byKittWinstonCover,©C.Moore/CORBIS;p.3,©ScienceVU/VisualsUnlimited;p.4,©LeonardL.T.Rhodes/AnimalsAnimals;p.5,p.6,©TomMcHugh/PhotoResearchers,Inc.;p.7,©StephenMcBrady/PhotoEdit;p.8–9,©CraigAurness/CORBIS;p.10,©GregVaughn/Alamy;p.11,©EarlScott/PhotoResearchers,Inc.;p.12,©Bettmann/CORBIS;p.13,©APPhoto/ReedSaxon;p.14,©SOQUITED/CORBISSYGMA.Copyright©byHarcourt,Inc.Allrightsreserved.Nopartofthispublicationmaybereproducedortransmittedinanyformorbyanymeans,electronicormechanical,includingphotocopy,recording,oranyinformationstorageandretrievalsystem,withoutpermissioninwritingfromthepublisher.RequestsforpermissiontomakecopiesofanypartoftheworkshouldbeaddressedtoSchoolPermissionsandCopyrights,Harcourt,Inc.,6277SeaHarborDrive,Orlando,Florida32887-6777.Fax:407-345-2418.HARCOURTandtheHarcourtLogoaretrademarksofHarcourt,Inc.,registeredintheUnitedStatesofAmericaand/orotherjurisdictions.PrintedinChinaISBN10:0-15-351541-4ISBN13:978-0-15-351541-5OrderingOptionsISBN10:0-15-351214-8(Grade4AdvancedCollection)ISBN13:978-0-15-351214-8(Grade4AdvancedCollection)ISBN10:0-15-358131-X(packageof5)ISBN13:978-0-15-358131-1(packageof5)Ifyouhavereceivedthesematerialsasexaminationcopiesfreeofcharge,HarcourtSchoolPublishersretainstitletothematerialsandtheymaynotberesold.Resaleofexaminationcopiesisstrictlyprohibitedandisillegal.Possessionofthispublicationinprintformatdoesnotentitleuserstoconvertthispublication,oranyportionofit,intoelectronicformat.1234567891098512111009080706byKittWinstonThetimeis25,000yearsago.Anenormous,woollycreaturewavesitsmassivetusksintheair.Acat-likeanimalsinksitsfangsintoitsprey.Agiantgroundslothlumbersofftofeedonleavesandtreebranches.Todayalloftheseanimalsareextinct.ThatmeanstheyaregonefromtheEarthforever.YoumightknowthatdinosaurslivedonEarthmillionsofyearsago.Asthedinosaursdiedout,newkindsofanimalsappeared.Mammalsandbirdsbegantoroamtheearth.TheGreatIceAgebeganabout1.5millionyearsagoandlasteduntilabout10,000yearsago.ItwasduringtheIceAgethatmanyoftheseanimalsbec...
