[second edition] Principles of B i o l o g y Robert J. Brooker University of Minnesota - Minneapolis Eric P. Widmaier Boston University Linda E. Graham University of Wisconsin - Madison Peter D. Stiling University of South Florida bro75121_fm_i-xxviii.indd 1 29/11/16 10:40 am PRINCIPLES OF BIOLOGY, SECOND EDITION Published by McGraw-Hill, a business unit of The McGraw-Hill Companies, Inc., 1221 Avenue of the Americas, New York, NY 10020. Copyright © 2018 by The McGraw-Hill Companies, Inc. All rights reserved. Printed in the United States of America. Previous edition © 2015. 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 The McGraw-Hill Companies, Inc., 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. 1 2 3 4 5 6 7 8 9 0 LWI 21 20 19 18 17 ISBN 978–1–259–87512–0 MHID 1–259–87512–1 Senior Vice President, Products & Markets: G. Scott Virkler Vice President, General Manager, Products & Markets: Marty Lange Vice President, Content Production & Technology Services: Betsy Whalen Managing Director: Lynn Breithaupt Brand Manager: Michelle Vogler Product Developer: Elizabeth M. Sievers Executive Marketing Manager: Patrick E. Reidy Director, Content Production: Linda Avenarius Program Manager: Angela FitzPatrick Content Project Manager (Print): Jayne Klein Content Project Manager (Media): Christina Nelson Senior Buyer: Sandy Ludovissy Senior Designer: David W. Hash Cover Image: © Chase Dekker Wild-Life Images/Moment/Getty Images Content Licensing Specialists: Carrie Burger/Shannon Manderscheid Compositor: MPS Limited Typeface: 10/12 STIX MathJax Main Printer: LSC Communications All credits appearing on page are considered to be an extension of the copyright page. Library of Congress Cataloging-in-Publication Data Brooker, Robert J., author. | Widmaier, Eric P., author. | Graham, Linda E., 1946- author. | Stiling, Peter D., author. Principles of biology/Robert J. Brooker, University of Minnesota-Minneapolis, Eric P. Widmaier, Boston University, Linda E. Graham, University of Wisconsin-Madison, Peter D. Stiling, University of South Florida. Second edition. | New York, NY : McGraw-Hill Education, [2018] | Includes index. LCCN 2016035146 | ISBN 9781259875120 (alk. paper) LCSH: Biology—Textbooks. LCC QH308.2 .B75 2018 | DDC 570—dc23 LC record available at https://lccn.loc.gov/2016035146 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 bro75121_fm_i-xxviii.indd 2 29/11/16 10:40 am Brief Contents 1 An Introduction to Biology 1 24 Microbiomes: Microbial Systems on and Around Us 494 25 Plant Evolution: How Plant Diversification Changed Unit I Chemistry 18 Planet Earth 512 2 The Chemical Basis of Life I: Atoms, Molecules, 26 Invertebrates: The Vast Array of Animal Life Without a and Water 19 Backbone 535 3 The Chemical Basis of Life II: Organic Molecules 35 27 Vertebrates: Fishes, Amphibians, Reptiles, and Mammals 569 Unit II Cells 56 Unit VI Flowering Plants 590 4 Evolutionary Origin of Cells and Their General Features 57 28 An Introduction to Flowering Plant Form 5 Membranes: The Interface Between Cells and Their and Function 591 Environment 95 29 How Flowering Plants Sense and Interact with Their 6 How Cells Utilize Energy 117 Environments 611 7 How Cells Capture Light Energy via Photosynthesis 143 30 How Flowering Plants Obtain and Transport Nutrients 628 8 How Cells Communicate with Each Other and with the Environment 162 31 How Flowering Plants Reproduce and Develop 651 Unit III Genetics 178 Unit VII Animals 670 9 The Information of Life: DNA and RNA Structure, DNA 32 General Features of Animal Bodies, and Homeostasis as Replication, and Chromosome Structure 179 a Key Principle of Animal Biology 671 10 The Expression of Genetic Information via Genes I: 33 Neuroscience I: The Structure, Function, and Evolution Transcription and Translation 200 of Nervous Systems 692 11 The Expression of Genetic Information via Genes II: 34 Neuroscience II: How Sensory Systems Allow Animals Non-coding RNAs 220 to Interact with the Environment 721 12 The Control of Genetic Information via Gene 35 How Muscles and Skeletons Are Adaptations for Regulation 240 Movement, Support, and Protection 742 13 Altering the Genetic Material: Mutation, DNA Repair, 36 Circulatory and Respiratory Systems: Transporting and Cancer 259 Solutes and Exchanging Gases 757 14 How Eukaryotic Cells Sort and Transmit Chromosomes: 37 Digestive and Excretory Systems Help Maintain Nutrient, Mitosis and Meiosis 277 Water, and Energy Balance and Remove Waste Products from Animal Bodies 790 15 Transmission of Genetic Information from Parents to Offspring I: Patterns that Follow Mendel’s Laws 300 38 How Endocrine Systems Influence the Activities of All Other Organ Systems 824 16 Transmission of Genetic Information from Parents to Offspring II: Epigenetics, Linkage, and Extranuclear 39 The Production of Offspring: Reproduction and Inheritance 318 Development 846 17 The Simpler Genetic Systems of Viruses and Bacteria 336 40 Immune Systems: How Animals Defend Against Pathogens and Other Dangers 871 18 Genetic Technologies: How Biologists Study Genes and Genomes 353 41 Integrated Responses of Animal Organ Systems to a Challenge to Homeostasis 891 Unit IV Evolution 374 Unit VIII Ecology 906 19 Evolution of Life I: How Populations Change from Generation to Generation 375 42 Behavioral Ecology: The Struggle to Find Food and 20 Evolution of Life II: The Emergence of New Species 403 Mates and to Pass On Genes 907 21 How Biologists Classify Species and Study Their 43 Population Growth and Species Interactions 923 Evolutionary Relationships 419 44 Communities and Ecosystems: Ecological Organization 22 The History of Life on Earth and Human Evolution 435 at Large Scales 940 45 How Climate Affects the Distribution of Species on Unit V Diversity 460 Earth 962 23 Diversity of Microbial Life: Archaea, Bacteria, Protists, 46 The Age of Humans 974 and Fungi 461 47 Biodiversity and Conservation Biology 1000 iii bro75121_fm_i-xxviii.indd 3 29/11/16 10:40 am About the Authors Robert J. Brooker Rob Brooker received his Ph.D. in genetics from Yale University in 1983. At Harvard, he studied lactose permease, the product of the lacY gene of the lac operon. He continued working on trans- porters at the University of Minnesota, where he is a Professor in the Department of Genetics, Cell Biology, and Development At the University of Minnesota, Dr. Brooker teaches undergraduate courses in biology and genetics. In addition to many other publica- tions, he has written two undergraduate genetics texts: Genetics: Analysis & Principles, Sixth Edition, copyright 2018, and Concepts of Genetics, Second Edition, copyright 2015; and he is the lead author of Biology, Fourth Edition, copyright 2017, all published by McGraw-Hill Education. Eric P. Widmaier Left to right: Eric Widmaier, Linda Graham, Peter Stiling, and Rob Brooker Eric Widmaier received his Ph.D. in 1984 in endocrinology from the University of California at San Francisco. His research focuses on the control of body mass and metabolism in mammals, the hormonal corre- She is also a coauthor of Biology, Fourth Edition, copyright 2017, lates of obesity, and the effects of high-fat diets on intestinal cell function. published by McGraw-Hill Education. Dr. Widmaier is currently Professor of Biology at Boston University, where he teaches undergraduate courses in human physiology, compara- Peter D. Stiling tive physiology, and endocrinology and recently received the universi- Peter Stiling obtained his Ph.D. from University College, Cardiff, ty’s highest honor for excellence in teaching. Among other publications, Wales, in 1979. Subsequently, he became a postdoctoral fellow at he is a coauthor of Vander’s Human Physiology: The Mechanisms of Florida State University and later spent two years as a lecturer at the Body Function, Fourteenth Edition, copyright 2017; and Biology, Fourth University of the West Indies, Trinidad. During this time, he began Edition, copyright 2017, both published by McGraw-Hill Education. photographing and writing about butterflies and other insects, which led to publication of several books on local insects. Dr. Stiling is Linda E. Graham currently a Professor of Biology at the University of South Florida Linda Graham received her Ph.D. in botany from the University of at Tampa. His research interests include plant-insect relationships, Michigan, Ann Arbor. Her research explores the evolutionary origin parasite-host relationships, biological control, restoration ecology, of algae land-adapted plants, focusing on their cell and molecular biol- and the effects of elevated carbon dioxide levels on plant–herbivore ogy as well as ecological interactions with microbes. Dr. Graham is interactions. He teaches graduate and undergraduate courses in ecol- now Professor of Botany at the University of Wisconsin–Madison. She ogy and environmental science as well as introductory biology. He has teaches undergraduate courses in microbiology and plant biology. She published many scientific papers and is the author of Ecology: Global is the coauthor of, among other publications, Algae, Third Edition, Insights and Investigations, Second Edition, copyright 2015, and is copyright 2015, a major’s textbook on algal biology; and Plant coauthor of Biology, Fourth Edition, copyright 2017, both published Biology, Third Edition, copyright 2015, both published by LJLM Press. by McGraw-Hill Education. Ian Quitadamo, Lead Digital Author University and holds a BA in biology, Masters degree in genetics and cell biology, and an interdisciplinary Ph.D. in science, education, and Ian Quitadamo is a Professor with a dual technology. Previously a researcher of tumor angiogenesis, he now appointment in Biological Sciences and investigates the behavioral and neurocognitive basis of critical think- Science Education at Central Washington ing and has published numerous studies of factors that improve stu- University in Ellensburg, Washington. He dent critical thinking performance. He has received the Crystal Apple teaches introductory and majors biology award for teaching excellence, led multiple initiatives in critical courses and cell biology, genetics, and thinking and assessment, and is active nationally in helping transform biotechnology, as well as science teaching © Ian J. Quitadamo, Ph.D. university faculty practice. methods courses for future science teach- ers and interdisciplinary content courses in alternative energy and sustainability. Dr. Quitadamo was educated at Washington State iv bro75121_fm_i-xxviii.indd 4 29/11/16 10:40 am A Note about Principles of Biology . . . A recent trend in science education is the phenomenon called “flipping the classroom.” This phrase refers to the idea that some of the activities that used to be done in class are now done out of class, and vice versa. For example, instead of spending the entire class time lecturing about textbook and other materials, some of the class time is spent engaging students in various activities, such as problem solving, working through case studies, and designing experiments. This approach is called active learning. For many instructors, the classroom has become more learner-centered rather than teacher-centered. A learner-centered classroom provides a rich environment in which students can interact with each other and with their instructors. Instructors and fellow students often provide formative assessment—immediate feedback that helps each student understand if his or her learning is on the right track. What are some advantages of active learning? Educational studies reveal that active learning usually promotes greater learning gains. In addition, active learning often focuses on skill development rather than the memorization of facts that are easily forgotten. Students become trained to “think like scientists” and to develop a skill set that enables them to apply scientific reasoning. A common concern among instructors who are beginning to try out active learning is that they think they will have to teach their students less material. However, this may not be the case. Although students may be provided with online lectures, “flipping the classroom” typically gives students more responsibility for understanding the text- book material on their own. Along these lines, Principles of Biology is intended to provide students with a resource that can be effectively used out of the classroom. Several key pedagogical features include the following: • Focus on Core Concepts: Although it is intended for majors in the biological sciences, Principles of Biology is a shorter textbook that emphasizes core concepts. Twelve principles of biology are enunciated in Chapter 1 and those principles are emphasized throughout the textbook with specially labeled figures. An effort has also been made to emphasize some material in bulleted lists and numbered lists, so students can more easily see the main points. • Learning Outcomes: Each section of every chapter begins with a set of learning outcomes. These outcomes help students understand what they should be able to do if they have mastered the material in that section. Certain learning outcomes, labeled as SCISKILLS, emphasize experimental skills needed in the study of biol- ogy. Skills such as analyze data, form hypotheses, make predictions, make calculations, are skills that scientists generally perform and students majoring in biology should practice. • Formative Assessment: When students are expected to learn textbook material on their own, it is imperative that they be given regular formative assessments so they can gauge whether or not they are mastering the material. Formative assessment is a major feature of this textbook and is bolstered by McGraw-Hill Connect®—a state-of- the-art digital assignment and assessment platform. In Principles of Biology, formative assessment is provided in multiple ways. 1. Each section of every chapter ends with multiple-choice questions. 2. Most figures have concept check questions so students can determine if they understand the key points in the figure. 3. End-of-chapter questions continue to provide students with feedback regarding their mastery of the material. 4. Further assessment tools are available in Connect. Question banks, Test banks, and Quantitative Question banks can be assigned by the professor. McGraw-Hill SmartBook® allows for individual study as well as assignments from the professor. • Quantitative Analysis: Many chapters have a subsection that emphasizes quantitative reasoning, an impor- tant skill for careers in science and medicine. In these subsections, the quantitative nature of a given topic is described, and then students are asked to solve a problem related to that topic. • BioConnections and Evolutionary Connections: To help students broaden their understanding of biology, two recurring features are BioConnections and Evolutionary Connections. BioConnections are placed in key figure legends in each chapter and help students relate a topic they are currently learning to another topic elsewhere in the textbook, often in a different unit. Evolutionary Connections provide a framework for understanding how a topic in a given chapter relates to evolution, the core unifying theme in biology. A Note about Principles of Biology vv bro75121_fm_i-xxviii.indd 5 29/11/16 10:40 am • New BioTIPS: In Connect, the digital partner to this textbook, we have a new feature called BioTIPS, which is intended to help students refine problem-solving skills. Most of the BioTIPS are called out with icons in the textbook, but additional BioTIPS are included in the SmartBook. The BioTIPS themselves are accessed through links in SmartBook. BioTIPS will focus on 11 strategies that will help students solve problems: 1. Make a drawing. 2. Compare and contrast. 3. Relate structure and function. 4. Sort out the steps in a complicated process. 5. Propose a hypothesis. 6. Design an experiment. 7. Predict the outcome. 8. Interpret data. 9. Use statistics. 10. Make a calculation.  11. Search the literature. BioTIPS will provide students with practice at applying these problem-solving strategies. Overall, the pedagogy of Principles of Biology has been designed to foster student learning. Instead of being a collection of “facts and figures,” Principles of Biology is intended to be an engaging and motivating textbook in which formative assessment allows students to move ahead and learn the material in a productive way. Content Changes to the Second Edition The author team of Principles of Biology is fully committed to keeping the content up to date; the second edition has five new chapters that reflect modern trends in the field. They are intended to achieve three goals: • Prepare Students for Careers in Modern Biology: Chapters 11, 16, and 24 are concerned with the topics of Non-coding RNAs, Epigenetics, and Microbiomes, respectively. The emerging importance of these areas in the field of medicine is dramatic. It’s difficult to pick up a newspaper and not see a story that concerns at least one of these areas and its impact on human health. For example, researchers are now studying how the manipulation of certain non-coding RNAs may be used as therapeutic tools to treat diseases such as cancer. Similarly, these same topics have broad importance in the fields of agriculture, biotechnology, and environ- mental science. • An Emphasis on Systems Biology: The first edition of Principles of Biology already had an emphasis on sys- tems biology and trying to relate topics in biology to its evolutionary foundation. In the second edition, we have added a new chapter to the animal unit (Chapter 41) that explores how the whole body responds to a major challenge to homeostasis (hemorrhage). This allows students to appreciate how various organs and organ sys- tems work together as a larger integrated system—the animal body. • Impact on Society: Not only do we want to help our students learn biology and prepare them for careers in this field, we also want them to appreciate their roles as citizens of the world. Chapter 46 pulls together many of the key topics involving the impact of humans on the environment, thereby making students aware of current and future problems. This chapter may inspire some students to pursue a career in ecology or environmental science, and may encourage others to educate the public regarding the negative effects that humans have had on the environment and ways to evoke positive changes. To make room for this material and other updated material, some chapters have been streamlined and combined, and obsolete methods have given way to new techniques described in these new chapters. The major content changes that have occurred in the second edition are summarized below. Chapter 1 An Introduction to Biology. Has a new section on the adaptations that have occurred during the evolution of polar bears. Chapter 4 Evolutionary Origin of Cells and their General Features. This chapter now begins with a section on the evolutionary origin of cells. vvii A Note about Principles of Biology bro75121_fm_i-xxviii.indd 6 29/11/16 10:40 am NEW Chapter 11 The Expression of Genetic Information via Genes II: Non-coding RNAs. This “first of its kind chapter” recognizes the great importance of non-coding RNAs in biology and devotes an entire chapter to this topic. The author team feels it is long overdue. NEW Chapter 16 Transmission of Genetic Information from Parents to Offspring II: Epigenetics, Linkage, and Extranuclear Inheritance. Due to the rapidly expanding topic of epigenetics, the inheritance chapter in the first edition has been split into two chapters. Chapter 16, which is the second chapter devoted to inheritance, has four sections on epigenetics and also includes the topics of linkage and extranuclear inheritance. Chapter 18 Genetic Technologies: How Biologists Study Genes and Genomes. Has a new section on CRISPR-Cas technology, which is used to introduce mutations into genes. Chapter 19 Evolution of Life I: How Populations Change from Generation to Generation. The Evolution unit has been reorganized so that it now begins with a description of the basic mechanisms that underlie evolutionary change. Chapter 22 The History of Life on Earth and Human Evolution. The topic of human evolution has been moved from the Diversity unit to the Evolution unit. The description of human evolution has been greatly expanded, and has new topics including how humans are still evolving and the level of genetic variation in modern human populations. Chapter 23 Diversity of Microbial Life: Archaea, Bacteria, Protists, and Fungi. This chapter on the diversity of prokaryotic and eukaryotic microbial life has been heavily revised to integrate material previously covered in separate chapters. Newer concepts of phylogenetic diversification of these groups have been incorporated into evolutionary tree diagrams. This revision provides several pedagogical advantages. A focus on microbial diseases of humans and crops, a continuing thread through coverage of bacteria, and also protists and fungi, reveals greater pathogen diversity than students may previously have realized. The diversity of technological applications involving microbes, previously described in several separate places, has now been aggregated at the end of the chapter. Long important in terms of food or antibiotic production, microbial applications are now taking on new relevance to the fields of environmen- tal pollution control and renewable biofuels. Finally, by integrating fundamental aspects of four microbial groups, Chapter 23 now provides the broad diversity background necessary to comprehend microbiomes, a topic of vast medical, ecological, and technological importance that is presented in a new chapter. NEW Chapter 24 Microbiomes: Microbial Systems on and Around Us. This entirely new chapter integrates information about the occurrence of microbes (archaea, bacteria, protists, and fungi) within complex organism- gene systems known as microbiomes, a major frontier of biological sciences. The new chapter expands the much briefer and scattered introductions to symbiotic relationships between microbes, plants, and animals presented in the first edition. New Chapter 24 begins by linking basic information on microbial life provided in Chapter 23 with important environments in which microbiomes occur: physical environments such as oceans, ice, and soils, and biotic environments that include the bodies of humans and agricultural plants. The new chapter then focuses on genetic methods that microbiologists use to comprehend and compare Earth’s microbiomes. This helps students to review and extend basic genetics presented earlier in the text and understand important applications of genetic and genomic technologies. The new chapter also focuses on evolutionary and diversity aspects of microbiomes that are key to fostering agricultural production and human health, thereby connecting students to previous text chapters describing fundamental principles of evolutionary biology. Chapter 25 Plant Evolution and Diversity. New information about the evolutionary history of plants has been incorporated to maximize currency, without increasing complexity or level of detail. A new BioTIPS feature, which aims to foster student understanding of experimental design in the scientific process, has been developed for the popular Feature Investigation on Cannabis secondary metabolites, of high societal significance. Chapter 26 Invertebrates: The Vast Array of Animal Life Without a Backbone. Our animal classification as depicted in Figure 26.2 has been reworked and redrawn to reflect the position of the Ctenophora or comb jellies, as the earliest diverging animal clade. Additional photographs have also been added to Figure 26.12 to illustrate the polyp A Note about Principles of Biology vviiii bro75121_fm_i-xxviii.indd 7 29/11/16 10:40 am and medusa form of cnidarians. We have also included a new multi-part figure, Figure 26.32, to illustrate the different echinoderm classes. Chapter 27 Vertebrates: Fishes, Amphibians, Reptiles and Mammals. The material on primates and human evolution has been moved to Chapter 22, The History of Life on Earth and Human Evolution. Chapter 28 An Introduction to Flowering Plant Form and Function. A BioTIPS feature designed to help students interpret graphical quantitative information has been developed for the Feature Investigation, which focuses on leaf structural variation. Chapter 29 How Flowering Plants Sense and Interact with Their Environments. Some new images have been incorporated. Chapter 30 How Flowering Plants Obtain and Transport Nutrients. Some new images have been incorporated. Chapter 31 How Flowering Plants Reproduce and Develop. A new BioTIPS feature, based on the Feature Investigation about flower blooming, not only fosters student ability to interpret graphical quantitative information, but also leads them to make additional calculations to answer new questions about the topic. Chapter 32 General Features of Animal Bodies, and Homeostasis as a Defining Principle of Animal Biology. This chapter now includes a section entitled “Principles of Homeostasis of Internal Fluids,” which has been moved here from later in the Animal Unit where it was previously covered (former Chapter 38). New “Test Yourself” questions and several improved figures and new concept checks have been added. Chapter 33 Neuroscience I: The Structure, Function, and Evolution of Nervous Systems. New figures, including an electron micrograph of a cross section through a nerve, have been added, while several existing figures have been modified with additional labeling or text boxes to improve clarity. Numerous SCISKILLS features have been incorporated throughout the section-opening learning outcomes. Chapter 34 Neuroscience II: How Sensory Systems Allow Animals to Interact with the Environment. Numerous subheadings are now interspersed in the chapter to help the reader navigate through difficult passages and to help the instructor and student organize the readings. Numerous SCISKILLS have been incorporated throughout the section-opening learning outcomes, and new concept checks have been added. Throughout the chapter, material has been updated to reflect key new research, particularly with respect to olfaction and balance. Chapter 35 How Muscles and Skeletons are Adaptations for Movement, Support, and Protection. In addition to numerous SCISKILLS features, a new conceptual question has been added and several figures have been improved for even greater clarity. Chapter 36 Circulatory and Respiratory Systems: Transporting Solutes and Exchanging Gases. The former chapters on circulation and respiration (chapters 36 and 37) have now been merged into one cohesive chapter that covers both topics in a fully integrated way. As one example, a new table has been added that covers the relationship between an animal’s body mass and various respiratory parameters; this table now parallels a similar one that was present in the former Circulatory System chapter that described the relationship between body mass and circulatory features. As with other chapters, numerous SCISKILLS features, figure modifications, and assessments have added or updated. A new figure depicting human bronchioles in health and disease has also been added. Chapter 37 Digestive and Excretory Systems Help Maintain Nutrient, Water, and Energy Balance and Remove Waste Products from Animal Bodies. The former chapters on digestion and nutrition, and the excretory system, have now been integrated into one chapter. The combined focus is now on nutrient processing and energy balance and the elimination of soluble wastes. Numerous text boxes and figure labels have been adjusted in the artwork to enhance understanding. The advantages and disadvantages of generating a particular type of nitrogenous waste are vviiiiii A Note about Principles of Biology bro75121_fm_i-xxviii.indd 8 29/11/16 10:40 am now elaborated. SCISKILLS features have been added to all sections. Two new concept checks and Bioconnection features have been added. Chapter 38 How Endocrine Systems Influence the Activities of all Other Organ Systems. Several text boxes, labels and figure legends have been modified for additional detail to improve understanding. SCISKILLS features have been added to each section, and the text has been updated to reflect modern research in endocrinology. Chapter 39 The Production of Offspring: Reproduction and Development. The Impact on Public Health section has been reorganized with numerous subheadings for clarity. SCISKILLS have been added, as has a new Bioconnections question. Certain key figures have been updated or modified for clarity. Chapter 40 Immune Systems: How Animals Defend Against Pathogens and Other Dangers. The opening section is now reorganized with subheadings for clarity, and includes discussions of some important animal diseases. Additional new subheadings also break up complex text throughout the chapter. SCISKILLS and a new test question have been added, and key figures have been improved for clarity or detail, or updated (such as latest figures on the number of people living with HIV/AIDS as of today). NEW Chapter 41 Integrated Responses of Animal Organ Systems to a Challenge to Homeostasis. This new chapter integrates the functions of all organ systems found in animals, using a challenge to homeostasis (hemorrhage) as the central theme. It introduces ten new figures and a new table covering topics such as baroreceptors, chemoreceptors, Starling forces and many others, all in the context of an integrated response to a large homeostatic insult. Chapter 43: Population Growth and Species Interactions. Two new BioTIPS questions have been added to better familiarize students with mark-recapture analyses and competition and resource utilization. The material on human population growth has been moved to Chapter 46. There are three new conceptual and collaborative questions. Chapter 44: Communities and Ecosystems: Ecological Organization of Large Scales. Chapter 44 has been reworked to include a discussion of both community and ecosystem ecology together in the same chapter. We have combined chapters 45 and 46 from the first edition. However, the material on biogeochemical cycles has been moved to Chapter 46. Chapter 45: How Climate Affects the Distribution of Species on Earth. This chapter uses elements of Chapter 43: Ecology and the Physical Environment, from the first edition and expands on them. In the first section, 45.1, Climate, we show what causes global temperature and precipitation differentials across the Earth. In the next section, 45.2, Major Biomes, we describe and illustrate the major biomes on Earth. NEW Chapter 46: The Age of Humans. This is a new chapter. We begin by introducing the concept of a new geological era, the Anthropocene, and then discuss the effects of humans on natural systems. We start with an examination of human population growth, which continues in an upward trend. Next, we explain how humans are contributing to climate change via global warming. This is followed by section 46.3, Pollution and Human Influences on Biogeochemical Cycles. In this section we describe human influences on the carbon, water, phosphorous, and nitrogen cycles from the burning of fossil fuels, the use of chemical fertilizers and pesticides, and other factors. This can lead to biomagnification, as explained next in section 46.4. One of the biggest effects of humans is habitat destruction and in section 46.5 we detail the effects of deforestation and agriculture on wildlife loss. In section 46.6, Overexploitation, we discuss the effects of overhunting and overfishing on land mammals, whales, birds, fishes, and plants. Lastly, in section 46.7, Invasive Species, we consider the many and varied effects of deliberate and accidental plant and animal introductions on native wildlife via competition, predation and parasitism. Chapter 47: Biodiversity and Conservation Biology. We have updated Table 47.1, which provides details of the world’s ecosystem services. The material on causes of extinction and loss of biodiversity has been moved to chapter 46. However, section 47.3, Conservation Strategies, has been expanded to include new material and figures on crisis ecoregions and “last of the wild” in addition to megadiversity countries and biodiversity hot spots. A Note about Principles of Biology iixx bro75121_fm_i-xxviii.indd 9 29/11/16 10:40 am