Difference between Unicellular and Multicellular Organisms

Our planet earth is a home for several living species. These include a wide variety of plants, animals, different types of birds, insects and lot more. Each and every living species existing are composed of the cell. A cell is the structural and functional unit of the life. The total number of cells present in an individual varies from one organism to the other. Based on the number of cells, organisms are classified into:

Unicellular Organisms

They are simple, minute, single-celled organisms, made up of a single cell which existed about 3.8 million years ago. Bacteria, amoeba, Paramecium archaea, protozoa, unicellular algae and unicellular fungi are the main groups of unicellular organisms. These unicellular organisms are mostly invisible to the naked eye, hence, they are also referred as microscopic organisms. Most of the unicellular organisms are prokaryotes.

Multicellular Organisms

Organisms which are composed of multiple cells are called as multicellular organisms. These cells are attached to each other to procedure a multicellular organism. Most of these cells are visible to the naked eye. Organisms including, animals, birds, plants, humans are the main groups of multicellular organism. Most of the multicellular organisms are eukaryotes.

Let us learn more in detail about the differences between unicellular organisms and multicellular organisms.

Unicellular Organisms

Multicellular Organisms

The body of the unicellular organism is composed of a single cell.

The body of the multicellular organism is composed of numerous cells.

Irregular in shape.

Have definite shape.

Simple body organization.

Complex body organization.

A single cell is responsible to carry the life processes.

Different cells are specialized to perform different functions.

The total cell body is exposed to the environment.

Only the outer cells are exposed to the environment.

Division of labour is at organelle level.

Division of labour is at cellular, tissue, organs and organ system level.

Includes both eukaryotes and prokaryotes.

Includes only eukaryotes.

A lifespan of a unicellular organism is usually short.

These multicellular organisms have a longer lifespan.

Injury to the cell leads to the death of the organism.

Injury to a cell leads to the death of the organism.

Reproduce by asexual reproduction.

Reproduce by sexual reproduction.

Cell differentiation is absent.

Cell differentiation is obvious.

They are heterotrophs.

They include both autotrophs and heterotrophs.

They are microscopic in nature.

They are macroscopic in nature.

All forms of bacteria, amoeba, paramecium yeast, are examples of unicellular organisms.

Human beings, animals, plants, birds, insects, are few examples of multicellular organisms.

For more detailed information regarding unicellular and multicellular organisms, visit BYJU’S.

Practise This Question

In the given cross section of testis, identify the labelled parts and match them with their relative description given alongside.


i. storage area for the sperm

ii. carry the sperm from the testes to the epididymis

iii. encases the testis and forms testicular lobules

iv. the seminiferous tubles open into this

v. has germinal and sertoli cells