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qed

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Posts posted by qed

  1. sunspot,

     

    If you have a model for all these things then draw scheme. Show its advantages compared to other models. If you arte citing known or established things, place a reference.

     

    Since you dont know how neurons work and since you are not studying current views of neurobiology, i consider this all as your own rethorical orgasm. Have fun, but do not confuse students. Your reasoning is really bad. The terms you use are defined by your self and most of them are no scientific categories.

     

    I strongly suggest that a mod moves this thread to the speculations forum.

  2. Although the internal current direction within neurons will flow from the dendrite, through the cell body toward the axon, the external surface current of a neuron flows opposite. In other words, the loss of surface charge on a dendrite, due to firing and the current entering the cell, will cause nearby surface charge to flow toward the dendrite to help fill in the deficit. In a general sense, the axon output circles back along the neuron surface to help out its own dendrites.

     

    This is wrong.

     

    I am teaching you guys and gals how the brain works and how it provides a natural potential for the creation of memory. The brain moves positive charge around, primarily sodium and potassium cations and can recycle this energy to create memory or do other tasks.

     

    This is wrong too. Before you start teaching other people how the brain works, you should learn the molecular basis of neuronal functions first.

     

    There is no current flow along the axon or the dendrites. There is only a current flow across the membrane. The surface charge alters at a given position for a very short time period when an action potential is passing by.

  3. They did get one basic thing wrong early on though. They say that the subject of genetic coding is "an impregnable bastion for critics". They point out that the principle of DNA->RNA->protein is called the 'central dogma',

     

    Despite the nonsense they are claiming, "Central dogma" is, although not often used today, really an official term.

  4. They appear to have linked interbreedability with diversification and environment suitedness

     

    There was an article in the german version of scientific american a few years ago, where they showed that an oocytic parasite causes reproductive isolation among insects. Different strains of the bacteria alter the cytoplasmic compatibility of a population, leading to a division into compatible sub-populations. I cant remember the name of the bacterium, but it acts among a huge variety of insects and has been considered as an explanation for the enormous diversity and radiation among insects.

     

    http://www.rochester.edu/college/BIO/faculty/Werren.html

  5. This problem only occures if one thinks of life as something special' date=' somthing that exists beyond the physical. I do not believe there is an "elan vital", a living force that seperates life from non life. Living entities are essentially a (very) complex chemical reaction. It is the complexity and emergent properties and behaviours od the "living" system that are important.

     

    The important properties of the system are that it maintains it's system integerety, self catalizing, growth, transfers energy through it internal systerm (the source of metabolism) to do work, organisation and disequilibrium with it's suroundings.[/quote']

     

    I fully agree on this view of a living system. Howerver, i ask myself it it is sufficient to create a disequillibrium system just by applying a model for it, (let me say "just information based"), or if it is required to have "real" energy potentials and real gradients that loead to energy AND information flow. How do you introduce entropic effects in your system, which are caused by complex interactions. Im not sure if im still able to follow on this complex topic.

    The point i want to reach with this reasoning is:

    Dont you think that you would have to "simulate" a whole universe in order to get your living systems? I think otherwise it would only be an idealization.

  6. What it looks like when you closely examine living systems is that they are system; processes that occure and they don't seem to be dependant on the constituants to a great degree.

    Im not sure if i got you right but i think i have to contradict.

    Have a look at structure-function relationships in biology. At the molecular level structure and function are the same thing. Every process that occurs strongly depends on the constituants.

     

    If we look at what is nessesary (DNA for instance) and look at what it does, it appears that the kinds of processes that DNA is involved with can be replicated on computers.

     

    Each individual component (that has been identified so far) seens to be able to be replicated accurately on computers.

    No. The models science developed in order to describe these processes can be "replicated" or simulated in an idealized fashion. Nothing more.

    A computer programme is a closed system where everything what happens is predictable. You cannot idealize life on the basis of scientific models and than claim that this should be alife. Even if all components were known your programme would still be a descriptive simulation.

  7. I didn't mean to imply that there is a purpose or goal.

     

    Sorry if i got you wrong.

     

    I could restate it to say, "evolution can occur when genotypes that have higher fitness reproduce more" but that's kind of redundant.

     

    Thats correct.

     

    But I think the "relevant aspect" of evolution depends not on how you view evolution, but on what kind of questions you, as a scientist, want to ask. Sure, there are certain questions that population ecologists can ask that can't be asked by people studying evolutionary genetics. And vice versa. Understanding mutations in terms of how, why and at what rate they occur is just as important as understanding how evolution affects populations.

     

    Absolutely. I think we have a consent.:)

     

    I only wanted to point at the population level because a lot of people blind this out when they try to understand evolution and focus on single genes and mutations. I think we all agree that that is not sufficient in order to get the big picture.

  8. Since mutations occur at the genetic level and individuals are selected out, I think it makes more sense to think of evolution happening at the genetic level.

     

    The cause for evolution lies on the genetic level, or changes on the genetic level. I think we all agree about that.

     

    Yes, natural selection is represented at the population level. But by saying that evolution occurs at the population level, I feel like you're implying that natural selection is occuring at the population level -- i.e. group selection is occurring. Group selection is not occurring.

     

    Yes, group selection is not occuring, as you said, individuals are selected out. Sometimes this selection is mediated by a single gene, thereby deleting itself from the genepool. But that is irrelevant for the further adaption or evolution of the population. The relevant aspect is, what genetic information remains in the pool after selection and what is its frequency and diversity. The manifestation (does that word fit here?) of evolutionary changes can first be seen in the following generations, and here we are on the population level. The individuals that survived didnt change, their genes didnt change. Life has to reproduce in order to change, and this is indeed reflected in the population.

     

    Evolution doesn't happen for the benefit and detriment of the group, it happens for the benefit or detriment of the gene.

     

    I definitely disagree. Evolution doesnt happen for the benefit and detriment of anything, there are just mechanisms. There are no trends, purposes or final goals or something like that.

    Its the genotype of an individual that gives the fitness in a certain environment. But its the genepool of a population that reflects its adaptive capacity and is therefor the more important aspect. An individual cannot adapt either a single gene.

  9. If we have a population of see gulls and one of the members is born with a better beak to catch a fish, natural selection will act upon the very gene that gave it this ability.

     

    This will not happen as long as the reproductive capacity of the rest of the population is similar to the individual with the new allele. The new sea gull may grow a little faster as the rest, but without selectional pressure on the whole the population, this new gene will not penetrate. This is especially true for large populations, where random genetic drift is low. The gene may persist in the genepool with low frequency unless the "genotype" of its carriers is not unfavorable in any way (that means if they dont die for any reason).

    The relative frequency of an allele is increased only by the decrease of other alleles by the death of individuals. Therefore only shrinking populations change their genepool.

     

    Believe it or not, evolution does never act on a particular gene. Only genotypes die or survive, and the evolution of a species takes place on the level of the population.

  10. I understand that most mutations are a disadvantage to the particular organism.

     

    I can see how a random mutation (tiger with bigger teeth' date=' faster antelope…)could be of benefit to a particular organism, and how that mutation would populate the entire species over a period of time.[/quote']

     

    I get the impression that some of you look at selection in the wrong way. Natural selection does not mean to increase the frequency of alleles that are somehow advantageous. It means the extinction of genetic constitutions that are unfavorable. I hope you see the difference. Natural selection is always negative, the only exception are mutations that directly affect the rate of reproduction.

     

    Remeber the Hardy-Weinber equillibrium. Evolution doesnt occur on the level of genes (of course mutations are the reason of evolution). It doesnt even occur on the level of organisms. Evolution occurs on the level of populations. That is what most people forget when they try to reconsider an evolutionary pathway.

     

    there are no mutations that have a general benefit. Genes wont increase in their frequency without selectional pressure. A population that evolves must shrink in order to adapt. in this case the extinction of the species is more likely than an adaptation that results in a new one. that means that for the survival of a population, genetic diversity in the genepool is essential for the capability to adapt. therefore there is no temporal correlation between a random mutation and the adaptation of a species. Its the combination of all genes in interaction with the environment that gives the fitness.

     

    Genes do not evolve, genotypes do not evolve either. Only genepools evolve.

    I just want you to bear this in mind.

  11. I am trying to find a way to detect whether a specific kinase is activated or not. Any good kits or procedures for how to do this?

     

    if you have purified substrate protein/peptide, you can measure the activity via standard enzym kinetics. Other possibility is to use radioactiv P as a tracer and detect the phosphorylation of your substrate.

  12. do you think the scientific community would be able to manage this kind of human research properly? like cloning, gene manipulation and culturing of human embryos?

    Even without being influenced by nonscientific politics, science would fail due its form of organization. There is too much competition and this work would be too important for scientific reputation.

    If there wouldnt be a restricted access to "objects" only for a few scientists (as it is currently in germany with repect to stem cells), everybody in the biomedical field would have to work on it in order to get high impact publications.

    And if we would start working on developmental aspects, experiments would be extended to later stages and so on. In order to study human brain development, we need a brain that develops. One step requires and legitimizes the next one.

    Where is the border? I do not believe in the sense of responsibility among scientists in general. There would be fake and bad taste.

     

    embryonic stem cell research has not proven to be that powerfull. Our understanding of the cell is, especially development and differentiation, is really poor. There are no basic questions in biology that require human embryos in order to achieve a major breakthrough. I mean basical not medical. Economic interests and pressure drives medical research forward and with human embryos that would be the real bad taste, probably without significant progress when compared to todays standards.

  13. Does the "selfish gene"-point of view explain anything that is not covered by general evolution theory?

    i didnt read all the links that were presented in this thread, but the essence that i got from this "theory" seems unlogical to me. What is the advantage of the concept to assign a general "purpose" to a species, just like being a host for a molecule that wants to be reproduced? I really do not get it.:confused:

     

    For me it sounds like this: "selfish biomass":D

    biomass has the purpose to expand spatially, no matter how it is achieved. that is why birds evolved, to transport Biomass to the sky, and the brain to develop a rocket to bring biomass into space.

     

    there is no purpose of anything in evolution, just mechanisms.

    did i miss something important to understand the theory?

  14. As far as I am aware it would be endothermic, producing a positive deltaH value and it produces glucose and oxygen[gas and solid] from water and carbon dioxide[gas and liquid]. This would cause a drop in entropy, therefore making the reaction impossible.

    Have I missed something critical?

     

    I wouldnt say impossible, just unlikely. the assimilation of co2 is indeed were unlikely and very slow. that is the reason why RUBISCO is the most abundant protein in the world. Each plant needs tons of it to get enough co2. under uncatalized circumstances, this reaction wouldnt take place.

  15. If they keep up the training for decades, the body will become more permanently alterred toward the larger muscularity in total contradiction to their orginal genetic potential.

     

    What is the "genetic potential" in that sense?

    How do you determine the pontential of a person or of anything else?

    I dont know "genetic potential" as a biological term. But it seems to be used in a restrictive way to set a range for adaptation or a limit for plasticity.

    I would say if something changes more than expected, then the potential was undervalued, and not that the potential itself changed.

  16. Hi, im new to this forum and id like to join this interesting discussion.

     

     

    We don't have all the details yet, but I can easily make a neural network on my laptop that learns from several examples and then generalizes this to correctly categorize new examples. And that is thinking, although ofcourse it is not the entire story, but a pretty good start.

     

    My impression is that a lot of people forget an important fact when they compare the brain to a computer. In a brain, hardware and software are the same thing. So learning and thinking is to remodel the architecture of the system in a certain extend. I hardly believe that a computer will be able to do this.

    Can they alter the program to adapt to situations or tasks or do they just add things to expand their capacity?

     

    Since the hydrogen proton is so universal with respect to the living state and defines the lion's share of bioactivity, theoretically, the functioning of the brain can be simplied to just the hydrogen bonding.

     

    Is this reduction satisfactory to you? In my opinion it doesnt explain anything.

    the hydrogen bond is important for specific interactions between molecules, but it doesnt produce information. 2 Proteins that bind to each other and induce conformational changes dont produce information. The biophysical interactions are only transducer of information. The biological function depends on the persistance of the information by following interactions and this only occurs when specific interactions take place in a specific temporal and spatial context. The hydrogen bond is not even sufficient to explain protein stability.

    I hope i didnt get you wrong. Sorry for strange english.

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