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Find out how chameleons use color to communicate.


Join scientists as they squeeze into narrow caves and fi nd a treasure trove of bones.


Asteroids may provide an answer for future space travel. Find out how.


EXPLORER Vol. 9 No. 4 DEVELOPMENT TEAM


Vice President and Publisher: Francis Downey Executive Editor: Richard Easby Creative Director: Karen Thompson Explorer Editor: Brenna Maloney Young Explorer Editor: Corinne Rucker Permissions Editor: Jean Cantu Production Specialist: Dreama Karnes-Bynane


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NATIONAL GEOGRAPHIC EXTREME EXPLORER (ISSN 1541-3357) is published seven times during the school year— September, October, November– December, January–February, March, April, May—by National Geographic Learning, 1125 17th Street NW, Washington, D.C. 20036. Postmaster: Please send address changes to NATIONAL GEOGRAPHIC EXTREME EXPLORER, PO Box 37863 Boone, IA 50037- 28633. Periodical postage paid at Washington, D.C., and additional mailing offi ces.


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Cover: a dolphin


PICTURE CREDITS COVER, PAGES 2-3 © MICHAEL NOLAN/ROBERT HARDING WORLD IMAGERY/CORBIS; PAGE 4 (TOP) BRIAN J. SKERRY/NATIONAL GEOGRAPHIC CREATIVE; PAGE 4 (BOTTOM) © AUGUSTO STANZANI/ARDEA.COM; PAGE 5 © JEFF FOSTER; PAGE 6 (TOP) CHRISTOPHER SWANN/SCIENCE SOURCE; PAGE 6 (BOTTOM) BRIAN J. SKERRY/NATIONAL GEOGRAPHIC CREATIVE; PAGE 7 © ROBERT HARDING WORLD IMAGERY/ALAMY STOCK PHOTO; PAGE 9 (TOP) © Z. DERYA YILDIRIM; PAGE 9 (BOTTOM) © JEFF FOSTER; PAGE 10 (TOP) © MARTIN HARVEY/CORBIS; PAGE 10 (CENTER LEFT) 578FOOT/SHUTTERSTOCK; PAGE 10 (CENTER RIGHT) FELIPE B. VARELA/SHUTTERSTOCK; PAGE 10 (BOTTOM) SERGEY GORUPPA/ SHUTTERSTOCK; PAGE 11 DIMITRI VERVITSIOTIS/GETTY IMAGES; PAGE 12 © BLEND IMAGES/ALAMY; PAGES 12-13 © ERIC BACCEGA/AGE FOTOSTOCK; PAGE 13 (SKY) SERG64/SHUTTERSTOCK; (BIRD) KRISTIAN SEKULIC/SHUTTERSTOCK; (ART) PRECISION GRAPHICS; PAGE 14 © OSF/ DAVID HARING/ANIMALS ANIMALS; PAGE 15 (TOP) IVANAGOTT/SHUTTERSTOCK; PAGE 15 (BOTTOM) ALEKSANDR DOODKO/SHUTTERSTOCK; PAGE 16 (TOP) © PIOTR NASKRECKI/MINDEN PICTURES/NATIONAL GEOGRAPHIC CREATIVE; PAGE 16 (CENTER) © CHRIS NEWBERT/ MINDEN PICTURES/NATIONAL GEOGRAPHIC CREATIVE; PAGE 16 (BOTTOM) VICTOR SHOVA/SHUTTERSTOCK; PAGE 17 HUIB THEUNISSEN/ SHUTTERSTOCK; PAGES 18-19 PHOTO ART BY MANDY/GETTY IMAGES; PAGES 20-23 (BACKGROUND) HAPPYKANPPY/SHUTTERSTOCK; PAGE 20 © MANUEL SILVESTRI/REUTERS; PAGES 20-21 PAUL BROWN/REX FEATURES VIA AP IMAGES; PAGES 22-23 FROM NATIONAL GEOGRAPHIC LADDERS SCIENCE 4: SUPER STRUCTURES (ON-LEVEL), 1E © 2014 SOUTH-WESTERN, A PART OF CENGAGE LEARNING, INC., REPRODUCED BY PERMISSION, WWW.CENGAGE.COM/PERMISSIONS; PAGE 24 VISUALS UNLIMITED, INC./MICHAEL KERN.


11/15/QGL/1 ISBN: 9781337083669


NELSON ISBN-13: 9780176758837


Find your online Teacher’s Guide, interactive whiteboard lessons, and projectable editions at ngexplorer.cengage.com.


(Note: The Teacher’s Guide and activity


masters can be printed on either black and white or color printers.)


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