Evolution

the genetic makeup of different organisums is very complex. the 'amount' of DNA for a given creature (usually expressed ad the number of genes) is not nesicerily an indication of that creatures complexity. infact the older the species is the more genes it seems to collect.
see this and the mirriad of other posts on the subject via google
http://www.madsci.org/posts/archives/may2000/959100341.Ge.r.html

Originally posted by Brimon
1)Could you expand on this? Are you saying that you could give examples of lifeforms which are becoming more compex genetically?
2)OK, but doesn't even the retina on the human eye have millions of light detectors and precisely engineered nerve fibres? A retina doesn't just appear one day does it?
I'm not putting forward my own very incomplete knowledge as proof of creation, but I think these are reasonable questions.

sensitivity to light is very common and is de-localised in many simple organisms. The progression isn't nothing to fully formed retina in one jump but gradual specialisation of cells that are already light sensitive.

read 'Science of Discworld: Darwins Watch". heck read the whole series of discworld books. TP rocks

Originally posted by Brimon
Well, to the best of my understanding it is true. What I mean is this. DNA carries information doesn't it? A one-celled organism would not have the DNA information to manufacture everything needed for, for example, a horse. So new information must have been added over the years for evolution to be true?
As creatures diversify the gene pools become increasing ...[text shortened]... ientists are evolutionists, and, secondly, scientists can get it wrong without being deranged.

speaking as a derranged scientist I'd recomend you read some basic biology. I don't argue theology on this forum because I haven't read enough about it; perhaps the anti evolutionists might extend the courtesy in the other direction until they have read some basic biology.

Please read some basic texts or STFU

well that was where I was going with the whole science of discworld thing. only they are possibly easyer to read than a biology text book. (one of the authers is a biologist). If you are going to read stuff before posting on it then some basic physics/maths might come in handy once in a while as well.

Originally posted by Brimon
Thank you for your respectful response to my question about genetics. So, with MRSA, is new genetic information actually being added? Is the organism actually more complex than it was before? I told you I am not an expert! I am willing to learn, if you could clarify for me.
Sorry to come back to these eyes again! I read that the trilobite fossil (I think evo ...[text shortened]... Never heard of them! If I ever have a more coherent response than that, I'll get back to you!

Okay, I'll do my best to explain the basics in, well, a basic way.

Most genomes are horrendously complex, and stuffed with lots of DNA which does nothing. Eukaryote genomes are organised into linear chromosomes, whilst bacterial genomes are a simple loop of DNA. Bacteria have a mechanism for genetic transfer, called plastids, which are basically little loops of DNA which can be transferred between bacteria. Now, I said that most DNA doesn't actually do anything. In fact about 95% of DNA in your cells does not encode for proteins. Most of it is redundant, broken copies of functional genes. Cells are pretty good at replicating DNA, only about 1 mutation in 1 million bases copied, but evolutionary theory would suggest that they used to be less good. Still when, like humans, you have a genome comprising approx 3.2 billion bases, that's quite alot of mistakes. One of the more common mistakes is when a piece of DNA gets replicated twice, making two copies of a gene, only one of which is normally functional. This is most common when you have palendromic loops, such as those found at the end of genes (pieces of DNA which code for proteins). You end up with extra DNA. Likewise, it's not uncommon for extra bases to simply be added in, both during replication, but also, more commonly, during the transcription, literally the 'reading', of the DNA code.

So we end up with extra DNA which is nearly functional. It certainly has the promoter sequences etc, necessary to work. There is no selection pressure on this DNA, which allows it to randomly mutate with absolutely no negative consequences for the organism at all. Occassionally, this leads to a new stable protein being formed. Now this might have little consequence for most organisms most of the time. If it does nothing, then it doesn;t matter, if it confers an advantage however, it will become more widespread in the population.

An excellent example of this is bacterial infections. We get infected by bacteria because our bodies represent nice places to live, plenty of food, warmth etc. The bacteria multiply in our bodies until there are billions of them, all randomly mutating. We take an antibiotic and it kills them right off. Except the single bacteria which has evolved, against odds of billions to one, a resistance to that antibiotic. The bacteria divides by binary fission, making copies of itself, which too, are randomly mutating. The new antibiotic resistance gene is now a predominant member of that organisms genome, and will be retained.

But this isn;t the end of the story. Remember those plastids I was talking about earlier? Well, they can be used to transfer these genes between organisms, a sort of bacterial sex. Staphylococcus aureaus lies inside all our throats and resides there pretty innocuously most of the time. Sometimes it gets into parts it shouldn't be, and has a party. MRSA is simply a variety (or 17) of Staph a. which has acquired, by exposure to antibiotics resistance from them. Even if these bacteria have gained the genes from others, it still represents genetic evolution.

As for the eyes, well, this isn;t an unreasonable question. The basics however.... Imagine a world where nothing has any kind of eye at all. Any organism which evolves some light sensing capability (which is easier than you'd think, pretty much all compounds react with light in some way) would have an advantage. If it is a predator which evolves it first, then the prey are under an immediate disadvantage, and will be hunted by the predators. The population size of the predators will increase and the prey decrease. This very scarcity itself will be the prey's saviour though, because it will lead to a die back in the predator, reducing the pressure on the prey. Eventually, a genetic mutation will lead to the prey developing an eye, because the pay off for having an eye will evolutionarily be so high. And it doesn't matter what eye. If it even confers a 1% advantage it will be conserved, and improved. It becomes an arms race.

As for your trilobites with compound eyes, well, I don;t see why that's a problem! A compound eye is just many many copies of a non compound eye. Many organs in biology come from distortions of previous organs. I think de novo evolution is extremely unlikely, but then, that's the whole point. De novo isn't how evolution is postulated to work.

Originally posted by scottishinnz
Still when, like humans, you have a genome comprising approx 3.2 billion bases, that's quite alot of mistakes. One of the more common mistakes is when a piece of DNA gets replicated twice, making two copies of a gene, only one of which is normally functional. This is most common when you have palendromic loops, such as those found at the end of gen ...[text shortened]... r, if it confers an advantage however, it will become more widespread in the population.

Ok, Im not understanding this, You say the "extra" DNA came in a random way, totaly by accident. So how come you state there is no negative consequences? To me it seems like if it came in a random way, it could either go backwards just as well as forward? or are you saying the the more DNA you have, the better?

it can have a positive, negative, or neutral effect. for example it might make your hair grow slightly faster. doesn't really effect you unless your energy ballence is really tight. (most of the effects would be internal and non obviouse however)

Originally posted by flyUnity
Ok, Im not understanding this, You say the "extra" DNA came in a random way, totaly by accident. So how come you state there is no negative consequences? To me it seems like if it came in a random way, it could either go backwards just as well as forward? or are you saying the the more DNA you have, the better?

Most DNA doesn't do anything. It's quite, quite possible to add DNA without having any net effect.

I don't understand what you mean by "backwards" and "forwards".

most dna isn't belived to do anything.
however the science on the subject isn't quite concrete enough for the definitive. it is quite possible for example to find bits of viruses (you have had) dna added into your genome, possibly a record of known threats might be part of it? not active in everyday protine activities but used as data storage. either way you can definately change dna without detrimental or advantagus side effects.

Originally posted by googlefudge
most dna isn't belived to do anything.
however the science on the subject isn't quite concrete enough for the definitive. it is quite possible for example to find bits of viruses (you have had) dna added into your genome, possibly a record of known threats might be part of it? not active in everyday protine activities but used as data storage. either way you can definately change dna without detrimental or advantagus side effects.

Re data storage; Very unlikely considering that antibodies for every antigen already exist, and are encoded for within our DNA. My own personal best guess based upon the evidence is that this "junk" DNA is merely there as part of a cost-benefit system. It doesn;t matter if mutations happen to Junk DNA, just to coding DNA. If only coding DNA exists then any mutation will typicall kill the organism outright or lead to such a detriment in efficiency that the organism will be outcompeted in a competitive environment. [note; in a less competitive environment, such as following a mass extinction, gene mutations may lead to speciation, since the organism can still survive even with a poor gene, until competition promotes efficiency. I'll follow this post with another explaining this with an analogy after coffee.] Thus junk DNA will be favoured, since it lessens the likelihood of deleterious mutations. But junk DNA requires copying, and that takes energy. Eventually the two processes balance each other out.

Originally posted by CreepySlash
Any one believe in evolution and why you do or don't.I personnely DO NOT!I'm a Christian and believe in Creation.

Evolution is NOT, I repeat, is NOT a believe. You cannot believe in it. There is scientific data that points to the fact that organisms change over time and can develop into new species. A species is defined as a group of organisms that do not breed with other groups of organisms.

But as far as believing in it, get your facts straight before making such an asinine statement. At one time gravity was a theory and now it is a law. Do you "believe" in gravity?

okay, my analogy is as follows.

Imagine, if you will, we have a new technology becomes available. Let's say the advent of personal computing. Initially, the technology is held by only one company. However, after a while the other companies will start to produce their competing systems. These systems may well be better than the original system, but the original system has an advantage based upon being first. We now have a scenario where we have several competitors, who perhaps launch upgrades to the original product. The original system could be basic, because it was better than anything else out there at the time, but that's true no longer. Now we have competitive effects, each company trying to oust the other from the top spot. Under most circumstances they will be unsuccessful, because of the relative interia of most people; the company from whom they purchase their first system will probably be the one they stay with. We reach a steady state with a dominant company and several smaller competitors, who may actually be better than the dominant company.

If we want an example of this look at computer operating systems. Microsoft's Windows OS has two main competitors; Apple OS and various flavours of Linux. Despite Apples computers and operating systems being better than Microsofts, and Linux being cheaper, Microsoft currently dominates the home PC OS market. Is that likely to change anytime soon? No. Why? Inertia.

Now imagine the world of home computing was turned upside down for some reason. Let's say an global virus attack wiped out 95% of Windows PCs, but left some untouched, such as those not networked to the internet. Linux may come to predominate under the new conditions. It's immune to the virus, which threatens (but not promises) to kill any Windows PC that is hooked up to the net. At this point we'd see something interesting happen. More releases of Linux would appear. Initially some of them might be pretty ropey, but they're better than Windows PCs and they're a heck of a lot better than nothing. Over time, those versions would have to become more robust though, in order to survive the competition against other versions, who can do the same things, only perhaps better and more stable.

So what we are starting to see is that these computer programs are evolving. KellyJay will comlpain that the selecting is being done by humans, however that's not a problem, because the selecting is being done by millions of humans independantly, not just one. The selection is being done by many independant agents on individual machines, not on the entire population of computers. Whilst each individual selection can change the relative proportion of machines running either Linux or Windows, no one person controls it overall.

Morals of the story?

1) A poor quality computer (or eye) is better than no computer (or eye), especially when everyone elses computer is similarly poor. Comparing two 15 year old computers is valid. Comparing a 15 year old computer with a brand new one isn't. Most eye arguments boil down to this "what good is a 15 year old computer?" Answer? Great in its day, but not now, because most computers aren't 15 years old. [edit; and still good for some jobs, such as a print server. Likewise many organisms who would benefit from no better eye still have poor eyes]

2) Sometimes established ideas, technologies and genes persist in a population simply because they were there first. However, mixes of different ideas (or computer OSs) are not abnormal, and are stable.

3) Selection works at an individual level. Evolutionary change works on the proportions of any given gene (or OS) in population of many many individuals.

Hey ScottishinNZ. I haven’t been around the last few months as you may have noticed, but now I back. Hope the evolution crusade has been going well. Anyway, just want to clear up a few things about your post. No offense intended.

The circular loops of DNA that bacteria transfer to one another are called Plasmids not Plastids (plastids are plant organelles). They are also found in yeast by the way.

Actually the more recent number is that only about 1.5% of the Human Genome codes for proteins. It should be noted that less ‘advanced” organisms tend to have better percentages there, and while we do have more genes than most (with some exceptions like corn and rice I believe), we also have more junk. It is thought that bacteria actually have some selective pressure to keep down the size of their genomes, unlike us. People should also keep in mind that non-coding doesn’t mean non-functional. Some non-coding sequence is involved in regulation of replication and other functions along with telomeres for example.

Most mutations happen during DNA replication rather than translation or transcription. This is when DNA is copied and mistakes are often made in the copying. Many of these mistakes are fixed by the body’s own mechanisms. But as you said, about 1 in 1 million replications of DNA has an unrepaired mutation.

Many functional mutations happen when DNA is replicated, not only by changes in non-functional copies of genes, but also by changes in functional genes. Addition, deletion, or substitution of a single base pair will change the amino acid that gene codes for, which leads to a change in the shape of the protein, and thus a change in its functionality.

Nice example with the bacteria. Because of the antibiotics in your body, only those who have randomly developed resistance will survive to divide, so the vast majority of the bacteria population will be resistant where almost none were before the antibiotics. PLASMIDS transfer DNA between bacteria both in conjugation, the bacterial sex you mention, but also through entering directly into the cell from outside.

I really like the arms race analogy. Very good point there. I should point out that there are even organisms alive today which have these early ‘eyes’, some species of roundworm among others I believe.

There is an article I remember reading on the evolution of compound vs. non-compound eyes. I will try to look it up and post the gist of it in the next few days. Anyway good job with the post, just a few errors I wanted to correct and a few things to expand upon.

Originally posted by UmbrageOfSnow
Hey ScottishinNZ. I haven’t been around the last few months as you may have noticed, but now I back. Hope the evolution crusade has been going well. Anyway, just want to clear up a few things about your post. No offense intended.

The circular loops of DNA that bacteria transfer to one another are called [b]Plasmids not Plastids (plast ...[text shortened]... y good job with the post, just a few errors I wanted to correct and a few things to expand upon.[/b]

Thanks, mere slips I assure you. I write largely from memory, and in this case only to give the reader the outline of where we're coming from, not all the detail. I agree that most mutations happen during copying, there is much more scope for mutation there. I think I mentioned that? Never mind, having a tired day.....


Good to see you back!