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What if cells would reproduce not by separating into two, but into three parts? This applies to all forms of life on the respective planet.

Just as normal cells, the cells would separate into smaller parts that themselves grow and then separate again. However, every cell division would bring up not two, but three new child cells.

My questions are:

  • How would life (both unicelluar and multicelluar, microscopic and macroscopic) be different from life on Earth? What advantages and disadvantages would this sort of celluar division have when compared to normal cell "duplication"? Would completely "alien" lifeforms evolve?
  • What would be the reason for such a development?
  • How would growth be different? Would this sort of cellular division mean that the amounts of biomass can increase more quickly?
  • Would ecosystems be different?
  • What would happen if an organism from this planet would be exposed to the Terran ecosystem?
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closed as too broad by fi12, Hohmannfan, J_F_B_M, Frostfyre, bilbo_pingouin Mar 11 '16 at 14:15

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ As it stands, this is much too broad. Try to split it in multiple questions. Even then, "How would X be different?" is usually still too broad, you likely have to set up some costraints. The question is not bad, but I could possibly write a book with hypothesises about it (which is too broad as well, though measured in width). $\endgroup$ – J_F_B_M Mar 11 '16 at 13:18
  • $\begingroup$ OK, I spent 20 minutes writing the long answer. I feel 10 points lower in IQ than before (not that I was a genius before this anyway). I demand a roasted turkey as appeasement. $\endgroup$ – Youstay Igo Mar 11 '16 at 13:32
  • $\begingroup$ @MedwedianPresident, Given that some cancer cells demonstrated division into 3 and up to 5 daughter cells I believe that at least one part of the question had merit. Article: scitechdaily.com/… Research paper: journals.plos.org/plosone/article?id=10.1371/… As: could one cell divide in three? Yes they do and the world you want to build around that can go any possible way and is up to you $\endgroup$ – Erik vanDoren Mar 11 '16 at 14:35
  • $\begingroup$ It would just be more complicated without notably adding any genetic diversity. If moved to the sex cells for reproduction having to find that third sex partner would be more complicated for a limited payoff. $\endgroup$ – Oldcat Mar 11 '16 at 23:16
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There is a very basic difference between all life on Earth and the type of life you are suggesting.

Earthly Life

Look at the image below.
enter image description here

This is a simplified image of a DNA double helix found in cells of Earthly life.

When a cell divides into two (mitosis), the DNA string divides into two strands and each strand is then joined in by a matching strand so that two sets of DNA are formed.
enter image description here

In your world, you want a cell to divide into not 2, but 3 children cells. This would require not a double but triple helix structure, so that each child cell inherits one part of it and completes it. Something like this:
enter image description here

Now lets refer to your questions.

1- How would life (both unicelluar and multicelluar, microscopic and macroscopic) be different from life on Earth? What advantages and disadvantages would this sort of celluar division have when compared to normal cell "duplication"? Would completely "alien" lifeforms evolve?

For one, that life would be very different from the life forms we know of, at least on cellular level. The whole method of protein coding would be different from Earthly life forms. We don't know different it would be on macroscopic level.

2- What would be the reason for such a development?

Because you want it to be like that.

Or the spaghetti monster ordered that.

Or the cells got bored of mitosis/meiosis one morning and get apeshit insane.

Or a super wizard cast a magic spell on those cells.

Or ...

3- How would growth be different? Would this sort of cellular division mean that the amounts of biomass can increase more quickly?

We have no idea how growth would be different. Cell growth and cell reproduction are completely different things.

No, this sort of cell division does not necessarily mean that the amount of biomass can increase more quickly. For example, in favorable conditions on Earth, a bacterium undergoes mitosis in about 20 minutes. If a bacterium undergoes this type of triple cell division and one cell takes 40 minutes to divide then that those organisms would proliferate slower than organisms on Earth.

4- Would ecosystems be different?

You are confusing cell division with ecology here. Although these subjects might be related on some higher-than-human level of understanding, at this time the best and brightest minds don't know what would/could be the direct impact of this type of cell division on the ecology of a habitat.

5- What would happen if an organism from this planet would be exposed to the Terran ecosystem?

That organism would feel very lonely and nostalgic. Nobody would make friends with him and he/it would cry in a dark, secluded corner.

OK enough sarcasm. Here again you are mixing cell division with ecosystem. The possibilities are endless. Maybe it would go on living happily on Earth and call it a new home. Maybe the oxygenated environment would be toxic for it (nothing to do with cell division mechanism btw) and it would die.

In short, you are asking a question like => if all gray monkeys were blue, would they choose to twerk with Scarlett Johanson or Condolisa Rice?

I am not a blue monkey so I can't say for them, but I would definitely choose Scarlett Johanson any day!

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  • $\begingroup$ this would be the best answer in between all of them except the assumpion that you need a 3rd strand, as cancerous cells demonstrated division in 3 and more in certain conditions. One then can make up any sort of consequence if they make it be normal behavior for cell division. $\endgroup$ – Erik vanDoren Mar 11 '16 at 14:43
  • $\begingroup$ Oh btw, a very important thing I forgot to mention in my answer is that the pace of evolution would be much faster in your hypothetical world because there would be 33% more chance for dna copy errors, resulting in mutations (and hence, evolution). And no, cancer cells don't make a good example, because that is erratic cell division, not normal. You would require a triple helix dna or you would have to incorporate a very complex method of cell division if you want to stay with the double helix structure. $\endgroup$ – Youstay Igo Mar 11 '16 at 15:13
  • $\begingroup$ I posted the research link in a comment to the question. IMO the fact that its cancer has little meaning when the discussion is limited to possible or not, the point is that that division is possible without a 3rd strand and its up to him to make it be the norm. Then again we are talking about a fictional world, the organisms could be blobs rolling around or a complete dead end or whatever else. If the author of the question did his work he could have given SE a very nice and much more specific question. $\endgroup$ – Erik vanDoren Mar 11 '16 at 15:34
  • $\begingroup$ As I stated, it is theoretically possible to have triple division with just a double helix dna structure. However (and it is a very important however) such cell genetics and the resulting proteins would be extremely complex. Basically we are talking about dna division into two and then one strand again dividing into two later so that there are 3 copies of the dna in the cell. It might be possible with healthy cells too, but the genetic codes would be very complex. $\endgroup$ – Youstay Igo Mar 11 '16 at 15:50
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Normally I'd say that you are asking too many questions in one here and need to focus it down but in fact we can answer it all just by looking at the second question:

What would be the reason for such a development?

There is no reason. The same mechanisms that would allow a three way split would also allow a two way split, whereas a two way split can be done without building up so much energy before hand. The only possible reason is if you say that the act of splitting is in some way risky but it would be very hard to justify needing to acquire twice as much resources before reproducing.

Someone needs to come up with a very compelling reason why and how this is happening before we can even start thinking about answering the other questions (and they should be asked separately anyway).

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The presence of such a system would imply a dramatically different environment which takes advantage of the particulars of one's particular implementation of splitting into three parts.

The main challenge you face is that dividing into three in a way which is not the same as dividing in two, dividing in two, then killing a cell. Dividing into two is a vastly simpler way to approach reproduction, so you're going to spend a lot of cellular effort managing the extra complication. You're going to need some benefit. There has to be something unique about dividing into three that cannot be accomplished by dividing into two.

The only case I can think of where this would be useful is for an extremely advanced cell, far more advanced than our own, where the time costs for reproducing the genetic material account for the vast majority of the time the cell spends or accounts for the vast majority of the time the cell spends in a compromised position where it isn't functioning well. In those cases, it may be useful to make 3 copies of the genetic material rather than 2. It would almost certainly not evolve that way at first, but only pick this behavior up after the quantity of genetic material it is dealing with gets very very very large.

Consider that, amongst the vast number of reproductive approaches we see in Earth life, we do not see anything like this. We see mitosis, both fission and budding, we see meosis, we see sporulation (which is a fascinating process to create a double walled cell where an organism divides in two, but doesn't cleave the membrane completely. It then dehydrates one of the two cells to form one cell with an extra thick double wall to protect against UV and other environments). We see an extraordinary volume of "creativity," but nothing like this. Nothing more than "divide twice, then kill a cell."

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