Monera, taxonomic kingdom that comprises the prokaryotes (bacteria and cyanobacteria). Prokaryotes are single-celled organisms that lack a membrane-bound nucleus and usually lack membrane-bound organelles (mitochondria, chloroplasts; see cell, in biology). They have a small ring of DNA as their genetic material and reproduce asexually. A recently proposed system classifies these organisms in two major groupings called Eubacteria and Archaebacteria, or archaea. Monera has been contrasted with the kingdoms of eukaryotic organisms (protists, fungi, plants, and animals; see eukaryote).