Male

This article is about the male sex. For the capital of the Maldives, seeMalé.For other uses, seeMale (disambiguation).

The symbol of the Roman godMars(god of war) is often used to represent the male sex. It also stands for the planetMarsand is thealchemical symbolforiron.

Male(symbol:♂) is thesexof anorganismthat produces thegamete(sex cell) known assperm,which fuses with the largerfemalegamete,orovum,in the process offertilisation.A male organism cannotreproduce sexuallywithout access to at least one ovum from a female, but some organisms can reproduce both sexually andasexually.Most malemammals,including male humans, have aY chromosome,which codes for the production of larger amounts oftestosteroneto developmale reproductive organs.

In humans, the wordmalecan also be used to refer togender,in the social sense ofgender roleorgender identity.The use of "male" in regard to sex and gender has been subject todiscussion.

Overview

The existence of separate sexes has evolved independently at different times and in differentlineages,an example ofconvergent evolution.The repeated pattern is sexual reproduction inisogamousspecies with two or moremating typeswith gametes of identical form and behavior (but different at the molecular level) toanisogamousspecies withgametesof male andfemaletypes tooogamousspecies 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.

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.

Male/female dimorphismbetween organisms or reproductive organs of different sexes is not limited to animals; male gametes are produced bychytrids,diatomsand landplants,among others. In land plants,femaleandmaledesignate not only the female and male gamete-producing organisms and structures but also the structures of thesporophytesthat give rise to male and female plants.

Evolution

See also:Evolution of sexual reproductionandSex § Evolution of sex

Theevolution of anisogamyled to the evolution of male and female function.Before the evolution of anisogamy,mating typesin a species wereisogamous:the same size and both could move, catalogued only as "+" or "-" types.In anisogamy, the mating type is called a gamete. The male gamete is smaller than the female gamete, and usually mobile.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.Anisogamy appears to have evolved multiple times from isogamy; for example, femaleVolvocales(a type of green algae) evolved from the plus mating type.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.One theory suggests male evolved from the dominant mating type (called mating type minus).

Symbol, etymology, and usage

Symbol

A commonsymbolused to represent the male sex is theMars symbol♂, a circle with an arrow pointingnortheast.TheUnicodecode-point is:

U+2642♂MALE SIGN(♂)

The symbol is identical to the planetary symbol ofMars.It was first used to denote sex byCarl Linnaeusin 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.

Etymology

Borrowed fromOld Frenchmasle,fromLatinmasculus( "masculine, male, worthy of a man" ), diminutive ofmās( "male person or animal, male" ).

Usage

In humans, the wordmalecan be used in the context ofgender,such as for gender role or gender identity of amanorboy.For example, according to Merriam-Webster, "male" can refer to "having a gender identity that is the opposite of female".According to the Cambridge Dictionary, "male" can mean "belonging or relating to men".

Malecan also refer toa shape of connectors.

Males across species

Species that are divided into females and males are classified asgonochoricin animals, asdioeciousinseed plantsand asdioicousincryptogams.

Males can coexist with hermaphrodites, asexual systemcalledandrodioecy.They can also coexist with females and hermaphrodites, a sexual system calledtrioecy.

Sex determination

Main article:Sex-determination system

Photograph of an adult male human, with an adultfemalefor 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),hermaphroditicanimals, such asworms,have both male and female reproductive organs.

Not all species share a commonsex-determination system.In mostanimals,includinghumans,sex is determinedgenetically;however, species such asCymothoa exiguachange sex depending on the number of females present in the vicinity.

Genetic determination

Mostmammals,includinghumans,are genetically determined as such by theXY sex-determination systemwhere males have XY (as opposed to XX in females)sex chromosomes.It is also possible in a variety of species, including humans, to beXX maleor 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.

The part of the Y-chromosome which is responsible for maleness is the sex-determining region of the Y-chromosome, theSRY.The SRY activatesSox9,which forms feedforward loops withFGF9andPGD₂in thegonads,allowing the levels of these genes to stay high enough in order to cause male development;for example, Fgf9 is responsible for development of thespermatic cordsand the multiplication ofSertoli cells,both of which are crucial to male sexual development.

TheZW sex-determination system,where males have ZZ (as opposed to ZW in females) sex chromosomes, may be found inbirdsand someinsects(mostlybutterflies and moths) and other organisms. Members of the insect orderHymenoptera,such asantsandbees,are often determined byhaplodiploidy,where most males arehaploidand females and some sterile males arediploid.However, fertile diploid males may still appear in some species, such asCataglyphis cursor.

Environmental determination

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.In tropicalclown fish,the dominant individual in a group becomes female while the other ones are male.

In manyarthropods,sex is determined by infection withparasitic,endosymbioticbacteriaof the genusWolbachia.The bacterium can only be transmitted via infected ova, and the presence of the obligate endoparasite may be required for female sexual viability.

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 theirfitness.Sexual selectionis 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.

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 organof 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.

Birds often exhibit colorfulplumagethat attracts females.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

• Male pregnancy
• Masculinity
• Gentleman

Further reading

• Wedgwood, Hensleigh(1855)."On False Etymologies".Transactions of the Philological Society(6): 68.