A species is a group of organisms capable of reproducing to produce fertile offspring. As millions of species were discovered, scientists realised that they could group different species based on their structure and the characteristics they share.

The Linnaean System

In the early 1700s, Carl Linnaeus began organising living organisms into groups based on the similarities and differences in their structure and characteristics.

Initially, Linnaeus divided living organisms into two kingdoms, which are the animal kingdom and the plant kingdom. Then he further divided each kingdom into smaller and more specialised categories. The sequence of classification is:

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
A representation of the biological classification hierarchy from most specific to most general. On the left side, colourful funnel shapes narrow from top to bottom, transitioning from red to green. Parallel to these funnels, on the right, are labelled categories in corresponding coloured rectangular shapes. From top to bottom, they read: 'SPECIES' in red, 'GENUS' in dark orange, 'FAMILY' in light orange, 'ORDER' in yellow, 'CLASS' in light green, 'PHYLUM' in dark green, and 'KINGDOM' in teal. An orange arrow pointing upwards is labelled 'VERY SPECIFIC', while a green arrow pointing downwards is labelled 'VERY GENERAL'.

The Binomial System

Linnaeus proposed the binomial system as a standardised way of naming organisms. This two-name system consists of the genus, which is followed by the species. The binomial system uses Latin names, and both the genus and species names are written in italics.

For example, human beings are classified as members of the genus Homo, and our species is sapiens; so, our scientific name is Homo sapiens.

  • The scientific name for brown bears is Ursus arctos
A visual representation of the biological classification hierarchy using the brown bear as an example. On the left, there's a grey, pyramid-like stacked structure with each layer labelled from top to bottom: 'Species', 'Genus', 'Family', 'Order', 'Class', 'Phylum', and 'Kingdom'. Corresponding coloured arrows point from each label towards the classification name for the brown bear. They read: 'Ursus arctos' for Species, 'Ursus' for Genus, 'Ursidae' for Family, 'Carnivora' for Order, 'Mammalia' for Class, 'Chordata' for Phylum, and 'Animalia' for Kingdom. On the far right, there's an illustration of a brown bear with a caption below stating 'Example of Animal Classification (Ursus arctos)'.

The binomial system is important because it allows us to easily categorise, name and identify individual species.

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