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

Ok, here's the point I'm getting around to making... very slowly.

I don't see any reason to call the whole passing on of resistance evolution. It is certainly natural selection of an existing genetic trait (or combination of traits), but not evolution. Why are we even calling these resistances mutations? Is there a real reason to do so? Are you just assuming they are mutations, or do you know for sure?

Deadwood,

Yeah sickle-cell anaemia is a good example of natural selection, and it's unusual due to the fact that it is a human example. Malaria is still the world's biggest killer I think.

I think we went over the moths pretty exhaustively a some posts ago .

"Evolution is simply natural selection over huge amounts of time." I would disagree with that statement. Natural selection needs raw material to work upon, i.e, polymorphism within population. This is generated by mutation and genetic drift. Gene flow is the way it is all distributed.

We are not trying to disprove the existence of a God in this forum. I personally am trying to explain evolution to the creationists who criticise it without understanding it

Potholer,

Yeah, if there were no mutation, there would be variation and we would all be identical. Hehehe,

Ste

ddombrow,

To call antibacterial resistance 'evolution' is pushing it a bit. It certainly isn't Neo-Darwinian Evolution is the classic sense. To evolve basically means to improve, so you could say that they are improving their defenses against drugs, hence evolving. I agree that it is certainly natural selection however.

There are a few types of antibiotics, I'll stick to the penecillin types as an example. Within the molecule of penecillin is a three carbon, one nitrogen structure called the 'beta-lactam ring'. Penecillin acts upon bacteria by inhibiting the synthesis of an important cell wall molecule called peptidoglycan, therefore stopping it's growth. Penecillin worked for decades until it was noticed that resistant strains appeared. These bacteria had evolved and enzyme which cut the beta-lactam ring, rendering the antibiotic useless. This enzyme is called beta-lactamase, unsuprisingly.

New antibiotics appeared that were similar to penecillin, but different enough to be not recognised by the beta-lactamase enzyme. Mutations of the gene that codes for beta-lactamase gave rise to many varieties of the enzyme. The intense survival pressures put on the bacteria due to the appliction of the new drugs selected these mutants.

ddombrow,

To call antibacterial resistance 'evolution' is pushing it a bit. It certainly isn't Neo-Darwinian Evolution is the classic sense. To evolve basically means to improve, so you could say that they are improving their defenses against drugs, hence evolving. I agree that it is certainly natural selection however.

There are a few types of antibiotics, I'll stick to the penecillin types as an example. Within the molecule of penecillin is a three carbon, one nitrogen structure called the 'beta-lactam ring'. Penecillin acts upon bacteria by inhibiting the synthesis of an important cell wall molecule called peptidoglycan, therefore stopping it's growth. Penecillin worked for decades until it was noticed that resistant strains appeared. These bacteria had evolved and enzyme which cut the beta-lactam ring, rendering the antibiotic useless. This enzyme is called beta-lactamase, unsuprisingly.

New antibiotics appeared that were similar to penecillin, but different enough to be not recognised by the beta-lactamase enzyme. Mutations of the gene that codes for beta-lactamase gave rise to many varieties of the enzyme. It only took one of these slightly different enzymes to make an entire culture resistant. The intense survival pressures put on the bacteria due to the appliction of the new drugs selected these mutants.

Oops, read the bottom one

ddombrow: Because "evolution" rolls off the tongue better than "the passing on of resistances." Plus, your term only addresses the selection side. Selection + Mutation = Evolution. First the minor mutations occur, then the environment acts on the gene pool to select those mutations which promote survivability, under those particular conditions.

Without malaria, sickle-celled people might have been selected to extinction.

And now, for a bit on how the evolutionary explosion thing works, because I seem to have caught your attention with it earlier...

We often think of evolution in local terms. Let's take it planet-wide. A massive catastrophe has just occurred, and all but some tiny pockets of life were destroyed (this saves us the trouble of arguing over the origins of life). In an ocean, there are a handful of plants. There is massive amounts of carbon dioxide in the air, as a result of the catastrophe. The available space is seemingly infinite.

Under these conditions, *everything* can survive. Every plant mutation has an opportunity to thrive, because there is zero competition for resources. Plus, the original comes from a very thin gene pool, so they combine too often, and produce genetic mutations with a greater degree of frequency.

Soon, plant varieties cover the planet. Now begins the natural selection, as some begin to die off because they can't compete successfully with the local varieties for soil, water, sunlight, and carbon dioxide. Worse yet, the CO2 levels are being depleted. However...

Here come the animals. Developed from one-celled organisms, they're unleashed into a world with an endless food supply (the plants) and plenty of oxygen, they spread like wildfire... until competition for food and territory among them becomes too great. Some evolve into smaller roles, taking foods no one else was eating, like tiny seeds. Some evolve larger roles, preying on animals instead of plants. Some fill another niche, eating the sick and dead animals that even the predators won't touch. As every ecological niche fills up, evolution slows down. Where we once saw the birth of a new species every few generations, now we see a new one every 1000 generations.

This process occurs faster if there is a greater amount of genetic material available from the start... which is another good explanation for the mammal explosion. Once the great reptiles were removed from the ecosystem, the tiny mammals had the opportunity to fill those niches.

The opportunity to test this theory is exactly why we need to boil some polar ice on Mars. A whole planet full of resources, a high-CO2 atmosphere for thermal purposes and temperature regulation, some regular rainfall, and a handfull of seed organisms to speed the process along, and we should have some brand-new organisms.... in only a few thousand years or so.

Sorry to repeat myself (and moths), I'm a bit new to all this.

I don't see why you say that natural selection and evolution are different things. Afterall, Darwin's book was called 'On The Origin Of The Species By Means Of Natural Selection'

It was a while ago when I did genetics and I'm perhaps not up to speed.

Please explain the difference, I'm struggling a bit with the technical terms, especially gene flow.

Thanks for your reply,

D.

Deadwood,

Welcome to the forum . Darwin didn't have a the more full picture we do today, that's why the current theory is called "neo-Darwinism"

Natural selection is a micro-evolutionary force. So is gene flow, genetic drift and mutation. Gene flow is basically the migration of genes around the gene pool. Genetic drift occurs when the frequencies of alleles (variants of genes) change over time within a population due to selection and random variation.

Ste

Thanks Ste

I'll go back and read my old lecture notes and get back to you!

Deadwood-

I'm getting tired of explaining this. Those moths were a hoax. A scientist named Kettlewell taped them to trees and photographed them. The moths don't rest on trees. Furthermore, there was no evidence that black moth populations increased. Furtherfurthermore, Even the worst polution does not turn trees black! So your example is false.

Resistant strains of bacteria are a good example, but they only make bacteria less likely to evolve, at least from my understanding of Darwin. If you practiced karate and went from being a beginner to a black belt, are you not still karate person? What I'm attempting to say here is that if a species becomes more and more perfect all the time, why does it change into something new?

Something else. If species evolve by becoming more adapted then does it follow that 1 million species were very much unadapted? Why then do we have crododiles and several other that have not changed since prehistoric times?

Finally, Sugar cane. My point in the sugar cane example was to show you an example of an inexplicable phenomenon called natural selection, which was discovered long before Darwin and causes species to abruptly stop changing after they near the barrier that separates them from becoming another species. Some other examples are humans (though major genetic mutations have occurred in height, pigment, etc. at an alarming rate, but these all suddenly ceased when these ethnic groups reached a point where they were in danger of no longer being able to breed with other humans), and Darwin's finches (their beaks differed by as much as 5 millimeters, but the average over a long period of time is infailably the same.

I don't know about all that but I concur that natural selection and evolution are two very different things. I don't think we (evolutionists and creationists that is) disagree on the effects of natural selection. They are observable, logical, and scientific. When we add the second part of evolutionary theory, mutation, speculation come into play. It is the major underlying assumption of the theory and also its weakest link.

I don't think resistance is caused by mutations at all. I think its a random variance in genes that proves to be beneficial under certain circumstances, thereby allowing it to be selected and passed on. Does that make sense? If it doesn't, show me how you know (or even think) that a mutation causes resistance.

Josh wrote:

"I'm getting tired of explaining this. Those moths were a hoax. A scientist named Kettlewell taped them to trees and photographed them. The moths don't rest on trees. Furthermore, there was no evidence that black moth populations increased. Furtherfurthermore, Even the worst polution does not turn trees black! So your example is false"

I cannot believe you wrote this. Especially with the "I'm tired of..." bit, imagine how I feel. No wonder you cannot bring yourself to understand simple logic if you do not even take on board anything.

The moths *were not* a hoax. The work of Kettlewell has been followed up since. Look at a study by Bisho and Cook (1980) showed a transect from industrial northern England the rural north Wales which OBSERVED black varieties in the industrial regions and lighter ones in the countryside. Look at the papers. Read papers by D. R. Lees, someone who has written and studied this phenomenon for 30 years. There is TONNES of evidence that the black moths increased in numbers, it has been extensively documented.

There IS pollution that turns stuff black. Particulates which create soot. Others in this forum also told you this before.

Every point you have raised has been easily answered, yet you just ignore it. If that's the way creationists deal with understanding the world, then no wonder they believe in such blatantly ridiculous things and practise flawed logic and circular reasoning.

Josh, you say: "Resistant strains of bacteria are a good example, but they only make bacteria less likely to evolve, at least from my understanding of Darwin".

You have demonstrated amply that you do not understand Darwin, even though his theory is 150-odd years old and has been extensively updated since.

Species do not become "more and more perfect". You're missing the point. Species adapt to their ecological niche, when that ecology changes, the species change, diversify and diverge to meet the new demands of the environment.

I have not heard of this "natural selection" you describe. It sounds like it has no basis to it, and no reason to think it is true. There are many examples of speciation occurring, but I can't be bothered to tell you any because you will either ignore them or pretend you didn't see them or something

*sigh*

ddombrow,

Why do you think mutation is speculation?

It does make perfect sense what you're saying. The "random variance" in the gene is created by mutations. Genes code for proteins. If you change the gene, you change the protein. A single amino acid change caused by a point mutation (i.e. single base pair) can change the properties of the protein (in this case an enzyme).

Do you know the basic lock and key illustration of enzymes? Well, the enzyme has to be able to perfectly 'fit' into or around it's substrate (in this case the attacking antibiotic) for it to be able to catalyse it. Changing the substrate (i.e. applying a new antibiotic) changes the 'lock' and the enzyme 'key' won't fit it any more. Generate enough different enzyme 'keys' through mutation (of the gene and therefore the subsequent protein) and one is bound to fit. That one will be selected and passed on.

I hope I have explained myself well . If I haven't tell me and I'll try to describe it better.

Ste

Gradient,

"Also, I read something last night that suggested we are nothing more than vehicles for memes.
A meme is an idea. There are countless memes floating around out there...check out the memecentral website for more details."

Interesting idea, but I don't think memes are as wildly fascinating as all that. It's like saying that humans are nothing more than devices for measuring the passage of time. I think that memes and God and Time are related in that they don't exist outside of human perception.

Mutations being passed on. How about bleeders? I think it is believed it was Queen Victoria who had a mutation, that she then has passed on to a large part of the royal family. This is not a beneficial mutation and has probably appeared in common people often, to just die out.

What about that African tribe where they all have feet like crab claws? That is probably a mutation passed on. And beneficial too, they use their feet like the rest of us use our hands.

Ste, you have an impressive knowledge about these things! And some patience too, which is even more impressive.

But the most striking thing, as you say, Colonel Sellers, is that these creationists try to scientifically (although by false understanding or lies) disprove Evolution while their version of creation is a childrens fairy tale only and does not stand the most simple reasoning.

"It's like saying that humans are nothing more than devices for measuring the passage of time. I think that memes and God and Time are related in that they don't exist outside of human perception."

I think I understand what you're saying.
Our perception of time is limited to an awareness of entropy, so we can agree that time is outside human perception. The existence of God is still in debate; if we assume for a moment that God exists we can perceive him in the same manner we look for Black Holes - by the effects he has on his surroundings. We could point to the existence of organised religion, people of faith and miracles as indications that God can be perceived. We can also percieve memes in the same way - we can't see them, but we can track their progress through humanity. In that sense at least, they lie within the realm of human perception.

The prospect of humans being nothing more than a DNA machine that has acquired the ability to host and transmit memes (we call this "conciousness") feels like belittling humanity; saying that we are somehow less than the pinacle of Evolution/God's creation. So here's a thought...

Either way, the movement of memes could be seen as the universe attempting to explore itself. Conscious humanity is, effectively, the creative mind of God. If there is no God, then humanity is part of the universe exploring itself. Either way, we have a purpose and a role, which perhaps we did not have before. Maybe DNA wasn't so far off the mark when he wrote that the Earth was a giant computer, devoted to making sense of existence.

There still seems to be some confusion by some people about mutation and natural selection. They are two completely separate things. Natural selection in no way determines, speeds up, or stops the rate at which organisms mutate. Natural selection happens in many ways: climate change, viruses, competition for scarce resources among organisms, cataclysmic disaster, human incursion, etc. The net effect being that organisms unsuited to the new status quo are eliminated, and the ones that are suited to it, thrive.

ddmbrow : A random variance in genes IS a mutation. What you have said makes complete sense. I would not disagree with you.

In a nutshell - mutation can make many differences out of one, natural selection cuts out the many to favour the few.

And one other thing - evolution got a bad name because many people have used this model to describe how human society should work too - ie. social darwinism. Evolution also got a bad name because some people have used it to try disprove God. Evolution is a fact, but it does not necessarily follow that these particular inferences are true.