How scientists name, group and relate living organisms
Taxonomy is the science of identifying, naming and classifying organisms. Binomial nomenclature, introduced by Linnaeus, gives each species a two-part Latin name, such as Mangifera indica for mango, with the genus capitalised and both words italicised. Organisms are arranged in a hierarchy of categories: kingdom, phylum or division, class, order, family, genus and species. Herbaria, museums, zoological parks and botanical gardens help scientists study and identify organisms.
Whittaker’s five-kingdom system groups life into Monera (prokaryotes such as bacteria), Protista (single-celled eukaryotes like Amoeba and diatoms), Fungi, Plantae and Animalia, based on cell type, body organisation, nutrition and reproduction. Viruses are not included because they are not cellular. The plant kingdom ranges from algae and bryophytes to pteridophytes, gymnosperms and angiosperms. Animals are classified by body symmetry, germ layers, body cavity and the presence of a notochord, which places humans in the phylum Chordata. Modern classification also uses DNA to reveal evolutionary relationships.
Why it matters
Correct classification lets scientists worldwide talk about the same species, identify disease-causing microbes and pests, and find relatives of crops for breeding. It helps conservationists track endangered species and explains how lineages of life are related. This topic is the base for plant and animal morphology, ecology and evolution.
Key terms
- Binomial nomenclature
- The system of naming each species with a genus name and a species name.
- Taxonomic hierarchy
- The ranked series of categories used to classify organisms, from kingdom to species.
- Five-kingdom classification
- Whittaker’s system dividing organisms into Monera, Protista, Fungi, Plantae and Animalia.
- Notochord
- A flexible rod along the back of an embryo, characteristic of chordates.