I'm going to sorta rehash Ron's contribution and add a little of what I've studied ...
Depending upon the gene pool, there can be a lot of variation within a species, or a sub-species [race]. But, as Ron & Darwin said, change happens. Sometimes the change is not affected in any way by the outside environment, but rather by a strange combination of the parent genes. Thus we can get something like an albino or a sport. If the changed entity survives to fertility, the progeny will be species normal. Mutations take place constantly, as do poor genetic combinations. In most cases -- say in the range of 99.9% -- the mutation is either of no use, or detrimental. Mutations, unlike sports and congenital anomalies, do breed true if they survive. Mutations are in the DNA itself, not in how the DNA combines into a new individual. Most congenital and mutational gametes do not survive. Seeds will be unable to germinate, eggs won't hatch, embryos will be flushed from the system [doctors now believe that spontaneous terminations at 4 to 6 weeks gestation are the norm rather than the exception for humans, so normal that they go unnoticed ... marked up to stress, or a "late period."] Those mutations which don't prove fatal prior to germination or birth can still prove to be dead ends; failure to thrive, failure to reach sexual maturity, infertility, inability to match chromosomes into viable progency ... add to that shunning, in all animate phyllums being "different" is something which generally precludes you from breeding within your species. Plants are dependent upon meeting the criteria of the pollinators far more than of other plants <G> which may explain why there are millions of varieties within thousands of species of advanced [pollinating] plants, and so little [comparitively speaking] variation in animals. I'd go so far as to say the "high up the ladder" animals are, the less likely is the chance that a "different" member of the species is to breed and pass on the mutation. Some mutations are miniscule. In my family I was the first of the original generation to show a mutation -- antrophy of muscles and tendons for the distal joint on the "ring finger" of both hands. Although it freaked my parents out, in the days when things like polio and diptheria were still every-day facts of life, the doctors simply told them they didn't know what was ... but it wasn't a disease. So they were past that when my brother developed the same thing, as did our children ... which made it pretty easy to verify that my son originally lost in adoption was my son when we met. <G> Obviously this mutated trait is not a "recessive." But many mutations are recessive, so it is possible for even the best of wonderful mutations to be bred out of existance. All of which proves that 1) the more we know, the more we realize we don't know AND 2) life is just a roll of the dice in more ways than most of us would be willing to admit. What I find most special about life is the surprises. Who would think [I certainly wouldn't have a couple of decades ago] that people from around the world who are all interested in a single DOS internet interface would also have much more knowledge they are willing and able to share, and that debate of differing views could take place without any flame wars! Perhaps that is a sign that Natural Selection still works ... where communication and sharing replace contention and agressiveness. Or so let up hope. l.d. -- Arachne V1.70;rev.3, NON-COMMERCIAL copy, http://arachne.cz/
