What is a distinct, more distantly related group of organisms on a cladogram called?

The term used to refer to a distinct, more distantly related group of organisms on a cladogram is an outgroup. In the context of cladistic analysis, an outgroup is a species or group of species that is thought to be outside the clade being studied. This group provides a point of reference that helps determine the evolutionary relationships and characteristics of the organisms within the clade.

By comparing the traits of the outgroup with those of the ingroup (the group of organisms being studied), scientists can identify which traits are shared and which are derived, thus clarifying the evolutionary pathways and relationships. This is particularly important in constructing phylogenetic trees, as it helps create a baseline for what the ancestral state of certain traits may have been, allowing for the determination of evolutionary changes over time.

In contrast, a clade refers to a group of organisms that includes a common ancestor and all its descendants, while lineage typically describes the sequence of species that lead back to a common ancestor. A node represents a point of divergence in a cladogram where a single ancestral lineage splits into two or more lineages. Thus, the outgroup serves a crucial role in helping to elucidate the evolutionary history depicted in cladograms.