What distinguishes Eukarya from the other domains of life?

The defining characteristic that distinguishes Eukarya from the other domains of life, Bacteria and Archaea, is the presence of a membrane-bound nuclear region. Eukaryotic cells have a true nucleus that encases their genetic material, which is organized into chromosomes. This nuclear envelope provides a distinct compartment for the DNA, allowing for more complex regulation of gene expression and cell function.

In contrast, both Bacteria and Archaea possess a nucleoid region without a surrounding membrane, where their genetic material is not compartmentalized. This fundamental structural difference is a key factor in the complexity and organization of eukaryotic cells, enabling the development of multicellular organisms and more advanced cellular processes.

The other choices highlight features that are not exclusive or distinguishing for Eukarya. For example, while some eukaryotes can photosynthesize, such as plants and some algae, not all eukaryotic organisms have this ability. Similarly, the claim regarding unicellular nature does not apply specifically, as both eukaryotes and prokaryotes can be unicellular. Therefore, the presence of a membrane-bound nuclear region is the most accurate and distinguishing feature of the Eukarya domain.