Hi Joanne,

> Hi Pete,
>
> We may be going from biology into philosophy here,
> but isn't the awareness of the cause dependant on
> the view one takes?

I'm not so sure there's a defining line

>IOW, if African violets
> experience a mutation that affects leaf pigment
> due to radiation (which happened), we tend to
> think of it as the radiation causing the mutation.
> However, if the mutation is a response to the
> environmental change (higher radiation), the
> pigment change could be seen as an adaption.
> *looks around and ducks*

I'm not sure exactly what you're getting at here. In my understanding of natural selection the environmental change - in this case higher (uV?) radiation - is the cause of the selection, not necessarily the mutation. Unless the mutation was sudden and propogated across all of the foliage and just happened to code for, for example, lighter leaves to reflect damaging uV levels. Of course that might happen but the odds seem vanishingly small.

> In the case of exposure to viruses in particular,
> how we can be sure which is the cause and which is
> the response?

Viruses are different because they are an active part of the process. Hitting something with higher uV radiation will cause genetic damage and heighten the mutation rate, but randomly. Since almost all mutations are harmful it seems likely that , in the event of a sudden environmental change, you wouldn't get lucky quickly enough and the plants would die. However, those with a pre-existing mutation (lighter leaves, or, in the case of humans, the ability to increase melanin production in response to received UV) would survive.

Viruses carry genetic information and are themselves subject to random mutation and natural selection. I can see that, in an infection that hits many areas of the body, viral DNA could, in combination with host DNA, trigger an immune response change. Again, though, the underlying reason would still be random mutation; this, howeer, would be reinforced in a feedback loop as time went on. in the case of the plague/AIDS relationship I guess we'll never know; we need to see it happen in real time.

> The trouble with many of these Internet
> discussions is lack of definition of terms...it's
> not just in threads dealing with genetics or
> evolution. It's anthropology, linguistics, etc.,
> etc. It probably would be a good idea if there was
> an on-site glossary with some basic terms defined
> that people could refer to as needed.

Then we could spend years arguing over what the definitions meant! We can't even agree on whether history can be classed as a science or whether pseudoscience refers to mythology

Pete
>
> Joanne




God is our guide! from field, from wave, From plough, from anvil, and from loom; We come, our country's rights to save, And speak a tyrant faction's doom: We raise the watch-word liberty; We will, we will,we will be free!