Cell Biology Custom Book LFS100

1 Introduction:
Themes in the Study of Life 1

OVERVIEW Inquiring About Life 1
CONCEPT 1.1 The themes of this book make connections across different areas of biology 2
Theme: New Properties Emerge at Each Level in the Biological Hierarchy 3
Theme: Organisms eInteract with Other Organisms and the Physical Environment 6
Theme: Life Requirs Energy Transfer and Transformation 6
Theme: Structure and Function Are Correlated at All Levels of Biological Organisation 7
Theme: The Cell Is an Organism’s Basic Unit of Structure and Function 8
Theme: The Continuity of Life Is Based on Heritable Information in the Form of DNA 8
Theme: Feedback Mechanisms Regulate Biological Systems 10
Evolution, the Overarching Theme of Biology 11
CONCEPT 1.2 The Core Theme: Evolution accounts for the unity and diversity of life 11
Classifying the Diversity of Life 12
Charles Darwin and the Theory of Natural Selection 14 The Tree of Life 16
CONCEPT 1.3 In studying nature, scientists make observations and then form and test hypotheses 18
Making Observations 18
Forming and Testing Hypotheses 19
The Flexibility of the Scientific Method 20
A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations 20
Theories in Science 23
CONCEPT 1.4 Science benefits from a cooperative approach and diverse viewpoints 23
Building on the Work of Others 23
Science, Technology, and Society 24
The Value of Diverse Viewpoints in Science 25

U N I T
1 The Chemistry of Life 28
Interview: Susan Solomon
2 The Chemical Context of Life 30
OVERVIEW A Chemical Connection to Biology 30
CONCEPT 2.1 Matter consists of chemical elements in pure form and in combinations called compounds 31
Elements and Compounds 31
The Elements of Life 32
Case Study: Evolution of Tolerance to Toxic Elements 32
CONCEPT 2.2 An element’s properties depend on the structure of its atoms 33
Subatomic Particles 33
Atomic Number and Atomic Mass 33 Isotopes 34
The Energy Levels of Electrons 35
Electron Distribution and Chemical Properties 36
Electron Orbitals 37
CONCEPT 2.3 The formation and function of molecules depend on chemical bonding between atoms 38
Covalent Bonds 38
Ionic Bonds 39
Weak Chemical Bonds 40
Molecular Shape and Function 41
CONCEPT 2.4 Chemical reactions make and break chemical bonds 42

3 Water and Life 46
OVERVIEW The Molecule That Supports All of Life 46
CONCEPT 3.1 Polar covalent bonds in water molecules result in hydrogen bonding 46
CONCEPT 3.2 Four emergent properties of water contribute to Earth’s suitability for life 47
Cohesion of Water Molecules 47
Moderation of Temperature by Water 48
Floating of Ice on Liquid Water 49
Water: The Solvent of Life 50
Possible Evolution of Life on Other Planets with Water 52
CONCEPT 3.3 Acidic and basic conditions affect living organisms 52
Acids and Bases 53
The pH Scale 53
Buffers 54
Acidification: A Threat to Water Quality 55

4 Carbon and the Molecular Diversity of Life 60
OVERVIEW Carbon: The Backbone of Life 60
CONCEPT 4.1 Organic chemistry is the study of carbon compounds 60
Organic Molecules and the Origin of Life on Earth 61
CONCEPT 4.2 Carbon atoms can form diverse molecules by bonding to four other atoms 62
The Formation of Bonds with Carbon 62
Molecular Diversity Arising from Carbon Skeleton Variation 63
CONCEPT 4.3 A few chemical groups are key to the functioning of biological molecules 65
The Chemical Groups Most Important in the Processes of Life 65
ATP: An Important Source of Energy for Cellular Processes 68
The Chemical Elements of Life: A Review 68

5 The Structure and Function of Large Biological Molecules 70
OVERVIEW The Molecules of Life 70
CONCEPT 5.1 Macromolecules are polymers, built from monomers 70
The Synthesis and Breakdown of Polymers 70
The Diversity of Polymers 71
CONCEPT 5.2 Carbohydrates serve as fuel and building material 71
Sugars 71
Polysaccharides 72
CONCEPT 5.3 Lipids are a diverse group of hydrophobic molecules 76
Fats 76
Phospholipids 78
Steroids 79
CONCEPT 5.4 Proteins include a diversity of structures, resulting in a wide range of functions 79
Polypeptides 79
Protein Structure and Function 82
CONCEPT 5.5 Nucleic acids store, transmit, and help express hereditary information 88
The Roles of Nucleic Acids 88
The Components of Nucleic Acids 89
Nucleotide Polymers 90
The Structures of DNA and RNA Molecules 90
DNA and Proteins as Tape Measures of Evolution 91
The Theme of Emergent Properties in the Chemistry of
Life: A Review 91

U N I T
2 The Cell 94
Interview: Bonnie L. Bassler
6 A Tour of the Cell 96
OVERVIEW The Fundamental Units of Life 96
CONCEPT 6.1 Biologists use microscopes and the tools of biochemistry to study cells 96
Microscopy 96
Cell Fractionation 99
CONCEPT 6.2 Eukaryotic cells have internal membranes that compartmentalise their functions 100
Comparing Prokaryotic and Eukaryotic Cells 100
A Panoramic View of the Eukaryotic Cell 101
CONCEPT 6.3 The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes 104
The Nucleus: Information Central 104
Ribosomes: Protein Factories 104
CONCEPT 6.4 The endomembrane system regulates protein traffic and performs metabolic functions in the cell 106
The Endoplasmic Reticulum: Biosynthetic Factory 106
The Golgi Apparatus: Shipping and Receiving Centre 107
Lysosomes: Digestive Compartments 108
Vacuoles: Diverse Maintenance Compartments 109
The Endomembrane System: A Review 110
CONCEPT 6.5 Mitochondria and chloroplasts change energy from one form to another 111
The Evolutionary Origins of Mitochondria and Chloroplasts 111
Mitochondria: Chemical Energy Conversion 112
Chloroplasts: Capture of Light Energy 112
Peroxisomes: Oxidation 113
CONCEPT 6.6 The cytoskeleton is a network of fibres that organises structures and activities in the cell 114
Roles of the Cytoskeleton: Support and Motility 114
Components of the Cytoskeleton 115
CONCEPT 6.7 Extracellular components and connections between cells help coordinate cellular activities 120
Cell Walls of Plants 120
The Extracellular Matrix (ECM) of Animal Cells 121
Cell Junctions 122
The Cell: A Living Unit Greater Than the Sum of Its Parts 124

7 Membrane Structure and Function 127
OVERVIEW Life at the Edge 127
CONCEPT 7.1 Cellular membranes are fluid mosaics of lipids and proteins 127
Membrane Models: Scientific Inquiry 127
The Fluidity of Membranes 129
Evolution of Differences in Membrane Lipid Composition 130
Membrane Proteins and Their Functions 131
The Role of Membrane Carbohydrates in Cell–Cell Recognition 132
Synthesis and Sidedness of Membranes 132
CONCEPT 7.2 Membrane structure results in selective permeability 133
The Permeability of the Lipid Bilayer 133
Transport Proteins 133
CONCEPT 7.3 Passive transport is diffusion of a substance across a membrane with no energy investment 134
Effects of Osmosis on Water Balance 135
Facilitated Diffusion: Passive Transport Aided by Proteins 136
CONCEPT 7.4 Active transport uses energy to move solutes against their gradients 137
The Need for Energy in Active Transport 137
How Ion Pumps Maintain Membrane Potential 138
Cotransport: Coupled Transport by a Membrane Protein 139
CONCEPT 7.5 Bulk transport across the plasma membrane occurs by exocytosis and endocytosis 140
Exocytosis 140
Endocytosis 140

8 An Introduction to Metabolism 144
OVERVIEW The Energy of Life 144
CONCEPT 8.1 An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics 144
Organisation of the Chemistry of Life into Metabolic
Pathways 144
Forms of Energy 145
The Laws of Energy Transformation 146
CONCEPT 8.2 The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously 148
Free-Energy Change, AG 148
Free Energy, Stability, and Equilibrium 148
Free Energy and Metabolism 149
CONCEPT 8.3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions 151
The Structure and Hydrolysis of ATP 151
How the Hydrolysis of ATP Performs Work 152
The Regeneration of ATP 153
CONCEPT 8.4 Enzymes speed up metabolic reactions by lowering energy barriers 154
The Activation Energy Barrier 154
How Enzymes Lower the EA Barrier 155
Substrate Specificity of Enzymes 155
Catalysis in the Enzyme’s Active Site 156
Effects of Local Conditions on Enzyme Activity 157
The Evolution of Enzymes 159
CONCEPT 8.5 Regulation of enzyme activity helps control metabolism 160
Allosteric Regulation of Enzymes 160
Specific Localisation of Enzymes Within the Cell 162

9 Cellular Respiration and Fermentation 165
OVERVIEW Life Is Work 165
CONCEPT 9.1 Catabolic pathways yield energy by oxidising organic fuels 166
Catabolic Pathways and Production of ATP 166
Redox Reactions: Oxidation and Reduction 166
The Stages of Cellular Respiration: A Preview 169
CONCEPT 9.2 Glycolysis harvests chemical energy by oxidising glucose to pyruvate 170
CONCEPT 9.3 After pyruvate is oxidised, the citric acid cycle completes the energy-yielding oxidation of organic molecules 172
Oxidation of Pyruvate to Acetyl CoA 172
The Citric Acid Cycle 172
CONCEPT 9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis 174
The Pathway of Electron Transport 174
Chemiosmosis: The Energy-Coupling Mechanism 175
An Accounting of ATP Production by Cellular Respiration 176
CONCEPT 9.5 Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen 179
Types of Fermentation 179
Comparing Fermentation with Anaerobic and Aerobic Respiration 180
The Evolutionary Significance of Glycolysis 181
CONCEPT 9.6 Glycolysis and the citric acid cycle connect to many other metabolic pathways 181
The Versatility of Catabolism 181
Biosynthesis (Anabolic Pathways) 184
Regulation of Cellular Respiration Via Feedback Mechanisms 184
10 Photosynthesis 188
OVERVIEW The Process That Feeds the Biosphere 188
CONCEPT 10.1 Photosynthesis converts light energy to the chemical energy of food 190
Chloroplasts: The Sites of Photosynthesis in Plants 190
Tracking Atoms Through Photosynthesis: Scientific Inquiry 191
The Two Stages of Photosynthesis: A Preview 192
CONCEPT 10.2 The light reactions convert solar energy to the chemical energy of ATP and NADPH 193
The Nature of Sunlight 193
Photosynthetic Pigments: The Light Receptors 194
Excitation of Chlorophyll by Light 196
A Photosystem: A Reaction-Centre Complex Associated with Light-Harvesting Complexes 196
Linear Electron Flow 197
Cyclic Electron Flow 199
A Comparison of Chemiosmosis in Chloroplasts and Mitochondria 200
CONCEPT 10.3 The Calvin cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar 202
CONCEPT 10.4 Alternative mechanisms of carbon fixation have evolved in hot, arid climates 203
Photorespiration: An Evolutionary Relic? 203
C4 Plants 204
CAM Plants 205
The Importance of Photosynthesis: A Review 207

11 Cell Communication 210
OVERVIEW Cellular Messaging 210
CONCEPT 11.1 External signals are converted to responses within the cell 210
Evolution of Cell Signalling 210
Local and Long-Distance Signalling 212
The Three Stages of Cell Signalling: A Preview 213
CONCEPT 11.2 Reception: A signalling molecule binds to a receptor protein, causing it to change shape 214
Receptors in the Plasma Membrane 214
Intracellular Receptors 218
CONCEPT 11.3 Transduction: Cascades of molecular interactions relay signals from receptors to target molecules in the cell 218
Signal Transduction Pathways 219
Protein Phosphorylation and Dephosphorylation 219
Small Molecules and Ions as Second Messengers 220
CONCEPT 11.4 Response: Cell signalling leads to regulation of transcription or cytoplasmic activities 223
Nuclear and Cytoplasmic Responses 223
Fine-Tuning of the Response 224
CONCEPT 11.5 Apoptosis integrates multiple cell-signalling pathways 227
Apoptosis in the Soil Worm Caenorhabditis elegans 228
Apoptotic Pathways and the Signals That Trigger Them 228

12 The Cell Cycle 232
OVERVIEW The Key Roles of Cell Division 232
CONCEPT 12.1 Most cell division results in genetically identical daughter cells 233
Cellular Organisation of the Genetic Material 233
Distribution of Chromosomes During Eukaryotic Cell Division 233
CONCEPT 12.2 The mitotic phase alternates with interphase in the cell cycle 234
Phases of the Cell Cycle 235
The Mitotic Spindle: A Closer Look 235
Cytokinesis: A Closer Look 238
Binary Fission in Bacteria 240
The Evolution of Mitosis 241
CONCEPT 12.3 The eukaryotic cell cycle is regulated by a molecular control system 242
Evidence for Cytoplasmic Signals 242
The Cell Cycle Control System 242
Loss of Cell Cycle Controls in Cancer Cells 246

U N I T
3 Genetics 250
Interview: Abigail Elizur
13 Meiosis and Sexual Life Cycles 252
OVERVIEW Variations on a Theme 252
CONCEPT 13.1 Offspring acquire genes from parents by inheriting chromosomes 252
Inheritance of Genes 253
Comparison of Asexual and Sexual Reproduction 253
CONCEPT 13.2 Fertilisation and meiosis alternate in sexual life cycles 254
Sets of Chromosomes in Human Cells 254
Behaviour of Chromosome Sets in the Human Life Cycle 255
The Variety of Sexual Life Cycles 256
CONCEPT 13.3 Meiosis reduces the number of chromosome sets from diploid to haploid 257
The Stages of Meiosis 257
A Comparison of Mitosis and Meiosis 261
CONCEPT 13.4 Genetic variation produced in sexual life cycles contributes to evolution 261
Origins of Genetic Variation Among Offspring 261
The Evolutionary Significance of Genetic Variation Within Populations 263

14 Mendel and the Gene Idea 266
OVERVIEW Drawing from the Deck of Genes 266
CONCEPT 14.1 Mendel used the scientific approach to identify two laws of inheritance 266
Mendel’s Experimental, Quantitative Approach 266
The Law of Segregation 268
The Law of Independent Assortment 271
CONCEPT 14.2 The laws of probability govern Mendelian inheritance 273
The Multiplication and Addition Rules Applied to Monohybrid Crosses 273
Solving Complex Genetics Problems with the Rules of Probability 274
CONCEPT 14.3 Inheritance patterns are often more complex than predicted by simple Mendelian genetics 275
Extending Mendelian Genetics for a Single Gene 275
Extending Mendelian Genetics for Two or More Genes 277
Nature and Nurture: The Environmental Impact on Phenotype 278
Integrating a Mendelian View of Heredity and Variation 279
CONCEPT 14.4 Many human traits follow Mendelian patterns of inheritance 279
Pedigree Analysis 279
Recessively Inherited Disorders 280
Dominantly Inherited Disorders 282
Multifactorial Disorders 283
Genetic Testing and Counselling 283

15 The Chromosomal Basis of Inheritance 290
OVERVIEW Locating Genes Along Chromosomes 290
CONCEPT 15.1 Mendelian inheritance has its physical basis in the behaviour of chromosomes 290
Morgan’s Experimental Evidence: Scientific Inquiry 292
CONCEPT 15.2 Sex-linked genes exhibit unique patterns of inheritance 293
The Chromosomal Basis of Sex 293
Inheritance of X-Linked Genes 294
X Inactivation in Female Mammals 295
CONCEPT 15.3 Linked genes tend to be inherited together because they are located near each other on the same chromosome 296
How Linkage Affects Inheritance 296
Genetic Recombination and Linkage 298
Mapping the Distance Between Genes Using Recombination Data: Scientific Inquiry 300
CONCEPT 15.4 Alterations of chromosome number or structure cause some genetic disorders 301
Abnormal Chromosome Number 301
Alterations of Chromosome Structure 302
Human Disorders Due to Chromosomal Alterations 303
CONCEPT 15.5 Some inheritance patterns are exceptions to standard Mendelian inheritance 304
Genomic Imprinting 304
Inheritance of Organelle Genes 305

16 The Molecular Basis of Inheritance 309
OVERVIEW Life’s Operating Instructions 309
CONCEPT 16.1 DNA is the genetic material 309
The Search for the Genetic Material: Scientific Inquiry 309
Building a Structural Model of DNA: Scientific Inquiry 312
CONCEPT 16.2 Many proteins work together in DNA replication and repair 315
The Basic Principle: Base Pairing to a Template Strand 315
DNA Replication: A Closer Look 316
Proofreading and Repairing DNA 320
Evolutionary Significance of Altered DNA Nucleotides 322
Replicating the Ends of DNA Molecules 322
CONCEPT 16.3 A chromosome consists of a DNA molecule packed together with proteins 324

17 From Gene to Protein 331
OVERVIEW The Flow of Genetic Information 331
CONCEPT 17.1 Genes specify proteins via transcription and translation 331
Evidence from the Study of Metabolic Defects 332
Basic Principles of Transcription and Translation 334
The Genetic Code 334
CONCEPT 17.2 Transcription is the DNA-directed synthesis of RNA: a closer look 337
Molecular Components of Transcription 337
Synthesis of an RNA Transcript 338
CONCEPT 17.3 Eukaryotic cells modify RNA after transcription 340
Alteration of mRNA Ends 340
Split Genes and RNA Splicing 340
CONCEPT 17.4 Translation is the RNA-directed synthesis of a polypeptide: a closer look 343
Molecular Components of Translation 343
Building a Polypeptide 346
Completing and Targeting the Functional Protein 348
CONCEPT 17.5 Mutations of one or a few nucleotides can affect protein structure and function 350
Types of Small-Scale Mutations 350
Mutagens 352
CONCEPT 17.6 While gene expression differs between the domains of life, the concept of a gene is universal 352
Comparing Gene Expression in Bacteria, Archaea, and Eukarya 352
What Is a Gene? Revisiting the Question 353

18 Regulation of Gene Expression 357
OVERVIEW Conducting the Genetic Orchestra 357
CONCEPT 18.1 Bacteria often respond to environmental change by regulating transcription 357
Operons: The Basic Concept 358
Repressible and Inducible Operons: Two Types of Negative Gene Regulation 359
Positive Gene Regulation 361
CONCEPT 18.2 Eukaryotic gene expression is regulated at many stages 362
Differential Gene Expression 362
Regulation of Chromatin Structure 363
Regulation of Transcription Initiation 364
Mechanisms of Post-Transcriptional Regulation 368
CONCEPT 18.3 Noncoding RNAs play multiple roles in controlling gene expression 370
Effects on mRNAs by MicroRNAs and Small Interfering RNAs 371
Chromatin Remodelling and Effects on Transcription by ncRNAs 372
The Evolutionary Significance of Small ncRNAs 372
CONCEPT 18.4 A program of differential gene expression leads to the different cell types in a multicellular organism 372
A Genetic Program for Embryonic Development 372
Cytoplasmic Determinants and Inductive Signals 373
Sequential Regulation of Gene Expression During Cellular Differentiation 373
Pattern Formation: Setting Up the Body Plan 375
CONCEPT 18.5 Cancer results from genetic changes that affect cell cycle control 379
Types of Genes Associated with Cancer 379
Interference with Normal Cell-Signalling Pathways 380
The Multistep Model of Cancer Development 382
Inherited Predisposition and Other Factors Contributing to Cancer 382
U N I T
4 Mechanisms of Evolution 458
Interview: Geerat J. Vermeij
25 The History of Life on Earth 515
OVERVIEW Lost Worlds 515
CONCEPT 25.1 Conditions on early Earth made the origin of life possible 515
Synthesis of Organic Compounds on Early Earth 516
Abiotic Synthesis of Macromolecules 517
Protocells 517
Self-Replicating RNA and the Dawn of Natural Selection 517
CONCEPT 25.2 The fossil record documents the history of life 518
The Fossil Record 518
How Rocks and Fossils Are Dated 520
The Origin of New Groups of Organisms 520
CONCEPT 25.3 Key events in life’s history include the origins of single-celled and multicelled organisms and the colonisation of land 522
The First Single-Celled Organisms 522
The Origin of Multicellularity 525
The Colonisation of Land 526
CONCEPT 25.4 The rise and fall of groups of organisms reflect differences in speciation and extinction rates 527
Plate Tectonics 527
Mass Extinctions 530
Adaptive Radiations 533
CONCEPT 25.5 Major changes in body form can result from changes in the sequences and regulation of developmental genes 535
Effects of Developmental Genes 535
The Evolution of Development 536
CONCEPT 25.6 Evolution is not goal oriented 539
Evolutionary Novelties 539
Evolutionary Trends 540

U N I T
5 The Evolutionary History of Biological Diversity 544
Interview: John Stanisic
27 Bacteria and Archaea 566
OVERVIEW Masters of Adaptation 566
CONCEPT 27.1 Structural and functional adaptations contribute to prokaryotic success 566
Cell-Surface Structures 567
Motility 568
Internal Organisation and DNA 569
Reproduction and Adaptation 570
CONCEPT 27.2 Rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotes 571
Rapid Reproduction and Mutation 571
Genetic Recombination 571
CONCEPT 27.3 Diverse nutritional and metabolic adaptations have evolved in prokaryotes 574
The Role of Oxygen in Metabolism 574
Nitrogen Metabolism 574 Metabolic Cooperation 575
CONCEPT 27.4 Molecular systematics is illuminating prokaryotic phylogeny 575
Lessons from Molecular Systematics 576
Archaea 576
Bacteria 577
CONCEPT 27.5 Prokaryotes play crucial roles in the biosphere 580
Chemical Recycling 580
Ecological Interactions 580
CONCEPT 27.6 Prokaryotes have both beneficial and harmful impacts on humans 581
Mutualistic Bacteria 581
Pathogenic Bacteria 581
Prokaryotes in Research and Technology 582

U N I T
6 Plant Form and Function 752
Interview: Luis Herrera-Estrella
35 Plant Structure, Growth, and Development 754
OVERVIEW Are Plants Computers? 754
CONCEPT 35.1 Plants have a hierarchical organisation consisting of organs, tissues, and cells 754
The Three Basic Plant Organs: Roots, Stems, and Leaves 755
Dermal, Vascular, and Ground Tissues 758
Common Types of Plant Cells 759
CONCEPT 35.2 Meristems generate cells for primary and secondary growth 762
CONCEPT 35.3 Primary growth lengthens roots and shoots 763
Primary Growth of Roots 763
Primary Growth of Shoots 765
CONCEPT 35.4 Secondary growth increases the diameter of stems and roots in woody plants 767
The Vascular Cambium and Secondary Vascular Tissue 767
The Cork Cambium and the Production of Periderm 770
Evolution of Secondary Growth 770
CONCEPT 35.5 Growth, morphogenesis, and cell differentiation produce the plant body 771
Model Organisms: Revolutionising the Study of Plants 771
Growth: Cell Division and Cell Expansion 772
Morphogenesis and Pattern Formation 774
Gene Expression and Control of Cell Differentiation 775
Shifts in Development: Phase Changes 775
Genetic Control of Flowering 776

36 Resource Acquisition and Transport in Vascular Plants 780
OVERVIEW Pathways for Survival 780
CONCEPT 36.1 Adaptations for acquiring resources were key steps in the evolution of vascular plants 780
Shoot Architecture and Light Capture 781
Root Architecture and Acquisition of Water and Minerals 782
CONCEPT 36.2 Different mechanisms transport substances over short or long distances 783
The Apoplast and Symplast: Transport Continuums 783
Short-Distance Transport of Solutes Across Plasma Membranes 784
Short-Distance Transport of Water Across Plasma Membranes 784
Long-Distance Transport: The Role of Bulk Flow 787
CONCEPT 36.3 Transpiration drives the transport of water and minerals from roots to shoots via the xylem 788
Absorption of Water and Minerals by Root Cells 788
Transport of Water and Minerals into the Xylem 788
Bulk Flow Transport via the Xylem 788
Xylem Sap Ascent by Bulk Flow: A Review 792
CONCEPT 36.4 The rate of transpiration is regulated by stomata 792
Stomata: Major Pathways for Water Loss 792
Mechanisms of Stomatal Opening and Closing 793
Stimuli for Stomatal Opening and Closing 793
Effects of Transpiration on Wilting and Leaf Temperature 794
Adaptations That Reduce Evaporative Water Loss 794
CONCEPT 36.5 Sugars are transported from sources to sinks via the phloem 795
Movement from Sugar Sources to Sugar Sinks 795
Bulk Flow by Positive Pressure: The Mechanism of Translocation in Angiosperms 796
CONCEPT 36.6 The symplast is highly dynamic 797
Changes in Plasmodesmata 798
Phloem: An Information Superhighway 798
Electrical Signalling in the Phloem 798

39 Plant Responses to Internal and External Signals 841
OVERVIEW Stimuli and a Stationary Life 841
CONCEPT 39.1 Signal transduction pathways link signal reception to response 841
Reception 842
Transduction 842
Response 843
CONCEPT 39.2 Plant hormones help coordinate growth, development, and responses to stimuli 844
The Discovery of Plant Hormones 845
A Survey of Plant Hormones 846
Systems Biology and Hormone Interactions 854
CONCEPT 39.3 Responses to light are critical for plant success 855
Blue-Light Photoreceptors 856
Phytochromes as Photoreceptors 856
Biological Clocks and Circadian Rhythms 858
The Effect of Light on the Biological Clock 858
Photoperiodism and Responses to Seasons 859
CONCEPT 39.4 Plants respond to a wide variety of stimuli other than light 861
Gravity 861
Mechanical Stimuli 862
Environmental Stresses 863
CONCEPT 39.5 Plants respond to attacks by herbivores and pathogens 865
Defences Against Herbivores 865
Defences Against Pathogens 866

U N I T
7 Animal Form and Function 870
Interview: Baldomero M. Olivera
40 Basic Principles of Animal Form and Function 872
OVERVIEW Diverse Forms, Common Challenges 872
CONCEPT 40.1 Animal form and function are correlated at all levels of organisation 873
Evolution of Animal Size and Shape 873
Exchange with the Environment 874
Hierarchical Organisation of Body Plans 874
Coordination and Control 877
CONCEPT 40.2 Feedback control maintains the internal environment in many animals 880
Regulating and Conforming 880
Homeostasis 881
CONCEPT 40.3 Homeostatic processes for thermoregulation involve form, function, and behaviour 883
Endothermy and Ectothermy 883
Variation in Body Temperature 884
Balancing Heat Loss and Gain 884
Acclimatisation in Thermoregulation 887
Physiological Thermostats and Fever 888
CONCEPT 40.4 Energy requirements are related to animal size, activity, and environment 889
Energy Allocation and Use 889
Quantifying Energy Use 889
Minimum Metabolic Rate and Thermoregulation 890 Influences on Metabolic Rate 890
Energy Budgets 891
Torpor and Energy Conservation 891
45 Hormones and the Endocrine System 996
OVERVIEW The Body’s Long-Distance Regulators 996
CONCEPT 45.1 Hormones and other signalling molecules bind to target receptors, triggering specific response pathways 997
Intercellular Communication 997
Endocrine Tissues and Organs 998
Chemical Classes of Hormones 998
Cellular Response Pathways 999
Multiple Effects of Hormones 1000
Signalling by Local Regulators 1001
Coordination of Neuroendocrine and Endocrine Signalling 1002
CONCEPT 45.2 Feedback regulation and antagonistic hormone pairs are common in endocrine systems 1003
Simple Hormone Pathways 1003
Feedback Regulation 1004
Insulin and Glucagon: Control of Blood Glucose 1004
CONCEPT 45.3 The hypothalamus and pituitary are central to endocrine regulation 1006
Coordination of Endocrine and Nervous Systems in Vertebrates 1006
Thyroid Regulation: A Hormone Cascade Pathway 1009
Evolution of Hormone Function 1010
Tropic and Nontropic Hormones 1011
CONCEPT 45.4 Endocrine glands respond to diverse stimuli in regulating homeostasis, development, and behaviour 1011
Parathyroid Hormone and Vitamin D: Control of Blood Calcium 1011
Adrenal Hormones: Response to Stress 1012
Gonadal Sex Hormones 1014
Melatonin and Biorhythms 1015
Appendix A Answers A–1
Appendix B Periodic Table of the Elements B–1
Appendix C The Metric System C–1
Appendix D A Comparison of the Light Microscope and the Electron Microscope D–1
Glossary G–1 Index I–1