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Biology · 术语表

什么是 Phylogenetic tree？

Definition 26.1 High School Biology · 第 26 章 — Reading Kinship: Phylogenetic Trees

A phylogenetic tree is a diagram of the kinship of a set of species (or other groups). Its tips are the species compared; each node where two branches meet represents their most recent common ancestor — a hypothetical population, not a known fossil; the root is the common ancestor of all. Two species are closer kin than a third when their common ancestor (their node) is more recent than the node they share with the third. Kinship is read from the nodes, never from the left-to-right position of the tips.

Two drawings of one tree. Rotating the branches at each node changes the order of the tips but not a single kinship: in both, mouse and human are sisters, the lizard is their closest relative, and the frog is the most distant. Reading "the lizard is between the frog and the mouse" from tree A would be a mistake.

示例

Example 26.3 (Misreadings to avoid)

"Humans descend from chimpanzees": no — on the tree, humans and chimpanzees are sister tips, descended from a common ancestor that was neither. "The frog is more primitive": no — every tip is a present species with the same length of history since the root; the frog lineage has evolved for as long as ours. "The lizard is closer to the frog than to the mouse" (from tree A): no — lizard and mouse share a more recent node.

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