An amoeba is a prototypical genus of unicellular organism found in decaying vegetation, wet soil, and animals such as humans. The amoeba is a relatively advanced form of unicellular organism. Amoebas are able to extend and remit their cytoplasm, or internal fluids, and form blob-like arms called pseudopodia. They use these to grasp food particles and propel themselves through microscopic terrain. Although the most famous amoeba species, Amoeba proteus, is about 700 microns in diameter, the larger Amoeba dubia can be as large as a millimeter in diameter and visible to the naked eye. The amoeba was first discovered by August von Rosenhof in 1755, using an early microscope.

The amoeba is a popular organism for testing and observation by scientists, called a “model organism.” Other model organisms include fruit flies and lab mice. The amoeba is useful as a model organism because its relative largeness allows it to be seen using a basic light microscope, and its mobility and complexity makes it much more interesting than more simplistic protists. That amoeba are largely transparent is also helpful. Amoebas have been poked and prodded by pretty much every device known to man.

Because an amoeba’s cell wall is so thin and mobile, it is largely transparent and the internal organs may be viewed. The most obvious are the nucleus, which stores the genetic material, and the vacuoles, where food is stored and digested. Depending on the salinity of the water where an amoeba is found, it will shrink or bloat in an attempt to equalize its density with that of the surrounding medium. If an amoeba is placed in water that contains no salt at all, it may swell so much that it bursts.

Amoebas reproduce by binary fission. The life cycle from birth to reproduction takes between 45 and 100 hours, depending on diet. When an amoeba enters a hostile environment, it can form itself into a ball and secrete a protective membrane to form a cyst. The amoeba then stays in this armor until external conditions improve. If the amoeba remains in cyst form for too long, it may die, but this strategy can help it get by hard times and live to see another day. The strategy is similar to that of hibernation.

Some amoebas are pathogenic to humans, causing diseases including amoebic meningitis, but most are benign, living in our digestive systems and stealing some food or living n the surface and consuming our dead skin cells. There could be amoebas crawling all over you right as you read this very sentence.