Darwin, wrote in his ‘B’ notebook in 1837,
And in one instant transformed the way that we all think about life on earth. This simple diagram unified science. It captured Linnaeus’ nomenclature and married it to the fossil progressions that geologist the world over were seeing in the rocks. It redefined how we understand species and laid the framework for a new view of life as being all related at some level, with some organisms sharing more characteristics with their closer relatives and less with those more distant. It allowed scientists more than a hundred years later to recognize that the biochemical foundations of bacteria and yeast and drosophila and humans were all the same. Because we are fundamentally one family. There was no need to identify a genetic code for each species. Instead, we share a common (universal) code of DNA triplets each calling for an Amino Acid in building proteins.
However, there has been a lot of thought about what it really does mean to be a species. Darwin’s book, The Origin of Species, addresses just this point. I raise this question on the first day of my general biology class and my microbiology class. In general biology we eventually rest on the idea that, at least in the larger plants and animals we are used to encountering – and will discuss in the course of our class, the ability to mate with, and produce fertile offspring from is necessary and sufficient to group two animals into the same species. Of course the mule comes up as a near exception necessitating the ‘produce fertile offspring’ clause, but this is a definition we can accept. In microbiology, we are forced, by the nature of the organisms we study, to discard that convenient description. Many micro-organisms replicate asexually and are capable of transferring genes horizontally.
knowing they’re in a bucket
and not knowing
In the November 1 issue of The Scientist, Axel G. Rossberg, Tim Rogers, and Alan J. McKane tackle the very existence of ‘species.’ Therein, they acknowledge the fact that we use the concept of ‘species’ for our own convenience and consider the possibility (or rater, probability) that the very idea of species delineation may be artificial. The article looks into the variety of life and how the definition must change depending upon the organisms in question and makes us face the assumptions we often take for granted. Click on ‘The Scientist’ below to see the full article.