Why was "tantrum" trending last week?
microevolution mi·cro·ev·o·lu·tion (mī'krō-ěv'ə-lōō'shən, -ē'və-)
Evolution resulting from a succession of relatively small genetic variations that often cause the formation of new subspecies.
Evolutionary change below the level of the species, resulting from relatively small genetic variations. Microevolution produces new strains of microorganisms, for example, or the rise of a new subspecies. The accumulation of many microevolutionary changes results in macroevolution.