| 1. | Every living thing has a physical boundary that separates it from its external enviroment . beginning with the bacteria and the simple cell and ending with man , every organism has a detectable limit which marks where it begins and ends . a short distance up the phylogenetic scale , however , another , non - physical boundary appears that exists outside the physical one 每一种生物都有一个可使之与外界环境分隔的边界,从细菌到单细胞到人,每一个有机体都有一个可探测到的边界用以界定其起止.然而,当上升一点儿到系统进化发育水平,则发现另有一个存在于有形的物理边界之外还有无形边界 |