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Linnaean system of classification

Living organisms are classified into groups depending on their characteristics. This system was developed in the 18th century by Carl Linnaeus.

The classification of species allows the subdivision of living organisms into smaller and more specialised groups.

Kingdoms

The first division of living things in the classification system is to put them into one of five kingdoms.

The five kingdoms are:

  • animals (all multicellular animals)
  • plants (all green plants)
  • fungi (moulds, mushrooms, yeast)
  • protists (Amoeba, Chlorella and Plasmodium)
  • prokaryotes (bacteria, blue-green algae)

Further divisions

Living things can then be ranked according to:

Phyla follow kingdoms and have many different organisms. The animal kingdom includes the three examples below:

  • chordata, which have backbones
  • arthropod, which have jointed legs and an exoskeleton
  • annelids, which are segmented worms

Class is an additional sub-division, which, for example, results in the chordata phylum being divided into:

  • mammals
  • birds
  • amphibians
  • fish
  • reptiles

Order follows class and, as an example, mammals can be further sub-divided into a variety of different groups such as:

  • carnivores
  • primates

Orders are broken down into families. Here are a few examples of families that carnivores can be divided into:

  • canidae – dogs
  • felidae – cats

Genus follows on from family. The felidae family can be sub-divided into four genus examples:

  • acinonyx – cheetah
  • panthera – lion and tiger
  • neofelis – clouded leopard
  • felis – domestic cats

Species is the final classification stage, and the genus panthera can be divided into:

  • Panthera leo (Lion)
  • Panthera tigris (Tiger)

As an example, the complete breakdown of the classification of lions:

  • kingdom - animal
  • phylum - vertebrate
  • class - mammal
  • order - carnivore
  • family - felidae
  • genus - panthera
  • species - leo

There are many ways to remember this order, for example using the mnemonic:

kids prefer candy over fresh green salad

Living organisms are classified into groups depending on their structure and characteristics. This system was developed in the eighteenth century by Carl Linnaeus.
Robin perched on a snow-covered branch
Erithacus rubecula, the European Robin

The binomial system of naming species uses Latin words. Each name has two parts, the genus and the species. Bi- means two, for example a bicycle has two wheels. Nom means name. Therefore binomial means ‘two name’.

Human beings belong to the genus Homo, and our species is sapiens - so the scientific binomial name is Homo sapiens.

The binomial system is important because it allows scientists to accurately identify individual species across the world without needing to know the scientist’s home language. The grouping of families was added to allow the large number of new species to be included in this system. Linnaeus’ original ideas have been adapted, but continue to be accepted and as new species are identified they can be fitted into the current classification system.

Originally, Linnaeus couldn’t distinguish between different types of organisms such as algae, lichens, fungi, mosses and ferns. The inability to examine such organisms in detail made classifying these organisms as different species difficult at that time.

As more scientific equipment - such as microscopes with higher magnification - became available, it allowed scientists to examine organisms in more detail and note important features, such as the identification of sex organs. This allowed more divisions in the classification system to be created. The advancement of technology further helped to develop Linnaeus’ classification system.