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AZPaul3
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Posts: 3945
From: Phoenix
Joined: 11-06-2006
Member Rating: 4.0


Message 16 of 22 (401149)
05-18-2007 2:51 PM
Reply to: Message 15 by ogon
05-18-2007 2:29 PM


Re: Very Close Indeed
If some genes lay around long enough do they become useless? do they cease to exist?

Please excuse my humor. Genes really don't just lay around. Back to eye color, when the gametes (sex cells) are formed one allele ends up in each gamete. So you will have a gamete with the blue allele and another one with the brown allele.

Now, to confuse matters, there are strands of our DNA (genes) that, at least for now, appear to be non-coding. The do not get expressed. You have probably heard of "junk DNA". These just get passed on, generation to generation, mutations and all without any noticable effect. In this case, changes or whole deletions can take place without affecting the population. I do not know of any examples to give you where any gene disappeard due to non-use, but others here may have some.

An allele may not be expressed in a specific individual. But, may indeed be expressed in one's offspring. It all depends on which two gametes fuse to form the offspring.


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Dr Adequate
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Posts: 16094
Joined: 07-20-2006
Member Rating: 5.5


Message 17 of 22 (401155)
05-18-2007 3:26 PM
Reply to: Message 15 by ogon
05-18-2007 2:29 PM


Genes In Decay?
If some genes lay around long enough do they become useless? do they cease to exist?

If by "lying around", you mean "performing no useful function", then yes, this can happen.

Primates have the non-functional remains of a gene for making vitamin C. The loss of it was no loss to monkeys, 'cos they eat fruit, and so they get plenty of vitamin C in their diet: so there was no selective pressure against the defective copy of the gene. If monkeys had had to eat the diet of a nineteenth century sailor instead of fresh fruit then the first such monkey would have died of scurvy and the broken gene could not have spread.

I hope this helps.


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Dr Adequate
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Posts: 16094
Joined: 07-20-2006
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Message 18 of 22 (401156)
05-18-2007 3:39 PM
Reply to: Message 10 by ogon
05-18-2007 4:02 AM


So really the development of a species is by chance?

"By chance" is a summary too far.

For example, you will know what eventually happens when we introduce a new antibiotic into our arsenal. Eventually, the bacteria we're targetting will evolve resistance. Now if someone said that this was "by chance", this would be a bit odd. We'd answer: "By chance? It was caused by the introduction of the antibiotic, we predicted that this would happen, it was not a coincidence in any way."

Saying that "evolution happens by chance" is an ambiguous statement, like saying that "a lion is a cat", without saying if you mean the species Felis cattus, the genus Felis or the family Felidae. But saying "not by chance" is wrong too, just as it is inaccurate to say that a lion is not a cat.

In order to say something unambiguous, you have to go into more detail, and say: "Lions are of the family Felidae; evolution works by selection acting on random variation."

Edited by Dr Adequate, : No reason given.


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subbie
Member (Idle past 96 days)
Posts: 3508
Joined: 02-26-2006


Message 19 of 22 (401159)
05-18-2007 3:59 PM
Reply to: Message 18 by Dr Adequate
05-18-2007 3:39 PM


By chance
ogon, in the sense that the devolpment and evolution of a population of organisms is not directed, it is indeed "by chance." Also, in the sense that mutations occur in genes that take a part in evolution, and these mutations are not directed to any particular goal, it is "by chance." In this manner of speaking, the answer to your question is yes, it is by chance.

However, as Dr. A points out, what happens to the population through time, and the manner in which the population tends to change, is not by chance and in some ways, but not all, it is rather predictable.

Populations tend to change in response to the selective pressures that are acting on them at any point in time. As in the simple example I contrived earlier in this thread, as the climate gets colder, we expect to see those organisms that are better adapted to the cold thrive. Although this is a very simple example, it serves to illustrate a point. Often those who do not understand evolution focus at the "randomness" of mutations and the "randomness" of how genes combine in each successive generation to try to establish that the whole process is "random" and that evolution happens "by chance." If this misunderstanding of the process were in fact accurate, it would be remarkable indeed if any sort of order arose out of the process. However, there is a kind of sorting mechanism, natural selection, that weeds out less efficient organisms. The selective pressures found in nature tend to push a population of organisms in the direction that will tend to maximize their reproductive potential.

Thus, while in one sense it is accurate to say that the creation of new species is "by chance," chance alone is completely insufficient to accomplish what mutation, genetic drift, sexual combination and natural selection accomplish when all operating at the same time.

I think we're starting to get a bit more complicated now, but I get the feeling that you do have a good grasp of the basics.


Those who would sacrifice an essential liberty for a temporary security will lose both, and deserve neither. -- Benjamin Franklin

We see monsters where science shows us windmills. -- Phat


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ogon
Member (Idle past 4265 days)
Posts: 70
Joined: 05-13-2007


Message 20 of 22 (401289)
05-19-2007 2:59 AM
Reply to: Message 19 by subbie
05-18-2007 3:59 PM


Re: By chance
So, if I can stop my head spinning a minute and try to think clearly!

Would it be true to say that

it isn't that life makes a calculated response to environments

it is, if you so happen to be suited to a particular environment you survive.

If I am getting it right then I can see where a lot of confusion could be coming from. I have always believed that evolutionists were saying life finds itself in all manner of changing environments and so makes changes. Intelligent genes! But really, if I am now seeing it clearly.

If I can use what was said earlier as an example. A drop in environmental temperature would find those guys with long hair better suited to the change and in a position to reproduce and pass on their genes. The poor guys with shorter hair don't have genes running around flapping their hands saying, okay let's change guys it's getting colder out there! These shorter haired guys just don't survive. We then end up with a bunch of long haired guys when once there were guys with long and short hair. evolution.

If that's right then I have just pulled my first wheelie!
ogon

Edited by ogon, : No reason given.


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NosyNed
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Posts: 8842
From: Canada
Joined: 04-04-2003
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Message 21 of 22 (401297)
05-19-2007 3:53 AM
Reply to: Message 20 by ogon
05-19-2007 2:59 AM


Dangerous Analogies
Analogies can often confuse as much as help but I'll try anyway:

You have it pretty darned right -- wheelie away!

Look at it another way:

When a modestly smart human is given a challenge of making a machine better they apply what they know and think about the problem. They may sketch some thoughts and do some calculations. They ask more about why the current version is not as good as desired or what has changed to need a new version.

Only then to they pick what might be changed. A lever arm longer somewhere, more horsepower in a motor or more insulation (longer hair?).

Nature produces designs in an utterly different way. The way some of us dummies often try to fix something broken when we have no idea how it works. We tinker. We change this and then that and hope it works.

Nature does this to an extreme. It has no idea there is anything to fix. It has no idea of what is needed. It doesn't "intend" to change anything.

It just produces a slightly different version of the machine every time it is manufactured. Each human has a few small changes so there are 6 billion different versions running around. How many new versions of "Acme Cockroach" is produced each year????

Then all the bizillions of "fixes" that don't work out are thrown away. Any that work ok or better are kept. Then the whole process is done again the next generation.

Imagine if humans designed this way. Research labs would be factories that produced millions of machines a year each with something changed a lot or a little. Out back would be a huge mountain of things that were just too dumb to be shipped and out the front would go those that worked. The next round would start from only those that worked and more changes would be made.

By the way animals are "thrown away" in huge numbers. About half of all human fertilizations are thrown away (usually before the mother is aware of it) because they are just too messed up to develop very far at all and spontaneously abort in the first days. I'm guessing this is true for most animals.

It is hugely wasteful in material and a company trying this by actually building things to try them out this way would go bankrupt fast. But the designs can "explore" all sorts of different "fixes" and find many, many that work well and then better.

The answer to a "problem" in nature when "asked" what shall we try is:
e v e r y t h i n g.

(The above leaves out a lot which can be discussed later. Evolution is more constrained than I am letting on.)


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ogon
Member (Idle past 4265 days)
Posts: 70
Joined: 05-13-2007


Message 22 of 22 (401324)
05-19-2007 7:43 AM
Reply to: Message 21 by NosyNed
05-19-2007 3:53 AM


Re: Dangerous Analogies
yes analogies can be mis interpreted! As a teacher I get reminded everyday by my students that we all have different learning styles and for me, a picture in my head says more than a thousand words!

What has been said so far, and from my constant reading on the subject, I think I have a lot more questions on the way and hopefully you guys will attempt to answer them.
ogon


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