Jump to content


Photo

Symbiotic Relationships


  • This topic is locked This topic is locked
19 replies to this topic

#1 notmyown87

notmyown87

    Newcomer

  • Member
  • Pip
  • 7 posts
  • Age: 24
  • Christian
  • Creationist
  • Texas

Posted 01 June 2012 - 10:16 AM

Hello all, I have been browsing these forums for some time, and thought it was time I created my first thread. Firstly let me ask that you forgive me any grammatical errors, as I am typing this from my cell phone.

Since I am new to this site I will start off by admitting that I am most certainly not a scientist and honestly have not formally studied any of natural science. To be perfectly honest,I am an oilfield worker from Texas. I am what I am, and I hope you'll forgive any ignorance I'm surely to display.

Now that my introduction is done I can get on to my question. From the studies I myself have done to try and better understand evolution, I've come across one problem that I cannot logically figure out an explanation to: The male and female reproduction systems.

Symbiotic relationships are a hindrance to the explanation of the process of evolution, and to me, two fairly complex bodily systems that are each a part of two separate bodies (male and female) is very hard for me to logically explain. I'm not necessarily saying there isn't or couldn't be an explanation, but from a logical standpoint with a rudimentary understanding of the evolutionary process, I can't seem to explain it.
So my questions are:

1) did " male and female" evolve at exactly the same time? If that is thought to be the case, the odds would seem almost astronomical that it would be possible for these two systems to have been randomly mutated at the same time. However, if they did not happen at the same time, how could one of the systems remained to be passed down, and wouldn't it have been passed down to both the future males and females?

2) What is believed to be the advantages of male and female procreation when compared to asexual reproduction?

I'm sure these topics have been discussed time and time again, but I'd like to know if maybe I just overlooked something obvious when contemplating these questions. Thanks for your time, and sorry again for any typos or ignorance. God bless.

#2 Portillo

Portillo

    Member

  • Veteran Member
  • PipPipPip
  • 136 posts
  • Gender:Male
  • Age: 26
  • Christian
  • Creationist
  • Sydney

Posted 01 June 2012 - 05:10 PM

Symbiotic relationships are amazing. Like the crocodile who allows a bird to jump inside its mouth to clean its teeth. I recommend the book Billions of Missing Links.

Posted Image

#3 notmyown87

notmyown87

    Newcomer

  • Member
  • Pip
  • 7 posts
  • Age: 24
  • Christian
  • Creationist
  • Texas

Posted 01 June 2012 - 06:14 PM

I thank you for the recommendation, and Iwill certainly check out that title as I expand my personal collection of books on evolution. I have to ask though, surely there is some scientific (for lack of a better word) guess to these issues?

#4 Portillo

Portillo

    Member

  • Veteran Member
  • PipPipPip
  • 136 posts
  • Gender:Male
  • Age: 26
  • Christian
  • Creationist
  • Sydney

Posted 01 June 2012 - 07:08 PM

Mostly just so stories. Symbiosis evolved because if it didnt, it wouldnt exist etc.

#5 notmyown87

notmyown87

    Newcomer

  • Member
  • Pip
  • 7 posts
  • Age: 24
  • Christian
  • Creationist
  • Texas

Posted 01 June 2012 - 08:16 PM

If that is the case then it is indeed interesting. I have seen in some of my studies where evolutionists will attempt to refute symbiotic relationships in nature, like that of the bird and crocodile you spoke of, by stating that because the two species aren't entirely dependent on one another then their relationship isn't necessarily symbiotic. With the male and female reproduction systems however this argument isn't possible because the two systems are entirely dependant on the other. I find it interesting that there could be a problem like this with procreation, since in my understanding it is the driving forces behind evolution. ( Survival of the fittest)

#6 aelyn

aelyn

    Member

  • Veteran Member
  • PipPipPip
  • 324 posts
  • Age: 30
  • no affiliation
  • Atheist
  • Denver, Colorado

Posted 02 June 2012 - 02:40 AM

Hello Newcomer !

First, note that the questions you are asking are about structures that appeared very early - s@xual reproduction is about as old as the eukaryotes. Understanding how it happened and why is very much an area of active research.

That said, your questions apply to any symbiotic relationship, and they're very basic in nature - you don't see how those things could logically have happened. To answer this question, a very general "here is a way such a system could logically arise" answer is perfectly appropriate.

So to answer your questions in that vein :

1) did " male and female" evolve at exactly the same time? If that is thought to be the case, the odds would seem almost astronomical that it would be possible for these two systems to have been randomly mutated at the same time. However, if they did not happen at the same time, how could one of the systems remained to be passed down, and wouldn't it have been passed down to both the future males and females?

That is the basic question for any interdependent system, and its premise is that the two parts of the system would have to have evolved independently. And of course interacting systems don't evolve independently; they can't, because since they interact they are part of each other's environment and it's the environment that determines what traits get selected for at any given time. So instead of one system and then the other evolving, what you have is two systems gradually changing in response to each other until they depend on each other in ways they didn't before.

So to answer your question, it's 1) : Males and females evolved at about the same time. But not at the same time as s@xual reproduction. For s@xual reproduction you only require two cells to fuse; they don't need to be different. And indeed many eukaryotes don't have genders but "mating types", sometimes more than two at that. When the the gametes are identical it's called "isogamy"; when they're different it's called "anisogamy"; the Wikipedia pages on those two terms might answer some of your questions further. There are a few theories for how isogamous species would become anisogamous, but the key is there is a tradeoff between how many gametes you make and how big they are (i.e. how viable they are). And given you need the resulting zygote to be big enough to survive itself, and you need the two gametes to find each other, once you get selection on one mating type to make smaller gametes, or to make larger but slower gametes, the other side needs to go the other way to compensate, so you get an amplifying feedback thingy until you have a few huge immobile gametes on one side and millions of tiny swimming gametes on the other - females and males. The question would be what provided the original impetus, as I said there are several theories but one paper linked to on the Wikipedia page for "Anisogamy" says that when you model a system where large gametes last longer and small gametes move faster, selecting for high encounter rates is enough to turn the system towards anisogamy.

And once you have that fundamental assymmetry in the gametes, all the assymmetries in the resulting organisms follow because the genders aren't quite under the same selection pressures anymore. That's called "disruptive selection", when the selection pressures on different members of the same population are different, so you end up with different "types" even though they're still the same interbreeding population. It doesn't only happen with gender, but that's the most obvious example.

As for what the advantages of s@xual reproduction are in the first place, there are many. They allow advantageous genes to spread through the population, instead of staying in a single lineage. This also allows for better combinations of advantageous genes to arise - you don't have to wait for all of them to appear in the same lineage. These advantages are so stark that even bacteria swap genes, in a process that's sometimes called "bacterial s@x" even though it isn't really s@xual reproduction. There are also advantages where parasites and immune systems are involved - when you look at immune systems as a "lock" that parasites need to find a "key" to, given the "lock" is genetically determined, once the parasites manage to crack it they've cracked it for all that organisms' descendants too. Unless the organism reproduces s*xually, in which case the "lock" gets randomized every generation.

There are some s*xually-reproducing organisms that switch to asexual reproduction, which also has advantages. But we observe that those organisms tend to switch back to s@xual reproduction as soon as there's some kind of disruption in the environment.

#7 notmyown87

notmyown87

    Newcomer

  • Member
  • Pip
  • 7 posts
  • Age: 24
  • Christian
  • Creationist
  • Texas

Posted 02 June 2012 - 07:41 AM

Thanks for your welcome, and also your response. That is exactly what I was looking for. However, genetics are out of my scope, so I'll be tanking some time to study your response and try to break it down into something I can grasp easier. Thanks for the information, and I would love to see this topic continue, perhaps with other hypotheses or a fellow creationist who has a better understanding of your response and would like to try and refute it.

#8 gilbo12345

gilbo12345

    Honorable Member

  • Veteran Member
  • PipPipPipPipPip
  • 5293 posts
  • Gender:Male
  • Interests:Completed BBiotech (Honours)

    Currently studying Masters of Teaching.

    Enjoys games of tactics and strategy.
  • Age: 25
  • (private)
  • Creationist
  • Australia

Posted 02 June 2012 - 08:07 AM

1. That is the basic question for any interdependent system, and its premise is that the two parts of the system would have to have evolved independently. And of course interacting systems don't evolve independently; they can't, because since they interact they are part of each other's environment and it's the environment that determines what traits get selected for at any given time. So instead of one system and then the other evolving, what you have is two systems gradually changing in response to each other until they depend on each other in ways they didn't before.

2. So to answer your question, it's 1) : Males and females evolved at about the same time. But not at the same time as s@xual reproduction.

3. For s@xual reproduction you only require two cells to fuse; they don't need to be different. And indeed many eukaryotes don't have genders but "mating types", sometimes more than two at that. When the the gametes are identical it's called "isogamy"; when they're different it's called "anisogamy"; the Wikipedia pages on those two terms might answer some of your questions further.

4. There are a few theories for how isogamous species would become anisogamous,

5. but the key is there is a tradeoff between how many gametes you make and how big they are (i.e. how viable they are). And given you need the resulting zygote to be big enough to survive itself, and you need the two gametes to find each other, once you get selection on one mating type to make smaller gametes, or to make larger but slower gametes, the other side needs to go the other way to compensate, so you get an amplifying feedback thingy until you have a few huge immobile gametes on one side and millions of tiny swimming gametes on the other - females and males.


6. And once you have that fundamental assymmetry in the gametes, all the assymmetries in the resulting organisms follow because the genders aren't quite under the same selection pressures anymore. That's called "disruptive selection", when the selection pressures on different members of the same population are different, so you end up with different "types" even though they're still the same interbreeding population. It doesn't only happen with gender, but that's the most obvious example.

7. As for what the advantages of s@xual reproduction are in the first place, there are many. They allow advantageous genes to spread through the population, instead of staying in a single lineage.

8. This also allows for better combinations of advantageous genes to arise - you don't have to wait for all of them to appear in the same lineage. These advantages are so stark that even bacteria swap genes, in a process that's sometimes called "bacterial s@x" even though it isn't really s@xual reproduction.

9. There are also advantages where parasites and immune systems are involved - when you look at immune systems as a "lock" that parasites need to find a "key" to, given the "lock" is genetically determined, once the parasites manage to crack it they've cracked it for all that organisms' descendants too. Unless the organism reproduces s*xually, in which case the "lock" gets randomized every generation.

10. There are some s*xually-reproducing organisms that switch to asexual reproduction, which also has advantages. But we observe that those organisms tend to switch back to s@xual reproduction as soon as there's some kind of disruption in the environment.



1. Too bad that claiming such is devoid of any scientific evidence and thus is merely a statement of evolutionary faith rather than of science.

2. Yet in order for the "male" and "female" parts to have any fitness benefit, S@xual reproduction needs to be available... Since that is where the increase of fitness comes from. Your method here assumes that male and female "parts" will evolve devoid of the fitness which is what is meant to select them.

3. These other forms of reproduction also have their own limits and regulations hence from where did they "evolve", all you have done is pushed the question further back rather than answered it. It would help if there was evidence of HOW they came to be, claiming evolution is not a sufficient explanation.

4. If they don't have evidence for them, as to the question of HOW, then they are not theories. Unless the establishment now use the word theory in replacement for the word model.

5. Evidence? Or is this merely a proposed MODEL on how it occured?

6. All other asymmetries ever observed in the S@xual reproduction method today, (baring eggs and sperm) causes death and genetic disorder... Asymmetric alignment / separation of DNA leads to death or Down's syndrome.. Yet here it is casually claimed that asymetries will build up and allow for this "evolution".. Perhaps consider the real world where such things will lead to detriment and a decrease in fitness. OR do you have evidence to fit this proposed method that flies in the face of today's observable logic.

7. Yet you say later on that genes are switched between bacteria lineages anyway... meaning that this line of advantage is rendered moot by your own words.

8. As I explained in 7 this is a contradicion of your earlier point

9. Considering that bacteria don't have an "immune system" per se, renders this point also moot.

10. Yes there are... though that has nothing to do with the question.

#9 jason777

jason777

    Moderator

  • Moderator Team
  • PipPipPipPip
  • 2670 posts
  • Gender:Male
  • Interests:Machining, Engine Building, Geology, Paleontology, Fishing
  • Age: 40
  • Christian
  • Young Earth Creationist
  • Springdale,AR.

Posted 04 June 2012 - 01:46 AM

Another interesting thing that you should consider is the fact that Darwin said that if any organism did anything solely for the benefit of another organism, then his theory would be falsified. Dandelions produce nectar for bees, yet they themselves reproduce asexually.

Enjoy.

#10 gilbo12345

gilbo12345

    Honorable Member

  • Veteran Member
  • PipPipPipPipPip
  • 5293 posts
  • Gender:Male
  • Interests:Completed BBiotech (Honours)

    Currently studying Masters of Teaching.

    Enjoys games of tactics and strategy.
  • Age: 25
  • (private)
  • Creationist
  • Australia

Posted 04 June 2012 - 02:54 AM

Another interesting thing that you should consider is the fact that Darwin said that if any organism did anything solely for the benefit of another organism, then his theory would be falsified. Dandelions produce nectar for bees, yet they themselves reproduce asexually.

Enjoy.


Cool didn't know that Jason


He also said that anything that can only have come about outside of a 'bit-by-bit' process, (ie- irreducible complexity), would also completely falsify his "theory" (or should I say model). Considering that the complexity of life has exposed many different processes which cannot have logically "evolved" ensures that evolution truely is a dead "theory".

#11 notmyown87

notmyown87

    Newcomer

  • Member
  • Pip
  • 7 posts
  • Age: 24
  • Christian
  • Creationist
  • Texas

Posted 04 June 2012 - 04:43 AM

That is the type of thing that baffles me. When there are obviously problems like this that undermine the entire theory, yet the theory is clung to with such unshakable "faith", it clearly shows an ulterior motive. I cannot get past the fact that time and time again you hear " things could not have happened this way." But then when examples are given showing that things had to have happened that exact way, the question is either ignored or you get two pages of theories based off of circumstances that are purely fabricated to be favorable for there explanation.

#12 aelyn

aelyn

    Member

  • Veteran Member
  • PipPipPip
  • 324 posts
  • Age: 30
  • no affiliation
  • Atheist
  • Denver, Colorado

Posted 04 June 2012 - 05:08 AM

That is the type of thing that baffles me. When there are obviously problems like this that undermine the entire theory, yet the theory is clung to with such unshakable "faith", it clearly shows an ulterior motive. I cannot get past the fact that time and time again you hear " things could not have happened this way." But then when examples are given showing that things had to have happened that exact way, the question is either ignored or you get two pages of theories based off of circumstances that are purely fabricated to be favorable for there explanation.

What a strange thing to say. "Things could not have happened this way" is what creationists say all the time - symbiotic relationships "could not" have evolved, irreducible complexity "could not" arise in a step-by-step fashion, this or that trait couldn't possibly have evolved...

Dandelions producing nectar while reproducing asexually is an anomaly that demands an explanation, but it isn't a particularly impossible one. For one thing sexuality in plants isn't very rigid - just because some species dandelions mostly reproduce asexually doesn't mean there won't outcross occasionally. Tons of species alternate S@xual and asexual reproduction depending on the circumstances. The fact that nectar production is a trait common to angiosperms means it could also just be a vestigial structure, a bit like the female lizards the reproduce asexually but still need to simulate copulation with each other to do so. How likely that is would depend on how persistent nectar production is as a trait and I have no idea on that front. Attracting insects could also have a purpose than pollination, some plants attract other insects of purposes of pest control for example. But that's less likely.

Naive falsificationism isn't how science actually works. Bayesian reasoning is closer to the mark.

#13 gilbo12345

gilbo12345

    Honorable Member

  • Veteran Member
  • PipPipPipPipPip
  • 5293 posts
  • Gender:Male
  • Interests:Completed BBiotech (Honours)

    Currently studying Masters of Teaching.

    Enjoys games of tactics and strategy.
  • Age: 25
  • (private)
  • Creationist
  • Australia

Posted 04 June 2012 - 08:18 AM

1. Dandelions producing nectar while reproducing asexually is an anomaly that demands an explanation,

2. but it isn't a particularly impossible one.

3. For one thing sexuality in plants isn't very rigid - just because some species dandelions mostly reproduce asexually doesn't mean there won't outcross occasionally. Tons of species alternate S@xual and asexual reproduction depending on the circumstances. The fact that nectar production is a trait common to angiosperms means it could also just be a vestigial structure, a bit like the female lizards the reproduce asexually but still need to simulate copulation with each other to do so. How likely that is would depend on how persistent nectar production is as a trait and I have no idea on that front. Attracting insects could also have a purpose than pollination, some plants attract other insects of purposes of pest control for example. But that's less likely.

4, Naive falsificationism isn't how science actually works. Bayesian reasoning is closer to the mark.


1. Certainly does, has an actual (scientific) explanation been forthcoming?

2. How do you know? This is merely an assumption on your part in an attempt to downplay that it could in fact be impossible.

3. You're grasping at straws here. The fact that you've given so many reasons and have used ambiguous language, (may could, etc) means that you don't really know.... (now see point 1)

4. Nor is, "lets ignore this problem because it means we have to rethink our current paradigm"

#14 notmyown87

notmyown87

    Newcomer

  • Member
  • Pip
  • 7 posts
  • Age: 24
  • Christian
  • Creationist
  • Texas

Posted 04 June 2012 - 09:51 AM

My point was that problems such as the dandelion " phenomenon" pose a problem for evolutionists current theory. Therefore, I would think that emphasis would be put on trying to explain the dandelions oddities, but instead I was able to find no viable explanations through searches on the internet. At what point do you say that there are enough of these anomalies thao you doubt the entire theory? Or do you continue to ignore these problemsbecause they don't match the current theory.

#15 aelyn

aelyn

    Member

  • Veteran Member
  • PipPipPip
  • 324 posts
  • Age: 30
  • no affiliation
  • Atheist
  • Denver, Colorado

Posted 04 June 2012 - 11:52 AM

My point was that problems such as the dandelion " phenomenon" pose a problem for evolutionists current theory. Therefore, I would think that emphasis would be put on trying to explain the dandelions oddities, but instead I was able to find no viable explanations through searches on the internet. At what point do you say that there are enough of these anomalies thao you doubt the entire theory? Or do you continue to ignore these problemsbecause they don't match the current theory.


I'm sure botanists that specialize in dandelions are looking into it. A google search won't get you much for such a hyper-specific field. It's an oddity as you say, but not a contradicts-the-whole-framework oddity given how many potential explanations there are for it.

How many such slight anomalies would you need before you doubted the entire theory ? Well, first they'd have to still be anomalous after the potential explanations had been ruled out ("X is impossible" is a strong claim that doesn't require proof X actually happened to contradict it; merely indications that X is possible). Now if you had an irreducible anomaly like that I imagine people would start to get interested. But one on its own can't overturn "the entire theory", because the theory of evolution is actually a collection of theories. If the dandelion anomaly were unexplainable (which I see no reason to think it is given I could think of two possible explanations off the top of my head and look up a third) then what it would suggest is that natural selection and neutral drift aren't the only mechanisms of evolution. To suggest natural selection and neutral drift aren't the main mechanisms you'd need a lot of anomalies distributed in a systematic way. To suggest common descent didn't happen you'd need a different kind of anomaly altogether (large unexplainable inconsistencies in the nested hierarchy for example).

That said, I've dug a little deeper on the dandelion thing, have you searched on Google Scholar ? With keywords like "Taraxacum", "apomixis" or "s*xual-asexual cycle" you can get quite a few papers on the subject. Having only the abstract isn't the best but maybe you can still get an idea from them; if there's a paper you're interested in reading I can see if I have access to it and send you the PDF. Anyway it turns out asexual dandelions do occasionally hybridize with s*xual dandelions, and the main difference between the two is chromosome count - diploid dandelions are all s*xual, while triploids and higher are usually completely or partly asexual. That means new asexual strains are being created all the time, because whenever a triploid or tetraploid dandelion reproduces with a diploid one some of the offspring will be triploid, i.e. asexual.
Given the s*xual and asexual strains are so closely related it's no wonder they're similar in almost every respect - which would include nectar and pollen production. Which the asexual varieties do use, since they sometimes hybridize.

Reading up on all this s*xual/asexual stuff I've also been reminded of an important advantage of s*xual reproduction over asexual : it pushes back Muller's ratchet. Muller's ratchet is when slightly harmful mutations add up too fast to be weeded out by natural selection. It's an issue with purely asexual reproduction where you always pass on your whole genome to the next generation, but when you mix the genes around as with s*xual reproduction or bacteria's gene-swapping it isn't a problem; the mutational load gets randomized every generation instead of always increasing.

#16 gilbo12345

gilbo12345

    Honorable Member

  • Veteran Member
  • PipPipPipPipPip
  • 5293 posts
  • Gender:Male
  • Interests:Completed BBiotech (Honours)

    Currently studying Masters of Teaching.

    Enjoys games of tactics and strategy.
  • Age: 25
  • (private)
  • Creationist
  • Australia

Posted 04 June 2012 - 02:06 PM

How many such slight anomalies would you need before you doubted the entire theory?


Actually, scientifically it should only take one contradiction in order to raise doubts, and those doubts should be investigated...... not explained away

#17 notmyown87

notmyown87

    Newcomer

  • Member
  • Pip
  • 7 posts
  • Age: 24
  • Christian
  • Creationist
  • Texas

Posted 04 June 2012 - 03:04 PM

Forgive me ,I don't know how to use the quote feature from my phone and am at work so I can not do much research, but in response to aelyn I believe the only way to conclude anything from the dandelion question would be to have a strain that was entirely asexual from the beginning and see is nectar was still being produced. Implausible I would imagine, but still interests me that a dandelion could mean so much to a discussion.

I'm still new to evolution as a whole and your post is the first time I've heard of mullers ratchet. Being new to evolution I have a question, if all species evolved from an ancestor that was asexual, why would so many species have lost the ability to reproduce this way. If dandelions and I'm sure other species can reproduce both ways, why not every species? Would it not be the most beneficial possibility to have kept that ability as well as the newly evolved reproduction system? Or is that not possible?

#18 aelyn

aelyn

    Member

  • Veteran Member
  • PipPipPip
  • 324 posts
  • Age: 30
  • no affiliation
  • Atheist
  • Denver, Colorado

Posted 05 June 2012 - 01:55 AM

Forgive me ,I don't know how to use the quote feature from my phone and am at work so I can not do much research, but in response to aelyn I believe the only way to conclude anything from the dandelion question would be to have a strain that was entirely asexual from the beginning and see is nectar was still being produced. Implausible I would imagine, but still interests me that a dandelion could mean so much to a discussion.

I'm not sure what you mean about a strain that was entirely asexual "from the beginning". Every strain is asexual from the beginning of when it started to be asexual.
Now what would be interesting is looking at different asexual strains, and if we can figure out how old they are, compare how much nectar they produce and see if the older ones produce less nectar.
But even here it isn't clear what this would show; if they did produce less nectar it could be positive selection for less nectar, or it could just be loss of function from neutral drift. Both are usually involved in the loss of a trait, but when asexual strains are involved I imagine the second would probably be more important (because asexual species have both lower adaptability and higher mutational loads). And if the older ones didn't produce less nectar it could just be because none of the strains were old enough for random drift to affect nectar production. There could be a theoretical basis for judging whether they were or not, in which case such a result could be meaningful, but I really have no idea.

I'm still new to evolution as a whole and your post is the first time I've heard of mullers ratchet. Being new to evolution I have a question, if all species evolved from an ancestor that was asexual, why would so many species have lost the ability to reproduce this way. If dandelions and I'm sure other species can reproduce both ways, why not every species? Would it not be the most beneficial possibility to have kept that ability as well as the newly evolved reproduction system? Or is that not possible?

Muller's ratchet is, as far as I know, a theoretical concern. That is, I don't know how much actual evidence there is of slightly harmful mutations always building up in asexual species until they go extinct. As for why most s*xually reproducing species don't have the ability to reproduce asexually, that's actually pretty interesting. It isn't just about everyone descending from an asexual species; asexual reproduction has its own advantages. You pass on 100% of your genes to every offspring instead of 50%. You don't need to worry about finding a mate (that one can be a HUGE deal if you're a rare species or can't move around much...). You can reproduce much faster. In a s*xually reproducing species, an asexual individual could overrun everyone else before concerns like "mutational load" or "susceptibility to parasites" or "low adaptability" came into play. This mostly doesn't happen because s*xually reproducing species have all kinds of systems that actually forbid asexual reproduction. You've got eggs that can't develop (even if they have enough chromosomes to be viable) unless they're stimulated by fertilization. You've got individuals that have only one gender, so they need another individual to reproduce with. And in hermaphrodites you've got all kinds of barriers to self-fertilization - S@xual organs that are far away from each other or don't develop at the same time, incompatible gametes, and so on. Species that become asexual tend to have mutations that broke down those barriers.

It is quite possible that species that have weak barriers to asexual reproduction would turn asexual all the time - and would be outcompeted over the long term by their brethren that had stronger barriers, and thus stuck to s*xual reproduction, and thus all those anti-asexual-reproduction systems would evolve. But given the huge variety of sexualities there are in nature it's hard to tell. (for me I mean - actual biologists might know more). It also seems to be very group-specific. You hardly see any asexuality at all in mammals for example. There are some rare cases in lizards. Some plants tend to asexual reproduction more than others.

#19 jason777

jason777

    Moderator

  • Moderator Team
  • PipPipPipPip
  • 2670 posts
  • Gender:Male
  • Interests:Machining, Engine Building, Geology, Paleontology, Fishing
  • Age: 40
  • Christian
  • Young Earth Creationist
  • Springdale,AR.

Posted 18 June 2012 - 03:44 AM

The fact that only one example falsifies the theory is sufficient. A hypothesis made a prediction and that predicton was falsified...Period. Not to mention the fact that dozens more can be put forth.

If selection could drive a species to asexual reprodution, it still doesn't change the fact that the same selection is producing nectar solely for the benefit of another organism.

Acropora are hermaphrodites, yet they are brilliantly colored simply because it's beautiful to look at. Wouldn't selection only favor the ones that are hard to see by predators?

Posted Image

Enjoy.

#20 aelyn

aelyn

    Member

  • Veteran Member
  • PipPipPip
  • 324 posts
  • Age: 30
  • no affiliation
  • Atheist
  • Denver, Colorado

Posted 29 June 2012 - 09:50 AM

The fact that only one example falsifies the theory is sufficient. A hypothesis made a prediction and that predicton was falsified...Period. Not to mention the fact that dozens more can be put forth.

If selection could drive a species to asexual reprodution, it still doesn't change the fact that the same selection is producing nectar solely for the benefit of another organism.

Except that natural selection doesn't magically adapt an organism to its environment instantaneously, it works on many many generations, and when there's gene flow between two groups those groups won't be able to diverge much regardless of natural selection. So an organism that became asexual a few generations ago only, and continues to interbreed with its S@xual relatives every few generations won't get rid of its S@xual traits.

Acropora are hermaphrodites, yet they are brilliantly colored simply because it's beautiful to look at. Wouldn't selection only favor the ones that are hard to see by predators?

Posted Image

Enjoy.

What predators, flatworms and sea-snails ? Fearfully sharp color vision those have.
Corals get their colors from a combination of the algae that live in them (which use those pigments to aid in photosynthesis) and pigments in the corals themselves that are thought to reduce the damage those algae can suffer in high light conditions.
http://www.coralcoe....h_ICRS_2006.pdf
http://espace.librar.../view/UQ:251950




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users