题干

某校四个生物兴趣小组用紫色洋葱不同部位进行了相关实验(如下表),但均未达到预期效果.下列分析中合理的是(    )

实验组别

甲组

乙组

丙组

丁组

实验材料

鳞片叶外表皮

鳞片叶内表皮

筒状绿叶

根尖

主要试剂、仪器

解离液、醋酸洋红溶液

蒸馏水、甲基绿染色剂

健那绿、光学显微镜

蔗糖溶液、光学显微镜

实验目的

观察细胞中染色体的形态

观察DNA分布

观察线粒体分布

观察质壁分离及复原

A:甲组实验所选取的细胞不应该先染色后漂洗

B:乙组实验所取细胞的细胞核无DNA

C:丙组实验中叶绿体的存在会干扰线粒体的观察

D:丁组实验未观察分生区的细胞

上一题 下一题 0.0难度 选择题 更新时间:2019-12-13 03:49:34

答案(点此获取答案解析)

C

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    Whether you live in Seattle or the Sahara desert, the time has come to invest in a good raincoat or umbrella, a new study suggests.

    As global temperatures continue to rise, more “extreme rain” events—intense, cats-and-dogs down pours—can be expected, said the study, published Monday in the journal Nature Climate Change. And that, scientists said, means an increased flood risk, particularly for the world's driest areas. The study challenges the idea that global warming is causing dry areas to become drier and wet areas wetter.

    “In both wet and dry regions, we see these great increases in heavy precipitation(冰雹),” lead author Markus Donat, a climate scientist at the University of New South Wales, told Nature.

    Donat and his team collected data from 1951 to 2010 on extreme precipitation events from 11, 000 weather stations around the world, Nature reported.

     In that time, the number of days with“extreme precipitation” increased 1 percent to 2 percent per decade.

  “We found a strong relationship between global warming and an increase in rainfall, particularly in areas outside of the tropics,” Donat said in a statement.

  “Importantly, this research suggests we will see these extreme rainfall events increases at regional levels in dry areas, not just as an average across the globe,” Donat added.

    Peter Stott, a senior climate scientistat Met Office, told Climate Central that the study's findings are important, because more violent rainfall and flooding will “challenge our capability toadapt to a rapidly changing climate.”

    As Nature reported, the researchaligns(结盟)with a 2015 study that found global warming has led to a sharp increase in record-breaking precipitation events. Donat told Nature that his study should come as a warning to world governments.