Sexual dimorphism - Knowledge

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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 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 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 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, 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 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.

1061:, 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 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, 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 is the 1316:

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 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 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.

2079: 1110: 1289:, and some species of flightless birds. Plumage dimorphism, in the form of ornamentation or coloration, also varies, though males are typically 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 the 'fittest' available male. 1991:, (black myotis bat) where females are substantially larger than males in terms of body weight, skull measurement, and forearm length. The interaction between the sexes and the energy needed to produce viable offspring makes it favorable for females to be larger in this species. Females bear the energetic cost of producing eggs, which is much greater than the cost of making sperm by the males. The fecundity advantage hypothesis states that a larger female is able to produce more offspring and give them more favorable conditions to ensure their survival; this is true for most ectotherms. A larger female can provide parental care for a longer time while the offspring matures. The gestation and lactation periods are fairly long in 979: 1238: 1999: 558: 1101:, 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 the sexual preference in colorful females due to higher egg quality. 1587: 2140: 1268: 537: 496:, size, weight, color, markings, or behavioral or cognitive traits. Male-male reproductive competition has evolved 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 965: 1256: 854: 1214: 521: 47: 12519: 11169: 9368: 80: 12545: 12532: 11179: 8925: 1226: 594:. 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 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 1654: 1924:

found in insects. In mammals this results in more frequent and severe infections in males and higher rates of autoimmune disorders in females. One potential cause may be differences in gene expression of immune cells between the sexes. Another explanation is that endocrinological differences between the sexes impact the immune system – for example, testosterone acts as an immunosuppressive agent.

1676: 1666: 1911:), the structural connectome of women are significantly "better" connected than the connectome of men. It was shown that the graph-theoretical differences are due to the sex and not to the differences in the cerebral volume, by analyzing the data of 36 females and 36 males, where the brain volume of each man in the group was smaller than the brain volume of each woman in the group. 1612:. Pinnipeds are known for early differential growth and maternal investment since the only nutrients for newborn pups is the milk provided by the mother. For example, the males are significantly larger (about 10% heavier and 2% longer) than the females at birth in sea lion pups. The pattern of differential investment can be varied principally prenatally and post-natally. 1995:, the females suckling their offspring until they reach nearly adult size. They would not be able to fly and catch prey if they did not compensate for the additional mass of the offspring during this time. Smaller male size may be an adaptation to increase maneuverability and agility, allowing males to compete better with females for food and other resources. 926:. 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. 1077:

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.

1031:, 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 679:, 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 the most common causes for mortality in young fish. 777:

discouraging further visits from pollinators. This 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.

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also display extreme sexual dimorphism. Females are more typical in appearance to other fish, whereas males are tiny rudimentary creatures with stunted digestive systems. A male must find a female and fuse with her: he then lives parasitically, becoming little more than a sperm-producing body in what

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In theory, larger females are favored by competition for mates, especially in polygamous species. Larger females offer an advantage in fertility, since the physiological demands of reproduction are limiting in females. Hence there is a theoretical expectation that females tend to be larger in species

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Sexual dimorphism in immune function is a common pattern in vertebrates and also in a number of invertebrates. Most often, females are more 'immunocompetent' than males. This trait is not consistent among all animals, but differs depending on taxonomy, with the most female-biased immune systems being

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advantage. Females have a higher sensitivity to pain due to aforementioned nerve differences that increase the sensation, and females thus require higher levels of pain medication after injury. Hormonal changes in females affect pain sensitivity, and pregnant women have the same sensitivity as males.

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show a range of sexual dimorphism, with average body mass between the sexes differing by roughly 15%. Substantial discussion in academic literature considers potential evolutionary advantages associated with sexual competition (both intrasexual and intersexual), as well as short- and long-term sexual

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Social organization plays 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.

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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 a significant role in male reproductive

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The handicap principle states that a male who survives despite possessing some sort of handicap thus proves that the rest of his genes are "good alleles". If males with "bad alleles" could not survive the handicap, females may evolve to choose males with this sort of handicap; the trait is acting as

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found in a 2004 study that "men and women apparently achieve similar IQ results with different brain regions, suggesting that there is no singular underlying neuroanatomical structure to general intelligence and that different types of brain designs may manifest equivalent intellectual performance".

1506:, which likely provided a function in sexual display. A biometric study of 36 skulls found sexual dimorphism 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. 1315:

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 a bird's lifetime. Activational

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in the left hemisphere of the brain in comparison to males. Males on average have larger brains than females; however, when adjusted for total brain volume, the gray matter differences between sexes are almost nonexistent. Thus, the percentage of gray matter appears to be more related to brain size

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The difference in strength relative to body mass is less pronounced in trained individuals. In Olympic weightlifting, male records vary from 5.5× body mass in the lowest weight category to 4.2× in the highest weight category, while female records vary from 4.4× to 3.8×, a weight-adjusted difference

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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 is known in ceratopsids, although there

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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 the sexes, and allometry, but their relative importance is still not fully understood . Sexual dimorphism

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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 ... from dwarf males to males more than

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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 is a good indicator for females because it shows that they are good at obtaining a

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The sexy son hypothesis states that females may initially choose a trait because it improves the survival of their young, but once this preference has become widespread, females must continue to choose the trait, even if it becomes harmful. Those that do not will have sons that are unattractive to

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observed that "because it is easier to manipulate hormone levels than the expression of sex chromosome genes, the effects of hormones have been studied much more extensively, and are much better understood, than the direct actions in the brain of sex chromosome genes." It concluded that while "the

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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 the degree of preservation. The availability of

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is an ontogenetic frog with dramatic differences in both color and pattern between 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

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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

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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 a less bright or less exaggerated color during the off-breeding season. This occurs because the species is more focused on

1233:, do not display sexual dimorphism through their plumage, and instead can be distinguished by other physiological or behavioural characteristics. Generally, male Mute swans, or cobs, are taller and larger than females, or pens, and have thicker necks and a more pronounced 'knob' above their bill. 1914:

Sexual dimorphism was also described in the gene level and shown to extend from the sex chromosomes. Overall, about 6500 genes have been found to have sex-differential expression in at least one tissue. Many of these genes are not directly associated with reproduction, but rather linked to more

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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 the costs and evolutionary implications vary from species to

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Migratory patterns and behaviors also influence sexual dimorphisms. This aspect also stems back to size dimorphism in species. It has been shown that the larger males are better at coping with the difficulties of migration and thus are more successful in reproducing when reaching the breeding

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was 53.4 mm vs. 40 mm in females. Different sizes of the heads in anoles have been explained by differences in the estrogen pathway. The sexual dimorphism in lizards is generally attributed to the effects of sexual selection, but other mechanisms including ecological divergence and

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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

1304:: black breeders, brown breeders, and brown auxiliaries. These differences arise in response to 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 2169:" and give rise to healthy offspring. In some species, however, females seem to choose males with traits that do not improve offspring survival rates, and even traits that reduce it (potentially leading to traits like the peacock's tail). Two hypotheses for explaining this fact are the 1877:. Sexual differentiation in the human brain from the undifferentiated state is triggered by testosterone from the fetal testis. Testosterone is converted to estrogen in the brain through the action of the enzyme aromatase. Testosterone acts on many brain areas, including the 1915:

general biological features. In addition, it has been shown that genes with sex-specific expression undergo reduced selection efficiency, which leads to higher population frequencies of deleterious mutations and contributes to the prevalence of several human diseases.

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In many non-monogamous species, the benefit to a male's reproductive fitness of mating with multiple females is large, whereas the benefit to a female's reproductive fitness of mating with multiple males is small or nonexistent. In these species, there is a

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argue that this difference in behaviour leads to radically different selection pressures on the two sexes, evidently favouring smaller males. Cases where the male is larger than the female have been studied as well, and require alternative explanations.

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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.

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differentiating effects of gonadal secretions seem to be dominant," the existing body of research "support the idea that sex differences in neural expression of X and Y genes significantly contribute to sex differences in brain functions and disease."

1485:. 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 the caudal 892:

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 is

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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

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had one of the most bizarre cases of sexual dimorphism in a bird; the larger female (right) had a long, curved bill adapted to probe into deep holes in living wood, while the smaller male (left) had a short, chisel-like bill to strip dead

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Frogs constitute another conspicuous illustration of 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.

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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

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where the female has a glandular area on her back that can serve to feed a male, which clings to her (although males can survive away from females, they generally are not free-living). This is taken to the logical extreme in the

1323:, 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 2864:

Donnellan, S. C., & Mahony, M. J. (2004). Allozyme, chromosomal, and morphological variability in the Litoria lesueuri species group (Anura : Hylidae), including a description of a new species. Australian Journal of

1088:, 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 1854:

Acute pain tolerance is also more consistent over a lifetime in females than males, despite these hormonal changes. Despite differences in physical feeling, both sexes have similar psychological tolerance to (or ability to

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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 is displayed in mimetic butterflies.

2054:, the southern yellowjacket. In this wasp species, the female workers are the smallest, the male workers are slightly larger, and the female queens are significantly larger than her female workers and male counterparts. 1489:

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.

1013:, 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 2406: 845:). 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. 5381:

Martin U, Grüebler HS, Müller M, Spaar R, Horch P, Naef-Daenzer B (2008). "Female biased mortality caused by anthropogenic nest loss contributes to population decline and adult sex ratio of a meadow bird".

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article for more on this subject.) Strict graph-theoretical analysis of the human brain connections revealed that in numerous graph-theoretical parameters (e.g., minimum bipartition width, edge number, the

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Salogni E, Galimberti F, Sanvito S, Miller EH (March 2019). "Male and female pups of the highly sexually dimorphic northern elephant seal (Mirounga angustirostris) differ slightly in body size".

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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.

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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

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Bell, R. C., & Zamudio, K. R. (2012). Sexual dichromatism in frogs: natural selection, sexual selection, and unexpected diversity. Proceedings of the Royal Society B: Biological Sciences.

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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.

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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 the body. For example, in

1368:- (two)) has been proposed for bird species in which "both sexes have basically the same plumage pattern, though the female is clearly distinguishable by reason of her paler or washed-out 8913: 1128:. 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 5418:

Owens, I. P. F., Short, R.V.,. (1995). Hormonal basis of sexual dimorphism in birds: Implications for new theories of sexual selection. Trends in Ecology & Evolution., 10(REF), 44.

1755:), but males, on average, surpass them in height in later adolescence and adulthood. In the United States, adult males are on average 9% taller and 16.5% heavier than adult females. 2030:, where the male injects itself into the female's body and becomes nothing more than sperm producing cells, to the point that the superorder used to be mistaken for hermaphroditic. 1888:

The relationship between sex differences in the brain and human behavior is a subject of controversy in psychology and society at large. Many females tend to have a higher ratio of

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and lower rates of cannibalism. In addition, female fecundity is positively correlated with female body size and large female body size is selected for, which is seen in the family

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Emlen DJ, Marangelo J, Ball B, Cunningham CW (May 2005). "Diversity in the weapons of sexual selection: horn evolution in the beetle genus Onthophagus (Coleoptera: Scarabaeidae)".

6236: 1881:, to create the masculinized brain pattern. The brains of pregnant females carrying male fetuses may be shielded from the masculinizing effects of androgen through the action of 4893:

Bravo CR, Bautista-Sopelana LM, Alonso JC (2024). "Revisiting niche divergence hypothesis in sexually dimorphic birds: Is diet overlap correlated with sexual size dimorphism?".

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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

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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.

4811:"A significant component of ageing (DNA damage) is reflected in fading breeding colors: an experimental test using innate antioxidant mimetics in painted dragon lizards" 899:, 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. 8914: 2455: 7143: 1940:

have a better muscle regeneration efficiency than male ones. There are reports of several metabolic differences between male and female cells and they also respond to

1736:, females have, on average, 50–60% of the upper body strength of males, and 80-90% of the lower body strength of males, relative to body size, but females have higher 6879: 1308:

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.

1205:. 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. 4796:

Pinto, A., Wiederhecker, H., & Colli, G. (2005). Sexual dimorphism in the Neotropical lizard, Tropidurus torquatus (Squamata, Tropiduridae). Amphibia-Reptilia.

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strategies. According to Daly and Wilson, "The sexes differ more in human beings than in monogamous mammals, but much less than in extremely polygamous mammals."

10901: 9404: 8476: 5839:"Evidence for Sexual Dimorphism in the Plated Dinosaur Stegosaurus mjosi (Ornithischia, Stegosauria) from the Morrison Formation (Upper Jurassic) of Western USA" 5482:"Experimental Manipulation of Maternal Effort Produces Differential Effects in Sons and Daughters: Implications for Adaptive Sex Ratios in the Blue-footed Booby" 1604:

show some of the greatest sexual size differences of mammals, because of sexual selection and environmental factors like breeding location. The mating system of

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Lindsay WR, Webster MS, Varian CW, Schwabl H (2009). "Plumage colour acquisition and behaviour are associated with androgens in a phenotypically plastic bird".

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Lopes AM, Ross N, Close J, Dagnall A, Amorim A, Crow TJ (April 2006). "Inactivation status of PCDH11X: sexual dimorphisms in gene expression levels in brain".

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Wiklund C, Lindfors V, Forsberg J (1996). "Early Male Emergence and Reproductive Phenology of the Adult Overwintering Butterfly Gonepteryx rhamni in Sweden".

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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.

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Ono KA, Boness DJ (January 1996). "Sexual dimorphism in sea lion pups: differential maternal investment, or sex-specific differences in energy allocation?".

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Progress in Botany / Fortschritte der Botanik: Structural Botany Physiology Genetics Taxonomy Geobotany / Struktur Physiologie Genetik Systematik Geobotanik

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Szalkai B, Varga B, Grolmusz V (June 2018). "Brain size bias compensated graph-theoretical parameters are also better in women's structural connectomes".

1748:). A study, carried out by analyzing annual world rankings from 1980 to 1996, found that males' running times were, on average, 10% faster than females'. 1724:

is about 6 percent higher in adolescent males than females and increases to about 10 percent higher after puberty. Females tend to convert more food into

4348: 2200: 1571:), and also behaviour of adult individuals. Hormones significantly affect human brain formation, and also brain development at puberty. A 2004 review in 11390: 11247: 6136:

Tarnawski BA, Cassini GH, Flores DA (2014). "Skull allometry and sexual dimorphism in the ontogeny of the southern elephant seal (Mirounga leonina)".

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Berns CM, Adams DC (11 November 2012). "Becoming Different But Staying Alike: Patterns of Sexual Size and Shape Dimorphism in Bills of Hummingbirds".

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that are fertilized if they contact one of the thousands of free-floating flowers released by a male. Sexual dimorphism is most often associated with

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Prenter J, Elwood RW, Montgomery WI (December 1999). "Sexual Size Dimorphism and Reproductive Investment by Female Spiders: A Comparative Analysis".

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Paxton RJ, Giovanetti M, Andrietti F, Scamoni E, Scanni B (1 October 1999). "Mating in a communal bee, Andrena agilissima (Hymenoptera Andrenidae)".

811:, a type of hemp, which have higher photosynthesis rates in males while growing but higher rates in females once the plants become sexually mature. 2078: 1342:, defined as sex differences in space and resource use. Most sexual segregation research has been done on ungulates, but such research extends to 6571: 5667:

Coulson G, MacFarlane AM, Parsons SE, Cutter J (2006). "Evolution of sexual segregation in mammalian herbivores: kangaroos as marsupial models".

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Ota K, Kohda M, Sato T (June 2010). "Unusual allometry for sexual size dimorphism in a cichlid where males are extremely larger than females".

2119:, because small sperm enable organisms to produce a large number of sperm, and make males (or male function of hermaphrodites) more redundant. 1745: 3345:"The genetic mating system of a sea spider with male-biased sexual size dimorphism: evidence for paternity skew despite random mating success" 873:, for example, 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 9775: 10650: 7711:"Sex of the cell dictates its response: differential gene expression and sensitivity to cell death inducing stress in male and female cells" 1152:

and lizards; the presence of specific sex-related behaviour is common to many lizards; and vocal qualities which are frequently observed in

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Every sexually reproducing extant species of the vascular plant has an alternation of generations; the plants we see about us generally are

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González-Solís J, Croxall JP, Wood AG (2000). "Sexual dimorphism and sexual segregation in foraging strategies of northern giant petrels,

9770: 9397: 1733: 2045:. There is some evidence that, in these genera, the dimorphism may be tied to a sex chromosome, or to chemical signalling from females. 821:, but their offspring are not the seeds that people commonly recognize as the new generation. The seed actually is the offspring of the 672:

have colorful spots and ornamentations, while females are generally grey. Female guppies prefer brightly colored males to duller males.

9760: 4647:"Does female nuptial coloration reflect egg carotenoids and clutch quality in the Two-Spotted Goby (Gobiusculus flavescens, Gobiidae)?" 4135:

Wilder SM, Rypstra AL (2008). "Sexual size dimorphism mediates the occurrence of state-dependent sexual cannibalism in a wolf spider".

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In some species, there is evidence of male dimorphism, but it appears to be for distinctions of roles. This is seen in the bee species

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explains that females prefer more elaborate males and select against males that are dull in color, independent of the species' vision.

1037:, but is more prominently selected for in less dimorphic species of spiders, which often selects for larger male size. In the species 12091: 8841: 4864: 3140:

Romero GA, Nelson CE (June 1986). "Sexual dimorphism in Catasetum orchids: forcible pollen emplacement and male flower competition".

2252: 53:, male (left) and female (right), illustrating the dramatic difference in plumage between sexes, a manifestation of sexual dimorphism 6253: 6175:"Equality for the sexes in human evolution? Early hominid sexual dimorphism and implications for mating systems and social behavior" 5514: 3199: 1162:

lizards show prominent size dimorphism with males typically being significantly larger than females. For instance, the average male

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and the usually large number of small male gametes relative to the larger female gametes usually lies in the development of strong

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and expendable circulating energy reserves. According to Tim Hewett, director of research in the department of sports medicine at

9073: 8989: 7611:"A role for cell sex in stem cell-mediated skeletal muscle regeneration: female cells have higher muscle regeneration efficiency" 4553:

Hendry A, Berg OK (1999). "Secondary sexual characters, energy use, senescence, and the cost of reproduction in sockeye salmon".

1629: 1330:

females are also the larger sex, and the growth rates of female chicks are more susceptible to limited environmental conditions.

141: 6966:

Marner L, Nyengaard JR, Tang Y, Pakkenberg B (July 2003). "Marked loss of myelinated nerve fibers in the human brain with age".

4310:

Sato T (1994). "Active accumulation of spawning substrate: a determinant of extreme polygyny in a shell-brooding cichlid fish".

3114: 9960: 9649: 9390: 7896: 4512:

Adams S, Williams AJ (2001). "A preliminary test of the transitional growth spurt hypothesis using the protogynous coral trout

908:

Weaponry leads to increased fitness by increasing success in male–male competition in many insect species. The beetle horns in

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for whatever traits enable a male to have more matings. The male may therefore come to have different traits from the female.

1893:

than it is to sex. Differences in brain physiology between sexes do not necessarily relate to differences in intellect. Haier

1849:

argue that females, interacting with other females and multiple offspring in social groups, have experienced such traits as a

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Some plant species also exhibit dimorphism in which the females are significantly larger than the males, such as in the moss

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also has distinct sexual and male dimorphism in head horns. Another beetle with a distinct horn-related sexual dimorphism is

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bee pollinators. The bees will then avoid other male flowers but may visit the female, which looks different from the males.

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of only 10–20%, and an absolute difference of about 30% (i.e., 492 kg vs 348 kg for unlimited weight classes; see

12071: 11279: 10274: 6887: 3713:"Evolution of male dimorphic allometry in a population of the Japanese horned beetle Trypoxylus dichotomus septentrionalis" 1319:

Sexual dimorphism may also influence differences in parental investment during times of food scarcity. For example, in the

5005:"The effect of dietary carotenoid access on sexual dichromatism and plumage pigment composition in the American goldfinch" 1455:

that allowed them to keep their tails elevated to aid in copulation. Discovering that this fusion occurred in only 50% of

11851: 11776: 11703: 11679: 11627: 11000: 9920: 5289: 5231:

Kissner KJ, Weatherhead PJ, Francis CM (January 2003). "Sexual size dimorphism and timing of spring migration in birds".

3508:

Danforth B (1991). "The morphology and behavior of dimorphic males in Perdita portalis (Hymenoptera : Andrenidae)".

2211: 7182: 4195:"Female preference for multi-modal courtship: multiple signals are important for male mating success in peacock spiders" 4172:"Males under attack: Sexual cannibalism and its consequences for male morphology and behaviour in an orb-weaving spider" 2884:

Ryan MJ, Rand AS (April 1993). "Species Recognition and Sexual Selection as a Unitary Problem in Animal Communication".

1521:

possessed sexes that were distinguishable based on frill and nasal prominence size. This is consistent with other known

12511: 12463: 12096: 11482: 11235: 10662: 10322: 4251: 3570:

Kukuk PF (1 October 1996). "Male Dimorphism in Lasioglossum (Chilalictus) hemichalceum: The Role of Larval Nutrition".

1247:). The difference between the sexes is apparent in the casque on the top of their bill. This pair is on display at the 7517:

Grossman C (1989). "Possible underlying mechanisms of sexual dimorphism in the immune response, fact and hypothesis".

6340:"The gender difference in distance running performance has plateaued: an analysis of world rankings from 1980 to 1996" 5780:"Males Resemble Females: Re-Evaluating Sexual Dimorphism in Protoceratops andrewsi (Neoceratopsia, Protoceratopsidae)" 1350:, and birds. Sex-specific conservation plans have even been suggested for species with pronounced sexual segregation. 11891: 5617: 5384: 5004: 2975: 2303: 10729: 886:

in which there is a small-headed morph, capable of flight, and large-headed morph, incapable of flight, for males.

12524: 12131: 11916: 11708: 11201: 10734: 10332: 9659: 9344: 9159: 2063: 658: 609:. Males are chromatically more yellow than females. It is believed that this is obtained by the ingestion of green 395: 230: 3813:

Teder, T., & Tammaru, T. (2005). "Sexual size dimorphism within species increases with body size in insects".

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Volvocine algae have been useful in understanding the evolution of sexual dimorphism and species like the beetle

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on opening, then shed the exhausted anthers after a day or two and perhaps change their colours as well while the

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Lüders E, Steinmetz H, Jäncke L (December 2002). "Brain size and grey matter volume in the healthy human brain".

7011:"Sex differences in brain gray and white matter in healthy young adults: correlations with cognitive performance" 2542: 1081:

In either case, females which change sex to males are larger and often prove to be a good example of dimorphism.

17: 996:, for example, adult females have a larger body size than adult males. Size dimorphism shows a correlation with 12384: 12344: 12299: 12006: 11829: 11399: 11336: 11107: 10974: 10754: 10498: 10296: 10200: 10089: 9267: 8254:

Hanschen, Erik R.; Herron, Matthew D.; Wiens, John J.; Nozaki, Hisayoshi; Michod, Richard E. (September 2018).

5972:

Cassini MH (January 2020). "A mixed model of the evolution of polygyny and sexual size dimorphism in mammals".

3477:"Late embryogenesis and immature development of Osmia rufa cornigera (Rossi) (Hymenoptera : Megachilidae)" 3225:"Wind of change: new insights on the ecology and evolution of pollination and mating in wind-pollinated plants" 2015:

amounts to an effectively hermaphrodite composite organism. A similar situation is found in the Zeus water bug

1977:. As an example, in some species, females are sedentary, and so males must search for them. Fritz Vollrath and 1405: 323: 8380:

Parker GA (May 1982). "Why are there so many tiny sperm? Sperm competition and the maintenance of two sexes".

7974:

Shaw AJ (2000). "Population ecology, population genetics, and microevolution". In Shaw AJ, Goffinet B (eds.).

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Figuerola J (1999). "A comparative study on the evolution of reversed size dimorphism in monogamous waders".

5669: 2154:, such as large size or weapons; or they could be traits that females, for whatever reason, prefer in mates. 1752: 1644: 768:

have what amounts to serial sexual dimorphism. The flowers of such species might, for example, present their

375: 10704: 8197:"Evolutionary trajectories explain the diversified evolution of isogamy and anisogamy in marine green algae" 7810:"Sexual size dimorphism in Myotis nigricans (Schinz, 1821) (Chiroptera: Vespertilionidae) from south Brazil" 7658:

Mittelstrass K, Ried JS, Yu Z, Krumsiek J, Gieger C, Prehn C, et al. (August 2011). McCarthy MI (ed.).

3877:"Female Bicyclus anynana butterflies choose males on the basis of their dorsal UV-reflective eyespot pupils" 12304: 12076: 11896: 11519: 11487: 11395: 11112: 10614: 9634: 9339: 9139: 9122: 6762: 6582:. Vol. 306. Baltimore: University Park Press (original from the University of Michigan). p. 511. 5558:

Main MB (March 2008). "Reconciling competing ecological explanations for sexual segregation in ungulates".

1882: 1339: 493: 390: 200: 8312: 990:

groups exhibit sexual dimorphism, but it is most widely studied in the spiders. In the orb-weaving spider

12550: 12116: 11351: 11182: 10776: 9068: 9063: 9058: 9053: 8982: 6678: 3204: 2927:

Rubolini D, Spina F, Saino N (2004). "Protandry and sexual dimorphism in trans-Saharan migratory birds".

2279: 1573: 136: 131: 126: 121: 12572: 12011: 11881: 11861: 11640: 11385: 10878: 10052: 9841: 9277: 9117: 8930: 8732: 5118: 4312: 2226: 2221: 2097: 942: 923: 333: 195: 8145: 3401: 2327: 1043:, the males are known for their characteristic colorful fan which attracts the females during mating. 668:

Similar sexual dimorphism and mating choice are also observed in many fish species. For example, male

12582: 12431: 12402: 12289: 12203: 12111: 12086: 11911: 11876: 11652: 10672: 10469: 10279: 10047: 9940: 9828: 9619: 9107: 8949: 6911: 5153:

Petrie M (1994). "Improved growth and survival of offspring of peacocks with more elaborate trains".

4895: 4698:"The relationship between sexual size dimorphism and habitat use in Greater Antillean Anolis lizards" 2814: 2758:"Plumage colour in nestling blue tits: sexual dichromatism, condition dependence and genetic effects" 2206: 2155: 2128:, where the females are larger than the males, are used to study its underlying genetic mechanisms. 1811: 1640: 1427:

have looked for sexual dimorphism among dinosaurs using statistics and comparison to ecologically or

1069: 895: 449: 185: 31: 10801: 6633: 5245: 4747:"The oestrogen pathway underlies the evolution of exaggerated male cranial shapes in Anolis lizards" 3775: 2941: 2434: 12324: 12208: 12081: 11901: 11834: 11696: 11669: 11524: 11299: 11262: 11095: 10959: 10931: 10906: 10863: 10766: 10699: 10574: 10447: 10415: 10388: 10378: 9836: 9048: 8961: 7364:"Reduced selection and accumulation of deleterious mutations in genes exclusively expressed in men" 6942: 6244: 5606:"Sex differences in population genetics, home range size and habitat use of the parti-colored bat ( 4068: 2124: 2017: 1237: 805:

Sexual dimorphism in plants can also be dependent on reproductive development. This can be seen in

676: 178: 116: 10579: 7854:"Allometry of litter mass in bats: comparisons with maternal size, wing morphology, and phylogeny" 6830:

Lombardo MV, Ashwin E, Auyeung B, Chakrabarti B, Taylor K, Hackett G, et al. (January 2012).

643:

is an example of a dynamic frog with temporary color changes in males during the breeding season.

12577: 12488: 12329: 12195: 12021: 12001: 11991: 11806: 11786: 11657: 11645: 11635: 11492: 11224: 11100: 11030: 10939: 10667: 10549: 10317: 9913: 9329: 8771: 6291: 5904: 4518: 3450: 2150:

These traits could be ones that allow him to fight off other males for control of territory or a

1057: 557: 380: 6737:"Acute Pain Tolerance Is More Consistent Over Time in Women Than Men, According to New Research" 6015:

Cappozzo HL, Campagna C, Monserrat J (1991). "Sexual Dimorphism in Newborn Southern Sea Lions".

4412:"Differing mechanisms underlie sexual size-dimorphism in two populations of a sex-changing fish" 12446: 12441: 12416: 12364: 12359: 12199: 12191: 12182: 12177: 12146: 12038: 11824: 11761: 11514: 11433: 11139: 10788: 10657: 10619: 10520: 10491: 10464: 10459: 10057: 9669: 9245: 9240: 9036: 9031: 8975: 7058:

Leonard CM, Towler S, Welcome S, Halderman LK, Otto R, Eckert MA, Chiarello C (December 2008).

5744: 5339: 5240: 4360: 3770: 2936: 2429: 2216: 2195: 1617: 1591: 1517: 1243: 1113: 1097: 301: 296: 104: 99: 10645: 7960: 7313:"The landscape of sex-differential transcriptome and its consequent selection in human adults" 6295: 3273: 12473: 12436: 12334: 12243: 12238: 12213: 11941: 11921: 11771: 11691: 11664: 11595: 11363: 11080: 10954: 10873: 10868: 10853: 10838: 10828: 10744: 10719: 10554: 10510: 10474: 10442: 10383: 10361: 10342: 10205: 10158: 10109: 10104: 10062: 9882: 9877: 9718: 9547: 9349: 6676:

McLaughlin M, Shryer T (8 August 1988). "Men vs women: the new debate over sex differences".

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Møller AP, Nielsen JT (2006). "Prey vulnerability in relation to sexual coloration of prey".

1998: 782: 400: 6575: 6283: 2652:"Visual pigments and oil droplets from six classes of photoreceptor in the retinas of birds" 2599:"Visual pigments and oil droplets from six classes of photoreceptor in the retinas of birds" 1586: 12426: 12233: 12218: 12186: 12173: 12034: 11946: 11814: 11781: 11756: 11610: 11574: 11468: 11438: 11257: 11054: 10949: 10883: 10684: 10599: 10515: 10427: 10410: 10337: 10327: 10037: 9945: 9929: 9872: 9284: 8945: 8591: 8485: 8440: 8389: 8208: 8157: 8110: 7911: 7858: 7774: 7709:

Penaloza C, Estevez B, Orlanski S, Sikorska M, Walker R, Smith C, et al. (June 2009).

7565: 7473: 7424: 7375: 7222: 6702: 6583: 6492: 6186: 6102: 6024: 5850: 5754: 5711: 5626: 5567: 5393: 5298: 5164: 5054:"Realized reproductive success of polygynous red-winged blackbirds revealed by DNA markers" 4904: 4658: 4596: 4527: 4478: 4423: 3933: 3724: 3606: 3517: 3356: 3149: 2831: 2496: 2421: 2139: 1899: 1721: 1503: 1305: 1297: 1201:. Male coloration appears to reflect innate anti-oxidation capacity that protects against 791: 645: 481: 442: 340: 10689: 10559: 9382: 8957: 7609:

Deasy BM, Lu A, Tebbets JC, Feduska JM, Schugar RC, Pollett JB, et al. (April 2007).

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is reflected by female selection on the basis of dorsal UV-reflective eyespot pupils. The

8: 12493: 12258: 12043: 11961: 11502: 11446: 11373: 11117: 11075: 11025: 10944: 10792: 10784: 10714: 10694: 10640: 10484: 10237: 10180: 10042: 10025: 10003: 9722: 9639: 9610: 9181: 9149: 8802:

Bonduriansky R (January 2007). "The evolution of condition-dependent sexual dimorphism".

8579: 4070:

Discovering the daily activity pattern of Zygiella x-notata and its relationship to light

3300:

Bonduriansky R (January 2007). "The evolution of condition-dependent sexual dimorphism".

3209: 3048: 2170: 2003: 1324: 1293: 1292:

Sexual dimorphism is a product of both genetics and environmental factors. An example of

1248: 1183: 1073: 888: 662: 571: 536: 221: 10395: 8595: 8489: 8444: 8393: 8212: 8161: 8114: 8006:. Vol. 2. Nichinan, Miyazaki, Japan: The Hattori botanical Laboratory. p. 891. 7915: 7778: 7569: 7477: 7460:

Gal-Oz ST, Maier B, Yoshida H, Seddu K, Elbaz N, Czysz C, et al. (September 2019).

7428: 7379: 7226: 6706: 6587: 6496: 6190: 6106: 6028: 5854: 5715: 5630: 5571: 5397: 5302: 5168: 4908: 4745:

Sanger TJ, Seav SM, Tokita M, Langerhans RB, Ross LM, Losos JB, Abzhanov A (June 2014).

4662: 4600: 4531: 4482: 4427: 3937: 3728: 3610: 3521: 3360: 3153: 2835: 2500: 2425: 2107:

The first step towards sexual dimorphism is the size differentiation of sperm and eggs (

929:

Sexual dimorphism within insects is also displayed by dichromatism. In butterfly genera

12592: 12451: 12294: 12284: 12253: 12048: 11996: 11906: 11856: 11715: 11674: 11590: 11497: 11477: 11331: 11309: 11304: 11090: 11042: 11035: 10632: 10544: 10405: 10366: 10190: 10134: 10124: 10084: 9998: 9993: 9988: 9906: 9808: 9598: 9560: 9417: 9294: 9272: 9257: 8868: 8854: 8827: 8615: 8555: 8528: 8509: 8501: 8413: 8313:"Anisogamy Does Not Always Promote the Evolution of Mating Competition Traits in Males" 8288: 8255: 8231: 8196: 8126: 8071: 8066: 8043: 7935: 7877: 7790: 7763:

Vollrath F, Parker GA (1992). "Sexual dimorphism and distorted sex ratios in spiders".

7737: 7710: 7686: 7659: 7635: 7610: 7591: 7494: 7461: 7339: 7312: 7293: 7245: 7212: 7200: 7174: 7084: 7059: 7035: 7026: 7010: 6991: 6856: 6831: 6812: 6621: 6609: 6518: 6320: 6118: 6075: 6036: 5997: 5954: 5881: 5838: 5814: 5779: 5748: 5642: 5537: 5462: 5356: 5314: 5266: 5180: 5135: 5086: 5073: 5053: 4985: 4840: 4771: 4746: 4727: 4714: 4697: 4539: 4446: 4411: 4377: 4329: 4292: 4219: 4194: 4152: 4104: 4044: 4017: 3993: 3968: 3949: 3901: 3876: 3852: 3827: 3796: 3784: 3693: 3579: 3533: 3432: 3377: 3344: 3325: 3249: 3224: 3181: 3165: 3068: 3024: 2999: 2901: 2847: 2790: 2777: 2757: 2733: 2708: 2684: 2671: 2651: 2623: 2598: 2583: 2570: 2295: 2174: 2144: 2133: 1866: 1759: 1263:

is an example of a bird where the female (right) is more colorful than the male (left).

1197:. are brightly conspicuous in their breeding coloration, but male colour declines with 1193: 1027: 997: 910: 901: 882: 874: 345: 328: 313: 207: 8881: 6209: 6174: 5723: 5337:

Adkins-Regan E (2007). "Hormones and the development of sex differences in behavior".

5023: 2519: 2484: 2165:

Females may choose males that appear strong and healthy, thus likely to possess "good

1267: 12544: 12537: 12531: 12314: 12309: 12223: 12025: 11766: 11733: 11600: 11461: 11368: 11346: 11314: 11178: 11132: 10858: 10806: 10584: 10400: 10301: 10259: 10215: 10210: 10163: 10129: 9629: 9578: 9299: 9085: 8819: 8779: 8757: 8736: 8619: 8607: 8560: 8456: 8405: 8401: 8360: 8332: 8293: 8275: 8236: 8173: 8130: 8090: 8022: 7979: 7927: 7834: 7742: 7691: 7640: 7583: 7534: 7530: 7499: 7442: 7393: 7344: 7285: 7250: 7166: 7162: 7124: 7120: 7089: 7040: 6983: 6946: 6915: 6905: 6861: 6804: 6718: 6656: 6599: 6547: 6510: 6458: 6448: 6361: 6356: 6339: 6299: 6284: 6214: 6067: 6001: 5989: 5946: 5886: 5868: 5819: 5801: 5758: 5583: 5454: 5449: 5432: 5258: 5254: 5091: 5027: 5012:

Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology

4977: 4930: 4844: 4832: 4827: 4810: 4776: 4719: 4681: 4671: 4646: 4624: 4619: 4584: 4494: 4490: 4451: 4284: 4247: 4224: 4171: 4112: 4049: 3998: 3906: 3857: 3800: 3788: 3740: 3685: 3622: 3424: 3382: 3317: 3279: 3254: 3173: 3120: 3093: 3029: 2971: 2909: 2795: 2738: 2689: 2628: 2524: 2447: 2443: 2372: 2299: 2258: 2116: 1850: 1320: 1018: 992: 952: 707: 501: 350: 158: 153: 8872: 8831: 8580:"Rapid evolution of sexual size dimorphism facilitated by Y-linked genetic variance" 8513: 8417: 7943: 7829: 7201:"Graph Theoretical Analysis Reveals: Women's Brains Are Better Connected than Men's" 6995: 6816: 6613: 6522: 6122: 6079: 5541: 5466: 5360: 5318: 5270: 5139: 4381: 4333: 4296: 4156: 3697: 3537: 3436: 3329: 3185: 941:, dimorphic wing patterns evolved due to sex-limited expression, which mediates the 11743: 11684: 11473: 11416: 10724: 10291: 10269: 10077: 9443: 9252: 9134: 8858: 8850: 8811: 8599: 8550: 8540: 8493: 8448: 8397: 8324: 8283: 8267: 8226: 8216: 8165: 8118: 8061: 7939: 7919: 7867: 7824: 7794: 7782: 7765: 7732: 7722: 7681: 7671: 7630: 7622: 7595: 7573: 7526: 7489: 7481: 7432: 7383: 7334: 7324: 7297: 7277: 7240: 7230: 7178: 7158: 7116: 7079: 7071: 7030: 7022: 6975: 6851: 6847: 6843: 6796: 6710: 6591: 6576: 6500: 6351: 6204: 6194: 6153: 6145: 6110: 6059: 6032: 5981: 5958: 5938: 5876: 5858: 5809: 5791: 5778:

Maiorino, Leonardo; Farke, Andrew A.; Kotsakis, Tassos; Piras, Paolo (7 May 2015).

5719: 5678: 5634: 5575: 5529: 5493: 5444: 5401: 5348: 5306: 5250: 5211: 5184: 5172: 5155: 5127: 5081: 5065: 5019: 4969: 4920: 4912: 4873: 4822: 4766: 4758: 4731: 4709: 4676: 4666: 4614: 4604: 4562: 4535: 4486: 4441: 4431: 4369: 4321: 4276: 4214: 4206: 4144: 4096: 4039: 4029: 3988: 3980: 3941: 3896: 3888: 3847: 3839: 3780: 3732: 3675: 3614: 3551:

Jaycox Elbert R (1967). "Territorial Behavior Among Males of Anthidium Bamngense".

3525: 3488: 3416: 3372: 3364: 3309: 3244: 3236: 3157: 3060: 3019: 3011: 2946: 2893: 2839: 2785: 2769: 2728: 2720: 2679: 2663: 2618: 2610: 2579: 2514: 2504: 2439: 2362: 2291: 2231: 2101: 2069: 2050: 1987: 1941: 1826: 1751:

In early adolescence, females are on average taller than males (as females tend to

1452: 1125: 978: 974:, displaying typical sexual differences in spiders, with dramatically smaller males 947: 905:

is a mining bee where the females only have a slightly larger head than the males.

754: 710:

species generally look similar to one another because plants provide rewards (e.g.

638: 595: 575: 497: 308: 11615: 10569: 5131: 5052:

Gibbs HL, Weatherhead PJ, Boag PT, White BN, Tabak LM, Hoysak DJ (December 1990).

4989: 4148: 3618: 3161: 1526:

have existed in ceratopsians include soft tissue variations such as coloration or

12483: 12374: 12339: 12248: 12136: 12030: 11986: 11966: 11839: 11555: 11534: 11289: 11085: 10709: 10536: 10525: 10479: 10422: 10371: 10151: 9955: 9471: 9425: 9334: 9316: 9262: 9206: 8726: 8545: 8350: 8122: 8052: 7676: 7235: 6936: 6832:"Fetal testosterone influences sexually dimorphic gray matter in the human brain" 6379: 5863: 5796: 5702: 5638: 5405: 4878: 4859: 4436: 2822: 2151: 1609: 1424: 1301: 1260: 1218: 1068:

Sexual dimorphism also occurs in hermaphroditic fish. These species are known as

1055:

There are cases where males are substantially larger than females. An example is

1033: 970: 807: 688: 630: 545: 385: 366: 318: 262: 8751: 3000:"A male sexually dimorphic trait provides antimicrobials to eggs in blenny fish" 1675: 1124:

In amphibians and reptiles, the degree of sexual dimorphism varies widely among

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species, which consist of most animals and some plants. Differences may include

11976: 11956: 11866: 11559: 11451: 11326: 10925: 10797: 10739: 10099: 10094: 10032: 10010: 9555: 9476: 9090: 8603: 8452: 8201:

Proceedings of the National Academy of Sciences of the United States of America

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Proceedings of the National Academy of Sciences of the United States of America

4589:

Proceedings of the National Academy of Sciences of the United States of America

2489:

Proceedings of the National Academy of Sciences of the United States of America

2093: 1904: 1779: 1691: 1653: 1601: 1389: 1354: 1085: 1065:, in which males are considerably larger than females and possess longer fins. 1039: 1009: 1001: 982:

Hammock Spiders (Pityohyphantes sp.) courting. Female left and male right.

787: 692: 624:. This diet also affects the sexually dimorphic colours in the human-invisible 562: 163: 8089:

Dies Alvarez ME, Rushton AW, Gozalo R, Pillola GL, Linan E, Ahlberg P (2010).

7329: 7281: 7009:

Gur RC, Turetsky BI, Matsui M, Yan M, Bilker W, Hughett P, Gur RE (May 1999).

6907:

Delusions of Gender: How Our Minds, Society, and Neurosexism Create Difference

6800: 5498: 5481: 5352: 5310: 4973: 4280: 4244:

Odd Couples: Extraordinary Differences between the Sexes in the Animal Kingdom

3736: 3420: 3368: 2564:

Slagsvold T, Lifjeld JT (1985). "Variation in plumage colour of the Great tit

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most females (since the preference is widespread) and so receive few matings.

1665: 12566: 12478: 12421: 12411: 11971: 11791: 11751: 11747: 11738: 11581: 11550: 11539: 11529: 11456: 11358: 11252: 11127: 11005: 10964: 10810: 10564: 10232: 10227: 9818: 9513: 9463: 9304: 9235: 9201: 9112: 9078: 8279: 8192: 8177: 6901: 6652: 6537: 6412: 6279: 6232: 6071: 5993: 5872: 5805: 5515:"Sex-specific growth in chicks of the sexually dimorphic Black-tailed Godwit" 4981: 3744: 3626: 3493: 3476: 3428: 2647: 2041: 1970: 1568: 1555:

In a large proportion of mammal species, males are larger than females. Both

1539: 1428: 1416: 1381: 1282: 1202: 1164: 964: 858: 430: 411: 355: 291: 257: 190: 146: 50: 8221: 7809: 7075: 6714: 6278:

Daly M, Wilson M (1996). "Evolutionary psychology and marital conflict". In

6199: 5216: 5199: 4916: 3712: 3664:"Sexual and male horn dimorphism in Copris ochus (Coleoptera: Scarabaeidae)" 2950: 2509: 1786:, hence greater oxygen-carrying capacity. They also have higher circulating 1300:. Red-backed fairywren males can be classified into three categories during 1255: 12268: 11569: 11546: 11122: 11070: 11015: 10848: 10843: 10437: 10195: 9691: 9674: 9605: 9565: 9481: 9453: 9438: 9371: 9223: 9100: 9095: 9041: 8883:

Sex, Size, and Gender Roles: Evolutionary Studies of Sexual Size Dimorphism

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Schuster RM (1984). "Comparative Anatomy and Morphology of the Hepaticae".

7931: 7838: 7746: 7695: 7644: 7587: 7503: 7446: 7397: 7348: 7289: 7254: 7170: 7128: 7093: 7044: 6987: 6865: 6808: 6514: 6462: 6413:"United States National Health and Nutrition Examination Survey, 1999–2002" 6218: 5950: 5890: 5823: 5587: 5458: 5262: 5095: 5069: 5031: 4934: 4836: 4780: 4762: 4723: 4628: 4609: 4566: 4498: 4455: 4325: 4288: 4228: 4210: 4116: 4053: 4002: 3984: 3910: 3892: 3861: 3843: 3792: 3689: 3386: 3321: 3258: 3177: 3033: 3015: 2913: 2799: 2773: 2742: 2724: 2667: 2614: 2528: 2402: 2376: 2023: 1978: 1933: 1908: 1767: 1712: 1465: 1373: 1213: 853: 599: 485: 279: 173: 168: 109: 61: 11193: 8933:

was created from a revision of this article dated 30 August 2019

8409: 7626: 7538: 7060:"Size matters: cerebral volume influences sex differences in neuroanatomy" 6722: 6365: 6149: 6114: 6063: 5035: 2693: 2632: 2451: 1334:

survival than on reproduction, causing a shift into a less ornate state.

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and leads to increased fitness in males. The sexual dichromatic nature of

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Székely T, Lislevand T, Figuerola J, Fairbairn D, Blanckenhorn W (2007).

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for many animals, so carotenoid dependent signals might indicate health.

625: 610: 425: 212: 46: 38: 10589: 8529:"Evolution of sexes from an ancestral mating-type specification pathway" 5610:, Linnaeus 1758) in Switzerland and their consequences for conservation" 4925: 4410:

McCormick MI, Ryen CA, Munday PL, Walker SP (May 2010). Briffa M (ed.).

3680: 3663: 3583: 1221:, showing that the male is much larger and more colorful than the female 914:

are enlarged growths of the head or thorax expressed only in the males.

12354: 12349: 12066: 11801: 11341: 11010: 10911: 10833: 10820: 10454: 10254: 10141: 10119: 10072: 10067: 10015: 9983: 9898: 9887: 9857: 9750: 9711: 9706: 9686: 9413: 8863: 8075: 7881: 7388: 7363: 6158: 4108: 4034: 3953: 3529: 3169: 3072: 2905: 2851: 2781: 2367: 2350: 2011: 1974: 1937: 1834: 1783: 1530:, which would be unlikely to have been preserved in the fossil record. 1482: 1447: 1137: 869: 838: 818: 746: 621: 614: 79: 30:"Sex differences" redirects here. For sexual dimorphism in humans, see 7437: 7412: 6979: 5985: 5579: 5533: 12016: 11144: 10995: 10604: 10222: 9970: 9813: 9803: 9780: 9727: 9624: 9614: 9525: 9498: 9486: 9448: 9211: 9186: 9176: 9164: 8505: 7786: 7660:"Discovery of sexual dimorphisms in metabolic and genetic biomarkers" 7462:"ImmGen report: sexual dimorphism in the immune system transcriptome" 6595: 5176: 5077: 4373: 3086:

Behnke H, Lüttge U, Esser K, Kadereit JW, Runge M (6 December 2012).

2675: 2112: 2108: 2086: 2027: 1842: 1815: 1791: 1771: 1737: 1605: 1595: 1478: 1415:

well-preserved remains is not a probable outcome as a consequence of

1241:

Skeletons of female (left) and Male (right) black-casqued hornbills (

1230: 1129: 1014: 1000:, which is prominent in spiders (it is also found in insects such as 734: 728: 509: 267: 247: 235: 7923: 7872: 7853: 7578: 7553: 5942: 5682: 4349:"Mate choice and sexual conflict in the size dimorphic water spider 4100: 3945: 3064: 2897: 2843: 484:

characteristics, including characteristics not directly involved in

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Yang JN (May 2010). "Cooperation and the evolution of anisogamy".

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Kelly CD, Stoehr AM, Nunn C, Smyth KN, Prokop ZM (December 2018).

6763:"Pain Tolerance and Sensitivity in Men, Women, Redheads, and More" 5200:"Protandry and sexual dimorphism in trans-saharan migratory birds" 4469:

Warner RR (June 1988). "Sex change and the size-advantage model".

3969:"Mimetic butterflies support Wallace's model of sexual dimorphism" 3451:"hackberry emperor – Asterocampa celtis (Boisduval & Leconte)" 3402:"On managing the red mason bee (Osmia bicornis) in apple orchards" 2483:

Zi J, Yu X, Li Y, Hu X, Xu C, Wang X, et al. (October 2003).

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constitute conspicuous illustrations of the principle. The ornate

544:. The male mallard has an unmistakable bottle-green head when his 12369: 10432: 10146: 9785: 9681: 9196: 9169: 8021:. Vol. 1. New York: Columbia University Press. p. 196. 1870: 1560: 1527: 1225: 1145: 1133: 937: 769: 738: 695:

but approximately 6% of species have separate males and females (

587: 583: 541: 525: 477: 252: 240: 8088: 6880:"Diverse Roles for Sex Hormone-Binding Globulin in Reproduction" 6829: 5929:

Arnold AP (September 2004). "Sex chromosomes and brain gender".

4809:

Olsson M, Tobler M, Healey M, Perrin C, Wilson M (August 2012).

4645:

Svensson PA, Pélabon C, Blount JD, Surai PF, Amundsen T (2006).

3596: 2755: 2351:"Quantifying avian sexual dichromatism: a comparison of methods" 9795: 9585: 9535: 9508: 9218: 9191: 9024: 8756:(1st ed.). Sunderland, Massachusetts: Sinauer Associates. 8146:"Darwin's sexual selection: Understanding his ideas in context" 7708: 7413:"Sexual dimorphism in immunity across animals: a meta-analysis" 2166: 1958: 1954: 1878: 1855: 1819: 1729: 1700: 1481:

possessed a retractable penis, a feature similar to modern day

1420: 1198: 1141: 842: 830: 822: 815: 795: 773: 719: 711: 700: 696: 617: 591: 529: 489: 420: 274: 8190: 6441:

Sexual Dimorphism in Human and Mammalian Biology and Pathology

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One example of this type of sexual size dimorphism is the bat

1181:. Sexual dimorphism in size is also seen in frog species like 10353: 9491: 8778:(3rd ed.). Malden, Massachusetts: Blackwell Publishing. 7057: 6965: 1803: 1775: 1564: 1556: 1469:

skeletons indicated that this is a sexually dimorphic trait.

1159: 1153: 1149: 1089: 669: 8310: 7897:"Insect behaviour: reversal of sex roles in nuptial feeding" 6286:

Sex, Power, Conflict: Evolutionary and Feminist Perspectives

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Johnsen A, Delhey K, Andersson S, Kempenaers B (June 2003).

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Common and easily identified types of dimorphism consist of

9412: 9019: 7978:. Cambridge: Cambridge University Press. pp. 379–380. 7142:

Haier RJ, Jung RE, Yeo RA, Head K, Alkire MT (March 2005).

5905:"Stegosaurus plates may have differed between male, female" 5115: 2257:. Vol. 2. Academic Press. 21 January 2019. p. 7. 1962: 1953:

that are monogamous. Females are larger in many species of

1807: 1272: 605:

Another example of sexual dichromatism is that of nestling

7657: 6693:

McEwen BS (March 1981). "Neural gonadal steroid actions".

5777: 4744: 4644: 4585:"Male mate choice selects for female coloration in a fish" 3400:

Gruber B, Eckel K, Everaars J, Dormann CF (30 June 2011).

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Sexual selection was observed for female ornamentation in

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Kaufmann P, Wolak ME, Husby A, Immonen E (October 2021).

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McGraw KJ, Hill GE, Stradi R, Parker RS (February 2002).

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Bowmaker JK, Heath LA, Wilkie SE, Hunt DM (August 1997).

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Phenotypic differences between sexes are evident even in

1725: 1343: 732:

orchids are one interesting exception to this rule. Male

473: 70: 8256:"Multicellularity Drives the Evolution of Sexual Traits" 8044:"Experimental taxonomy of some British species of genus 6938:

Brain Storm: The Flaws in the Science of Sex Differences

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Wang MQ, Yang D (2005). "Sexual dimorphism in insects".

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Proceedings of the Royal Society B: Biological Sciences

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Siljestam, Mattias; Martinossi-Allibert, Ivain (2024).

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Giacomello E, Marchini D, Rasotto MB (September 2006).

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Another complicated example of sexual dimorphism is in

1822:(except in pregnant women, who follow a male pattern). 699:). Sexual dimorphism is common in dioecious plants and 590:

of peacocks, as used in the courting display, attracts

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Ramawat KG, Merillon JM, Shivanna KR (19 April 2016).

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at a faster rate than males, hence they develop fewer

862:

mating. The male is a brighter yellow than the female.

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dispersal in males vs pollen capture in females, e.g.

7808:

Bornholdt R, Oliveira LR, Fabián ME (November 2008).

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