80-622: Valene Gender Male Origin Word/name Latin nomen Valentinus Region of origin Italy Valene may refer to: Valene Kane , Northern Irish actress Valene Maharaj (born 1986) was the Miss Trinidad and Tobago World 2007 title holder, and Miss World of the Caribbean for 2007 Valene Ewing , fictional character in
160-495: 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
240-501: A bird's lifetime. Activational hormones occur during puberty and adulthood and serve to 'activate' certain behaviors when appropriate, such as territoriality during breeding season. Organizational hormones occur only during a critical period early in development, either just before or just after hatching in most birds, and determine patterns of behavior for the rest of the bird's life. Such behavioral differences can cause disproportionate sensitivities to anthropogenic pressures. Females of
320-452: 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
400-459: A diverse array of sexually dimorphic traits. Aggressive utility traits such as "battle" teeth and blunt heads reinforced as battering rams are used as weapons in aggressive interactions between rivals. Passive displays such as ornamental feathering or song-calling have also evolved mainly through sexual selection. These differences may be subtle or exaggerated and may be subjected to sexual selection and natural selection . The opposite of dimorphism
480-454: 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
560-553: A large role in the changing of sex by the fish. It is often seen that a fish will change its sex when there is a lack of a dominant male within the social hierarchy. The females that change sex are often those who attain and preserve an initial size advantage early in life. In either case, females which change sex to males are larger and often prove to be a good example of dimorphism. In other cases with fish, males will go through noticeable changes in body size, and females will go through morphological changes that can only be seen inside of
640-1007: A less bright or less exaggerated color during the off-breeding season. This occurs because the species is more focused on survival than on reproduction, causing a shift into a less ornate state. Consequently, sexual dimorphism has important ramifications for conservation. However, sexual dimorphism is not only found in birds and is thus important to the conservation of many animals. Such differences in form and behavior can lead to sexual segregation , defined as sex differences in space and resource use. Most sexual segregation research has been done on ungulates, but such research extends to bats , kangaroos , and birds. Sex-specific conservation plans have even been suggested for species with pronounced sexual segregation. The term sesquimorphism (the Latin numeral prefix sesqui - means one-and-one-half, so halfway between mono - (one) and di - (two)) has been proposed for bird species in which "both sexes have basically
720-425: A naturally occurring part of development, for example plumage. In addition, the strong hormonal influence on phenotypic differences suggests that the genetic mechanism and genetic basis of these sexually dimorphic traits may involve transcription factors or cofactors rather than regulatory sequences. Sexual dimorphism may also influence differences in parental investment during times of food scarcity. For example, in
800-414: A significant role in male reproductive success. Males have a propensity to be larger than females of a comparable age but it is unclear whether the size increase is due to a growth spurt at the time of the sexual transition or due to the history of faster growth in sex changing individuals. Larger males are able to stifle the growth of females and control environmental resources. Social organization plays
880-537: A speciation phenomenon if the variation becomes strongly drastic and favorable towards two different outcomes. Sexual dimorphism is maintained by the counteracting pressures of natural selection and sexual selection. For example, sexual dimorphism in coloration increases the vulnerability of bird species to predation by European sparrowhawks in Denmark. Presumably, increased sexual dimorphism means males are brighter and more conspicuous, leading to increased predation. Moreover,
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#1732876545195960-418: 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
1040-474: Is Lamprologus callipterus , a type of cichlid fish. In this fish, the males are characterized as being up to 60 times larger than the females. The male's increased size is believed to be advantageous because males collect and defend empty snail shells in each of which a female breeds. Males must be larger and more powerful in order to collect the largest shells. The female's body size must remain small because in order for her to breed, she must lay her eggs inside
1120-537: Is Lasioglossum hemichalceum , which is a species of sweat bee that shows drastic physical dimorphisms between male offspring. Not all dimorphism has to have a drastic difference between the sexes. Andrena agilissima is a mining bee where the females only have a slightly larger head than the males. Weaponry leads to increased fitness by increasing success in male–male competition in many insect species. The beetle horns in Onthophagus taurus are enlarged growths of
1200-627: Is monomorphism , when both biological sexes are phenotypically indistinguishable from each other. Common and easily identified types of dimorphism consist of ornamentation and coloration, though not always apparent. A difference in the coloration of sexes within a given species is called sexual dichromatism, commonly seen in many species of birds and reptiles. Sexual selection leads to exaggerated dimorphic traits that are used predominantly in competition over mates. The increased fitness resulting from ornamentation offsets its cost to produce or maintain, suggesting complex evolutionary implications, but
1280-423: Is a good indicator for females because it shows that they are good at obtaining a food supply from which the carotenoid is obtained. There is a positive correlation between the chromas of the tail and breast feathers and body condition. Carotenoids play an important role in immune function for many animals, so carotenoid dependent signals might indicate health. Frogs constitute another conspicuous illustration of
1360-407: Is a sexually dimorphic trait. Theropoda It has been hypothesized that male theropods possessed a retractable penis, a feature similar to modern day crocodilians . Crocodilian skeletons were examined to determine whether there is a skeletal component that is distinctive between both sexes, to help provide an insight on the physical disparities between male and female theropods. Findings revealed
1440-423: Is advantageous to both parties because it avoids damaging the developing fruit and wasting the pollinator's effort on unrewarding visits. In effect, the strategy ensures that pollinators can expect a reward every time they visit an appropriately advertising flower. Females of the aquatic plant Vallisneria americana have floating flowers attached by a long flower stalk that are fertilized if they contact one of
1520-587: Is also displayed by dichromatism. In butterfly genera Bicyclus and Junonia , dimorphic wing patterns evolved due to sex-limited expression, which mediates the intralocus sexual conflict and leads to increased fitness in males. The sexual dichromatic nature of Bicyclus anynana is reflected by female selection on the basis of dorsal UV-reflective eyespot pupils. The common brimstone also displays sexual dichromatism; males have yellow and iridescent wings, while female wings are white and non-iridescent. Naturally selected deviation in protective female coloration
1600-456: 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
1680-673: Is also seen in frog species like P. bibroni i . Male painted dragon lizards, Ctenophorus pictus . are brightly conspicuous in their breeding coloration, but male colour declines with aging . Male coloration appears to reflect innate anti-oxidation capacity that protects against oxidative DNA damage . Male breeding coloration is likely an indicator to females of the underlying level of oxidative DNA damage (a significant component of aging) in potential mates. Possible mechanisms have been proposed to explain macroevolution of sexual size dimorphism in birds. These include sexual selection, selection for fecundity in females, niche divergence between
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#17328765451951760-470: Is believed that this is obtained by the ingestion of green Lepidopteran larvae, which contain large amounts of the carotenoids lutein and zeaxanthin . This diet also affects the sexually dimorphic colours in the human-invisible ultraviolet spectrum. Hence, the male birds, although appearing yellow to humans, actually have a violet-tinted plumage that is seen by females. This plumage is thought to be an indicator of male parental abilities. Perhaps this
1840-410: Is displayed in mimetic butterflies. Many arachnid groups exhibit sexual dimorphism, but it is most widely studied in the spiders. In the orb-weaving spider Zygiella x-notata , for example, adult females have a larger body size than adult males. Size dimorphism shows a correlation with sexual cannibalism , which is prominent in spiders (it is also found in insects such as praying mantises ). In
1920-687: Is known in ceratopsids, although there is evidence that the more primitive ceratopsian Protoceratops andrewsi possessed sexes that were distinguishable based on frill and nasal prominence size. This is consistent with other known tetrapod groups where midsized animals tend to exhibit markedly more sexual dimorphism than larger ones. However, it has been proposed that these differences can be better explained by intraspecific and ontogenic variation rather than sexual dimorphism. In addition, many sexually dimorphic traits that may have existed in ceratopsians include soft tissue variations such as coloration or dewlaps , which would be unlikely to have been preserved in
2000-678: Is more prominently selected for in less dimorphic species of spiders, which often selects for larger male size. In the species Maratus volans , the males are known for their characteristic colorful fan which attracts the females during mating. Ray-finned fish are an ancient and diverse class, with the widest degree of sexual dimorphism of any animal class. Fairbairn notes that "females are generally larger than males but males are often larger in species with male–male combat or male paternal care ... [sizes range] from dwarf males to males more than 12 times heavier than females." There are cases where males are substantially larger than females. An example
2080-402: Is of a subdued brown coloration. The plumage of the peacock increases its vulnerability to predators because it is a hindrance in flight, and it renders the bird conspicuous in general. Similar examples are manifold, such as in birds of paradise and argus pheasants . Another example of sexual dichromatism is that of nestling blue tits . Males are chromatically more yellow than females. It
2160-434: Is seen in the bee species Macrotera portalis in which there is a small-headed morph, capable of flight, and large-headed morph, incapable of flight, for males. Anthidium manicatum also displays male-biased sexual dimorphism. The selection for larger size in males rather than females in this species may have resulted due to their aggressive territorial behavior and subsequent differential mating success. Another example
2240-480: Is selected for, which is seen in the family Araneidae . All Argiope species, including Argiope bruennichi , use this method. Some males evolved ornamentation including binding the female with silk, having proportionally longer legs, modifying the female's web, mating while the female is feeding, or providing a nuptial gift in response to sexual cannibalism. Male body size is not under selection due to cannibalism in all spider species such as Nephila pilipes , but
2320-423: 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
2400-407: Is strong when the factor of environmental selection is also introduced. Environmental selection may support a smaller chick size if those chicks were born in an area that allowed them to grow to a larger size, even though under normal conditions they would not be able to reach this optimal size for migration. When the environment gives advantages and disadvantages of this sort, the strength of selection
2480-504: Is the dragonet , in which males are considerably larger than females and possess longer fins. Sexual dimorphism also occurs in hermaphroditic fish. These species are known as sequential hermaphrodites . In fish, reproductive histories often include the sex-change from female to male where there is a strong connection between growth, the sex of an individual, and the mating system within which it operates. In protogynous mating systems where males dominate mating with many females, size plays
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2560-424: 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
2640-408: 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. Sexual dimorphism Sexual dimorphism is the condition where sexes of
2720-411: Is weakened and the environmental forces are given greater morphological weight. The sexual dimorphism could also produce a change in timing of migration leading to differences in mating success within the bird population. When the dimorphism produces that large of a variation between the sexes and between the members of the sexes, multiple evolutionary effects can take place. This timing could even lead to
2800-604: The blue-footed booby , the female chicks grow faster than the males, resulting in booby parents producing the smaller sex, the males, during times of food shortage. This then results in the maximization of parental lifetime reproductive success. In Black-tailed Godwits Limosa limosa limosa females are also the larger sex, and the growth rates of female chicks are more susceptible to limited environmental conditions. Sexual dimorphism may also only appear during mating season; some species of birds only show dimorphic traits in seasonal variation. The males of these species will molt into
2880-489: The ovules ). Each pollen grain accordingly may be seen as a male plant in its own right; it produces a sperm cell and is dramatically different from the female plant, the megagametophyte that produces the female gamete. Insects display a wide variety of sexual dimorphism between taxa including size, ornamentation and coloration. The female-biased sexual size dimorphism observed in many taxa evolved despite intense male-male competition for mates. In Osmia rufa , for example,
2960-407: The 'fittest' available male. Sexual dimorphism is a product of both genetics and environmental factors. An example of sexual polymorphism determined by environmental conditions exists in the red-backed fairywren . Red-backed fairywren males can be classified into three categories during breeding season : black breeders, brown breeders, and brown auxiliaries. These differences arise in response to
3040-641: The CBS primetime soap operas Knots Landing and Dallas [REDACTED] Name list This page or section lists people that share the same given name . If an internal link led you here, you may wish to change that link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Valene&oldid=1082556531 " Category : Given names Hidden categories: Articles with short description Short description with empty Wikidata description All set index articles Male Male ( symbol : ♂ )
3120-650: 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
3200-533: The bird's body condition: if they are healthy they will produce more androgens thus becoming black breeders, while less healthy birds produce less androgens and become brown auxiliaries. The reproductive success of the male is thus determined by his success during each year's non-breeding season, causing reproductive success to vary with each year's environmental conditions. Migratory patterns and behaviors also influence sexual dimorphisms. This aspect also stems back to size dimorphism in species. It has been shown that
3280-995: The body. For example, in sockeye salmon , males develop larger body size at maturity, including an increase in body depth, hump height, and snout length. Females experience minor changes in snout length, but the most noticeable difference is the huge increase in gonad size, which accounts for about 25% of body mass. Sexual selection was observed for female ornamentation in Gobiusculus flavescens , known as two-spotted gobies. Traditional hypotheses suggest that male–male competition drives selection. However, selection for ornamentation within this species suggests that showy female traits can be selected through either female–female competition or male mate choice. Since carotenoid-based ornamentation suggests mate quality, female two-spotted guppies that develop colorful orange bellies during breeding season are considered favorable to males. The males invest heavily in offspring during incubation, which leads to
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3360-470: The caudal chevrons of male crocodiles, used to anchor the penis muscles, were significantly larger than those of females. There have been criticisms of these findings, but it remains a subject of debate among advocates and adversaries. Ornithopoda Studies of sexual dimorphism in hadrosaurs have generally centered on the distinctive cranial crests , which likely provided a function in sexual display. A biometric study of 36 skulls found sexual dimorphism
3440-621: 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,
3520-400: The costs and evolutionary implications vary from species to species. The peafowl constitute conspicuous illustrations of the principle. The ornate plumage of peacocks, as used in the courting display, attracts peahens . At first sight, one might mistake peacocks and peahens for completely different species because of the vibrant colours and the sheer size of the male's plumage; the peahen
3600-654: The degree of preservation. The availability of well-preserved remains is not a probable outcome as a consequence of decomposition and fossilization . Some paleontologists have looked for sexual dimorphism among dinosaurs using statistics and comparison to ecologically or phylogenetically related modern animals. Apatosaurus and Diplodocus Female Apatosaurus and Diplodocus had interconnected caudal vertebrae that allowed them to keep their tails elevated to aid in copulation. Discovering that this fusion occurred in only 50% of Apatosaurus and Diplodocus skeletons and 25% of Camarasaurus skeletons indicated that this
3680-425: 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
3760-448: The empty shells. If she grows too large, she will not fit in the shells and will be unable to breed. The female's small body size is also likely beneficial to her chances of finding an unoccupied shell. Larger shells, although preferred by females, are often limited in availability. Hence, the female is limited to the growth of the size of the shell and may actually change her growth rate according to shell size availability. In other words,
3840-510: The estrogen pathway. The sexual dimorphism in lizards is generally attributed to the effects of sexual selection, but other mechanisms including ecological divergence and fecundity selection provide alternative explanations. The development of color dimorphism in lizards is induced by hormonal changes at the onset of sexual maturity, as seen in Psamodromus algirus , Sceloporus gadoviae , and S. undulates erythrocheilus . Sexual dimorphism in size
3920-443: The exhausted anthers after a day or two and perhaps change their colours as well while the pistil matures; specialist pollinators are very much inclined to concentrate on the exact appearance of the flowers they serve, which saves their time and effort and serves the interests of the plant accordingly. Some such plants go even further and change their appearance once fertilized, thereby discouraging further visits from pollinators. This
4000-400: 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,
4080-417: The female is larger/broader than males, with males being 8–10 mm in size and females being 10–12 mm in size. In the hackberry emperor females are similarly larger than males. The reason for the sexual dimorphism is due to provision size mass, in which females consume more pollen than males. In some species, there is evidence of male dimorphism, but it appears to be for distinctions of roles. This
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#17328765451954160-564: The female, which looks different from the males. Various other dioecious exceptions, such as Loxostylis alata have visibly different sexes, with the effect of eliciting the most efficient behavior from pollinators, who then use the most efficient strategy in visiting each gender of flower instead of searching, say, for pollen in a nectar-bearing female flower. Some plants, such as some species of Geranium have what amounts to serial sexual dimorphism. The flowers of such species might, for example, present their anthers on opening, then shed
4240-651: The form of reduced survival. This means that even if the trait causes males to die earlier, the trait is still beneficial so long as males with the trait produce more offspring than males lacking the trait. This balance keeps dimorphism alive in these species and ensures that the next generation of successful males will also display these traits that are attractive to females. Such differences in form and reproductive roles often cause differences in behavior. As previously stated, males and females often have different roles in reproduction. The courtship and mating behavior of males and females are regulated largely by hormones throughout
4320-723: The fossil record. Stegosaurians A 2015 study on specimens of Hesperosaurus mjosi found evidence of sexual dimorphism in the shape of the dermal plates. Two plate morphs were described: one was short, wide, and oval-shaped, the other taller and narrower. In a large proportion of mammal species, males are larger than females. Both genes and hormones affect the formation of many animal brains before " birth " (or hatching ), and also behaviour of adult individuals. Hormones significantly affect human brain formation, and also brain development at puberty. A 2004 review in Nature Reviews Neuroscience observed that "because it
4400-700: The head or thorax expressed only in the males. Copris ochus also has distinct sexual and male dimorphism in head horns. Another beetle with a distinct horn-related sexual dimorphism is Allomyrina dichotoma, also known as the Japanese rhinoceros beetle . These structures are impressive because of the exaggerated sizes. There is a direct correlation between male horn lengths and body size and higher access to mates and fitness. In other beetle species, both males and females may have ornamentation such as horns. Generally, insect sexual size dimorphism (SSD) within species increases with body size. Sexual dimorphism within insects
4480-475: 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
4560-529: 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 ,
4640-444: The larger males are better at coping with the difficulties of migration and thus are more successful in reproducing when reaching the breeding destination. When viewing this from an evolutionary standpoint, many theories and explanations come into consideration. If these are the result for every migration and breeding season, the expected results should be a shift towards a larger male population through sexual selection. Sexual selection
4720-514: 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
4800-508: The male's ability to collect large shells depends on his size. The larger the male, the larger the shells he is able to collect. This then allows for females to be larger in his brooding nest which makes the difference between the sizes of the sexes less substantial. Male–male competition in this fish species also selects for large size in males. There is aggressive competition by males over territory and access to larger shells. Large males win fights and steal shells from competitors. Another example
4880-494: 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
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#17328765451954960-560: 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
5040-593: The more ornamented or brightly colored sex. Such differences have been attributed to the unequal reproductive contributions of the sexes. This difference produces a stronger female choice since they have more risk in producing offspring. In some species, the male's contribution to reproduction ends at copulation, while in other species the male becomes the main (or only) caregiver. Plumage polymorphisms have evolved to reflect these differences and other measures of reproductive fitness, such as body condition or survival. The male phenotype sends signals to females who then choose
5120-692: The most common causes for mortality in young fish. Most flowering plants are hermaphroditic but approximately 6% of species have separate males and females ( dioecy ). Sexual dimorphism is common in dioecious plants and dioicous species. Males and females in insect-pollinated species generally look similar to one another because plants provide rewards (e.g. nectar ) that encourage pollinators to visit another similar flower , completing pollination . Catasetum orchids are one interesting exception to this rule. Male Catasetum orchids violently attach pollinia to euglossine bee pollinators. The bees will then avoid other male flowers but may visit
5200-436: The plants become sexually mature. Every sexually reproducing extant species of the vascular plant has an alternation of generations; the plants we see about us generally are diploid sporophytes , but their offspring are not the seeds that people commonly recognize as the new generation. The seed actually is the offspring of the haploid generation of microgametophytes ( pollen ) and megagametophytes (the embryo sacs in
5280-418: The presence of specific sex-related behaviour is common to many lizards; and vocal qualities which are frequently observed in frogs . Anole lizards show prominent size dimorphism with males typically being significantly larger than females. For instance, the average male Anolis sagrei was 53.4 mm vs. 40 mm in females. Different sizes of the heads in anoles have been explained by differences in
5360-410: The principle. There are two types of dichromatism for frog species: ontogenetic and dynamic. Ontogenetic frogs are more common and have permanent color changes in males or females. Ranoidea lesueuri is an example of a dynamic frog with temporary color changes in males during the breeding season. Hyperolius ocellatus is an ontogenetic frog with dramatic differences in both color and pattern between
5440-467: 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
5520-408: The production of more exaggerated ornaments in males may come at the cost of suppressed immune function. So long as the reproductive benefits of the trait due to sexual selection are greater than the costs imposed by natural selection, then the trait will propagate throughout the population. Reproductive benefits arise in the form of a larger number of offspring, while natural selection imposes costs in
5600-572: 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
5680-404: The same species exhibit different morphological characteristics, including characteristics not directly involved in reproduction . The condition occurs in most dioecious species, which consist of most animals and some plants. Differences may include secondary sex characteristics , size, weight, color, markings, or behavioral or cognitive traits. Male-male reproductive competition has evolved
5760-585: The same plumage pattern, though the female is clearly distinguishable by reason of her paler or washed-out colour". Examples include Cape sparrow ( Passer melanurus ), rufous sparrow (subspecies P. motinensis motinensis ), and saxaul sparrow ( P. ammodendri ). Examining fossils of non-avian dinosaurs in search of sexually dimorphic characteristics requires the supply of complete and articulated skeletal and tissue remains. As terrestrial organisms, dinosaur carcasses are subject to ecological and geographical influence that inevitably constitutes
5840-479: The sexes, and allometry, but their relative importance is still not fully understood . Sexual dimorphism in birds can be manifested in size or plumage differences between the sexes. Sexual size dimorphism varies among taxa, with males typically being larger, though this is not always the case, e.g. birds of prey , hummingbirds , and some species of flightless birds. Plumage dimorphism, in the form of ornamentation or coloration, also varies, though males are typically
5920-526: The sexes. At sexual maturity, the males display a bright green with white dorsolateral lines. In contrast, the females are rusty red to silver with small spots. The bright coloration in the male population attracts females and is an aposematic sign to potential predators. Females often show a preference for exaggerated male secondary sexual characteristics in mate selection. The sexy son hypothesis explains that females prefer more elaborate males and select against males that are dull in color, independent of
6000-511: The sexual preference in colorful females due to higher egg quality. In amphibians and reptiles, the degree of sexual dimorphism varies widely among taxonomic groups . The sexual dimorphism in amphibians and reptiles may be reflected in any of the following: anatomy; relative length of tail; relative size of head; overall size as in many species of vipers and lizards ; coloration as in many amphibians , snakes , and lizards, as well as in some turtles ; an ornament as in many newts and lizards;
6080-414: The size dimorphic wolf spider Tigrosa helluo , food-limited females cannibalize more frequently. Therefore, there is a high risk of low fitness for males due to pre-copulatory cannibalism, which led to male selection of larger females for two reasons: higher fecundity and lower rates of cannibalism. In addition, female fecundity is positively correlated with female body size and large female body size
6160-567: The species' vision. Similar sexual dimorphism and mating choice are also observed in many fish species. For example, male guppies have colorful spots and ornamentations, while females are generally grey. Female guppies prefer brightly colored males to duller males. In redlip blennies , only the male fish develops an organ at the anal-urogenital region that produces antimicrobial substances. During parental care, males rub their anal-urogenital regions over their nests' internal surfaces, thereby protecting their eggs from microbial infections, one of
6240-537: The thousands of free-floating flowers released by a male. Sexual dimorphism is most often associated with wind-pollination in plants due to selection for efficient pollen dispersal in males vs pollen capture in females, e.g. Leucadendron rubrum . Sexual dimorphism in plants can also be dependent on reproductive development. This can be seen in Cannabis sativa , a type of hemp, which have higher photosynthesis rates in males while growing but higher rates in females once
6320-454: The whinchat in Switzerland breed in intensely managed grasslands. Earlier harvesting of the grasses during the breeding season lead to more female deaths. Populations of many birds are often male-skewed and when sexual differences in behavior increase this ratio, populations decline at a more rapid rate. Also not all male dimorphic traits are due to hormones like testosterone, instead they are
6400-470: Was exhibited in the crest of 3 species of hadrosaurids. The crests could be categorized as full (male) or narrow (female) and may have given some advantage in intrasexual mating-competition. Ceratopsians According to Scott D. Sampson, if ceratopsids were to exhibit sexual dimorphism, modern ecological analogues suggest it would be found in display structures, such as horns and frills. No convincing evidence for sexual dimorphism in body size or mating signals
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