How is a species placed into a genus, family, order, class, phylum, kingdom, and domain?

In zoology, the placement of a species into a hierarchical system of ranks—domain, kingdom, phylum, class, order, family, genus, and species—is the process of taxonomy, which aims to reflect the natural relationships of organisms based on phylogeny.

The Taxonomic Process

Taxonomists classify organisms by evaluating their resemblances to and differences from known forms. This involves:

• Recognizing Groups: Taxonomists identify natural groups of organisms. There are no explicit, universal characters that define a specific rank (such as a phylum or class); rather, classification relies on a consensus among experts regarding which features are most significant for defining a group.1
• Assigning Rank: Once a group is recognized, it is assigned a rank within the hierarchy. If an organism is a new species within a well-known genus, it is simply added to that genus. If it is highly distinct, it may require the creation of a new genus, family, or higher taxon.1
• Phylogenetic Basis: Modern classification is based on evolutionary descent. Cladistics is the primary method used, which classifies groups based solely on their most recent common ancestor and shared derived characteristics, known as synapomorphies.2

As new information is obtained, these classifications are subject to revision to ensure they accurately reflect the tree of life.31