Two organisms belong to the same species if they are able to produce fertile offspring. Courtship behaviour as a necessary precursor to successful mating. The role of courtship in species recognition.

A phylogenetic classification system attempts to arrange species into groups based on their evolutionary origins and relationships. It uses a hierarchy in which smaller groups are placed within larger groups, with no overlap between groups. Each group is called a taxon (plural taxa).

One hierarchy comprises the taxa: domain, kingdom, phylum, class, order, family, genus and species.

Recall of different taxonomic systems, such as the three domain or five kingdom systems, will not be required.

Each species is universally identified by a binomial consisting of the name of its genus and species, eg, Homo sapiens.

Students should be able to appreciate that advances in immunology and genome sequencing help to clarify evolutionary relationships between organisms.