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| Author |
Message |
| 14 new of 62 responses total. |
gull
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response 49 of 62:
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Jan 25 04:24 UTC 2006 |
Re resp:19: Natural selection tends not to remove things that are now
useless, but don't actually inhibit survival and reproduction.
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rcurl
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response 50 of 62:
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Jan 25 06:25 UTC 2006 |
Also Re #19: I suspect we have two kidneys because we have two of a lot of
things. It depends from which hox genes various tissues arise. We are a
bilateral creature, like almost all higher organisms. So we have two kidneys,
two adrenal glands, two lungs, two testes or ovaries, etc. The stuff we have
one of arise from a different tissue set.
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tod
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response 51 of 62:
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Jan 25 16:30 UTC 2006 |
My understanding is that we start with 2 of everything but then as we develop
into a foetus that some of these things merge to create one organ or tissue.
An example would be that thingy that hangs down in your throat right over your
tongue..I'm too lazy to look up the name for it. Anyway...one of my sons
doesn't have one of those and the other one does. I had to do a lil armchair
Biology 101 to find out how that happens.
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mcnally
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response 52 of 62:
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Jan 25 17:18 UTC 2006 |
(you're probably referring to the uvula..)
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rcurl
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response 53 of 62:
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Jan 25 18:09 UTC 2006 |
While we may "have two kidneys because we have two of a lot of things" (re
#50) I should have added that we have two of a lot of things because
bilateral organization has a lot of adaptational value in terrestrial
metazoa. That mobility is enhanced with paired feet is so obvious that it
is hard to think of another form that would accomplish the same thing.
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mcnally
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response 54 of 62:
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Jan 25 18:28 UTC 2006 |
n-way symmetry for any n >= 2?
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aruba
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response 55 of 62:
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Jan 25 19:08 UTC 2006 |
Starfish, for example.
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rcurl
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response 56 of 62:
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Jan 25 19:15 UTC 2006 |
That's why I said "terrestrial" in the meaning (OED) "4. Of, or
pertaining to, the land of the world, as distinct from the waters.". Any
mobile land animals that are not bilateral symmetric?
By the way - the starfish larva is bilateral symmetric.
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mcnally
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response 57 of 62:
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Jan 25 19:33 UTC 2006 |
What you said, and what I was responding to, was: "That mobility is enhanced
with paired feet is so obvious that it is hard to think of another form that
would accomplish the same thing."
I was simply pointing out that there's nothing inherently better about
pairing (2-way symmetry)and that it wasn't hard to think of other forms that
could have accomplished the same thing.
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albaugh
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response 58 of 62:
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Jan 25 20:41 UTC 2006 |
> I was simply pointing out that there's nothing inherently better about
> pairing (2-way symmetry)
I might agree about the symmetry aspect of having 2 of something, but in terms
of redundancy, where 2 instances of something share the load and don't
interfere with each other, that would seem "better" than a "single point of
failure". But in the case of the heart, could you really have 2 that wouldn't
interfere with each other? Perhaps not.
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rcurl
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response 59 of 62:
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Jan 25 21:00 UTC 2006 |
Animals have unilateral digestive tracts and several other visceral organs
(though the blood system is bilateral except for the heart....and perhaps
even the heart is based in part on bilateral hox genes). I'm ignorant of
how this arises relative to other bilateral symmetries, but I suspect that
metazoans are made of different tissue types, and only certain types
convey adaptational utility by being bilateral.
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tod
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response 60 of 62:
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Jan 25 21:03 UTC 2006 |
N'stuff
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bhelliom
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response 61 of 62:
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Jan 26 05:09 UTC 2006 |
resp:49 - So that's why my father's still around!
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wilt
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response 62 of 62:
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May 16 23:52 UTC 2006 |
HACKED BY GNAA LOL JEWS DID WTC LOL
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