Unicellular organisms are part of our lives through everyday elements such as bread or wine (which are made with ferments or yeasts, unicellular organisms), we even have them regularly in the intestine or on the skin, without this meaning being sick.
We also consume dietary supplements based on algae, for example, or apply cosmetic products that are obtained from them.
All living beings present different degrees of complexity in terms of their structure or internal organization, that is why we have:
- superior organisms. They are characterized by having organs and tissues, the latter is made up of numerous specialized cells, and the cells of the different tissues have some differential characteristics.
- lower organisms. They are much simpler in structure, to the point that sometimes they are made up of only one undifferentiated cell: these organisms are known as unicellular organisms.
In the latter, all vital functions depend on that single cell, which can be prokaryotic (with free nuclear material in the cytoplasm) or eukaryotic (with nuclear material enclosed in the nuclear membrane). That single cell regulates itself and directs all vital functions.
See also: Prokaryotic and eukaryotic cells
Characteristics of unicellular organisms
Obviously unicellular organisms cannot be seen with the naked eye (since a cell is always something very small), but they can be seen with microscopes.
The fact of being such small individuals supposes a series of advantages:
- The high surface/volume ratio. That facilitates contact with the external environment and therefore nutrition.
- Have cell compartments in close proximity. Which contributes to their typical accelerated metabolism and the rapid rate of reproduction that characterizes them.
In general, they reproduce by bipartition (cell division), some may also present budding and sporulation phenomena, all these processes are based on mitosis.
Many single-celled organisms group together to form colonies. In the case of bacteria, which are unicellular, outside the cell there is an additional structure called a wall, which has important functions.
We can find unicellular organisms in three of the five kingdoms into which living things are divided:
- monera . Kingdom is represented by bacteria and in which all its members are unicellular.
- Protist. Only some members are.
- fungi. Only yeasts are unicellular.
Examples of Unicellular Organisms
| Saccharomyces cerevisiae (brewer’s yeast) | Chlorella |
| Escherichia coli | rhodotorula |
| Pseudomonas aeruginosa | Bacillus subtilis |
| Diatoms | pneumococci |
| Dinoflagellates | Streptococci |
| amoebas | Hansenula |
| protozoa | Candida albicans |
| Algae | Mycobacterium tuberculosis |
| paramecia | Micrococcus luteus |
| Spirulina | Staphylococci |
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