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Author Topic:   Genuine Puzzles In Biology?
Akhlut
Junior Member (Idle past 4697 days)
Posts: 6
From: Illnois, US
Joined: 06-16-2010


Message 31 of 153 (565354)
06-16-2010 10:43 AM
Reply to: Message 3 by Dr Jack
05-27-2010 2:59 PM


quote:
How does consciousness work, and why did it evolve?
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:
Why haven't plants closed the green gap?
Either it is unnecessary or having black plants would lead to problems via heat dissipation.
quote:
Why hasn't a version of Rubisco without the oxidase activity evolved?
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:
What, exactly, is the evolutionary relationship of viruses to the rest of life and to each other?
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:
What is the nature of the link between Archaea and Eukarya?
Why do Archaea have such different membrane lipids to the other two domains of life?
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:
How did life get started anyway?
Well, if the following article is accurate, pyrophosphite might be responsible: http://news.yahoo.com/.../newtheoryforlifesfirstenergysource

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 Message 3 by Dr Jack, posted 05-27-2010 2:59 PM Dr Jack has not replied

Akhlut
Junior Member (Idle past 4697 days)
Posts: 6
From: Illnois, US
Joined: 06-16-2010


Message 32 of 153 (565357)
06-16-2010 10:46 AM
Reply to: Message 22 by Dr Adequate
06-06-2010 7:55 PM


quote:
Not on the inside, we're not, and in particular the kidneys aren't quite symmetrically placed --- the left kidney is somewhat higher in the abdomen.
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 4697 days)
Posts: 6
From: Illnois, US
Joined: 06-16-2010


Message 33 of 153 (565358)
06-16-2010 10:48 AM
Reply to: Message 28 by Europa
06-07-2010 6:01 PM


Re: Mind and Brain
quote:
--------------------------------------------------------------------------------
I tried to post this as a new topic. Because it is sitting idle in the proposed topics category, I thought may be I should post it here.
1. How does thought originate?
2. How do you recall something from your memory?
Probably these two questions are similar. But I think they are different. May be their mechanism of origin is similar.
If you believe in mind body dualism, then, they may have an easy answer. But is the mind different from brain? Or is it a 'metaphor' used to signify the collective out put of the brain?
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 284 days)
Posts: 16113
Joined: 07-20-2006


Message 34 of 153 (580352)
09-08-2010 7:50 PM


Hox Genes?
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?

Jeff Davis
Junior Member (Idle past 4918 days)
Posts: 29
Joined: 09-05-2010


Message 35 of 153 (581576)
09-16-2010 12:01 PM
Reply to: Message 1 by Dr Adequate
05-27-2010 12:05 PM


quote:
The hairlessness of humans is one instance, there's been a lot of debate about that.
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.

This message is a reply to:
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Replies to this message:
 Message 36 by Taq, posted 09-16-2010 2:47 PM Jeff Davis has replied

Taq
Member
Posts: 9972
Joined: 03-06-2009
Member Rating: 5.5


Message 36 of 153 (581598)
09-16-2010 2:47 PM
Reply to: Message 35 by Jeff Davis
09-16-2010 12:01 PM


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.

This message is a reply to:
 Message 35 by Jeff Davis, posted 09-16-2010 12:01 PM Jeff Davis has replied

Replies to this message:
 Message 37 by Jeff Davis, posted 09-26-2010 3:42 PM Taq has not replied

Jeff Davis
Junior Member (Idle past 4918 days)
Posts: 29
Joined: 09-05-2010


Message 37 of 153 (583367)
09-26-2010 3:42 PM
Reply to: Message 36 by Taq
09-16-2010 2:47 PM


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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Replies to this message:
 Message 38 by NoNukes, posted 09-27-2010 12:54 PM Jeff Davis has not replied

NoNukes
Inactive Member


Message 38 of 153 (583462)
09-27-2010 12:54 PM
Reply to: Message 37 by Jeff Davis
09-26-2010 3:42 PM


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:
Okay, now a few facts. Most mammals attempt to keep their skin temperature at about 85 degrees F (29 deg C). The sun can heat the tip of a hair to more than 150 degrees F (66 deg C). Plug in those temps to the formula and you get (Ta - Ts) is (150 - 85) which is "65," a big number. Now, divide that number by the length of the hair (for metric-philes, just use cms).
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 4924 days)
Posts: 48
From: MD
Joined: 07-07-2006


Message 39 of 153 (584675)
10-03-2010 1:13 PM


regarding green plants
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.

Replies to this message:
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barbara
Member (Idle past 4802 days)
Posts: 167
Joined: 07-19-2010


Message 40 of 153 (584734)
10-03-2010 9:36 PM
Reply to: Message 39 by AlienInvader
10-03-2010 1:13 PM


Re: Perhaps a dumb question
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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Replies to this message:
 Message 41 by Nij, posted 10-03-2010 11:15 PM barbara has replied

Nij
Member (Idle past 4889 days)
Posts: 239
From: New Zealand
Joined: 08-20-2010


Message 41 of 153 (584753)
10-03-2010 11:15 PM
Reply to: Message 40 by barbara
10-03-2010 9:36 PM


Re: Perhaps a dumb question
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.

This message is a reply to:
 Message 40 by barbara, posted 10-03-2010 9:36 PM barbara has replied

Replies to this message:
 Message 42 by barbara, posted 10-03-2010 11:50 PM Nij has replied

barbara
Member (Idle past 4802 days)
Posts: 167
Joined: 07-19-2010


Message 42 of 153 (584756)
10-03-2010 11:50 PM
Reply to: Message 41 by Nij
10-03-2010 11:15 PM


Re: Perhaps a dumb question
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.

This message is a reply to:
 Message 41 by Nij, posted 10-03-2010 11:15 PM Nij has replied

Replies to this message:
 Message 43 by Nij, posted 10-04-2010 1:00 AM barbara has not replied
 Message 44 by Wounded King, posted 10-04-2010 8:31 AM barbara has replied

Nij
Member (Idle past 4889 days)
Posts: 239
From: New Zealand
Joined: 08-20-2010


Message 43 of 153 (584767)
10-04-2010 1:00 AM
Reply to: Message 42 by barbara
10-03-2010 11:50 PM


Re: Perhaps a dumb question
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: 04-09-2003


Message 44 of 153 (584800)
10-04-2010 8:31 AM
Reply to: Message 42 by barbara
10-03-2010 11:50 PM


Mixed up on olfactory receptors
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

This message is a reply to:
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Replies to this message:
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barbara
Member (Idle past 4802 days)
Posts: 167
Joined: 07-19-2010


Message 45 of 153 (585150)
10-06-2010 6:55 AM
Reply to: Message 44 by Wounded King
10-04-2010 8:31 AM


Re: Mixed up on olfactory receptors
Sorry bad source of website information.

This message is a reply to:
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