The Eukarya may only be unified in the sense that the cells are a community derived from bacteria and archaea; opinions vary. Like the Protista, the Eukarya may be a polyphyletic assembly, though a useful one. However, as mentioned above, all branches of the Eukarya have sexual reproduction. That, and the general organisation of the nucleus, are the defining features. These two points are the main evidence for monophyletic origin.