Both Archaea and Bacteria have ribosomes and can be found in extreme and harsh environments such as hot springs and human bodies. They also both reproduce asexually through binary fission and fragmentation. However, they have different cell walls and the Archaea are part of the kingdom of single-celled microorganisms while Bacteria constitute a large domain of prokaryotic microorganisms. The Archaea have no cell nucleus. Bacteria can also form spores which remain dormant over years but the Archaea cannot.