Kingdom: This is the highest level of classification and divides all living organisms into five major groups: Animalia (animals), Plantae (plants), Fungi, Protista, and Monera (bacteria).
Phylum: Within each kingdom, organisms are further classified into phyla. There are 35 animal phyla, 14 plant phyla, and several fungal and protist phyla.
Genus: Each phylum is divided into genera, which group together species with similar characteristics. Organisms within the same genus share a common ancestor and have many similarities.
Species: The species is the basic unit of classification and is the most specific rank. Organisms of the same species can interbreed and produce fertile offspring.
For example, consider the scientific classification of the common house cat (Felis catus):
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Felidae
Genus: Felis
Species: catus
This classification shows that the house cat belongs to the animal kingdom, the phylum of chordates, the class of mammals, the order of carnivores, the family of Felidae, the genus of Felis, and the species of catus.