Systematics

(This column was first published in the September 4, 2000 Buffalo News.)

    When I studied school biology, much of the course was devoted to sorting all life into classifications -- what is formally termed systematics. We followed Linnaeus' scheme, first dividing all living organisms into animals -- they moved -- and plants -- they didn't. At that point we set aside the plants and divided the animals into their categories.

    We went through the animals phylum by phylum, Latin names and all. I can recall only a few: porifera (sponges), arthropoda (spiders and insects), mollusca (clams), chordata. Chordates include us so we went on through the rest of the hierarchy -- class (mammals), order (primates), family (hominids) to our own genus and species -- Homo sapiens.It wasn't exciting but we learned a great deal about Earth's life forms.

    This summer I learned how much systematics has changed from Colin Tudge's excellent new book, The Variety of Life: A Survey and a Celebration of all the Creatures that Have Ever Lived (Oxford), an up-to-date and encyclopedic reintroduction to this field.

    Indeed, much is different and unfortunately the terminology has gotten even more tongue-tied. But the basis of classification continues to be "shared derived features," what systematists call synapomorphies. Chordates, for example, share backbones passed down through the ages. These carefully identified features group life into clades that the scientists carefully examine for evolutionary links. Superficial evidence is often misleading so that, for example, dolphins are less like fish than they are like us.

    Even before the cladists entered the picture, however, in the 1950s Robert Whittaker of Cornell separated three kingdoms from Linnaeus' plants and animals. He added Fungi, Monera (bacteria) and Protoctista (various algae like the seaweeds) to make five in all.

    But even this major change was not enough for the cladists. Carl Woese of the University of Illinois and others have identified further profound differences that so influence the overall organization as to question the entire Linnaean superstructure. Some purists reject the old categories -- kingdom, phylum, etc. -- but to retain some semblance of order most researchers retain them.

    A whole new category, domain, is now added above kingdom. There are three: bacteria, archaea and eucarya. The first two lack cell nuclei but together outweigh all other life forms "at least tenfold." They are, says Tudge, "everywhere. They influence our lives in a thousand ways. They can live perfectly well without us and our kind, and did so for several billion years before we came on the scene. Sometimes they kill us. Yet we could not live without them." Their new domain assignment raises at least a dozen groups of these mostly microscopic organisms to kingdom status.

    The other domain, eucarya, whose cells have nuclei, now include not only the plants, animals and fungi but about 20 other kingdoms as well. Overall the picture is very different and the discovery of additional living organisms and fossils continues to change not only details but often whole categories.

    Some other aspects of the new systematics: Instead of searching for fossilized "missing links", scientists identify "sister" populations and DNA techniques estimate the approximate date of separation. By this means it turns out, for example, that animals are more closely related to fungi than to plants.

    And finally, we are no longer considered to represent the top of the tree of life. "Ecologically and individually," says Tudge, "human beings are, of course, wonderful, just as planet Earth is wonderful. But phylogenetically we are an outpost, a tiny figment of life, just as Earth is a cosmological nonentity that no other intelligent life-form in the Universe would bother to put on their celestial maps."

    This book makes clear once again that our ever-expanding knowledge base and our new inves tigatory tools force us to rethink long accepted fundamentals. -- Gerry Rising