Explaining the Taxonomic Classification System

Every living organism on Earth has a scientific name. These don’t just exist to give scientists long words in order to look clever, but have an important role in understanding the living world around us.

Not only do these names supply an internationally consistent name for species, whose common names may vary in different regions, let alone languages, but also give information on an organism’s kinship with other species, through a process of heirarchical taxonomy.

The father of this systematic system was Swedish botanist, zoologist and pysicist Carl Linnaeus, who laid the foundation of the modern system of classification in the 18th Century. The system divides the living world into several groups, starting with Kingdom and ending with Species (and indeed subspecific levels such as Subspecies, Race and Variety).

Linnaeus started the system with just two Kingdoms, those of Animals and Vegetables, although modern science sees several more.

These are the subdivisions of the taxonomic system, choosing at random a tiger as an example species as we go through the different groups. Note there are extra subdivisions excluded here for the sake of space and simplicity, as well as some recent changes in nomenclature.


These days, it is commonplace to consider there are six Kingdoms of life – Eubacteria and Archaebacteria (both types of bacteria that show different evolutionary origins), Protista (single-celled animals such as amoebas and most algae), Fungi, Plantae (plants) and Animala (animals). Some scientists recognise there is a greater evolutionary similarity between the last four groups here, and create a three Domain system instead – Bacteria (containing the Eubacteria), Archaea (containing the Archaebacteria), and Eukarya (containing everything else).

Our tiger would, of course, belong to Animalia (or Eukarya on the Three Domain System).


A Phylum (plural Phyla) is a subdivision of Kingdom. Examples of animal phyla include Arthropoda (all insects, arachnids, crustaceans etc.) Mollusca (including snails, shellfish, octopuses etc.) and Cnidaria (corals, jellyfish, sea anemones etc.).

To show how many diverse species a phylum can contain, the Phylum our tiger belongs to is Chordata, which contains all animals with a backbone or backbone-like structure. It includes all fish, sharks and rays, amphibians, reptiles, birds and mammals, as well as such bizarre primitive Chordates as hagfish, sea squirts and lancelets.


A Class os a subdivision of Phylum. Staying with Chordata, it contains Classes such as Chondrichthyes (sharks and rays), Actinopterygii (ray-finned fish), Amphibia (amphibians), Reptilia (reptiles) and Aves (birds).

Our tiger belongs to Mammalia, the mammals, a group discerned from the others from their ability to produce milk to suckle their young.


Order is a subdivision of Class. Orders of mammals include Cetacea (whales), Primates (primates, including humans), Artiodactyla (even-toed hoofed animals), Rodentia (rodents) and Chiroptera (bats).

Our tiger belongs to Carnivora, a group of mammals adapted to flesh-eating (although some are now vegetarians).


Orders are divided into Families. Families within Carnivora include Canidae (dogs, wolves, jackals), Mustelidae (weasels, badgers, otters etc.), Ursidae (bears) and Procyonidae (raccoons and relatives).

The tiger belongs to Felidae, the family that contains all species of cat.


Genus (plural Genera) is a subdivision of Family. Genera form the first part of an organism’s scientific name.

In this case the tiger belongs in the genus Panthera (other genera include Felis, which contains small cats, including the domestic cat).

(Note – genera should be written in italics, which can’t be inserted in Helium).


The (general) definition of a species is an organism that can only produce fertile young with members of its own kind. Tiger is a species within the genus Panthera, therfore its scientific, or binominal, name is Panther tigris. Other species within this genus include the lion (Panthera leo), and the leopard (Panthera pardus).

Again, species should always be written in italics. Genus should always start with a capital letter, and species in lower case.

Also note that research may mean scientists decide a species should be placed in a different genus to that previously thought, and with it its binominal name will change. An example of this is the puma, which was once thought to be part of the genus Felis (and therefore known as Felis puma), but is now placed in a different genus Puma (and known as Puma puma).


A level under species is Subspecies. These are distinct populations, usually geographically separated, that show some evolutionary difference to other subspecies. However, when these populations meet they can produce viable offspring.

The tiger has several subspecies, including the Bengal tiger (Panthera tigris tigris), Malayan tiger (Panthera tigris malayensis) and Siberian tiger (Panthera tigris altaica).


This is a very simplified version of taxonomic classification, and there are many subgroups and complexities to be found within it, but hopefully this is a useful overview of the topic.