Amoeba – simplest organism
An amoeba is a one-celled creature that is among the simplest of all living organisms. Most amoebas are so small that they can only be seen though a microscope. They look like tiny blobs of colorless jelly. The word amoeba is derived from the Greek word ameibein (to change), which describes the amoeba’s most easily distinguishable feature, the continuous changing of shape by repeated formation of pseudopods (Greek: false feet). Pseudopods serve two important functions—locomotion and food capture.
Amoebas live in fresh and salt water. They also live in the moist body parts of other animals and in moist soil. In human beings are found at least six types of amoeba.
An amoeba has a membrane, a nucleus, food vacuoles, and a contractile vacuole. The food vacuoles digest food. The contractile vacuole gets rid of extra water.
Amoebas move by changing their shape. The streaming of protoplasm inside the pseudopods moves the amoeba forward.
They eat mainly plants and other one-celled animals.
To reproduce, the nucleus of the amoeba simply splits into two pieces. The two halves pull apart, and each half takes part of the cytoplasm.
Amoeba proteus is commonly used for teaching and cell biology research. Chaos carolinense, one of the larger species, has multiple nuclei and can reach a length of 3 mm.
Amebiasis (infection with Entamoeba histolytica) is a serious intestinal disease also called amoebic dysentery. It is characterized by diarrhea, fever, and dehydration. Although amebiasis is usually limited to the intestine, it can spread to other areas of the body, especially the liver. Once inside the intestine, Entamoeba histolytica multiplies by means of binary fission.
Acanthamoeba cause primary amebic meningoencephalitis especially in individuals who are ill and whose immune systems are weakened.