been hunted to extinction to satisfy the hu- man demand for its feathers eggs and meat. Also susceptible to overharvesting are large organisms with low reproductive rates such as elephants whales and rhinoceroses. Te decline of Earth’s largest terrestrial animals the African elephants is a classic example of the impact of overhunting. Largely because of the trade in ivory elephant populations have been declining in most of Africa for the last 50 years. An international ban on the sale of new ivory resulted in increased poaching illegal hunting so the ban had little effect in much of central and eastern Africa. Only in South Africa where once-decimated herds have been well protected for nearly a century have elephant populations been stable or increasing see Figure 40.18. Conservation biologists increasingly use the tools of mo- lecular genetics to track the origins of tissues harvested from endangered species. Researchers at the University of Washing- ton have constructed a DNA reference map for the African el- ephant using DNA isolated from elephant dung. By comparing this reference map with DNA isolated from samples of ivory harvested either legally or by poachers they can determine to within a few hundred kilometers where the elephants were killed Figure 43.8. Such work in Zambia suggested that poaching rates were 30 times higher than previously estimated In almost all cases habitat fragmentation leads to species loss because the smaller populations in habitat fragments have a higher probability of local extinction. Prairie covered about 800000 hectares ha of southern Wisconsin when Europeans first arrived in North America but occupies less than 800 ha today most of the original prairie in this area is now used to grow crops. Plant diversity surveys of 54 Wis- consin prairie remnants conducted in 1948–1954 and re- peated in 1987–1988 showed that the remnants lost between 8 and 60 of their plant species in the time between the two surveys. Habitat loss is also a major threat to aquatic biodiversity. About 70 of coral reefs among Earth’s most species-rich aquatic communities have been damaged by human activities. At the current rate of destruction 40–50 of the reefs home to one-third of marine fish species could disappear in the next 30 to 40 years. Freshwater habitats are also being lost often as a result of the dams reservoirs channel modification and flow regulation now affecting most of the world’s rivers. For example the more than 30 dams and locks built along the Mobile River basin in the southeastern United States changed river depth and flow. While providing the benefits of hydroelectric power and increased ship traffic these dams and locks also helped drive more than 40 species of mussels and snails to extinction. Introduced Species Introduced species also called exotic species are those that humans move intentionally or accidentally from the species’ native locations to new geographic regions. Human travel by ship and airplane has accelerated the transplant of species. Free from the predators parasites and pathogens that limit their populations in their native habitats such transplanted species may spread rapidly through a new region. Some introduced species disrupt their new community of- ten by preying on native organisms or outcompeting them for resources. Te brown tree snake was accidentally introduced to the island of Guam from other parts of the South Pacific after World War II: It was a “stowaway” in military cargo. Since then 12 species of birds and 6 species of lizards that the snakes ate have become extinct on Guam which had no native snakes. Te devastating zebra mussel a filter-feeding mol- lusc was introduced into the Great Lakes of North America in 1988 most likely in the ballast water of ships arriving from Europe. Zebra mussels form dense colonies and have disrupted freshwater ecosystems threatening native aquatic species. Tey have also clogged water intake structures causing billions of dollars in damage to domestic and industrial water supplies. Humans have deliberately introduced many species with good intentions but disastrous effects. An Asian plant called kudzu which the U.S. Department of Agriculture once introduced in the southern United States to help control erosion has taken over large areas of the landscape there Figure 43.7. ▲ Figure 43.7 Kudzu an introduced species thriving in South Carolina.

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