The differences between the groups and the similarities within each group made it seem certain to most biologists that the treeoflife had only two stems.
类群之间的差异和每个类群内部的相似性使大多数生物学家确信，生命之树只有两个树干。
2
The number comes from studying relationships between the branches and leaves of the "family treeoflife".
这个数字是通过研究“生命谱系树”的“分枝”和“树叶”的关系得出的。
3
As scientists decode more and more genomes, the treeoflife gets pretty complicated.