What unicellular organisms are and their importance

Traditionally it has been more attractive and accessible to the general public to study organisms that can be observed with the naked eye, large and therefore multicellular. But this does not mean that single-celled organisms lack interest to the human being or of importance in nature. In fact, these small ones composed of a single cell have great relevance in the biogeochemical cycles of the planet, greatly allow oxygen breathing by many other organisms on the planet and are very useful in the development of products of interest to all people.

From we bring this article about what unicellular organisms are, their characteristics and examples to clarify what their nature is and where the relevance of this group of living beings lies in nature.

What unicellular organisms are and their importance

Unicellular, or single-celled organisms, are those that are made up of a single cell and represent the oldest way of life in life on Earth. These organisms are very diverse and include bacteria, arches, protozoa, algae and yeast. The importance of single-celled organisms lies in their functions, among which we can highlight some examples:

  • One of the most important roles of single-celled organisms is their role in biogeochemical cycles. For example, bacteria and algae are responsible for the fixing of nitrogen and carbon dioxide in aquatic and terrestrial ecosystems. These cells are also important in the decomposition of organic matter and soil formation.
  • Uniquel organisms are important in the production of food and medicine. Some yeasts are used in the production of bread, beer and wine, while others are used in the production of medicines and enzymes.
  • In terms of biotechnology, single-celled organisms are used in a variety of applications, such as the production of bioplastics, biochemicals and bioenergy. Some bacteria and yeasts are able to metabolize organic compounds and turn them into useful products, such as ethanol. We encourage you to read this other article on Biotechnology: what it is, what it is for and examples.

In general, single-celled organisms are an essential part of the ecosystem and have a crucial role in the functioning of ecosystems and life on Earth. Their study is essential for understanding biological processes and developing sustainable technologies and applications in the industry.

Organismos unicelulares: qué son, características y ejemplos – Qué son los organismos unicelulares y su importancia

Characteristics of unicellular organisms

Uniqueular living beings are very diverse and therefore their characteristics can also be very different between each group. However, there are certain common characteristics for all of them:

  • The first is its size, as single-celled organisms are fundamentally microscopic.
  • As their own name suggests, they are made up of a single cell.
  • They can develop crazies and scourges for their locomotion in the environment in which they live.
  • Also noteworthy is its ability to reproduce asexually. Many of these organisms reproduce through cell division, where a single cell is divided into two identical daughter cells. Other organisms, such as some algae and yeasts, can be reproduced by spores, fragmentation or groem.
  • Given their diversity, single-celled organisms have adapted to almost all environments. Bacteria, for example, can live in a variety of conditions, including extremely hot or cold environments, and in environments with high concentrations of salts or heavy metals. Some algae and protozoa are also able to live in aquatic and terrestrial environments.
  • They are very important in biogeochemical cycles. Bacteria and algae are responsible for the fixing of nitrogen and carbon dioxide in aquatic and terrestrial ecosystems, while other single-celled organisms are important in the decomposition of organic matter and soil formation.

Types of unicellular organisms

As we have seen, there is a wide variety of single-celled organisms. Their bodies are made up of a single cell, but this may be one of the two great types of cell organization known:

  • Pro-canteen organisms: prokarist single-celled organisms are considered as the oldest living beings on the planet. Its main characteristic is the lack of nucleus where to contain the genetic material and the absence of organelles. Although the fact that they are old does not mean that they are less evolved organisms, as these living beings possess complex structures that most eukaryote cells do not have and have also been able to adapt to all ecosystems on the planet. This cell type belongs to bacteria and arches.
  • Eukaryote organisms: are generally more structurally complex and are characterized by an intracellular nucleus and organelles. Unicelular eucariotic organisms include protozoan, algae and single-celled fungi. Protozoa, such as amoeba and parameth, are able to move through crazies or scourges. Single-celled algae, such as spirulina, are important oxygen producers in aquatic ecosystems. Single-celled fungi, such as the yeast fungus, are important in nature because they play the role of decomposers, while in the human sphere they are used for fermentation and in the production of food and drink.

Examples of unicellular organisms

A multitude of examples of single-celled organisms of interest can be found, either for their role in the ecosystem or their possible usefulness and use by the human being.

Amoeba proteus

An example of a single-cell organism is the Amoeba proteus amoeba. It is a protozoa that is in aquatic environments and is able to change its shape by the extension and contraction of its pseudopods. It is a heterotrophic organism and feeds mainly on bacteria and suspended particles. This organism is reproduced by binary division, i.e. asexually, and sexual reproduction has not been observed to date between the amoebas.

Paramecium caudatum

Another example is the paramecio Paramecium caudatum, another protozoa that is also found in aquatic environments. Paramecio is a ciliated organism, which means it has cilia on its surface that it can use to move and capture food. Heterotrophic paramege and feeds mainly on bacteria and algae. It is also reproduced by binary division.


Changing the metabolic type, an example of photosynthetic single-celled organism is cyanobacteria in general, of which the genus Anabaena can be cited. This is a diverse group of bacteria found in aquatic and terrestrial environments. They are able to perform photosynthesis and represent an important source of oxygen in the environment.



Among the single-celled algae we can find the diatoms, which are photosynthetic organisms that are found in sweet and salted aquatic environments. They are known for their characteristic silicea structure, which gives them a series of distinctive ways and protects them against predators. They can live in free water or as part of a community of bentos (organisms living at the bottom of the water). They are an important source of food for marine organisms and also play an important role in the production of oxygen and the carbon cycle in aquatic ecosystems. A specific example of diatom is Cyclotella meneghiniana.

Saccharomyces cerevisiae

Among the single-celled mushrooms you can highlight the species Saccharomyces cerevisiae, a heterotroph yeast widely used in the making of bread and beer. In nature, single-celled fungi play a very relevant role in the carbon cycle and recycling the nutrients of ecosystems. Here you can read about the Carbon Cycle.

Single and multicellular organisms

As is clearly understood when reading their names, single-cell and multicellular organisms have a fundamental difference, which is the number of cells that make up their body. But their differences do not end on this point, but, as we see below, there are others that are also worthy of being highlighted:

  • Size: as is evident, single-celled organisms are generally smaller than multicellular organisms, as the latter are made up of numerous cells.
  • Cell type: While multicellular organisms are always eukaryotes, single-cells can be as prokaryote as eukaryotes.
  • Cell differentiation: in a cell organism, the only cell performs all the vital functions necessary to stay alive and thus keep the organism alive. In the case of a multicellular organism, the existence of cell differentiation is very frequent, which leads to the existence of a multitude of different cells in terms of their function and structures in the same organism. Examples of this are sensory cells, muscle cells, and epithelial cells.
  • Reproduction: Single-celled organisms reproduce asexually, while multicellular organisms can be reproduced through sexual or asexual reproduction.
  • Structures: single-celled organisms cannot be organized to form tissues, while multicellular organisms can and give rise to tissues, organs and systems.

Once you know better what single-celling organisms, their characteristics and examples are, we recommend you continue learning about cell issues by reading this other article about cell types.

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