esbo Posted March 12, 2012 Author Posted March 12, 2012 You're starting to sound very much like a troll. The question you asked was 'why are plants green?' followed by, 'surely black would be better?'. The answer is, because they evolved that way. Because most plants live in habitats that have variable light conditions and as such they need to have a pigment that optimises energy harvesting when there is not much light, but protects the plant when there is too much. Under the highly variable light conditions I mentioned before, green-reflecting pigments are well suited to both of these functions, where as a pigment that absorbs the full visible spectrum would result in a dead plant. You are misrepresenting what I said entirely. My quote was this: Not sure how you evolved to think I am a troll, possibly something in the water. You have not supplied an answer to the question why are they green mere to why are they not black. Can you troll an answer to that? -2
hypervalent_iodine Posted March 12, 2012 Posted March 12, 2012 I don't know that there is an exact answer to that. What we do know is that they evolved that way and they seem to work just fine. You could possibly view it as analogous to localised energy minima. In protein folding, as well folding of small molecular compounds and probably a lot of other things, a protein chain doesn't necessarily adopt the structural confirmation that is the most stable. If we consider the following image: Image from here. The bottom of this plot represents the lowest energy state - i.e. the state in which a protein is the most stable. Starting from the highest energy state - the unfolded protein - getting to that end point through protein folding means that the protein will often fall into energy traps (the dips in the plot). These traps aren't the lowest energy conformation, but often the energy barrier to move out of the trap is so high that it simply stays where it is. You end up with a structure that might not be the most stable, but one that is stable enough. You could extrapolate this model to the evolution of plant pigments. Let's say that the highest level of fitness of a plant is represented by the tip of the above plot and further assume that the ultimate fitness of a plant is one that is black and is able to dispose of excess heat easily. Higher plants inherited chlorophyll from aquatic ancestors. Moving from that to a black pigment would necessitate the evolution of not only a new pigment, but an efficient mechanism to get rid of all the excess heat. Looking at the explanation I gave regarding protein folding, we could say that, yes, perhaps a plant that absorbs red and blue light is not the most ideal, but perhaps it is simply good enough. I think it's also worth going back to the fact that chlorophyll didn't originate on land and that light penetration of water provides conditions different to those out of the water - i.e. selection pressures would have been different. 2
DrRocket Posted March 12, 2012 Posted March 12, 2012 I don't know that there is an exact answer to that. What we do know is that they evolved that way and they seem to work just fine. Yep. Now, if the process were that of an "intelligent designer" rather than that messy evolutioin thing, then perhaps the color would be different. Or maybe it is just a matter of being green with envy. 1
Arete Posted March 12, 2012 Posted March 12, 2012 You could extrapolate this model to the evolution of plant pigments. We use likelihood surfaces a fair bit in evolutionary biology. Imagine the likelihood surface hypervalent posted as a fitness surface, with the hypothetical optimal phenotype as the highest peak. Imagine a population has ascended the phenotypic cline into one of the suboptimal peaks on the fitness surface. Because it is a local fitness peak, stabilizing selection begins to reduce stochastic variation within the population and reduce the likelihood of the persistence of reduced fitness phenotypes in the saddle between the suboptimal peak and the optimal peak. As such, it's highly plausible and in some cases highly likely that a lot of organisms have evolved a specific, suboptimal phenotype on a given surface. Add into the concept of fitness surfaces the fact that you have multiple optimal phenotypes for different selection pressures and the landscape becomes quite complicated. So, even without the paper that hypervalent iodine posted suggesting that green is the optimal phenotype, the suggestion becomes an non issue for current evolutionary theory - in fact it took me a while to even realize why you presented it as a flaw. 1
esbo Posted March 12, 2012 Author Posted March 12, 2012 I think it is wrong to think that evolution is not intelligent, evolution is an intelligent design process.
StringJunky Posted March 13, 2012 Posted March 13, 2012 (edited) I think it is wrong to think that evolution is not intelligent, evolution is an intelligent design process. Evolution is not anthropomorphic in any way; everything it does to advance a species, it does by random mutation and serendipity which, in reality, means exponentially more failures than successes. It's taken an awful lot of throws of the dice and time for Life to get where it is today. Edited March 13, 2012 by StringJunky
esbo Posted March 13, 2012 Author Posted March 13, 2012 Evolution is not anthropomorphic in any way; everything it does to advance a species, it does by random mutation and serendipity which, in reality, means exponentially more failures than successes. It's taken an awful lot of throws of the dice and time for Life to get where it is today. Evolution is a theory, not a fact!! -1
zapatos Posted March 13, 2012 Posted March 13, 2012 (edited) Evolution is a theory, not a fact!! Yes, thanks for pointing out that the theory of evolution is a theory. I would like to also point out that it is about evolution. What is your point? Edited March 13, 2012 by zapatos
Arete Posted March 13, 2012 Posted March 13, 2012 (edited) Evolution is a theory, not a fact!! Held to the same standards as any other directly observed phenomena in a lay sense it's a fact. Any other lay fact held to scientific validation is also a theory.Like gravity, time and the theory that we are using computers to communicate. Edited March 13, 2012 by Arete
hypervalent_iodine Posted March 13, 2012 Posted March 13, 2012 Well it took you 6 pages, but we got to the motivation behind your thread eventually. esbo, this is a mainstream science forum. If you have issues with the arguments presented to you pertaining to the topic of the thread, you argue them with science, not baseless speculation. If you have a problem with evolution, you start a new topic in the Speculations forum.
esbo Posted March 13, 2012 Author Posted March 13, 2012 Well it took you 6 pages, but we got to the motivation behind your thread eventually. esbo, this is a mainstream science forum. If you have issues with the arguments presented to you pertaining to the topic of the thread, you argue them with science, not baseless speculation. If you have a problem with evolution, you start a new topic in the Speculations forum. Actually you didn't, someone started making out I was an advocate of intelligent design or something like that so I just 'played along with it' for a while because it seems that is what they want, or rather they wanted some sort of excuse to avoid answering the question. Actually I am not too sure what "Dr Rocket" was on about, I am struggling with his 'green with envy bit'. However intelligent design is as good as any answer offered so far so a bit premature to rule it out. No the only motivation was way nobody else seems to know, that's all. Held to the same standards as any other directly observed phenomena in a lay sense it's a fact. Any other lay fact held to scientific validation is also a theory.Like gravity, time and the theory that we are using computers to communicate. Last time I look it up gravity was a law, if it has been down graded to a theory then nobody has told me!! Gravity has been proven evolution has not. Evolution is not anthropomorphic in any way; everything it does to advance a species, it does by random mutation and serendipity which, in reality, means exponentially more failures than successes. It's taken an awful lot of throws of the dice and time for Life to get where it is today. We do not see many of these random mutations do we? We do not see many mutant humans, or at least not 'better humans' from mutations. That's one of the problems with evolution theory. All we witness is extinction, which is quite different from evolution.
hypervalent_iodine Posted March 13, 2012 Posted March 13, 2012 Actually you didn't, someone started making out I was an advocate of intelligent design or something like that so I just 'played along with it' for a while because it seems that is what they want, or rather they wanted some sort of excuse to avoid answering the question. Actually I am not too sure what "Dr Rocket" was on about, I am struggling with his 'green with envy bit'. However intelligent design is as good as any answer offered so far so a bit premature to rule it out. No the only motivation was way nobody else seems to know, that's all. Except that it's not. ID is not science. It never has been and it never will be. We have already given you plenty of answers to your questions. The only person who really seems to have a problem with them is you, and yet you can give no valid, scientific reason for why our answers are unacceptable. You need to start by refuting our answers with science (and I remind you again that ID is not science); tell us why you think we are wrong in what we are saying and provide some evidence to counter our assertions. The 'green with envy' bit is quite obviously a joke. Last time I look it up gravity was a law, if it has been down graded to a theory then nobody has told me!! Gravity has been proven evolution has not. Science cares not for what you have or have not been told. We do not see many of these random mutations do we? We do not see many mutant humans, or at least not 'better humans' from mutations. That's one of the problems with evolution theory. All we witness is extinction, which is quite different from evolution. I'm going to preface this next bit by saying that normally I don't advocate the abrupt, 'go read a damned book' responses unless they are absolutely needed. Your arguments are based entirely on misconceptions about a very widely accepted facet of science and a refusal to actually look at the evidence. Pro-tip: before you say you don't believe something or you think a scientific theory is absolute rubbish, you need to have a firm understanding of the theory itself and why it is accepted within the scientific community as being the best and most correct model for what we observe in nature. In other words, go read a damned book.
StringJunky Posted March 13, 2012 Posted March 13, 2012 Actually you didn't, someone started making out I was an advocate of intelligent design or something like that so I just 'played along with it' for a while because it seems that is what they want, or rather they wanted some sort of excuse to avoid answering the question. Actually I am not too sure what "Dr Rocket" was on about, I am struggling with his 'green with envy bit'. However intelligent design is as good as any answer offered so far so a bit premature to rule it out. No the only motivation was way nobody else seems to know, that's all. Last time I look it up gravity was a law, if it has been down graded to a theory then nobody has told me!! Gravity has been proven evolution has not. We do not see many of these random mutations do we? We do not see many mutant humans, or at least not 'better humans' from mutations. That's one of the problems with evolution theory. All we witness is extinction, which is quite different from evolution. The fact we have to produce a new vaccine for the latest flu virus is due to and evidence of evolution. Evolution happens much quicker on the scale and numbers of micro-organisms.
Moontanman Posted March 13, 2012 Posted March 13, 2012 (edited) Why are plants green? All plants are not green. You have photosynthetic organisms that are Purple Blue green Golden brown Brown Red and Green Oh! So you mean complex organisms... Well then you have Brown Red and Green Please specify what color organism you are talking about Ok, I'll get down to brass tacks, for the most part as hypervalent_iodine has said it has to do with the chlorophyll and energy levels of photons, photon saturation levels, yada yada yada, you guys should really listen to him, he knows what he is talking about. The plants, complex plants at least, that are not Green still use chlorophyll as their primary way of making sugars but they also use other pigments to harvest the photons/energy and then transfer it to the chlorophyll to make sugars. the reason for the various pigments colors is the primary colors of the light available. Red algae harvest, green and blue light. Brown algae harvest pretty much all colors of light but most intensely blue and violet. If you are going to grow brown algae you need blue and violet light. If you really need the info i can look up the exact light absorption curves but I see no reason to do that in this conversation. Before you say "yes well, they are algae and not complex plants" you should spend some time scuba diving. Brown algae form immense forests, sometimes more than 100 feet tall in water that is less than clear and the algae must harvest every possible photon to exist. Red algae form huge mats over rocks in water that is deep enough at least part of the day to filter out most of the red light. Under water red algae appear black, if you have ever cut your self under water deeper than 30 feet or so you might have noticed the blood appears to be florescent green not red because there is no red light to reflect off the blood to your eyes, with out red light the other pigments in blood reflect the light our eyes see. If you want to use evolution to support or show some lack of support for the reasons vascular land plants are green you should as it was suggested read a few science books. maybe develop some expertise at a hobby that requires the reasons why plants use the colors of the spectrum they do to be successful. I can also add that some animals use pigments that harvest UV light to transfer energy to plants that use chlorophyll to grow and feed the animals... any one want to guess what animals they are? So... evolution has indeed produced other pigments to harvest light from the sun, it could be as simple as chlorophyll was the first (I'm not sure about the purple sulfur bacteria) and the other pigments were easier to evolve as supplements to chlorophyll than evolving new chemical pathways from scratch. I'm not as much of a chemist to tell you how this is done but hypervalent_iodine has the knowledge to tell you this, listen to him. Another thing to remember is that the human eye is a very inefficient way to judge light color and intensity, all is not as it seems to the human eye... Light and color are unusual things, hard to really pin down, in air under sunlight there is no need to use other pigments to supplement chlorophyll it is also true that vascular plants have not been evolving as long as the red and purple and brown plants have. It is also true that vascular plants use other pigments as well, its the reason the fall tree leaf colors are so vivid and striking, I'm not sure how much these pigments have to do with harvesting photons but I'd be surprised if they had nothing at all to do with it. Edited March 13, 2012 by Moontanman 2
hypervalent_iodine Posted March 13, 2012 Posted March 13, 2012 Moontanman, a great post but I do have to add some minor corrections: *her *she
swansont Posted March 13, 2012 Posted March 13, 2012 Evolution is a theory, not a fact!! ! Moderator Note This is not the appropriate place for a discussion of the validity of evolution; questions posted in science sections are to be answered in the context of accepted science. Evolution is accepted biology. Further, esbo, you need to educate yourself on the scientific definitions of theory and law, at the very least. Do not continue the discussion along these lines, and do not respond to this modnote.
Arete Posted March 13, 2012 Posted March 13, 2012 I know it's in violation of the modnote (sorry) but I thought it may be useful for posterity to have a decent explanation of how scientific laws and theories differ: http://science.kenne...3380theory.html " Some scientists will tell you that the difference between them is that a law describes what nature does under certain conditions, and will predict what will happen as long as those conditions are met. A theory explains how nature works. Others delineate law and theory based on mathematics -- Laws are often times mathematically defined (once again, a description of how nature behaves) whereas theories are often non-mathematical. Looking at things this was helps to explain, in part, why physics and chemistry have lots of "laws" whereas biology has few laws (and more theories). In biology, it is very difficult to describe all the complexities of life with "simple" (relatively speaking!) mathematical terms. Regardless of which definitions one uses to distinguish between a law and a theory, scientists would agree that a theory is NOT a "transitory law, a law in waiting". There is NO hierarchy being implied by scientists who use these words. That is, a law is neither "better than" nor "above" a theory. From this view, laws and theories "do" different things and have different roles to play in science. Furthermore, notice that with any of the above definitions of law, neither scientists nor nature "conform" to the law. In science, a law is not something that is dictated to scientists or nature; it is not something that a scientist or nature has to do under threat of some penalty if they don't conform." We do not see many of these random mutations do we? Phenotypic variation (i.e. - "random mutations") is observed in virtually every population and species http://www.sciencema.../6002/372.short http://onlinelibrary...10.00858.x/full http://onlinelibrary...09.04229.x/full We do not see many mutant humans, or at least not 'better humans' from mutations. Some human phenotypes are better at say - resisting disease than others. http://www.nature.co...ature07175.html http://hmg.oxfordjou...8/R2/R202.short That's one of the problems with evolution theory. Given they're not actually true, they aren't problems. All we witness is extinction, which is quite different from evolution. Speciation has been observed, many times. http://rstb.royalsoc.../1587/354.short http://www.sciencema.../5915/737.short http://dspace.mit.ed...le/1721.1/61788 1
Moontanman Posted March 13, 2012 Posted March 13, 2012 Moontanman, a great post but I do have to add some minor corrections: *her *she
esbo Posted March 14, 2012 Author Posted March 14, 2012 (edited) Why are plants green? All plants are not green. You have photosynthetic organisms that are Purplelue greenGolden brownBrownRedandGreenOh! So you mean complex organisms...Well then you haveBrownRedand Green Please specify what color organism you are talking about Ok, I'll get down to brass tacks, for the most part as hypervalent_iodine has said it has to do with the chlorophyll and energy levels of photons, photon saturation levels, yada yada yada, you guys should really listen to him, he knows what he is talking about. The plants, complex plants at least, that are not Green still use chlorophyll as their primary way of making sugars but they also use other pigments to harvest the photons/energy and then transfer it to the chlorophyll to make sugars. the reason for the various pigments colors is the primary colors of the light available. Red algae harvest, green and blue light. Brown algae harvest pretty much all colors of light but most intensely blue and violet. If you are going to grow brown algae you need blue and violet light. If you really need the info i can look up the exact light absorption curves but I see no reason to do that in this conversation. Before you say "yes well, they are algae and not complex plants" you should spend some time scuba diving. Brown algae form immense forests, sometimes more than 100 feet tall in water that is less than clear and the algae must harvest every possible photon to exist. Red algae form huge mats over rocks in water that is deep enough at least part of the day to filter out most of the red light. Under water red algae appear black, if you have ever cut your self under water deeper than 30 feet or so you might have noticed the blood appears to be florescent green not red because there is no red light to reflect off the blood to your eyes, with out red light the other pigments in blood reflect the light our eyes see. If you want to use evolution to support or show some lack of support for the reasons vascular land plants are green you should as it was suggested read a few science books. maybe develop some expertise at a hobby that requires the reasons why plants use the colors of the spectrum they do to be successful. I can also add that some animals use pigments that harvest UV light to transfer energy to plants that use chlorophyll to grow and feed the animals... any one want to guess what animals they are? So... evolution has indeed produced other pigments to harvest light from the sun, it could be as simple as chlorophyll was the first (I'm not sure about the purple sulfur bacteria) and the other pigments were easier to evolve as supplements to chlorophyll than evolving new chemical pathways from scratch. I'm not as much of a chemist to tell you how this is done but hypervalent_iodine has the knowledge to tell you this, listen to him. Another thing to remember is that the human eye is a very inefficient way to judge light color and intensity, all is not as it seems to the human eye... Light and color are unusual things, hard to really pin down, in air under sunlight there is no need to use other pigments to supplement chlorophyll it is also true that vascular plants have not been evolving as long as the red and purple and brown plants have. It is also true that vascular plants use other pigments as well, its the reason the fall tree leaf colors are so vivid and striking, I'm not sure how much these pigments have to do with harvesting photons but I'd be surprised if they had nothing at all to do with it. I think we can all agree that most plants are green that is pretty much self evident. I don't think there is much mileage in an answer about the energy levels of chlorophyll, all that is doing is explaining the mechanics of the energy levels of chlorophyll, that is really not an answer, you have to explain why chlorophyll is used in the first place, otherwise the answer is null and void. As for algae, well they are not really plants, or at least not the plants I had in mind in my question, fair enough I did not specifically specify I was talking about land plants but for most people a plant is something which grows on land, unless you specifically specify sea plants (I didn't), Fortunately I have never cut myself under water but I will take your word for it. Books will not tell me why plants are green so I don't know what I will gain from reading them. I think the plants have vivid colours in fall is because the chlorophyll is breaking down, but that in itself does not explain why they are green. Bit of a coincidence in that I am growing tobacco and one of the problems is getting the leaves to turn from green to brown!!! Science cares not for what you have or have not been told. Nobody can tell me anything Anyway science is not actually a person it's just a broad word to cover the things people think they know. Anyway the fact is the Darwin's musings are always refereed to as his theory of evolution, I don't think any respected scientist would use the phrases Darwin's Law of evolution. Worth adding here that neither Charles Darwin nor Richard Dawkins (despite their reputations) knows why plants are green but I do. So who is the better scientist? Edited March 14, 2012 by esbo
questionposter Posted March 14, 2012 Posted March 14, 2012 (edited) No reptiles can have heat vision because their own bodies are cooler than their surroundings and that allows them to use heat as vision better. Their own body heat doesn't interfere with their heat vision. A mammal with heat vision would get lots of interference from their own body heat, it's why really sensitive infrared telescopes use liquid helium to cool their detectors. Well, that does make sense too, but then why don't most reptile species have infra-red vision if it's that simple? How can you sweepingly say it " they absorb those colors is because those colors are most efficient to absorb for most plants" clearly that is a very weak and flawed statement, it would be most efficient to absorb the whole of the spectrum. infact your statement is full of such vague and wooley statements. ie "probably because of random genetic mutations that have survived.". That is really not a good enough answer becasue you fail to explain why they survived, ie you omit to answer the question at all. You might as well say 'because that how it is". It's not really flawed it's just that you can't do two opposite actions at once, otherwise you get 0, which obviously isn't how plants get energy. Plants "could" reflect other light and probably do, but we can't see the red past infra-red or the violet in the ultra-violet spectrum The plants on Earth happen to reflect green and usually that's the most efficient. They can absorb green, but if they absorb green they can't reflect it, and in some situations that's not efficient trait, so the trait of absorbing green doesn't survive as much. If plants were black then they would absorb too much energy, dehydrate and die, so the trait of absorbing all colors does not survive long enough for a plant with that trait to reproduce and thus modern plants are not green. Every once in a while there can be a mutation to make a black plant, but it won't survive long enough to pass that trait down and make other plants black unless its in a very unique environment. So the answer is because no previous plant that can absorb all colors has survive and passed that trait down. Edited March 14, 2012 by questionposter
esbo Posted March 14, 2012 Author Posted March 14, 2012 Well, that does make sense too, but then why don't most reptile species have infra-red vision if it's that simple? It's not really flawed it's just that you can't do two opposite actions at once, otherwise you get 0, which obviously isn't how plants get energy. Plants "could" reflect other light and probably do, but we can't see the red past infra-red or the violet in the ultra-violet spectrum The plants on Earth happen to reflect green and usually that's the most efficient. They can absorb green, but if they absorb green they can't reflect it, and in some situations that's not efficient trait, so the trait of absorbing green doesn't survive as much. If plants were black then they would absorb too much energy, dehydrate and die, so the trait of absorbing all colors does not survive long enough for a plant with that trait to reproduce and thus modern plants are not green. Every once in a while there can be a mutation to make a black plant, but it won't survive long enough to pass that trait down and make other plants black unless its in a very unique environment. So the answer is because no previous plant that can absorb all colors has survive and passed that trait down. I never asked why plants do not absorb all colours, I asked why they are green and that is question you need to answer.
StringJunky Posted March 15, 2012 Posted March 15, 2012 I think it is wrong to think that evolution is not intelligent, evolution is an intelligent design process. Can you elaborate on this?
esbo Posted March 15, 2012 Author Posted March 15, 2012 Can you elaborate on this? I am not sure the forum rules allow me to. However as we are intelligent and we are believed to have evolved then that intelligence must have been built into the process of evolution? Or are we to believe that that intelligence magiced out of nowhere? Similar to energy or mass for example, those thinks do no magic out of nowhere generally at least not in our experience. Although one may change into another it seems to be a zero sum game, ie we can't create any more than was initially present? If you see what I mean?
Moontanman Posted March 15, 2012 Posted March 15, 2012 (edited) I am not sure the forum rules allow me to. However as we are intelligent and we are believed to have evolved then that intelligence must have been built into the process of evolution? Or are we to believe that that intelligence magiced out of nowhere? Well if not evolution then where did intelligence come from? magiced out of a imaginary sky daddy? Similar to energy or mass for example, those thinks do no magic out of nowhere generally at least not in our experience. Although one may change into another it seems to be a zero sum game, ie we can't create any more than was initially present? If you see what I mean? Are you suggesting that no new information can not come from natural selection? It's also true that "evolutionary progress" often occurs by small steps building on things that are already present. It should be noted that the chemical reactions of photosynthesis are similar to the chemical reaction of Chemo-synthesis that is used by the various Bacteria and Archaea and almost certainly evolved from it, in fact Hemoglobin is similar to Chlorophyll but where Chlorophyll has a magnesium atom Hemoglobin has an iron atom. http://en.wikipedia.org/wiki/Metalloprotein http://alliedhealthblog.com/2010/11/the-similarities-between-chlorophyll-and-hemoglobin/ Edited March 15, 2012 by Moontanman
questionposter Posted March 15, 2012 Posted March 15, 2012 I never asked why plants do not absorb all colours, I asked why they are green and that is question you need to answer. They're green because the trait of being green has survived, and other traits like black or red or blue haven't so much.
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