Take the 2-minute tour ×  I understand that both are similar in
structure  But how can they be easily identified as one or the
other?  Is it simply based on the presence or lack of a named
root (the root is identified as a particular ancestor) or
outgroup?  share|improve this question At which "stage" do you
want to identify the tree? When it's a file (Newick), or when
it's a drawn figure? –  Michael Kuhn Dec 15 '11 at 8:32 I'd say
a drawn figure? Like something you would find on a google search
for phylogenetic tree
(images.google.com/search?tbm=isch&q=phylogenetic%20tree) – 
arcyqwerty Dec 15 '11 at 8:36 add comment  2 Answers  up vote 5
down vote accepted  In case of a drawn figure, either look for
the a short stem to the left, or for an explicitly labelled
outgroup. Trees derived from phylogenetic analyses are unrooted
by default, you need to root it by either making an arbitrary
(but hopefully informed) decision or by adding an outgroup.
share|improve this answer So when you say root it by making an
arb