On Fri, 09 Aug 2013 09:29:41 +0100, Jeff Layman
wrote:

It's interesting that nature didn't come up with the wheel, one of the
most energy-efficient ways of moving around (or did I read a few years
ago that there was some strange organism which could move like a wheel?

That's a question which comes up frequently.

There's an interesting paper on it at:
http://www.jstor.org/discover/10.230... 102539587717

The current consensus is that the main problem with biological wheels
is blood flow, but this author addresses a different argument.