Final answer:
Primitive traits are characteristics present in the common ancestor, while derived traits have evolved in a specific group. They are used to determine evolutionary relationships through cladistics.
Step-by-step explanation:
In biology, primitive and derived traits are used to determine evolutionary relationships. Primitive traits are characteristics that are present in the common ancestor of a group of organisms, while derived traits are characteristics that have evolved in a specific group after their common ancestor. These traits can be identified using cladistics, a method of visually distinguishing between ancestral and derived characteristics on a cladogram.
Primitive traits are important for determining the common ancestry of different species or groups, while derived traits help in understanding the evolutionary relationships and branching pattern within a specific group. For example, opposable thumbs are a primitive trait in primates that can be used to establish their common ancestry, while the chin is a derived trait that is unique to modern humans.
By analyzing both primitive and derived traits, scientists can construct phylogenetic trees or cladograms that show the evolutionary relationships between different species or groups based on shared characteristics. These trees are based on both physical and genetic evidence and help in understanding the complexity and diversity of life.