Final answer:
The phylogenetic species concept identifies species by the unique characteristics they share, which are not found in other species. Phylogenetic trees, constructed using cladistics, represent the evolutionary relationships between species, and they are revised as new genetic and molecular data become available.
Step-by-step explanation:
The phylogenetic species concept identifies species by analyzing the shared possession of unique characteristics within a group of organisms. For instance, if a set of fossil leg bones all possess a distinct trait (Trait A) not found in any other species, these bones would be classified as a new species. This approach helps overcome the difficulties associated with the biological species definition, which relies on breeding behavior and is less applicable to the fossil record and situations where interbreeding is not observable. Scientists construct phylogenetic trees using cladistics, a methodology that organizes organisms into clades or monophyletic groups. These clades consist of organisms that have descended from a single ancestor. Cladistics relies on the identification of homologous traits — characteristics inherited from a common ancestor — and sorts these traits to understand the evolutionary relationships between organisms.