The theory that groups of organisms change with passage of time, mainly as a result of natural selection, so that descendants differ morphologically and physiologically from their ancestors.

主要由于自然选择的结果，生物体群经历了阶段性的变化，使后代在形态和生理上都与它们的祖先有所不同的理论。

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Partly the change has to do with the simple passage of time, refurbishing an aging display.

这次改变部分是纯粹由于年代久远，需要对老旧的展览物进行修缮保养。

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But love will change its composition with the passage of time.

但是，爱的成分会在年月中改变。

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Although Masters is not going to change what he eats, with the passage of time he sees that he may need to date a non-vegan if he is to find his life partner.

BBC: Vegan dating: Finding love without meat or dairy