Unicellular organisms such as fungi devide when they have enough food and energy to replicate. In multicellular organisms I suspect that this is not the case.
I mean even if the organism has plenty of food the cells will not devide faster just becouse they could am I right?

If that were the case I would weigh 300,000 pounds.

Seriously, though, I'm sure the amount of food a multicellular organism gets partly determines its rate of growth. Poorer nutrition is one of the reasons people were shorter in the 19th Century.

But there have to be many levels of control besides nutrient intake, or we'd all be tumors. Our individual cells have to remain sociable with each other. They're in constant communication with each other. And sometimes they kill themselves without complaining, if it serves the common good.

And some cells tend to just get bigger and bigger without dividing (up to a point). I think fat cells might be an example.

Multicellular organisms have strict constraints on maintaining their developmental and differentiation identity in the context of their extracellular environment. They are constantly processing and responding to signals from other cells, the extracellular matrix, etc. This is why cellular proliferation will only occur under certain criteria (such as growth and repair) unless cancer occurs. When we take cells out of their native environment and try to grow them in a petri dish for example, they will often appear morphologically and physiologically confused. This is becuase they are no longer able to receive instructions from their environment on how to behave. Cultured human embryonic stem cells, for instance, must be grown on top of a layer of mouse fibroblasts in order for their pluripotential state to be maintained. In a nutshell: the rules of cell division in multicellular organisms are more complex that those for single-celled organisms.

1/10 of Harold's comments I can easily reply to without the aid of my ADD meds. This one is not so bad, but I'd still have to look up at least one word.

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If it is so that the cells of a multicellular organism devide slighly faster if gets more food resources, this could be a hypothetical explenation for longer life due to less telomere loss. I dont think this is very importent myself though.


Now from basic question level to a speculative question level...

For unicellular organism the "fitness/healthyness" of the cell must determine its ability to devide. A cell with maximal "fitness/healthyness" in some environment will devide with a frequency proportional to its "fitness/healthyness". A less healthy cell (with some non letal mutations e.tc.) will devide at a lower rate. Would you say this is also the case for cells in a multicellular organism? (If you for a moment disregard cancer cells). Is it generally so in a multicellular organism that cells devide with a frequency proportional to their "healthyness" or is it not so? Since cells in multicellular do not devide by their maximal rate limited by their healtyness one could suspect that cells that are not fully healthy still could devide at the maximal division rate for this kind of multicellular cells. Could it be said that the freqency of cell division in a multicellular cell is disconnected from its "fitness/healthyness" status?

There are some cells that can be very healthy and people think they never divide (neurons, heart muscle). If they are turned over, the replacements come from stem cells.

Also, cancer is a gradual process. For example, a clone of hematopoietic stem cell can be damaged in such a way that it divides just a little faster then all the other hematopoietic stem cells and thus slowly takes over the bone-marrow. Then one of these cells can mutate again, so that it divides yet another little bit faster and slowly takes over again, until you have a full blown-cancer. So even a little faster division can be less healthy.

Because most mutations happen during cell division, one could say that having cells divide as slowly as is consistent with fitness, is a mechanism to suppress mutations.