evolution of advanced math ability I am trying to convince a friend that human beings evolved from primates, and he challenged me that advanced mathematical ability couldn't have been the product of mutation and natural selection because this ability wouldn't have conferred any reproductive advantage until the last few hundred years, and the process of mutation and natural selection would have taken much longer than this to produce the extensive genetic basis of advanced mathematical ability. How do we refute this?

Just to avoid misunderstandings
Just to avoid potential misunderstandings on your side, I wanted to talk about the saying that

human [are] evolved from primates

Humans are primates, so did our common ancestor with other primates.
Our ancestors are different from modern day primates. Chimps for example (which are great apes, like us) are not our ancestor more than we are their ancestors. We just share a common ancestor (who lived about 13 millions years ago).

Spandrel, exaptation and panselectionist arguments
Your are doing two mistakes. 1) The mistake of the spandrel (named after the title of the famous and old paper Gould and Lewontin (1979)) and the exaptation and 2) a panselectionist mistake.
1. Spandrel and exaptation
Spandrel

In evolutionary biology, a spandrel is a phenotypic characteristic that is a byproduct of the evolution of some other characteristic, rather than a direct product of adaptive selection

See also What is the “Spandrels” debate about?.
Exaptation

Exaptation [..] describe[s] a shift in the function of a trait during evolution.

While the existence of a spandrel in an evolutionary process does not necessarily cause the existence of an exaptation, but I will not go into these semantics details for simplicity.
Consider for example the two following wrong statements.

Birds have feathers to fly. It is impossible that birds evolved feather to fly because early feathers would have served no purpose to flight.

Bird feather actually probably first evolved for temperature regulation. Once this was done feathers were an exaptation for early flying tools.

Humans have nose to wear glasses. It is impossible that nose would have evolved because there was no glasses before

Noses evolved for another purpose and happen to be an exaptation for wearing glasses.

Humans have a big brain for advanced mathematical skills. It is impossible that humans evolved such big brains as such mathematical skills were useless in a time where we did not invent/discover much of the most basic math concept yet.

Humans evolved a big brain, mainly for social reasons incl. social hunting and social communication and probably because it was/is under sexual selection (see wikipedia > evolution of human intelligence). It just happen that logical reasoning, abstract thinking and other cognitive skills are an exaptation for advanced math skills.
2. Panselectionist view of evolution
I just want to highlight that there is much more to evolution than just mutations and natural selection. Not every trait has been selected for (otherwise we would not have any genetic disease).
On this subject, you might want to have a look at the paragraph Did you say Natural Selection? of this answer to Why don't mammals have more than 4 limbs? and to Why do some bad traits evolve, and good ones don't?

Thanks to B for posting this question -- I asked him to post it to biology.stackexchange, so that our interaction might be useful to others. My answer is a quickly-typed email but might be useful anyway.

My answer follows:

Hi B -- briefly, advanced mathematical ability WASN'T the product of mutation and natural selection.  Neither was writing, poetry, symphonic music, representative democracy, genius comedy, etc. etc. yadda yadda.

All of these cultural achievements are the product of a very long line of causes, very roughly,

A. general human physical and mental traits

B. hundreds of thousands of years of co-evolution of human brains, societies, and fundamental human technologies like the making of spearpoints, fishing hooks, clothes, rock art, etc. in stone-age, hunter-gatherer societies

C. farming and subsequent large, high-densities human societies

D. writing

E. well-organized governments, nation-states, and subsequent "space" for "high arts" (science, math, opera, whatever)

F. substantial economic and technological progress (better ship-building, international trade, the Mediterranean mercantile revolution before/during the Renaissance)

G. A long history of cultural development within each of the specialities in (E). Each of these began seriously building and expanding, generation on generation.  E.g. for math specifically, we only really got going seriously with the introduction of Arabic numerals, the idea of the numeral "0", etc., into the context of the European economic and academic structure, and their linkage to the general Scientific Revolution (e.g. the massive success of Kepler, Galileo, Newton etc. in applying math to physics and astronomy)

H. A concurrent massive expansion of organized, formalized educational system, ranging from childhood education through to university and postgraduate education

I. Massive growth in the human population, and generation of a huge leisure class, creating a relatively large number of people that can do advanced math.  Most of us still can't!

I suspect that advanced mathematical ability is roughly on a bell-curve.  Most of us have the aptitude/ability/focus to do things like counting, which would have been useful even in stone-age times, and which clearly exist even in animals.  It is relevant to know that you have better odds getting by 1 lion, instead of 10 lions.

The rest of the explanation of math ability is mostly due to the cultural factors above, which, through massive training (20 years plus for advanced math), take human's general counting abilities, language ability, good memory, etc., and produce mathematicians ranging from OK (like me) through to amazing (Einstein or someone).

Natural selection only has a role in explaining A and B.  The rest is culture, which (very slowly) built on humans' general intelligence, language ability, sociality, etc.

Repeat this explanation for any other remarkable cultural achievement.

And, anyone else wondering about evolution and some major cultural achievement, should ask themselves the following:

Can I myself produce a similar cultural achievement in the same area? Is everyone as good as Mozart and Einstein were in their specialties?  If not, why not?
For humans, language is easy, but any non-trivial math is hard.  But for computers, math is easy and language is hard.  Why is that?  Hmm, which one was useful back in the Stone Age?
Similar question: Why is math hard for most people?  Why is producing new advances in math basically always hard, even for extreme experts?

Cheers!
Nick Matzke
nick.matzkeATanu.edu.au


What is the fundamental reason for death from too high or low internal temperature? I have read something about why we die from over/underheat, but always found too general reasons. Such that the liver fails. But why does the liver fail? I would like to know the most fundamental reason why not having the right internal temperature can make us die. Ignoring the very extremes where it is I think obviuos, like temperatures below 0°C and above 100°C when the water freezes and vaporizes.

So, a little bit of what I thought could be the reasons. If anything here is wrong, please correct my thinking.

As far as I understood, as the temperature changes, the speed of chemical reactions changes as well. Temprerature goes up, the reactions happen faster and if the temperature decreases, the reactions slow down. So if our body temperature changes, the speed of everything in our body should change as well. So with higher internal temperature we should just be more active, speedy and so, and with low temperature we should become slower. But that does not fit into the fact that we die from too high internal temperature. So, is it that the speed of different reactions changes in different rates, so the organism is not kept "in sync" and dies for that reason?

Or - as temperature changes, the volume of all materials changes as well. I think that's called thermal expansion. But different materials have different rates of that process. So as our temperature changes, something inside us just literally breaks or deforms too much and we die?

So why do we (and other organisms) die from not having the right temperature? Am I on the right track or am I completely wrong? Thanks for any answer.

Jakub

As mentioned in the comments, half of your question is answered elsewhere. Generally you are right, different processes change at different rates. Blood viscosity changes. Some complex systems, such as the heart, may completely fail to function. The other half of your question has a simpler answer. As heat increases, yes in theory so should enzyme performance. However enzymes have a tendency to denature if they get too hot. When heat is excessive, heat shock proteins are released which are naturally stable in hot conditions and which attempt to stabilize other proteins. This is only possible up to a limited extent, and sufficient heat will cause proteins to become entirely non-functional.


I found this on the beach at Breamlea in Vic Australia and wondered if you could tell me what it is please It is about 6.5 x 5 centimetres and semi transparent.
It has quite a tough skin and is hollow inside. Like a tight clear tooth shaped balloon. I have put a coin next to it for you to see the size.

It's a swim bladder, probably a porcupinefish swim bladder. They can be found washed ashore still inflated. They've been described as "molar shaped". (Picture from Australian Museum.)

It's hard to tell exactly, but if I had to bet I'd say it's a small part of an algae called Neptune's necklace:

Some species are native to New Zealand and Australia. Where two "branches" split, the shape you found can be produced.

Looks like they're also found in your area: http://bie.ala.org.au/species/NZOR-4-7414


Pink growth (aka pink slime) in bathtub or shower I was wondering if anybody had studied or was knowledgeable about the pink growth that people often find around water fixtures in their homes, especially bath tubs and showers?

My understanding is that this pink growth is actually a bacteria and not a fungus as many assume (source1,source2). Supposedly, the bacteria, Serratia marcescens is airborne and thrives in areas of retained moisture and fatty residue.

My main questions are:

How ubiquitous is this bacteria? What is the bacteria's geographical range of occurrence?

For example, is this species more prevalent in more humid environments?

Are there other species of Serratia that can create similar pink biofilms in tubs? (Are the sources of "pink" separated by geographic location?)

Is S. marcescens even forming a biofilm in these pink stains??

What likely introduces S. marcescens into a bathroom?

I ask, because I've seen this bacteria both present or absent from similarly clean or dirty bathrooms, and thus far have not really seen any consistent patterns in the bacteria's spatial occurrence.

Any other interesting facts or sources on S. marcescens would be great!

I live in St. Louis, MO and get this in my bathtub over time, but not in my other sinks. I actually think @Christiaan is correct here, but with a few additional observations:

I don't think it's bacteria. When dry, it's not slimy, nor does it grow back quickly when wiped away. It feels much more like a mineral deposit.
It was no longer pink when using a different shampoo. Upon returning to an older brand, the color returned to pink.
It's only directly around the drain, it isn't on the walls or anywhere else.

These lead me to think it's a mix of mineral deposits from the hard water and potential reactions with certain soaps/shampoos, at least in my case. These are only based on my own observations though, there very well could be a pink bacteria/fungi that tends to inhabit damp areas.

It could be Haloarchaea

so @theforestecologist not Bacteria but Archaea!

https://en.wikipedia.org/wiki/Haloarchaea


Is starch and glycogen digestion intra or extracellular? Do humans have the enzyme for starch intracellular digestion?
Also, do plants have the ability to digest Glycogen? Intra or extracellular, or both?

The problem with your question is that, right now, you have three different questions:

Is the starch/glycogen digestion intra or extracellular?
Do humans have the enzyme for intracellular digestion of starch?
Do plants have the ability to digest glycogen?

Unfortunately, that goes against Bio SE rules: you have to pick one question, otherwise your post will be closed as too broad ("Avoid asking multiple distinct questions at once.").

That being said, I'll address only this question:

  Do humans have the enzyme for intracellular digestion of starch?

The answer is yes. Intracellular digestion in humans (as in any animal) is performed by lysosomes, organelles that contain hydrolytic enzymes.

Lysosomes can digest proteins, lipids, carbohydrates, nucleic acids etc. Regarding digestion of carbohydrates, this is a short list of enzymes (the complete list is way bigger) found in human lysosomes:

alpha-Galactosidase
alpha-L-Fucosidase beta-Galactosidase-1
beta-Glucuronidase Chitinase
Chondroitin B Lyase/Chondroitinase B
Chondroitinase
Cytosolic beta-Glucosidase
Galactosylceramidase
Heparanase
Hyaluronidase
Lysosomal alpha-Glucosidase
O-GlcNAcase
O-Glycosidase

Among the enzymes listed above, this is the one that answers your question:
 Lysosomal alpha-Glucosidase.

That enzyme, which is a α-1,4-glucosidase, breaks down starch (and glycogen) to glucose.

Source:

Lübke, T., Lobel, P. and Sleat, D. (2009). Proteomics of the lysosome. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 1793(4), pp.625-635..

DIGESTION IN THE MOUTH:

Starch digesting enzymes are extracellular in human beings.All starches and some glycogen are hydrolysed in the mouth by the time the food is swallowed due to the effect of ptyalin(alpha amylase)enzyme in our saliva.

DIGESTION IN THE DUODENUM OF SMALL INTESTINE:

Pancreatic juice containing pancreatic amylase promotes extracellular starch digestion.And almost all the starch in food is completely hydrolysed to maltose, limit dextrin and isomaltose in its effect.

The same enzyme pancreatic amylase also causes the total extracellular digestion of glycogen in the duodenum and forms maltose and other products like limit dextrin, isomaltose.

DIGESTION IN THE UPPER JEJUNUM OF SMALL INTESTINE:

Products like limit dextrin and isomaltose is digested extacellularly in the small intestine by the enzyme isomaltase and maltose by maltase in intestinal saccus entericus to form glucose.

NATUREOF INTERCONVERSION OF GLYCOGEN AND GLUCOSE IN HUMAN:

The principal glycogen storing organ in human is the liver and glycogen formation or hydrolysis in the organ is 'intracellular'.

NATURE OF INTERCONVERSION OF STARCH AND GLUCOSE IN PLANTS:

Similarly in starch storing organs in plants the hydrolysis or formation is 'intracellular'.

REFERENCES:
https://en.m.wikipedia.org/wiki/Starch

https://en.m.wikipedia.org/wiki/Glycogen

https://www.ncbi.nlm.nih.gov/books/NBK21190/

https://en.m.wikipedia.org/wiki/Carbohydrate_digestion

http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2004.01101.x/pdf


Why do we define anaerobic respiration as not requiring oxygen, while utilization of the Krebs cycle and electron transport chain both require oxygen? We have an electron transport chain with the final e- acceptor as SO4 2-. We say this is an anaerobic process, or specifically a case of anaerobic respiration. Elsewhere, as with fermentation and glycolysis, we have anaerobic processes that do not require oxygen. Would it be more appropriate to call these processes with the final e- acceptor as anything other than oxygen to be pseudo-anaerobic?  I say this as it seems misleading to call a process anaerobic that inherently is composed of aerobic processes.

Because oxygen is not the majority of the energy.

Krebs cycle relies on sugars. Other processes use oxygen but can do without it or primarily use carbon fuels. So they are called anaerobic.


Could bone marrow transplants help make xenotransplants viable? So the immune system doesn't calibrate (for want of a better euphemism) to recognize it's own cells until fairly well along in fetal development & the major components of the immune system (antibodies, white blood cells, etc) are all produced by the bone marrow.

Those are the known details that cause me to wonder if this (below) might not be a viable approach.

Introduce the patients cells to a pig fetus before it's immune system has been set & it will be born with an immune system that recognizes both it's own cells & the patients cells as it's own.
Kill the patients own marrow (as per a normal bone marrow transplant) & transplant the pigs bone marrow into him giving him an immune system that recognizes both his cells & the pigs as it's own.

If my understanding is correct you should then be able to transplant any other organs from the pig into the patient without any tissue rejection issues.
I am only interested in the science so (any legal & moral issues aside) are there any major factors I'm unaware of to suggest this approach is a non-starter?

See Xeno: The Promise of Transplanting Animal Organs into Humans By David K. C. Cooper M.D., Robert P. Lanza M.D. Published 23 March 2000 by Oxford University Press, specifically the section on "The Induction of Chimerism Before Birth" from page 117 onward in this link.
That talks about my suggested first step (though in reverse), creating a human with immunity to cell rejection of a donor animals cells, which isn't much use to anyone who's already been born.
So I flipped the idea.

A Thymus transplant might be needed as well.

I feel I've enough sources & data to venture an answer on this one myself now, so here goes.
Step one: Can we produce the pig in the first place?

Fetal Inoculation With Donor Cells in Cardiac
Xenotransplantation 1996
Perinatal induction of immunotolerance to cardiac and pulmonary allografts July 1997
Induction of donor-specific tolerance to cardiac xenografts in utero: 1998 Sep
Cell Transplantation January 1 2003
IMMUNO-INTERVENTION FOR THE INDUCTION OF TRANSPLANTATION TOLERANCE THROUGH MIXED CHIMERISM: 2011 Aug 11
In utero hematopoietic cell transplantation: induction of donor specific immune tolerance and postnatal transplants: 2014 Nov 12

another link to the same article
In utero hematopoietic cell transplantation: induction of donor specific immune tolerance and postnatal transplants 12 November 2014

First human-pig 'chimera' created in milestone study 26 Jan 2017
Interspecies Chimerism with Mammalian Pluripotent Stem Cells 2018 Jan 26
Interspecies Chimeras and the Generation of Humanized Organs 3 Jan 2019

Yes, an animal can be produced with donor specific tolerance to the patients organs, it's a known procedure & observed effect that has been replicated numerous times in experiments, its immune system would not attack either the patients cells or its own.
Step two : Can we transplant this animals bone marrow to the patient?

Stem cell and bone marrow transplants

Yes, bone marrow transplants involving the complete removal of the original bone marrow is a long established procedure for the treatment of leukaemia.

And now being used for treatment of other severe autoimmune diseases in a way which may make this idea moot, I'll have to look into that further, not read that article in full yet.

Step three : Will we then be able to transplant other organs from this (or a genetically identical) animal to the patient without tissue rejection?
The immune system isn't seated entirely in the bone marrow & its products (the thymus, spleen & lymphatic system also have roles) so for best results some of these may also need to be replaced.
If so it must be hopped the lymph nodes play no role in in the development & tuning of the immune system, there are 500-600 of them around the body so replacing them all would be no small task.
Conclusion :
Still in progress / just saving work so far

No, this will likely never work - but chimeric trans plantations of 'humanised' organs might become possible.

Firstly, the process of injecting human/patient cells into an embryo would - if it works - create a chimera. Experiments of creating pig-human chimeras have (to my surprise) actually been performed, however the amount of humans cells that didn't immediately kill the embryos was very low (~0.001%), so even if they embryos would be able to reach adulthood (which the researchers didn't test) the organs wouldn't be human-like enough to allow transplantation. (source1, source2)

If the chimeric embryo's indeed survive then it might be possible to create animals that have a completely 'human' bone marrow that can be transplanted, by removing part of the pig genome that allows for the generation of bone marrow so that the injected human cells take over that role (this technique has been used successfully in rats & mice for other organs). If organs other than the bone marrow could be 'humanised' this way in pig chimeras is probably unclear since the difference between pig and human is much larger than mice and rat and might cause immune rejection issues.

Transplanting actual chimeric organs will likely never be done, since some of the cells will always be of the 'wrong' species, which would cause a lot of immune issues in some way.
Since chimeras unlike hybrids will never have individual cells that combine two species, it will also not be possible to make a thymus that 'trains' the whole immune system against two species - individual T-cells might only see one type of species during maturation and therefore cause immune reactions later on.


Is there a balance or feedback between O₂ and CO₂ in the atmosphere? Is there, globally, a balance of the concentrations of oxygen and carbon dioxide  in the atmosphere?

Plants convert CO₂ to O₂,
and with the concentration of O₂, the tendency of plants to oxidize to CO₂ increases. That is, plants burn better with more oxygen.

Based on this there may be a feedback of increasing CO₂ concentration to increasing O₂ concentration back to increasing CO₂.

This feedback requires that plant growth increases with increasing CO₂ concentration.

Otherwise there would be only a limit to the oxygen concentration as at some concentration of O₂, even a wet rainforest burns explosively.

Does a feedback loop like that exist?

Yes, increase in CO₂ concentration increases the rate of photosynthesis in plants. The rate of photosynthesis is linealy proportinal to CO₂ concentration in range up to 225ppm  and  slowly increases range 225-650ppm.[Limiting Factors in Photosynthesis, Plant Physiol. (1984) 75, 82-86] (Now CO2 concentration is about 400ppm).
You can read more in Educational article on Nature journal website or in
More scientific review on the topic.


Does the Miller-Urey experiment explain the origin of life? According to the Miller-Urey experiment, the early earth atmosphere could have supported the formation of amino acids - and the experiment is hailed as being important in the explanation for the origin of life. However, I do not understand how life could have started from amino acids (or proteins) which do not self replicate. Certain types of RNA do self-replicate, and it is plausible how life could have evolved from there.
Does it matter if amino acids came before RNA if they did? Is it correct to assume that in the RNA world, life somehow learnt how to use amino acids?

This is a common question. I think the experiment and its conclusions are often misunderstood.
Originally, the null hypothesis was that the ingredients for life could not have come about spontaneously, from inert, inorganic molecules. There was no evidence of strictly physical, non-biological processes being able to produce compounds that were necessary for the proteinaceous life as we know it. In other words, abiogenesis was therefore not supported by any line of positive evidence... until the Miller-Urey experiment. The experiment showed that the ingredients could arise through plausible, natural conditions prior to the existence of life! It bridges the gap between inert, inorganic, non-biological, and the rich soup of complex molecules that would - arguably - be necessary for anything like abiogenesis to even be a consideration based on empirical observation.
Of course the presence of amino acids is not evidence for the abiogenic origin of life. Life is not protein nor amino acid alone. But demonstrating that complex biological ingredient chemistry occurs spontaneously in large abundance - that sounds like a great take-off point for an abiogenic origin of life! That's really all the experiment achieved. In its historical context, it is a very impressive discovery, but it is certainly not a complete explanation, merely something that makes myriad biochemical explanations possible (and perhaps even plausible!). Perhaps you can now better appreciate why it excited and continues to excite biochemists working on trying to understand the chemical origins of life. The Miller-Urey experiment is foundational.
As for the transition from RNA to an RNA-protein origin of life, I quote briefly from another answer elsewhere here:

Regarding the transition from RNA-only to RNA-protein world, peptides
function as cofactors for some ribozymes. Amino acids and peptides are
known to have existed in the prebiotic environment and have been found
in space (glycine has been found in comets, along with other 70 amino
acids).

The Miller-Urey experiment does not explain the origin of life. It just propose a plausible way to develop life from organic matter, as part of the abiogenesis model of the origin of life. A better approach to understand the theories of life origin is looking for a context.
We already know, by the cellular theory, that cell are the main component of organisms and that just cells could originate others cells. So, the research is focused on finding a way to create at least one cell. From knowed compounds, cells could be modeled as a set of autoregulated biomolecules. Just two of them are used explicitly for replication: nucleic acid and proteins. If you think about this two components, the Miller-Urey experiment just propose a way to develop simple proteins from aminoacids, and aminoacids from inorganic matter. Amazing, but not enough for explaining the complexity of actual proteins and enzymes.
But there are other theories and facts that works well with this experiment. Some non-translated olygopeptides have intracellular functions. The PAHs world theory proposes a way to develop nitrogenated bases from aromatic hydrocarbons. This bases are precursors for RNAs and DNAs. The RNAs world hypothesis establish a way to develop life from RNA and not DNA or proteins. The phospholipid bilayer have some common patterns with micelles and all this mechanisms would be part of the Last Universal Common Ancestor (LUCA). But there is no evidence of the relationships between this theories and maybe there are just too simple for explaining life.
Maybe the first cell had come from the space, where a pre-term version the krebs cycle have been demostrated to work. We could think on it as "biogenesis" until "abiogenesis" could be demonstrated.


What is an extinction test? In Stolerman & Olufsen (2001) I read the sentence:

After drug-appropriate responding with the training mixtures reached
85%, generalisation to ethanol was examined in extinction tests.

Here is the entire section from the article on the subject of extinction testing:

Extinction test procedure
Effects of test drugs were determined in brief extinction tests of 3 > min duration that took place twice weekly, with normal training sessions continuing on the interven- ing days. Initially, rats were tested once with vehicle and once with the training mixture; they all reached a cri- terion of at least 80% correct responding and they were all used in subsequent experiments. The effects of saline, the single drugs used for training and the training drug mixture were determined in 3-min extinction tests. The different drug treatments were given in random order. Prior to each test, two injections were always given (via the appropriate routes) to equate handling.

What is an extinction test?

It's a behavioral thing.
The abstract of the paper says: "...mixtures of two drugs from vehicle in two-lever procedures with food reinforcers..."

In operant behavior, rats (in this case) are trained to associate a stimulus (a tone, an odor, a light, etc.) with an action that leads to a reward, the association is trained by delivering a reward only when the 'correct' action is performed, e.g.:

stim A -> press left lever -> get a reward

stim A -> press right lever -> get nothing (or a punishment, but that is a whole different question)

One can quantify the performance of the animal by looking at the probability of responding left (in this case) when stim A is presented.

Now, we think of the association between stim A and left pressing as being reinforced whenever a reward is present, we call it extinction whenever the reward is not present, basically because the reinforced behavior will eventually extinguish, and we say its extinguished when the probability of response to the left and right is 50%.

"...generali[z]ation to ethanol was examined in extinction tests..."
basically means that they substituted stim A for ethanol (I imagine its all olfactory, just read the abstract sorry) and characterize the response to ethanol without ever reinforcing it, hence the extinction.


How some virus are able to reach the CNS? I know that the lymphocytic choriomeningitis virus (LCMV) could provoke meningitis and encephalitis when this virus reaches the brain. However, there are other viruses like Varicella (VSV), Cytomegalovirus (CMV) or Herpes (HSV) that are able to reach the brain, hence, to pass trough the blood-brain barrier (BBB) and damage the central nervous system (CNS).

1) Since the blood-brain barrier allows only the free diffusion of some molecules such as water, some gasses and lipid soluble molecule, I was wondering by which mechanism a virus is able to pass trough the BBB.

2) Since the CNS is an immuno-privileged space (where basically the immune system is down-regulated), how does the body eliminate a virus that had reached the brain?

some viruses like rabies get into the peripheral nerves, and travel through those to the spine , unimpeded by any obstacle.


What are the difficulties/challenges against developing a coronavirus vaccine? Multiple groups of scientists are trying to develop a coronavirus vaccine but they are not yet being fruitful. What challenges or difficulties are there in the process that slowing down and/or causing failure in development of vaccine?

There are multiple challenges presented, and many of those are not limited to coronavirus vaccine.

As mentioned above, it just takes time. Before a vaccine can be used in patients, clinical trials must be performed to validate the safety and efficiency of the vaccine candidate. A Clinical trial includes three phases, which again, just takes time.

But to really answer your question, what are some challenges of developing a vaccine?

To begin with, from the perspective of lab research, we first need to develop a vaccine candidate. What protein on the virus should we take as an antigen? There are many many proteins on the virus, and for CoV, we know it is a protein called Spike protein. It is the neutralizing target on the virus. Which means, when an antibody bound to this site, it could prevent the virus from infecting the cells. Okay, then we have to know, do we need to do something to this protein to make a vaccine? For example, when we try to manufacture this protein into a vaccine, what if the protein is degraded? Or it somehow becomes a 'bad' protein that simply cannot stimulate immune responses in human? These are just some examples of roadblocks of developing vaccine.

Let's suppose we finally work those out. Then what's next? Each candidate vaccine needs to be tested in animals before going into human clinical trial. This step is time-consuming.

Now we are finally ready to start clinical trials. According to FDA, the vaccine for human trials (also for each drug) needs to be produced under Good Manufacturing Practices (GMP). It's basically a standard operating procedure to make sure that the vaccine candidate can be manufactured in a large-scale, quality-controlled manner. There are many many challenges, like how to purify the protein? How to scale-up production. This is partly of the reason why the first vaccine in trial in USA is an mRNA, and in China is a DNA, both of which does not require complicated protein purification.

As you can see, the list of challenges can go on and on. But there are scientists and doctors working diligently on it. Hopefully we'll get there.

A vaccine needs to be able to neutralize the virus (bind to it and masking from entering the cell) with high affinity. Now the virus is a large complex structure, so it is not immediately clear how to design a vaccine that can achieve that.

Screening antibodies from recovered patients might be a good idea, but it takes effort and time. What is more, the antibodies isolated from those patients may not be optimal for a vaccine, and some rational design based on those antibodies might be needed.

Another challenge is how to get a sustained level of vaccine proteins in the human body. The cutting-edge in the field right now is to use mRNA instead of proteins. You can read something about Moderna, which spearheaded this effort in the pandemic. But we still do not know what those RNAs are doing and where they are going in the body, so it takes many experiments and creativity to send those mRNAs into the human body so it can function properly.

To make a vaccine, you also need very strict production standard known GMP to make sure that the product is clean, pure and safe. This is not very easy and not every lab in the world can do.


Why do people eat meat? My main question is why do people eat meat?
Can we not survive without meat?

I recently became a vegetarian and I have not yet felt any impact on my health. Can any one explain this phenomenon from the perspective of nutrition?

There are many reasons for why people eat meat. Some of them are to be discussed here and some of them have nothing to do with biology.

Reasons that have nothing to do with biology

There are many reasons that are not to be discussed on Biology.SE. These include cultural reasons, the reasons related to taste and appreciation, farming and availability, price and economy and of course for reason related to political ecology (incl. water and energy consumption of meat production).

Reasons that has to do with biology / medicine

We can talk about nutritional value though. According to a number of websites (sorry nothing peer reviewed; monitor.co.uk; rd.com; sparkpeople.com), people not eating meat may suffer from lack of

protein
iron
zinc
calcium
vitamin D
vitamin B12
omega–3 fatty acids

It is not impossible to get all of these nutrients without meats. However, when becoming vegetarian, some people need to be careful and rethink their diet to ensure not to suffer from the lack of these nutrients.

People eat meat for the same reasons they eat non-meat food. Taste, nutrition, availability etc. Nutrition comparison is a medical question.


How do tumor cells 'gravitate' towards each other? In a popular article it is mentioned that in centrifugal experiments with cancer cells that

  When subjected to microgravity-conditions, the cancer cells were unable to sense each other and therefore had a very hard time coming together.

which is because

  [...] the process through which cancer grows and spreads would seem to indicate that there is a means through which the cells are able to sense each other and gravitate together to form a tumor.

I would now be interested in the role of such fundamental forces in cell-signaling.

How does gravity interact with cell-signaling and lead to the 'gravitation' of tumor cells towards one another?

To my knowledge, cell signaling is a bunch of processes that involve the propagation of electrical signals by chemical means, so I am rather surprised that gravity would play any role in this.

It is reported that 99 genes are significantly upregulated in presence of normal gravity, whereas in absence of gravitational force no gene expression is seen in case of T cell activation. Research article attached concluded  that gravity is important for regulating various essential T-cell activation signalling pathways, which play key role in cell proliferation and apoptosis.

Transcription factors like NF-kB, CREB, ELK, AP-1, and STAT are responsible for tumor cell development. And NF-kB and CREB showed gravity-mediated gene expression. As, the PKA
signaling pathway regulates expression of these transcription factor, so it means that gravitational force moderates PKA signalling. And PKA signalling also mediates tumorigenesis. So, by regulating various cell signalling pathways, gravity controls the tumor cells.

Gravity also modulates the activity of Epidermal growth factor, which are implicated in tumor progression. (Via: https://www.ncbi.nlm.nih.gov/pubmed/7757250)


Why is sexual reproduction so much more common than asexual (in macroscopic organisms)? Fundamentally, what makes it better? I'm experimenting with an evolutionary method of creating a neural network. I use an asexual approach, but I've seen others use sexual approaches.

So I'm interesting in learning what's better about sexual reproduction as apposed to asexual, and biology is probably the best way to approach that question. So, why is sexual reproduction so much more common than asexual (in macroscopic organisms)? Fundamentally, what makes it better?

I'm struggling to understand what the combination of two gene sets does that couldn't be achieved by mutations to a child of asexual reproduction.

Genetic diversity is needed to prevent everyone from dying of the same disease. This is the problem with monocultures. Higher organisms are more susceptible to disease and thus reproduce sexually.

Furthermore, basically all organisms exchange DNA so they are effectively sexual.


Can mold grow on copper pipes? Couple months ago noticed something was literally, for lack of a better term, eating paint off of lead pipes.  And I noticed joints in copper pipe seemed to be "leaking" flux. Now all the water in my house causes lips and tongue to feel as if they have cold sores or anesthesised.  taste could be rusty.

Copper inhibits growth of organisms. See " Antimicrobial properties of copper" in Wikipedia.


Optimization of Signal Peptides We are looking at modifying the signal peptide of a receptor in a common immortalized human cell line.  The cell line already expresses an unusually high amount of the protein, but much of it is not surface expressed.

When we compared the sequence of the signal peptide in the cell line (in this specific case the first 19AA), we found 2 mutations vs the wild type (WT) sequence.  One obvious idea, which we will do, is to restore the peptide to the WT version.

But I've been curious about options that increase trafficking to the plasma membrane over WT.  When I've looked up groups that have actually done this, it's normally been with large screens against every possible mutation in the signal peptide.

Are there targeted approaches to choosing a small number of signal peptides to increase surface expression?

I'm playing around with swapping it out some viral peptides that are totally unrelated to see if we can get increased expression with a receptor that's still (semi) functional.

You could upregulate the transcription of the receptor gene you are interested in. More receptors being produced = more receptors being expressed on the cell's surface.


Is this spider venomous? I found this spider in bathroom. Just wanted to know more about it.

Location : India(South India,Hyderabad)
Temperature : 30°C
Humidity : 74%

Your spider shows an apparently large size, a large round cephalothorax, with smaller and thinner abdomen, very long and sturdy legs, with a long 'foot', and is a general brown color, with some darker markings on the legs.
This is consistent with one of the larger varieties of spider found in the warmer areas of the world, and trading under the name of Huntsman Spider, or Giant Crab Spider.  There are a number of species of these spiders in the family Sparassidae.
As it happens, the most common variety of Huntsman, Heteropoda venatoria, is found pretty commonly in southern India (reference link example included: http://www.southindianspiders.org/south-indian-spiders2.htm ), and I'm quite confident that this is what you have there.  Here is an example, from the US website Bug Guide, of this species:

Like almost all spiders, this spider is venomous, but like almost all spiders, its venom is not particularly troublesome to us humans.  A bite from a spider this big would be moderately painful simply from the large fangs, and the venom doesn't appear to usually add too much to it.  Here's a short but amusing discussion of such bites, from an Australian website: http://sciabc.us/IL2pR

These are sort of the spider equivalent of Geckos - commonly foraging in human homes for the various critters that like to make pest of themselves (cockroaches, mice, etc.) - but they never try to sell us insurance.

I don't know the species (could be a wolf spider), but I am certain they are not dangerous. I have seen these all over my bathroom, dining room and bedroom before. They are all over in South India. No one in my family seamed concerned by them. I am quite certain I even had one crawl on me once.


Why have humans evolved conciousness? Why did humans/animals evolve to become self-aware of their own thoughts.  That is, why don't humans act and compute like a machine, or walking zombie.  In my mind, such creatures would still be as smart and equally capable of surviving, the only difference being they don't experience the phenomenon of self-awareness. (To understand my question think: unconsciously sleep walking)

There have been many proposals over the years as to why human consciousness has emerged and how, or even what it is.

Most of us will not be surprised to know that there is no consensus about an answer here.  Its hard to draw a trend from a single example.

Here is a little survey of the one's I've heard.

We are intelligent because we have opposable thumbs and can use tools, which evolved our brains.  This is an old one - maybe as old as Darwin's time.  I think its mostly ignored now because so many animals - including pandas and other non primates have opposable thumbs or use tools or both.  (monkeys and chimps use tools, and recently crows have also been observed to use tools.)
brain size.  We do have a large brain to body size ratio.  There are other animals with similar ratios and they don't have internets.
We are 'self-aware'.  That is to say we recognize ourselves as an individual.  It was proven that other primates can recognize themselves in mirrors (putting a red dot on their forehead. when they see their reflection, they touch their own forehead).  So that's not exclusive either.  its not a bad idea, but so far it doesn't seem to make the
'We ate something' I once read a discussion of how humans might have ingested psychotropic plants or fungi.  As you can see, this was 2010.  Its not the worst idea, but its hard to prove.  Lots of experiments on cats since the '60s have not produced cat's who care to tell us if they are intelligent.  Maybe they are just too smart in the first place.

These theories, from when I was a student are so discounted now, you can't find too much record of anymore since they were pre-internet and also they seem so unlikely now.

More modern theories have locked onto social configurations of human societies which drive intelligent adaptations.  This is stemming from observations that human evolution (the rate at which genetic variants are retained in the gene pool) are accelerating since humans have become social.

These new theories while standing on some amazing evidence are still feeling around in the dark - stuff about how social interactions have created a preference for intelligence-like traits. There is probably something to that - once intelligence gets a toehold it is a clear advantage.  But how did it show up only once and why us? I think that's the hard part that science has, for the moment, given a rest.

Animals are not self aware, sentience is the quality of placing yourself in time and space, and the capability of introspection. We humans know we exist, we know we live in a universe, we ponder what's the meaning of life, where we came from and how we came to exist, where we go after we die, animals don't, they act by instinct and have different levels of intelligence, their behavior is written in their DNA code, but they aren't self-aware, this is the basic trait that separates us from animals.

Concerning how we became self-aware, that will depend on your beliefs (another trait of our advanced intelligence), but those who believe in evolution pretty much agree that we developed sentience because our brains developed much further than that of any other species, our advanced cortex and cognitive system gave us this ability. Different religions also have different accounts to our origin and history, in the proto-Indo-European cosmology for example, we are descendant of aliens, called pleiadians or nordic aliens, they came to earth through a portal in the sun, and brought their seed to our planet and gave origin to us, all our knowledge and manifestation of our humanity, like science, art... come from them.


Does evolution produce organisms perfectly adapted to their environment? I have this biology assignment with this chosen topic. I have no idea where to start researching. I have studied the mechanisms and theories of evolution. I just don't know which relates to the topic. The task is to persuade an audience of one side, either yes evolution produces perfectly adapted organisms or no evolution does not produce perfectly adapted organisms. I have started research on the blind spot of the vertebrate eye and that might be case scenario for the topic. If you have anything to add at all that would help me complete this project. It is much appreciated. Thank you in advance!

You should most definitely have a look at a very introductory course to evolutionary biology such as evo101 for example.

  Does evolution produce organisms perfectly adapted to their environment?

There is a lot to say about this question. The question is very broad and cannot be fully answered in a single post. The very very short answer is "no". I will very briefly develop this "no" below.

Concept of perfection

There are semantic (and hence philosophical) issues of the concept of perfection in this question but I shall not go into these issues. Typically, in the fact of sexual selection (and other arms race), the concept of "perfection" becomes very unclear (see S Pr's answer).

There is variation in populations

Evolution is all about genetic variance in populations. The fact that variance exists makes that necessarily there is no notion of perfectly adapted for a population (or for a species) as not all individuals are the same!

"Drivers" of evolution

Evolution is a change in allele frequency over time. There are a number of drivers of such changes, including natural selection, genetic drift and mutations.

While natural selection is a deterministic process, genetic drift and mutations aren't. There is hence constantly departure from a "hypothetical perfect" caused by genetic drift and mutations.

Mutations, while being a "random process" (see Are mutations random?), most mutations are deleterious, hence constantly inputting "imperfection" into populations.

The term "perfectly" is a problem because perfect adaptations may not be available via mutation and because the environment is constantly changing anyway, so what is perfect in one environment when selection occurred may not be perfect a minute or an hour later.


Peach pits with two seeds: Are the seeds identical twins? I have Prunus persica peach pits that have two seeds.

My question is simple:

Do the seeds have the same DNA? (are they identical twins?)

Polyembryony occurs when a single fertilized egg produces more than 1 embryo. This is the process that produces genetically identical twins.

Although polyembryony is common in some plants, I found limited information about polyembryony in peaches. I decided to broaden my search into drupes more generally. Drupes or "stone fruits" are the fruits with a fleshy outside (exocarp and mesocarp) and a hard inner shell (endocarp) around typically a single seed. Peaches are part of this category, as are almonds (the almond itself is the inner seed), cherries, and coffee.

The best citations I found reach back into history a bit.

From Webber, J. M. (1940). Polyembryony. The Botanical Review, 6(11), 575-598.:

  Cases of the first class of false polyembryony
  commonly occur in such drupes as almonds, plums and peaches.
  Although these drupes normally have a single seed within the hard
  seed-like endocarp, sometimes two or even three are found. ' During
  formation, each of the plural seeds develops from a separate
  ovule, provided with a separate funiculus and micropyle. Similar
  cases of such false polyembryony have recently been reported in
  Coffea (63) and Sandoricum (47, 49).

This passage would suggest that most likely what you are observing is false polyembryony. Immediately prior to this passage, the "first class" refers to:

  those in which more than one ovule develops in a normally 1-ovulate seed-like structure or locule

as contrasted with the second type:

  occasionally two of the developing ovules unite to form what appears to be a single composite ovule.

Another source, Zdruikovskaya-Rikhter, A. I. (1970). The phenomenon of polyembryony in the peach. Tr. Nikitsk. botan. sad, 46, 173-177. is in Russian and only available to me in abstract form in English. The abstract reads:

  In a number of varieties, two and sometimes three megaspores were functional, giving rise to several embryo sacs. On fertilization, embryos develop in these, causing the phenomenon of pseudopolyembryony.

Therefore this source seems to agree with the first.

However, a more recent paper Martínez-Gómez, P., & Gradziel, T. M. (2003). Sexual polyembryony in almond. Sexual plant reproduction, 16(3), 135-139., focused on almonds, suggests that certain almond cultivars are prone to true polyembryony, though it seems like the additional seeds are often a bit stunted and have high mortality. They also reference a paper purporting to mention polyembryony in peach, Toyama, T. K. (1974). Haploidy in peach. HortScience, 9, 187-188., though I cannot find this article in anything but Japanese - the title, however, suggests that these may be haploid polyembryos, which also occur with the almonds - these are indeed from division of the same embryo, but because they are haploid they would not actually be genetically identical, since each is taking half of the diploid chromosomes.

With only these limited descriptions to go by, which seem to be mostly observational rather than backed by any systematic study, I would hesitantly conclude that most likely what you are seeing is a fruit in which two separate ovules developed together, and therefore could be as genetically different as any two different peaches from the same tree. True polyembryos seem to be possible in stone fruits, but as a mostly rare occurrence that is only common in particular strains - when it does occur, it may be via haploidy, which means the seeds will still be genetically distinct.

Of course they are.

They're both from the same peach, so they both have identical DNA. It's like when a mother has twins or triplets, all of the babies will have the same genetic code, since they all came from the same egg. So if there are two cores in a peach, since the peach and both of it's cores are from the same tree, both cores will have identical DNA. :)


What is the viability of Intelligent Design as a supplement to chemical abiogenesis and Darwinian Evolution? First of all I am not endorsing Intelligent Design (Wikipedia link); I'm asking this because I (someone who does not have a background in biology, organic chemistry, or philosophy) got into a conversation with someone who does endorse it, and I'm trying to see his point of view as far as rationality can allow. Second of all, I apologize for any vagueness; Intelligent Design isn't well enough defined as a theory for me to help that. I also apologize if this is rehashing content already plentiful on the Internet, but for my purposes I can't simply depend on the likes of Wikipedia or Talk Origins, so what I'm looking for here instead is to take the opposite approach and see, based on your informed minds, if there could possibly be any reasonable likelihood of an ideal ID theory being adopted.

  I'm looking for the most favorable consideration for what ID might be
  if it were best developed as a viable hypothesis or theory to get an
  idea of how far such a discussion is worth taking. An unbiased,
  informed Devil's advocate, if you will.

My cursory investigation of what Stephen Meyers (video link) and Michael Behe (video link) say (correct me if I'm wrong) seems to be that either the first cell was likely designed intelligently judging by the complex code of DNA and that evolution took course from there, or that the first cells were made and many instances of evolution were from some kind of intelligently guided mutations as was needed to make "irreducibly complex" cells or body functions (whether the guidance stops after the Cambrian or continued even to the point of making different types of new bacteria and different types of apes/humans or whether every single mutation and adaptive ability is being guided, I'm not sure if they're at any consensus, and that's why I don't know if I should stop my question at abiogenesis or include evolution). The person I spoke with also brought up some specific claims (everything looks designed, DNA has ordered, complex information, blood clotting is irreducibly complex, ID can and has make predictions like decades ago that "Junk DNA" wasn't junk) that I don't need you to debunk (I have Google).

But if there could be any possible support or truth to any of the above, I would appreciate knowing about that. (Again, Devil's advocate so I can be informed and understand where the points come from.) Reading an ID book alone, it would be in places hard to know where they differ from actual scientific conclusions. After all, when someone who seems to know what they're talking about and can explain something in technical detail says that something is impossible or extremely unlikely, it's hard for me to know why they would be wrong (are they ignoring other possibilities? misrepresenting facts? are they really right and just getting the cold shoulder from an atheistic scientific community because it implies a deity?). So I focus on mainstream sources, even if they don't bother entertaining ID and leave me ignorant of its possible virtues. And thus I'm hoping someone from this informed community might enlighten me to what those possible virtues might be.

I think the issue with Intelligent Design is not so much that its patently proven wrong.  On the contrary, the problem is that it not a scientific hypothesis and so it really isn't a scientific question.

If I may, the basis of the scientific method, as formulated by Karl Popper, but commonly in use today, is that science is the putting forth of theories of cause and effect which are testable (or if we are being precise, falsifiable).

That is to say, you put forth a theory such as 'God/some diety figure made all living things' and then you perform an experiment which can differentiate whether the hypothesis or its null version (i.e. 'no intelligence is the source of life / biology is the result of accidents') is more likely true.

This question will not be testable in a way to answer enough of the reasonable skeptical questions ( or at least so far it has not).  Experiments have been tried, but they are often not acceptable to everyone.  For instance the idea that some biological structures such as the eye or the flagellar motor are too complex to have evolved through a typical Darwinian process which involves a series of small changes are almost biological theology - one can always hypothesize a more inhuman God (probably appropriate) who acts and 'thinks' in such an inhuman manner that anything you see could be created/inspired.  While I think you should feel free to believe either way, I also believe that this is not an argument that can be won or lost.  The tendency for any experiment to confirm both the hypothesis and its inverse seem inescapable.

That is to say, that biology and physics will ultimately fail where philosophy and logic also did in proving the existence of God, besides the less interesting truism that if God does exist, the deity is consistently elusive to proof.

On the other side of the coin, the proof that life has emerged from naturally occurring phenomena such as lighting strikes in a prebiotic environment are interesting since it shows that nucleotides and amino acids might have been available without metabolic pathways to synthesize them.  In its way, the molecular origins of life on earth is a question which is really testable only in theory.

Anyone who thinks they are going to re-create the event of the beginning of life itself is scientifically on thin ice - the prebiotic environment may have extended to the entire surface and atmosphere of the earth as well as down into mud and bodies of water and sat incubating for maybe hundreds of millions of years.  The idea that the fundamental moment of life generation is just going to show up on a well chosen set of conditions in a 500 ml flasks with some electrodes attached is an idea that workers in the field don't even entertain.

Until such an experiment produces life, the work will have to rely upon the idea that there was a moment in time where the necessary elements came together.

This being said, cosmology, biogenesis work has approached the moment of the genesis of life asymptotically with amazing clarity.

The RNAWorld hypothesis strongly supports the idea that an early biotic system might have been very simple - maybe only RNA and its four nucleotides.  Clearly after what Dawkins calls a replicator exists, then the pathway to living things as we know them is pretty easy to envision.

I should add that I'm not one of those people who think that science is everything - the trend that is impoverishing some humanities program is alarming to me.  Its just that some things are not science.

There's really two components to ID:

A No-Go Theorem (http://en.wikipedia.org/wiki/No-go_theorem) on the likelihood of spontaneously arising life, or of it reaching some threshold in evolutionary development naturally.
...which leads to "the design inference", which posits that the characteristic of intelligence is able to overcome the problem established by the no-go: that life exist, but could not allegedly have arisen from a random process.

Now certain no-go theorems claim something is physically impossible, like transmitting information faster than the speed of light, some are about the provability in mathematics like Godel Incompleteness theorem, but the ID no-go theorem is about being statistically imprlausible- but what is implausible in a Big, Old Universe? Something like 1/Number of atoms in the universe is sufficiently low (2^82), and you can demonstrate this easily by thinking of DNA code 1/4^N where N = min num of base pairs for self-replication, where N~100,000 M genitalium. This is a very naive model, but it's a start: see George Chaitan's work for better maths: http://www.youtube.com/watch?v=RlYS_GiAnK8

The design inference is really Stephen Meyer's domain, and I'll refer you to him, this is much more a philosophic argument. One thing that's important to note for people who are dismissive of ID is that this is about reasoning about intelligence in the abstract, not the manifestation in physical form, not "some being".

What's my opinion? Could I get back to you in 300 years? We'll finally have data on thousands of other planets and whether any of them have ever harbored life, and that I think would be the falsification of ID if other life was found. But I think both a barren universe, and one with other life are both plausible given what we know now. That's why I don't get why people are so staunch on this issue: it's impossible to know the one key thing we need to know in this debate in our lifetime. But in a few generations we in fact will have this answer. We get to live in some interesting times.


Is it possible for two people to repopulate earth? Today I was wondering this question whether it is possible for two people to repopulate Earth.

What if everyone else disappeared, except for two people (man & woman)? Can they repopulate? In that case, what are the odds against and in favour of that ever happening?

Well, mathematically it might be possible. But, I would rather worry about the low amount of genetic diversity that the growing population would have, which would make it extremely sensitive to external stresses.

To repopulate earth from such a small pool of genetic material, one would need an organism that is much more sturdy as compared to humans in extreme conditions, multiplies fast and is much more prone to mutations that actually convert to a phenotypic significance so as to increase the genetic diversity of the total population.

Update (after receiving many comments)

Before you read answer, note that this is hypothetical question and I am trying to answer it by creating hypothetical situations with some reasonable numbers

Short answer: Yes, hypothetically it is possible for two people to repopulate earth.

Quoting from Popsci website:

  Maybe, but they'd be very busy

Hypothetically it is possible but practically it has very less probability. Let us calculate probability of repopulating earth to it's 10% population.

Let us assume one female can give birth to 50 children throughout her reproductive life spam and assume there is no death/disease/natural crises and other factors which might restrict this 'ideal' growth.
To get 'maximum' number of births in next generation, assume she gives birth to 1 male child and 49 female children. Probability of having that is $\left(\frac{1}{2}\right)^{50}$.
Now again assume all 49 females gives birth to again same ratio of children (too much work for male :P). Probability of happening this will be $\left(\frac{1}{2}\right)^{50+49}$.
If you go by same logic, you need at least 5 generations to make 10% of earth's population. That gives probability of $\left(\frac{1}{2}\right)^{50+49+49+49+49+49} = \left(\frac{1}{2}\right)^{295}  = 1.57 \times 10^{-89}$

It is much lower than probability of we finding electron in nucleus :P

Now if you want to consider little bit realistic model where each couple will have two more couples and so on, It will need at least $2^{30}$ generations to repopulate to 10% of today's population. Considering average lifespan of 60 years, it will take $2^{30}\times60 = 6.4 \times 10^{10}$ years to do that. It is higher than entire biological evolution time scale.

Point of these calculations are to show that, hypothetically repopulating earth with one couple is possible but very less probable.


Why does spiral or annular thickening occur in water conducting plant vessels? From what I behold, spiral and annular thickening of xylem and trachied cell walls leaves a lot of not thickened regions of cell wall. Lignin is the material which prevents water from escaping these water conduits. If lignin is absent from certain regions, does not that mean that water flows out of the xylem vessels and trachieds through their cell walls? If so, is not this disadvantageous to a plant? Why can't a plant simply thicken the cell walls with uniform lignin deposition, only sparing pits to allow lateral flow into the required tissue? I would appreciate your kind response.

Non uniform lignification of xylem vessels is beneficial to a plant in that it enables growth. It is at the unlignified parts of plants that growth occurs since fully lignified tissues are dead and so can not grow. Spiral and annular thickening allows for vessels to elongate and thus allows tissues to expand without breaking the vessel walls.

Water cannot just go on flowing from plant cells because they are not lignified, plant cells have cellulose cell walls and cell membranes which prevent water loss. In addition, water in the xylem is not under pressure so I do not think water would be able to flow out of the xylem vessels except in cases where water is forced to move to adjacent phloem tissues by osmosis during phloem translocation.


Why are riboswitches mostly present in bacteria and not in eukaryotes? Riboswitches are a rather elegant way to regulate gene expression without any additional machinery. A small ligand binds to the mRNA and directly influences transcription or translation.

Most of the known riboswitches are found in bacteria, there are few examples of riboswitches in eukaryotes. There are no classical riboswitches in humans as far as I know (there is one example, but triggered by a protein and not a metabolite), it seems that more complex organisms tend to use other methods of gene regulation.

Are there any known reasons for this? What are the drawbacks of regulating gene expression with riboswitches compared to using regulatory proteins? Is there an explanation for the lack of riboswitches in more complex organisms?

You get higher accuracy and more timely control at a post translational level (think about the time it takes to affect a pathway with cofactor stimulation compared to gene expression stimulation). You also have more points of control throughout the pathway if you affect activity post translationally allowing for a more complex interaction between stimulating and repressing factors.


Why our body does not produce polyunsaturated fatty acids? Our body does not produce two polyunsaturated fatty acids (PUFA): linoleic acid and alfa-linolenic acid.

I am thinking reasons for it.

Saturated fatty acids have more energy than unsaturated.
Saturated fatty acids do not need NADPH and some many other enzymes as unsaturated in beta oxidation.
This means that less storage places in the body needed to have energy in the form of saturated fatty acids such as for muscles and heart.

There are four main reasons why our body does not use PUFAs as the primary source of the energy but saturated:

PUFAs lower metabolism and interfere with thyroid function
PUFAs spontaneously oxidize, speed up the process of glycation, since too much glucose
PUFAs decrease mitochondrial respiration - more oxygen and CO2, less lactate

where one reason is missing.

One complication of PUFA is

PUFAs promote diabetes, cancer, inflammation and biological stress

which cannot be thought as a reason why our body does not use PUFAs as the primary source of the energy.

There are positive sides of the PUFAs when they are used in other way.
- PUFAs replace trans fats and saturated fats in certain types of foods.
- PUFAs can help your body to eliminate high cholesterol levels
- PUFAs decrease the risk of heart disease

There are also some types of essential fats that your body cannot produce on its own - omega-6 and omega-3 fatty acids.
PUFAs are used to create these.
You can get PUFAs from vegetable oil, fish and nuts for instance.
Balanced diet is essential.

Normal lipid metabolism depends directly on food lipids.
Both the essential fatty acids and right amounts of PUFAs can be obtained from food.
Body converts the essential fatty acids to long PUFAs, which serve as the precursors of prostaglandins and leucotrienes for instance.

There are so many reasons why our body does not produce polyunsaturated fatty acids.

Why our body does not produce polyunsaturated fatty acids?

Simply, it’s because our bodies add double bonds in MUFAs by delta 9 desaturase which adds double bonds between delta 9 and delta 10 carbons, hence additional double bonds can be formed between existing double bond and the carboxilc group but cannot be formed between the existing double bond and the omega carbon. As a result, our body cannon synthesize parent omega 3 alpha linolenic acid and parent omega 6 linoleic acid, but can form timnadoneic acid which is an omega 3 PUFA


What is the evolutionary purpose of the topology of the human ear? What is the evolutionary purpose of the topology of human ears? I understand why the ears may have a funnel-like shape but if the various "hills and valleys" do not amplify incoming sound, what purpose do they have?

Humans do not have the ability to move their outer ear in response to sound. Many animals can do that, and use it to determine the source of the sound waves. Thus, human outer ears are equipped with many "hills and valleys". It does not provide amplification (because the waves can lose their energy bouncing around the ridges), but rather gives the brain more information about the sources' location in space. The brain calculates that location by determining minute differences in the time it takes for the sound to reach sensory cells in the inner ear on both sides. The shape basically attenuates the raw information. That way you get different properties of the sound wave that enters your ear depending on the angle at which it fell on you outer ear.

Evolution doesn't have a purpose. In that light, it's quite possible for an ear to be poorly adapted to hearing - which in fact it is compared to other species.

Stereo hearing (two ears, so you can better detect where the sound is coming from) is heritage from our ancestors, and I know for a fact it didn't evolve further in humans because there was no evolutionary pressure.

In any case, the topology isn't exclusive to our species and is heritage from our mammalian lineage. At some point in our lineage, the species/individuals who had this topology of the ear were able to gather sound waves better and that affected their survival so they passed on the trait to their offspring. Ear topology didn't evolve in humans.


What bird is this (found at Alice Springs Desert Park in Australia)? I was reviewing photographs of the animals we found on our trip to Australia during the past September and I cannot find what is the bird in the picture. It was found inside Alice Springs Desert Park, so it has to be a native bird, same as all the others.

Could anyone please help me?

It is a Cisticola exilis as stated by @cezar
If someone has any objection please reopen this.


What British bat is this? What kind of bat is this? I saw it flying quickly between trees in Buckinghamshire, UK, at about 4pm in September (so about three hours before sunset). I think it might be a common noctule but I was surprised to see that there are something like fourteen other British species to choose from.

Sorry the photo quality isn't amazing but it was hard to capture anything at all!

I would guess that it's a noctule (Nyctalus noctula) also.  The Bat Conservation Trust has a nice UK section with fact sheets for the 18 different species of bats found there.  It seems you can rule out the long eared bats by the photo and the pipistrelle because you didn't mention it flying eratically.  The fact that it was out so early seems to narrow it down to either the noctule, which is usually the first to appear, or the leislers (Nyctalus leisleri) which appears shortly after the noctule.  A distinguishing feature of the noctule is a mushroom shaped tragus, and for the leislers is long fur around the shoulder and back.  Although this is a great photo, it's going to be hard to make a definitive determination without knowing size and some of the other finer details.  Photos of the noctule and leislers can be found on the linked data sheets and the link to the UK section can help you determine if there are any other possible candidates I missed.

It is a Big Brown Bat (Eptesicus fuscus).

From Wikipedia:

The big brown bat (Eptesicus fuscus) is a widespread species of bat found throughout North America, Central America, the Caribbean, and extreme northern South America.

It is a relatively large microbat, weighing 15–26 g (0.53–0.92 oz).

Adult body length is 110–130 mm (4.3–5.1 in). Its forearm is usually longer than 48 mm (1.9 in). Its wingspan is 32.5–35 cm (12.8–13.8 in). Its dorsal fur is reddish brown and glossy in appearance; ventral fur is lighter brown. Its snout, uropatagium, and wing membranes are black and hairless. Its ears are also black; they are relatively short with rounded tips. The tragi also have rounded tips. Its dental formula is
2.1.1.3
3.1.2.3
, for a total of 32 teeth.

One study of a population in Colorado found that their average life expectancy was a little over 6.5 years; the oldest known big brown bat was 19 years of age (!) and documented in Canada.


Can we produce synthetic red blood cells lacking antigens? I had an idea come to me during Biology class and I immediately asked my teacher, but she couldn't really answer the question, so I'll ask it here.

What are the limiting factors in the production of synthetic red blood cells with no antigens? I mean, we do have the human genome mapped, but am I naive to think that we have genetic technology capable of doing this?

If red blood cells are too complex to manufacture, is it feasible to manufacture much smaller particles of just hemoglobin inside small spheres of cell membrane and use that as a temporary replacement for red blood cells?

(I was at a medical research talk a while ago and one professor was explaining that there are many other proteins bound onto a red blood cell that aren't of the ABO or RH system. Normally this isn't a problem for recipients who only occasionally received transfusions but for people who need a long-term supply of blood, their bodies do get sensitized to the foreign proteins and will eventually start attacking the foreign red blood cells).

Actually there are such particles. It is estimated that about 20% of the hemoglobin (HGB hereafter) is in HGB vesicles (HbV hereafter) formed by RBCs. So sure, it is possible to use small particles instead of RBCs, but these vesicles have major and minor antigens on their surface. According to some of the articles they cause other complications too by blood transfusions and they are destroyed by the immune system within 3 to 7 days. So they don't solve the problem.

In Vivo Volume and Hemoglobin Dynamics of Human Red Blood Cells
Artificial Oxygen Carriers (Hemoglobin-Vesicles) as a Transfusion Alternative and for Oxygen Therapeutics
Red blood cell vesiculation in hereditary hemolytic anemia
The red cell revisited--matters of life and death.
Red blood cell microparticles and blood group antigens: an analysis by flow cytometry
Hemoglobin-Vesicles as Oxygen Carriers
Physiological Capacity of the Reticuloendothelial System for the Degradation of Hemoglobin Vesicles (Artificial Oxygen Carriers) after Massive Intravenous Doses by Daily Repeated Infusions for 14 Days

HGB vesicles without major and minor antigens are not a perfect solution either (I think), because the immune system tends to attack such things. For example by viral infections the MHC1 levels are low (in cells with nucleus) to avoid T cell response and the NK cells does not like that, so they destroy such cells. I am almost sure something similar would happen with this kind of vesicles as well. At least afaik. the immune system checks not just the presence of these antigens, but their composition as well. So if a RBC is under stress, then it changes the antigen composition on its surface and the leukocytes destroy it if necessary. According to some of the experiments PEG can cover HbV antigens and increase immune compatibility, so having less surface antigens seems to be a better choice than having more.

Development of a Synthetic Blood Substitute Utilizing Hemoglobin Vesicles
Biocompatibility of Hemoglobin Vesicles, a Cellular-Type Artificial Oxygen Carrier, on Blood Cells and Plasma Proteins In Vitro and In Vivo
Artificial Oxygen Carriers, Hemoglobin Vesicles and Albumin−Hemes, Based on Bioconjugate Chemistry
Hemoglobin Vesicles, Polyethylene Glycol (PEG)ylated Liposomes Developed as a Red Blood Cell Substitute, Do Not Induce the Accelerated Blood Clearance Phenomenon in Mice

HGB vesicles have another problem. The HGB inactivates in them without reduction (metHb formation). Only Fe2+ HGB can carry oxygen. This can be solved with methylene blue according to this study.

Red Blood Cells Donate Electrons to Methylene Blue Mediated Chemical Reduction of Methemoglobin Compartmentalized in Liposomes in Blood
Inhibition of methemoglobin formation in aqueous solutions under aerobic conditions by the addition of amino acids

We cannot use free HGB either, because it would decrease the NO levels and lead to endothelial dysfunction. I think to small particles would have the same effect because of increased surface.

Mechanisms of Slower Nitric Oxide Uptake by Red Blood Cells and Other Hemoglobin-containing Vesicles
Microparticles in stored red blood cells as potential mediators of transfusion complications
Removal of Cellular-Type Hemoglobin-Based Oxygen Carrier (Hemoglobin-Vesicles) From Blood Using Centrifugation and Ultrafiltration

According to other studies RHSA-heme (serum albumin bound to synthetic heme) is another option. It seems to be safe if you replace only 20% of blood volume (of rats). I think a complete transfusion is not safe, because it would reduce the NO levels as we already discussed. I have not found an experiment which does complete transfusion.

Safety evaluation of an artificial O2 carrier as a red blood cell substitute by blood biochemical tests and histopathology observations.
Exchange transfusion with synthetic oxygen-carrying plasma protein “albumin-heme” into an acute anemia rat model after seventy-percent hemodilution

So there is ongoing research in the topic. There is progress, but none of the current solutions is perfect I think.

Artificial blood Substitute is an artificially developed substitute for red blood cells which is use for transporting oxygen and nutrients to the body cells and transporting back carbon dioxide, ammonia and other waste products away from cells.

Six potential application markets have been identified based on the possibility of replacing donor blood in critical medical treatments-

Injuries,
Cardiovascular diseases,
Malignant neoplasms,
Neonatal Conditions,
Organ transplants,
Maternal condition


metabolism preference by the body What I know about metabolism is that,during exercise body uses carbohydrate first then fats and then protein,so my question is why does body prefer glucose first as fuel for energy and what makes glucose biochemically preferred molecule to be metabolized first

None of them can be directly use for energy. We all talk about aerobic oxidation, which is the major process for metabolism.

They all need to go into the tricarboxylic acid cycle (TCA cycle) and oxidation phosphorylation to produce ATP, which is the energy used in organism.

For glucose, they can break down into two pyruvate and enter the TCA cycle. That is the fastest pathway organism use to produce energy.

For fat, since they have long carbon skeleton chain, they cut off 2 carbon compounds from the fatty acid every time. And under a series of process, it become pyruvate and go into the TCA cycle. So it really takes long time and complicated pathway to oxidate the whole fatty acid molecules.

For protein, it is much more complicated. Since protein is not energy store form, it need to become a energy store form first. First it need to be degraded into amino acid, and different amino acids takes different procedure to go into the TCA cycle. Here is the picture I found on the book  by John L. Tymoczko, Jeremy M. Berg and Lubert Stryer.

In sum, glucose is the fastest energy form that body can use to take metabolism, oxidate fatty acid or proteins take much more complicated pathway.

I already forget all of the structure of carbohydrate, fat and also protein. But I still remember the reason for body using order of these compounds is related to the structure.

None all of carbohydrate can be directly used, only simple carbohydrate, like glucose, can be directly used.

For fat, it can be turn by carbohydrate for storage, and of course they are storage form, then they won't be easy for using. Even fat need to be used, they will turn to be carbohydrate again then using.

For proteins are another story, they aren't storage form, but they have some ability to form carbohydrate. So if the body is very starving and there is no other resource, the body will begin turn the protein to carbohydrate for using.


Does body temperature affect human lifespan? If a human body were somehow to be kept at a cold temperature (say 30C) for the entire life of the given individual. And somehow the brain could be fooled into thinking that this 30C feels nice and warm.

Would that given individual live longer as a consequence?
What effect does a tempreature have on lifespan?

I am assuming that you are referring to a baseline human cooled to a core body temperature of 30C from birth. I am also assuming that you are ignoring the fact that the environmental temperature (and thus the temperature of the extremities) has to be much lower than 30C to cause a core temperature of 30C. Thus, I am ignoring hypothermia-based gangrene, necrosis, and extremity loss.

If you had a normal human with a 30C core temperature starting at birth, I have doubts that it would live any longer than a human at 36.8C. Unlike flies, which are ectotherms, humans need to have a more or less constant temperature to successfully complete most of their metabolic processes efficiently. Since humans are not built to withstand extremely low temperatures, it is likely that lowering the core body temperature to 30C will cause it to have organ impairment, causing organ failure, followed by death. Though you might be able to "fool" the brain on thinking that 30C is normal, it is unlikely that the organ functions can follow. It could be possible to breed successive generations of humans in ever-lower temperatures, but it is unlikely for a baseline human to withstand such a large temperature drop. Sensory neuron adaptation =/= bodily adaption. However, lowering the core human body temperature by 1-2 degrees (typical of sleep) may have a chance of altering a human's lifespan in a more meaningful way. Though cooling may prolong the lifespan of temperature-conformers and single-celled animals, it is unlikely that the same can be said for endotherms. Endotherms have had biological processes that run on a fixed temperature for a long time already.  One more thing: @Hermann: Their core body temperature may not have been much lower than the baseline.

Movement is life. If the human body where to undergo this kind of temperature that would be below the normal temperature for the human body, we would in fact either have to move more and or do more as in eat, exercise, communicate etc. If your body did not have this mental capacity basic survival skill you would be in the process of slowing the function of your body down leading to death.

Also the person who had swam in freezing water had a better tolerance to the cold than normal, but this does not mean that if a person had the capacity to tolerate cold temperatures that this kind of treatment of the body whould be good for you.
Over a short period of time your body can undergo extream circumstamces so it was a basic survival skill that had kicked in from the metal material of that persons being telling their physicsal as in nervous system that if they were going to survive they would have to move in order to regulate their body temperature.


In endochondral bone formation, why does only hyaline cartilage get ossified to form bone? There are three types of cartilage: hyaline, fibrous and elastic cartilage.
Fibrous cartilage does not have perichondrium...so it does not take part in ossification because perichondrium needs to develop into periosteum.
Hyaline cartilage has more matrix in comparison to elastic cartilage. Hence, during ossification the quicker spreading of calcification of the matrix will lead to the death of the chondrocytes which will develop into osteoprogenitor cells. Is my theory correct?

yes this is correct, i think hyline cartilage gets transformed to bone more quickly due to the fact that is has the matrix which is closest to bone in terms of density, also the cells are located more closely, therefore it is easier to convert this tissue to bone.


SARS-CoV-2 : does vaccination provide a better immunity than being sick and recover? I recently read in the news that countries are thinking to offer a "green passport" based on the vaccination against SARS-CoV-2, allowing vaccinated people to do things with less restrictions than the non-vaccinated :
New York Times
BBC News
Bloomberg
IATA
If those passports are to be put in place, why do they not include people that were exposed naturally to SARS-CoV-2, this number being bigger days after days (60 millions people, 17/02/2021) ?
Does that mean that vaccines offer more immunity than being exposed naturally to SARS-CoV-2 and recover ?
My questions don't address the ethical aspect of implementing a "green passport", I'm only trying to figure out if vaccination offers more immunity than being exposed to the virus. A possible answer to this question can simply be "we don't know so far" because of the lack of feedback on a long term view.

As @MikeyC and @jamesqf pointed in the comments, vaccines are better documented than the actual cases, whereas qualifying the immunity conferred by having recovered from Covid-19 would require large cohort studies.
However, one can follow up thir argument in many ways:

It would be reallys urprizing, if large-scale cohort studies have not been udnerway or already available by now: while nationwide testing may still be lacking in many countries, masive and repeated testing campaigns in specific regions are not a rarity by now. (see, e.g., here and here)
Hospitalization is not a necessary requirement for attesting a covid case - one could test unvaccinated persons for the presence of the Covid-specific antibodies.
There is much still unknown about the vaccines themselves - particularly about whether the immunity conferred is a lasting one, and whether.
Moreover, the fact that many people might have lived light cases of Covid does not make it easier for attesting the efficacy of the vaccines. Public authorities openly warn that the vaccine might be inefficient and a vaccinated person might be still a carrier of the disease.

In other words, "we don't know" is the most likely answer.
As the OP, I forgo the ethical issues raised by the "green passport" - these are not only those related to the restrictions on the individual freedom, but also the discrimination against the individuals to whom the vaccine is counter-indicated (e.g., allergics, pregnant women, people with weakened immunity, etc.)

It is said vaccines are over 90% effective. But I think natural obtained antibodies from Covid-19 and recovery offer more immunity than vaccines. The problem is that no pne can be sure to survive the infection.


Specificity of the adaptive lymphocytes T cells are known for their ability to bind multiple antigens, owing to the degeneracy of the recognition sites on their receptors. [I] When examining the structure of the T cell receptor, we can observe the ɑ and β chains which have a highly variable region, in their extracellular domain:

From what I understand, TCR degeneracy means that one receptor can bind to different antigens.

In comparison, the B cell receptor consists of a recognition site that contains a membrane-bound isotope of immunoglobulin. Again, from what I gather, variation in both the Ig on B cells and the TCR occur as a result of genetic recombination. [II]

Question:

Does the membrane-bound Ig in the BCR exhibit the same degeneracy as TCRs? Does variation caused by V(D)J recombination work the same way for both these receptors?

References:

[I] https://en.wikipedia.org/wiki/T_cell_receptor

[II] https://en.wikipedia.org/wiki/V(D)J_recombination

[Images] http://what-when-how.com/acp-medicine/adaptive-immunity-antigens-antibodies-and-t-cell-and-b-cell-receptors-part-2/

This is incredibly oversimplified, but the short answer is that both T and B cells can have degenerate recognition, though the molecular mechanisms are somewhat different.

T cells recognize linear sequences of amino acids that have been excised from their parent proteins, from 8 to 16 or so amino acids long, and that are associated with MHC proteins.  The association with MHC proteins depends on the specific sequence of amino acids, and you can think of this association as depending on a number of amino acids (let's say 4 or 5) that point "down" into the MHC.  That leaves maybe 4-10 amino acids pointing "up" that can interact with the T cell receptor.  If you search for a random set of 4 amino acids with a given spacing, it's quite likely that it will turn up several times in a large protein database; even more often if you allow some degeneracy (similar amino acids can substitute sometimes).  Therefore, yes, T cells tend to have a moderate amount of degeneracy in their epitope recognition.  However, while search a whole database may find duplicates, the degeneracy is not terrible, and the MHC binding requirement also reduces it quite a bit. Also, of course, during T cell development, TcRs that have broad and degenerate recognition of many structures are selected against.  So T cells are definitely cross-reactive, and sometimes extensively so, but in single individuals it's probably not a common thing.  (Ray Welsh and Liisa Selin have looked at cross-recognition between viruses and find quite a bit of cross-reactivity, though, so this may be understated.)

Antibodies, unlike T cells, recognize conformational epitopes rather than linear sequences.  However, just as with linear epitopes, it's not impossible for two unrelated proteins to end up with similar conformations, even with rather different amino acids.  As well, antibodies can be more or less "forgiving" in their recognition; some are extremely specific, but others can interact with a wider range of shapes.  You can imagine a "flat" antibody binding surface that is rather generic, that could interact with many different shapes. Again, B cells with broad cross-recognition are selected against during development, though not as rigorously as are T cells.

First of all, you have to distinguish between the term antigen and epitope. An epitope is a specific amino acid sequence that is recognized by the TCR/BCR. The epitope does not have to be a linear amino acid sequence, a BCR can also be recognize conformational epitope. An antigen is composed of multiple epitopes. Since there are many conserved structures among the proteins, it more than convincing that one TCR can bind more than one antigen as long as the antigens contain the epitope (https://en.wikipedia.org/wiki/Antigen).


Is epimysium same as fascia? I have read that epimysium is dense regular connective tissue made covering the a muscle like bicep brachi. at the same time we have fascia that is made of dense regular tissue and covers muscles. so are they same or different how can we describe it and differentiate it?

Epimysium is the specialized fascia located at the muscle.

  Epimysium is a layer of connective tissue, which ensheaths the entire muscle. It is composed of dense irregular connective tissue. It is continuous with fascia and other connective tissue wrappings of muscle including the endomysium, and perimysium [1].

The fascia that covers muscle is named deep fascia:

  The deep fasciae envelop all bone (periosteum and endosteum); cartilage (perichondrium), and blood vessels (tunica externa) and become specialized in muscles (epimysium, perimysium, and endomysium) and nerves (epineurium, perineurium, and endoneurium) [2].

References:

Wikipedia contributors, "Epimysium," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Epimysium&oldid=540536396 (accessed June 27, 2014).
Wikipedia contributors, "Deep fascia," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Deep_fascia&oldid=593605746 (accessed June 27, 2014).

Fascia is a widely used yet indistinctly defined anatomical term that is concurrently applied to the description of soft collagenous connective tissue, distinct sections of membranous tissue, and a body pervading soft connective tissue system. Inconsistent use of this term is causing concern due to its potential to confuse technical communication about fascia in global, multiple discipline- and multiple profession-spanning discourse environments. The Fascia Research Society acted to address this issue by establishing a Fascia Nomenclature Committee (FNC) whose purpose was to clarify the terminology relating to fascia. This committee has since developed and defined the terms a fascia, and, more recently, the fascial system. This article reports on the FNC's proposed definition of the fascial system.

Reference:
http://www.bodyworkmovementtherapies.com/article/S1360-8592(16)30259-5/fulltext


How can the layperson test whether a UVC light sold as "germicidal" is a fake or probably the correct wavelength? Are there simple ways to test whether a light is likely short wave / UV-C, or at least whether it is probably a fake?
Real Example:
2 lights are allegedly germicidal and supposedly emit germicidal 254nm radiation.

Light 1 darkens transition glasses and emits the smell of chlorine / ozone.
Light 2 does neither but appears much brighter than Light 1.

Does the ozone smell of Light 1 entail that it at least emits radiation within the UVC band?
Assuming the glasses do darken outdoors and do darken in response to Light 1, given that they do not darken with Light 2, is it safe to conclude Light 2 emits no UV at all?

You can do the banana test to identify if it is real or fake.
Get a green banana and cover parts of it with a sticker you now need to expose the banana with the uv light for about one hour,the green banana will get brown/yellow at the exposed part and stay green under the sticker if the uv-c light is genuine..
It is best to do this in a dark room and the banana can not be in a plastic bag or any covering as this might stop the uv-c light.
The uv source needs to be close to the banana for this to work.
If the color of the green banana stay the same after the test your uv-c light is fake.
Never look directly at the uv-c light and do not shine the light on your bare skin.
source https://www.reddit.com/r/BigCliveDotCom/comments/gj9ymb/uvc_the_green_banana_test/


Localization of B and T cell What does localization of B-Cell mean?? "Localization of B and T cell in allergens may not coincide". What does this statement mean? (I have not studied biology since last 8 years and now I am going through it because I need it for my research. So if someone can describe it in simple language it would be very helpful)

I think the reason you are having trouble discerning the statement is because it doesn't really make much sense, nor is it in my opinion sufficiently explained in the paper. The sentences preceding the it give a little explanation as to what the author may be getting at:

  So far, 1500 allergenic structures have been identified. Online allergen databases and allergy prediction tools are being used to find cross-reactivity between known allergens. Localization of B and T cells in the allergen may not coincide.

During an exaggerated immune response (allergy) the lymphocytes (B and T) will localize (travel or accumulate at) to the site of the antigen (allergen).

If I could guess I would say the author is stating that data has shown that no immune response is taking place (data generated by assessing the accumulation of lymphocytes near the allergen), despite the fact that these online allergen predictors say that an immune response should be generated.

The statement in my opinion moves to discredit these online allergen predictors.

I did look over some of the rest of the manuscript, and found two other ambiguities within.

The author does cite another paper in your sentence that may shed more light on this:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2686541/?report=reader

An overview of it provided little clarity however.

I fear that only  a crystal ball or this question addressed to the senior author may answer your question with complete certainty:

Dr. Rajat Kumar De
Professor
Machine Intelligence Unit
Indian Statistical Institute
203 Barrackpore Trunk Road, Kolkata 700108, India.

"Localization of B and T cell in allergens may not coincide".
That sentence is written poorly, it confuses more than inform.

What the author means is: The epitopes that B cells and T cells can recognize are not the same in one particular allergen.
We have to remember that almost all allergens are proteins and proteins are made up of aminoacids, and that's what make up epitopes.
For one same particular structure or say, an allergen, the T cell can only recognize LINEAR epitopes whereas the B cell can recognize LINEAR or CONFORMATIONAL epitopes (that is, they recognize a 3d-like structure and not just a sequence of aminoacids).

What I always tell my students so they can grasp the concept is that the T cells are able to "see" a photograph of a chair to recognize it. While a B cell can do that and even more it can actually "see" a chair for what it is.