What is the biological advantage to having a dual penis in certain reptiles?
399423
Snakes, lizards and amphisbaena (which most of you won't have heard of, but they're neat!) have "hemipenes", basically dual penises.  It has no real advantage, it's just how they evolved.  They only use one at a time.  It's just a different way to evolve a penis structure on a bilaterally symmetrical animal.
344675
Courtship, mating and reproduction : Like all snakes and lizards, male sea snakes have two penises. They are called hemipenes, but each is an autonomous independently functioning penis and only one is used during mating. Mating takes place for long periods and sea snakes must surface for air during that time. The female controls breathing and as she swims to the surface the male is pulled along attached via the hemipenis. At the surface the male needs to gulp for air or he has to wait til the next time the female comes up the the surface to breathe. Males are unable to disengage until mating is finished. \n\nIn species where courtship has been studied, eg olive and turtlehead sea snakes, one or more males follow the female very closely and occasionally prod the head and neck of females. \n\nAll sea snakes except the latidcaudids give birth to live young after gestation periods that range from four to eleven months, depending on the species. Most species reproduce every year. The timing of the reproductive cycle varies enomously between species and also differs between geographical locations for the same species. \n\nYoung are born underwater and must be independent immediately to swim to the surface to breathe. There is no parental care. In some species look quite different to the adults eg juvenile olive sea snake are strongly banded while the adults are not.
566806
"Variation in Diet\nAlthough helodermatid lizards are specialists on vertebrate nests, they appear to be generalists regarding the kinds of nests they exploit.\nA diversity of prey species and sizes has been documented in the diets of Beaded Lizards and Gila Monsters.  Although some of these prey items are relatively small lizard and snake eggs, others, such as quail nets and nestling rabbits, are large and provice substantial energy gains per food item.  A meal of cottontail nestlings can weigh over one-third the mass of an adult Gila Monster and provide nearly one-third of a Gila Monster's annual energy budget (Beck 1990; chap. 4).  Along with these energy benefits come the basic mechanical challenges of swallowing a large meal or a hard-shelled egg.  Egg-eating snakes of the genera Dasypeltis and Elachistodon have modifications of the jaws, teeth, skull, and even the vertebrae that allow them to efficiently swallow eggs (Gans 1974). Although helodermatid lizards are not so specialized, they do appear to use a few "tricks" to make eggs go down easier.\n\nFeeding Behavior\nHow Prey are Eaten\nHerrel et al. (1997) describe five stages of H. horridum eating quail eggs: approach, pierce, uptake, crush, and swallow.  A Beaded Lizard first locates the egg, both visually and by tongue-flicking, then rises on its front legs and bites the egg with its front teeth, piercing it without breaking it.  The piercing bite may be repeated several times, yet the egg remains intact.  During the uptake phase, the lizard maneuvers its jaws around the egg by either flicking the egg in the air or pushing it against an object or the ground.  The tongue aids in maneuvering the food object into the oral cavity, but the primary force used during the uptake phase is inertia generated by movements of the lizard's head, neck, and jaws.  Such a feeding mechanism, called inertial feeding, contrasts with lingual feeding mechanisms (using the tongue to deliver food objects into the mouth) shown by most other lizards (Gans 1969)..."\n\nNot information about the actual digestive system, but information about diet and feeding.  This is an excerpt from Daniel D. Beck's new book.\n\nLet me know if you want a photo of a Gila Monster!
841963
This is really common in the animal kingdom. There is a type of snake where in which the male performs female mimicry and allows other males to mate with it. This ensures reproductive success, as only they will fertilise the females (the other males exhausted themselves on what they thought were females). Bonobos, for example, use sex in order to establish and maintain social relationships and even perform face-to-face copulation, rare amongst primates. Members of the dolphin family (such as Orca's) rub themselves against other males. There are species of lizard that are only females (and produce only clones of female offspring), and females will mount and imitate mating. It's interesting because the lizards that are mounting are "reproductively inactive" which means that they are male-like, whereas the mounted female is "reproductively active". There are also mites that mimic females, again to ensure reproductive success. \nThese are just a few examples!
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.
449512
lookin at your avatar & reading this question is far to sweet & innocent...hermaphrodites are human like you & I except hermaphrodites have both a vagina & a penis...some may tend to lean on one gender more than the other i.e.choosing to be more female than male(dress & look like female)...or the other way around.Hermaphrodites go through tough trials & tribulations in life in/out of family relationships due to having both sex organs...sometimes leaving them abused/molested as children many times by family members & what not.
1022095
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, urinary, and genital tracts of certain animal species. The word comes from Latin, and means "sewer". All birds, reptiles, and amphibians possess this orifice, by which they simultaneously evacuate both urine and feces. Monotremes also possess one. In contrast, each individual among most species of placental mammals and bony fishes has, in lieu of a cloaca, a specialized opening for at least one of these tracts.\n\nExcretory systems with analogous purpose in certain invertebrates are also sometimes referred to as "cloaca".\n\nIn birds the reproductive system must be regrown prior to the mating season of each species. Such regeneration usually takes about a month. Birds generally produce one batch of eggs per year, but they will produce another batch if the first is taken away (they have the ability to produce more).\n\nThe cloacal region is also often associated with a secretory organ, the cloacal gland, which has been implicated in the scent marking behaviour of some reptiles, amphibians and monotremes.\n\nSome turtles, especially those specialized in diving, are highly reliant on cloacal respiration during dives. [1] They accomplish this by having a pair of accessory air bladders connected to the cloaca which can absorb oxygen from the water. [2][3]
272720
yes there are all types my fav is the hermaphrodite this person has both penis and vagina from birth there are sex change operation as well need more look up hermaphrodite or sex change on yahoo
611709
Yes...it really has no other "use" other than to produce pleasurable sensations and orgasms. Technically speaking, it is the female equivalent of the penis (it develops from tissues in the same area, and has a similar structure)... and since we all start out life as heading towards female if there isn't a "Y" chromosome around to say "male", really the penis is just an outsized clitoris that happens to have some plumbing running through it.
1102060
Yes.The are called hermorphodites.They are born with both male and female sex organs.
351459
I know you're probably needing a more direct answer, but there are _loads_ of information on polyandrous animals. Try using Google Scholar for serious scientific papers:\nhttp://scholar.google.com/scholar?hl=en&lr=&q=polyandry+evolution
40335
Some reptile species are parthenogenetic (from Greek: virgin + originate, generate). That is, the development of the ovum can be triggered without sperm intervention.\nAs a consequence, these populations are only formed by females and all the offspring are genetically identical to their mothers (unless there is some recombination at cross-over, which I'm not sure about). \nThere are only a few lizards and snakes that present this mechanism; see the links below for the best known parthenogenetic snake species (there are probably others that have not been studied yet). \nHere in Argentina we have some parthenogenetic lizards! :)
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The disadvatages are largely the advantages of a dimorphic lifestyle, reversed.\n\nBy occupying totally separate ecological and physical niches the dimorphic lifstyle allows adults and juveniles to avoid competing with each other for food and other resources.  Once an organism starts down the path to neoteny the competition between adult and juvenile becomes ever tighter. By the time you reach the level of the axolotls the adults are literally stealing food out of the mouths of their own young (and occasionally eating them).\n\nNeoteny also has the drawback of making it harder to pick appropriate sexual partners. By losing the distint adult and juvenile charcteritics such species are dependent on secondary characteristics which .\n\nNeoteny also produces various species specific problems. In axolotls for exmaple dispersal in the neotenic form is very limited since overland travel is limited. In humans neoteny has resulted in problems with the development of the molars, especially the wisdom teeth. In dogs neoteny often results in breathing difficulties due foreshortening of the muzzle. And so on for individual cases.
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One unusual feature of the hyena is that females have an enlarged clitoris called a Pseudo-penis. Female hyenas give birth, copulate, and urinate through their protruding genitalia, which stretches to allow the male penis to enter for copulation, and it also stretches during birth. The anatomical position of the genitalia gives females total sexual control over who is allowed to mate with them. Researchers originally thought that one of the things that causes this characteristic of the genitals is androgens that are expressed to the fetus very early on in its development. However, it was discovered that when the androgens are held back from the fetus, the development of the female genitalia was not altered.
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because males MAY use them as stimulation receptors, they aren't ruled out by evolution\nso infact that are used, just not like females use them (think about it, if a male has nipples and uses them this way, then he would be able to spread his charateristic to more females thereby increasing the popularity and favorability of the trait)\nas for the question of why they there in the first place...\nits one of those characteristics that are kept when the baby is developing in the womb
1033143
the blue whale . it also has the most semen about 2 hundred gallons a shot. The typical limp adult human penis is about 3 centimeters in diameter at the base and somewhere between 8.5 and 10.5 cm long (measured along the top)–but fathers have been shorter than 3 cm, and lengths as great as 30 cm are reported. In general, smaller penises lengthen proportionally more than large ones do during an erection, but though the difference between small and large is reduced, the larger remain larger. The erect penis is about 15 to 19 cm long, with, again, many functioning very well outside this range.\n\nAs penises go, humans' are not wonders of the animal world. In many mammals–the raccoon, for example–the penis is stiffened with a bone, something men must pay a surgeon to achieve, and in plastic at that.  In size humans are dwarfed: the bull's is 3 feet, the elephant's 5 feet, the blue whale's 7 to 8 feet, and even a small animal like a pig, domestic or wild, has 18 inches.\n\nCounsellors, marriage handbooks, and sensitive females assure us that there is no correlation between penile size and lovemaking ability. Xaviera Hollander, an author who claims professional expertise of a practical sort, agrees about the lovemaking but says size does matter, and comments: “Men worry mainly about length, whereas women care more for girth.… If he's all the way in, up against her cervix, yet there are still two inches on the outside, those are two useless inches. Girth is another matter.… A penis is hardly ever too thick.”1\n\nOne of the most curious facts about the human penis is that, of all the organs of the male body, e.g., heart, lungs, brain, liver, and so on, the size of the penis is least related to skeletal size.2
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hermaphrodites have both sets of sex organs.