Preview Biology,12th Edition by Peter H. Raven, George B. Johnson, Kenneth A. Mason, Jonathan Losos, Tod Duncan (2019) Preview Biology,12th Edition by Peter H. Raven, George B. Johnson, Kenneth A. Mason, Jonathan Losos, Tod Duncan (2019) Preview Biology,12th Edition by Peter H. Raven, George B. Johnson, Kenneth A. Mason, Jonathan Losos, Tod Duncan (2019) Preview Biology,12th Edition by Peter H. Raven, George B. Johnson, Kenneth A. Mason, Jonathan Losos, Tod Duncan (2019)
Trang 2Peter H Raven
President Emeritus, Missouri Botanical Garden;
George Engelmann Professor of Botany Emeritus, Washington University
George B Johnson
Professor Emeritus of Biology, Washington University
Twelfth Edition
Trang 3BIOLOGY, TWELFTH EDITION
Published by McGraw-Hill Education, 2 Penn Plaza, New York, NY 10121 Copyright © 2020 by McGraw-Hill Education All rights
reserved Printed in the United States of America Previous editions © 2017, 2014, and 2011 No part of this publication may be reproduced
or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written consent of McGraw-Hill
Education, including, but not limited to, in any network or other electronic storage or transmission, or broadcast for distance learning.
Some ancillaries, including electronic and print components, may not be available to customers outside the United States.
This book is printed on acid-free paper
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Library of Congress Cataloging-in-Publication Data
Mason, Kenneth A., author | Losos, Jonathan B., author | Duncan, Tod, author
Biology / Kenneth A Mason, University of Iowa, Jonathan B Losos,
Washington University, Tod Duncan, University of Colorado, Denver;
contributors, Charles J Welsh, Duquesne University
Twelfth edition | New York, NY : McGraw-Hill Education, [2020]
| “Based on the work of Peter H Raven, President Emeritus, Missouri
Botanical Garden; George Engelmann, Professor of Botany Emeritus,
Washington University, George B Johnson, Professor Emeritus of Biology,
Washington University.” | Includes index
LCCN 2018036968| ISBN 9781260169614 (alk paper) |
ISBN 9781260565959
LCSH: Biology—Textbooks
LCC QH308.2 R38 2020 | DDC 570—dc23
LC record available at https://lccn.loc.gov/2018036968
The Internet addresses listed in the text were accurate at the time of publication The inclusion of a website does not indicate an
endorsement by the authors or McGraw-Hill Education, and McGraw-Hill Education does not guarantee the accuracy of the information
presented at these sites.
mheducation.com/highered
Trang 4Brief Contents
Committed to Excellence xi
Preparing Students for the Future xv
1 The Science of Biology 1
2 The Nature of Molecules and the Properties of Water 18
3 The Chemical Building Blocks of Life 35
4 Cell Structure 63
5 Membranes 92
6 Energy and Metabolism 112
7 How Cells Harvest Energy 128
8 Photosynthesis 154
9 Cell Communication 176
10 How Cells Divide 194
11 Sexual Reproduction and Meiosis 217
12 Patterns of Inheritance 231
13 Chromosomes, Mapping, and the Meiosis–Inheritance
Connection 250
14 DNA: The Genetic Material 268
15 Genes and How They Work 290
16 Control of Gene Expression 317
17 Biotechnology 340
18 Genomics 366
19 Cellular Mechanisms of Development 389
20 Genes Within Populations 416
21 The Evidence for Evolution 443
22 The Origin of Species 463
23 Systematics, Phylogenies, and Comparative Biology 484
24 Genome Evolution 504
25 The Origin and Diversity of Life 523
37 Plant Nutrition and Soils 807
38 Plant Defense Responses 825
39 Sensory Systems in Plants 838
40 Plant Reproduction 866
41 The Animal Body and Principles of Regulation 900
42 The Nervous System 924
43 Sensory Systems 955
44 The Endocrine System 982
45 The Musculoskeletal System 1006
46 The Digestive System 1026
47 The Respiratory System 1047
48 The Circulatory System 1066
49 Osmotic Regulation and the Urinary System 1088
50 The Immune System 1106
51 The Reproductive System 1135
Trang 5Kenneth Mason maintains an association with the University of Iowa, Department of Biology after having served
as a faculty member for eight years His academic positions, as a teacher and researcher, include the faculty of the University of Kansas, where he designed and established the genetics lab, and taught and published on the genetics of pigmentation in amphibians At Purdue University, he successfully developed and grew large intro- ductory biology courses and collaborated with other faculty in an innovative biology, chemistry, and physics course supported by the National Science Foundation At the University of Iowa, where his wife served as president of the university, he taught introductory biology and human genetics His honor society memberships include Phi Sigma, Alpha Lambda Delta, and, by vote of Purdue pharmacy students, Phi Eta Sigma Freshman Honors Society.
Jonathan Losos is the William H Danforth Distinguished University Professor in the Department of Biology
at Washington University and Director of the Living Earth Collaborative, a partnership between the university, the Saint Louis Zoo and the Missouri Botanical Garden Losos’s research has focused on studying patterns
of adaptive radiation and evolutionary diversification in lizards He is a member of the National Academy
of Sciences, a fellow of the American Academy of Arts and Science, and the recipient of several awards, including the Theodosius Dobzhanksy and David Starr Jordan Prizes, the Edward Osborne Wilson Naturalist Award, and the Daniel Giraud Elliot Medal, as well as receiving fellowships from the John Guggenheim and David and Lucile Packard Foundations Losos has published more than 200 scientific articles and has written two books, Lizards in an Evolutionary Tree: Ecology and Adaptive Radiation of Anoles (University of California Press, 2009) and Improbable Destinies: Fate, Chance, and the Future of Evolution (Penguin-Random
House, 2017).
Tod Duncan is a Clinical Assistant Professor at the University of Colorado Denver He currently teaches first semester general biology and coordinates first and second semester general biology laboratories Previously, he taught general microbiology, virology, the biology of cancer, medical microbiology, and cell biology A bachelor’s degree in cell biology with an emphasis on plant molecular and cellular biology from the University of East Anglia in England led to doctoral studies in cell cycle control, and postdoctoral research on the molecular and biochemical mechanisms of DNA alkylation damage in vitro and in Drosophila melanogaster Currently, he is interested in factors affecting retention and success of incoming first-year students in diverse demographics He lives in Boulder, Colorado, with his two Great Danes, Eddie and Henry.
About the Authors
©Kenneth Mason
©Lesley Howard
©Jonathan Losos
Trang 61 The Science of Biology 1
1.1 The Science of Life 1 1.2 The Nature of Science 4 1.3 An Example of Scientific Inquiry: Darwin and Evolution 8
1.4 Core Concepts in Biology 12
2 The Nature of Molecules and the
Properties of Water 18
2.1 The Nature of Atoms 19 2.2 Elements Found in Living Systems 23 2.3 The Nature of Chemical Bonds 24 2.4 Water: A Vital Compound 26 2.5 Properties of Water 29 2.6 Acids and Bases 30
3 The Chemical Building Blocks of Life 35
3.1 Carbon: The Framework of Biological Molecules 36 3.2 Carbohydrates: Energy Storage and Structural Molecules 40
3.3 Nucleic Acids: Information Molecules 43 3.4 Proteins: Molecules with Diverse Structures and Functions 46
3.5 Lipids: Hydrophobic Molecules 56
4 Cell Structure 63
4.1 Cell Theory 63 4.2 Prokaryotic Cells 67 4.3 Eukaryotic Cells 69
4.4 The Endomembrane System 73 4.5 Mitochondria and Chloroplasts: Cellular
Generators 77 4.6 The Cytoskeleton 79 4.7 Extracellular Structures and Cell Movement 83 4.8 Cell-to-Cell Interactions 86
5 Membranes 92
5.1 The Structure of Membranes 92 5.2 Phospholipids: The Membrane’s Foundation 96 5.3 Proteins: Multifunctional Components 98 5.4 Passive Transport Across Membranes 100 5.5 Active Transport Across Membranes 103 5.6 Bulk Transport by Endocytosis and Exocytosis 106
6 Energy and Metabolism 112
6.1 The Flow of Energy in Living Systems 113 6.2 The Laws of Thermodynamics and Free Energy 114
6.3 ATP: The Energy Currency of Cells 117 6.4 Enzymes: Biological Catalysts 118 6.5 Metabolism: The Chemical Description of Cell Function 122
7 How Cells Harvest Energy 128
7.1 Overview of Respiration 129 7.2 Glycolysis: Splitting Glucose 133 7.3 The Oxidation of Pyruvate Produces Acetyl-CoA 136
7.4 The Citric Acid Cycle 137 7.5 The Electron Transport Chain and Chemiosmosis 140
7.6 Energy Yield of Aerobic Respiration 143 7.7 Regulation of Aerobic Respiration 144 7.8 Oxidation Without O 2 145
7.9 Catabolism of Proteins and Fats 147 7.10 Evolution of Metabolism 149
8 Photosynthesis 154
8.1 Overview of Photosynthesis 154 8.2 The Discovery of Photosynthetic Processes 156
8.3 Pigments 158 8.4 Photosystem Organization 161 8.5 The Light-Dependent Reactions 163 8.6 Carbon Fixation: The Calvin Cycle 167 8.7 Photorespiration 170
©Soames Summerhays/Natural Visions
©Dr Gopal Murti/Science Source
Trang 714 DNA: The Genetic Material 268
14.1 The Nature of the Genetic Material 268 14.2 DNA Structure 271
14.3 Basic Characteristics of DNA Replication 275 14.4 Prokaryotic Replication 278
14.5 Eukaryotic Replication 283 14.6 DNA Repair 285
15 Genes and How They Work 290
15.1 The Nature of Genes 290 15.2 The Genetic Code 293 15.3 Prokaryotic Transcription 296 15.4 Eukaryotic Transcription 299 15.5 Eukaryotic pre-mRNA Splicing 301 15.6 The Structure of tRNA and Ribosomes 303 15.7 The Process of Translation 305
15.8 Summarizing Gene Expression 309 15.9 Mutation: Altered Genes 311
16 Control of Gene Expression 317
16.1 Control of Gene Expression 317 16.2 Regulatory Proteins 318 16.3 Prokaryotic Regulation 321 16.4 Eukaryotic Regulation 325 16.5 Chromatin Structure Affects Gene Expression 328 16.6 Eukaryotic Posttranscriptional Regulation 330 16.7 Protein Degradation 334
17 Biotechnology 340
17.1 Recombinant DNA 340 17.2 Amplifying DNA Using the Polymerase Chain Reaction 345
17.3 Creating, Correcting, and Analyzing Genetic Variation 348
17.4 Constructing and Using Transgenic Organisms 350 17.5 Environmental Applications 354
17.6 Medical Applications 356 17.7 Agricultural Applications 360
18 Genomics 366
18.1 Mapping Genomes 366 18.2 Sequencing Genomes 370 18.3 Genome Projects 373 18.4 Genome Annotation and Databases 374 18.5 Comparative and Functional Genomics 378 18.6 Applications of Genomics 383
19 Cellular Mechanisms of Development 389
19.1 The Process of Development 389 19.2 Cell Division 390
Receptors 186
10 How Cells Divide 194
10.1 Bacterial Cell Division 195
10.2 Eukaryotic Chromosomes 197
10.3 Overview of the Eukaryotic Cell Cycle 200
10.4 Interphase: Preparation for Mitosis 201
10.5 M Phase: Chromosome Segregation and the Division
of Cytoplasmic Contents 203 10.6 Control of the Cell Cycle 206
10.7 Genetics of Cancer 211
Biology
11 Sexual Reproduction and Meiosis 217
11.1 Sexual Reproduction Requires Meiosis 217
11.2 Features of Meiosis 219
11.3 The Process of Meiosis 220
11.4 Summing Up: Meiosis Versus Mitosis 225
12 Patterns of Inheritance 231
12.1 The Mystery of Heredity 231
12.2 Monohybrid Crosses: The Principle of
Segregation 234 12.3 Dihybrid Crosses: The Principle of Independent
Assortment 238 12.4 Probability: Predicting the Results of Crosses 240
12.5 The Testcross: Revealing Unknown Genotypes 241
13.3 Exceptions to the Chromosomal Theory of
Inheritance 255 13.4 Genetic Mapping 255
13.5 Human Genetic Disorders 260
©Steven P Lynch
Trang 819.3 Cell Differentiation 392 19.4 Nuclear Reprogramming 397 19.5 Pattern Formation 400 19.6 Evolution of Pattern Formation 406 19.7 Morphogenesis 409
Part IV Evolution
20 Genes Within Populations 416
20.1 Genetic Variation and Evolution 416 20.2 Changes in Allele Frequency 418 20.3 Five Agents of Evolutionary Change 420 20.4 Quantifying Natural Selection 425 20.5 Reproductive Strategies 426 20.6 Natural Selection’s Role in Maintaining Variation 430
20.7 Selection Acting on Traits Affected by Multiple Genes 432
20.8 Experimental Studies of Natural Selection 434 20.9 Interactions Among Evolutionary Forces 436 20.10 The Limits of Selection 437
21 The Evidence for Evolution 443
21.1 The Beaks of Darwin’s Finches: Evidence of Natural Selection 444
21.2 Peppered Moths and Industrial Melanism: More Evidence
of Selection 446 21.3 Artificial Selection: Human-Initiated Change 448
21.4 Fossil Evidence of Evolution 450 21.5 Anatomical Evidence for Evolution 454 21.6 Convergent Evolution and the Biogeographical Record 456
21.7 Darwin’s Critics 458
22 The Origin of Species 463
22.1 The Nature of Species and the Biological Species Concept 463
22.2 Natural Selection and Reproductive Isolation 468 22.3 The Role of Genetic Drift and Natural Selection in Speciation 469
22.4 The Geography of Speciation 471 22.5 Adaptive Radiation and Biological Diversity 473 22.6 The Pace of Evolution 478
22.7 Speciation and Extinction Through Time 479
23 Systematics, Phylogenies, and
Comparative Biology 484
23.1 Systematics 484 23.2 Cladistics 486
23.3 Systematics and Classification 489 23.4 Phylogenetics and Comparative Biology 493 23.5 Phylogenetics and Disease Evolution 499
24 Genome Evolution 504
24.1 Comparative Genomics 504 24.2 Genome Size 508
24.3 Evolution Within Genomes 511 24.4 Gene Function and Expression Patterns 515 24.5 Applying Comparative Genomics 516
on Earth
25 The Origin and Diversity
of Life 523
25.1 Deep Time 525 25.2 Origins of Life 525 25.3 Evidence for Early Life 528 25.4 Earth’s Changing System 530 25.5 Ever-Changing Life on Earth 531
26 Viruses 537
26.1 The Nature of Viruses 538 26.2 Viral Diversity 542 26.3 Bacteriophage: Bacterial Viruses 544 26.4 Viral Diseases of Humans 546 26.5 Prions and Viroids: Infectious Subviral Particles 552
27 Prokaryotes 557
27.1 Prokaryotic Diversity 558 27.2 Prokaryotic Cell Structure 562 27.3 Prokaryotic Genetics 567 27.4 The Metabolic Diversity of Prokaryotes 571 27.5 Microbial Ecology 573
27.6 Bacterial Diseases of Humans 575
©tamoncity/Shutterstock
©Jeff Hunter/Getty Images
Trang 929 Seedless Plants 608
29.1 Origin of Land Plants 608
29.2 Bryophytes Have a Dominant Gametophyte
Generation 611 29.3 Tracheophytes Have a Dominant Sporophyte
Generation 613 29.4 Lycophytes Diverged from the Main Lineage
of Vascular Plants 616 29.5 Pterophytes Are the Ferns and Their
Relatives 617
30 Seed Plants 623
30.1 The Evolution of Seed Plants 623
30.2 Gymnosperms: Plants with “Naked Seeds” 624
30.3 Angiosperms: The Flowering Plants 628
31.4 Fungal Parasites and Pathogens 650
31.5 Basidiomycota: The Club (Basidium)
Fungi 652 31.6 Ascomycota: The Sac (Ascus) Fungi 654
31.7 Glomeromycota: Asexual Plant Symbionts 656
31.8 Zygomycota: Zygote-Producing Fungi 656
31.9 Chytridiomycota and Relatives: Fungi with
Zoospores 658 31.10 Microsporidia: Unicellular Parasites 659
32 Animal Diversity and the Evolution
of Body Plans 664
32.1 Some General Features of Animals 664
32.2 Evolution of the Animal Body Plan 666
32.3 Animal Phylogeny 670
32.4 Parazoa: Animals That Lack Specialized
Tissues 674 32.5 Eumetazoa: Animals with True Tissues 677
33.9 Arthropods (Arthropoda) 707
34 Deuterostomes 720
34.1 Echinoderms 721 34.2 Chordates 723 34.3 Nonvertebrate Chordates 725 34.4 Vertebrate Chordates 726 34.5 Fishes 728
34.6 Amphibians 733 34.7 Reptiles 737 34.8 Birds 742 34.9 Mammals 746 34.10 Evolution of the Primates 751
36 Transport in Plants 788
36.1 Transport Mechanisms 789 36.2 Water and Mineral Absorption 792 36.3 Xylem Transport 795
36.4 Rate of Transpiration 797 36.5 Water-Stress Responses 799 36.6 Phloem Transport 801
37 Plant Nutrition and Soils 807
37.1 Soils: The Substrates on Which Plants Depend 807 37.2 Plant Nutrients 811
37.3 Special Nutritional Strategies 813 37.4 Carbon–Nitrogen Balance and Global Change 816 37.5 Phytoremediation 819
38 Plant Defense Responses 825
38.1 Physical Defenses 825 38.2 Chemical Defenses 827 38.3 Animals That Protect Plants 831 38.4 Systemic Responses to Invaders 832
39 Sensory Systems in Plants 838
39.1 Responses to Light 838 39.2 Responses to Gravity 843 39.3 Responses to Mechanical Stimuli 845
©Susan Singer
Trang 1039.4 Responses to Water and Temperature 847 39.5 Hormones and Sensory Systems 849
40 Plant Reproduction 866
40.1 Reproductive Development 867 40.2 Making Flowers 869
40.3 Structure and Evolution of Flowers 874 40.4 Pollination and Fertilization 877 40.5 Embryo Development 882 40.6 Germination 888 40.7 Asexual Reproduction 891 40.8 Plant Life Spans 893
Part VII Animal Form and
41.5 Nerve Tissue 909 41.6 Overview of Vertebrate Organ Systems 910 41.7 Homeostasis 913
41.8 Regulating Body Temperature 915
42 The Nervous System 924
42.1 Nervous System Organization 925 42.2 The Mechanism of Nerve Impulse Transmission 928 42.3 Synapses: Where Neurons Communicate with Other Cells 933
42.4 The Central Nervous System: Brain and Spinal Cord 939
42.5 The Peripheral Nervous System: Spinal and Cranial Nerves 946
43 Sensory Systems 955
43.1 Overview of Sensory Receptors 956 43.2 Thermoreceptors, Nociceptors, and Electromagnetic Receptors: Temperature, Pain, and Magnetic Fields 958
43.3 Mechanoreceptors I: Touch, Pressure, and Body Position 959
43.4 Mechanoreceptors II: Hearing, Vibration, and Balance 961
43.5 Chemoreceptors: Taste, Smell, and pH 967 43.6 Vision 969
43.7 Evolution and Development of Eyes 975
44 The Endocrine System 982
44.1 Regulation of Body Processes by Chemical Messengers 983
44.2 Overview of Hormone Action 988 44.3 The Pituitary and Hypothalamus: The Body’s Control Centers 991
44.4 The Major Peripheral Endocrine Glands 996 44.5 Other Hormones and Their Effects 1000
45 The Musculoskeletal System 1006
45.1 Types of Skeletal Systems 1007 45.2 A Closer Look at Bone 1009 45.3 Joints 1012
45.4 Muscle Contraction 1013 45.5 Vertebrate Skeleton Evolution and Modes
of Locomotion 1020
46 The Digestive System 1026
46.1 Types of Digestive Systems 1027 46.2 The Mouth and Teeth: Food Capture and Bulk Processing 1029
46.3 The Esophagus and the Stomach: The Early Stages
of Digestion 1030 46.4 The Intestines: Breakdown, Absorption, and Elimination 1032
46.5 Accessory Organ Function 1035 46.6 Neural and Hormonal Regulation of the Digestive Tract 1037
46.7 Food Energy, Energy Expenditure, and Essential Nutrients 1038
46.8 Variations in Vertebrate Digestive Systems 1042
47 The Respiratory System 1047
47.1 Gas Exchange Across Respiratory Surfaces 1048 47.2 Gills, Cutaneous Respiration, and Tracheal Systems 1049
47.3 Lungs 1052 47.4 Structures, Mechanisms, and Control of Ventilation
in Mammals 1055 47.5 Transport of Gases in Body Fluids 1059
48 The Circulatory System 1066
48.1 Invertebrate Circulatory Systems 1066 48.2 The Components of Vertebrate Blood 1068
48.3 Vertebrate Circulatory Systems 1071 48.4 Cardiac Cycle, Electrical Conduction, ECG, and Cardiac Output 1074
48.5 Blood Pressure and Blood Vessels 1078
49 Osmotic Regulation and the Urinary System 1088
49.1 Osmolarity and Osmotic Balance 1088 49.2 Nitrogenous Wastes: Ammonia, Urea, and Uric Acid 1090
©Dr Roger C Wagner, Professor Emeritus of
Blologlcal Sciences, University of Delaware
Trang 1149.3 Osmoregulatory Organs 1091
49.4 Evolution of the Vertebrate Kidney 1093
49.5 The Mammalian Kidney 1095
49.6 Hormonal Control of Osmoregulatory
50.4 Humoral Immunity and Antibody Production 1119
50.5 Autoimmunity and Hypersensitivity 1125
50.6 Antibodies in Medical Treatment and
Diagnosis 1127 50.7 Pathogens That Evade the Immune System 1130
51 The Reproductive System 1135
51.1 Animal Reproductive Strategies 1135
51.2 Vertebrate Fertilization and Development 1138
51.3 Structure and Function of the Human Male
Reproductive System 1142 51.4 Structure and Function of the Human Female
Reproductive System 1146 51.5 Contraception and Infertility Treatments 1150
53.1 The Natural History of Behavior 1189
53.2 Nerve Cells, Neurotransmitters, Hormones, and
Behavior 1190 53.3 Behavioral Genetics 1191
54 Ecology of Individuals and Populations 1218
54.1 The Environmental Challenges 1218 54.2 Populations: Groups of a Single Species in One Place 1221
54.3 Population Demography and Dynamics 1224 54.4 Life History and the Cost of Reproduction 1227 54.5 Environmental Limits to Population Growth 1230 54.6 Factors That Regulate Populations 1232
54.7 Human Population Growth 1235
56 Dynamics of Ecosystems 1265
56.1 Biogeochemical Cycles 1266 56.2 The Flow of Energy in Ecosystems 1272 56.3 Trophic-Level Interactions 1277 56.4 Biodiversity and Ecosystem Stability 1281 56.5 Island Biogeography 1284
57 The Biosphere and Human Impacts 1289
57.1 Ecosystem Effects of Sun, Wind, and Water 1289 57.2 Earth’s Biomes 1294
57.3 Freshwater Habitats 1297 57.4 Marine Habitats 1300 57.5 Human Impacts on the Biosphere: Pollution and Resource Depletion 1304
57.6 Human Impacts on the Biosphere: Climate Change 1310
58.5 Approaches for Preserving Endangered Species and Ecosystems 1339
Appendix A Glossary G-1 Index I-1
©K Ammann/Bruce Coleman Inc./Photoshot
Trang 12Committed to Excellence
With the new 12th edition, Raven and Johnson’s Biology continues
the momentum built over the last four editions We continue to
pro-vide an unmatched comprehensive text fully integrated with a
con-tinually evolving, state-of-the-art digital environment We have
used this revision to recommit ourselves to our roots as the majors
biology text that best integrates evolution throughout We have
added material emphasizing the relevance of evolution throughout
the ecology section, not only in all four ecology chapters, but also
in the chapters on behavior and conservation biology In the animal
form and function section we have done extensive revision to
mod-ernize, and to emphasize evolution in the context of physiology
Important contributions to this effort came from Dr Charles Welsh
(Duquesne University), who provided his knowledge and
experi-ence to this important section We have also moved the examples
and insights from the chapter devoted to the evolution of
develop-ment to place them into the appropriate context throughout the
book This emphasizes the importance of evolution and
develop-ment by continually providing examples rather than gathering them
together in a single chapter
We have also renewed our commitment to the ideas set forth
in the Vision and Change report from the AAAS, which provides a
framework for modern undergraduate biology education This
re-port will have been with us for a decade coincident with our 12th
edition One important idea articulated by Vision and Change was
an emphasis on core concepts One of the key differences between
the way an expert organizes information in their brain compared to
a novice is that the expert has a conceptual framework in place to
incorporate new information We have designed the new
Connect-ing the Concepts feature to address this disparity We emphasize
core concepts in each chapter, then at the end of the chapter show
how these can be used to build a conceptual framework, and
en-courage the student to begin building their own At the end of each
part of the book we expand this to show how core concepts are
interrelated and how a much larger conceptual framework is
constructed
One unanticipated consequence of the Vision and Change movement was how publishers chasing new approaches would
produce books so “feature-laden” as to be virtually unreadable by
the average student We have not abandoned the idea that
narra-tive flow is important, even in a science textbook While we
include a variety of features to improve student learning, they are
integrated into the text and not at the expense of the concise,
ac-cessible, and engaging writing style we are known for We
main-tain the clear emphasis on evolution and scientific inquiry that
have made this a leading textbook of choice for majors biology
students
Faculty want textbooks that emphasize student-centered proaches, and core concepts for the biological sciences As a team,
ap-we continually strive to improve the text by integrating the latest
cognitive and best practices research with methods that are known
to positively affect learning We emphasize scientific inquiry,
in-cluding an increased quantitative emphasis in the Scientific
Thinking figures Our text continues to be a leader with an organization that emphasizes important biological concepts, while keeping the student engaged with learning outcomes that allow as-sessment of progress in understanding these concepts An inquiry-based approach with robust, adaptive tools for discovery and assessment in both text and digital resources provides the intellec-tual challenge needed to promote student critical thinking and en-sure academic success
We continue to use our digital environment in the revision of
Biology A major strength of both text and digital resources is ment across multiple levels of Bloom’s taxonomy that develops critical-thinking and problem-solving skills in addition to com-prehensive factual knowledge
assess-McGraw-Hill Education’s Connect® platform offers a powerful suite of online tools that are linked to the text and in-cludes new quantitative assessment tools We now have avail-able interactive exercises that use graphical data, controlled by the student, to engage them in actively exploring quantitative aspects of biology Our adaptive learning system helps students learn faster, study efficiently, and retain more knowledge of key concepts
The 12th edition continues to employ the aesthetically
stunning art program that the Raven and Johnson Biology text
is known for Complex topics are represented clearly and cinctly, helping students to build the mental models needed to understanding biology
suc-We continue to incorporate student usage data and input, rived from thousands of our SmartBook® users SmartBook “heat maps” provided a quick visual snapshot of chapter usage data and the relative difficulty students experienced in mastering the con-tent This “heat-mapping” technology is unique in the industry, and allows direct editing of difficult areas, or problem areas for students
de-■ If the data indicated that the subject was more difficult than other parts of the chapter, as evidenced by a high proportion
of students responding incorrectly to the probes, we revised
or reorganized the content to be as clear and illustrative as possible
■ In other cases, if one or more of the SmartBook probes for a section was not as clear as it might be or did not appropriately reflect the content, we edited the probe, rather than the text
We’re excited about the 12th edition of this quality textbook providing a learning path for a new generation of students All of
us have extensive experience teaching undergraduate biology, and we’ve used this knowledge as a guide in producing a text that is up
to date, beautifully illustrated, and pedagogically sound for the dent We are also excited about the continually evolving digital environment that provides unique and engaging learning environ-ment for modern students We’ve worked hard to provide clear ex-plicit learning outcomes, and more closely integrate the text with
Trang 13stu-its media support materials to provide instructors with an excellent
complement to their teaching
Ken Mason, Jonathan Losos, Tod Duncan
Cutting Edge Science
Changes to the 12th Edition
Part I: The Molecular Basis of Life
Chapter 1—New section added that elaborates on the core
concepts and prepares the student for the use of the Connecting
the Concepts feature
Chapter 2—Edited for clarity, especially regarding atomic
structure and the periodic table
Chapter 3—Edited for clarity especially regarding the structure
of nucleotides, the role of ATP in cells, and secondary structure
in proteins
Part II: Biology of the Cell
Chapter 4—The section on the endomembrane system has been
completely rewritten This includes new material on lipid
droplets Material on adhesive junctions has been rewritten to
give a more evolutionary perspective
Chapter 5—New material on proteins that can alter membrane
structure has been added This provides information on how the
different cellular membranes can have different structures Figure
on Na+/K+ pump was redone to address errors in mechanism
Material on diffusion and facilitated diffusion was rewritten
Chapter 6—The material on free energy and chemical
reac-tions was completely rewritten, including redoing the figures
These changes significantly improve clarity and accuracy
Material on the role of ATP in cells was rewritten for clarity
Discussions of energy throughout the chapter were rewritten to
improve clarity and accuracy of chemical concepts
Chapter 7—The nature and action of cofactors in redox
reactions and the role of ATP in cells were improved
Chapter 8—The nature and structure of photosystems was
rewritten for clarity and accuracy
Chapter 10—The section on chromosome structure was
completely rewritten to reflect new data and views of this
important topic The material on cancer was expanded and
updated, producing a new section “Genetics of Cancer.” This
contains significant new information and pulls together
material on cancer from this chapter and others
Part III: Genetic and Molecular Biology
The overall organization of this section remains the same We
have retained the split of transmission genetics into two chapters
as it has proved successful for students
Chapter 11—Edited for clarity and readability for the student,
especially regarding the events of meiosis I
Chapter 12—The material on extensions to Mendel was
rewritten for clarity and accuracy
Chapter 13—The material on analyzing and mapping genetic
variation in humans was updated and rewritten The section on human genetic disorders was completely rewritten to reflect new information, and to make more accessible for the student A new figure on imprinting in mouse was added to clarify this important and difficult concept
Chapter 14—The material on eukaryotic DNA replication was
rewritten and updated Particular emphasis was placed on the evolution of DNA replication The section on DNA repair was rewritten and updated and information on mismatch repair was added
Chapter 15—Content on process of transcription was rewritten
to reflect new data on elongation machinery New data on alternative splicing was included, along with information on the integration of RNA modification during transcription The section on the nature of mutations was rewritten and includes latest data on human mutation rates
Chapter 16—Overview of control of eukaryotic transcription
was rewritten to reflect modern views Continued updating of the material on chromatin structure and the control of gene expression Material on control of gene expression at the level
of transcription was updated
Chapter 18—New section added on the 1000 Genomes project
to illustrate how fast information on genetic diversity is mulating The material on the wheat genome was updated, which provides both new information and approaches to complex genomes
accu-Chapter 19—Added a new section on the evolution of pattern
formation using new material and material from chapter 25
This consolidates material on this subject, and provides a clear vision for the student
Part IV: Evolution
Chapter 20—The topic of sexual selection was moved into this
chapter from the Behavioral Biology chapter Some material on Lamarck was eliminated, natural selection was explicitly defined, information on snp variation in humans and other animals was added New examples of pleiotropy were added, and new data on how the speed of racehorses has not changed through time were added along with a revised figure A new section was added on the role of sensory exploitation as a mechanism for traits to evolve under sexual selection
Chapter 21—A number of points were updated and an
exam-ple of vestigial traits involving the toenails of manatees was added
Trang 14Chapter 23—The figure on the evolution of feathers in
dino-saurs was updated to incorporate new paleontological findings
Discussion of HIV evolution and other points were also revised
in light of new science
Chapter 24—Updated material on comparative genomics of
vertebrates New data on Neanderthal and Denisovan genomes
have been added Presentation of genes unique to humans has
been updated and edited for clarity
Note: Evolution of Development (chapter 25 in the 11th edition)
was eliminated and material moved to other chapters, placing the
topic of evolution of development into the appropriate context
This reflects the view that evolution and development are now so
clearly intertwined with all of biology that setting off the material
in a separate chapter no longer made sense
Part V: Diversity of Life on Earth
Chapter 26—This chapter has been largely rewritten and now
includes material on viral diversity, classification, metagenomics,
and taxonomy The latter part of the chapter now focuses on viruses
of medical importance to promote student engagement and interest
Chapter 27—This chapter has been largely rewritten In addition
to the traditional discussion of prokaryotic structure and function,
and taxonomy, there is new emphasis placed on microbial
ecology and medical microbiology with relevant examples
Chapter 31—The chapter has been rewritten for clarity The
chapter has also been reordered to bring material most relevant to
society to the front of the chapter The reorganization includes
expanding and moving the fungal ecology up earlier in the chapter,
as well as expanding and moving the fungal parasites and
patho-gens up earlier in the chapter The chapter now ends with the
coverage of fungal classification
Chapter 32—Aspects of taxonomy and natural history were
updated in line with new findings
Chapter 33—The presentation of taxonomic relationships was
revised as a result of new findings based primarily on molecular
phylogenetic studies, specifically with regards to
Platyhelmin-thes, lophotrochozoans (formerly Spiralia) and a few others
New natural history information was included
Chapter 34—The discussion of the evolutionary history of
vertebrates was substantially revised, especially the sections on
lobe-finned fishes/early tetrapods/early amniotes (emphasizing
now those terms, rather than referring to all of the early diverging
lineages as amphibians or reptiles) Also, the terminology about
human evolution was revised to acknowledge the new meaning of
“hominin” and “hominid.” A new paragraph on Homo naledi was
added to discuss recent discoveries
Part VI: Plant Form and Function
There have been no major changes in the plant form and function
chapters There has been overall editing for readability and
responding to recommendations by reviewers and users of the 11th edition
Part VII: Animal Form and Function
Charles Welsh of Duquesne University, brought his expertise
in animal anatomy and physiology as a Contributor to the Animal Form and Function Part in the 12th edition, placing greater emphasis on evolutionary aspects of animal biology
Chapter 41—The discussion of the evolution of tissues in
invertebrates and vertebrates was expanded, including the addition of a phylogeny and an image of cnidarian tissues
Chapter 42—The graph of an action potential was revised
and improved Discussions and images of glial cells and cranial nerves were added
Chapter 43—The chapter was revised and reorganized
with regards to the general senses The evolution of eyes material found in chapter 25 in the 11th edition was moved
to this chapter with a revised phylogeny added The illustration depicting the evolution of the inner ear has been revised to make it more clear, concise, and informative
Chapter 44—Section 44.2 was formerly organized as action
of lipophilic vs hydrophilic hormones This has now been reorganized to be a complete overview of how hormones work This organization should improve clarity for students
Chapter 45—The chapter was extensively revised This
included the addition of images for the human skeleton, ossification, osteoporosis, invertebrate muscle, comparative anatomy of flying vertebrates, and a new phylogeny that reveals the evolution of various vertebrate skeletal characters
Chapter 46—The structure of the latter half this chapter
was completely reorganized for better conceptual flow
Chapter 47—The images for the bicarbonate buffering
system and the mechanics of breathing have been revised
The discussion of lung volumes and capacities was
expand-ed with the addition of an accompanying figure
Chapter 48—The chapter was reorganized and extensively
revised Invertebrate circulatory systems is now the first section in the chapter The sections on Cardiac Cycle, ECG, Electrical Conduction, and Cardiac Output have been reorga-nized and revised The discussions of blood vessels and blood pressure are now in the same section The phylogeny of the evolution of vertebrate hearts has been revised
Chapter 50—Material on innate immunity was updated
and rewritten for clarity The coverage on effects of AIDS was also updated to reflect new information
Chapter 51—A discussion of some select invertebrate
repro-ductive strategies has been added, with accompanying images
Trang 15Chapter 52—A section detailing the classic experiments
regarding pattern formation in chick limb buds has been added
This includes a discussion of AER, ZPA, FGF, Hox genes, and
Shh The material on gene regulation from chapter 25 in the
11th edition has also been added
Part VIII: Ecology and Behavior
Chapter 53—Stronger emphasis on phylogenetic and
evolution-ary perspectives was added throughout the chapter, including a
new section on evolution and behavior
Chapter 54—Human population trends and other timely data were
updated to stay current An evolutionary perspective on population
adaptation was added to the beginning of the chapter
Chapter 55—An evolutionary perspective was added in several
places
Chapter 56—New material on the impact of anthropogenic
changes on nutrient cycling was added An evolutionary
perspec-tive to discussion of the species-area relationship was incorporated
Chapter 57—Evolution was discussed more thoroughly in the
section on microclimate adaptation during adaptive radiation
All of the data on biosphere impacts of humans were updated to
stay current
Chapter 58—The chapter was substantially revised, including
much new discussion of the relevance of evolution to
conserva-tion biology, including the role of natural selecconserva-tion, the
impor-tance of phylogenetic perspectives, and how speciation can lead
to biodiversity hotspots
A Note From the Authors
A revision of this scope relies on the talents and efforts of many
people working behind the scenes and we have benefited greatly
from their assistance
Dr Charles Welsh made significant contributions to the Animal
Form and Function section He updated them to provide a more
modern perspective, and added new examples
Beth Bulger was the copyeditor for this edition She has bored many hours and always improves the clarity and consis-tency of the text She has made significant contributions to the quality of the final product
la-We were fortunate to work again with MPS to update the art program and improve the layout of the pages Our close collabora-tion resulted in a text that is pedagogically effective as well as more beautiful than any other biology text on the market
We have the continued support of an excellent team at McGraw-Hill Education Andrew Urban, preceded by Justin
Wyatt, the portfolio managers for Biology have been steady
leaders during a time of change Senior Product Developer Liz Sievers, provided support in so many ways it would be impossi-ble to name them all Kelly Hart, content project manager, and David Hash, designer, ensured our text was on time and elegantly designed Kelly Brown, senior marketing manager, is always a sounding board for more than just marketing, and many more people behind the scenes have all contributed to the success of our text This includes the digital team, whom we owe a great deal for their efforts to continue improving our Connect assessment tools
Throughout this edition we have had the support of spouses and families, who have seen less of us than they might have liked because of the pressures of getting this revision complet-
ed They have adapted to the many hours this book draws us away from them, and, even more than us, looked forward to its completion
In the end, the people we owe the most are the generations of students who have used the many editions of this text They have taught us at least as much as we have taught them, and their ques-tions and suggestions continue to improve the text and supple-mentary materials
Finally, we need to thank instructors from across the country who are continually sharing their knowledge and experience with
us through market feedback and symposia The feedback we ceived shaped this edition All of these people took time to share
re-their ideas and opinions to help us build a better edition of Biology
for the next generation of introductory biology students, and they have our heartfelt thanks
Reviewers for Biology, 12th edition
Carron Bryant East Mississippi Community
Mark Levenstein University of Wisconsin, Platteville
Cindy Malone California State University Northridge
David McClellan University of Arkansas Fort Smith
Shilpi Paul SUNY College at Old Westbury Crima Pogge City College of San Francisco
Josephine Rodriguez The University of Virginia’s College at Wise Connie Rye East Mississippi Community College
Devinder Sandhu USDA—Agricultural Research Service
Ken Saville Albion College Steven Shell The University of Virginia’s College at Wise
Walter Smith The University of Virginia’s College at Wise
Qiang Sun University of Wisconsin, Stevens Point
Christopher Vitek University of Texas Rio Grande Valley
D Alexander Wait Missouri State University Maureen Walter Florida International University
Darla Wise Concord University
Trang 16Scientific Thinking Figures
Key illustrations in every chapter highlight how the frontiers
of knowledge are pushed forward by a combination of
esis and experimentation These figures begin with a
hypoth-esis, then show how it makes explicit predictions, tests these
by experiment and finally demonstrates what conclusions can
be drawn, and where this leads Scientific Thinking figures
provide a consistent framework to guide the student in the
logic of scientific inquiry Each illustration concludes with
open-ended questions to promote scientific inquiry
Hypothesis: The plasma membrane is fluid, not rigid.
Prediction: If the membrane is fluid, membrane proteins may
diffuse laterally.
Test: Fuse mouse and human cells, then observe the distribution
of membrane proteins over time by labeling specific mouse and human proteins.
Result: Over time, hybrid cells show increasingly intermixed proteins.
Conclusion: At least some membrane proteins can diffuse laterally in
the membrane.
Further Experiments: Can you think of any other explanation for
these observations? What if newly synthesized proteins were inserted into the membrane during the experiment? How could you use this basic experimental design to rule out this or other possible explanations?
SCIENTIFIC THINKING
Mouse cell
Human cell
Fuse cells
Intermixed membrane proteins
Allow time for mixing to occur
Data Analysis Questions
It’s not enough that students learn concepts and memorize scientific facts, a biologist needs to analyze data and apply that knowledge Data Analysis questions inserted throughout the text challenge students to analyze data and Interpret experimental results, which shows a deeper level of understanding
Inquiry Questions
Questions that challenge students to think about and engage in what they are reading at a more sophisticated level
Preparing Students for the Future
Developing Critical Thinking with the Help of
Figure 5.5 Test of membrane fluidity.
?
24 26 28 30 32
Air Temperature (°C)
24 26 28 30 32
open habitat shaded forest
Figure 55.3 Behavioral adaptation. In open habitats, the
Puerto Rican crested lizard, Anolis cristatellus, maintains a relatively
constant temperature by seeking out and basking in patches of sunlight; as a result, it can maintain a relatively high temperature even when the air is cool In contrast, in shaded forests, this behavior is not possible, and the lizard’s body temperature conforms to that of its surroundings
(inset) ©Melissa Losos
Inquiry question When given the opportunity, lizards regulate their body temperature to maintain a temperature optimal for physiological functioning Would lizards in open habitats exhibit different escape behaviors from those of lizards in shaded forest?
Data analysis Can the slope of the line tell us something about the behavior of the lizard?
Trang 17Soil properties determine plant nutrient availability Life is subject
to chemical and physical laws
Living systems transform energy & matter
Plants can detoxify certain contaminated environments
• Positively charged soil
nutrients must be actively
transported into roots due
to their sequestration by
anionic soil particles.
• Porous soils leach water
rapidly and can contribute
to water stress.
• The chemical properties of
clay make it adsorb water
and minerals tightly.
• The water potential of the
soil affects the transport of
minerals into the root.
• Low soil pH can cause toxic
aluminum to leach from
rocks.
• Salt accumulation in soil
can affect soil water
potential and cause loss of
plant cell turgor.
C O N N E C T I N G T H E C O N C E P T S
This feature is intended to give you practice in organizing information using core concepts We use a metaphor of gears and cogs to represent a conceptual
hierarchy with each core concept represented as a gear Secondary concepts are the cogs, and tertiary concepts, which are particular examples from the chapter,
are presented as a list of bulleted points Using the completed conceptual unit as a guide, build from material in the chapter a list of tertiary concepts that
support the open secondary concept.
Connecting the Concepts
There are two new but related features in Biology, 12th edition
that help students build a conceptual framework into which they
can insert new knowledge The Connecting the Concepts feature
at the end of the chapters identifies core concepts that are
related to material in the chapter The conceptual framework
begins with a core concept that is represented by a gear icon
Examples from the chapter that relate to the core concept are
secondary concepts that are placed on the cogs Each cog
contains a list of observations from the chapter that connects the secondary concept to the core concept
At the chapter level:
The Connecting the Concept shows the student a completed concept (core concept, secondary concept, list of observations)
A second cog or gear is presented that lacks the list of tions The student is challenged to identify examples from the chapter that demonstrate how the secondary concept is related
observa-to the core concept
At the Part level:
As valuable as that exercise is, the full understanding of a
conceptual framework and how that helps students see the
connections to core concepts is when the chapter-ending
Connecting the Concepts are pulled together This happens at
the Part level, which themselves present a higher level to the
conceptual framework When these are built, students see how topics that appear unrelated fit into the conceptual framework
of the core concepts Once students begin to see these tions, the topics and information in biology make
connec-more sense
Trang 18Connecting the Concepts Part VI Plant Form and Function
Vascular plants are comprised of roots and shoots, which in turn are made of three principal tissue types Each of these tissues has distinct cell types that express the genes needed to produce the proteins necessary for their specialized functions Plants move fluids using differ- ences in solute concentration and pressure Plant form is often an evolutionary compromise between competing needs such as maximizing the surface area of leaves for photosynthesis while minimizing water loss when exchanges gases The reproductive structures of plants are organized into flowers that have evolved to facilitate the dissemination of genetic information.
Living systems depend on information transactions
• Positively charged soil nutrients must be actively transported into roots due to their sequestration by anionic soil particles.
• Porous soils leach water rapidly and can contribute to water stress
• The chemical properties of clay make it adsorb water and minerals tightly
• The water potential of the soil affects the transport of minerals into the root
• Low soil pH can cause toxic aluminum to leach from rocks.
• Salt accumulation in soil can affect soil water potential and cause loss of plant cell turgor.
• Light can be perceived by plant cell receptors such as P fr
• Signal transduction pathways communicate information received in light signals to plant response mechanisms.
• Plants can respond to perceived light with changes in gene expression.
• Differences in received light wavelength can cause specific plant growth responses.
• The environment can signal seeds to germinate using light of specific wavelengths.
• Light containing blue wavelengths can signal phototropic responses.
• Some plants can change behavior based on the day/night cycle.
• Gravitational fields can trigger directional growth responses.
• Some plants can respond to touch.
• Gibberellins, a family of growth hormones, can be produced by bacteria infecting certain plants’
roots and influence plant growth.
• Allelopathy is a form of signaling where one plant releases compounds that inhibit seed germination or the growth of neighboring plants.
• Toxins produced by plants communicate to potential predators that the plant is not safe to eat.
• Chemical signals can modulate the behaviors of insects that protect plants from predation.
• Chemicals released by plants as a wound response can attract insects
to defend the plant against herbivores.
• The plant hormone jasmonic acid transduces long distance wound response signals in plant bodies.
• The cohesion and adhesion of water molecules allows forces generated by transpiration to move water great distances in plants
• The rate of osmosis limits water movement into roots, but is accelerated
by facilitated diffusion through rins
aquapo-• The combined effects of solute potential and pressure potential determine the direction of water movement into and out
of plant cells
• Water transport from roots to shoots is driven by a gradient of water potential with lowest values in the leaves.
• Chemical and physical properties of membranes and cell walls restrict the movement of solutes through the plant
• Leaves are arranged on stems to maximize light capture
• Stems may have secondary growth to provide support to the plant body
• Axillary buds produced by the shoot apical meristem allow leaves or flowers to be produced
on the stem
• Horizontal stems allow a plant to spread laterally above ground.
• Tubers can be packed with starch for storage purposes.
• Flattened stems of some cacti capture light energy for photosynthesis.
determine plant nutrient availability
Physics and chemistry dictate movement of water into and around the plant
Life is subject
to chemical and physical laws
Information can be communicated
in chemical ways
non-Signaling plant health
Stems and modified stems carry out a variety of functions
Structure determines function
• Gametes are produced in the gametophytes of flowers
• The calyx protects the budding flower
• The petals collectively form the corolla and their colors attract animal pollinators
• Wind-pollinated plants don’t have elaborate corollas because they don’t need to attract pollinators.
• The long stamens make pollen more accessible to animal pollinators or wind.
• The carpel houses the female reproductive structures with the elongated style being more accessible to pollinators or pollen carried by the wind
Flowers adapted for reproduction
Preparing Students for the Future xvii
Connecting the Concepts Part VI Plant Form and Function
Vascular plants are comprised of roots and shoots, which in turn are made of three principal tissue types Each of these tissues has distinct cell types that express the genes needed to produce the proteins necessary for their specialized functions Plants move fluids using differ- ences in solute concentration and pressure Plant form is often an evolutionary compromise between competing needs such as maximizing the surface area of leaves for photosynthesis while minimizing water loss when exchanges gases The reproductive structures of plants are organized into flowers that have evolved to facilitate the dissemination of genetic information.
Living systems depend on information transactions
• Positively charged soil nutrients must be actively transported into roots due to their sequestration by anionic soil particles.
• Porous soils leach water rapidly and can contribute to water stress
• The chemical properties of clay make it adsorb water and minerals tightly
• The water potential of the soil affects the transport of minerals into the root
• Low soil pH can cause toxic aluminum to leach from rocks.
• Salt accumulation in soil can affect soil water potential and cause loss of plant cell turgor.
• Light can be perceived by plant cell receptors such as P fr
• Signal transduction pathways communicate information received in light signals to plant response mechanisms.
• Plants can respond to perceived light with changes in gene expression.
• Differences in received light wavelength can cause specific plant growth responses.
• The environment can signal seeds to germinate using light of specific wavelengths.
• Light containing blue wavelengths can signal phototropic responses.
• Some plants can change behavior based on the day/night cycle.
• Gravitational fields can trigger directional growth responses.
• Some plants can respond to touch.
• Gibberellins, a family of growth hormones, can be produced by bacteria infecting certain plants’
roots and influence plant growth.
• Allelopathy is a form of signaling where one plant releases compounds that inhibit seed germination or the growth of neighboring plants.
• Toxins produced by plants communicate to potential predators that the plant is not safe to eat.
• Chemical signals can modulate the behaviors of insects that protect plants from predation.
• Chemicals released by plants as a wound response can attract insects
to defend the plant against herbivores.
• The plant hormone jasmonic acid transduces long distance wound response signals in plant bodies.
• The cohesion and adhesion of water molecules allows forces generated by transpiration to move water great distances in plants
• The rate of osmosis limits water movement into roots, but is accelerated
by facilitated diffusion through rins
aquapo-• The combined effects of solute potential and pressure potential determine the direction of water movement into and out
of plant cells
• Water transport from roots to shoots is driven by a gradient of water potential with lowest values in the leaves.
• Chemical and physical properties of membranes and cell walls restrict the movement of solutes through the plant
• Leaves are arranged on stems to maximize light capture
• Stems may have secondary growth to provide support to the plant body
• Axillary buds produced by the shoot apical meristem allow leaves or flowers to be produced
on the stem
• Horizontal stems allow a plant to spread laterally above ground.
• Tubers can be packed with starch for storage purposes.
• Flattened stems of some cacti capture light energy for photosynthesis.
properties nutrient availability
Physics and chemistry dictate movement of water into and around the plant Life is subject
to chemical and physical laws
Information can be communicated
in chemical ways
non-Signaling mediates plant health
Stems and modified stems carry out a variety of functions
Structure determines function
• Gametes are produced in the gametophytes of flowers
• The calyx protects the budding flower
• The petals collectively form the corolla and their colors attract animal pollinators
• Wind-pollinated plants don’t have elaborate corollas because they don’t need to attract pollinators.
• The long stamens make pollen more accessible to animal pollinators or wind.
• The carpel houses the female reproductive structures with the elongated style being more accessible to pollinators or pollen carried by the wind
Flowers adapted for reproduction
Preparing Students for the Future xvii
Each Connecting the Concept unit (a Core concept, secondary concept, and bulleted list) is picked
up from the end-of-chapter features This reinforces the overarching hierarchy of the Core concepts, tying together seemingly unrelated
same Core concepts are found throughout the book, establishing the conceptual framework into which they can insert new knowledge
Trang 19Detailed Feedback in Connect®
Learning is a process of iterative development, of making
mistakes, reflecting, and adjusting over time The question and
test banks in Connect® for Biology, 12th edition, are more than
direct assessments; they are self-contained learning
experi-ences that systematically build student learning over time
For many students, choosing the right answer is not
necessarily based on applying content correctly; it is more a
matter of increasing their statistical odds of guessing A major
fault with this approach is students don’t learn how to process
the questions correctly, mostly because they are repeating and
reinforcing their mistakes rather than reflecting and learning
from them To help students develop problem-solving skills, all
higher level Blooms questions in Connect are supported with
hints, to help students focus on important information for
answering the questions, and detailed feedback that walks
students through the problem-solving process, using Socratic
questions in a decision-tree-style framework to scaffold
learning, where each step models and reinforces the learning process
The feedback for each higher level Blooms question (Apply, Analyze, Evaluate) follows a similar process: Clarify Question, Gather Content, Choose Answer, Reflect on Process
Unpacking the Concepts
We’ve taken problem solving a step further In each chapter, three to five higher level Blooms questions in the question and test banks are broken out by the steps of the detailed feedback Rather than leaving it up to the student to work through the detailed feedback, a second version of the ques-tion is presented in a stepwise format Following the problem-solving steps, students need to answer questions about earlier steps, such as “What is the key concept addressed by the question?” before proceeding to answer the question A professor can choose which version of the question to include
in the assignment based on the problem-solving skills of the students
Strengthen Problem-Solving Skills with Connect ®
Trang 20Graphing Interactives
To help students develop analytical skills, Connect® for Biology,
12th edition, is enhanced with interactive graphing questions
Students are presented with a scientific problem and the
opportunity to manipulate variables, producing different results
on a graph A series of questions follows the graphing activity
to assess if the student understands and is able to interpret the data and results
Quantitative Question Bank
Many chapters also contain a Quantitative Question Bank
These are more challenging algorithmic questions, intended to
help your students practice their quantitative reasoning skills
Hints and guided solution options step students through a
problem
Trang 21You’re in the driver’s seat.
Want to build your own course? No problem Prefer to use our turnkey,
prebuilt course? Easy Want to make changes throughout the semester?
Sure And you’ll save time with Connect’s auto-grading too
They’ll thank you for it.
Adaptive study resources like SmartBook® help your students be better prepared in less time You can transform your class time from dull definitions to dynamic debates Hear from your peers about the benefits of Connect at www.mheducation.com/highered/connect
Make it simple, make it affordable.
Connect makes it easy with seamless integration using any of the
major Learning Management Systems—Blackboard®, Canvas,
and D2L, among others—to let you organize your course in one
convenient location Give your students access to digital materials
at a discount with our inclusive access program Ask your
McGraw-Hill representative for more information
Solutions for your challenges.
A product isn’t a solution Real solutions are affordable, reliable, and come with training and ongoing support when you need it and how you want it Our Customer Experience Group can also help you troubleshoot tech problems—although Connect’s 99% uptime means you might not need to call them See for yourself at status.mheducation.com
Students—study more efficiently, retain more and achieve better outcomes Instructors—focus
on what you love—teaching.
SUCCESSFUL SEMESTERS INCLUDE CONNECT
65%
Less Time Grading
©Hill Street Studios/Tobin Rogers/Blend Images LLC
For Instructors
Trang 22Effective, efficient studying.
Connect helps you be more productive with your
study time and get better grades using tools like
SmartBook, which highlights key concepts and creates
a personalized study plan Connect sets you up for
success, so you walk into class with confidence and
walk out with better grades
Study anytime, anywhere.
Download the free ReadAnywhere app and access your online eBook when it’s convenient, even if you’re offline
And since the app automatically syncs with your eBook in Connect, all of your notes are available every time you open
it Find out more at www.mheducation.com/readanywhere
No surprises
The Connect Calendar and Reports tools
keep you on track with the work you need
to get done and your assignment scores
Life gets busy; Connect tools help you
keep learning through it all
Learning for everyone
McGraw-Hill works directly with Accessibility Services Departments and faculty to meet the learning needs of all students Please contact your Accessibility Services office and ask them to email accessibility@mheducation.com, or visit www.mheducation.com/about/accessibility.html for
more information
made it easy to study when
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Eastern Washington University
Chapter 7 Quiz Chapter 13 Evidence of Evolution Chapter 11 DNA Technology
Chapter 7 DNA Structure and Gene
and 7 more
©Shutterstock/wavebreakmedia
For Students
Trang 23This page intentionally left blank
Trang 24Part I The Molecular Basis of Life
Introduction
You are about to embark on a journey—a journey of discovery about the nature of life More than 180 years ago, a young English
naturalist named Charles Darwin set sail on a similar journey on board H.M.S Beagle; a replica of this ship is pictured here What
Darwin learned on his five-year voyage led directly to his development of the theory of evolution by natural selection, a theory that has
become the core of the science of biology Darwin’s voyage seems a fitting place to begin our exploration of biology—the scientific
study of living organisms and how they have evolved Before we begin, however, let’s take a moment to think about what biology is
and why it’s important.
This is the most exciting time to be studying biology in the history
of the field The amount of information available about the natural world has exploded in the last 42 years, since the construction of the first recombinant DNA molecule We are now in a position to ask and answer questions that previously were only dreamed of.The 21st century began with the completion of the sequence
of the human genome The largest single project in the history of biology took about 20 years Yet less than 15 years later, we can sequence an entire genome in a matter of days This flood of se-quence data and genomic analysis are altering the landscape of biology These and other discoveries are also moving into the
Chapter Contents
1.1 The Science of Life
1.2 The Nature of Science
1.3 An Example of Scientific Inquiry:
Darwin and Evolution
1.4 Core Concepts in Biology
The Science of Biology
Learning Outcomes
1 Compare biology to other natural sciences.
2 Describe the characteristics of living systems.
3 Characterize the hierarchical organization of living systems.
©Soames Summerhays/Natural Visions
Trang 25Organ system Organism Population Species Community Ecosystem
clinic as never before, with new tools for diagnostics and
treat-ment With robotics, next-generation DNA sequencing
technolo-gies, advanced imaging, and analytical techniques, we have tools
available that were formerly the stuff of science fiction
In this text, we attempt to draw a contemporary picture of the
science of biology, as well as provide some history and
experimen-tal perspective on this exciting time in the discipline In this
intro-ductory chapter, we examine the nature of biology and the
foundations of science in general to put into context the
informa-tion presented in the rest of the text
Biology unifies much of natural science
The study of biology is a point of convergence for the information
and tools from all of the natural sciences Biological systems are
the most complex chemical systems on Earth, and their many
func-tions are both determined and constrained by the principles of
chemistry and physics Put another way, no new laws of nature can
be gleaned from the study of biology—but that study does
illumi-nate and illustrate the workings of those natural laws
The intricate chemical workings of cells can be understood
using the tools and principles of chemistry And every level of
bio-logical organization is governed by the nature of energy
transac-tions first studied by thermodynamics Biological systems do not
represent any new forms of matter, and yet they are the most
com-plex organization of matter known The comcom-plexity of living
sys-tems is made possible by a constant source of energy—the Sun
The conversion of this radiant energy into organic molecules by
photosynthesis is one of the most beautiful and complex reactions
known in chemistry and physics
The way we do science is changing to grapple with ingly difficult modern problems Science is becoming more interdis-ciplinary, combining the expertise from a variety of traditional disciplines and emerging fields such as nanotechnology Biology is at the heart of this multidisciplinary approach because biological prob-lems often require many different approaches to arrive at solutions
increas-Life defies simple definition
In its broadest sense, biology is the study of living things—the
science of life. Living things come in an astounding variety of shapes and forms, and biologists study life in many different ways
They live with gorillas, collect fossils, and listen to whales They read the messages encoded in the long molecules of heredity and count how many times a hummingbird’s wings beat each second
What makes something “alive”? Anyone could deduce that a galloping horse is alive and a car is not, but why? We cannot say,
“If it moves, it’s alive,” because a car can move, and gelatin can wiggle in a bowl They certainly are not alive Although we cannot define life with a single simple sentence, we can come up with a series of seven characteristics shared by living systems:
■ Cellular organization All organisms consist of one or
more cells Often too tiny to see, cells carry out the basic activities of living Each cell is bounded by a membrane that separates it from its surroundings
■ Ordered complexity All living things are both complex and
highly ordered Your body is composed of many different kinds of cells, each containing many complex molecular structures Many nonliving things may also be complex, but they do not exhibit this degree of ordered complexity
Trang 26Organ system Organism Population Species Community Ecosystem
■ Sensitivity All organisms respond to stimuli Plants grow
toward a source of light, and the pupils of your eyes dilate when you walk into a dark room
■ Growth, development, and reproduction All organisms
are capable of growing and reproducing, and they all possess hereditary molecules that are passed to their offspring, ensuring that the offspring are of the same species
■ Energy utilization All organisms take in energy and use it
to perform many kinds of work Every muscle in your body
is powered with energy you obtain from your diet
■ Homeostasis All organisms maintain relatively constant internal
conditions that are different from their environment, a process
called homeostasis For example, your body temperature
remains stable despite changes in outside temperatures
■ Evolutionary adaptation All organisms interact with other
organisms and the nonliving environment in ways that influence their survival, and as a consequence, organisms evolve adaptations to their environments
Living systems show hierarchical organization
The organization of the biological world is hierarchical—that is, each level builds on the level below it:
1 The cellular level At the cellular level (figure 1.1), atoms, the fundamental elements of matter, are joined together into clusters called molecules Complex
biological molecules are assembled into tiny structures
called organelles within membrane-bounded units
we call cells The cell is the basic unit of life Many
independent organisms are composed only of single
cells Bacteria are single cells, for example All animals and plants, as well as most fungi and algae, are multicellular—composed of more than one cell
2 The organismal level Cells in complex multicellular
organisms exhibit three levels of organization The most
basic level is that of tissues, which are groups of similar
cells that act as a functional unit Tissues, in turn, are
grouped into organs—body structures composed of
several different tissues that act as a structural and functional unit Your brain is an organ composed of nerve cells and a variety of associated tissues that form protective coverings and contribute blood At the third
level of organization, organs are grouped into organ systems The nervous system, for example, consists of
sensory organs, the brain and spinal cord, and neurons that convey signals
Figure 1.1 Hierarchical organization of living systems. Life forms a hierarchy of organization from atoms to complex multicellular organisms Atoms are joined together to form molecules, which are assembled into more complex structures such as organelles These in turn form subsystems that provide different functions Cells can be organized into tissues, then into organs and organ systems such
as the goose’s nervous system pictured This organization then extends beyond individual organisms to populations, communities, ecosystems, and finally the biosphere (Organelle): ©Keith R Porter/Science Source; (Cell):
©STEVE GSCHMEISSNER/Getty Images; (Tissue): ©Ed Reschke; (Organism):
©Russell Illig/Getty Images; (Population): ©George Ostertag/age fotostock;
(Species): ©iStockphoto/Getty Images; ©Pictureguy/Shutterstock; (Community):
©Ryan McGinnis/Alamy; (Ecosystem): ©Robert and Jean Pollock; (Biosphere):
Source: NASA
Trang 273 The populational level Individual organisms can
be categorized into several hierarchical levels within
the living world The most basic of these is the
population—a group of organisms of the same species
living in the same place All populations of a particular
kind of organism together form a species, its members
similar in appearance and able to interbreed At a higher
level of biological organization, a biological community
consists of all the populations of different species living
together in one place
4 The ecosystem level At the highest tier of biological
organization, populations of organisms interact with
each other and their physical environment Together
populations and their environment constitute an
ecological system, or ecosystem For example, the
biological community of a mountain meadow interacts
with the soil, water, and atmosphere of a mountain
ecosystem in many important ways
5 The biosphere The entire planet can be thought of as an
ecosystem that we call the biosphere
As you move up this hierarchy, the many interactions occurring at
lower levels can produce novel properties These so-called
emergent properties may not be predictable Examining
individ-ual cells, for example, gives little hint about the whole animal
Many weather phenomena, such as hurricanes, are actually
emer-gent properties of many interacting meteorological variables It is
because the living world exhibits many emergent properties that it
is difficult to define “life.”
This description of the common features and organization of
living systems provides an introduction for our exploration of
biol-ogy Before we continue, we will consider the broader question of
the nature of science itself
Learning Outcomes Review 1.1
Biology as a science brings together other natural sciences, such
as chemistry and physics, to study living systems Life does not
have a simple definition, but living systems share a number of
properties that together describe life Living systems can be
organized hierarchically, from the cellular level to the entire
biosphere, with emergent properties that may exceed the sum of
the parts.
■ Can you study biology without studying other sciences?
Learning Outcomes
1 Compare the different types of reasoning used by biologists.
2 Demonstrate how to formulate and test a hypothesis.
Much like life itself, the nature of science defies simple
descrip-tion For many years scientists have written about the “scientific
method” as though there is a single way of doing science
This oversimplification has contributed to confusion on the part of nonscientists about the nature of science
At its core, science is concerned with developing an ingly accurate understanding of the world around us using observa-tion and reasoning To begin with, we assume that natural forces acting now have always acted, that the fundamental nature of the uni-verse has not changed since its in ception, and that it is not changing now A number of complementary approaches allow understanding
increas-of natural phenomena—there is no one “scientific method.”
Scientists also attempt to be as objective as possible in the interpretation of the data and observations they have collected
Because scientists themselves are human, this is not completely possible, but because science is a collective endeavor subject to scrutiny, it is self-correcting One person’s results are verified by others, and if the results cannot be repeated, they are rejected
Much of science is descriptive
The classic vision of the scientific method is that observations lead
to hypotheses that in turn make experimentally testable tions In this way, we dispassionately evaluate new ideas to arrive
predic-at an increasingly accurpredic-ate view of npredic-ature We discuss this way of doing science later in this section but it is important to understand that much of science is purely descriptive: In order to understand anything, the first step is to describe it completely Much of biol-ogy is concerned with arriving at an increasingly accurate descrip-tion of nature
The study of biodiversity is an example of descriptive ence that has implications for other aspects of biology in addition
sci-to societal implications Efforts are currently under way sci-to classify all life on Earth This ambitious project is purely descriptive, but it will lead to a much greater understanding of biodiversity as well as the effect our species has on biodiversity
One of the most important accomplishments of molecular biology at the dawn of the 21st century was the completion of the sequence of the human genome Many new hypotheses about human biology will be generated by this knowledge, and many experiments will be needed to test these hypotheses, but the determination of the sequence itself was descriptive science
Science uses both deductive and inductive reasoning
The study of logic recognizes two opposite ways of arriving at logical conclusions: deductive and inductive reasoning Science makes use of both of these methods, although induction is the primary way of reasoning in hypothesis-driven science
Deductive reasoning
Deductive reasoning applies general principles to predict
spe-cific results More than 2200 years ago, the Greek scientist Eratosthenes used Euclidean geometry and deductive reasoning
to accurately estimate the circumference of the Earth ( figure 1.2)
Deductive reasoning is the reasoning of mathematics and phi- losophy, and it is used to test the validity of general ideas in all
Trang 28at midday
Well
Light rays parallel
Height of obelisk
Distance between cities = 800 km
Length of shadow a
a
Observation
Predictions
Predictions confirmed
Question
Hypothesis 1 Hypothesis 2 Hypothesis 3 Hypothesis 4 Hypothesis 5
Potential hypotheses
Remaining possible hypotheses
Last remaining possible hypothesis
Reject hypotheses
2 and 3
Reject hypotheses
1 and 4
Hypothesis 2 Hypothesis 3 Hypothesis 5
branches of knowledge For example, if all mammals by
defini-tion have hair, and you find an animal that does not have hair,
then you may conclude that this animal is not a mammal A
bi-ologist uses deductive reasoning to infer the species of a
speci-men from its characteristics
Inductive reasoning
In inductive reasoning, the logic flows in the opposite direction,
from the specific to the general Inductive reasoning uses specific
observations to construct general scientific principles For example,
if poodles have hair, and terriers have hair, and every dog that you
observe has hair, then you may conclude that all dogs have hair
In-ductive reasoning leads to generalizations that can then be tested
Inductive reasoning first became important to science in the 1600s
in Europe, when Francis Bacon, Isaac Newton, and others began to
use the results of particular experiments to infer general principles
about how the world operates
An example from modern biology is the role of homeobox
genes in development Studies in the fruit fly, Drosophila
melano-gaster, identified genes that could cause dramatic changes in
de-velopmental fate, such as a leg appearing in the place of an antenna
These genes have since been found in essentially all multicellular
animals analyzed This led to the general idea that homeobox
genes control developmental fate in animals
Hypothesis-driven science
makes and tests predictions
Scientists establish which general principles are true from among
the many that might be true through the process of systematically
testing alternative proposals If these proposals prove inconsistent
with experimental observations, they are rejected as untrue
Figure 1.3 illustrates the process
Figure 1.2 Deductive reasoning: How Eratosthenes estimated the circumference of the Earth using deductive reasoning. 1 On a
day when sunlight shone straight down a deep well at Syene in Egypt, Eratosthenes measured the length of the shadow cast by a tall obelisk in the city
of Alexandria, about 800 kilometers (km) away 2. The shadow’s length and the
obelisk’s height formed two sides of a triangle Using the recently developed
principles of Euclidean geometry, Eratosthenes calculated the angle, a, to be 7°
and 12´, exactly 1 ⁄ 50 of a circle (360°) 3 If angle a is 1 ⁄ 50 of a circle, then the distance between the obelisk (in Alexandria) and the well (in Syene) must be equal to 1 ⁄ 50 the circumference of the Earth 4 Eratosthenes had heard that
it was a 50-day camel trip from Alexandria to Syene Assuming a camel travels about 18.5 km per day, he estimated the distance between obelisk and well as 925 km (using different units of measure, of course)
5. Eratosthenes thus deduced the circumference of the Earth to be
50 × 925 = 46,250 km Modern measurements put the distance from the well to the obelisk at just over 800 km Using this distance Eratosthenes’s value would have been 50 × 800 = 40,000 km The actual circumference is 40,075 km.
Figure 1.3 How science is done. This diagram illustrates how scientific investigations proceed First, scientists make observations that raise a particular question They develop a number
of potential explanations (hypotheses) to answer the question Next, they carry out experiments in an attempt to eliminate one or more of these hypotheses Then, predictions are made based on the remaining hypotheses, and further experiments are carried out to test these predictions The process can also be iterative As experimental results are performed, the information can be used to modify the original hypothesis to fit each new observation.
Trang 29After making careful observations, scientists construct a
hypothesis, which is a suggested explanation that accounts for
those observations A hypothesis is a proposition that might be
true Those hypotheses that have not yet been disproved are
re-tained They are useful because they fit the known facts, but they
are always subject to future rejection if, in the light of new
infor-mation, they are found to be incorrect
This is usually an ongoing process with a hypothesis
chang-ing and bechang-ing refined with new data For instance, geneticists
George Beadle and Edward Tatum studied the nature of genetic
information to arrive at their “one-gene/one-enzyme” hypothesis
(see chapter 15) This hypothesis states that a gene represents the
genetic information necessary to make a single enzyme As
inves-tigators learned more about the molecular nature of genetic
infor-mation, the hypothesis was refined to “one gene/one polypeptide”
because enzymes can be made up of more than one polypeptide
With still more information about the nature of genetic
informa-tion, other investigators found that a single gene can specify more
than one polypeptide, and the hypothesis was refined again
Testing hypotheses
We call the test of a hypothesis an experiment Suppose you enter
a dark room To understand why it is dark, you propose several
hypotheses The first might be, “There is no light in the room
be-cause the light switch is turned off.” An alternative hypothesis
might be, “There is no light in the room because the lightbulb is
burned out.” And yet another hypothesis might be, “I am going
blind.” To evaluate these hypotheses, you would conduct an
ex-periment designed to eliminate one or more of the hypotheses
For example, you might test your hypotheses by flipping the
light switch If you do so and the room is still dark, you have
dis-proved the first hypothesis: Something other than the setting of the
light switch must be the reason for the darkness Note that a test
such as this does not prove that any of the other hypotheses are
true; it merely demonstrates that the one being tested is not A
suc-cessful experiment is one in which one or more of the alternative
hypotheses is demonstrated to be inconsistent with the results and
is thus rejected
As you proceed through this text, you will encounter many
hypotheses that have withstood the test of experiment Many will
continue to do so; others will be revised as new observations are
made by biologists Biology, like all science, is in a constant state of
change, with new ideas appearing and replacing or refining old ones
Establishing controls
Often scientists are interested in learning about processes that are
influenced by many factors, or variables To evaluate alternative
hy-potheses about one variable, all other variables must be kept constant
This is done by carrying out two experiments in parallel: an
experi-mental treatment or group and a control treatment or group In
the experimental treatment, one variable is altered in a known way to
test a particular hypothesis In the control treatment, that variable is
left unaltered In all other respects the two experiments are identical,
so any difference in the outcomes of the two experiments must result
from the influence of the variable that was changed
Much of the challenge of experimental science lies in
de-signing control experiments that isolate a particular variable from
other factors that might influence a process
Using predictions
A successful scientific hypothesis needs to be not only valid but also useful—it needs to tell us something we want to know A hy-pothesis is most useful when it makes predictions because those predictions provide a way to test the validity of the hypothesis If
an experiment produces results inconsistent with the predictions, the hypothesis must be rejected or modified In contrast, if the pre-dictions are supported by experimental testing, the hypothesis is supported The more experimentally supported predictions a hy-pothesis makes, the more valid the hypothesis is
As an example, in the early history of microbiology it was known that nutrient broth left sitting exposed to air becomes con-taminated Two hypotheses were proposed to explain this observa-tion: spontaneous generation and the germ hypothesis Spontaneous generation held that there was an inherent property in organic mol-ecules that could lead to the spontaneous generation of life The germ hypothesis proposed that preexisting microorganisms that were present in the air could contaminate the nutrient broth
These competing hypotheses were tested by a number of periments that involved filtering air and boiling the broth to kill any contaminating germs The definitive experiment was per-formed by Louis Pasteur, who constructed flasks with curved necks that could be exposed to air, but that would trap any con-taminating germs When such flasks were boiled to sterilize them, they remained sterile, but if the curved neck was broken off, they became contaminated (figure 1.4)
ex-Result: No growth occurs in sterile swan-necked flasks When the
neck is broken off, and the broth is exposed to air, growth occurs.
Conclusion: Growth in broth is of preexisting microorganisms.
SCIENTIFIC THINKING
Question: What is the source of contamination that occurs in a flask
of nutrient broth left exposed to the air?
Germ Hypothesis: Preexisting microorganisms present in the air
contaminate nutrient broth.
Prediction: Sterilized broth will remain sterile if microorganisms are
prevented from entering flask.
Spontaneous Generation Hypothesis: Living organisms will
spontaneously generate from nonliving organic molecules in broth.
Prediction: Organisms will spontaneously generate from organic
molecules in broth after sterilization.
Test: Use swan-necked flasks to prevent entry of microorganisms To
ensure that broth can still support life, break swan-neck after sterilization.
Flask is sterilized
by boiling the broth. Unbroken flaskremains sterile. Broken flask becomescontaminated after
exposure to germ-laden air.
Broken neck
of flask
Figure 1.4 Experiment to test spontaneous generation versus germ hypothesis.
Trang 30This result was predicted by the germ hypothesis—that when the sterile flask is exposed to air, airborne germs are depos-
ited in the broth and grow The spontaneous generation
hypothe-sis predicted no difference in results with exposure to air This
experiment disproved the hypothesis of spontaneous generation
and supported the hypothesis of airborne germs under the
condi-tions tested
Reductionism breaks larger systems
into their component parts
Scientists use the philosophical approach of reductionism to
un-derstand a complex system by reducing it to its working parts
Reductionism has been the general approach of biochemistry,
which has been enormously successful at unraveling the complexity
of cellular metabolism by concentrating on individual pathways
and specific enzymes By analyzing all of the pathways and their
components, scientists now have an overall picture of the
metabo-lism of cells
Reductionism has limits when applied to living systems, however—one of which is that enzymes do not always behave
exactly the same in isolation as they do in their normal cellular
context A larger problem is that the complex interworking of
many interconnected functions leads to emergent properties that
cannot be predicted based on the workings of the parts For
ex-ample, ribosomes are the cellular factories that synthesize
pro-teins, but this function could not be predicted based on analysis
of the individual proteins and RNA that make up the structure
On a higher level, understanding the physiology of a single
Canada goose would not lead to predictions about flocking
be-havior The emerging field of systems biology uses mathematical
and computational models to deal with the whole as well as
understanding the interacting parts
Biologists construct models
to explain living systems
Biologists construct models in many different ways for a variety of
uses Geneticists construct models of interacting networks of
proteins that control gene expression, often even drawing cartoon
figures to represent that which we cannot see Population biologists
build models of how evolutionary change occurs Cell biologists
build models of signal transduction pathways and the events
leading from an external signal to internal events Structural
biolo-gists build actual models of the structure of proteins and
macromo-lecular complexes in cells
Models provide a way to organize how we think about a problem Models can also get us closer to the larger picture and
away from the extreme reductionist approach The working parts
are provided by the reductionist analysis, but the model shows how
they fit together Often these models suggest other experiments
that can be performed to refine or test the model
As researchers gain more knowledge about the actual flow of molecules in living systems, more sophisticated kinetic models
can be used to apply information about isolated enzymes to their
cellular context In systems biology, this modeling is being applied
on a large scale to regulatory networks during development, and
even to modeling an entire bacterial cell
The nature of scientific theories
Scientists use the word theory in two main ways The first meaning
of theory is a proposed explanation for some natural phenomenon, often based on some general principle Thus, we speak of the prin-ciple first proposed by Newton as the “theory of gravity.” Such theories often bring together concepts that were previously thought
to be unrelated
The second meaning of theory is the body of interconnected concepts, supported by scientific reasoning and experimental evi-dence, that explains the facts in some area of study Such a theory provides an indispensable framework for organizing a body of knowledge For example, quantum theory in physics brings together
a set of ideas about the nature of the universe, explains experimental facts, and serves as a guide to further questions and experiments
To a scientist, theories are the solid ground of science, pressing ideas of which we are most certain In contrast, to the gen-
ex-eral public, the word theory usually implies the opposite—a lack of
knowledge, or a guess Not surprisingly, this difference often sults in confusion In this text, theory will always be used in its scientific sense, in reference to an accepted general principle or body of knowledge
re-Some critics outside of science attempt to discredit evolution
by saying it is “just a theory.” The hypothesis that evolution has occurred, however, is an accepted scientific fact—it is supported
by overwhelming evidence Modern evolutionary theory is a plex body of ideas, the importance of which spreads far beyond explaining evolution Its ramifications permeate all areas of biol-ogy, and it provides the conceptual framework that unifies biology
com-as a science Again, the key is how well a hypothesis fits the vations Evolutionary theory fits the observations very well
obser-Research can be basic or applied
In the past it was fashionable to speak of the “scientific method” as consisting of an orderly sequence of logical, either–or steps Each step would reject one of two mutually incompatible alternatives, as though trial-and-error testing would inevitably lead a researcher through the maze of uncertainty to the ultimate scientific answer
If this were the case, a computer would make a good scientist But science is not done this way
As the British philosopher Karl Popper has pointed out, cessful scientists without exception design their experiments with a pretty fair idea of how the results are going to come out They have what Popper calls an “imaginative preconception” of what the truth might be Because insight and imagination play such a large role in scientific progress, some scientists are better at science than others—just as Bruce Springsteen stands out among songwriters or Claude Monet stands out among Impressionist painters
suc-Some scientists perform basic research, which is intended to
extend the boundaries of what we know These individuals cally work at universities, and their research is usually supported
typi-by grants from various agencies and foundations
The information generated by basic research contributes to the growing body of scientific knowledge, and it provides the scien-
tific foundation utilized by applied research Scientists who
con-duct applied research are often employed in some kind of industry Their work may involve the manufacture of food additives, the cre-ation of new drugs, or the testing of environmental quality
Trang 31Research results are published in scientific journals, where
the experiments and conclusions are reviewed by other scientists
This process of careful evaluation, called peer review, lies at the
heart of modern science It helps to ensure that faulty research or
false claims are challenged and not accepted without examination
Recently, there have been problems raised with reproducibility in
some areas of biology That this is being examined indicates the
self-reflective nature of science
With some idea of what science is and how it functions, we
will consider a single example in detail What better example than
the development of one of the most important ideas in the history
of science: Darwin’s theory of evolution by natural selection
Learning Outcomes Review 1.2
Much of science is descriptive, amassing observations to gain an
accurate view Both deductive reasoning and inductive reasoning
are used in science Scientific hypotheses are suggested
explanations for observed phenomena Hypotheses need to
make predictions that can be tested by controlled experiments
Theories are coherent explanations of observed data, but they
may be modified by new information.
■ How does a scientific theory differ from a hypothesis?
2 Describe the evidence that supports the theory of evolution.
Darwin’s theory of evolution explains and describes how
organ-isms on Earth have changed over time and acquired a diversity of
new forms This famous theory provides a good example of how a
scientist develops a hypothesis and how a scientific theory grows
and wins acceptance
Charles Robert Darwin (1809–1882; figure 1.5) was an
English naturalist who, after 30 years of study and observation,
wrote one of the most famous and influential books of all time
This book, On the Origin of Species by Means of Natural Selection,
created a sensation when it was published, and the ideas Darwin
expressed in it have played a central role in the development of
human thought ever since
The idea of evolution existed prior to Darwin
In Darwin’s time, most people believed that the different kinds of
organisms and their individual structures resulted from direct
ac-tions of a Creator (many people still believe this) Species were
thought to have been specially created and to be unchangeable over the course of time
In contrast to these ideas, a number of earlier naturalists and philosophers had presented the view that living things must have
changed during the history of life on Earth That is, evolution has
occurred, and living things are now different from how they began
Darwin’s contribution was a concept he called natural selection,
which he proposed as a coherent, logical explanation for this process, and he brought his ideas to wide public attention
Darwin observed differences
in related organisms
The story of Darwin and his theory begins in 1831, when he was
22 years old He was part of a five-year navigational mapping expedition around the coasts of South America ( figure 1.6),
aboard H.M.S Beagle During this long voyage, Darwin had the
chance to study a wide variety of plants and animals on continents and islands and in distant seas Darwin observed a number of phenomena that were of central importance to his reaching his ultimate conclusion
Repeatedly, Darwin saw that the characteristics of similar species varied somewhat from place to place These geographical patterns suggested to him that lineages change gradually as species migrate from one area to another On the Galápagos Islands,
960 km (600 miles) off the coast of Ecuador, Darwin encountered
a variety of different finches on the various islands The 14 species, although related, differed slightly in appearance, particularly in their beaks (figure 1.7)
Darwin thought it was reasonable to assume that all these birds had descended from a common ancestor arriving from the South American mainland several million years ago Eating differ-ent foods on different islands, the finches’ beaks had changed during their descent—“descent with modification,” or evolution (These finches are discussed in more detail in chapters 21 and 22.)
Figure 1.5 Charles Darwin. This newly rediscovered photograph taken in 1881, the year before Darwin died, appears to be the last ever taken of the great biologist ©Huntington Library/SuperStock
Trang 32British Isles Western Isles
E U R O P E
A F R I C A
Madagascar Mauritius Bourbon Island
Friendly Islands
Philippine Islands
Marquesas
Galápagos Islands
Valparaiso Society
Islands Straits of Magellan
Tierra del Fuego Cape Horn
Falkland Islands
N O R T H
A M E R I C A
Canary Islands
Keeling Islands
Woodpecker Finch (Cactospiza pallida) Large Ground Finch (Geospiza magnirostris) Cactus Finch (Geospiza scandens)
In a more general sense, Darwin was struck by the fact that the plants and animals on these relatively young volcanic islands
resembled those on the nearby coast of South America If each one
of these plants and animals had been created independently and
simply placed on the Galápagos Islands, why didn’t they resemble
the plants and animals of islands with similar climates—such as
those off the coast of Africa, for example? Why did they resemble
those of the adjacent South American coast instead?
Darwin proposed natural selection
as a mechanism for evolution
It is one thing to observe the results of evolution, but quite another
to understand how it happens Darwin’s great achievement lies in his ability to move beyond all the individual observations to for-mulate the hypothesis that evolution occurs because of natural selection
Figure 1.6 The five-year voyage of H.M.S Beagle. Most of the time was spent exploring the coasts and coastal islands of South
America, such as the Galápagos Islands Darwin’s studies of the animals of the Galápagos Islands played a key role in his eventual development
of the concept of evolution by means of natural selection.
Figure 1.7 Three Galápagos finches and what they eat. On the Galápagos Islands, Darwin observed 14 different species of finches differing mainly in their beaks and feeding habits These three finches eat very different food items, and Darwin surmised that the different
shapes of their bills represented evolutionary adaptations that improved their ability to eat the foods available in their specific habitats.
Trang 33Darwin and Malthus
Of key importance to the development of Darwin’s insight was his
study of Thomas Malthus’s An Essay on the Principle of Population
(1798) In this book, Malthus stated that populations of plants and
animals (including humans) tend to increase geometrically, while
humans are able to increase their food supply only arithmetically
Put another way, population increases by a multiplying factor—for
example, in the series 2, 6, 18, 54, the starting number is multiplied
by 3 Food supply increases by an additive factor—for example, the
series 2, 4, 6, 8 adds 2 to each starting number Figure 1.8 shows the
difference that these two types of relationships produce over time
Because populations increase geometrically, virtually any
kind of animal or plant, if it could reproduce unchecked, would
cover the entire surface of the world surprisingly quickly Instead,
populations of species remain fairly constant year after year,
be-cause death limits population numbers
Sparked by Malthus’s ideas, Darwin saw that although every
organism has the potential to produce more offspring than can
sur-vive, only a limited number actually do survive and produce further
offspring Combining this observation with what he had seen on the
voyage of the Beagle, as well as with his own experiences in breeding
domestic animals, Darwin made an important association: als possessing physical, behavioral, or other attributes that give them
Individu-an advIndividu-antage in their environment are more likely to survive Individu-and produce than those with less advantageous traits By surviving, these individuals gain the opportunity to pass on their favorable character-istics to their offspring As the frequency of these characteristics in-creases in the population, the nature of the population as a whole will
re-gradually change Darwin called this process selection.
Natural selection
Darwin was thoroughly familiar with variation in domesticated
animals, and he began On the Origin of Species with a detailed
discussion of pigeon breeding He knew that animal breeders selected certain varieties of pigeons and other animals, such as dogs, to produce certain characteristics, a process Darwin called
artificial selection.
Artificial selection often produces a great variation in traits
Domestic pigeon breeds, for example, show much greater variety than all of the wild species found throughout the world Darwin thought that this type of change could occur in nature, too Surely if pigeon breeders could foster variation by artificial selection, nature
could do the same—a process Darwin called natural selection.
Darwin drafts his argument
Darwin drafted the overall argument for evolution by natural tion in a preliminary manuscript in 1842 After showing the manu-script to a few of his closest scientific friends, however, Darwin put it in a drawer, and for 16 years turned to other research No one knows for sure why Darwin did not publish his initial manuscript—
selec-it is very thorough and outlines his ideas in detail
The stimulus that finally brought Darwin’s hypothesis into print was an essay he received in 1858 A young English naturalist named Alfred Russel Wallace (1823–1913) sent the essay to Dar-win from Indonesia; it concisely set forth the hypothesis of evolu-tion by means of natural selection, a hypothesis Wallace had developed independently of Darwin After receiving Wallace’s es-say, friends of Darwin arranged for a joint presentation of their ideas at a seminar in London Darwin then completed his own book, expanding the 1842 manuscript he had written so long ago, and submitted it for publication
The predictions of natural selection have been tested
More than 130 years have elapsed since Darwin’s death in 1882
During this period, the evidence supporting his theory has grown progressively stronger We briefly explore some of this evidence here; in chapter 21, we will return to the theory of evolution by natural selection and examine the evidence in more detail
The fossil record
Darwin predicted that the fossil record would yield intermediate links between the great groups of organisms—for example, be-tween fishes and the amphibians thought to have arisen from them, and between reptiles and birds Furthermore, natural selection pre-dicts the relative positions in time of such transitional forms We now know the fossil record to a degree that was unthinkable in the
Figure 1.8 Geometric and arithmetic progressions. A
geometric progression increases by a constant factor (for example, the
curve shown increases ×3 for each step), whereas an arithmetic
progression increases by a constant difference (for example, the line
shown increases +2 for each step) Malthus contended that the human
growth curve was geometric, but the human food production curve
was only arithmetic.
constant factor for a geometric progression? How would this
change the curve in the figure?
Inquiry question Might this effect be achieved with
humans? How?
?
Trang 34Human Cat Bat Porpoise Horse
Number of Amino Acid Differences in a Hemoglobin Polypeptide
?
19th century, and although truly “intermediate” organisms are
hard to determine, paleontologists have found what appear to be
transitional forms and found them at the predicted positions
in time
Analysis of microscopic fossils extends the history of life on Earth to about 3.5 billion years ago (bya) The discovery of other
fossils has supported Darwin’s predictions and has shed light on
how organisms have, over this enormous time span, evolved from
the simple to the complex For vertebrate animals especially, the
fossil record is rich and exhibits a graded series of changes in form,
with the evolutionary sequence visible for all to see
The age of the Earth
Darwin’s theory predicted the Earth must be very old, but some
physicists argued that the Earth was only 100 million years old
This bothered Darwin, because this did not seem to allow enough
time for the evolution of all living things from a common ancestor
Using evidence obtained by studying the rates of radioactive
de-cay, we now know that the physicists of Darwin’s time were very
wrong: The Earth was formed about 4.5 bya
The mechanism of heredity
Darwin received some of his sharpest criticism in the area of
he-redity At that time, no one had any concept of genes or how
hered-ity works, so it was not possible for Darwin to explain completely
how evolution occurs
Even though Gregor Mendel was performing his ments with pea plants in Brünn, Austria (now Brno, the Czech
experi-Republic), during roughly the same period, genetics was
estab-lished as a science only at the start of the 20th century When
sci-entists began to understand the laws of inheritance (discussed in
chapters 12 and 13), this problem with Darwin’s theory vanished
Comparative anatomy
Comparative studies of animals have provided strong evidence for
Darwin’s theory In many different types of vertebrates, for
exam-ple, the same bones are present, indicating their evolutionary past
Thus, the forelimbs shown in figure 1.9 are all constructed from
the same basic array of bones, modified for different purposes
These bones are said to be homologous in the different
vertebrates—that is, they have the same evolutionary origin, but
they now differ in structure and function They are contrasted with
analogous structures, such as the wings of birds and butterflies,
which have similar function but different evolutionary origins
Molecular evidence
Evolutionary patterns are also revealed at the molecular level By comparing the genomes (that is, the sequences of all the genes) of different groups of animals or plants, we can more precisely spec-ify the degree of relationship among the groups A series of evolu-tionary changes over time should involve a continual accumulation
of genetic changes in the DNA
This difference can be seen clearly in the protein bin (figure 1.10) Rhesus monkeys, which like humans are pri-mates, have fewer differences from humans in the 146-amino-acid
hemoglo-Figure 1.9 Homology among vertebrate limbs.
The forelimbs of these five vertebrates show the ways in which the relative proportions of the forelimb bones have changed
in relation to the particular way of life of each organism.
Figure 1.10 Molecules reflect evolutionary patterns.
Vertebrates that are more distantly related to humans have a greater number of amino acid differences in the hemoglobin polypeptide.
Inquiry question Where do you imagine a snake might fall on the graph? Why?
Trang 35hemoglobin β chain than do more distantly related mammals, such
as dogs Nonmammalian vertebrates, such as birds and frogs,
dif-fer even more This kind of analysis allows us to construct
phylo-genetic trees that provide a graphic representation of these
evolutionary relationships
We will explore these ideas in much more detail in Part IV
For now we will conclude our introduction to biology by
consider-ing how we can use core concepts to organize our thinkconsider-ing and deal
with the enormous amount of information that is modern biology
Learning Outcomes Review 1.3
Darwin observed differences in related organisms and proposed
the hypothesis of evolution by natural selection to explain these
differences The predictions generated by natural selection have
been tested and continue to be tested by analysis of the fossil
record, genetics, comparative anatomy, and even the DNA of
living organisms.
■ Does Darwin’s theory of evolution by natural selection
explain the origin of life?
Learning Outcome
1 Discuss the core concepts that underlie the study of biology.
At the fundamental level of neurochemistry, the brain of a novice
is largely the same as that of an expert There are however,
signifi-cant differences in how experts organize the information they
col-lect over time As you are starting to gather information about
biology, it is worth considering how you can begin to organize this
information in your mind like an expert thinker
You may be trying to organize the flood of information
about biology by topics The problem with this approach is that
there are just too many topics for this to be successful A better way
to organize ideas in your mind is using a conceptual framework
Most disciplines, including biology, are based on information that
is readily organized around concepts You can think of concepts as
a place in your mind to hold specific ideas that relate to many
top-ics For example, consider a hammer, a sunflower, and DNA
These seem quite disparate, but can actually be organized
concep-tually A hammer has a long handle to create leverage and a heavy
head to drive nails Sunflowers have broad leaves that maximize
their ability to absorb light for photosynthesis, and DNA has a
structure that allows storage of information These descriptions
can be organized into the concept “structure determines
function”: the function of something arises from its form When
you encounter new information, you can fit it into a framework of
core concepts like “structure determines function.”
There has been a recent movement to emphasize core
con-cepts in biology education The authors applaud this and have
in-corporated this approach in this text We have emphasized five
core concepts: life is subject to chemical and physical laws; ture determines function; living systems transform energy and matter; living systems depend on information transactions; and evolution explains the unity and diversity of life
struc-Core concepts are, by their very nature, high level and thus general These are used to organize more specific secondary con-cepts, which in turn arise from observations, experiments, or de-scriptions of biological phenomenon For example, the core concept
“structure determines function” could lead to the secondary concept
“Genetic information is encoded in the structure of DNA.” This can then be used to organize a series of observations about the nature of genetic information and how it is used, such as these: “base pairing involves specific patterns of hydrogen bonds,” and “the genetic code consists of four nucleotides that are abbreviated: A,T,G,C,” and
“DNA is used as a template to synthesize RNA,” and so on
To keep you focused on the core concepts, and how they late to the material of each chapter, we present a Connecting the Concepts feature at the end of each chapter In each of these, we present one example of how the authors organize different ideas under a core concept A second core concept is provided for you to practice organizing ideas into your own conceptual framework
re-Then at the end of each of the eight Parts of the book is a larger Connecting the Concepts feature that does the same thing, but with
a much larger scope Due to space limitations this will not sarily include material from every chapter or section, and is in-tended as an example and not an exhaustive list
neces-The five core concepts
Life is subject to chemical and physical laws
It may seem obvious, but it is important to emphasize that living systems operate according to known chemical and physical prin-ciples For this reason, almost all introductory textbooks, including this one, begin with several sections on chemistry This is because biological systems are the ultimate application of some very com-plex chemistry However, there are no new chemical or physical laws to be found in biology, just the consistent application of famil-iar chemical principles and laws This means that some knowledge
of atomic structure, chemical bonding, thermodynamics, kinetics, and many other topics from basic chemistry and physics is crucial for understanding biological systems
It may seem that some physics and chemistry would only be relevant in the “cell and molecular” sections of the book, but in fact, those principles are applied throughout the book The move-ment of water in plants depends on the basic chemistry of water, the kidney is an osmotic machine, energy flow and nutrient cycling
in ecosystems are driven by thermodynamic laws, and the cycling
of many important elements involves biogeochemical cycles
Structure determines function
A major unifying theme of biology is the relationship between structure and function Said simply, the proper functioning of mol-ecules, of cells, and of tissues and organs depends on their struc-ture Although this observation may seem trivial, it has far-reaching implications When we know the function of a particular structure,
we can infer the function of similar structures found in different contexts, such as in different organisms
Trang 36For example, suppose we know the structure of a human cell’s surface receptor for insulin, the hormone that controls the
uptake of glucose We then find a similar molecule in the
mem-brane of a cell from a very different species, such as a worm We
might conclude that this membrane molecule acts as a receptor
for an insulin-like molecule produced by the worm In this way,
we might be able to hypothesize an evolutionary relationship
between glucose uptake in worms and in humans When structure
is altered, function is disrupted, with potential physiological
consequences
Living systems transform energy and matter
From single cells to the highest level of biological organization,
the biosphere, living systems have a constant need for energy If we
trace this all the way back, the original energy source for the
bio-sphere is the sun Without this energy, living systems would not
exhibit their characteristic highly organized state While this
sounds simple, it means that the basic nature of life is to constantly
transform both energy and matter We break down “food”
mole-cules for energy, then use this energy to build up other complex
molecules
The energy from the sun is trapped by photosynthetic isms, which use this energy to reduce CO2 and produce organic
organ-compounds The rest of us, who need a constant source of energy
and carbon, can oxidize these organic compounds back to CO2,
releasing energy to drive the processes of life As all of these
en-ergy transactions are inefficient, a certain amount of enen-ergy is also
randomized as heat
This constant input of energy allows living systems to tion far from thermodynamic equilibrium At equilibrium, you are
func-a pool of func-amino func-acids, nucleotides, func-and other smfunc-all molecules, func-and
not the complex dynamic system reading this sentence
Nonequi-librium systems also can exhibit the property of self-organization
not seen in equilibrium systems Macromolecular complexes, such
as the spindle necessary for chromosome separation, can self-
organize (figure 1.11) A flock of birds, a school of fish, and the
bacteria in a biofilm all also display self-organization, exhibiting
properties not seen in the individual parts alone
Living systems depend on information
transactions
The most obvious form of information in living systems is the
genetic information carried in every cell in the form of
deoxyribonucleic acid (DNA) Each DNA molecule is formed
from two long chains of building blocks, called nucleotides, wound
around each other (figure 1.12) Four different nucleotides are found
in DNA, and the sequence in which they occur encodes the
informa-tion to make and maintain a cell
The continuity of life from one generation to the next—
heredity—depends on the faithful copying of a cell’s DNA into
daughter cells The entire set of DNA instructions that
speci-fies a cell is called its genome The sequence of the human
genome, 3 billion nucleotides long, was decoded in rough-draft
form in 2001
However, the importance of information goes beyond genomes and their inheritance Cells are highly complex nanoma-
chines that receive, process, and respond to information The
Figure 1.11 The spindle In this dividing cell, microtubules have organized themselves into a spindle (stained red), pulling each chromosome (stained blue) to the central plane of the dividing cell
©Waheeb K Heneen/Swedish University of Agricultural Sciences
Figure 1.12 DNA, the genetic material All organisms store their hereditary information as sequences of DNA subunits, much as this textbook stores information as sequences of alphabet letters
©Science Photo Library/Alamy Stock Photo
information stored in DNA is used to direct the synthesis of lar components, and the particular set of components can differ from cell to cell The way proteins fold in space is a form of infor-mation that is three-dimensional, and interesting properties emerge from the interaction of these shapes in macromolecular complexes The control of gene expression allows the differentiation of cell
Trang 37cellu-Learning Outcome Review 1.4
Understanding biology requires higher-level concepts We are using five core concepts throughout the book: Life is subject to chemical and physical laws, structure determines function, living systems transform energy and matter, living systems depend on information transactions, and evolution explains the unity and diversity of life.
■ How do viruses fit into our definitions of living systems?
Mus musculus (animal) Saccharomyces cerevisiae(fungus)
Saccharomyces cerevisiae
Arabidopsis thaliana (plant)
Arabidopsis thaliana (plant)
MEIS KN BEL1 MATa1
HB8 HAT GL2 PAX6 PEM
Figure 1.13 Tree of homeodomain proteins.
Homeodomain proteins are found in fungi (brown), plants (green), and animals (blue) Based on their sequence similarities, these 11 different
homeodomain proteins (uppercase letters at the ends of branches) fall into two groups, with representatives from each kingdom in each group That means, for example, the mouse homeodomain protein PAX6 is more closely related to fungal and flowering plant proteins, such as PHO2 and GL2, than it is to the mouse protein MEIS.
1.1 The Science of Life
Biology unifies much of natural science.
The study of biological systems is interdisciplinary because solutions
require many different approaches to solve a problem.
Life defies simple definition.
Although life is difficult to define, living systems have seven characteristics
in common They are composed of one or more cells; are complex and
highly ordered; can respond to stimuli; can grow, reproduce, and transmit
genetic information to their offspring; need energy to accomplish work;
can maintain relatively constant internal conditions (homeostasis); and are
capable of evolutionary adaptation to the environment.
Living systems show hierarchical organization.
The hierarchical organization of living systems progresses from atoms
to the biosphere At each higher level, emergent properties arise that are greater than the sum of the parts.
1.2 The Nature of Science
At its core, science is concerned with understanding the nature
of the world by using observation and reasoning.
Much of science is descriptive.
Science is concerned with developing an increasingly accurate description of nature through observation and experimentation.
Chapter Review
types in time and space, leading to changes over developmental
time into different tissue types—even though all cells in an
organ-ism carry the same genetic information
Living systems are able to collect information about the
environment, both internal and external, and then respond to
this information As you are reading this page, you are
famil-iar with this process, but it also occurs at the level of cells, in
terms of both single-celled organisms and the cells of
multi-cellular organisms Cells acquire information about their
en-vironment, send and receive signals, and respond to all of this
information with signal transduction systems that can change
cell morphology, behavior, or physiology (the subject of
chapter 9)
Evolution explains the unity and diversity of life
Biologists agree that all organisms alive today on Earth
descend-ed from a simple cellular organism that arose about 3.5 bya
Some of the characteristics of that organism have been preserved
through evolutionary history into the present The storage of
he-reditary information in DNA, for example, is common to all
living things
The retention of these conserved characteristics in a long
line of descent implies that they have a fundamental role in the
success of the organism A good example is provided by the
homeodomain proteins, which are critical regulators of the
pro-cess of development Conserved characteristics can be seen in
approximately 1850 homeodomain proteins, distributed among
three kingdoms of organisms (figure 1.13) The homeodomain
proteins are powerful developmental tools that evolved early;
they have been used and modified to provide new forms
The unity of life that we see in certain key characteristics
shared by many related life-forms contrasts with the incredible
di-versity of living things in the varied environments of Earth The
underlying unity of biochemistry and genetics argues that all life
evolved from the same origin event The incredible diversity of life
we see today arose by evolutionary change, much of it visible in
the fossil record
Trang 38Science uses both deductive and inductive reasoning.
Deductive reasoning applies general principles to predict specific results
Inductive reasoning uses specific observations to construct general
scientific principles.
Hypothesis-driven science makes and tests predictions.
Hypotheses are based on observations, and generate testable predictions
Experiments involve a test where a variable is manipulated, and a control
where the variable is not manipulated If the predictions cannot be
verified the hypothesis is rejected.
Reductionism breaks larger systems into their component parts.
Reductionism attempts to understand a complex system by breaking
it down into its component parts It is limited because parts may act
differently when isolated from the larger system.
Biologists construct models to explain living systems.
A model provides a way of organizing our thinking about a problem;
models may also suggest experimental approaches.
The nature of scientific theories.
Scientists use the word theory in two main ways: as a proposed
explanation for some natural phenomenon and as a body of concepts that
explains facts in an area of study.
Research can be basic or applied.
Basic research extends the boundaries of what we know; applied research
seeks to use scientific findings in practical areas such as agriculture,
medicine, and industry.
1.3 An Example of Scientific Inquiry: Darwin
and Evolution
Darwin’s theory of evolution shows how a scientist develops a
hypothesis and sets forth evidence, as well as how a scientific theory
grows and gains acceptance.
The idea of evolution existed prior to Darwin.
A number of naturalists and philosophers had suggested living things had
changed during Earth’s history Darwin’s contribution was the concept of
natural selection as a mechanism for evolutionary change.
Darwin observed differences in related organisms.
During the voyage of the H.M.S Beagle, Darwin had an opportunity to
observe worldwide patterns of diversity.
Darwin proposed natural selection as a mechanism for evolution.
Darwin noted that species produce many more offspring than will
survive and reproduce He observed that traits can be changed by
artificial selection Darwin proposed that individuals possessing traits that increase survival and reproductive success become more numerous in populations over time Darwin called this descent with modification (natural selection) Alfred Russel Wallace independently came to the same conclusions.
The predictions of natural selection have been tested.
Natural selection has been tested using data from many fields
Among these are the fossil record; the age of the Earth, determined
by rates of radioactive decay to be 4.5 billion years; genetic experiments showing that traits can be inherited as discrete units;
comparative anatomy and the study of homologous structures;
and molecular data that provide evidence for changes in DNA and proteins over time
Taken together, these findings strongly support evolution by natural selection No data to conclusively disprove evolution have been found.
1.4 Core Concepts in Biology
We use core concepts to organize information about the world around us
We introduce five core concepts to be used throughout this book, to help organize your thinking.
Life is subject to chemical and physical laws.
All living systems function based on the laws of chemistry and physics.
Structure determines function.
The function of macromolecules is dictated by and dependent on their structure Similarity of structure and function may indicate an evolutionary relationship.
Living systems transform energy and matter
Living systems have a constant need for energy, which is ultimately provided by the sun The nature of life is to constantly transform energy
We break down food molecules to provide energy to build up complex structures.
Living systems depend on information transactions
Hereditary information found in the DNA molecule is passed
on from one generation to the next This information is read out
to produce proteins, which themselves have information in their structures Living systems can also acquire information about their environment.
Evolution explains the unity and diversity of life
The underlying similarities in biochemistry and genetics support the contention that all life evolved from a single source The diversity found
in living systems arises by evolutionary change.
2 The process of inductive reasoning involves
a the use of general principles to predict a specific result.
b the generation of specific predictions based on a belief system.
c the use of specific observations to develop general principles.
d the use of general principles to support a hypothesis.
Trang 393 A hypothesis in biology is best described as
a a possible explanation of an observation.
b an observation that supports a theory.
c a general principle that explains some aspect of life.
d an unchanging statement that correctly predicts some aspect
of life.
4 A scientific theory is
a a guess about how things work in the world.
b a statement of how the world works that is supported by
experimental data.
c a belief held by many scientists.
d Both a and c are correct.
5 The cell theory states that
a cells are small.
b cells are highly organized.
c there is only one basic type of cell.
d all living things are made up of cells.
6 The molecule DNA is important to biological systems because
a it can be replicated.
b it encodes the information for making a new individual.
c it forms a complex, double-helical structure.
d nucleotides form genes.
7 The organization of living systems is
a linear with cells at one end and the biosphere at the other.
b circular with cells in the center.
c hierarchical with cells at the base, and the biosphere at the top.
d chaotic and beyond description.
8 The idea of evolution
a was original to Darwin.
b was original to Wallace.
c predated Darwin and Wallace.
d Both a and b are correct.
A P P LY
1 What is the significance of Pasteur’s experiment to test the germ
hypothesis?
a It proved that heat can sterilize a broth.
b It demonstrated that cells can arise spontaneously.
c It demonstrated that some cells are germs.
d It demonstrated that cells can arise only from other cells.
2 Which of the following is NOT an example of reductionism?
a Analysis of an isolated enzyme’s function in an experimental
d An evaluation of the overall behavior of a cell
3 How is the process of natural selection different from that
of artificial selection?
a Natural selection produces more variation.
b Natural selection makes an individual better adapted.
c Artificial selection is a result of human intervention.
d Artificial selection results in better adaptations.
4 If you found a fossil for a modern organism next to the fossil of a dinosaur, this would
a argue against evolution by natural selection.
b have no bearing on evolution by natural selection.
c indicate that dinosaurs may still exist.
d Both b and c are correct.
5 The theory of evolution by natural selection is a good example of how science proceeds because
a it rationalizes a large body of observations.
b it makes predictions that have been tested by a variety
of approaches.
c it represents Darwin’s belief of how life has changed over time.
d Both b and c are correct.
6 In which domain of life would you find only single-celled organisms?
a Eukarya
b Bacteria c Archaead Both b and c are correct.
7 Evolutionary conservation occurs when a characteristic is
a important to the life of the organism.
b not influenced by evolution.
c no longer functionally important.
d found in more primitive organisms.
2 The classic experiment by Pasteur (figure 1.4) tested the hypothesis that cells arise from other cells In this experiment cell growth was measured following sterilization of broth in a swan-necked flask or
in a flask with a broken neck.
a Which variables were kept the same in these two experiments?
b How does the shape of the flask affect the experiment?
c Predict the outcome of each experiment based on the two hypotheses.
d Some bacteria (germs) are capable of producing heat-resistant spores that protect the cell and allow it to continue to grow after the environment cools How would the outcome of this experiment have been affected if spore-forming bacteria were present in the broth?
Trang 40C O N N E C T I N G T H E C O N C E P T S
This feature is intended to give you practice in organizing information using core concepts We use a metaphor of gears and cogs to represent a
conceptual hierarchy with each core concept represented as a gear Secondary concepts are the cogs, and tertiary concepts, which are particular
examples from the chapter, are presented as a list of bulleted points Using the completed conceptual Evolution explains the unity and diversity of life unit as a guide, build a list of examples from the chapter that illustrate how the secondary concept “Natural selection is a mechanism for evolution”
supports the core concept “Evolution explains the unity and diversity of life.”
Evolution explains the unity and diversity of life
Natural selection is a mechanism for evolution
Life’s diversity is overwhelming
• Living systems are organized hierarchically.
• Living systems are composed of cells, which are organized into tissues, which are organized into organs.
• Evolution has resulted in incredible diversity of life, from single-celled bacteria to multicellular plants and animals.
• Classifying organisms based on morphological and molecular characteristics led to two unicellular domains and a third domain composed of more complex single-celled and multicellular organisms.