part of developmental process involved in reproduction multicellular organism development sex differentiation development of animal secondary sexual characteristics https://github.com/geneontology/go-ontology/issues/31051 biological_process development of secondary sexual characteristics, sensu Metazoa GO:0045136 development of secondary sexual characteristics The process whose specific outcome is the progression of the secondary sexual characteristics over time, from their formation to the mature structures. In mammals, examples include growth of axillary, chest, and pubic hair, voice changes, testicular/penile enlargement, breast development and menstrual periods. Development occurs in response to sex hormone secretion.