Science desk
< June 25	<< May \| June \| Jul >>	June 27 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

June 26[edit]

laying of unfertilized eggs[edit]

For animals which lay eggs with shells, do most of them have the capability of laying unfertilized eggs? If so, do they follow some cycle like the menstrual cycle? If not, what determines whether they lay unfertilized eggs? Thieh (talk) 00:42, 26 June 2014 (UTC)[reply]

That would seem to waste a lot of resources. Even in chickens, I bet that trait was rare, until people bred them specifically for that trait. StuRat (talk) 01:18, 26 June 2014 (UTC)[reply]

There is the exception of certain reptilian species which sometimes reproduce by parthenogenesis, in which case laying unfertilized aggs is not a waste of resources, but an alternative reproductive strategy. I am not aware of any birds that reproduce by parthenogenesis, but, if there are, all of those offspring would be males due to ZW sex-determination. Robert McClenon (talk) 01:28, 26 June 2014 (UTC)[reply]

Turkey parthenogenesis is a fascinating example of a higher vertebrate that can regularly reproduce asexually. Here's a photo of a poult. Most resources agree: they're always born male! Nimur (talk) 04:21, 26 June 2014 (UTC)[reply]

They would always be male, because of ZW sex determination. If the unfertilized egg has a Z chromosome, and becomes diploid parthenogetically, it becomes ZZ, male. If the unfertilized egg has a W chromosome, and becomes diploid parthenogetically, it becomes WW, which is not viable. This is a disadvantage to parthenogenesis in birds, because only half of the eggs will survive. I don't know of any mammals that reproduce by parthenogenesis, but, if they did, they would have a better survival rate, because they would all go from X to XX, and so would all be females. Robert McClenon (talk) 22:28, 26 June 2014 (UTC)[reply]

I suppose there could be one advantage to laying unfertilized eggs, if they are mixed in with a clutch of fertilized eggs, they might act as decoys to keep predators away from the fertilized eggs. And, if the chicks which hatch then eat the unfertilized eggs, the resources wouldn't be wasted. Of course, fertilizing all the eggs seems an even better strategy. StuRat (talk) 01:33, 26 June 2014 (UTC)[reply]

All egg-laying animals initially produce unfertilized eggs in the hope that they will be fertilized. In the wild most of them get fertilized, but with birds such as chickens we artificially separate the males and females so that can't happen. I have read that chickens only keep laying if you keep removing the eggs so that they can't sit on a full clutch but I can't confirm that with a reliable source. It does say in our chicken article "Under natural conditions, most birds lay only until a clutch is complete, and they will then incubate all the eggs. Many domestic hens will also do this–and are then said to "go broody". The broody hen will stop laying and instead will focus on the incubation of the eggs (a full clutch is usually about 12 eggs)". There is an interesting discussion about laying unfertilized eggs here Richerman (talk) 09:48, 26 June 2014 (UTC)[reply]

Domestic chickens kept as layers have been selectively bred to produce lots of eggs. Also, they can only do so because the food we give them is designed to give them all the nutrients necessary for egg production - chickens kept for meat are given a different diet that is designed to produce muscle mass. Chickens tend to produce eggs during the summer months and stop laying as the days get shorter. To maximise production, commercially kept caged chickens are kept inside under artificial light with a fixed day length. If you think about other species such as fish or frogs they produce lots of eggs which are fertilized outside the body as they are laid - the chances are that some of these will not get fertilized. Queen Honey bees produce some unfertilized eggs and these develop into male drones. Richerman (talk) 16:00, 26 June 2014 (UTC)[reply]

Bees and other eusocial Hymenoptera have a different sex determination system than mammals or birds, in which males are haploid and females (including workers, who are technically sterile females) are diploid. Robert McClenon (talk) 22:28, 26 June 2014 (UTC)[reply]

Detached aircon units[edit]

I know this is slightly similar to the question about fridges above, but: In a hot room, not long ago, we had an air cooling machine, only it was located entirely inside the room, so no air could be transferred between it and the outside. The relevant articles are air conditioning#evaporative coolers, air conditioning#portable units and evaporative cooler, but there seems to be some confusion over terminology, since the first two sections I linked will both link to the article evaporative cooler. The first of those refers to models that exchange air with the outside; the second does not. I'm thinking about the second type. Am I right that it can only work for a brief period, because in a room full of people, the body heat will bring the temperature back to exactly the same equilibrium point, with a higher humidity? In other words, after the brief time for which the cooler works, the air should be just as hot, but more humid. Am I right? IBE (talk) 05:18, 26 June 2014 (UTC)[reply]

That's right. If the system is closed then the neat heating effect of the aircon is positive, and the absolute humidity will have increased. In my opinion the equilibrium temp will be higher than before because of the additional heat load of the aircon's motor. RH could go either way. Greglocock (talk) 06:21, 26 June 2014 (UTC)[reply]

Could it have been a ductless conditioner? That is, rather than the AC unit supplying chilled air directly to the room (sometimes via a duct), it cools water which is circulated around the building. This means all there is in each room is a box with the heat exchanger and usually a fan to draw the warm room air over the exchanger. The equipment in the room is much smaller and quieter, and in some buildings it can be easier to route the small diameter water pipes rather than larger air ducts; and its easier for maintenance personnel to work in a single plant room than to have to disturb people in their offices. The box in the room (usually attached to the ceiling or wall, or in a panel in a suspended ceiling) is often called the chiller; several chillers may be connected to a single larger AC unit on the roof or wall of the building. All of this is still a "real" air conditioner, not just a swamp cooler - it's as effective as a ducted system (although more complicated, and a bit less efficient, because of the water circulation system). -- Finlay McWalterᚠTalk 13:35, 26 June 2014 (UTC)[reply]

In a closed, evaporative system, the dew point will rise in the room as the air saturates with water vapor and the air cools with the removal of latent heat. The higher the dew point, the lower the efficiency. Evaporative systems are usually open systems because the ambient air dew point is very low and doesn't rise. The difference between dew point and ambient temperature is similar to the temperature difference in a compressor-style air conditioner (the A/C temperature difference is constant and is affected by ambient temperature.) If you close off an evaporative cooler, the latent heat in the air that can be removed becomes less as the humidity/dew point rises. At the point where the dew point and air temperature are the same, the air is saturated and there is no more evaporative cooling. This temperature will be less than the the starting temperature and will happen as long as it's closed. Adding the heat of the motor/pump becomes a rate equation as to whether the system can add water as fast as the air can absorb it. --DHeyward (talk) 10:59, 27 June 2014 (UTC)[reply]

what is[edit]

semicolon cancer? — Preceding unsigned comment added by 121.7.234.202 (talk) 06:55, 26 June 2014 (UTC)[reply]

If you want to make bad jokes here, please ask or answer a legitimate question first. 24.5.122.13 (talk) 07:37, 26 June 2014 (UTC)[reply]

if it's from here, then it's a play on words (see colon cancer and semicolons). Perlis's quote itself is an observation on programming language syntax presented as nutritional advice. Asmrulz (talk) 07:46, 26 June 2014 (UTC)[reply]

That kind of joke was going around in 1985, that President Reagan had a semicolon. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:24, 26 June 2014 (UTC)[reply]

oh.... Asmrulz (talk) 07:04, 27 June 2014 (UTC)[reply]

One can safely say that "semicolon cancer" (a half-life-threatening condition BTW) is a multi-word portmanteau, just like the saying, "It's pissing racehorses."

Contrast period pain.

On a slightly more serious note, see San Serriffe, a fictional island shaped like a semicolon. - ¡Ouch! (^{hurt me} / _{more pain}) 09:47, 27 June 2014 (UTC)[reply]

Hippo's mouth[edit]

The excellent photo at the top of this BBC News page shows the inside of a Hippo's mouth very well. What are the interesting frilled structures to the left and right of the throat (just below the upper teeth) and what is their function? --Dweller (talk) 09:25, 26 June 2014 (UTC)[reply]

Tonsils? Richerman (talk) 13:04, 26 June 2014 (UTC)[reply]

Salivary glands. If you look in a mirror under your tongue, ours look rather similar. StuRat (talk) 13:20, 26 June 2014 (UTC)[reply]

I googled "hippopotamus mouth parts" and came up with nothing except pictures of hippos with their mouths open. StuRat might have it. To me the interesting thing is, what if they don't do something to curb this burgeoning wild hippo problem. Imagine biologists a few millennia from now being completely baffled as to how the hippo came to exist in South America. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:23, 26 June 2014 (UTC)[reply]

But those frilled structures aren't under the tongue, they seemed to be attached to the inside of the cheeks. In humans that is close to where the parotid glands are, but whether hippos have parotids is a subsidiary question. I don't have anything similar under my tongue (should I worry?). Richard Avery (talk) 07:36, 27 June 2014 (UTC)[reply]

Wharton's ducts are the relevant human structure - a Google image search (perhaps not immediately after breakfast) gives us lots of photographs of them in various states of blockage and infection. You should, of course, contact your doctor or dentist if you are worried about them. Tevildo (talk) 07:55, 27 June 2014 (UTC)[reply]

Salivary glands are usually "lumpy" or "frilly" to increase surface area. The area under a human tongue is usually more in the "lumpy" category. The placement of the salivary glands can move around the mouth a bit in different species, too, much as, say, hair patterns vary by species. StuRat (talk) 01:51, 28 June 2014 (UTC)[reply]

aeolinite definition[edit]

Geotechnical term. I believe it is limestone. However, I would feel more comfortable if this can be confirmed. Thank you24.226.73.86 (talk) 21:56, 26 June 2014 (UTC)[reply]

See BITUMEN STABILISATION OF A LIMESTONE (CALCAREOUS AEOLINITE) used as a pavement material in Australia. 84.209.89.214 (talk) 22:13, 26 June 2014 (UTC)[reply]

I'm not an rock expert, but from the Eolianite and Limestone articles, it sounds like the most common form of eolianite is a kind of limestone, but some eolianite isn't limestone, and some limestone isn't eolianite. The defining characteristic of eolianite is that it is formed by the lithification of sediment deposited by the wind. Red Act (talk) 22:23, 26 June 2014 (UTC)[reply]