qid int64 2 112k | question stringlengths 61 6.7k | positives listlengths 1 1 | negatives listlengths 1 10 |
|---|---|---|---|
9 | <p>I shipped 10 µL of my vector miniprep to a collaborator in a 1.5 mL eppendorf parafilmed shut and stuffed into a 50 mL conical with some paper-towel padding. However, something happened on the way and there was nothing (no liquid) in the tube when it arrived. They didn't make any comments about the microcentrifuge tube popping open or broken parafilm, so nothing crazy happened but something did.</p>
<p>What's the most reliable way to ship plasmids?</p>
| [
{
"answer_id": 36,
"pm_score": 5,
"text": "<p><strong>Summary</strong></p>\n\n<ul>\n<li>the 10 uL of plasmid miniprep may have been splattered in the cap of the tube (AnnaF)</li>\n<li>the eppendorf tube may have depressurized during air shipment and allowed the 10 uL to escape and evaporate</li>\n<li><s... | [
{
"answer_id": 17,
"pm_score": 4,
"text": "<p>Did they try to centrifuge the tube when it got there to push all the liquid to the bottom? I know that especially when working with such little amounts that even shaking it up a little can disperse the contents all over the tube.\nWe have received plasmids ... |
38 | <p>I'm trying to find a good protocol for plasmid minipreps and I'm looking at 3 preps I've found:</p>
<ol>
<li><a href="http://openwetware.org/wiki/One_step_%27miniprep%27_method_for_the_isolation_of_plasmid_DNA" rel="nofollow">Using phenol/chloroform</a>
<ul>
<li>extract with phenol:chloroform:isoamylalcohol,</li>
<li>isopropanol precipitation, 12,000g spin down,</li>
<li>rinse with cold 70% ethanol. </li>
</ul></li>
<li><a href="http://openwetware.org/wiki/Miniprep/Kit-free_high-throughput_protocol" rel="nofollow">Using lysozyme</a>
<ul>
<li>lyse with lysozyme,</li>
<li>remove pellet, </li>
<li>isopropanol precipitation,</li>
<li>wash with cold 80% ethanol.</li>
</ul></li>
<li><a href="http://biotech.biology.arizona.edu/labs/DNA_isolation_plasmid.html" rel="nofollow">Using alkaline lysis</a>
<ul>
<li>open cells with 80% glucose in EDTA buffer,</li>
<li>add SDS and NaOH,</li>
<li>pellet protein/membrane with acetic acid/acetate,</li>
<li>ispropanol precipitation,</li>
<li>wash with cold 70% ethanol.</li>
</ul></li>
</ol>
<p>They all differ in how to break open the cells and separate plasmids from the rest of the cell -- quite a bit. Can anyone help me figure out which protocol is best here? </p>
| [
{
"answer_id": 55,
"pm_score": 3,
"text": "<p>In my experience, the P:C:I method will get you higher yields, and is a bit more simple (in steps and chems involved), but as @Mad Scientist has said, phenol use might be an issue. It depends on the age of your students.</p>\n"
}
] | [
{
"answer_id": 47,
"pm_score": 3,
"text": "<p>The protocol I used in my genetics lab course was alkaline lysis followed by ethanol precipitation <a href=\"http://www.protocol-online.org/cgi-bin/prot/view_cache.cgi?ID=1667\">similar to this one</a>. Nothing terribly toxic or requiring a fume hood (at le... |
58 | <p>We suspect a bi-directional transcription event is happening at a locus in our organism where two genes are directly adjacent to each other. The annotation data is not well established. The intergenic distance is probably less than 200 base pairs.</p>
<p>The two genes are expressed in opposite directions towards each other. Base on the preliminary transcriptomics data, it seems like one gene is over transcribing (3' UTR perhaps?) into the adjacent gene, possibly resulting in some kind of transcriptional regulation of the adjacent gene. </p>
<p>Here is a rough diagram of what we think might be happening:</p>
<pre><code>------------------------==========gene A================>----------------------
----------------------------------------<====gene B=====-----------------------
</code></pre>
<p>Of course we need to first confirm this by designing primers to see if this over transcription is actually happening. </p>
<p>If this is happening, we intend to do some knock down experiments. We have no transgenesis available in our organism, only RNAi by dsRNA. It is possible to specifically knock down geneA by introducing dsRNA to the 5' region of geneA that does not overlap with geneB. Perhaps this will lead to ectopic/over expression of geneB. </p>
<p>Is there anyway to knock down geneB specifically without knocking down geneA? It looks like designing dsRNA for geneB would knock down both A and B.</p>
| [
{
"answer_id": 55,
"pm_score": 3,
"text": "<p>In my experience, the P:C:I method will get you higher yields, and is a bit more simple (in steps and chems involved), but as @Mad Scientist has said, phenol use might be an issue. It depends on the age of your students.</p>\n"
}
] | [
{
"answer_id": 47,
"pm_score": 3,
"text": "<p>The protocol I used in my genetics lab course was alkaline lysis followed by ethanol precipitation <a href=\"http://www.protocol-online.org/cgi-bin/prot/view_cache.cgi?ID=1667\">similar to this one</a>. Nothing terribly toxic or requiring a fume hood (at le... |
90 | <p>I'm by no means an expert in the field, merely a curious visitor, but I've been thinking about this and Google isn't of much help. Do we know of any lifeforms that don't have the conventional double-helix DNA as we know it? Have any serious alternatives been theorized?</p>
| [
{
"answer_id": 106,
"pm_score": 6,
"text": "<p>To follow up what mbq said, there have been a number of \"origin of life\" studies which suggest that RNA was a precursor to DNA, the so-called \"RNA world\" (1). Since RNA can carry out both roles which DNA and proteins perform today. Further speculations... | [
{
"answer_id": 95,
"pm_score": 5,
"text": "<p>There has been a recent report on Science, which had much return in the general press, in which a bacteria was identified that could live in an environment where arsenic was subsituted to phosphorus (one of the components of DNA, forming the backbone of the ... |
257 | <p>I am looking for video lectures to go through to guide my reading in intro molecular and cellular biology. I've had intro bio and I study evolutionary theory, but my molecule- and cell-level knowledge is weak. </p>
<p>I'm finding it impossible to know where to look in a big book like Alberts, or to read Lodish without a guide, so I really need lectures to help me out. I've tried the MIT OCW assignments and a few other similar sites, but I can't seem to find a course that includes lectures. Does anyone know of any? Ideally they'd follow Watson et al. for molecular and Lodish for cellular, but I can find other textbooks too.</p>
| [
{
"answer_id": 266,
"pm_score": 4,
"text": "<p>MIT's OCW is weak when it comes to biology videos. </p>\n\n<p>UC Berkeley has some good video content for molecular and cell biology.</p>\n\n<ul>\n<li><p>See, for example, this playlist:\n<a href=\"http://www.youtube.com/playlist?list=59C08AE05E752758\">ht... | [
{
"answer_id": 258,
"pm_score": 3,
"text": "<p>This one is not precisely molecular and cell biology, but rather systems biology. It might help you as some kind of introduction, though:</p>\n\n<p><a href=\"http://www.youtube.com/watch?v=Z__BHVFP0Lk\">Systems biology lecture 1</a></p>\n\n<p>Also, if you a... |
328 | <p>In what ways has DNA been studied to see if there a "programmable" aspect to it? </p>
<p>Has nature produced anything resembling a Turing machine within the cell, perhaps using the "junk DNA" as its code? I expect nature's way would probably be very round-about and not compact.</p>
<p>NOTE: I am not asking about building DNA computers, as this question had recently been contorted to become.</p>
| [
{
"answer_id": 427,
"pm_score": 5,
"text": "<p>Perhaps this question is whether the regions between genes sometimes known as 'junk DNA' has any function. </p>\n\n<p>In the human genome, out of ~5 billion bases <a href=\"http://www.ornl.gov/sci/techresources/Human_Genome/faq/genenumber.shtml\">there are ... | [
{
"answer_id": 418,
"pm_score": 3,
"text": "<p>By programmable, I suppose you mean that it contains information or can be altered in response to some input or stimulus. The answer is \"no\" for both. Well, sort of.</p>\n\n<p>Does noncoding DNA contain information? By definition, no. There are probab... |
344 | <p>There seem to be a number of ideas about why we age. Hypotheses include the gradual accumulation of cell metabolic products affecting organism function and the reduction of <a href="https://biology.stackexchange.com/questions/186/is-telomere-length-a-reliable-measure-of-health-lifespan">telomere length</a> during cell division.
My hand-wavey idea would be "wear and tear".</p>
<p>Are we anywhere near a consensus theory of senescence?</p>
| [
{
"answer_id": 362,
"pm_score": 6,
"text": "<p>The 'wear and tear' argument is most likely true but it is also interesting to reason about ageing as inevitable from the evolutionary point of view.</p>\n\n<p>To set up the argument, we need two things:\nFirst, each individual has got a 'reproductive poten... | [
{
"answer_id": 404,
"pm_score": 3,
"text": "<p>Once could argue that we die because it is advantageous to get rid of mature individuals once they have reproduced. Because mature individuals have no more offspring to convey beneficial genes, those offspring which will benefit from knocking off their anc... |
378 | <p>I am very interested in the evolution of the evolution process itself. There are of course a lot of things that influence how evolution will work, but for this question, I am interested in things that are only related to the evolution process. Examples could be increase chance of mutations in newborns, change in reproduction age, and similar. I am specifically interested in observation where the evolution process itself has adapted to a change in the environment.</p>
| [
{
"answer_id": 382,
"pm_score": 6,
"text": "<p>Bacteria such as E. coli are known to increase their mutation rate (by switching to a more error prone polymerase among other things) when under stress. This can mean being placed in a medium where it's not adapted to grow (<a href=\"http://www.ncbi.nlm.nih... | [
{
"answer_id": 379,
"pm_score": 4,
"text": "<p>I think this falls into your criteria but correct me if i'm wrong :).</p>\n\n<p>The <a href=\"http://en.wikipedia.org/wiki/HIV\">HIV</a> reverse transcriptase protein has evolved to have relatively low fidelity (leading to a high mutation rate in replicated... |
450 | <p>I know plants are green due to chlorophyll.</p>
<p>Surely it would be more beneficial for plants to be red than green as by being green they reflect green light and do not absorb it even though green light has more energy than red light.</p>
<p>Is there no alternative to chlorophyll? Or is it something else?</p>
| [
{
"answer_id": 462,
"pm_score": 8,
"text": "<p>Surely it would be even more beneficial for plants to be black instead of red or green, from an energy absorption point of view. And <a href=\"http://en.wikipedia.org/wiki/Solar_cell\" rel=\"noreferrer\">Solar cells</a> are indeed pretty dark.</p>\n\n<p>But... | [
{
"answer_id": 451,
"pm_score": 5,
"text": "<p>I believe it is because of a trade off between absorbing a wide range of photons and not absorbing too much heat. Certainly this is a reason why leaves are not black - the enzymes in photosynthesis as it stands would be denatured by the excess heat that wo... |
452 | <p>My biology teachers never explained why animals need to breathe oxygen, just that we organisms die if we don't get oxygen for too long. Maybe one of them happened to mention that its used to make ATP. Now in my AP Biology class we finally learned the specifics of how oxygen is used in the <a href="http://www.science.smith.edu/departments/Biology/Bio231/etc.html">electron transport chain</a> due to its high electronegativity. But I assume this probably isn't the only reason we need oxygen. </p>
<p>What other purposes does the oxygen we take in through respiration serve? Does oxygen deprivation result in death just due to the halting of ATP production, or is there some other reason as well? What percentage of the oxygen we take in through respiration is expelled later through the breath as carbon dioxide?</p>
| [
{
"answer_id": 456,
"pm_score": 6,
"text": "<p>Oxygen is actually highly toxic to cells and organisms – <a href=\"http://en.wikipedia.org/wiki/Reactive_oxygen_species\" rel=\"noreferrer\">reactive oxygen species</a> cause <a href=\"http://en.wikipedia.org/wiki/Oxidative_stress\" rel=\"noreferrer\">oxida... | [
{
"answer_id": 455,
"pm_score": 5,
"text": "<p><a href=\"http://en.wikipedia.org/wiki/Superoxide\" rel=\"noreferrer\">Superoxide</a>, O<sub>2</sub><sup>−</sup> is created by the immune system in <a href=\"http://en.wikipedia.org/wiki/Phagocyte\" rel=\"noreferrer\">phagocytes</a> (including neutrophils, ... |
551 | <p>I have many friends who are interested in Biology and want to know more about the subject in general (like a history of biology, from Darwin's theory, to DNA structure discovery, to the human genome project). Of course, I cannot suggest to them to read Alberts or Lenninger. Do you know whether such a book exist? I guess that a book that covers most fields of biology cannot be compiled, but even more focused book would do. </p>
<p>Let me try to narrow it down: something like the greatest discoveries in the field of biology (like <a href="http://science.discovery.com/convergence/100discoveries/big100/biology.html">this article</a>) would be an interesting book to read.</p>
<p>I am not sure how appropriate this question is for SE, but I am sure that I will get the best answer here. Besides, it would be great if lay people can be more excited about biology and contribute to the site growth.</p>
| [
{
"answer_id": 556,
"pm_score": 4,
"text": "<p>It doesn't have very many reviews, but <a href=\"http://rads.stackoverflow.com/amzn/click/073820577X\">The Epic History of Biology</a> sounds like it's perfect.</p>\n\n<p>Flipping through the first chapter in the preview, it doesn't seem overly technical in... | [
{
"answer_id": 552,
"pm_score": 2,
"text": "<p>I don't know very many books that might be referred to as the Grand History of Biology or anything like that. That's...a big topic. Really big. How about some suggestions for good Biology/Medical History books accessible to lay people:</p>\n\n<ul>\n<li>And ... |
594 | <p>Why are nearly all amino acids in organisms left-handed (exception is glycine which has no isomer) when abiotic samples typical have an even mix of left- and right-handed molecules?</p>
| [
{
"answer_id": 615,
"pm_score": 6,
"text": "<p>I know that you are referring to the commonly ribosome-translated L-proteins, but I can't help but add that there are some peptides, called nonribosomal peptides, which are not dependent on the mRNA and can incorporate D-amino acids. They have very importan... | [
{
"answer_id": 597,
"pm_score": 4,
"text": "<p>As far as I know, it is unknown why we only see left-handed and not right–handed amino acids. A <a href=\"http://www.nature.com/news/frontier-experiments-tough-science-1.9723\">recent article</a> speculates that the <a href=\"http://en.wikipedia.org/wiki/We... |
623 | <p>From what I can tell and what thus far all people with whom I discussed this subject confirmed is that time appears to "accelerate" as we age.</p>
<p>Digging a little, most explanations I found basically reduced this to two reasons:</p>
<ul>
<li>As we age physically, a time frame of constant length becomes ever smaller in contrast to the time we spent living</li>
<li>As we age socially, we are burdened with an increasing amount of responsibility and thus an increasing influx of information which impairs our perception of the present</li>
</ul>
<p>To be honest, neither sounds entirely convincing to me because:</p>
<ul>
<li>In my perception "local time" (short time frames that I don't even bother to measure on the scale of my lifetime) is also accelerating. Just as an example: When I wait for the bus, time goes by reasonably fast as opposed to my childhood tortures of having to wait an eternity for those five minutes to pass.</li>
<li>Even after making a great effort to cut myself off from society and consciously trying to focus on the moment, the perceived speed of time didn't really change. (Although I did have a great time :))</li>
</ul>
<p>Which leads me to a simple question (and a few corollaries):</p>
<ul>
<li>Am I just in denial of two perfectly plausible and sufficient explanations, or are there actual biological effects (e.g. changes in brain chemistry) in place, that cause (or at least significantly influence) this?</li>
<li>Is there a mechanism, that "stretches out" time for the young brain so that weight of an immense boredom forces it to benefit from its learning ability, while it "shrinks" time as the brain "matures" and must now act based on what it has learned, which often involves a lot of patience?</li>
<li>If there is such a mechanism, are there any available means to counter it? (not sure I'd really want to, but I'd like to know whether I could)</li>
</ul>
| [
{
"answer_id": 1240,
"pm_score": 6,
"text": "<p>This is not really a biological answer, but a psychological one:</p>\n\n<p>One important fact to consider is that the perception of time is essentially a recollection of past experience, rather than perception of the present.</p>\n\n<p>Researchers who stud... | [
{
"answer_id": 713,
"pm_score": 3,
"text": "<p>There may be some clues in neurobiology.</p>\n\n<p>A possibility may be that a person's general emotional state may affect their perception of the passage of time, as argued in this <a href=\"http://www.robinson.cam.ac.uk/academic/robinson_rationality_luchi... |
757 | <p>As far as I understand, various abilities like flying, sight, hearing etc. were caused by slow evolution, where those with a greater ability to to these things had better chance of survival. (If this assumption is wrong, then I am happy to delete this question). </p>
<p>Are there, however, any documented examples of by evolutionary leaps being made, over the course of just a few generations? I understand, that some abilities have a tipping point where one gets the ability suddenly, but there is not a lot of physiological change made. An example of this would be the ability to climb a tree, which could suddenly be possible if the body weight is reduced with just a few percent. What my question is about, are sudden changes to the characteristics of a creature.</p>
| [
{
"answer_id": 7921,
"pm_score": 4,
"text": "<p>@kmm and @shigeta provided you with a nice observational account of sudden leaps in large organisms. However, if you want to look at where this is the norm and try to build a mathematical theory then you need to look at something much smaller; the prime ca... | [
{
"answer_id": 759,
"pm_score": 4,
"text": "<p><a href=\"http://rsbl.royalsocietypublishing.org/content/2/4/521.full?sid=36ce9d7f-9cc9-4c07-92f4-4808ec90f451\">Zuk et al. (2006)</a> document the rapid evolution of song-less crickets in a population of crickets that previously used song for courtship.</p... |
762 | <p>Humans have, in a relatively short amount of time, evolved from apes on the African plains to upright brainiacs with nukes, computers, and space travel. </p>
<p>Meanwhile, a lion is still a lion and a beetle is still a beetle.</p>
<p>Is there a specific reason for this? Do we have a particular part of brain that no other animal has?</p>
| [
{
"answer_id": 766,
"pm_score": 6,
"text": "<p>We have the <a href=\"http://en.wikipedia.org/wiki/Human_accelerated_regions\">Human Accelerated Regions</a> (HARs) which are some of the most rapidly evolving RNA genes elements. While heavily conserved in vertebrates, they go haywire in humans and are lin... | [
{
"answer_id": 767,
"pm_score": 3,
"text": "<p>The ability to walk on two legs was hugely significant in human evolutionary development. This led to the hands being freed up to develop into precision tools rather than having to be durable for walking on rough terrain. Increased dexterity in the hands l... |
832 | <p>A student asked me this the other day and I thought that I would ask it again here. If one organism is said to be "more evolved" than another, what exactly does this mean?</p>
| [
{
"answer_id": 833,
"pm_score": 6,
"text": "<p>\"More evolved\" is actually meaningless in all contexts. See terdon's answer for a good explanation.</p>\n\n<p>In the strictest sense, an organism can be said to be more divergent than another when comparing both to an outgroup, such that there is an infer... | [
{
"answer_id": 834,
"pm_score": 4,
"text": "<p>I cannot improve on Thomas Ingalls' description of when \"more evolved\" is appropriately used, but the inappropriate/lazy use of the phrase is so prevalent that it deserves further comment. In my experience, the most common use of the phrase \"more evolved... |
884 | <p>This came up in a talk with a friend. I wanted to clear this doubt. I've read about it before and did again after her remark (my thoughts didn't change: her concept is Lamarck's, not Darwin's), but wanted to clarify.</p>
<p>Regarding Evolution, nothing, absolutely nothing, that a person does to herself in life can be genetically inherited. It does not matter how much this person drinks, the changes they do to their body, how dark their skin gets over life etc. Such changes can not be transmitted to their offspring in any way, correct?</p>
<p>*Summary:*Is the assertion "You can not change in life what will be genetically inherited in any possible way" true?</p>
| [
{
"answer_id": 886,
"pm_score": 5,
"text": "<p>The assertion \"You cannot change in life what will be genetically inherited in any possible way\" is true, as you cannot (healthily) change the DNA in your germ cells.</p>\n\n<p>However, the assertion \"You cannot change in life what will be inherited in a... | [
{
"answer_id": 887,
"pm_score": 4,
"text": "<p>In general, Darwin's theory has been supported over and over again by experiments - our modern understanding of evolution is fundamentally what Darwin suggested. However, apart from appreciating many more details than Darwin ever could have, we also now kno... |
1,228 | <p>I am working with an Arabidopsis mutant with an F-box protein knocked out. It has been shown that F-box proteins targets must first be phosphorylated (<a href="http://www.sciencedirect.com/science/article/pii/S0092867400804031">Skowrya et al., 1997</a>). I have heard of phosphorylation sites, but I can't find out whether every protein has them. Can any protein be phosphorylated?</p>
<ul>
<li><a href="http://www.sciencedirect.com/science/article/pii/S0092867400804031">Skowyra, D., Craig, K.L., Tyers, M., Elledge, S.J. & Harper, J.W. (1997) F-Box Proteins Are Receptors that Recruit Phosphorylated Substrates to the SCF Ubiquitin-Ligase Complex. <em>Cell</em>. <strong>91</strong> (2), 209–219.</a></li>
</ul>
| [
{
"answer_id": 1231,
"pm_score": 5,
"text": "<p>Phosphorylation can occur on specific amino acids only, what you have called phosporylation sites. These amino acids are Ser, Tyr, Asp, Thr and His. In theory any of these amino acids may be phosphorylated, but in reality it may not actually occur for a nu... | [
{
"answer_id": 1230,
"pm_score": 3,
"text": "<p>Phosphorylation requires exposed serine, threonine, tyrosine, or histidine residues (in eukaryotes). This is because the transfer of phosphate groups to proteins is mediated by a class of proteins called kinases. Kinases can have broad or specific activi... |
1,446 | <p>I don't know if this question applies to only humans but why can cones see much greater detail than rods? Is it possible to have a rod that can detect light intensity and color?</p>
| [
{
"answer_id": 1461,
"pm_score": 6,
"text": "<p>The spectral sensitivity of photoreceptors expressed is the key to color vision. See figure below for the sensitivity of three-types of cone cells (S, M, L) and rod cell (R, dashed line).\n<img src=\"https://i.stack.imgur.com/fF2eT.png\" alt=\"Spectral sen... | [
{
"answer_id": 1454,
"pm_score": 4,
"text": "<p>Cone cells are each connected to their own neurone. This allows them a great deal of resolution as the brain can interpret the exact position of the cone cell that was stimulated by a light photon. However in order to improve low light vision, multiple r... |
1,448 | <p><a href="http://www.uniprot.org/uniprot/P36659">CbpA</a> is DNA binding protein found in E. coli and binds non-specifically to curved DNA (<a href="http://dx.doi.org/10.1111/j.1365-2958.2010.07292.x">Cosgriff et al., 2010</a>), when the bacterium is in a static phase of growth. </p>
<p>The use of "curved DNA" confuses me. Is the term "curved DNA" essentially the same as "Circular DNA"?</p>
<hr>
<p><a href="http://dx.doi.org/10.1111/j.1365-2958.2010.07292.x">Cosgriff, S. et al. Dimerization and DNA-dependent aggregation of the Escherichia coli nucleoid protein and chaperone CbpA. Mol. Microbiol. 77, 1289–1300 (2010).</a></p>
| [
{
"answer_id": 1461,
"pm_score": 6,
"text": "<p>The spectral sensitivity of photoreceptors expressed is the key to color vision. See figure below for the sensitivity of three-types of cone cells (S, M, L) and rod cell (R, dashed line).\n<img src=\"https://i.stack.imgur.com/fF2eT.png\" alt=\"Spectral sen... | [
{
"answer_id": 1454,
"pm_score": 4,
"text": "<p>Cone cells are each connected to their own neurone. This allows them a great deal of resolution as the brain can interpret the exact position of the cone cell that was stimulated by a light photon. However in order to improve low light vision, multiple r... |
1,495 | <p>I know death and cancer doesn't hurt humans' reproductive success. It's not helping either.</p>
<p>Why do we die? Why dying humans (all of us) are common? What's the point of dying?</p>
| [
{
"answer_id": 1496,
"pm_score": 6,
"text": "<p>Death is not only for humans. All 'complicated enough' organisms die (with a notable exception of <a href=\"http://en.wikipedia.org/wiki/Hydra_(genus)\" rel=\"nofollow noreferrer\">Hydra</a>, though you may argue when it comes to the complexity). It is is ... | [
{
"answer_id": 1497,
"pm_score": 3,
"text": "<p>Who is to say that having living Humans isn't hurting our reproductive success? Older non-reproducing humans cost the human network valuable resources and take up a sizeable portion of our living niche. Metabolically unstreamlined aged organisms are certai... |
1,515 | <p>This is my first post here, so please be gentle. I recently learned that I have Rh- blood (I'm A-), and was idly looking into blood types on Wikipedia. I was surprised to find that relatively few (~15% of all) humans have it, and most of those seem to be European. Looking just a little further, I found a bunch of crackpot-looking sites that try to explain how people got Rh- blood, and what weird abilities they possess as a result.</p>
<p>I managed to find one site that seemed at least less laughable, which suggested that interbreeding with <em>Homo neanderthalensis</em> (or possibly <em>Homo sapiens neanderthalensis</em>, since the site seemed to indicate that there was some question about how different <em>H. s. sapiens</em> were from <em>H. neanderthalensis</em>) might have accounted for the introduction of the condition.</p>
<p>It seems that from more reputable (medical) sources, the only difference between Rh+ and Rh- is that complications can arise during pregnancy if the mother is Rh- and the fetus is Rh+. Indeed, most sites (e.g., WebMD) seem to explicitly state that there are no other differences of note.</p>
<p>I am not a biologist, or an anthropologist, or a life-science kind of guy at all. However, as a computer scientist, I like to think that I have both an open mind but one which demands scientific and/or logico-mathematical evidence for claims. Lots of the pseudo-scientific, paranormal, etc. theories on the web I basically dismiss out of hand, as explanations which are almost certainly fantasies, but most definitely baseless and untestable.</p>
<p>My question:</p>
<blockquote>
<p>What, if any, is the current scientific understanding of the origin, or source, of rhesus negative blood in human beings? Do individuals with Rh- blood have any common (in a statistically significant sense) characteristics or health issues, aside from the issue with pregnancy and tending to be more European than not? Is there anything to continuing to look into this?</p>
</blockquote>
<p>For context, I got started down this rabbit hole while looking into different dieting strategies, and found the "blood type diet". Just as an aside, I don't think there's a lot of merit to that diet... sounds like a fad thing. Any sources or information or help on this subject are appreciated.</p>
<p>EDIT:</p>
<p>I have been looking a little more, and I stumbled across a paper entitled, "The influence of RhD phenotype on toxoplasmosis and age-associated changes in personality profile of blood donors" which looks at the effect of the Rh- trait on personality changes caused by toxoplasmosis (if you Google the title, you should be able to download). Using Cloninger's and Cattel's personality factors, they seem to show a variety of things, including (a) personality differences between Rh+ and Rh- individuals not affected by toxoplasmosis, and (b) different reactions to prolonged toxoplasmosis affection in Rh+ and Rh- individuals.</p>
<p>I didn't even know that parasites could affect your behavior; that seems frightening on the one hand, but on the other, it's fascinating if it's for real, especially since the incidence of toxoplasmosis is not insignificant in most people. Anybody who knows anything about this or who reads the paper and can help me understand what it's saying would be doing me a great favor to answer/comment/chat. Thanks!</p>
| [
{
"answer_id": 1539,
"pm_score": 4,
"text": "<p>Your question has many questions in it. </p>\n\n<p>As for the evolution of Rh factor, <a href=\"http://jhered.oxfordjournals.org/content/91/3/205.abstract\">Blancher and Apoil (2000)</a> attribute the high level of sequence similarity (92%) of the two <em>... | [
{
"answer_id": 9033,
"pm_score": -1,
"text": "<p>It's my opinion the rh antigen developed from toxoplasmosis infection. I only recently learned that this protozoan can actually insert its genes into a host's genome. Once it's in the genes, it can be passed in the germline. Toxoplasmosis can infect all p... |
1,838 | <p>On news, articles etc. experts talking about <strong>Genetically Modified Foods and Organisms</strong> often mentions about their disadvantages like, </p>
<ul>
<li>their potential to harm human health</li>
<li>allergies may become more intense, new allergy types may develop</li>
<li>possible damages to the environment</li>
</ul>
<p>So I wonder, what's the aim of genetically modifying of foods/organisms? In other words, what are advantages of that? </p>
| [
{
"answer_id": 1844,
"pm_score": 5,
"text": "<p>GMO foods have a huge potential to make food cheaper to produce and more nutritious.</p>\n\n<p>The most common GMO foods have at least one gene added to them - an enzyme that makes the plant resistant to RoundUp - an herbicide made by the same company (Mon... | [
{
"answer_id": 1840,
"pm_score": 2,
"text": "<p>In terms of crops, plants that are grown for food, one advantage is the targeted modification of a single gene. Classical plant breeding is slow, imprecise and carries many traits of negative benefit. For example, if you cross plant variety A with variety ... |
2,075 | <p>A number of companies have started marketing LED lamps that can be switched to a red mode. The claim is that red light is less harmful to one's night vision. Given that our eyes are less sensitive to red light, though, I'm not convinced that that red light is any better than dim white light. So if "equivalent" luminosity is defined where it's equally easy to, say, read a book in both light types, is there some physiological reason that red light is better than the equivalent white light? </p>
| [
{
"answer_id": 3471,
"pm_score": 5,
"text": "<p>This is a very good question. Red light is routinely used by scientific laboratories to do low light dissections of retinas, and of course it is used in other low light contexts such as printing plate development.</p>\n\n<p>In both of the above contexts, ... | [
{
"answer_id": 2083,
"pm_score": 3,
"text": "<p>Another reason why red lights are now sponsorized for night illumination is because they are supposed to be safer in terms of interference on the circadian cycle. This is not related to better vision, but better health.</p>\n\n<p>The mammalian eye senses t... |
2,246 | <p>I have a gene of of interest that I would like to compare between homologues. How does one go about finding a gene from known coding sequences across phyla? Afterwards I imagine I could do a Clustal sequence alignment to see how the sequences match.</p>
| [
{
"answer_id": 2258,
"pm_score": 4,
"text": "<p>There are various databases of homologs, for example:</p>\n\n<ul>\n<li><a href=\"http://eggnog.embl.de\">eggNOG</a></li>\n<li>Ensembl Compara (accessible via <a href=\"http://www.ensembl.org/biomart/martview\">BioMart</a>, I think)</li>\n<li><a href=\"http... | [
{
"answer_id": 2247,
"pm_score": 3,
"text": "<p>If I understand your question adequately, the <a href=\"http://genome.ucsc.edu\">Genome Browser</a> at UCSC is a great place to start. If you know the name of the gene, you can search for it. For example, <a href=\"http://genome.ucsc.edu/cgi-bin/hgTracks?p... |
2,574 | <p>The main paper for the <em>Plasmodium palciparum</em> genome project (Gardner et al., 2002) repeatedly mentioned that the unusually high A+T content (~80%) of the genome caused problems. For example they imply that it prevented them using a clone-by-clone approach:</p>
<blockquote>
<p>Also, high-quality large insert libraries of (A + T)-rich P. falciparum DNA have never been constructed in Escherichia coli, which ruled out a clone-by-clone sequencing strategy.</p>
</blockquote>
<p>And that it made gene annotation difficult:</p>
<blockquote>
<p>The origin of many candidate organelle-derived genes could not be conclusively determined, in part due to the problems inherent in analysing genes of very high (A + T) content. </p>
</blockquote>
<p><strong>Question:</strong><BR>
What is the biological significance of high A+T content, and why would it cause problems in genome sequencing?</p>
<p><strong>Ref:</strong><br>
<a href="http://dx.doi.org/10.1038/nature01097">Gardner, M.J., Hall, N., Fung, E., White, O., Berriman, M., Hyman, R.W., Carlton, J.M., Pain, A., Nelson, K.E., Bowman, S., Paulsen, I.T., James, K., Eisen, J.A., Rutherford, K., et al. (2002) Genome sequence of the human malaria parasite Plasmodium falciparum. Nature. 419 (6906), 498–511.</a></p>
| [
{
"answer_id": 2612,
"pm_score": 4,
"text": "<p>The sequencing technologies that were developed in the last 20 years have a range of optimal use at an average A+T/G+C rate. Both highly AT-rich and GC-rich regions are complicated to process by the different sequencing technologies. Each technology has di... | [
{
"answer_id": 2575,
"pm_score": 3,
"text": "<p>I can't comment on how A+T richness complicates the sequencing process itself, but I can comment on complications that arise when annotating the sequence. <em>Ab initio</em> gene predictors are often based on hidden Markov models that are very sensitive to... |
2,602 | <p>I'm curious how much damage is potentially inflicted by shear stress by pipetting. I know that syringes used for stem cell injection can cause a lot of damage. However, to what extent does this happen with P20 and P200 pipette tips? Understandably the shear modulus of bacterial cells is significantly different from that of cancer cells, which will be different from that of stem cells.</p>
| [
{
"answer_id": 20890,
"pm_score": 5,
"text": "<p>This is an excellent question, I have been training people to culture cells for about 12 years and students have a hard time grasping this and appreciating the importance etc.</p>\n\n<p>What cells are usually experiencing during pipetting is analogous to ... | [
{
"answer_id": 2603,
"pm_score": 4,
"text": "<p>It's an easy experiment to do. Take your cells aliquot them into 10 microfuge tubes, and pipette each suspension increasing amount of times, stain with trypan blue and count.</p>\n\n<p>The most important factors will be which pipette-type you use; I would ... |
2,790 | <p>When people try to explain evolution, they tell me that evolution is a cumulative result of mutations & natural section of the more superior individuals of a particular species. I think I'm fairly convinced with this explanation.</p>
<p>But when I think about it, all of them assume that there was an organism, however simple, that was capable of self replication & occasionally mutate. How did such an organism come into existence? Can anyone explain this?</p>
<p>An answer I found <a href="http://www.reddit.com/r/explainlikeimfive/comments/upb42/eli5_evolution_how_can_human_beings_pop_out_of/c4zdmf4">on Reddit</a> didn’t really convince me.</p>
| [
{
"answer_id": 2806,
"pm_score": 5,
"text": "<p>Evolution or (as Darwin called it) \"descent with modification\" is a theory which explains the origin of the species NOT the origin of life. How the first life arose is <strong>completely irrelevant</strong> to the theory of evolution. What evolution do... | [
{
"answer_id": 2793,
"pm_score": 3,
"text": "<blockquote>\n <p>They teach us in Physics that the entropy of an isolated system is always increasing or at least constant. Then how can an organism be born under these conditions?</p>\n</blockquote>\n\n<p>The sun sends energy to the Earth, allowing for a d... |
3,177 | <p>We use electromagnetic communication everywhere these days. Cell phones, wifi, old-school radio transmissions, television, deep space communication, etc.</p>
<p>I'm curious about some of the possible reasons we have never seen biological systems having evolved to use electromagnetic, i.e. radio, for communication. The one obvious exception to this are organisms that generate their own light, i.e. bioluminescence. Cuttlefish are masters of this, and many other species as well.</p>
<p>It seems like bio-radio could have offered all kinds of evolutionary advantages for animals capable of using it.</p>
<p>Are their basic physical limits in chemistry, or excess energy requirements or something that would basically have made this impossible? Or was this perhaps just something that life never evolved to use, but would otherwise be possible in evolution?</p>
| [
{
"answer_id": 3180,
"pm_score": 6,
"text": "<p>There is a very different mechanism for generation (and detection) of ultraviolet, visible and infrared light vs radio waves.</p>\n\n<p>For the first, it is possible to generate it using chemical reactions (that is, <a href=\"http://en.wikipedia.org/wiki/C... | [
{
"answer_id": 3178,
"pm_score": 2,
"text": "<p>A quick comparison between light and sound vs. Radio</p>\n\n<ul>\n<li><a href=\"http://en.wikipedia.org/wiki/Light\" rel=\"nofollow noreferrer\">Light</a>: Wavelength 380 nm -740 nm</li>\n<li><a href=\"http://en.wikipedia.org/wiki/Sound\" rel=\"nofollow no... |
3,304 | <p>Layman here. So I have never really quite understood this facet of human evolution, (or any other for that matter), in that, I understand the evolutionary process, but I get lost on the 'border' cases. </p>
<p>For example, we, as humans, evolved from monkeys, (to use the colloquial term, I am not a biologist by any measure). </p>
<p>My question is, doesn't this mean that at some, discrete point, there had to have been a human, whose parents were not? If that is true, how does that work, in the sense that we now have species1 giving birth to species2. </p>
<p>If not, then how exactly does this border case work? The only other alternative I see, is that the borders are 'fuzzy', but then that necessarily means that the definition of a species is itself fuzzy, which I understand is not the case. </p>
<p>Thanks!</p>
| [
{
"answer_id": 3305,
"pm_score": 6,
"text": "<p>Actually, your last paragraph is more the case than not.</p>\n\n<p><strong>There are currently three common definitions for delineating discrete species:</strong></p>\n\n<p>1) Phenotypically different from related species (looks or acts differently).</p>\n... | [
{
"answer_id": 3306,
"pm_score": 5,
"text": "<blockquote>\n <p>but I get lost on the 'border' cases.</p>\n</blockquote>\n\n<p>Not surprisingly, since there are no borders, and this is probably the greatest misunderstanding: Evolution is gradual. It’s not generally possible to say where a complex featur... |
3,315 | <p><a href="http://en.wikipedia.org/wiki/Hijra_%28South_Asia%29" rel="nofollow">Hijra</a> are people who have a penis (not sure if sexually active) but look much like a female (perhaps for some feminine biological property). Wikipedia says they are <em>"physiological males who have feminine gender identity"</em></p>
<p>Also, I just came to know there are some more types of <a href="http://en.wikipedia.org/wiki/Third_gender" rel="nofollow">third gender</a> people.</p>
<p>Now, <strong>is there really any <em>BIOLOGICAL</em> third gender</strong> which cannot be categorized as male or female? Or its always possible to categorize them to male or female?</p>
| [
{
"answer_id": 3317,
"pm_score": 5,
"text": "<p>When dealing with <em>humans</em>, there are only two <strong>Biological</strong> genders as defined by the presence or absence of the Y-Chromosome. If the Y-Chromosome is not present, or through some process gets totally deactivated, the human will appear... | [
{
"answer_id": 3318,
"pm_score": 0,
"text": "<p>As I read the Wikipedia article you reference, its useful to remember that conventional chromosomal definitions of gender, the genitals are soft tissue which has many recorded morphological abnormalities. <a href=\"http://en.wikipedia.org/wiki/Hermaphrodi... |
3,365 | <p>I have an AP Bio class where I have to name 3 properties of water and I chose adhesion and cohesion for one of them. I'm having trouble finding out how exactly trees use adhesion and cohesion to move water. There is a lot of different answers out there on the net. How do trees use adhesion and cohesion to move water against gravity?</p>
| [
{
"answer_id": 3378,
"pm_score": 4,
"text": "<p>In high school, we did an experiment that showed this.</p>\n\n<p>Basically, if you take a glass of water, and let it sit out, perhaps in front of an open window, it will eventually lose water due to evaporation. It may take a few days/weeks to really see a... | [
{
"answer_id": 3367,
"pm_score": 3,
"text": "<p>The mechanism is called \"capillary action\". It requires a tube of a small diameter and happens because of the adhesion of water to the walls and the cohesion within the water (=surface tension).</p>\n"
},
{
"answer_id": 60862,
"pm_score": 0,
... |
3,427 | <p>I've recently seen the term <em>synthetic biology</em> being used to describe research involving genetic modification of organisms. What is the difference between <em>synthetic biology</em> and <em>genetic engineering</em>?</p>
<p>Is it just a new term for the same thing, or is it something different? Does one of the two terms encompass the other?</p>
| [
{
"answer_id": 3434,
"pm_score": 4,
"text": "<p>My understanding is that synthetic biology is genetic engineering 2.0. The difference is in the approach. Whereas genetic engineering projects are usually ad hoc, synthetic biology aims to apply proper engineering principles such as standardisation, modula... | [
{
"answer_id": 3428,
"pm_score": 2,
"text": "<p>In genetics engineering we use and manipulate natural genetic elements but in synthetic biology we make new gene elements and network.</p>\n"
},
{
"answer_id": 3429,
"pm_score": 3,
"text": "<p>It seems to me that the difference is mainly se... |
5,007 | <p>I would like to know if evolution is continuing to happen in modern humans, assuming things like existence of the nuclear family structure, fidelity to one partner, etc. It seems to me the answer would be NO because evolution depends on differential reproductive rates, but in the modern world, all male humans have roughly 2.5 (or whatever the number) kids. Add in the process of culturally modified selection pressure, and it seems to me that even an "unfit" male would end up having a couple of offspring. The fittest male (or female) is no better off than his or her contemporaries because of this "leveling" effect. </p>
<p>However, the impression I get from the popular science media is that scientists think evolution is continuing to happen. I would like to know what the actual scientific consensus is, and why. Thanks. </p>
| [
{
"answer_id": 5008,
"pm_score": 6,
"text": "<p>It is certainly not true that \"all male humans have roughly 2.5 (or whatever the number) kids\". First of all, male and female humans have <em>exactly</em> the same reproductive rate. For obvious reasons, every time a male has offspring, a female must hav... | [
{
"answer_id": 5058,
"pm_score": 2,
"text": "<p>Darwin used the term “<em>descent with modification</em>” to describe evolution. That means <strong>a change between generations</strong> in the characteristics, or traits, of a population. It is a process which occurs by four processes - mutation, migrati... |
5,148 | <p>If a hermaphrodite animal (like slug, snail, etc) finds a partner they can mate immediately.</p>
<p>If another animal with "normal" reproduction (lets say a mouse) finds a partner they can only mate if they are opposite genders.</p>
<p>So it seems logical that the hermaphrodite way of reproduction is more successful than the "normal" way.</p>
<p>But it is not, as far as I know all higher developed species are using, the standard way of reproduction (male and female).</p>
<p>Why? What are the disadvantages of hermaphroditism?</p>
| [
{
"answer_id": 5150,
"pm_score": 6,
"text": "<p>Firstly I'll clarify that you are talking about <em>simultaneous</em> hermaphrodites rather than <em>sequential</em> hermaphrodites (1st one sex, then the other e.g. the limpet Patella vulgata).</p>\n\n<p>It is perhaps easiest to address the question by co... | [
{
"answer_id": 5347,
"pm_score": 1,
"text": "<p>I have been pondering this question for a while and I get what RG255 is saying. I'm just not sure I entirely buy it. Take earthworms, for example. They are simultaneous true hermaphrodites (as far as I understand). The anatomy doesn't have to be <em>that</... |
5,445 | <p>From the moment we learn to communicate, we always get told, whether by our parents, or our teachers, or by anyone else, to avoid the cold, or to put a jacket on to avoid catching a cold, to dry our hair before we go outside, because we'll get sick otherwise, so on and so forth. I also was diagnosed with a pneumonia last year, while in Switzerland under chilly conditions ($-20^◦\text{C}$). This made me wonder, why does the cold make us sick? It doesn't seem logical to me that a viral infection like the common cold, or a viral/bacterial infection such as a pneumonia is more prevalent when it's colder outside. I always figured it was because our bodies are less 'effective' under cold temperatures, but this seems lacking to me. Can anyone explain? </p>
| [
{
"answer_id": 5511,
"pm_score": 5,
"text": "<p>it does not, really. unless we're talking about things like frostbite or severe hypothermia.</p>\n<p>it's a myth that it does.\nthe virus is more stable in colder air, however.</p>\n<p>see more here:</p>\n<p><a href=\"http://www.nytimes.com/2007/12/05/heal... | [
{
"answer_id": 5498,
"pm_score": -1,
"text": "<p>Most likely the energy to stay warm is not being used to fight infection. Also the virus is likely designed to operate with your respiratory system at a colder temperature more effective that the immune system is at that cooler temperature.</p>\n"
},
... |
5,524 | <p>Imagine humans were to colonize a distant planet and it was a single one-way trip. How many people would they need to bring?</p>
<p>Obviously 2 is the minimum, but that would result in a lot of inbreeding.</p>
<p>So what number is the minimum number of people you can have in an isolated community and still maintain a healthy diversity?</p>
| [
{
"answer_id": 5526,
"pm_score": 6,
"text": "<p>Actually it is a very important question for laboratory animals (and, I imagine, endangered species) and was calculated to be 25 couples.</p>\n\n<p>With any number of animals (including humans), there is always some inbreeding happening, but you can reduce... | [
{
"answer_id": 15686,
"pm_score": -1,
"text": "<p>Inbreeding isn't negative at all, so one couple would suffice for colonization.</p>\n\n<p>Inbreeding fixes recessive traits and the ones displaying unwanted traits can be culled. Actually, inbreeding is one of the most potent weapons of evolution, it spe... |
5,588 | <p>Mammals, reptiles, arachnids, insects, etc are all as far as I am aware symmetrical in appearance.</p>
<p>Take a human for instance, make a line from the top of our head right down the middle. However, internally it is not the same. Our organs <em>excluding</em> the kidneys, lungs, reproductive organs, etc are not symmetrically placed in our body.</p>
<ul>
<li>Why do we not have an even number of each organ so it can be placed symmetrically?</li>
<li>If we have a single organ why is it not placed in the middle like the brain or bladder is for instance?</li>
<li>Is there some evolutionary advantage that led to this setup?</li>
</ul>
| [
{
"answer_id": 5601,
"pm_score": 6,
"text": "<p>First, I think it worthwhile considering 'Why would internal symmetry be beneficial?' Developmental simplicity jumps to mind immediately. You can also consider relationship to external organs; the stomach and esophagus are lined up with the mouth which is ... | [
{
"answer_id": 5760,
"pm_score": 3,
"text": "<p>Building on the answer given by Sean Connolly above, it would be very easy to imagine evolutionary scenarios where organs are more likely to develop asymmetrically than symmetrically.</p>\n\n<p>For instance, imagine an organism that has a simple digestive ... |
6,827 | <p>Why did humans/animals evolve to become self-aware of their own thoughts. That is, why don't humans act and compute like a machine, or walking zombie. In my mind, such creatures would still be as smart and equally capable of surviving, the only difference being they don't experience the phenomenon of self-awareness. (To understand my question think: unconsciously sleep walking)</p>
| [
{
"answer_id": 6831,
"pm_score": 4,
"text": "<p>There have been many proposals over the years as to why human consciousness has emerged and how, or even what it is. </p>\n\n<p>Most of us will not be surprised to know that there is no consensus about an answer here. Its hard to draw a trend from a sing... | [
{
"answer_id": 13624,
"pm_score": 2,
"text": "<p>I don't think you can ever ask or answer for that matter WHY questions in biology. The only answer there is: because it works. Asking why questions implies that there was a reason, and reason cannot exist alone by itself. Reason is held by someone or some... |
6,915 | <p>Obviously, the temperature of water does not affect its chemical composition. At least not in the ranges we are likely to drink it in. Yet it is clearly far more pleasant and refreshing to drink cool water than it is to drink tepid or warm water.</p>
<p>Is there actually any difference to the organism or is this just a matter of perception? Is cool water somehow more efficient at rehydrating a cell? In any case, surely by the time water reaches individual cells it will have warmed up to body temperature. </p>
<p>So, what, if any, is the difference between drinking cool and warm water in terms of its effect on the human (or other animal) body?</p>
<p>Extra bonus for explaining why the <em>taste</em> of water changes when it is cold.</p>
| [
{
"answer_id": 30657,
"pm_score": 5,
"text": "<p><strong>Short answer</strong>: Cold is pleasant only when your are not already freezing and cold might satiate thirst better because it acts as enhancer of the \"water intake flow meter\".</p>\n\n<hr>\n\n<p><strong>Is cold water more tasty than warm water... | [
{
"answer_id": 6922,
"pm_score": 3,
"text": "<p>I think it's because we are more often thirsty in a warm/hot/dry environment.<br>\nSince almost all of us have a house with a household furnace creating that warm/dry environment. </p>\n\n<p>Thus cold water would be more refreshing since it also cools us... |
7,492 | <p>I've been to local zoo the other day and one lizard caught my attention: its pupils are circular, which, I thought, is not usual for reptiles. Turns out it is, but now I can't find any explanation on why some animals have one kind of pupil and others have the other. Lizards can have both, and so can snakes. The only difference I have found is that circular pupil can't shrink quite as much as a cat's-eye pupil, but that hardly explains why circular pupil even evolved in the first place as I don't see any advantage to it. </p>
<p>Ideas?</p>
<p>P. S. Fish only have circular pupils so that shape is older, right?..</p>
| [
{
"answer_id": 7514,
"pm_score": 5,
"text": "<p>Circular pupils are <em>always</em> functionally superior to vertical pupils; a slit does not correctly focus light from all directions whereas a circular pupil does. If you observe cats when they're hunting at dawn and dusk*, they have big, circular pupil... | [
{
"answer_id": 7500,
"pm_score": 2,
"text": "<p>Your mention of cats hinted that vertical pupils have to do with night vision, and <a href=\"http://www.newscientist.com/article/mg16422167.600-the-last-word.html\" rel=\"nofollow\">indeed they do.</a></p>\n\n<p>The retinas of cats and other nocturnal anim... |
7,847 | <p>According to Wikipedia, muscle cramps are caused by the inability of myosin fibers to break free from the actin filaments during contraction, resulting in a prolonged contraction.</p>
<p>A lack of ATP would obviously produce cramping, as myosin requires ATP to become free from actin.</p>
<p>However, I have heard that potassium and sodium are useful for treating cramps and that their deficiencies can lead to cramping.</p>
<p>So, how does a deficiency in sodium or potassium result in the inability of myosin fibers to break free from the actin filaments during contraction?</p>
| [
{
"answer_id": 7859,
"pm_score": 4,
"text": "<p>The quick and simple answer:</p>\n\n<p>Cramps of a hypokalemic origin are much more common than those of a hyponatremic origin because the Na-K pump is more effective at moving potassium in comparison to sodium.\nAt the onset of a muscle contraction, the p... | [
{
"answer_id": 11302,
"pm_score": 2,
"text": "<p>Muscle contraction occurs when the brain tells the body to move. The brain then starts an action potential down the motor neurons, until it reaches the terminal bouton. At the terminal bouton, it releases the neurotransmitter, acetylcholine, which travels... |
7,854 | <p>A plasmid is a small DNA molecule that is physically separate from, and can replicate independently of, chromosomal DNA within a cell. </p>
<p>In general, in eukaryotes, episomes are closed circular DNA molecules that are replicated in the nucleus. Viruses are the most common examples of this, such as herpesviruses, adenoviruses, and polyomaviruses. Episomes in eukaryotes behave similarly to plasmids in prokaryotes in that the DNA is stably maintained and replicated with the host cell. </p>
<p><a href="http://en.wikipedia.org/wiki/Plasmid" rel="nofollow">Source is wikipedia.</a> </p>
| [
{
"answer_id": 7859,
"pm_score": 4,
"text": "<p>The quick and simple answer:</p>\n\n<p>Cramps of a hypokalemic origin are much more common than those of a hyponatremic origin because the Na-K pump is more effective at moving potassium in comparison to sodium.\nAt the onset of a muscle contraction, the p... | [
{
"answer_id": 11302,
"pm_score": 2,
"text": "<p>Muscle contraction occurs when the brain tells the body to move. The brain then starts an action potential down the motor neurons, until it reaches the terminal bouton. At the terminal bouton, it releases the neurotransmitter, acetylcholine, which travels... |
7,932 | <p>In physics, "almost everything is already discovered, and all that remains is to fill a few unimportant holes." (See <a href="http://en.wikipedia.org/wiki/Philipp_von_Jolly" rel="noreferrer">Jolly</a>.) Therefore, on Physics SE, people are veering off into different directions: <em>biology</em>, for example.</p>
<p>Thus, it happens that <a href="https://physics.stackexchange.com/q/61174/17609">a question about bicycles</a> generates some discussion about evolution in biology and animals with wheels.</p>
<p>Three explanations are offered for the apparent lack of wheely animals (also on <a href="https://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems#Biological_barriers_to_wheeled_organisms" rel="noreferrer">Wikipedia</a>, where, by the way, most Physics SE questions are answered perfectly).</p>
<ol>
<li><p>Evolutionary constraints: "[A] complex structure or system will not evolve if its incomplete form provides no benefit to an organism."</p></li>
<li><p>Developmental and anatomical constraints.</p></li>
<li><p>Wheels have significant disadvantages (e.g., when not on roads).</p></li>
</ol>
<p>Now, I suggest that all three can be "solved".</p>
<ol>
<li><p>With time.</p></li>
<li><p>With a symbiotic relationship between a wheel-like animal and a "driver"-like animal, although this gets awfully close to a <a href="https://www.youtube.com/watch?v=R8XAlSp838Y" rel="noreferrer">"driver"-animal</a> to jump onto an actual (man-made) wheel. (So, perhaps, you can suggest a better loophole around this constraint.)</p></li>
<li><p>Roads are presumably not the only ecological niche where animals with wheels could thrive. I'm thinking of frozen lakes, although there skates would be better than wheels.</p></li>
</ol>
<p><strong>What, therefore, is <em>the</em> explanation for there not being any wheeled animals?
Please consider, in your answer, the counterfactual: What assumption of yours would be falsified once a wheely animal <em>is</em> discovered?</strong></p>
| [
{
"answer_id": 7937,
"pm_score": 7,
"text": "<p>Wheels are possible on the molecular level — bacterial flagella are rotating cores inside a molecular motor, but wheels larger than the flagellum have not really been found.</p>\n<p><img src=\"https://i.stack.imgur.com/1YlbP.jpg\" alt=\"enter image descrip... | [
{
"answer_id": 7938,
"pm_score": 4,
"text": "<p>Shigeta's molecular answer is spot on. However, at the large scale level I think the key problem with a biological wheel needs to be spelled out clearly: how does an organism with separate parts maintain these parts? Let's suppose that an organism evolves ... |
9,172 | <p>I made an answer on the Scifi.SE that can be read <a href="https://scifi.stackexchange.com/questions/37780/how-did-they-clone-other-breeds-of-dinosaur-other-than-the-one-in-the-blood-of-t/37806#37806">here</a>. It is about how the characters in the story Jurassic Park might have gotten DNA for all the species shown.</p>
<p>In my answer, I said this:</p>
<blockquote>
<p>Apes and Humans, for example, share over 99% of their genes. That means the difference between our species is less than 1% of our genes. In fact, all life on Earth shares about 50% of it's genes.</p>
</blockquote>
<p>but in the original posting (before someone edited it) I chose to use the word DNA instead of genes.</p>
<p>He left this comment in the section to explain the edit:</p>
<blockquote>
<p>Sorry, I'm a biologist, I can't help it. Humans and apes share 99% similarity in the coding sequences of their DNA, the ~5% that codes for genes, not on all the DNA. I simplified this to genes for the answer.</p>
</blockquote>
<p>I have a basic high school understanding of DNA and genes, so I'm afraid I fail to see the difference between using "DNA" or using "genes" in my statement. I understand that genes are specific sequences of DNA that are used by the cell in some way. I understand that DNA is more generic, including all of the strands, whether they are used or not, whether they seem to code for something or not.</p>
<p>So is it wrong then to say that apes and humans share 99% of their DNA or is it equally correct to say "genes"?</p>
| [
{
"answer_id": 9174,
"pm_score": 6,
"text": "<p>So, a quick molecular biology lesson. </p>\n\n<ul>\n<li><strong>Proteins</strong> are the things that make up a good percentage of our cells (which make up a good percentage of <em>us</em>), and are the things that do the work of the cells - many are catal... | [
{
"answer_id": 9173,
"pm_score": 3,
"text": "<p>Just to clarify definitions, your <a href=\"http://en.wikipedia.org/wiki/Genome\" rel=\"noreferrer\">genome</a> is made up of sequences of DNA. DNA is constructed pairs of four nucleic acids, or nucleotides (A,G,T,C). That DNA has many <a href=\"http://en.... |
9,419 | <p>Reading this question, <a href="https://biology.stackexchange.com/questions/7932/why-are-there-no-wheeled-animals">Why are there no wheeled animals?</a>, I wondered why <strong>no organisms seem to make use of the tensile and other strengths of metal</strong>, as we do in metal tools and constructions. I am obviously not talking about the microscopic uses of metal, as in human blood etc.</p>
<p>Why are there no plants with metal thorns? No trees with "reinforced" wood? No metal-plated sloths? No beetles with metal-tipped drills? Or are there?</p>
<p>I can think of some <strong>potential factors</strong> why there are none (or few), but I do not know whether they are true:</p>
<ol>
<li>Is metal too <strong>scarce</strong> near the surface?</li>
<li>Are there certain chemical properties that make metal <strong>hard to extract and accumulate in larger quantities</strong>?</li>
<li>Is metal <strong>too heavy</strong> to carry around, even in a thin layer or mesh or tip?</li>
<li>Can metal of high (tensile etc.) strength only be forged under <strong>temperatures too high</strong> to sustain inside (or touching) organic tissue, and is <strong>crystallised metal too weak</strong>?</li>
<li>Are functionally comparable organic materials like horn, bone, wood, etc. in fact <strong>better at their tasks than metal</strong>, and do we humans only use metal because we are not good enough at using e.g. horn to make armour or chitin to make drills?</li>
</ol>
<p>As a predator, I would like to eat a lot of vertebrates and save up the metal from their blood to reinforce my fangs...</p>
<hr />
<p>A bonus question: are there any organisms that use the high <strong>electric conductivity</strong> of metal? Animals depend upon electric signals for their nervous system, but I do not think nerves contain much metal. The same applies to the few animals that use electricity as a weapon.</p>
| [
{
"answer_id": 9420,
"pm_score": 7,
"text": "<p>There are some cases, as hinted at by the comments. But these are relatively small amount of metal.</p>\n<p>It's not that there is no metal available. Iron in particular <a href=\"https://www.livescience.com/29263-iron.html\" rel=\"nofollow noreferrer\">is... | [
{
"answer_id": 9426,
"pm_score": 5,
"text": "<p>A few minor points to add to shigeta's excellent answer:</p>\n\n<p>Biological enzymes don't work well on metals. Some often incorporate metals (see <a href=\"https://en.wikipedia.org/wiki/Chelation\">chelation</a>) but elemental atoms aren't easy to proce... |
9,438 | <p>The recent <a href="http://www.the-scientist.com/?articles.view/articleNo/36624/title/New-Giant-Viruses-Break-Records/">news</a> about a new supermassive virus being discovered got me thinking about how we define viruses as non-living organisms whilst they are bigger than bacteria, and much more complex than we first gave them credit for. </p>
<p>What biological differences between viruses and cellular organisms have made viruses be deemed non-living?</p>
| [
{
"answer_id": 9455,
"pm_score": 7,
"text": "<p>If this is a topic that really interests you, I'd suggest searching for papers/reviews/opinions written by <a href=\"https://www.ncbi.nlm.nih.gov/pubmed/?term=Didier+Raoult+mimivirus\">Didier Raoult.</a> Raoult is one of the original discoverers of the ma... | [
{
"answer_id": 9439,
"pm_score": 4,
"text": "<p>There are quite some different definitions of being \"alive\", but a common one includes the need to have responsiveness, growth, metabolism, energy transformation, and reproduction (found from the <a href=\"http://www.britannica.com/EBchecked/topic/340003... |
9,500 | <p>If we somehow remove pheromones, <strong>do animals experience a phenomenon similar to human "visual beauty" when looking at members of the opposite sex?</strong> For example, given a set of 20 female ducks observed through a glass panel, would male ducks attempt to court/mate with a small subset of female ducks first(more attractive ones), or is it based on some other criteria (most receptive, random, closest, fittest, pheromones, etc?)</p>
<p>If there is some "visual attractiveness selection criteria", <strong>is there a requirement of certain complexity of the brain and/or visual system for an animal before this phenomenon starts to occur?</strong> </p>
<p>I'm aware of the existence of this question: <a href="https://biology.stackexchange.com/questions/7568/why-does-sexual-selection-evolve-beautiful-features">Why does sexual selection evolve beautiful features?</a>, and my question deals with the members of the same generation, not long-term evolution. </p>
| [
{
"answer_id": 9503,
"pm_score": 4,
"text": "<p>There are numerous examples of visual attraction in animals. An absolute classic of an experiment, taught to most/all evolutionary biology students, is the <a href=\"http://www.treknature.com/gallery/photo139613.htm\" rel=\"nofollow\">widowbird</a> tail le... | [
{
"answer_id": 9502,
"pm_score": 3,
"text": "<p>Absolutely. Quality by appearance is sometimes a big part of mate selection and sometimes it is not. </p>\n\n<p>The size and cognitive capacity brain is probably important but not always. Primates are closest to us and have most similar tastes to us, <a ... |
10,376 | <p>I'm a maths major and I have an interest in learning biology. I know very, very little; I know how babies are made and that's about it. Could anyone recommend a stimulating text to read for its own sake and also to use to learn biology?</p>
| [
{
"answer_id": 10386,
"pm_score": 5,
"text": "<p>I found the Campbell Biology textbook to be quite comprehensive and approachable. I think many introductory biology courses use it.</p>\n\n<p><a href=\"http://rads.stackoverflow.com/amzn/click/0321558235\">http://www.amazon.com/Campbell-Biology-Edition-Ja... | [
{
"answer_id": 10378,
"pm_score": 3,
"text": "<p>There are tons of books and it is quite hard to find one that gives such a broad overview. <a href=\"https://www.amazon.ca/Campbell-Biology-9th-Jane-Reece/dp/0321558235/ref=sr_1_2?ie=UTF8&qid=1513808241&sr=8-2&keywords=campbell+biology\" rel=\... |
13,595 | <p>I read a story this week on Richard Lenski who has been 'evolving' <em>E. coli</em> for more than 50,000 generations now. One comment I read was from someone who doesn't accept Evolution who pointed out that we haven't seen a single celled organism 'evolve' into a multi-celled organism. Another person responded and said that a bacteria is not going to evolve into something that isn't a bacteria.</p>
<p>So, if Evolution created single celled organisms and then multi-celled organisms how might that change have happened? And is it possible to recreate that set of driving forces to make a bacteria something other than a bacteria?</p>
<p>To that end, what advantage does being multi-cellular have over being unicellular (if that's even a word)?</p>
| [
{
"answer_id": 21525,
"pm_score": 5,
"text": "<blockquote>\n <p>How did multicellularity evolved?</p>\n</blockquote>\n\n<p><strong>It is an ongoing field of research - Some insights about the origin of multicellularity</strong></p>\n\n<p>This is a big ongoing field of research. To start with an example... | [
{
"answer_id": 13597,
"pm_score": 3,
"text": "<p>For one thing, larger organisms are much more energy efficient. This is what is known as <a href=\"http://en.wikipedia.org/wiki/Kleiber%27s_law\" rel=\"nofollow\">Kleiber's Law</a> where the caloric requirement scales as the 3/4 power to the body mass. <... |
14,414 | <p>After my online research on the subject, I learnt that, biologically speaking, many scientists believe that there is no such thing as a race. <em>Homo sapiens</em> as a species is only 200,000 years old, which has not allowed for any significant genetic diversification yet, and our DNA is 99.99% similar. I've read statements that there can be more genetic variation inside a racial group than between different racial groups, meaning that, for example, two individuals from the same "race" can have less in common with each other than with an individual from another "race".</p>
<p><a href="http://en.wikipedia.org/wiki/Race_(human_classification)" rel="noreferrer">Wikipedia on Race (human classification) quote</a>:</p>
<blockquote>
<p>Scientists consider biological essentialism obsolete, and generally discourage racial explanations for collective differentiation in both physical and behavioral traits</p>
</blockquote>
<hr>
<p><strong>Q1:</strong> If <em>Homo sapiens</em> has no races (according to biologists), why are we so different morphologically? (hair/eyes/skin colour and even athletic performance seem to differ between human populations)</p>
<p><strong>Q2:</strong> Is it common for other species too, when genetically close populations have very different morphological traits? Are there any other mammal or animal species that exhibit biological diversity comparable to human diversity, and how do taxonomists treat these species? (excluding intentionally bred domestic species to keep the comparison fair)</p>
<hr>
<p><em>The question has been paraphrased to emphasize that it is the <strong>biological</strong> debate that is in question, not the <strong>sociopolitical</strong>. I.e., why is there no consensus in evidence and opinions of scientists?</em></p>
| [
{
"answer_id": 14419,
"pm_score": 7,
"text": "<p>Firstly, it's not true that you can't tell racial background from DNA. You most certainly can; it's quite possible to give fairly accurate phenotypic reconstruction of the features we choose as racial markers from DNA samples alone and also possible to id... | [
{
"answer_id": 14416,
"pm_score": 4,
"text": "<p><strong>Bias</strong></p>\n\n<p>When you say <code>phenotype</code> you mostly mean \"skin color\", \"size of the nose\", \"hair color\", \"shape of the eyes\", \"height\", and some others. All these traits that we manage to find to explain <a href=\"http... |
14,888 | <p>Approximately, how many <a href="https://en.wikipedia.org/wiki/Family_%28biology%29">families</a> have been identified?</p>
<p>I've often often come across figures for the total number of species on Earth. Recently, I found myself wondering about the encompassing ranks above them, specifically family, but I can't recall any figures on family and it's a little difficult finding what I want by typing "family" into a Google search. ;)</p>
| [
{
"answer_id": 59068,
"pm_score": 4,
"text": "<p>The 2011 paper <a href=\"http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001127\" rel=\"noreferrer\">How Many Species Are There on Earth and in the Ocean?</a> indirectly answers this question as well as any other source you'll find I... | [
{
"answer_id": 14890,
"pm_score": 3,
"text": "<p>I don't know about other groups, but about plants, number of families depends on the system you follow. Recent version of The Plant List (1.1) estimates about 352 000 species of Angiosperms and lists over 400 families. See <a href=\"http://www.theplantlis... |
15,514 | <p>I've often heard that a population, human or otherwise, will continue to grow as long as there is food available (assuming nothing else is killing them off). It makes sense: if you have food you can live, and if nothing is hunting you you'll survive to reproduce.</p>
<p>I recently designed a piece of software to simulate an ecosystem, with groups of creatures of different species eating and hunting and reproducing alongside each other. It was very simplified (each animal had simple attack/defense/speed/stealth values, etc), but something became rapidly apparent: in every simulation the predators overwhelmed the prey, reproducing until their numbers could not be sustained by the herbivores, and leading to an inevitable die-off of both groups. I could delay the die-off by adjusting different values and initial population counts, but it would always happen eventually. The predators would eat and breed and eat and breed until the entire system collapsed.</p>
<p>At first I thought it was just the product of my over-simplified system, but it got me thinking: <strong>what prevents predators from overpopulating in real life?</strong></p>
<p>It seems like the natural tendency would be for (for example) the sharks to continue breeding and eating until all the fish are gone, or the wolves to eat all the deer, etc. Obviously some predators have predators of their own, but that's just putting off the question: if the hyenas don't overpopulate because the lions eat them, then what's keeping the lions from overpopulating? I can't come up with anything that would prevent the apex predators from growing too numerous, then fighting each other over a dwindling prey population, then dying off entirely when there was no more food to find.</p>
<p>Do predator populations self-regulate to prevent putting undo stress on their prey populations? Or is there some other mechanism to keep the predator hierarchy from becoming top-heavy?</p>
| [
{
"answer_id": 15516,
"pm_score": 6,
"text": "<p>No, I don't think auto-regulation explain much in the population sizes of predators. Group selection may explain such auto-regulation but I don't think it is of any considerable importance for this discussion.</p>\n\n<p>The short answer is, as @shigeta sa... | [
{
"answer_id": 15681,
"pm_score": 3,
"text": "<p>One of the possible adjustments of these mathematical models is to introduce a \"place to hide\", making some (small) percent of the prey population not accessible (or much more difficult to access) for predators. After the number of predators decreases f... |
15,555 | <p>So obviously, viruses are nonliving. But when my teacher was teaching viruses in the video (we're doing "flip" learning this semester), the way he described it, it seemed like the viruses responded to their environment in that they moved around until they found a cell of the right type, and then they latched on and hijacked it. </p>
<p>I had always thought of it more like that they were just kind of floating around, carried by the host system (blood in animals for example), until they "bumped into" the right kind of cells and both sets of membrane proteins "docked". But my theory/idea doesn't really make sense because it doesn't account for how viruses would be able to infect bacteria.</p>
<p>But, the idea that viruses propel themselves doesn't make much sense either, because viruses are nonliving, and one of the characteristics of life that they do not meet is that living things acquire and use energy.</p>
<p>In summary my question is, how are viruses propelled? Do they move themselves, or are they moved by external forces?</p>
| [
{
"answer_id": 15559,
"pm_score": 5,
"text": "<p>All of your reasoning is correct - viruses are <strong>not</strong> motile (i.e. not self-propelled). </p>\n\n<p>I don't understand why you think this would cause a difficulty in the case of bacteria.</p>\n\n<p><strong>Edit in response to comment @Remi.b<... | [
{
"answer_id": 15562,
"pm_score": 3,
"text": "<p>You are right, viruses are neither alive, nor are they moving by themselves. They are moved by passive movements (e.g. the bloodstream or movements of the air) until they meet their target cells. This can be either a cell in the human body (for flu viruse... |
15,736 | <p>I had laser eye surgery a decade ago, but in recent years my eyesight has become significantly myopic. I consulted an ophthalmologist to see if this was eye strain because I work at computers a lot, or part of a natural degradation of the eye over time, or both. My ophthalmologist seems to believe that in my case I'm youngish enough that the natural degradation with age is minimal, and that it's mostly eye strain that is my problem. She believes I can get my eyesight back to roughly 90% of my post-surgery sight ability, if I can reduce eye strain. She gave me some eye drops to help with dryness, and recommended various ways to for me to help my eyes recuperate.</p>
<p>I decided to look into eye strain to learn more about what conditions cause it and what can alleviate it. What I learned is that the lens of <a href="http://en.wikipedia.org/wiki/Accommodation_of_the_eye#Theories_of_mechanism" rel="noreferrer">the eye needs to be flatter to accommodate focusing on far objects</a>, and rounded to focus on near objects. The way the lens becomes flat is by using spring-like connective tissue called <em><a href="http://en.wikipedia.org/wiki/Choroid" rel="noreferrer">choroids</a></em> that pull it taught. Attached to these choroids are muscles called <em><a href="http://en.wikipedia.org/wiki/Ciliary_muscle" rel="noreferrer">ciliary muscles</a></em> that stretch the choroids out when they contract. This action causes the choroids to stop pulling on the lens, and the lens will retract into a more rounded shape. So, when the ciliary muscles are relaxed, you can see far. When the ciliary muscles are contracted, you can see close up. <a href="http://www.yorku.ca/eye/ciliary.htm" rel="noreferrer">This diagram from the York University website</a> was the clearest explanation I have come across:</p>
<p><img src="https://i.stack.imgur.com/tM4cr.gif" alt="ciliary muscles and choroids"></p>
<p>Thus, the reason for my current inability to focus on far objects is that so much focusing on close objects, mainly computer monitors, is straining my eyes. In order to regain the ability to focus on far objects, I need to reduce strain and allow the muscles to relax. If they relax, the choroids can pull the eye to the flatter shape needed to see far.</p>
<p>However, I can't reconcile that model with how I understand the mechanics of the other muscles in my body. If I go to the gym and run or lift weights, or in any way expose my muscles to work, they respond by getting stronger without sacrificing the ability to stop contracting. The muscles in my body don't lose the ability to relax, no matter how much I train them. I have never heard of anyone who worked out too hard or too long such that their bicep would remain in a permanent state of contraction.</p>
<p>In fact, in my experience, after a hard workout, it's <em>impossible</em> to prevent my muscles from relaxing and resisting doing more work. When I do a bicep curl at the gym, and I do it to the point that I can't lift the weight anymore, my muscle gives up and I drop the weight. Similarly, if I've spent a long time looking at close up objects, shouldn't my ciliary muscles give up, allowing the choroids to take over, making clear far vision the unavoidable outcome?</p>
<p>The idea that my ciliary muscles need to relax in order to see far also seems to contradict my personal anecdotal experience. Sometimes I am able to see far away, but I can't hold it for more than a few seconds. If I try to maintain focus on far objects for too long, I get an uncomfortable feeling in my eyes that is hard to describe, but it's a form of pain that forces me to give up. My vision goes blurry, and I can only see close objects again. If my bicep worked the same way, it would be as if it hurt to let my arm hang straight down with a weight, and the only way to alleviate it would be to raise the weight, which makes no sense. I feel like the effort is in seeing far, and that when I'm tired, I can only see close up.</p>
<p>It's not that the case that I think that all medical research on the eye has it backwards, it must be that there is some aspect of this that I am not seeing (pun intended).</p>
<p>How can it be that the ciliary muscles, unlike other muscles, lose their ability to relax?</p>
<p>Why is it that my ciliary muscles don't become exhausted and allow the choroids to take over by default?</p>
| [
{
"answer_id": 15902,
"pm_score": 4,
"text": "<p>First of all, I should correct some points that were misunderstood. \nDon't change the question because this will lead to confusion.</p>\n\n<p>\"The way the lens becomes flat is by using spring-like connective tissue called choroids that pull it taught.\"... | [
{
"answer_id": 48445,
"pm_score": 2,
"text": "<p>I'm not a eye doctor but I do workout. I would like to say something about your metaphor or comparison from the ciliary muscle to the body muscles. </p>\n\n<p>Let's look at a workout. In a workout, you strain the muscle then relax the muscle repeatedly un... |
16,854 | <p>Why don't we breathe nitrogen while it makes most of the air?</p>
<p>Why do we always tend to breathe oxygen, not hydrogen and nitrogen?</p>
| [
{
"answer_id": 16864,
"pm_score": 5,
"text": "<p>I'd argue that we do \"breathe\" all those gases. Air that we inhale (at sea level) is about 78% N$_2$, 20.9% O$_2$, 1% argon, and smaller percentages of CO$_2$, neon, methane, etc. So all those gases are going into the lungs with every breath in.</p>\n\n... | [
{
"answer_id": 16856,
"pm_score": 0,
"text": "<p>Basically when air fills our alveoli, by the process of diffusion, only oxygen in the air is taken into the blood stream while the other gases along with the waste CO2 is exhaled. So you do breathe in nitrogen, but it is exhaled as it is by the body. The ... |
16,899 | <p>I'm trying to look at relationships between parasite and host phylogenetic trees. I have done a bit of searching for software with which to do this, and I have tried using Dendroscope and TreeMap, but can't get to grips with them. </p>
<p>I want to produce something along the lines of this;</p>
<p><img src="https://i.stack.imgur.com/XXsaO.gif" alt="enter image description here"></p>
| [
{
"answer_id": 16923,
"pm_score": 5,
"text": "<h1>Dendroscope</h1>\n\n<p>Using <a href=\"http://ab.inf.uni-tuebingen.de/software/dendroscope/\" rel=\"noreferrer\">Dendroscope</a>, I opened the provided example file <code>trees.new</code>. This opens a new window with 16 trees in it.</p>\n\n<ol>\n<li>Shi... | [
{
"answer_id": 16900,
"pm_score": 2,
"text": "<p>I have to confess that I know nothing about phylogenetics and the associated software but according to the abstract of <a href=\"http://onlinelibrary.wiley.com/doi/10.1111/zoj.12027/abstract\" rel=\"nofollow noreferrer\">this article</a> it seems that the... |
17,077 | <p>Why does evolution not make life longer for humans or any other species?</p>
<p>Wouldn't evolution favour a long life?</p>
| [
{
"answer_id": 17091,
"pm_score": 7,
"text": "<p>Why do we age is a classical question in Evolutionary Biology. There are several things to consider when we think of how genes that cause disease, aging, and death to evolve.</p>\n\n<p>One explanation for the evolution of aging is the <a href=\"http://www... | [
{
"answer_id": 17078,
"pm_score": 5,
"text": "<p>This is a very good question.</p>\n\n<p>There is a big ongoing field of research called \"evolution of aging/senescence\" that tackles this question. I won't give you a complete overview of the different hypothesis the could explain why we age but here is... |
19,762 | <p>As I understand it, various animal traits have to evolve gradually, but what happens to the species that are "neither here nor there"?</p>
<p>To put it differently, if a species evolved from another, it did so because it's somehow better, right? So why are there examples of the original species not being extinct?</p>
<p>What factors determine weather some species "stick"?</p>
| [
{
"answer_id": 19764,
"pm_score": 5,
"text": "<p><strong>Short answer</strong></p>\n\n<blockquote>\n <p>Why are there species rather than a long continuum?</p>\n</blockquote>\n\n<p>Three important reasons I could think of are sex, non-uniform adaptive landscape and ancestry.</p>\n\n<p><strong>Long answ... | [
{
"answer_id": 19763,
"pm_score": 3,
"text": "<p>Typically when both new and old species still exist it is because evolution pushed the new one into a different habitat or role. </p>\n\n<p>As a hypothetical example reef fish vs. deep water fish and their relative size. Let's say deep water fish evolve... |
19,873 | <p>Would I be able to genetically modify a plant at home? What equipment will be necessary? I think it might be a fun change from the 'norm' of regular hybridisation, to try some inter-family gene insertion, instead of staying within a genus. Are some plants easier to modify than others?</p>
| [
{
"answer_id": 19875,
"pm_score": 4,
"text": "<p>Well, that depends on your home. ;) I think it is not an easy process.</p>\n\n<p>There are <strong>two main methods</strong> that are used to genetically modify plants:</p>\n\n<p><strong>Using the bacterium</strong>, Agrobacterium tumifaciens, as a vector... | [
{
"answer_id": 19874,
"pm_score": 2,
"text": "<p>Yes, It is.</p>\n\n<p>An Indian Company IndieBB can help you get one.\n<a href=\"https://www.indiegogo.com/projects/indiebb-your-first-gmo\" rel=\"nofollow\">IndieBB: a DNA system designed to help you and your friends to explore genetic engineering and sy... |
20,437 | <p>recently i got into a debate with <a href="https://hinduism.stackexchange.com/posts/comments/4386?noredirect=1">this</a> question on hinduism.se ,</p>
<p>as the link given above shows, are sperms considered as living or non-living </p>
<p>as far as my knowledge is concerned, sperms undergo locomotion, senescence, more over the best thing to say they are living is they contain genome, i.e. haploid sets of chromosomes</p>
<p>so in short are sperms living or non-living</p>
| [
{
"answer_id": 20442,
"pm_score": 3,
"text": "<p>The question of what is living is nothing but a matter of definition. We can only tell you what are the standard definitions of what is a living thing but no absolute truth exist behind these definitions. Therefore, I am afraid that all discussions here w... | [
{
"answer_id": 20438,
"pm_score": -1,
"text": "<p>One requirement most biologists have to consider something living is the ability to reproduce. This is why viruses are generally not considered alive. They contain proteins and DNA or RNA, but require infecting a host cell and hijacking its replication m... |
20,657 | <p>Some people say that it's awful that humans eat animals. They feel that it's barbaric, because you're killing life and then on top of that, you're eating it, and that you should eat vegetation instead.</p>
<p>But isn't vegetation life too? Personally, I see no difference between animals and veg as all life has cells, dna etc</p>
<p>So my question is, is it possible for humans to live healthy long lives without eating any type of life, i.e no animals, no plants, no cells (dead or alive) etc? If it is possible, how would it be done?</p>
| [
{
"answer_id": 20664,
"pm_score": 7,
"text": "<p>The answer to your question is <strong>yes</strong> it is certainly possible. </p>\n\n<p>At one time it was thought that there was something special about \"organic\" chemicals which meant that they could not be artificially synthesised out of fundamental... | [
{
"answer_id": 20659,
"pm_score": 5,
"text": "<p>Living organisms can be divided into hetrotrophs and autotrophs. Autotrophs like plants and algae are able to produce complex <em>organic</em> compounds from relatively simple <em>inorganic</em> components. They are satisfied with sunlight, water and othe... |
20,709 | <p>A vast majority of humans get at least some grey hair as they age. As far as I know this applies to both genders and all races. Presumably this means that at least some grey haired humans have noticeable reproductive advantage, or maybe they had it in the recent past.</p>
<p>Theoretically, because this feature is so prevalent, there must be a strong evolutionary pressure to keep it. Am I right? If so, what is it?</p>
| [
{
"answer_id": 20715,
"pm_score": 4,
"text": "<blockquote>\n <p>Presumably this means that at least some grey haired humans have\n noticeable reproductive advantage, or maybe they had it in the recent\n past.</p>\n</blockquote>\n\n<p>No it doesn't. Natural selection is not that strong, it doesn't op... | [
{
"answer_id": 20721,
"pm_score": 2,
"text": "<p>I do not think there is a reproductive advantage in gray hair - it's the other way around: </p>\n\n<p>Normal colored hair has a reproductive advantage.\nBut it also has a cost in terms of substances needed to build it.</p>\n\n<p>I make the assumption here... |
20,912 | <p>Throughout high school, I remember learning about Darwin's theory of evolution as if it were near-fact. But something always seemed wrong about the ideas presented.</p>
<ul>
<li>Survival of the fittest</li>
<li>Random mutation</li>
<li>Natural Selection</li>
</ul>
<p>All of these things seem to account for some margin of evolutionary progress, but I always remained skeptical that the extremely complex features of life could have formed from these methods alone, even after hundreds of millions of years.</p>
<p>Here's what I notice:</p>
<p>Any time a species has needed the development of a specific feature to survive, it has developed that feature, and that feature precisely.</p>
<hr>
<p>I'm going to use this example:</p>
<p><strong>Turtles on an island where shrubbery grew higher up developed longer necks, to reach the leaves.</strong></p>
<p>I imagine that turtle looking up at that food, and sub-consciously wishing to get to it, constantly straining, for its entire lifetime. </p>
<hr>
<p>It seems plausible to me that we (advanced life) could have a biological mechanism to "write" needed alterations into either our own DNA or our reproductive DNA over time, triggering the very specific evolutionary developments necessary to our survival without relying on random mutation.</p>
<p>My question:</p>
<p><strong>Is this possible?</strong> Does any similar mechanism exist that we know of? <em>If not, how can so many specific (advanced) evolutionary leaps be otherwise explained?</em><br></p>
| [
{
"answer_id": 20913,
"pm_score": 6,
"text": "<p>This entire answer will be long, so read the short part first, then read the rest if you (or anyone else) is curious. Citations are included in the long section. I can include additional citations in the short section if needed.</p>\n\n<p><strong>Long Sto... | [
{
"answer_id": 20914,
"pm_score": 4,
"text": "<p><strong>About your question</strong></p>\n\n<p>This kind of very basic question has the drawback to need a very long answer. In consequence, your question might get some close vote. I'll do my best to help but you might want to look at some source of info... |
20,992 | <p>From what I understand, your body needs certain amounts of vitamins and minerals to maintain health. Why can't we just take enough pills to obtain these vitamins and minerals?</p>
| [
{
"answer_id": 20993,
"pm_score": -1,
"text": "<p>This is more of a biochemistry question and to be honest its a little bit out of my league because I have not had the necessary grad classes to explain nutrition but indeed I will try.</p>\n<p>Unknown metabolite cofactors and things like ionization, oxid... | [
{
"answer_id": 21338,
"pm_score": 3,
"text": "<p>I think the piece of missing information here is the distinction between <a href=\"http://fnic.nal.usda.gov/food-composition/macronutrients\" rel=\"nofollow noreferrer\"><i>macro</i>nutrients</a> and <a href=\"http://www.who.int/nutrition/topics/micronutr... |
23,873 | <p>This is a cross-cutting question but I think its core is about biology. Our society's need for energy is dramatically growing and we are messing up with our environment to answer them. Maybe another way to proceed would be to use the primary energy source that is the sun in the same way as it has been used throughout the ages: photosynthesis.</p>
<p>I know the energy effiency is not as good as a solar panel's but it could clearly be compensated by volume. I found surprisingly little information about harvesting energy from photosynthesis which is why I began to wonder where we are at today. </p>
<p>Thanks!</p>
<p><strong>Edit</strong>
I meant transforming the chemical energy generated by photosynthesis into electrical energy. For instance, the first algae powered building was unveiled at the International Building Exhibition hosted in Hamburg. This is a whole different approach.
The most basic example of what I would like to talk about seems to be the algae powered lamp that has (apparently) been developped. In other words, it seems that some sort of plant solar panels are under development and I don't understand how it's done.</p>
| [
{
"answer_id": 23882,
"pm_score": 4,
"text": "<blockquote>\n <p>The most basic example of what I would like to talk about seems to be\n the algae powered lamp that has (apparently) been developped.</p>\n</blockquote>\n\n<p>I think you misunderstood the idea. That lamp uses <a href=\"http://en.wikipedi... | [
{
"answer_id": 23875,
"pm_score": 3,
"text": "<p>It is not possible to do this directly. Indirectly, it is possible, this is actually done by harvesting fruits - they contain the energy of the sunlight conserved in chemical compounds like sugars or starch and their cellular structures. The basic process... |
24,090 | <p>Corneas are donated and transplanted, but not the eyeball. </p>
<p>I don't understand. What is the purpose of donating a cornea without an eyeball to a blind person?</p>
| [
{
"answer_id": 24101,
"pm_score": 4,
"text": "<p>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 t... | [
{
"answer_id": 24092,
"pm_score": 2,
"text": "<p>The eyeball is basically the sclera that surrounds the delicate inner structures of the eye (<a href=\"http://en.wikipedia.org/wiki/Eye\" rel=\"nofollow\">see wiki on the eye</a>). The cornea is the transparent window in front of the pupil that transmits ... |
24,126 | <p>Does each cell contain only a single copy of its genome? Or are there ever 'extra' copies present. </p>
<p><strong>Reason behind question</strong>: <em>Wondering whether gene mutations could be corrected by referencing a 'backup copy'.. If such a thing exists..</em></p>
| [
{
"answer_id": 24127,
"pm_score": 5,
"text": "<p>As a quick answer, yes, most human cells carry 2 copies of the genome and are known as <a href=\"http://en.wikipedia.org/wiki/Ploidy#Diploid\">diploid</a> cells. One copy comes from each of your parents, so they aren't identical, but usually pretty close.... | [
{
"answer_id": 24128,
"pm_score": 3,
"text": "<p>Diploid cells contain two copies of the genome. Additionally, each copy of the genome can have multiple copies of certain genes. Which can provide a level of protective redundancy.</p>\n\n<p>However, there are a number of potential problems with having mu... |
28,177 | <p>Lately I have seen a number of unrelated "scientific" debates over whether certain substances should be outlawed because they are toxic to humans. My initial, informal reaction is usually to respond that anything is toxic to humans if you give them a sufficiently large dose.</p>
<p>However, formally I don't know if that's really true for <em>everything</em> a human being could ingest in some way. I started to wonder if there were some substances that our body could handle unlimited amounts of without any negative consequences.</p>
<p>As this question has been (correctly) identified as a bit vague, I'll try to explain what i'm looking for. For the purposes of this question, I'm willing to ignore the limitations of actually ingesting a given substance in "the usual way". For example, if you can't physically drink enough of some liquid fast enough to kill you without your stomach filling up and vomiting, but that same liquid injected intravenously <em>could</em> be lethal, I could consider that toxic. I also recognize that the body can only physically contain a certain volume of stuff, after which sheer pressure would cause it to fail; I'm more interested in "biochemical toxicity" as opposed to any physical damage (I just don't know the term for what I'm looking for.)</p>
<p>In other words, one of my goals is to learn if, under laboratory conditions, a properly motivated researcher could <em>always</em> find a dose that would be toxic, regardless of the impracticality of a real person ingesting that dose under normal circumstances.</p>
<p>So, with that qualification, my ultimate question is:</p>
<p><strong>Is there any substance we know of that is completely non-toxic to humans at arbitrarily large doses ingested over an arbitrarily short period of time?</strong></p>
| [
{
"answer_id": 28179,
"pm_score": 6,
"text": "<p>I’ll answer this theoretically, since that’s how it has been posed. And if we’re ignoring practicalities, we may as well posit that the substance in question will be introduced directly into the bloodstream (This is, of course, simple to do in reality, bu... | [
{
"answer_id": 28178,
"pm_score": 3,
"text": "<p>There is a problem with definition of toxicity — things that are dangerous in large amounts aren't usually called toxic. In spite of this, you're right: everything can be dangerous to a human in large enough amounts, or if delivered improperly.</p>\... |
29,679 | <p>Does the brain really function like a computer as in, ultimately every response is related to a binary sequence based on whether particular neurons fire or not?</p>
| [
{
"answer_id": 29685,
"pm_score": 5,
"text": "<p>First of all, I would like to point out that making analogy between digital computers and the brain is often very misleading.</p>\n\n<p>That being said, my answer is, some scientists believe so, some don't.</p>\n\n<p>Several things to consider:</p>\n\n<ol... | [
{
"answer_id": 29734,
"pm_score": 3,
"text": "<p>While action potentials are usually binary, you should note that <a href=\"http://en.wikipedia.org/wiki/Synapse\">synaptic communication</a> between neurons is generally not binary. Most synapses work by <a href=\"http://en.wikipedia.org/wiki/Neurotransmi... |
29,795 | <p>How does a virus like HIV mutate into so many strains, and yet all of them are harmful to our immune system? What gives this virus the ability to mutate so efficiently?</p>
| [
{
"answer_id": 29960,
"pm_score": 3,
"text": "<p>Others have already touched the important points. Consider this as a summary.</p>\n\n<blockquote>\n <p>What gives HIV the ability to mutate?</p>\n</blockquote>\n\n<p>All organisms mutate by two mechanisms:</p>\n\n<ol>\n<li>Replication errors</li>\n<li>Mu... | [
{
"answer_id": 29796,
"pm_score": 2,
"text": "<p>Viral recombination produces genetic variation that contributes mostly to the evolution of the HIV-1 virus.</p>\n\n<p>HIV being an RNA Virus utilizes an enzyme called reverse transcriptase, which produces DNA from RNA. HIV also has <strong>two</strong> R... |
30,116 | <p>Does DNA have anything like IF-statements, GOTO-jumps, or WHILE loops?</p>
<p>In software development, these constructs have the following functions:</p>
<ul>
<li><strong>IF-statements:</strong> An IF statement executes the code in a subsequent code block if some specific condition is met.</li>
<li><strong>WHILE-loops:</strong> The code in a subsequent code block is executes as many times as specified, or as long as a specific condition is met.</li>
<li><strong>Function calls:</strong> The code temporarily bypasses the subsequent code block, executing instead some other code block. After execution of the other code block the code returns (sometimes with some value) and continues the execution of the subsequent block.</li>
<li><strong>GOTO-statements:</strong> The code bypasses the subsequent code block, jumping instead directly to some other block.</li>
</ul>
<p>Are constructs similar to these present in DNA? If yes, how are they implemented and what are they called?</p>
| [
{
"answer_id": 30120,
"pm_score": 8,
"text": "<p>Biological examples similar to programming statements:</p>\n\n<ul>\n<li><code>IF</code> : Transcriptional activator; when present a gene will be transcribed. In general there is no termination of events unless the signal is gone; the program ends only wit... | [
{
"answer_id": 30117,
"pm_score": 4,
"text": "<p>There are certainly some comparisons that could be made between the way genes are expressed from DNA and logic functions, but they aren't great.</p>\n\n<p>But synthetic Biology is really a blossoming new field that is attempting to integrate logic functio... |
30,468 | <p>Why is the action of flexing the foot so that the toes move anteriorly/superiorly (i.e. in the direction opposite that which they move during plantar flexion) described as "dorsiflexion?" In the same vein, why is the top surface of the foot called the "dorsal surface?" </p>
<p>If anything, the action opposite to plantar flexion moves the foot in the ventral direction, doesn't it? And surely if you've ever seen a human in the anatomical position, you can see that there's nothing dorsal about the top surface of the foot - it's superior, perhaps, but by no means dorsal.</p>
| [
{
"answer_id": 30470,
"pm_score": 5,
"text": "<p>Anatomical terms must be able to fit a wide variety of organisms, from insects to fish, dogs, horses, chimpanzees to humans. That's why the terms are sometimes confusing to people who are thinking only of bipedal humans.</p>\n\n<p>In anatomy, the dorsum i... | [
{
"answer_id": 30469,
"pm_score": 2,
"text": "<p><em>Dors/dorsum</em> in Latin simply means \"back\", and it is rather normal and reasonable to use the equivalent term in English with regard to the extremities (hands and feet), see \"<a href=\"http://dictionary.cambridge.org/dictionary/british/know-sth-... |
31,546 | <p>Does anyone know of sources for learning bioinformatics, focused on genomics? I would like to learn a lot of skills I could apply potently in the workforce if I ever became adept at the fields. My computer science knowledge is weak, and my biology knowledge is mediocre, but I find the topics to be interesting.</p>
<p>I have read "The dynamic Genome, A Darwinian Approach", by Fontdevila, and it was a bit rough for me. I have also read some of a introduction to genomics textbook, by Arthur M Lesk, and found it to be very "academic".</p>
| [
{
"answer_id": 31558,
"pm_score": 4,
"text": "<p><a href=\"http://unixandperl.com/\" rel=\"nofollow\">Unix and Perl to the Rescue</a> by Keith Bradnam and Ian Korf is an excellent introductory book and guide for bioinformatics (Linux and Perl) in genomics. It includes exercises and starts with the very ... | [
{
"answer_id": 31552,
"pm_score": 3,
"text": "<p>Beginning Perl for Bioinformatics by Jim Tisdall <a href=\"http://shop.oreilly.com\">http://shop.oreilly.com</a> is quite good, in my opinion, and his sequel, Mastering Perl for Bioinformatics is also great. The focus is largely, but not exclusively genom... |
32,964 | <p>I'm an engineer by training and teaching myself the basics of cell and developmental biology. I'm using Scott F. Gilbert's Developmental Biology and Alberts' Essential Cell Biology right now, and they are both great resources.</p>
<p>Can you recommend good books on similar topics that are written in a non-textbook format?</p>
<p>EDIT: For example, I found books like The Greatest Show on Earth, Extended Phenotype, and Nature via Nurture really useful to learn about the basics of evolution while I was reading Watson's Molecular Biology of the Gene. Are there similarly well-written books for cell biology, developmental biology, or biochemistry? I know this sounds broad, but I'm not asking for textbook recommendations. I'd like to read something that isn't a textbook alongside my current studies.</p>
<p>SECOND EDIT: I'd be like to extend this question to recommendations of broad review articles in Cell and Developmental Biology too. For example 'How do cells know where they are?' is an excellent article on different strategies cells may use to assess distance in a developing embryo.</p>
| [
{
"answer_id": 52730,
"pm_score": 2,
"text": "<p>For Biochemistry:</p>\n\n<p><a href=\"https://i.stack.imgur.com/uvPKf.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/uvPKf.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>For Molecular Genetics:</p>\n\n<p><a href=\"https:... | [
{
"answer_id": 33010,
"pm_score": 0,
"text": "<p>Would you consider the New York Times a suitable level of detail (while admittedly not a book)? If so then you may want to peruse this collection:\n<a href=\"http://topics.nytimes.com/top/news/science/topics/biology_and_biochemistry/index.html\" rel=\"nof... |
35,337 | <p>Across the electromagnetic spectrum, 400-700 nm is a narrow spectrum of frequencies and focused in the region of short wavelengths. For example, radio waves cover a large range of frequencies unexploited by the visual system. So what biological reason is there that evolved us to use such a small frequency bandwidth for vision?</p>
| [
{
"answer_id": 35353,
"pm_score": 6,
"text": "<p><strong>Short answer</strong><br>\nThe visible spectrum has the highest energy in sunlight at the earth's surface, explaining the gross location of the visible spectrum in life on earth. The specific frequency range varies across species and can be explai... | [
{
"answer_id": 35342,
"pm_score": -1,
"text": "<p>These wavelengths happen to satisfy two conditions.</p>\n\n<p>First, shorter wavelength photons (EM radiation) tend to be dangerous for biology. Even UV light (<350nm) is already can damage DNA. That is due to the fact that bond energies in biological... |
35,446 | <p>There are plenty of different hand soaps out there, as well as hand sanitizers. Is there an advantage to soaps that claim that they're antibacterial vs soaps that just say soap?</p>
<p>In particular I'm looking at Softsoap who offers normal soap and antibacterial soap. </p>
<p><strong><em>Examples:</em></strong></p>
<p>Normal:</p>
<p><img src="https://i.stack.imgur.com/KICCXm.jpg" alt="Regular Softsoap"></p>
<p>Antibacterial: </p>
<p><img src="https://i.stack.imgur.com/jYnyam.jpg" alt="Antibacterial Softsoap"></p>
| [
{
"answer_id": 35451,
"pm_score": 7,
"text": "<p>Short answer: There is no benefit for their use in households. </p>\n\n<p>Long answer: These soaps (see <a href=\"http://www.colgate.com/app/Softsoap/US/EN/Ingredients.cvsp\">here</a> for the complete list) contain the so called quaternary ammonium compou... | [
{
"answer_id": 35450,
"pm_score": 4,
"text": "<p>Chris has correctly identified the antibacterial agent in the hand soap depicted in the image in the question, and therefore his answer is superior as a direct answer. </p>\n\n<p>Nevertheless, other members of the Softsoap series of hand soap uses <a href... |
39,374 | <p>It's easy to find information about the biggest animals at land / at sea / in the air. But what was the biggest underground-living animal that ever existed?</p>
<ul>
<li>No animals that were forced to live underground (e.g. pit ponies)</li>
<li>The animal should live at least 95% of its life under the earth (e.g. foxes)</li>
</ul>
<p>There are two possible answers:</p>
<ol>
<li>By length</li>
<li>By mass</li>
</ol>
<p>My first guess was a mole</p>
| [
{
"answer_id": 57393,
"pm_score": 4,
"text": "<p><strong>Microchaetus rappi</strong>\nMicrochaetus rappi, the African giant earthworm, is a large earthworm in the Microchaetidae family, the largest of the segmented worms (commonly called earthworms). It averages about 1.36 m (4.5 ft) in length, but can ... | [
{
"answer_id": 39375,
"pm_score": 3,
"text": "<p>I don't know if there is a bigger animal, but the biggest <strong>mole</strong> is the <a href=\"https://en.wikipedia.org/wiki/Russian_desman\" rel=\"noreferrer\">Russian desman</a> with 400-520g and a length of \n18-21 cm (35-41cm including the tail)</p>... |
39,664 | <p>To be clear, I'm not doubting that <em>Homo sapiens</em> and <em>Homo neanderthalensis</em> did interbreed: of that much I'm convinced.</p>
<p>Within the past few years I've seen an upcropping of pop-sci articles discussing the interbreeding between pre-historic species of humans. In everything that I see in these articles, as well as in scientific literature (my college Bio textbook, among others), I see these different human groups being referred to as separate species.</p>
<p>This conflicts with my understanding of a species. Given the following definition, wouldn't <em>Homo sapiens</em> and <em>Homo neanderthalensis</em> be the same species?</p>
<blockquote>
<p>A species is often defined as the largest group of organisms where
two hybrids are capable of reproducing fertile offspring, typically
using sexual reproduction. <a href="https://en.wikipedia.org/wiki/Species" rel="nofollow noreferrer">~Wikipedia</a></p>
</blockquote>
<ul>
<li>Is this definition incorrect?</li>
<li>Are the publications using "species" colloquially, as opposed to scientifically?</li>
<li>Is "species" still a poorly defined concept? (see <a href="https://en.wikipedia.org/wiki/Ring_species" rel="nofollow noreferrer">Ring Species</a>)</li>
</ul>
<p>Thanks!</p>
| [
{
"answer_id": 39669,
"pm_score": 8,
"text": "<h1>Short answer</h1>\n<p>The concept of species is poorly defined and is often misleading. The concepts of <a href=\"https://en.wikipedia.org/wiki/Lineage_(evolution)\" rel=\"noreferrer\">lineage</a> and <a href=\"https://en.wikipedia.org/wiki/Monophyly\" r... | [
{
"answer_id": 39668,
"pm_score": 4,
"text": "<p>The definition of species is open for debate, and this is especially the case when you try to define it from a paleontology perspective. </p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Neanderthal\">Homo neanderthalensis</a> was first discovered and de... |
40,156 | <p>Let me explain... A friend and I read some articles, part of a Biology book, and watched a video on evolution. We then tried to explain what Evolution is to each other.</p>
<p>My friend said that Natural Selection is a mechanism inside the organism that mutates the DNA to make its offspring survive in an environment; that natural selection mutates the DNA beneficially and that random mutations are not useful (like blue eyes). But I disagree and think that it is closer to Lamarkian theory.</p>
<p>I told him that DNA from male and female recombines and randomly mutates making a new "recipe" for the offspring (adding a new characteristic(s)). If the offspring is well suited for the environment, then it survives and passes on its characteristics to its offspring. If it does not have fitness for its environment, it dies. So, Natural Selection is were nature "selects" who survives and reproduces a lot.</p>
<p>So is the DNA mutation process random or is mutation directed to make an organism that is suited to survive its environment?</p>
<p>None of my friends are Biology students, so I can't ask then which explanation is correct (or at least more valid).</p>
<p>I'd prefer you don't answer: "None of these explanations are correct," but to say which one is more valid and correct misconceptions or add more that is missing (of course these are only summaries of our discussion). But of course, you can answer that neither of our explanations is correct...</p>
| [
{
"answer_id": 40165,
"pm_score": 5,
"text": "<p>I accidentally wrote a lot!</p>\n\n<p>I first discuss the term <em>Darwinian evolution</em>. I then describe the main evolutionary processes insisting on the two elements of interest in your question, that is <em>mutations</em> and <em>natural selection</... | [
{
"answer_id": 40158,
"pm_score": 1,
"text": "<p>Your description of Evolution seems more accurate than your friends. DNA cannot mutate with a particular goal in mind, mutations are random. Most mutations have no effect on an organism's survival, but some will be detrimental, and a few will helpful. Hel... |
40,964 | <p>I'm trying to find out how many molecules of nucleoside triphosphates (ATP, GTP, UTP and/or CTP) it takes to release enough energy to link two amino acid monomers together with a peptide bond, specifically during the process of mRNA translation.</p>
<p>I've tried to do some research online, but I could not find a reputable source that will say definitely how much energy is consumed in the process. The best answer I could find is formulated based on <em>'Molecular Biology of the Cell'</em> 4th edition by Alberts B, Johnson A, Lewis J, et al., which is that at least one molecule of ATP is consumed for every peptide linkage. Is this correct?</p>
<p>I've also read on a science forum that the amount of ATP consumed during translation is different for every amino acid, but I could not find a reliable source to back up that claim. Is this true?</p>
| [
{
"answer_id": 65168,
"pm_score": 4,
"text": "<p>Although the question shows considerable effort to achieve clarity, the way it is phrased as:</p>\n\n<blockquote>\n <p>How many molecules of nucleoside triphosphate… [does] it take <em>to release enough energy</em></p>\n</blockquote>\n\n<p>still allows a... | [
{
"answer_id": 40973,
"pm_score": -1,
"text": "<p>First, during the initiation of translation, a small ribosomal subunit binds to a molecule of mRNA. In a bacterial cell, the mRNA binding site on this subunit recognizes a specific nucleotide sequence on the mRNA just upstream of the start codon. An init... |
42,050 | <p>In my <a href="https://biology.stackexchange.com/questions/42033/what-are-we-missing-about-the-real-workings-of-the-evolutionary-process">last question</a> I asked why we don't see increased complexity in artificial life simulations of evolution. It seems I had fallen for a common misconception, that evolution was about <em>improvement by increasing complexity</em>. One comment discussing that post read</p>
<blockquote>
<p>"... he [David Deutsch] is falling for one of the biggest
misconceptions about evolution that you can, that evolution is about
<em>improvement</em>. Evolution has simply only ever been about change..." </p>
</blockquote>
<p>However, when you look at the history of life you see increases in complexity. You see this increasing complexity evolving over billions of years, suggesting that it requires an explanation.</p>
<p><strong>My question</strong><br>
If evolution is not about increasing complexity then how does so much complexity evolve?</p>
| [
{
"answer_id": 42053,
"pm_score": 7,
"text": "<p>I think possibly the problem here is the way you're approaching the issue.</p>\n\n<p>You're considering <em>improvement</em> as anything that increases the abilities or complexity of the organism—that isn't necessarily what an <em>improvement</em> is thou... | [
{
"answer_id": 42063,
"pm_score": 4,
"text": "<p><strong>Evolution is simply a process of change.</strong> It is a change in trait values of populations over time. It results from four mechanisms: mutation, migration, drift, and selection. The first three lead to random change from one generation to th... |
42,273 | <p>On <a href="http://ericturkheimer.blogspot.com/2015/05/the-heritability-of-everything.html">his blog</a>, Eric Turkheimer writes:</p>
<blockquote>
<p>[T]aken as a number, a unit of analysis, heritability coefficients are
funny things to aggregate on such a massive level. What exactly are
we supposed to make of the fact that twins studies in the
ophthalmology domain produced the highest heritabilities? Should eye
doctors, as opposed to say dermatologists, be rushing to the genetics
lab because their trait turns out to be more heritable? No. Whatever
else a heritability may be, it is not an index of how "genetic"
something is. It is not, for example, a useful indicator of how
successful gene-finding efforts are likely to be. If nothing else,
differences in reliability of measurement are confounded every
heritability tallied here. My point is this-- although it's nice to
know that on average everything is 50% heritable, it's hard to attach
much meaning to the number itself, or especially to deviations from
that number, to the fact that eye conditions have heritabilities
around .7 and attitudes around .3. Having two arms has a heritability
of 0.</p>
</blockquote>
<p>As I understand this, one reason Turkheimer believes heritability coefficients are not an index of how genetic a trait is is that they are confounded by varying levels of measurement error. So, for example, maybe the relatively low heritabilities in skin conditions compared to eye conditions are because there is more measurement error in relation to skin conditions.</p>
<p>Turkheimer implies that there are other reasons why it's not appropriate to say a heritability coefficient is an index of "how genetic" something is. What are those other reasons?</p>
| [
{
"answer_id": 42280,
"pm_score": 6,
"text": "<p>Rather than discussing what heritability is not through wordy sentences, let's just talk about what heritability <strong>is</strong>. There are two \"types of heritability\":</p>\n\n<ul>\n<li><em>Heritability in the broad sense</em></li>\n<li><em>Heritabi... | [
{
"answer_id": 42445,
"pm_score": 3,
"text": "<p>Briefly, because remi.b gives a lot of good detail about this in his answer, (narrow sense) heritability is essentially a measure of how much of the phenotypic variance is explained by (additive) genetic variance. Phenotype (P) in an individual is the res... |
43,095 | <p>For me it seems reasonable that if I kept my gaze on a fixed point in a room with low light, a progressively brighter and better picture would appear before my eyes, just like a camera can see in the dark if the shutter speed is really slow, e.g. 4 seconds exposure. Why can't our brain do this trick as well (accumulate visual information over time)? Or is it a limitation of the eyes?</p>
<p><em>edit:</em></p>
<p>To further clarify what I'm after; I will show a concrete example from the world of photography (images taken from <a href="http://www.media-division.com/photoshop-tricks-solving-common-photography-problems-using-image-stacks/" rel="noreferrer">this website</a>).</p>
<p>Here is an example where we have a series of underexposed images - this would be what the brain receives:
<a href="https://i.stack.imgur.com/QaCQy.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/QaCQy.jpg" alt="Series of under exposed images"></a></p>
<p>Now, combining all of them with a simple add-operation reveals one image that has normal exposure.
<a href="https://i.stack.imgur.com/AH0yj.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/AH0yj.jpg" alt="Sum of all images equals one normal exposed image"></a></p>
<p>This seems like a simple trick for our powerful brain - surely it can add incoming signals?</p>
| [
{
"answer_id": 43100,
"pm_score": 7,
"text": "<p>For simplicity's sake, let's really reduce this to something like photography.</p>\n\n<p>A camera's aperture can stay open indefinitely, allowing the plate (or whatever is receiving and recording light) to \"collect and save the effect of photons\" over t... | [
{
"answer_id": 43097,
"pm_score": 2,
"text": "<p>What I believe you are referring to, is the phenomenon by which the camera adjusts light exposure by adjusting aperture. We can also do this, but it happens very fast. Go from a dark room to a brighter room and you will be blinded, but that effect soon su... |
45,942 | <p>A human encountering a tiger or a malaria plasmodium is likely to suffer, and the tiger/plasmodium is likely to gain from the transaction. Not necessarily a good example, and I am aware that a successful parasite avoids prematurely killing its host, but I can't see any fundamental difference.</p>
<p>Of course it's like pornography: "we know it when we see it". But is there a formal, generally-accepted distinction? </p>
| [
{
"answer_id": 45964,
"pm_score": 4,
"text": "<p>Good question.</p>\n\n<p>There is no fundamental difference between parasites and predators.</p>\n\n<p><strong>Ecological Interaction</strong></p>\n\n<p>In terms of <a href=\"https://en.wikipedia.org/wiki/Ecological_relationship\" rel=\"nofollow noreferre... | [
{
"answer_id": 45946,
"pm_score": -1,
"text": "<p>A parasite may or may not kill the host. It's basic motive is to constantly derive nutrition from the host. More a sort of one time investment and as an interest you keep getting the nutrition.\nWhereas a predator's motive is to kill the host to satisfy ... |
46,016 | <p>I'm trying to establish if it's required to add a NLS to Cas9 when expressed (or transfected) in a Eukaryotic cell. Several papers report using a viral NLS, but is it absolutely necessary? Could Cas9 be trafficked to nucleus without addition of a NLS?</p>
| [
{
"answer_id": 45964,
"pm_score": 4,
"text": "<p>Good question.</p>\n\n<p>There is no fundamental difference between parasites and predators.</p>\n\n<p><strong>Ecological Interaction</strong></p>\n\n<p>In terms of <a href=\"https://en.wikipedia.org/wiki/Ecological_relationship\" rel=\"nofollow noreferre... | [
{
"answer_id": 45946,
"pm_score": -1,
"text": "<p>A parasite may or may not kill the host. It's basic motive is to constantly derive nutrition from the host. More a sort of one time investment and as an interest you keep getting the nutrition.\nWhereas a predator's motive is to kill the host to satisfy ... |
49,209 | <p>How has evolution created our blood, lungs and the heart?</p>
<p>We can't exist without blood, which transports the oxygen to all areas of our body. However, the blood needs a lung, which gives it the oxygen to transport. The blood also needs something which lets it flow through the whole body, which are our veins. And in order to allow the blood to flow through our veins, an organ is needed to pump the blood, which is our heart. We also need a brain which controls all that, and the brain in turn needs the blood in order to function right.</p>
<p>Evolution makes very slow steps....."it just doesn't jump". So, How did evolution manage to create all that?</p>
| [
{
"answer_id": 49218,
"pm_score": 6,
"text": "<p>While others have addressed the big picture aspects of your question, I think it would be useful to look at the specifics. </p>\n\n<p>Have a look at the heart (or more accurately, the <em>hearts</em>) of the earthworm: <a href=\"https://i.stack.imgur.com/... | [
{
"answer_id": 49211,
"pm_score": 3,
"text": "<p>This is a good question, but it has a vast scope, as you're talking about the progression of millions of different living animals over hundreds of millions of years, none of which are still alive, so we have to make inferences based on what we observe in ... |
49,214 | <p>In the Krebs cycle, where do the hydrogens and electrons that NAD+ and FAD accept come from? It seems that citric acid only loses two hydrogens because it starts out with eight hydrogens and then becomes oxaloacetic acid, which has four hydrogens. </p>
| [
{
"answer_id": 49218,
"pm_score": 6,
"text": "<p>While others have addressed the big picture aspects of your question, I think it would be useful to look at the specifics. </p>\n\n<p>Have a look at the heart (or more accurately, the <em>hearts</em>) of the earthworm: <a href=\"https://i.stack.imgur.com/... | [
{
"answer_id": 49211,
"pm_score": 3,
"text": "<p>This is a good question, but it has a vast scope, as you're talking about the progression of millions of different living animals over hundreds of millions of years, none of which are still alive, so we have to make inferences based on what we observe in ... |
50,420 | <p>What was the first piece of work in computational biology? I'm ideally looking for a paper.</p>
<p>I am not interested in works that involve data management or data analysis but work that model biological processes through numerical simulations or numerical approximations of analytical results.</p>
| [
{
"answer_id": 50445,
"pm_score": 4,
"text": "<p>Another nomination, if you include infectious disease epidemiology as part of biology and hence computational simulations of epidemics as part of computational biology:</p>\n\n<p><a href=\"http://www.jstor.org/stable/2342553\" rel=\"noreferrer\">Measles p... | [
{
"answer_id": 50423,
"pm_score": 3,
"text": "<p>I don't believe you'll ever find the <em>first</em> work in bioinformatics (or computational biology, as you put it), however the field really <strong>began</strong> in the times of accumulating data about protein biochemistry. Computational biologists (b... |
50,599 | <p>I have a modest collection of insect specimens that I caught, prepared, mounted, and dried myself. I'm entirely an amateur collector, so my procedure may be causing me this trouble now, but here's how I preserved them.</p>
<ol>
<li>Killed in the freezer</li>
<li>Placed in a sealed container on a dry platform, with a 50% isopropyl alcohol solution under it. This lets the specimen thaw and remain moist, while the alcohol prevents rotting.</li>
<li>Kept in container for two to three days.</li>
<li>Stretched over foam and held in place with paper and pins.</li>
<li>Kept on stretching board for three weeks.</li>
<li>Placed in a consumer grade display box.</li>
<li>Stored in a dark, dry closet.</li>
</ol>
<p>It's been a while since I worked on this hobby, but I do like to pull the collection out from time to time and admire it. Today, I was surprised and disappointed to find that some of my best specimens have been turned to dust by a small caterpillar type bug. There are live bugs in my display case, eating my bugs!</p>
<p>I've had these for years without issue, and now I find this. What can I do about it? How can I keep this from happening again? Should my preservation procedure include some other step? How are they even surviving? There's no moisture in there at all!</p>
<p>I'd rather not put something toxic in my display case, as I like to take them out and examine them without the glass in the way. I don't want to be exposed to toxic things every time I look at them. I hope there's some effective, cheap, and safe thing I can do. I've become rather proud of my collection, but it's disheartening to have worms eating them before they've even eaten me.</p>
<p>Here's some pictures of the devastation:</p>
<p><a href="https://i.stack.imgur.com/pAAvf.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/pAAvf.jpg" alt="Bird's eye view."></a></p>
<p>That stain on the right used to be a specimen.</p>
<p><a href="https://i.stack.imgur.com/6f0N7.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/6f0N7.jpg" alt="Formerly a praying mantis."></a>
The big pile of dust there on the left used to be a praying mantis. I don't even know what the pile on the right use to be.</p>
<p><a href="https://i.stack.imgur.com/L0LUV.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/L0LUV.jpg" alt="Beetle missing insides"></a>
This beetle's entire insides have been eaten.</p>
<p><a href="https://i.stack.imgur.com/jkjDE.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jkjDE.jpg" alt="Horsefly is now dust."></a>
This horsefly looks like it was mounted a hundred years ago.</p>
<p><a href="https://i.stack.imgur.com/eYvng.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eYvng.jpg" alt="Butterflies and moths don't taste very good."></a>
Apparently moths and butterflies don't taste very good.</p>
<p><a href="https://i.stack.imgur.com/J2wJY.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/J2wJY.jpg" alt="The culprit!"></a>
The culprit! This little guy and his pals are responsible. You can see exoskeleton sheddings all throughout the other pictures.</p>
| [
{
"answer_id": 50619,
"pm_score": 5,
"text": "<p>I ran into the same issue when collecting bees in a hot, humid environment. As <code>arboviral</code>stated, freezing is a great way to help with the infection but keep in mind:</p>\n\n<ul>\n<li>It may not kill all of your pests</li>\n<li>It will not kee... | [
{
"answer_id": 50613,
"pm_score": 3,
"text": "<p>As @picapica says, these look like beetles of the genus <em>Anthrena</em>: museum beetles, furniture carpet beetles or something similar. I'd lean towards furniture carpet beetle (<em>Anthrena flavipes</em>) myself, but this isn't a species ID question.</... |
51,556 | <p>We heard this animal outside in Western Washington (Port Townsend area) during the late evening. I think it is a bird, but it honestly sounds sort of like some creepy woman singing or something. The audio is linked below. The sound (in the audio) was repeated for a long time at random intervals averaging probably every ten seconds. </p>
<p><a href="https://clyp.it/tzybty1w" rel="nofollow">https://clyp.it/tzybty1w</a></p>
<p>Anyone know for certain?</p>
| [
{
"answer_id": 51572,
"pm_score": 3,
"text": "<p>I asked the same question on another forum here: <a href=\"http://www.birdforum.net/showthread.php?p=3454684\" rel=\"nofollow\">http://www.birdforum.net/showthread.php?p=3454684</a>. </p>\n\n<p>It looks like another possibility is a <strong>barred owl</st... | [
{
"answer_id": 51563,
"pm_score": 2,
"text": "<p>My guess is an owl, possibly a great horned owl, which are found in the <a href=\"https://www.google.com.sg/search?q=owls+in+western+washington&gws_rd=cr&ei=IQnZV8GdMMLO0gT6gqCQAg\" rel=\"nofollow\">area</a> and can <a href=\"http://www.learner.or... |
52,046 | <p>I hope this is a good place to ask such question. I have to do some data analysis on RNA-seq data from human cells. I am currently searching for tools to help me with that. Specifically, I would need some tools to analyze the gene expression from the data. Something to help me plot the expression of selected genes in each fastq file and compare the differences in the expression with the possibility to export the results or some command line interface for scripting. Basically I need something where I can put a fastq file and perhaps also a human genome annotation file as input and get gene expression as output. I have looked at bioconductor and it's packages and on <a href="https://en.wikipedia.org/wiki/List_of_RNA-Seq_bioinformatics_tools">Wikipedia's List of RNA-Seq bioinformatics tools</a>. I suppose some of these tools have to be able to do what I need, but I have been unable to find out which one and how should they be used to achieve that. Could someone please give me some advice?</p>
| [
{
"answer_id": 52112,
"pm_score": 4,
"text": "<p>You will likely need a tool to \"map\" the reads on the reference genome.\nYou may find such a reference genome, together with annotations, here:\n<a href=\"ftp://ussd-ftp.illumina.com/\" rel=\"nofollow noreferrer\">ftp://ussd-ftp.illumina.com/</a>.</p>\n... | [
{
"answer_id": 52261,
"pm_score": 2,
"text": "<p>While I also agree @bli that R and Python (in particular <code>Bioconductor</code>) have more than enough packages for you to compare gene expression. You <em>shouldn't</em> align your reads with bwa or bowtie because they don't take introns into consider... |
53,313 | <p>Is there a lower limit to the difference in wavelength (colour) our eyes can detect? If so, is this consistent between individuals? Are there any other traits correlated with precise colour vision?</p>
| [
{
"answer_id": 54449,
"pm_score": 3,
"text": "<p>The eye really on can sense 3 colors, or to be more precise it only has three types color sensitive each of which detects a large range of wavelengths with no way to distinguish between them within the same cone. We only determine color by the different l... | [
{
"answer_id": 53472,
"pm_score": 0,
"text": "<p>First, it depends a lot of the brightness. And also, of the part of the spectrum: we have high accuracy between red-green (since 2 of the cone have close sensitiveness), and very few in deep red and violet (were mostly a single cone reacts).</p>\n\n<p>As ... |
53,328 | <p>Imagine you hit your foot at a table leg and it hurts a while or you got a tiny graze. Those injuries aren't an infection but could these things still be called an inflammation?</p>
<p>Is it necessary that in both cases cells are damaged to induce a cascade of hormones? Or with other words, is there always an inflammation when cells are damaged or is needed more?</p>
| [
{
"answer_id": 54449,
"pm_score": 3,
"text": "<p>The eye really on can sense 3 colors, or to be more precise it only has three types color sensitive each of which detects a large range of wavelengths with no way to distinguish between them within the same cone. We only determine color by the different l... | [
{
"answer_id": 53472,
"pm_score": 0,
"text": "<p>First, it depends a lot of the brightness. And also, of the part of the spectrum: we have high accuracy between red-green (since 2 of the cone have close sensitiveness), and very few in deep red and violet (were mostly a single cone reacts).</p>\n\n<p>As ... |
57,128 | <p>How forgetting things is helpful for the brain or the human body biologically? This <a href="https://www.google.co.in/url?sa=t&source=web&rct=j&url=https://www.psychologytoday.com/blog/mind-blender/201403/why-forgetting-the-past-can-be-good-thing&ved=0ahUKEwj41aGi1MjSAhWMtY8KHaoJBbwQFghaMAg&usg=AFQjCNFFycom7b3voykO4S9tVv62-a9kDQ" rel="noreferrer">web page</a></p>
<blockquote>
<p>After some moment of being rude, selfish, or weak, either we are able to put it behind us, or the person who suffered at the result of our imperfection moves on. The reason for this is our ability to forget about it. We forget not because we have an imperfect hippocampus (our brain’s memory organ); it's actually an evolved solution. The ability to lose information allows new information to come in that is more relevant, more pertinent to an ongoing reality. Forgetting allows us to update.</p>
</blockquote>
<p>and this Huffington post <a href="http://www.huffingtonpost.com/hale-dwoskin/the-benefits-of-forgettin_b_6117964.html" rel="noreferrer">article</a></p>
<blockquote>
<p>According to a study in Nature, our awareness is limited to only three or four objects at any given time. To be able to think at your highest level, you therefore must be very efficient at filtering out all of the background noise: Your racing thoughts, the ringing phone, your neighbor’s barking dog, and the list goes on.</p>
<p>The Nature study found that when participants were asked to “hold in mind” certain objects while ignoring others, there are significant variations in how well each of us can keep irrelevant objects out of our awareness.</p>
<p>The researchers concluded that our memory capacity is therefore not simply about storage space, but rather “how efficiently irrelevant information is excluded from using up vital storage capacity.”</p>
</blockquote>
<p>provide some backgrounds.</p>
| [
{
"answer_id": 57136,
"pm_score": 6,
"text": "<p><strong>Short answer</strong><br>\nIt has been shown that loss of long-term memories may enhance the retrieval of others. Short-term working memory is explicitly designed to be volatile and non-lasting. However, there are many other types of memories wher... | [
{
"answer_id": 57133,
"pm_score": 3,
"text": "<p>Memory is formed by building connections between nerve cells (i.e. neurons). These connections are called synapses. The synapses form a network between several (or tens or hundreds) of neurons, therefore giving us the ability to retrieve something we had ... |
57,145 | <blockquote>
<p>A recent study has provided evidence that two types of equine (horse) herpes viruses have an unusually broad host range. This fact supports which of the following statements?</p>
<p>a. The lytic cylce occurs in horses while the lysogenic cycle occurs only in other species.</p>
<p>b. The virus is transmitted from one host to another by mosquitoes.</p>
<p>c. In a population of horses, many of the individuals will become infected</p>
<p>d. Horses, rhinoceroses, and polar bear can become infected</p>
<p>e. In an individual horse, many different type of cells will be infected</p>
</blockquote>
<p>According to the answer key, the answer is D. My question is why isn't E also a correct answer? I thought host range means "the range of cells that can act as a host to a virus".</p>
| [
{
"answer_id": 57136,
"pm_score": 6,
"text": "<p><strong>Short answer</strong><br>\nIt has been shown that loss of long-term memories may enhance the retrieval of others. Short-term working memory is explicitly designed to be volatile and non-lasting. However, there are many other types of memories wher... | [
{
"answer_id": 57133,
"pm_score": 3,
"text": "<p>Memory is formed by building connections between nerve cells (i.e. neurons). These connections are called synapses. The synapses form a network between several (or tens or hundreds) of neurons, therefore giving us the ability to retrieve something we had ... |
57,356 | <p>My science textbook says this:</p>
<blockquote>
<p>Evolution should not be equated with progress. In fact, there is no real 'progress' in the idea of evolution. Evolution is simply the generation of diversity and the shaping of the diversity by environmental factors. The only progressive trend in evolution seems to be that more and more complex body designs have emerged over time. However, again it is not as if older designs are inefficient! So many of the older and simpler designs still survive [..] In other words, human beings are not the pinnacle of evolution, but simply yet another species in the teeming spectrum of life.</p>
</blockquote>
<p>I am not sure if I agree with this; after all, humans do seem to be more <strong>advanced</strong> than dogs. Many people have asked me why I thought this was true, so here is my answer: <em>Today, humans could wipe out dogs from Earth if they wanted, but you can hardly imagine a scenario in which dogs would do the same to humans.</em></p>
<p><em><strong>What am I missing here?</strong></em></p>
| [
{
"answer_id": 57454,
"pm_score": 5,
"text": "<p>I'm glad you've asked the question as it is a common layman misunderstanding.</p>\n\n<h1>Dog vs Human</h1>\n\n<p>Your example comparing humans and dogs is actually very central to the logical flaw that yields many to equate evolution with progress.</p>\n\... | [
{
"answer_id": 57360,
"pm_score": 2,
"text": "<p>When you say, humans are more advanced than dogs, from what perspective are you saying that from? Is it in the capacity to use intelligence, to build and create, to do the math, to climb trees? If it is any of these, you are right: humans are better at us... |
57,479 | <p>As far as I know, humans have 23 pairs of chromosomes, each one which contains a particular amount of genes. But in the "last" pair, men have a XY pair chromosome, and women have a XX pair chromosome. Does the missing "leg" of the XY pair make men to have fewer genes than women, and if so, how many genes do each sex have?</p>
| [
{
"answer_id": 57480,
"pm_score": 6,
"text": "<p>It is true that the Y chromosome is shorter than the X chromosome and that there are more genes on the X chromosome.</p>\n\n<blockquote>\n <p>Do men have fewer genes?</p>\n</blockquote>\n\n<p>One could (mis)understand three things in the expression \"num... | [
{
"answer_id": 57501,
"pm_score": 0,
"text": "<p>Note - this is a very simple way to present things, and don't have the ambition to be a biology thesis. </p>\n\n<p>Men do not have fewer genes than women, but fewer allels (variations of a gene); the allels on the x-y chromosome pair are not necessarily t... |
58,769 | <p>Inbreeding increases the risk of getting two identical recessive genes, alleles, that cause a disease which wouldn't have been activated with mixed genes. That's how I understand it anyway. But I sometimes read and hear that inbreeding among humans also causes decreased intelligence, especially emotional and social intelligence. Is there any support for such claims, and if so how does that work?</p>
| [
{
"answer_id": 59018,
"pm_score": 4,
"text": "<p>There is indeed evidence that inbreeding in humans lowers intelligence of offspring. </p>\n\n<blockquote>\n <p>In summary, our comprehensive assessment revealed that parental consanguinity and degree of inbreeding was significantly associated with depres... | [
{
"answer_id": 59022,
"pm_score": 2,
"text": "<p>Inbreeding, in nature at large, has one primary effect, as you said. It increases the chances of two copies of harmful, recessive alleles. Consequently, offspring are much more likely to suffer from genetic and/or degenerative diseases.</p>\n\n<p>As for i... |
59,062 | <p>Some sources say that gametes are haploid, some say that they are diploid.</p>
<p>I'm confused.</p>
| [
{
"answer_id": 59111,
"pm_score": 3,
"text": "<p>Actually there is some confusion here, and that's quite excusable, because it's extremely common reading that <strong>monoploid</strong> and <strong>haploid</strong> are synonyms and have the same meaning. However, they are different terms. According to H... | [
{
"answer_id": 59063,
"pm_score": 1,
"text": "<p>Don't get confused by the number of chromosomes. Haploid refers to 1 set of chromosome, diploid refers to 2 set of chromosomes, triploid means 3 set of chromosomes. They don't represent the numbers of chromosome present on a set. </p>\n\n<p>We human being... |
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