The hierarchy among organisms

To understand the system within each realm one needs to know the hierarchy within the realm. Each level in the hierarchy has a scientific name. Above genus level some names have a specific suffix. The hierarchy of the wood anemone is as follows:

Level: Example: Suffix:
Realm Plantae
Division Anthophyta -phyta
Class Dicotyledones
Order Ranunculales -ales
Family Ranunculaceae -aceae
Genus Anemone
Species Anemone nemorosa

The hierarchy and naming looks a bit different for the housefly since it is an animal:

Level: Example: Suffix:
Realm Animalia
Phylum Arthropoda
Class Insecta
Order Diptera
Family Muscidae -idae
Genus Musca
Species Musca domestica

A species can be further divided into smaller groups. An abbreviation of the type of subgroup and an additional name is then added after the species name:

Level: Abbreviation:
Subspecies ssp.
Variety var.
Form f.

In the Swedish alpine area there is a subspecies of common sorrel named Rumex acetosa ssp. lapponicus. For animals the abbreviation is usually not provided. The narrow billed subspecies of Eurasian nutcracker is just written: Nucifraga caryocatactes macrorhynchus.

How to describe a new species

Tortoise shells from Linnaeus’ collections in London.
Photo: Hans Odöö.

All the time new species are discovered. They have to be described and given scientific names. The names are then used in many different ways by people who work with plants and animals. It is therefore very important to know exactly which plant species each specific name is tied to.

The name of the new species has to be published in a scientific journal. To show exactly what plant or animal the name refers to, a reference to a collected specimen of the species, a type specimen, is given. Even though the author of the species always tries to make an accurate description of the species, it is important that other scientists can see the specimen with their own eyes. The type specimens are kept in scientific collections in museums.

In the past there was no rule about type specimens. Linnaeus described thousands of species without telling what individual he had looked at. To be certain of what he meant some detective work has to be done to try to find out what specimens he had studied. Often the answer is found in Linnaeus’ own collections of plants and animals, or other collections he had studied. Most of those collections are today found in London, but also in the herbarium (plant collection) of the Swedish Museum of Natural History and in the Zoological Museum at Uppsala University.

Each species has two names

All known organisms have scientific names. The wood anemone is named Anemone nemorosa and the elk is named Alces alces. The scientific names might feel more difficult to learn than the native names, but they are easy compared to the names used in Linnaeus’ time. They could be very long and consist of a long string of Latin words describing the plant or animal. The wood anemone was then called Anemone seminibus acutis foliolis incisis caule unifloro, which means: anemone with pointed seeds, leaves with incisions and stalk with one flower.

The sabre fish pictured in Linnaeus’ journey to Scania 1751.

Linnaeus was not happy with the long names. In the account of his journey to Scania he writes about a fish, the sabre fish, which had been given a name longer than the fish. The scientific name of the fish consisted of no less than 63 words!

Since Linnaeus had the talent to simplify and rationalise, he figured out a much better system for naming organisms. In the book Species Plantarum he used, for the first time, his new naming system throughout the whole book. This book had all known plants of the world listed following the sexual system. Linnaeus introduced the two names principle, the binary nomenclature, in Species Plantarum. The binary nomenclature means that each species has a genus name and a species name. The genus name of the wood anemone is Anemone, a genus name common to all closely related anemones. The species name of the wood anemone is nemorosa, and that of the closely related yellow anemone is ranunculoides (Anemone ranunculoides).

By the two names principle of Linnaeus, short and useful working names for the plants were introduced. The new names became very popular, not least among the student who had to learn them by heart. Linnaeus introduced the same principle for the names of animals in 1758, in the 10th edition of Systema Naturae. It was an ingenious rationalisation that is still used. The system with a genus name and a species name is used worldwide and is one of Linnaeus’ most important inventions.

Last modified: 2021-06-21