The symbol of the Roman godMars (god of war) is often used to represent the male sex. It also stands for the planetMars and is thealchemical symbol foriron.
The existence of separate sexes has evolved independently at different times and in differentlineages, an example ofconvergent evolution.[9][10] The repeated pattern is sexual reproduction inisogamous species with two or moremating types with gametes of identical form and behavior (but different at the molecular level) toanisogamous species withgametes of male andfemale types tooogamous species in which the female gamete is very much larger than the male and has no ability to move. There is a good argument that this pattern was driven by the physical constraints on the mechanisms by which two gametes get together as required forsexual reproduction.[11][page needed]. But in some species males can reproduce by themselves asexually, for example viaandrogenesis.[12][13]
Accordingly, sex is defined across species by the type of gametes produced (i.e.: spermatozoa vs. ova) and differences between males and females in one lineage are not always predictive of differences in another.[10][14][15]
Male/female dimorphism between organisms or reproductive organs of different sexes is not limited to animals; male gametes are produced bychytrids,diatoms and landplants, among others. In land plants,female andmale designate not only the female and male gamete-producing organisms and structures but also the structures of thesporophytes that give rise to male and female plants.[citation needed]
Theevolution of anisogamy led to the evolution of male and female function.[16] Before the evolution of anisogamy,mating types in a species wereisogamous: the same size and both could move, catalogued only as "+" or "-" types.[17]: 216 In anisogamy, the mating type is called a gamete. The male gamete is smaller than the female gamete, and usually mobile.[18] Anisogamy remains poorly understood, as there is no fossil record of its emergence. Numerous theories exist as to why anisogamy emerged. Many share a common thread, in that larger female gametes are more likely to survive, and that smaller male gametes are more likely to find other gametes because they can travel faster. Current models often fail to account for why isogamy remains in a few species.[19] Anisogamy appears to have evolved multiple times from isogamy; for example, femaleVolvocales (a type of green algae) evolved from the plus mating type.[19][17]: 222 Although sexual evolution emerged at least 1.2 billion years ago, the lack of anisogamous fossil records make it hard to pinpoint when males evolved.[20] One theory suggests male evolved from the dominant mating type (called mating type minus).[21]
Symbol, etymology, and usage
Symbol
A commonsymbol used to represent the male sex is theMars symbol ♂, a circle with an arrow pointingnortheast. TheUnicode code-point is:
U+2642♂MALE SIGN (♂)
The symbol is identical to the planetary symbol ofMars. It was first used to denote sex byCarl Linnaeus in 1751. The symbol is sometimes seen as a stylized representation of the shield and spear of the Roman godMars. According toWilliam T. Stearn, however, this derivation is "fanciful" and all the historical evidence favours "the conclusion of the French classical scholarClaude de Saumaise (Salmasius, 1588–1683)" that it is derived fromθρ, the contraction of a Greek name for the planet Mars, which isThouros.[22]
Etymology
Borrowed fromOld Frenchmasle, fromLatinmasculus ("masculine, male, worthy of a man"), diminutive ofmās ("male person or animal, male").[23]
Usage
In humans, the wordmale can be used in the context ofgender, such as for gender role or gender identity of aman orboy.[7] For example, according to Merriam-Webster, "male" can refer to "having a gender identity that is the opposite of female".[24] According to the Cambridge Dictionary, "male" can mean "belonging or relating to men".[25]
Photograph of an adult male human, with an adultfemale for comparison. Both models have partially shaved body hair; e.g. clean-shaven pubic regions.
The sex of a particular organism may be determined by a number of factors. These may be genetic or environmental, or may naturally change during the course of an organism's life. Although most species have only two sexes (either male or female),[9][10][2]hermaphroditic animals, such asworms, have both male and female reproductive organs.[28] Species that are divided into females and males are classified asgonochoric in animals, asdioecious inseed plants[2] and asdioicous incryptogams.[29]: 82 Males can coexist with hermaphrodites, asexual system calledandrodioecy. They can also coexist with females and hermaphrodites, a sexual system calledtrioecy.[30]
Mostmammals, includinghumans, are genetically determined as such by theXY sex-determination system where males have XY (as opposed to XX in females)sex chromosomes. It is also possible in a variety of species, including humans, to beXX male or have otherkaryotypes. Duringreproduction, a male can give either an X sperm or a Y sperm, while a female can only give an X egg. A Y sperm and an X egg produce a male, while an X sperm and an X egg produce afemale.[32]
The part of the Y-chromosome which is responsible for maleness is the sex-determining region of the Y-chromosome, theSRY.[33] The SRY activatesSox9, which forms feedforward loops withFGF9 andPGD2 in thegonads, allowing the levels of these genes to stay high enough in order to cause male development;[34] for example, Fgf9 is responsible for development of thespermatic cords and the multiplication ofSertoli cells, both of which are crucial to male sexual development.[35]
In some species of reptiles, such asalligators, sex is determined by the temperature at which the egg is incubated. Other species, such as somesnails, practice sex change: adults start out male, then become female.[37] In tropicalclown fish, the dominant individual in a group becomes female while the other ones are male.[38]
Male animals have evolved to use secondary sex characteristics as a way of displaying traits that signify theirfitness.Sexual selection is believed to be the driving force behind the development of these characteristics. Differences in physical size and the ability to fulfill the requirements of sexual selection have contributed significantly to the outcome of secondary sex characteristics in each species.[39]
In many species, males differ from females in more ways than just the production of sperm. For example, in some insects and fish, the male is smaller than the female. In seed plants, thesporophyte sex organ of a single organism includes both the male and female parts.
In mammals, including humans, males are typically larger than females. This is often attributed to the need for male mammals to be physically stronger and more competitive in order to win mating opportunities. In humans specifically, males have more body hair and muscle mass than females.[40][page needed][41][page needed]
Birds often exhibit colorfulplumage that attracts females.[42][page needed] This is true for many species of birds where the male displays more vibrant colors than the female, making them more noticeable to potential mates. These characteristics have evolved over time as a result of sexual selection, as males who exhibited these traits were more successful in attracting mates and passing on their genes.
^Lehtonen, Jussi (2017), "Gamete Size", in Shackelford, Todd K.; Weekes-Shackelford, Viviana A. (eds.),Encyclopedia of Evolutionary Psychological Science, Cham: Springer International Publishing, pp. 1–4,doi:10.1007/978-3-319-16999-6_3063-1,ISBN978-3-319-16999-6
^Kumar R, Meena M, Swapnil P (2019). "Anisogamy". In Vonk J, Shackelford T (eds.).Anisogamy.Encyclopedia of Animal Cognition and Behavior. Cham: Springer International Publishing. pp. 1–5.doi:10.1007/978-3-319-47829-6_340-1.ISBN978-3-319-47829-6.
^J. Richard Johnson (1962).How to Build Electronic Equipment. New York: Rider. p. 167.To minimize confusion, the connector portions with projecting prongs are referred to as the 'male' portion, and the sockets as the 'female' portion.
^Richard Ferncase (2013).Film and Video Lighting Terms and Concepts. Hoboken Taylor and Francis. p. 96.ISBN978-0-240-80157-5.female[:] Refers to a socket type connector, which must receive a male connector
^Buck WR; Goffinet, B (August 2000). "Morphology and classification of mosses". In Shaw AJ & Goffinet B (ed.).Bryophyte Biology. New York: Cambridge University Press.ISBN978-0-521-66794-4.
^Cahill, Abigail E.; Juman, Alia Rehana; Pellman-Isaacs, Aaron; Bruno, William T. (December 2015). "Physical and Chemical Interactions with Conspecifics Mediate Sex Change in a Protandrous Gastropod Crepidula fornicata".The Biological Bulletin.229 (3):276–281.doi:10.1086/bblv229n3p276.ISSN0006-3185.PMID26695826.S2CID22783998.
