Scientific Name: Phascolarctos cinereus

Common Name: Koala, koala bear, native bear

Domain: Eukarya
    Kingdom: Animalia
        Phylum: Chordata
            Class: Mammalia
                Infraclass: Marsupialia
                    Order: Diprotodontia
                        Family: Phascolarctidae
                            Genus: Phascolarctos
                                Species: Phascolarctos cinereus
 

Koalas are eukaryotic organisms because their cells contain organelles and a nucleus.  They are members of the animal kingdom because they are multicellular, heterotrophic, and the species is capable of locomotion.  They have backbones so they are classified as chordates.  They are mammals because they produce milk to feed their young.  They are marsupials because they carry their young in pouches.  The diprodontia classification comes from the arrangement of the teeth on the jaw and from the fused second and third digits on its back paw.  To be classified in the family Phascolarctidae, different characteristics of the animal, including the number and kinds of teeth, along with the number of digits on the feet were taken into account.  It is important to note that the koala is the only extant member of its family.  Koalas were classified in their genus and species by examining their urinogenital tract (see diagrams below), spermatozoa, karyotype, and serology, along with the aforementioned traits.  The name Phascolarctos cinereus literally means ash-colored, leather-pouched bear (Phascolarctos = leather-pouched bear, cinereus ash-colored).  The name "koala" comes from the Aboriginal word meaning "no drink" because koalas get most of their water from the eucalypts leaves that they consume. 
                                

The urinogenital tracts of the koalas are taken into consideration in order to classify the organism into its genus and species.  The image on the left is of the male anatomy.  The male has a heart-shaped penis that is unique to koalas.  The female anatomy is shown on the right. 

Who are its relatives?

The phylogenetic tree of the koala shows its closest relatives, both extant and extinct.  The closest living relative to the koala is the wombat.  Other diprontodonts, such as kangaroos, are still extant but are not as closely related to the koala as the wombat.  All of the other species of koala listed in the phylogenetic tree are extinct. 

based off of Lee and Martin pg. 17