托福TPO阅读31原文+答案解析.docx

托福TPO阅读31原文+答案解析 小编为托福考生们准备了托福阅读TPO31原文,希望各位考生们在TPO真题里能够得到锻炼，祝广大托福考生能够取得理想成绩 Speciation in Geographically Isolated Populations Evolutionary biologists believe that speciation,the formation of a new species, often begins whensome kind of physical barrier arises and divides apopulation of a single species into separatesubpopulations. Physical separation between subpopulations promotes the formation of newspecies because once the members of one subpopulation can no longer mate with members ofanother subpopulation, they cannot exchange variant genes that arise in one of thesubpopulations. In the absences of gene flow between the subpopulations, genetic differencesbetween the groups begin to accumulate. Eventually the subpopulations become sogenetically distinct that they cannot interbreed even if the physical barriers between themwere removed. At this point the subpopulations have evolved into distinct species. This routeto speciation is known as allopatry (“alio-” means “different”，and “patria” means “homeland”). 进化生物学家认为物种形成(也就是新物种的产生)经常是某种物理障碍(地理隔离)的出现把一个单一物种群分为隔离的亚种群。

亚种群的身体隔离促进了新物种的产生，因为一旦亚种群中的成员无法与其他亚种群中的成员交配，那么亚种群之间就没有变种基因的交换缺乏了基因交流，亚种群之间的遗传差异就开始变大最终这些亚种群的基因差异变得十分明显，以至于它们无法进行种族内的交配，即使它们之间的物理障碍已经消除这时，这些亚种族就演化成了独立的物种这样的物种形成的方式被称作异域性(“alio-”意思是“不同的”,“patria”意为“故乡”) Allopatric speciation may be the main speciation route. This should not be surprising,since allopatry is pretty common. In general, the subpopulations of most species areseparated from each other by some measurable distance. So even under normal situationsthe gene flow among the subpopulations is more of an intermittent trickle than a steadystream. In addition, barriers can rapidly 小编为托福考生们准备了托福阅读TPO31原文,希望各位考生们在TPO真题里能够得到锻炼，祝广大托福考生能够取得理想成绩。

Speciation in Geographically Isolated Populations Evolutionary biologists believe that speciation,the formation of a new species, often begins whensome kind of physical barrier arises and divides apopulation of a single species into separatesubpopulations. Physical separation between subpopulations promotes the formation of newspecies because once the members of one subpopulation can no longer mate with members ofanother subpopulation, they cannot exchange variant genes that arise in one of thesubpopulations. In the absences of gene flow between the subpopulations, genetic differencesbetween the groups begin to accumulate. Eventually the subpopulations become sogenetically distinct that they cannot interbreed even if the physical barriers between themwere removed. At this point the subpopulations have evolved into distinct species. This routeto speciation is known as allopatry (“alio-” means “different”，and “patria” means “homeland”). 进化生物学家认为物种形成(也就是新物种的产生)经常是某种物理障碍(地理隔离)的出现把一个单一物种群分为隔离的亚种群。

亚种群的身体隔离促进了新物种的产生，因为一旦亚种群中的成员无法与其他亚种群中的成员交配，那么亚种群之间就没有变种基因的交换缺乏了基因交流，亚种群之间的遗传差异就开始变大最终这些亚种群的基因差异变得十分明显，以至于它们无法进行种族内的交配，即使它们之间的物理障碍已经消除这时，这些亚种族就演化成了独立的物种这样的物种形成的方式被称作异域性(“alio-”意思是“不同的”,“patria”意为“故乡”) Allopatric speciation may be the main speciation route. This should not be surprising,since allopatry is pretty common. In general, the subpopulations of most species areseparated from each other by some measurable distance. So even under normal situationsthe gene flow among the subpopulations is more of an intermittent trickle than a steadystream. In addition, barriers can rapidly 。