The distinction between reversible and irreversible phenomena in biological information systems provides a basis for distinguishing microevolution from macroevolution. Biological transitions encompass the entire class of irreversible changes in biological systems, including physiological and developmental phenomena. Evolutionary transitions are the subset of biological transitions that have an impact on the quality and quantity of biological information transmitted to future generations. Evolutionary transitions are manifested empirically as macroevolutionary changes, i.e. evolutionary changes that can be detected only through phylogenetic analysis among groups of species sharing a unique common ancestry.