Classification, or taxonomy, is the process of identifying, naming and categorizing living things based on their physical and biological characteristics. According to the Natural History Museum, scientists believe there are more than 31 million species of micro-organisms, animals and plants living on Earth today. Classification of living things helps scientists and students organize their research. It also helps to explain the interrelationships among diverse groups of organisms.
According to Windows to the Universe, living things are categorized into three groups based on their genetic characteristics. These three groups are Archaea, Eubacteria and Eukaryota, and these are known as domains. For example, the Eukaryota domain is divided into four kingdoms: kingdom Protista, kingdom Fungi, kingdom Plantae and kingdom Animalia. Kingdom Protista includes all organisms that have one eukaryotic cell. Kingdom Fungi features mushrooms and all other fungi. Kingdom Plantae includes all plants including trees, flowers and grass. Meanwhile, kingdom Animalia includes all animals, insects, birds and human beings. In each kingdom, species are further categorized into specific groups based on their similarities. This system of classification creates a specific hierarchy where all living things fit into categories. The hierarchy of living things allows classification by kingdom, phylum, class, order, family, genus and species.