Ahmad

Originally posted by Radical Edward

 

is that part of the reason for dizziness or light headedness sometimes if you have been exercising really hard then relax suddenly?

That's as fas as I know, yes.

Note that this only applies to what is called dynamic exercise, in which the muscles keep contracting forcefully and periodically. It doesn't apply to static exercise, like weight lifting. So it depends on what you are talking about.

Bioweapons research in the field of molecular biology are more toward targetting specific people.

Imagine a virus that can only affect white men, because of the similarity in their genome. The US army as an example contains people from different gene pools, but you have the chineese army for example.

Chineese have an isolated gene pool and will probably have similar responses to specific types of diseases.

Originally posted by Radical Edward

 

yeap... then you get those interesting cases such as some cyclists who have to be very careful after they have been cycling to have a proper warm-down period, since their resting heart rate is so low. My Biology teacher had a heart with unusually large capacity, and he was very healthy too.

I'm not sure how related is that to the heart rate, but the warm-down period is very important in this case for the pressure change.

In this case, an individual is doing a dynamic exercise in which his muscles are contracting. These muscles have blood vessels going through them, and when they contract, they help in moving the blood towards the heart. They also cause a rise in mean arterial perssure. In this context, these muscles are called "booster pumps".

When these muscles are working very hard, their componenet in the mean arterial pressure will be very high. If they stop working suddenly, their large contribution to the current mean arterial pressure will go away, and there will be a large pressure drop because of that.

This is why you should stop your muscle action gradually, to allow the regulatory mechanisms to follow up until you reach resting state.

Originally posted by Skye

If you are healthier then you should have a lower resting heart rate, your heart needs to pump less often to keep you going. Regular exercise keeps you healthier overall, and I've read that anaerobic exercise can make you heart muscles more flexible which should give it a higher capacity thus lower resting heart rate. Unless you are working really hard, like running all day, then your lower resting heart from regular exercise should oversome the period of higher heart rate during the exercise.

Just to add to that, the heart of a trained athlete does have a lower heart rate, but that doesn't mean that it is not doing the same amount of work. It will be beating less frequently, but each beat will be stronger. Each beat will use a higher amount of energy than that used in the beat of an untrained person. This is because it needs to pump more amount of blood per beat.

The amount of work a person has to do is better correlated with the amount of blood he is pumping per unite time, or the cardiac output, which is basicly the same for trained and untrained individuals in the resting state.

Originally posted by MrL_JaKiri

What you see as green, I could see as purple.

 

But since we're taught the words 'green' and 'purple' with reference to the colours (THEYRE JUST LABLES) everyone thinks 'green' is the colour they see when they look at a 'green' object.

 

This could explain people's fashion sense.

This is exactly what I used to think long ago, but I'm not sure anymore. There are still many things about color that we still all agree upon ..

One such a thing is the colors most people percieve as matching. There is also how most of us agree that two colors are "close" to each other.

Don't you agree that green is more similar to blue that red?

This could also be attributed to the physical properties of these colors, but if I was to immagine in my head the colors green and blue, I would still think they are close to each other.

Originally posted by blike

Or perhaps different response results in different structure

The other way around.

Originally posted by fafalone

There's a difference between a genetic basis and a genetic cause. I haven't seen any studies that infertility and homosexuality are linked.

Some people where argueing that homosexuality is a reason for infertility, and based on that, they said that it cannot have any genetic causes, because infertility is against natural selection.

So my point is this: even if it reduced fertility and fertility rate for homosexuals was zero (the lowest), that doesn't mean that there can't be any genetic cause (or influence) fot it. To better show my point, I refered to an arbitrary article about several diseases that can cause complete infertility, yet they are influenced by genetics.

I'm not saying weather it is genetic or not, I'm just argueing a certain point that was made during the discussion.

I think that Skye made my point very clear. Thank you Skye

Anyway, I think that homosexuality does decrease the rate of fertility. The means by which homosexuals can reproduce are not possible in most of the world population because of social and technical problems.

I'm not sure about the terminology: genetic causes, genetic influence?

In all my discussion before this post, when I mentioned any of these terms I mean that it can be inherited. i.e.: can run in families. i.e.: you be more likely to have it because your father and your mother are who they are.

For those who still think that homosexuality cannot be genetic because it is against natural selection, please read this paper with a lot of information about genetic causes of infertility:

http://urology.ucsf.edu/patientGuides/pdf/maleInf/Genetic_Causes_Infertili.pdf

Originally posted by DocBill

I cannot imagine such an experiement being carried out, Besides, if she was to become completely Male, most of her frontal cortex would begin to shut down from atrophy, and her limbic system would take over. She would grunt and curse about property rights, the stupid people in the world, and generally babble incoherently. I have witnessed this myself on a number of occassions at meetings. I believe the technical term is "Testoterone Toxicity."

 

Bill

This occurs if the testosteron level was high during a certain period of development. I can't imagine anything like this happening by testosterone administered after birth.

The same goes for genital organs.

Sorry DocBill, I didn't mean to be rude. I was really serious about what I'm writing, but your sarcasm shocked me.

Also, as the mechanism of loosing useless phenotypes is mutations, which is the same mechanism for gaining new phenotypes.

So phenotypes are added and eliminated from the species all the time by the same mechanism. What is it in this mechanism that makes removing useless mutations more favorable than adding new ones?

You are obviosly missing my point. Maybe you didn't read my comments from the beginning.

In case you did read them but didn't understand them, let me explain them more to you.

Defining weither ones life is convenient or not is something very relative and not part of my speciality. The point I was making is that some features that we have make our lives more convenient that if we didn't have them.

Again my example, how did we acquire voluntary control over macturition and defecation? Why isn't it involuntary like in other animals? Why did we get that feature and keep it?

Let me explain this more to you. If the only driving force for life and evolution was natural interactions and trial and error with different combinations of genes, then, statistically, we are supposed to see a HUGE number of phenotypes that aren't neccessary for sustaining life in hour bodies, but we must supposingly acquire them through the process of trial and error that we've gone through.

So your reply is that these phenotypes that we would have aquired will get lost because there is no pressure keeping them. As I barely find any un-necessary phenotypes in my body, this mechanism of eliminating such genes must be very efficient.

Now my comment on this is: what is keeping these phenotypes that are not necessary to sustain life or preserve the species, while they are useful to us.

Still, that doesn't say why do we get to keep many things that make our lives more convenient, yet they are not necessary for our existance. While we don't keep many other things that we might as well have had.

Originally posted by Skye

So is there a suggestion that a genetic basis for homosexuality can be selected for? If so, how?

 

I can understand that a genetic basis for homosexuality can be maintained by having other effects that counteract the energy spent on homosexual lovin' but just not that being gay is an advantage. But it's not even close to selectively neutral, so it's not like you can drift over to the Isle of Lesbos.

Actually, nothing is selected for. Things are always selected out!

Anyway, many things stay in the genome because they are recessive. They are carried by some people, and when they reproduce they give an individual with the phenotype.

Just like many of the purely genetic diseases that cause mental retardation or other types of disorders that prevent them from being able to reproduce.

This is so funny.

Funny, but not convinceable.

OK then ..

Why is it that we have voluntary control over defecation and urination?

What kind of pressures is keeping that?

Originally posted by Giles

Generally, higher capacity, redundancy and safety margins are better - you can't win a marathon on one lung. You think about exercise when you need to exercise, and it prepares you (think how useful this would be in predator-prey interactions.) Your immune system can handle more diseases than it will ever encounter. You can survive injuries.

So they do serve a purpose?

Even redundancy serves a purpose. Either to make our lifes easier, or that we needed it to survive.

There is a muscle in the midline, just above the pubic bone called pyramidalis. Only 40% of the population have it. It tenses the long line of connective tissue in the midline, called lina alba. So it makes movement easier, but it is not neccessary for survival. There are other things too that could have been selected out, but are still there, and they do serve a purpose.

I suspect the amino acid code is a matter of chance in some degree. once you've got one you can see how hard it would be to change. Nevertheless it does vary to some extent. There are also certain likely pressures on it.

What I mean is, why did the system develop this way in the first place. Why didn't it develop in 4 bases for a codon instead?

It should be mentioned it's not exactly the same in all organisms, but it's always three base pairs to a codon. There are more than four bases though, if not more than four at a time, and more than 20 amino acids.

Yeah, always three bases per a codon, but some codons code for different amino acids in different organisms. In the DNA, there is only the four bases, unless there is a mutation (somtimes a cytosine is converted into a thymine). In RNA, however, there are more bases.

it's probably at least partly a matter of stability. A redundant coding system is more stable in the face of mutation (please note that natural selection favours a LOW rate of mutation in the short term - higher organisms have other ways of generating variation).

What I'm saying is that the coding system is not actually redundant. There are only 64 codons, it couldn't have been less, because it would be 16, which is not enough. But it is not any more than that.

Conversely, four base types is more concise than two (2 bits/pair rather than 1). Because of the way pair matching is carried out, another base with similar chemical properties to an existing one would be a liability.

So, it is concise in here too.

Your post seems a little confused. Life is no as concise as it could plausibly be with a similar underlying chemical structure; nor is it very long-winded (unlike me). Finally, it shows signs of being constrained by past design. I'm not sure there's much problem for evolutionary theory in that.

Well, that's the point. It is more relative in here. We can't say if this is the most concise system or not, because for that we need to understand the purpose of every piece of the system.

Still, when we are talking probabilities, the overall picture should be that everything should add up to seem almost exactly between complete conciseness and the opposite of that. And it seems to me that it is much nearer to complete conciseness. And that is for the facts I'm mentioning.

The only explanation I can find for that based on evolution is that evolution has been lucky most of the time.

I think we both need to learn more biochemistry to discuss this with confidence.

I'm not sure if I'm gonna ever learn any more of that. We have already finished the molecular biochemistry unit. Unless I make it my specialty after I graduate (which is not very unlikely), I might never come to that later.

liljohnak ..

Billions of years ago, that was actually the case. People could only use physical expressions as means of conveying thoughts and information. Then a mutation happened and some people gained the ability to speak. So there were two colonies: the mutas (can't talk) and the spichas (can talk).

One day, the king of the spichas sent the king of mutas a gift, spichas' most advanced and sophisticated mobile phone with GPRS, bluetooth, color display and all the goodies. The king of mutas felt so offended and declared war against the spichas.

The two armies were lined up against each other, and war there was. After 15 minutes, the spichas sent their secret batch of army men from behind. Mutas' observers could easily see the spichas coming, and they wanted to warn their troops. Of course, that was too hard, because the troops were busy fighting and they couldn't see the message (being broadcasted in physical expressions).

That is actually how natural selection selected out people without the ability to speack.

Sorry, for the OT.

OK. You can add to that this questions:

How did we aquire these features that makes our lives more convenient, yet we could still survive without them, although life would have been harder.

For example, when you want to exercise, just by thinking about starting, your muscles will get more blood flow.

The same thing for the lungs' size. We don't need it to survive, but we need it to live a better life. How come we still have these features even though we don't need them to survive?

Why don't we have other features like these that are not useful to us in any way, and that wouldn't make our lifes better?

Looking at a much lower level, we have 20 amino acids that we need to code for in our DNA. We use three nucleotides for each amino acid. Why did it happen that we have exactly three nucleotides?

1 for an amino acid wouldn't be sufficient,

2 for an amino acid wouldn't be sufficient either,

3 would be sufficient,

but why not 4 or 5?

This all makes me think life is very concise.

Gene knock-out animals always have several problems. I even heared that cancer risks are higher in people that had their appendix removed!

For all these things, I can't find an answer in natural selection. They all make me think that life is concise, and thus can never come randomly.

Hi Giles,

I get your point. I see it amazing though. There are always those who are asking, why don't we witness a mutation to something good? Why can't we find a realy example of a mutation that happened and created a big leap from a species to another? One that changes even the number of chromosomes and the distribution of the genes over the chromosomes?

And the answer is that these things take time.

Why is it then that it doesn't take mutations that much time to remove extra features that we don't need. It happens in no time that we can't even find something without such an extra feature.

Originally posted by Giles

could you be more specific or give a source?

Studies on infants around the world show that they all go through the same stages in learning a language. They start by learning words (from their own parents' languages), then by using telegraphic speech, and so on.

Our psychology professor also suggested that if you have two people that are isolated from the outside word, they would develop their own language. He even said that twins in many cases develop their own languages that is only understood by them.

Of course, the language itself is learned, the ability is what is innate.

From my understanding of natural selection, it can only select things out, not select things in. So as fafalone said, if it is not harmful (i.e.: causes distinction of the species), it won't be selected out.

Now, fafalone, you said that if something doesn't have a need now, it once did. Did you mean once in the history of a specific species, or once as in the species we originated from?

I would assume evolution went this way:

asexual organism -> bisexual organism -> sexual organisms

Hydra, for example, was capable of doing all three types of reproduction: asexual reproduction, self-fertilization, and cross fertilization.

Asexual reproduction was achieved in hydra by its ability to regenrate into complete organisms if they were chopped into pieces. As organisms grown in size and had more specialization, this became impossible to achieve, so the ability was lost.

But why did organisms lose their bi-sexuality? I don't know.

Originally posted by grazzhoppa

Communication and sharing of information makes all that possible. Why don't tiny mice have time to make a language? Because they are too busy trying to survive...to live, if word got around on how to get food easily and hide from or even kill a predator (snake) easily...they would have more time and would develope faster (as a species). You see the exponential growth of our technology and understanding of the world (science) because we develope better ways to communicate with each other which saves us time and that leads to us doing more as a species. Why should you and another human work on the same problem when one could be doing it while the other works on the next step? Then you share your information...and you now have more time to go onto bigger and better things. I'd say from this logic that the printing press was the greatest invention of all time...it was probably equivalent to the impact of the Internet.

Language, actually, was proven to be innate in human beings. Language in human beings is important not only as means of communication, but for logical thinknig too. It is something in our genome.

It is logical that a 'species', by definition, must have all its needs (i.e.: natural selection). But why is it that we almost need all we have?

Whenever something is discovered in a living thing, it is always paired to a function, or said to be of an unknown function. We never say that it doesn't have a function!