nothing in biology make sense except under the light of evolution!

are you a….???

March 2, 2009 at 6:48 pm (evolution)

Stats:
12…….13…….12……..16……..7……6……14….
WHAT DOES PREVENT YOU FROM LEAVING A COMMENT INSTEAD OF SENDING FEW E-MAILS FOR ME???

Anyway,Before telling you the rest of the story I’m up to ask you a question!
What is an organism?? What are you in detail as an organism?
Please give me a complete definition!

……….. …………

Permalink 3 Comments

coordinate, unit, purposefull!

February 1, 2009 at 6:30 pm (evolution)

In the end of a course , people like me, feel miserable! I won’t pass some of my EASY types of exams, it’s a fiasco to fail!

Anyway!   let’s go through the rest of our story…

life must be measured not in decades but in thousands and millions of years….

and survival machines began a receptacle for the genes passively ,providing something more than a wall to protect them against chemical warfare of  their rivals and accidental molecular bombardment. In the early days they ‘fed’ on organic  molecules available in the soup. This comfortable life came to an end when the organic food in the food-which had been  built up slowly under influence of centuries of sun light-was over… A major branch of survival machines, now called plants, started to use sunlight directly themselves to build up complex molecules from simple ones, reenacting at much higher speed the synthetic processes of the original soup. Another branch, now known as animals, ‘discovered’ how to exploit the chemical labors of the plants, either by eating them, or by eating other animals.

Both main branches of survival

machines evolved more and more ingenious tricks to increase their efficiency in their various ways of life, and new ways of life were continually being opened up. Subbranches and sub-subbranches evolved, each one excelling in a particular specialized way of making a living: in the sea, on the ground, in the air, underground, up trees, inside other living bodies. Both main branches of survival machines evolved more and more ingenious tricks to increase their efficiency in their various ways of life, and new ways of life were continually being opened up. Subbranches and sub-subbranches evolved, each one excelling in a particular specialized way of making a living: in the sea, on the ground, in the air, underground, up trees, inside other living bodies. let’s think of the body as a colony of genes, and of the cell as a convenient working unit for the chemical industries of the genes. Colonies of genes they may be but, in their behavior, bodies have undeniably acquired an individuality of their own. An animal moves as a coordinated whole, as a unit. Selection has favored genes which cooperate with others. In the fierce competition for scarce resources, in the relentless struggle to eat other survival machines, and to avoid being eaten, there must have been a premium on central coordination rather than anarchy within the communal body. Nowadays the intricate mutual coevolution of genes has proceeded to such an extent that the communal nature of an individual survival machine is virtually unrecognizable. Indeed many biologists do not recognize it!

One of the most striking properties of survival-machine behavior is its apparent purposiveness. By this I do not just mean that it seems to be well calculated to help the animal’s genes to survive, although of course it is. I am talking about a closer analogy to human purposeful behavior. When we watch an animal ‘searching’ for food, or for a mate, or for a lost child, we can hardly help imputing to it some of the subjective feelings we ourselves experience when we search. Each one of us knows, from the evidence of his own introspection, that, at least in one modern survival machine, this purposiveness has evolved the property we call ‘consciousness’.and I actually know that what exactly this term mean in neuroscience and somehow I’m not philosopher enough to say this meaning from that point of view but notice that it doesn’t matter in our PRESENT discussion! because it is easy to talk about machines which behave as if motivated by a purpose, and to leave open the question whether they actually are conscious. These machines are basically very simple, and the principles of unconscious purposive behavior are among the commonplaces of engineering science. The classic example is the Watt steam governor.

The fundamental principle involved is called negative feedback, of which there are various different forms. In general what happens is this. The ‘purpose machine’, the machine or thing that behaves as if it had a conscious purpose, is equipped with some kind of measuring device which measures the discrepancy between the current state of things and the ‘desired’ state. It is built in such a way that the larger this discrepancy is, the harder the machine works. In this

way the machine will automatically tend to reduce the discrepancy—this is why it is called negative feedback—and it may actually come to rest if the ‘desired’ state is reached. Modern purpose machines use extensions of basic principles like negative feedback to achieve much more complex ‘lifelike’ behavior.

They involve negative feedback of various kinds, ‘feed-forward’, and other principles well understood by engineers and now known to be extensively involved in the working of living bodies. Nothing remotely approaching consciousness needs to be postulated, even though a layman, watching its apparently deliberate and purposeful behavior, finds it hard to believe that the missile is not under the direct control of a human pilot.

To be continued …

p.s: in the end I would like to suggest you to have a glace on the following paper-which I came across when I was searching for something else. It’s about degree distribution for network of the cell- metabolism and correlated to evolution! Have fun!

Minnhagen P, Bernhardsson S (2008 ) The Blind Watchmaker Network: Scale-Freeness and Evolution. PLoS ONE 3(2): e1690. doi:10.1371/journal.pone.0001690

Permalink Leave a Comment

and genes???!

November 30, 2008 at 6:49 pm (evolution)

Once upon a time , natural selection consisted of different survival of replicators floating  free in primeval soup. And now the natural selection favorite survival machines are genes which are good at the art of controlling the embryonic development! And now the process is no longer conscious and purposeful, the same process in automatic selection of general molecule’s properties (fecundity, longevity and copying-fidelity), still go on  blindly and as inevitably as they went on far off-days. Genes have NO foresight. They just go ahead without planning. Genes just are , some of genes more so than the others…. But the quality which determines the genes properties are not so simple as they were…

In recent years- last 6 millions years ago or more- (:P believe me, it’s just recent in evolution! ) the replicators have privileged noticeably in some aspects of survival machines technology. Such as muscles, eyes, heart(evolved several times independently). Before that, they radically altered fundamental features of their way of life as replicators.

A survival machine is a vehicle containing not just a gene but thousands. The manufacture of a body is a cooperative venture of such intricacy that it is almost impossible to disentangle the contribution of one gene from that of another. A particular gene may affect differently on different parts of a body and a given part of a body may be influenced by affection of different genes. some genes act like masters to control a cluster of inferior genes. And action of one gene depends on interaction of many other genes. This intricate interdependence of genes may make you wonder why we use the word ‘gene’ at all. Why not use a collective noun like ‘gene complex’? The answer is that for many purposes that is indeed quite a good idea. But if we look at things in another way, it does make sense too to think of the gene complex as being divided up into discrete replicators or genes. This arises because of the phenomenon of sex. Sexual reproduction has the effect of mixing and shuffling genes. This means that any one individual body is just a temporary vehicle for a short-lived combination of genes. The combination of genes that is any one individual may be short-lived, but the genes themselves are potentially very long-lived. Their paths constantly cross and re-cross down the generations. One gene may be regarded as a unit which survives through a large number of successive individual bodies….

Natural selection in its most general form means the differential survival of entities. Some entities live and others die but, in order for this selective death to have any impact on the world, an additional condition must be met. Each entity must exist in the form of lots of copies, and at least some of the entities must be potentially capable of surviving—in the form of copies—for a significant period

of evolutionary time. Small genetic units have these properties; individuals, groups, and species do not. It was the great achievement of Gregor Mendel to show that hereditary units can be treated in practice as indivisible and independent particles. Nowadays we know that this is a little too simple. Even a cistron

is occasionally divisible and any two genes on the same chromosome are not wholly independent. A gene is not indivisible, but it is seldom divided. It is either definitely present or definitely absent in the body of any given individual. A gene travels intact from grandparent to grandchild, passing straight through the intermediate generation without being merged with other genes. If genes continually blended with each other, natural selection as we now understand it would be impossible. Incidentally, this was proved in Darwin’s lifetime, and it caused Darwin great worry since in those days it was assumed that heredity was a blending process. Mendel’s discovery had already been published, and it could have rescued Darwin, but he never knew about it: nobody seems to have read it until years after Darwin and Mendel had both died. Mendel perhaps did not realize the significance of his findings, otherwise he might have written to Darwin!!!

Another aspect of the particulateness of the gene is that it does not grow senile; it is no more likely to die when it is a million years old than when it is only a hundred. It leaps from body to body down the generations, manipulating body after body in its own way and for its own ends, abandoning a succession

of mortal bodies before they sink in senility and death. The genes are the immortals, or rather, they are defined as genetic entities which come close to deserving the title. We, the individual survival machines in the world, can expect to live a few more decades. But the genes in the world have an expectation of life which must be measured not in decades but in thousands and millions of years….

sorry to say this but….

To be continued…:D

Puuuffff……

Permalink 2 Comments

the evolution lingers on…

September 22, 2008 at 6:42 pm (evolution)

It seems to be an evolutionary trend toward great longevity…

But is the ‘longevity’ the only property of dominance??? Another property was probably not equal! The property must have had more importance in spreading through the population and it is the speed of replication. It‘s an evolutionary trend toward ‘fecundity’. Replicator by low fecundity becomes outnumbered sooner that having higher ability of this case, even by high longevity. The third characteristic property of positive selected replicator is accuracy of replicating. For example the molecule type A and type B having the same lasting time and replicating rate, but A makes mistakes an average per tenth replication and B makes per hundred replication . type B become obviously more numerous than A ….

But something in the last point somehow seems paradoxical. Can we reconcile replication errors as an essential requisite for evolution to occur??! You may notice the natural selection favorites….. my answer is : although the evolution from this part of view (in sense of vague ) a “good thing” that has happened but actually nothing wants to evolve intentionally! Can you feel why???

To return to the topic, the primeval soup must be populated by the varieties of the three individual properties . evolutionary trends toward these three kind of stability took place in this sense: if you had sampled the soup in 2 different times, the later sample must have included the high proportion of varieties of these 3 properties that mentioned! This would be essentially what a biologist means of evolution when he speaks of living creatures, and the mechanisms is Natural Selection….

Hmmmmm…. And now should we call the original replicators living?? Who cares? I might say Darwin was the standard of greatness, but you may say “ no, it was the Einstein” ! (I hope we wouldn’t prolong argument anymore ) The point is that no conclusion of substance would be affected whichever way our argument was resolved. We are labeling the facts of their life and achievements “great”…..Whether we call the early replicators living or not, they were the ancestors of life; they were our founding fathers.

But another important factor comes to the argument. The earth’s size is finite, the primeval soup wasn’t able to support all kind of varieties, and other limiting factors in the earth makes a definition that plays an important role in evolution and it’s competition. We can now
see that less-favored varieties must actually have become less numerous because of competition, and ultimately many of their lines must have gone extinct. There was a struggle for existence among replicator varieties. They did not know they were struggling, or worry about it( ); the struggle was continues without any hard feelings, indeed without feelings of any kind. But they were struggling, in the
sense that any miss-copying which resulted in a new higher level of stability, or a new way of reducing the stability of rivals, was automatically preserved and multiplied. The process of improvement was cumulative. Ways of increasing stability and of decreasing rivals’ stability became more elaborate and more efficient.Some of them may even have ‘discovered’ how to break up molecules of rival varieties chemically! ( notice that it was an accident!) Other replicators perhaps discovered how to protect themselves, either chemically or by building a physical wall of protein around themselves. This may have been how the first living cells appeared. Replicators began not merely to exist, but to construct for themselves containers, vehicles for their continued existence. This is what Dawkins calls survival machines. The first survival machines were just a protection wall but after times they got bigger and better and the process was cumulative and progressive….

And the main question in the evolution: is there any end to the gradual improvement in the techniques that the “livings” use to ensure their presence in the world??There would be plenty of time for improvement. Four thousand million years on, what was to be the fate of the ancient replicators?
Dawkins says:
They are in you and in me; they created us, body and mind; and their preservation is the ultimate rationale for our existence. They have come a long way, those replicators. Now they go by the name of genes, and we are their survival machines….

To be continued….

Permalink 3 Comments