Severian Posted August 22, 2005 Share Posted August 22, 2005 How did the Venus Fly Trap evolve? There seem to me to be some organisms which have features that are difficult to come by through evolution, and the Venus Fly Trap seems particularly difficult to explain. To catch a fly, it needs to have 3 properties: 1. Attract the fly. This is presumably quite easy. All it needs to do is be a rotten flesh colour (and perhaps smell - do VFT's smell?) and flys will come. However this property has to be developed in conjunction with the other properties, otherwise there is no advantage to the plant in attracting flies. This is the same problem that flowers face in attracting bees (ie there has to be something for the bees to do). In that case, the pollen was possibly just being blown in the wind without the bees, and so the precence of bees helped carry it further. This can't work for the VFT since there seems to be no gain to the VFT unless it can digest the fly, so we need some other mechanism. 2. Trap the fly. To me this seems the hardest to evolve. The VFT has to sense the presence of the fly and close very quickly to trap it. The problem here is that it is all or nothing. If the fly escapes, nothing is gained. So we can't evolve a 'half-way-house' mechanism where the trap shuts more slowly. On the other hand it seems too big an evolutionary jump to move to a fast closing mechanism in one step! 3. Digest the fly. There is no point in trapping the fly if the VFT doesn't digest it. However, there is no point in trapping it if it isn't going to digest it. So it seems as if this would have to evolve simultaneously with property 2. The main problem here seems to be that it seems unlikely to evolve all of these properties at once, but all three are needed for an evolutionary advantage. So I suspect that they didn not all evolve at once, and there was some other advantage to be had for each one, perhaps by having some other complimentary mechanism already in place which was later lost. For example, there are other types of plant that eat flys, which catch the fly in some sort of liquid or sticky glue. There is a goblet like flower with sticky liquid in it, and why a fly comes to investigate, it gets stuck and is digested. There is no problem with this evolving because the plant could still photosynthesis normally, not using the dead flys it traps, until one day it's offspring mutates into something which absorbes the nutrients from the liquid. (It is not clear to me how the glue evolves, but presumably it had some other evolutionary use.) Could a similar mechanism have evolved the venus fly trap? For example, a fly might be able to crawl out of the liquid given enough time, so a flower which closes (a chance mutation) could be more efficient. Then closing faster and faster would help the plant, eventually evolving into a VFT. Does anyone know the 'official' explanation of how the VFT evolved? The few links I could dig up, aren't very helpful: http://www.strato.net/~crvny/sa03005.html http://www.talkdesign.org/faqs/icdmyst/ICDmyst.html The last one seems to support the proposal that there was a sticky substance which was lost. But why would a VFT without the sticky 'glue' be more efficient than the one with the glue? (Disclaimer: this post is not intended to disprove evolution or in any way imply that evolution is not the correct theory for the origin of species. It is simply a non-expert asking a (presumably dumb) question about something he would like to know more about. (So that I have a good answer when arguing with creationists!)) Link to comment Share on other sites More sharing options...
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