| Genetic
Switches ? |
Edward
Frank |
| Jun
27, 2007 23:03 PDT |
ENTS,
I have been thinking. Recently I read an article about
researchers
investigating RNA molecules that seemed to turn on or off
certain genes
encoded in the cell's DNA. The research involved finding cures
or
relief from certain hereditary diseases. I know of a cave fish
in
Mexico, that when it is grown in complete darkness under low
food
conditions, it grows as an albino without eyes. If placed in an
environment with light and/or more food, the next generation is
pigmented and has eyes. So these drastic characteristics for the
cave
adaptations are turned on and off in a single generation.
I am wondering about trees like the Live Oak and Sycamore that
develop
such magnificent wide spreads and short trunks when grown in the
open,
but grow tall with smaller spreads when grown in a forest
setting. Are
the forms of these trees dictated by competition, or lack of
competition, on an individual branch by branch basis, or do they
have
some sort of a genetic switch that turned on and off by the
presence of
competition that dictates a general form the tree will take as
it grows?
It has been noted in previous emails that biological forms do
not
necessarily optimize for the best efficiency, but tend to do
just enough
to get by. (They also progress by lurches when a particular
adaptation
or mutation works well.) It would be better for the trees if
they had
two different shapes to "choose from" rather than
reinvent their general
overall shape with each tree.
All trees seem to express a shorter height and broader spread
when grown
in the open. A tree of a particular species grown in the open
tends to
have the same shape as others of the same species grown under
similar
conditions. Different tree species have different characteristic
open
grown shapes. Do they have a general forest grown shape to
match, or
are the forest shapes simply a product of die-off and
competition from
the less common programmed open-grown shape? That really sound
kind of
silly to me that the more common occurrence, forest grown, would
simply
e a sub-set of the generalized open grown shape for a particular
species.
Ed Frank |
|