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From unicellular to multicellular reproduction. paradox?

  1. Jan 29, 2007 #1
    I'm having a little trouble picturing how this would happen and I can't find any information on this.
    I understand that the jump from a unicellular organism to a multicellular matrix can happen, but I'm having trouble picturing how a matrix of genetically identical cells can evolve into a breeding organism with organ systems, etc.

    here's my problem:
    - for that first multicellular organism (which would look more like a membrane of cells than an animal) to reproduce and evolve, wouldn't it need a mate/reproductive system? but in order to have a mate, the organism would have had to reproduce in the first place (that is, there would have to be more than one of these), which is impossible without having a mate...

    I'm guessing there is a flaw in my logic, any website/book/video that describes this in detail would be helpful.
    Last edited: Jan 29, 2007
  2. jcsd
  3. Jan 30, 2007 #2
    You should just think of some more intermediate stages, that will make it seem less problematic.

    The first stage could be something like a ball of cells that stick together. Now and then some cells split off and form balls of cells themselves. Later on different cells within the ball get different functions based on their relative position within the ball. Some part may get the function to produce cells that leave the ball to form new balls. This would still be an asexual stage. Again later there may be two kinds of cells that leave the ball both with only halve the genetic material that is needed to function, and thus two of those need to combine to from a complete cell. These cells would be reproductive cells (gametes), at this stage they are not very specialized yet and any two can combine, no matter whether they came from the same ball or from different ones. Later on you might get too different “shapes” of gametes and only two complementary ones can combine. Every ball could be producing both of them tough, i.e. it could be a hermafrodite. Later on again, you could get balls that only produce one kind of these productive cells. There might be a period where you have all three possibilities, hermafrodites, males and females. They would just all throw out gametes into the sea for them to find and combine with complementary ones.
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