Unicellular and multicellular

The organisms are living things that are formed by one or more cells. Cells are the minimum units of life that have different degrees of complexity depending on their structure or organization.

Unicellular organisms are those that are made up of a single cell, for example, bacteria and yeastsMulticellular organisms are those that are made up of two or more cells, for example, shark, vulture, eucalyptus

Unicellular organisms

Single-celled organisms are microscopic organisms that unite all their vital functions in a single cell. Almost all prokaryotic organisms (that have a cell without a cell nucleus) and some eukaryotic organisms (that have cells with a cell nucleus) are unicellular.

Within the Monera are unicellular organisms all bacteria, eg Escherichia coli, salmonella typhi, and all archaea, for example, the methanogenic archaea. Within the fungi kingdom, yeasts, for example, Pichia, saccharomyces cerevisiae (brewer’s yeast ) ; within the protist kingdom, the protozoa, for example, paramecium and dinoflagellates.

Multicellular organisms

Multicellular organisms are made up of two or more cells that specialize in different vital functions (neurons, epithelial cells, red blood cells). These specialized cells form tissues that in turn make up the organs of the living being.

All animals and plants are multicellular organisms, for example, mammals like the lion, amphibians like the frog, trees like the oak, herbaceous plants like the onion. Some fungi and some organisms of the protist kingdom are also multicellular, for example, mushrooms, algae.  

Characteristics of single-celled organisms

  • They are present in all ecosystems.
  • The number of them far exceeds multicellular organisms.
  • They are considered more primitive than multicellular organisms.
  • They reproduce asexually.
  • There are heterotrophic and autotrophic unicellular organisms.
  • They can group together forming colonies.

Characteristics of multicellular organisms

  • They are also called multicellular.
  • They are eukaryotic organisms.
  • They are made up of specialized cells that can be very different from each other.
  • The cells that make them up are related to each other and need each other.
  • They are microscopic organisms more complex and developed than single-celled organisms.
  • They initially arise from a single cell that multiplies through mitosis or meiosis.

Examples of single-celled organisms

Amoeba Cyanidiophytin Yeast
Arches Diatom Microalgae
Bacterium Dinoflagellates Paramecium
Chlorella Euglena Protozoa


  • More examples in Unicellular organisms

Examples of multicellular organisms

Avocado Kelp Dog
Brown algae Lettuce Porphyra
Horse Daisy flower Portobello
Hen Mosquito Oak
Sparrow Nematodes Chinese mushroom
Hydrangea Palmaria palmata Black truffle


  • More examples in Multicellular organisms

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