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Male

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This article is about the male sex. For the capital of the Maldives, see Malé. For other uses, see Male (disambiguation).

The symbol of the Roman god Mars (god of war) is often used to represent the male sex. It also stands for the planet Mars and is the alchemical symbol for iron.

Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete,[1][2][3] or ovum, in the process of fertilisation. A male organism cannot reproduce sexually without access to at least one ovum from a female, but some organisms can reproduce both sexually and asexually.[4] Most male mammals, including male humans, have a Y chromosome,[5][6] which codes for the production of larger amounts of testosterone to develop male reproductive organs.

In humans, the word male can also be used to refer to gender, in the social sense of gender role or gender identity.[7][better source needed] The use of "male" in regard to sex and gender has been subject to discussion.

Overview

The existence of separate sexes has evolved independently at different times and in different lineages, an example of convergent evolution.[8][9] The repeated pattern is sexual reproduction in isogamous species with two or more mating types with gametes of identical form and behavior (but different at the molecular level) to anisogamous species with gametes of male and female types to oogamous 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 for sexual reproduction.[10][page needed]

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.[9][11][12]

Male/female dimorphism between organisms or reproductive organs of different sexes is not limited to animals; male gametes are produced by chytrids, diatoms and land plants, among others. In land plants, female and male designate not only the female and male gamete-producing organisms and structures but also the structures of the sporophytes that give rise to male and female plants.[citation needed]

Evolution

See also: Evolution of sexual reproduction and Sex § Evolution of sex

The evolution of anisogamy led to the evolution of male and female function.[13] Before the evolution of anisogamy, mating types in a species were isogamous: the same size and both could move, catalogued only as "+" or "-" types.[14]: 216  In anisogamy, the mating type is called a gamete. The male gamete is smaller than the female gamete, and usually mobile.[15] 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.[16] Anisogamy appears to have evolved multiple times from isogamy; for example, female Volvocales (a type of green algae) evolved from the plus mating type.[16][14]: 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.[17] One theory suggests male evolved from the dominant mating type (called mating type minus).[18]

Symbol, etymology, and usage

Symbol

A common symbol used to represent the male sex is the Mars symbol ♂, a circle with an arrow pointing northeast. The Unicode code-point is:

U+2642 ♂ MALE SIGN (♂)

The symbol is identical to the planetary symbol of Mars. It was first used to denote sex by Carl Linnaeus in 1751. The symbol is sometimes seen as a stylized representation of the shield and spear of the Roman god Mars. According to William T. Stearn, however, this derivation is "fanciful" and all the historical evidence favours "the conclusion of the French classical scholar Claude de Saumaise (Salmasius, 1588–1683)" that it is derived from θρ, the contraction of a Greek name for the planet Mars, which is Thouros.[19]

Etymology

Borrowed from Old French masle, from Latin masculus ("masculine, male, worthy of a man"), diminutive of mās ("male person or animal, male").[20]

Usage

In humans, the word male can be used in the context of gender, such as for gender role or gender identity of a man or boy.[7] For example, according to Merriam-Webster, "male" can refer to "having a gender identity that is the opposite of female".[21] According to the Cambridge Dictionary, "male" can mean "belonging or relating to men".[22]

Male can also refer to a shape of connectors.[23][24]

Males across species

Species that are divided into females and males are classified as gonochoric in animals, as dioecious in seed plants[2] and as dioicous in cryptogams.[25]: 82 

Males can coexist with hermaphrodites, a sexual system called androdioecy. They can also coexist with females and hermaphrodites, a sexual system called trioecy.[26]

Sex determination

Main article: Sex-determination system
Photograph of an adult male human, with an adult female 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),[8][9][2] hermaphroditic animals, such as worms, have both male and female reproductive organs.[27]

Not all species share a common sex-determination system. In most animals, including humans, sex is determined genetically; however, species such as Cymothoa exigua change sex depending on the number of females present in the vicinity.[28][better source needed]

Genetic determination

Most mammals, including humans, are genetically determined as such by the XY 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 be XX male or have other karyotypes. During reproduction, 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 a female.[29]

The part of the Y-chromosome which is responsible for maleness is the sex-determining region of the Y-chromosome, the SRY.[30] The SRY activates Sox9, which forms feedforward loops with FGF9 and PGD2 in the gonads, allowing the levels of these genes to stay high enough in order to cause male development;[31] for example, Fgf9 is responsible for development of the spermatic cords and the multiplication of Sertoli cells, both of which are crucial to male sexual development.[32]

The ZW sex-determination system, where males have ZZ (as opposed to ZW in females) sex chromosomes, may be found in birds and some insects (mostly butterflies and moths) and other organisms. Members of the insect order Hymenoptera, such as ants and bees, are often determined by haplodiploidy,[13] where most males are haploid and females and some sterile males are diploid. However, fertile diploid males may still appear in some species, such as Cataglyphis cursor.[33]

Environmental determination

In some species of reptiles, such as alligators, sex is determined by the temperature at which the egg is incubated. Other species, such as some snails, practice sex change: adults start out male, then become female.[34] In tropical clown fish, the dominant individual in a group becomes female while the other ones are male.[35]

In many arthropods, sex is determined by infection with parasitic, endosymbiotic bacteria of the genus Wolbachia. The bacterium can only be transmitted via infected ova, and the presence of the obligate endoparasite may be required for female sexual viability.[36]

Secondary sex characteristics

Main article: Secondary sex characteristic

Male animals have evolved to use secondary sex characteristics as a way of displaying traits that signify their fitness. 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.[37]

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, the sporophyte 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.[38][page needed][39][page needed]

Birds often exhibit colorful plumage that attracts females.[40][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.

See also

References

  1. ^ Lehtonen, Jussi; Parker, Geoff A. (2014-12-01). "Gamete competition, gamete limitation, and the evolution of the two sexes". Molecular Human Reproduction. 20 (12): 1161–1168. doi:10.1093/molehr/gau068. ISSN 1360-9947. PMID 25323972.
  2. ^ a b c Fusco, Giuseppe; Minelli, Alessandro (2019-10-10). The Biology of Reproduction. Cambridge University Press. pp. 111–113. ISBN 978-1-108-49985-9.
  3. ^ Hine, Robert; Martin, Elizabeth (2015). A Dictionary of Biology. Oxford University Press. p. 354. ISBN 978-0-19-871437-8.
  4. ^ Lively, Curtis M. (2010-03-01). "A Review of Red Queen Models for the Persistence of Obligate Sexual Reproduction". Journal of Heredity. 101 (suppl_1): S13–S20. doi:10.1093/jhered/esq010. ISSN 0022-1503. PMID 20421322.
  5. ^ Reference, Genetics Home. "Y chromosome". Genetics Home Reference. Retrieved 2020-07-22.
  6. ^ "Y Chromosome". Genome.gov. Retrieved 2020-09-07.
  7. ^ a b Palazzani, Laura; Bailes, Victoria; Fella, Marina (2012). Gender in Philosophy and Law. SpringerBriefs in law. Dordrecht : Springer. p. v. ISBN 9789400749917. 'gender' means human gender, male/female gender (eBook)
  8. ^ a b Berrill, N.J. "Sex". Encyclopedia Britannica. Retrieved 2020-07-22.
  9. ^ a b c Klymkowsky, Michael W.; Melanie M., Cooper (2016-06-04). "4.9: Sexual dimorphism". Biology LibreTexts. Retrieved 2020-07-22.
  10. ^ Dusenbery, David B. (2009). Living at Micro Scale. Cambridge, Massachusetts: Harvard University Press. Chapter 20. ISBN 978-0-674-03116-6..
  11. ^ Wilcox, Christie (23 April 2020). "Why Sex? Biologists Find New Explanations". Quanta Magazine. Retrieved 2020-07-22.
  12. ^ 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, ISBN 978-3-319-16999-6
  13. ^ a b Bachtrog, Doris; Mank, Judith E.; Peichel, Catherine L.; Kirkpatrick, Mark; Otto, Sarah P.; Ashman, Tia-Lynn; Hahn, Matthew W.; Kitano, Jun; Mayrose, Itay; Ming, Ray; Perrin, Nicolas (2014-07-01). "Sex Determination: Why So Many Ways of Doing It?". PLOS Biology. 12 (7): e1001899. doi:10.1371/journal.pbio.1001899. ISSN 1545-7885. PMC 4077654. PMID 24983465.
  14. ^ a b Sawada, Hitoshi; Inoue, Naokazu; Iwano, Megumi (2014-02-07). Sexual Reproduction in Animals and Plants. Springer. ISBN 978-4-431-54589-7.
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  16. ^ a b Togashi, Tatsuya; Cox, Paul Alan (2011-04-14). The Evolution of Anisogamy: A Fundamental Phenomenon Underlying Sexual Selection. Cambridge University Press. pp. 1–15. ISBN 978-1-139-50082-1.
  17. ^ Butterfield, Nicholas J. (2000). "Bangiomorpha pubescens n. gen., n. sp.: implications for the evolution of sex, multicellularity, and the Mesoproterozoic/Neoproterozoic radiation of eukaryotes". Paleobiology. 26 (3): 386. Bibcode:2000Pbio...26..386B. doi:10.1666/0094-8373(2000)026<0386:BPNGNS>2.0.CO;2. S2CID 36648568. Retrieved 12 April 2021.
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  22. ^ "male". Cambridge Dictionary.
  23. ^ 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.
  24. ^ Richard Ferncase (2013). Film and Video Lighting Terms and Concepts. Hoboken Taylor and Francis. p. 96. ISBN 9780240801575. female[:] Refers to a socket type connector, which must receive a male connector
  25. ^ Buck WR; Goffinet, B (August 2000). "Morphology and classification of mosses". In Shaw AJ & Goffinet B (ed.). Bryophyte Biology. New York: Cambridge University Press. ISBN 978-0-521-66794-4.
  26. ^ Leonard, Janet L. (2019-05-21). Transitions Between Sexual Systems: Understanding the Mechanisms of, and Pathways Between, Dioecy, Hermaphroditism and Other Sexual Systems. Springer. pp. 1–3. ISBN 978-3-319-94139-4.
  27. ^ "hermaphroditism | Definition, Types, & Effects". Encyclopedia Britannica. Retrieved 2020-07-22.
  28. ^ Creighton, Jolene. "The Most Horrifying Parasite: The Sex-Changing Tongue-Eating Cymothoa Exigua". From Quarks to Quasars. Archived from the original on November 7, 2013. Retrieved 7 April 2014.
  29. ^ "43.1C: Sex Determination". Biology LibreTexts. 2018-07-17. Retrieved 2020-07-22.
  30. ^ Reference, Genetics Home. "SRY gene". Genetics Home Reference. Retrieved 2020-07-22.
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  32. ^ Kim, Y.; Kobayashi, A.; Sekido, R.; Dinapoli, L.; Brennan, J.; Chaboissier, M. C.; Poulat, F.; Behringer, R. R.; Lovell-Badge, R.; Capel, B. (2006). "Fgf9 and Wnt4 Act as Antagonistic Signals to Regulate Mammalian Sex Determination". PLOS Biology. 4 (6): e187. doi:10.1371/journal.pbio.0040187. PMC 1463023. PMID 16700629.
  33. ^ Doums, Claudie (2013). "Fertile diploid males in the ant Cataglyphis cursor: a potential cost of thelytoky?". Behavioral Ecology and Sociobiology. 67 (12): 1983–1993. Bibcode:2013BEcoS..67.1983D. doi:10.1007/s00265-013-1606-6. hdl:10261/88167. S2CID 18141328. Retrieved 2 October 2021.
  34. ^ 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. ISSN 0006-3185. PMID 26695826. S2CID 22783998.
  35. ^ Bull, J. J. (March 1980). "Sex Determination in Reptiles". The Quarterly Review of Biology. 55 (1): 3–21. doi:10.1086/411613. ISSN 0033-5770. S2CID 85177125.
  36. ^ Zimmer, Carl (2001). "Wolbachia: a tale of sex and survival". Science. 292 (5519): 1093–1095. doi:10.1126/science.292.5519.1093. PMID 11352061. S2CID 37441675.
  37. ^ Campbell B (2017). Human Evolution: An Introduction to Man's Adaptations. Routledge. pp. 392–393. ISBN 978-1351514415.
  38. ^ Ellis, Lee; Hershberger, Scott; Field, Evelyn; Wersinger, Scott; Pellis, Sergio; Geary, David; Palmer, Craig; Hoyenga, Katherine; Hetsroni, Amir (2013-05-13). Sex Differences: Summarizing More than a Century of Scientific Research. Psychology Press. ISBN 978-1-136-87493-2.
  39. ^ Richards, Julia E.; Hawley, R. Scott (2010-12-12). The Human Genome. Academic Press. ISBN 978-0-08-091865-5.
  40. ^ switze, International Conference on Comparative Physiology 1992 Crans; Bassau, Short & (1994-08-04). The Differences Between the Sexes. Cambridge University Press. ISBN 978-0-521-44878-9.{{cite book}}: CS1 maint: numeric names: authors list (link)

Further reading

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