archive-org.com » ORG » B » BIOLOGY-ONLINE.ORG

Total: 791

Choose link from "Titles, links and description words view":

Or switch to "Titles and links view".
  • Biology-Online • View topic - The evolution of facilitation and semelparity
    to you they are the characteristics of an r selected species Large number of offspring low amount of parental investment This is the most optimal strategy for an annual species as due to the life cycle there is a little opportunity for repeated reproduction and b Little opportunity for parental care All of this deduced from just the fact that A is semelparous If the environment is highly variable investment in a small number of offspring as in iteroparity will not be optimal due to the risk of bad years costing the life of the parent and thus losing any offspring she might have produced in the future if she had not died Thus the fitness of the parent is lowered as a result Remember if she had managed to produce these offspring she will have been more successful in terms of fitness Thus semelparity is better as the parent can now reproduce when conditions are temporarily favourable producing a large brood and exploiting this environment allowing the best chances of offspring survival hence maximizing fitness Fecundity future reproduction vs offspring current reproduction There are costs to both iteroparity and semelparity This is illustrated above For a semelaprous species the cost is fecundity If one dies while reproducing then one can never reproduce again in the future Simple For an iteroparous animal with repeated reproduction the cost is in terms of current reproduction If you wish to be able to survive to reproduce again in the future you must necessarily not risk all of your fitness for the current brood For example if you were say a cat rearing a litter you must decide how much milk you are willing to give to your kittens Giving too much could endanger your life by weakening you physically At some point you

    Original URL path: http://www.biology-online.org/biology-forum/about41352.html (2016-02-17)
    Open archived version from archive


  • Biology-Online • View topic - Evolutionary psychology
    purpose of fulfilling a specific need American Heritage Science Dictionary 1 inherited emotion has a genetic basis 2 tendency while perhaps even strong tendencies emotions are not irresistible 3 reaction to its environment emotions are triggered by environmental cues 4 purpose of fulfilling a specific need emotions are strategic and facilitate behaviors that were adaptive in the ancestral environment Wouldn t some people benefit from knowing that their emotions especially emotions that push them toward destructive and self destruction actions are simply evolved mechanisms designed for a long gone ancestral environment Like outdated computer software that with certain environmental cues generates output that may or may not still be in their best interests Your thoughts Reply with quote Hrushikesh Hrushikesh Posts 5 Joined Tue Nov 11 2014 12 01 am Thu Dec 04 2014 8 58 pm I don t have an expertise in this area but have some guesses to offer I see that it is a possibility that such useless or harmful instincts prevail for some time but it is also likely that such instincts may undergo mutation mutation in its broader sense and selection to establish useful replacements Longer the time since becoming not of use more the chance that some useful mutation takes it over Reply with quote Korrhil Korrhil Posts 1 Joined Mon Dec 22 2014 11 35 am Mon Dec 22 2014 4 22 pm Yeah some of our instincts are well outdated But if u look it on evolutionary time scale that long gone ancestral enviroment is actually not that far behind tho Time our race has spent in modern culture is far from enough for evolution to eliminate some of our unusable inherited psychological mechanisms Personally i think alot of modern psychiatric disorders arise from conflict between our out dated instincts and

    Original URL path: http://www.biology-online.org/biology-forum/about39756.html (2016-02-17)
    Open archived version from archive

  • Biology-Online • View topic - Mutuation saturation at a particular locus
    2014 8 43 pm Hi guys newbie here but no less enthusiastic Quick question in regards to mutation saturation at a locus What is it in the context of comparing two lineages I know that it occurs most in hyper variable regions like in mitDNA but what effect does this have on comparing two species in the context of molecular phylogenetics Thanks in advance Post a reply Jump to Select

    Original URL path: http://www.biology-online.org/biology-forum/about41348.html (2016-02-17)
    Open archived version from archive

  • Biology-Online • View topic - Can human body hair disappear as a result of... clothing?
    we ve created clothes which are a better way to control body temperature So what will happen to human pelage in future generations Theory 1 Humankind will probably be hairy until its end because it doesn t have an impact significant enough to trigger an evolutionary response Wearing clothes when you already have hair doesn t kill anybody Theory 2 At one point humans will probably stop growing body hair because of an evolutionary mechanism that will influence mutation and cause our offspring to not have hair follicles because they are not necessary or helpful anymore Which one is closer to reality scientific knowledge Reply with quote Cat Cat Posts 635 Joined Thu Feb 14 2008 7 40 pm Re Fri Oct 31 2014 2 02 am jplr wrote Theory 2 At one point humans will probably stop growing body hair because of an evolutionary mechanism that will influence mutation and cause our offspring to not have hair follicles because they are not necessary or helpful anymore Point 1 Mutations are random They do not select to happen when they are helpful Point 2 Evolutionary mechanism is called natural selection What it means if none of the hairy individuals are unable to find mates at some point only then hair within population would disappear Point 3 As of right now we are fully capable of growing hair all over our bodies This does not happen only because of hormones we express Therefore changes in hormones influence hair growth not absence presence of hair follicles Point 4 Going with your argument closing has nothing to do with hair growth because females do not have beard while males do independent of clothing Reply with quote Hrushikesh Hrushikesh Posts 5 Joined Tue Nov 11 2014 12 01 am Re Can human body hair

    Original URL path: http://www.biology-online.org/biology-forum/about41052.html (2016-02-17)
    Open archived version from archive

  • Biology-Online • View topic - Dr. Jobe Martin Arguments
    have more evidence than you could go through in your lifetime The only trouble is that it is not a picture book and you need to use your brain to put the pieces of the puzzle together Because for every billion animals that have existed there are about 5 that have left evidence of there existence Basically it is like trying to show a picture of puzzle that has a billion pieces but you only have a few thousand Now most of the ones you have go together so you can see bits of the picture but the rest you need to guess at But you know what I bet if I showed even you a digital photograph that could easily have a billion pixels but one in which they were all white except for a few thousand of them I bet even you could probably make out what it is a picture of AND THAT is how we know evolution to be true Because enough of the bits have been found and put together to paint enough of the picture that we have a good sense of what the picture actually looks like You don t need evidence of every single stage and in reality there isn t evidence because it is incredibly rare for an animal to be trapped in the perfect conditions that allow it to be found as a fossil So to your point arguing is useless with someone who is completely out of touch with REALITY and thinks it is more possible that man was made of dirt and woman was made of man s rib That bedtime story is the only one that requires faith it almost makes Harry Potter sound more plausable You KNOW nothing of evolution you may think you do but you don t because if you did you would no there are not answers to every question for a process that has taken billions of years But really I find it hard to understand how you could not believe since I am guessing you believe in magic and that all the animals just appeared just as they are and that man is the one who must of hunted the dinosaurs to extinction and that s why they are not around anymore or don t you believe in dinosaurs I suppose if you believe the bible then you don t must be one of god s tricks And you must also believe than an old guy built a big boat and put a pair of every single animal on earth into it and I m sure you have lots of evidence for that one to go with all your jesus evidence But in the end it doesn t matter you don t need to believe in evolution and it doesn t matter that I only believe in reality because we are going to end up in the same place and chances are in 10 000 years there will be absolutely zero evidence that either one of us ever existed and I am fine with that ANd since I am sure that scares you then you can keep telling yourself you are going to go to heaven just like that group of young men convince themselves when they flew planes into the world trade center You can do anything as long as you believe Reply with quote solong4now solong4now Posts 3 Joined Wed Jun 13 2012 6 58 am Sat Aug 25 2012 5 14 am I m sorry but I just watch a bit more of this Jobe Martin DDS that s dentist and his is not even an argument All he is really saying is I can t wrap my head around how this could have evolved so here is what I think must have happened that grand designing who has absolutely no skill as an engineer or designer slapped these animals together and then jerry rigged everything in true Rube Goldberg fashion so that it all works but in the most remarkably convoluted way AND he did this by magic That s his argument I don t know so it must have been magic or some other word you want to use to describe making an animal appear out of essentially nothing Creation is just another way of saying I don t know I don t understand and I don t care But please stop making yourself look like such and idiot by arguing god must have done it I am getter pretty tired of people toting the bible and scriptures as some kind of proof of anything and then try to argue actual evidence is proof of nothing Defend evolution I don t have to it s actual and there is plenty of actual evidence but just try to defend creation If you know for a fact that there is a higher power then good for you I don t know that But I am very confident that the god or gods that are written in any book including the bible are only made up They have come strictly from the imaginations of man And the only reference anyone can ever come up with as any proof of god is those books that are made up from the imaginations of man So if you believe in a higher power great but you can not use any book or anything written down as an example or proof of anything other than that man has an incredible imagination There is no documentation that is evidence of god And even the documentation of Jesus is pretty damn sketchy Reply with quote green3611 green3611 Posts 1 Joined Sat Aug 30 2014 8 41 pm Sat Aug 30 2014 9 26 pm Hi I don t know how old the posters here are or the age of the girl who started the argument the girl referred to in the first post of the thread I am a convinced Christian who goes to a

    Original URL path: http://www.biology-online.org/biology-forum/about23545.html (2016-02-17)
    Open archived version from archive

  • Biology-Online • View topic - Theories - Origin of Life
    in Ch 8 I was quite impressed by the theory it is logical However I don t know if there is much evidence for it Reply with quote canalon canalon Posts 3909 Joined Thu Feb 03 2005 2 46 pm Location Canada Thu Sep 25 2008 3 36 pm It is Cairn Smith but if I remember some people that know their chemistry better than I do have been able to point multiple flaw in that otherwise interesting and elegant theory Reply with quote chilipanda chilipanda Posts 2 Joined Sat Sep 20 2008 5 30 pm Thu Sep 25 2008 5 40 pm Carins smith has two books about the clay theory seven clues to the origin of life and genetic takeover i believe seven clues is very well and easy written in a sherlock holmes style that is somewhat enjoyable to read genetic takeover is much more in depth but has been given very positive reviews i havent had time to read either myself but i plan on finishing seven clues when i finish my paper Reply with quote Alberts Alberts Posts 16 Joined Thu Jan 08 2009 3 39 pm Wed Mar 04 2009 3 04 pm I think you d better write about protein first and nucleic acid first paradox The research articles of Joyce Orgel Eigen and Dyson can be an useful reference for you Best wishes Reply with quote mcar mcar Posts 493 Joined Fri May 27 2005 8 58 am Location Pilipinas a k a Three Stars and a Sun 300 000 sq Km Fri Mar 06 2009 7 42 am I remember some Biblical biogenesis spontaneous physico chemical and cosmozoic theories alextemplet wrote At my university a group of students recently conducted experiments in which RNA was found to spontaneously isolate itself inside protective spheres of phospholipids I ll have to see if I can get a copy of the research paper they think this could lead to explaining the formation of the first cells I have thought if they re viruses but since you have said phospholipids my thought lead me to a true cell It just reminded me of some questions like what made the certain elements to react with one another and form such first biomolecules of life or perhaps their interactions were spontaneous indeed Reply with quote MrMistery MrMistery Posts 6832 Joined Thu Mar 03 2005 10 18 pm Location Romania small and unimportant country Sat Mar 07 2009 5 52 pm by the way alex i hope your peers published their results cause if not jack szostack beat them to it http www nature com nature journal v4 07018 html Reply with quote futurezoologist futurezoologist Posts 131 Joined Tue Jun 10 2008 12 21 pm Location Western Australia Panspermia Wed Mar 11 2009 9 39 am I am assuming you mean how it started and the above posts pretty much sum it up but if you mean where it started youve got panspermia hypothesis life came from another

    Original URL path: http://www.biology-online.org/biology-forum/about14351.html (2016-02-17)
    Open archived version from archive

  • Biology-Online • View topic - Theories - Origin of Life
    that you might be missing some pieces is that such an extraordinary claim I m not making a strong statement here I m defending an obvious possibility And If you still demend the almighty rigorous evidence I can only refer you to the extracts from the article I posted before again http www newyorker com reporting 2010 ntPage all selective reporting is everywhere in science We cannot escape the troubling conclusion that some perhaps many cherished generalities are at best exaggerated in their biological significance and at worst a collective illusion nurtured by strong a priori beliefs often repeated Such anomalies demonstrate the slipperiness of empiricism We like to pretend that our experiments define the truth for us But that s often not the case Just because an idea is true doesn t mean it can be proved And just because an idea can be proved doesn t mean it s true When the experiments are done we still have to choose what to believe Reply with quote Nick7 Nick7 Posts 23 Joined Tue Nov 08 2011 10 21 pm Re Theories Origin of Life Sat Mar 31 2012 1 17 am Wbla3335 canalon I referred to you as third people throughout the post sorry It s not the sign of disrespect I was just trying to squeeze everything in one post Sorry again Reply with quote AstraSequi AstraSequi Posts 102 Joined Fri Jan 27 2012 6 14 am Re Theories Origin of Life Sat Mar 31 2012 7 09 am I ll make a few comments since this was a separate conversation I m not replying to everything though and I probably won t make another large scale response here after this one Unless I get tempted anyways Yes there is absolutely zero chance for something to happen if the necessary preconditions are absent And you don t need any rigorous mathematical proof just go to you kitchen and make an omelet without eggs You most certainly do need a rigorous mathematical proof to show that it is impossible to make matter from something else You said there is absolutely zero chance for something to happen if the necessary preconditions are absent my emphasis This is a truism because of the word necessary which implies an absolute requirement However you cannot specify that the preconditions are necessary without mathematics I assume you are including in your statement the claim it is impossible to create matter This definitely does have to be mathematically proven in fact it s been done and shown to be possible E mc 2 from energy and virtual particles from nothing I recognize that your statement is actually allows for the use of non egg matter as well but I m assuming you intended to make the stronger argument which I just replied to If you allow matter there is no reason why you could not take other foods break them down at the molecular level and reassemble them into an omelet It s not possible with current technology but it is possible in theory if you like rigorous mathematics I can offer you some consider Gödel s incompleteness theorem Simply put it states that the system can not be objectively evaluated from within the system I think the incompleteness theorem says quite a bit less than you would like it to It is a theorem about mathematical systems and says that all consistent mathematical systems contain some statements which are true but unprovable within the system I am not a mathematician or physicist so I am willing to be corrected but it seems that you are adding the premises that 1 the universe or reality is a mathematical system 2 certain specific postulates are unprovable within this system the theorem does not say that all postulates are unprovable and 3 we do not have any way to leave the system or access anything outside of it I d love to step out of the anthropic principle but then I m going to have to argue about biology with an evolutionary biologist and becoming a kamikaze has always been the last item on my things to do before I die list And it s not that a biologist s atheistic views are right or wrong It s just he is a pro and I m not I m not sure what you re trying to say I think you re making a faulty generalization though not all biologists or even close to all are atheists So being a resident of only this universe knowing nothing about what s outside of it in space and time and considering only anthropic principle for the sake of this particular argument I say that unguided and guided creation of our universe are equally possible So am I guilty of the selection bias here The anthropic principle is about selection bias I agree that it says nothing about the likelihood of a creator or creators I was only trying to point out that a fine tuning argument which you seemed to be making cannot distinguish between a creator and a many worlds interpretation Second I m not sure about claiming the two are equally possible Just because there are two possibilities does not necessarily mean that the probability is 50 since it should be possible to interpret information about any creator from the structure of our universe You might find this link interesting although I m not really sure whether it s related http lesswrong com lw mm the fallacy of gray It also feels like you ve also chosen an arbitrary way to divide up possible causes for the universe If I change the statement to Either the universe is a quantum fluctuation or it was caused by a nonrandom but unintelligent event in some other universe or it was created do these now all have a possibility of 33 But then the likelihood of a designer would be lower than before Since no new knowledge has been gained this is a contradiction Reply with quote AstraSequi AstraSequi Posts 102 Joined Fri Jan 27 2012 6 14 am Sat Mar 31 2012 7 09 am Nick7 wrote AstraSequi wrote Nick7 wrote Evolution doesn t really seem to falsify creation it falsifies the meaning you put into the word creation the way you believe it should ve happened if it were true I don t think this makes sense The only thing that you can falsify is a hypothesis I ll allow you to refute your own statement Here AstraSequi wrote there is no way to falsify the hypothesis that our universe was created by highly advanced aliens The two statements are consistent I did not say that all hypotheses can be falsified specifically unfalsifiable hypotheses cannot be falsified The point was that the word falsify only refers to hypotheses you cannot falsify a meaning In mathematical terms the set of all falsifiable statements is a strict subset of the set of all hypotheses Of course I was not saying that the alien hypothesis I proposed is unfalsifiable in principle but that we cannot do it based on our current knowledge AstraSequi wrote So you understand that proving evolution false would not mean that creationism were true since the two are separate things It is possible for both to be true as long as you don t insist on interpreting your scripture literally or for neither to be true although I see no need to publically endorse a position on that here since it s not relevant to this argument So broadly speaking can you really seriously create a scientific hypothesis explaining how blind the blind watchmaker really is without a ton of assumptions and axioms I don t understand The blind watchmaker generally refers to evolution so if we wanted to explain something more about evolution we would update the theory itself rather than try and invent a new theory to explain it AstraSequi wrote Nick7 wrote Scientific method works well with the evidence which supports purely mechanistic and consistently replicable natural phenomena The scientific method works well with consistently replicable phenomena As long as causality exists and remains consistent the scientific method will work What if the causality exists but it is not consistent What if the causality exists but it is not consistent AND it s beyond observable reality I assume that these are not rhetorical questions For the first question if causality exists but is not consistent and is not probabilistic either then the scientific method does not apply to that circumstance However we have not observed causality to be inconsistent in any way before so we can infer that it is consistent in most if not all cases For the second question it would again not apply but we wouldn t even know about it anyways because you specified that we can t observe it I m not sure where this question is intended to lead but I ll point out that if you want to draw any conclusions based on it you would first have to determine that something really is unobservable AstraSequi wrote The probability of bias or error in a single study is much higher than the probability that a supernatural force exists times the probability that this force enables telepathy over long distances times the probability that it is occuring in this circumstance times the probability that nobody else would have found rigorous evidence for it even though it actually existed This is where you get the phrase extraordinary claims require extraordinary evidence That being said a possibility Sure the only impossibilities are those that have mathematical proofs behind them However the probability is so low given our current state of knowledge about how the universe works that it is not reasonable to think that it might be true The probability higher than probability times the probability The use of the dice and probabilities is getting completely out of control I m getting a feel that we were discussing the game of Craps or something And that is sufficient reason to dismiss the argument The point is that for the claim to be true it would require several other highly improbable claims to also be true and the probability of all of these claims being true is far lower than that it is the product of all the probabilities The claim has an incredibly low prior probability based on other evidence which is not directly related to the experiment but which is still relevant Sheldrake didn t take his research material from a thin air The occurrence the he studied has been observed for generations So it s not exactly the case of nobody else would have found the evidence it s the evidence itself that triggered Sheldrake s attention It has not been observed under conditions that screen out bias For example when you run actual blinded and or otherwise controlled experiments testing psychic phenomena you get far more negative results than positive And of course small numbers of positive results are unsurprising in statistics with the exact proportion depending on what your p values are If dogs don t empress you try homing pigeons Every possible experiment to pinpoint what physical senses they use to get to a loft from great distances up to 1800 km has been done frosted lenses for sight anesthesia and isolated containers to deprive a pigeon from outward journey info use of magnets and release in the spots with magnetic anomalies to affect a possible internal compass navigation etc etc etc If you put ALL the results together you will see a picture that looks either mixed or negative or inconclusive There is no rigorous evidence that would allow us to state without a shadow of a doubt what physical senses homing pigeons are exclusively relying on I did not say that anybody necessarily knows the answer to everything only that some explanations are more likely than others What if there are missing elements in this picture That s why I used quantum entanglement as an example when you see the effect but you have NO idea what the cause of it is by definition We don t know what the cause is because we haven t figured it out yet There is no definition of quantum entanglement that involves not understanding the cause as an intrinsic part of the phenomenon However IF only quantum entanglement were not as mechanistic and replicable as it is you would ve rejected it too because given our current state of knowledge about how the universe works the principle of locality in physics is supposed to work everywhere you look No it is not supposed to work everywhere based on our current knowledge Our current knowledge since the discovery of quantum entanglement is that the principle of locality may work everywhere and it may not Secondly science does not care about the term mechanistic which is a philosophical term and not a scientific one but only replicable But again what if just like with quantum entanglement we can t quite connect all the ends together for the same reasons the invisible elements in the equation extraordinary claims require extraordinary evidence If you continuously failing to complete a jigsaw puzzle and I m suggesting that you might be missing some pieces is that such an extraordinary claim I m not making a strong statement here I m defending an obvious possibility No it is not an extraordinary claim However it is an extraordinary claim that particular pieces are missing out of the huge number of pieces that could be and that is what you seem to be doing selective reporting is everywhere in science We cannot escape the troubling conclusion that some perhaps many cherished generalities are at best exaggerated in their biological significance and at worst a collective illusion nurtured by strong a priori beliefs often repeated Such anomalies demonstrate the slipperiness of empiricism We like to pretend that our experiments define the truth for us But that s often not the case Just because an idea is true doesn t mean it can be proved And just because an idea can be proved doesn t mean it s true When the experiments are done we still have to choose what to believe And yet science is still better at predicting the world around us than any other method tried to date Reply with quote JackBean JackBean Posts 5694 Joined Mon Sep 14 2009 7 12 pm Re Theories Origin of Life Fri May 04 2012 7 58 am Reply with quote JorgeLobo JorgeLobo Posts 424 Joined Mon Nov 17 2008 12 12 am Sun May 06 2012 10 17 am very sophomoric Reply with quote JackBean JackBean Posts 5694 Joined Mon Sep 14 2009 7 12 pm Sun May 06 2012 8 07 pm I m sorry Reply with quote TheMatrixDNA TheMatrixDNA Posts 14 Joined Sat Sep 10 2011 9 09 am Location New York USA Amazon Brasil Website Re Theories Origin of Life Fri Aug 03 2012 11 35 pm scottie wrote Continuing on with the problem ID has not addressed As I stated in my last post They are shying away from the obvious implications of what design means Design is always the product of a purpose the Designer has in mind Ok In my opinion this is the most instructive thread in the Internet for those that are interested in the question of theories about origin of life It seems to me that this thread is death abandoned and I can t understand it because this question wouldn t have an end till the day that scientifically someone prove how life has emerged The normal behavior here I think should be everyone trying to reinforce his her theory bringing on more evidences while bringing on new evidences that deconstruct the other theories Then this thread must have no end because everyday the news are showing new facts that can be used as positive or negative evidence to the current theories I had driven for a new theory of origins of life and even the universe when I was living in Amazon jungle and observing the systems that composes that biosphere and inquiring how must be the state of the world in its astronomic atomic and even the dimension of quantum fluctuations aspects that has produced our kind of life Of course my goal now must be testing the whole theory against real facts But I and the scientific enterprise has no the necessary tools for doing it just now Then what I can do with this theory The same others are doing here searching more thoughtful brains for doing a rational scrutiny of this theory while showing the news about facts that are evidences in favor and showing evidences that I think does not fit in another theories Introducing the people to a new big theory which requires a change of his her world vision is a difficult task Maybe only high intellectuals individuals with open minds that are retired and has time for spent here like Scottie could invest attention in your theory and debating it with you The fundamental requirement is that you can communicate it in a language understandable and that your theory makes same sense in the light of modern known facts For instance we had a poster here Leopol with two problems poor Google translations from Russian a lack of evidences and a world vision that is not tasteful But it is not justice and intellectually productive rejecting Leopol s theory we must deal with the details giving him the opportunity to advocate his world vision till he can not resisting anymore for lack of positive evidences same thing I think must be the reactions about my theory called The Universal Matrix DNA of natural Systems and Life s Cycles I am reading the whole thread it is a lot of stuff 45 pages When finishing everything I will begin

    Original URL path: http://www.biology-online.org/biology-forum/about14351-528.html (2016-02-17)
    Open archived version from archive

  • Biology-Online • View topic - Theories - Origin of Life
    by the blood stream Most of these small particles travel from the intestines to the liver which filters and converts the food into nourishment that the blood stream delivers to the cell How these nutrients pass into the cell of course is another area we are not even going to go into for now So the obvious question is Which came first The genes that code for the proteins using the amino acids that the body can make OR The genes that codes for the entire digestive tract that provides the cell with the amino acids that body can t make but which the body cannot do without Isn t it obvious that that the whole show has to be in place before any of these individual parts can functionally operate But of course the obvious is not acceptable Instead we have these doctrinal statements promulgated with a religious fervour and any dissent from that view is considered heretical The problem with all these just so stories is that they fall apart when the detail is examined Wouldn t it be nice to see some real science showing how Natural Selection produces a gene But that s hoping for too much after all what has science got to do with a good story This whole idea gets more farcical when we consider what the latest research on genes throws up That however is better left for another time Reply with quote Luxorien Luxorien Posts 55 Joined Fri Jan 20 2012 1 27 am Wed Sep 19 2012 2 55 am Let me see if I ve got this straight Someone says to you beneficial mutations exist Example antibiotic resistance And your response is this bacterium got antibiotic resistance from lateral gene transfer therefore beneficial mutations do not exist That s like saying the grocery store couldn t possibly be selling DVDs because Best Buy sells DVDs In order to demonstrate that mutation is not responsible for antibiotic resistance you would have to go through all cases of antibiotic resistance and show how lateral gene transfer is the cause in each and every one of them A much better approach would be to look for papers which detail the spontaneous mutation of antibiotic resistance in the lab If you fail to find such papers that would be an indication that such mutations do not exist It took me about thirty seconds to find such papers I m not sure how many you require but logic says even one is enough to invalidate your argument I ve selected three to reference The abstract for the first one can be found here http www ncbi nlm nih gov pubmed 17184282 Unfortunately the full text is not available online at least not that I could find but the abstract gives a good idea of the content This article reviews the current research on mutations which confer antibiotic resistance It acknowledges that horizontal gene transfer is responsible for the spread of many mutations but also references many instances where antibiotic resistance has arisen as the direct result of mutation I was able to get a copy of the second source through my public library s subscription to EBSCO It s an American Scientist article from 11 6 06 called Free Upgrades Unfortunately The article describes a study where the researchers took samples of bacteria from people infected with M tuberculosis They did this at two different points in time once early on in the infection and then again later when the bacteria had had time to mutate inside the person s body They found mutations that conferred antibiotic resistance Okay you might say but what if the patients picked up some resistant bacteria somehow Those bacteria could have spread the resistance to them Not only did antibiotic resistant bacteria show up out of nowhere in the patients they also showed up in the lab Researchers started with normal M tuberculosis and exposed them to the antibiotic They were easily able to produce several antibiotic resistant strains I intended to present this simply as an example of beneficial mutations but it coincidentally contradicts your assertion that antibiotic resistance always comes at a price The whole point of this study was not to demonstrate that mutations can cause antibiotic resistance that s well established and they completed that task only incidentally as part of their methodology but to see if antibiotic resistant strains evolved in vivo are as hardy as non resistant ones They found that in many cases they were Now I realize that citing papers which are not freely available online might seem like kind of a cop out so here s one that is available in full text http aac asm org content 44 7 1771 short Again the ability of mutation to cause resistance is taken for granted the focus of the article is on the technicalities of measuring mutation rates But there are still copious examples in this article of bacteria acquiring resistance through mutation These mutations have been observed clinically as well as in the lab Researchers can actually induce these mutations to order They can cook up any resistance they want using nothing more than their knowledge of mutation rates and the rapid reproduction of these organisms I will mention something else about the costs of resistance Though the American Scientist article indicates that there is not always a cost I don t mean to imply that there is never a cost Of course there are costs This is what I have been saying all along the terms advantageous and deleterious are highly relative They depend almost exclusively on context A bacterium living in an antibiotic free environment will probably not be as successful if it has a resistance mutation But as soon as antibiotics enter the environment suddenly it s a stud out reproducing all its fellow bacteria That is whole point of the combination of random mutations with directional selection one fuels the variation on which the other acts And steady mutation rates mean that even alleles which are eliminated from the population can pop up again later You are somewhat correct to point out that clinically we can never be sure that a mutation has arisen because the conditions are not controlled But many of these cases of resistance mutations occur in the lab These are cultures that are carefully kept from contamination No lateral gene transfer is possible in these situations The only possible argument left to you is to contend that these variants are not arising spontaneously but were always there hidden in the bacterial colonies in such small numbers that they were undetectable until exposure to antibiotics brought them roaring to life If that is indeed your argument then I have two challenges to offer 1 If mutation cannot cause antibiotic resistance then why do mutagens increase the speed with which resistance conferring variants arise 2 If these variants exist in such small numbers and they get no benefit from their antibiotic resistance until an antibiotic is introduced to the environment then how do they survive for so long and occur so frequently Wouldn t their relative disadvantage small numbers increase the likelihood that they would by chance fail to reproduce and thus remove their alleles from the population I mean we might expect that some would survive by chance but why is it that scientists can generate antibiotic resistance under controlled conditions in literally any population of bacteria they decide to test How do you account for that without steady mutation rates Edited to add a third question how do these preexisting alleles for antibiotic resistance elude researchers who create pure strains from a single bacterium and even sequence the DNA of that bacterium to ensure that the allele is not present in its genome To wrap up your assertion that bacteria never get antibiotic resistance from mutation is astounding given the abundance of evidence to the contrary You seem very concerned about the latest research but the fact is that we ve known about these beneficial mutations for decades The latest research is way beyond that investigating the details of how often these mutations occur what other effects they have on the bacteria how the mutations spread once they are introduced etc Reply with quote Luxorien Luxorien Posts 55 Joined Fri Jan 20 2012 1 27 am Re Theories Origin of Life Wed Sep 19 2012 3 23 am scottie wrote This is not exactly correct and at least 5 years out of date but let s stick with it for the moment I m not touching this trollbait with a ten foot pole lol scottie wrote Wouldn t it be nice to see some real science showing how Natural Selection produces a gene I m not interested in debating the origin of genes with you As I said previously I m only concerned with the issue of beneficial mutations However you might be interested in watching if you haven t already What Darwin Never Knew It has some good visuals of the complexity of genomic interactions The simple answer to your question is that genes are legos made of legos Nothing is created de novo it s all built modularly Do a Google search on gene origins Reply with quote scottie scottie Posts 214 Joined Tue Apr 12 2011 9 41 pm Re Theories Origin of Life Thu Sep 20 2012 4 13 pm Luxorien For the sake of clarity and I have stated this before and will probably have to continue ad nauseam My position is not that random mutations do not happen They do Does NS act upon random mutations Yes I believe that may also happen In other words does evolution change over time happen Yes However Does this mechanism account for species change let alone the Origin of Species remember this is the subject of this thread I argue NO Aside from a lot of adolescent rhetoric not necessary from you I see no evidence Now I have also clearly stated about14351 480 html There are random mutations that rearrange the DNA of the cell These mutations are invariably the result of copying errors breakdown in regulating functions like error correction and DNA damage from environment like from chemical or UV radiation sources There are also more mutations in DNA by orders of magnitude as a result of regulated cell processes than those that are random in nature The random mutations that do occur are invariably deleterious to the organism and are quite naturally the subject of intense study to solve or prevent health problems like cancers I went on to state not to you The point I make is this The reality is that most genetic changes occur as a result of cellular processes in response to stress damage and copying errors and are rectified in various ways I have not taken account of the developmental changes that occur while most other mutations which for some reason not corrected are deleterious to the organism I haven t even begun to talk about transposons and their part in genome restructuring All these processes are under the control and regulation of the cell as it responds to stress and the maintaining of it s own equilibrium In the light of all this actual evidence and with respect not logic that you appear to rely upon what does Natural Selection actually have to do Where are the functional phenotypes that random mutation is supposed to have produced in order for NS to select from It is no wonder that Darwin himself acknowledged he could recount no evidence for species change by NS The reality is that NS has very eloquently described how species may survive but has nothing to say about how they arrived Which is about where you came in So let me turn to your question Let me see if I ve got this straight Someone says to you beneficial mutations exist Example antibiotic resistance And your response is this bacterium got antibiotic resistance from lateral gene transfer therefore beneficial mutations do not exist This is what I have stated What the empirical evidence shows is that it is the direct clinical intervention that induces the acquisition of these natural occurring mobile genetic elements in tetracyclines that produces the resistance I also went on to state Even if a mutation occurs in the ribosome that may provide an advantage to the bacterium it would come at a cost Ribosomal mutations while providing antibiotic resistance for the organism slow the process of protein synthesis slow growth rates and reduce the ability of the affected bacterium to compete in an environment that is devoid of a specific antibiotic Furthermore a mutation that confers resistance to one antibiotic may make the bacterium more susceptible to other antibiotics These are deleterious effects and are completely inconsistent with the evolutionary model of natural selection acting on random mutations It appears to me that you are raising straw man arguments here The abstract you refer to is certainly not inconsistent with my statements In fact if I may refer you to a more recent and complete paper in 2009 http www ncbi nlm nih gov pmc articles PMC2684669 entitled The role of natural environments in the evolution of resistance traits in pathogenic bacteria This is how the abstract begins Antibiotics are among the most valuable compounds used for fighting human diseases Unfortunately pathogenic bacteria have evolved towards resistance One important and frequently forgotten aspect of antibiotics and their resistance genes is that they evolved in non clinical natural environments before the use of antibiotics by humans All I have argued is that this resistance is already there in nature The question is not how did the resistance in humans come about We know that well sort of The question is how did these genes come about in the first place That is what I found amusing about the wiki posit ie that NS is what done it For that statement to be valid then empirical evidence is required But what do we get Well antibacterial resistance proves this Perhaps not you but others do claim this With all due respect it does nothing of the kind What it does show is that clinical intervention passes on a resistance that already exists in nature That sounds to me very much like artificial selection Not a very good one at that since we are now having to deal with the consequences The 5 years out of date comment has to do with the latest Encode definition of a gene Nothing to do with trollbait Ok so you are not interested in discussing the origin of genes with me but you do know the simple answer Genes are legos made of legos My my however did I miss that one Errr yep I ve got it I have been accused of lacking imagination that s what it must be Got to keep working at it Reply with quote Luxorien Luxorien Posts 55 Joined Fri Jan 20 2012 1 27 am Re Theories Origin of Life Sun Sep 23 2012 6 57 am scottie wrote My position is not that random mutations do not happen They do Does NS act upon random mutations Yes I believe that may also happen In other words does evolution change over time happen Yes So in other words you agree that beneficial mutations exist When you said Where are the functional phenotypes that random mutation is supposed to have produced in order for NS to select from you did not mean to deny that an organism may acquire a beneficial trait from a random mutation You simply meant that you didn t think beneficial mutations sufficient to account for complex adaptations By functional phenotype you mean the whole mouse trap not just a piece of it It sounds like what you re saying is that natural selection can t account for complex structures like eyes and blood clotting cascades because random mutation can t produce eyes or blood clotting cascades This is an argument I can understand I don t agree with it but I can understand why someone would take this position However your statement that The random mutations that do occur are invariably deleterious to the organism seems to contradict the aforementioned argument Hence my initial incredulity But if we can agree that a random mutation might confer a benefit for the mutated organism then we can agree that the variation on which natural selection acts is at least in part the result of random mutation scottie wrote All I have argued is that this resistance is already there in nature The question is not how did the resistance in humans come about We know that well sort of The question is how did these genes come about in the first place Then there are three steps to antibiotic resistance First the bacteria evolves a gene that confers resistance to some dangerous substance This substance is natural in the sense that it is not man made not an artificial antibiotic Second the bacteria encounters the man made antibiotic The gene that conferred resistance to the natural substance isn t much use against the man made antibiotic until a random mutation tweaks it in such a way that it confers resistance to that man made antibiotic Third the bacteria becomes successful because it is immune to the man made antibiotic So it freely proliferates and passes its resistance to the man made antibiotic on to all its friends and even to other types through horizontal gene transfer So If I understand you correctly putting forth antibiotic resistance as an example of beneficial mutation is flawed for this reason the gene that is altered by the mutation was already conferring resistance to dangerous substances therefore the mutation didn t really confer any benefit it tweaked a benefit that was already there What I don t understand is why you tried to

    Original URL path: http://www.biology-online.org/biology-forum/about14351-540.html (2016-02-17)
    Open archived version from archive



  •