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Author Topic:   Evolution......?
singularity
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Message 51 of 60 (14375)
07-29-2002 6:24 AM
Reply to: Message 1 by quicksink
04-07-2002 8:26 AM


To address a single point:
I think it might be useful to point out that Sundews and Venus fly traps are very closely related, sharing flower and seed structure, and I would imagine their homology has been also shown by genetic methods by now.
Sundews rely mainly on their sticky tentacles to trap insects but also engage in leaf folding to enhance digestion of their prey (Drosera burmanii is one of the faster ones- folds its leaf within one minute on a warm day). It doesn't seem inconceivable that a simpler ancestor diverged into the more refined modern forms which rely on different means to trap prey. The process is as conceptually simple as a sundew ancestor loosing its tentacles except at the leaf margin (to become teeth) and centre (to become trigger hairs). The extent of genetic change necessary for this will not be known until both genomes are sequences and a better understanding of genetic control of plant development is formulated. Current work on Arabidopsis indicate that small genetic changes can produce large and functional changes in plant anatomy.
As for starting the process of carnivory there are other examples of primitive carnivorous plants (eg Ibicella from the Martyniaceae, Bybils in the Byblidaceae, Triphyophyllum from the Dioncophyllaceae and Drosophyllum in the Droseraceae) which use simple immobile sticky exudates to trap and digest insects. Beyond this many plants use sticky exudates as a form of defence against predators with no obvious carnivory.
Distantly related groups like the Lentibulariaceae have simple fly paper traps in the butterworts (Pinguicula) which engage in slow leaf rolling. Interestingly this group also has the bladderworts which use an even more complex trap than venus fly traps.
In general plants have been shown to respond to touch (sometimes fast enough to be readily observed as in Mimosa pudica) so the origin of motion in plants is not restricted to Venus fly traps, and the biochemical mechanisms seems to be common. And proteolytic enzymes aren't unique to carnovorous plants either- all plants use them to recycle their own endogenous proteins.
If the venus fly trap existed and there were no familial relatives which displayed carnivory, no variation in the complexity of its ancestors carnivory and the fly trap used radically different biochemistry to other plants then we would have a foundation to question its origins from other plants. But the way the family trees neatly fan out and functionally similar (but distict) adaptations appear in other plant families suggests that the venus flytrap isnt a miracle, its just one of the more highly specialised members of a whole series of amazing plants.
These patterns alone aren't direct mechanistic evidence of the process of evolution, but they are self consistent examples of its results. It is the lack of any fundamental and inexplicable differences between extant organisms (especially on a biochemical level) that makes evolution a good theory based on current observations.
Given that the genetic revolution has only been taking place for the last few decades I think it is unreasonable to expect the precise mechanisms of major genetic change to be known. We are still having great difficulty coming to grips with the amount of information in a single eukaryotic genome and its functional implications. At this stage I think we can only judge trends, and the evidence keeps pointing to evolution in some form. I don't think anyone can point to any concrete evidence which has strengthened creationism in the minds of the majority in the recent past (though many have modified ToC). We have a long way to go before we know the whole story, but I for one hope that there are a few surprises yet left in store.
Shane

This message is a reply to:
 Message 1 by quicksink, posted 04-07-2002 8:26 AM quicksink has not replied

Replies to this message:
 Message 53 by Quetzal, posted 08-01-2002 10:38 AM singularity has not replied

  
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