Systematics is the name for the branch of biology concerned with the study of the kinds of organisms, their relationships to one another, and their evolutionary history.
Taxonomy, a term often used interchangeably with systematics, is the part of systematics involved in the description, naming, and classification of organisms.
Phylogenetics, another part of systematics, is the study of the phylogeny or evolutionary history of an organism or a group of organisms. Two underlying goals of plant systematics, thus, are to:
- Find, describe, give unique names to, and organize into categories the species of plants of the world (a goal of taxonomy).
- Organize plants and plant groups to reflect their evolutionary relatedness and their descent from a common ancestor (a goal of phylogenetics).
Systematics today is a vigorous and exciting field that has been given great impetus by the discoveries of molecular biologists, who now are describing organisms at their most fundamental level—the DNA sequences of the cells—and providing the systematists new data on which to base their phylogenetic trees. Phylogenetic trees are the graphic representation of the evolutionary divergences of organisms that put together on the same branches the organisms most closely related, with oldest ancestors near the base, youngest descendants near the top. The trees obtained from the DNA sequences basically trace the history of how the genes have changed through time.