第一段arge stretches of salmon habitat have been eliminated by human activity: .........The 【numerical effect】 is obvious: there are 【fewer】 salmon in degraded regions than in pristine ones
第一段说The numerical effect is obvious: there are fewer salmon in degraded regions than in pris- tine ones; however, habitat loss also has the potential to reduce genetic diversity.第二段开始解释这种对基因多样性的影响。第三段说即便不能确定失踪率的变化是否是人类活动造成,但没理由认为这种影响和火山喷发有什么实质差别,并再次重申increase in straying results in substantial gene flow。
E:描述环境恶化如何导致了除数字减少以外的salmon数量的变化(即,基因多样性方面的变化)。
很多证据表明鸟源自于theropod dinosaurs,但一些科学家不信。科学家怀疑的原因有三个:第一个是theropod dinosaurs出现的比鸟晚,证据是fossil,但investigators新发现的证据反驳了这一点;第二个是锁骨不同,又被新的发现否定了;第三个是肺,用证据不足被反驳了。所以文章主要是对那些批评鸟源自于t.d.的科学家做出回应(respond to criticisms of the theory that birds evolved from ground-dwelling theropod dinosaurs)
取非。rate的影响一样大