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- ARB: a Short Introduction
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# Trees

- OCCURRENCE
- DESCRIPTION

## OCCURRENCE

### ARB_NT

## DESCRIPTION

### A tree consists of two types of 'nodes':

- tips or terminal nodes: species
  connected to exactly one father
- inner nodes: hypothetical ancestors
  connected to one father (and in the binary case to two children). A group_name may be assigned to an inner node; in this case, the node and all its children become a group. <ARB_NT/INFO_MODE/M>

### There are significant differences between phylogenetic trees and binary trees:

    phylogenetic trees                      binary trees:
    -------------------------------------------------------------------------
    unrooted                                rooted
    inner nodes have n children             all inner nodes have two children

### Since binary trees are much easier to handle, ARB converts phylogenetic trees to binary trees.