Tue Feb 28, 2012 7:27 am
Then what is your objection?
The occurrence of natural selection is based on a logical argument, with four premises. (Can you reconstruct the argument?)
- the offspring of animals are never exactly the same as their parents, but rather have small variations.
- some of this variation gives an advantage to an animal that possesses it
- these variations can be passed down to the next generation
- in each generation, not all animals survive.
If you wish to dispute the occurrence of natural selection, you have to deny one of the premises.
The genetic variation that occurs in a population because of mutation is random-but selection acts on that variation in a very non-random way: genetic variants that aid survival and reproduction are much more likely to become common than variants that don't. Natural selection is NOT random!
The term mutation can refer to any process that changes the genetic information in the genome, including DNA insertions, deletions and rearrangements.
Genetic variation is generated continuously by the mutational process, but its persistence in the genome is determined by different historical and genomic factors.
Mutations are "random" in the sense that the sort of mutation that occurs cannot generally be predicted based upon the needs of the organism.
Thu Mar 01, 2012 7:16 am
scottie wrote:I have tried to catch up with the postings, now I am not sure but is this the question you wish me to address.
Fri Mar 02, 2012 10:23 am
It is important to realize that mutations do not occur in response to the environment. They simply happen.
Sat Mar 03, 2012 8:12 am
scottie wrote:yes I intend to address your entire post.
But I do have to start somewhere don't I?
Sat Mar 03, 2012 8:37 am
Sat Mar 03, 2012 5:23 pm
I can wait for you to finish; in attempting to devise answers, I think you will be able to get closer to resolving any confusion. I see no contradictions or "differing views" in any of the phrases you have quoted - for example, as you think, you might try to specifically identify what you think the difference is.
“Some sensing mechanism must be present in these instances to alert the cell to imminent danger, and to set in motion the orderly sequence of events that will mitigate this danger. The
responses of genomes to unanticipated challenges are not so precisely programmed. Nevertheless, these are sensed, and the genome responds in a descernible but initially unforeseen manner.
(my emphasis)In the future attention undoubtedly will be centered on the genome, and with greater appreciation of its significance as a highly sensitive organ of the cell, monitoring genomic activities and correcting common errors, sensing the unusual and unexpected events, and responding to them, often by restructuring the genome. We know about the components of genomes that could be made
available for such restructuring. We know nothing, however, about how the cell senses danger and instigates responses to it that often are truly remarkable.
Genomic rearrangements are associated with many human genomic disorders, including cancers. It was previously thought that most genomic rearrangements formed randomly but emerging data suggest that many are nonrandom, cell type-, cell stage- and locus-specific events. Recent studies have revealed novel cellular mechanisms and environmental cues that influence genomic rearrangements.
Sun Mar 04, 2012 12:34 am
Again, the possibilities are:
- the mutations might be common enough that they happen all the time
- the mutations might occur once or twice and then spread through the population by interbreeding
- the mutations might have already been present in the ancestral population
From my post above, I think it should be fairly clear that the third option is the most likely. However, even if it is incorrect, the others are still quite possible.
The interpretation "developed" is an inference that is not part of the data. Nobody has observed any population with no inversions.
I will also point out that changes can indeed happen quite fast, so long as the environment also changes fast - it is mainly the major innovations (like fins turning into legs) that take large amounts of time.
Sun Mar 04, 2012 12:47 am
Where are the functional phenotypes that random mutation is supposed to have produced in order for NS to select from?
Sun Mar 04, 2012 8:19 am
Since you see no difference in the views I have presented, you have answered my question.
Sun Mar 04, 2012 12:38 pm
AstraSequi wrote:Actually, I can't figure out what the views you have presented are.
Sun Mar 04, 2012 5:24 pm
Try convincing a sufferer of sickle cell of the cleverness of these so called relative terms.(my favorite example of how relative the terms "beneficial" and "deleterious" are - it all depends on the environment)
Sun Mar 04, 2012 7:42 pm
It depends what you mean by "unlikely." While any individual mutation is unlikely, that doesn't mean that it will not happen on a regular basis if you give it enough chances.
Suppose there is a mutation that has a one in a million chance of happening - you can call this unlikely. However, if a million fruit flies are born, then it will probably happen around once. If you then wait for a thousand generations, it will probably happen around a thousand times.
(I will also point out that for a fruit fly, a thousand generations is only about 40 years.)
I think this might be an important point that you're missing - in statistics, this is called a Bonferroni correction. If you roll a pair of dice, your chance of a double 6 is quite low (1/36). However, if you try twice, your chance doubles - and if you try a hundred times times, your chance of getting it at least once is very high - in fact, it would be more surprising if you didn't get it at least once. The probability of something happening increases as the number of times it is possible to occur increases.
The probability of something happening increases as the number of times it is possible to occur increases.