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CliffsAP
Biology

3RD EDITION

by Phillip E. Pack

CliffsAP
Biology

3RD EDITION

by Phillip E. Pack

About the Author Phillip E. Pack taught AP Biology for eleven years. He is currently Professor of Biology at Woodbury University in Burbank, California. He teaches courses in biology, human biology, botany, field botany, environmental studies, and evolution, and co-teaches various interdisciplinary courses, including energy and society (with architecture faculty) and natural history of California and nature writing (with English faculty). Author??™s Acknowledgments To Mary and Megan
CliffsAP?® Biology, 3rd Edition Published by: Wiley Publishing, Inc. 111 River Street Hoboken, NJ 07030-5774 www.wiley.com Copyright ?© 2007 Phillip E. Pack Published by Wiley, Hoboken, NJ Published simultaneously in Canada Library of Congress Cataloging-in-Publication Data

Publisher??™s Acknowledgments Editorial Project Editor: Kelly Dobbs Henthorne Acquisitions Editor: Greg Tubach Composition Proofreader: Jennifer Stanley Wiley Publishing, Inc. Composition Services

Note: If you purchased this book without a cover, you should be aware that this book is stolen property. It was reported as ???unsold and destroyed??? to the publisher, and neither the author nor the publisher has received any payment for this ???stripped book.???

Pack, Phillip E. CliffsAP biology / by Phillip E. Pack. ??” 3rd ed. p. cm. ISBN-13: 978-0-470-09764-9 (pbk.) ISBN-10: 0-470-09764-7 1. Biology??”Examinations??”Study guides. 2. Universities and colleges??”United States??”Entrance examinations??”Study guides. 3. Advanced placement programs (Education)??”Study guides. I. Title. II. Title: Cliffs AP biology. III. Title: Cliffs advanced placement biology. IV. Title: Advanced placement biology. QH316.P34 2007 570.76??”dc22 2007015552 ISBN: 978-0-470-09764-9 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400, fax 978-646-8600, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Legal Department, Wiley Publishing, Inc., 10475 Crosspoint Blvd., Indianapolis, IN 46256, 317-572-3447, fax 317-572-4355, or online at http://www.wiley.com/go/permissions. THE PUBLISHER AND THE AUTHOR MAKE NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS WORK AND SPECIFICALLY DISCLAIM ALL WARRANTIES, INCLUDING WITHOUT LIMITATION WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE. NO WARRANTY MAY BE CREATED OR EXTENDED BY SALES OR PROMOTIONAL MATERIALS. THE ADVICE AND STRATEGIES CONTAINED HEREIN MAY NOT BE SUITABLE FOR EVERY SITUATION. THIS WORK IS SOLD WITH THE UNDERSTANDING THAT THE PUBLISHER IS NOT ENGAGED IN RENDERING LEGAL, ACCOUNTING, OR OTHER PROFESSIONAL SERVICES. IF PROFESSIONAL ASSISTANCE IS REQUIRED, THE SERVICES OF A COMPETENT PROFESSIONAL PERSON SHOULD BE SOUGHT. NEITHER THE PUBLISHER NOR THE AUTHOR SHALL BE LIABLE FOR DAMAGES ARISING HEREFROM. THE FACT THAT AN ORGANIZATION OR WEBSITE IS REFERRED TO IN THIS WORK AS A CITATION AND/OR A POTENTIAL SOURCE OF FURTHER INFORMATION DOES NOT MEAN THAT THE AUTHOR OR THE PUBLISHER ENDORSES THE INFORMATION THE ORGANIZATION OR WEBSITE MAY PROVIDE OR RECOMMENDATIONS IT MAY MAKE. FURTHER, READERS SHOULD BE AWARE THAT INTERNET WEBSITES LISTED IN THIS WORK MAY HAVE CHANGED OR DISAPPEARED BETWEEN WHEN THIS WORK WAS WRITTEN AND WHEN IT IS READ. Trademarks: Wiley, the Wiley Publishing logo, CliffsNotes, the CliffsNotes logo, Cliffs, CliffsAP, CliffsComplete, CliffsQuickReview, CliffsStudySolver, CliffsTestPrep, CliffsNote-a-Day, cliffsnotes.com, and all related trademarks, logos, and trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc. and/or its affiliates. AP is a registered trademark of the College Board, which was not involved in the production of, and does not endorse, this product. All other trademarks are the property of their respective owners. Wiley Publishing, Inc. is not associated with any product or vendor mentioned in this book. For general information on our other products and services or to obtain technical support please contact our Customer Care Department within the U.S. at 800-762-2974, outside the U.S. at 317-572-3993 or fax 317-572-4002. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. For more information about Wiley products, please visit our web site at www.wiley.com.

Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
How You Should Use This Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 What to Bring to the Exam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Exam Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Exam Grading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 What??™s on the Exam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Hints for Taking the Multiple-Choice Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Hints for Taking the Essay Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Must-Know Essay Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Some Final Suggestions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

PART I: SUBJECT AREA REVIEWS WITH SAMPLE QUESTIONS AND ANSWERS
Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Atoms, Molecules, Ions, and Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Properties of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Organic Molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Carbohydrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Lipids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Nucleic Acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Chemical Reactions in Metabolic Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Structure and Function of the Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Prokaryotes and Eukaryotes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Movement of Substances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Cellular Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Glycolysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 The Krebs Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Oxidative Phosphorylation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 How Many ATP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Mitochondria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Chemiosmosis in Mitochondria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Two Types of Phosphorylation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Anaerobic Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Alcohol Fermentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Lactic Acid Fermentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Noncyclic Photophosphorylation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Cyclic Photophosphorylation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Calvin Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 Chloroplasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Chemiosmosis in Chloroplasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

CliffsAP Biology, 3rd Edition

Photorespiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 C4 Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 CAM Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Cell Division . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Mitosis and Cytokinesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Meiosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Mitosis versus Meiosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Genetic Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Regulation of the Cell Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

Heredity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Complete Dominance, Monohybrid Cross . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 Complete Dominance, Dihybrid Cross . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Test Crosses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 Incomplete Dominance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 Codominance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 Multiple Alleles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 Epistasis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Pleiotropy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Polygenic Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Linked Genes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Sex-Linked Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 X-Inactivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 Nondisjunction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 Human Genetic Defects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Molecular Genetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 DNA Replication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Replication of Telomeres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Protein Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Transcription . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 mRNA Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Translation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 Mutations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 DNA Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 The Molecular Genetics of Viruses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 The Molecular Genetics of Bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 Regulation of Gene Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 Recombinant DNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 Evidence for Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 Natural Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 Sources of Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 Causes of Changes in Allele Frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 Genetic Equilibrium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 Speciation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Maintaining Reproductive Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Patterns of Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Macroevolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

iv

Table of Contents

The Origin of Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

Biological Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 Domain Archaea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 Domain Bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 Domain Eukarya . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 Kingdom Protista . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 Kingdom Fungi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Kingdom Plantae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154 Kingdom Animalia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 Plant Tissues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 The Seed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 Germination and Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 Primary Growth Versus Secondary Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Primary Structure of Roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Primary Structure of Stems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 Secondary Structure of Stems and Roots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 Structure of the Leaf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 Transport of Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 Control of Stomata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 Transport of Sugars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 Plant Hormones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 Plant Responses to Stimuli . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 Photoperiodism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

Animal Form and Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 Thermoregulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 The Respiratory System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186 The Circulatory System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 The Excretory System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 The Digestive System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192 The Nervous System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 The Muscular System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 The Immune System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 The Endocrine System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

Animal Reproduction and Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Characteristics That Distinguish the Sexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Human Reproductive Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Gametogenesis in Humans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 Hormonal Control of Human Reproduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 Embryonic Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214 Factors That Influence Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

Animal Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 Genetic Basis of Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 Kinds of Animal Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

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CliffsAP Biology, 3rd Edition

Animal Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 Communication in Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 Foraging Behaviors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 Social Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

Ecology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 Population Ecology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 Human Population Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Community Ecology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Coevolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241 Ecological Succession . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 Biogeochemical Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 Biomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 Human Impact on the Biosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

PART II: LABORATORY REVIEW
Laboratory Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 Graphing Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 Designing an Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258 Laboratory 1: Diffusion and Osmosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 Laboratory 2: Enzyme Catalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 Laboratory 3: Mitosis and Meiosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 Laboratory 4: Plant Pigments and Photosynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 Laboratory 5: Cell Respiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264 Laboratory 6: Molecular Biology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 Laboratory 7: Genetics of Drosophila . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Laboratory 8: Population Genetics and Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 Laboratory 9: Transpiration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 Laboratory 10: Physiology of the Circulatory System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 Laboratory 11: Animal Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 Laboratory 12: Dissolved Oxygen and Aquatic Primary Productivity . . . . . . . . . . . . . . . . . 274 Sample Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

PART III: AP BIOLOGY PRACTICE TESTS
Practice Test 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
Section I (Multiple-Choice Questions) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 Section II (Free-Response Questions) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 Answer Key for Practice Test 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 Scoring Your Practice Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 Answers and Explanations for Practice Test 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310

Practice Test 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
Section I (Multiple-Choice Questions) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323 Section II (Free-Response Questions) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337 Answer Key for Practice Test 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340 Scoring Your Practice Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Answers and Explanations for Practice Test 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342

vi

Introduction
How You Should Use This Book
The Advanced Placement Program is designed to encourage students to take challenging courses in high school and receive college credit for their efforts. Many high schools offer classes especially designed for the AP program, but any course or program of study, whatever it is called, is appropriate as preparation for taking the AP exam if the content is college level. This book helps you to prepare for the Advanced Placement Examination in Biology. It does this in three ways:

First, it reviews the important material that you need to know for the actual AP exam. These reviews are detailed but written in an organized and condensed format, making them especially useful for studying. Second, after each section review, the book provides you with questions that reinforce the review. These questions are typical of AP exam questions, and many of them, like those on the AP exam, require considerable thought to determine the correct answer. In addition, some of the review questions ask you to apply the reviewed material to new situations and, as a result, increase your breadth of understanding. Answers with complete explanations are provided. Third, two complete practice tests are provided, giving you the opportunity to evaluate your knowledge and your test-taking skills. Taking these practice tests helps to improve your AP exam score because these tests are similar in content and format to the actual AP exam. Complete explanations are given for each question, and a scoring worksheet is provided to help you determine your score.

For more test-taking practice, a companion book by the author of this book is available. CliffsAP: 5 Biology Practice Exams provides five additional practice exams, complete with answers and explanations. The 500 multiple-choice questions and 20 essay questions in the companion book and the more than 650 multiple-choice questions and 75 essay questions in this book are unique; little overlap of content exists among the questions. The entire range of potential AP exam content is thoroughly covered. When preparing for a test, have you ever wished that you had a copy of your teacher??™s lecture notes The review sections in this book are very much like lecture notes. Each section contains all the important terminology with brief descriptions. All the important biological processes are outlined with a key word or phrase, listed in an easy-to-remember sequence. After each key word or phrase, a short explanation is given. When you study the material the first time, you can read the key words and the short explanations. When you review, you can just study the key words, rereading the explanations only as needed. You should consider this book, however, as a supplement to your textbook, your laboratory exercises, and your teacher??™s lectures. Much of the excitement and adventure of biology can be obtained only through hands-on activities and discussions with teachers. In addition, textbooks provide background information, extensive examples, and thought-provoking questions that add depth to your study of biology. Each time you study a topic in class, after listening to the lectures and reading the textbook, use this book to review. Underline or highlight material to help you remember it. Write in the margins any additional material that you heard in lectures or read in your textbook that you or your teacher thinks is important. Then answer the questions and read the answers at the end of each section. This will reinforce your learning. At the end of your biology course, this book will be a single, condensed source of material to review before the AP exam. Begin your final preparation several weeks before the AP exam by reviewing the material in each section. Then take the two practice AP exams at the end of the book.

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Introduction

What to Bring to the Exam
1. A No. 2 pencil and an eraser are required for the multiple-choice section. 2. A pen with black or dark-blue ink is required for the free-response (essay) section. 3. You are not allowed to bring your own scratch paper. For the multiple-choice section, you can use the margins of the test. For the free-response section, scratch paper is provided. 4. No calculators are allowed. Any calculations that might be required to answer a question will be basic enough to complete without a calculator. If while answering a question you find that you need a calculator to complete a calculation, you are probably doing the calculation incorrectly.

Exam Format
The AP exam in biology consists of two parts. The first part is a 100-question, multiple-choice test. You have 80 minutes to complete this section. The second part of the exam consists of four free-response, or essay, questions. First, you are given a 10-minute reading period to read the four questions, organize your thoughts, and record notes or create an outline on provided paper. Then you have 90 minutes to write your essay response to all four questions. The multiplechoice section counts for 60 percent of the exam, and the essay section counts for the remaining 40 percent. The exam is administered in May of each year along with AP exams in other subjects. Section I Section II Multiple Choice Reading Period Writing Period 4 questions 100 questions 80 minutes 10 minutes 90 minutes 40% 60%

Exam Grading
Exams are graded on a scale of 1 to 5, with 5 being best. Most colleges accept a score of 3 or better as a passing score. If you receive a passing score, colleges give you college credit (applied toward your bachelor??™s degree), advanced placement (you can skip the college??™s introductory course in biology and take an advanced course), or both. You should check with the biology department at the colleges you??™re interested in to determine how they award credit for the exam. The distribution of student scores for some recent AP exams in biology is as follows.
Percentage of Students Exam Grade Extremely well qualified Well qualified Qualified Possibly qualified No recommendation Mean Score (1 to 5) 5 4 3 2 1 2004 18.9 20.2 21.9 24.6 14.4 3.05 2005 18.2 20.1 22.9 23.3 15.5 3.02 2006 19.6 20.3 21.2 23.3 15.6 3.05

The multiple-choice section is designed with a balance of easy and difficult questions to produce a mean score of 50 out of 100 (on one recent test, the actual mean was 55 percent). Essay questions are also designed to obtain a 50 percent mean score, but scores vary significantly with individual questions and from year to year. On the 2005 exam, mean

2

Introduction

scores for an essay question ranged from 2.78 to 4.88 (out of a possible 10 points) for the four questions. Clearly, both sections of the exam are difficult. They are deliberately written that way so that the full range of students??™ abilities can be measured. In spite of the exam difficulty, however, 61 percent of the students taking the exam in 2006 received a score of 3 or better. Therefore, the AP exam is difficult, but most (prepared) students do well.

What??™s on the Exam
The multiple-choice section of an AP exam is written with a certain number of questions from each area in biology. Generally, each of the major topics is represented by the percentages given in the following table. These same percentages were used to choose the questions for the two exams in this book. Since 100 questions are on the exam, a topic with a 7 percent representation, such as chemistry, is addressed in 7 questions. However, many questions address topics in more than one area, so the number of questions per topic may be higher than indicated here.
Area I. Molecules and Cells Topic 1: Topic 2: Topic 3: Topic 4: Topic 5: Area II. Chemistry Cells Photosynthesis Respiration Cell Division 25% 7% 6% 4% 4% 4% 25% 8% 9% 8% 50% 8% 12% 10% 6% 4% 10%

Genetics and Evolution Topic 6: Topic 7: Topic 8: Heredity Molecular Genetics Evolution

Area III.

Organisms and Populations Topic 9: Five-Kingdom Survey

Topic 10: Plants Topic 11: Animal Structure and Function Topic 12: Animal Reproduction and Development Topic 13: Animal Behavior Topic 14: Ecology

In order to make your review as easy as possible, the sections in this book are organized in the same order used in most college textbooks. For this reason, the percentages given in the table differ somewhat from those given in the official AP Course Description in Biology (called the ???Acorn Book??? for its acorn logo), because its content outline is organized differently. Laboratory experience contributes a very important component to the AP biology course. So that all students taking the AP exam have appropriate laboratory preparation, the College Board provides a laboratory manual with 12 laboratory exercises. The exercises accompanying these labs provide valuable skills in experimental design and collecting and analyzing data. About 10 percent of the multiple-choice questions and usually one essay question are devoted to evaluating your laboratory knowledge. To help you review for the AP exam, Part II in this book reviews all twelve of the AP laboratory exercises.

3

Introduction

Hints for Taking the Multiple-Choice Section
In the AP exam, questions for the multiple-choice section are provided in a booklet. While reading the questions in the booklet, feel free to cross out answers you know are wrong or underline important words. After you??™ve selected the answer from the various choices, you carefully fill bubbles, labeled A, B, C, D, or E, on an answer sheet. Mark only your answers on the answer sheet. Since unnecessary marks can produce machine-scoring errors, be sure to fill the bubbles carefully and erase errors and stray marks thoroughly. Some specific strategies for answering the multiple-choice questions follow. 1. Don??™t let easy questions mislead you. The multiple-choice questions range from easy to difficult. On one exam, 92 percent of the candidates got the easiest question right, but only 23 percent got the hardest question right. Don??™t let the easy questions mislead you. If you come across what you think is an easy question, it probably is. Don??™t suspect that it??™s a trick question. 2. Budget your time by skipping hard questions. You have 80 minutes to answer 100 questions, 48 seconds per question. If you come across a hard question that you can??™t answer quickly, skip it, and mark the question to remind you to return to it if time permits. If you can eliminate some of the answer choices, mark those also so that you can save time when you return. It??™s important to skip a difficult question, even if you think you can eventually figure it out, because for each difficult question you spend three minutes on, you could have answered three easy questions. If you have time at the end of the test, you can always go back. If you don??™t have time, at least you will have had the opportunity to try all the questions. Also, if you never finish the test, don??™t be overly concerned. Since the test is designed to obtain a mean score of 50 percent, it is not unusual for a student to leave some answers blank. 3. Make only educated guesses. If you??™re not sure of the answer to a question, don??™t guess unless you can make an educated guess. You make an educated guess when you can reduce the answer to two or three choices. If you get an answer right, you receive one point. If you leave it blank, you receive no points. However, for each wrong answer, 1?4 point is deducted from your score. 4. Avoid wrong-answer penalties. One-fourth point is deducted for each wrong answer. The one-fourth point deduction for wrong answers adjusts for random guessing. Since each question has five choices, you have a one-in-five chance that you can randomly select the correct answer. If you choose five answers randomly for five questions, probability predicts that you will guess one correct answer and four wrong answers. Your total score for the five guesses would be 1 ??“ 1?4 ??“ 1?4 ??“ 1?4 ??“ 1?4 = 0. By deducting one-fourth point for each of the wrong answers, your total score would be zero. That??™s reasonable because you really didn??™t know any of the answers. But if you can reduce your choices to two or three, the odds are in your favor that the number of questions you get right will exceed the number of points deducted. That??™s also reasonable, because you knew some of the answer choices were wrong. 5. Carefully answer reverse multiple-choice questions. In a typical multiple-choice question, you need to select the choice that is true. On the AP exam, you will find many reverse multiple-choice questions where you need to select the false choice. These questions usually use the word ???EXCEPT??? in sentences such as ???All of the following are true EXCEPT . . .??? or ???All of the following occur EXCEPT. . . .??? A reverse multiple-choice question is more difficult to answer than regular multiple-choice questions because it requires you to know four true pieces of information about a topic before you can eliminate the false choice. It is equivalent to correctly answering five true-false questions correctly to get one point; if you get one of the five wrong, you get them all wrong. Reverse multiple-choice questions are also difficult because halfway through the question, you can forget that you??™re looking for the false choice. To avoid confusion, do the following: After reading the opening part of the question, read each choice and mark a T or an F next to each one to identify whether it is true or false. If you??™re able to mark a T or an F for each one, then the correct answer is the choice marked with an F. Sometimes you won??™t be sure about one or more choices, or sometimes you??™ll have two choices marked F. In these cases, you can concentrate on the uncertain choices until you can make a decision.

Hints for Taking the Essay Section
Four questions are on the essay section of the test. One of the questions is taken from Area I (molecules and cells), one from Area II (genetics and evolution), and two from Area III (organisms and populations). One of the four questions also evaluates your ability to design experiments or to analyze experimental results. Each of the four questions can earn a maximum of 10 points. The 40 points on this section of the exam count as 40 percent of your total test score.

4

Introduction

The essay questions are provided in a green (or lavender) booklet. During the 10-minute reading period, read the questions thoroughly, circling key words. Next, write a brief outline using key words to organize your thoughts. When the writing period begins, begin writing your answer on the answer sheets that are provided separately. If for some reason you don??™t write an outline, go back and reread the question halfway through writing your answer. Make sure that you??™re still answering the question. It??™s easy to get carried away, and by the end of your response, you might be answering a different question. Strategies for answering the essay questions follow. 1. Don??™t approach the essay section with apprehension. Most students approach the essay section of the exam with more anxiety than they have when approaching the multiple-choice section. However, in terms of the amount of detail in the knowledge required, the essay section is easier. On essay questions, you get to choose what to write. You can get an excellent score without writing every relevant piece of information. Besides, you don??™t have time to write an entire book on the subject. A general answer that addresses the question with a limited number of specifics will get a good score. Additional details may (or may not) improve your score, but the basic principles are the most important elements for a good score. In contrast, a multiple-choice question focuses on a very narrow and specific body of knowledge, which you??™ll either know or you won??™t. The question doesn??™t let you select from a range of correct information. This isn??™t true for the essay questions. 2. Give specific information in your answer. You need to give specific information for each essay question. Don??™t be so general that you don??™t really say anything. Give more than just terminology with definitions. You need to use the terminology to explain biological processes. The combination of using the proper terminology and explaining processes will convince an AP exam reader that you understand the answer. Give some detail when you know it??”names of processes, names of structures, names of molecules??”and then tell how they??™re related. The reader is looking for specific information. If you say it, you get the points. You don??™t have to say everything, however, to get the maximum 10 points. 3. Answer each part of an essay question separately. Many of the AP essay questions ask several related questions. A single question, for example, might have two or three parts, each requesting specific information. You should answer each part of the question in a separate paragraph, which helps the reader recognize each part of your answer. Some questions are formally divided into parts, such as a, b, c, and d. Again, answer these questions separately, in paragraphs labeled a, b, c, and d. 4. Answer all parts of an essay question. When you answer the essay questions, it is extremely important that you give a response for each part of the question. Don??™t overload the detail on one part at the expense of saying nothing in another part because you ran out of time. Each part of the question is apportioned a specific number of points. If you give abundant information on one part, and nothing on the remaining parts, you receive only the maximum number of points allotted to the part you completed. In a four-part question, that??™s often only 2.5 points. You won??™t get any extra points above the maximum 2.5, even if what you write is Nobel-Prize quality. 5. Budget your time. You have 90 minutes for four questions, about 23 minutes each. Just as it??™s most important to answer all parts of a question, it??™s best to respond to all the essay questions rather than to answer two or even three of them extremely well, with no response on the last one or two. You??™ll probably know something about every question, so be sure you get that information written for each question. If you reach the last question with five minutes remaining, for example, use that time to write as much information as possible. One or two points is a lot better than zero. 6. Don??™t worry if you make a factual error. What if you write something that is incorrect The AP exam readers look for correct information. They search for key words and phrases and award points when they find them. If you use the wrong word to describe a process, or identify a structure with the wrong name, no formal penalty is assessed (unlike the deduction for guessing on the multiple-choice test). If you??™re going to get any points, however, you need to write correct information. 7. Don??™t be overly concerned about grammar, spelling, punctuation, or penmanship. The AP exam readers don??™t penalize for incorrect grammar, spelling, or punctuation or for poor penmanship. They are interested in content. However, if your grammar, spelling, or penmanship impairs your ability to communicate, then the readers cannot recognize the content, and your score will suffer. 8. Don??™t write a standard essay. Don??™t spend your time writing a standard essay with introduction, support paragraphs, and conclusion. Just dive right into your outline and answer the question directly. On the other hand, your essay response cannot be an outline; it must have complete sentences written in paragraph form.

5

Introduction

9. Drawings can improve your score. Drawings and diagrams may sometimes add as much as 1 point to your essay score. But the drawings must be explained in your essay, and the drawings must be labeled with supporting information. If not, the AP exam reader will consider them doodles, and you will get no additional points. 10. Pay attention to direction words. A direction word is the first word in an essay question that tells you how to answer the question. The direction word tells you what you need to say about the subject matter that follows. Here are the most common direction words found on the AP exam: ??? Discuss means to consider or examine various aspects of a subject or problem. ??? Describe means to characterize or give an account in words. ??? Define means to give a precise meaning for a word or phrase. ??? Explain means to clarify or make understandable. ??? Compare means to discuss two or more items with an emphasis on their similarities. ??? Contrast means to discuss two or more items with an emphasis on their differences. Specialized direction words are used for the laboratory essays. These words include design (an experiment), calculate (a value), and construct and label (a graph). These words have specific meanings for laboratory analyses and are discussed in the lab section later in this book.

Must-Know Essay Questions
Some AP Biology teachers try to predict which essay questions will be on the next AP test. For example, reviewing old AP exams might reveal some questions that haven??™t been asked in a while. A new scientific discovery or research that receives a Nobel Prize might suggest an AP question. Unfortunately, guessing questions in this way is very unreliable. Here is a better way. Questions on the essay section of the AP exam generally address fundamental principles or processes in biology. Here is a list of the most important principles??”the ones on which questions keep reappearing on AP exams. Being able to answer these questions is an absolute requirement for being prepared. So, at the very least, know this material. Sample responses to questions on these topics appear at the end of the appropriate subject area reviews and in the answer sections following each practice exam. Additional responses appear at the end of each practice exam in CliffsAP: 5 Biology Practice Exams, also published by Wiley. 1. Topic 2: Cells: Cell structure, especially structure and function of the plasma membrane 2. Topic 3: Respiration: Respiration and mitochondria 3. Topic 4: Photosynthesis: Photosynthesis and chloroplasts 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. Topic 5: Cell Division: Mitosis and meiosis Topic 7: Molecular Genetics: DNA structure and replication Topic 7: Molecular Genetics: Protein synthesis Topic 8: Evolution: Natural selection Topic 8: Evolution: Speciation Topic 10: Plants: Reproduction in flowering plants Topic 10: Plants: Plant tropisms and hormones (especially auxin) Topic 11: Animal Structure and Function: Nerve transmission Topic 11: Animal Structure and Function: Muscle contraction Topic 12: Animal Reproduction and Development: Menstrual cycle Topic 14: Ecology: Succession Topic 14: Ecology: Biogeochemical cycles

There??™s no guarantee that questions on these topics will appear on your AP exam, but these topics appear so often that you should be prepared. In any case, the multiple-choice section of the exam will certainly include questions on these topics. So you can??™t lose by focusing on these areas.

6

Introduction

Some Final Suggestions
For each of the practice tests, a scoring template is provided for the multiple-choice questions of the exam. The test is followed by an answer key for the multiple-choice questions, explanations for the multiple-choice questions, and scoring standards for the free-response questions (often called a rubric). To get the full benefit of simulating a real AP exam, set aside at least three hours for each exam. Begin the multiplechoice section and after 80 minutes, stop and move on to the essay section. Spend 10 minutes outlining your answers to each essay question and then allow yourself 90 minutes to write out your full answers. By using the actual times that the real AP exam allows, you will learn whether the time you spend on each multiple-choice and each essay question is appropriate. When you??™re done taking a practice exam, score your exam using the multiple-choice answers that follow the exam and the free-response scoring standards that follow the multiple-choice answer explanations. Then go back and answer any multiple-choice questions that you were unable to complete in the allotted 80 minutes. When you are done, read all the multiple-choice explanations, even those for questions you got right. The explanations are thorough and provide you with information and suggestions. Even if you know the answers, reviewing the provided explanations is good review. Although you??™ve heard it so many times, practice will improve your test performance (although it??™s unlikely to make you perfect). So be sure to complete both tests and review all the answers. Good luck.

7

PART I

S U BJ E CT AR EA R EVI EWS W ITH SAM PLE Q U E STI O N S AN D AN SW E R S

Chemistry
Review
A major difference between an AP biology course and a regular high school biology course is the emphasis on detail. In many cases, that detail derives from a description of the molecular structure of molecules and the chemistry of metabolic reactions. It is the understanding of biological processes at the molecular level that provides you with a more thorough understanding of biology. The AP examiners want to know whether you have this kind of understanding. With that in mind, your studying should begin with a brief review of chemistry and the characteristics of major groups of biological molecules.

Atoms, Molecules, Ions, and Bonds
An atom consists of a nucleus of positively charged protons and neutrally charged neutrons. Negatively charged electrons are arranged outside the nucleus. Molecules are groups of two or more atoms held together by chemical bonds. Chemical bonds between atoms form because of the interaction of their electrons. The electronegativity of an atom, or the ability of an atom to attract electrons, plays a large part in determining the kind of bond that forms. There are three kinds of bonds, as follows: 1. Ionic bonds form between two atoms when one or more electrons are transferred from one atom to the other. This bond occurs when the electronegativities of the atoms are very different and one atom has a much stronger pull on the electrons (high electronegativity) than the other atom in the bond. The atom that gains electrons has an overall negative charge, and the atom that loses electrons has an overall positive charge. Because of their positive or negative charges, these atoms are ions. The attraction of the positive ion to the negative ion constitutes the ionic bond. Sodium and chlorine form ions (Na+ and Cl??“), and the bond formed in a molecule of sodium chloride (NaCl) is an ionic bond. 2. Covalent bonds form when electrons between atoms are shared, which means that neither atom completely retains possession of the electrons (as happens with atoms that form strong ionic bonds). Covalent bonds occur when the electronegativities of the atoms are similar. Nonpolar covalent bonds form when electrons are shared equally. When the two atoms sharing electrons are identical, such as in oxygen gas (O2), the electronegativities are identical, and both atoms pull equally on the electrons. Polar covalent bonds form when electrons are shared unequally. Atoms in this kind of bond have electronegativities that are different, and an unequal distribution of the electrons results. The electrons forming the bond are closer to the atom with the greater electronegativity and produce a negative charge, or pole, near that atom. The area around the atom with the weaker pull on the electrons produces a positive pole. In a molecule of water (H2O), for example, electrons are shared between the oxygen atom and each hydrogen atom. Oxygen, with a greater electronegativity, exerts a stronger pull on the shared electrons than does each hydrogen atom. This unequal distribution of electrons creates a negative pole near the oxygen atom and positive poles near each hydrogen atom. Single covalent, double covalent, and triple covalent bonds form when two, four, and six electrons are shared, respectively. 3. Hydrogen bonds are weak bonds between molecules. They form when a positively charged hydrogen atom in one covalently bonded molecule is attracted to a negatively charged area of another covalently bonded molecule. In water, the positive pole around a hydrogen atom forms a hydrogen bond to the negative pole around the oxygen atom of another water molecule (Figure 2-1).

11

Part I: Subject Area Reviews

oxygen O H + H + O h y d ro g e n + + H
O H

+ + +
H O H
O H H

H

O

H

O H
+ ionic bonds

+

+

+ H
O H

H

H
+

+ Hydrogen bonding between water molecules.

A space-filling model of a water molecule showing polarity created by covalent bonds.

Figure 2-1 When you think of chemical bonds, imagine a continuum based on the differences of electronegativities (Figure 2-2). The left end represents bonds that form when no differences exist in the electronegativities of the atoms. Electrons are shared equally, and nonpolar bonds form. The right end represents bonds that form when very large differences in electronegativities exist. Electrons are transferred from one atom to another, and ionic bonds form. When the electronegativities of the atoms are different, but not strongly so, the electrons are shared unequally, and polar covalent bonds form. This activity is represented by the center of Figure 2-2. The kind of bond that forms between two atoms and the strength of that bond depend upon the difference of electronegativities of the atoms and might occur any place along the line shown in Figure 2-2.
nonpolar covalent bonds electrons shared equally increasing difference of electronegativity between bonding atoms polar covalent bonds electrons shared unequally

H

+

+

electrons transferred

Figure 2-2

Properties of Water
The hydrogen bonds among water molecules contribute to some very special properties for water. 1. Water is an excellent solvent. Ionic substances are soluble (they dissolve) in water because the poles of the polar water molecules interact with the ionic substances and separate them into ions. Substances with polar covalent bonds are similarly soluble because of the interaction of their poles with those of water. Substances that dissolve in water are called hydrophilic (???water loving???). Because they lack charged poles, nonpolar covalent substances do not dissolve in water and are called hydrophobic (???water fearing???).

12

H

H H

O O

+

+

O

H

H

+

+

+

Chemistry

2. Water has a high heat capacity. Heat capacity is the degree to which a substance changes temperature in response to a gain or loss of heat. Water has a high heat capacity, changing temperature very slowly with changes in its heat content. Thus, the temperatures of large bodies of water are very stable in response to the temperature changes of the surrounding air. You must add a relatively large amount of energy to warm (and boil) water or remove a relatively large amount of energy to cool (and freeze) water. When sweat evaporates from your skin, a large amount of heat is taken with it and you are cooled. 3. Ice floats. Unlike most substances that contract and become more dense when they freeze, water expands as it freezes, becomes less dense than its liquid form, and, as a result, floats in liquid water. Hydrogen bonds are typically weak, constantly breaking and reforming, allowing molecules to periodically approach one another. In the solid state of water, the weak hydrogen bonds between water molecules become rigid and form a crystal that keeps the molecules separated and less dense than its liquid form. If ice did not float, it would sink and remain frozen due to the insulating protection of the overlaying water. 4. Water has strong cohesion and high surface tension. Cohesion, or the attraction between like substances, occurs in water because of the hydrogen bonding between water molecules. The strong cohesion between water molecules produces a high surface tension, creating a water surface that is firm enough to allow many insects to walk upon it without sinking. 5. Water has strong adhesion. Adhesion is the attraction of unlike substances. If you wet your finger, you can easily pick up a straight pin by touching it because the water on your finger adheres to both your skin and the pin. Similarly, some people wet their fingers to help them turn pages. When water adheres to the walls of narrow tubing or to absorbent solids like paper, it demonstrates capillary action by rising up the tubing or creeping through the paper.

Organic Molecules
Organic molecules are those that have carbon atoms. In living systems, large organic molecules, called macromolecules, may consist of hund

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