noun, plural: microevolutions
Evolution involving small-scale changes, i.e. within the species, occurring over a short period of time that results in the formation of new species.
Example of small-scale change is the relatively small genetic variations or mutations leading to new varieties within a species. Other factors of change include natural selection, gene flow and genetic drift.
Microevolution differs from macroevolution in its approach to the analysis of the evolution process. Microevolution is reductionist whereas macroevolution is holistic.
Word origin: Greek: mīkrós, small + evolution.
Related forms: microevolutionary (adjective).