Difference Between Unicellular And Multicellular Organisms

Unicellular And Multicellular Organisms - Differences, Functions and Examples

What is Unicellular Organism?

A unicellular organism is an organism that is made of up of a single cell and the life processes such as reproduction, feeding, digestion, and excretion occur in one single cell. There are some examples of unicellular organisms like Amoeba, bacteria, and plankton. These unicellular organisms are typical microscopic which cannot be seen with the naked eyes. Unicellular organisms are of different types including bacteria, protozoa, and unicellular fungi. Asexual reproduction is famous among unicellular organisms. To make you more understanding, below are the details of types of bacteria.

Types of Unicellular Organisms

The one element taxonomy that scientist use to categorize all living organisms into groups based on certain characteristics. In this, taxonomy can be broken down into more specific kingdoms. In all, there are six kingdoms and four these four types can further be divided into two groups such as Eukaryotic or prokaryotic organisms.

Eukaryotic organisms

This organism is unique because it can be both unicellular and multicellular. To fit this category, a cell must have membrane-bound organelles. These cells have a nucleus that consists of DNA, mitochondria for energy and other organelles to carry out the cell functions.

Prokaryotic organisms

On the other hand, prokaryote consists of a single cell with no membrane-bound organelles. This organism has to adopt other ways of carrying out reproduction, feeding and waste excretion. 

Examples of a unicellular organism


The structure of bacteria is too tiny and every bacterial cell id different from an animal and plant cell. The size of bacterial cell is about micrometers across. Even bacteria are of a single cell but it consists of different parts like Chromosomal DNA, Plasmid DNA, Cell Wall, Cell Membrane, and Flagellum.


It is a type of unicellular organism that lives in water or in damp places. Protozoa have adaption that it behaves like an animal a bit. It produces pseudopodia that let it move to surround food and let it take inside the cell. Once the process of taking food inside is done, contractile vacuoles appear inside the cell then combine with the surface to remove waste.


Yeast is another type of unicellular fungi. It may be possible you are familiar from seeing mushrooms and toadstools. Yeast has cell walls like plant cells and no chloroplasts that mean sugar is the main nutrition for them as they are not able to make their own food by photosynthesis. 


The cyanobacterium is also known as Blue-Green Algae (BGA). It is the process of characteristics of both bacteria and algae. It resembles algae as photosynthesis for food production whereas the prokaryotic nature of BGA forms it similar to bacteria. Other than this, diatoms, euglena, chlorella, and Chlamydomonas includes in the example of cyanobacteria. 

Functions of Unicellular Organisms

There are many unicellular organisms that live in extreme environments like hot springs, thermal ocean vents, polar ice, and frozen tundra. These unicellular organisms are called extremophiles. This unicellular organism is specially adapted to live in places where multicellular organisms cannot survive because they are resistant to extremes of temperature or pH. Although, not every unicellular organism are extremophiles because many live under the same range of living condition as multicellular organisms, but still necessary things to all life forms on earth. For instance, phytoplankton is a type of unicellular that lives in the ocean. 

What are Multicellular Organisms?

A multicellular organism, tissue or organ is organisms that are made up of many cells. Animals, plants, and fungi are multicellular organisms. Multicellular organisms are much bigger in size and are very complex and intricate in their composition along with structure. Human beings, animals, plants insects are the example of a multicellular organism. 

Examples of a Multicellular Organism

Organs and tissues
These organisms delegate biological responsibilities like barrier function, digestion, circulation, respiration and sexual reproduction to a particular organs such as heart, skin, lungs, stomach, and sex organs. These organs are compromised of many different cells and cell type that work together to perform a particular task. For instance, cardiac muscle cells have more mitochondria that produce adenosine triphosphate to beat and power the circulation of blood through a circulatory system. 


Organisms are made up of numerous cells that are categorized as a multicellular organism. Formation of unicellular organisms took one billion of years to appear on the planet. Humans are the best example of multicellular organisms that are created by the fusion of two single cells specialized for sexual reproduction commonly produced egg and the sperm. 

Only fusion is the single egg gamete with a single sperm leads to the formation of a zygote or fertilized egg cell. The zygote contains both sperm and egg which are the genetic material. 

Let us learn more in details with the help of differentiation between organisms and multicellular organisms. 

Difference between Unicellular and Multicellular Organisms 

s. no.Unicellular organismMulticellular organisms
1.The structure of the unicellular is made up of a single cell.The structure of the multicellular organisms is made up of numerous cells.
2.Amoeba, paramecium, yeast all are examples of unicellular organisms. Few examples of multicellular organisms are human beings, plants, animals, birds, and insects.
3.The shape of the unicellular organism is irregular.The multicellular organisms have a definite shape.
4.The unicellular organism has a simple body organization.They have complex body organization.
5.In a unicellular organism, a single cell is responsible to carry the process of lifeIn a multicellular organism, different cells are specialized to perform different functions.
6.Unicellular organism includes both eukaryotes and prokaryotes.Whereas, multicellular organisms only include eukaryotes.
7.The overall body cell of a unicellular organism is exposed to the environment.In a multicellular organism, only the outer cells are exposed to the environment.
8.Division of labor, in a unicellular organism, is at organelle levelOn the other hand, a division of labor, in a multicellular organism, is at cellular, organ system level and organs.
9.Usually, a lifespan is short.A lifespan of a multicellular organism is long.
10.The unicellular organism is reproduced by asexual reproduction.Multicellular organisms are reproduced by sexual reproduction.
11.If there is any injury to a cell it can lead to the death of the organism.Similarly, it happens in multicellular organisms.
12.In a unicellular organism, cell differentiation is absent.Cell differentiation is obvious in a multicellular organism.
13.The unicellular organism is heterotrophs in nature. Multicellular organisms are both heterotrophs and autotrophs in nature.
14.Certain specialized cells in unicellular organisms do not lose the power of division.Power of division may lose.
15.In a unicellular organism, a well-marked capacity of regeneration is present.On the other hand, the capacity of regeneration decreases with increasing specialization.
16.Cells of a unicellular organism play the same role of both whether for itself or other organisms.But in multicellular organisms, cells have a double role for themselves and other organisms.
17.It can be visible under a microscope only but not with naked eyes.Multicellular organisms can be visible with naked eyes.
18.As the transport mechanism, simple diffusion is used.In the multicellular mechanism, simple diffusion, active and passive is used as transport mechanisms.