John H. Postlethwait Janet L. Hopson


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About the Authors

The legacy of Modern Biology extends from 1921, when the first edition was published under the title Biology for Beginners. The original author was Truman Moon, a high school teacher in Middletown, New York. Moon believed that a strong grounding in the basic concepts and vocabulary of biology was the best way to prepare students for college biology. Paul Mann, a science teacher in New York City, shared Moon's passion for teaching biology and later became a coauthor.

In the mid-1940s, James Otto, a biology teacher from George Washington High School in Indianapolis, took over authorship of the book, which by then was titled Modern Biology. Otto added another hallmark to the program—an emphasis on the latest developments in biology at a level appropriate for young learners. In 1958, Dr. Albert Towle, a professor of biology at San Francisco State University, was added to the program as a coauthor. After the death of Otto in 1972, Towle remained the primary author until he completed the 2002 edition after which he passed away.

Now, to continue the legacy of more than eight decades of exceptional authorship, Modern Biology adds two more distinguished authors: John Postlethwait and Janet Hopson.

John H. Postlethwait

John Postlethwait received his Ph.D. in developmental genetics from Case Western Reserve University and completed his postdoctoral fellowship in genetics at Harvard University. During a teaching career that has spanned more than 30 years, he has received several research awards and the Ersted Distinguished Teaching Award. Dr. Postlethwait now teaches general biology, embryology, and genetics at the University of Oregon and, is the coauthor of several college-level textbooks.

Janet L. Hopson

Jan Hopson received her B.A. in biology from Southern Illinois University and her M.A. in science writing from the University of Missouri. Ms. Hopson has taught science writing at two campuses of the University of California and has authored and coauthored several collegelevel biology textbooks and popular science books. She won the Russell L. Cecil Award for magazine writing. Ms. Hopson's news and feature articles have appeared in publications such as Science News, Smithsonian, Newsweek, Psychology Today, and Science Digest.

On the cover: The white-faced owl is found in most regions of Africa south of the Sahara. Recent DNA research suggests that the owl differs significantly from members of the genus Otus, to which it was once assigned. As a result, taxonomists have reclassified this owl into two species: the Southern white-faced owl— Ptilopsis granti and the Northern white-faced owl—Ptilopsis leucotis.

Copyright © 2006 by Holt, Rinehart and Winston

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HOLT, MODERN BIOLOGY and the "Owl Design" are trademarks licensed to Holt, Rinehart and Winston, registered in the United States of America and/or other jurisdictions.

SCIENTIFIC AMERICAN and the Scientific American logo are trademarks of Scientific American, Inc.

SCILINKS is a registered trademark owned and provided by the National Science Teachers Association. All rights reserved. Printed in the United States of America


Contributing Writers

Barbara Christopher

Science Writer Austin, Texas

Freelance Science Editor and Writer Columbus, Ohio

Epidemiologist Department of State Health

Services Austin, Texas

Charlotte W. Luongo, MSc

Science Writer Austin, Texas

Annette Ratliff

Science Writer and Assessment

Specialist Austin, Texas

Linda B. Thornhill, M.S.

Science Writer Columbus, Ohio

Inclusion Specialist

Joan Altobelli

Special Education Director Austin Independent School District Austin, Texas

Teacher Edition Development

Freelance Science Editor and Writer Columbus, Ohio

Alan Eagy

Biology Teacher Columbia Gorge High School The Dalles, Oregon

Charlotte W. Luongo, MSc

Science Writer Austin, Texas

Annette Ratliff

Science Writer and Assessment

Specialist Austin, Texas

Linda B. Thornhill, M.S.

Science Writer Columbus, Ohio

Biology Field Testers

Adam Ashby

Biology Teacher Cactus High School Glendale, Arizona

Collette E. Baughman


Wichita Heights High School Wichita, Kansas

Jessica Bolson

Washington Irving High School Brooklyn, New York

Aruna Chopra

Biology Teacher

Benjamin Franklin High School

Philadelphia, Pennsylvania

Dora Coleman

Department Chair

G. W. Carver High School

Memphis, Tennessee

Christy C. Collins

Science Department Chair Charles B. Aycock High School Pikeville, North Carolina

Beau Gee

Biology Teacher Waccamaw High School Pawleys Island, South Carolina

Bissoon Jarawar


William H. Taft High School Bronx, New York

Mary E. Kelley


Bethel High School Hampton, Virginia

Chris Mante


Science Department Parma Senior High School Parma Ohio

Diane McKinney

Biology Teacher Cloudland High School Roan Mountain, Tennessee

Dr. L. Eugene Morton


South Stanly High School Norwood, North Carolina

Babtunde Oronti


Olney High School Philadelphia, Pennsylvania

Gail Porter


Chipley High School Chipley, Florida

Terry Smith


Bradford County High School Starke, Florida

Biology Field Testers


Mike Trimble


Corona Del Sol High School Tempe, Arizona

Barry Tucker


Colerain High School Cincinnati, Ohio

Lois G. Walsh


A.D. Harris High School Panama City, Florida

Janet F. Washington


Hunters Lane High School Nashville, Tennessee

Jacqueline M. Wilson


Sidney Lanier High School Montgomery, Alabama

Patricia E. Wrocklage


Hayden High School Topeka, Kansas

Academic Reviewers

Renato J. Aguilera, Ph.D. Professor and Director of the

Graduate Program in Biology University of Texas at El Paso El Paso, Texas

David M. Armstrong


Ecology and Evolutionary Biology University of Colorado Boulder, Colorado

Nigel Atkinson, Ph.D.

Associate Professor of Neurobiology Section of Neurobiology University of Texas at Austin Austin, Texas

Jerry Baskin

Professor of Biology Biology Department University of Kentucky Lexington, Kentucky

Life Science Consultant Austin, Texas

Professor of Cellular Biology Cellular Biology Department University of Georgia Athens, Georgia


Biology Department Wake Forest University Winston-Salem, North Carolina

James Denbow, Ph.D.

Associate Professor Department of Anthropology University of Texas at Austin Austin, Texas

Epidemiologist Department of State Health

Services Austin, Texas

Herbert Grossman, Ph.D.

Associate Professor of Botany and

Biology (retired) Biology

Pennsylvania State University University Park, Pennsylvania

William B. Guggino, Ph.D.

Professor of Physiology and

Pediatrics Physiology Department Johns Hopkins University School of Medicine Baltimore, Maryland

David Haig

Professor of Biology Organismic and Evolutionary

Biology Harvard University Cambridge, Massachusetts

Professor of Biology Department of Biology Millersville University Millersville, Pennsylvania

Associate Professor of Biology Biological Sciences Sam Houston State University Huntsville, Texas

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