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Bobandirus

Physist question: How can a single photon physically travel through 2 slits at the same time?

Biologist question: Given that plant genomes are generally so much shorter than animals, why do we see so much less variation in animal colour and design than with plants?

I think I have a good answer to this, I just want to try and get the biologists who stalk this thread to answer and get talking!

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Yes, I do believe I now "get it"...

If anyone would like me to explain what I think the joke (or, more accurately, "spoof") is, I'll try. :)

Please. :)

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A Long Time Ago

Physist question: How can a single photon physically travel through 2 slits at the same time?

First, it turns out that all particles will do that, even electrons, protons, entire atoms, etc.

The reason that they do that is the same. Describing them as purely a particle is inaccurate (it was actually the double slit experiment that tells us this). What we call particles are described by waves. It is their wave nature that allows them to propagate through both slits and diffract and it is their particle nature that allows them to be detected on a photographic plate or other detector. These concepts seem very contradictory but this is what the experiments and observations show.

The resolution is that every particle is described by a wave in a special way. The particle exists as a wave (by adding different waves together, one can make a composite wave that is localized, dispersed, or anywhere in between) that propagates by the laws of quantum mechanics (the Schrodinger Wave Equation describes its propagation which is why it is called a wave equation). At the same time, measurements (certain types of interactions with other particles) cause the wave the suddenly "collapse" to be localized to a very small region. So when a photon or other particle heads for the double slit, if its wave is dispersed enough (not localized) such that its magnitude is significant at both slits, then the wave (particle) will propagate through both slits, diffract and interfere with itself (it is a wave so interference happens). Now if we put a photographic plate, other instrument, or something else to interact with the photon, electron, etc. when the wave gets to the object, it collapsed to being localized to a very small region. Where it collapses to is probabilistic with the probability being proportional to the wave magnitude at that point.

Due to this, it is best to say that matter is composed of particles but that particles move as/are described as waves. I personally like what Eugene Hecht suggested about calling them wavicles instead of particles or waves.

Biologist question: Given that plant genomes are generally so much shorter than animals, why do we see so much less variation in animal colour and design than with plants?

I think I have a good answer to this, I just want to try and get the biologists who stalk this thread to answer and get talking!

Not a biologist but my guess would be that animal coloration patterns have to be narrower for camouflage to protect against predation whereas plants don't do camouflage (herbivores are going to find the plant no matter what color it is) and are thus not restricted by that limitation.

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Bobandirus

[snip]

Although I can't quite get my head around wave/partial idea, thank you very much for that answer!

I think the problem with the wave/particle idea is that I have always been taught that a wave is a pressure differential in several atoms atleast, so how can it work in a single photon?

Biologist question: Given that plant genomes are generally so much shorter than animals, why do we see so much less variation in animal colour and design than with plants?

I think I have a good answer to this, I just want to try and get the biologists who stalk this thread to answer and get talking!

Not a biologist but my guess would be that animal coloration patterns have to be narrower for camouflage to protect against predation whereas plants don't do camouflage (herbivores are going to find the plant no matter what color it is) and are thus not restricted by that limitation.

Thinking about it, that could be a good reason as to why all plants are green. All the other wavelengths of light would be just as good energy wise, yet the colour thats left out in almost all forms of chlorophyll is green. What I'm thinking is that this could be so that the plats are camouflaged into a green sea for the herbivores to try and make the plant less noticeable, and hence less likely to be eaten. So maybe its a type of camouflage, them all being green.

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Biologist question: Given that plant genomes are generally so much shorter than animals, why do we see so much less variation in animal colour and design than with plants?

I haven't heard that plants tend to have shorter genomes than animals. On the contrary, animals turned out to have far fewer genes than were expected.

Early estimates of the number of human genes that used expressed sequence tag data put it at 50 000–100 000.[17] Following the sequencing of the human genome and other genomes, it has been found that rather few genes (~20 000 in human, mouse and fly, ~13 000 in roundworm, >46 000 in rice) encode all the proteins in an organism.[18] These protein-coding sequences make up 1–2% of the human genome.[19] A large part of the genome is transcribed however, to introns, retrotransposons and seemingly a large array of noncoding RNAs.[18][19] Total number of proteins (the Earth's proteome) is estimated to be 5 million sequences.[20]

So you have less than half the genes in a grain of rice. Take pride.

I don't see why anyone would consider the number of genes in an organism especially interesting, or certainly predictive of complexity. The idea that humans should be ashamed of their tiny genomes doesn't make any sense; do we ascribe quality or complexity to a book based entirely upon its length? No.

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Bobandirus

Ill reply better in the morning, but for now Ill say that rice isn't a good example to use, its nearly always highly hibredised, and that means that it will have a very long genome compared to wild rice. As an example, I mean that wild, original grain only had around 4 chromosome pairs, but the stuff you see growing in fields has something like 16 or 32 pairs depending on which variety it it.

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Thinking about it, that could be a good reason as to why all plants are green. All the other wavelengths of light would be just as good energy wise, yet the colour thats left out in almost all forms of chlorophyll is green. What I'm thinking is that this could be so that the plats are camouflaged into a green sea for the herbivores to try and make the plant less noticeable, and hence less likely to be eaten. So maybe its a type of camouflage, them all being green.

Are you suggesting that plants get energy from green light (I can't really tell from the quote)? If this is the case, you have it backwards. The green color means the plant is reflecting green light. In fact, plants get most energy from blue light.

In theory, photosynthesis might have evolved in other ways, but in reality, in evolution, it tends to be a case of "if it ain't broke, don't fix it". When something really simple evolves, it might only evolve once, like maybe cellular respiration or DNA. And that might just be the path of least resistance.

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Bobandirus

Thinking about it, that could be a good reason as to why all plants are green. All the other wavelengths of light would be just as good energy wise, yet the colour thats left out in almost all forms of chlorophyll is green. What I'm thinking is that this could be so that the plats are camouflaged into a green sea for the herbivores to try and make the plant less noticeable, and hence less likely to be eaten. So maybe its a type of camouflage, them all being green.

Are you suggesting that plants get energy from green light (I can't really tell from the quote)? If this is the case, you have it backwards. The green color means the plant is reflecting green light. In fact, plants get most energy from blue light.

In theory, photosynthesis might have evolved in other ways, but in reality, in evolution, it tends to be a case of "if it ain't broke, don't fix it". When something really simple evolves, it might only evolve once, like maybe cellular respiration or DNA. And that might just be the path of least resistance.

I do know that they don't get it from green light, its just not my best worded piece of writing.

I also know that if it aint broke dont fix it is the rieson that a lot of things are the way they are. I was just idly pondering why dark chlorophylls (like in black grasses and copper beech trees) are not so well used, because they should give an advantage because they should pick up the green light that passes through all the other leaves, as well as the wavelengths that the standers chlorophylls absorb.

I do appoligise if thats not easy to make sense off, Im very tired having been sailing for a few days. Ill try and make it make more sense tomorow.

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If anyone would like me to explain what I think the joke (or, more accurately, "spoof") is, I'll try. :)

Yes, please. I can tell it somewhat resembles the BO equation, but I don't "get it." :( Is it funny? When you have enough free time, could you please explain it? I'm itching to know. THANKS!!! :)

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Thinking about it, that could be a good reason as to why all plants are green. All the other wavelengths of light would be just as good energy wise, yet the colour thats left out in almost all forms of chlorophyll is green. What I'm thinking is that this could be so that the plats are camouflaged into a green sea for the herbivores to try and make the plant less noticeable, and hence less likely to be eaten. So maybe its a type of camouflage, them all being green.

Are you suggesting that plants get energy from green light (I can't really tell from the quote)? If this is the case, you have it backwards. The green color means the plant is reflecting green light. In fact, plants get most energy from blue light.

In theory, photosynthesis might have evolved in other ways, but in reality, in evolution, it tends to be a case of "if it ain't broke, don't fix it". When something really simple evolves, it might only evolve once, like maybe cellular respiration or DNA. And that might just be the path of least resistance.

I do know that they don't get it from green light, its just not my best worded piece of writing.

An interesting plot is this one:

photo.png

We see that in the rate of photosynthesis vs. wavelength, we have two peaks--one in the blue and one in the red. I cannot find it now, but I have seen more detailed studies that show the same thing. Growing plants in red or blue light would work OK.

We also see on the same plot the absorption spectrum of chlorophyll. It has absorption peaks in the blue and red. It absorbes the wavelengths that help cause photosynthesis. It has very little absorption in the green region, and so it reflects that light.

That is why leaves are green.

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Bobandirus

[snip]

I know, I was just not typing very well at all. What I'm intrigued by is why there are not nearly so many plants which absorb and use green and hence have very dark leaves.

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[snip]

I know, I was just not typing very well at all.

Understood. I just hoped to state why leaves are usually green. :)

What I'm intrigued by is why there are not nearly so many plants which absorb and use green and hence have very dark leaves.

That is a good question.

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