It uses strict monophyly as the only criterion for grouping related species. In cladistic taxonomy, evolution is seen as a process of progressive bifurcations of lineages. Every species, therefore, has a sister species whether recognisable or not, and this pair derived from an ancestral species. Anagenetic component of evolutionary change is ignored in cladistics. Cladistics is accepted as the best method available for phylogenetic analysis because it recognises and employs evolutionary theory.
All cladograms are hypothetical and none can be proved correct for sure.
A grouping of taxa which show similar modifications with respect to their ancestors. Grade taxa may be polyphyletic, paraphyletic or monophyletic. A paraphyletic taxon is the lowest grade in a phylogenetic tree. It is based on overall similarity. It accepts all monophyletic, paraphyletic and polyphyletic groups.