The Archaea are a diverse group, both physiologically and morphologically. Their shape varies from spheres, rods, spirals, squares, triangles, lobes, and plates to various irregular shapes. They may exist as single cells, ranging in size from 0.1 to 15 microns in diameter, or as filaments up to 200 microns long. They reproduce in three ways: binary fission, budding, and fragmentation. These organisms may be aerobic or anaerobic (facultative or strict) and may acquire their nutrients either chemoautotrophically or autotrophically. Perhaps because they prefer extreme environments, 34% of the prokaryotic biomass in Antarctic surface waters is made up of archaeans, so it is likely that they are also important in the Arctic.
Archaeans can be either motile or non-motile. Motile species owe their locomotion to one or more flagella. Their DNA consists of a single circular loop and they have a cell wall and membrane that together form a semi-rigid coat. This cell wall is not composed of cellulose or chitin as in plants and fungi, but is instead made primarily of peptidoglycan.