A unicellular organism and a multicellular organism are different because, those that are unicellular consist of only a single cell. Those cells are very simple because they lack a nuclei and their DNA is not separated from the rest of the cell. Any injury or death of cell in unicellular organism leads to death's. life span is short and theirs cell is comparatively large.Multicellular organisms on the other hand, are made of many cells and are major complex.
Tweet. : This page is part of the section about the structure and function of different Tissue Types, which is related to the section about Histology and Cells (incl. structure of animal cells, cell division, mitosis, meiosis).
1 organ system A group of organs that work together to complete a specific function. 2  specialised A cell that has become differentiated to carry out a particular function, eg red blood cell. 3  tissue A group of similar cells that carry out the same function, eg muscle tissue.  unicellular A single-celled organism.