Taxing taxonomy
Taxonomy provides a way of characterising living things and documenting family relationships
Our planet is teeming with perhaps 100 million species (although estimates vary wildly), but only about 1.5 million have actually been catalogued.
With so many species there has to be a system of classifying them. The most common system of classification was developed by a naturalist called Linnaeus in the 18th century.
1.5 million
The approximate number of species that have actually been catalogued
This system is known as taxonomy and divides organisms into ranks, or ‘taxa’: kingdom, phylum, class, order, family, genus and species. Usually we stick to genus and species when talking about organisms, such as E. coli (gut bacterium) or Homo sapiens (humans).
The Red Admiral butterfly, for example, is known as Vanessa atalanta in taxonomic terms. Its full classification is as follows:
Kingdom: animalia
Phylum: arthropoda
Class: insecta
Order: Lepidoptera
Family: nymphalidae
Genus: Vanessa
Species: atalanta
Over time, biological classifications change owing to to improved techniques and better knowledge about the biology and the evolutionary relationships of different living things. Nowadays, species are often subdivided into different subspecies or strains.
Since physical characteristics are derived from genes, genetic analysis is increasingly used to analyse relationships between organisms.
References
- Scientific American: Are we any closer to knowing how many species there are on Earth?
- Catalogue of Life: an index of the world’s known species
Related resources
Whose gene is it anyway?
Genes are widely shared but adapt to take on new roles in different organisms
Are humans different?
Are we different from the rest of the natural world?
Close cousins
Chimpanzees are our closest relatives, and genome sequence comparisons are beginning to identify the key genes that distinguish us from them