Re: Questions about the life and death of prokaryotes

r norman wrote:
> On Wed, 14 Dec 2005 11:09:59 -0500, Walter Bushell <proto@xxxxxxxxx>
> wrote:
>
>
>>In article <1134542482.267812.235030@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
>>"rev.goetz" <jimgoetz316@xxxxxxxxx> wrote:
>
>
>>>However, in the case of reproduction by mere cell division, if the
>>>ancestor does not die from the cell division, the ancestor lives in the
>>>next generation, and so on. Now if some of the lineages eventually
>>>evolve into lineages that reproduce strictly by sexual reproduction,
>>>then the cycle of ancestors living after reproductive cell division
>>>ends. But for the lineages that continue to reproduce by cell division,
>>>then the process continues till extinction. However, all of this
>>>depends upon whether the so-called parent prokaryote continues to exist
>>>after it divides into two cells. And I am not sure if the parent
>>>prokaryote continues to exist after it divides into two cells.
>>
>>>Yes, we come from a cellular lineage that is roughly 4 billion years,
>>>but sexually reproductive animals die sometime after reproduction.
>>
>>Most, of course, die long before reproduction. Seen the movies of the
>>sea turtles and their scramble to the water? On the grand average of all
>>the eggs a she sea turtle lays only two can survive to reproduce.
>>
>
>
> In fact if you take the average time between cell divisions as one
> "generation", half of all microbes die each generation assuming the
> population size is relatively stable.
>
> Incidentally, when a cell divides, the two daughter cells are
> generally considered "new" and the age clock is reset.

What age clock? Prokaryotes don't have teleomeres. However, there is
apparently some sort of a biochemical timer that determines when the
next cell division takes place. This must get "reset" following a cell
division.


--dkomo@xxxxxxxx

(Cell
> divisions within a multicellular eukaryote are a bit different --
> these can show age.) So "life" may be billions of years old and there
> is a continuity of living cells dividing from the earliest time until
> now, but no currently living "thing", cell or organism, is that old.
>
>

.

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