Both rooted and unrooted phylogenetic trees show the relationships between organisms, but only rooted trees indicate the relative divergence times from the common ancestor of all organisms in the tree.

Question

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Rooted trees use an outgroup that is known to share a common ancestor with all organisms in the tree, which means that the relative time of divergence from the common ancestor of all the organisms in the tree can be estimated. In unrooted trees, no common ancestor of all the organisms is used, and so relative divergence time cannot be estimated.

Both Rooted and Unrooted Phylogenetic Trees Show the Relationships Between