Nonsynonymous-synonymous substitution rate ratio (d_N/d_s) is an important measure for evaluating selective pressure based on the protein-coding sequences. Maximum likelihood (ML) method with codon-substitution models is a powerful statistic tool for detecting amino acid sites under positive selection and adaptive evolution.
3．非同义-同义置换速率比值(d_N／d_S)是藉蛋白质编码序列评价选择压力的一种重要测度，而基于密码子置换模型的最大似然法业已成为检测承受正选择的氨基酸位点及适应性进化的统计分析工具。
参考来源 - 基于密码子水平的生物信息学分析及进化研究·2,447,543篇论文数据，部分数据来源于NoteExpress
This would lead to a selective pressure on men to take the task of propositioning very seriously indeed.
这就导致选择性的压力，当一个男人必须相当严肃的对待他试图接近的异性。
If the individual populations' environments were exerting strong selective pressure, such differences should have been apparent.
但如果某一人群的环境真正具有很强的选择压力那么上述差异会很明显。
Scientists had assumed that great mass would have produced selective pressure for the larger sacrum, but now they know that the sacral enlargement came first.
科学家以前猜测可能是种群太大导致的竞争压力使蜥脚龙最终产生了，不过现在他们知道了蜥脚龙从何处分化而来的。
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