What term describes the central trunk of a cladogram?

The term that describes the central trunk of a cladogram is referred to as the root. In phylogenetic trees or cladograms, the root represents the most recent common ancestor of all the organisms depicted in that diagram. It serves as the foundational point from which all branches emanate, illustrating the evolutionary relationships among the different species.

The root is critical for understanding the evolutionary timeline, as it establishes the starting point for the branching patterns that follow, leading to the various nodes and leaves in the cladogram which represent species or groups of species. The branches that extend from the root connect to nodes, which indicate divergence points where lineages split, while leaves represent the actual taxa being studied.

In contrast, nodes are points where one lineage diverges into two or more, branches are the lines that connect nodes to illustrate these relationships, and leaves are the endpoints that represent specific species or group of organisms under observation. Therefore, the concept of the root serves to anchor the entire cladogram, illustrating the common ancestry of all depicted life forms.