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Today & Tomorrow

5e

Cecie Starr | Christine A. Evers | Lisa Starr

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1 Invitation to Biology

Unit 1 How Cells work

2 Molecules of Life

3 Cell Structure

4 Energy and Metabolism

5 Capturing and Releasing Energy

Unit 2 GenetiCs

6 DNA Structure and Function

7 Gene Expression and Control

8 How Cells Reproduce

9 Patterns of Inheritance

10 Biotechnology

Unit 3 evolUtion and diversity

11 Evidence of Evolution

12 Processes of Evolution

13 Early Life Forms and the Viruses

14 Plants and Fungi

15 Animal Evolution

Unit 4 eColoGy

16 Population Ecology

17 Communities and Ecosystems

18 The Biosphere and Human Effects

Unit 5 How animals work

19 Animal Tissues and Organs

20 How Animals Move

21 Circulation and Respiration

22 Immunity

23 Digestion and Excretion

24 Neural Control and the Senses

25 Endocrine Control

26 Reproduction and Development

Unit 6 How Plants work

27 Plant Form and Function

28 Plant Reproduction and Development

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1 Invitation to Biology 1.1 the secret life of earth 4

1.2 life is more than the sum of its Parts 4

1.3 How living things are alike 6

Organisms Require Energy and Nutrients 6

Organisms Sense and Respond to Change 6

Organisms Grow and Reproduce 6

1.4 How living things differ 8

What Is a Species? 8

A Rose by Any Other Name 10

1.5 the science of nature 11

Thinking About Thinking 12

How Science Works 12

Examples of Experiments in Biology 13

1.6 the nature of science 16

Bias in Interpreting Experimental Results 16

Sampling Error 17

Scientific Theories 18

The Scope of Science 19

UNIT 1 HOw CELLS wORk

2 Molecules of Life 2.1 Fear of Frying 24

2.2 start with atoms 25

Why Electrons Matter 26

2.3 From atoms to molecules 28

Ionic Bonds 28

Covalent Bonds 28

2.4 Hydrogen Bonds and water 29

Water Is an Excellent Solvent 30

Water Has Cohesion 31

Water Stabilizes Temperature 31

2.5 acids and Bases 32

2.6 organic molecules 33

What Cells Do to Organic Compounds 33

2.7 Carbohydrates 34

2.8 lipids 36

Fats 36

Phospholipids 36

Waxes 37

Steroids 37

2.9 Proteins 38

The Importance of Protein Structure 39

2.10 nucleic acids 41

3 Cell Structure 3.1 Food for thought 46

3.2 what, exactly, is a Cell? 46

The Cell Theory 46

Components of All Cells 47

Constraints on Cell Size 47

How Do We See Cells? 48

3.3 Cell membrane structure 50

Membrane Proteins 51

3.4 introducing Prokaryotic Cells 52

Biofilms 53

3.5 introducing eukaryotic Cells 54

The Nucleus 54

The Endomembrane System 54

Mitochondria 55

Chloroplasts 56

The Cytoskeleton 56

Extracellular Matrix 58

Cell Junctions 58

3.6 the nature of life 59

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4 Energy and Metabolism 4.1 a toast to alcohol dehydrogenase 64

4.2 life runs on energy 65

4.3 energy in the molecules of life 66

Why Earth Does Not Go Up in Flames 67

Energy In, Energy Out 68

4.4 How enzymes work 68

The Need for Speed 68

Factors That Influence Enzyme Activity 69

Cofactors 70

Metabolic Pathways 71

Controlling Metabolism 71

Electron Transfers 72

4.5 diffusion and membranes 73

Semipermeable Membranes 73

4.6 membrane transport mechanisms 75

Passive Transport 75

Active Transport 76

Membrane Trafficking 76

5 Capturing and Releasing Energy

5.1 a Burning Concern 82

5.2 to Catch a rainbow 83

Storing Energy in Sugars 84

5.3 light-dependent reactions 85

5.4 light-independent reactions 87

Alternative Carbon-Fixing Pathways 87

5.5 a Global Connection 89

Aerobic Respiration in Mitochondria 89

5.6 Fermentation 92

5.7 Food as a source of energy 94

Complex Carbohydrates 94

Fats 94

Proteins 95

UNIT 2 GENETICS

6 DNA Structure and Function 6.1 Cloning 100

6.2 Fame, Glory, and dna structure 102

Discovery of DNA’s Function 102

Discovery of DNA’s Structure 104

DNA Sequence 105

6.3 dna in Chromosomes 106

6.4 dna replication and repair 108

How Mutations Arise 108

7 Gene Expression and Control 7.1 ricin, riP 114

7.2 Gene expression 115

7.3 transcription: dna to rna 116

RNA Modifications 117

7.4 the Genetic Code 118

7.5 translation: rna to Protein 119

7.6 Products of mutated Genes 122

7.7 Control of Gene expression 124

Master Genes 124

Sex Chromosome Genes 125

Lactose Tolerance 125

DNA Methylation 126

CONTENTS v

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8 How Cells Reproduce 8.1 Henrietta’s immortal Cells 132

8.2 multiplication by division 133

Cytoplasmic Division 136

8.3 mitosis and Cancer 137

Cell Division Gone Wrong 137

Cancer 138

Telomeres 139

8.4 sex and alleles 140

On the Advantages of Sex 140

8.5 meiosis in sexual reproduction 142

How Meiosis Mixes Alleles 144

From Gametes to Offspring 144

9 Patterns of Inheritance 9.1 menacing mucus 150

9.2 tracking traits 151

Mendel’s Experiments 151

Inheritance in Modern Terms 151

9.3 mendelian inheritance Patterns 152

Monohybrid Crosses 153

Dihybrid Crosses 154

9.4 Beyond simple dominance 155

Incomplete Dominance 155

Codominance 155

Pleiotropy and Epistasis 156

9.5 Complex variation in traits 158

Continuous Variation 159

9.6 Human Genetic analysis 160

Types of Genetic Variation 160

9.7 Human Genetic disorders 161

The Autosomal Dominant Pattern 162

The Autosomal Recessive Pattern 163

The X-Linked Recessive Pattern 164

9.8 Chromosome number Changes 165

Autosomal Change and Down Syndrome 166

Change in the Sex Chromosome Number 166

9.9 Genetic screening 168

10 Biotechnology 10.1 Personal Genetic testing 174

10.2 Finding needles in Haystacks 175

Cutting and Pasting DNA 175

DNA Libraries 176

PCR 177

10.3 studying dna 178

Sequencing the Human Genome 178

Genomics 179

DNA Profiling 179

10.4 Genetic engineering 181

Genetically Modified Microorganisms 181

Designer Plants 181

Biotech Barnyards 182

10.5 modifying Humans 184

Gene Therapy 184

Eugenics 185

UNIT 3 EVOLUTION AND DIVERSITy

11 Evidence of Evolution 11.1 reflections of a distant Past 190

11.2 Confusing discoveries 191

11.3 a Flurry of new ideas 192

Squeezing New Evidence Into Old Beliefs 192

Darwin and the HMS Beagle 193

A Key Insight—Variation in Traits 194

Great Minds Think Alike 195

11.4 Fossil evidence 196

The Fossil Record 196

vi CONTENTS

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CONTENTS vii

Radiometric Dating 197

Missing Links 199

11.5 drifting Continents 200

Putting Time Into Perspective 201

11.6 evidence in Form 204

Morphological Divergence 204

Morphological Convergence 205

11.7 evidence in Function 206

Patterns in Animal Development 207

12 Processes of Evolution 12.1 superbug Farms 212

12.2 alleles in Populations 213

An Evolutionary View of Mutations 213

Allele Frequency 214

12.3 modes of natural selection 215

Directional Selection 215

Stabilizing Selection 217

Disruptive Selection 217

12.4 natural selection and diversity 218

Survival of the Sexiest 218

Maintaining Multiple Alleles 219

12.5 Genetic drift and Gene Flow 220

Bottlenecks and the Founder Effect 220

Gene Flow 221

12.6 speciation 222

Reproductive Isolation 222

Allopatric Speciation 224

Sympatric Speciation 224

12.7 macroevolution 226

Evolutionary Theory 228

12.8 Phylogeny 229

Applications of Phylogeny 230

13 Early Life Forms and the Viruses 13.1 the Human micobiome 236

13.2 on the road to life 237

Conditions on the Early Earth 237

Origin of the Building Blocks of Life 237

Origin of Metabolism 238

Origin of Genetic Material 238

Origin of Cell Membranes 239

13.3 origin of the three domains 240

Reign of the Prokaryotes 240

Origin of Eukaryotes 241

13.4 viruses 242

Viral Structure and Replication 242

Bacteriophages 242

Plant Viruses 243

Viruses and Human Health 243

HIV—The AIDS Virus 244

Ebola 245

New Flus 245

13.5 Bacteria and archaea 246

Structure and Function 246

Reproduction and Gene Transfers 246

Metabolic Diversity 247

Domain Archaea 248

Domain Bacteria 248

13.6 Protists 250

Flagellated Protozoans 250

Foraminifera 251

Ciliates 251

Dinoflagellates 252

Apicomplexans 252

Water Molds, Diatoms, and Brown Algae 254

Red Algae 255

Green Algae 255

Amoebas and Slime Molds 256

Choanoflagellates 257

14 Plants and Fungi 14.1 Fungal threats to Crops 262

14.2 Plant traits and evolution 263

Life Cycle 263

Structural Adaptations to Life on Land 264

Reproduction and Dispersal 264

14.3 nonvascular Plants 265

Mosses 265

Liverworts and Hornworts 266

14.4 seedless vascular Plants 266

Ferns 266

Horsetails and Club Mosses 267

14.5 rise of the seed Plants 269

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14.6 Gymnosperms 270

Conifers 270

Cycads and Ginkgos 271

Gnetophytes 271

14.7 angiosperms—Flowering Plants 272

Floral Structure and Function 272

A Flowering Plant Life Cycle 273

Keys to Angiosperm Diversity 273

Major Groups 273

Ecology and Human Uses of Angiosperms 274

14.8 Fungal traits and diversity 274

Yeasts, Molds, Mildews, and Mushrooms 274

Lineages and Life Cycles 275

14.9 ecological roles of Fungi 277

Decomposers 277

Parasites 277

Fungal Partnerships 278

Human Uses of Fungi 279

15 Animal Evolution 15.1 medicines From the sea 284

15.2 origins and diversification 285

Animal Origins 285

Evidence of Early Animals 285

Major Groups and Evolutionary Trends 286

15.3 invertebrate diversity 288

Sponges 288

Cnidarians 288

Flatworms 289

Annelids 290

Mollusks 290

Roundworms 291

Arthropods 292

Echinoderms 296

15.4 introducing the Chordates 297

Chordate Traits 297

Invertebrate Chordates 297

Vertebrate Traits and Trends 298

15.5 Fishes and amphibians 299

Jawless Fishes 299

Jawed Fishes 299

Early Tetrapods 300

Modern Amphibians 301

15.6 escape From water—amniotes 302

Amniote Innovations 302

Nonbird Reptiles 302

Birds 303

Mammals 303

15.7 Human evolution 305

Primate Traits 305

Primate Origins and Diversification 305

Australopiths 306

Early Humans 307

Homo Sapiens 308

Neanderthals and Denisovans 308

UNIT 4 ECOLOGy

16 Population Ecology 16.1 a Honkin’ mess 314

16.2 Characteristics of Populations 315

Demographic Traits 315

Collecting Demographic Data 316

16.3 Population Growth 317

Exponential Growth 317

Carrying Capacity and Logistic Growth 318

Density-Independent Factors 319

16.4 life History Patterns 320

Biotic Potential 320

Describing Life Histories 320

Evolution of Life Histories 321

Predation and Life History Evolution 322

viii CONTENTS

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CONTENTS ix

16.5 Human Populations 323

Population Size and Growth Rate 323

Fertility Rates and Future Growth 324

Effects of Industrial Development 325

17 Communities and Ecosystems 17.1 Fighting Foreign Fire ants 330

17.2 Community structure 331

Nonbiological Factors 331

Biological Factors 331

17.3 direct species interactions 332

Commensalism and Mutualism 332

Interspecific Competition 333

Predator–Prey Interactions 334

Plants and Herbivores 335

Parasites and Parasitoids 335

17.4 How Communities Change 337

Ecological Succession 337

Adapted to Disturbance 338

Species Losses or Additions 338

17.5 the nature of ecosystems 339

Overview of the Participants 339

Food Chains and Webs 339

Primary Production and Inefficient Energy Transfers 341

17.6 Biogeochemical Cycles 342

The Water Cycle 342

The Phosphorus Cycle 342

The Nitrogen Cycle 344

The Carbon Cycle 345

The Greenhouse Effect and Global Climate Change 346

18 The Biosphere and Human Effects 18.1 Going with the Flow 352

18.2 Factors that affect Climate 353

Air Circulation Patterns 353

Ocean Circulation 354

18.3 the major Biomes 355

Forest Biomes 355

Grasslands and Chaparral 356

Deserts 356

Tundra 356

18.4 aquatic ecosystems 358

Freshwater Ecosystems 358

Marine Ecosystems 358

18.5 Human impact on the Biosphere 360

Increased Species Extinctions 360

Deforestation and Desertification 362

Acid Rain 362

Biological Accumulation and Magnification 363

The Trouble With Trash 363

Destruction of the Ozone Layer 364

Global Climate Change 364

18.6 maintaining Biodiversity 366

The Value of Biodiversity 366

Conservation Biology 366

Ecological Restoration 367

Reducing Human Impacts 368

UNIT 5 HOw ANIMALS wORk

19 Animal Tissues and Organs 19.1 Growing replacement Parts 374

19.2 animal structure and Function 375

Organization and Integration 375

Evolution of Structure and Function 376

19.3 types of animal tissues 376

Epithelial Tissues 376

Connective Tissues 378

Muscle Tissues 379

Nervous Tissue 380

19.4 organs and organ systems 380

Organ Systems 382

19.5 regulating Body temperature 384

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20 How Animals Move 20.1 Bulking Up muscles 390

20.2 skeletal systems 391

Types of Skeletons 391

The Human Skeleton 392

Bone Structure and Function 392

Where Bones Meet—Skeletal Joints 393

20.3 Functions of skeletal muscles 395

20.4 How muscle Contracts 396

Muscle Components 396

Sliding Filaments 397

20.5 Fueling muscle Contraction 398

20.6 exercise and inactivity 398

21 Circulation and Respiration 21.1 a shocking save 404

21.2 How substances are moved through a Body 405

Open and Closed Circulatory Systems 405

Evolution of Vertebrate Cardiovascular Systems 406

21.3 Human Cardiovascular system 407

21.4 the Human Heart 408

The Cardiac Cycle 409

Setting the Pace of Contractions 409

21.5 Blood and Blood vessels 410

Components and Functions of Blood 410

High-Pressure Flow in Arteries 410

Adjusting Resistance at Arterioles 411

Capillary Exchange and Function of the Lymph Vessels 411

Back to the Heart 412

21.6 Blood and Cardiovascular disorders 412

Blood Disorders 412

Cardiovascular Disorders 413

21.7 animal respiration 414

Two Sites of Gas Exchange 414

Respiratory Systems 414

21.8 Human respiratory Function 416

From Airways to Alveoli 416

How You Breathe 417

Exchanges at Alveoli 418

Transport of Gases 418

Respiratory Disorders 418

22 Immunity 22.1 Frankie’s last wish 424

22.2 responding to threats 425

The Defenders 426

22.3 innate immunity mechanisms 427

Normal Flora 427

Surface Barriers 427

Complement 428

Phagocytosis 428

Inflammation and Fever 429

Examples of Innate Responses 430

22.4 antigen receptors 431

Antigen Processing 432

22.5 adaptive immune responses 434

Example of an Antibody-Mediated Response 434

Example of a Cell-Mediated Response 436

22.6 immunity Gone wrong 438

Overly Vigorous Responses 438

Immune Deficiency and AIDS 439

22.7 vaccines 441

23 Digestion and Excretion 23.1 Causes and effects of obesity 446

23.2 two types of digestive systems 446

23.3 digestive structure and Function 448

In the Mouth 448

Swallowing 448

The Stomach 449

Digestion in the Small Intestine 450

Absorption in the Small Intestine 451

Concentrating and Eliminating Wastes 452

23.4 Human nutrition 453

Carbohydrates 453

Fats 454

Proteins 454

Vitamins and Minerals 454

USDA Dietary Recommendations 455

23.5 Fluid regulation 456

Fluid Homeostasis 456

Fluid Regulation in Invertebrates 456

Vertebrate Urinary System 457

x CONTENTS

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CONTENTS xi

23.6 kidney Function 458

How Urine Forms 458

Feedback Control of Urine Formation 459

Impaired Kidney Function 460

24 Neural Control and the Senses 24.1 impacts of Concussions 466

24.2 animal nervous systems 467

Invertebrate Nervous Systems 467

Vertebrate Nervous Systems 467

24.3 neuron Function 468

Three Types of Neurons 468

Neuroglia—Neuron Helpers 469

Resting Potential 469

The Action Potential 470

The Chemical Synapse 471

Disrupted Synaptic Function 472

Psychoactive Drugs 472

24.4 the Central nervous system 474

Regions of the Human Brain 474

A Closer Look at the Cerebral Cortex 476

The Limbic System—Emotion and Memory 476

The Spinal Cord 477

24.5 the Peripheral nervous system 478

24.6 the senses 480

Sensory Reception and Diversity 480

Sensation to Perception 480

The Chemical Senses—Smell and Taste 481

Detecting Light 482

The Human Eye 482

At the Retina 484

Hearing 484

Sense of Balance 486

The Somatosensory Cortex 487

25 Endocrine Control 25.1 endocrine disrupters 492

25.2 Hormone Function 493

Types of Hormones 494

Hormone Receptors 494

25.3 the Hypothalamus and Pituitary 496

Posterior Pituitary Function 496

Anterior Pituitary Function 496

Growth Disorders 496

25.4 thyroid and Parathyroid Glands 498

Thyroid Hormone 498

Regulation of Calcium 499

25.5 the Pancreas 500

Controlling Blood Glucose 500

Diabetes Mellitus 501

25.6 the adrenal Glands 502

25.7 Hormones and reproductive Function 504

Gonads 504

The Pineal Gland 504

26 Reproduction and Development 26.1 assisted reproduction 510

26.2 modes of reproduction 511

Asexual Reproduction 511

Sexual Reproduction 511

Variations on Sexual Reproduction 511

26.3 stages of animal development 512

26.4 Human reproductive Function 514

Female Reproductive Anatomy 514

Egg Production and Release 515

The Menstrual Cycle 516

Male Reproductive Anatomy 517

How Sperm Form 518

Sexual Intercourse 518

A Sperm’s Journey 519

26.5 reproductive Health 520

Contraception 520

Infertility 521

Sexually Transmitted Diseases 522

26.6 Human development 523

Fertilization 523

From Cleavage to Implantation 524

Embryonic and Fetal Development 525

Functions of the Placenta 528

Maternal Effects on Prenatal Development 528

26.7 Birth and milk Production 529

Childbirth 529

Nourishing the Newborn 529

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UNIT 6 HOw PLANTS wORk

27 Plant Form and Function 27.1 leafy Cleanup Crews 534

27.2 tissues in a Plant Body 535

Eudicots and Monocots 537

27.3 stems, leaves, and roots 538

Stems 538

Leaves 540

Roots 542

27.4 Fluid movement in Plants 544

Water Moves Through Xylem 544

Sugars Flow Through Phloem 545

27.5 Plant Growth 546

28 Plant Reproduction and Development

28.1 Plight of the Honeybee 554

28.2 sexual reproduction 555

A New Generation Begins 558

28.3 seeds and Fruits 560

28.4 early development 562

28.5 asexual reproduction 564

Agricultural Applications 564

28.6 Plant Hormones 565

Auxin 566

Cytokinin 567

Gibberellin 568

Abscisic Acid 568

Ethylene 568

28.7 Growth responses 570

Tropisms 570

Photoperiodic Responses 572

appendix i answers to self-Quizzes

appendix ii Periodic table of the elements

appendix iii a Plain english map of the Human Chromosomes

appendix iv Units of measure

xii CONTENTS

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P

P r

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Biology is a huge field, with a wealth of new discover- ies being made every day, and biology-related issues such as climate change, stem cell research, and per- sonal genetics often making headlines. This avalanche of information can be intimidating to non-scientists. This book was designed and written specifically for students who most likely will not become biologists and may never again take another science course. It is an accessible and engaging introduction to biology that provides future decision-makers with an under- standing of basic biology and the process of science.

a wealth of applications This book is packed with everyday applications of biological processes. At every opportunity, we enliven discussions of biologi- cal processes with references to their effects on human health and the environment. This edition also con- tinues to focus on real world applications pertaining to the field of biology, including social issues arising from new research and developments. Descriptions of current research, along with photos of scientists who carry it out, underscore the concept that biology is an ongoing endeavor carried out by a diverse commu- nity of people. Discussions include not only what was discovered, but also how the discoveries were made, how our understanding has changed over time, and what remains to be discovered. These discussions are provided in the context of an accessible introduction to well-established concepts that underpin modern biology. Every topic is examined from an evolutionary perspective, emphasizing the connections between all forms of life.

accessible text Understanding stems from mak- ing connections between concepts and details, so a text with too little detail reads as a series of facts that beg to be memorized. However, excessive detail can overwhelm the introductory student. Thus, we con- stantly strive to strike the perfect balance between level of detail and accessibility. We once again revised the text to eliminate details that do not contribute to a basic understanding of essential concepts. We also know that English is a second language for many introductory students, so we avoid idioms and aim for a clear, straightforward style.

Analogies to familiar objects and phenomena will help students understand abstract concepts. For exam- ple, in the discussion of transpiration in Chapter 27 (Plant Form and Function), we explain that a column of water is drawn upward through xylem as a drinker draws fluid up through a straw.

in-text learning tools To emphasize connections between biological topics, each chapter begins with an application section that explores a current event or controversy directly related to the chapter’s content. For example, a discussion of binge drinking on col- lege campuses introduces the concept of metabolism in Chapter 4. This section presents an overview of the metabolic pathway that breaks down alcohol, linking the function of enzymes in the pathway to hangovers, alcoholism, and cirrhosis. The section is illustrated with a photo of a tailgate party that preceded a recent Notre Dame–Alabama football game, and also a photo of Gary Reinbach just before he died at age 22 of alcoholic liver disease. (In the index, you’ll find health-related applications denoted by red squares and environmental applications by green squares.)

To strengthen a student’s analytical skills and offer insight into contemporary research, each chapter includes an exercise called digging into data that is placed in a section with relevant content. The exer- cise consists of a short text passage—usually about a published scientific experiment—and a table, chart, or other graphic that presents experimental data. A student can use information in the text and graphic to answer a series of questions. For example, the exercise in Chapter 2 asks students to interpret results of a study that examined the effect of dietary fat intake on “good” and “bad” cholesterol levels.

The chapter itself consists of several numbered sections that contain a manageable chunk of informa- tion. Every section ends with a boxed take-home message in which we pose a question that reflects the critical content of the section, and then answer the question in bulleted list format. Every chapter has at least one figure it out question with an answer immediately following. These questions allow students to quickly check their understanding as they read. Mastering scientific vocabulary challenges many stu- dents, so we have included an on-page glossary of key terms introduced in each two-page spread, in addition to a complete glossary at the book’s end. The end-of-chapter material features a visual summary that reinforces each chapter’s key concepts. A self- quiz poses multiple choice and other short answer questions for self-assessment (answers are in Appen- dix I). A set of more challenging critical thinking questions provides thought-provoking exercises for the motivated student. The end matter of several chapters now includes a visual question that rein- forces learning in a nonverbal style.

Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).

Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.

xiv PREFACE

design and Content revisions Throughout the book, text and art have been revised to help students grasp difficult concepts. The following list highlights some of the revisions to each chapter.

Introduction 1 Invitation to Biology Renewed and updated emphasis on the rel-

evance of new species discovery and the process of science.

Unit 1 How Cells work 2 Molecules of Life New graphic illustrates radioactive decay. 3 Cell Structure Application section updated with current statistics

and ‘pink slime’ story. Micrograph comparisons now feature Para- mecia and include a confocal image. Essay about the nature of life expanded to add Gerald Joyce’s “life is squishy” concept.

4 Energy and Metabolism Application section now illustrated with a real-life example. Diffusion illustrated with a tea bag in hot water.

5 Capturing and Releasing Energy Application section updated with current statistics and illustrated with a current photo of air pollu- tion in China. Yogurt production added to fermentation section.

Unit 2 Genetics 6 DNA Structure and Function Content reorganized: material on clon-

ing folded into Application section for concept connection, and chromosome structure now appears after DNA structure. New art demonstrates how replication errors become mutations.

7 Gene Expression and Control Ricin discussion revised to include medical applications. New material includes hairlessness mutation (in cats), evolution of lactose tolerance, heritability of DNA meth- ylations, telomeres.