题目内容

The passage depicts the difficulty of stem cell research in South Korea.

查看答案

搜索结果不匹配？点我反馈

更多问题

按照清查范围不同，财产清查分为全面清查和局部清查。( )

A. 对
B. 错

If I’ve done anything wrong, you are welcomed to (critically) ______ me.

I hate to see you (leave) ______ so soon.

Scientists Say Plants Helped Ants Evolve Ants evolved far earlier than (1) believed, as far back as 140 million to 168 million years ago -- and they have plants to (2) for their diversity, U.S. researchers reported on Thursday. Researchers at Harvard University used a genetic clock to reconstruct the history of ants, and found that the ant family (3) arose more than 40 million years (4) than previously thought. The family did not diversify into different genera and species (5) flowering plants came (6) the scene, they said. The study sheds light on one of the (7) important and numerous animals, which includes hundreds of (8) species. "We (9) that ant diversification took off (10) 100 million years ago, along with the rise of flowering plants, the angiosperms," Naomi Pierce, a professor of biology who (11) the study, said in a statement. "These (12) provided ants with new habitats (13) in the forest canopy and in the more complex leaf litter on the forest floor, and the herbivorous insects that evolved alongside flowering plants provided food for (14) ." Writing in Friday’s (15) of the journal Science, the researchers said they reconstructed the ant family tree (16) DNA sequencing of six genes from 139 ant genera, encompassing 19 of 20 ant subfamilies around the world. Such "molecular clocks" are (17) used, alongside fossil and other evidence, to (18) how old species are. They work on the basis that DNA mutates at a steady and calculable (19) . "Ants are a dominant feature of nearly all terrestrial ecosystems, and yet we know surprisingly little about their evolutionary history: the major groupings of ants, how they are (20) to each other, and when and how they arose," said graduate student Corrie Moreau.