How do taxonomists perform their work?

Answer 1

First, you find something that every organism has. Then you look at how different it is in each organism. For example, if the human version and the chimpanzee version were very similar, you would say that humans and chimpanzees were closely related. On the other hand, the human version may be very different from the oak tree version, indicating that humans and oak trees are not closely related.

These days, the most significant markers are molecular in nature. The cytochrome c protein was the big thing in the not too distant past. Now I think they usually go for the genetic sequence of the 16S or 18S small ribosomal subunit.

Of course, comparing one gene to another isn't as simple as it sounds. You can't simply line them up and count how many bases are different. Most homologous genes aren't even going to have the same number of bases from one organism to the next. How do you compare the genes when they all have gaps relative to each other? Remember that taxonomists are not just interested in deciding whether things are closely or distantly related, they want to know *how* closely or distantly related they are. In other words, they want to calculate numbers. For that, they need some kind of algorithm for comparing two sequences and determining a quantitative value that reflects the strength of the relation. I confess that I only know a tiny bit about how that is done, and not enough to explain it in any sort of coherent fashion. You'll just have to take my word for it (or find someone more knowledgeable than me on the subject) that they calculate quantitative values reflecting how closely related things are. Once they do that, they can start clustering things into a hierarchical structure.

So what does a 'taxonomist' actually do in his everyday life? He could be involved in any one--or all--of those steps. He could be collecting and/or sequencing DNA samples. He could be sitting in front of the computer analyzing and comparing data. He could be developing better algorithms for comparing and clustering genes, etc.