amoeba

Scientific classification Domain: Eukaryota

Kingdom: Amoebozoa

Phylum: Tubulinea

Order: Tubulinida

Family: Amoebidae

Genus: Amoeba

Bory de Saint-Vincent, 1822 Species

Amoeba proteus

Amoeba dubia

Amoeba (sometimes amœba or ameba, plural amoebae) is a term used either to describe protists that that moves by crawling[1] via pseudopods, or to refer to a genus that includes species that move by this mechanism.[2] Contents [hide] 1 Terminology 2 History 3 Anatomy 4 Genome 5 Reaction to stimuli 5.1 Hypertonic and hypotonic solutions 5.2 Amoebic cysts 5.3 Marine amoeba 5.4 Food scarcity 6 Pathogenic interactions with other organisms 7 References 8 External links //

Terminology

In the past, it was believed that organisms moving via pseudopods were closely related. However, it is now understood that many different unrelated organisms have evolved to shed their external structure and "taken up the amoeboid way of life".[3]. Because of this, classifying all these organisms together because of their method of locomotion would be similar to classifying all flying and gliding animals in a single group. Still, because the means of locomotion is one of the easiest traits to identify upon microscopy, the broader sense of the term has endured.

There are many closely related terms that can be the source of confusion: "Amoeba" is a genus that includes species such as Amoeba proteus Amoebidae is a family that includes the Amoeba genus, among others. Amoebozoa is a kingdom that includes the Amoebidae family, among others. Amoeboids are organisms that move by crawling. Many (but not all) Amoeboids are Amoebozoa.

History

The amoeba was first discovered by August Johann Rösel von Rosenhof in 1757.[4] Early naturalists referred to Amoeba as the Proteus animalcule after the Greek god Proteus who could change his shape. The name "amibe" was given to it by Bory de Saint-Vincent[5], from the Greek amoibè (aµ??ß?), meaning change.[6]

Anatomy Anatomy of an amoeba

The cell's organelles and cytoplasm are enclosed by a cell membrane, obtaining its food through phagocytosis. Amoebae have a single large tubular pseudopod at the anterior end, and several secondary ones branching to the sides. The most famous species, Amoeba proteus, is 700-800 µm in length but the species Amoeba dubia is as large as a millimeter, and visible to the naked eye. Its most recognizable features include one or more nuclei and a simple contractile vacuole to maintain osmotic equilibrium. Food enveloped by the amoeba is stored and digested in vacuoles. Amoebae, like other single-celled eukaryotic organisms, reproduce asexually via mitosis and cytokinesis, not to be confused with binary fission, which is how prokaryotes (bacteria) reproduce. In cases where the amoeba are forcibly divided, the portion that retains the nucleus will survive and form a new cell and cytoplasm, while the other portion dies. Amoebas