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View Full Version : Re: Summer Science Quiz #2



dlloyd80
05-17-2001, 10:56 AM
Hi all,

Attached are some personal replies I have had about kangaroos and tails.
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From
>Dan Barker
>Biomechanical Engineer
>Lund University Hospital
-
>As a fellow aussie, this is interesting. Does the tail act purely as an
>added balance mechanism or is there a more active role in the gait of the
>kangaroo. I think the question should be 'why is there little bilateral
>asymmetry in nature'. To me this is obvious. Animals evolve in an
>environment in which there will, in general, be equal stimulus on either
>side, L-R, of the body. An animal that had a weakness on the left or right
>side only would surely have a smaller chance of dominating a gene pool vs a
>balanced animal. Perhaps there are animals which do live in an environment
>where there are predominantly unilateral stimuli.
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From Chuck Pell

>Functionally, yes. Same goes for several monkeys
>and marsupials: five. They have prehensile tails.

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And my reply to continue the discussion

>As a fellow aussie, this is interesting. Does the tail act purely as an
>added balance mechanism or is there a more active role in the gait of the
>kangaroo.

I have seen kangaroos walk by pushing with their tail. The tail probably
also acts as stabiliser to counter angular momentum in the saggital plane
when hopping. Bipedal lizards may also use their tails as angular momentum
stabilisers in all probably all planes of rotation.

>I think the question should be 'why is there little bilateral
>asymmetry in nature'.

I agree. The midline location tail of kangaroo and lizards does not have
asymmetry.

Cheers

David


David Lloyd PhD
Senior Lecturer - Biomechanics Group
Department of Human Movement and Exercise Science
University of Western Australia
35 Stirling Highway
CRAWLEY WA 6009
AUSTRALIA
Phone: +61 8 9380 3919
Fax: +61 8 9380 1039
Email: dlloyd@cyllene.uwa.edu.au
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