Teori Darwin telah dibuktikan benar.

Mutasi telah dibuktikan memang terjadi.

Evolusi telah dibuktikan memang terjadi.

Dan boleh dibilang tiap hari para ahli diberbagai bidang menyempurnakan dan
melengkapi teori Darwin itu...

Nggak heran bahwa aklhirnya gereja katolik Roma juga mengakui kebenaran teori

    Web address:

Evolution Of Fins And Limbs Linked With That Of Gills

Gill skeletons. The shark arch gill skeleton (left) shows primitive gill rays 
that are found only in sharks and other cartilaginous fishes. The gills of 
other fishes (right) are also arched but lack gill rays. This primitive feature 
of sharks allowed the researchers to link the developmental genetic program for 
fins and limbs to the more primitive one for gill rays. (Credit: Image by J. 
Andrew Gillis, University of Chicago)

ScienceDaily (Mar. 25, 2009) — The genetic toolkit that animals use to build 
fins and limbs is the same genetic toolkit that controls the development of 
part of the gill skeleton in sharks, according to a new study.

The research is published in Proceedings of the National Academy of Sciences on 
March 23, 2009, by Andrew Gillis and Neil Shubin of the University of Chicago, 
and Randall Dahn of Mount Desert Island Biological Laboratory.

"In fact, the skeleton of any appendage off the body of an animal is probably 
patterned by the developmental genetic program that we have traced back to 
formation of gills in sharks," said Andrew Gillis, lead author of the paper and 
a graduate student in the Department of Organismal Biology and Anatomy at the 
University of Chicago. "We have pushed back the evolutionary origin of the 
developmental genetic program that patterns fins and limbs."

This new finding is consistent with an old theory, often discounted in science 
textbooks, that fins and (later) limbs evolved from the gills of an extinct 
vertebrate, Gillis added. "A dearth of fossils prevents us from definitely 
concluding that fins evolved from gills. Nevertheless, this research shows that 
the genetic architecture of gills, fins and limbs is the same."

The research builds on the breakthrough discovery of the fossil Tiktaalik, a 
"fish with legs," by Neil Shubin and his colleagues in 2006. "This is another 
example of how evolution uses common developmental programs to pattern 
different anatomical structures," said Shubin, who is the senior author on the 
PNAS paper and Professor and Associate Dean of Organismal and Evolutionary 
Biology at the University of Chicago. "In this case, shared developmental 
mechanisms pattern the skeletons of vertebrate gill arches and paired fins."

The research also showed for the first time that the gill arch skeleton of 
embryonic skates (a living relative of sharks that has gill rays) responds to 
treatment with the vitamin A derivative retinoic acid in the same way a limb or 
fin skeleton does: by making a mirror image duplicate of the structure as the 
embryo develops. According to the researchers, the genetic circuitry that 
patterns paired appendages (arms, legs and fins) has a deep evolutionary origin 
that actually predates the origin of paired appendages themselves.

"These findings suggest that when paired appendages appeared, the mechanism 
used to pattern the skeleton was co-opted from the gills," Gillis said. 
"Perhaps we should think of shark gills as another type of vertebrate 
appendage—one that's patterned in essentially the same way as fins and limbs."

The deep structural, functional, and regulatory similarities between paired 
appendages and developing gill rays, as well as the antiquity of gills relative 
to paired appendages, suggest that the signaling network that is induced by 
retinoic acid had a patterning function in gills before the origin of 
vertebrate appendages, the research concludes. And this function has been 
retained in the gill rays of living cartilaginous fishes.

Journal reference:

   1. J. Andrew Gillis, Randall D. Dahna, and Neil H. Shubin. Shared 
developmental mechanisms pattern the vertebrate gill arch and paired fin 
skeletons. Proceedings of the National Academy of Sciences, 2009; DOI: 

Adapted from materials provided by University of Chicago Medical Center, via 
EurekAlert!, a service of AAAS.
Email or share this story:  
Need to cite this story in your essay, paper, or report? Use one of the 
following formats:

University of Chicago Medical Center (2009, March 25). Evolution Of Fins And 
Limbs Linked With That Of Gills. ScienceDaily. Retrieved April 17, 2009, from 
http://www.sciencedaily.com­ /releases/2009/03/090323212021.htm

Jusfiq Hadjar gelar Sutan Maradjo Lelo

Allah yang disembah orang Islam tipikal dan yang digambarkan oleh al-Mushaf itu 
dungu, buas, kejam, keji, ganas, zalim lagi biadab hanyalah Allah fiktif.


Kirim email ke