Final answer:
Homologous traits are similarities in structure, morphology, or genes that indicate evolutionary relatedness. Synapomorphies are a special type of homologous trait that help identify evolutionary relationships, such as feathers in birds.
Step-by-step explanation:
Homologous traits are special because they are inherited from a common ancestor, indicating evolutionary relatedness. These traits are similarities in structure, morphology, or genes that are found in different species. An example of a homologous trait is the grasping hand found in humans and chimpanzees, suggesting a common ancestor. Synapomorphy, on the other hand, refers to shared derived traits that are unique to a particular group of organisms within a larger evolutionary tree.
It is a special type of homologous trait that helps to identify evolutionary relationships. For example, feathers are a synapomorphy of birds, as they are found only in birds and their extinct relatives.