Some taxonomists are thinking of a major revision based on cladistics. I had a hard time getting my teeth around it because of some of the rather interesting statements made about the approach. One statement says that something can not be descended from a group to which it does not belong. There can be branches of that group that are still part of the group. This place mammals in the same large group as fish. They would be particular types of fish but still fish. Birds would be placed in a branch of fish that also includes reptiles. Such ideas as these seem strange and need a little getting used to but do have advantages when trying to place organisms into realistic categories.

The bit I said about species is based on the observation that it is frequently very difficult to tell where one species starts and another ends. How different is different? Where do we draw the line? The lumpers and splitters are constantly bickering over this. Rana pipiens, a common frog, formerly was one species throughout a large range. It was then divided into IIRC about seven different species. The poor old frogs could not care less what we humans call it, but we humans have a need to hang a name on about everything. Species designations change all the time. Someone mentioned the rainbow trout as an example. That changed not only the species name but also the name of the genus. That is just one of many examples. My ichthyology professor wrote a very nice book about the fish of Tennessee that came out in about 1991. Many of the names in it were quite different from the names he taught me in his class back in 1973. I took a class that spent almost half the quarter discussing the different definitions of species. None of the commonly accepted definitions worked all the time for all organisms. This is not to say that the concept of species is not useful. It is quite useful. Just don't try to force it beyond its ability to reflect reality. Some people, unfortunately, try to do just that, especially when they are talking about evolution.

Last edited by Notropis; 11/18/09. Reason: spelling