Hooray for thinking inside the box!

It’s cylinder shaped, about three metres long, lives 2500 metres down on the ocean floor, loves sulphur and has roots instead of a mouth. Fascinating creature, the giant tube worm, or Riftia pachyptila, but pretty hard to put in a box. Nevertheless, that’s one of the first things a biologist does with a new species: classify it.

Labelling flora and fauna

It all started with Linnaeus, who in the mid-18^th century suggested giving two names (genus and species) to plants and animals, for example. Although he was not the first to try to describe and classify nature, his practical system of labelling soon caught on. He classified thousands of plants and animals (and even minerals) in a hierarchical family tree on the basis of common physical characteristics. About a century later, Darwin’s findings would give this scientific work a new dimension. Classification now described the evolutionary relationships between species. Together these two famous biologists laid the groundwork for our present system of taxonomy.

Where does each creature belong?

Ever since, the classification of organisms on the basis of relationships has become a permanent fixture of biology. Almost every secondary school pupil learns about the tree of life and the associated classifications: Kingdom, Phylum, Class, Order, Family, Genus and Species. This tree is uncomplicated near its trunk, but it quickly branches into a huge tangle of sections, parts and subcategories. So how do you allocate a species to its place in this enormous tree of life? How do you know what place in the tree is the most suitable?

Hard to label

Time and time again, newly discovered species cause classification dilemmas. All those little animals, plants, bacteria, fungi and other single-cell organisms that seem to belong everywhere and nowhere at the same time are very impractical. Should we classify them on the basis of their shape, means of propulsion or manner of obtaining food? Or based on the pigment in their leaves or their metabolic processes? In the Science LinX exhibition you can test your knowledge of life on earth. You will discover just how arbitrary the classification criteria can be when you’re looking for the right ‘box’ in which to put evolutionary oddballs.

Using genes for classification

It became clear that classification on the basis of physical characteristics can be misleading when genomics appeared on the scene and was integrated in taxonomy (phylogenomics). After comparing their genetic material it became clear that many organisms had been ‘incorrectly’ classified! Some have since been reclassified. Although genomics can certainly contribute to the knowledge of relationships in the tree of life, it does not have all the answers. The fact that the genetic material of two species is very similar is not proof of a relationship. The question arises: are they related but did they evolve in different directions? Or are they unrelated and did they develop a similar set of characteristics independently? In actual fact, the genetic composition of a plant, animal, bacterium or fungus is no more than just another characteristic, to be taken into account alongside all the other characteristics.

Research in Groningen

Two research groups in Groningen, Evolutionary Genetics and Marine Biology, have spent years studying how genetic organization and variation influence evolutionary and ecological processes and how this affects distribution. Genetic variation is to a large extent determined by selection pressure in the environment. But how does this work exactly? And how important is genetic variation? Researchers are trying to find the answers to these and other questions. By the way, for their research in the lab they use fruit flies and wasps, which are much more practical than tube worms!

Links

Colophon

Special thanks to: Dr Eize Stamhuis and Edith Liemburg. Please contact Science LinX if you should have been included in the acknowledgements.

Author

Siëlle Gramser