Sex allocation is the allocation of resources to male versus female reproduction in sexual species (Charnov 1982; West 2009). Sex allocation depends upon the breeding system of a species, as well as how reproduction is carried out within each breeding system. Breeding systems can be categorised as dioecious, in which individuals are either male or female for their entire lifetime (e.g. birds and mammals) or hermaphroditic, in which the same individual can produce both male and female gametes. Hermaphrodites can be either sequential or simultaneous. Sequential hermaphrodites, or sex changers, function as one sex early in their life, and then switch to the other (e.g. some reef fish such as angelfish, and some invertebrates such as Pandalid shrimps). Simultaneous hermaphrodites are capable of both female and male reproduction at the same time (e.g. most flowering plants).
Read more about Sex Allocation: The Fundamental Problems of Sex Allocation Are As Follows (Charnov 1982; West 2009), A Potted History, Modern Research, Developments