题目内容：
This useful，attractive，oversize volume uses its height well，employing a tree metaphor to show the earth’s various kinds of life and how aU living things．from bacteria to the largest mammals，are related．Each spread covers one branch of the animal kingdom．To make the enormity of species understandable．Strauss equates individual species(e．g．，1 0，000 bacteria)with one leaf on the tree．
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