【小站原创】TPO42托福阅读文本及答案解析（Geographic Isolation of Species）
- 2016年05月10日10:48 来源：小站教育作者：小站托福编辑
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Geographic Isolation of Species
Biologist Ernst Mayr defined a species as “an actually or potentially interbreeding population that does not interbreed with other such populations when there is opportunity to do so.” A key event in the origin of many species is the separation of a population with its gene pool (all of the genes in a population at any one time) from other populations of the same species, thereby preventing population interbreeding. With its gene pool isolated, a separate population can follow its own evolutionary course. In the formation of many species, the initial isolation of a population seems to have been a geographic barrier. This mode of evolving new species is called allopatric speciation.
1. The word “key” in the passage is closest in meaning to 【词汇题】
A. early B. crucial C. noticeable D. frequent
Early, 早期的。Crucial, 重要的，决定性的。Noticeable, 显而易见的，值得注意的。Frequent, 频繁的。所以B选项正确。