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Author | Topic: Genuine Puzzles In Biology? | |||||||||||||||||||||||
Akhlut Junior Member (Idle past 4720 days) Posts: 6 From: Illnois, US Joined: |
quote: I don't know how, but, as for why: because it apparently helps survival immensely. I'd say it is probably a function of having a relatively complex brain.
quote: Either it is unnecessary or having black plants would lead to problems via heat dissipation.
quote: My guess is that the molecule simply cannot be improved anymore just due to molecular conformation. That is to say, the molecule has improved since the past, but it has reached a point where there can be no improvements upon the current molecule and it would take a completely alternate molecule to have better function.
quote: Having read Parasite Rex by Carl Zimmer, it seems that viruses might be unusual anti-immune system products from parasites. For instance, a parasitic wasp produces endogenous viruses from its own genetic code to attack the immune system of caterpillars so that its eggs/larvae aren't killed by the host's immune system. So, I think it is likely, given that some ~80% of eukaryotic organisms are parasites, that such endogenous viruses simply 'escaped' and became independent, rather than a tool of parasites for performing some function.
quote: I can't really answer the first, but the second seems to be related to their extremophile natures. As such, a classic phospholipid bilayer breaks apart rather easy in hot, alkaline environments, like they favor. Any archaea that didn't have a membrane to withstand such a habitat wouldn't live to pass on offspring with more traditional membranes.
quote: Well, if the following article is accurate, pyrophosphite might be responsible: http://news.yahoo.com/.../newtheoryforlifesfirstenergysource
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Akhlut Junior Member (Idle past 4720 days) Posts: 6 From: Illnois, US Joined: |
quote: However, we're completely symmetrical during development, especially during organogenesis. It is only after about 10 weeks of development (for humans) that the heart stops being a symmetrical organ and assumes a lopsided shape and moves toward the left side of the body, with the lungs moving to accomodate it. The GI-tract is initially just a straight tube, only later lengthening and coiling about all throughout the gut. Similar stories for all the other organs. Originally, everything developed on the midline or on the sides in pairs, and only later on in development does everything shift around to fit in our torsos.
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Akhlut Junior Member (Idle past 4720 days) Posts: 6 From: Illnois, US Joined: |
quote: I recommend reading "How the Mind Works" by Stephen Pinker. I don't think he's 100% right on everything in that book, but I think he's right about the vast majority (75%). I can't even really summarize it well, because it is over 600 pages long and details a lot of function and form of the brain.
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Dr Adequate Member (Idle past 306 days) Posts: 16113 Joined: |
Why should the order of Hox genes in chromosomes be the same as the head-to-tail order of the bits of the phenotype they control?
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Jeff Davis Junior Member (Idle past 4940 days) Posts: 29 Joined: |
quote: Greetings all, I would like to take a stab at this from a natural selection perspective. It may be completely wrong, but it is most certainly testable. Why are humans the only generally hairless primates? One correlation is that human beings are the only bipedal primates. Note that hair is still found in hot spots, such as the head (most heat is lost from the head), the armpits, and the groin. Hair loss could very well be a balance between energy gain/energy loss, or conservation of energy. The fossil record shows that homonid evolution occurred in hot areas. The constant production of hair is certainly expensive in terms of calorie usage. If an organ or feature becomes relatively useless, a reduction can occur in a population because maintaining it wastes so much energy. In a hot desert climate hair is an excellent radiator. I watched an athlete running on a treadmill through an infrared video on TV, and when the runner was really heated up, you could easily make out his hair line. Wherever there was hair on the head, it was effectively radiating the excess heat. A plausible reason why humans still have hair in the hot spots is because the body needs radiation in these areas to run more efficiently. Too hot is bad. This explanation explains why humans are the only primates relatively hairless and it also explains why our hotspots still have hair. It also conforms to the fossil evidence. This explanation could be entirely wrong, but since it is a natural explanation it can be tested. best, Edited by Jeff Davis, : No reason given. Edited by Jeff Davis, : No reason given. Edited by Jeff Davis, : No reason given.
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Taq Member Posts: 10045 Joined: Member Rating: 5.3 |
In a hot desert climate hair is an excellent radiator. Actually, it's not. Hair is a good insulator. For many species who take it easy during the heat of the day it acts like a ice cooler, keeping the relatively cooler body insulated from the relatively hotter air. Humans do not take it easy during the hottest time of the day. We evolved to hunt during these periods. How can we do this? Evaporative cooling. We sweat. When water evaporates off of our skin it takes heat away from the body. Most animals use a similar technique by panting, but this is only capable of using the small surface areas. In humans, we use the entire surface of our skin. So how does this give us an advantage? We can actually run down animals until they collapse from heat exhaustion while we remain relatively unaffected. Some human tribes still use this technique to this day.
I watched an athlete running on a treadmill through an infrared video on TV, and when the runner was really heated up, you could easily make out his hair line. Was the scalp/hair warmer or cooler than the rest of the body? Also, using a treadmill effectively eliminates evaporative cooling compared to someone running down the road.
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Jeff Davis Junior Member (Idle past 4940 days) Posts: 29 Joined: |
Actually Taq, that's not correct. You are only taking into account the insulation power of hair, of which I agree with you. You also need to take into account heat transfer. Dr. Russell does a better job of explaining it than I do: http://sonic.net/~cdlcruz/GPCC/library/hairlength.htm
best,
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NoNukes Inactive Member |
Jeff Davis writes:
You are only taking into account the insulation power of hair, of which I agree with you. You also need to take into account heat transfer. Dr. Russell does a better job of explaining it than I do Probably off topic to take this too far, but Dr. Russell's analysis seems flawed. He models heat transfer as conductive from the air down the length of the dog's hair to the skin.
quote: Although the link does not give the doctor's complete formula, I don't think the doctor's analysis is correct. For most long haired dogs, much of the length of the dogs hair is exposed directly to the air, and for short hair dogs, much of the dog's skin and hair is exposed directly to the air. In either case the doctor's simplistic assumption that the rate of conductive heat transfer is proportional to hair length seems suspect. Even worse, a note in the article acknowledges that an essential constant relied on has never been measured for any dog. Further, I don't see any treatment of convective heat transfer which has to be the primary method of heat transfer in most doggy situations. I suspect that hair is so close to non heat conductive that conduction is almost never a significant issue. I wonder what subject Russell's PHD is in. I'm guessing something life science related rather than something like physics or engineering.
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AlienInvader Member (Idle past 4947 days) Posts: 48 From: MD Joined: |
pure theorycraft-
i'd imagine that absorbing non-green light was sufficient at some point for the single-celled ancestors of plants, and they moved forward into the multicellular stages at which point other forms of mutation conferred more survivability than covering the gap would, at less risk. you'd probably need a second non-functional form of chlorophyll to mess with, which would cost a lot in a living multicellular organism. i mean, evolution doesn't work towards the optimal, just until it's sufficient to beat your brother.
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barbara Member (Idle past 4824 days) Posts: 167 Joined: |
Considering that everything living today is the result of every generation prior lived long enough to reproduce the next that goes back to the Cambrian era, wouldn't the entire DNA sequence be nothing but mutations?
To go from a small multi-cellular organism with parts and the continuous alteration that has occurred since it all began I would think that everything in our DNA is a mutation.
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Nij Member (Idle past 4911 days) Posts: 239 From: New Zealand Joined: |
Considering that everything living today is the result of every generation prior lived long enough to reproduce the next that goes back to the Cambrian era, wouldn't the entire DNA sequence be nothing but mutations?
Yeah, basically.Although it would sometimes be a useful tool to set an arbitrary ancestor as having no mutations for comparison or whatnot. To go from a small multi-cellular organism with parts and the continuous alteration that has occurred since it all began I would think that everything in our DNA is a mutation
It's most probable that everything in our current genome is a mutation, but only because the chances of any portion of DNA surviving that long without any change at all is so miniscule as to be almost impossible.Note that this includes mutations which reversed themselves back to the "original". I would say the same also holds for any other species' genome for the same reason. Had you shouted bingo as well, you'd have received the prize But it raises another interesting question: at what point would we find a truly original genome, one that had zero mutations?Effectively that's similar to asking at what point we would find the UCA, a kind of discussion may be more suited to its own thread.
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barbara Member (Idle past 4824 days) Posts: 167 Joined: |
Maybe if they look at the genes that start with only one gene for example: olfactory. In chimps they have one gene while we have 8 or 9 genes. Clearly our olfactory abilities are reduced in humans while chimps olfactory abilities are excellent.
Just a thought.
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Nij Member (Idle past 4911 days) Posts: 239 From: New Zealand Joined: |
By that, do you mean "genes" or "alleles"?
I also wouldn't think there's any correlation between the number of possible alleles, or the number of genes involved, and the ability of that species.Any other numbers to compare with?
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Wounded King Member Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
Hi Barabara,
I think you have things a little confused. There is no such gene as Olfactory, what there are are a large number of distinct olfactory receptor (OR) genes, which encode a variety of different membrane bound receptor proteins. What we find with these genes is not what you state, Humans have roughly the same number of functional OR genes as chimpanzees. There are ~400 human OR genes that appear to be functional as protein coding genes and ~353 similarly functional OR genes in the chimpanzee (Gilad et al., 2005). Exactly what you are talking about is unclear. TTFN, WK
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barbara Member (Idle past 4824 days) Posts: 167 Joined: |
Sorry bad source of website information.
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