【单选题】I don’t know the reason _____you were absent from the meeting, but I am sure that someone will tell me the reason____you haven’t told me.
【单选题】从分子水平来说,自然选择淘汰一些稀少的等位基因,结果就是拥有这些等位基因的个体不能留下后代或留下较少的后代,这种自然选择的类型是:
A.
正选择( positive selection )
B.
负选择( negative selection or purifying selection )
【简答题】光电感烟探测器类型:在光路上测量烟雾对光的衰减(吸收)作用的______;在光路以外的地方测量烟雾的散射光能量的_________。
【单选题】I don’t know the reason _____you were absent from the meeting, but I am sure that someone will tell me the reason____you haven’t told me.
【多选题】种群的进化与选择中自然选择的类型有哪几种。()