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55-713: Maschio (Italian, ' male ' or 'castle keep ') is an Italian surname. People with this surname include: Aurelius Maschio (died 1996), Italian priest and missionary in India Francisco Maschio (born 1890s), an Argentinian horse race trainer Humberto Maschio (born 1933), an Italian Argentine footballer Mickaël Maschio (born 1973), a French motocross racer Robert Maschio (born 1966), an American actor See also [ edit ] All pages with titles containing Maschio [REDACTED] The dictionary definition of maschio at Wiktionary Ciao maschio ,

110-495: A sexual system called androdioecy . They can also coexist with females and hermaphrodites, a sexual system called trioecy . 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), hermaphroditic animals, such as worms , have both male and female reproductive organs. Not all species share

165-741: A 1978 Italian-French film Nebbieul Maschio , a grape variety Maschio Angioino , a castle in Naples, Italy [REDACTED] Surname list This page lists people with the surname Maschio . If an internal link intending to refer to a specific person led you to this page, you may wish to change that link by adding the person's given name (s) to the link. Retrieved from " https://en.wikipedia.org/w/index.php?title=Maschio&oldid=1106963080 " Category : Surnames Hidden categories: Articles with short description Short description with empty Wikidata description All set index articles Male Male ( symbol : ♂ )

220-452: 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. 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

275-502: A female, forcing fertilization and overriding female choice. Since this can often be dangerous for the female, an evolutionary arms race between the sexes is often an outcome. Charles Darwin wrote that anisogamy had an impact on the evolution of sexual dimorphism . He also argued that anisogamy had an impact on sexual behavior. Anisogamy first became a major topic in the biological sciences when Charles Darwin wrote about sexual selection . Mathematical models seeking to account for

330-454: A few species. Anisogamy appears to have evolved multiple times from isogamy; for example, female Volvocales (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). A common symbol used to represent

385-458: A fit male would be one that is fast, has more refined sensory organs, and spatial awareness. Some secondary sex characteristics are not only meant for attracting mates, but also for competing with other males for copulation opportunities. Some structures, such as antlers in deer, can provide benefits to the male's reproductive success by providing a weapon to prevent rival males from achieving reproductive success. However, other structures such as

440-416: A larger number of gametes that 'seek out' those of the larger type. However, because zygotes formed from larger gametes have better survival prospects, this process can again lead to the divergence of gametes sizes into large and small (female and male) gametes. The end result is one where it seems that the numerous, small gametes compete for the large gametes that are tasked with providing maximal resources for

495-440: A male reproductive advantage. Since females are often the limiting factor in a species reproductive success, males are often expected by the females to search and compete for the female, known as intraspecific competition . This can be seen in organisms such as bean beetles, as the male that searches for females more frequently is often more successful at finding mates and reproducing. In species undergoing this form of selection,

550-411: A potential mate. This process, known as sexual selection , results in the development of traits to ease reproductive success rather than individual survival, such as the inflated size of a termite queen. It is also important for females to select against potential mates that may have a sexually transmitted infection , for the disease could not only hurt the female's reproductive ability, but also damage

605-483: A process by which the female can store excess sperm from a mate, and fertilize her eggs long after the reproductive event if mating opportunities drop or quality of mates decreases. By being able to save sperm from more desirable mates, the female gains more control over its own reproductive success, thus allowing for the female to be more selective of males as well as making the timing of fertilization potentially more frequent if males are scarce. For males of all species,

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660-469: A trade-off between larger gamete number and gamete size (which in turn affects zygote survival), because the total resource one individual can invest in reproduction is assumed to be fixed. The first formal, mathematical theory proposed to explain the evolution of anisogamy was based on gamete limitation: this model assumed that natural selection would lead to gamete sizes that result in the largest population-wide number of successful fertilizations. If it

715-418: 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. In many species, males differ from females in more ways than just

770-456: 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 . The part of the Y-chromosome which is responsible for maleness is the sex-determining region of

825-405: Is assumed that a certain amount of resources provided by the gametes are needed for the survival of the resulting zygote, and that there is a trade-off between the size and number of gametes, then this optimum was shown to be one where both small (male) and large (female) gametes are produced. However, these early models assume that natural selection acts mainly at the population level, something that

880-449: Is considered to be male (a sperm cell ), whereas the larger gamete is regarded as female (typically an egg cell , if non- motile ). There are several types of anisogamy. Both gametes may be flagellated and therefore motile . Alternatively, as in flowering plants , conifers and gnetophytes , neither of the gametes are flagellated. In these groups, the male gametes are non-motile cells within pollen grains, and are delivered to

935-469: Is high in reproduction since they typically expend more energy throughout a single reproductive event. This can be seen as early as oogenesis , for the female sacrifices gamete number for gamete size to better increase the survival chances of the potential zygote; a process more energetically demanding than spermatogenesis in males. Oogenesis occurs in the ovary , a female-specific organ that also produces hormones to prepare other female-specific organs for

990-423: 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

1045-424: Is the sex of an organism that produces the gamete (sex cell) known as sperm , which fuses with the larger female gamete, 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 . Most male mammals , including male humans, have a Y chromosome , which codes for

1100-422: Is today known to be a very problematic assumption. The first mathematical model to explain the evolution of anisogamy via individual level selection, and one that became widely accepted was the theory of gamete or sperm competition. Here, selection happens at the individual level: those individuals that produce more (but smaller) gametes also gain a larger proportion of fertilizations simply because they produce

1155-399: 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. Anisogamy Anisogamy most likely evolved from isogamy . Since

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1210-399: The 'selfish' evolutionary force of gamete competition stronger than the 'cooperative' force of gamete limitation even if gamete limitation is very acute (approaching 100% of eggs remaining unfertilized). There is then a relatively sound theory base for understanding this fundamental transition from isogamy to anisogamy in the evolution of reproduction, which is predicted to be associated with

1265-476: The Greek verb gameo (meaning to have sex/to reproduce), eventually meaning "non-equal reproduction" obviously referring to the enormous differences between male and female gametes in size and abilities. The first known use of the term anisogamy was in the year 1891. Anisogamy is the form of sexual reproduction that involves the union or fusion of two gametes which differ in size and/or form. The smaller gamete

1320-650: The Y-chromosome, the SRY . The SRY activates Sox9 , which forms feedforward loops with FGF9 and PGD 2 in the gonads , allowing the levels of these genes to stay high enough in order to cause male development; 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. 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

1375-458: The biological definition of male and female is based on gamete size, the evolution of anisogamy is viewed as the evolutionary origin of male and female sexes . Anisogamy is an outcome of both natural selection and sexual selection , and led the sexes to different primary and secondary sex characteristics including sex differences in behavior. Geoff Parker , Robin Baker , and Vic Smith were

1430-412: The changes necessary in the reproductive organs to facilitate egg delivery in external fertilizers, and zygote development in internal fertilizers. The egg cell produced is not only large, but sometimes even immobile, requiring contact with the more mobile sperm to instigate fertilization. Since this process is very energy-demanding and time-consuming for the female, mate choice is often integrated into

1485-405: The conditions. These selection pressures also act in the same direction (to increase gamete numbers at the expense of size) and at the same level (individual selection). Theory also suggests that gamete limitation could only have been the dominant force of selection for the evolutionary origin of the sexes under quite limited circumstances, and the presence on average of just one competitor can makes

1540-621: The context of gender , such as for gender role or gender identity of a man or boy . 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". Male can also refer to a shape of connectors . Species that are divided into females and males are classified as gonochoric in animals, as dioecious in seed plants and as dioicous in cryptogams . Males can coexist with hermaphrodites,

1595-548: The differing phenotypes found between the sexes of the same species. This sex-specific selection between sexes over time also leads to the development of secondary sex characteristics , which assist males and females in reproductive success. In most species, both sexes choose mates based on the available phenotypes of potential mates. These phenotypes are species-specific, resulting in varying strategies for successful sexual reproduction. For example, large males are sexually selected for in elephant seals because their large size helps

1650-425: The dominant individual in a group becomes female while the other ones are male. 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. Male animals have evolved to use secondary sex characteristics as

1705-528: The egg cell allow for the production of pheromones , which attract the swimming sperm cells. Anisogamy is a core element of sexual dimorphism that helps to explain phenotypic differences between sexes. Researchers estimate that over 99.99% of eukaryotes reproduce sexually. Most do so by way of male and female sexes, both of which are optimized for reproductive potential. Due to their differently sized and shaped gametes, both males and females have developed physiological and behavioral differences that optimize

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1760-432: The egg cells by means of pollen tubes . In the red alga Polysiphonia , non-motile eggs are fertilized by non-motile sperm. The form of anisogamy that occurs in animals , including humans , is oogamy , where a large, non-motile egg (ovum) is fertilized by a small, motile sperm ( spermatozoon ). The egg is optimized for longevity, whereas the small sperm is optimized for motility and speed. The size and resources of

1815-489: The evolution of anisogamy were published as early as 1932, but the first model consistent with evolutionary theory was that published by Geoff Parker , Robin Baker and Vic Smith in 1972. Although its evolution has left no fossil records, it is generally accepted that anisogamy evolved from isogamy and that it has evolved independently in several groups of eukaryotes including protists, algae, plants and animals. According to John Avise anisogamy probably originated around

1870-400: The female and male gamete-producing organisms and structures but also the structures of the sporophytes that give rise to male and female plants. The evolution of anisogamy led to the evolution of male and female function. Before the evolution of anisogamy, mating types in a species were isogamous : the same size and both could move, catalogued only as "+" or "-" types. In anisogamy,

1925-509: The female's behavior. Females will often be very selective of the males they choose to reproduce with, for the phenotype of the male can be indicative of the male's physical health and heritable traits. Females employ mate choice to pressure males into displaying their desirable traits to females through courtship , and if successful, the male gets to reproduce. This encourages males and females of specific species to invest in courtship behaviors as well as traits that can display physical health to

1980-400: The first to provide a mathematical model for the evolution of anisogamy that was consistent with modern evolutionary theory. Their theory was widely accepted but there are alternative hypotheses about the evolution of anisogamy. Anisogamy (the opposite of isogamy ) comes from the ancient Greek negative prefix a(n)- ( alpha privative ), the Greek adjective isos (meaning equal) and

2035-475: 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 . Borrowed from Old French masle , from Latin masculus ("masculine, male, worthy of a man"), diminutive of mās ("male person or animal, male"). In humans, the word male can be used in

2090-429: The individual's fecundity . Since most egg laying females typically must bear the offspring and have a more limited reproductive cycle, this typically makes females a limiting factor in the reproductive success rate of males in a species. This process is also true for females selecting males, and assuming that males and females are selecting for different traits in partners, would result in phenotypic differences between

2145-529: The insect order Hymenoptera , such as ants and bees , are often determined by haplodiploidy , 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 . 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. In tropical clown fish ,

2200-429: The large colorful tail feathers found in male peacocks, are a result of Fisherian runaway as well as several more species specific factors. Due to females selecting for specific traits in males, over time, these traits are exaggerated to the point where they could hinder the male's survivability. However, since these traits greatly benefit sexual selection, their usefulness in providing more mating opportunities overrides

2255-423: The male fight off other males, but small males are sexually selected for in spiders for they can mate with the female more quickly while avoiding sexual cannibalism . However, despite the large range of sexually selected phenotypes, most anisogamous species follow a set of predictable desirable traits and selective behaviors based on general reproductive success models. For internal fertilizers , female investment

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2310-514: The male sex is the Mars symbol ♂, a circle with an arrow pointing northeast . The Unicode code-point is: 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

2365-618: The male's gametes are energetically cheap and abundant in every ejaculation, a male can greatly increase his sexual success by mating far more frequently than the female. Sperm, unlike egg cells, are also mobile, allowing for the sperm to swim towards the egg through the female's sexual organs. Sperm competition is also a major factor in the development of sperm cells. Only one sperm can fertilize an egg, and since females can potentially mate with more than one male before fertilization occurs, producing sperm cells that are faster, more abundant, and more viable than that produced by other males can give

2420-494: 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

2475-560: The mechanisms by which two gametes get together as required for sexual 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 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

2530-425: The offspring. Some recent theoretical work has challenged the gamete competition theory, by showing that gamete limitation by itself can lead to the divergence of gamete sizes even under selection at the individual level. While this is possible, it has also been shown that gamete competition and gamete limitation are the ends of a continuum of selective pressures, and they can act separately or together depending on

2585-399: The organisms used in such comparative studies do not fit the theoretical assumptions well. A valuable model system to the study of the evolution of anisogamy is the volvocine algae, which group of chlorophytes is quite unique for its extant species exhibit a diversity of mating systems ( isogamy and anisogamy) in addition to its extremes in both unicellularity and multicellularity with

2640-424: The possibility that the trait could lead to a shortening of its lifespan through predation or starvation. These desirable traits extend beyond physical body parts, and often extend into courtship behavior and nuptial gifts as well. Although some behaviors in males are meant to work within the parameters of female choice, some male traits work against it. Strong enough males, in some cases, can force themselves upon

2695-467: 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 . The use of "male" in regard to sex and gender has been subject to discussion . The existence of separate sexes has evolved independently at different times and in different lineages , an example of convergent evolution . The repeated pattern

2750-572: 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. Birds often exhibit colorful plumage that attracts females. This

2805-533: The resulting offspring. Although not uncommon in males, females are more associated with parental care . Since females are on a more limited reproductive schedule than males, a female often invests more in protecting the offspring to sexual maturity than the male. Like mate choice, the level of parental care varies greatly between species, and is often dependent on the number of offspring produced per sexual encounter. In many species, including ones from all major vertebrate groups females can utilize sperm storage ,

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2860-598: The same time sexual reproduction and multicellularity occurred, over 1 billion years ago. Anisogamy first evolved in multicellular haploid species after different mating types had become established. The three main theories for the evolution of anisogamy are gamete competition, gamete limitation, and intracellular conflicts, but the last of these three is not well supported by current evidence. Both gamete competition and gamete limitation assume that anisogamy originated through disruptive selection acting on an ancestral isogamous population with external fertilization, due to

2915-478: The sexes over many generations. This hypothesis, known as the Bateman's Principle , is used to understand the evolutionary pressures put on males and females due to anisogamy. Although this assumption has criticism, it is a generally accepted model for sexual selection within anisogamous species. The selection for different traits depending on sex within the same species is known as sex-specific selection, and accounts for

2970-406: The sperm cells they produce are optimized for ensuring fertilization of the female egg. These sperm cells are created through spermatogenesis, a form of gametogenesis that focuses on developing the most possible gametes per sexual encounter. Spermatogenesis occurs in the testes , a male specific organ that also produces hormones that trigger the development of secondary sex characteristics. Since

3025-492: The transition to multicellularity. In fact, Hanschen et al. (2018) demonstrate that anisogamy evolved from isogamous multicellular ancestors and that anisogamy would subsequently drive secondary sexual dimorphism. Some comparative empirical evidence for the gamete competition theories exists, although it is difficult to use this evidence to fully tease apart the competition and limitation theories because their testable predictions are similar. It has also been claimed that some of

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