Archaea is the most ancient of the bacteria. They are single celled organisms which don't have a true nuclei, and live in the most extreme environments on earth. Bacteria is the most abundant organisms on earth. Bacteria is also a single celled organism without a true nuclei called a prokaryote. A Protist is both unicellular and eukaryotic, meaning that it is an organism that has only one cell and that cell contains a nucleus. When compared to the highly evolved members of the Protista kingdom, the viruses and bacteria are really simple little critters. Fungi are eukaryotic heterotrophs, meaning that the cells of this organism has a true nuclei, and it has to rely on other organisms for their energy needs. Plants are the most common producers
