Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Rooted describes a phylogenetic tree that has a single common ancestor for all the organisms represented. It helps illustrate the direction of evolutionary time from this ancestor.
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A rooted tree has a distinct root, which represents the most recent common ancestor (MRCA).
Rooted trees help in understanding evolutionary relationships and lineage diverging over time.
The root provides a reference point to determine ancestral and derived traits within the tree.
Outgroup analysis is often used to root an unrooted phylogenetic tree by comparing it with a distantly related species.
Rooted trees can be contrasted with unrooted trees, which show relationships without indicating a common ancestral point.
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Related terms
Phylogenetic Tree: A diagram that represents evolutionary relationships among various biological species based on their physical or genetic characteristics.
Most Recent Common Ancestor (MRCA): The most recent individual from which all organisms in a group are directly descended.
Outgroup: A species or group of species that is closely related but not part of the group being studied, used to help root the phylogenetic tree.