B I O L O G YSeventh Edition

Neil A. CampbellUniversity of California, Riverside

Jane B. ReeceBerkeley, California

CONTRIBUTORS

Lisa UrryManuel Molles

Carl ZimmerChristopher Wills

Peter Minorsky

Mary Jane NilesAntony Stretton

AND ADVISORS

Mills College, Oakland, California

University of New Mexico, Albuquerque

Science writer, Guilford,\Connecticut

University of California, San Diego

Plant Physiology and Mercy College,Dobbs Ferry, New York

University of San Francisco, California

University of Wisconsin-Madison

PEARSON

BenjaminCummings

San Francisco Boston New YorkCape Town Hong Kong London Madrid Mexico City

Montreal Munich 'Paris Singapore Sydney Tokyo Toronto

Detailed ContentsExploring Life 2OVERVIEW: Biology's Most Exciting Era 2

CONCEPT 1.1 Biologists explore life from the microscopic tothe global scale 2

A Hierarchy of Biological Organization 3A Closer Look at Ecosystems 6A Closer Look at Cells 6

CONCEPT i.2 Biological systems are much more than thesum of their parts 9

The Emergent Properties of Systems 9 ••The Power and Limitations of Reductionism 9Systems Biology 10Feedback Regulation in Biological Systems 11

CONCEPT i.3 Biologists explore life across its greatdiversity of species 12

Grouping Species: The Basic Idea 12The Three Domains of Life 13Unity in the Diversity of Life 14

CONCEPT i.4 Evolution accounts for life's unity anddiversity 15 -J

Natural Selection 16The Tree of Life 17

CONCEPT 1.5 Biologists use various forms of inquiry toexplore life 19

Discovery Science 19Hypothesis-Based Science 20A Case Study in Scientific Inquiry: Investigating Mimicry

in Snake Populations 21Limitations of Science 24Theories in Science 24Model-Building in Science 24The Culture of Science 25Science, Technology, and Society 25

CONCEPT i.6 A set of themes connects the concepts ofbiology 26

UNIT ONE

The Chemistry of LifeThe Chemical Context of Life 32OVERVIEW: Chemical Foundations of Biology 32

CONCEPT 2.1 Matter consists of chemical elements in pureform and in combinations called compounds 32

Elements and Compounds 32Essential Elements of Life 33

CONCEPT 2.2 An element's properties depend on thestructure of its atoms 34

Subatomic Particles 34Atomic Number and Atomic Mass 34Isotopes 35The Energy Levels of Electrons 36Electron Configuration and Chemical Properties 37Electron Orbitals 38 s

CONCEPT 2.3 The formation and function of moleculesdepend on chemical bonding between atoms 39

Covalent Bonds 39Ionic Bonds 41Weak Chemical Bonds 42Molecular Shape and Function 42

CONCEPT 2.4 Chemical reactions make and break chemicalbonds 44

Water and the Fitness of theEnvironment 47OVERVIEW: The Molecule That Supports All of Life 47

CONCEPT 3.1 The polarity of water molecules results inhydrogen bonding 47 .

CONCEPT 3.2 Four emergent properties of water contributeto Earth's fitness for life 48

Cohesion 48Moderation of Temperatures 49Insulation of Bodies of Water by Floating Ice 50The Solvent of Life 51

CONCEPT 3.3 Dissociation of water molecules leads toacidic and basic conditions that affect livingorganisms 53

Effects of Changes in pH 53The Threat of Acid Precipitation 55

Carhon and the Molecular Diversity ofLife 58OVERVIEW: Carbon—The Backbone of BiologicalMolecules 58

CONCEPT 4.1 Organic chemistry is the study of jcarboncompounds 58

XXV

CONCEPT 4.2 Carbon atoms can form diverse molecules bybonding to four other atoms 59

The Formation of Bonds with Carbon 59Molecular Diversity Arising from Carbon Skeleton

Variation 61

CONCEPT 4.3 Functional groups are the parts of moleculesinvolved in chemical reactions 63

The Functional Groups Most Important in the Chemistryof Life 63

ATP: An Important Source of Energy for CellularProcesses 66

The Chemical Elements of Life: A Review 66

The Structure and Function ofMacromolecules 68OVERVIEW: The Molecules of Life 68

CONCEPT 5.1 Most macromolecules are polymers, builtfrom monomers 68

The Synthesis and Breakdown of Polymers 68Diversity of Polymers 69

CONCEPT 5.2 Carbohydrates serve as fuel and buildingmaterial 69

Sugars 70Polysaccharides 71

CONCEPT 5.3 Lipids are a diverse group of hydrophobicmolecules 74

Fats 75Phospholipids 76Steroids 77

CONCEPT 5.4 Proteins have many structures, resulting in awide range of functions 77

Polypeptides 78Protein Conformation and Function 81

CONCEPT s.5 Nucleic acids store and transmit hereditaryinformation 86

The Roles of Nucleic Acids 86The Structure of Nucleic Acids 87The DNA Double Helix 88DNA and Proteins as Tape Measures of

Evolution 89

The Theme of Emergent Properties in the Chemistry ofLife: A Review 89

UNIT TWO

The Cell 926 A Tour of the Cell 94

OVERVIEW: The Importance of Cells 94

CONCEPT 6.1 To study cells, biologists use microscopes andthe tools of biochemistry 94

Microscopy 95Isolating Organelles by Cell Fractionation 97

CONCEPT 6.2 Eukaryotic cells have internal membranes thatcompartmentalize their functions 98

Comparing Prokaryotic and Eukaryotic Cells 98A Panoramic View of the Eukaryotic Cell 99

CONCEPT 6.3 The eukaryotic cell's genetic instructions arehoused in the nucleus and carried out by theribosomes 102

The Nucleus: Genetic Library of the Cell 102Ribosomes: Protein Factories in the Cell 102

CONCEPT 6.4 The endomembrane system regulates proteintraffic and performs metabolic functions in the cell 104

The Endoplasmic Reticulum: Biosynthetic Factory 104The Golgi Apparatus: Shipping and Receiving Center 105 •Lysosomes: Digestive Compartments 107Vacuoles: Diverse Maintenance Compartments 108The Endomembrane System: A Review 108

CONCEPT 6.5 Mitochondria and chloroplasts change energy^from one form to another 109

Mitochondria: Chemical Energy Conversion 109Chloroplasts: Capture of Light Energy 110Peroxisomes: Oxidation 110

CONCEPT 6.6 The cytoskeleton is a network of fibers thatorganizes structures and activities in the cell 112

Roles of the Cytoskeleton: Support, Motility, andRegulation 112

Components of the Cytoskeleton 113CONCEPT 6.7 Extracellular components and connectionsbetween cells help coordinate cellular activities 118

Cell Walls of Plants 118The Extracellular Matrix (ECM) of Animal Cells 119 ^Intercellular Junctions 120

THE CELL: A Living Unit Greater Than the Sum of ItsParts 120

Membrane Structure and Function 124OVERVIEW: Life at the Edge 124

CONCEPT ?.i Cellular membranes are fluid mosaics oflipids and proteins 124

Membrane Models: Scientific Inquiry 125The Fluidity of Membranes 126 iMembrane Proteins and Their Functions 127

The Role of Membrane Carbohydrates in Cell-CellRecognition 129

Synthesis and Sidedness of Membranes 129CONCEPT 7.2 Membrane structure results in selectivepermeability 130

The Permeability of the Lipid Bilayer 130Transport Proteins 130

CONCEPT 7.3 Passive transport is diffusion of a substanceacross a membrane with no energy investment 130

Effects of Osmosis on Water Balance 131Facilitated Diffusion: Passive Transport Aided by

Proteins 133CONCEPT 7.4 Active transport uses energy to move solutesagainst their gradients 134

The Need for Energy in Active Transport 134Maintenance of Membrane Potential by Ion Pumps 134'Cotransport: Coupled Transport by a Membrane

Protein 136

CONCEPT 7.5 Bulk transport across the plasma membraneoccurs by exocytosis and endocytosis 137

Exocytosis 137Endocytosis 137

8 An Introduction to Metabolism 141OVERVIEW: The Energy of Life 141

CONCEPT 8.1 An organism's metabolism transforms matterand energy, subject to the laws of thermodynamics 141

Organization of the Chemistry of Life into MetabolicPathways 141

Forms of Energy 142The Laws of Energy Transformation 143

CONCEPT s.2 The free-energy change of a reaction tells uswhether the reaction occurs spontaneously 145

Free-Energy Change, AG 145Free Energy, Stability, and Equilibrium 145Free Energy and Metabolism 146

CONCEPT 8.3 ATP powers cellular work by couplingexergonic reactions to endergonic reactions 148

The Structure and Hydrolysis of ATP 148How ATP Performs Work 149The Regeneration of ATP 150

CONCEPT 8.4 Enzymes speed up metabolic reactions bylowering energy barriers 150

The Activation Energy Barrier 150How Enzymes Lower the EA Barrier 152Substrate Specificity of Enzymes 152Catalysis in the Enzyme's Active Site 152Effects of Local Conditions on Enzyme Activity 154

CONCEPT 8.5 Regulation of enzyme activity helps controlmetabolism 156

Allosteric Regulation of Enzymes 156Specific Localization of Enzymes Within the Cell 157

9 Cellular Respiration: HarvestingChemical Energy 160OVERVIEW: Life Is Work 160

CONCEPT 9.1 Catabolic pathways yield energy by oxidizingorganic fuels 161

Catabolic Pathways and Production of ATP 161Redox Reactions: Oxidation and Reduction 161The Stages of Cellular Respiration: A Preview 164

CONCEPT 9.2 Glycolysis harvests chemical energy byoxidizing glucose to pyruvate 165

CONCEPT 9.3 The citric acid cycle completesthe energy-yielding oxidation of organic molecules 168

CONCEPT 9.4 During oxidative phosphorylation,chemiosmosis couples electron transport to ATPsynthesis 170

The Pathway of Electron Transport 170Chemiosmosis: The Energy-Coupling

Mechanism 171An Accounting of ATP Production by Cellular

Respiration 173

CONCEPT 9.5 Fermentation enables some cells toproduce ATP without the use of oxygen 174

Types of Fermentation 175Fermentation and Cellular Respiration

Compared 175The Evolutionary Significance of Glycolysis 176

CONCEPT 9.6 Glycolysis and the citric acid cycle connect tomany other metabolic pathways 176

The Versatility of Catabolism 176Biosynthesis (Anabolic Pathways) 177Regulation of Cellular Respiration via Feedback

Mechanisms 177

Photosynthesis 181OVERVIEW: The Process That Feeds the Biosphere 181

CONCEPT 10.1 Photosynthesis converts light energy to thechemical energy of food 182

Chloroplasts: The Sites of Photosynthesis in Plants 182Tracking Atoms;Through Photosynthesis: Scientific

Inquiry 183'The Two Stages of Photosynthesis: A Preview 184

CONCEPT 10.2 The light reactions convert solar energy tothe chemical energy of ATP and NADPH 186

The Nature of Sunlight 186Photosynthetic Pigments: The Light Receptors 186Excitation of Chlorophyll by Light 188A Photosystem: A Reaction Center Associated with Light-

Harvesting Complexes 189Noncyclic Electron Flow 190Cyclic Electron Flow 191A Comparison of Chemiosmosis in Chloroplasts

and Mitochondria 192

CONCEPT 10.3 The Calvin cycle uses ATP and NADPH toconvert CO2 to sugar 193

CONCEPT 10.4 Alternative mechanisms of carbon fixationhave evolved in hot, arid climates 195

Photorespiration: An Evolutionary Relic? 195C4 Plants 196CAM Plants 196The Importance of Photosynthesis: A Review 197

Contents XXVll

Cell Communication 201OVERVIEW: The Cellular Internet 201

CONCEPT 11.1 External signals are converted into responseswithin the cell 201

Evolution of Cell Signaling 201Local and Long-Distance Signaling 202The Three Stages of Cell Signaling: A Preview 203

CONCEPT 11.2 Reception: A signal molecule bindsto a receptor protein, causing it to change shape 204

Intracellular Receptors 205Receptors in the Plasma Membrane 205

CONCEPT 11.3 Transduction: Cascades of molecularinteractions relay signals from receptors to targetmolecules in the cell 208

Signal Transduction Pathways 208Protein Phosphorylation and Dephosphorylation 209Small Molecules and Ions as Second Messengers 210

CONCEPT 11.4 Response: Cell signaling leads to regulationof cytoplasmic activities or transcription 212

Cytoplasmic and Nuclear Responses 212Fine-Tuning of the Response 213

The Cell Cycle 218OVERVIEW: The Key Roles of Cell Division 218

CONCEPT 12.1 Cell division results in genetically identicaldaughter cells 219

Cellular Organization of the Genetic Material 219Distribution of Chromosomes During Cell Division 219

CONCEPT 12.2 The mitotic phase alternates with interphasein the cell cycle 221

Phases of the Cell Cycle 221The Mitotic Spindle: A Closer Look 221Cytokinesis: A Closer Look 224Binary Fission 226The Evolution of Mitosis 227

CONCEPT 12.3 The cell cycle is regulated by a molecularcontrol system 228

Evidence for Cytoplasmic Signals 228The Cell Cycle Control System 229Loss of Cell Cycle Controls in Cancer Cells 232

UNIT THREE

Genetics 23613 Meiosis and Sexual Life Cycles 238

OVERVIEW: Hereditary Similarity and Variation 238

CONCEPT 13.1 Offspring acquire genes from parents byinheriting chromosomes 238

Inheritance of Genes 239Comparison of Asexual and Sexual Reproduction 239

CONCEPT 13.2 Fertilization and meiosis alternate in sexuallife cycles 240

Sets of Chromosomes in Human Cells 240Behavior of Chromosome Sets in the Human Life

Cycle 241The Variety of Sexual Life Cycles 242

CONCEPT 13.3 Meiosis reduces the number of chromosomesets from diploid to haploid 243

The Stages of Meiosis 243A Comparison of Mitosis and Meiosis 247

CONCEPT 13.4 Genetic variation produced in sexual lifecycles contributes to evolution 247

Origins of Genetic Variation Among Offspring 247Evolutionary Significance of Genetic Variation Within

Populations 248

Mendel and the Gene Idea 251OVERVIEW: Drawing from the Deck of Genes 251

CONCEPT 14.1 Mendel used the scientific approach toidentify two laws of inheritance 251

Mendel's Experimental, Quantitative Approach 252The Law of Segregation 253The Law of Independent Assortment 256

CONCEPT 14.2 The laws of probability govern Mendelianinheritance 258

The Multiplication and Addition Rules Applied toMonohybrid Crosses 258

Solving Complex Genetics Problems with the Rules ofProbability 259

CONCEPT 14.3 Inheritance patterns are often more complexthan predicted by simple Mendelian genetics 260

Extending Mendelian Genetics for a Single Gene 260Extending Mendelian Genetics for Two or More

Genes 262Nature and Nurture: The Environmental Impact on

Phenotype 264Integrating a Mendelian View of Heredity and

Variation 264CONCEPT 14.4 Many human traits follow Mendelianpatterns of inheritance 265

Pedigree Analysis 265Recessively Inherited Disorders 266Dominantly Inherited Disorders 267Multifactorial Disorders 268Genetic Testing and Counseling 268

15 The Chromosomal Basis ofInheritance 274OVERVIEW: Locating Genes on Chromosomes 274

CONCEPT 15.1 Mendelian inheritance has its physical basisin the behavior of chromosomes 274

Morgan's Experimental Evidence: Scientific Inquiry 276CONCEPT 15.2 Linked genes tend to be inherited togetherbecause they are located near each other on the samechromosome 277

How Linkage Affects Inheritance: Scientific Inquiry 277Genetic Recombination and Linkage 278Linkage Mapping Using Recombination Data: Scientific

Inquiry 279CONCEPT 15.3 Sex-linked genes exhibit unique patterns ofinheritance 282

The Chromosomal Basis of Sex 282Inheritance of Sex-Linked Genes 283X Inactivation in Female Mammals 284

CONCEPT 15.4 Alterations of chromosome number orstructure cause some genetic disorders 285

Abnormal Chromosome Number 285Alterations of Chromosome Structure 286Human Disorders Due to Chromosomal Alterations 287

CONCEPT 15.5 Some inheritance patterns are exceptions tothe standard chromosome theory 288

Genomic Imprinting 288Inheritance of Organelle Genes 289

16 The Molecular Basis of Inheritance 293OVERVIEW: Life's Operating Instructions 293

CONCEPT 16.1 DNA is the genetic material 293The Search for the Genetic Material: Scientific

Inquiry 293Building a Structural Model of DNA: Scientific

Inquiry 296CONCEPT 16.2 Many proteins work together in DNAreplication and repair 299

The Basic Principle: Base Pairing to a TemplateStrand 299

DNA Replication: A Closer Look 300Proofreading and Repairing DNA 305Replicating the Ends of DNA Molecules 306

17 From Gene to Protein 309OVERVIEW: The Flow of Genetic Information 309

CONCEPT 17.1 Genes specify proteins via transcription andtranslation 309

Evidence from the Study of Metabolic Defects 309Basic Principles of Transcription and Translation 311The Genetic Code 312

CONCEPT 17.2 Transcription is the DNA-directed synthesisof RNA: a closer look 315

Molecular Components of Transcription 315Synthesis of an RNA Transcript 316

CONCEPT 17.3 Eukaryotic cells modify RNA aftertranscription 317

Alteration of mRNA Ends 317Split Genes and RNA Splicing 318

CONCEPT 17.4 Translation is the RNA-directed synthesis ofa polypeptide: a closer look 320

Molecular Components of Translation 320Building a Polypeptide 323Completing and Targeting the Functional

Protein 324

CONCEPT 17.5 RNA plays multiple roles in the cell: areview 327

CONCEPT 17.6 Comparing gene expression in prokaryotesand eukaryotes reveals key differences 327

CONCEPT 17.7 Point mutations can affect protein structureand function 328

Types of Point Mutations 328Mutagens 329What is a Gene? Revisiting the Question 330

18 The Genetics of Viruses andBacteria 334OVERVIEW: Microbial Model Systems 334

CONCEPT 18.1 A virus has a genome but can reproduce onlywithin aLhost cell 334

The Discovery of Viruses: Scientific Inquiry 334Structure of Viruses 335General Features of Viral Reproductive Cycles 336Reproductive Cycles of Phages 337Reproductive Cycles of Animal Viruses 339Evolution of Viruses 342

CONCEPT 18.2 Viruses, viroids, and prions are formidablepathogens in animals and plants 343

Viral Diseases in Animals 343Emerging Viruses 344Viral Diseases in Plants 345Viroids and Prions: The Simplest Infectious

Agents 345

CONCEPT 18.3 Rapid reproduction, mutation, and geneticrecombination contribute to the genetic diversity ofbacteria 346

The Bacterial Genome and Its Replication 346Mutation and Genetic Recombination as Sources of

Genetic Variation. 346Mechanisms of Gene Transfer and Genetic Recombination

in Bacteria 348Transposition of Genetic Elements 351

CONCEPT 18.4 Individual bacteria respond to environmentalchange by regulating their gene expression 352

Operons: The Basic Concept 353Repressible and Inducible Operons: Two Types of

Negative Gene Regulation 354Positive Gene Regulation 356

19 Eukaryotic Genomes: Organization,Regulation, and Evolution 359OVERVIEW: How Eukaryotic Genomes Work andEvolve 359

CONCEPT 19.1 Chromatin structure is based on successivelevels of DNA packing 359

Nucleosomes, or "Beads on a String" 360Higher Levels of DNA Packing 360

Contents xxix

CONCEPT 19.2 Gene expression can be regulated at anystage, but the key step is transcription 362

Differential Gene Expression 362Regulation of Chromatin Structure 363Regulation of Transcription Initiation 364Mechanisms of Post-Transcriptional Regulation 368

CONCEPT 19.3 Cancer results from genetic changes thataffect cell cycle control 370

Types of Genes Associated with Cancer 370Interference with Normal Cell-Signaling Pathways 371The Multistep Model of Cancer Development 373Inherited Predisposition to Cancer 374

CONCEPT 19.4 Eukaryotic genomes can have manynoncoding DNA sequences in addition to genes 374

The Relationship Between Genomic Composition andOrganismal Complexity 374

Transposable Elements and Related Sequences 375Other Repetitive DNA, Including Simple Sequence

DNA 376Genes and Multigene Families 377

CONCEPT 19.5 Duplications, rearrangements, and mutationsof DNA contribute to genome evolution 378

Duplication of Chromosome Sets 378Duplication and Divergence of DNA Segments 378Rearrangements of Parts of Genes: Exon Duplication and

Exon Shuffling 380How Transposable Elements Contribute to Genome

Evolution 380

20 DNA Technology and Genomics 384OVERVIEW: Understanding and ManipulatingGenomes 384

CONCEPT 20.1 DNA cloning permits production of multiplecopies of a specific gene or other DNA segment 385

DNA Cloning and Its Applications: A Preview 385Using Restriction Enzymes to Make Recombinant

DNA 386Cloning a Eukaryotic Gene in a Bacterial Plasmid 386Storing Cloned Genes in DNA Libraries 388Cloning and Expressing Eukaryotic Genes 390Amplifying DNA in Vitro: The Polymerase Chain Reaction

(PCR) 391

CONCEPT 20.2 Restriction fragment analysisdetects DNA differences that affect restriction sites 392

Gel Electrophoresis and Southern Blotting 392Restriction Fragment Length Differences as Genetic

Markers 394

CONCEPT 20.3 Entire genomes can be mapped at the DNAlevel 394

Genetic (Linkage) Mapping: Relative Ordering ofMarkers 396

Physical Mapping: Ordering DNA Fragments 396DNA Sequencing 396

CONCEPT 20.4 Genome sequences provide clues toimportant biological questions 398

Identifying Protein-Coding Genes in DNA Sequences 399Determining Gene Function 400Studying Expression of Interacting Groups of

Genes 400Comparing Genomes of Different Species 400Future Directions in Genomics 402

CONCEPT 2o.s The practical applications of DNAtechnology affect our lives in many ways 402

Medical Applications 402Pharmaceutical Products 404Forensic Evidence 404Environmental Cleanup 405Agricultural Applications 406Safety and Ethical Questions Raised by DNA

Technology 407

21 The Genetic Basis of Development 411OVERVIEW: From Single Cell to MulticellularOrganism 411

CONCEPT 21.1 Embryonic development involvescell division, cell differentiation, andmorphogenesis 412

CONCEPT 21.2 Different cell types result from differentialgene expression in cells with the same DNA 415

Evidence for Genomic Equivalence 415Transcriptional Regulation of Gene Expression During

Development 418Cytoplasmic Determinants and Cell-Cell Signals in Cell

Differentiation 420

CONCEPT 21.3 Pattern formation in animals and plantsresults from similar genetic and cellular mechanisms 421

Drosophila Development: A Cascade of GeneActivations 421

C. elegans: The Role of Cell Signaling 425Plant Development: Cell Signaling and Transcriptional

Regulation 429

CONCEPT 21.4 Comparative studies help explain how theevolution of development leads to morphologicaldiversity 431

Widespread Conservation of Developmental GenesAmong Animals 431

Comparison of Animal and Plant Development 433

UNIT FOUR

Mechanisms of Evolution 43622 Descent with Modification: A Darwinian

View of Life 438OVERVIEW: Darwin Introduces a Revolutionary Theory 438

CONCEPT 22.1 The Darwinian revolution challengedtraditional views of a young Earth inhabited byunchanging species 438

Resistance to the Idea of Evolution 439Theories of Gradualism 440Lamarck's Theory of Evolution 440

CONCEPT 22.2: In The Origin of Species, Darwin proposedthat species change through natural selection 441

Darwin's Research 441The Origin oj Species 443

CONCEPT 22.3 Darwin's theory explains a wide range ofobservations 446

Natural Selection in Action 446Homology, Biogeography, and the Fossil Record 448

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What Is Theoretical about the Darwinian View ofLife? 451

23 The Evolution of Populations 454OVERVIEW: The Smallest Unit of Evolution 454

CONCEPT 23.1 Population genetics provides a foundationfor studying evolution 454

The Modern Synthesis 455Gene Pools and Allele Frequencies 455The Hardy-Weinberg Theorem 456

CONCEPT 23.2 Mutation and sexual recombination producethe variation that makes evolution possible 459

Mutation 459Sexual Recombination 460

CONCEPT 23.3 Natural selection, genetic drift, and geneflow can alter a population's genetic composition 460

Natural Selection 460Genetic Drift 460Gene Flow 462

CONCEPT 23.4 Natural selection is the primary mechanismof adaptive evolution 462

Genetic Variation 462A Closer Look at Natural Selection 464The Preservation of Genetic Variation 466Sexual Selection 468The Evolutionary Enigma of Sexual

Reproduction 469Why Natural Selection Cannot Fashion Perfect

Organisms 469

24 The Origin of Species 472OVERVIEW: That "Mystery of Mysteries" 472

CONCEPT 24.n The biological species concept emphasizesreproductive isolation 473

The Biological Species Concept 473Other Definitions of Species 476

CONCEPT 24.2 Speciation can take place with or withoutgeographic separation 476

Allopatric ("Other Country") Speciation 477Sympatric ("Same Country") Speciation 478Allopatric and Sympatric Speciation: A

Summary 480Adaptive Radiation 480Studying the Genetics of Speciation 481The Tempo of Speciation 481

CONCEPT 24.3 Macroevolutionary changes can accumulatethrough many speciation events 482

Evolutionary Novelties 482Evolution of the Genes That Control

Development 484Evolution Is Not Goal Oriented 486

25 Phylogeny and Systematics 491OVERVIEW: Investigating the Tree of Life 491

CONCEPT 25.1 Phylogenies are based on common ancestriesinferred from fossil, morphological, and molecularevidence 492

The Fossil Record 492Morphological and Molecular Homologies 492

CONCEPT 25.2 Phylogenetic systematics connectsclassification with evolutionary history 495

Binomial Nomenclature 496Hierarchical Classification 496Linking Classification and Phylogeny 496

CONCEPT 25.3 Phylogenetic systematics informs theconstruction of phylogenetic trees based on sharedcharacters 497

Cladistics 498Phylogenetic Trees and Timing 499Maximum Parsimony and Maximum

Likelihood 501Phylogenetic Trees as Hypotheses 501

CONCEPT 25.4 Much of an organism's evolutionary historyis documented in its genome 504

Gene Duplications and Gene Families 505Genome Evolution 505

CONCEPT 25.5 Molecular clocks help track evolutionarytime 506

Molecular Clocks 506The Universal Tree of Life 507

UNIT FIVE

The Evolutionary History ofBiological Diversity 51026 The Tree of Life: An Introduction to

Biological Diversity 512OVERVIEW: Changing Life on a Changing Earth 512

CONCEPT 26.1 Conditions on early Earth made the origin oflife possible 513

Synthesis of Organic Compounds on EarlyEarth 513

Abiotic Synthesis of Polymers 514Protobionts 515The "RNA World" and the Dawn of Natural Selection 515

CONCEPT 26.2 The fossil record chronicles life onEarth 517

How Rocks and Fossils Are Dated 517 ,The Geologic Record 518Mass Extinctions 518

Contents XXXI

CONCEPT 26.3 As prokaryotes evolved, they exploited andchanged young Earth 521

The First Prokaryotes 522Electron Transport Systems 521Photosynthesis and the Oxygen Revolution 522

CONCEPT 26.4 Eukaryotic cells arose from symbioses andgenetic exchanges between prokaryotes 523

The First Eukaryotes 523Endosymbiotic Origin of Mitochondria and

Plastids 523Eukaryotic Cells as Genetic Chimeras 524

CONCEPT 26.5 Multicellularity evolved several times ineukaryotes 525

The Earliest Multicellular Eukaryotes 525The Colonial Connection 526The "Cambrian Explosion" 526Colonization of Land by Plants, Fungi, and

Animals 527Continental Drift 527

CONCEPT 26.6 New information has revised ourunderstanding of the tree of life 529

Previous Taxonomic Systems 529Reconstructing the Tree of Life: A Work in

Progress 529

27 Prokaryotes 534OVERVIEW: They're (Almost) Everywhere! 534

CONCEPT 27.1 Structural, functional, and geneticadaptations contribute to prokaryote success 534

Cell-Surface Structures 534Motility 536Internal and Genomic Organization 537Reproduction and Adaptation 537

CONCEPT 27.2 A great diversity of nutritional and metabolicadaptations have evolved in prokaryotes 538

Metabolic Relationships to Oxygen 539Nitrogen Metabolism 539Metabolic Cooperation 539

CONCEPT 27.3 Molecular systematics is illuminatingprokaryotic phylogeny 540

Lessons from Molecular Systematics 540Bacteria 541Archaea 541

CONCEPT 27.4 Prokaryotes play crucial roles in thebiosphere 544

Chemical Recycling 544Symbiotic Relationships 545

CONCEPT 27.5 Prokaryotes have both harmful and beneficialimpacts on humans 545

Pathogenic Prokaryotes 545Prokaryotes in Research and Technology 546

28 Protists 549OVERVIEW: A World in a Drop of Water 549

CONCEPT 28.1 Protists are an extremely diverse assortmentof eukaryotes 549

Endosymbiosis in Eukaryotic Evolution 550CONCEPT 28.2 Diplomonads and parabasalids havemodified mitochondria 552

Diplomonads 552Parabasalids 553

CONCEPT 28.3 Euglenozoans have flagella with a uniqueinternal structure 553

Kinetoplastids 553Euglenids 554

CONCEPT 28.4 Alveolates have sacs beneath the plasmamembrane 555

Dinoflagellates 555Apicomplexans 555Ciliates 556

CONCEPT 28.5 Stramenopiles have "hairy" and smoothflagella 558

Oomycetes (Water Molds and Their Relatives) 558Diatoms 559Golden Algae 560Brown Algae 560

CONCEPT 28.6 Cercozoans and radiolarians have threadlikepseudopodia 563

Foraminiferans (Forams) 563Radiolarians 563

CONCEPT 28.7 Amoebozoans have lobe-shapedpseudopodia 564

Gymnamoebas 564Entamoebas 564Slime Molds 564

CONCEPT 28.8 Red algae and green algae are the closestrelatives of land plants 567

Red Algae 567Green Algae 567

29 Plant Diversity I: How Plants ColonizedLand 573OVERVIEW: The Greening of Earth 573CONCEPT 29.1 Land plants evolved from greenalgae 573

Morphological and Biochemical Evidence 573Genetic Evidence 574Adaptations Enabling the Move to Land 574

CONCEPT 29.2 Land plants possess a set of derivedterrestrial adaptations 575

Defining the Plant Kingdom 575Derived Traits of Plants 575

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The Origin and Diversification of Plants 575CONCEPT 29.3 The life cycles of mosses and otherbryophytes are dominated by the gametophyte stage 580

Bryophyte Gametophytes. 580Bryophyte Sporophytes 580The Ecological and Economic Importance of

Mosses 583

CONCEPT 29.4 Ferns and other seedless vascular plantsformed the first forests 584

Origins of Vascular Plants 584Classification of Seedless Vascular Plants 586The Significance of Seedless Vascular Plants 588

30 Plant Diversity II: The Evolution of SeedPlants 591OVERVIEW: Feeding the World 591

CONCEPT 30.1 The reduced gametophytes of seed plantsare protected in ovules and pollen grains 591

Advantages of Reduced Gametophytes 591Heterospory: The Rule Among Seed Plants 592Ovules and Production of Eggs 592Pollen and Production of Sperm 592The Evolutionary Advantage of Seeds 593

CONCEPT 30.2 Gymnosperms bear "naked" seeds, typicallyon cones 593

Gymnosperm Evolution 596A Closer Look at the Life Cycle of a Pine 596

CONCEPT 30.3 The reproductive adaptationsof angiosperms include flowers and fruits 598

Characteristics of Angiosperms 598Angiosperm Evolution 601Angiosperm Diversity 602Evolutionary Links Between Angiosperms and

Animals 604

CONCEPT 30.4 Human welfare depends greatly on seedplants 605

Products from Seed Plants 605Threats to Plant Diversity 606

31 Fungi 608OVERVIEW: Mighty Mushrooms 608

CONCEPT 3i.i Fungi are heterotrophs that feed byabsorption 608

Nutrition and Fungal Lifestyles 608Body Structure 609

CONCEPT 31.2 Fungi produce spores through sexual orasexual life cycles 610

Sexual Reproduction 610Asexual Reproduction 611

CONCEPT 31.3 Fungi descended from an aquatic, single-celled, flagellated protist 612

The Origin of Fungi 612The Move to Land 612

CONCEPT 31.4 Fungi have radiated into a diverse set oflineages 612

Chytrids 613Zygomycetes 613

Glomeromycetes 615Ascomycetes 616Basidiomycetes 618

CONCEPT 31.5 Fungi have a powerful impact on ecosystemsand human welfare 620

Decomposers 620Symbionts 620Pathogens 622Practical Uses of Fungi 623

32 An Introduction to Animal Diversity 626OVERVIEW: Welcome to Your Kingdom 626

CONCEPT 32.1 Animals are multicellular, heterotrophiceukaryotes with tissues that develop from embryoniclayers 626

Nutritional Mode 626Cell Structure and Specialization 626Reproduction and Development 627

CONCEPT 32.2 The history of animals may span more than abillion years 628

Neoproterozoic Era (1 Billion-542 Million YearsAgo) 628

Paleozoic Era (542-251 Million Years Ago) 629Mesozoic Era (251-65.5 Million Years Ago) 629Cenozoic Era (65.5 Million Years Ago to the

Present) 629

CONCEPT 32.3 Animals can be characterized by "bodyplans" 630

Symmetry 630Tissues 630Body Cavities 631Protostome and Deuterostome Development 631

CONCEPT 32.4 Leading hypotheses agree onmajor features of the animal phylogenetictree 633 ";

Points of Agreement 633Disagreement over the Bilaterians 634Future Directions in Animal Systematics 636

33 Invertebrates 638OVERVIEW: Life Without a Backbone 638

CONCEPT 33.1 Sponges are sessile and have a porous bodyand choanocytes 642

CONCEPT 33.2 Cnidarians have radial symmetry,a gastrovascular cavity, and cnidocytes 643

Hydrozoans 644Scyphozoans 644Cubozoans 645Anthozoans 645

CONCEPT 33.3 Most animals have bilateral symmetry 646Flatworms 646Rotifers 648Lophophorates: Ectoprocts, Phoronids, and

Brachiopods 649Nemerteans 649

CONCEPT 33.4 Molluscs have a muscular foot, a visceralmass, and a mantle 650

Chitons 651Gastropods 651

Contents XXXll l

Bivalves 652Cephalopods 652

CONCEPT 33.5 Annelids are segmented worms 653Oligochaetes 653Polychaetes 655Leeches 655

CONCEPT 33.6 Nematodes are nonsegmentedpseudocoelomates covered by a tough cuticle 655

CONCEPT 33.7 Arthropods are segmented coelomates thathave an exoskeleton and jointed appendages 656

General Characteristics of Arthropods 656Cheliceriforms 658Myriapods 659Insects 660Crustaceans 664

CONCEPT 33.8 Echinoderms and chordates aredeuterostomes 665

Echinoderms 665Chordates 667

34 Vertebrates 671OVERVIEW: Half a Billion Years of Backbones 671

CONCEPT 34.1 Chordates have a notochord and a dorsal,hollow nerve cord 671

Derived Characters of Chordates 673Tunicates 673Lanceletes 674

Early Chordate Evolution 674

CONCEPT 34.2 Craniates are chordates that have a head 675Derived Characters of Craniates 676The Origin of Craniates 676Hagfishes 676

CONCEPT 34.3 Vertebrates are craniates that have abackbone 678

Derived Characters of Vertebrates 678Lampreys 678Fossils of Early Vertebrates 678Origins of Bones and Teeth 679

CONCEPT 34.4 Gnathostomes are vertebrates that havejaws 679

Derived Characters of Gnathostomes 679Fossil Gnathostomes 680Chondricthyans (Sharks, Rays, and Their

Relatives) 680Ray-Finned Fishes and Lobe-Fins 682

CONCEPT 34.5 Tetrapods are gnathostomes that have limbsand feet 684

Derived Characters of Tetrapods 684The Origin of Tetrapods 684Amphibians 685

CONCEPT 34.6 Amniotes are tetrapods that have aterrestrially adapted egg 687

Derived Characters of Amniotes 688Early Amniotes 688Reptiles 688Birds 691

CONCEPT 34.7 Mammals are amniotes that have hair andproduce milk 694

Derived Characters of Mammals 694

Early Evolution of Mammals 694Monotremes 695Marsupials 695Eutherians (Placental Mammals) 697

CONCEPT 34.8 Humans are bipedal hominids with a largebrain 701

Derived Characters of Humans 701The Earliest Hominids 702Australopiths 703Bipedalism 704Tool Use 704Early Homo 704Neanderthals 705Homo sapiens 705

UNIT SIX

Plant Form and Function 71035 Plant Structure, Growth, and

Development 712OVERVIEW: No Two Plants Are Alike 712

CONCEPT 35.1 The plant body has a hierarchy of organs,tissues, and cells 712

The Three Basic Plant Organs: Roots, Stems, andLeaves 713

The Three Tissue Systems: Dermal, Vascular, andGround 717

Common Types of Plant Cells 717CONCEPT 35.2 Meristems generate cells for new organs 720CONCEPT 35.3 Primary growth lengthens roots andshoots 721

Primary Growth of Roots 721Primary Growth of Shoots 723

CONCEPT 35.4 Secondary growth adds girth to stems androots in woody plants 725

The Vascular Cambium and Secondary VascularTissue 725

Cork Cambia and the Production of Periderm 728CONCEPT 35.5 Growth, morphogenesis, and differentiationproduce the plant body 728

Molecular Biology: Revolutionizing the Study ofPlants 728

Growth: Cell Division and Cell Expansion 729Morphogenesis and Pattern Formation 730Gene Expression and Control of Cellular

Differentiation 732Location and a Cell's Developmental Fate 732Shifts in Development: Phase Changes 733Genetic Control of Flowering 734

3© Transport in Vascular Plants 738OVERVIEW: Pathways for Survival 738

CONCEPT 36.1 Physical forces drive the transport ofmaterials in plants over a range of distances 738

Selective Permeability of Membranes: A Review 738The Central Role of Proton Pumps , 739Effects of Differences in Water Potential 740

Three Major Compartments of Vacuolated Plant Cells 743Functions of the Symplast and Apoplast in Transport 743Bulk Flow in Long-Distance Transport 743

CONCEPT 36.2 Roots absorb water and minerals from thesoil 744

The Roles of Root Hairs, Mycorrhizae, and CorticalCells 744

The Endodermis: A Selective Sentry 744

CONCEPT 36.3 Water and minerals ascend from roots toshoots through the xylem 746

Factors Affecting the Ascent of Xylem Sap 746Xylem Sap Ascent by Bulk Flow: A Review 748

CONCEPT 36.4 Stomata help regulate the rate oftranspiration 749

Effects of Transpiration on Wilting and LeafTemperature 749

Stomata: Major Pathways for Water Loss 750Xerophyte Adaptations That Reduce

Transpiration 751

CONCEPT 36.5 Organic nutrients are translocated throughthe phloem 751

Movement from Sugar Sources to Sugar Sinks 752Pressure Flow: The Mechanism of Translocation in

Angiosperms 753

37 Plant Nutrition 756OVERVIEW: A Nutritional Network 756

CONCEPT 37.1 Plants require certain chemical elements tocomplete their life cycle 756

Macronutrients and Micronutrients 757Symptoms of Mineral Deficiency 758

CONCEPT 37.2 Soil quality is a major determinant of plantdistribution and growth 759

Texture and Composition of Soils 759Soil Conservation and Sustainable Agriculture 760

CONCEPT 37.3 Nitrogen is often the mineral that has thegreatest effect on plant growth 763

Soil Bacteria and Nitrogen Availability 763Improving the Protein Yield of Crops 764

CONCEPT 37.4 Plant nutritional adaptations often involverelationships with other organisms 764

The Role of Bacteria in Symbiotic NitrogenFixation 764

Mycorrhizae and Plant Nutrition 766

Epiphytes, Parasitic Plants, and CarnivorousPlants 767

38 Angiosperm Reproduction andBiotechnology 771OVERVIEW: To Seed or Not to Seed 771

CONCEPT 38.1 Pollination enables gametes to come togetherwithin a flower 771

Flower Structure 772Gametophyte Development and Pollination 774Mechanisms That Prevent Self-Fertilization 775

CONCEPT 38.2 After fertilization, ovules develop into seedsand ovaries into fruits 776

Double Fertilization 776From Ovule to Seed 777From Ovary to Fruit 778Seed Germination 779

CONCEPT 38.3 Many flowering plants clone themselves byasexual reproduction 781

Mechanisms of Asexual Reproduction 781Vegetative Propagation and Agriculture 781

CONCEPT 38.4 Plant biotechnology is transformingagriculture 783

Artificial Selection 783Reducing World Hunger and Malnutrition 784The Debate over Plant Biotechnology 784

39 Plant Responses to Internal and ExternalSignals 788OVERVIEW: Stimuli and a Stationary Life 788

CONCEPT 39.1 Signal transduction pathways link signalreception to response 788

Reception. 789Transduction 789Response 790

CONCEPT 39.2 Plant hormones help coordinate growth,development, and responses to stimuli 791

The Discovery of Plant Hormones 792A Survey of Plant Hormones 793Systems Biology and Hormone Interactions 801

CONCEPT 39.3 Responses to light are critical for plantsuccess 802

Blue-Light Photoreceptors 802Phytochromes as Photoreceptors 802Biological Clocks and Circadian Rhythms 805The Effect of Light on the Biological Clock 806Photoperiodism and Responses to Seasons 806

CONCEPT 39.4 Plants respond to a wide variety of stimuliother than light 808

Gravity 809Mechanical Stimuli 809Environmental Stresses 810

CONCEPT 39.5 Plants defend themselves against herbivoresand pathogens 812

Defenses Against Herbivores 813Defenses Against Pathogens 813 i

Contents XXXV

CONCEPT 46.5 In humans and other placental mammals, anembryo grows into a newborn in the mother's uterus 978

Conception, Embryonic Development, andBirth 978

The Mother's Immune Tolerance of the Embryo andFetus 982

Contraception and Abortion 982Modern Reproductive Technology 983

47 Animal Development 987OVERVIEW: A Body-Building Plan for Animals 987

CONCEPT 47.1 After fertilization, embryonic developmentproceeds through cleavage, gastrulation, andorganogenesis 988

Fertilization 988Cleavage 992Gastrulation 994Organogenesis 997Developmental Adaptations of Amniotes 998Mammalian Development 999

CONCEPT 47.2 Morphogenesis in animals involves specificchanges in cell shape, position, and adhesion 1001

The Cytoskeleton, Cell Motility, and ConvergentExtension 1001

Roles of the Extracellular Matrix and Cell AdhesionMolecules 1002

CONCEPT 47.3 The developmental fate of cells depends ontheir history and on inductive signals 1003

Fate Mapping 1004Establishing Cellular Asymmetries 1004Cell-Fate Determination and Pattern Formation by

Inductive Signals 1006

48 Nervous Systems 1011OVERVIEW: Command and Control Center 1011

CONCEPT 48.1 Nervous systems consist of circuits ofneurons and supporting cells 1012

Organization of Nervous Systems 1012Information Processing 1013Neuron Structure 1013Supporting Cells (Glia) 1014

CONCEPT 48.2 Ion pumps and ion channels maintain theresting potential of a neuron 1015

The Resting Potential 1016Gated Ion Channels 1017

CONCEPT 48.3 Action potentials are the signals conductedby axons 1017

Production of Action Potentials 1018Conduction of Action Potentials 1020

CONCEPT 48.4 Neurons communicate with other cells atsynapses 1021

Direct Synaptic Transmission 1022Indirect Synaptic Transmission 1023Neurotransmitters 1024

CONCEPT 48.5 The vertebrate nervous system is regionallyspecialized 1026

The Peripheral Nervous System 1026Embryonic Development of the Brain 1028The Brainstem 1029The Cerebellum 1030The Diencephalon 1030The Cerebrum 1031

CONCEPT 48.6 The cerebral cortex controls voluntarymovement and cognitive functions 1032

Information Processing in the Cerebral Cortex 1032Lateralization of Cortical Function 1033Language and Speech 1034Emotions 1034Memory and Learning 1035Consciousness 1036

CONCEPT 48.7 CNS injuries and diseases are the focus ofmuch research 1037

Nerve Cell Development 1037Neural Stem Cells 1038Diseases and Disorders of the Nervous Systems 1039

Sensory and Motor Mechanisms 1045OVERVIEW: Sensing and Acting 1045

CONCEPT 49.1 Sensory receptors transduce stimulus energyand transmit signals to the central nervous system 1046

Functions Performed by Sensory Receptors 1046Types of Sensory Receptors 1048

CONCEPT 49.2 The mechanoreceptors involved with hearingand equilibrium detect settling particles or movingfluid 1050

Sensing Gravity and Sound in Invertebrates 1050Hearing and Equilibrium in Mammals 1050Hearing and Equilibrium in Other Vertebrates 1053

CONCEPT 49.3 The senses of taste and smell are closelyrelated in most animals 1054

Taste in Humans 1055Smell in Humans 1056

CONCEPT 49.4 Similar mechanisms underlie visionthroughout the animal kingdom 1057

Vision in Invertebrates 1057The Vertebrate Visual System 1058

CONCEPT 49.s Animal skeletons function in support,protection, and movement 1063

Types of Skeletons 1063Physical Support on Land 1064

CONCEPT 49.6 Muscles move skeletal parts bycontracting 1066

Vertebrate Skeletal Muscle 1066Other Types of Muscle 1072

CONCEPT 49.7 Locomotion requires energy to overcomefriction and gravity 1073

Swimming 1073Locomotion on Land 1073Flying 1074Comparing Costs of Locomotion 1074

XXXVlll Contents

UNIT EIGHT

Ecology 107850 An Introduction to Ecology and the

Biosphere 1080OVERVIEW: The Scope of Ecology 1080

CONCEPT 50.1 Ecology is the study of interactions betweenorganisms and the environment 1080

Ecology and Evolutionary Biology 1081Organisms and the Environment 1081Subfields of Ecology 1082Ecology and Environmental Issues 1083

CONCEPT so.2 Interactions between organisms and theenvironment limit the distribution of species 1083

Dispersal and Distribution 1084Behavior and Habitat Selection 1085Biotic Factors 1085Abiotic Factors 1086Climate 1087

CONCEPT 50.3 Abiotic and biotic factorsinfluence the structure and dynamics ofaquatic biomes 1092

CONCEPT 50.4 Climate largely determinesthe distribution and structure of terrestrialbiomes 1098

Climate and Terrestrial Biomes 1098General Features of Terrestrial Biomes 1098

51 Behavioral Ecology 1106OVERVIEW: Studying Behavior 1106

CONCEPT 5i.i Behavioral ecologists distinguish betweenproximate and ultimate causes of behavior 1106

What Is Behavior? 1107Proximate and Ultimate Questions 1107Ethology 1107

CONCEPT 51.2 Many behaviors have a strong geneticcomponent 1109

Directed Movements 1110Animal Signals and Communication 1111Genetic Influences on Mating and Parental

Behavior 1112

CONCEPT 51.3 Environment, interacting with an animal'sgenetic makeup, influences the development ofbehaviors 1113

Dietary Influence on Mate Choice Behavior 1113Social Environment and Aggressive Behavior 1114Learning 1114

CONCEPT 51.4 Behavioral traits can evolve by naturalselection 1118

Behavioral Variation in Natural Populations 1118Experimental Evidence for Behavioral

Evolution 1120

CONCEPT si.5 Natural selection favors behaviors thatincrease survival and reproductive success 1121

Foraging Behavior 1122

Mating Behavior and Mate Choice 1123Applying Game Theory 1127

CONCEPT si.6 The concept of inclusive fitness can accountfor most altruistic social behavior 1128

Altruism 1128Inclusive Fitness 1129Social Learning 1131Evolution and Human Culture 1132

52 Population Ecology 1136OVERVIEW: Earth's Fluctuating Populations 1136

CONCEPT 52.1 Dynamic biological processes influencepopulation density, dispersion, and demography 1136

Density and Dispersion 1137Demography 1139

CONCEPT 52.2 Life history traits are products of naturalselection 1141

Life History Diversity 1141"Trade-offs" and Life Histories 1142

CONCEPT 52.3 The exponential model describes populationgrowth in an idealized, unlimited environment 1143

Per Capita Rate of Increase 1143Exponential Growth 1144

CONCEPT 52.4 The logistic growth model includes theconcept of carrying capacity 1145

The Logistic Growth Model 1145The Logistic Model and Real Populations 1146The Logistic Model and Life Histories 1147

CONCEPT 52.5 Populations are regulated by a complexinteraction of biotic and abiotic influences 1148

Population Change and Population Density 1148Density-Dependent Population Regulation 1148Population Dynamics 1150Population Cycles 1151

CONCEPT 52.6 Human population growth has slowed aftercenturies of exponential increase 1152

The Global Human Population 1152Global Carrying Capacity 1155

Contents XXXIX

53 Community Ecology 1159OVERVIEW: What Is a Community? 1159

CONCEPT 53.1 A community's interactions includecompetition, predation, herbivory, symbiosis, anddisease 1159

Competition 1160Predation 1161Herbivory 1163Parasitism 1163Disease 1163Mutualism 1164Commensalism 1164Interspecific Interactions and Adaptation 1164

CONCEPT 53.2 Dominant and keystone species exert strongcontrols on community structure 1165

Species Diversity 1165Trophic Structure 1166Species with a Large Impact 1168Bottom-up and Top-Down Controls 1170

CONCEPT 53.3 Disturbance influences species diversity andcomposition 1171

What Is Disturbance? 1172Human Disturbance 1173Ecological Succession 1173

CONCEPT 53.4 Biogeographic factors affect communitybiodiversity 1175

Equatorial-Polar Gradients 1176Area Effects 1176Island Equilibrium Model 1177

CONCEPT 53.s Contrasting views of community structureare the subject of continuing debate 1178

Integrated and Individualistic Hypotheses 1178Rivet and Redundancy Models 1180

54 Ecosystems 1184OVERVIEW: Ecosystems, Energy, and Matter 1184

CONCEPT 54.1 Ecosystem ecology emphasizes energy flowand chemical cycling 1184

Ecosystems and Physical Laws 1185Trophic Relationships 1185Decomposition 1185

CONCEPT 54.2 Physical and chemical factors limit primaryproduction in ecosystems 1186

Ecosystem Energy Budgets 1186Primary Production in Marine and Freshwater

Ecosystems 1188Primary Production in Terrestrial and Wetland

Ecosystems 1190

CONCEPT 54.3 Energy transfer between trophic levels isusually less than 20% efficient 1191

Production Efficiency 1191The Green World Hypothesis 1193

CONCEPT 54.4 Biological and geochemical processes movenutrients between organic and inorganic parts of theecosystem 1195

A General Model of Chemical Cycling 1195Biogeochemical Cycles 1195

Decomposition and Nutrient Cycling Rates 1198Vegetation and Nutrient Cycling: The Hubbard Brook

Experimental Forest 1198

CONCEPT 54.5 The human population is disruptingchemical cycles throughout the biosphere 1200

Nutrient Enrichment 1200Acid Precipitation 1201Toxins in the Environment 1202Atmospheric Carbon Dioxide 1203Depletion of Atmospheric Ozone 1205

55 Conservation Biology and RestorationEcology 1209OVERVIEW: The Biodiversity Crisis 1209

CONCEPT S5.i Human activities threaten Earth'sbiodiversity 1209

The Three Levels of Biodiversity 1210Biodiversity and Human Welfare 1211Four Major Threats to Biodiversity 1212

CONCEPT 55.2 Population conservation focuses onpopulation size, genetic diversity, and criticalhabitat 1215

Small-Population Approach 1215Declining-Population Approach 1218Weighing Conflicting Demands 1219

CONCEPT 55.3 Landscape and regional conservation aim tosustain entire biotas 1220

Landscape Structure and Biodiversity 1220Establishing Protected Areas 1222

CONCEPT 55.4 Restoration ecology attempts to restoredegraded ecosystems to a more natural state 1224

Bioremediation 1225Biological Augmentation 1225Exploring'Restoration 1225

CONCEPT 55.5 Sustainable development seeks to improvethe human condition while conserving biodiversity 1228

Sustainable Biosphere Initiative 1228Case Study: Sustainable Development in Costa

Rica 1228Biophilia and the Future of the Biosphere 1229

APPENDIX A Answers

APPENDIX B The Metric System

APPENDIX c A Comparison of theLight Microscope andthe Electron Microscope

APPENDIX D Classification of Life

CREDITS

GLOSSARY

INDEX

xl Contents