Sunday, December 6, 2009

More abstruse words.

     On page 89 in Phylogenetic Systematics is when things start to supercharge in difficulty. Several new words are introduced that the author does not define very well, nor are they words I have ever seen prior to reading this material. Even worse, the words are used often, which means if one is not intimately familiar with them, then all the processing is spent on dealing with the words and being further frustrated by the difficult content.
     So a different type of reading strategy must be used in order to successfully read this book. I am accustomed to reading books within a few days and dashing over to my dictionary whenever an unfamiliar word appears. What I am accustomed to cannot be maintained when reading something of this caliber. I have to take time out and research words before I can continue reading. Here are some more of them:

     1. Plesiomorphous, Plesiomorphy - As with most words in phylogenetics, the authors seem to enjoy putting them together out of Greek roots. This reminds me of when I used to study calculus; the authors enjoyed using Greek letters in the equations. It was not necessary as standard Roman characters would have sufficed. But in phylogenetics it seems to me that it is necessary, perhaps not with Greek, but most certainly with something. In order to cope with these words, one must know that plesio-, plesi- correspond to "near" or "close". And morph- corresponds to "form", "shape", or "structure". In phylogenetics, the meaning refers to traits that are similar within a group, but not unique to that group. As an example, all mammals have a backbone, but so do fish and reptiles. Thus, the backbone is plesiomorphic to mammals, because they were not the first to evolve it, but they all have one. (Most common example I could find.)

     2. Apomorphous, Apomorphy - apo- corresponds to "separate", "away from", "derived from" and refers to traits that are derived from a different group. As an example, the "arms" of birds are used as wings. Thus, having wings is an apomorphy for birds because they did not evolve limbs and they use them for a different purpose. (My example.)

     3. Symplesiomorphous, Symplesiomorphy - sym- corresponds to "together with", "united", or "similar". This simply refers to plesiomorphous traits in different species. I decided to consult wikipedia for an example:

"A famous example is pharyngeal gill breathing in bony and cartilaginous fishes. The former are more closely related to Tetrapoda (terrestrial vertebrates, which evolved out of a clade of bony fishes) that breathe via their skin or lungs, rather than to the sharks, rays, et al.. Their kind of gill respiration is shared by the "fishes" because it was present in their common ancestor and lost in the other living vertebrates."

     4. Synapomorphous, Synapomorphy - This refers to the presence of apomorphous traits in different species. As an example, the opposable thumb in some new world monkeys is synapomorphic. It is a derived condition that they share with each other but not with all other mammals. I suppose that if all mammals had opposable thumbs, then the trait would be apomorphous. (I found that example doing a google search.)

     5. Autapomorphous, Autapomorphy - I can't find a definition that is pleasingly simple. All I can seem to find is that it refers to "uniquely defined traits". My guess is that abstract reasoning would be an autapomorphic trait for humans, even though such reasoning is without structure itself. Or is it? Morphology does not need to be restricted to those structures that are readily visible. The folds of the brain could also be a part of morphology, as well as the new "structures" in the brains of humans; the thinking that we do might have an actual shape in the brain, traceable by synapses.

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