h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Ah, but the sun produces mainly heat, which increases entropy even more.

I don't think superbugs are evidence of evolution. After all, they had to have a trait that makes them resistant to begin with to survive right? Or am I not understanding the process?

The development of antibiotic-resistant bacteria is a slightly more complex matter than evolution within a species.
Since bacteria of different species can exchange genetic material with each other, there is the possibility of resistance developed in one kind of bacteria being passed on to a different kind.

However, that shouldn't be taken to imply that bacteria can't evolve resistance themsleves, but more as an indication that nature can be very efficient when it comes to finding ways of speeding up evolution.

Going back to the point about long timescales and the fossil record, I'd suggest that even *without* fossils being present, and/or radioactive rock dating, some idea of geological timescales can be gained from the observation of the typical range of current rates of sediment deposition, and the thickness of some sedimentary rocks.
There has to be some kind of upper limit on sedimentation rates, given maximum imaginable precipitation, and/or availability of source material for the sediment.

Heat can be captured to make useful energy, just as coal burning power stations make electricity, petrol combustions make a car move, and plants absorb sunlight to grow and reproduce. The second law does not deny this - it just says that not all the original heat created can be used productively. That makes sense, because we only need a tiny tiny amount of the heat released by the sun here on earth to keep life ticking.

Fully antibiotic resistant superbugs did not just appear on the stage when antibiotics were introduced in the 1940's. The process was much more gradual. As antibiotics became stronger and more lethal, so did the bugs they were fighting. If fully resistant bugs were around from day 1, antibiotics would have been much less effective than they have been and millions of people who are currently alive would be dead.

Potholer, I agree with you that different mechanisms might be involved but the end result is the same - a new breed of organism better adapted to the environment it finds itself in : an evolution has taken place.

So could anyone explan to me the law of biogenesis? It seems strange to me how you could ever come up with a law that showed life had to come from life.

Life does of course not go against entropy. As mentioned before, it's a matter of wether it is a closed system or not. Just look at something like an egg turning into a chicken. The chicken embryo has acess to some food(energy) and can therefore increase it's own complexity. As for the sun, it does produce heat. That is basically all it produces(besides helium and a few other heavier elements). But heat cannot transfer through the vacuum of space, it of course needs some sort of a medium. So the heat from the sun is instead transferred with EM-radiation, sunlight.

As for height, it has changed up and down over the centuries. It is not genetic, it is about nutrition. Of course no matter how much you feed a midget, you won't make him grow. But not having enough nutrition was what caused people during the middle ages to shrink.

Mutations, most are said to be bad. In a complex system it would also seem strange if random changes had a 50% success rate. But that does not mean evolution cannot happen. But if mutations were mostly beneficial, it would probably have gone a lot faster. I have heard some claims that mutations should be beneficial most of the time, but I haven't looked much into it, I will go do that now.

Hello ddombrow

Genetic material is "added" in a variety of ways. Sex is the most obvious one; the jumbling up of the genetic combinations every generation is the powerhouse of evolution. DNA itself is selfish and just loves to copy itself and expand everywhere. Then you have stuff like chromosome aberrations (breakages, rejoining, ploidy number increases, etc.), genetic mutation, 'jumping genes' which all strive to mix stuff up to create a bit of a mess. Out of this mess, ever so often, something just happens to be beneficial in the environmental niche that the individual who is 'hosting' these genes happens to be in. It is inherited.

Punctuated equilibrium came about because of the fossil record. There is little evidence of a smoothe gradual change of the fossils (though we only have the bones to look at, which is quite a limited source).

Imagine a time of relative ecological stability, a population of individuals is happily sitting there accruing mutuation and genetic diversity over time. Along comes an ecological change (climate, food source, habitat whatever) and we have a genetic 'bottleneck'. Only the individuals that happen to be suited to the new ecological niche survive. Life is sculpted by the environment, if the environment isn't changing gradually and smoothly, why should life?

I think Ab-resistant bacteria is an example of natural selection on a limited scale and not really good to illustrate evolution. Bacteria are asexual after all, but can still exchange a little genetic material through plasmids (little circular bits of DNA).

>>I don't think superbugs are evidence of evolution. After all, they had to have a trait that makes them resistant to begin with to survive right? Or am I not understanding the process?
No, they do not. All it takes is one single bacterial cell out of trillions in a small culture to mutate one gene to gain a new resistance. Work out the odds for yourselves, the chances that it would happen are great. If antibiotics are not used, this gene wouldn't do anything. But if you use an antibiotic that this new mutant happens to be newly resistant to, you get another bottleneck. Only that bacteria lives plus the few that it has managed to pass it's plasmids around to. Bacteria replicate exponentially, it won't take long to get back to it's former pre-anitbiotic numbers. Hence you have just inadvertantly selected for a superbug.

The point I'm trying to make with the resistant bugs is. They had to come in contact with the antibiotic or whatever at least once right?

So for whatever reason, they had to survive it at least once? Or am I still not understanding?

They do not have to be in contact with AB to become resistant. But we wouldn't know they were then. The bacterias just have some mutations now and then. Every now and then a bacteria will come along that is resistent to whatever drug. It might die out because it is weaker than the others in some way. Untill the day the bacterias are doused in that drug, and the bacteria will flourish instead.

The antibiotic is selecting the resistant bugs. The bacteria can generate the resistance without the antibiotic, but without the application of the drug the mutation would not be beneficial in any way. So, the antibiotic is not actively *creating* resistance, just *selecting for* resistance.

I apologise for interrupting. I might have missed the part I'm about to address.
Superbug resistance to antibiotics does not exist without surviving hosts. The antibodies produced during exposure and incubation mean a mutation may occur during the carrier stage, sometimes when the bacteria is dormant and waiting for a new host. Thus, those who survive the first go-round of an epidemic may not survive the second because instead of allowing the autoimmune system to do it's job, many folks have begun to douse themselves with whatever drugs remain in their medicine cabinets in the hopes that that would do the trick. Unfortunately, since a lot of antibiotics are sterilized bacteria, because of the fear of their taking on the host, the bug gets to sample a tamed version and when it comes around again, it brings the whip.

Bacteria live everywhere, you don't need a host. You could create a superbug on a kitchen counter if you decided to wipe it with antibiotics instead of detergent.

No antibiotics are 'sterilised bacteria'. Sterilisation is the killing of bacteria, no bacteria can survive it. You might be getting mixed up with viruses there . Antibiotics are molecules that interfere with bacterial metabolic processes, such as cell wall synthesis.

The over-use of antibiotics is a huge problem though. Many doctors prescribe abs for a sore throat, knowing that it is caused by a virus, just because of the phychological effect that is has.

Ugh, that's rather irresponsible of them.

OK, let's take this one step further then. When the Black Plague rolled in through Europe, some people were immune. Is this then a similar mutation effect in humans?

Hmm, yeah I suppose it is broadly similar. Pure chance meant that some people were immune, the effects weren't realised until they were exposed to it.

Or it could be that some people's immune system reacted to it quickly. I'm not sure how far you could compare antibiotics and bacteria with viruses and humans...

Is there some sort of point you're leading us up to?

Immune response is another complex issue - On top of inheritance and mutation, there's a significant combinatorial scrambling effect within the immune system of a single animal that generates a huge variety of molecules to help in the identification of foriegn molecules.

And let us not forget that given a long enough period of time in a dynamic environment, evolution will inevitably produce creationists.
Frogbit

I would be interested in hearing examples of mutations actually spreading through populations. After an extensive study of genetic mutations I can't find one example of a mutation that wasn't rapidly snuffed out.
Mutations are just like their root word, mutant. Irregularities that are corrected by an unseen force. Take sugar cane for example. When genetic engineering was first discovered, scientists altered sugar cane plants and tripled their output of sugar. The next year, they did it again, tripling it again. They were able to triple it yet again the next year, producing nine times the sugar than they had before. Then, on the fourth year, their exact same procedure offered no improvements. You see, God does not want his species to become to far removed from their original characteristics, so, there is an inexplicable barrier surrounding all species (there are other examples besides sugar cane) where genetic mutations cease. This theory was around long before evolution and by coicidence, called natural selection.
It's ironic that Darwin would use evidence that cripples his theory in its name.

You do realise that all domesticated animals and farm crop species bare absolutley no resemblance to their ancestral plants, which man selectively bred into what we eat today. Where was God's "inexplicable barrier" (!!!) then?

The sugar cane example offers no proof of God's will. It is more likely to be a biochemical reason rather that the work of an almighty diety.

Gene flow enables a beneficial mutation to spread.

An example of a mutation spreading: Tolerance of plants to heavy metals. Copper mines contaminate the soil with heavy metals, so much so that the plants die off. Most metal ore in Britain is now gone, leaving behind wastelands. In the last few decades however plants have started to become resistant to heavy metals in these areas. A mutation arose that enable plants to metabolise the metal, to cope with it. This is very advantageous and enables the new plants to use the otherwise unused soil.

Another example: DDT resistance and malaria.

Another example: Bacterial resistance to antibiotics

Another example: Industrial melanism in Phigalia pilosaria

Genetic material spreads all the time because of sex. Hence if a mutation arises in the genome of an individual, and that individual produces offspring, it will have a passes the mutation on.

We're forgetting that there are mechanisms in the world that can *induce* genetic change. Certain STD's are intreatable because they reside in the DNA itself, and, short of gene therapy, there is no way to address the cause. We have malignant and symbiotic bacterias... why not beneficial viruses? Buried in our DNA where we couldn't find them if we wanted to, but we don't even know to look because they don't cause us any harm?

Genetic change is a part of the equation, but so too is selection. Imagine, if you will, a very slight, completely unnoticed genetic change that boosted one's ability to fight off viral attacks. This person continues life as normal, lives fully, and passes on his gene. Some several generations down the road, his gene is not common, but, due to the survival properties it passes on to its carrier, it has become common enough that one person in ten possesses it.

One year, a Bubonic Plague runs rampant across the Western world, slaughtering untold people. Those who survive either manage to avoid it, or carry this gene. The gene now makes up such a large proportion of the surviving population that it takes one generation to spread it to the rest of the gene pool.

A few hundred years later, this gene pool arrives at the New World, and makes contact with a new gene pool. These people are virtually wiped out by viruses which had no effects on the Europeans.

Ok, how about sickle cell disease. This is a terrible, painful dibilitating genetic disease. It results from a change in one base-pair of DNA. That is one of the links in the chain of DNA is replaced by a different one, like putting the wrong letter in a sentence, easy to occur by chance.

This results in the production of haemoglobin which cannot stand low levels of oxygen. Haemoglobin (Hb) is the protein that carries oxygen in the red blood cells, in this mutated form it cannot perform properly. When it is low on oxygen it malfunctions and binds to other molecules of Hb instead of oxygen, and this really messes up the red blood cell. These messed up cells are then destroyed by the body.

The reason that this disease still exists (and that all the people suffering from it have not gradually died out) is because it offers resistance to malaria (which, I think, is the worlds biggest killer). The malarial parasite lives in red blood cells and uses their oxygen, causing low oxygen concentration which leads to the destruction of the infected cell.

This is a mutation that offers a survival advantage to the person affected. On average the people affected with the disease survive longer and have have more offspring than those who aren't (in the presence of malaria). Thus the mutation stays in the population.

This is natural selection - survival of the fittest (ie. those who are better suited to their environment).

Mutations are not all bad. Take the classic example of the moth species (I forget which one) that changed colour with the increased use of fossil fuels. This moth used camoflage to evade preditors, initially it was light coloured, to hide on tree trunks. As more and more soot was deposited the trees got darker. The moths all varied in colour (due to mutation, random variation), the same way that my brothers hair is a darker colour than mine.

The ones that were naturally darker were harder for predators to find, and more of them survived to reproduce. These gave dark coloured offspring, the darkest of these were more likely to survive, and so on. Eventually the whole species was on average darker than before the soot appeared on the trees. Selective pressure resulted in natural selection, which resulted in a new genetic make-up of the species.

This can be seen as the beginnings of the evolution of a new species, divergence.

Evolution is simply natural selection over huge amounts of time. Incomprehensible lengths of time. How can there be one without the other?

Another quick point. Although we may share 99% of our DNA with chimps, we also share 50% of a banana's DNA. The amount of DNA we share is not as important as the way we use it. For example it takes lots and lots of genes to make hair, but only a few to tell the body where to grow it. This is controlled by HOX (homeotic box) genes. The developement of these led to the 'pre-cambrium explosion' when suddenly lots of new species developed, because small mutations in them would have wide ranging effects.

Also in closing, I don't see how evolution disproves the existance of a deity, God moves in mysterious ways after all. If he or she does exist he must be more clever than us, and perhaps God created us all by evolution. I don't think so, but keep an open mind.

Cheers, get back to me if this doesn't make sence to to you,

D.

Ok, how about sickle cell disease. This is a terrible, painful dibilitating genetic disease. It results from a change in one base-pair of DNA. That is one of the links in the chain of DNA is replaced by a different one, like putting the wrong letter in a sentence, easy to occur by chance.

This results in the production of haemoglobin which cannot stand low levels of oxygen. Haemoglobin (Hb) is the protein that carries oxygen in the red blood cells, in this mutated form it cannot perform properly. When it is low on oxygen it malfunctions and binds to other molecules of Hb instead of oxygen, and this really messes up the red blood cell. These messed up cells are then destroyed by the body.

The reason that this disease still exists (and that all the people suffering from it have not gradually died out) is because it offers resistance to malaria (which, I think, is the worlds biggest killer). The malarial parasite lives in red blood cells and uses their oxygen, causing low oxygen concentration which leads to the destruction of the infected cell.

This is a mutation that offers a survival advantage to the person affected. On average the people affected with the disease survive longer and have have more offspring than those who aren't (in the presence of malaria). Thus the mutation stays in the population.

This is natural selection - survival of the fittest (ie. those who are better suited to their environment).

Mutations are not all bad. Take the classic example of the moth species (I forget which one) that changed colour with the increased use of fossil fuels. This moth used camoflage to evade preditors, initially it was light coloured, to hide on tree trunks. As more and more soot was deposited the trees got darker. The moths all varied in colour (due to mutation, random variation), the same way that my brothers hair is a darker colour than mine.

The ones that were naturally darker were harder for predators to find, and more of them survived to reproduce. These gave dark coloured offspring, the darkest of these were more likely to survive, and so on. Eventually the whole species was on average darker than before the soot appeared on the trees. Selective pressure resulted in natural selection, which resulted in a new genetic make-up of the species.

This can be seen as the beginnings of the evolution of a new species, divergence.

Evolution is simply natural selection over huge amounts of time. Incomprehensible lengths of time. How can there be one without the other?

Another quick point. Although we may share 99% of our DNA with chimps, we also share 50% of a banana's DNA. The amount of DNA we share is not as important as the way we use it. For example it takes lots and lots of genes to make hair, but only a few to tell the body where to grow it. This is controlled by HOX (homeotic box) genes. The developement of these led to the 'pre-cambrium explosion' when suddenly lots of new species developed, because small mutations in them would have wide ranging effects.

Also in closing, I don't see how evolution disproves the existance of a deity, God moves in mysterious ways after all. If he or she does exist he must be more clever than us, and perhaps God created us all by evolution. I don't think so, but keep an open mind.

Cheers, get back to me if this doesn't make sence to to you,

D.

B******s - I just wrote a reply based on sickle-cell disease as well, though not as good as yours

Regarding the 'all mutations are bad' idea, If all mutations were bad, then logically there would be an 'ideal' original unmutated human genome. Given that pratcically everyone has a different genome to everyone else, then it would seem that everyone is a mutant.