Concept of phylogenetic tree

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A phylogenetic tree is a branching diagram or a tree showing the evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical or genetic characteristics. All life on Earth is part of a single phylogenetic tree, indicating common ancestry.  Types Dendrogram. Cladogram. Phylogram. Dahlgrenogram. Phylogenetic network. Spindle diagram. Coral of life. Parts of a phylogenetic tree include: The "tips" of the tree branches represent the taxa in the study. Taxa may be at any taxonomic level - orders, species, populations, etc. These taxa may be called OTUs, or Operational Taxonomic Units. The lines within the tree are called the "branches". The points at which branches connect, or the tips of branches, are both called nodes. Internal nodes connect branches; external nodes are the tips that represent taxa. Some trees will have a basal node, known as the "root". A grouping of an ancestor and all of its descendants is known as a clade. The "goal" of phylogenetic analysis is to recover "bifurcating" trees, in which each taxon is linked to one other taxon through a node. Bifurcating trees are usually the most informative, because they tell which OTUs are most closely related. Polychotomous trees (those with multiple branches coming from one node) are usually less informative because they indicate that multiple OTUs are related to each other, but not how. (Some polytomies can be real, e.g. adaptive radiations).