托福阅读素材解析精选
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Geographic isolation creates opportunities for new species to develop, but it does not necessarily lead to new species because speciation occurs only when the gene pool undergoes enough changes to establish reproductive barriers between the isolated population and its parent population.
必背生词：
isolation: one group, person, or thing is separate from others.
speciation: speciation is the evolutionary process by which new biological species arise.
gene pool: the gene pool is the set of all genes, or genetic information, in any population, usually of a particular species.
整句结构，并列复合句：
句1 Geographic isolation creates opportunities for new species to develop，
句2 but it does not necessarily lead to new species because speciation occurs only when the gene pool undergoes enough changes to establish reproductive barriers between the isolated population and its parent population.
其中句2含有because引导的原因状从和when引导的时间状从。
逐步分析，句1中：
geograhic isolation 主语， creates 谓语，opportunities 宾语， for new species 介词结构作定语，to develop, 目的状语。本部分意思：地理隔离创造了新物种发展的机会。
句子2 主句部分 ：
but it does not necessarily lead to new species
it 主语，指代geographic isolation， does not necessarily lead：谓语部分， to new species：宾语。本部分意思：但它不一定会导致新物种
原因状语从句：
because speciation occurs
speciation是主语，occurs 谓语。
本部分意思：因为新物种的出现（产生）。
时间状语从句：
when the gene pool undergoes enough changes to establish reproductive barriers between the isolated population and its parent population.
the gene pool，主语；undergoes，作谓语；enough changes 宾语。
to establish 状语。其中，reproductive barriers是establish的宾语。
between the isolated population and its parent population,介词结构作定语，说明是isolated population 和 its population之间的障碍。
本部分意思：因为只有当基因库产生足够的变化，使得分割种群与其总群之间产生繁殖障碍时。
整句翻译：地理隔离创造了新物种发展的机会，但它不一定会导致新物种，因为只有当基因库产生足够的变化，使得分割种群与其总群之间产生繁殖障碍时才会产生新的物种。
