Sex allocation is the allocation of resources to male versus female reproduction in sexual species.[1][page needed] Sex allocation theory tries to explain why many species produce equal number of males and females.[2]
In dioecious species, where individuals are either male or female for their entire lifetimes, the allocation decision lies between producing male or female offspring. In sequential hermaphrodites, where individuals function as one sex early in life and then switch to the other, the allocation decisions lie in what sex to be first and when to change sex. Animals may be dioecious or sequential hermaphrodites. Sex allocation theory also applies to flowering plants, which can be dioecious, simultaneous hermaphrodites, have unisexual plants and hermaphroditic plants in the same population, have unisexual flowers and hermaphroditic flowers on the same plant or to have only hermaphroditic flowers.[3]