What is the biological significance of sexual bimorphism?
84022
I think you are refering to Sexual Dimorphism,\n\nSexual dimorphism is a phenomenon seen in almost all animal species, and some plants.\nSexual dimorphism (SD for short) is a system that promotes a larger genetic pool. Example...\n\nAn Oak tree is not SD, so both sexes (male and female flower parts) are found on the same tree. So essentially, the oak's pollen can pollenate its flowers. This oak is said to be Monecious (meaning "one house" in greek). This means that the oak can produce acorns with 100% genetic material from its parent.\n\nA holly tree is Diecious ("two houses"). It only has male plants (with male flowers that produce pollen) or female plants (with female flowers that have the ovaries). This ensures genetic diversity in that 50% of the genetic code will come from each parent, thus ensuring diversity.\nThis Holly is an example of a Sexual Dimorphic (diecious) plant.
1114858
Neither one is more important than the other, since both are required to keep the system going.  However, as the limiting factor in reproduction is how fast women can gestate young, give birth, and recover enough to gestate another child, you need far fewer males than females (as males can continually impregnate other females while pregnant females gestate young).\n\nHowever, to dispel a myth, while females do comprise slightly more of the population than males, nature produces 105 males to every 100 females in human beings.  \n\nThe difference which leads to the female majority in humans is the result of the fact males are much more likely to be victims of murder, are much more likely to die accidental deaths, are more likely to be killed in the line of work, be killed during wars or battles, are more likely to suffer from a chronic genetic disease (most are carried on the X chromosome, so while you have to have two defective copies of the gene in females in order for them to be afflicted by it and not be a carrier, males only have one copy of the genes on the X chromosome, so they need only receive one defective copy to cause them to suffer from the disease... and no, this doesn't make females biologically superior since it proves the mother of the offspring specifically had defective genetic traits which were passed on to the male offspring) etc... etc... etc...\n\nAnd nature seems to understand this, and hedges its bet by producing more males to shore up the numbers.\n\nP.S.-- We cannot clone viable sperm.  Males still have to manufacture the stuff au naturel for the process to work.
347404
Well, if a hermaphodite is both sexes, then the opposite would naturally be something with no sex. Asexual.
62582
Many scientists believe that male nipples are an evolutionary vestige which is simply the result of males and females shareing virtually identical genetic structures.  Some evolutionists belief that evolution has not phased male nipples out because there is no evolutionary advantage to phasing them out.  Also, male nipples do serve a limited function in sexual arrousal.  Further still, male lactation does occur, though rarely, and is no doubt the result of the simularities in the genetic code with females.
1115380
Because sexual differentiation occurs rather late in the development of the fetus. Prior to that point, males and females are virtually indistinguishable.\nPlus, they kinda break up the chestal area, don't they?
404089
drift and/or sexual selection. Most likely sexual selection as the things you listed are essentially cosmetic.
197609
bi-racial or bi-sexual?
872787
Factors determining sexual attraction to human males\nGustav Klimt's The Kiss (Klimt painting), oil on canvas, illustrates a couple sharing a kiss.\nEnlarge\nGustav Klimt's The Kiss (Klimt painting), oil on canvas, illustrates a couple sharing a kiss.\n\nThe initial attraction usually begins with the physical features of the human form and attire, and by a positive expression of the face and body.\n\nFor heterosexual and bisexual females as well as homosexual and bisexual males across the world, regardless of culture, the one near-universal trait of attractiveness for a man to have is a V-shaped torso: a relatively narrow waist offset with broad shoulders. While some cultures prefer their males huskier and others leaner, the rule of a V-shaped torso generally holds true.[citation needed]\n\nIt has been studied that women prefer more masculine men during the fertile period of the menstrual cycle and more feminine men during other parts of the cycle. Masculine facial features are characterized by a strong brow and a broad jaw while feminine features are less pronounced.\n\nIt is thought that sexual attractiveness of a man to some women is somewhat determined by the height of the man. In modern culture it is usually an importance that the male be at least slightly taller than the female for a long term relationship to form. Some women prefer that the man be at least a little above the average in height in the given population of males because it unconsciously seems to them as a sign of dominance and masculinity. Although height is one aspect of male to male dominance as men mature this aspect becomes less so. Height says very little about one's health and fitness in most cases in areas of the world where the vast majority of people reach their genetic growth potential.\n\nThose who believe that the muscular contour of a male is attractive will choose males with well-defined muscles. Males who make use of their hormone, testosterone through exercise or bodybuilding techniques typically find themselves more attractive as their muscles take shape.\n\nAt various times in history and throughout various cultures and sub-cultures the growth, maintenance and display of facial or body hair produced as a by-product of testosterone activity within male bodies has been considered a primary characteristic of sexual attractiveness, and of a display of masculinity in general. Cultural development seems to oscillate through multi-generational cycles from one pole to another: extreme hair growth, especially of facial hair accompanied by elaborate grooming rituals is often followed within a couple of generations by a widespread antipathy to body hair and the widespread adoption of depilatory practices.\n\nThe causal mechanism for this oscillation has not been established but differences in the simultaneous characterization of body hair attractiveness within a culture between different social classes may indicate that the dynamic force driving the diffusion of differing male body hair social practices is in fact mate selection by females.
449989
No, but sex might.\n\nGender: is a socially acquired characteristic, and includes psychological, social and cultural characteristics, such as ideas about "masculinity" and "femininity".\n\nSex: A biological construct premised upon biological characteristics enabling sexual reproduction
77951
There are many different types of "sex" practiced in the plant and animal kingdoms besides the type we humans are familiar with. There are species in which the fathers get pregnant (like seahorses). There are species where males will turn into females (or vice-versa) if it would help the species survive. There are lots of examples of parthenogensis (virgin birth). There are cases where a single individual (like a plant) will pollinate itself, but others where biology tries to prevent this, although the plant might be hermaphroditic. There are plants which have several different reproduction mechanisms; a piece of the root can produce a new individual, for example. Some organisms can engage in both sexual and asexual reproduction as well; earthworms, honeybees, and geckos can asexually reproduce. There are species with 3 or even more sexes (like the clam shrimp in the US, for example, which has 3 sexes, or possibly  the New Zealand lizard the tuatara, which appears to have 4 sexes. There are species where males just fertilize the eggs deposited by the female in some location (most fish). Bacteria and viruses reproduce in strange ways, by dividing, or by taking over the reproduction mechanism of some other organism. \n\nThe astounding variety of "sex" and/or reproduction just goes on and on and on. We are still learning about the amazing diversity of life on this planet. \n\nIf and when we ever discover life on other planets, you can be sure that they will have different ways to reproduce, that may or may not have anything to do with what we might recognize as sex, and probably using mechanisms we cannot even imagine.
271982
Good point Pazion. But I still say in millions of years we still have seen no physical evidence that this is genetic. There have been no new emergence of a new gender. We are still born male and female. Again, in the next million years we may find that we were wrong in our assumptions. But we will be dead and therefore we still will not care. So it's a lost point even discussing it.
749265
Homosexuality has been linked to an X chromosome as well as differences in the structure of the hypothalamus of the brain between homosexual and heterosexual people.
918768
Genetics may play a partial role in sex-preference but there is no "gay gene".  Obviously this would be an evolutionary dead-end.  It is more likely a combination of genetics and childhood development.
317556
Flower\nIf both sexes are in the same flower (and plant) then it is a HERMAPHRODITE\nIf not, then they will be female and male plants (of the same species)
1153424
There are a number of scientific studies that do just that. I've linked to Wikipedia which sums up some of them, but the overall conclusion is that sexual orientation is determined in utero and is due to a number of factors, not just genetics.\n\nThe identical twin studies, especially those where one twin was straight and one gay, indicated that there's more going on than genetics.\n\nSimon Levay's study of brain structure indicated that homosexuals have a larger hypothalamus than heterosexuals. There have been other studies showing that gay men think like straight women as the brain activity was observed.\n\nThere's a finger-length study, indicating that women with a certain middle finger length are more likely to be gay.\n\nThere are birth order studies, where straight male children were born first and a gay male child later, suggesting that there may be hormonal influence on sexual orientation.\n\nBut whatever you think, know that it is not chosen. No one would choose to be ostracized, ridiculed, and made to feel a lesser citizen.
607312
I am not sure what you mean by uni-sex in biology....\n\nIn biology, sexual reproduction is not said to have been started with only females per se! Uni sexual is not the same as hermaphroditic either. Monoecious and dieocious are the usual terms. Monoecious means hermaphrodite and dioecious means separate sexes. But reproduction can be either sexual or asexual (and sometimes some organisms do both, like, mosses, liverworts, ferns with alternation of generations.) \n\nThere are a few species of animals who have only females, though....at least 22 species of parthenogenic lizards identified last I checked! They lay eggs, mate like "lesbian lizards" without sperm and have babies. Wild!\n\nHowever, a "male" is usually described in biology as any organism that makes "sperm" gametes, so in that case, hermaphroditic organisms like most flowering plants (sperm is in pollen) have males as PART of the often hermaphroditic flower known as the stamen.  (some flowers are dioecious) So males are found in plants or animals.  In fact the anther is the pollen producing part of the stamen and is sorta comparable to the testes of the animal. In fungus there are opposite strains of hyphae that reproduce "sexually" but not with gametes and they are described as + and - branches, which some claim are m-f, but it is still considered sexual reproduction, whereby genetic information is exchanged and a genetically DIFFERENT offspring is produced. Asexual produces gentically identical offspring-clones. Bacteria usually reproduce asexually, but sexual conjugation can occur (sexual) in bacilli. Paramecium are the most famous for their sexual reproduction-conjugation too. In the cases of fungi, bacteria, paramecia, however, the gender is not considered even though it is considered SEXUAL. So what biologists consider as very "primative" organism are capable of sexual reproduction.
530067
bi-ology.....the study of bisexual ppl...hehe