We are proud to present the ninth edition of Concepts in Biology. The origin of this book is deeply rooted in our concern to provide a useful, interesting, and user-friendly text that will serve students who are sampling the field or beginning a program of study in the biological sciences.

We continue to believe that large, thick books intimidate students, particularly introductory-level students without significantly increasing the level of understanding of the students. In addition, larger books are more expensive, and their production expends more natural resources. The printing of our text on recycled paper reflects this philosophy.

Concepts in Biology is arranged in a traditional manner. It begins with a discussion of the meaning, purpose, and future of biology as a scientific endeavor. It then covers biological concepts as an expanding spiral of knowledge. Thus chemistry is followed by cell biology, cell division, genetics, ecology, evolution, anatomy and physiology, and the diversity and classification of living things.

As always, we greatly appreciate the suggestions of users of the text and reviewers of the current edition. We carefully considered their comments and responded by making appropriate changes.

The text material was significantly rewritten to ensure a flow of ideas that will best enable students to link information in a logical way. "For Your Information," "Experience This," and feature boxes ("How Science Works," "Outlooks," and the new "Check This Out") were revised to include topical information of interest to students.

The illustrations are a vital and integrated part of the text. They were carefully chosen to clarify textual material and provide new insights. Fully one-quarter of all the illustrations were revised. Captions were critically examined for accuracy and appropriateness.

Concepts in Biology, ninth edition, contains a number of features intended to actively involve students in the learning process. Each chapter contains these elements:

The following supplementary materials were developed to accompany Concepts in Biology, ninth edition:

The Instructor's Manual/Test-Item File provides a rationale for the use of each chapter as well as explanations about "Experience This" and an answer key for text questions.

Classroom Testing Software, a computerized test bank of the test items in the instructor's manual, is available in Windows and Macintosh formats.

A revised Student Study Guide, in a reformatted version, features an overview/outline as well as multiple-choice, fill-in-the-blank, and label/diagram/explain questions. Answers to the objective questions are provided in an appendix to allow for immediate feedback. The study guide is available through your college bookstore.

Seventy-five full-color transparencies are available free to adopters of Concepts in Biology. The transparencies are taken from the text and represent the important figures that merit extra visual review and discussion.

A new CD-ROM tutorial, the Essential Study Partner (ESP), is packaged free with the ninth edition of Concepts of Biology. This ESP tutorial contains high-quality 3-D animations, interactive study activities, illustrated overview of key concepts in the text, and supplementary quizzing and exams that the students will find extremely valuable. This is a study tool that your students must have, so they receive it free.

A text-specific web site is available with the ninth edition of Concepts in Biology. You can find our web site at http://auth.mhhe.com/biosci/genbio/enger/. It contains a wealth of information for students and instructors. These include readings, quizzes, web links, and other valuable study aids and instructional materials.

The Laboratory Manual features 29 carefully designed, class-tested exploratory investigations that may be used in the laboratory.

The Laboratory Resource Guide provides information on acquiring, organizing, and preparing laboratory equipment and supplies. The guide follows the arrangement of exercises in the laboratory manual, enabling instructors to efficiently select learning experiences most appropriate for their students. Estimates of the time required for students to complete individual laboratory experiences are also provided, along with answers to questions in the laboratory manual.

The second edition of this excellent workbook by Fred Drewes of Suffolk County Community College offers students helpful suggestions for meeting the considerable challenges of a science course. It offers tips on how to take notes, how to get the most out of laboratories, and how to overcome science anxiety. The book's unique design helps students develop critical thinking skills while facilitating careful note-taking. (ISBN 0-697-15905-1)

Life Science Living Lexicon CD-ROM

The CD-ROM A Life Science Living Lexicon by William N. Marchuk of Red Deer College, contains a comprehensive collection of life science terms, including definitions of their roots, prefixes, and suffixes as well as audio pronunciations and illustrations. The Lexicon is student-interactive, providing quizzing and note-taking capabilities. It contains 4,500 terms, which can be broken down for study into the following categories: anatomy and physiology, botany, cell and molecular biology, genetics, ecology and evolution, and zoology. (ISBN 0-697-37993-0)

The Life Science Animations 3-D videotape contains 42 high-quality 3-D animations. These animations bring visual movement to biological processes that are difficult to understand. The 42 animations also appear as part of the essential Study Partner CD-ROM, which provides the students with a wonderful reinforcement of concepts and biological processes. (ISBN 0-07-290652-9)

The Dynamic Human CD-ROM Version 2.0

This guide to anatomy and physiology interactively illustrates the complex relationships between anatomical structures and their functions in the human body. Realistic, 3-D visuals are the premier feature of this exciting learning tool. (ISBN 0-697-38935-9)

A large number of people have knowingly or unknowingly helped us write this text. Our families continued to give understanding and support as we worked on this revision. We acknowledge the thousands of students in our classes who have given us feedback over the years concerning the material and its relevancy. They were the best possible sources of criticism.

We gratefully acknowledge the invaluable assistance of the following reviewers throughout the development and preparation of the manuscript:

David Allard, Texarkana College; Rose Bast, SSND, PhD, Mount Mary College; Jerry Beilby, Northwestern College; Robert Bergard, Century College; Deborah Fahey, Wheaton College; Gary B. Hanson, PhD, Concordia University-Portland; Laura Hebert, Angelina College; Dr. Anne Marie Helmenstine, Tusculum College; William Hightower, Southside Virginia Community College; O. Ray Jordan, Tennessee Technological University; Gregory Kerr, Bluefield College; Katharine Lormand, Arapahoe Community College; Michael L. McMahan, Union University; Karen McReynolds, Bethany College; Dr. Bob Nash, Southern Wesleyan University; Jose Ramirez-Domenech, Xavier University of Lousiana; James R. Rastorfer, Professor of Botany, Chicago State University; Dr. Fred Schindler, Indian Hills Community College; James L. Shepherd, CET. MED, Muskingum Area Technical College; Linda Sigismondi, University of Rio Grande; Jerry Skinner, Keystone College; Bradley W. Smith, Sauk Valley Community College; Marc Allen Smith, Sinclair Community College; Deena K. Spielman, Cloud County Community College; Professor Jan Stevens, Wabash Valley College; Barbara L. Stewart, J. Sargeant Reynolds Community College; L. Duane Thurman, Oral Roberts University; Timothy Wood, Wright State University; Dr. Gordon Woods, Trinity Baptist College; Michael Craig, Central College

This text is designed to make understanding biological principles easier. Each chapter is subdivided into topics separated by headings. These headings are listed in the outline at the beginning of each chapter. The subdivisions contain logical chunks of material; they should make learning more manageable for you. The outline includes the major topics covered in the chapter and also the new terms introduced in the chapter.

As with most science classes, you are likely to find biological vocabulary a difficult hurdle. To help you approach this "foreign language," important terms are printed in boldface the first time they are used in the text. Each new term is defined at least three times: first, in the narrative when the term becomes a functional part of biological thought; second, in the chapter glossary at the end of the chapter in which it first appears; and third, in the comprehensive glossary at the end of the book. As you review a chapter, you should mentally define each of the new terms. If you are unsure of the meaning of a term, check yourself against the definition in the book. We have also provided a phonetic pronunciation guide for each glossary term so that you will learn to pronounce each term correctly as you discover its meaning.

Numerous illustrations appear throughout the text. These illustrations should do more than just attract your attention. Each has been carefully chosen to help you understand a point or tie a concept to something you already know. Use these illustrations and their captions to acquire and understand the ideas presented.

Each chapter ends with a summary. As you finish studying a chapter, read the summary, sentence by sentence. If you come across information that seems new, you may not have thoroughly studied part of the chapter.

Following the summary we have presented a thought-provoking situation entitled "Thinking Critically." It asks you to use your newfound knowledge and previous experience to consider a situation. Most often, there is no one right answer. You will be stimulated to think something through and to raise points for discussion.

The most valuable aspect of an introductory biology course is not the tidbits of factual information you gather, but the new ways in which you see yourself and your environment. The section entitled "Experience This" will help you apply basic biological concepts to real situations.

Immediately preceding the chapter glossary is a series of review questions and activities. You can use them to direct your attention as you study a chapter or as a review to check that you are well prepared for a test on the chapter material. The concept map is designed to help you relate ideas to one another in a logical way. Use the concept map activities to challenge yourself to see relationships and make connections among the terms presented.

The questions at the end of the chapter are designed to help you determine if you understand the content of the chapter. Most of the questions are conceptual in nature and do not require you to search for specific tiny bits of information in the text. You should be able to answer most of the questions after reading and studying the material in the chapter. All the questions are directly answered either in the chapter narrative or in the illustrations.