At the behest of the biology will be named as unicellular to that organism that is composed of a single cell, meanwhile, in that single cell are found reunited all its vital functions. For instance, bacteria and protozoa they are the best exponents of single-celled organisms. It should be noted that unicellular organisms are the most abundant on planet earth, far surpassing the rest of living beings.
Conversely, multicellular or multicellular organisms are those who have made up of two or more cells, such as animals, plants, among others, however, it is important to mention that all organisms arise from a single cell, which then multiplies giving way to the organism. In this type of living being, cells are differentiated and are capable of performing various special functions, meanwhile, they can reproduce from mitosis.
Multicellular organisms are formed when cells are identified and joined to others, in addition, the cell unions that they generate will be permanent, that is, the cells will not be able to live in isolation and they will need an association. Now, this conjunction must occur in a framework in which the various types of cells trigger cellular organization in tissues, organs and systems, which are then capable of forming the complete organism.
Unicellular organisms are mostly prokaryotes, such is the case of bacteria, although there are some eukaryotes, such is the case of protozoa.
The circulation in these organisms is effected through the movement of the cytoplasm, known as cyclosis. Basically, this movement, caused by the cytoskeleton or micro filaments that make it up, facilitates the intracellular exchange of substances between the cell and its exterior.
In another vein, this type of unicellular organism is considered the most primitive within our planet, it even surpasses multicellular in this sense and surely this reason we will find it in something that we just mentioned and that is that all organisms, inclusive the multicellular ones, in the initial moment of their life were a single cell.
