Ross Koning wrote:
>> Hi David!
> So you have an interesting question...but if we limit the
> discussion to LIVING cells (NOT Xylem Elements, Cork Cells, etc.)
> and include all eukaryotic organisms, then we would have the
> cell membrane and nucleus (except during mitosis in many organisms),
> some kind of ribosomes in a cytosol...but going any further might
> leave some organisms/cells out. MOST will have mitochondria of
> one form or another...but there could be organisms functioning
> in some obligate fermentation mode that have no mitochondria.
> Cytoskeletal elements might be common to many, maybe even to all
> in at least some form or some phase of development.
>> There will be exceptions to all rules, though. A good example is
> the human red blood cell (lacking nucleus) and phloem sieve tube
> element (lacking most organelles). So you have to be sure to
> distinguish "typical" from "least common denominator". Anyway it
> makes for a fun discussion with students!
To summon up the comments gathered from different postings, we can sofar
say, that a "normal eukaryotic cell" is not a valid conception (we did
not think that either), due to
1) the diversity of eukaryotic organisms, and
2) the diversity of the differentiated cells.
We could speculate about the most abundant organism group, but I do not
like comparing "algae", "plants" or "protozoan" since each group
consists of a broad variety of cell types. Has anybody anytime suggested
a species/genus/family regarded as the most abundant?
We could also talk about the "least common denominator" (nucleus,
mitochondria, cell wall, cytoskeleton) - (perhaps with a statistical
formula), but personally I think that it is not a useful conception
either. It is something you might learn by heart, but never understand
Regarding all life, we could neither find a "normal" organism, but we
could describe what is living. So the question of the normal eukaryotic
cell perhaps should more "metaphysic": What is it to be a eukaryote and
how is that solved in different eukaryotic organisms?
Thanks for your effort!