Final answer:
To determine if two species are closely related, scientists study morphologic and genetic data to identify homologous structures. Advanced computational methods help distinguish actual evolutionary relationships, culminating in the construction of a phylogenetic tree or cladogram.
Step-by-step explanation:
Determining Relatedness Between Two Species
To determine if two species are closely related, scientists collect data that allow them to make evolutionary connections between organisms, similar to detective work. They rely on morphologic (form and function) and genetic evidence. Similar physical features and genomes often imply a close relationship, and such features are referred to as homologous structures. These structures stem from developmental similarities based on common evolutionary paths, such as the similar bone arrangements in the wings of bats and birds.
However, sometimes similar DNA segments can be misleading, as distantly related organisms may randomly share a high percentage of bases in the same locations. To overcome this, scientists use computer-based statistical algorithms to help identify the actual relationships, ultimately relying on both morphologic and molecular data to determine phylogeny. After identifying homologous traits and genes, they use a method called cladistics to organize these similarities and construct a phylogenetic tree or cladogram, which visually represents the evolutionary relationships between species.
If the common ancestor of two species can be found in the fossil record, scientists can figure out whether the species have diverged into separate species or remain as one. This evidence, along with genetic data, helps scientists determine the relationships between species accurately.