Convergent evolution ( convergence ) the development of similar ( analogous ) structures in unrelated organisms as result of living in similar ecological conditions 趋同进化（趋同性） ：发生在完全不同的物种或类群中，由于生活在极为相似的环境条件下，经过选择作用而出现相类似的性状。
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But the recent discovery of detailed similarities in the skeletal structure of the flippers in all three groups undermines the attempt to explain away superficial resemblance as due to convergent evolution ? the independent development of similarities between unrelated groups in response to similar environmental pressures 但是，最近的发现，这三种动物的鳍足的骨骼结构都有详细的类似之处，这个发现削弱了下文的企图，即把表面上的类似解释为趋同进化的结果? ?是指类似结构的独立发展，在不相关的种群之间，对于类似的环境压力的反应。
