>and put it in the sun they will usually have smaller leafs than ones in the
>shade. But switch conditions and they turn back. Not genetic change just
>adjusting to conditions.
Brian, Survival of the fittest or natural selection does exactly that.
Natural selection will 'select' what genetic characters are best suited to a
certain niche in the evironment. Amorphophallus for example has many, many
species which have adapted a pattern on their petioles which, in some
species, looks like lichens. Lichens normally occur on woody stems of plants
that persist year after year. As we know the amorphophallus petiole is
herbaceous and is very soft......a tasty morsel for some herbivore. But the
herbivore sees that there appear to be lichens on this particular 'stem' and
they pass it by knowing that it is woody and not palitable .......the plant
survives and reproduces.
The brother to the above amorphophallus, through the genetic coupling of an
egg (1/2 of the genetic material) and a sperm (pollen and the other 1/2 of
the genetic material), got a set of genes which does not have the character
which places these lichen like marks on its petiole. Along comes the
herbivore which left this one's brother alone and eats it. The Amorph
without the markings dies and does not get to reproduce.
This is how genes are selected by nature and how genetic material changes.
If a drastic enough change occurs and the population stabilizes and
reproduces...Viola...a new species is born.
The dividing mark between species can become very blurred in genera were
there is active evolution occuring. the orchid family is a good example. Or
in genera where there is a tremendous amount of hybrizing going on
(naturally) such as the oaks (quercus).
A natural hybrid may create a 'swarm' in its habitat and may actually
stabilize and reproduce true to the parents at some point....we now have a
new species. And one that does not have to have all of the inbetween steps
(long teeth to short teeth and everything in between).
Changes which occur in an individual due to environment (large leaves in the
shade and small leaves in the sun) does not change the genetics of the
individual plant in any way....BUT if the population of a species is
suddenly subjected to a dramitic change in environment (such as an ice age
or geologic catastrophy) then many of that population will perish. There may
be an individual or two in this population that survive because of some
unique genetic character that they have and the other individuals in the
population did not. They may go on to change enough to be considered a new
species.
The inundation of the Panamanian Isthmus is an excellent example. Just about
every mountain peak in Panama has unique flora. Due to isolation during
higher water (making the peaks islands) each island developed its own unique
flora and then when the waters subsided they maitained their positions, now
on the tops of the mountains.
Some species of plant and animal are of such 'perfect' design that they
survive the test of time. Some designs are not very adaptable and perish.
Genetic change due to natural selection is no myth it is very real.
Neil
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