bioinformatics - How can rooted and unrooted (phylogenetic) trees be distinguished from one another

I understand that rooted and unrooted phylogenetic trees 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?

Answer

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 normally unrooted by default, you need to root them by either making an arbitrary (but hopefully informed) decision or by adding an outgroup.