Posted by
Russell Standish on
URL: http://friam.383.s1.nabble.com/Cambrian-Explosion-tp521557p521565.html
As I understand it, repetition of units is controlled by the homeobox
gene, one of the earliest "meta" gene. The mechanism is essentially
unchanged between fruit flys and humans.
The appearance for the first time of a gene that controlled genetic
expression just prior to the Cambrian is about as good an explanation
of the Cambrian explosion as any I've heard. Basically, the event is
still a mystery.
Cheers
On Mon, Mar 13, 2006 at 08:13:11PM +0100, Jochen Fromm wrote:
>
> There is no doubt that environmental changes and
> chemical/physical stress are among the causes for the
> Cambrian explosion (Snowball Earth, glaciation, etc.).
> Certainly there is a connection between "emergence"
> and "extinction", between complexity and catastrophes.
> My question was more about the "how" (how does the
> underlying code define the development of individuals?
> is there such a code for the body plan?) and
> less about the "why".
>
> The form or "architecture" of plants for example can
> be described well by fractals, IFS and L-Systems. Skeletons
> and animal bodies have a certain amount of self-similarity,
> too: a typical modern animal body has a certain amount of limbs
> (2-6 legs or arms), and each limb has further sub-limbs
> (2-6 toes or fingers). Therefore it must be possible to
> describe bodies and their development with simple iterative
> rules. I wonder what kind of rule set or code is really used?
>
> The "three-lobed" trilobite for example, one of the first
> animals that appeared in the Cambrian period has a very
> simple repetitive head-body/thorax-tail structure, where the
> body is composed of many similar repetitive segments.
>
http://en.wikipedia.org/wiki/Trilobite>
> -J.
>
>
> ============================================================
> FRIAM Applied Complexity Group listserv
> Meets Fridays 9a-11:30 at cafe at St. John's College
> lectures, archives, unsubscribe, maps at
http://www.friam.org--
*PS: A number of people ask me about the attachment to my email, which
is of type "application/pgp-signature". Don't worry, it is not a
virus. It is an electronic signature, that may be used to verify this
email came from me if you have PGP or GPG installed. Otherwise, you
may safely ignore this attachment.
----------------------------------------------------------------------------
A/Prof Russell Standish Phone 8308 3119 (mobile)
Mathematics 0425 253119 (")
UNSW SYDNEY 2052 R.Standish at unsw.edu.au
Australia
http://parallel.hpc.unsw.edu.au/rks International prefix +612, Interstate prefix 02
----------------------------------------------------------------------------