Unit3UndertheseaⅠ
阅读理解A体裁:说明文话题:海洋词数:318时间:7′Theseaishometobillionsofplantsandanimals
Manyliveonlynearthesunlitsurface
Oceanographersclassifymarinelivingbeingsbyseparatingthemintotwomaingroups:plantsandanimals
Therearetwogeneraltypesofplantsfoundintheocean,thosehavingrootsthatareattachedtotheoceanbottomandthosenothavingrootswhichsimplydriftaboutwiththewater
Therootedplantsintheoceanareonlyfoundinshallowwaterbecausethereisnotenoughsunlighttosustainphotosynthesis(光合作用)indeeperwaters
Sincesunlightdoesnotpassmorethanafewhundredfeetintotheocean,mostoftheoceanisnotcapableofsupportingrootedplants
Themostplentyplantsintheoceanareknownasphytoplankton(浮游生物).Theseareusuallysingle-celled,minutefloatingplantsthatdriftthroughoutthesurfacewatersoftheocean
Togrow,phytoplanktonneednutrientsfromtheseawatera