'Armored' fish study helps strengthen Darwin's natural selection theory
August 28, 2008Shedding some genetically induced excess baggage may have helped a tiny fish thrive in freshwater and outsize its marine ancestors, according to a UBC study published today in Science Express.
Measuring three to 10 centimetres long, stickleback fish originated in the ocean but began populating freshwater lakes and streams following the last ice age. Over the past 20,000 years - a relatively short time span in evolutionary terms - freshwater sticklebacks have lost their bony lateral plates, or "armour," in these new environments.
"Scientists have identified a mutant form of a gene, or allele, that prohibits the growth of armour," says UBC Zoology PhD candidate Rowan Barrett. Found in fewer than one per cent of marine sticklebacks, this allele is very common in freshwater populations.
Barrett and co-authors UBC post-doctoral fellow Sean Rogers and Prof. Dolph Schluter set out to investigate whether the armour gene may have helped sticklebacks "invade" freshwater environments. They relocated 200 marine sticklebacks with the rare armour reduction allele to freshwater experimental ponds.
"By documenting the physical traits and genetic makeup of the offspring produced by these marine sticklebacks in freshwater, we were able to track how natural selection operates on this gene," says Rogers.
"We found a significant increase in the frequency of this allele in their offspring, evidence that natural selection favours reduced armour in freshwater," says Barrett.
Barrett and Rogers also found that offspring carrying the allele are significantly larger in size. "It leads us to believe that the genetic expression is also tied to increased growth rate," says Barrett.
"If the fish aren't expending resources growing bones - which may be significantly more difficult in freshwater due to its lack of ions - they can devote more energy to increasing biomass," says Barrett. "This in turn allows them to breed earlier and improves over-winter survival rate."
Celebrating its 150th anniversary this week, Darwin's first publication of his natural selection theory proposed that challenging environments would lead
to a struggle for existence, or "survival of the fittest." Since then, scientists have advanced the theory by contributing an understanding of how genes affect evolution.
"This study provides further evidence for Darwin's theory of natural selection by showing that environmental conditions can directly impact genes controlling physical traits that affect the survival of species," says Barrett.
Source: University of British Columbia
Aug 05, 2009 |
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However, I believe a lot of mistakes were made in this study - which makes it pretty useless as an endorsement.
HOWEVER, natural selection cannot by definition "directly impact genes controlling physical traits". it can only impact the behaviors of individual species thereby impact individuals ability to mate, thereby affecting the gene pool in proceeding generations, and only bu that method impacting genes (not so direct hu?).
Its a common misconception that Darwin [fill-gap-with-any-theory] changes genes in anything but a disruptive way (mutations). Very VERY rarely do mutations create benefit for organisms. And not one single study, experiment or computer simulation has shown that by strictly Darwinian theory useful, constructive, innovative genes have been produced.
How new genetic information is create? I have no idea. But within the context of an individual organism or species it is proved, in the real world, by study and by experiment, that new genes are ACQUIRED by some form of horizontal gene transfer. Its only once these new genes have been successfully integrated into the new host, that Darwin's Natural Selection can determine how good those genes are for the host and the host species.
Senpu, it really sounds to me like you have a very basic fundamental misunderstanding of the nature of genes. Your posting makes it sound like you think there's a gene for "arm" or "leg" and an organism can't just "develop" this gene.
That isn't how mutations work, that isn't how genetics work. As someone (Gell-Mann?) once said, you're so far off that you're not only not right, you're not even wrong. (I'm sure I've butchered the quote).
Your point about horizontal gene transfer is a good one -- we're discovering more and more how much viruses are involved in genetic changes. But understand this: EVERY SPECIES ON EARTH has the genetic information necessary to make a feather, or an arm, or a tentacle. Just not in the correct order to do so. In the end, it's just GATC.
All are so obviously similar at the core fundamentals that its more logical than not to conclude they all began from a single ancestor.