Final answer:
Molecular phylogeny, or cladistics, is a method using molecular evidence to determine evolutionary relationships and form clades, which include an ancestor and all its descendants, displayed in cladograms.
Step-by-step explanation:
Molecular phylogeny (cladistics) is a classification method that uses molecular evidence to identify phylogenetic relationships among organisms. Cladistics sorts organisms into clades, or monophyletic groups, which are groups of organisms that originated from a common ancestor and include all the descendant species. By using traits in related species, cladistics determines ancestor-descendant relationships. Cladograms visually present these relationships by distinguishing between homologous ancestral and derived characteristics.
For example, in a cladogram, mammals, reptiles, and birds may be sorted into clades based on shared evolutionary traits like amniotic eggs. This method focuses on shared derived characteristics to establish the relationships and the branching of the phylogenetic tree. Cladistics relies on maximum parsimony — the simplest explanation with the fewest evolutionary steps — when constructing phylogenetic trees.