The goals of systematics include assigning names to organisms using binomial nomenclature and organizing or classifying species into larger groups that have a biological meaning.

The Linnaean classification system, which is arranged from the largest to smallest, starts with the kingdom, phylum, class, order, family, genus, and species. The taxonomic rank of species has the most number of physical similarities and this group of individuals can mate and produce fertile offsprings. In this case, organisms in the same order are more closely related than the members of the same kingdom.

A domain is larger than a kingdom. To fit the six kingdoms in the three domains, scientists classified the key characteristics and grouped them accordingly. The domain Bacteria has the kingdom Eubacteria, while the domain Archaea, contains the kingdom Archaebacteria. These two domains contain single-celled prokaryotes. On the other hand, all eukaryotes are placed under the domain Eukarya. These eukaryotes include kingdoms Protista, Fungi, Plantae, and Animalia.

In the early times, one animal has different common names that often confuse the people, especially the scientists when they try to talk about it.

To solve the confusion, Carolus Linnaeus proposed a standardized system, which is called binomial nomenclature, to assign a two-word name to organisms. Moreover, he introduced the Linnaean classification system in order to identify and classify species into larger groups that have a biological meaning. Organisms are grouped into a taxon based on their similarities and differences.

Aside from sharing the same phylum, sea cucumbers and starfishes also share the same kingdom. Both organisms are under the kingdom Animalia.

Platypus belongs to a genus that survived the early branching of mammals from a reptilian ancestor. This is the reason why it possesses some characteristics that are similar to reptiles and birds. It is unique to other mammals because it lays egg instead of giving birth to a live young. It has a beak, which resembles a duck, and a furry body, which is a mammalian trait.