Final answer:
All organisms on a phylogenetic tree, including the domains Bacteria, Archaea, and Eukarya, share a common ancestor. The tree illustrates how these domains diverge from a single ancestral lineage, showing the evolutionary relationships among species.
Step-by-step explanation:
According to a phylogenetic tree, which is used to map evolutionary history, all organisms represented in the diagram share a common ancestor. In a rooted tree, a single ancestral lineage from which all organisms descend is shown. The diagram indicates that the three domains: Bacteria, Archaea, and Eukarya diverge from a single point. A lineage that evolved early from the root and remains unbranched would demonstrate a direct continuation without divergence. Therefore, the basis of the question, which asks about organisms that do not share a common ancestor, is a misunderstanding of how phylogenetic trees work. They depict relationships among species, and even though the rates of evolution or the physical characteristics may differ, all organisms on the tree share a common ancestral lineage.