To: All Msg #109, Feb1793 02:28PM Subject: Re: Gill Slits In article 1993Feb11.210050.2481

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From: Stan Friesen To: All Msg #109, Feb-17-93 02:28PM Subject: Re: Gill Slits Organization: NCR Teradata Database Business Unit From: swf@tools3teradata.com (Stan Friesen) Message-ID: <1988@tdat.teradata.com> Newsgroups: talk.origins In article <1993Feb11.210050.24814@microsoft.com>, russpj@microsoft.com (Russ Paul-Jones) writes: |> |> Now, just as a demonstration, let me compare creationism to biology. |> Now, I'm not biologist, but I think I can do a little test. As I |> pretend to be a biologist, I find that I'm (really) only certain of |> embryonic gill slits in fish, reptiles, and mammals. Now, I wouldn't |> be too surprised if amphibians had embryonic gill slits (they must have |> embryonic gills), I don't know whether or not birds do. Now, I'll |> ask myself the question, "Should I expect embryonic gill slits in |> birds?" |> |> As a biologist, my answer would be, "Yes." ... And you would be right. *All* *known* vertebrates have embryonic gills slits, without exception. [Wow, a nearly absolute statement - a rarity in biology]. In fact the early stages avian, reptilian, and mammalian embryology are well-nigh indistinguishable, save for the presense of yolk in the first two, and the extreme speed of the formation of the amnion in the latter. That is why embryology classes use chick embryos for laboratory work, they are easy to get, and they show all the main features one needs to see. [I should know, I took the lab course in enbryology]. |> So, any experts on bird embryology out there? For that matter, if |> there are any biologists or creationists out there, do my answers |> need correcting? Not from my perspective, based on my bachelor's degree in biology. -- sarima@teradata.com (formerly tdatirv!sarima) or Stanley.Friesen@ElSegundoCA.ncr.com --- Squish v1.01 * Origin: Universal Electronics Inc [714 939-6401] HST/DS (1:103/208) From: Stan Friesen To: All Msg #110, Feb-17-93 02:32PM Subject: Re: Gill Slits Organization: NCR Teradata Database Business Unit From: swf@tools3teradata.com (Stan Friesen) Message-ID: <1989@tdat.teradata.com> Newsgroups: talk.origins In article <109532@netnews.upenn.edu>, rowe@pender.ee.upenn.edu (Mickey Rowe) writes: |> Even there, though, the gill holes (they're more or |> less circular, so I don't know as that I'd call them slits) remain Well, using the biological definitions these are still called gill slits. It would get too difficult to talk about things if we had to change the word for a homologous structure every time it changed shape! It's bad enough having to switch around amoung 'leg', 'arm', 'fin' and 'wing', picking nits about the shape of the hole would be a little too much. |> these holes that the forelimbs emerge. |> |> I'm afraid I don't know enough about early bird development to comment |> on the other questions you raised. |> |> >-Russ Paul-Jones |> |> Mickey Rowe (rowe@pender.ee.upenn.edu) -- sarima@teradata.com (formerly tdatirv!sarima) or Stanley.Friesen@ElSegundoCA.ncr.com --- Squish v1.01 * Origin: Universal Electronics Inc [714 939-6401] HST/DS (1:103/208) From: Stan Friesen To: All Msg #111, Feb-17-93 02:46PM Subject: Re: Gill Slits Organization: NCR Teradata Database Business Unit From: swf@tools3teradata.com (Stan Friesen) Message-ID: <1990@tdat.teradata.com> Newsgroups: talk.origins In article <1993Feb12.121030.17332@hemlock.cray.com>, robd@cherry09.cray.com (Robert Derrick) writes: |> And that is, they are not gill |> slits at all, and they share nothing in common with gill slits other |> than a vague similarity of appearance, and in fact, they are nothing |> more than folds of skin. ... |> |> Are they really gill slits? Is there enough morphological/genetic/ |> etc. information to say what they are with certainty? Well, they are identical in form in embryonic fish and embryonic tetrapods (land vertebrates) - they form at the same stage, they occur in the same *numbers*, they are associated with the same internal anatomical features, and with the same relationships to other organ primordia. And in fish they develope *directly* into the adult gills, with very little change other than elaboration of structure. They are *certainly* more than just 'folds of skin'. Let us take just one of those associated features I mentioned - the blood vessels. In embryonic tetrapods the earliest form of the circulatory system includes a series of arched vessels leaving the heart and passing through the bars between the gill slits (called, naturally, the gill bars). Since there are always six gill slits (except in agnathans and some sharks), there are six aortic arches (as they are called) on *each* *side*. In mammals all but two of these arches subsequently disappear. One becomes the aorta, and the other becomes part of the one brachial artery. In birds a similar thing happens, except that the aorta is on the *other* *side*! So, not only do we have the formation of twelve holes that all eventually disappear, we have the formation of 10 arteries which also disappear. [In fish the aortic arches *all* remain, and provide blood to the gills for oxygenation]. Similar statements could be made about the innervation of the embryonic gill slits, their incipient musculature, and so on. Now, you tell me, are thse gill slits or not? I say, if it walks like a duck ...

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