Mathematical formulaes are just about the only thing that can be proven, because we make up the rules.
No science can be truly proven, there can be evidence, even i suppose some proof depending on how you read into the word, but no absolute proof.
The bacteria, i was actually thinking about doing something like this as my final year project, but taking it to the extremes that creationists seem to need.
The original bacteria could be sequenced, and it would not have the specific resistance encoded in its DNA, otherwise it would be resistant. All of its progeny will be almost exact replicates of it, because most bacteria are asexual (though some transfer of plasmids can occur, this is still not the same, as we still start with just one cell). However mutations will occur along the way, and the number of bacteria in a lawn on the average petri dish is going to be some truly absurdly high number. With this number of bacteria there will have been a lot of mutation (prokaryotes (bacteria etc, eukaryotes are more advanced organisms, (basically "before" and "with" a seperated nucleus)) do not have as advanced mechanisms to prevent mistakes occuring in the replication) With all these mutations occuring, a few of them will have developed a resistance to the phage.
This resistance probably involves the changing of a certain sequence (im not familiar with the experiment myself). The sequence will be the one that the virus uses to target the bacteria. Of course it could be due to other things such as restriction enzymes (enzymes that can destroy foreign DNA).
Now the phage has torn through the population leaving only these select few, the select few can now spread once more forming a lawn. As Rrhian said if you then reinfect the phage can also mutate (tho i assume you must use extremely large amounts of phage so to allow for one to have had the necessary mutations.)
Now this is evolution. Random mutation is acted upon by a selection process that allows one organism to thrive over its intraspecific competitors. Just because it is done in a lab means nothing, there have been cases of evolution occuring in the field as well. One example i learnt today was that of Fasicola (a trematode worm that infects sheep) these worms were taken from England to Austrailia in the sheep stocks, however the worm requires a certain species of snail to complete its life cycle, this snail does not occur in Aus, however the worm evolved and adapted so that it could complete its life cycle in another snail.
Random mutation with some sort of selection pressure, it all just works up from there really.
Unseul
edit to correct spellings etc
This message has been edited by Unseul, 05-10-2004 04:49 PM
Give a man a fire and he's warm for a day. Set a man on fire and he's warm for the rest of his life....