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nornerator

As I was reading through some of the arguments in the thread, Evolution or Grand Design, I noticed many people are confused about natural selection and its implications on the origin of life.

I hope that this post will clear up some of the misunderstandings about natural selections role in originating life, and hopefully misunderstandings about natural selection in general.

I am entering my senior year of my undergraduate degree in professional biochemistry, as such, I have a fairly solid background on which the following post is based upon. Although I am far from infallible, and I invite everyone to point out my mistakes. It is only through the continual correcting of mistakes that real knowledge can be obtained.

Imagine shrinking down to microscopic scales. Shrinking past the size of a mouse, then algae, shrinking down past the size of a bacteria, shrinking further smaller than a virus, and shrinking even further down to the size of molecules. This is the true level of biology, this is the level that provides the basis upon which biology is built. It is on this level that organized chemical reactions take place in order to maintain adequate amounts of energy, maintain cellular structures, and replicate.
Now an important question most people who are not chemists will never ask is, why do chemical reactions take place? Instead of answering this question with specific answers, I am going to present a broad view which can be easily understood and visualized. Chemical reactions happen so that the chemicals that are interacting reach a more stable position within their immediate environment. To understand this, imagine a piece of fabric and draping it over an eclectic pile of books and toys on the living room floor. The surface of the fabric is now elevated in some regions and depressed in others. Now imagine placing a ball on top of the fabric directly on top of a flat book region. This area of fabric is elevated, and the ball stays put on top of the book, it is stable. However in the system overall (the entire piece of fabric) this ball has a lot of potential energy, because if it is knocked to the side of the book, it will roll down the fabric until it reaches the lowest point of the fabric. The ball with potential energy is stable until it is provoked to fall to the lowest point of the fabric where it no longer has this potential energy. Now imagine the fabric is placed over two books of different lengths, standing upright with 3inches between them, but 5 inches of fabric. There are two plateau's the one on the left (in your minds eye) being taller than the one on the right, but between the two books, there is a third plateau where the fabric sags lower than the book on the right. So imagine the ball on top of the plateau on the left falling into the fabric in the middle. It is stable here, yet this is not the lowest point in the system, but it would take energy to move the ball to either the plateau on the right, or plateau on the left, and so without having energy added, the ball sits nicely in between the two plateau's. If given enough energy it can reach the plateau on the right and then perhaps slide off and roll along the fabric until it reaches the floor, which is the lowest point in this system.
Now imagine that this fabric is draped over a violent sea, and not static objects like books. When the sea changes the ball rolls into whatever the lowest point in its immediate environment. Likewise, the sea can be uneven. So a ball will only be in the lowest point in its immediate environment and not necessarily the lowest point of the entire system.

Now this ball that I am talking about can be thought of as a molecule. A molecule will react with other molecules only if their products fall into the lowest point of their immediate environment. Now keep in mind, their immediate environment may be highly elevated in reference to the whole system, but a chemical reaction will not happen unless the products are more stable than the starting materials.

Now for those of you a bit more familiar with chemistry may be confused because chemical reactions happen all the time where the product has more potential energy than the starting materials, but in order to do this these sorts of reactions require energy from the environment, either through heat, microwave, or what have you, the total energy of chemical products cannot exceed the sum of their reactants unless energy is funneled in through the environment. This is simply a restatement of the law, that energy/matter cannot be created or destroyed.

Many of you might be thinking, "Ok, so chemical reactions only occur when their products are going to fall into a more stable position within their immediate environment than their starting materials, and energy cannot be created or destroyed, what does this have to do with evolution and the origin of life?"

The life we know today probably started out as a single molecule that was able to self replicate.

There are an uncountable number of ways in which molecules can be put together, all of them falling into the most stable position within their immediate environment. Given extraordinary amounts of time and events that significantly raise the fabric, heat from vents, lightening strikes, solar radiation from the sun, some molecules will be created that have the property of self replication. Self replication will of course require energy being put into the system. So say by chance a self replicating molecule finds itself at a hot vent in the ocean, a constant supply of heat energy, and lucky for this molecule this is the type of energy needed so that it can self replicate. The energy provides an elevated fabric on which the chemical reaction that normally would not happen will happen, because the reaction, normally requiring a large amount of energy to reach a stable plateau is now given a constant supply of energy which raises the fabric so much that the product of replication (two self replicating molecules) is actually much lower in comparison to the height at which the fabric is raised.

Now these molecules are not 100% correct when they copy themselves, perhaps they are 99.999999% correct, so once out of 100million copies it changes slightly. Now these molecules that are near the heat vent will continue to replicate as long as there is heat for energy. Inevitably many of these molecules fall away from the heat and can no longer replicate. Now given enough time and enough replication, it is easy to imagine that the copying error will lead to a self replicating molecule that can extract energy from other high energy molecules, and heat energy, as opposed to just heat energy. These self replicators when they wander off from the vent can still replicate as long as there are molecules from which they can derive chemical energy to self replicate. Once the high energy molecules that they are deriving energy from become less and less abundant, only the replicators who extract energy the most efficiently can go on to self replicate. The process continues for long periods of time until life as we know it, cells, come into existence.

I will post more on this topic later... I am getting tired, but my next installment will focus more on evolution of life rather than the origin of life.

I hope some of this was able to be followed

 

nornerator

Essentially the molecules that are best able at extracting energy from the environment and multiplying will be in higher abundance than the molecules that are not as good at extracting energy and replicating.

Think about it, things that make more copies of themselves will exist in greater number than things that make less copies of themselves.

When applied to living organisms in an environment, those organisms which are best at using the environment to produce offspring will be in higher numbers than those who are not as good.

When resources are scarce the organisms that are best able to take advantage of the scarce resources will be in higher abundance than organisms that cannot take advantage of scarce resources.

It seems so simple, and so obvious, but once you realize this, you will understand, evolution is absolutely inevitable.

Either a species continues to evolve, or becomes extinct. The members of the species best able to reproduce in a given environment, exist in highest numbers.



I would highly highly recommend the book "The Selfish Gene" by Richard Dawkins for those who are interested. It is well written, and easy to understand.


If you have any questions, or would like to point out an error, please post a comment.