To coelenterate or not to coelenterate, that is the question...
Whether 'tis Nobler in the nomenclature to correlate
The Threads and Barbs of nematocysts,
With the colloblasts of the ctenophores,
And by opposing end their correlation: to declassify, to reclassify
No more; and by classify, to say we reorganize
The Heart-ache, and the thousand Natural shocks
That gelatinous bodies are heir to? 'Tis a re-classification
Devoutly to be wished. To declassify, to reclassify,
To reclassify, perchance to genetically code; aye, there's the rub,
For in that coding, what truth may come,
Comprehending these evolutionary differences,
Must give us pause. There's the respect
That makes Joy of so long life...
(with deepest apologizes to The Bard)
Science is active, it is about observing, testing, considering, and refining. With Science we learn additional information and refine our perspectives, the case of the cnidarians and the ctenophores is an excellent example; Science utilizes the method of using our best-current-facts to comprehend the
world around us. Our ability to *see* the natural world around us
changes greatly over time due to advancing technologies (microscopes, telescopes, genetic coding, etc.) and of course
the effect of standing-on-the-shoulders-of-those-that-went-before
(discovery builds on discovery, comprehension on comprehension... ).
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| E. Haeckel- Cnidaria |
To quote- science is "the intellectual and practical activity encompassing the
systematic study of the structure and behavior of the physical and
natural world through observation and experiment"... Anyone can do it, but Science demands from the *researcher/observer* open-ness not only to new ideas but to being able to follow the evidence where it leads and acknowledge changes/updates in information.
So... what does this have to do with our coelenterate controversy?
 |
| ...any excuse for a Haeckel! Ctenophora |
Cnidarians (anemones, corals, and jellyfish) and ctenophores (comb jellies) *used to* be categorized in the same Phylum, Coelenterata; both are very simply structured, gelatinous-bodied, and lack a backbone (invertebrate). BUT! research over time (which is *how* research happens : ) has shown that the differences between the cnidarians and the ctenophores are substantial enough to place them in separate phyla: Coelenterata (a.k.a Cnidaria) and Ctenophora; because of some similarities and a history of grouping them together the two phyla are sometimes still colloquially (non-scientifically) grouped together for convenience and called coelenterates (so, be gentle, sometimes change takes time! ;) ).
So, what are some of those differences which led scientists to go to the lengths of creating a whole new PHYLUM?!?
(and how the heck do you pronounce
coelenterate,
cnidaria (
UK), and
ctenophore anyway?!?)
|
Cnidarians (Coelenterates)
|
Ctenophores
|
Symmetry -body
|
Radial
|
Bi-radial
|
Digestive tract
|
Incomplete (single) digestive opening,
food enters and leaves the body through the same opening
|
Complete (one way) digestive tract
with 2 openings: oral (mouth) and anal.
|
Prey capture
|
*Stinging cells- cnidocytes/ nematocysts
|
Sticky cells- colloblasts
|
Larval form
|
Planula
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Cydippid
|
Development
|
Diploblastic, with true tissue
|
Triploblastic
|
(by the way, any terms/words you are
uncertain of can easily be found online! I’m in a rush today! : )
*Those stinging cells are key by the way!
It appears that cnidarians are more directly in-line evolutionarily, and that the ctenophores are more of a sibling group to all other animals. Ctenophores have muscle and
nervous systems that seem to have evolved independently from other modern animals (google Hox and Homeotic gene contingents!). Where the ctenophores sit in their forms and functions excluded them from being grouped in the Phylum Coelenterata.
So, you see, what some people may think of as a negative, "controversy", Science sees as normal growth and development. We start with basic information, and then, based on observation, testing, and consideration we develop and refine the information. Since our abilities and technologies improve our ability to perceive more of the natural world improves also; consider the path to what we know about genetics ...
 |
| Double Helix |
...in 1866, the monk, Gregor Mendel published a paper based on his plant experiments (done in the garden of the monastery) that became the basis for the Mendelian laws of inheritance, Meischer published his first paper identifying "nuclein" (now called DNA) in the cell nucleus in 1871 (without the microscope *that* would have been rather impossible), 1900 Mendel's work was rediscovered by several researchers (confirming their work), in 1910 Kossell received the first Physiology/ Medicine Nobel Prize based on the discovery of the 5 nucleotide bases (go google that, it's something you should know!), Hershey and Chase demonstrated that DNA carries our genetic material in 1952, 1953 was the "discovery" of the double helix (yeah, the double helix was always there, but until we could "see" it we couldn't *see* it! ... y'know?), in 1977 Sanger developed a sequencing technique to sequence (read) the first full genome (the complete set of genes in an organism), 1990 saw the launch of The Human Genome Project (yes, that would be the sequencing/reading of ALL of the genes in a human), in 2001 the first draft of the human genome was released with the project completed in 2003 (to 99.99% accuracy and 2 years early), in 2008 due to technological advancements the costs of genetic sequencing drops with the development of next-generation sequencing platforms, the first comprehensive analysis of cancer genomes is published in 2009...
...and one of the RESULTs of all of that scientifically acquired knowledge? Modern medicine that allows targeted treatment of many genetics illnesses.
Science builds on *small* steps...
... ok, sometimes we get lucky and we get a big step, but you know what I mean...
And we *still* have a lot to learn about genetics!
This is how science is supposed to function, always improving on it's self, and how we see our world.
