text:
Can you bleed from your bones?
I was talking to my science teacher about the body specifically the red bone marrow.
She said that blood is created in the red bone marrow. Does that mean that if you were to cut a fresh bone open it would bleed?

What research have you done before asking it here? Bone marrow is a solid spongy tissue, and won't bleed.

@another'Homosapien' but don't harvasian canals have blood vessels and nerves?

@another'Homosapien' Yes. Harvesian canal. It ought to bleed right?

@Homosapien. I looked at the  make-up of a bone.

No one really knows where the term dry as bone came from, many assume it comes from sun bleached bone which was the easy way to dry bone for other uses.

I edited your question removing the last part of the question as it was unrelated to biology and the overall question. Feel free to rollback to your original question but I believe the edits will get you more upvotes for the attention you need to award the bounty. You could also add what you already know to the question to give answerers a starting point to go from

Yes, bones too bleed if they get damaged (break or bruise). This is because bones are highly vascularised organs and breaking of bones will indeed rupture the blood vessels causing bleeding. Main artery which supplies blood to bone is nutrient artery , others are epiphyseal, metaphyseal and periosteal arteries. Skeletal system receives about 15.6% of cardiac output.
Since bones contain very low percentage of water ( about 31% ) comapred to others like skin(64%),brain and heart (73%) and lungs ( 83%). So the saying "as dry as bone " stills holds well.

Sources:
1-https://www.mananatomy.com/basic-anatomy/blood-supply-bones
2-https://water.usgs.gov/edu/propertyyou.html

You can also have bone bruises, which I believe are the result of bleeding inside the bone.

Thanks for the information. It feels good to actually "know" people that will help me with questions. If you ever need anything tell me and I'll try to help.


text:
Excessive sweating in dry heat
It's pre-monsoon season here in India. The temperatures in the Northwest of the country really take a spike around mid April. Apparently the heatwave-like conditions seem to have announced themselves quite early this year. The mercury is at 42°C for most of this past week.
I'm new to this region and even though the relative humidity is quite low, such weather conditions prove unbearable to me. A few minutes walk down the Avenue and I start to sweat in bucket loads.  However, I find locals here don't sweat too much even in this hell of a weather. They say this weather is still bearable and that the monsoon phase proves to be the worst.
Having witnessed monsoon in other parts of the country I find favorable weather conditions prevailing at that time. The rain brings down the temperature and the air seems to get cooler. Most people here and elsewhere in the world would disagree with me on that. They say humidity is the worst and than dry heat can be combated by drinking enough fluids. I also see people sweating more in humid conditions compared to in temperatures of 42°C. The opposite applies to me. I barely break a sweat in temperatures of mid 30s despite there being high humidity.
What is this anomaly? Is there evidence that some bodies are just meant to excel in certain weather conditions while finding life difficult in others? Kindly help me understand the science behind it all.

It's not so much that you sweat more in humid conditions, but that the sweat doesn't evaporate as fast.  Beyond that, I'd say you have two kinds of adaptation going on.  First is personal adaptation: since you're new to the region, your body hasn't gotten used to the heat yet.  (Especially if you spend a significant amount time in air conditioned buildings.)  Second is genetic adaption: the locals and their ancestors have spent millenia in that climate.  People who couldn't handle it either left or died.

My assumption is that if you're sweating excessively, you could also be suffering from a condition called hyperhidrosis. This is a condition whereby your hands and feet sweat excessively. I would suggest that you try looking into using a solution like an iontophoresis machine to be able to treat this condition. I too have suffered from sweaty hands for a long time, and after trying different options, I found that using an iontophoresis machine provided me with the best results.

Suggesting the OP to use a device to combat a condition based on your assumption would be a bad way to answer this question.

I'm pretty sure I don't suffer from hyperhidrosis. I don't sweat excessively unless I'm working out or being physically active. I figured my choice of clothes had something to do with my woes against dry heat. Simply tricks such as walking in shade and walking at a slow pace as opposed to a brisk one, latter being inherent in nature, have made a huge difference.

Another thing I noticed about my body is that it likes being wet. As long as I have water on my skin, my body stays cool. However, the moment water has dried off, the body gets hot. I notice this after the bath. My understanding is that there's nothing unusual about it. But this phenomenon absolutely plays to my advantage in humid weather, where the sweat doesn't evaporate. With sweat on the skin, acting almost like water, my body doesn't warm up too much.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

sort: votes


text:
Why Poisson Process for neural firing?
I am new to the world of neuroscience and I would like to understand how come every paper in neuroscience that I read uses a Poisson process to model neural firing. Do I just have a biased sample of the papers I chose to read, or is it a biological fact that neural firing must follow a Poisson process? Why can't it follow, say, binomial, since it either spikes or it doesn't in a given time period. Also, where can I read more about how such a biological phenomena was discovered?
A small correction: I do appreciate the explanation on the difference between the two distributions but I am a statistician who is trying to understand my neuroscience colleagues and communication is key in statistics. I am just trying to comprehend why everyone in the field is using Poisson as opposed to using Binomial even when the bin size you decided on is sufficiently small. In other words, why would you not use Binomial, the bin size is so small that your data is only 0's and 1's (i.e. the spike happened or did not happen within this bin). Is it because Poisson counts discrete occurrences in a continuous domain? What discipline-specific papers would you recommend to read that justify/discuss/explain the continuous domain on neural spiking?

At the limit of small bin size, there isn't much difference. For large bin size, Poisson works better since you don't need to know the max # of events. Also there are plenty of non-Poisson point process models out there in neuroscience. I tend to use autoregressive point process models.

You can read about the differences between a binomial and poisson distribution at this other question on Math.SE.
First, since spikes are discrete events, it makes most sense to use a probability distribution that is discrete. A Poisson process is a process where an event occurs randomly with no "memory" for how long it has been since the last event. A Poisson distribution is the number of events if you integrate draws above some threshold from an infinitesimally small uniform distribution. Therefore, the Poisson distribution is the distribution you choose if occurrences of an event are only dictated by an underlying rate parameter - this turns out to be a reasonable, if ultimately false, assumption for neurons.
There is definitely no biological fact that neurons must follow a Poisson distribution - in fact, no neuron can be truly Poisson because, if nothing else, the refractory period makes it impossible. Rather, Poisson behavior is sort of the simplest behavior you would expect from neurons in a system where they are firing occasionally due to random noise - sort of a "null hypothesis." For many modeling approaches, this is close enough, and it allows the modeler to avoid making more nuanced assumptions. It turns out to be a decent assumption when you look at individual cells, but if you look at populations the activity deviates a lot from Poisson.
Note that the Poisson distribution is often only valid for spontaneous data; it is possible to use a nonstationary Poisson distribution to model responses to some external stimulus, but the results are likely to deviate more from experimentally derived data.

Thank you for your response. I am a statistician and discreteness and independence are also the features of Binomial distribution, so even in those cases when bin size is small enough that you data is 1's and 0's why would you not use Binomial? Is it because Poisson counts discrete occurrences in a continuous domain?

and wouldn't it make more sense to use Binomial if there is a refractory period between spikes? Sorry, I am just really lost on the whole process of neural spiking even after 1 MOOC course and a ton of Youtube videos (I made sure those are from reputable sources at least)

@Jen A poisson is essentially equivalent to integrating a binomial with infinitely brief windows (and a correspondingly infinitely small probability). Neither can really account for a refractory period. For spike rates in most typical neurons, the rates are low enough that you rarely generate spikes within a refractory period, but an alternative is to generate interspike intervals (ISI) from an exponential distribution (this is exactly the same as drawing Poisson counts), and discard very short intervals (this part deviates from Poisson slightly).

@Jen Poisson and binomial become nearly identical for small enough bins but the larger your bins the more they deviate, and the underlying function of the binomial just doesn't describe spiking processes very well: Poisson distribution works well when you know the underlying rate of events, Binomial works when you know the probability in a given interval. The former is a better description of the way people usually think about spiking neurons.

just a silly clarification: "when you know the probability in a given interval" -i.e., the probability of a spike (within a small bin for example) occurring/not occurring?

@Jen Yes. If you are talking about a single bin then you have the special case of a Bernoulli distribution. If you have a sequence of bins then the two parameters for binomial are a) the probability within each bin, and b) the number of bins. The binomial distribution will describe how many of those bins are occupied (i.e., by a spike).

When trying to look at the firing of a neuron as a way to encode information, a useful trick is to model each spike as a Dirac delta function. What this means is any time point is a "spike" or "no spike." It's binary.
http://www.cns.nyu.edu/~david/handouts/poisson.pdf
It doesn't tell you anything about the internal dynamics of the neuron, that is, its electrotonic properties, but at a "macro-level" looking at spikes as delta function is a good way to look at a rate code.
A Poisson distribution gives you the probability of a given number of spikes in a span of time if you know the average rate and are independent.  Because of this, you can model spike trains of "dummy" cells.
Neurons are very irregular. This has to do a lot with stochastic forces that make the interspike intervals (the time between two spikes) highly unpredictable. For convenience, a random process is used to model them. At the higher "systems" level, patterns emerge and this is how your brain makes sense of it all.
Thus, you can model on three scales:
Individual Cell, dynamical system (e.g. the Hodgkin-Huxley model)
Individual Cell, rate code (e.g. a Poisson distribution model)
Systems Neuroscience
https://www.tu-chemnitz.de/informatik/KI/scripts/ws0910/Neuron_Poisson.pdf

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
What is sequential passaging?
I have read a journal that describes sequential passaging with the purpose of measuring resistance development in bacteria. I would like to know more about how the method works ie. what does "passage" mean?
https://www.nature.com/nature/journal/v517/n7535/pdf/nature14098.pdf, Methods part, under resistance studies

Can you please link the article?

The word "passage" in biological research methods generally refers to transferring a part of a culture (cell/bacterial/animal) from old medium to new medium.

I am normally reluctant to cite Wikipedia articles, however, the one for Sequential or Serial Passaging explains it quite nicely.
In short:

In microbiology, sequential or serial passaging refers to the process
  of growing bacteria or viruses in iterations. In essence this means
  that a virus or a strain of bacteria will be isolated and allowed to
  grow for a period of time. After the sample has grown for some time,
  part of it will be transferred to a new environment and allowed to
  grow for the same period of time.This process will be repeated as many
  times as desired. The final product is studied, often in comparison with the original virus or bacterial strain to see whether it has evolved or any other changes have occurred.


text:
Database of cancer cells
I am looking for a database(or any kind of information source) of cancer cells, which has information about the speed of reproduction of these cells, how fast they grow, etc.
So I could make my simulation as accurate as possible, as close to reality as possible (I am working on developing a software that simulates how cancerous cells spread).
Edit

Are you interested in growth rates in culture or in vivo (e.g. tumours)

Okay, I am a noob in biology, so let me explain it like that.
I am using Voronoi graphs for simulation, so I think that I am interested in tumor level, how each cell interacts with each other, and thus how fast can cancerous cells overpopulate healthy(or other cancerous) cells.

I suggest making your title more specific. You should at least mention proliferation, growth rate or a similar term.

Are you interested in growth rates in culture or in vivo (e.g. tumours)

The National Cancer Institute (NCI) has a list of doubling times for a variety of commonly used cell lines, see
https://dtp.cancer.gov/discovery_development/nci-60/cell_list.htm
I my experience, these doubling times are quite stable/reproducible, provided that cells are kept in standard culture conditions. While doubling times differ a lot between cell lines, they are also very different in size, and larger cells tend to have longer doubling times so that the biomass growth rate is actually rather similar between lines.
Note: these doubling times refer to cell culture conditions. Actual tumors in vivo grow much more slowly, due to lack of nutrients, suppression by immune cells, and what not. Estimating cell growth rates in tumors is a much more complicated business, and I don't know of any database for that.


text:
Praying mantis identification
I found this praying mantis in Bangalore, India. It is around 6 cms in length and has a distinct marking on the forelimbs. Can I know the species ?

@charles, There's another angle. I'm pretty sure it is a mantis and in fact according to a taxonomical key that I found, I think it may belong to the genus 'Hestiasula' . I'm just waiting for a specific confirmation.


text:
Moth identification
This moth was found lying on the road in Bengaluru, India. Although it was damaged very badly from the under side, the wing pattern was still intact. Is it still possible to identify it?
It is 9cms from head to wing tip

Hi, the identification process is easier if you can tell us a bit more about it. It's better if you can provide an image without a flash (no bright light either). Where was this bug found (country, state, etc.)? How big is it?

Oh yes I'm sorry I forgot to mention, it was found in Bangalore

I have inserted a new picture taken under normal lighting conditions. Thank you for pointing out the error @Aravind Suresh

This is a hawkmoth, Sphingidae. One of the largest and arguably most beautiful of all moths. I am not familiar enough to  India to pinpoint the species, it might be a member of the genus Agrius or Manduca.
Here's a picture of a resembling, species from the Manduca genus.

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

@Charles the forewing is much longer than the body and covers the (hence much smaller) hindwings.  The forewing is also strongly curved towards the tip. I can't think of any other genus with this shape&size, but am open to learn something! The wing pattern is quite worn, at the tip of the left wing you can see through. That makes thw wing pattern less reliable in this case.

This isn't a hawk moth; the forewing venation is not correct for that family (it is possible to see that two anal veins reach the wing margin in the OP photo; compare with figure 5 on page 5 here; the veins aren't labelled there, but the anal vein is the last vein of the wing).

@Arthur I see the difference. However, I can't find in the text that this anal vein is a distinctive feature of all Hawk moths (though it very well might be). Do you have any better suggestions? AFAIK most Notodontidae and Noctuidae also have an anal vein reaching the outer margin.

@RHA while some elements of wing venation vary within Lepidoptera families, the number of anal veins reaching the wing margin in the fore wing isn't one of them (see here for another discussion of hawk moth wing venation -- sorry that there aren't pictures with this one; that same discussion lists other moth families which have the hind wings much smaller than the fore wings).

@Arthur I can't find anything about veins on that page.

@RHA sorry about that; I'd forgotten that not everyone is familiar with insect wing vein names.  It's in the fourth paragraph under the "Adults" header: the abbreviations R2 and R3 refer to the second and third branches  of the radius vein (the third major vein of an insect's wing after the costa -- at the leading margin -- and subcosta -- just after that); in the OP photo the forked vein we can see just past the fore wing apex is the last two branches of the radius: R4 and R5; the next five veins are the three branches of the media and two branches of the cubitus, all off the discal cell.


text:
Does chicken embryo form the disc called "discoblast" in the cleavage and blastulation of chicken?
This thread is related to my previous thread which is still unsolved mainly. I need to be able to compare chick and human cleavage and blastulation of zygote.
My friend says that

Chicken have discoblast, human not. That is the main thing to get the idea of the difference.

I know that chicken have yolk sac with yolk, while human have yolk sac without yolk.
My notes say that

Cleavage in birds is partial discoidal (embryo forms disc and cells called blastodisc are on top of the yolk).

So embryo forms some disc, lets call it #1. Some cells called blastodisc are on top of the yolk. So are the cells called blastodisc on top of the yolk and the disc #1?
What is the name of the given disc that chick embryo forms?
It seems that human is not forming the given disc. Apparently, the name of the given disc is discoblast, the thing he says is very important.

It is a mnemonic of two words: discoidal + blastula = discoblastula.
So it suggests that cleavage is partial discoidal in birds.
Embryo forms disc.
Cells called blastodisc are on top of the yolk.
It seems that the formed disc is blastodisc.

The cleavage in birds is restricted to the blastodisc lying on the top of the yolk towards the animal pole of the zygote, this type of cleavage is termed as discodial cleavage because the embryo forms disc and cells that are also on the top of the yolk.


text:
Is it possible to grow any kind of plant soilless (hydroponics)?
Hydroponics is a subset of hydroculture and is a method of growing plants using mineral nutrient solutions, in water, without soil. [wikipedia]
My question is if is it possible to grow any kind of plant soilless (hydroponics)?

Carrots and other root vegetables do not do well in hydroponics with LE(CSG)A ( light expanded [clay, shale, glass] aggregates).  Its not an issue of them developing but being drowned out.   The solution in industry has been to use dual-zone beds ( half peatmoss/potting soil and the other half LECA with a canvas sheet divider and careful attention to water levels ).

Are you asking about "all kinds of plants" or "some kinds of plants"?

Yes, There are a few i know of, a quick "air plant" google search will get you quiet a lot.
wiki 1
wiki 2
Edit: I just glanced through the hydroponics article, and now I wonder if my answer actual answers your question.

Thanks for quick reply, I didn't know about the title Epiphytes. I still think, there are maybe for some reason  "impossible to grow without soil plants" but I don't know. I want to wait and search a little more.

from what i have read so far, plants do not need soil to grow. You can grow potatoes in a pot just filled with water, they don't need the soil as long as they get the nutrients and oxygen from their surroundings.

....so I dont understand what you are trying to ask. @pikk

Yes it is possible, and as far as I can see, there should not be any plant which would be impossible to grow in a such an environment, just more or less difficult, although this is just my speculation.
I have myself grown tomatoes from only a liquid solution of minerals and nutrients, but you have to change the solution from time to time to prevent bacteria and fungi growing starting to grow in it. The reason why this is not a method used in industrious growing is because it is a lot more expensive than using soil and fertilisers, and more work.

Do you have a source for the fact that it is a lot more expensive and requires more work ? Thanks.

No, I was just thinking in general terms. Small scale use I'd say definitely (based upon my own experience) more work as you'd have to refresh the water constantly and probably more expensive depending on your sources of the required minerals. But I would assume that there are a lot different relationships if you scale things up enough.

Aquaponics ( aquaculture w/hydroponics ) dramatically simplifies water treatment/maintenance at the cost of not being able to grow high acidity or high potassium plants.  Otherwise 1000 gallon systems take only 15-30 minutes a day to keep maintained.


text:
Subtracting shared DNA with half-sibling
I want to note that I am not a biologist. I've been on a nearly 20-year search for the identity of the parents of my 4th great grandfather (not an easy task.)
I'm using ancestry.com DNA, GEDmatch, and family trees of my matches in hopes of using DNA triangulation to find my ancestors. In addition, I have a half-sibling who also had his DNA tested which allows me to find common ancestors on this side of the family.
I read the article "Relatedness" on the topic of inherited parental dna with two half-siblings and I'm not sure I understand what the writer means when she says:

In other words, you and your half-brother should be able to figure
out what part of your DNA came from your mom.  And if you subtract out
that shared DNA, what is left must have come from your dad!

My first thought was that a person and their half-sibling wouldn't inherit exactly the same DNA from their mother, could they? For example, the mother has two different alleles for some trait. Her son could get a copy of one and the daughter could get a copy of the other. Therefore, in the author's example, how could subtracting out the shared DNA with the brother give the girl the ability to identify exactly which DNA must have come from her dad?
I read on and the author addresses this by saying:

One brother inherited the green version of the mother’s chromosome 2, while the other brother inherited the blue version.  This means that none of the chromosomes match!  So testing wouldn’t tell the brothers which version of chromosome 2 came from which parent.
It turns out, though, that it’s really unlikely that siblings would
have two totally different versions of a chromosome.  This is because
of something called recombination.

She's talking on entire chromosomes here which is different, but it doesn't seem to address fully why the girl should be able to 100% identify what DNA came from her dad by subtracting the shared DNA with her brother. I read that half-siblings share 25% of the DNA, but the mother here surely contributed more than 25% to each of her children.
In practice, my half-sibling shows a genetic relationship to people on our shared parent's side that I do not (and likewise, I have genetic relationships to people on our shared parent's side that he does not.) Therefore, I'm positing that my brother and I each inherited some different DNA from our shared parent.
I would take the writer's word for it, but I'm confused. Where am I going wrong? (Sorry about the bad biology background.)

The website is just wrong when it says for DNA tests on a person and their half-sibling:

In other words, you and your half-brother should be able to figure out what part of your DNA came from your mom.  And if you subtract out that shared DNA, what is left must have come from your dad!

Consumer autosomal DNA tests do not identify which of the two chromosomes present in the sample a detected variant can be assigned to.  The tests show only the two variant values detected at each location tested, and not which chromosome they come from.
Using this data from two tests, comparisons can show stretches of chromosomes which have matching patterns of variants which indicate with good probability that the corresponding pieces of chromosome have the same origin.  The tests do not tell you about the source of the pieces outside these stretches.
Each of two half-siblings do get half of their autosomal DNA from their common parent.  On average, half of the DNA each gets from that parent will also be inherited by the other half-sibling, and so will show up as matching stretches when the tests are compared.  Thus half-siblings will show around 25% shared DNA (around half of the 50% that comes from the shared parent).
Given a matching stretch of DNA results, one can determine the DNA variants that came from the other, non-shared, parent for the locations within that stretch of chromosome.  However, the locations outside the set of matching stretches cannot be identified with a particular parent (without testing of the parents).
There are two spots on that web page that do get this right.  One is in this diagram:

In the above, the bracketed area does identify the associated parents, but the unbracketed areas cannot be so identified.  (The colors shown are not reported by the DNA tests, so you can't just "follow the color" to identify matching chromosome areas outside the brackets.)
The other spot the web page gets it right is in this paragraph:

By finding the shared DNA, the brothers can find the pieces of the 23 chromosomes that came from their shared parent, just like we did for chromosome 1.  Any genetic information from the DNA on the corresponding sites on the other 23 chromosomes will tell the brothers about their fathers.

Outside of these two places the web page seems to mislead one into thinking that all the DNA can be associated with the correct parent, which is not the case without the parents being tested.

Oh, that's really disappointing given it appears to be a Stanford public education outreach type of program in charge of the website's Q&A. Thank you!


text:
Size of deoxyribonucleotide
What is the diameter of each type of deoxyribonucleotide (if the types are significantly different in diameter, if they are fairly similar one value would suffice)? I.e., if a hole was to be created through which only a single deoxyribonucleotide could pass at a time, how small would it have to be?

DNA is about 20 angstroms wide, so each of the two strand is about 10 angstroms wide. That width is the average between a larger purine unit and smaller pyrimidine unit, so let's round up to 12 or 13 angstroms for the larger unit.

While this answer gives a reasonable approximation for nucleotides constrained in a double helix, it should be noted that nucleotides have conformational isomers and they could potentially be smaller when free in solution. Purines especially can form a syn conformation which is much more compact than the anti conformation found in B-DNA.


text:
A Designer Virus
An article at Wikipedia describes color changes that viruses have produced in tulips (without any human intention). And another article (elsewhere on the web) describes viruses that were designed to fight diseases in people. This makes me wonder:
Would it be possible to design a virus to produce certain coloration in tulips -- for example, if I want tulips to have white petals with blue streaks? Would this create a new strain of tulips that propagate that coloration without further human interference?

Welcome to Biology.SE! What research have you done before asking it here?

@another 'Homo sapien' In response to your comment I enhanced the question yesterday.


text:
Does all the citrus fruit contain Citric acid and Ascorbic acid?
While reading a sixth class book about acid bases and salts. I figured that that citrus fruits like lemon, orange etc.. contains citric acid. But in the same book they also given that amla contains Ascorbic acid. Amla being a citrus fruit should contain Citric acid. I am just confused with this.

Just tell me whether all the citrus fruits contains both citric acid as well as ascorbic acid.

I checked in wikipedia & also in oxford dictionary.

Welcome to Biology.SE! What research have you done before asking it here?

You might be interested in the meaning of citrus.

It seems most of the fruits has citric acid! @another'Homosapien'


text:
How does a cell know what function it has within an organism?
Given that all cells in a multicellular organism contain the same DNA (ignoring random mutations during mitosis), how does any given cell know what purpose it is supposed to have within an organism.
For example, how does a cell know to become a muscle cell, a neuron or a liver cell?

As this is a very shallow question, I've voted to close. Search the topic "epigenetic regulation", and you will find your answer. If anything specific about this topic confuses you, please open a new question and we will be happy to help.

Your question is basically answered in a full semester course in Developmental Biology. It is far to broad for this forum. Suffice it to say it has to do with chemokine gradients and signaling producing differential translation in the cells of a developing multicellular organism.

The answer to this question can be split into two parts: cell differentiation from stem cells and simple mitosis. Also, the answer I am providing mainly only applies to species that sexually reproduce.
During the primary stages of growth, immediately following the fertilisation of the female gamete, the zygote begins to divide. Most of these initial cells will not be specialised, they will be stem cells and these have the potential to asymmeterically divide. When they do this, each of the daughter cells will have a specific specialisation path to follow. Which path they will follow, muscular, neural etc. is determined by transcription proteins.
Once the stem cells have produced the correct daughter cells, the general structure of the organism will begin to take form. Once this happens and the cells have followed their development paths until they hit their final specialisation, mitosis takes over. This means that a muscle cell will divide, causing the organism to grow. A muscle cell, will only ever divide into a muscle cell, the same goes for all specialised cells. This is how an organism grows and maintains itself.
However, some stem cells do remain after the organism has matured. For instance, a mature neuron is unable to undergo mitosis, so stem cells are needed to allow for the production of new neurons to replace those that die, to take one example.
You can find out more here.

But how is specific path recognized ? Arent the stem cell equiped with the same transcription proteins and DNA ? I assume for each type of cells there are different genes, how they will evolve, but the stem cell must be told which genes are to be translated.

@Marvin Cell fate is controlled by intercellular signalling. A lot is not well characterized. See this answer: https://biology.stackexchange.com/a/24022/6307

But yet, the signalling toggles the dna demethylation and histone modification, which changes genes promotors. So two same stem cells with different fate dont have same intracrine hormones at the begining ?


text:
Why do food items expire?
Why do food items and medicines expire after sometime?

Because the FDA requires it.

There are a number of reasons

bacterial infection
fungi infection

Most fungi are not toxic in themselves but they release mycotoxins in the food, which are definitely toxic

Maggot infection
Other infections
Growth

E.g. a potato will slowly attempt to develop into a plant, slowly consuming the tuber (the tuber being the potato you would like to eat).

Oxidation
Unstable chemicals

Mainly for medicines. Note however that (from health.harward.edu; thank you @Charles for pointing that out):

Most of what is known about drug expiration dates comes from a study conducted by the Food and Drug Administration at the request of the military. ... What they found from the study is 90% of more than 100 drugs, both prescription and over-the-counter, were perfectly good to use even 15 years after the expiration date ... So the expiration date doesn't really indicate a point at which the medication is no longer effective or has become unsafe to use.

The main reasons are probably the first two (bacterial and fungi infection). Note that the list is incomplete.

Expiring food items is obvious: for fresh food, it's almost always due to bacterial or fungal decay (spoilage).
Oxidization and sunlight doesn't really ruin food; it might alter the taste or decrease its appeal, although it remains edible even by first-world standards. However, it might destroy vitamins and other nutrients.
Medicines are a different matter. Some chemical compounds are slightly unstable, with half-lives measured in years. Instability can cause the compounds to randomly break into subcompounds that are ineffective for treating the intended condition at best and poisonous at worst. Unlike food, it's imperative to keep medicines away from sunlight (and oxidation in some cases) as both of these can further promote instability and breakage into subcompounds.
On the comment that Charles posted about medicine shelf life being much longer than advertised: The reason why they underestimate the shelf life is that it's better to have people throwing out potentially OK medicine than to have it sitting on a shelf for 20 years, going bad and sickening people, and prompting numerous lawsuits against the manufacturer. This type of deliberate underestimation in the name of safety is common in engineering - usually with weight limits advertised below the real weight limit. For example, an elevator able to haul 6000 pounds might be advertised as only 2000 because the manufacturer knows there's always going to be a few idiots who disregard the posted limit.

Thanks @Charles for the link, it is helpful. I would not down vote personally. user1258361 does not make any opposing claim but mainly explain why there is a need for expiration date on medicine and what could happen to medicines.

"90% of more than 100 drugs, both prescription and over-the-counter, were perfectly good to use even 15 years after the expiration date" So 10% weren't perfectly good. In this age of excessive litigation, industry prefers to err on the side of extreme caution to avoid being sued in case they end up in that 10%.

Degradation of substances and chemicals don't happen only thru oxydation but also many other factors like light, microorganisms and othwr stuff. The chemical substance will also suffer a degradation without any external factors, and some are more likely to go thru such processes than others.

Food expires because its growing. Constantly. Every ingredient you put into making specific foods has a Date when its time has ended. Just like our bodies as we age. We are one year closer to expireing. We Grow old and Our skin starts to Wrinkle. Its just a way of life. If nothing ever expired we would over populate everything. Not to mention, if our foods didnt expire they wouldnt break down in our Bodies making it hard to gain nutrients from. Ending in a result of Death. We need the foods to break down in order to survive.

Umm... What? When food is thoroughly cooked, it isn't "alive" anymore and ceases to grow. The main cause of food expiration is due to decomposers (mostly fungi and bacteria) eating the food and converting parts of it into waste products ranging from "tastes bad" to "dangerous poison" depending on the decomposer. Oxidation and radiation exposure can slightly change the chemical composition of certain foods, although food generally remains edible after oxidation and irradiation.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Decomposition of human body after death
What causes decomposition of human body after death? Here it says autolysis, while Here it says that bacteria decompose the body. If bacteria decompose the body, why don't they do while we are living?

Bacteria don't decompose the body while your alive (or even when your at the office)
Because your immune system keeps the population safe, by eating them.
Both autolysis and bacteria cause decomposition.
But there are 2 types of decomposition. The kind that keeps you from being able to be rescusitated happens within 5 minutes at room temp after death.
This is oncosis.
The kind where you smell like French cheese happens later, as the cells pop and disintegrate, and then get eaten by bacteria, which release stinky chemicals.


text:
Electric Shock To Human Body
What happens in our body when we get an electric shock?

Many different things happen, and there are various reasons why people survive.

Ok. So, first of all, it depends on the power of the shock.
This relates to volts (electrical pressure) and amps (amount of electricity)
I strongly suggest you read
this article
That article explains what happens in great detail, but if you're still curious, here are some other things that would obviously happen:
If it is a constant DC Current, negative ions will rush to the anode, and positive ones will rush to the cathode. The negative ions (including oxygen and chlorine) will bleach the cells in the area and kill them.
The positive ones in the cathode area will raise the ph drastically and liquefy the adjacent cells.
If the current is high enough, the cells will heat, which will denature the proteins and enzymes within and kill them.


text:
Oxygen mask to patients
Why are oxygen masks given to patients? Can't they take in the  atmospheric oxygen? Also, why do they die if the oxygen mask stops providing oxygen?

these patients are being given oxygen in higher concentrations than the atmosphere contains. usually due to an in ability to uptake oxygen effectively.

Oxygen masks can provide up to near 100% oxygen, whereas the atmosphere contains only ~20%. Typically, oxygen is provided in cases where patients' blood oxygen saturation is low or is likely to be low.
Giving a patient supplemental oxygen helps them to achieve oxygen saturation even if their breathing or circulation is impaired, and allows slightly more oxygen to be dissolved in the blood, which can be helpful in cases of blood loss or other traumatic insults.
I'm not sure of any cases where patients simply die immediately if their oxygen mask fails, outside of movies/TV; it's more of an issue of trying to provide the best outcome possible in a difficult situation.
There are also some negative side effects of oxygen supplementation. Overall, Wikipedia has a reasonable overview of these, as well as the indications for oxygen supplementation.

70 children died in India because the oxygen supply was cut. Why did that happen?

I might have misread an immediacy in your statement (like they die immediately when oxygen is removed), based on the common media trope, not realizing you were motivated by a recent news event. The children most likely died because they had illnesses that prevented them from getting enough oxygen through normal breathing; supplemental oxygen could improve their blood oxygenation enough to keep them alive.  When the supplemental oxygen was withdrawn, they would asphyxiate.


text:
Why do we drink clean water
Most of the street/feral animals (cats, dogs, cows, some wild animals too) drink tap water or dirty water, but it doesnt seem to affect them. So, why do humans drink pure water?

We can drink dirty water, and have through much of history (until we discovered fermentation and later, sanitation). Dirty water is bad for you regardless though. That's part of why we live to 80+ these days, but died younger in the past. You'd probably find you'd be even more ill from drinking unclean water nowadays vs several hundreds/thousands of years back (in the West at least) since our levels of hygiene have reduced our immunity to many of the nasties in dirty water

@JoeHealey - Or, many of the nasties in the water now weren't yet invented by man. It's not only bacteria that pollutes.


text:
Structure of adenoids
I am not sure this question belongs in biology, but I can't find a more suitable stack exchange site, feel free to delete it if this doesn't fit here.
Also, this question is going to be slightly gross, just a warning, but I promise it comes to a point.
I have read that the adenoids have a texture to them but, unlike say the palatine tonsils, they don't have crypts.
Last year my palatine tonsils became fairly badly infected and had to be removed over the summer. Before the surgery, I discovered I could reach back to the tonsils with my tongue, enabling me to remove the tonsil stones that built up. Gross, I know, but I believe it actually did make the infection noticeably better. After the surgery, and after the area had healed, I resumed discovering the back of my throat and, eventually, up the nasal cavity, all the way to the back of the nasal septum, which means I can reach the Eustachian tubes, adenoids, and posterior nares. If that sounds impossible, I assure you, it is perfectly achievable, and only mildly uncomfortable. With my tongue I can feel the texture of the adenoids but, more toward the posterior nares, this texture changes and resembles folds or crypts like I remember the texture of the palatine tonsils. Three times, always in the morning after waking up, I have discovered debris in this region strongly resembling tonsil stones but green instead of off white. The mucus, however, is always clear.

My question has several parts:

What are these crypts? Are they even crypts at all? Are they part of the adenoids?
Why can I not find mention to these structures in any diagrams or medical articles?
Why can I not find mention to tonsil stone like debris except in the palatine tonsils? I am quite convinced that, if these are not tonsil stones of a sort, they are closely related.

The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.

This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids.

I would say that this question is borderline to medical advice (which is not allowed at SE Biology), especially since it is so closely related to your personal experiences. Have you discussed this with your doctor? Either way, I think it would be useful if you could post a diagram of the pharynx and nasal cavity to make your question more clear. I would also consider rephrasing it to get the question more up-front and general, with less personal details.

Well I can't seem to separate out the personal details as it's kinda hard to explain to someone what you feel in your adenoids with you tongue without a back-story! I'm not looking for medical advice. I've already had a doctor look at my adenoids. He said everything was fine but I'm afraid there wasn't time to discuss the finer points of tonsil structure. I'm looking for a good explanation or reference to medical literature that doesn't completely suck like most seems to. I've only seen one cross section of the head that shows the back of the nasal septum! What an omission!

@BigEndian: I've tried to cut out a sentence or two that was veering towards medical advice (the bit about the infection).  Perhaps you might consider putting a disclaimer near the start of the question saying that you've made some anatomical discoveries because of a medical condition, and you'd like to know more (and you've been to a doctor already who said your anatomy was normal). It's not at all necessary to have a disclaimer but someone might vote to close before they manage to read your comment, and I think that would be a mistake.

I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:

Above the pharyngeal tonsil, in the middle line, an irregular
  flask-shaped depression of the mucous membrane sometimes extends up as
  far as the basilar process of the occipital bone; it is known as the
  pharyngeal bursa.

I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)

Well that's a heck of a lot more than I could find. Thanks.


text:
Do men have significant hormonal cycles?
I know there's a similar question here. But that discussion dissolved into lunar cycle and a correlation with it.  I want to find more towards the original question of is there a periodic hormone cycle in men.
The links i have read suggest that there's probably a daily one for sure. But few hint at monthly ones too.
 That link seems to have very shaky science, but my biology is too weak for me to find the actual studies. Anyone else with more informed opinions? Any studies tracking purely hormone levels in men over a period of couple of months/years?
[EDIT]
   I understand it's clear there are cycles within the day or around the 24-hr mark now. I still am looking for studies focusing on longer term cycles like week,months etc.

I found this -

Celec et al. (2003) Circatrigintan cycle of salivary testosterone in human male. Biological Rhythm Research 34: 305-315
Conclusion. We believe that this is the first study demonstrating the existence of circatrigintan and circavigintan rhythms of testosterone in human males. Our findings might have implications in human physiology and pathophysiology.

(circatrigintan = ~30 day period; circavigintan = ~20 day period
also:

Celec et al (2006) Infradian rhythmic variations of salivary estradiol and progesterone in healthy men Biological Rhythm Research 37: 37-44
Discussion. We believe that this is the first study to describe a 12-day (duodecimal) rhythm of salivary estradiol in men. This finding might be of importance for physiological and pathophysiological research though the pattern needs to be investigated in larger studies.

However these papers have not been widely cited so their significance is unclear. The citing articles do not lead to a body of literature on this topic.
Finally, the entire text of this book:

INTRODUCING BIOLOGICAL RHYTHMS A Primer on the Temporal Organization of Life,
with Implications for Health,Society,Reproduction and the Natural Environment
Willard L. Koukkari and Robert B. Sothern. (2006) Springer, New York.

is available here. There is a long discussion of infradian rhythms in men starting at page 273.

Short answer: yes.
Although clearly the infradian changes in steroid hormones in females are quite "obvious", other changes are less evident, but happen nonetheless in males as well as in females.
Most of the hormones produced by endocrine organs such as the hypothalamus (a region at the base of the brain) or the hypophisis are not secreted in a continuous manner but rather in pulses. The exact frequency/amplitude etc. of these pulses can be different depending on the species considered, but (as fare as we know) the undelying mechanism are fairly conserved.*
In general, you can find circadian (~24 h), ultradian (<24h) and infradian (>24h) rhythms.
For instance these graphs show the concentration of cortisol, aldosteron and renin in a man, showing a strong circadian rhythm.

From: Charloux et al. - Am J Physiol Endocrinol Metab 1999
You can see that on top of the circadian rhythm, an ultradian pulsatility (every ~2-3h) is also quite clear.
Another example is that of GH (growth hormone): here you see secretion of GH in an healthy women (top) and an healthy men (bottom)

From: van den Bergh et al. - J Clin Endocrinol Metab. 1996
Many other hormones show this type of rhythmicity in males, such as testosterone, LH, GnRH, and probably many other.
I am not aware of long term studies on this matter.

* Actually, the mechanisms underlying pulsatility are still poorly understood.

Thanks for the answer, though I was looking for some studies/answer focusing on (>24 hr) rhythms. Yours is still new information to me.

authors: Дмитро Попович


text:
Neurons during Numb feeling
We become numb when there is short supply of blood to some parts, as mentioned here.
If that is the reason, why don't neurons and other cells die at that part if they don't receive oxygen and other things needed?

A lower supply of blood does not mean no supply of blood, so my guess is there's generally enough to keep stuff alive for some time. But if the supply is restricted for long periods (think frostbite), then stuff starts to die.
Also, the sensory neuron endings in the skin are normally just one long projection from a cell body, the major components of the neuron are protected by being located in e.g. The Dorsal Root Ganglion.

True, I was thinking more from a frostbite point of view, i.e. stuff will die eventually, but mostly surface tissue rather than neurons etc.

@mgkrebbs I'll remove my comment, as it's a bit misleading. I meant to refer to the article which says "reduced supply of blood to the limbs" implying that blood flow to the limbs is lost, which isn't true.

Simply put, the cells and "other stuff" WOULD die if the blood flow and/or oxygen were too severe, and would be cut off for too long.
It would probably take some time though.

The neurons stop working in lack of blood, why dont other cells stop?

@Charles Is it speculation to say cells will die in the end if blood flow stops? Do I really have to provide sources for this? Now seriously.... as they say, "LOL".... You could as well ask me to prove to you an apple will fall downwards if it detaches itself from the tree.

@Ram Keswani, your question doesn't make sense to me. I don't understand what you are asking. Do you mean to say you believe cells go on living if no oxygen is provided anymore?

@Charles And besides why don't you ask the same thing of user Oliver Houston? He too seems to blindly assume cells don't survive without nourishment.... LOL

@ObiwanKeNoobie Sir see, we feel numb because neurons stop working, or work less efficient because of lack of oxyegn. Then the other cells near that area also lack blood and oxygen. If neurons work less efficiently, why don't other cells in that area not work less efficiently or stop working? Or do they work less efficiently and it doesn't matter much?

@Charles - "@ObiwanKeNoobie "and "other stuff" WOULD die .. " what "other stuff"? This is way too general for a scientific community." I bet it is. I was merely quoting the asker, that's why I put brackets around it as I found this not very scientific. And you are now pretending it is me ? LOL... I understand you want to be right but please, be fair. It should be clear to you the asker merely edited his question meanwhile, and rest assured I will have to say something about this in the meta talk.

@Charles - "@ObiwanKeNoobie Is it speculation to say cells will die in the end if blood flow stops?" -- depending on the amount of time that's lapsed, yes, most definitely that's a speculative statement. Also, when you say "..in the end", are you implying that eventually all cells die without blood supply? If so, then this is a trivial statement to make, since it is so obvious, as you yourself have pointed out. And, since that is the entirely of your response, respectfully speaking, I find your response not helpful. – Charles 1 hour ago" - Charles my boy as soon as I have the means I am going

... going to report you for pestering me OK? Read again the nonsense you were replying to me. I have other things to do.

Sorry, impossible. I can't. I have spent almost the whole day on SE. It will have to wait for another day.


text:
Drinking and eating ability of infants soon after birth
How do infants know how to eat, drink without being taught? How do they get this ability soon after birth?

It's called instinctual behavior. And they have very, very many abilities after birth: the ability to swim (rudimentarily, not like Michael Phelps), take steps on a hard surface, to cry, to open their eyes, etc., etc.

These are just reflexes which are executed involuntarily, they need not to be learned , but are present naturally in the neural circuitry.


text:
Why do we get bored of certain food items after repeatedly eating them?
Why do many people not like certain food items after eating them for long? They seem tasty first, and after eating many times, it feels like we get bored.

Who's we here?  As Unicorn13601 says, some people eat the same food for decades without boredom, e.g. I've eaten the same brand of cereal (with whatever fruit is seasonally available) most mornings for the past few decades, because I don't want to think about food choices at that time of the morning.  You might also ask why people get bored with any activity, not just food.  And whether there's an evolutionary advantage to seeking a varied diet.


text:
How to distinguish processionary from other caterpillars
Processionary caterpillars have a vast and harmful presence in southern Europe. In northern Italy, in parks and gardens, I often see caterpillar nests in trees, but I do not know how to tell if they are processionary, with dangerous urticating hair, or other innocous (for humans and pets) kinds of caterpillar (such as tent caterpillar, for example).
I've read from Wikipedia and other sources that processionary "usually" nest in pines and oaks, but it is not clear to me if it is only a matter of preference or if they cannot nest in other trees. Does seeing a caterpillar nest in an another kind of tree safely imply that it is not a processionary nest?
Besides, the photos I have found show very different kinds of caterpillars,  what easy visual clues could I use to tell them apart? Ideally, I would like to be able from a distance to decide if I should get my dog away from an "infested" tree or if I can safely ignore it.

Hi, and welcome to Bio.SE. Your question could use a bit more context to demonstrate that you've tried answering this on your own. We always ask that the poster provide some evidence of prior research. Thanks!

I've tried to explain a bit more context in an edit. I know nothing of entomology, it is hard for me to find specific sources besides a generic internet search, which has not helped me so far, hence the question.


text:
Are there any animals that celebrate communally?
Are there any animals that are known to celebrate events? For example, we humans might celebrate a birthday or passing an important test. An event causes us to perform some sort of celebration that is motivated simply by joy and not any sort of survival instinct.

To clarify, I am more interested in positive celebrations. I know a number of animals having mourning behaviors (which absolutely count as a response to external events, no denying); I'm just more interested in celebrations in a positive sense.

I'd like to take this one step further.
Are there any cases proven or postulated of animals celebrating. I don't necessarily need something firm and proven, could be a theory.

This is a very interesting question! Thanks for the clarification as well.

What is the difference between a celebration and a bunch of animals happy about something together?  For example, a bunch of happy dogs racing around like crazy because their owner came home?

I expect there are two elements to what a "celebration" is, maybe three: social animals displaying joy to each other over the same event (where Will's happy dogs might apply); 2) doing so in a ritualized fashion (this is where I expect most examples to fail); 3) doing so on a differed timescale (ie not exactly after the celebrated event happened) (this one I not only expect not to happen much if at all, it seems it would be hard to impossible to observe). I think if any animal does this it would be highly intelligent and social ones, ie orcas, elephants, bonobos, parrots...

So far I've found "greeting ceremonies" among orcas; I can't seem to find a definite source on them but you'll see references if you google it, it's a ritualized behavior when orcas from a certain group meet each other after being separated awhile. Might not be what we'd call a "celebration" (after all we have "greeting ceremonies" too and we don't always call them "celebrations" per se). Orcas do illustrate one potential problem tho: if it's culture-related it's a behavior we're unlikely to observe in captivity, and might be disrupted by environmental change/human intervention.

Hmmm, good question Will. I suppose that does qualify.

Rozenn, If you can make an answer I'd gladly flag it best answer. Definitely matches what I was looking for :)

Koko (the gorilla) celebrates Christmas.

The communal yipping of coyotes?  https://www.adirondackalmanack.com/2014/03/coyotes-decoding-yips-barks-howls.html  Of course determining whether this counts as "celebration" requires getting into the coyotes' heads...

An event causes us to perform some sort of celebration that is motivated simply by joy and not any sort of survival instinct.

Celebrations usually mean large group activity but a play can be considered an event which is simply by joy and not any sort of survival instinct, and hence would fit your question. One can easily spot their pet playing around with objects when they are sitting around, busy in something 'boring' for the pets, like - reading a newspaper. But here it can be argued that pets have learned to do this to get the attention of the owner, and hence associated benefits.
Well, plays of pure enjoyment have been documented in wild animals too.

I once observed a young elk in Rocky Mountain National Park, Colorado, running across a snow field, jumping in the air and twisting his body while in flight, stopping, catching his breath and doing it again and again. There was plenty of grassy terrain around but he chose the snow field. Buffaloes will also follow one another and playfully run onto and slide across ice, excitedly bellowing “Gwaaa” as they do so (Canfield et al. 1998).

Certainly, there was no motive here apart from having fun.
I would encourage you to go through this article - Bekoff, M. (2000). Animal Emotions: Exploring Passionate NaturesCurrent interdisciplinary research provides compelling evidence that many animals experience such emotions as joy, fear, love, despair, and grief—we are not alone. BioScience, 50(10), 861-870.
Speaking of the celebration, such as - birthday, or the largest homo sapiens gathering Kumbh Mela, I would also be interested to know of some group of animals doing it periodically.
Reference:

Canﬁeld, J., Hansen, M. V., Becker, M., & Kline, C. (1998). Chicken Soup for the Pet Lover’s Soul. Deerﬁeld Beach, FL: Health.

Exactly what I was looking for :)

Good answer but this answers the question "Do animals have fun?" and it is much more evident. Celebration is very different.

You want scientists to measure animal emotions and social behaviours, and they rarely agree about animal psychology unless it's measured chemically and physically.
Celebration (behaviour for events) is not a word defined zoological science research. You can imagine that thirsty elephants that walk for 3 days to find a riverbank have a celebration when they arrive there.
Scientists don't use the word alien planet to mean exoplanet, and they don't use the word cyberspace to mean internet. For that reason, the word celebration is mostly a dramatic and reporting term that a scientist would be uncomfortable to use with proof as the basis of a document.

Could you please add sources for your claims?


text:
Basic behaviour patterns of animals for a modeling project?
I am working on a project (a tool) for my GIS class that models natural habitat of an animal based on landcovers, distance to the nearest watersource and distance from developed area in Kansas, USA. I need these numerical values for at least a couple of animal species (larger herbivores that can occur in Kansas) so the user can enter these values and visualize the natural habitat.
Now, I know it is very difficult to determine such values (and modeling natural habitat is much much more complex than this) but these values don't need to be very accurate as it aims at showing the capabilities of the GIS software rather then producing real-world output (again, its a school project).
I've contacted a professor at the Department of Biology but she only provided me with tons of over-detailed information and links to scientific research which are of no use for me.
For example: a deer goes to drink water twice a day and doesn't move more than 10 miles a day -> it is most likely to occur within 5 miles from a water source. I know it is a crude simplification but it really doesn't matter in this case.
Is there a source of such information?

I am pretty confident you won't find a source that has the data you want in a nice table format - you will have to extract the information from scientific literature gathered for other purposes. I'd suggest searches on scholar.google.com for specific species you want to track, and pairing that species with some other terms of interest. For example, "white tailed deer GPS" might turn up some papers relevant to you (I tried this search and several seem applicable). Like you say, you don't need precise data, but you can make some estimates from these types of sources.

Also note: it seems like there is a lot of GIS work with white tailed deer in particular, so you can even just search for "white tailed deer GIS" and maybe add in other keywords that are relevant to you like "water." I'd also suggest you go back over the work provided by the professor you talked to: I very much doubt she was steering you wrong, probably the information she provided is very useful, you just need to apply some search strategies within that information to extract what you need. That is an essential skill to have and probably more important than 95% of your coursework.

You might be better off looking for gps tracking data and pulling the relevant information out of it.

\You are not going to find a lot of what you are looking for, generalizations like that are not often published together. As Bryan mentioned you need to search the sources you have in detail, statements like that are not going to be prominent but will be dispersed as minor details in many many studies. You will have to compile them. worse these will rarely be consistent animals change behavior depending on the conditions. You will also have to become very familiar with the terminology involved.

This kind of study is what you are looking for, https://academic.oup.com/jmammal/article/96/2/279/900871/Purposeful-wanderings-mate-search-strategies-of

Thanks a lot to both of you, Bryan and John! This is definitely going to help. And I am sure the professor provided me with very useful information it's just way too complex considering what I am looking for & how much time I have.


text:
How to stop a mosquito from flying?
Researchers have found mosquitoes cannot fly in dense fog because fog particles adhere to its halteres and stop them working. Is it possible to disrupt mosquitoes flight by mimicking fog particles?

Welcome to Biology.SE. Remove its wings by pulling on them is one way to stop a mosquito to fly "artificially". Does it answer your question? If not, then you should probably clarify your question.

It would be good if you shared the link of the paper with this discovery.

@Tytoalba link has been added - it's pretty cool! :-) Anything that gives mosquitos a hard time around me is a good thing. I'm going out to buy some custom Krypton/Oxygen mix now.

@VictorChung this is a really interesting paper, thanks for bringing it to people's attention! Can you consider focusing your question on something specific that could be answered? Something that's not necessarily answered in the paper itself?


text:
How does a tiny spider interpret/cope with gravity?
The Question:
Does a tiny spider know that it is walking on a wall or a ceiling as opposed to the (horizontal) ground? Does gravity play a role in this knowledge?
Further thoughts:
I am interested in how other organisms sense gravity, and how they are affected by it. I have read how gravity played an important role in the physical evolution of all animals, but am interested in how the animals perceive gravity, and to what extent they are aware of/affected by it.
Can you point me to any research in this area?
The following is an excerpt from work of the German Aerospace Center, showing how the orientation of a fish is guided via a mixture of gravity and light:


text:
What happens when I pop my ears?
What happens when my ears are popped?
I understand it increases the air inside there which makes my volume louder, what happens after that, do my ears gradually readjust back to the air pressure that they were before?
What causes ears to (need to) be pressurized/depressurized?

To whoever downvoted, please comment your problem with my question.

The downvote probably comes from the fact your question is an anecdotal report and a self help question, both essentially being off topic here.

The outer ear canal ends at the eardrum, and beyond that is the middle ear.  The middle ear is normally a closed chamber, but can be connected to the outside world by flexing the jaw or muscles related to.  The flexing opens the Eustachian tube, which runs from the middle ear to the back of the nose and mouth.

Hearing is best when the air pressure in the middle ear is the same as the pressure of the outside air.  If it is different, the ear drum is forced to bend outwards or inwards depending on whether the pressure is higher or lower in the middle ear.  In either case the ears senses less sound, and the volume is reduced more for some frequencies than others.
When you pop your ears, the Eustachian tubes open enough to allow your middle ears to equalize pressure with the outside world.  This restores the ear drum to its normal position and your hearing returns to your normal, optimal state which is louder and more balanced than the previous condition.  As time passes, your brain adapts to the new sound sensing state and you no longer notice any unusual loudness. The pressure in the middle ear doesn't change as your Eustachian tubes usually remain closed, and so the ear continues to hear well (as long as the outside air pressure remains little changed).


text:
What is operating temperature of the human brain?
I've heard several times that human brain can die in temperatures over 40 °C, or under 10 °C, as an engineer I'm curious.
In what temperature region can brain properly work?
And just an underlying question what is a TDP (thermal design power) of human brain?

What did your research tell you, and how/why did it confuse you?

@anongoodnurse Most articles on this differ, and I wasn't able to find any that would have sufficient sample size (more than 1) or would be peer reviewed. Also I'm not very good at searching for medical papers, there is a chance I've missed something that would be good.


text:
How cnidocytes work?
I have googled  for the structure of cnidocyte but images of google is unclear or complex .so please draw a simple understandable structure of cnidocyte .I know that cnidocyte works by osmosis but I don't know how exactly osmosis make cnidocyte to function .so please explain the mechanism of cnidocyte.

A cnidocyte is a poison-loaded harpoon connected to a pressure plate, implemented at the microscale level in a cell. Something triggers the plate, the harpoon jets out. Simple enough.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Is it possible to cure dandruff?
If dandruff is caused due to oleic acid released by fungi malassezia then is it possible to control it by applying any base in our scalp ? Since base nullify the effect of oleic acid or base cause any further hairloss complication?

isn't just anything possible in the future? What are you after?

It might be a better fit for worldbuilding.SE but I am not sure

why did you totally change the question and post? Just leave this one closed as it was, and take your new question and post it as a new post.

we already transfer memories with books and movies, If are talking about direct transfer then the answer is no, because different brains already have different patterns of connections, so even if you could somehow for an exact copy of a single small pattern to form in someone's brain it will interact with the rest of the brain if very different ways.


text:
How to solve these kinds of problems?
16% of people in a population can not roll their tongue .what is the frequency of people which are heterozygous of this character? Please ,any one help and guide me to solve these kind of problems.
 I tried to solve it using punnet square but i failed .
So i tried my best please help me to solve this.

Homework questions are off-topic on Biology unless you have shown your attempt at an answer. For more information see our homework policy.

@David  He show some attempt.

Possible duplicate of Solving Hardy Weinberg problems

Hint: The very first step is to define which genotype can not roll their tongue. Then, you know that 16% of the population have these genotypes. From this, you can find out the frequency of heterozygote in the population thanks to Hardy-Weinberg. For more information, please look at the post marked as duplicate.

I definitely recommend looking at your calculations. The "unable to roll tongue" trait is recessive, not dominant. Look at the Hardy-Weinberg equation $p^2 + 2pq + q^2 = 1$. Try to extract the root of $q^2$ and you will get the right solution.

https://www.nature.com/scitable/definition/hardy-weinberg-equation-299 this might help you too.


text:
What is the name of this thorny plant?
Location: South India
Month: June
Tree:

Leaf:

Its Flower:

EDIT:
For avoid confusion about ID this species, I even added its flower now.

Your tree appears to be from the Genus Dichrostachys.
It has several species, quiet a number of them have been reported only in Madagascar.
There are two species found in India, D. santapaui and D. cinerea.

How have I reached this plant?

The leaves of your plant are bipinnately compound. They gave me the impression of Mimosa pudica.
Of course it is not one. Mimosa pudica become creepers with time
and have short and thin prickly thorns.
Resemblance of an unknown organism with a known one can indicate shared derived character(s) (Synapomorphy), meaning they can be related.
Google's algorithm is often able to trace this relation. Look at the keywords I had used. If it doesn't one needs to experiment with the keyworks, note the word Fabaceae, it is the family to which Mimosa belongs.
Wikipedia  often is just the right place to start one's research.
The description of Dichrostachys cinerea is what I checked next, after having ascertained that is found in India.

Dichrostachys cinerea is a tree characterized by bark on young branches, dark grey-brown fissures on older branches and stems and smooth on the spines.
They typically grow up to 7 metres (23 ft) in height and have strong alternate thorns, generally up to 8 cm (3.1 in) long.
  Flowers of the Dichrostachys cinerea are characteristically in bicoloured cylindrical spikes that resemble Chinese lanterns and are 6–8 cm long and fragrant.
The species tends to grow in rainforest zones.In India, it can occur in dry deciduous forest.

Every thing fits well upto Genus Dichrostachys.

Dichrostachys is an Old World genus of legumes in the Fabaceae family.
Their Acacia-like leaves are bi-pinnately compound.
Unlike Acacia their thorns are hardened branchlets rather than modified stipules. They are native from Africa to Australasia...

The next thing I exhaustively checked were the species under this
    genus. I checked their
    locations,
    out of all two species have only been reported in India; D.
    santapaui and D. cinerea.
The reason behind this unusual format is to show you  how to fish. I will leave the rest of the hard work of digging up the species to you .

Few interesting facts about this genus:

Its name is derived from the Greek words dis (two), chroos (colour) and stachys (grain ear or spike), which in combination suggests their bi-colored inflorescences.

Dichrostachys cinerea, known as Sicklebush, Bell mimosa, Chinese lantern tree or Kalahari Christmas tree (South Africa).
D. cinerea is used in Ayurveda.

Great answer! You know what they say Give a man a fish, he'll eat for a day; teach a man how to fish, he'll eat for a lifetime. By explaining how to find the name of a species on our own, you have taught me and the OP how to identify on our own. Brilliant job I say!

Maybe it's
Prosopis juliflora:

It's popularily known in South India as சீமை கருவேல (translitered as:Seemai karuvelam). It's an invasive weed introduced in 1880.
It belongs to the Fabaceae family of plants. It flowers quickly after leaves form:

I hope this helps.

I added flowers also now.


text:
Is it possible to Breed an Animal to have more Females than Males?
Minute Earth talked about environmental factors that cause animals and humans to have more male or female children: https://www.youtube.com/watch?v=3IaYhG11ckA
Presuming that is accurate, I was wondering if you could artificially select for people or animals who have more children of a certain gender?
As far as I know, there are no animals that do produce notably more males than females, or vice versa, except maybe some insects.

Presuming that is accurate, I was wondering if you could artificially select for people or animals who have more children of a certain gender? As far as I know, there are no animals that do produce notably more males than females, or vice versa, except maybe some insects. natural-selection pregnancy gender

I guess this answer is accidental?

Do you have some limiting criteria for "animal". Various animals have different influences in sex determination, and some have factors that are easier to adjust than others (e.g. some amphibians and reptiles will have an entire nest of eggs result in one gender based on temperature, which isn't an influence for mammals).

@HarrisWeinstein The question is related to a fictional race of reptiles (snake based), so that's pretty relevant. It's a story about the Naga, said to be spirits of rivers and snakes (like a centaur or mermaid, upper body human, lower body snake). I also wanted to learn about the subject in general, as I was taught that all creatures have a 50/50 split in gender.

Yes.
 What you are looking for is a meiotic drive, it's a genetic factor that favors its own transmission. Sex linkage is very common in these due to sex chromosomes not undergoing recombination. Once such driver, R2D2 (I shit you not) is a Y linked gene that drastically increases the number of male offspring in a mouse that carries it, to the point it can cause a population collapse from lack of females.
Several such drives are known, none quite as drastic as R2D2.

That is awesome! Thank you, I never heard of this. If I may ask, is there any comparable gene known of in the human genome?

I don't know of any sex linked ones in humans, but there are a few other kind. https://www.nature.com/ng/journal/v31/n3/abs/ng910.html


text:
Need help identifying multi-colored grasshopper
I was out hiking with my friend when we ran across what I presume to be a grasshopper. It didn't seem very startled by our presence, and we were able to get some pretty cool pictures. I've been having trouble finding out what species it is. I was hiking near Albuquerque, New Mexico, and the grasshopper was about 1 - 1.5 inches in size. It was about midday when I saw it.

Welcome to Biology.SE! Please take the (tour)[https://biology.stackexchange.com/tour]. Can you add some more detail to the post - where you saw this insect, when, and what size it was?

It's what's called a Rainbow or Painted Grasshopper (Dactylotum bicolor).

You can learn more at Bug Guide Species Dactylotum bicolor (where the picture is found) or Wikipedia' article on Dactylotum bicolor. The colour and pattern is very unmistakable.

I edited to add a picture (as is the custom when identifying something. Hope that's ok. :)

Perfectly fine if you edit it. I don't have enough time to help out in that department on SE so if others do, I'm only too happy for the help!


text:
What are the differences between Trachinotus and Bramidae species?
What are the differences between Trachinotus(Pompanos) and Bramidae(Pomfrets) ?
...like the difference between where they live/can be found, bone structure, etc.

Can you add more context to your question? Simply repeating the title is not acceptable. What do you want to know specifically? There are very broad differences, sufficient for systematists to put them into different families.

Pomfrets comes from the order Perciformes (the largest order of fishes) and are part of the Bramidae family. They strictly live in marine environments, mainly the Atlantic, Indian, and Pacific Oceans. They have a dorsal fin extending over the length of the body in some and anterior dorsal fin spines unbranched.
http://www.fishbase.org/summary/FamilySummary.php?ID=319
Pompano comes also comes from the order Perciforme and are part of the Carangdide family which includes jacks, mackerels, scads, and runners. Most are fast-swimming predatory fish that hunt in the waters above reefs and in the open ocean. They also mainly live in marine environments such as the Atlantic, Indian, and Pacific Oceans, and are rarely found in brackish waters. Their body is generally compressed, although body shape extremely variable from very deep to fusiform.
Quote about Pompanos from Fishbase.org:

Most species with only small cycloid scales. Scales along lateral line often modified into spiny scutes. Detached finlets, as many as nine, sometimes found behind dorsal and anal fins. Large juveniles and adults with 2 dorsal fins. Anterior dorsal fin with 3-9 spines; the second having 1 spine and usually 18-37 soft rays. Anal spines usually 3, the first 2 separate from the rest; soft rays usually 15-31. Widely forked caudal fin. Caudal peduncle slender. Pelvic fins lacking in Parona signata. Vertebrae 24-27 (modally 24).

Unfortunately, I can only post one link due to my rep, but it fairly easy to search fishbase.org for information on both species.


text:
Health benefits & enzymes different between Thermophilic and Mesophilic Probiotic cultures?
Is there a difference between the Enzymes produced by Thermophilic vs Mesophilic Probiotic cultures ? are there any other differences in health benefits between the two types of cultures ?


text:
Is there a organ or type of cell that makes Nagalase?
Schindler disease / Kanzaki disease is being described as alpha-N-acetylgalactosaminidase deficiency. So then, which organ or cell(s) produce this alpha-N-acetylgalactosaminidase (Nagalase) ?


text:
I found this bug in my closet. Could someone help me identify?
It looks like it recently died. The shell was shiny and smooth and fairly brittle. I've been having trouble identifying what it is because it doesn't quite look like any of your common house pests.
The bug is at most 4 mm. I live in a relatively old apartment in New York City and my best guess is that this guy crawled out of a crack in my closet wall.

Welcome to Biology.SE. Can you please add 1) approximative scale 2) where do you live (country and lower scale information about the ecology around your place) 3) How is your house (do you live in an old wooden house or in a modern concrete building)?

I've updated the original post. Thanks in advance :)

I agree This is definite a spider beetle


text:
Why does an electric shock contract the muscle?
From what I understand, the electrical impulse in our nerve cells is not made of electrons, but of ions that move from different environments with different concentrations, which is totally not related to the electricity we use, which is made of electrons. The electricity we use makes our muscles contract, why? Does it have to do with the fact, that when we put electrodes with electricity in an electrolyte, ions move?

Nice Question! Lets first introduce ourselves to the topic i.e. Electrical Muscle Stimulation.

Electrical muscle stimulation (EMS), also known as neuromuscular electrical stimulation (NMES) or electromyostimulation, is the elicitation of muscle contraction using electric impulses...The impulses mimic the action potential coming from the central nervous system, causing the muscles to contract.

Now, lets come to the main point. Its actually not about flow of electrons or ions, but the change in voltage that plays the pivotal role in muscle stimulation. See this:

Crystallographic structural studies of a potassium channel have shown that, when a potential difference is introduced over the membrane, the associated electric field induces a conformational change in the potassium channel. The conformational change distorts the shape of the channel proteins sufficiently such that the cavity, or channel, opens to allow influx or efflux to occur across the membrane. This movement of ions down their concentration gradients subsequently generates an electric current sufficient to depolarize the cell membrane.

In short, when you touch a wire, you become a part of the circuit i.e. any 2 points on your hand (or your hand and foot, if you're barefeet) act as part of the circuit i.e. there is potential difference between them, which generates an electric field. This electric field causes the voltage-gated channels in neurons/muscles to open which, in turn, generates an action potential and causes the muscle to contract.

References:

Electrical Muscle Stimulation - Wikipedia
Voltage-gated Ion Channel - Wikipedia


text:
When did human ancestors learn to walk?
Where does our ancestor learn to walk from? How do we control our legs whenever we take a step?  I confuse every time whenever I take one step.

Are you asking about the evolution of upright walking in hominids or the physiology of human walking (balance etc)?

I think this questions should be better focused since as pointed out by @fileunderwater there are at least two broad issues here to develop.

Perhaps this previous question answers the evolutionary part of your question: http://biology.stackexchange.com/questions/27475/why-did-humans-become-bipedal. If you could elaborate on the issues you have with leg control (balance? neuromuscular system? ...) then this question may be answerable. As of now I vote to close because your question is too broad and unclearly stated.

It is unclear what you mean by "Where" in your first sentence. In addition to that you seem to be asking about the phsysiology of upright walking (which is too a broad question in itself) AND about its evolution. You should restrict your post to only one question.

In a sense, there's an easy answer to your question.  Humans became bipedal in Africa, since bipedality is well-established for the first species in the human lineage to leave Africa (Homo erectus/Homo ergaster).  This can be verified in many textbooks.  However if you ask the question when, in what species, or why, there's no easy answer to your question. The question comes down to (a) which fossils are specifically ancestral to humans (b) what fossils have evidence for bipedality, and (c) theories as to why those species became bipedal.
The narrow sense of humans, Homo sapiens, has been bipedal ancestrally.  Other closely related species were almost certainly bipedal (Homo neanderthalensis and Homo heidelbergensis for example).  In fact, the species or species complex from which humans likely arose, Homo erectus, was also likely bipedal (discussion below).  If we take the broadest sense of what "human" means, it could mean any species which split from the human lineage after the split with the extant great apes (specifically, post split with chimpanzees).  Here there's reasonable evidence for bipedality exists around the same time as this split, but not in all species.  Specifically, Orrorin tugenensis is a 6 million year old specimen with some (but not conclusive) evidence for bipedalism.
Question b, how do we know a fossil creature is bipedal, is a challenging question.  Homo sapiens, the only completely bipedal primate, have many adaptations which facilitate walking on two legs.  The shape of our pelvis facilitates the muscle attachments necessary for walking by flaring the ilium (the bone which forms the upper part of the pelvis).  This same flaring is found in Australopithecus afarensis (which includes the famous "Lucy" specimen), about 3 million years ago.  Australopithecus also has a fossil of footprints, which seems to indicate bipedal movement.  The human femur is bent inwards and the neck is thickened to support the weight of someone walking upright.  This same thickening is found in Orroin tugenensis and the angle in Homo erectus/Homo ergaster (these are two names which are either closely related species or the same species, depending on who you ask). The human big toe is also in line with the others in the foot, which likely allows us better motion on the ground.  This feature is also true of Ardipithecus ramidus, at about 4.5 million years ago.
The third part of your question, why humans became bipedal, is largely speculative.  Many theories exist for the process which lead to bipedalism.  A popular theory in the 1970s and 1980s was that humans became bipedal to enhance our abilities to see across tall grass, because many people thought Homo erectus/Homo ergaster was the first upright walking species, and grasslands dominated east Africa at the time.  However since earlier evidence for bipedality, many people have abandoned this hypothesis in favor of others.  These other hypotheses include that bipedalism arose after scaffolding on to arboreal (tree-living) adaptations.  If human ancestors lived in trees, they may have moved in a vertical posture, leading to many of the adaptations needed to move vertically on the ground.  Others include an increased reliance on meat, caught through endurance hunting, or even wading into tidal waters being the key feature (notably this is not the aquatic ape hypothesis, which is pseudoscience), and this reliance on key marine resources provided the essential stable food supply for brain enlargement.  The short answer is that there's a tremendous amount of speculation in this area, and few firm facts.
Whichever of these species you choose as the "first bipedal human," and how confident you want to be about that bipedality, they all evolved in Africa.


text:
How many mega pixels does the eye have?
What is the number of mega pixels available in the human eye? It seems that newer camera models continuously keep increasing their pixel count. However, they never seem to be capable of reproducing what the eyes can see.

According to calculations done on this it is around 576 MP

@Ghost A quote from my late answer on that question: "None of these calculations are scientifically accepted." This still stands and the question is purely subjective and speculative.

@GoodGravy - while the subjective conscious perceptual representation of the visual field cannot be expressed in megapixels, the retinal composition of photoreceptors and their relative contributions to the image can be approximated. It is not purely subjective and speculative at the retinal level.

Short answer
The total number of photoreceptors ('pixels') in the human retina is 63 million. Approximately 3 million of them transmit focused, color-coded information.
Background
In essence, each photoreceptor on the retina acts as a photosensitive sensor. We have rods and cones in our retinae. Rods confer gray scale vision, while cones are responsible for color vision.
The raw average tally of rods in the human retina is 60 million, and cones count a little over 3 million (Jonas et al, 1992). Hence, we could conclude we have 63 megapixels per eye available.
However, this does not mean that 63 million pixels are sent off to the brain. Instead, just as with a JPG image, it's instantly reduced in size even before the information leaves the retina.
Most importantly, rods are specialized for scotopic (night) vision and 10 to 30 rods connect to a single bipolar cell (Kolb, 2011). Hence, this feat only reduces the number of 'rod pixels' to about 3 million. Cones generally synapse onto a single bipolar. Hence, 6 megapixels leave the retina approximately.
The retinal image is generally focused onto the fovea, which is the central 18o of the total ~160o that is covered by a retina (Fig. 1). The remainder of the retina may receive a blurred image projection.

Fig. 1. Image focussing through accommodation on the retina. Source: Health Problem and Solutions
The fovea is densely packed with cones and contains nearly all of them (fig. 2).

Fig. 2. Distribution of rods and cones in human. Source: (Kolb, 2011)
Hence, the focused part of the image may be encoded by as little as 3 million cones. Since rods don't provide color information, it can be concluded that focused, color-coded information is conveyed by 3 million photoreceptors per retina.
Ultimately, however, it is important to note that the brain fills in missing gaps. For example, the optic disc, i.e. the point where the optic nerve leaves the eye, measures about 1.5 mm in diameter (Kolb, 2011). Given that the total diameter of the retina is about 30-40 mm this is quite a big blind spot. The brain simply fills in that gap by estimating what supposed to be there. In fact, many people with degenerative diseases of the retina don't even notice their deficits until they start bumping into objects that they did not notice. However, they do not see black holes, but instead their brain has been filling in the gaps with the information available in the remaining image, just like it does with the optic disc in normally-seeing people.
References
- Jonas et al, Graefes Arch Clin Exp Ophthalmol (1992); 230(6):505-10
- Kolb, Webvision, The Organization of the Retina and Visual System, Simple Anatomy of the Retina (2011)
- Kolb, Webvision, The Organization of the Retina and Visual System,
Circuitry for Rod Signals Through The Retina (2011)

Actually the human eye has variable resolution, with higher resolution around the fovea and lower as we move away from it. So I don't think the 576 MP is correct.
Our eyes are really horrible in many optical properties. The brain makes up for these errors and corrects everything, so in this sense your question is a poorly proposed one, as we should probably perhaps stop improving resolution of camera sensors and start improving the software that analyses the data they receive.

+1 for a reasonable answer, but can you back this up with citations?


text:
Any nerves/fibers in foot similar to ulnar nerve in elbow?
I just noticed that when I gently run my fingers along the top of my right foot, I get the same exact "funnybone" sensation in my toes that I get when I hit the ulnar nerve in my elbow.
So I ask: are there similar nerves/fibrous structures running along the top of your foot as whatever is going on in your elbow with the ulnar nerve?
Not medical advice; just curious about the anatomy here.

Why would peripheral anatomy determine subjective sensation? In the end, the cerebral cortex determines the sensation associated with peripheral input. Rewired hamsters can have visual sensations in their auditory cortex (Frost et al., 2000) and visual sensations through tactile stimulation have been reported in man (Ortiz et al., 2011).
The sensations you describe are related to tactile stimulation of peripheral nerves. Peripheral nerves are pretty homogenous, and typically carry a bunch of afferent nerve fibers up to the somatosensory cortex.
References
- Frost et al., PNAS (2000); 97(20): 11068–73
- Ortiz et al., PLOSone (2011)

Thanks @Christiaan (I'd upvote you if I had the rep to do so) - however, as someone who is totally green in this field (biology), I find your answer a bit cryptic and vague! It sounds like you're saying that, no, there aren't any similar structures in my foot that would be causing this sensation, and instead, the sensation is coming from the way my "somatosensory cortex" is processing the tactile input. If that's the case, why would this happen all the sudden? Thanks again!

In the 2nd paragraph I try to explain that peripheral nerves are pretty similar all over. And linking peripheral anatomy to subjective percept may be tricky. That's all I'm saying. 5 more rep and you can upvote :)