Linnaean Classification System

How Linnaeus Taxonomy Works

The Linnaean classification system organized plants, animals, and minerals.
The Linnaean classification system organized plants, animals, and minerals. SHEILA TERRY/SCIENCE PHOTO LIBRARY / Getty Images

 In 1735, Carl Linnaeus published his Systema Naturae, which contained his taxonomy for organizing the natural world. Linneaus proposed three kingdoms, which were divided into classes. From classes, the groups were further divided into orders, families, genera (singular: genus), and species. An additional rank beneath species distinguished between highly similar organisms. While his system of classifying minerals has been discarded, a modified version of the Linnaean classification system is still used to identify and categorize animals and plants.

Why Is the Linnaean System Important?

The Linnaean system is important because it led to the use of binomial nomenclature to identify each species. Once the system was adopted, scientists could communicate without the use of misleading common names. A human being became a member of Homo sapiens, no matter what language a person spoke.

How to Write a Genus Species Name

A Linnaean name or scientific name has two parts (i.e., is binomial). First is the genus name, which is capitalized, followed by the species name, which is written in lowercase letters. In print, a genus and species name is italicized. For example, the scientific name for the house cat is Felis catus. After the first use of a full name, the genus name is abbreviated using only the first letter of the genus (e.g., F. catus).

Be aware, there are actually two Linnaean names for many organisms. There is the original name given by Linnaeaus and the accepted scientific name (often different).

Alternatives to Linnaean Taxonomy

While the genus and species names of Linneaus' rank-based classification system are used, cladististic systematics is increasingly popular. Cladistics categorizes organisms based on traits that can be traced to the most recent common ancestor. Essentially, it's classification based on similar genetics.

Original Linnaean Classification System

When identifying an object, Linnaeus first looked at whether it was animal, vegetable, or mineral. These three categories were the original domains. Domains were divided into kingdoms, which were broken into phyla (singular: phylum) for animals and divisions for plants and fungi. Phyla or divisions were broken into classes, which in turn were divided into orders, families, genera (singular: genus), and species. Species in zoology were divided into subspecies. In botany, species were divided into varietas (singular: variety) and forma (singular: form).

According to the 1758 version (10th edition) of the Imperium Naturae, the classification system was:

Animals

  • Classis 1: Mammalia (mammals)
  • Classis 2: Aves (birds)
  • Classis 3: Amphibia (amphibians)
  • Classis 4: Pisces (fish)
  • Classis 5: Insecta (insects)
  • Classis 6: Vermes (worms)

Plants

  • Classis 1. Monandria: flowers with 1 stamen
  • Classis 2. Diandria: flowers with 2 stamens
  • Classis 3. Triandria: flowers with 3 stamens
  • Classis 4. Tetrandria: flowers with 4 stamens
  • Classis 5. Pentandria: flowers with 5 stamens
  • Classis 6. Hexandria: flowers with 6 stamens
  • Classis 7. Heptandria: flowers with 7 stamens
  • Classis 8. Octandria: flowers with 8 stamens
  • Classis 9. Enneandria: flowers with 9 stamens
  • Classis 10. Decandria: flowers with 10 stamens
  • Classis 11. Dodecandria: flowers with 12 stamens
  • Classis 12. Icosandria: flowers with 20 (or more) stamens
  • Classis 13. Polyandria: flowers with many stamens
  • Classis 14. Didynamia: flowers with 4 stamens, 2 long and 2 short
  • Classis 15. Tetradynamia: flowers with 6 stamens, 4 long and 2 short
  • Classis 16. Monadelphia; flowers with the anthers separate, but the filaments united at the base
  • Classis 17. Diadelphia; flowers with the stamens united in two groups
  • Classis 18. Polyadelphia; flowers with the stamens united in several groups
  • Classis 19. Syngenesia; flowers with 5 stamens having anthers united at the edges
  • Classis 20. Gynandria; flowers having stamens united to the pistils
  • Classis 21. Monoecia: monoecious plants
  • Classis 22. Dioecia: dioecious plants
  • Classis 23. Polygamia: polygamodioecious plants
  • Classis 24. Cryptogamia: organisms that resemble plants but don't have flowers, which included fungi, algae, ferns, and bryophytes

Minerals

  • Classis 1. Petræ (rocks)
  • Classis 2. Mineræ (minerals)
  • Classis 3. Fossilia (fossils)
  • Classis 4. Vitamentra (possibly meant minerals with nutritional value or some vital essence)

The mineral taxonomy is no longer in use. The ranking for plants has changed, since Linnaeus based his classes on the number of stamens and pistils of a plant. The animal classification is similar to the one in use today.

For example, the modern scientific classification of the house cat is kingdom Animalia, phylum Chordata, class Mammalia, order Carnivora, family Felidae, subfamily Felinae, genus Felis, species catus.

Fun Fact About the Taxonomy

Many people assume Linnaeus invented ranking taxonomy. In actuality, the Linnaean system is simply his version of ordering. The system actually dates back to Plato and Aristotle.

Reference

Linnaeus, C. (1753). Species Plantarum. Stockholm: Laurentii Salvii. Retrieved 18 April 2015.