Domain Eukarya

Domain Eukarya comprises every organism whose cells possess a true, membrane-bound nucleus along with other membrane-bound organelles such as mitochondria and endoplasmic reticulum — a cellular architecture considerably more complex than that of prokaryotic Bacteria or Archaea. Inside the eukaryotic nucleus, DNA is organised as linear chromosomes wrapped around histone proteins, unlike the unassociated circular DNA found in bacteria.

Eukaryotic cells also differ internally by location: the cytosol contains larger 80S ribosomes, while ribosomes inside chloroplasts and mitochondria are of the smaller, bacteria-like 70S type — a clue that these organelles likely originated from ancient engulfed prokaryotes. Every organism belonging to any of the traditional eukaryotic kingdoms — Protista, Fungi, Plantae and Animalia — is classified under Domain Eukarya, meaning this single domain spans ev …