Final answer:
A geneticist creating diagrams that show relationships between species is making a phylogenetic tree, which is a hypothesis of evolutionary relationships based on genetic and physical traits.
Step-by-step explanation:
A geneticist constructing tree-like diagrams that visually indicate relationships between species is engaged in creating a phylogenetic tree. A phylogenetic tree is a diagram showing the evolutionary relationships among various biological species based on similarities and differences in genetic or physical traits or both. Such diagrams are considered a hypothesis about the evolutionary connections between species and are constructed by analyzing data such as DNA sequence alignments.
The process involves detailing the evolutionary pathways and connections among organisms, where each branching point, or node, represents the common ancestor of the species that diverge from that point. The speciation events are thus recorded, allowing scientists to visualize the divergent evolutionary paths of species. Phylogenetic trees serve as a visual representation of the tree of life, illustrating when different organisms evolved and the relationships among them.