Sunday, September 2, 2012

animal relationships

There are many ways to envision the relationships among all the animals on the planet, and phylogenetic trees offer a potent visual, as I discussed the last time I taught invertebrate zoology.  For a somewhat different message, you can compare the numbers of described species in various animal groups with the numbers of species known in other kingdoms, as in this drawing.
It's a few years old, but it still delights me as much as it did the first time I saw it described here by Chris Taylor. Even though each drawing is not a taxonomically equivalent group (the protists, plants, and fungi are all kingdoms that warrant a single sketch, while one animal phylum, the Chordata, gets a separate drawing for each of its 5 vertebrate classes), it is an arresting graphic.  Most of the space is taken up by the huge fly and by the bulbous tick in the lower left, which represent the arthropods.  Although we'll be spending plenty of time on crustaceans in class, a group oddly neglected in this drawing, I'll be leaving those terrestrial arthropods alone and focusing instead on the marine invertebrates, especially those groups with abundant and diverse local examples.

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