Since parasites like these stop any one group of animal getting the upper hand. 这种寄生虫能阻止某种生物种群的优势
Finding the fungus isn't a problem for the grubs since their caring parents actually show them the way. 幼虫寻找菌类当然比较困难 不过在父母的领引下不费吹灰之力
and since this discovery more than 120 miles of passageways have been mapped. 自从那次发现之后 迄今已测绘了120多英里的地道
Since the last Ice Age they've become cut off from the outside world. 自从上一个冰川期以来 它们便已和外界隔绝
it's six months since she last fed 它已经6个月没有吃东西了
It's six days since the bears emerged 现在是北极熊现身后的第6天
the only food the cubs have known since they were born deaf and blind beneath the snow some two months ago. 自从熊崽们两个多月前又聋又瞎地 在雪下出生以来 母乳就是它们唯一的食物