Classification of living things

The classification of living beings is carried out in 8 levels, from lowest to highest evolutionary specificity, each of the groups being called a taxon (taxa in the plural):

  • Domain
  • Kingdom
  • Wire
  • Class
  • Order
  • Family
  • Gender
  • Species

The criteria for the classification of living beings is based on various characteristics:

  • morphology : the shape of your body;
  • genetics – similarities in the composition of the DNA sequence;
  • metabolism : the chemical reactions they carry out to obtain energy;
  • development : the pattern of how organisms develop.

The science in charge of the classification of living beings is in charge of the Systematics , which orders the great diversity of existing organisms on Earth. The taxonomy is the analysis of the characteristics of an organism in order to assign it to a taxon.


The species is the basic unit of biological classification. It is characterized by:

  • Morphologically similar individuals.
  • Genetic background with great similarity.
  • Ability to interbreed or mate with each other.
  • Production of fertile offspring.

Species in turn can be subdivided into subspecies and varieties. For example, the dog Canis lupus familiaris is a subspecies of the wolf Canis lupus . In turn, we know that there are hundreds of varieties or breeds of dogs, with particular characteristics.


The genus is the taxonomic category that groups similar species. For example, the genus Vespa includes at least 22 species, characterized by being black, yellow and brown wasps that build their nests by chewing on wood fibers.

The genus can be subdivided into subgenera and infragenus. Furthermore, the genus name is part of the scientific name of the organism; We can make the analogy that the genus is the surname of the living being, for example, Homo sapiens is the scientific name of the human species, where Homo is the genus.


Families are made up of genera with some distinctive characteristics. Its botanical designation ends as ”  aceae”, for example the Fabaceae family (legumes). In zoology, the ending for the family taxon is “-idae”, for example, the feline family is Felidae .


The order is the taxonomic category that groups the families. There may also be suborder, infraorder and parvorden.

Among the orders, we can highlight:

  • Hymenoptera : includes the set of insect animals that have membranous wings, such as bees, wasps and bumblebees.
  • Carnivore : includes animals that eat meat, such as dogs, cats, and bears.
  • Mucorales : is the largest order of fungi, where the bread mold Rhizopus stolonifer is found .
  • Poales : order of plants where corn, bamboo and bromeliads are found.


The class is the taxonomic category that groups the orders. They can in turn be subdivided into subclass and underclass.

In plants, the class designation must end with “-opsida”, such as Magnoliopsida (dicots) and Liliopsida (monocots). The ending in fungi is “-mycetes” and in algae “-phyceae”. For animals and bacteria there is no specific ending: Mammalia, Insecta.

It may interest you to see the difference between monocots and dicots .

Edge or division

The edge or division groups beings with a distinctive characteristic. Each kingdom encompasses a diversity of edge. It can be subdivided in turn into sub-phylum, infra-phylum and microfilm.

For example, in the Animalia kingdom the most emblematic phyla are:

  • Chordata : animals that have a notochord or dorsal cord, such as vertebrates.
  • Arthropoda – Arthropods with jointed legs, such as crabs, butterflies, and dragonflies.
  • Mollusca : mollusks with soft bodies, such as squid.
  • Porifera : sponges with pores.
  • Platyhelminthes : flatworms or flatworms.
  • Nematoda : round worms.
  • Annelida : worms with small rings, like earthworms.
  • Echinodermata – Echinoderms with spiny skin, like starfish.

In the kingdom of plants and fungi the category of Division is used .


There are currently six kingdoms:

  • Kingdom Animalia : animals.
  • Kingdom Plantae : mosses, ferns and plants.
  • Kingdom Fungi : fungi, molds and yeasts.
  • Protist Kingdom : Eukaryotic protozoa.
  • Kingdom Archaeabacteria : microorganisms without a nucleus that live in extreme environments.
  • Kingdom Eubacteria : includes bacteria.

You may be interested in seeing the kingdoms of nature .


Domain is the highest level of classification, proposed by Carl R. Woese et al. In 1990, based on differences in ribosomal RNA. From here three domains are derived:

  • Eukarya : which concentrates eukaryotic organisms, formed by cells that have a nucleus.
  • Archaea : group of prokaryotic microorganisms, that is, they do not have a nucleus, which in the evolutionary line are more similar to eukaryotes.
  • Bacteria : prokaryotic microorganisms without a cell nucleus.

It may interest you to see the difference between Archeas and bacteria .

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