Where information about phylogenetic relationships is available, organisms are preferentially grouped into clades. Where data is lacking, or two clades of uncertain relationship are to be compared, the cladistic method is limited; then, the grade provides a useful tool for comparing organisms.
As an example, mosses and liverworts were long thought to represent a clade, but molecular evidence shows the two are in fact separate lineages. However, they have a similar degree of complexity, and the "bryophyte grade" is a useful benchmark when analysing early plants - it contains information about the status of fossils which we cannot classify into extant groups. When referring to a group of organisms, the term "grade" is usually enclosed in quotation marks to denote its status as a paraphyletic term.