QUOTE (Supes @ Feb 8 2004, 08:04 PM)
There is a moth that currently exists ( the name of which escapes me at the moment) but it is a current example of evolution in action. Currently one half of the species exhibits a trait that soes not exist in the other half of the population. This trait relates to a developed survival mechanism to help them from being eaten by bats. It is apparent that some of the moths have developed the ability to "hear" the bats sonar. As such, when they are about to be made a meal of they dive out of the way at the last second. Of course those without this ability get eaten. Soon you will find that all of the moths in this species will exhibit this trait because all the others that don't will get eaten and thus not breed to pass on their deficient defence traits.
Most moths have some ability to detect the sonar of bats. Some go even further than that: the Tiger Moth has the ability to flex its chitin, sending off ultrasonic clicking that has the ability to startle and/or confuse the bat. It will do this, again, in response to hearing the sonar. Then there are "whispering bats," whose sonar is at such a low frequency that the moths may not hear it until it is too late. Of course, their range is not so good, so they are not a danger to all moths everywhere.
Some moths have no ability to hear bats, but have the defense of being very large. Many bats are quite small, and will ignore large moths on the grounds that picking them up would make it difficult to remain aloft.
A common misconception about evolution is that it's all about the survival of the fittest, that once a new trait is introduced it must either outcompete the older trait or it will disappear altogether. This is the origin of the common complaint "If man evolved from apes, why are there stil apes?" (To which I say ask that question again in 100 years) Actually, however, the notion of evolution has to do with a species finding a favourable mutation and the mutation thiving, though not necessarily at the cost of the pre-adapted species. Say a fish evolves to survive on land, and later leaves the water altogether. This is not to say that there are no more fish in the sea, any more than to say that if the Inuit people migrated south and are the ancestors of the Incas, then there should be no more Inuit in Alaska. Somtimes an adaptation will outsurvive a previous incarnation of the species, but this would likely only be if the previous incarnation were going to die anyway, like the no-sonar moths might have in your example.
"I had a lot of different ideas. At one point, Luke, Leia and Ben were all going to be little people, and we did screen tests to see if we could do that." -George Lucas, in STAR WARS: the Annotated Screenplays (p197).