the hard, variously colored, calcareous skeleton secreted by certain marine polyps. 2. such skeletons collectively, forming reefs, islands, etc. 3. the solitary or colonial polyp that secretes this calcareous skeleton.
There are three major known groups of Archaebacteria: methanogens, halophiles, and thermophiles. The methanogens are anaerobic bacteria that produce methane. They are found in sewage treatment plants, bogs, and the intestinal tracts of ruminants.
Archaebacteria are the oldest organisms living on the Earth. They are unicellular prokaryotes and belong to the kingdom, Archaea. Remember that prokaryotes do not have a nucleus that surrounds their Chromosomes.All Eukaryotes, including animal and plants have their chromosomes contained within a nucleus.rchaebacteria are the oldest organisms living on the Earth. They are unicellular prokaryotes and belong to the kingdom, Archaea. Remember that prokaryotes do not have a nucleus that surrounds their Chromosomes.