懂你英语Level-4-unit-’,,,scientistsestimatethatmorethan99%ofthemarenowextinct.-Whendidthefirstplantappearonearth?–,manylifeforms,orspeciesoflife,,.-Whathappensinanextinctionevent?–,,,,likeachain.-Whatmayhavecausedtheextinctionofthedinosaurs?–,,plantsandplant-,thefoodchaincollapsedThisledtothedeathsofmanymorespecies.-Whatcausedthefoodchaintocollapse?–Thedeathsofmanyplantsandplant-,,somemammalslivedthroughtheageofthedinosaurs,buttheycouldn’,,,perhapswewouldn’tbeheretoday.-eleratetheevolutionofmammals?–’essfullywiththedinosaurs,
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