Continent Continent A continent is one of several very large landmasses of the world. Generally identified by convention rather than any strict criteria, up to seven regions are commonly regarded as continents. Ordered from largest in area to smallest, they are: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Geologically, the continents largely correspond to areas of continental crust that are found on the continental plates. However, some areas of continental crust are regions covered with water not usually included in the list of continents. Zealandia is one such area (see submerged continents below). Islands are frequently grouped with
Smallest organisms on the archaeon "Ignicoccus"; it must be in contact with the host organism to survive. Prasinophyte algae of the genus "Ostreococcus" is the smallest free-living eukaryote. The single cell of an "Ostreococcus" measures only 0.8 μm across. Several species of Myxozoa (obligately parasitic cnidarians) never grow larger than 20 µm. One of the smallest species ("Myxobolus shekel") is no more than 8.5 µm when fully grown. The shell of the nut clam "Condylonucula maya" grows only 0.54 mm long. The smallest water snail (of all snails) is "Ammonicera minortalis" in North America, originally described from Cuba. It measures 0.32 to