Table of contents for Life on earth / Teresa Audesirk, Gerald Audesirk, and Bruce E. Byers.

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Contents
Preface 000
Chapter 1 An Introduction to Life on Earth 000
1.1 Why Study Biology? 1
Biology Helps You Understand Your Body 1
Biology Helps You Become an Informed Citizen 1
Biology Can Open Career Opportunities 2
Biology Can Enrich Your Appreciation of the World 2
1.2 How Do Biologists Study Life?
The Scientific Method Is the Basis for Scientific Inquiry 3
Scientific Inquiry: Controlled Experiments, Then and Now 4
Life Can Be Studied at Different Levels of Organization 6
Science Is a Human Endeavor 7
Scientific Theories Have Been Thoroughly Tested 8
1.3 What Is Life? 8
Living Things Are Both Complex and Organized 8
Living Things Grow and Reproduce 9
Living Things Respond to Stimuli 9
Living Things Acquire and Use Materials and Energy 9
Living Things Use DNA to Store Information 10
1.4 Why Is Life So Diverse? 10
Evolution Accounts for Both Life's Unity and Its Diversity 10
Natural Selection Causes Evolution 10
Earth Watch: Why Preserve Biodiversity? 4
Life's Diversity Is Currently Threatened 11
Links to Life 12
Chapter Review 12
UNIT ONE
Life of a Cell 15
Chapter 2 Atoms, Molecules, and Life 16
Improving on Nature? 17
2.1	What Are Atoms? 18
Atoms Are Composed of Even Smaller Particles 18
Electrons Orbit the Nucleus, Forming Electron Shells 18
2.2	How Do Atoms Form Molecules? 19
Atoms Interact When There Are Vacancies in Their Outermost Electron Shells 19
Charged Atoms Interact to Form Ionic Bonds 20
Uncharged Atoms Share Electrons to Form Covalent Bonds 20
Hydrogen Bonds Form between Molecules with Polar Covalent Bonds 21
2.3 Why Is Water So Important to Life? 22
Water Interacts with Many Other Molecules 22
Many Molecules Dissolve Easily in Water 22
Water Molecules Tend to Stick Together 22
Water Can Form Ions 23
2.4 Why Is Carbon So Important to Life? 24
2.5 How Are Biological Molecules Joined Together or Broken Apart? 25
2.6 What Are Carbohydrates? 26
A Variety of Simple Sugars Occur in Organisms 27
Disaccharides Store Energy and Serve As Building Blocks 27
Polysaccharides Store Energy and Provide Support 27
2.7 What Are Lipids? 28
Oils, Fats, and Waxes Contain Only Carbon, Hydrogen, and Oxygen 29
Health Watch: Cholesterol; Friend and Foe 30
Phospholipids Have Water-Soluble Heads and Water-Insoluble Tails 30
Steroids Consist of Four Carbon Rings Fused Together 30
2.8 What Are Proteins? 30
Proteins Are Formed from Chains of Amino Acids 31
Earth Watch: Deadly Elements 32
Amino Acids Join to Form Chains by Dehydration Synthesis 32
Three-Dimensional Shapes Give Proteins Their Functions 32
2.9 What Are Nucleic Acids? 33
DNA and RNA, the Molecules of Heredity, Are Nucleic Acids 34
Other Nucleotides Perform Other Functions 34
Improving on Nature? Revisited 34
Links to Life 35
Chapter Review 35
Chapter 3 Cell Membrane Structure and Function 38
Can Teens Have Heart Attacks? 39
1 What Does the Plasma Membrane Do? 40
2 What Is the Structure of the Plasma Membrane? 40
Membranes Are "Fluid Mosaics" 40
The Phospholipid Bilayer Is the Fluid Portion of the Membrane 40
A Mosaic of Proteins Is Embedded in the Membrane 41
3 How Does the Plasma Membrane Play Its Gatekeeper Role? 42
The Phospholipid Bilayer Blocks the Passage of Most Molecules 42
The Embedded Proteins Selectively Transport, Respond to, and Recognize Molecules 42
4 What Is Diffusion? 42
Molecules in Fluids Move in Response to Gradients 43
A Drop of Dye in Water Illustrates Diffusion 43
Summing Up: The Principles of Diffusion 44
5 What Is Osmosis? 44
Summing Up: The Principles of Osmosis 45
6 How Do Diffusion and Osmosis Affect Transport Across the Plasma Membrane? 45
Plasma Membranes Are Selectively Permeable 45
Some Molecules Move Across Membranes by Simple Diffusion 45
Other Molecules Cross the Membrane by Facilitated Diffusion 46
Water Can Move Across Plasma Membranes by Osmosis 47
7 How Do Molecules Move Against a Concentration Gradient? 47
Active Transport Uses Energy to Move Molecules against Their Concentration Gradients 48
Membrane Proteins Regulate Active Transport 48
Cells Engulf Particles or Fluids by Endocytosis 48
Exocytosis Moves Material out of the Cell 48
Some Plasma Membranes Are Surrounded by Cell Walls 48
Evolutionary Connections: Caribou Legs and Membrane Diversity 50
Can Teens Have Heart Attacks? Revisited 50
Links to Life 51
Chapter Review 51
Chapter 4 Cell Structure and Function 54
Can Lost Limbs Grow Back? 55
1 What Features Are Shared by All Cells? 56
Cells Are Enclosed by a Plasma Membrane 56
Cells Use DNA as a Hereditary Blueprint 56
Cells Contain Cytoplasm 56
Cells Obtain Energy and Nutrients from Their Environment 56
Cell Function Limits Cell Size 56
Scientific Inquiry: The Search for the Cell 58
2 How Do Prokaryotic and Eukaryotic Cells Differ? 60
3 What Are the Main Features of Eukaryotic Cells? 61
4 What Role Does the Nucleus Play? 62
The Nuclear Envelope Controls Passage of Materials 62
The Nucleus Contains Chromosomes 62
Ribosome Components Are Made at the Nucleolus 62
5 What Roles Do Membranes Play in Eukaryotic Cells? 63
The Plasma Membrane Isolates the Cell and Helps It Interact with Its Environment 63
The Endoplasmic Reticulum Forms Channels within the Cytoplasm 63
The Golgi Complex Sorts, Chemically Alters, and Packages Important Molecules 64
We Can Follow the Travels of a Secreted Protein 65
Lysosomes Serve as the Cell's Digestive System 65
6 Which Other Structures Play Key Roles in Eukaryotic Cells? 65
Vacuoles Regulate Water and Store Substances 65
Mitochondria Extract Energy from Food Molecules 65
Chloroplasts Capture Solar Energy 66
The Cytoskeleton Provides Shape, Support, and Movement 66
Cilia and Flagella Move the Cell or Move Fluid Past the Cell 66
7 What Are the Features of Prokaryotic Cells? 67
Can Lost Limbs Grow Back? Revisited 68
Links to Life 68
Chapter Review 68
Chapter 5 Energy Flow in the Life of a Cell 72
A Missing Molecule Makes Mischief 73
1 What Is Energy? 74
Energy Cannot Be Created or Destroyed 74
Energy Tends to Become Distributed Evenly 74
Matter Tends to Become Less Organized 74
Living Things Use the Energy of Sunlight to Create Low-Entropy Conditions 75
2 How Does Energy Flow in Chemical Reactions? 75
Exergonic Reactions Release Energy 75
Endergonic Reactions Require an Input of Energy 76
All Reactions Require an Initial Input of Energy 76
Exergonic Reactions May Be Linked with Endergonic Reactions 76
3 How Is Energy Carried between Coupled Reactions? 77
ATP Is the Principal Energy Carrier in Cells 77
Electron Carriers Also Transport Energy within Cells 78
4 How Do Cells Control Their Metabolic Reactions? 78
At Body Temperatures, Many Spontaneous Reactions Proceed Too Slowly to Sustain Life 78
Catalysts Reduce Activation Energy 79
Enzymes Are Biological Catalysts 79
The Structure of Enzymes Allows Them to Catalyze Specific Reactions 79
The Activity of Enzymes Is Influenced by Their Environment 80
A Missing Molecule Makes Mischief Revisited 81
Links to Life 81
Chapter Review 81
Chapter 6 Capturing Solar Energy: Photosynthesis 84
Did the Dinosaurs Die from a Lack of Sunlight? 85
1 What Is Photosynthesis? 86
Photosynthesis Converts Carbon Dioxide and Water to Glucose 87
Plant Photosynthesis Takes Place in Leaves 87
Leaf Cells Contain Chloroplasts 87
Photosynthesis Consists of Light-Dependent and Light-Independent Reactions 87
2 How Is Light Energy Converted to Chemical Energy? 88
Light Energy Is First Captured by Pigments in Chloroplasts 88
The Light-Dependent Reactions Generate Energy-Carrier Molecules 88
Splitting Water Maintains the Flow of Electrons Through the Photosystems 89
Summing Up: Light-Dependent Reactions 90
3 How Is Chemical Energy Stored in Glucose Molecules? 90
The C3 Cycle Captures Carbon Dioxide 90
Carbon Fixed During the C3 Cycle Is Used to Synthesize Glucose 91
Summing Up: Light-Independent Reactions 91
4 What Is the Relationship Between Light-Dependent and Light-Independent Reactions? 91
5 How Does the Need to Conserve Water Affect Photosynthesis? 91
Earth Watch: Can Forests Prevent Global Warming? 92
When Stomata Are Closed to Conserve Water, Wasteful Photorespiration Occurs 92
An Alternative Pathway Reduces Photorespiration in C4 Plants 93
C3 and C4 Plants Are Each Adapted to Different Environmental Conditions 94
Did the Dinosaurs Die from a Lack of Sunlight? Revisited 94
Links to Life 94
Chapter Review 95
Chapter 7 Harvesting Energy: Glycolysis and Cellular Respiration 98
When Athletes Boost Their Blood Counts: Do Cheaters Prosper? 99
1 What Is the Source of a Cell's Energy? 100
Glucose Is a Key Energy-Storage Molecule 100
Photosynthesis Is the Ultimate Source of Cellular Energy 100
Glucose Metabolism and Photosynthesis Are Complementary Processes 100
2 How Do Cells Harvest Energy from Glucose? 101
3 What Happens During Glycolysis? 101
Activation Consumes Energy 102
Energy Harvest Yields Energy-Carrier Molecules 102
Summing Up: Glycolysis 102
4 What Happens During Cellular Respiration? 102
The Krebs Cycle Breaks Down Pyruvate in the Mitochondrial Matrix 104
Summing Up: The Mitochondrial Matrix Reactions 104
Energetic Electrons Are Carried to Electron Transport Chains 104
Energy from a Hydrogen-Ion Gradient Is Used to Produce ATP 105
Summing Up: Electron Transport and Chemiosmosis 105
5 What Happens During Fermentation? 106
Some Cells Ferment Pyruvate to Form Alcohol 106
Other Cells Ferment Pyruvate to Lactate 106
Fermentation's Effects Limit Human Muscle Performance 107
When Athletes Boost Their Blood Counts: Do Cheaters Prosper? Revisited 107
Links to Life 108
Chapter Review 108
UNIT TWO
INHERITANCE 111
Chapter 8 DNA: The Molecule of Heredity 112
Modern Showdown in the Old West 113
1 What Are Genes Made Of? 114
2 What Is the Structure of DNA? 114
DNA Is Composed of Four Different Subunits 114
A DNA Molecule Contains Two Nucleotide Strands 115
Hydrogen Bonds Hold the Two DNA Strands Together in a Double Helix 115
Scientific Inquiry: The Discovery of the Double Helix 116
3 How Does DNA Encode Information? 116
4 How Is DNA Copied? 117
Why Does DNA Need to Be Copied? 117
DNA Is Copied before Cell Division 117
DNA Replication Produces Two DNA Double Helixes, Each with One Original Strand and One 
New Strand 117
Proofreading Produces Almost Error-Free Replication of DNA 118
Mistakes Do Happen 118
5 What Are the Mechanisms of DNA Replication? 118
DNA Helicase Separates the Parental Strands 118
DNA Polymerase Synthesizes New DNA Strands 120
DNA Ligase Joins Together Segments of DNA 120
Modern Showdown in the Old West Revisited 121
Links to Life 121
Chapter Review 121
Chapter 9 Gene Expression and Regulation 124
Snakes and Snails and Puppy Dogs' Tails 125
9.1	How Is the Information in DNA Used in a Cell? 126
Most Genes Contain Information for the Synthesis of a Single Protein 126
RNA Intermediaries Carry the Genetic Information for Protein Synthesis 126
Overview: Genetic Information Is Transcribed into RNA, Then Translated into Protein 126
9.2	What Is the Genetic Code? 127
A Sequence of Three Bases Codes for an Amino Acid 127
9.3	How Is the Information in a Gene Transcribed into RNA? 129
Transcription Begins When RNA Polymerase Binds to the Promoter of a Gene 129
Elongation Generates a Growing Strand of RNA 129
Transcription Stops When RNA Polymerase Reaches the Termination Signal 129
Transcription Is Selective 130
9.4	What Are the Functions of RNA? 130
Messenger RNA Carries the Code for a Protein from the Nucleus to the Cytoplasm 130
Ribosomal RNA and Proteins Form Ribosomes 131
Transfer RNA Molecules Carry Amino Acids to the Ribosomes 131
9.5	How Is the Information in Messenger RNA Translated into Protein? 131
Translation Begins When tRNA and mRNA Bind to a Ribosome 131
Elongation Generates a Growing Chain of Amino Acids 133
A Stop Codon Signals Termination 133
Summing Up: Transcription and Translation 133
9.6	How Do Mutations Affect Gene Function? 133
Mutations May Be Nucleotide Substitutions, Insertions, or Deletions 134
Mutations Affect Proteins in Different Ways 134
Mutations Are the Raw Material for Evolution 135
9.7	Are All Genes Expressed? 136
Gene Expression Differs from Cell to Cell and over Time 136
Environmental Cues Influence Gene Expression 136
9.8	How Is Gene Expression Regulated? 136
Regulatory Proteins That Bind to Promoters Alter the Transcription of Genes 136
Health Watch: Mutations and Gender 137
Some Regions of Chromosomes Are Condensed and Not Normally Transcribed 137
Entire Chromosomes May Be Inactivated and Not Transcribed 137
Snakes and Snails and Puppy Dogs' Tails Revisited 138
Links to Life 138
Chapter Review 139
Chapter 10 The Continuity of Life: How Cells Reproduce 142
Cloning Controversy 143
10.1	Why Do Cells Divide? 144
Cell Division Is Required for Growth and Development 144
Cell Division Is Required for Asexual Reproduction 144
Meiotic Cell Division Is Required for Sexual Reproduction 144
10.2	What Occurs During the Prokaryotic Cell Cycle? 146
10.3	What Occurs During the Eukaryotic Cell Cycle? 146
There Are Two Types of Division in Eukaryotic Cells: Mitotic Cell Division and Meiotic Cell 
Division 147
The Life Cycles of Eukaryotic Organisms Include Both Mitotic and Meiotic Cell Division 147
10.4	How Is DNA in Eukaryotic Cells Organized into Chromosomes? 148
Eukaryotic Chromosomes Consist of DNA Bound to Proteins 148
A Chromosome Contains Many Genes 148
Duplicated Chromosomes Separate During Cell Division 149
Eukaryotic Chromosomes Usually Occur in Pairs 149
10.5	How Does Mitotic Cell Division Produce Genetically Identical Daughter Cells? 150
During Prophase, the Chromosomes Condense and Are Captured by the Spindle 151
During Metaphase, the Chromosomes Line Up along the Equator of the Cell 152
During Anaphase, Sister Chromatids Separate and Move to Opposite Poles of the Cell 153
Scientific Inquiry: Carbon Copies: Cloning in Nature and in the Laboratory 154
During Telophase, Nuclear Envelopes Form Around Both Groups of Chromosomes 156
During Cytokinesis, the Cytoplasm Is Divided between Two Daughter Cells 156
10.6	How Does Meiotic Cell Division Produce Haploid Cells? 156
Meiosis Produces Four Haploid Daughter Nuclei 157
Meiosis I Separates Homologous Chromosomes into Two Haploid Daughter Nuclei 157
Meiosis II Separates Sister Chromatids into Four Haploid Daughter Cells 157
10.7	How Do Meiotic Cell Division and Sexual Reproduction Produce Genetic Variability? 160
Shuffling of Homologues Creates Novel Combinations of Chromosomes 160
Crossing Over Creates Chromosomes with Novel Combinations of Genetic Material 162
Fusion of Gametes Creates Genetically Variable Offspring 162
Cloning Controversy Revisited 162
Links to Life 163
Chapter Review 163
Chapter 11 Patterns of Inheritance 166
Sudden Death on the Court 167
11.1	What Is the Physical Basis of Inheritance? 168
Genes Are Sequences of Nucleotides at Specific Locations on Chromosomes 168
An Organism's Two Alleles May Be the Same or Different 168
11.2	How Were the Principles of Inheritance Discovered? 168
Doing It Right: The Secrets of Mendel's Success 169
11.3	How Are Single Traits Inherited? 169
The Pattern of Inheritance of Single Traits Can Be Explained by the Inheritance of Alleles of a 
Single Gene 170
Simple "Genetic Bookkeeping" Can Predict Genotypes and Phenotypes of Offspring 172
Mendel's Hypothesis Can Predict the Outcome of New Types of Single-Trait Crosses 173
11.4	How Are Multiple Traits Inherited? 173
Mendel Concluded That Multiple Traits Are Inherited Independently 173
In an Unprepared World, Genius May Go Unrecognized 174
11.5	How Are Genes Located on the Same Chromosome Inherited? 174
Genes on the Same Chromosome Tend to Be Inherited Together 175
Crossing Over Can Create New Combinations of Linked Alleles 175
11.6	How Is Sex Determined? 175
11.7	How Are Sex-Linked Genes Inherited? 176
11.8	Do the Mendelian Rules of Inheritance Apply to All Traits? 176
Incomplete Dominance Produces Intermediate Phenotypes 176
A Single Gene May Have Multiple Alleles 177
A Single Trait May Be Influenced by Several Genes 177
A Single Gene May Have Multiple Effects on Phenotype 178
The Environment Influences the Expression of Genes 178
Scientific Inquiry: Cystic Fibrosis 179
11.9	How Are Human Genetic Disorders Investigated? 180
11.10	How Are Single-Gene Disorders Inherited? 180
Some Human Genetic Disorders Are Caused by Recessive Alleles 180
Some Human Genetic Disorders Are Caused by Dominant Alleles 181
Some Human Genetic Disorders Are Sex-Linked 182
11.11	How Do Errors in Chromosome Number Affect Humans? 182
Abnormal Numbers of Sex Chromosomes Cause Some Disorders 183
Abnormal Numbers of Autosomes Cause Some Disorders 184
Sudden Death on the Court Revisited 186
Links to Life 186
Chapter Review 187
Chapter 12 Biotechnology 192
Guilty or Innocent? 193
12.1	What Is Biotechnology? 194
12.2	How Does DNA Recombine in Nature? 194
Sexual Reproduction Recombines DNA 195
Transformation May Combine DNA from Different Bacterial Species 195
Viruses May Transfer DNA between Species 196
12.3	How Is Biotechnology Used in Forensics? 197
The Polymerase Chain Reaction Amplifies DNA 197
Scientific Inquiry: Hot Springs and Hot Science 198
Differences in Short DNA Segments Can Identify Individuals 198
Gel Electrophoresis Separates DNA Segments 199
DNA Probes Are Used to Label Specific Nucleotide Sequences 199
A DNA Fingerprint Is Unique to Each Person 200
12.4	How Is Biotechnology Used in Agriculture? 200
Many Crops Are Genetically Modified 200
Genetically Modified Animals May Be Useful in Agriculture and Medicine 201
12.5	How Is Biotechnology Used to Learn About the Human Genome? 202
Biotechnology Watch: Bonanza from the Sea or Frankenfish? 202
12.6	How Is Biotechnology Used for Medical Diagnosis and Treatment? 203
DNA Technology Can Be Used to Diagnose Inherited Disorders 203
DNA Technology Can Be Used to Treat Disease 204
Health Watch: Prenatal Genetic Screening 206
12.7	What Are the Major Ethical Issues of Biotechnology? 207
Should Genetically Modified Organisms Be Permitted in Agriculture? 207
Should the Human Genome Be Changed by Biotechnology? 209
Guilty or Innocent? Revisited 210
Links to Life 210
Chapter Review 210
UNIT THREE
Evolution 213
Chapter 13 Principles of Evolution 214
What Good Are Wisdom Teeth? 215
13.1	How Did Evolutionary Thought Evolve? 216
Early Biological Thought Did Not Include the Concept of Evolution 216
Exploration of New Lands Revealed a Staggering Diversity of Life 216
A Few Scientists Speculated That Life Had Evolved 216
Fossil Discoveries Showed That Life Has Changed over Time 217
Some Scientists Devised Nonevolutionary Explanations for Fossils 218
Geology Provided Evidence That Earth Is Exceedingly Old 219
Some Pre-Darwin Biologists Proposed Mechanisms for Evolution 219
Darwin and Wallace Proposed a Mechanism of Evolution 219
13.2	How Does Natural Selection Work? 220
Scientific Inquiry: Charles Darwin; Nature Was His Laboratory 222
Modern Genetics Confirmed Darwin's Assumption of Inheritance 223
Natural Selection Modifies Populations over Time 223
13.3	How Do We Know That Evolution Has Occurred? 223
Fossils Provide Evidence of Evolutionary Change over Time 223
Comparative Anatomy Gives Evidence of Descent with Modification 224
Embryological Similarity Suggests Common Ancestry 226
Modern Biochemical and Genetic Analyses Reveal Relatedness among Diverse Organisms 
227
13.4	What Is the Evidence That Populations Evolve by Natural Selection? 228
Controlled Breeding Modifies Organisms 228
Evolution by Natural Selection Occurs Today 228
13.5	A Postscript by Charles Darwin 230
What Good Are Wisdom Teeth? Revisited 231
Links to Life 231
Chapter Review 231
Chapter 14 How Populations Evolve 234
Evolution of a Menace 235
14.1	How Are Populations, Genes, and Evolution Related? 236
Genes and the Environment Interact to Determine Traits 236
The Gene Pool Is the Sum of the Genes in a Population 236
Evolution Is the Change of Allele Frequencies within a Population 237
The Equilibrium Population Is a Hypothetical Population in Which Evolution Does Not Occur 237
14.2	What Causes Evolution? 238
Mutations Are the Original Source of Genetic Variability 238
Allele Frequencies May Drift in Small Populations 238
Genotypes Are Not All Equally Beneficial 241
14.3	How Does Natural Selection Work? 242
Natural Selection Stems from Unequal Reproduction 242
Natural Selection Acts on Phenotypes 243
Some Phenotypes Reproduce More Successfully Than Others 243
14.4	What Is a Species? 245
Biologists Need a Clear Definition of Species 245
Species Are Groups of Interbreeding Populations 245
Appearance Can Be Misleading 246
14.5	How Do New Species Form? 246
Geographical Separation of a Population Can Lead to Speciation 246
Under Some Conditions, Many New Species May Arise 247
14.6	How Is Reproductive Isolation between Species Maintained? 247
Premating Isolating Mechanisms Prevent Mating between Species 248
Biotechnology Watch: Cloning Endangered Species 249
Postmating Isolating Mechanisms Limit Hybrid Offspring 249
14.7	What Causes Extinction? 250
Interactions with Other Species May Drive a Species to Extinction 250
Earth Watch: Endangered Species: From Gene Pools to Gene Puddles 251
Habitat Change and Destruction Are the Leading Causes of Extinction 251
Evolutionary Connections: Scientists Don't Doubt Evolution 252
Evolution of a Menace Revisited 252
Links to Life 252
Chapter Review 253
Chapter 15 The History of Life on Earth 256
Dinosaurs Singing in the Backyard? 257
15.1	How Did Life Begin? 258
Experiments Refuted Spontaneous Generation 258
The First Living Things Arose from Nonliving Ones 258
Organic Molecules Can Form Spontaneously under Prebiotic Conditions 259
Organic Molecules Can Accumulate under Prebiotic Conditions 259
Organic Molecules May Have Become Concentrated in Tidal Pools 259
RNA May Have Been the First Self-Reproducing Molecule 260
Membrane-Like Microspheres May Have Enclosed Ribozymes 261
But Did All This Happen? 261
15.2	What Were the Earliest Organisms Like? 262
The First Organisms Were Anaerobic Prokaryotes 262
Some Organisms Evolved the Ability to Capture the Sun's Energy 262
Photosynthesis Increased the Amount of Oxygen in the Atmosphere 262
Scientific Inquiry: How Do We Know How Old a Fossil Is? 264
Aerobic Metabolism Arose in Response to the Oxygen Crisis 265
Some Organisms Acquired Membrane-Enclosed Organelles 265
15.3	What Were the Earliest Multicellular Organisms Like? 266
Some Algae Became Multicellular 266
Animal Diversity Arose in the Precambrian Era 266
15.4	How Did Life Invade the Land? 268
Some Plants Became Adapted to Life on Dry Land 268
Some Animals Became Adapted to Life on Dry Land 269
15.5	What Role Has Extinction Played in the History of Life? 271
Evolutionary History Has Been Marked by Periodic Mass Extinctions 272
Climate Change Contributed to Mass Extinctions 272
Catastrophic Events May Have Caused the Worst Mass Extinctions 272
15.6	How Did Humans Evolve? 273
Humans Inherited Some Early Primate Adaptations for Life in Trees 273
The Oldest Hominid Fossils Are from Africa 274
The Earliest Hominids Could Stand and Walk Upright 274
Several Species of Australopithecus Emerged in Africa 276
The Genus Homo Diverged from the Australopithecines 2.5 Million Years Ago 276
The Evolution of Homo Was Accompanied by Advances in Tool Technology 276
Neanderthals Had Large Brains and Excellent Tools 277
Modern Humans Emerged Only 150,000 Years Ago 277
Cro-Magnons and Neanderthals Lived Side by Side 278
Dinosaurs Singing in the Backyard Revisited 278
Links to Life 279
Chapter Review 279
Chapter 16 The Diversity of Life 282
An Unsolved Mystery: How Many Species Are There? 283
16.1	How Are Organisms Named and Classified? 284
Each Species Has a Unique, Two-Part Name 284
Classification Originated As a Hierarchy of Categories 284
Biologists Identify Features That Reveal Evolutionary Relationships 285
Anatomy Plays a Key Role in Classification 285
Molecular Similarities Are Also Useful for Classification 286
16.2	What Are the Domains of Life? 286
The Five-Kingdom System Improved Classification 286
A Three-Domain System More Accurately Reflects Life's History 286
Kingdom-Level Classification Remains Unsettled 287
16.3	Bacteria and Archaea 287
Bacteria and Archaea Are Fundamentally Different 287
Prokaryotes Differ in Shape and Structure 288
Prokaryotes Reproduce by Binary Fission 289
Prokaryotes Are Specialized for Specific Habitats 289
Prokaryotes Exhibit Diverse Metabolisms 290
Prokaryotes Perform Functions Important to Other Organisms 290
Some Bacteria Pose a Threat to Human Health 290
16.4	Protists 293
Most Protists Are Single Celled 293
The Chromists Include Photosynthetic and Nonphotosynthetic Organisms 293
The Alveolates Include Parasites, Predators, and Phytoplankton 294
Slime Molds Are Decomposers That Inhabit the Forest Floor 295
Various Protists Move by Means of Pseudopods 296
Green Algae Live Mostly in Ponds and Lakes 296
16.5	Fungi 297
Fungi Obtain Their Nutrients from Other Organisms 297
Most Fungi Can Reproduce Both Sexually and Asexually 298
Fungi Attack Plants That Are Important to People 298
Fungi Cause Human Diseases 298
Fungi Can Produce Toxins 299
Many Antibiotics Are Derived from Fungi 299
Fungi Make Important Contributions to Gastronomy 299
Fungi Play a Crucial Ecological Role 300
16.6	Plants 300
Bryophytes Lack Conducting Structures 300
The Vascular Plants Have Conducting Vessels That Also Provide Support 301
The Seedless Vascular Plants Include the Club Mosses, Horsetails, and Ferns 301
The Seed Plants Dominate the Land, Aided by Two Important Adaptations: Pollen and Seeds 
301
Gymnosperms Are Nonflowering Seed Plants 302
Angiosperms Are Flowering Seed Plants 302
16.7	Animals 304
Most Animals Lack a Backbone 304
Sponges Have a Simple Body Plan 304
Cnidarians Are Well-Armed Predators 305
Annelids Are Composed of Identical Segments 306
Arthropods Are the Dominant Animals on Earth 306
Most Mollusks Have Shells 309
The Chordates Include Both Invertebrates and Vertebrates 310
Earth Watch: Frogs in Peril 313
An Unsolved Mystery Revisited 316
Links to Life 316
Chapter Review 316
UNIT FOUR
PLANT ANATOMY AND PHYSIOLOGY 321
Chapter 17 Plant Form and Function 322
Sunscreen for Maple Trees? 323
17.1	How Are Plant Bodies Organized? 324
Flowering Plants Have a Root System and a Shoot System 324
Flowering Plants Can Be Divided into Two Groups 324
17.2	How Do Plants Grow? 324
During Growth, Meristem Cells Give Rise to Differentiated Cells 324
Different Processes Are Responsible for Growth in Length and Width 325
17.3	What Are the Tissues and Cell Types of Plants? 326
Dermal Tissue Covers the Plant Body 326
Ground Tissue Makes Up Most of the Young Plant Body 326
Vascular Tissue Consists of Xylem and Phloem 326
17.4	How Do Roots Grow and What Do They Do? 327
Roots Elongate by Primary Growth 328
The Epidermis of the Root Is Very Permeable to Water 328
The Cortex Controls the Absorption of Water and Nutrients 329
The Vascular Cylinder Contains Xylem and Phloem and Meristem for Branch Roots 329
17.5	How Do Stems Grow and What Do They Do? 329
The Epidermis of the Stem Retards Water Loss While Allowing Carbon Dioxide to Enter 329
The Cortex and Pith Support the Stem, Store Food, and Photosynthesize 330
Vascular Tissues in Stems Transport Water, Dissolved Nutrients, and Hormones 330
Branches Form from Lateral Buds Consisting of Meristem Cells 330
Secondary Growth Produces Thicker, Stronger Stems 330
17.6	What Is the Structure of Leaves and What Do They Do? 332
Leaves Have Two Major Parts 332
Specialized Leaves May Provide Support, Store Food, or Even Capture Insects 333
17.7	How Do Plants Acquire Nutrients? 333
Roots Take Up Minerals Dissolved in Water 333
Fungi and Bacteria Help Plants Acquire Nutrients 333
17.8	How Do Plants Acquire Water and Transport Water and Minerals? 334
Transpiration Provides the Force for Water Movement in Xylem 335
Water Enters Roots Mainly by Pressure Differences Created by Transpiration 335
Adjustable Stomata Control the Rate of Transpiration 335
Earth Watch: Plants Help Regulate the Distribution of Water 336
Sunscreen for Maple Trees? Revisited 336
Links to Life 337
Chapter Review 337
Chapter 18 The Plant Life Cycle 340
Fountain of Youth for Fruit 341
18.1	What Is the Life Cycle of Plants? 342
Two Types of Plant Bodies Alternate in the Sexual Life Cycle 342
Alternation of Generations Is Less Obvious in Flowering Plants 343
18.2	What Is the Structure of Flowers? 344
Flowers Evolved from Leaves 344
Flowers Incorporate Male and Female Reproductive Structures 345
18.3	What Are the Gametophytes of Flowering Plants? 345
The Pollen Grain Is the Male Gametophyte 345
The Embryo Sac Is the Female Gametophyte 345
18.4	How Does Pollination Lead to Fertilization? 346
18.5	How Do Seeds and Fruits Develop? 346
The Seed Develops from the Ovule and Embryo Sac 346
The Fruit Develops from the Ovary Wall 346
18.6	How Do Seeds Germinate and Grow? 347
Brotechnology Watch: Edible Vaccines 348
Seed Dormancy Helps Ensure Germination at an Appropriate Time 348
The Root Emerges First 348
The Shoot Tip Must Be Protected 349
Cotyledons Nourish the Sprouting Seed 349
Development Is Regulated throughout the Life Cycle 350
18.7	What Are Plant Hormones, and How Do They Act? 350
18.8	How Do Hormones Regulate the Plant Life Cycle? 350
Scientific Inquiry: How Were Plant Hormones Discovered? 351
Abscisic Acid Maintains Seed Dormancy 352
Gibberellin Stimulates Germination 352
Auxin Controls the Orientation of the Sprouting Seedling 352
Stem Branching Is Influenced by Auxin and Cytokinin 353
Gradients of Auxin and Cytokinin Create a Balance between the Root and Shoot Systems 353
Daylength Controls Flowering 353
Hormones Coordinate the Development of Seeds and Fruit 354
Senescence and Dormancy Prepare the Plant for Winter 355
Evolutionary Connections: Adaptations for Pollination and Seed Dispersal 355
Fountain of Youth for Fruit Revisited 358
Links to Life 358
Chapter Review 358
UNIT FIVE
Animal Anatomy and Physiology 363
Chapter 19 Homeostasis and the Organization of the Animal Body 364
Surviving a Dive 365
1 How Do Animals Maintain Internal Constancy? 366
Negative Feedback Reverses the Effects of Changes 366
Positive Feedback Drives Events to a Conclusion 367
2 How Is the Animal Body Organized? 368
3 How Do Tissues Differ? 368
Epithelial Tissue Covers the Body and Lines Its Cavities 369
Some Epithelial Tissues Form Glands 369
Connective Tissues Have Diverse Structures and Functions 369
Muscle Tissue Has the Ability to Contract 371
Nerve Tissue Transmits Electrical Signals 371
4 How Are Tissues Combined into Organs? 372
Skin Is an Organ That Contains All Four Tissue Types 372
Organ Systems Consist of Two or More Interacting Organs 372
The Body's Organ Systems Act in Concert 374
Surviving a Dive Revisited 374
Links to Life 375
Chapter Review 375
Chapter 20 Circulation and Respiration 378
Organ Farmers 379
1 What Are the Major Features and Functions of Circulatory Systems? 380
Animals Have Two Types of Circulatory Systems 380
The Vertebrate Circulatory System Transports Many Substances 380
2 How Does the Vertebrate Heart Work? 381
The Vertebrate Heart Consists of Muscular Chambers 381
The Atria and Ventricles Contract in a Coordinated Cycle 382
Valves Prevent Blood from Moving in the Wrong Direction 383
Electrical Impulses Coordinate the Sequence of Contractions 383
The Heart's Contractions Result from Movement of Filaments in Muscle Cells 384
Injury and Disease Can Impair Heart Function 384
3 What Is Blood? 384
Plasma Is Primarily Water and Dissolved Substances 385
Red Blood Cells Carry Oxygen from the Lungs to the Tissues 385
White Blood Cells Help Defend the Body against Disease 386
Platelets Are Cell Fragments That Aid in Blood Clotting 386
Health Watch: Matters of the Heart 387
4 What Are the Types and Functions of Blood Vessels? 388
Arteries and Arterioles Carry Blood Away from the Heart 388
Capillaries Are Microscopic Vessels through Which Nutrients Are Exchanged 388
Venules and Veins Carry Blood Back to the Heart 389
5 How Does the Lymphatic System Work with the Circulatory System? 390
Lymphatic Vessels Resemble the Capillaries and Veins of the Circulatory System 390
The Lymphatic System Returns Fluids to the Blood 390
The Lymphatic System Transports Fats from the Small Intestine to the Blood 390
The Lymphatic System Helps Defend the Body against Disease 390
6 How Are Oxygen and Carbon Dioxide Exchanged in Animal Bodies? 391
Aquatic Animals May Have Gills 391
Terrestrial Animals Have Internal Respiratory Structures 392
7 How Does the Human Respiratory System Work? 392
The Conducting Portion Carries Air to the Lungs 392
Gas Exchange Occurs in the Alveoli 393
Health Watch: Smoking; A Life and Breath Decision 394
The Lungs Are Protected by an Airtight Cavity 395
Air Is Inhaled Actively and Exhaled Passively 395
Breathing Rate Is Controlled by the Respiratory Center of the Brain 396
Organ Farmers Revisited 396
Links to Life 397
Chapter Review 397
Chapter 21 Nutrition, Digestion, and Excretion 400
Is There a Magic Bullet for Obesity? 401
21.1	What Nutrients Do Animals Need? 402
The Primary Sources of Energy Are Lipids and Carbohydrates 402
Lipids Include Fats, Phospholipids, and Cholesterol 402
Carbohydrates Are a Source of Quick Energy 403
Proteins Provide Amino Acid Building Blocks 404
Minerals Are Elements and Small Inorganic Molecules 404
Vitamins Play Many Roles in Metabolism 405
Nutritional Guidelines Help People Obtain a Balanced Diet 406
Are You Too Heavy? 406
21.2	How Is Digestion Accomplished? 407
Health Watch: Eating Disorders; Betrayal of the Body 408
Digestion Includes Several Processes 408
A Sac with One Opening Forms the Simplest Digestive System 409
Digestion in a Tube Allows More Frequent Meals 409
21.3	How Do Humans Digest Food? 410
The Mechanical and Chemical Breakdown Begins in the Mouth 411
The Pharynx Connects the Mouth to the Rest of the Digestive System 411
The Esophagus Conducts Food to the Stomach 411
The Stomach Stores and Further Breaks Down Food 412
Most Digestion Occurs in the Small Intestine 412
Most Absorption Occurs in the Small Intestine 413
Water Is Absorbed and Feces Are Formed in the Large Intestine 414
Digestion Is Controlled by the Nervous System and Hormones 414
21.4	What Are the Functions of Urinary Systems? 415
Flame Cells Filter Fluids in Flatworms 415
Health Watch: When the Kidneys Collapse 416
Nephridia Filter Fluid in Earthworms 416
21.5	How Does the Human Urinary System Work? 417
The Urinary System Produces, Transports, and Excretes Urine 417
The Kidneys Are Important Organs of Homeostasis 417
Urine Forms in the Kidneys 418
Kidneys Contain Filters Called Nephrons 418
Urine Becomes Concentrated in the Collecting Duct 419
Negative Feedback Regulates the Water Content of the Blood 419
Is There a Magic Bullet for Obesity? Revisited 420
Links to Life 420
Chapter Review 420
Chapter 22 Defenses Against Disease: The Immune Response 424
Will a Vaccine Make the Woods Safer? 425
22.1	How Does the Body Defend against Invasion? 426
The Skin and Mucous Membranes Are Nonspecific External Barriers to Invasion 426
Nonspecific Internal Defenses Combat Invaders 427
22.2	What Are the "Soldiers" of the Immune Response? 429
White Blood Cells Are Key Components of the Immune System 430
Immune Cells Originate in the Bone Marrow 430
22.3	How Does the Immune System Recognize Invaders? 430
Invaders' Cell Surface Molecules Are Recognized 430
Antibodies Recognize and Bind to Antigens 430
T-Cell Receptors Also Recognize and Bind Antigens 431
The Immune System Can Recognize Millions of Different Molecules 431
The Immune System Distinguishes "Self" from "Non-Self" 432
22.4	How Does the Immune System Launch an Attack? 432
Humoral Immunity Is Produced by Antibodies Dissolved in Blood 433
Cell-Mediated Immunity Is Produced by T Cells 434
22.5	How Does the Immune System Remember Its Past Victories? 434
22.6	How Does Medical Care Assist the Immune Response? 434
Antibiotics Slow Down Microbial Reproduction 435
Health Watch: Can We Beat the Flu Bug? 436
Vaccinations Stimulate the Development of Memory Cells 437
22.7	What Happens When the Immune System Malfunctions? 437
Scientific Inquiry: How Vaccines Were Discovered 438
Allergies Are Misdirected Immune Responses 438
An Autoimmune Disease Is an Immune Response against the Body's Own Cells 439
An Immune Deficiency Disease Eliminates the Immune Response 439
Cancer Can Evade or Overwhelm the Immune Response 441
Will a Vaccine Make the Woods Safer? Revisited 442
Links to Life 443
Chapter Review 443
Chapter 23 Chemical Control of the Animal Body: The Endocrine System 446
Are Some Pollutants "Gender Benders"? 447
23.1	What Are the Characteristics of Animal Hormones? 448
Many Different Molecules Serve As Hormones 448
Hormones Bind to Specific Receptors on Target Cells 448
Hormone Release Is Regulated by Feedback 450
23.2	What Are the Structures of the Mammalian Endocrine System? 452
Some Glands Are Not Part of the Endocrine System 452
Hormone-Producing Glands Are Enmeshed in Blood Vessels 452
23.3	What Are the Functions of the Hypothalamus and Pituitary Gland? 452
Hormones from the Hypothalamus Control the Anterior Pituitary 453
The Anterior Pituitary Produces and Releases Several Hormones 454
The Posterior Pituitary Releases Hormones from the Hypothalamus 455
23.4	What Does the Thyroid Gland Do? 456
Thyroxine Influences Metabolism 456
Thyroxine Release Is Controlled by the Hypothalamus 456
23.5	What Does the Pancreas Do? 456
Pancreatic Hormones Control Glucose Levels in the Blood 457
Diabetes Results from Malfunctions of the Insulin Control System 457
23.6	What Are the Endocrine Functions of Sex Organs? 458
Sex Hormone Levels Increase During Puberty 458
23.7	What Do the Adrenal Glands Do? 458
The Hormones of the Adrenal Medulla Prepare the Body to Flee or Fight 459
The Hormones of the Adrenal Cortex Raise Blood Glucose in Response to Stress 459
23.8	What Are Some Other Sources of Hormones? 459
Health Watch: Losing on Artficial Hormones 460
Are Some Polllutants "Gender Benders"? Revisited 461
Links to Life 461
Chapter Review 462
Chapter 24 The Nervous System and the Senses 464
Can You Live with a Hole in Your Head? 465
24.1	How Do Nerve Cells Work? 466
Dendrites Respond to Stimuli 466
The Cell Body Receives Signals from Dendrites 466
Axons Are the Neuron's Distribution Lines 466
Signals Are Transmitted at Synaptic Terminals 467
24.2	How Do Nerve Cells Produce and Transmit Signals? 467
The Potential inside a Neuron Changes During an Action Potential 467
Neurons Communicate at Synapses 467
Excitatory and Inhibitory Potentials Are Produced at Synapses 468
Excitatory and Inhibitory Potentials Are Integrated in the Cell Body 468
The Nervous System Uses Many Neurotransmitters 468
24.3	How Do Nervous Systems Process Information? 468
The Type of Stimulus Is Distinguished by Wiring Patterns in the Brain 469
The Intensity of a Stimulus Is Revealed by the Frequency of Signals 469
Health Watch: Drugs, Diseases, and Neurotransmitters 470
Information from Many Sources Converges in Certain Neurons 471
Complex Responses Require Divergence of Signals 471
24.4	How Do Nervous Systems Direct Behavior? 471
24.5	How Is the Human Nervous System Organized? 471
The Peripheral Nervous System Links the Central Nervous System to the Body 472
The Central Nervous System Consists of the Spinal Cord and Brain 474
The Spinal Cord Is a Cable of Axons Protected by the Backbone 474
The Brain Consists of Many Parts 475
Health Watch: Healing the Spinal Cord 476
The Hindbrain Controls Breathing, Sleep, and Movement 476
The Midbrain Filters Input 477
The Forebrain Gives Us Our Emotions, Thoughts, and Perceptions 477
24.6	How Does the Brain Produce the Mind? 479
The "Left Brain" and "Right Brain" Have Different Specialties 479
Learning and Memory Are Areas of Active Investigation 480
Insights on How the Brain Creates the Mind Come from Diverse Sources 480
24.7	How Do Sensory Receptors Work? 481
24.8	How Is Sound Sensed? 482
The Ear Captures and Transmits Sound 482
Sound Is Converted into Electrical Signals in the Cochlea 483
24.9	How Is Light Sensed? 483
The Eye Collects and Focuses Light 484
The Adjustable Lens Can Focus on Distant and Nearby Objects 484
Light Striking the Retina Is Captured by Photoreceptors 485
Rods and Cones Differ in Distribution and Light Sensitivity 485
24.10	How Are Chemicals Sensed? 485
The Ability to smell Arises from Olfactory Receptors 486
Taste Receptors Are Clustered on the Tongue 486
Pain Is a Specialized Chemical Sense 486
Evolutionary Connections: Uncommon Senses 487
Can You Live with a Hole in Your Head? Revisited 488
Links to Life 488
Chapter Review 489
Chapter 25 Animal Reproduction and Development 000
Making Far-Reaching Choices 000
25.1	How Do Animals Reproduce? 000
In Asexual Reproduction, There Is No Fusion of Sperm and Egg 000
Sexual Reproduction Requires the Union of Sperm and Egg 000
Gametes Are Brought Together for Fertilization in Various Ways 000
25.2	How Does the Human Reproductive System Work? 000
The Male Reproductive System Includes the Testes and Other Structures 000
The Female Reproductive System Includes the Ovaries and Other Structures 000
Copulation Allows Internal Fertilization 000
25.3	How Does Animal Development Proceed? 000
The Fertilized Egg Develops into a Hollow Ball of Cells 000
Next, Three Tissue Layers Form 000
Eventually, Adult Structures Form 000
25.4	How Do Humans Develop? 000
Differentiation and Growth Are Rapid in the First Two Months 000
Growth and Development Continue During the Last Seven Months 000
The Placenta Exchanges Materials between Mother and Fetus 000
Development Culminates in Labor and Delivery 000
Pregnancy Hormones Stimulate Milk Secretion 000
25.5	How Can People Limit Fertility? 000
Sterilization Provides Permanent Contraception 000
There Are Three General Approaches to Temporary Contraception 000
Making Far-Reaching Choices Revisited 000
Health Watch: Sexually Transmitted Diseases 000
Scientific Inquiry: High-Tech Reproduction 000
Biotechnology Watch: The Promise of Stem Cells 000
Links to Life 000
Chapter Review 000
Chapter 26 Animal Behavior 000
Sex and Symmetry 000
26.1	How Do Innate and Learned Behaviors Differ? 000
Innate Behaviors Can Be Performed without Prior Experience 000
Learned Behaviors Are Modified by Experience 000
There Is No Sharp Distinction between Innate and Learned Behaviors 000
26.2	How Do Animals Communicate? 000
Visual Communication Is Most Effective over Short Distances 000
Communication by Sound Is Effective over Longer Distances 000
Chemical Messages Persist Longer But Are Hard to Vary 000
Communication by Touch Helps Establish Social Bonds 000
26.3	How Do Animals Compete for Resources? 000
Aggressive Behavior Helps Secure Resources 000
Dominance Hierarchies Help Manage Aggressive Interactions 000
Animals May Defend Territories That Contain Resources 000
26.4	How Do Animals Find Mates? 000
Signals Encode Sex, Species, and Individual Quality 000
26.5	What Kinds of Societies Do Animals Form? 000
Group Living Has Advantages and Disadvantages 000
Sociality Varies among Species 000
Forming Groups with Relatives Fosters the Evolution of Altruism 000
Honeybees Live Together in Rigidly Structured Societies 000
Naked Mole Rats Form a Complex Vertebrate Society 000
26.6	Can Biology Explain Human Behavior? 000
The Behavior of Newborn Infants Has a Large Innate Component 000
Young Humans Acquire Language Easily 000
Behaviors Shared by Diverse Cultures May Be Innate 000
Humans May Respond to Pheromones 000
Studies of Twins Reveal Genetic Components of Behavior 000
Biological Investigation of Human Behavior Is Controversial 000
Evolutionary Connections: Why Do Animals Play? 000
Sex and Symmetry Revisited 000
Links to Life 000
Chapter Review 000
UNIT SIX
Ecology 000
Chapter 27 Population Growth 000
The Mystery of Easter Island 000
27.1	How Are Populations Distributed in Space and Time? 000
Individuals in Many Populations Clump Together in Groups 000
Some Individuals Disperse Themselves Evenly 000
In a Few Populations, Individuals Are Distributed at Random 000
27.2	How Do Populations Grow? 000
Births, Deaths, and Migration Determine Population Growth 000
A Population's Growth Rate Depends on Patterns of Reproduction 000
27.3	How Is Population Growth Regulated? 000
Rapid Growth Cannot Continue Indefinitely 000
Environmental Resistance Limits Population Growth 000
27.4	How Is the Human Population Changing? 000
Technological Advances Have Increased Earth's Carrying Capacity for Humans 000
Population Growth Continues Today But Is Unevenly Distributed 000
The Age Structure of a Population Predicts Its Future Growth 000
The U.S. Population Is Growing Rapidly 000
Scientific Inquiry: Cycles in Predator and Prey Populations 000
Earth Watch: Have We Exceeded Earth's Carrying Capacity? 000
The Mystery of Easter Island Revisited 000
Links to Life 000
Chapter Review 000
Chapter 28 Community Interactions 000
The Case of the Vanishing Sea Otters 000
28.1	Why Are Interactions in Ecological Communities Important? 000
Community Interactions Help Limit Population Size 000
Community Interactions Influence Evolutionary Change 000
28.2	What Are the Effects of Competition among Species? 000
Each Species Has a Unique Place in Its Ecosystem 000
The Ecological Niches of Coexisting Species Never Overlap Completely 000
Competitive Exclusion Helps Determine How Populations Are Distributed 000
Species Evolve to Reduce Niche Overlap 000
28.3	What Are the Effects of Predator/Prey Interactions? 000
Predator and Prey Coevolve 000
Camouflage Conceals Both Predators and Their Prey 000
Bright Colors Often Warn of Danger 000
Some Organisms Gain Protection through Mimicry 000
Some Animal Predators and Prey Engage in Chemical Warfare 000
Plants Have Defenses against Herbivores 000
Herbivores Have Adaptations for Overcoming Plant Defenses 000
28.4	What Is Symbiosis? 000
Parasites Harm, But Do Not Immediately Kill, the Host 000
In Mutualistic Interactions, Both Species Benefit 000
28.5	What Are Keystone Species? 000
28.6	How Does a Community Change over Time? 000
There Are Two Main Types of Succession 000
Ponds and Lakes Eventually Fill In 000
Succession Culminates in the Climax Community 000
Some Ecosystems Are Maintained in a Subclimax State 000
Evolutionary Connections: Is Camouflage Splitting a Species? 000
Earth Watch: Exotic Invaders 000
The Case of the Vanishing Sea Otters Revisited 000
Links to Life 000
Chapter Review 000
Chapter 29 How Do Ecosystems Work? 000
A World in a Bubble 000
29.1	How Do Ecosystems Obtain Energy and Nutrients? 000
29.2	How Does Energy Flow through Ecosystems? 000
Energy Enters Ecosystems through Photosynthesis 000
Energy Captured by Producers Is Available to the Ecosystem 000
Energy Passes from One Trophic Level to Another 000
Feeding Relationships within Ecosystems Form Chains and Webs 000
Detritus Feeders and Decomposers Release Nutrients for Reuse 000
Energy Transfer through Trophic Levels Is Inefficient 000
Energy Pyramids Illustrate Energy Transfer between Trophic Levels 000
29.3	How Do Nutrients Move within and among Ecosystems? 000
Carbon Cycles through the Atmosphere, Oceans, and Communities 000
The Major Reservoir for Nitrogen Is the Atmosphere 000
The Major Reservoir for Phosphorus Is Rock 000
Water Remains Unchanged During the Water Cycle 000
29.4	What Is Causing Acid Rain and Global Warming? 000
Overloading the Nitrogen and Sulfur Cycles Causes Acid Rain 000
Disruption of the Carbon Cycle Contributes to Global Warming 000
Earth Watch: Food Chains Magnify Toxic Substances 000
Biotechnology Watch: Are Genetically Modified Crops Safe for the Environment? 000
A World in a Bubble Revisited 000
Links to Life 000
Chapter Review 000
Chapter 30 Earth's Diverse Ecosystems 000
Can Coffee Save Songbirds? 000
30.1	What Factors Influence Earth's Climate? 000
Both Climate and Weather Are Driven by the Sun 000
Sunlight Strikes Earth at Various Angles 000
Air Currents Produce Regional Climates 000
Ocean Currents Moderate Nearshore Climates 000
Continents and Mountains Complicate Weather and Climate 000
30.2	What Conditions Does Life Require? 000
30.3	How Is Life on Land Distributed? 000
Terrestrial Biomes Have Characteristic Plant Communities 000
Rainfall and Temperature Determine the Vegetation a Biome Can Support 000
30.4	How Is Life in Water Distributed? 000
Freshwater Lakes Have Distinct Regions of Life 000
Marine Ecosystems Cover Much of Earth 000
Earth Watch: The Ozone Hole; A Puncture in Our Protective Shield 000
Earth Watch: Humans and Ecosystems 000
Can Coffee Save Songbirds? Revisited 000
Links to Life 000
Chapter Review 000
Appendix I: Metric System Conversion 000
Appendix II: Classification of Major Groups of Organisms 000
Appendix III: Periodic Table of Elements 000
Glossary G-1
Selected Answers A-1
Photo Credits P-1
Index I-1
Preface
Will scientists clone a person in the foreseeable future? Are genetically engineered crops safe? Are 
people causing climate change? Is AIDS still spreading? Will physicians soon be transplanting pig 
hearts into people? Why are antibiotic medicines becoming less effective? Many of today's most 
important and controversial social, medical, environmental, and ethical issues are related to biology. 
The need for citizens to understand the basic concepts of biology has never been more urgent. 
Many of the students who will use this text are enrolled in a course that will provide their final 
exposure to biology before they go out into the world. We hope that they will emerge from the course 
prepared to ask intelligent questions, make informed choices, and scrutinize science articles in the 
popular press with an educated and critical eye. We also hope that students will better understand 
and appreciate their own bodies, the other organisms with which we share Earth, the evolutionary 
forces that molded all life-forms, and how complex interactions within ecosystems sustain us and all 
other life on Earth. Perhaps most of all, we hope that students will develop a fascination with life that 
will inspire them to keep learning. To help instructors achieve these teaching goals, we offer this 
revision of Life on Earth. Now in its fourth edition, Life on Earth Effectively Manages a Wealth of 
Scientific Information and Motivates Students
The fourth edition of Life on Earth; which is more than a textbook, but rather a complete package of 
teaching aids for the instructor and learning aids for students; has been revised with three specific 
goals:
-	To help instructors manage the presentation of biological information with the goal of producing 
scientifically literate students
-	To help students build familiarity with the process of science through an engaging storyline
-	To help students relate this information to their own lives so as to understand its importance and 
relevance
Life on Earth
. . . Is Organized Clearly and Uniformly
Throughout each chapter, students will find aids that help them navigate through the information.
-	"At a Glance" at the start of each chapter brings together the chapter's major subheadings and 
now includes the titles of Essays as well. Instructors can easily assign; and students can easily 
locate; key topics within the chapter.
-	Major sections are introduced as questions to which the student will find answers in the section, 
while minor subheadings are presented as summary statements that reflect content. A crucial 
outgrowth of this organizational scheme is that it imparts an understanding of biology as a 
hierarchy of interrelated concepts, rather than a set of isolated, independent subjects.
-	The "Summary of Key Concepts" pulls together important concepts using the major subheadings as 
an organizing feature. Both "At a Glance" and the "Summary of Key Concepts" use the heading-
based numbering system featured within the chapters themselves, allowing instructors and students 
to move efficiently among the different components within a chapter.
-	Information is integrated and easily managed within the total package. Media Activity tabs within 
each chapter direct the student to OneKey, which contains relevant activities, animations, and 
practice tests; the Media Activity numbers in the book correspond with OneKey for easy 
navigation. Detailed descriptions of each Media Activity are found at the end of each chapter.
. . . Contains Revitalized Illustrations for Greater Clarity, Consistency, and Reader Interest
Benefiting from the advice of reviewers, a talented biological illustrator, and careful scrutiny by the 
authors and development editor, we have extensively revised the illustration program. For the fourth 
edition, we have:
-	Expanded the consistent use of color. We have been vigilant in tracking the use of color to provide 
consistency in illustrating specific atoms, structures, or processes. We have also made the colors 
more vibrant to better distinguish individual parts of a figure, to help engage the readers' interest, 
and to focus attention on the most important aspects of the illustration.
-	Improved overall quality. We have redrawn the more diagrammatic figures for greater interest and 
accuracy.
-	Enhanced label clarity. We have revised the size, placement, and font of figure labels for more 
consistency and readability.
-	Organized content more efficiently. We have modified the placement of parts of multipart figures 
for easier navigation through the figure.
-	Explained figure content more clearly. Through the judicious use of "talking boxes," we have 
placed more explanatory statements within figures for greater clarity.
-	Modified figure captions to enhance function. Our figure titles summarize the content; we have 
made the captions more concise, and have added thought questions to several captions within each 
chapter.
_ Actively Engages and Motivates Students
Scientific literacy cannot be imposed on students; they must actively participate in acquiring both the 
necessary information and skills. Thus, it is crucial for students to recognize that biology is about their 
personal lives as well as the life all around them. To help engage and motivate students, this new 
edition incorporates the following:
_ Openers/Closers. Each chapter opens with a strikingly illustrated brief essay. The 
opener essays are based on recent news items, on situations in which students might 
find themselves, or on particularly fascinating biological topics. For example, students will 
investigate blood doping by elite athletes (p. 00); contemplate the use of DNA to solve 
historical mysteries (p. 00) and crimes (p. 00); see cloned, genetically engineered pigs 
that are being raised as potential organ donors for humans (p. 000); and follow along as a 
scientist estimates the number of species on Earth (p. 000). Each opener is revisited at 
the end of the chapter, allowing students to explore the topic a bit further in light of what 
they have learned and, often, to find answers to questions raised in the initial piece. The 
"revisited" essays conclude with a new "Consider This" segment that poses an open-
ended question to encourage deeper thinking about the topic.
_ Links to Life. A new feature in the fourth edition, Links to Life ends each chapter on a 
relevant note. These short, informally written segments relate to subjects that are both 
very familiar to the student and relevant to the chapter. 
_ Caption Queries: New in this edition, selected figure captions in each chapter include 
questions designed to encourage readers to review and extend their new knowledge of the 
pictured structure or process. 
_ Bioethics: Another new feature in the fourth edition, many topics explored in the text have 
ethical implications. Many of these topics are now identified by an icon that alerts students 
and teachers to the possibility of further discussion and exploration.
_ Essays. We retain our full suite of essays, including "Earth Watch," environmental essays 
that explore issues such as the loss of biodiversity, the growing ozone hole, and invasions of 
exotic species, and our medically related "Health Watch" essays, which investigate topics 
such as sexually transmitted diseases, the dangers of artificial steroids, and how smoking 
damages the lungs. New in this edition, "Biotechnology Watch" essays examine the impact 
of new technologies such as cloning, in vitro fertilization, and genetic modification of 
organisms.
É Emphasizes Scientific Reasoning 
In order to made sound decisions at the voting booth or to evaluate assertions made by the 
media, students need to think critically. To develop scientific reasoning skills, we have added the 
following:
_ Openers/Closers. In addition to the engaging, relevant biological storyline, the opener 
essays are designed to build students' familiarity with the process of science and to 
demonstrate how scientists use the process to reach conclusions. The opening and the closing 
essays incorporate many examples of questions posed, hypotheses stated, predictions made, 
and experimental tests performed. Our aim is to show by example how scientists gather 
objective evidence about interesting questions relevant to students' lives. We hope that 
student readers of Life on Earth will begin to think like scientists. Nothing would please us 
more than a student who, upon hearing an assertion on television or reading a claim on the 
internet, instinctively asks, "What is the evidence and how was it gathered?"
_ Is This Science. We have added new "Is This Science?" questions to the "Applying the 
Concepts" critical-thinking questions at the end of each chapter. The new questions are 
designed to help students practice their scientific reasoning and critical thinking skills. 
_ Provides Print and Media Resources That Aid User Exploration
_ OneKey (www.prenhall.com/audesirk4): OneKey provides instructors and students 
with a single internet location for a superb collection of teaching and learning resources. 
OneKey for Life on Earth 4e supplies anywhere, anytime access to conveniently 
organized course materials. OneKey also includes everything instructors need to plan 
and administer courses. All instructor resources are consolidated in one location for 
maximum effectiveness and efficiency. 
_ Instructor Resource Center on CD: This single CD contains all digital resources, 
easily searchable with the included search tool. The material can also be browsed by 
chapter or resource type. The included Resource Manager makes it easy to post images, 
questions, animations, and more to your course web site. 
_ Instructor Resource Guide: This booklet is the print companion to the Instructor's 
Resource Center on CD. It includes the Resource Directory, Chapter At a Glance, 
Lecture Activities, Lecture Resources, Key Terms, end-of-chapter questions and 
answers, and figure caption questions and answers.
_ Instructor Toolbox: The Toolbox contains all print supplements, organized by chapter. 
Included are all of the materials in the Instructor Resource Guide, plus overhead 
transparences.
_ Accelerator CD: Each copy of this text includes an Accelerator CD. The CD works 
with One Key to provide a faster internet experience. The Accelerator CD stores some 
OneKey content, so that even dial-up connections can provide snappy performance.
_ Student Study Companion: The printed Companion provides OneKey questions and 
review materia to students without access to the internet.
Acknowledgments
Life on Earth is truly a group effort. To meet the dauntingly complex challenge of putting together a 
text and supplement package of this magnitude, Prentice Hall has assembled an experienced and 
skilled development team. The text benefited considerably from the thoughtful suggestions of 
Developmental Editor Anne Reid. She helped us keep the text clear, consistent, and student-friendly. 
Tim Flem, our Production Editor, coordinated the efforts of the photo researcher, copy editor, art 
studio, and authors. He skillfully brought the art, photos, and manuscript together into a seamless 
whole while dealing good-naturedly with last-minute improvements. Formatting this book is not an 
easy endeavor, but Tim applied his expertise with great attention to detail. Photo Researcher Yvonne 
Gerin tracked down excellent photos. Margo Quinto tackled the job of copyediting with exceptional 
skill. 
We also wish to thank Art Director John Christiana for guiding the text and cover design with flair 
and talent, and Art Editor Sean Hogan for coordinating such an immense art program.
Travis Moses-Westphal, our Media Editor, deftly carried the vision for the media program and 
oversaw the seamless integration of the text, media, and print supplements. Assistant Editors Colleen 
Lee and Andrew Sobel provided invaluable support and assistance. Editorial Assistant Marilyn Coco 
cheerfully and efficiently trafficked the manuscript.
Andrew Gilfillan, our Marketing Manager, oversees a large and dedicated sales force with energy, 
talent, and enthusiasm. Andrew provides inspired marketing concepts, shares success stories, and 
makes sure that user's comments always get through to the authors. We thank Paul Corey, now 
president of the Engineering, Science, and Mathematics Division of Prentice Hall, for his confidence 
and support through this and the past three editions. Finally, but most importantly, our editors: Editor 
in Chief John Challice has supported us from the very beginning. Executive Editor Teresa Ryu Chung 
has assumed leadership of the team with talent and zeal, combined with a clear sense of where the 
project should be going and how to get it there without killing the authors. Her total commitment to 
the project, her organizational ability, and her sensitivity to all the people involved have been crucial 
to its success.
So here we acknowledge, with deep appreciation, our "coach" and all our teammates!
Terry and Gerry Audesirk
Bruce E. Byers

Library of Congress Subject Headings for this publication:

Biology.