Re: Colors of alien plants -- Scientific American

On Mar 31, 9:41=A0pm, James A. Donald <jam...@[EMAIL PROTECTED]
> wrote:

> Once evolution gets a system going, it will optimize the hell out of
> it, but the actual design does not look like a design, but rather like
> the random aggregation of a pile of parts in a junkyard by a tornado,
> which pile of junk then gets the superficial appearance of design by
> each part being carefully polished and perfectly fitted to the other
> parts.

:) You don't have to tell me, I teach a 100-level class in Biophysics
about once a year, in a rather fundamentalist section of the
community. Lots of interesting questions & discussions.

>> it leads me to wonder what happened to the
>> green-light photosynthesizers.
>
> They are still around, still using hydrogen sulfide: The purple sulfur
> bacteria.

Hmm. I thought Purple Sulfur Bacteria used photosystems also built
around Chlorophyll (bacteriachlorophyll in this case). So in that case
it would seem green-wasting photosynthesis was evolved first, then
later patched by accessory pigments to try to take advantage of the
green sections of the spectrum. That's fine (& how I've previously
viewed the process), but not quite match the scenario laid out. It's
not "we had efficient photosynthesis, wasting the all but the odd
frequencies" leading to "something evolved photosynthesis not
optimized for for green light to take advantage of the holes". The
upper level photosynthesizers, already based on chlorophyll, should
already have taken those frequencies.

--
Brian Davis