What is classification?

  • Updated
    27/02/20
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    3 minutes

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All living organisms are classified based on basic, shared characteristics. Organisms within each group are then further divided into smaller groups. These smaller groups are based on more detailed similarities within each larger group. This grouping system makes it easier for scientists to study certain groups of organisms. Characteristics such as appearance, reproduction, mobility, and functionality are just a few ways in which living organisms are grouped together.

The Australian Museum specialises in taxonomic and systematic research. Taxonomy and systematics comprise the describing, naming and classifying of plants and animals, and studying their origins and interrelationships. This type of research is essential for environmental assessments. It forms the basic building blocks of the study of nature, and is a key science on which many others depend.

Morpho & Pieridae Butterflies
Blue Butterflies are Morpho spp. from Brazil, belong to the largest family of butterflies, Nymphalidae, with more than 6,000 species distributed throughout most of the world. The orange and yellow butterflies are in the family Pieridae (whites, yellows and sulphurs), and come from Brazil, Peru, Malaysia and Indonesia. The colours in these species are from pigments (in contrast to the blue in Morpho.) The series of specimens set upside down are the jewelled Nawab Polyura delphis. These specimens come from Malaysia, but the species is also found in India. Image: Stuart Humphreys
© Australian Museum

Levels of classification

Taxonomists classify all organisms into a hierarchy, and give them standardised names, that are often Latin or Greek, or derived from other languages and even people's names.These specialised groups are collectively called the classification of living things. There are seven main levels of classification in the hierarchy. They are, from the most to the least inclusive:

Kingdoms is the most basic classification of living things.

Currently there are five kingdoms-Animal, Plant, Fungi, Protist and Monera (unicellular). Living things are placed into certain kingdoms based on how they obtain their food, the types of cells that make up their body, and the number of cells they contain.

Phylum is the next level following kingdom in the classification of living things. It is an attempt to find physical similarities among organisms within a kingdom. These physical similarities suggest that there is a common ancestry among those organisms in a particular phylum.

Classes are way to further divide organisms of a phylum. Organisms of a class have even more in common than those in an entire phylum.

Order Organisms in each class are further broken down into orders. A taxonomy key is used to determine to which order an organism belongs. A taxonomy key is a checklist of characteristics that determines how organisms are grouped together.

Families Orders are divided into families. Organisms within a family have more in common than with organisms in any classification level above it. Because they share so much in common, organisms of a family are said to be related to each other.

Genus is a way to describe the generic name for an organism. The genus classification is very specific so there are fewer organisms within each one. For this reason, there are a lot of different genera among both animals and plants. When using taxonomy to name an organism, the genus is used to determine the first part of its two-part name.

Species are as specific as you can get. It is the lowest and most strict level of classification of living things. The main criteria for an organism to be placed in a particular species is the ability to breed with other organisms of that same species. The species of an organism determines the second part of its two-part name.