What trait differentiates the archaea from the other two phylogenetic branches of life?

Answer;

-Ctyoplasmic membrane structure.

Explanation;

-A unique characteristic of Archaea is the presence of ether linkages in the lipids of their cytoplasmic membranes which distinguishes archaea form eukaryotes and most bacteria.

-The structure of cytoplasmic membranes of many archaea is a lipid bilayer composed of glycerol diether lipids which is analogous (similar or parallel) to lipid layers of bacterial and eukaryotic membranes. The cytoplasmic membrane in same of the archaea bacteria or archaea are monolayers made of glycerol tetra-ether lipids.