Amoebas are varied tiny unicellular organisms. They were classified as protozoans of the genus Amoeba or related genera, but are now known to be part of the Unikonts. They have no solid form, instead consisting of a mass of protoplasm containing one or more nuclei surrounded by a flexible outer membrane. Most amoebae live in soil and are anaerobic. They move by means of pseudopods formed by fibronectin. Some amoeba are parasites that cause amoebic dysentery and some forms of septicaemia.
According to the Colonial Theory, in evolution history, amoeba-like organisms are believed to have contributed to the origin of multicellular organisms by clumping together to form colonies during food shortage, and eventually differentiating into various types of cells to give rise to the first multicellular organisms.
- John O. Corliss: Systematic Zoology, Vol. 8, No. 4 (Dec., 1959), pp. 169-190