Final answer:
The correct answer is option d. Shared derived traits are known as synapomorphies, which are key in cladistics for determining evolutionary relationships. They are exclusive to descendants of an ancestral species, differentiating them from homologous traits seen in a wider array, and important in defining a clade in a phylogenetic tree.
Step-by-step explanation:
Shared derived traits are also known as synapomorphies. These traits are crucial in the study of cladistics because they help establish evolutionary relationships between organisms. A synapomorphy is a characteristic found in an ancestral species and shared exclusively by its evolutionary descendants. This is different from homologies, which are traits inherited from a common ancestor that may be found across a wider range of species, beyond the more immediate descendants.
Analogous traits, or homoplasies, while they may appear similar and serve similar functions, do not share an evolutionary path - these traits have evolved independently in response to similar environmental pressures. Phylogenetic trees utilize homologous characteristics to outline evolutionary connections. A monophyletic group, or a clade, includes species that share a common ancestor and thus, share synapomorphies. It is important to differentiate synapomorphies from homoplasies when defining evolutionary relationships because synapomorphies provide evidence of common descent which is essential for constructing a valid phylogenetic tree.