AND WHATITACCOMPLISHESreproductionoccursatthecellularlevelreproduction EXAMPLE liketheskinonyourarm skincellsareconstantlyreproducingthemselvesandmovingtowardtheoutersurfacereplacingdeadcellsthathaverubbedoffthisremovaloftheskingoesonthroughoutlifeandwhentheskingetsinjuredthereproductionofcellsiswhathelpstohealthewoundMM I3whenacellundergoesreproductiontheprocess is calledcelldivisionThe 2daughtercellsthatresultfromcelldivisionaregeneticallyidenticaltoeachotherandtotheoriginal parent cellBeforetheparentcellsplitsin 2 itduplicateschromosomesandthenduringcelldivisioneachdaughtercellreceivesoneidenticalsetofchromosomesfromtheoriginalparentcellcelldivisionplaysseveralImportantrolesinthelivesof organismsthefunctionsof EXAMPLE withinthebodymillionsofcellsmustdividecelldivision everysecondtoreplacedamaged orlostcellsanotherfunctionofcelldivisionISgrowthall ofthemanycellsinyourbodyaretheresultofrepeatedcelldivisionsthatbeganinthemother'sbodyw asinglefertalizedeggreproductionisanothervitalfunctionofcelldivision Manysinglecelledorganisms likeamoebasreproducebydividinginhalfandtheoffspringaregeneticreplicasoftheparentGthisis asexualreproductionasexualreproduction thecreationofgeneticallyidenticaloffbyasingleparentwithouttheparticipationofspermandeggoffspringproducedby asexualreproductionasexualreproduction inheritalltheirchromosomesfromasingleparentandthereforetherearegeneticduplicatesAnindividualthatreproducesasexuallygivesrisetoaclone agroupofgeneticallyidenticalindividualsmanymulticellularorganismscanreproduceasexuallyaswellEXAMPLE Someseastarspeciescangrownewindividualsfromfragmentedpieces or ingrowinghouseplantsfromclippings asexualreproductioninplantsin asexualreproductionthereisonesimpleprincipleofinheritanceTheloneparentandeachofitsoffspringhaveidenticalgenesThetypeofcelldivisionresponsibleforasexualreproductionandforthegrowth4maintenance ofmulticellularorganismsiscalledmitosis sexualreproductionrequiresthefertilizationofaneggby aspermtheproductionofgametes sperm egg meiosissexualreproduction 6meiosisa aspecialkindofcelldivisionthatonlyoccursinreproductiveorgansthelifecycleofamulticellularorganismisthesequenceofgenerationmeiosis togenerationstagesfromfertilizationtotheproductionofitsownoffspringGAMETES THELIFE thekeyfactortothelifecycleishaving2setsofchromosomesoneCYCLEOFASEXUALORGANISM Inheritedfromeachparenthumansarediploidorganismsbcalltypicalbodycellssomaticcellscontainpairsofhomologouschromosomesmatchingsetsthegameteseggandspermcellsaren'tdiploidI madebymeiosisinanovaryortestisa eachgametehasasinglesetofchromosomes 22autosomes t lsexchromCRIMIFEE Someeitherxorywww asinglecellchromosomesetisahaploidcell Itonlyhasonepairofhomologouschromosomesfertilizationcycleahaploidspermfusesw ahaploideggtheresultingfertilizedeggzygote diploideggIthas2SetsofchromosomesonesetfromeachparentThelifecycleiscompletedasasexuallymatureadultdevelopsfromthezygotemioticcelldivisionensuresthatallsomaticcellsofthehumanbodyreceiveacopyofallofthezygote's46chromosomes everyoneofthetrillionsofcellsinthebodycantraceitsancestrybackthroughmioticdivisionstothesinglezygoteproducedproducinghaploidgametesbymeiosiskeepsthechromosome fromdoublingineverygenerationEXAMPLEHOWMEIsosisHALVESCHROMOSOMENUMBER meiosisproduceshaploidgametesindiploidorganismstheprocessof duringmeiosisthenumberofchromosomesiscutinhalfmeiosis inmeiosis acellthathasduplicateditschromosomesundergoes 2consecutivedivisions meiosis1andmeiosis11eachofthe4daughtercellsresultingfrommeiosishasahaploidsetofchromosomes 42asmanychromosomes asthestartingcellGBthisisb coneduplicationofthechromosomesISfollowedby2divisionsmeiosisalsoinvolvesanexchangeofgeneticmaterial piecesofchromosomesbetweenhomologouschromosomesthisexchangeiscalledcrossingoverwhichisthefirstprophaseofmeiosisSTAGESOFMEIOSISbenigntumoralumpofabnormalcellsthatremainsattheoriginalcancer siteeventhoughitgrowsoutofcontrolmalignanttumor anabnormallygrowingmassofcellsactivelyspreadingthroughthebodymetastasisthespreadofcancercellsfromtheiroriginsitetoothersitesanindividualw amalignanttumorissaidtohavecancer