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Re: Summer science quiz #2 -- Wheeled animals

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  • Re: Summer science quiz #2 -- Wheeled animals

    Here are three replies which were sent to me directly.


    Hello Liming,

    About your comment on the wheel - there are actually wheel-like structures
    in micro-organisms (no particular ones come to mind). I remember reading
    about one that has a fagella (tail) attached to it and this tail rotates
    by a wheel-like mechanism - actually, imagine the tail joined through a
    molecular ball bearing.

    As for larger animals, wheels may be too complex to evolve - there can be
    no physical connection unless you "unwind" your tendons and blood vessels
    that connect to the wheel-limb. Otherwise, your tendons/vessels will just
    wrap around the wheel like a plastic bag on a shopping cart and the wheel
    stops moving... You need connections to send/recieve signals and
    nutrients, both of which may also move through diffusion, but for larger
    animals the amount of surface area that this would require will probably
    be way too much.

    Did I say too complex to evolve? I know, I know, the current systems are
    complex enough, and I can't really justify why the wheeled structure has
    not evolved, but I just wanted to share a few thoughts.


    Jerry Hu
    Musculoskeletal Bioengineering Laboratory
    Rice University
    Department of Bioengineering - MS 142
    P.O. Box 1892, Houston, Texas 77251-1892
    Tel: (713) 348-6393
    Fax: (713) 348-5877

    ************************************************** ***************
    I saw somewhere that there are some baboons in Africa that tumble or
    cartwheel down hills. It's not a wheel but it's along those lines.

    If you had an appendage that served the same purpose as a wheel, how would
    it continue to rotate without getting ligaments, tendons, and muscles all
    tangled up?

    Bryan St. Laurent

    ************************************************** ********************
    I assume a wheel is different to rolling the whole organism. If that
    is the case then reasons why the wheel has not developed in the
    animal kingdom could include:
    1. All wheeled systems have the rotatory component not connected to
    the main framework. This would cause problems for a) transmission of
    feedback from the wheel. b) how the rotation force is transmitted to
    the wheel - assuming there is a drive wheel otherwise other limbs
    could do the driving i.e like a wheel chair.
    c.) the ability to provide a safe protection of the skin interface at
    the 'universal joint' which would also meet the various needs for
    stability, low friction, ability to rotate..

    2. Finally, if the wheel developed then that would mean my lectures
    on stretch shortening cycles would have to be changed to stepper
    motor or cam shaft development.. .. phew.
    Garry T Allison Associate Professor of Physiotherapy
    The Centre for Musculoskeletal Studies
    Department of Surgery, The University of Western Australia.
    Level 2 Medical Research Foundation Building
    Rear 50 Murray Street
    Perth Western Australia 6000.
    ph: (618) 9224 0219
    Fax (618) 9224 0204

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