Seperation of Sexes

[blike]

How and why did there become two sexes? I understand that it greatly sped up the evolutionary process, but its not advantageous to sustaining life. Also, many mechanisms would have had to developed for sexual reproduction to be effective. These would have been unlikely to occur all in one generation. This would have left many organisms unable to reproduce, because all the mechanisms are not there; hence the genes for sexual reproduction would not be passed on and it would terminate.

[fafalone]

It's advantageous to have one specialized structure instead of two.

[chris]

Why did we become 2 sexes? Well, no one knows why. But ask your self this question.. Why not? It just happened. It also depends on wheater or not you are religious. Because God did create a man and a women. So, yes there could of been ways to reporodcue without man/female. But you that the species would of died out millions of years ago.

[blike]

I am religious, but I still believe that evolution occured.

 

It's advantageous to have one specialized structure instead of two.

 

Yes, so why did two specialized structures evolve?

[Radical Edward]

one can't assume that all forms of life, terran and alien would evolve into two sexes, however it is proabbly likely.

 

two sexes has the advantage that it allows mixing of genes, branted spoecies could also become hemaphrodites, and this is true for some, such as plants and worms, however for more complex organisms, it becomes more difficult, and would be impractical for mammals. any more than two sexes would become very difficult to organise in terms of handing genes and such round, and would be far less likely to evolve.

[chris]

But evolution can only take you so far. If you can show me where non-living became living on the evolutionary table. then i'll believe u. But I believe god created the first people. thats me. and 2 are always better then 1.

[fafalone]

Sexual reproduction creates more variance, therefore is an advantage. As organismal complexity increased, so did the reproductive structures. Eventually seperation of sexes became an advantage; the organism carrying the young would stay hidden by it, having less of a chance to be killed. So it was an advantage to seperate.

[blike]

Yes but in the process wouldn't there be non-reproductive generations; thereby terminating the trait?

[fafalone]

Why? It started with all of a group having both working, then the two sub-groups shifted over time.

[blike]

I understand that a group could have both working reproduction mechanisms, but how did it develop sexual reproduction? It wasn't necessary for survival, and evolution doesn't have a goal in mind. Its not like in a single generation an organism would develop that would function sexually and asexually. There would have to be an in-between non-working stage, and evolution eliminates useless adaptions.

[aman]

Since a natural tendency for survival would be strength in numbers it would foster socializing and contact which would be a positive evolutionary pressure toward sexual reproduction.

Also virus forms were reproducing in hosts and possibly taking stolen RNA from host to host. Maybe it was positive pressure to develop sexes also until it was finally refined.

The survival of the species pressure would also push for maximizing genetic exchange. Just food for thought.

Just aman

[Radical Edward]

Originally posted by chris

But evolution can only take you so far. If you can show me where non-living became living on the evolutionary table. then i'll believe u. But I believe god created the first people. thats me. and 2 are always better then 1.

 

self replicating structures... that's all life is. considering that amino acids have been found all over the place, such as in residue from lightning storms to drifting around the cosmos, then it becomes clear that amino acids are pretty common. since amino acids are the basis of life, and one of the constituents of DNA, RNA and such, then just statistically, you would get self replicating organisms, which then stand a chance of becoming more and more complex and so on. in terms of simple organisms, anything with even a slight advantage will win, and so you have evolution.

[aman]

If God created man and women then I feel it was done by stirring the soup millions of years earlier and standing back. There's no evidence we just popped up from behind some tree.

That's my opinion.

Just aman:cool:

[dronezero]

Originally posted by blike

I understand that a group could have both working reproduction mechanisms, but how did it develop sexual reproduction? It wasn't necessary for survival, and evolution doesn't have a goal in mind. Its not like in a single generation an organism would develop that would function sexually and asexually. There would have to be an in-between non-working stage, and evolution eliminates useless adaptions.

 

The first sexually reproducing organisims were in fact microbes (approximately 2 billion years ago). This eliminates complex systems for sexual reproduction that would take many generations to develop. So my basic understanding is that the first occurance of sexual reproduction would have been very simple and crude and then developed from there.

 

I got my info from Carl Sagan's Cosmos.

[fafalone]

Originally posted by blike

I understand that a group could have both working reproduction mechanisms, but how did it develop sexual reproduction? It wasn't necessary for survival, and evolution doesn't have a goal in mind. Its not like in a single generation an organism would develop that would function sexually and asexually. There would have to be an in-between non-working stage, and evolution eliminates useless adaptions.

 

 

Good god you're so ignorant about evolutionary theory. Seriously, how can you take general biology and be this unfamiliar with evolution?

Sexual reproduction is about VARIANCE. There would be no evolution without variance. Sexual reproduction evolved quickly because it greatly increased variance. From non-sexual reproduction, organisms whose reproductive process was influenced by variance causing factors survived better, thus a complex system such as sexual reproduction evolved.

You really need to read a book on this stuff.

 

Furthermore, Mr. Lamark, "useless adaptions" are only eliminated if they are a disadvantage. Ever heard of "vestigial structures"? No? WELL THAT'S BECAUSE IT'S IN THE EVOLUTION BOOK YOU NEVER READ. The theory of use and disuse was debunked ages ago.

[blike]

fafaIone (12:31:20 PM): i think you should just refrain from posting anything about evolution, you're just embarassing yourself now =P

 

Good god you're so ignorant about evolutionary theory. Seriously, how can you take general biology and be this unfamiliar with evolution?

Sexual reproduction is about VARIANCE. There would be no evolution without variance. Sexual reproduction evolved quickly because it greatly increased variance. From non-sexual reproduction, organisms whose reproductive process was influenced by variance causing factors survived better, thus a complex system such as sexual reproduction evolved.

You really need to read a book on this stuff.

 

Blah blah sexual reproduction produced more variance blah blah better survival blah blah.

 

You missed my first quote "I understand that it greatly sped up the evolutionary process." This implies that I understand that evolution greatly diversified things.

 

Furthermore, Mr. Lamark, "useless adaptions" are only eliminated if they are a disadvantage. Ever heard of "vestigial structures"? No? WELL THAT'S BECAUSE IT'S IN THE EVOLUTION BOOK YOU NEVER READ. The theory of use and disuse was debunked ages ago.

 

Exactly.

 

Now that you wasted a whole post, I'll be clearer on my statement.

 

--

 

How did the leap from asexual reproduction to sexual reproduction occur? Assuming an organism's offspring spontaneously had all the mechanisms necessary for sexual reproduction, it would be feasable. However, it likely took many intermediate stages. Within these intermediate stages, sexual reproduction would be impossible, so the organism would have had to retain the ability to reproduce asexually. Any organism that wasn't able to reproduce asexually would be terminated, because sexual reproduction had not fully developed. It seems to me that in these intermediate stages, it would be advantageous to be able to asexually reproduce, thereby eliminating any organisms that were not asexually reproducing. Keep in mind, while in these intermediate stages, it is not advantageous to have sexual reproduction, because it is not functional and has no effect on reproduction. Of course, this does not mean it is eliminated, however, it is unlikely that these organisms would be favored by natural selection because they have no advantage at this point. Eventually we come to an offspring that is able to both asexually reproduce and sexually reproduce. How this occurs is part of my dilemma. Since natural selection doesn't play much of a role in this scenario, how did a trait evolve into something useful? Spontaneous mutations? How could natural selection have screened for something that has no bearing on sexual reproduction? Lets assume we have two, fully developed organisms that are able to sexually reproduce and asexually reproduce. Now we have sexual reproduction, and, if necessary, asexual reproduction. According to our resident evolutionary expert "Furthermore, Mr. Lamark, "useless adaptions" are only eliminated if they are a disadvantage. " At what point does asexual reproduction become a disadvantage? It seems to me that retaining the ability to asexually reproduce would be more advantageous than solely relying on sexual reproduction, especially in the absence of a mate.

 

There would be no evolution without variance. Remember, diversity is not a goal of the ecosystem, merely an emergent property of natural laws. An organism that can asexually reproduce 100 times in its lifetime is more successful than a sexual organism that reproduces 4 times in its lifetime. It is true that these organisms will have little to no diversity, however, diversity is not a requirement for survival. Asexual reproduction cannot be disadvantageous.

 

--

 

You continually display great mastery of putting words into people's mouths. Perhaps it is a lack of reading comprehension, or maybe it is an inherent desire to twist words enough so you can make a point. Regardless, you create the illusion of an argument by tiptoeing around the issues and stating the obvious; namely "sexual reproduction is about variance".

[fafalone]

Originally posted by blike

and evolution eliminates useless adaptions.

 

 

This is the theory of use and disuse. Word for word. These are the words that came from your mouth, and those words describe the theory of use and disuse.

 

 

 

 

 

 

Furthermore, intermediary steps would NOT be useless since those steps would be all increasing in variance, which is the advantage that resulted in sexual reproduction.

 

And what's more, your last post demonstrated even more of a lack of understanding of evolution than your first one. I don't even have time right now to go through it all. Go ask your bio professor so he/she can laugh in your face. I put no words in your mouth, I merely responded to the literal meaning of your post. You seriously need to get a basic understanding of evolution, because you have no idea what you're talking about.

[blike]

"and evolution eliminates useless adaptions"

 

You're right, I was wrong. My Anthropology professor told me in a direct answer that this is true. I was wrong, but it doesn't weaken my argument.

 

"I don't even have time right now to go through it all."

 

When does asexual reproduction become a disadvantage?

 

Variance is not an evolutionary advantage in and of itself. Variance brings about changes that can have evolutionary advantages.

 

Lets assume I have a useless internal organ in me that only me and my brother's have. It does not effect anything else about my body. It is simply and extra structure. Are you telling me that this variance would be an advantage? Would we have more offspring because of this? No, speaking in terms of natural selection, I have the same advantage as Joe sitting next to me sitting here in the computer science lab; so as-long as this structure has no effect on me. Once it has an effect, there is a possibility for advantage or disadvantage, but in its useless stage it is neither advantageous or disadvantageous.

 

So in intermediate stages, variance cannot be considered an evolutionary advantage.

 

Right?

 

I'm not trying to say I'm right and so-and-so is wrong. I'm just searching for answers.

[fafalone]

Depends on the particular variance. Anything moving towards sexual reproduction would be an advantage, because it would increase variance in f generations.

[Radical Edward]

Originally posted by blike

So in intermediate stages, variance cannot be considered an evolutionary advantage.

 

Right?

 

exactly, and this is one of the arguments aainst excessive use of antibiotics to treat bacterial infections.... say you have a bacteria which develops some resistance to an antibiotic and it is sitting there, say in someone's throat. If they don't take antibiotics and just let the illness run it's course with the body doing all the work, then it is likely that particular bacteria will not have any distinct advantage over it's neighbours, and will not survive long enough, and produce enough offspring to become an infectios agent for someone else. so it dies out. However, if you flood the system with an antibiotic killing all the others, then suddently it is the only one that can survive and breed, and hence that resistant bacteria will be the one that spreads. Pretty much the same can be said of any other variation.. they are useless unless there is some evolutionary forces at work, so something like sexual reproduction may be a great advantage when it comes to dealing with things like infection, since a particular organism with say a resistance to a virus or somesuch would spread it's genes around, rather than produce almost identical offspring. In effect, advantageous mutations in several different organisms can be mixed and spread around, producing an organism with a multiplicity of advantageous characteristics, which would probably not have come about purely by asexul reproduction alone, giving these particular organisms a distinct advantage over their less well equipped brethren.

[fafalone]

Ok, once against the lack of understanding of evolution is apparent here.

 

Let's look at the example of giraffes. Each time the neck became longer, it was more of an advantage. A giraffe with a neck half as long as the ones now would still be an advantage over previous contemporary generations. Intermediates ARE more of an advantage.

[blike]

Let's look at the example of giraffes. Each time the neck became longer, it was more of an advantage. A giraffe with a neck half as long as the ones now would still be an advantage over previous contemporary generations. Intermediates ARE more of an advantage.

 

"Lets assume I have a useless internal organ in me that only me and my brother's have. It does not effect anything else about my body. It is simply and extra structure."

 

My statement was only valid with non-functional, intermediate structures.

[fafalone]

I wasn't talking to you. But if it has no advantge or disadvantage, it wouldn't be eliminated.

[Radical Edward]

Originally posted by fafalone

But if it has no advantge or disadvantage, it wouldn't be eliminated.

 

indeed. I have a couple of little things on my neck and ears (no - not the rest of me ha ha) that are entirely useless, but haven't been bred out of the family for generations so far as I can tell. Who knows, in my offspring they could be the key to vast cosmic intelligence

[Sayonara]

Radical...

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It's called a 'head', dude.