Final answer:
A phylogenetic tree of vertebrates can indeed be constructed using both shared derived and primitive characters. Shared derived characters like the amniotic egg, provide information about the unique evolutionary changes within a clade. With modern technologies, the combination of morphological and molecular data aids in the accurate construction and updating of these trees.
Step-by-step explanation:
A phylogenetic tree of vertebrates can be constructed using both shared derived and primitive characters. Shared derived characters provide information about evolutionary changes that distinguish a group of organisms, while shared primitive characters are traits that are ancestral. When we consider the amniotic egg characteristic, it is a shared derived character for organisms like lizards, rabbits, and humans. However, it's a shared ancestral character within the Amniota clade. The construction of a phylogenetic tree involves analyzing morphological, molecular, and genetic data to place organisms in a tree based on these shared characteristics.
With advancements in molecular technologies, such as DNA and RNA analysis, modern phylogenetics can confirm and update evolutionary relationships. Scientists often use computer programs to handle the complex task of drafting phylogenetic trees, which are then refined with the use of cladistics, a method that distinguishes between homologous ancestral and derived characters to clarify relationships between species.