What's in a Name? 

Why, you may ask, would anyone want to study taxonomy?  What's in a name, after all?  A rose by any other name would smell as sweet.  Ah, but there's the rub  taxonomy is so much more than naming things! 

For starters, taxonomy is more properly known as the science of classification, of which naming is only a small part.  In biology, it's all about deducing the relationships between living things  a job both infinitely subtle and highly rewarding.  At its heart it merges naturally into such fascinating fields as evolution, biochemistry, and ecology.  And that's where the life sciences display their most profound and powerful insights into the hidden workings of the universe around us. 

The Swedish botanist, physician, and zoologist (he was a busy man) Carl Linnaeus (1707-1778) is often credited with being the father of modern taxonomy, while in fact his contribution was primarily just standardization -- granted, one all biologists should be eternally grateful for, given the complexity of scientific names used before him.  (For example, fan aloe (Aloe plicatilis) was first christened with the absurdly long name "Aloe africana arborescens montana non spinosa folio longissimo, plicatili, flore rubro".)[1][NOTE]

At least as important in my mind are the partial contributions of such visionaries as the Italian Andrea Caesalpino (1519-1603), who first proposed the methodical arrangement of plants into "higher genera"[NOTE]; the Englishman John Ray (1627-1705), who proposed classification by observed similarities[NOTE]; the German Augustus Rivinus (1652-1723), who based classification on microscopic flower characteristics, and (with John Ray) introduced our dearly beloved dichotomous keys; and the Frenchman Joseph Tournefort (1656-1708), who introduced two higher levels of classification[NOTE], and started the process of standardization that Linnaeus finally perfected and took credit for.  But however one disentangles the history, all can agree that Linnaeus left us with our modern naming convention (the single-word genus and species epithets  the so-called binomial nomenclature), and a good approximation of our system of classification (class, order, genus, species, and variety).  [3]

I don't know what you learned in grade school, but I was quite surprised to find that there have even been changes in the levels of hierarchy within just the last few years.  Here is a list of the major levels now:[NOTE]

Yes, botanists and mycologists changed "phylum" to "division"  hey, I don't make the rules!  And someone else (apparently Carl Woese is the culprit) got tired of the proliferation of kingdoms and added the level "domain" at the very top.  There's still some question where viruses belong: perhaps their own domain, perhaps even more ancient (another level, for heaven's sake?!), or just as likely, they've derived multiple times from various existing domains and kingdoms. [4]

Originally it was assumed that all life fit into a nice neat tree, that is, each taxon had a single parent taxon the next level up.  For example, all species of sunflowers belong to the genus Helianthus, which in turn is contained in the family Asteraceae, and so on.  (It gets really messy above family: botanists, biochemists, and geneticists are still heatedly debating how the various vascular plant families are related!) It now seems fairly clear, however, that the three domains  Archaea, Bacteria, and Eukaryota -- have horizontally transferred genes, a nasty incestuous habit that resulted in a bit of a tangled tree at the top-most levels.  Some have suggested that a ring is a more appropriate for the domains. [Need ref, maybe Kevin's book?]

Somewhere along the line it was realized that this "tree of life" actually represents something more than just morphological relationships; it is a vast family tree.  Now called the theory of universal common descent, it actually, believe it or not, pre-dates Darwin by more than a century.  The Frenchman Pierre-Louis de Maupertuis (1698-1759), for example, suggested that all organisms might have had a common ancestor and diverged through random variation and natural selection. [5] Thus while species of the same genus have a relatively recent common ancestor, species of the same family have a more distant common ancestor, and so on.  The farther up the tree, the farther back in history.

The spectacular improbability of self-replicating molecular systems arising spontaneously argues strongly that there is, in fact, only a single ancestor from which sprang all life on Earth.  Stop for a second to appreciate the implications of this: prior to that fateful moment, all molecules and chemical processes that ever arose by chance in the primordial soup, however complex and stupendous they may have been in their own right, left no trace when they broke down.  But finally one "figured out" how to replicate itself, creating an exponential explosion of life that ratcheted subsequent generations up through billions of years to attain the nearly inconceivable complexity and diversity we find all around us.  This single ancestor, so small you wouldn't have been able to see it even with the highest powered light microscope, left a legacy that in the fullness of time completely changed the face of the planet. 

[Need to include something about Jussieu and Adanson as well.]