I would disagree with Phillip's sentence 'There is also the aspect that
"mutations have produced a wide range of new colours" is at least in
most cases wrong as well '
If a bird is green because it produces a blue and yellow pigment, and a
mutation gives rise to a blue bird, then the mutation has given rise to
a new color; The mutation may have caused the loss of yellow pigment as
he clearly points out in the rest of the paragraph, but it has
definitely given rise to a new color, one that didn't exist before (at
least in this bird).
Secondly I am intrigued by the sentence " ......... before such wide
publicity of the appalling non-scientific methodology used in the whole
peppered moth saga was exposed, .................." about the paragraph
which is quoted as
"Only very rarely does a mutational change assist an organism to
survive. In the case of the Biston betularia moth, for example. it is
""thought"" that the black variety originally arose as a result of a
mutation. This mutation proved to be beneficial for the moth, as its
environment was changing at the same time.........."
What exactly is this "appalling non-scientific methodology" with regard
to the peppered moth.
Michael Tarburton wrote:
Phillip veerman & I have engaged in a little dialogue about the text
(& what they might have meant) that made this claim. Some
clarifications have been made that might be of some use to some of you
so I forward them to the list.
Thanks for that. It appears that I was on the right track partly
because I was wondering WHY a book would make such a statement, as in
why would a text book bother to mention what colour budgerigars are.
Even if the point is worth making, it is very poor quality research,
understanding and/or editing. There is also the aspect that "mutations
have produced a wide range of new colours" is at least in most cases
wrong as well In terms of the word "produced". Most (or all?) the
colour variants that are now established in captive populations are
not the result of producing new colours as much as loss of the ability
to make the standard colours. So blue birds are blue not because of a
new gene producing blue but due to the loss of the ability to make
yellow pigment, so that the parts that normally show as green now show
as blue, the genes to produce the blue structural colour were always
there. Likewise yellow birds are yellow not because of a new gene
producing yellow but due to the loss of the ability to make blue
structural colour, so that the parts that normally show as green now
show as yellow, the genes to produce the yellow were always there.
These are the most basic features, there are many other variants
further enhancing those two.
This principle comes in potentially useful in regard to a wild bird of
any species that has colouration different from the normal. Of course
hybridisation is another quite different source of oddities.
Maybe this extra comment could go to the B-A list to fill in the
story. That is up to you, as in you first put it on.