题目

As we all know, the UK is divided into four countries: England, Scotland and Northern Ireland. You can clarify this question 61._______ you study British history. GreatBritain was the name 62______(give) by other people when the England and Wales were joined to Scotland. They were united 63._______(peace). The four countries do work together in some areas, 64.________they are still very different. They developed different 65.________ (education) and legal systems as well 66._______different football teams. England is the largest of the four countries and for convenience it is divided 67.小麦与偃麦草的杂交属于远缘杂交。远缘杂交的难题主要有三个：杂交不亲和、杂种不育和后代性状分离。（1）普通小麦（六倍体）与偃麦草（二倍体）杂交所得的F1不育，其原因是 。要使其可育，可采取的方法是 。（2）假设普通小麦与偃麦草杂交得到的F1可育但更象偃麦草，如果要选育出具有更多普通小麦性状的后代，下一步的办法是 。（3）小麦与偃麦草属于不同的物种，这是在长期的自然进化过程中形成的。请运用现代生物进化理论解释物种的形成，在下面填出图中相应的生物学名词。① ② ③