192.orchid TW: fossilized orchid pollen发现àdedicateflowers existed时间 1.kw1: fossilized orchid pollen发现àdedicateflowers existed时间(文章内在思路) 2.kw2: pollenàorchidsolder (对kw1具体化) kwo: 26 million years old kwn: 80 million years old-much older aw-:旧观点 3.kw3: the reason why the largestand the most diverse orchids have been absent from the fossil record (the largestand the most diverse和absent形成对比) x: bloom infrequently y: live in tropical places-humidity and heatprevent fossilizing 4.kw4: fossilized orchid pollen的发现、研究、结论 发现: orchid pollen and the insects that carriedit preserved in amber (形式), 地点 2005年,他被送往了哈佛比较动物学博物馆。蜂蜜携带了orchids用来装花粉的结构。 5.kw5: orchids发展现状 6.kw6:对fossilizedorchid pollen发现的评价 aw+ a: resolve the debate over the age ofthe orchid b: the first direct evidence ofancient pollination-both pollinators and plant
|