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 a lot more. Each and every living species existing are composed of the cell. A cell is the structural and functional unit of 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
  • Multicellular Organisms

Unicellular Organisms

They are simple, minute, single-celled organisms, made up of a single cell. They are the oldest form of life, 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 to as microscopic organisms. Most of the unicellular organisms are prokaryotes.

Also read:  Microbes

Examples of Unicellular Organisms

Some of the examples of unicellular organisms are:

  • Amoeba
  • Euglena
  • Paramecium
  • Plasmodium
  • Nostoc, Salmonella ( Prokaryotic Unicellular organisms)
  • Protozoans, Fungi, Algae ( Eukaryotic Unicellular organisms)

Multicellular Organisms

Organisms which are composed of multiple cells are called 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 a multicellular organism. Most of the multicellular organisms are eukaryotes.

Multicellular Organisms Examples

Some of the examples of multicellular organisms are listed below:

  • Animal – Hydra
  • Plant – Spirogyra
  • Cyanobacteria such as Chara (Multicellular prokaryotic organisms)
  • Species of gymnosperms and angiosperm plants (Multicellular eukaryotic organisms)

Difference Between Unicellular And Multicellular Organisms

Let us learn more in detail about the differences between unicellular 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 a 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 the 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 does not cause the cell to die in a multicellular organism.
Reproduce by asexual reproduction. Reproduce by sexual reproduction.
Cell differentiation is absent. Cell differentiation is obvious.
They can be autotrophs or 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 a few examples of multicellular organisms.

Also refer: Difference between Prokaryotic and Eukaryotic Cells

For more information on the difference between unicellular and multicellular organisms, their examples and other related topics, keep visiting BYJU’S website or @ BYJU’S Biology.

Frequently Asked Questions

How do unicellular entities move?

Movement in unicellular entities is brought about through cilia, pseudopodia, flagella, etc. They can locomote in search of light of food and respond to reflexes by moving away in case they sense danger or even environmental factors such as heat etc.

How do unicellular organisms eat and reproduce?

Unicellular entities fulfil their nutritional requirements through a process known as phagocytosis which enables the single-celled entities to take food to the inside of the cell body in order to digest food. They reproduce through asexual means through the process of replication. The process of cell replication and reproduction in unicellular entities is the same in contrast to that observed in multicellular organisms.

State one similarity between unicellular and multicellular organisms.

Multicellular and unicellular organisms are similar in a way that they show almost all the life functions and processes such as reproduction, metabolism. They possess RNA and DNA which can display a range of lifestyles that are essential to most of the ecosystem that we currently exist in.

What is cytoplasm?

The cytoplasm is the cell substance that is present between the nucleus and the cell membrane. It contains the organelles, the cytosol, the cytoskeleton, and different other particles.

What is an organelle?

An organelle is a cell structure with specified functions that are dangled in the cytoplasm of eukaryotic cells. Vacuoles and the nucleus are the largest organelles that are prominent enough.

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