Difference Between Unicellular Organism vs. Multicellular Organism

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Main Difference

As we know that cell is the smallest structural and functional unit of an organism. There are mainly two types of organisms, divided on the basis of the cell. The organisms which have only one cell are unicellular, whereas the organisms, which have the numerous cells are known as the multicellular. The unicellular organisms are simpler in nature as they mainly rely on the process of diffusion for the different functions, and have an only single cell to perform the different life functions. On the other hand, the multicellular organism is more complex and has numerous specialized cells which are assigned to perform the specific functions within the body. As unicellular organism are single-celled, they are smaller in size as compared to the multi-cellular.

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Comparison Chart

Unicellular OrganismMulticellular Organism
Number of CellsThe unicellular organism’s body is composed of a single cell.The multicellular organism’s body is composed of more than one cell.
LifespanShorter LifespanLonger Lifespan
Size & VisibilityThe unicellular organism area of smaller size, that most of them are even not visible to the naked eye.The multicellular organism is of large size, and most of them are easily visible to the naked eye.
Division of LaborThe work divisions in unicellular organisms are on the organelle level.The work division in the multicellular organism is on the tissue, organ, and system level.
Life ProcessesThe single available cells carry out all of the life processes in unicellular organisms.The multicellular organisms have specialized cells to perform different tasks.
ExamplesAmoeba and ParameciumPlants and animal
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What is Unicellular Organism?

The organisms composed of the single cell are known as the unicellular organisms. The unicellular organism have a short lifespan as the only available cell has to different tasks at the same time. In other words, we can say that due to the workload on the cell, the unicellular organism has the short-life span. It would be pertinent to mention here that the injury to the cell can even lead to the death of unicellular organisms. Unicellular organisms have less surface area to volume ratio, therefore, the cell body cannot attain the large size within the organism’s body. The unicellular organisms are mainly classified into four groups; bacteria archaea, protozoa, unicellular algae, and unicellular fungi. Furthermore, the unicellular organisms are divided into two general categories: eukaryotic organism and prokaryotic organisms. The unicellular organism is known as one of the ancient forms of life, which was simpler in nature and was enough for the survival and reproduction of the organisms that time. According to the famous biologists, the unicellular organism existed about 3.8 million years ago. The single cell in them regulates all the functions of the body, which made it quite difficult for them to survive. One of the main reason behind their short life span is the cell’s exposure to the environment. The unicellular organisms are quite smaller in size, that they cannot even be seen with the naked eye. Amoeba and Paramecium are some of the prominent examples of the unicellular organisms.

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What is Multicellular Organism?

The organisms consisting of more than one cell are known as the multicellular organisms. The multicellular organisms are made up of numerous cells which depend on the complexity and the size of the organism. For instance, we human being are one of the most complex multicellulars, we have around 37.2 trillion cells in our body. Out of the numerous cells, many of them are the specialized cells which perform the specific task assigned to them. In our body these cells combine with each other to form the tissues, and later the tissues combine to form the different organs within the organism’s body. Some of the prominent specialized cells in the human body which are assigned to perform the specific task are muscle cells, nerve cells and blood cells. The multicellular organism is comparatively large, and is mostly visible to the naked eye. At the same time, multicellulars have a longer life span as cells have no workload upon them as the division of labor is available to them. Moreover, they have the specialized type of cells to face the external environment. The multicellular organisms also once started from a single cell, and later grew up to harbor the numerous cells.

Unicellular Organism vs. Multicellular Organism

  • The unicellular organism’ body is composed of a single cell, whereas the multicellular organism body is composed of more than one cell.
  • The unicellular organisms have a shorter life span as compared to the multicellular organisms.
  • The unicellular organism area of smaller size, that most of them are even not visible to the naked eye. On the other hand, the multicellular organism is of large size, and most of them are easily visible to the naked eye.
  • The work divisions in unicellular organisms are on the organelle level, whereas the work division in the multicellular organism is on the tissue, organ, and system level.
  • The single available cells carry out all of the life processes in unicellular organisms. Contrary to this, multicellular organisms have specialized cells to perform different tasks.

Comparison Video