What process involves classifying organisms primarily based on their evolutionary relationships?

The process of classifying organisms primarily based on their evolutionary relationships is known as systematics. This approach encompasses the study of the diversification of living forms, both past and present, and the relationships among them. Systematics uses various types of data, including morphological characteristics and genetic information, to construct evolutionary trees or phylogenies that illustrate these relationships.

While phylogenetics is closely related and specifically focuses on the evolutionary history and relationships determined through genetic data, systematics has a broader scope, integrating multiple lines of evidence (e.g., morphology, behavior, and genetics). Cladistics, a subset of systematics, emphasizes grouping organisms based on shared derived characteristics to illustrate evolutionary relationships. Genetics pertains to the study of heredity and variation, but it does not specifically focus on classification and relationships in the broader sense that systematics does.

Therefore, systematics is the most comprehensive term for the classification of organisms based on their evolutionary relationships.