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Your teacher was passing on a myth. This false belief might be related to the equally false belief that hot exerted horses should not be fed cold water. It could also be down to someone downing a big glass of ice-cold water in one go as a child, get a brief stomach ache and spin a health-advice on it.


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If you with 'humans' refer to our genus Homo (which is often the case), we do have multiple species, see wikipedia for an overview. The difference to many other organism groups is just that all species except Homo sapiens are extinct. Also, taxonomic ranks below the species level - such as breed, subspecies, population and race - are very poorly definined ...


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Humans are a species and within our species we, arguably, have races. Although the term 'race' is highly controversial and ill-defined, as pointed out by @fileunderwater in his elegant answer, I just want to express that races can be, in a way, compared to breeds and hence that the human species does have some of the species-subdivisions you are addressing. ...


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Humans and other animals have lots of innate behaviors that are not learned from observation, i.e. behaviors that are hard-wired into our nervous system, and this is one of them. Suckling reflexes in mammals and the Moro reflex is human babies (which we grow out of) are other simple examples. The stretching behaviours you are referring to are usually ...


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Chlorine is a reactive substance and an oxidizing agent. It can cause damage to surfaces exposed to it such as eyes, skin etc but it cannot penetrate deeper. Chlorine can damage your hair by oxidation — hair becomes rough and brittle. This is not same as hair loss — chlorine doesn't cause hair to fall out because it cannot penetrate to the follicles. See ...


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It seems to me that really your whole question seems to be much simpler than it seems and it is just "why are eye banks called eye banks when they can't transplant eyes, just bits of them like corneas" The answer is: In the english language and in various cultures, the names of things often have a loose and not entirely accurate relationship to the ...


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In addition to providing tissue for transplant, eye banks also provide tissue from all parts of the eye to medical schools and universities for teaching and research purposes. There are many medically relevant questions that can only be answered by examining human tissue, and eye banks facilitate this research.


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I used to work at an eye bank so I have a bit of knowledge about this, though some of it may be out of date. There are several aspects to an eye bank. The corneas are one of the primary things that are kept for transplantation. Of course, this will not repair blindness in someone that has problems in other areas of the eye, but corneal transplants are ...


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You are asking two questions that you think are connected but are actually not. Question 1 - What is the use of eye banks? Answer: It's to store corneas for transplant for people with cornea damage. Question 2 - What use is cornea transplant to a completely blind person? Answer: It depends. If the blindness is due to clouded cornea (several ...


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No-one can re-implant an entire eye, because the optic nerve has been severed in one who has lost an eye. A cornea can't be grafted to a glass eye. But blindness isn't only caused by loss of the entire orbit. It's also caused by cloudy corneas, which is the purpose of eye-banks. The optic nerve is a cable of nerve fibers that carry visual information from ...


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The eyeball is basically the sclera that surrounds the delicate inner structures of the eye (see wiki on the eye). The cornea is the transparent window in front of the pupil that transmits light to the retina. It needs replacement when it turns opaque, often due to damage or infections. The cornea can be replaced on its own, without the need for ...


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The capture area of the eye is a bit fuzzier and harder to define than that of a camera. A camera captures consistent, fully detailed data right up to the edge of its sensor, and no data at all beyond it. Captured data is clipped by an ideally uniform sensor, augmented a bit by the lens, and is well-defined during design and manufacturing. The eye can ...


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The problem with Bateman is that he was only looking at zygote production. There are many more factors influencing reproductive variance aside from number of sperm vs. number of eggs. If I were you, I'd read the book titled "Dr. Tatiana's Sex Advice to All Creation: The Definitive Guide to the Evolutionary Biology of Sex." The author is Olivia Judson (by the ...


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With regard to the vacuum - Apparently nothing happens as long as you don't hold your breath, just like you shouldn't hold your breath when ascending after scuba diving and the pressure drops. See NASA's answer to the same question. Of course there's the radiation that does other funny things in space, see the NASA link.


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The term was pioneered by Mendel, who had no knowledge of chromosomes, so definition 1 would perhaps be the best answer. However, we now know that definition 1 arises from definition 2 (chromosomes are inherited independently of each other) and from the fact that chromosomes recombine (cross-over). That said, independent assortment does apply to linked ...


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This depends on a lot of factors, including how you take your first sip. If you sip with air, you are altering the temperature of the liquid as you sip, as well as decreasing the volume of hot liquid in your mouth, so that the increased surface area of your exposed tongue can quickly alter the temperature of a borderline scalding liquid into a non-scalding ...


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Afaik the tongue is not more heat tolerant than other parts of the body, so the minimum temperature to cause burn is about drinking a beverage having 45°C temperature for a long time (more than 5 minutes). The pain threshold of tongue is around 47°C, so you will feel when it really burns. According to studies the hedonic value of coffee has a maximum by ...


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I found an interesting article in Scientific American (Coates, 2005), and I quote part of it: The condition of having no more than five fingers or toes [...] probably evolved before the evolutionary divergence of amphibians (frogs, toads, salamanders and caecilians) and amniotes (birds, mammals, and reptiles in the loosest sense of the term). This event ...


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It's a conversion factor. $$ 1~lbs = 0.453592~kg \\ 1~in = 0.0254000~m $$ $$ \frac{lbs}{in^2} = \frac{0.453592~kg}{(0.0254~m)^2} = \frac{703.069~kg}{m^2} $$


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Vitamin D does not bind to Calcium. It is a pre-hormone which is converted to calcitriol. Calcitriol has an intracellular receptor (VDR) that, as a heterodimer with Retinoid-X receptor, regulates gene expression. I guess the "should not be had together" is because of possible over-absorption of Calcium. There are commercially available supplements (e.g. 1, ...


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I heard somewhere that cells ………………………… so they regulate where they use up the energy. Yes NADP/H is primarily employed in anabolic pathways such as fatty acid synthesis, while NAD/H is employed in catabolic pathways such as glycolysis. I don't think there is a general rule for other "energy-currency" molecules (pyrimidine triphosphates are not used ...


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I heard somewhere that activating any receptor results in the same intracellular response (signaling) which involves NF-κB. I don't think all receptors activate NF-κB (Pro-growth signals activate it, mostly). how the cells distinguish between different types of stimulis coming from different types of receptors. The cell need not, sometimes, know ...


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To add my 2 cents worth: Breathing rate and depth is regulated by chemoreceptors in the medulla. These chemoreceptors primarily respond to pH of the blood, but the pH is for an important part determined by the CO2/HCO3- equilibrium as explained by @TomD. Essentially it is the increase in CO2 that is sensed by the medulla and which increases breathing ...


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Our body maintains a very delicate balance between the concentration of metabolites and substrates. If a pathway is not regulated, excess of a particular metabolite can disturb the whole process. Let's take cholesterol metabolism pathway for example. there are various means by which the cells control the production of cholesterol. For example AMP controlled ...


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Interesting question. I concur with @Chris. Color constancy and size constancy are neural mechnisms. As an analogy: they are photoshopped representations, i.e., subjective representations manufactured by higher-level visual processing. However, focus is determined by optics. An out-of-focus picture, to push the analogy, cannot be fixed by fotoshop, nor the ...


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Short Answer What you're referring to is called Delayed Onset Muscle Soreness (DOMS). We don't really know what causes DOMS, but it's most likely caused by a cascade effect started my muscle injury. Also, we aren't sure if massages (or what type of massages) really help relieve the pain. What is Delayed Onset Muscle Soreness (DOMS)? Delayed onset ...


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In short, it's because your brain processes external and self-produced stimuli differently. If someone tickles you, you feel that ticklish feeling, but when trying to tickle yourself, there is a reduction in the sensation. When you are tickled by someone, a part of your brain activates causing you to laugh, etc., but it seems that when you trying tickling ...


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Two reasonably close relatives of the most recent chimpanzee-human ancestor (CHA) are Sahelanthropus tchadensis and Orrorin tugenensis, but both are poorly attested. One better candidate is Ardipithecus ramidus, which has a fairly-complete skeleton ("Ardi") among other fossils. It's a bit young (4.4 Ma), perhaps, to be a CHA but should be a close relative. ...


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Note: This is based on literature searches I've done a while ago out of general curiosity. I'm in no way an expert on human reproduction. If I understand you correctly you are basically asking if there are any evidence for sex biases in offspring between families, that has a heritable genetic basis. This has been an active research topic for a long time ...


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The question you're asking is essentially a version of an old riddle: If you flip a coin ten times and it comes up heads each time, what are the odds that the coin will come up heads when you flip it for an eleventh time? And of course the answer is that the odds are fifty-fifty. You could instead argue that 10 heads in a row is evidence that the coin is ...


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Another lead are sleep spindles, closely related to the RTN as mentioned before. Basically the thalamus enters a state of high-frequency firing to a low-frequency synchronous one, thereby taking the cortex with it. Sleep spindles are slow-wave potentials as apparent on the EEG that block out the normal flow of peripheral sensory information from thalamus to ...


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I hope you might edit your question to give examples of such comparative injuries. I'm trying hard to imagine an example of this phenomenon, but I can't. The human body doesn't have a tripwire, or a lower limit of injury under which it will not respond. Normally the body mounts appropriate defenses against all injuries from the very minor, like a paper cut, ...


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An older answer that referred to the physiological feats of ancient humans, and why modern humans are wimps made me look up a couple of papers on running speeds a while ago. One of the examples used to support the statement that modern humans are "wimps" is a study of ancient fossilized footprints from Australia, which claim that the individuals making the ...


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My experience that it depends on it. You sleep in cycles, each cycle has about a 90 min duration. I think the quality depends on how many cycles you ended. It seems like you need to sleep more by an interruption. Sleep was recorded on 10 nights in each of seven older subjects (mean age 55) and nine younger normal subjects (mean age 22). The duration ...


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This question is at least two questions. Dividing cells In terms of a dividing human cell line, every time a division occurs the telomeres capping the ends of the chromosomes get a little bit shorter. Once the telomeres get short enough they act as a signal that triggers apoptosis, destroying the cell. There is some human-to-human variation in the initial ...


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The meaning of the term microenvironment depends on the scale of the system that you're looking at. It's a sort of weasel word that loosely means "context" or "stuff in the immediate surroundings of the system of interest that has some kind of an effect on it". I've seen it used to describe everything from the chemical microenvironment of a cell (e.g. a ...



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