interactivestudenteditionLevelBlueThisfurnaceisusedintheproductionofsteel.Steelisformedbyheatingmoltenironandscrapsteelat1550°C.TheGrandCanyonwasformedbyoveronebillionyearsoferosion.Thesetropicalfisharefoundinwatersthatmaintainaconstanttemperaturebetween70°Cand78°C.Colormaygivethesefishawaytocommunicatewithorattractmates.Sendallinquiriesto:Glencoe/McGraw-Hill8787OrionPlaceColumbus,OH43240-4027ISBN:978-0-07-877810-0MHID:0-07-877810-7PrintedintheUnitedStatesofAmerica.12345678910079/04309080706Copyright©2008byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ExceptaspermittedundertheUnitedStatesCopyrightAct,nopartofthispublicationmaybereproducedordistributedinanyformorbyanymeans,orstoredinadatabaseorretrievalsystem,withoutpriorwrittenpermissionofthepublisher.TheNationalGeographicfeaturesweredesignedanddevelopedbytheNationalGeographicSociety’sEducationDivision.Copyright©NationalGeographicSociety.Thename“NationalGeographicSociety”andtheYellowBorderRectanglearetrademarksoftheSociety,andtheiruse,withoutpriorwrittenpermission,isstrictlyprohibited.The“ScienceandSociety”andthe“ScienceandHistory”featuresthatappearinthisbookweredesignedanddevelopedbyTIMESchoolPublishing,adivisionofTIMEMagazine.TIMEandtheredborderaretrademarksofTimeInc.Allrightsreserved.(bkgd)ArnulfHusmo/GettyImages,(l)GeorgetteDouwma/GettyImages,(r)JohnLawrence/GettyImagesContentsInBriefContentsInBriefHumansandHeredity............................................2Chapter1TheNatureofScience..................................4Chapter2TraitsandHowTheyChange...........................36Chapter3InteractionsofHumanSystems.........................62Ecology........................................................90Chapter4InteractionsofLife...................................92Chapter5TheNonlivingEnvironment..........................120Chapter6Ecosystems.........................................148Earth’sChangesoverTime......................................178Chapter7PlateTectonics..................................
