Organisms of many species are specialized into male and femalevarieties, each known as a sex.[1][2] Sexual reproduction involvesthe combining and mixing of genetic traits: specialized cells knownas gametes combine to form offspring that inherit traits from eachparent. The gametes produced by an organism define its sex: malesproduce small gametes (e.g. spermatozoa, or sperm, in animals)while females produce large gametes (ova, or egg cells). Individualorganisms which produce both male and female gametes are termedhermaphroditic.[2] Gametes can be identical in form and function(known as isogamy), but, in many cases, an asymmetry has evolvedsuch that two different types of gametes (heterogametes) exist(known as anisogamy). Physical differences are often associatedwith the different sexes of an organism; these sexual dimorphismscan reflect the different reproductive pressures the sexesexperience. For instance, mate choice and sexual selection canaccelerate the evolution of physical differences between the sexes.Among humans and other mammals, males typically carry an X and a Ychromosome (XY), whereas females typically carry two X chromosomes(XX), which are a part of the XY sex-determination system. Humansmay also be intersex. Other animals have various sex-determinationsystems, such as the ZW system in birds, the X0 system in insects,and various environmental systems, for example in reptiles andcrustaceans. Fungi may also have more complex allelic matingsystems, with sexes not accurately described as male, female, orhermaphroditic. This app is about history and for research Purpose.