Wikipedia:Reference desk/Archives/Science/2017 April 30

= April 30 =

Feed conversion ratio / Efficiency of food conversion

 * Known articles: Feed conversion ratio (FCR), Efficiency of food conversion (ECI)

The definitions given in the articles cited above either explicitly refer to mass (FCR, with the discussion noting that substantial problems exist with respect to dry/wet mass) or seem to be undefined (ECI). I am looking for conversion ratios that allow an understandable comparison for human food production. An example would be human consumable calories and human consumable protein (2 different values). The sum of the caloric input fed during the raising of an animal would be divided by the sum of all calories of products generated from the animal. Thus, the weight of bones and skin etc. would not go into the equation, neither would fodder not consumable by humans (grass) enter the equation. The desire for a "primary" conversion ratio relates to the case, where the fodder itself has a feed conversion ratio (raising fish from plant matter to be fed to other fish). Here the fodder would be accounted with the primary calories used to produce it. Do this or similar definitions exist? Do data for this or similar parameters exist? --Vigilius (talk) 09:26, 30 April 2017 (UTC)

Why are multicellular, eukaryotic organisms more difficult to kill than prokarotic, unicellular organisms?
A long time ago, I learned that bacterial and viral infections are relatively easy to treat. Bacterial infections can easily be treated with antibiotics. Viral infections can easily be prevented by and treated with vaccines. Then come fungal infections. Fungal infections are harder to treat, because they resemble animal cells. Then come parasitic infections, like worms. They are said to be difficult to treat, because they're multicellular. Why are multicellular organisms difficult to kill because they are multicellular? Also, if insects are treated with insecticides, then what would be used to treat large, vertebrate mammals (deer, rabbits, field mice, humans) who may steal food from produce farms, along with carnivorous, large, vertebrate, mammalian predators (wolves, foxes, cats, maybe humans from neighboring tribes) who may be attracted to the herbivorous prey on the farms? 50.4.236.254 (talk) 12:14, 30 April 2017 (UTC)
 * I would have to disagree with your statements that bacterial and viral infections are easy to treat. Some are, but both still kill plenty of people. As for why treating eukaryotic infections can be more difficult, they are more similar to human cells (eukaryotes as well, of course) than prokaryots. Therefore finding therapeutic targets in them that do not case unacceptable side effects on the host cells can be more difficult. Fgf10 (talk) 12:28, 30 April 2017 (UTC)
 * Note in particular that viral diseases are rarely treated using vaccines. Most vaccines targetting viral diseases are prophylactic and intended to prepare the immune system to combat the viral disease before exposure, or rarely, soon after. For example, although post exposure prophylaxis for rabies can involve use of the rabies vaccine for minor incidents of possible exposure, rabies immunoglobulin is recommended for more major exposure like a significant bite . Therapeutic vaccines are still a very rare thing and I'm not aware of any therapeutic vaccine targetting a viral disease approved for use in humans.   (Oncophage or Sipuleucel-T are often said to be the first therapeutic vaccines but they're both cancer vaccines, used for cancer immunotherapy.) Interestingly one of the few therapeutic vaccines currently in an advanced stage of development which isn't a cancer vaccine seems to be PEV7 which targets recurrent vulvovaginal candidiasis, i.e. a fungal disease. (Although we should be careful about reading too much into what's being developed since it can reflect funding as much as anything.) Nil Einne (talk) 13:46, 30 April 2017 (UTC)
 * Large, multi-cellular organisms are not necessarily and heartier, more resilient, or more difficult to kill than bacteria, such as prokaryotic. In fact, the opposite is likely true. Bacteria are quite resilient, and many can survive extreme conditions that few, if any, eukaryotes could survive. What you are talking about isn't the organisms' resilience, but rather our ability to treat them as infections. That's a very different problem. Antibiotics work great on bacteria because the mechanisms by which they were attack and kill bacteria, but do little to nothing against eukaryotic cells. This is because we are so different/distantly related from bacteria that we have a lot less in common with them. For example, penicillin attacks the peptidoglycan cell walls of bacteria, but we (humans) do not have peptidoglycan cell walls in our cells. Thus, something attacking peptidoglycan won't harm us. A fungal infection or, even more so, a parasitic worm is much harder to treat as it is more closely related to us. There are tons of things that are completely effective at killing fungi or parasitic worms, but most of them will kill you as well. A treatment isn't of much value if it kills the patient. This is even more apparent in cancer treatment; cancer cells ARE your cells, just slightly mutated, so almost anything really good at killing cancer cells is also really good at killing you. With cancer, we often have to accept a tradeoff of trying to find a chemotherapy that kills the cancer faster than it kills you, but that is why chemotherapy is often so unpleasant for the patient. Killing cancer is easy. We can light it on fire or expose it to cyanide, both of which will also kill a fungal infection or a parasitic worm... but would also kill you. Ideally, you'd want to do something like program the immune system to attack fungal infections, parasites, or, most especially, cancer cells, which is the basis of immunotherapy. Barring deficiencies, the immune system is excellent at discriminating between your own cells, which it wants to leave alone, and invading cells. So again, just to clarify, it isn't that fungi or parasites are any more resilient or difficult to kill than bacteria that makes them hard to treat, it's that they are difficult to kill without killing you because their cells and biochemistry are much close to our own. --OuroborosCobra (talk) 16:46, 30 April 2017 (UTC)

Life on the sun/stars
I know this is a very hypothetical question, but since I was a child I thought that the idea life couldn't exist in extreme environments was ridiclous. And now we are finding life in more and more environments.

So, based on our knowledge of physics could it be possible for a life form to exist on a star? 95.148.212.198 (talk) 14:22, 30 April 2017 (UTC)


 * I don't believe we have the knowledge to answer that at present. However, the complex magnetic fields on stars could be one possible indication of "life". StuRat (talk) 14:46, 30 April 2017 (UTC)


 * Stu, did you make that theory up or do you have a reference? HenryFlower 20:14, 30 April 2017 (UTC)


 * As I said "I don't believe we have the knowledge to answer that at present". Also, see emergence. StuRat (talk) 23:56, 30 April 2017 (UTC)
 * You must be having trouble sitting after that one. Ian.thomson (talk) 00:01, 1 May 2017 (UTC)


 * How should we know about life in the universe? We checked out one system and about half of its planets and moons. We are also still about to discover/develop our first/own artificial intelligence. Maybe wait 20-30 years and ask them! --Kharon (talk) 22:50, 30 April 2017 (UTC)
 * My reason for asking is because scientists (maybe more scientific press) say that life needs certain conditions, but conditions for our lifeforms don't mean that is necessary for other life. Thanks for replies anyway 95.148.212.198 (talk) 13:53, 1 May 2017 (UTC)
 * "There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – the ones we don't know we don't know" (Donald Rumsfeld, 2002). :-) Alansplodge (talk) 16:09, 1 May 2017 (UTC)
 * It would be nice to know some unknown unknowns sometime before i pass on :-) 95.148.212.198 (talk) 16:25, 1 May 2017 (UTC)
 * Oh, we will probably, but everyone will find it disappointing. Humans have mastered telepathy, but we complain it is too expensive. Tigraan Click here to contact me 15:20, 2 May 2017 (UTC)
 * @Tigraan No, Telephony != Telepathy. Blooteuth (talk) 22:32, 2 May 2017 (UTC)


 * The answer is quite simply "no". While life could take many forms, it would be hard to imagine any form of life which does not rely at least basically on condensed matter, that is where atoms and molecules combine in some way to form stable forms such as liquids and solids.  Stars are, quite simply, too hot for any condensed matter to form, the consists mostly of a form of matter called plasma, where even neutral atoms find it hard to exist; such matter consists mostly of ions and free electrons.  There's no way for life to self-organize in such an environment (a pre-requisite for Abiogenesis), or indeed to maintain any semblance of order.  Any solid matter would be vaporized in short order if placed close enough to a star such as the Sun.  -- Jayron 32 15:32, 2 May 2017 (UTC)
 * What about flattened-flatfish shaped (the gravity!) life on the surface of neutron stars based on the strong force? Or would that only be science fiction? Sagittarian Milky Way (talk) 21:08, 2 May 2017 (UTC)
 * The last one. -- Jayron 32 21:17, 2 May 2017 (UTC)
 * Thanks for the links. I still hope life can exist in very extreme conditions but you answered my question (i.e. based on our current knowledge of physics) 95.148.212.198 (talk) 20:41, 2 May 2017 (UTC)

Feynman Lectures. Exercises 1964. Exercise 1-3
I have seen a solution from the solution book (translation):

I think that the approach is taken from lecture 39 and speed $$v$$ and number density $$n$$ are not known. I have made a solution from specific heat of evaporation (for water $$2\cdot 10^6 \text{J/kg}$$). Also the power of the sun = $$1000 \text{W/m}^2$$. And assuming area of the glass as $$16 \text{cm}^2$$ I got 6 days. But I want to calculate somehow the power of heating by air (if the glass is put not at direct sun rays). How to do this?
 * I think we could use the psychrometric tables to find temperature difference of air and water (for humidity 70% - average for Caltech location), and then use formula for heat conduction $$P=\tfrac{\lambda }{d}A(T_H - T_L)$$.
 * $$P=\tfrac{0.2}{0.003\text{ m}}0.0064\text{ m}^2(5\text{ K})=2 \text{ W}$$.
 * Is it acceptable?

Username160611000000 (talk) 16:00, 30 April 2017 (UTC)

Pouring hot water into a glass with a spoon inside
That sounds like one of those pieces of information "from the gut" or that "just feel right". However, could it be that a metal spoon in the glass changes the thermal shock on the glass? Metal is very good conductor of heat, and maybe it absorbs some heat avoiding a break. --Clipname (talk) 17:23, 30 April 2017 (UTC)


 * Yes, that's just common sense. The spoon also spreads the flow so that the temperature gradient in the glass is reduced.  It's still possible to crack a cold glass with boiling water, of course, even with a silver spoon inside.   D b f i r s   20:18, 30 April 2017 (UTC)
 * I'd think that the thermal shock would be so quick that the spoon wouldn't have enough time to make a difference. Sure, it's going to absorb some heat and then conduct it but it would take time to do that. Glasses break in the second you pour in too hot a liquid. 95.148.212.198 (talk) 14:01, 1 May 2017 (UTC)
 * Has anyone actually ever managed to break a glass by pouring in hot water, or dropping it into a bowl of hot water? Ever since I was warned against it as a child I've been trying to make it happen, and never succeeded. DuncanHill (talk) 14:21, 1 May 2017 (UTC)
 * Try putting it in the fridge first. If the glass is already warm, then the temperature gradient is lower, of course.  It's probably easier to achieve (if that's your aim) with older, thicker glass.   D b f i r s   15:29, 1 May 2017 (UTC)
 * Back in the 70s, McDonalds sold Star Wars glasses. They were very thin glass and easy to break by quickly making them either hot or cold. 209.149.113.5 (talk) 16:25, 1 May 2017 (UTC)
 * I broke two glasses by pouring in boiling water when I was younger, so it's definitely possible even without cooling the glass down beforehand. Maybe glass is more resilient now, but I stopped putting hot water into cold glasses after the second time one cracked.95.148.212.198 (talk) 16:35, 1 May 2017 (UTC)
 * I had a glass bowl that exploded (like shattered and sprayed glass around the kitchen) when I put hot mashed potatoes in it. It does happen.  Also read this. -- Jayron 32 17:03, 1 May 2017 (UTC)
 * Whether it will shatter does depend both on the "starting temperature" of the cup (hence the suggestion to put it in the fridge first), and the type of glass. Duralex, for example, can handle significant temperature swings without cracking. 14:09, 2 May 2017 (UTC)
 * A Prince Rupert's Drop is an interesting example of the stress in glass due to temperature change. DMacks (talk) 05:22, 3 May 2017 (UTC)

Separately living transitional species
Are there any living species with both evolved and separately living transitional form? That is, when one group parted ways with the other and retained transitional form, while the other group evolved further. Thanks.--212.180.235.46 (talk) 17:44, 30 April 2017 (UTC) 50.4.236.254 (talk) 19:02, 30 April 2017 (UTC)
 * "A neat way to see how you may have evolved is to lay your arm on a flat surface so that the underside and the palm of your hand face up. Touch and press together your pinky finger and thumb and then raise your hand up at the wrist just a little bit, as shown in the video. If there is a raised band in the middle of your wrist, you have a vestigial muscle in your forearm called the palmaris longus. The ridge you see is a tendon that connects to it and that muscle is either absent from both arms, or missing from one arm, in an estimated 10-15% of the population. If you’re missing this muscle there’s no need to worry because it’s essentially useless! Studies have shown that it has absolutely no effect at all on a person’s grip or pinch strength."
 * Courtesy link & image added. --2606:A000:4C0C:E200:3CF4:5668:5FB:EC43 (talk) 22:22, 1 May 2017 (UTC)
 * Any species is transitional between what it had been and what it will become. That said, the lungfish still have many of the characteristics of the last common ancestor of most land-living tetrapods. --Stephan Schulz (talk) 15:53, 1 May 2017 (UTC)
 * The many versions of the Flatfish, initially left/right symmetric, show it has achieved the feat of "evolving" one eye to the same side as the other eye, going through transitional stages that are recapitulated in the embryo. Blooteuth (talk) 17:58, 1 May 2017 (UTC)
 * Please stop linking to " a largely discredited biological hypothesis" as though it has any explanatory power here. Like the geocentric universe and phlogiston theory, it's a historical curiosity but has no relevance to modern understanding.  -- Jayron 32 11:14, 2 May 2017 (UTC)
 * I warmly recommend anyone interested to read Wikipedia's peer-reviewed article Recapitulation theory that provides a balanced view of its historical significance in on-going study of Developmental biology. Apropos evolution of the flatfish eye, it would be remiss not to note that the migration of the lower eye is actually observed during larval development (Martinez & Bolker 2003). The Transitional fossil Amphistium is evidence of the same continuum of variation between fish that exist or existed. It would be equally arrogant to neglect what can be learned from this dramatic example of evolutionary adaptation as to neglect the supplanting of geocentrism by Copernican/Galilean heliocentrism or the supplanting of the hypothetical phlogiston element by oxidation chemistry. There are good reasons to teach these subjects and to have Wikipedia articles about them. Please improve our responses to OP's by offering good references rather than by heckling another responder. Blooteuth (talk) 12:28, 2 May 2017 (UTC)
 * [[file:Speciation_modes.svg | thumb | right |200 px|Different modes of speciation, any of which could result in species with different levels of a certain trait, i.e "intermediate" or "transitional" forms that have roughly stabilized.]] This sort of thing is happening all the time, and yes, all species are in some sense transitional. You may want to read up on the various ways species split. See speciation. SemanticMantis (talk) 18:44, 1 May 2017 (UTC)


 * OMG, OMG, OMG, OMG! Homer Simpson something! I lack the muscle! Ho Mer Simp Son!μηδείς (talk) 14:42, 2 May 2017 (UTC)