A grade is a taxon or group of organisms united by a shared level of morphological or physiological complexity, rather than by strict common descent. The British biologist Julian Huxley coined the term to contrast with a clade, which is defined strictly by phylogenetic relationship. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/
Sources
Evolutionary grade (Wikipedia)
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