Wikipedia:Reference desk/Archives/Science/2007 November 20

= November 20 =

Could gold jewelry, such as a necklace, have toxic amounts of mercury or other heavy metals on
its surface? I know someone who has jewelry from Pakistan. She has a visible ring of excema around her neck where a necklace would be. The excema seems to have spread from there down her back. ThanksRich (talk) 06:27, 20 November 2007 (UTC)


 * Well, mercury is sometimes used in the processing and extraction of gold - and it's possible that her supposedly gold jewellery is really made of something else with a gold coating - so it's certainly possible that there are other heavy metals present. Eczema isn't a symptom of mercury poisoning - but we aren't allowed to give medical advice here - it would certainly be wise to seek the services of a doctor. SteveBaker (talk) 06:39, 20 November 2007 (UTC)


 * This is not medical advice just jewellery facts. Nickel is very commonly used in cheaper gold jewellery as an alloy to reduce the cost. A significant number of people suffer local allergic reactions from nickel in such jewellery. Try 'nickel allergy' on google and you will be surprised. Richard Avery (talk) 09:29, 20 November 2007 (UTC)

Is Universe expanding or deflating?
If either is the case, how sure are we? -- Taku (talk) 07:23, 20 November 2007 (UTC)


 * Expanding. We're very sure because distant galaxies appear to be moving away fro Earth (their light is red shifted) extremely quickly, and not only that, the speed they appear to be receding at is proportional to their distance from us.  See Hubble's law.  I know of no way to explain this relationship between distance and speed other than with an expanding universe.  --Bowlhover (talk) 08:44, 20 November 2007 (UTC)


 * We're absolutely certain it's expanding - you can look out at distant galaxies and see that the light from them is redder than it should be - and that's a sure sign that the universe is expanding. The 'big bang' theory for the origins of the universe is firmly established - and what happens to something after it goes "BANG!" is that debris gets flung out in all directions...and that's essentially what we have.  Since the 1930's, until just recently - it hadn't been clear whether the expansion was fast enough to avoid a gradual slowing of the rate of expansion - followed by a reversal, a collapse and then a 'big crunch' at the end.  However, it turns out that we're actually in the puzzling position of finding that the rate of expansion is actually gradually increasing - this is quite surprising and I don't think we have a firm grasp of why that is yet.  It's almost like there is some kind of anti-gravity that's only stronger than regular gravity over very long distances. SteveBaker (talk) 21:27, 20 November 2007 (UTC)


 * Thanks for the answers. Can I ask then: is that the case that the Universe has been expansing so far (accepting the Big Bang) but might the process be reversed in the future? If the rate of the expansion is accelerating (e.g., due to the known value on the cosmological constant?), the idea of the continuously expanding universe is counterintuitive. -- Taku (talk) 23:02, 20 November 2007 (UTC)


 * Well, this was a question that was in doubt until maybe ten years ago - before that, it was considered that if there was too little mass in the universe then there wouldn't be enough gravity to prevent the universe from expanding forever (as the universe expands, so the attraction between the galaxies would get weaker as the distance between them increases) - if there was too much mass then the gravity would be strong enough that the expansion would gradually slow down, then stop, then reverse - falling faster and faster together until there would be a "big crunch". What we found in 1998 was neither of these things.  The universe is not just expanding - the rate of expansion is actually increasing.  So for sure we're not going to have a 'big crunch' with everything collapsing back together again.  The consensus of opinion right now (I believe) is that the ultimate fate of the universe is what is currently being called "the big rip" - in which space gets stretched out so such a high degree that eventually, all matter will get pulled to shreds - the atoms themselves getting ripped to fundamental particles.  Another similar theory is called the big freeze.


 * I don't find an expanding universe counter-intuitive - what I find counter-intuitive is that the rate of expansion is increasing. Cosmologists don't seem to have a good explanation.  They talk about dark matter and dark energy somehow being the cause - but since we don't have a clue what these 'dark' things are, this explanation is little better than "I have no idea".  Anyway, I recommend our article Ultimate fate of the universe which is quite approachable by the layperson. SteveBaker (talk) 00:11, 21 November 2007 (UTC)


 * There's no consensus that there will be a big rip; in fact it's not considered an especially likely possibility. For the big rip to happen, the cosmological "constant" would have to increase with time (which it might). A big crunch also remains possible if it decreases instead. If it's really constant, the ultimate fate of the universe is roughly de Sitter space, which wouldn't seem much different from now except that you couldn't see any other galaxies. (But eventually heat death sets in -- this is the big freeze scenario.) -- BenRG (talk) 12:30, 22 November 2007 (UTC)

There's another possibility. We are in a big crunch. As we fall together, we're speeding up. Furthermore, as we fall we come apart (expand).

Sure. If you drop a system, the part of the sysytem nearest Earth will get a stronger gravitational pull than the parts of the system furthest away. I'm sure you can see how, over time, and especially if the system is falling 'end over end', the system can be seen to expand.

The Cosmos has also clumped up. Wmap and other observations have shown the early Cosmos was almost completely smoothly spread out. Since then we've clumped up, and clumping up is a feature of a vortex. When you stir your cofee, where do the bubbles go? When you put a tablespoonful of sand in a bucket of water and stir, where does the sand go? To the center, of course. I don't know anywhere else but a vortex, or whirlpool, to look for clumping up.

If the Cosmos is a Whirlpool, maybe shaped just like the Whirlpool galaxy, or our own Milky-Way, then probably therew's also a Black Hole there too, at the center of the Universe.

Could be...

How sharp is that knife?
Is there an official standard (ASTM or similar) for measuring how sharp a knife is? --67.185.172.158 (talk) 08:50, 20 November 2007 (UTC)
 * I found a link to an abstract of an article (Engineering Fracture Mechanics. Volume 74, Issue 14, September 2007, Pages 2205-2224.) that says "To date, there is no standard definition, measurement or protocol to quantify blade sharpness." I'm as surprised as you are. I googled on [scalpel "sharpness" standard], thinking that if anybody would care that much it would be surgeons. --Milkbreath (talk) 12:21, 20 November 2007 (UTC)
 * What do the brackets do in the search query?--droptone (talk) 12:34, 20 November 2007 (UTC)
 * Good question. Let's see.... Nothing. Whew! What's the approved way of reporting a search string to include double quotes? --Milkbreath (talk) 13:28, 20 November 2007 (UTC)
 * I suggest italicizing the "search string". &mdash; Lomn 13:48, 20 November 2007 (UTC)
 * I would write: I googled on "scalpel", "sharpness", and "standard". Of course, the double quotes in the particular example had no effect anyway, as they did not enclose a phrase.  --Anon, 05:10 UTC, November 21.
 * Au contraire, mon frere, if you don't use the quotes on the single word "sharpness" you get hits on "sharp", "sharps", etc. Google didn't used to do that in the beginning, but now it does. --Milkbreath (talk) 11:10, 21 November 2007 (UTC)


 * Take a look at the Obsidian article, which has a reference for how sharp a blade can be, at least for Obsidian blades. --Mikenorton (talk) 17:10, 20 November 2007 (UTC)


 * 17th century Japanese samurai sword makers had a standard - the number of body-thicknesses it would cut through in one swing...determined experimentally of course! A good sword might be rated as "5 bodies". (See Tameshigiri) This is perhaps not what you were looking for though! SteveBaker (talk) 21:16, 20 November 2007 (UTC)


 * A problem with such a rating system is that the act of cutting blunts the knife - so once a knife had been rated, it would no longer be as sharp as it was. I am also reminded of the episode in the Crusades, when Richard the Lionheart and Paladin compared swords. Richard's was sharp enough to cut through an iron bar, while Paladin could cut through a silk cushion, and therefore won!. —Preceding unsigned comment added by DuncanHill (talk • contribs) 21:26, 20 November 2007 (UTC)

Take a look at ISO 8442.5. --80.229.152.246 (talk) 23:57, 20 November 2007 (UTC)

ISO 8442.5 sharpness and knife durability system has been in use ( prior to standardisation) since the late 1960's primarily in the UK. CATRA who pioneeered the system, manufacture a machine that is used widely throughout the World for the measurement of sharpness of knives and blades ranging from utility razor blades to large industrial cutters. They also make another sharpness and edge life durability system for more delicate blades such as surgeons scalpels and shaving razor blades. see for further details — Preceding unsigned comment added by 91.85.162.215 (talk) 18:03, 31 July 2008‎

Growing up in zero-g
It must have been asked before but: Is it possible and what are the problems for a child to be conceived, born and to grow to adulthood in a zero-g, weightless environment? Let's say have a litlle family on the ISS for example. Would he survive, what imperative measures should be taken for his survival, what consequences would it have on his appearence? Keria (talk) 13:45, 20 November 2007 (UTC)
 * This (referenced in sex in space) has some speculations, but of course there's no direct evidence as yet. Algebraist 14:06, 20 November 2007 (UTC)


 * Extended time in low gravity has various harmful effects on the body, such as blood concentrating in the upper body, muscular weakness, and bone density loss. Our space medicine article is sadly inadequate, but it's a big concern for *-onauts.  Presumably it would be much more severe for a person who had never been in Earth-normal gravity; it's possible that person could not safely go to the Earth at all.  --Sean 14:29, 20 November 2007 (UTC)


 * Even with rigourous exercise courses, people who have been in space for just one year come back pretty much as invalids for many months afterwards and can take years to fully recover. It's really hard to believe that a child would survive for very long - let alone grow to adulthood without problems.  You can't have a 3 week old baby doing crunches with bungee cords tied to them for resistance - and bone density loss is bad enough for someone who is not trying to double in size after one year and double again within two.  It's really hard to imagine how this could work.   If we're going to be spending any amount of time in space, we need spinning spacecraft - and that means big spacecraft (in order to minimise weird coriolis and tidal effects) - and that means a strong spacecraft (the classic donut-shaped spinning space stations from the movie 2001 would be really tough to construct because all of that 1g donut would have to be supported like a suspension bridge here on earth) - and that means a heavy spacecraft - which makes it HIDEOUSLY expensive to launch.  We need to get out space elevator working first.  Sadly, I don't think this is happening any time soon. SteveBaker (talk) 21:08, 20 November 2007 (UTC)


 * People coming back from long duration spaceflight aren't 'invalids for many months' by any stretch of the imagination. But your point about people having trouble adjusting to 1 g after months in space is valid. Experiments of this sort using animals could be performed currently, and would probably yield very interesting results, though I don't know what they might be. anonymous6494 02:49, 21 November 2007 (UTC)


 * According to this abstract, no mammals have been born in weightlessness so far. There have been studies with pregnant rats like this one, however. Icek (talk) 09:08, 21 November 2007 (UTC)

Sound from Jupiter
The Jupiter article says:
 * In 1955, Bernard Burke and Kenneth Franklin detected bursts of radio signals coming from Jupiter at 22.2 MHz
 * Decametric radio bursts (with a wavelength of tens of meters) vary with the rotation of Jupiter, and are influenced by interaction of Io with Jupiter's magnetic field.
 * Decimetric radio emission (with wavelengths measured in centimeters) was first observed by Frank Drake and Hein Hvatum in 1959.

Does that mean it can be listened to? If so where can I find a recording? Keria (talk) 13:49, 20 November 2007 (UTC)


 * You can indeed listen to Jupiter. A Google search for Jupiter sounds will get you a multitude of hits.
 * This page from NASA has a number of sound samples as well as a whole bunch of other information about where the signals come from.
 * Radio JOVE is a NASA-sponsored educational project that records and studies astronomical radio sources, including Jupiter.
 * Radio-Jupiter Central is for the advanced amateur. It has sound samples, and also describes the equipment that you will need if you want to receive Jupiter signals directly.
 * Hope that helps. TenOfAllTrades(talk) 14:15, 20 November 2007 (UTC)

Crack, pop, whizzz! Thank you very much TenOffAllTrades it helped a great deal. Keria (talk) 15:36, 20 November 2007 (UTC)
 * Aww, and here I was hoping it would be "Drops of Jupiter" on repeat. :( shoy  (words words) 17:20, 20 November 2007 (UTC)


 * Note that this electromagnetic radiation can't actually be heard unassisted by the human ear because they aren't "sound". Your ear picks up mechanical pressure disturbances in the range of about 20-22,000 Hz, which we usually call sound.  Radio waves are more akin to light than sound, and even if they were pressure disturbances (which don't travel too well in a vacuum), they are too high a frequency for you to hear.  The sound you're actually hearing in these samples is a radio's "interpretation" of the electromagnetic signals into audible output. - Katavothron (talk) 18:11, 20 November 2007 (UTC)


 * And of course there are a nearly infinite number of ways of 'interpreting' radio waves as sound - so what one person did to the radio to get audio may not be the same as what someone else did. SteveBaker (talk) 20:58, 20 November 2007 (UTC)


 * Quite right. I'm inclined to think of a listening radio's rendering of such astronomical signals as an "artistic interpretation" more than anything else.  That's not to say that no useful data can be extracted from the sounds that the radio interprets, but for serious study it's probably most useful to look at the raw signals received. - Katavothron (talk) 21:47, 20 November 2007 (UTC)
 * So they didn't just scale up the signal a thousand to a million times (from 22MHz to 20-22,000Hz)? Keria (talk) 08:20, 21 November 2007 (UTC)


 * How do you "scale" a signal? You could massively downsample it, yielding audio that contains low harmonics of the RF signal, which is one possible route for making sound.  You could play it back at a much lower rate, letting you hear the events over a significantly longer period of time than they actually occurred.  Short wave radios actually perform some demodulation of the signal they receive, typically assuming an AM scheme.  That's why we said that what you hear is just an interpretation of the signal, and there are many ways of interpreting it.  You can't actually hear the signal as it is received by the radio, so the radio does some modifications to yield something that is audible. - Katavothron (talk) 19:53, 21 November 2007 (UTC)

physiology
how is human gastro intestinal tract moves? —Preceding unsigned comment added by 59.92.102.100 (talk) 14:26, 20 November 2007 (UTC)
 * Peristalsis. --Sean 14:32, 20 November 2007 (UTC)

Can nanomachines potentially cure RNA viruses?
I heard nanomachines can be used in medicine. Are there any thought experiments on using them to cure RNA viruses? 64.236.121.129 (talk) 14:32, 20 November 2007 (UTC)


 * Today? No, we're not that advanced yet.  Someday?  Absolutely.  It would just have to mimic the portions of the human immune system that normally deal with these problems.  In theory, anything that can be done naturally could be duplicated with nanotechnology.  The toughest problems would be dealing with the mutations that are common in RNA viruses, not accidentally attacking other things, such as the host or its symbiotic bacteria, keeping the host's immune system from attacking the nanomachines, and keeping the nanomachines from being toxic in some way.  Still, this technology is probably a long way off, a couple of decades at least. --  Hi  Ev  15:28, 20 November 2007 (UTC)
 * There are of course problems relating to such technological advances.  Lanfear's Bane |  t  16:46, 20 November 2007 (UTC)
 * I wondered if someone was going to bring that up... shoy  (words words) 17:21, 20 November 2007 (UTC)


 * We're really too far away to tell. Generally, when a technologist predicts something will be here in 5 years or less, they are about right.  When they say "two decades" they really mean "I have no clue if this is even a practical possibility, much less when we'll have one to play with".  Somewhere between 5 and 20 years is a region where we're pretty sure something can be done - but we don't know exactly when.  Nanotechnology (as in little autonomous robots) is in the "eh - maybe twenty years" class.  We don't know if they will remain stable under chemical attack or survive the rigors of brownian motion even - and we really have no clue how we'd actually build one.  Speculating on what such a machine might or might not be capable of is kinda crazy at this point. SteveBaker (talk) 20:29, 20 November 2007 (UTC)

interaction of infrared with skin
can an infrared beam give unique signature when reflecting from skin or flesh. also can an IR penetrate in flesh and reflect from bones? Neel shah556 (talk) 14:33, 20 November 2007 (UTC)


 * In IR photography with Kodak HIE, it is common to see the blood vessels under the skin. Apparently, there are biometric systems using this phenomenon.  I've never noticed bones being visible in IR photography. -- Coneslayer (talk) 15:11, 20 November 2007 (UTC)


 * For a little context, see previous related questions from the OP, leading to this line of discussion. I would be surprised if infrared photography could reveal bones, as water absorbs radiation in most of the IR range very readily (in something on the order of thousandths of an inch.) In fact, the above article says "These wavelengths also penetrate a few millimeters into skin and give a milky look to portraits". Are there any places where bones come within a few millimeters of the skin? If so, you might get an image of them at that point. jeﬀjon (talk) 19:26, 20 November 2007 (UTC)


 * I used to design simulations of InfraRed cameras for military flight simulators - so I've spent altogether too much time worrying about these things! What you see depends strongly on where you are in the IR section of the spectrum.  In the medium wave ("mid range") IR part of the spectrum, what you see is pretty much dominated by radiation from warm objects - not so much IR light reflected from them.  That's why you can see veins and such - they are generally a little warmer than the surrounding flesh so they give off more IR light.  But IR light doesn't penetrate skin very well, so you can't see deep into the body - probably why you don't see any bones.  You won't see much by reflected light either because IR reflectivity isn't all that large or variable.  However long-wave or "far" IR is getting up into the realms of microwaves and shortwave radio (it's a kinda fuzzy boundary) - which includes stuff like millimeter band radar that does refract through things like bones quite well but is hard to bring to a focus to make a decent image.  However, you don't want to be irradiating people with microwaves at short range - and at longer distances, long wave IR gets blocked by water vapor in the air so there isn't much to see except at a few very specific frequencies.  Short-wave or "near" IR is almost in the visible band - and (predictably) behaves a lot like ordinary red light. SteveBaker (talk) 20:24, 20 November 2007 (UTC)

If you had a gallon of pure white blood cells would it look white?
If not, what would it look like? 64.236.121.129 (talk) 15:41, 20 November 2007 (UTC)
 * A buffy coat is nearly all white blood cells (spinning down blood in a tube separates the red blood cells from white blood cells - the layer of white blood cells is called the buffy coat). It has that name because it is buff in color, which is kind of a whitish tan.  I suspect a gallon of WBCs would retain that color.  --Joelmills (talk) 17:43, 20 November 2007 (UTC)
 * I'm sure this is related to the fact that we call "brown people" "black", and "flesh people" "white". White and black chess pieces were probably not always actually black and white (probably made from wood and what not). Rfwoolf (talk) 18:53, 20 November 2007 (UTC)

Can radar detect organic flying creatures?
Birds and stuff? Or maybe a human skydiver? If not, is it possible to detect them through other means? 64.236.121.129 (talk) 15:58, 20 November 2007 (UTC)
 * Yup, according to radar "Clutter refers to actual radio frequency (RF) echoes returned from targets which are by definition uninteresting to the radar operators in general. Such targets mostly include natural objects such as ground, sea, precipitation (such as rain, snow or hail), sand storms, animals (especially birds), atmospheric turbulence, and other atmospheric effects, such as ionosphere reflections and meteor trails. Clutter may also be returned from man-made objects such as buildings and, intentionally, by radar countermeasures such as chaff." -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 16:02, 20 November 2007 (UTC)


 * (After edit conflict) Yes, flocks of birds and swarms of insects are routinely seen on weather radar. -- Coneslayer (talk) 16:05, 20 November 2007 (UTC)


 * I see. Hmm, so we can detect them, but they are usually ignored. Can't this be exploited to make a weapon? Maybe a small ornithopter strapped with explosives? 64.236.121.129 (talk) 16:09, 20 November 2007 (UTC)


 * Or how about a full-sized plane whose radar cross-section is as small as a bird? I can assure you that military exploitation of radar limitations is not a new idea. -- Coneslayer (talk) 16:17, 20 November 2007 (UTC)


 * In theory, perhaps, but it's difficult to envision a scenario in which that would be preferable to a cruise missile or a helicopter or something else that already uses ground clutter to avoid radar. Additionally, I would expect that trained radar operators wouldn't have much trouble distinguishing the flight characteristics of organics from artificial sources. &mdash; Lomn 16:22, 20 November 2007 (UTC)
 * Ever see an ornithopter in the sky? Looks almost exactly like a bird. 64.236.121.129 (talk) 16:29, 20 November 2007 (UTC)
 * How much explosive material can they carry, while remaining capable of flight and still looking like a bird on radar? -- Coneslayer (talk) 16:50, 20 November 2007 (UTC)
 * Dono. Depends on how well you make it. 64.236.121.129 (talk) 16:56, 20 November 2007 (UTC)
 * I don't think it's so much a question of "looks" as "behaves". Birds aren't likely to fly attack vectors.  While you could conceivably stretch the imitation to full-out flock behavior by the birdbombs, you're back to the question of why you'd spend the effort when other weapon systems fill the role.  Here's a thought, though -- a recon ornithopter might be an interesting prospect.  I'm pretty sure the military is mostly looking at fixed-wing designs for man-portable aerial recon, though -- probably due to power efficiency. &mdash; Lomn 19:01, 20 November 2007 (UTC)
 * Yet the ornithopter article suggests that flapping-wing designs are highly efficient compared to fixed-wing designs. Maybe the lack of popularity of ornithopters has more to do with the cyclic motion in the fuselage/body, and the higher stress loads? jeﬀjon (talk) 19:30, 20 November 2007 (UTC)
 * That's right. A flapping-wing design is more efficient. Btw, Lomn, you would spend the effort if it worked better. Which it potentially can, depending on what it is capable of, and what it can do. If it has the manuverability of a humming bird, I think that's a serious advantage. The lack of popularity I think has more to do with technological complexity. Using crappy gears and motors isn't how birds or insects flap their wings. 64.236.121.129 (talk) 19:58, 20 November 2007 (UTC)
 * Good point, I hadn't noticed the efficiency section. Given that, technological complexity is probably the correct reason, which would suggest that research will move in the ornithopter direction sooner or later.  &mdash; Lomn 20:10, 20 November 2007 (UTC)


 * Unfortunately, the efficiency section is not very accurate. Ornithocopters are not efficient for high-speed flight, as the wing-section required for lift is miniscule already. At supersonic speeds, I believe flight would be impossible for an ornithocopter. Current aircraft are more efficient for their mass and speed than birds are. Comfort has nothing to do with why we don't build ornithocopters, otherwise why wouldn't our reconnaissance drones have flapping wings? It is in fact a "failing" of biology to evolve a species to occupy a high-speed, high-mass, high-altitude niche, because to do so would require some kind of rotary muscle that does not exist in any animal we know of. The phenomenon is similar to why our ships use propellers instead of flippers. In this case, engineering firmly wins out, as many sea animals can compete with the weight and speed of our ships. SamuelRiv (talk) 18:30, 21 November 2007 (UTC)
 * I don't think anyone is claiming an ornithopter can move at supersonic speed, nor is it supposed to. It's efficient at the speed it moves at, that's all that matters. Our recon drones don't have flapping wings because the technological complexity of such a system is great, and we can't properly emulate flapping wings that well yet. We still use rather primitive technology compared to how complex animals are. If we can emulate muscles, and ligaments, then we are on the right track. Malamockq (talk) 00:49, 26 November 2007 (UTC)

Why do cows moo?
Why? 64.236.121.129 (talk) 16:20, 20 November 2007 (UTC)


 * According to a 2002 book, "the social contexts in which [moos] are used have not been studied critically. Sancho 16:37, 20 November 2007 (UTC)


 * Communication between cattle does not seem to be particularly sophisticated. Cows moo primarily to announce their presence. A louder moo means they are objecting to something, often discomfort. AFAIK that's about it. See animal communication for a more general discussion.--Shantavira|feed me 18:19, 20 November 2007 (UTC)
 * From having walked by and through fields at night with (nice) dogs, I can say they do make noise in order to sound the alarm when intruders walk in their pasture (I don't think they were greeting me). Keria (talk) 20:52, 20 November 2007 (UTC)

Why hasn't the Polar Bear been reclassified as a subspecies of brown bear?
The Grizzly–polar bear hybrid is a fertile offspring of a grizzly (subspecies of brown bear), and a polar bear. That would make it a sub species of brown bear. It even says so here, http://en.wikipedia.org/wiki/Polar_bear#Speciation So why is it still classified as a seperate species of bear? Shouldn't this have been corrected by now? 64.236.121.129 (talk) 16:38, 20 November 2007 (UTC)
 * The following is a quote directly from the section of the article that you referenced in your question:
 * "But neither species can survive long in the other's niche, and with distinctly different morphology, metabolism, social and feeding behaviors, and other phenotypic characters, the two bears are generally classified as separate species."
 * Sancho 16:45, 20 November 2007 (UTC)


 * See also Species problem. The definition you offer (species are capable of producing fertile offspring) is not the only definition used.  The definition of a species is a matter of controversy.  -- Coneslayer (talk) 16:49, 20 November 2007 (UTC)
 * Hmm, interesting. I'm not sure allowing for social behaviors and things is a good idea though for classification of species. The scientific classification system is based on common ancestry.64.236.121.129 (talk) 16:59, 20 November 2007 (UTC)
 * Yes, the classification system uses common ancestry to define the relatedness of organisms, however, there is no clear-cut definition of when two organisms are different species. Often, morphology, ethology and physiology are also used, because they can affect mating populations, for example, mate selection, or even capability of producing offspring.  (For example, chihuahua and mastiffs would likely be considered a different species since mating would probably be a physical impossibility without human intervention). --  JSBillings  18:56, 20 November 2007 (UTC)


 * The thing is, some subspecies of living beings (which are scientifically accepted) fit that criteria anyway 64.236.121.129 (talk) 20:03, 20 November 2007 (UTC)


 * This is another one of those things like "Is Pluto a Planet?" - in terms of scientific value, the debate has zero relevence. It's just a matter of what words we choose to use.  What matters here is what the genetics of Brown and Polar bears have in common - or not.  Whether we call them the same species or not is entirely irrelevent.  Continually renaming plants and animals to fit the whim of some classification nut simply causes more confusion in the formal naming of species and makes otherwise useful text books become useless prematurely.   It's just not worth the hassle to rename either or both kinds of bear.  Their relative similarity is well understood by those who care. SteveBaker (talk) 19:48, 20 November 2007 (UTC)
 * That sounds more like your own personal opinion. It just seems like you could say that about anything. Anything is a matter of what words we choose to fit them. 64.236.121.129 (talk) 20:05, 20 November 2007 (UTC)


 * No - not at all. It is a fact that iron is a metal.  That fact is true because the word "metal" has a fairly precise definition - and the fact is testable.  Knowing that it's a metal tells me things I may not have known before - that iron is likely to be shiney, that it conducts heat well, that it's ductile.


 * But the term "species" doesn't have a clear black and white definition - it is NOT the case that "If two animals can interbreed successfully then they are defined to be of the same species" or "If two animals have more than 92% of their DNA in common then they are of the same species" - there is absolutely no hard-and-fast rule you can point to. It's a vague and fuzzy term.  You can say that brown and polar bears share such and such percentage of genes or that they have similar or dissimilar habits in dietary matters or that they can interbreed - those are facts...but our classification words (like "species", "family" and "genus") are like "planet" - they are arbitary cutoffs within a continuous function with poorly defined boundaries.


 * Arguing whether two kinds of bear are or are not close enough in objective criteria to fall within the span of this fuzzy term is not an argument about bears - it's an argument about the meaning of "species" - and that's linguistics. Once you've decided on an answer, you know NOT ONE SINGLE THING about brown and polar bears that you didn't know at the outset.  If you decide that they are indeed of the same species - you can't actually use that information to tell you whether these bears have similar diets or similar lifespans or anything that you didn't know before.  That's not to say that the word "species" isn't useful - it's great for expressing larger, more obvious gaps - if you asked whether a polar bear and a giraffe were different species - we could immediately say "yes" - and if you asked whether my wife and I are from different species, we could certainly say "no".  But if you ask whether a Cocker spaniel is a different species from a German Shepherd - we should have the guts to say "it really doesn't matter - it's entirely an arbitary thing" because knowing whether they are or are not considered to be of the same species conveys absolutely no useful information.


 * It really doesn't matter - it's a pointless and annoying debate - you might just as well flip a coin to decide.


 * SteveBaker (talk) 22:32, 20 November 2007 (UTC)


 * Sure, you know useful information if they are classified as the same species. You know they can breed with each other, and produce fertile offspring. If they are the same species, they should do that. I see what you are getting at though, but I'm not sure the analogy to the definition of a planet is comparable. Malamockq (talk) 05:15, 21 November 2007 (UTC)
 * Actually, this is not so black-and-white. What does "can breed" mean? Many human couples, even male/female ones, even of the proper age, fail to conceive, and not for lack of trying. Are they different species? Breeding success is always a probability. And as for even trying: Some animals of the same species will not breed in captivity, while some of different species will only if artificially brought into close contact. --Stephan Schulz (talk) 12:44, 21 November 2007 (UTC)
 * Yep - exactly. Lions and tigers can interbreed too (See: Liger and Tigon) - are they the same species? SteveBaker (talk) 21:06, 21 November 2007 (UTC)


 * No, they are not the same species because their offspring is infertile. At least the males are. But I already said that. Produce fertile offpsring, I said that was one of the criteria for being the same species. The fact that they can produce offspring shows that they are very closely related and had a common ancestor not long ago. Being the same species, can tell a lot. I don't agree with your comparison to pluto. It's completely different. Malamockq (talk) 00:40, 26 November 2007 (UTC)


 * I could easily argue that the definition of a metal is far too imprecise to be worthwhile: for a start, what about metalloids? Knowing whether an element is a metal doesn't tell you anything specific about its chemical or physical properties.  Since the vast majority of elements are metals, and there are few enough elements for people to be familiar with most of them, it isn't really necessary to classify them in this way.  However, there are so many different 'types' of living things that it is very useful to have some way of classifying them, and this is obviously going to be arbitrary to some extent. 130.88.79.77 (talk) 14:13, 22 November 2007 (UTC)


 * The biggest problem with invoking the strict "Can interbreed" definition of "species" is that out there in the real world, you can have four slightly different kinds of animals: A,B,C and D such that A can breed with B and B can breed with C - but A cannot breed with C. So under the "can breed with" definition, A is the same species as B and B is the same species as C - but A is not the same species as C!  Worse still, you'll find that bot A and C can breed with D!  So now you have a wonderfully circular collection of interbreeders and a definition for 'species' that requires that you redefine the common English phrase "is the same as" in a horrifyingly new and alarming way!  Worse still, you may well find that a MALE 'A' can breed with a FEMALE 'C' but a FEMALE 'A' has no luck with a MALE 'C'.  Now where is your definition?  Males A's are the same species as C but females A's aren't?  If you're going to use the word 'species' at all, then you have to admit that it's a loose approximation - and therefore you can't answer the question "Are brown and polar bears the same species".  SteveBaker (talk) 21:19, 21 November 2007 (UTC)
 * ...unless of course you use another definition, that e.g. includes morphological differences, ecological niche, or regional distribution. You may not be able to clearly assign each individuum, but you can distinguish both species.--Stephan Schulz (talk) 21:47, 21 November 2007 (UTC)
 * Certainly you COULD come up with a clear definition of the word 'species'. But the fact is that there is no such standard definition - so the word still means very little.  The "Can interbreed with" rule is the one that's most often quoted - but it's not a hard and fast rule - nor can it be (as earlier arguments clearly demonstrate). SteveBaker (talk) 07:03, 22 November 2007 (UTC)
 * The one I'm more familiar with is "can and do interbreed if given a reasonable chance" (i.e. overlapping ranges, but not e.g. artificial insemination) with quite a bit of handwaving for historical precedence (e.g. dogs). --Stephan Schulz (talk) 09:58, 22 November 2007 (UTC)

Extinction
What problems are caused from a species going extinct? The ones I know are species naturally producing chemicals that are useful and can't be easily synthesized, and that one species going extinct could cause another one to die out (that one's recursive, but it still works, so long as there is another reason). Both of these would apply to plants more than animals, yet people seem to care more about protecting animals than plants. Why is that? Is this more of a humanities desk question? — Daniel 17:03, 20 November 2007 (UTC)
 * Lots of people care about protecting plants. Deforestation is a big issue. If you mean, people care more about the killing of animals than plants, then that just has to do with personal opinions and psychology. There is no universal law that says killing anything is wrong, it's just how we as a people decide for ourselves what is right or wrong. Some people only care about humans, and don't care about other animals. Some people draw the line at complex animals, but don't care about bugs or other lifeforms as much. No one is truly right or wrong in this way of thinking. Just a point of view. 64.236.121.129 (talk) 17:08, 20 November 2007 (UTC)


 * The organisations who do the publicity (because governments don't seem to care very much) know that people are not going to radically change their habits in order to save a freshwater snail. Polar bears and elephants however, make excellent publicity.  Plants are even less impressive to most people.  Heck, if some species of fern dies off, hardly anyone will notice...but if there are no cuddlywuddly white bears left - then that makes an impact.  We love to anthropomorphise and while we can identify with a meercat - we can't with a snail.  Sadly, this is human nature.   Fortunately, in order to save the high-profile animals, we pretty much have to save the entire ecological pyramid on which they are perched - so in the end, so long as people do the right thing, the reason is less important.


 * The things we mostly lose when some species disappears is it's DNA. Often that can be saved and stored with the idea that at some time in the future we could use cloning techniques to bring the species back again.  That might work for one species - but when an entire ecosystem vanishes - you'd have an impossible job restoring it all.  The interesting pharmacological stuff could be recovered by cloneing a long-gone species, growing a few individuals and testing them for useful chemicals.  The nasty problem of one species vanishing is that (as you say) whatever ate it will also die - but also whatever it ate may have a population boom and choke out a whole bunch of other species.  These kinds of domino effects could reach a catastrophy point (in the mathematical sense) where the entire ecosystem goes into runaway boom/bust cycles leaving very little biodiversity at the end.   With so little diversity, the world becomes very vulnerable to one disease sweeping through the population. The world will doubtless continue - but it may be a world which is exceedingly harmful to humans.  Think about things like algal 'blooms' (Red tides for example, which release nasty neurotoxins into the ocean).  A sufficiently monsterous one of those - which could perhaps be due to the extinction of some teeny-tiny shrimp that eats them or something - could quite easily kill off all of the marine life that humans eat across the entire planet.  This would be devastating to human populations all over the world.  The interconnectedness of all of the species on the planet make the present high rate of extinctions cause hard-to-predict (and therefore potentially dangerous) results.  SteveBaker (talk) 19:40, 20 November 2007 (UTC)


 * One species going extinct usually isn't a huge problem for us, but when a large number of species become extinct, say by global warming or deforestation, you might be looking at entire ecosystems collapsing, and since we humans also rely on nature and the environment for food, shelter, medicine, etc, a large number of ecosystems becoming extinct can become a huge problem for us. Just think of all the nessecities nature provides; if a lot of those became extinct, we could run into some big problems. An extremely large ecosystem with a species going extinct may be slow to affect the whole ecosystem, but eventually the results could be worse than if a smaller self-dependant ecosystem had a key species becoming extinct. Of course ecosystems also rely on each other, so if enough of them collapsed, we might eventually go down with them. The most likely source of massive ecosystem collapse in the future would likely be globalwarmingsealevelrisedeforestationdesertificationexpandingofcitiesoveruseofresourcesetc. If the fossil fuels are depleted in a few decades though, the long-term effects will probably not extend for as many millenia as if we found a larger fossil fuel resource. I'm not an expert on this stuff, though. Hope this helps. Thanks. ~ A H  1 (TCU) 00:58, 21 November 2007 (UTC)

Being sliced
A common trope in action films is that during a dramatic fight, one combatant will rush past the other with a sword, or shoot a laser through the enemy. The enemy will laugh, apparently unhurt (although the sword is usually covered in blood), shrug this off... then fall apart a couple of seconds later (off the top of my head, I think this happens in Kill Bill, Underworld, Resident Evil and Cube, not to mention countless anime). How much of this is true; I can't imagine that being sliced would be painless, no matter how quick and sharp the blow, but could someone function for a few seconds cut in half provided that the halves stayed together? Laïka 18:42, 20 November 2007 (UTC)
 * I really, really don't think so. It's conceivable that some supervillains are just immune to pain and will laugh their evil laugh even a moment after being sliced in half. However, according to current knowledge it is not actually possible to go on functioning normally right up the point where one falls apart into pieces; lots of problems will be happening to your body right from the point where you get hit. So for the time being, this kind of thing lies strictly in the realm of fiction. I also recommend against doing any experiments to test this. ;P - green_meklar  20:04, 20 November 2007 (UTC)
 * If you think how much force is needed to cut meat even with a very sharp knife, and even more force to cut bone, a lot of force is going to be applied to the victim and they will be knocked about or over.  Also don't expect that any nerves will function across the cut, so the distal part of the body will go limp and paralyzed. Graeme Bartlett (talk) 20:20, 20 November 2007 (UTC)


 * Even in the presense of massive blood loss, it takes time for the brain to die, so for cuts that are not directly thru the head, yes the person might continue functioning for "seconds". Also, from personal experience, I know that very sharp cuts can be virtually painless initially (until oxygen exposure starts killing cells).  I don't think it is humanly (or physically) possible to cut a person in half with anything near the cleanness of the movie images, but if you could make that magic cut, I suspect that the unaware reaction is a plausible result.  Dragons flight (talk) 20:38, 20 November 2007 (UTC)


 * In response to an earlier question, I just discovered that Japanese samurai swords were rated for sharpness according to the number of human bodies (typically cadavers) they could slice through with a single stroke. A good sword had a rating of 5 bodies.  So, yeah - amazingly, I think we have to admit that such a sharp cut is possible.  I agree that you'd have a few seconds of life left - but what bothers me about those movies is that the top and bottom halves of the body stay together so well - I don't think that is possible given the kinetic energy of a fast swinging sword. SteveBaker (talk) 21:53, 20 November 2007 (UTC)
 * The sharper a sword is, the less energy it delivers to its target. A sharp sword can easily make a cut without the user having to use too much force. --Bowlhover (talk) 06:13, 21 November 2007 (UTC)
 * In principle, I don't see that it's much different from the magician's trick of pulling a tablecloth out from under a setting without disturbing that setting -- that is, possible, but highly unlikely if you look at random tablecloth yanks. &mdash; Lomn 23:04, 20 November 2007 (UTC)


 * Hey Steve - do you know of any swords that are sharp enough to perform the much-seen-in-anime longitudinal 'top of head to crotch' bisection with a single stroke? --Kurt Shaped Box (talk) 23:25, 20 November 2007 (UTC)


 * I'm no expert - I've just been reading around articles about Japanese swords today. The various articles we have (most notably Tameshigiri) suggest that a diagonal slice starting at the shoulder and emerging on the opposite hip (cutting the victim completely in half) was the easiest and most common Japanese Katana stroke.  Certainly the best swords were more than capable of getting all the way through a body with one of those strokes (which is utterly amazing).  Going vertically through that heavy bones in the skull sounds tougher - so I don't know.  I don't think it's obviously impossible - but it's not likely to be the kind of stroke a genuine Katana swordsman would routinely use. SteveBaker (talk) 23:48, 20 November 2007 (UTC)


 * Mass graves at various European battle grounds also show that this was the preferred method of killing an opponent in the West as well. (My source comes from a book on European sword technique in the middle ages, which I’m having trouble finding on Amazon at the moment.) I wonder why this is apparently one of the preferred methods of killing with a sword? --S.dedalus (talk) 07:34, 21 November 2007 (UTC)


 * I practice kendo and iaido, and in both we do something called tenouchi, which is a wringing of the hands as you make contact with the body of the opponent. The idea is to stiffen the sword to be able to cut through bone, and this type of cut is indeed practiced in iai from the top of the head to the crotch. Apparently it gets much easier once the initial break through the skull is made. Also remember that you get a hell of a lot of leverage through your extended arms and the blade as you make a cut, and you have the momentum of your body weight that transfers to the sword through your footwork. SamuelRiv (talk) 00:55, 21 November 2007 (UTC)


 * So, what's the accepted wisdom when it comes to the spine? Are you supposed to cut directly down through it - or is the idea to slice slightly to the left/right of the column itself? Top of skull -> base of spine, straight through is a *lot* of bone to cleave... --Kurt Shaped Box (talk) 08:40, 21 November 2007 (UTC)


 * I remember reading a William Gibson book at some point where a guy had a garrote-type device with a weight on the end where the wire was "only one molecule thick" or some such thing. He would swing it through people and they wouldn't notice for a moment, then fall apart.  I remember being nonplussed that it would damage the victim at all.  Surely the severed bonds would just reattach?  Also perhaps relevant is the urban legend about the invisible jet of steam that can cut you in half: Cecil Adams takes the case.  --Sean 02:33, 21 November 2007 (UTC)
 * The device you're referring to is a monomolecular wire, and it only exists in fiction. -- Hi  Ev  11:26, 21 November 2007 (UTC)


 * Related scenario: Darth Maul is cut in half in The Phantom Menace and emits a groan and facial expression change, falls in one piece into the reactor shaft behind him, then separates about halfway down. Also, Sean, we have an article about that: monomolecular wire. - Woo ty   [ Woot? ]  [Spam! Spam! Wonderful spam! ] 05:33, 21 November 2007 (UTC)


 * Regarding the pain factor: I got bit on my face by a dog once. There were several cuts and I ended up with 36 stitches on the outside of my face, and a few more stitches on the inside of my face in the deeper cuts.  Still, I didn't feel any pain until much later.  The only way I knew I was cut was from the look on everyone else's face, and when I touched my face my hand came away bloody.  Not a pleasant experience, but it helps answer your question.  I've heard of people even getting shot before and not realizing it until later, so it might be possible to be sliced up painlessly. --  Hi  Ev  11:26, 21 November 2007 (UTC)


 * Re:spine-cutting, the practice is not to actually cut the spine in both kendo and iaido shomen, since the skull is cut with the last sixth of the blade only. The sternum seems to be the only main bone to cut through after the skull. Also keep in mind that there are a variety of other cuts that avoid the bone, and indeed pre-WWII Japanese police and military practiced these cuts extensively (the shoulder-to-hip being the most common, I think, but armpit-to-throat, hip-to-hip, slashes through the eyes and stabs to the throat and heart are also practiced). I'm no expert so this last statement should not be taken to heart, but the shomen head-to-groin cut seems to often be more of a technique to train precision and swordsmanship than actual combat. This of course, like everything, comes with many exceptions. SamuelRiv (talk) 15:10, 21 November 2007 (UTC)


 * As a point of reference, it's been said that when people were executed by decapitation (as with a Guillotine), their dis-embodied heads were able to function for a short time afterwards (a few seconds). Supposedly, there have been instances where convicted criminals have agreed to blink repeatedly after execution, with someone counting the time. Compare this to the "chicken with its head cut off" . -- 20:23, 21 November 2007 (UTC)  —Preceding unsigned comment added by 128.104.112.120 (talk)
 * Since this IS Wikipedia, and it's a matter of tradition, one cannot help but follow that reply with a link to Mike the Headless Chicken. SteveBaker (talk) 20:56, 21 November 2007 (UTC)

A recent issue of New Scientist had a feature on death. The phrase "then, after the standard 10 seconds, you loose consciousness" turned up several times. It appeared in decapitation, heart failure, exposure to vacuum, blood loss. Apparently 10 seconds is how much (more or less) useful consciousness you've got after your brain stops getting blood/oxygen. You miss out on the 10 seconds in situations like "head first into the pavement at terminal velocity" and "bullet to an important part of the brain". --Psud (talk) 12:19, 22 November 2007 (UTC)

molecular weight help
help, I was given this equation about chemistry. Here, I'll show you how it looks like:

A + B -> C + D

I was given the molecular weight for both a, and d; the grams for a and b. I'm supposed to figure out the molecular weight for d. What do I do-I've been trying lots of ways, but I don't know which way is right. —Preceding unsigned comment added by 142.132.6.16 (talk) 19:16, 20 November 2007 (UTC)
 * Could you clarify this question? You said you were "given the molecular weight for […] d" and you are "supposed to figure out the molecular weight for d." Perhaps the molecular weight, chemical equation, and/or conservation of mass pages would be helpful? DMacks (talk) 19:21, 20 November 2007 (UTC)

Oh, sorry. I fixed it. I wasn't given the MW for d. :D


 * Terribly sorry, could you restate what you've been given? It still isn't that clear. If you could also list some of your thoughts on how to approach the problem, it will make it easier to know how to help you approach it in a way that makes sense to you. Skittle (talk) 20:20, 20 November 2007 (UTC)

whole breast tumour samples
"fewer [than expected] natural killer cells found in cancer component of whole breast tumour samples" - what's a "whole breast tumour sample"? Do they actually mean a whole breast? Like it's been amputated in its entirety and cut into sections? Methods section isn't part of the paper and I don't have access to it. --Seans Potato Business 19:48, 20 November 2007 (UTC)


 * It could just refer to the "whole tumor" [whole (breast tumor)]. If you're talking about the same paper that I just read, I agree that it's ambiguous (they change the specific wording several times).  You could always email them and request clarification.  Someguy1221 (talk) 20:13, 20 November 2007 (UTC)

Density of nerves as the body grows
If a human rapidly gains weight and the surface area of their skin increases do the nerves spread further and further apart, thereby making the skin less sensitive?

24.117.4.88 (talk) 20:00, 20 November 2007 (UTC)MLOvan

Good Viruses?
Just like there are beneficial and non-beneficial bacteria for human beings, are there viruses that human beings need/benefit from? --WonderFran (talk) 20:12, 20 November 2007 (UTC)


 * Complicated question. Firstly, the reason bacteria can be beneficial at all is that their proliferation in the human body only requires the availability of something they can consume.  This allows for bacteria that consume material we wouldn't ordinarily digest at all, and many of these turn out to be either beneficial or entirely inconsequential.  Viruses, on the other hand, operate by hijacking living cells and basically turning them into virus factories.  They don't consume "unconsumables" or generate anything to benefit us (viruses only use human cells to make other viruses, so no side benefits).  However, there are viruses that attack bacteria (bacteriophage), and these can benefit humans by attacking harmful bacteria (see Phage therapy).  Additionally, gene therapy often involves using a viral vector to introduce a (hopefully) beneficial new gene into human cells.  These vectors are usually something of a "neutered" virus that can't actually hijack human cells to benefit their own replication.  Someguy1221 (talk) 20:27, 20 November 2007 (UTC)


 * And scientists are also looking into manipulating viruses so they will attack and kill cancer cells which would be quite beneficial for some... - Mgm|(talk) 20:43, 20 November 2007 (UTC)
 * The previous answers looked to the future, but don't forget the past! Snorting a powdered scab that you picked off of someone with a cowpox lesion was the original smallpox vaccine, and the smallpox vaccine that eventually eradicated that disease in the wild was also virus-based.  --Sean 02:48, 21 November 2007 (UTC)
 * Human society is the wild? o_O Someguy1221 (talk) 08:52, 21 November 2007 (UTC)
 * You don't know the phrase, "extinct in the wild"? Lol. That's a common phrase used in science. Geeze man. No offense, but that is basic knowledge. 64.236.121.129 (talk) 14:52, 26 November 2007 (UTC)


 * I just meant smallpox doesn't exist in nature anymore, just in some hopefully-but-probably-not-well-guarded freezers here and there. --Sean 14:44, 22 November 2007 (UTC)
 * On the same note see Inoculation. Keria (talk) 08:50, 21 November 2007 (UTC)


 * The Adeno-associated virus is somewhat neutral and could be used to create viral vectors. Keria (talk) 08:55, 21 November 2007 (UTC)
 * Also, the Serotype 2 and cancer section in that article makes a rather interesting and relevant claim. It's not as surprising as it might sound at first — there'd certainly be an evolutionary advantage to a virus that actually helped its host stay alive and healthy while still managing to replicate itself.  AAV is a clever little thing anyway, lying dormant and essentially harmless in cells until they are infected by another virus, and then hitching a ride on the other virus's replication machinery.  In fact, I wouldn't be at all surprised if it even actually managed to slow down the replication of those other viruses as a side effect.  —Ilmari Karonen (talk) 16:35, 22 November 2007 (UTC)
 * HERVs make a significant showing on the human genome, so I suppose you could say that viruses have added DNA to humans, but I cannot say if this was good or bad. Graeme Bartlett (talk) 20:56, 21 November 2007 (UTC)

Amoeba have more DNA than a human?
Is the reason for this because of redundant information? 64.236.121.129 (talk) 20:14, 20 November 2007 (UTC)


 * I would guess it is because ameobas have need of a greater variety of proteins and such. Many micro-organisms tolerate a much greater variety of living environments and a wider range of food sources than people.  In a nebulously defined way, you could easily say that an ameoba is more "complex" than a comparable human cell, since individual human cells are quite limited in what they can accomplish and tolerate.  Dragons flight (talk) 20:27, 20 November 2007 (UTC)


 * What a cell can accomplish function-wise is more a result of specialization than anything to do with its DNA. But yes, toleration of a larger variety of environments could be one reason. I'm actually sceptical. Human cells contain A LOT of DNA --that's why it took so long to have it sequenced. DNA or RNA sequences of smaller less complicated organisms and viruses where sequenced a lot earlier and somehow I don't think amoeba DNA is more complex than that of Arabidopsis or Drosophila (fruit fly). - Mgm|(talk) 20:41, 20 November 2007 (UTC)
 * FYI, ameobas have a genome with ~100 times as many base pairs as people.  They are substantially more complicated then mere flies.  Dragons flight (talk) 22:56, 20 November 2007 (UTC)


 * There's a term for this. See C-value paradox.  128.163.224.222 (talk) 21:07, 20 November 2007 (UTC)


 * One thing that has always bothered me about ameobas is that they reproduce by splitting in two. This means that - in effect (a) they live forever and (b) they are all clones of each other.  I presume this makes it harder for them to evolve because all change has to come from random mutations and transcription errors - and no change comes from some happy coincidence of genes obtained from a mommy amoeba and a daddy amoeba who "loved each other very much".  Which in turn leads me to suppose that in order to be adaptable to a reasonably wide range of conditions, they need a lot of DNA which is pre-programmed for all kinds of tricky situations that the species has lived through in the past.  But I don't know enough to know whether this is a reasonable supposition...can anyone comment usefully?  SteveBaker (talk) 16:07, 21 November 2007 (UTC)
 * This is true of any asexually reproducing organism, as I'm sure you're well aware. Asexually reproducing organisms generally benefit from relatively rapid lifespans (from birth to giving birth, in whatever methods this might entail). So you put an amoeba in an environment, and you'll very quickly (relatively) get lots of amoebas with lots of mutations. I'm not sure your "pre-programmed for all kinds of tricky situations that the species has lived through in the past" actually works; Sexual reproduction doesn't increase the rate of mutation, but merely produces semirandom combinations of available alleles for each gene, thus increasing diversity of traits.  If these amoeba are used to their environment's regularly changing in a drastic manner, entire phenotypical subsets of their population would be regularly outcompeted, and I'm not sure asexual reproduction would give them anything of a leg up in that situation.  As a point of fact that disagrees with my assessment, rotifers reproduce sexually only when under environmental stress, though that is possibly only because their sexually created eggs are more survivable than asexually created rotifer-babies. Someguy1221 (talk) 16:28, 21 November 2007 (UTC)


 * As an organism that eats by phagocytosis, it is possible that it occassionally incorporates DNA from bacteria it eats. Dragons flight (talk) 19:57, 21 November 2007 (UTC)


 * Also, think of the proposed hypotheses so far for junk DNA. Amoeba have more need of mutations than we do, so they need more "raw material" to mutate. It's not so much as their complexity, but the fact that if you have more DNA, you get a higher rate of mutation as well as a bigger "shield" for your existing genes against things like free radicals or radiation. (Effect: more mutations spawning new genes, less mutations affecting existing genes.) Amoebas live in much more volatile environments, do they not? Elle vécut heureuse à jamais  (Be eudaimonic!) 03:10, 23 November 2007 (UTC)

Anyone know what this is?
Does anyone know what this creature is called?unkown animal Thanks! Robert Beck (talk) 22:39, 20 November 2007 (UTC)
 * Dunno. It might be a kind of slipper lobster. --Milkbreath (talk) 00:11, 21 November 2007 (UTC)


 * Looks like it might be Parribacus antarcticus, do an image search to see more. 70.171.229.76 (talk) 01:37, 21 November 2007 (UTC)