text:
evolutionary reason behind sharing the same path for food and air?
What is the evolutionary reason behind sharing the same path for food and air?
For example, we have a nose and lungs, yet they are linked by the pharynx, which is shared with the mouth and oesophagus.
Wouldn't it make more evolutionary sense for the nose + lungs to have their own "path", while the mouth and stomach have a separate system? This would prevent "choking", allow for breathing while eating/drinking, etc.

Note that this does not go for all animals. For instance, the respiratory system in insects is based on a network of "tubes" (tracheae) that penetrate the entire body. This is ventilated through spiracle valves which are distributed over the body of the insect, so in insects the paths of food and oxygen are separated.

While it might make more logical sense to have separate passageways for air and food/water, this did not happen in evolutionary history due to the peculiarities of lung development. Vertebrate lungs develop as an outpouching of the gut tube, which itself has a very long evolutionary history (probably homologous among all deuterostomes).
In the image below, the trachea has budded off the esophagus. Further lung development will involve the differentiation of main, secondary, and tertiary bronchi as well as the alveoli, etc.

Additional images and description at http://www.uoguelph.ca/zoology/devobio/210labs/lung1.html
Air-filled organs like lungs and swim bladders actually have a broad distribution going way down into fishes. Human (and other mammalian) lungs are likely homologous with ancestral air-filled organs of fishes. We can't be certain, but there is no reason to think that mammalian lungs are a de novo evolutionary innovation. So our airway and food-ways are tied together developmentally and are constrained by evolutionary history.
As for breathing and eating (swallowing) at the same time, most mammals can do this, and baby humans can as well.
Like most anatomical systems that seem as though they could have evolved better, this system works most of the time and has worked well enough for hundreds of millions of years.


text:
Known MicroRNA - Gene Systems?
Have there been any experimentally-verified systems of microRNAs targeting a gene set (e.g., in cancer, perhaps)?

Yes. Below is a link to a review of ncRNA (non-coding RNAs) and their role in disease. There are many examples in this review in all sorts of diseases, one of which is miR-200, which is thought to play a role in some cancers.
There are also some tables in the paper that list the miRNA and the disease they are linked to. They also have a reference for each one, so you could read more about that particular miRNA and its function, including the gene it regulates.
http://www.nature.com/nrg/journal/v12/n12/full/nrg3074.html
Im not sure if that article is open to the public or not. If you cant access it you could always check out the wikipedia entry for miR-200
http://en.wikipedia.org/wiki/Mir-200

source: Stack Exchange

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

sort: votes


text:
Is "Fight or Flight" distance genetic
If you took a newborn animal and completely isolated it from its species, would it be capable of assuming a fight or flight distance preset by its species, due to their being no basis for what could harm the animal?

What do you mean by "distance"? Can you give an example?

It probably is somewhat genetic.  A good example is pigeons.  When you approach them, they turn their back to you so that if you get close enough they can escape / fly away.  I'd be surprised if this is only a learned behavior, but I also note that pigeons who have been fed let you approach to a closer distance than other birds, so in this example a distance is not completely hard wired.
Such behaviors are more likely a combination of learned and genetic, especially as the animal becomes more complex (has a larger brain).  This is a major concern of 'ethology'.
I think few inherited behaviors are completely inflexible.

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


text:
Are there women that can always "select" a spermatozoon with X or Y chromosome?
In women when there are spermatozoons near to perform a fecundation, their egg cells emit some substances to attract the spermatozoons they "consider" would be a best match.
Here a link for that study: https://royalsocietypublishing.org/doi/10.1098/rspb.2020.0805
I'd like to know if in that selection there would be cases where the female would only select spermatozoons with the X or the Y chromosome; this would explain cases along the history where a woman couldn't give birth to a child of a certain sex.
Is this selection possible in some women?

I would say almost impossible to answer because 1) you'd need to extract eggs and work on it, 2) statistics says that the observed even will happen just by chance. For historical cases; how do you know that their next pregnancy wouldn't have been the opposite sex?

@bob1, if they have done the study that the eggs get to "select" the spermatozoons, I see no reason they could go on the study further to check what it exactly can "select". About historical cases sure, there are not evidence for anything, but they support my hypothesis.

I'm not sure that there has been any study that shows that the ovum selects sperm based on anything other than being the first to reach it. There are selections based on motility and survival in the different environments of the genital tract in women (pH, mucus, distance...) but nothing to do with the egg. see here for a review (2015).

I looked at the study briefly and I honestly don't see evidence of a "selection" effect in the way that you're talking about. They find that there are non-random attractant effects between particular male/female donors. But I don't find a convincing mechanism, or even any evidence that particular kinds or classes of sperm can be chosen. There is simply no evidence that the eggs "consider" or "choose" sperm, as opposed to more or less random attraction phenomena. Granted, the researches themselves misleadingly frame it as "mate choice", but that appears to just be hype.

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


text:
How are two species with similar phenotypes identified as different?
How are two species with similar phenotypes identified as different? Have two different individuals  that were thought to be different species ever been determined  to be from the same species ( or one a subspecies of the other's species ) ?

More information about the semantic difficulties of the concept of species can be found in this answer.

Species are difficult to define. This is because they form over a gradual continuous spectrum via evolution, one species does not suddenly become two, but lineages diverge (perhaps because there is some kind of barrier - like a mountain range - in the way) eventually reaching a point where we class them as separate species. How we define species is debated but the most generally accepted definition is the Biological Species Concept (BSC). Roughly the BSC defines a species as "a group of individuals that do, or could, successfully breed." Other species concepts do exist, some have their merits, but the BSC is most widely accepted and normally taken with a pinch of salt - it's not always possible to perfectly define a species because evolution and speciation are ongoing processes. Therefore, according to the BSC, two groups can be called different species even if the individuals look identical as long as there is true reproductive isolation.
Reproductive isolation can occur because of physical barriers such as rivers, oceans, mountains, environmental change. This is the cause of allopatric speciation. One species could become split when a subpopulation forms on an island (e.g. if humans take them to an island). If enough time passes without migration they will become reproductively incompatible. Another mechanism is sympatric speciation, when two species form without geographic isolation. This could be by the evolution of new behavioural, morphological or physiological forms which create division within the initial meta-population in to distinct sub-populations which over time become more reproductively isolated. Traits related to reproduction are amongst the fastest evolving and can quickly reinforce speciation (e.g. sperm morphology is extremely varied between species, see Sperm Biology: An evolutionary perspective, chapter 3).
The higher up the tree of biological classification you go the easier it becomes to classify things in to distinct groups, e.g. An oak tree is clearly a plant, and a whale is clearly and animal; further towards species definitions a whale is a mammal and a sparrow is a bird and both are animals; and perhaps less clearly, carrion crows and hooded crows are two different bird species in the Corvus genus. (Formerly these two were considered the same species!)
Obviously problems begin to occur when we consider species that reproduce through means other than sexual reproduction - e.g. bacteria which clonally reproduce. Traditionally this has been done by phenotypic information. We are now in the genomics era which opens new possibilities. This article discusses modern techniques by which utilise genetic similarity & difference between cells to define species and they suggest it to be a good method. However, this article seems to suggest that genomic methods need some refining first before we start classifying species with them.

Currently, it appears more pragmatic and efficient to preserve the current species definition than to replace it, because it is serviceable as a first level of screening and current phylogenetic knowledge is too limited for a universal and sound change in the definition.

As for whether two species have been reclassified in to one I know there are examples but Google is not throwing up anything and there's nothing I can remember off of the top of my head - if I remember correctly the male and female mallard were once considered separate species because they look so different but I can't find anything to back this up. Species formerly described as one have been split in to two as well - gorilla's are one such example.


text:
Loss of nerves in asthma
This site says:

VIP [vasoactive intestinal peptide] nerves are absent in severely asthmatic subjects. Mice with targeted deletion of the VIP gene exhibit histopathologic features of airway inflammation (Said et al., 2010).

So can we consider asthma as a neurodegenerative  disorder?
What will be the mechanism of destruction of nerves if the above statement is true? If the above statement is not correct then how there is reduction in VIP ? I think of two possibilities either VIP is not synthesised in the neurons (Gene is down regulated, if so, by what?) or it is readily destroyed after its synthesis?
Could anyone please correct me?

You also have to consider if the nerves were there to begin with, and whether it's an issue of development rather than degeneration. I think an overarching suggestion is that while asthma is mediated by immune cells, there are other events including neurological that mediate the response. And this is for me a good source, though not recent.


text:
Effect of light intensity on the frequency of stomata
According to this article, the frequency of stomata increases with an increase in the intensity of light. What I inferred from this is, since the rate of photosynthesis increases at higher light intensities, more C02 is is required and hence the frequency of stomatal openings increases.
I know that the Light Harvesting Complexes inside chloroplasts use light to release electrons, which are then subsequently used in photophosphorylation. If we compare the process with the photoelectric effect, we shouldn't see an effect of the intensity of light, but instead we should see changes for different frequencies(which we already do).
So how does the rate of photosynthesis increase with higher light intensities?
Is the mechanism of light absorbtion by LHCs similar to that of a photoelectric cell?

You are misunderstanding photoelecric effect.
Intensity of light does not have effect on maximal kinetic energy of individual ejected electrons. Maximal kinetic energy of ejected electron is determined by energy it can get from single photon which is in turn determined by frequency of light.
However, intensity of light definitely does have effect on number of ejected electrons. More incident photons (higher intensity of light) result in more ejected electrons (and higher measured electric current).
In photosynthesis number of utilized photons is more important than their energy. Photon either does have enough energy for separating the electron (e.g. red or blue light) or it does not (e.g. infrared light). If a photon with energy higher than needed (e.g. blue light) is captured then the excess energy dissipates to heat.

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


text:
Hebbian theory "fire together" clarification
Donald Hebb states it as follows:

"Let us assume that the persistence or repetition of a reverberatory activity (or "trace") tends to induce lasting cellular changes that add to its stability.… When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A's efficiency, as one of the cells firing B, is increased."
  Or we can conclude in short: "Neurons that fire together, wire together".

As I understand it, this means that synapses that already exist become stronger between neurons.

Could new synapses form between neighboring neurons that "fire together", but are not necessarily directly connected through an axon?
And if so, what is the mechanism to direct the new synapse formation towards that other neighboring neuron that "fires together"?

Strictly stated, Hebb's rule applies only to existing synapses, and not to the formation of new synapses. (This answer applies to biological neurons, not to ANNs).
Synapse formation is a topic of active research. During development (and in fact continuously even during adulthood), many synapses are created and destroyed. It is not unreasonable to suspect that a similar form of rule is used to decide which synapses are removed and which should remain.
Synaptic connections between neurons show a good deal of specificity -- for example, in the projection from the retina to the optic tectum, synaptic connections are made only with target neurons at an appropriate retinotopic location. This happens because growing axons follow molecular gradients.
Within a cortical column, some possible connection pathways seem to be actively sought -- for example, axo-axonal cells connect specifically to the axon initial segments of target neurons. Neurons certainly have membrane molecules that could be used to identify target cell classes.
So there are probably a number of rules used to determine when a new synapse is made. However, I am not aware of a mechanism for a pre-synaptic neuron to detect how a putative post-synaptic parter is firing, without a synapse already being present. So it seems likely that some form of random process is involved to form new synapses with reasonable post-synaptic partners, after which some activity-dependent rule (like Hebb's) could be applied.

It probably depends on what stage of development the neurons are in and what region of the brain.  If there's not branching still going on, then probably not.  Hebbian learning is generally considered a concept of neuron connections strengthening (more synapses forming and dendritic spines growing larger) and not the initial formation, particularly in artificial neural networks, where a non-zero weight is already assigned to the neurons, and it's just a matter of strong vs. weak connections.

Hebb himself (Hebb 2002) actually thought that both the formation of new or the enlargement of pre-existing synaptic contacts (what he called "synaptic knobs") were the most likely possibilities. However, he did not exclude a role for metabolic processes, such as the alteration of intrinsic firing properties of the neuron that could lead to increased synchronicity or a change in the firing threshold, or a limited role for microscopic motility ("neurobiotaxis"). From his language, it is unclear if he had a concept of pre- and post-synaptic elements. Indeed, evidence for the existence of the synapse from electron microscopy were presented about a decade later after the publication of his book.
It is pretty straightforward how the strengthening of pre-existing synaptic contacts can contribute to the proposed model. However, one can also imagine that the postsynaptic element, most often dendritic spines in the neocortex, could actively reach an already active presynaptic bouton. Even if spines are formed completely independently of presynaptic activity, it is still reasonable to think that only those that find an active presynaptic partner will stabilise by forming a synapse. See my answer here for more details on this matter.
Except from the temporal coincidence that is explicitly posited in the famous postulate, Hebb also predicted that the spatial proximity of two neuronal processes could result in synaptic contacts forming or strengthening. The hypothesis of spatial synaptic clustering, as we may call it, is actively investigated with modern methodological tools (Harvey and Svoboda 2007) and it is thought to be important in learning (Fu et al. 2012).

References

Hebb, D. O. (2002). The Organization of Behavior. Routledge.
https://doi.org/10.4324/9781410612403
Harvey, C. D., & Svoboda, K. (2007). Locally dynamic synaptic
learning rules in pyramidal neuron dendrites. Nature, 450(7173),
1195–1200. https://doi.org/10.1038/nature06416
Fu, M., Yu, X., Lu, J., & Zuo, Y. (2012). Repetitive motor learning
induces coordinated formation of clustered dendritic spines in vivo.
Nature, 483(7387), 92–95. https://doi.org/10.1038/nature10844


text:
What is an irreversible reaction?
There are reactions with large Delta G negative values. Why these reactions are irreversible? As in: out of 10 steps of Glycolysis, 3 are irreversible steps. I need an explanation for why they are irreversible.

About which reactions do you think?

A short answer is that they are irreversible because in the conditions of the cell they happen far from equilibrium (which is actually what having a "large \Delta G" means).

The term "irreversible" means that the reverse reaction occurs so rarely that it is considered negligible. This means that you do not have to consider equilibrium, as you have to for reversible reactions. Instead, you can assume that all of the reactants will eventually become product.
As you stated, this is true for reactions that have a very negative Gibbs free energy.  Remember the formulation of the Gibbs free energy in terms of the equilibrium constant:
$$
\Delta G^o =  -RTln(K)
$$
This can be rewritten as follows:
$$
K = e^{-\Delta G^o/RT}
$$
As $\Delta G^o$ gets very negative, you can see that $K$ gets very positive.
The equlibrium constant has two definitions that are both useful. First, it is the ratio of the products to the reactants. Therefore as $K$ gets very positive, the equilibrium ratio of products to reactants approaches infinity, implying that all of the reactants will be consumed.
More useful is the definition of the equilibrium constant as the ratio of the rates of the forward and reverse reaction. From this definition we can see that as $K$ gets very large, the ratio of the rates of the forward and reverse reaction approaches infinity. This means that the rate of the reverse reaction becomes negligible compared to the rate of the forward reaction. This is exactly what it means to be irreversible.
Note that it is possible to make (what I think is) a more convincing argument using the concept of activation energy, using Hammond's Postulate to describe the character of the transition state. If you'd like, I can write this out. However, I think the argument given above is more easily understood with a basic chemistry background.

yes! all chemical reactions are reversible.  its not said enough in frosh chem.

I understood it properly, its very helpful but if you are comfortable to explain by using the concept of activation energy then, Then i want to understand that concept too.. :)

@katherinebridges Have a look into the Wikipedia on activation energy. It contains an image which explains the concept pretty nicely. Basically most chemical reactions (even those which set free energy) doesn't start on its own. To do so, they need an initial amount of energy to start. Think of a sparkler. It contains chemicals which are capable of setting free a lot of energy when reacting, but under normal conditionss nothing happens. If you add the activation energy through a match, the reaction will go off and set off a lot of energy.

@Chris Ok, I will consult wikipedia to understand that concept,Thanx for the help..

"[...] you can assume that all of the reactants will eventually become product" this characterises a total reaction. A total reaction is irreversible by definition, but the opposite is not necessarily true.

The confusion between irreversible and total is also here when you write that "as $K$ gets very positive, the equilibrium ratio of products to reactants approaches infinity, implying that all of the reactants will be consumed". A reaction can be irreversible whatever the value of its equilibrium constant or of its standard Gibbs free energy of reaction. Again, total implies irreversible, but not the contrary.

I'm not familiar with this concept of a "total reaction" that you propose, and I don't see it referenced in a quick search in google or google scholar. Maybe this is terminology of your specific field? Could you give a reference?

Whether a reaction is reversible or irreversible, in the presence or absence of an enzyme, is not related to activation energy. An enzyme lowers activation energy in both directions.
A reaction is reversible or irreversible depending on the conditions in which this reaction occurs. If there's a sustained high concentration of substrates, most of the reaction flux goes from substrates to products, and the reaction is practically irreversible. The same happens the other way. Note that whether the concentrations are high enough or not depends on the kinetic constants involved.


text:
Is it possible to calculate the energy required to speak a word?
I was discussing with a colleague whether speaking would require more energy than communicating via instant message (GTalk, etc..).
If this is possible, then I'm particularly interested in whether certain sounds may consume more energy that others, and consequently could one language be more efficient than another.

It may be more useful to consider the total amount of sound required to convey information. It has always seemed to me that Italian is particularly profligate. Example chosen at random: bread maker (English, 3 syllables); macchina per il pane (Italian, 7 syllables). But, of course, this isn't really a biology question.

https://www.popsci.com/ask-us-anything-how-much-exercise-do-we-get-talking/

For animals to check the amount of energy used for a certain behavior you can use a RESPIROMETER. It basically calculates the oxygen consumption.
In your case you could calculate for writing a sentence vs speaking the same sentence.
Regarding your second question:
At least in birds more than the type of sound (the frequency modulation) what matters for energy consumption is the amplitude --> how loud is your sound.

adding to this answer; hence you would feel more tired if you'd been shouting the whole day-

It could be theoratically possible if you fitted a glucose sensor to a person's body and asked that person to do nothing other than talk, for say a period of 1 minute. Then, when he/she talks, the amount of glucose metabolized during that time period could be measured, and subsequently, the no. of calories required for speech. Of course, the amount of calories required for breathing and even doing nothing (sitting, which consumes 75 calories of energy per hour) must be deducted.

Sitting consumes more than negligible amounts of energy. In fact, sleep consumes energy.

Most of the energy consumed by the body is required to keep the body temperature stable, and keep the brain alive. Even physical activity (if not extreme) doesn't come close to it.

I don't think measuring glucose would be sensitive enough.


text:
What is the mechanism behind plants losing their leaves?
Do plants that lose their leaves (i.e., deciduous plants) do so because of external conditions (e.g., drought, cold), or because of an internal process?
Another way of looking at it: if you take a deciduous plant that loses its leaves during cold winters with long nights (e.g., Canada), and plant it in an environment where it is always warm and sunny (i.e., at the equator), would this plant continue to shed its leaves and re-grow them according to the seasons in Canada, or would it behave as an evergreen instead?

I edited the question to improve clarity. Please feel free to roll back. Nice question! +1

The process of a deciduous plant losing its leaves seasonally is known as abscission. It occurs when a layer of cells known as the abscission zone elongate and weaken, causing the leaf to fall off. It is mediated mainly by the hormones auxin and ethylene.
The functional purpose of abscission is to remove leaves when they are no longer producing a net gain of biomass. Leaves decrease in productivity during drought, decreased day length, and when under the effect of herbivory.
In some species (according to the day-length source), "When the daylength exceeds a certain 'critical' duration, growth may be
maintained continuously for at least 18 months under favourable temperature conditions, e.g., in Liriodendron tulipifera, Robinia pseudacacia". So, to answer your final question, some deciduous species (but not all) may indeed retain their leaves if they are grown in favorable conditions. One reason why not all deciduous trees retain their leaves even in favorable conditions is that internal ageing can also induce abscission: "In such species, growth is determined primarily by the endogenous ageing process and is only modified by environmental factors, including daylength"

So, to understand correctly, the plant produces the hormons because the growth is unsustainable. So my next question would be, why not all deciduous retain their leaves in favorable conditions? the answer stems from your answer or I make a new question?

You can edit your post to include your new question and I'll try to answer it

The shedding of leaves has more to do with the condition of the leaf itself. When leaves become inefficient and unable to produce food and
growth regulators, a process of abscission starts.
Abscission a step in the planned senescence process within tree leaves. Senescence is a series of events that allow trees to conserve resources, prepare for a dormant period, and shed inefficient tissues. Senescence is not disruptive and not always caused by climatic factors.
Senescence is a highly ordered and carefully controlled set of steps initiated in preparation for a resting period of a tree (winter).

Are the signalling and detachment mechanisms different in the case of senescence vs. seasonality of the environment?


text:
Why does ostrich and other birds like pigeon swallow stones?
I have read in my book that birds swallow stone to help in their digestion process. What is the need of swallowing stones? And how does it aid them?

I have suggested an edit for your post for a possibility which I also think but not sure

Mention not :-)

there should be a textbook biology forum and an advanced one on here. it's confusing prefer to interact on a forum with a 1h incomplete response time, instead of geting a complete instant answer from google with illustrations and nice pages.

Birds do not have teeth so stones help in the process of grinding food.
Before even going to the stomach the food it starts to be processed in the "Crop". However is in the "Gizzard"  that the stones play a big role helping this muscular sack to mince and grind the food (the link sends you to an image of an open gizzard with pebbles inside).
Food and stones are present at the same time into this organ, therefore during peristaltic and contraction movements the friction between stones and food allow more efficient grinding.

Here you can a detailed description of the chicken digestive system that can be largely applied to birds in general.


text:
What are the reasons that soap has so different smell and flavour?
Everybody has tried to taste soap in their childhood. One would think that if soap has a tasty smell it would have tasty flavor too. But we know it is not true (in the common cases). But why is there is difference in the senses to our noses and tongues for the same soap?

I am having difficulty understanding your question. Do you mean: "How is it possible for soap to smell tasty, but not be tasty?", or more generally: "why is our instinctive of guess of how a substance will taste, given how it smells, not perfect"?

Exactly, you understand.

I like the taste of soap :) I retracted my close-vote, but I think the question is quite opinion-based.

It is possible for a substance to not smell very much, but to taste very strongly - chili peppers are a great example. They (in my experience) have a rather weak spicy odor, but the taste is much much more intense. In the case of soaps, very small amounts of essential oils are used to give soaps their odors. You may be able to slightly taste them were you to eat some of the soap (definitely NOT recommended!), but the major taste you'd experience is the actual soap - the saponified surfactants that do the cleaning.


text:
How do we feel sensations from a tooth surface that is made up of enamel?
If enamel does not have any sensory receptors, how do we feel the tactile sensations when we touch our teeth with an object/finger nail?

How do we feel the tactile sensations when we touch our teeth

The same way you feel tactile sensations when you tap a bicycle helmet on you head: the motion (or vibration) is transferred through the material to your head & the nerve endings in your scalp the same as tapping a tooth sends vibrations to the nerves in & at the base of the tooth.


text:
Is there any evidence for secondarily poikilothermic vertebrate?
Is it possible that an endothermic physiology can evolve into an ectothermic (poikilothermic) physiology? I have a non-scientific gut feeling that it is irreversible. Whales and dolphins are evolved from land mammals, and they've remained warm blooded. While it doesn't give them any obvious advantage in the water, apparently they've compensated with massive amounts of body fat instead of devolving. If the ocean offers opportunity for mammals, then why haven't fish evolved to be warm blooded directly?

You may want to use a term other than devolve. http://en.m.wikipedia.org/wiki/Devolution_(biology)

What do you mean by cold-blooded?
There's an issue with what you mean when saying "cold blooded". The correct words you may want to use are homeotherm, poikilothermic, ectotherm, and endotherm. In short…
Source of heat

endo = inside
exo = outside

Variance in warmth

Poikilo = varies
homeo = does not vary

Any combination of these two axes exist. For example: If the temperature in the environment never varies you can be homeotherm without needing to be endotherm. A fun example also are the large dinosaurs that are thought to be homeotherms because their metabolism produce some heat and they are so large that they remain warm thanks to this heat source. However, they were probably not able to regulate actively their temperature. Therefore, I would tend to qualify dinosaurs as homeo-exo-therm but I wouldn't be surprised if someone prefers to call large dinosaur home-endo-therm individuals. Hope that makes sense to you.
Note that the terminology might be a bit more complicated in reality as the diversity of mechanisms of body temperature regulation is important.
What did you mean in your question when talking about "cold blooded" species?
Transition from endothermy to ectotherm
Thanks to @tchrist. naked mole rat is ectotherm while its ancestors where endotherm.

This perfectly makes sense so far and what I tried to ask exclusively is if there is an example of a mammal that devolved to an ectotherm. But appearantly the transition that I'm looking for isn't really obvious. I would still be interested in any potential example though.

With "cold blooded" species I meant to say ectothermic species, but I wasn't familiar with those scientific terms yet.

@user43058 I don't think there is any ectotherm mammal. Some have important variation in temperature during hibernation though. The question of the benefits and costs of being ectotherm verus endotherm and how endothermy can evolve - is very broad. And it is a very interesting question! I encourage you to ask this question in a separate post. I had a lecture on the subject during my Bachelor degree, I personally may be able to help you on another post if I go back to this lecture.

The naked mole rat (Heterocephalus) has some rather odd thermoregulation characteristics for a mammal.

@tchrist Indeed, according to wiki the naked mole rat is the only mammal ectotherm. Thanks


text:
Ligation without purifying insert
I am planning to insert a 45 bp sequence in a vector. After restricting my insert to create compatible sticky ends, I am finding no way to clean it up. Is there any way for cleaning this fragment after restriction or should I proceed without clean-up?

Proceeding without cleanup will reduce your efficiency but may still work. Have you tried purifying via gel extraction? A high density gel should allow you to separate the band to some degree.

Hi Joe, I can locate the band in high density gel, but would it be possible to extract 45bp sequence through gel extraction protocol?

I think so, though you may need to ensure you use a column designed specifically for small fragment retention. There are columns for purification of miRNAs, so I’d have thought there might be a column you could source which will do a similar thing for dsDNA, but I am guessing somewhat. I believe there are some old-school chemical techniques for precipitating away melted gel without needing a column too that you could try. You could then concentrate with a rotorvap or heatblock.

“GeneClean” which involves adding powdered glass and potassium iodide solution to an agarose gel slice would work for this.  I believe QIAgen sells a matrix like this.  The glass is extremely fine, and has to be prepared by boiling in nitric acid.  Once upon a time there was a company named Bio 101 that sold a product named GeneClean, but they may have been bought by somebody else.  For unknown reasons, nucleic acids will bind to glass in the presence of a chaotrope.

A much simpler way to insert sequences that are really small is to order the DNA as oligos and anneal the complementary oligos such that they have compatible overhangs with the overhangs from  your restriction digest

Thanks all for your comments guys. I tried purifying using PCR purification kit. I could recover 120 ng of purified fragment from 500 ng. It is ok for my further work.

That's not too bad for a fragment of this size, the efficiency of the column kits (actually almost all DNA preps) goes down with decreasing size. If you wanted higher efficiency you could use a magnetic bead based kit such as Dynabeads or  AMPure XP ($$$, but the best).


text:
Are there hyoid bones of Homo habilis in the fossil record?
Hyoid bones have been found for Homo erectus, Homo neanderthalensis, Australopithecus afarensis, and some more hominids. Have hyoid bones been found from Homo habilis?

References:
Capasso, L., E Michetti., & R, D'Anastasio. (2009). A Homo Erectus Hyoid Bone: Possible Implications for the Origin of the Human Capability for Speech. Coll. Antropo. 32(4), 1007–1011
Alemseged, Z., Spoor, F., Kimbel, W. H., Bobe, R., Geraads, D., Reed, D., & Wynn, J. G. (2006). A juvenile early hominin skeleton from Dikika, Ethiopia. Nature, 443(7109), 296-301.
Steele, J., Clegg, M., & Martelli, S. (2013). Comparative morphology of the hominin and african ape hyoid bone, a possible marker of the evolution of speech. Human biology, 85(5), 639-672.


text:
How some virus are able to reach the CNS?
I know that the lymphocytic choriomeningitis virus (LCMV) could provoke meningitis and encephalitis when this virus reaches the brain. However, there are other viruses like Varicella (VSV), Cytomegalovirus (CMV) or Herpes (HSV) that are able to reach the brain, hence, to pass trough the blood-brain barrier (BBB) and damage the central nervous system (CNS).
1) Since the blood-brain barrier allows only the free diffusion of some molecules such as water, some gasses and lipid soluble molecule, I was wondering by which mechanism a virus is able to pass trough the BBB.
2) Since the CNS is an immuno-privileged space (where basically the immune system is down-regulated), how does the body eliminate a virus that had reached the brain?

What on god's green earth is the "SNC"?

@4DNeuron sorry is CNS, I've already edit the question

you should do some homework before posting, maybe start with https://en.wikipedia.org/wiki/Central_nervous_system_viral_disease and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3367119/

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


text:
Why would a bumblebee regularly hover over a arborvitae hedge?
I have observed bumblebees hover over an a abrborvitae (Thuja occidentalis) hedge. A bumblebee will hover in a in one spot over the hedge for about 5-7 seconds, zip to another spot, hover for about 5-7 seconds, then another spot, then another. The bees will never land on the hedge. At any one time during anyone day, there will be only one bee hovering over the hedge. This behavior will go on like this all day.
Why do the bees do this?

The behavior sounds more like a hoverfly than a bumblebee.

It's not a hover fly,they don't fool me. I've walked right up to it and it didn't move. I considered that it might be guarding something,I've seen them guarding an especialy fragant viburnum. This bush was covered in bumble bees. I had to crawl backward to get out of there or one would have stung me.

Perhaps it is a solitary bee that has a mud nest on the Thuya tree, or another variety that has a burrow.

Could you perhaps make a picture of the bee? BTW: Bumblebees rarely sting.

I can't get a picture of it in september,that's for sure.

Could actually be a male carpenter bee. They hover around like that waiting for females to pass by. If it is a male carpenter bee dont worry about it, they arent equipped with a stinger.

I'll check to see what it is,but why would a male carpenter bee do this? Can you include some kind of reference for this? Maybe a link?

Today I hit the arborvitae In my yard, in which at least 5 or six HUGE bumblebees fell to the ground. After my initial shock, I hit each of the arborvitae along my fence and a dozen more fell out.
I believe these Bumbles have nested in my trees, which  may explain the hovering behavior; they are either scouting out a place to rest or visiting their young, not entirely sure. Hope this helps


text:
Does incomplete dominance follow or not follow the law of segregation?
The law of segregation says that in hetrozygotes, dominant and recessive alleles remain together without mixing into one another. In incomplete dominance, two alleles blend with each other, and the hetrozygote is a new individual with blend of both. So can it mean that incomplete dominance does not follow the law of segregation and also the law of dominance? What about law of segregation? Does it follows it?

Hello @Rabik  Why do you mean by "mixing into one another"? Do you mean phenotypes are not mixing? Alleles are versions of a gene, so they don't really "blend" or anything, what could happen is dominance of one over the other making the phenotype look like the expression of the dominant allele.

I mean each allele, either dominant or recessive. Maintain its individuality one is dominant over other but they donot blend ;according to law of dominance ,and incomplete dominance disobeys this,so I just wanted to know that does incomplete dominance obeys law of segregation?

I think you are mixing different notions, you need to be clear on what you are talking and then your answer will appear as evident to you. I invite you to check this site to get the definitions. Firstly
What is law of segregation also called first law of Mendel?

It is the hypothesis that during the formation of reproductive cells (gametes), pairs of hereditary factors (alleles of genes) for a specific trait separate so that offspring receive one allele from each parent.

Note that there is nothing here about expression (which is what is visible), it's all about genes and alleles.
What is law of dominance also called third law of Mendel?

It states that one of the allele for a pair of inherited allele will be dominant and the other recessive.

This one is about expression, you know you can have two different alleles but this law says one will always be dominant over the other (which means the allele will be expressed whether the other one will be silenced or not visible).
And what about incomplete dominance?
Well Mendel during his studies encounter more complicated case than simple dominance, sometimes the two alleles will express equally (co-dominance)  giving a third observable phenotype (like blood-type AB for example). In reality, most of time the observable phenotype is nearer of one phenotype given by the domniant allele.
To conclude: incomplete dominance doesn't break the first law of mendel (segregation) as alleles will be equally transmitted to offspring but it breaks the law of dominance because the phenotype is not exactly one given by a unique  allele but rather a mix between both.
Remember: Segregation law is not about expression or phenotype

What a perfectly phrased answer +1

Thanks untitpoi!I will make my basics more strong. There is one more thing that bothers me a lot that;one allele is a pair of genes on homologous chromosomes. I wanted to  know that in a pair of homologous chromosomes there are two alleles on" each" chromosome ? Or there is only one allele on "both" ?Or it's like that out of a pair of genes in allele one gene is on one chromosome and other gene is on another homologous chromosome?

For one given gene, there could be multiple version of that gene in a population like allèle A B and O for blood type. But one individual only has two alleles one coming from mom and one from dad. What could have make you think there is four allèle per individual is the bad double chromosome visualisation(In X form you know). But that happens only during meiosis and is NOT the normal state of DNA


text:
Would all the different species evolve to their respective next form of life eventually?
Would  all the different species evolve to their respective next form of life eventually? Like this generation apes to humans in next million years? Or does all the different species exist to only show how evolution happened to humans?
For example, it seems foxes can evolve into dogs by domestication, is that so?

There are a lot of misconceptions in your question. The better for you would be to simply start with an intro course to evolutionary biology such as Evo101 by UC Berkeley for example. I will answer your question directly in the text.

would all the different species evolve to their respective next form of life eventually?

You seem to have a very discrete conceputalization of what form living things can take. Current species won't all of a sudden change into a new one, like a "pokemon evolves". But all current lineages are still evolving. They keep changing gradually.

Like this generation apes to humans in next million years?

Humans have not "evolved from apes". Humans ARE apes. Humans and other apes have a common ancestor who already was an ape. The most closely related species to humans are chimpanzees and bonobos. The Most Recent Common Ancestor (MRCA) between humans and either chimpanzee or bonobos lived about 6 millions years ago.
See this answer for a short intro to phylogeny. You might also want to explore the tree of life by yourself on OneZoom.org. You'll find the human lineage here.

Or does all the different species exist alive now to only show how evolution happened, to humanz?

No, there is no intention. Nobody made evolution happen for humans to witness it. Evolution just happened and keeps happening. Nothing has stopped it and nothing (except extinction of all life on earth) can stop it.
If you follow a very short intro to evolutionary biology (such as the Evo101 suggested above), you'll understand what evolution is and why it always happens.

Though it seems foxes can evolve into dogs by domestication?

No. Some foxes are currently being domesticated and they manage to select for typical domestication traits (e.g. lower aggressivity). These domesticated foxes are not dogs and never will be. They are domesticated foxes. If those domesticated fox become different enough from wild foxes (typically if there is reproductive isolation), then we will eventually consider them as a new species and give a name to this species. But we should not call them dogs, they are not dogs (just like cats, cows, chicken or corn are different from dogs, yet all are domesticated).

Or even cats: domestication has made them different from the ancestral wild cat, just as dogs are different from the ancestral wolf, but few people would have trouble telling them apart.

I would say the first quote - specifically the "their respective next form of life" part - also implies the "ladder of evolution" misconception here.

to add, the foxes in question developed a couple of traits we associate with dogs, it  turns out these traits are linked to traits we select for, either consciously or unconsciously. basically it is showing that many of the unique physical traits of dogs may be just as much as result of domestication as behavioral ones.

You have so many misconceptions about evolution, it is impossible to give you a complete answer in a small text box
There is no "next form".  Populations change in response to their environment, and how that happens is in large part dependent on chance.
Foxes do not evolve into dogs.  Nothing the scientists did in that experiments was anything remotely like making foxes evolve into dogs.  All they did as put the population under enormous pressure by culling all but the friendliest animals.


text:
Why is a cellular structure necessary to satisfy the definition of alive?

I was looking at this image and reading through the Wikipedia page for viruses and it says that to satisfy the definition of "being alive" the organism must have a cellular structure, but it seems to me that if an organism has all these other factors without a cellular structure, it is still seemingly alive, no?
So why exactly does an organism need a cellular structure to be alive? What is the rationale for that criteria?

A quote I remember from the Campbell's Biology textbook said something like "if you take all the individual components of a chloroplast and put them all together in a tube, you won't have a functional chloroplast"... That's why the structure of a cell and its organsiation matter, even if it doesn't explain why the structure is absolutely necessary for a cell to work. Similarly, the textbook would say that having all the pieces of a bike in a box won't lead you anywhere, but a little bit more structure could make a bike and lead you somewhere. I hope these examples can help.


text:
Do Black Hair Fuzzy Caterpillars bite?
I saw a caterpillar in my bathroom. It's about 2 inches long and 3/4 inches in diameter. It has long (about 1 inches) long hair on his body.
I live in eastern India, Asia. I don't know if it was alive, as I didn't see any remarkable movement.
Are they dangerous? Do they bite? How to get rid of them?

It would be better if you would post some pictures of them

I can nearly guarantee that there are nearly zero species of caterpillar that have a nasty bite. Some caterpillars like the pine processionary cause skin rashes. some caterpillars can Kill you, better check it on this list: https://www.ranker.com/list/caterpillars-that-can-kill-you/eric-vega


text:
Endomembrane system
I learned that the endomembrane system includes the nuclear membrane, ER, the golgi, lysosome, endosomes etc. But why doesn't it include the mitochondria and the chloroplast?

Another clue in favour of the Endosymbiotic theory? For instance Mitochondria having both in inner and an outer membrane.

Small vesicules continuously bud from the ER membrane and fuse into the Golgi, and this vesicule trafficking is also involved in adjusting the cytoplasmic membrane's composition and extent. This is a defining feature of the endomembrane system.
The membranes of chloroplasts and mitochondria are not involved in this vesicule trafficking, which is why they are not considered part of the endomembrane system (even though they "have membranes" and "are inside the cell", which is the etymology of the term "endomembrane").


text:
Why do zoologists classify sponges as animals rather than plants?
Sponges are fixed, do not move settle at one place, do not have a reproductive apparatus, respiratory apparatus, or organs, and live in marine environments. Why then zoologists consider that sponges are animals? In the past, zoologists considered them as plants and then considered them animals. What is the principe that zoologists have adopted to classify sponges are animals rather than plants?

Organisms are classified, not by their behavior, but by their phylogeny (evolutionary relationships). Sponges have unique and complex molecules in their intracellular matrix that developed in a common ancestor of sponges, and are shared with sponges and all other animals. These molecules include collagen, proteoglycans, integrin, and adhesive glycoproteins. These molecules are made by the cells, exist outside the cells, and fill the space between them.

@Ναείστεαισιόδοξοι If you think Karl's answer answered your question, you can click on the check mark next to his answer.

Their cells are typical of animal cells: no cellulose cell walls, for one thing. They are also heterotrophic, feeding on small cellular life or bits of organic matter taken into individual cells (collar cells or "choanocytes.")


text:
What absorbs light at 380 nm in a sample of DNA oligonucleotide extracted from a PAGE gel?
I have extracted DNA oligonucleotide of size 77 bp from a crushed 10% PAGE gel using 3 rounds of $\ce{LiClO4}$ in water. The extracted elute was dried down in a vacuum centrifuge to a certain volume and then precipitated with 5 volumes of Ethanol before taking a spec on a NanoDrop. I do have a significant peak, characteristic of a DNA oligonucleotide, at 260 nm with a $A260/A280 ≃ 1.75$.
However, I also get a peak at 380 nm. I used to get this since a long time but I could not understand what it meant (did not find any literature reference). I do not want to worry about it too much, as long as I have my oligo, but I would like to know what it is. A colleague of mine also got the same peak, though not very prominent, who did not do a PAGE purification but direct UV Spec after Phenol/Chloroform extraction and $\ce{LiClO4}$ in acetone precipitation.
What would you suggest?
[Note: For your information, I have already asked this question here on ResearchGate. Out of all the answers, Paul's seem to be quite rational. However, I wanted to see if anyone has any other opinions]
Thanks a lot for your answers.

I did not understand what was the edit that you made @kmm?

I was fixing some of the mathjax formatting.

I guess I would like to close this question. I have already got answers on the ResearchGate forum. Thank you!


text:
Why can't a corn cob have 13 rows of seeds?
Every time before eating a corn, I count its lines. I would always find 12 or 14 rows of seeds, but never 13.
Is there any biological/scientific reason behind this?

Most varieties of corn bred for modern use have between 8-20 rows of kernels (Bommert et al. 2013.. Nearly all varieties have an even number of kernel rows.  This is due to the early development of the ear.  Ears of corn are developed from pistillate flowers on the ear (Bortiri and Hake 2007). Pistillate flowers are the female flowers, so they will bear seeds. The seeds are the individual kernals.
Long before the ear of corn has the kernels, it has several rows of flowers. The flowers develop on the ear in long rows. Early in development of the ear, the individual rows of flowers double, forming rows of double flowers, as shown in the simple diagram from Bortiri and Hake (2007). Both male flowers (left) and female flowers (right) have this two-row structure.

You can see the doubled pattern forming in this scanning electron micrograph of the very early development of the ears, also from Bortiri and Hake (2007). Notice the tip of the ear still has the single rows but the rows begin to double a little farther away from the tip. You can usually see this even on mature ears of corn.

You can see remnants of this arrangement if you look carefully at a cross section of an ear of corn. I've drawn arrows to show the connections where the flowers once connected together. If you look carefully at the ear of corn, you can identify the rows. The doubled rows have the kernels exactly opposite of each other. Each doubled row is staggered slightly from the neighboring rows. I've drawn lines to highlight each doubled row.  These two photos are from the agriculture extension office at Purdue University.

The development of corn flowers and all other flowers follows what is called the ABC model of floral development (Krizek and Fletcher 2005). The model has been greatly expanded since molecular genetics has increased our understanding of flower development. Many genes are involved, and the genes are used in different ways by different species of plants. The pattern of gene usage is similar in most grasses, which explains the double-flower arrangement of corn. Most grasses have the double-flower arrangement, and corn is a type of grass.
Some highly inbred variety of corn can produce odd numbers of kernel rows, as shown in figure below, taken from Bommert et al. (2013). KRN is kernel row number.  RIL is recombinant inbred lines, which means different varieties that have been inbred for particular traits. Thirteen is possible, as are other odd row numbers. An odd number of rows is unusual, however.

Citations
Bomblies, K. et al. 2003. Duplicate FLORICAULA/LEAFY homologs zfl1 and zfl2 control inflorescence architecture and flower patterning in maize. Development 130: 2385-2395.
Bommert, P. et al. 2013. Quantitative variation in maize kernel row number is controlled by the FASCIATED EAR2 locus. Nature Genetics 45: 334-337.
Bortiri, E. and S. Hake. 2007. Flowering and determinacy in maize. Journal of Experimental Botany 58: 909-916.
Krizek, B.A. and J.C. Fletcher. 2005. Molecular mechanisms of flower development: An armchair guide. Nature Reviews Genetics 6: 688-698.

The FFA logo must be at the upper limit of kernals, spent 4 years in FFA and never took the time to count.

@user31782 - Sure, happy to help. If you find the answer satisfactory, feel free to click on the green check mark by the top of the answer. That's the StackExchange way of saying thanks! :)

@MikeTaylor yeah I know that. Actually I have just started to study biology, so I will accept your answer after I understand it completely.

@user31782 Absolutely.  If there is something I can clarify for you, just ask. :)


text:
Can you identify this mystery bur?
I found this strange bur on a stray cat in my neighborhood.  I've never seen anything like it, and Google reverse image search thinks it's an earring.  Found in in northern California, just south of Clearlake.  (38.90 N, 122.60 W)
The spike structure is almost exactly one inch long.

A friend has informed me this is from the redstem Filaree, and there are some cool time-lapse videos on Youtube of their spinning behavior when they are exposed to water, which is thought to help them burrow into the soil.  (I'm just glad it didn't get a chance to burrow into the kitty!)

Well done, and fascinating! +1


text:
Why does the clavicle ossify intramembraneously?
The clavicle is the only long bone which ossifies as a membrane bone. I studied this process, but I can't find the reason why it features intramembraneous ossification?


text:
How to obtain normalised ECG given ECG readings across lead 1, 2, and 3?
I saw this youtube video on ECG readings and cardiac dipole vector locus of the heart across the three leads. Posting screenshots from it:

My question is how to obtain the graph (2nd image) from the 3 graphs in the first image? Should I simply add them or is there something more to it?

link: https://www.youtube.com/watch?v=H8jVRhQkRjg


text:
why male penis not considered as cartilage?
Penis don't have bone like ears & nose, then why why male penis not considered as cartilage?
en.wikipedia.org/wiki/Cartilage

Because it's not cartilaginous…

Welcome to BiologyBeta. Everything is not either cartilage or bone. We have many other tissues. Have a look to this wiki article. The penis contain neither bones nor cartilage.

Btw, Are you sure the Botany tag was a good choice? The tag human-biology or anatomy would be better choices.

@Remi.b Also see baculum: http://www.mapoflife.org/topics/topic_203_Baculum-%28penile-bone%29-in-mammals/

If it doesn't have fur like a cow it must be a chicken? ....

feel the tip of your nose. Mush it around, It's got a certain stale gummy bear feeling to it. Now feel your ears, all over. The outer edge, the back, the hard part in the front where the ear meets the face. Feel your adam's apple. This is cartilege.
When you feel your penis, does anything even feel close? Nope. It's just soft. Soft tissue, to be precise.
When stimulated, there are comparmemts within the penis which engorge with blood.

When they fill up with blood, the penis gets hard. That's all there is to it. No bones, no cartelidge.
If you have any questions, noe's the time to ask.

+1. And you are telling me I am nice? Answering this question is the nicest thing one could ever do. I deleted two nasty comments to this question.. and left the third :) respect


text:
Functional unit
What is meant by functional unit of a system?
Like when we say that the neuron is the basic unit of neural system, do we mean that all those things that are performed by neural system can be performed by an isolated  neuron?
If yes, how? And if not, then why do we call it as functional unit of neural system?
Like we say hepatic lobule functional unit of the liver is not hepatocytes, because we say that liver has complex functions, and single hepatocytes cannot perform it. So the functional unit of liver is the hepatic lobule.
Basically I am asking can a single  neuron perform the most complex functions of neural system: like memory storage, control and coordination (to a smaller extent) regulation of  a cell.
How can a single neuron control or regulate another cell, because wouldn't it need other neurons for processing of stimulus?
Can an isolated neuron process any stimulus and make other cell to respond in some way? If not so why we call it the functional unit of neural system?

In biology, functional unit of a system refers to the smallest structural element that is capable of performing the tasks typical for that system (MP Hlastala, Physiology of Respiration).
In the nervous system, a neuron is usually considered a functional unit, because it is capable of performing the basic task of this system, that is transmitting signals. But to perform more complex tasks, more neurons need to be organized into structures, which are usually not called functional units but, for example, pathways (visual pathway, somatosensory pathway) or centers (respiratory center, cardiovascular center, etc.).
Functional unit smaller than a cell
In the muscle cells, the proteins myosin and actin form myofilaments, which are organized into sarcomeres, which are considered functional units of the skeletal muscles, because the main muscle function (contraction) occurs on the level of a sarcomere.
Functional unit as a single cell
A single fat cell (adipocyte) is a functional unit of the adipose tissue, because it can perform its main task, that is to store fat.
Functional unit as a structural element
A structural element can consist of various cells, ducts, small blood vessels, etc.:

A nephron in the kidneys
A hepatic acinus in the liver (not a hepatic lobule)
A pulmonary acinus in the lungs (a respiratory bronchiole and its alveolar ducts and alveolar sacs, not a pulmonary lobule)
An acinus in the exocrine and Langerhan's islets in the endocrine part of the pancreas (Access Medicine)
A lymhoid lobule in the lymph nodes
An osteon in bones

"Functional unit" doesn't have a very specific meaning. It's mostly a term used to help biology students imagine organs as collections of parts.
The entities named functional units in a textbook don't typically perform every single function of a whole organ. A cardiomyocyte, for example, is a functional unit of the heart. It can perform really important heart-related functions like spontaneous rhythmic contraction. However, it can't pump any blood.
Similarly, neurons do important nervous system functions by themselves, like firing action potentials, and ultimately things like memory occur due to changes within individual neurons. They can't, however, do anything useful to the whole organism alone.

A functional unit can be taken as that part of a system that sort of imitates the function of the whole system. The work done by a group of "functional units" eventually gives us the function of the whole system as one.

Hi @seera-deborah! It would be helpful if you can expand on what exactly neurons do and they appear as if they imitate the function of the whole system.

Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.


text:
Can the regeneration mechanism of lizards be used in humans?
Is there any mechanism or specific protein which helps lizards to regrow their tail? Can the mechanism of regeneration be used in humans to regenerate our limbs? Is there any other animal which has this kind of ability?

Here is a list of animals that can from wikipedia: https://en.wikipedia.org/wiki/Regeneration_(biology)#In_animals . I think the regeneration mechanism is due to stem cells and how cells differentiate. https://en.wikipedia.org/wiki/Regeneration_(biology)#Tissues

Actually there are some studies to find out your answer. Some of the studies claim that they have found a special enzyme and some say micro RNAs give salamanders the capacity of regeneration. But until now, humans couldn't use salamander's regenerative ability. Maybe you would like to know there is a mammal (african spiny mouse) with special regenerative capacities which include regeneration of its skin and cartilage without scarring.
References:

'Skin shedding and tissue regeneration in African spiny mice (Acomys)' Ashley W. Seifert,   Stephen G. Kiama,   Megan G. Seifert, Jacob R. Goheen, Todd M. Palmer & Malcolm Maden
Microarray analysis of microRNA expression during axolotl limb regeneration.
For further studies I recommend searching "salamander and regeneration", "african spiny mouse and regeneration" in pubmed ;)

Since you weren't able to get them on, I suggest you provide the name of the website(s), so that we know which ones to look at :)


text:
Are boat-tailed grackles efficient flyers?
The boat-tailed grackle's deep-V tail would seem to cause a great deal of drag or even downward deflection (like an airplane's elevators). How much does this actually affect the bird's flight?

It's considered a requisite on biology.se that at least some reading/research is carried out and presented with your question. [For example, do you have any evidence that boat-tailed grackles fly less efficiently than other birds? What criteria would you use to measure that?] Otherwise it will be closed as homework. The site tour and the help center  provide guidance on how to use this site. Please take a few minutes to read about the kind of questions which are on topic here.

@anongoodnurse: A Google search for this information turned up no satisfactory information. Now, 50 minutes after posting, this question turns up as the number one result and a duplicate of this very question on a copy-cat site shows up a few entries lower. I have no evidence other than my intuition and curiosity. You can be sure that I'm quite familiar with how StackExchange works.

I don't know... perhaps Physics.se would be a better site for your question. Yeah, copying happens. If you think it's iffy, flag a mod with the info.

Aside from a detailed study of the flight envelope of many bird species(which might not exist), the answer might have to be 'They're efficient enough, according to the  boat-tailed grackle at least'. Lots of birds have ridiculous plumage or other things that impede their flight. See: peacocks, birds of paradise, etc. Birds, weirdly enough, aren't designed to fly very well. Some are designed to look good or hide efficiently or whatever it is birds do.

@Resonating: Of the birds with unusual plumage shapes that I'm aware of, the only ones I've had the opportunity to observe with any frequency are the grackle which fly a lot and (with much less observation) peacocks which don't seem to fly nearly as much. I don't imagine lyrebirds, for an example which I haven't had the opportunity to observe, fly very well - the same (observation or flight ability) probably goes for many of the birds of paradise that you mentioned. As for a general statement of whether birds are designed to fly very well - I can think of many counter examples.

I added an image of the boat-tailed grackle for the unfamiliar.

I should have been more accurate. Not all birds are designed to fly very well. Albatrosses, swallows, all birds of prey, etc clearly are. From kmm's excellent answer, I'd conclude a soft 'not very much' given the lack of sexual dimorphism, which implies it's not for sexual selection. Does it flatten while in flight?

@Resonating - I completely agree with you, but, having raised peacocks, you'd be astonished on what those large and showy birds can actually do in the air. It took my breath away.

@Resonating: The female is quite different. So I would say that it's all about sexual dimorphism.

Are they? I have only pictures to go by, so I'll take your word for it.

@Resonating: The Wikipedia article has pictures for comparison. (I could take my own pictures and post them. I could choose from among many thousand specimens.) The male is iridescent black and the female is dull brown and lacks the tail V.

They seem to have roughly similar length tails but if the female is missing the V shape that's significant. If the females don't have the boat tail then it doesn't have an adaptive purpose, and we can conclude it's for sexual selection reasons and probably at least a little bit of a hindrance.

I don't know of studies specifically of boat-tailed grackle flight, so I'll focus on elongated tails in general and come back to grackles at the end.
Long tails in birds are obviously interesting from the standpoint of sexual selection. Going all the way back to Darwin, one hypothesis has been that females prefer males with long tails. There seems to be evidence for this, although experimental reduction or elongation of tail feathers is perhaps of questionable success. See this back and forth in Behavioral Ecology.
Those interested in the study of flight have also studied elongate tail feathers to get at the questions you ask: are long tail feathers aerodynamically costly?
Balmford (1993) compared the aerodynamic properties of different tail shapes. He found that:

A forked tail that has a triangular planform when spread to just over 120° gives the best aerodynamic performance and this may be close to a universal optimum, in terms of aerodynamic efficiency, for a means to control pitch and yaw.

But the results were more complicated. Forked tails are only used in extreme maneuvers, they are more unstable, and suffer from greater loss of performance when damaged. He leaves open the possibility that natural selection, rather than or in addition to sexual selection, has played a role in shaping bird tails, possibly for increased aerodynamic performance.
More relevant here, Balmford et al. (1993) studied pairs of species, one with a long tail and one without, to assess the aerodynamic cost of long tail feathers. They studied ~600 specimens and used aerodynamic modeling to predict cost. Their results are summarized in this figure:

Graduated (rounded) tails are costliest over all lengths. Forked tails are notably less costly over all lengths, and shallow forks more efficient than deep forks (but there the difference is not great).
They conclude:

Our model suggests that as long forked tails deepen, it becomes more likely that they are aerodynamically costly..., and therefore increasingly probable that sexual rather than natural selection explains their evolution.

And of the species pairs:

... then among species with long forked tails, sexual dimorphism in tail length should increase with fork depth. Pairwise comparisons of closely related species support this prediction.

What of boat-tail grackles then?
From what images I could find, it looks like boat-tailed grackles appear to have graduated tails when spread. If so, then these tails would be very inefficient and males with longer tails would incur a proportionately higher cost of flight than males with shorter tails.
Balmford, A., A. L. R. Thomas, and I. Jones. 1993. Aerodynamics and the evolution of long tails in birds. Nature 361:628–631.
Thomas, A. L. R. 1993. On the Aerodynamics of Birds' Tails. Philosophical Transactions of the Royal Society of London B: Biological Sciences 340:361–380.

Instead of a fork or a simple graduated shape, boat-tailed grackles have a deep V (you might say in the vertical direction as opposed to a fork in the horizontal direction. They don't flatten that V in flight.


text:
How far is stem cell research from being to generate a new organ?
How far are we from being able to use stem cell research to generate a sperm, a heart, a liver, and a kidney?
In stem cell research, my understanding is that you must start off with some cell to initiate the process. Can this be any cell, or must it be an embryonic cell made out of a sperm and an egg?

What is the measure of "far"? How can anyone tell when in future will something happen? It may happen tomorrow or not even in 10 years.

Sperm can already be generated using stem cells http://blogs.discovermagazine.com/d-brief/2016/02/25/scientists-grow-working-sperm-from-stem-cells/#.V-UADBV94o8
Also, heart, liver and kidney cells as well.
http://www.popsci.com/scientists-grow-transplantable-hearts-with-stem-cells
http://www.ncbi.nlm.nih.gov/pubmed/26458176
Full organs are still far. The main problems are to grow them separately from the rest of the body (embryonic development) and to vascularize them.
One solution is to grow them in other animals http://www.dailymail.co.uk/sciencetech/article-3442818/Growing-human-organs-farm-creatures-takes-step-closer-New-guidelines-allow-research-human-animal-hybrids.html
There are experiments done with some success in using "decellularized" kidneys as a scaffold to "grow" a new kidney by perfusing stem cells into it. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4927010/
There are the so-called organoids, very little agglomerates of different organ-specific cells differentiated from stem cells. They are far from being functional organs but it's definitely a start. http://hub4organoids.eu/organoid-technology/
Some labs are experimenting with 3D printing. They use stem cells to derive all the organ-specific cells needed and then they try to rebuild a functional organ by printing cell by cell, layer after layer. http://www.nature.com/nbt/journal/v32/n8/full/nbt.2958.html
Lastly, embryonic stem cells are not strictly needed anymore, they can be substituted (in most of the cases) by iPS that can be derived from many different adult cells (i.e. no embryo is needed).


text:
Does the growth in size of hippocampus of London taxi drivers affect their net number of brain cells?
In the paper, London Taxi Drivers and Bus Drivers: A Structural MRI
and Neuropsychological Analysis in the Journal Hippocampus, the authors state that changes in the hippocampus of taxi drivers in London results from their specific occupation. The authors stated this was more pronounced than in bus-drivers.
What accounts for grey matter change? Do their brains have more brain cells than other people? Or the increased in size of the posterior hippocampus means some other region of their brain must have less brain cells to have enough to grow their hippocampus?

The study you linked was very interesting, and there is a reason that the authors of this paper and many others like it refer to grey matter density or grey matter volume.
From another study on grey matter (density), Neurolinguistics: structural plasticity in the bilingual brain,

Whether grey-matter reorganization in this region is related to changes in neuropil, neuronal size, dendritic or axonal arborization will be revealed by methods other than whole-brain magnetic resonance imaging.

Meaning, there's really no way to know without autopsy and histological studies whether this means more neurons, increase in neuron size, more dendrites, more connections between neurons, etc. So, the answer to your question is, no one knows exactly.
Histopathological studies are usually done on diseased patients (e.g. Alzheimer's), not healthy taxi drivers.
However, one mouse study of loss of hippocampal grey matter did correllate MRI studies and histopathological studies, with the result that

no changes in the number or volumes of the somas of neurons, astrocytes or oligodendrocytes were detected. A loss of synaptic spine density of up to 60 % occurred on different-order dendrites in the ACC and hippocampus...

Loss is not the same as gain, however, so the definitive cause cannot be ascertained yet.
Stress-Induced Grey Matter Loss Determined by MRI Is Primarily Due to Loss of Dendrites and Their Synapses


text:
Does pepsin enzyme digest other enzymes like other pepsin molecules
Pepsin digests proteins, as we know, but can it digest other enzymes that are actually made up of proteins, like digesting other pepsin molecules?

Pepsin does cleave itself (Ingram, 1951) - this is termed autolysis. Pepsin (and other proteases) act on proteins with the right amino acid sequences. Pepsin prefers to cleave at phenylalanine, tryptophan or tyrosine residues (Lehninger, A. Principles of Biochemistry).
* Pepsin can also cleave inactive 'zymogen' enzymes to activate them. One of these zymogens is pepsinogen (an inactive form of pepsin itself). So you could argue that pepsin is cleaving itself here but I personally wouldn't, since pepsinogen isn't really pepsin.

Confusingly, pepsin does cleave itself - or, rather pepsinogen does to make pepsin (autocatalysis). Hmm, it also does autolysis, so I'm not sure your answer is correct ...

@gilleain I've added a note about it. I was initially going to talk about zymogens but I felt that it would be muddying the answer. Personally I'd say pepsin and pepsinogen are different things, plus (to my mind) the question is asking whether a solution of purified pepsin will eventually eat itself.

Jam, indeed - that's autolysis! Apparently, you should store pepsin at a low temperature to stop it eating itself

@gilleain Well I'll be! Never realised it did eat itself! Thanks for letting me know

Regarding your note on terminology: (1) digestion is common parlance for proteases and nucleases. (2) not all enzymes are proteins.

@canadianer Thanks for the notes - my mistake on both parts.


text:
Are human teeth only diphyodont or both diphyodont and monodont?
Many books say human teeth are only diphyodont .But premolars appear only once and one molar appears later which should be considered monophyodont.
 Dental Formulae :
CHILD -
 1. Incissor -2/2
 2. Canine -1/1
 3. Premolar-0/0
 4. Molar-2/2
ADULT-
 1. Incissor-2/2
2.Canine-1/1
3.Premolar-2/2
4.Molar 3/3 .
Here the 3rd molar and two premolar appear only once. Therefore human teeth should be both diphyodont and monophyodont

I wrote the dental formula for child and adult..

The definitions from the Oxford Dictionary of Dentistry:
Diphyodont

Describing the development of two successive dentitions, one primary
  and another secondary (permanent), as found in most mammals including
  humans.

Monophyodont

Possessing only one generation of teeth. It is a characteristic of
  some mammals, including the manatee, seal, and walrus.

As you can see, the term diphyodont is generally not used to refer to the individual teeth, but rather to the whole animal (i.e. the sets of teeth). A monophyodont is an animal that has only one set of teeth.


text:
What percent of genetic disease are preventable?
I like to know what percentage of genetic disease are preventable before birth?
Also, when we can detect all of them? I heard in a TV show a doctor said about 5 years later we can prevent all genetic disease! Is this estimation true?

Five years to prevent all genetic disease is ridiculously, insanely wrong.

There is no simple answer to either of your questions.
There are many monogenic diseases where mutations in single genes result in disease phenotype.
There are far more diseases that have a genetic component where mutations in one or more gene increase the baseline risk of disease and this risk is then modified by the environment the individual encounters throughout their life-time (see Multiple Genes).
To get an overview of the functions of genes that have been so far identified, mutations within them and the diseases they have been linked to see Online Mendelian Inheritance in Man (OMIM).
If you want to get a feel for just how complex genetics is then a recently published paper on the genetics of hair colour would be worth reading...
Genome-wide study of hair colour in UK Biobank explains most of the SNP heritability

I like to know what percentage of genetic disease are preventable
  before birth?

Essentially 0%. There have been a few experimental applications of gene thereapy, but we're talking about a few thousand of people in the entire world. None are available in the context of ordinary medical care. Some genetic diseases can treated after birth with drugs that moderate the worst effects: haemophilia, PKU, and cystic fibrosis for example, but the underlying genetic problem remains.

I think this answer should clarify that it's talking about what's currently preventable, not what's theoretically preventable.


text:
Genes-of-interest analysis between organisms
I am interested in identifying the differential expression between several genes-of-interest of different organisms.
I am trying to assess the benefits of RNA sequencing over microarrays. Both techniques are a means to an end. With both of these two methods one can "count" the differences between two conditions, e.g. cell types, time points etc. They do use different technology to achieve it, but they both give a certain number 't' in the end, which can be looked at as the strength of the expression of a specific gene under a certain cellular condition. One can than compare the two (or more) conditions to get a picture of what is different in the cell due to the changes.
As I am new to this field, can someone tell me what the advantages are of RNA sequencing over micro arrays? Alternatively, information on comparisons between microarrays and RNA sequencing methods are welcome.

Welcome to Biology SE! What is GOI (G of interest)? Don't assume everyone's a molecular biologist and avoid technical acronyms and technical jargon. I've slightly type-edited your question. Please remove acronyms (RNA is fine)

No worries :)  - Aha genes of interest, that makes sense. Obviously, I am not able to answer your question (otherwise I would have known) but I'm just trying to polish up your question :)  Lastly, a bit more background may help you to get your question answered. I mean, sequencing and micro arrays are quite a different thing? The one is sequencing, the other one is expression profiling is it not?

Thanks for the excellent elaboration! Adding this to the question may be a good thing (At Biology.SE many questions are closed due to a lack of underlying research effort, that's why I am bugging you :-). +1 for your question. Good luck!

@AliceD RNA-seq is a gene expression profiling technique akin to microarrays. The sequencing step is just a technical detail.

Microarrays are pretty much dead. Go for a RNA-seq.

In RNA sequencing, total RNA is extracted, then mRNAs are purified out from the sample using polyT columns (since mRNAs have a polyA tail, this will attach to a polyT DNA chunk that is attached to some solid surface). This step is necessary because ribosomal RNAs are much more abundant than mRNAs, and for sequencing you only want to use mRNAs. Then the purified mRNA is transcribed to DNA using reverse-transcriptase and finally the cDNA is sequenced.
As for microarray a set of single stranded oligonucleotids (short DNA sequences) (aka. probes) are attached to a solid (usually glass) surface as small dots. This the so called DNA/RNA-chip. Then the chip is washed with the fluorescently labelled singlestranded sample, and the complementary strands attach to each other, the rest is washed away - this is a so called hybridization technique. The signal is then detected by reading the fluorescence signals at each spot.
The microarray technique is quite old and is less sensible and the number of probes are limited / array, while with RNA sequencing you can sequence the total mRNA population of each organism and examine anything you want. Also since most sequencing techniques include a PCR step less starting material is sufficient, and has higher sensitivity and specificity.
These wiki pages on RNA-seq and microarray technique provide detailed info on both.

To complete this answer, here a link to a study that compares microarray and RNA-seq. RNA-seq is definitely considered better and microarrays are less and less used.


text:
How do viruses such as COVID-9 and flu return in the winter if they disappear in the summer?
COVID-19 is gone from the body after a short time, and the maximum time of exposure to showing the symptoms is two weeks. So if no one gets sick for two or three months, how would it return in the winter?
How can it survive so long? Nobody got sick from nowhere except the first one and that things happened once to a lot of years.

I think the first step in answering your question, is correcting part of it. Influenza does not disappear in the Summer. Infection rates decline, but people can still become infected in the off season. Remember, we live in a globally connected society. Summer in the Northern Hemisphere is winter in the Southern Hemisphere. Influenza also has a number of animal reservoirs and intermediate hosts, which can contribute to persistant survival.
As far as the seasonality of infection rates, there are a number of contributing factors. This article from Harvard University discusses a few factors:

"1) During the winter, people spend more time indoors with the windows sealed, so they are more likely to breathe the same air as someone who has the flu and thus contract the virus.
2) Days are shorter during the winter, and lack of sunlight leads to  low levels of vitamin D and melatonin, both of which require sunlight for their generation. This compromises our immune systems, which in turn decreases ability to fight the virus.
3) The influenza virus may survive better in colder, drier climates, and therefore be able to infect more people."

For a more exhaustive discussion of the underlying causes of influenza seasonality, here's an open access review article on the subject.
Some researchers suspect that the SARS-CoV-2 virus, the causitive agent of COVID-19 infections, may have a similar patern of seasonality, but it's probably too early to know for sure how influential each of these factors will be in the long term.

I see there is no  lockdown or test when there is Influenza  virus so it just keep going from heuman been to queman being but  for example in china every body has been checked so no way of second wave there?

+1, Summer in the Northern Hemisphere is winter in the Southern Hemisphere -- it's surprising how many "It disappears in the summer" arguments I've seen that have neglected this simple fact.

I'm not a public health expert, but I would probably never go as far as to say there's no chance of a second wave given any real-world circumstance. Presumably, most travel and lockdown restrictions will eventually lift. Even if everyone was tested, all testing has a finite limit of detection, and people shedding virus below this limit could remain undetected. And human to human transmission might not be the only concern. There is still the possibility of animal reservoirs. We already know that some animals can contract and trasmit the virus in a lab setting.


text:
Influence of artificial sunlight on the human body
In a hypothetical scenario, where a large, permanently manned craft is in a continual orbit, and natural sunlight cannot be used as the craft may keep moving and turning, artificial sunlight is used in the form of LED panels.
My question is this: Will the LEDs have any adverse effect on the human body? The LEDs are of the SoLED variety which have very low IR levels and almost nil UV light levels, have any adverse effects on the body? I suppose the lack of UV may cause some disturbance in Vitamin D and melanin levels. Is this valid? Would there be any other problems?

You could easily supplement Vitamin D.

But will that be the only issue?

Yes. Natural sunlight doesn't have a good substituent.
Melatonin levels and circardian rhythms are directly affected by natural sunlight.
As far as LEDs goes, a french study concluded that blue light may have photochemical risks and affect our retina.
Source
http://www.ledinside.com/knowledge/2014/4/effect_of_artificual_and_natural_light_on_the_human_body


text:
Do puffin beaks have vertical slits or cracks?
I have seen a photo where puffins seem to have vertical lines on their beaks.  It is uncertain if those are just line or actual slits or cracks in the beaks.  Do puffin beaks have slits or cracks?

Can you add a photo showing what you mean?

an image would be important, puffins shed portions of their bill, have varying thickness, and have color patterns anyone, then there are growth lines and cracks ass possibilities. Any of those could be what you are talking about.

No, as far as I am concerned a healthy puffin hasn't got any slits or cracks in its beak. The lines that you see are literally just that - or little grooves. Obviously, beaks might show signs of wear and tear, so cracks may be observed. However, there are no genes in a puffin's genome that would lead to the expression of slits and cracks in its beak.
I think the photos below might help visualising.

(Photo: Tycho Anker-Nilssen, NINA)

(Photo: Will Nicholls)


text:
Growing bacterial culture on gelatin
I'm very new to experimental biology and don't know much about it. So, i was looking to grow some bacteria in petri dishes and looked up how to do it. Unfortunately, I'm finding it difficult to get my hands on the 'agar-agar' required to make the culture medium. So, is it possible to use any other alternative which would give the same results? Like for example regular gelatin?
My school lab teachers have also shown little to no interest in helping me with my project, so I'm on my own here. Any tips would be greatly appreciated!

You can try using agar powder also known as falooda powder which can substitute gelatine.it is used in Indian homes to make jelly.

You can use Gelatin - actually this was used by microbiologists before agar came in use. That gelatin is more or less completely abandoned in this field tells quite a story, right?
Gelatin has the main disadvantage that it cannot be autoclaved together with the medium to sterilize it. Using it would need some experience and probably advanced techniques to which you have no access.
But there are some good news as well: Agar is also used as a geling agent when making food, and when you cannot find it in your local supermarket, Amazon can deliver it. You don't need much, around 15 gram/litre.

sadly Amazon doesn't ship products to my country :( (Bangladesh)

what other option would i have?

You can use gelatin. The problem you will find is that many more common organisms are able to break it down. Hence, it won't hold up very well. Depending what you put on it, it might work.

Can you add some references to your answer just to back it up a bit? Also, if there are any special preparation methods that should be followed or anything of that sort, please add that information and/or some reliable links to webpages with those instructions. PS... Welcome to Biology S.E., if you have any questions or concerns, please feel free to visit the Help Center, here https://biology.stackexchange.com/help :)


text:
How did biologists find out that bacterial plasmids were circular?
I was always curious how it was determined that bacterial plasmids were circular, since there isn't an obvious way to find this out. I heard somewhere that there was a difference when gel electrophoresis was conducted. Could anyone give an explanation?

Where did you hear this? Having a reference would help.

i searched google that exact question and the first few pages talked about gel electrophoresis but sadly none of them gave a clear explanation


text:
Are there examples of animals that live in groups, where all have the same role?
For animals that live in groups, are there examples where all of them have the same role? For example, in animals we know there are bee queens or alpha, beta and omega mammals. But are there groups of animals where all the members have the same role? My question is aimed at 2 different groups actually, first animals in general (which includes reptiles, insects, etc.) and second to mammals only.

Since you mention alpha/beta/omega, it's worth noting that with wolves, that organization only shows up in captivity.  In the wild, a wolf pack is simply a breeding pair and their offspring.

Yes, there are many examples. Those species are said to be gregarious. See below for examples.
Level of sociality
When it comes to social behaviour, it is common to categorize species into one of four categories: Solitary, gregarious, presocial, and eusocial.
Note that definitions may vary among authors and that there are limit cases that make the question of categorizing much richer than the simple definitions I am using below.
Solitary
Solitary species are species where individuals mainly live alone and are independent of each other (They may still meet to mate, though).
Examples: fox, polar bear
Gregarious
Gregarious species are species that gather into a group but do not share any labour. Each individual is selfish. Such gregarious behaviour can be driven by safety (typically during migration), to taxis toward a resource, or any other reason that may cause these individuals to gather!
Note, when you say "have the same role," it is clear that different individuals may use different life strategies (like typically territorial males vs. sneaker males in birds).
Examples: wildbeest (during migration), many insects attracted to a given lightsource.
Presocial
Presocial species are species that are gregarious and have a separation of labour but no separation of the the reproductive labour.
Examples: Humans, many hymenopterans, vampire bats
Eusocial
Eusocial species are species that have a separation of labour including separation of the reproductive labour.
Examples: Termites, ants, naked mole-rat

Does Gregarious include species who gather in groups and share the same labours ? That's what I'm more interested to know. Like for example, all hunt for the group, all gather for the group, or all dig for the group, etc.

Gregarious species do not share labours. It means that they all do the same thing (that is doing their best to survive and reproduce) although they may use different strategy (like being territorial vs a sneaker in birds).

Creatures that 'flock' or 'school' ['shoal'] benefit from shared awareness and their movements can confuse predators.

Insects attracted to a light source is rather an awkward example, as this is no social behaviour they benefit from. On the contrary, many die.

What about migrating birds (e.g. geese, crane that fly in groups) or wintering groups such as Starling or Tits.

@RHA that's the point of gregarious animals. As long as they father, whatever the reason is, they are called gregarious. At least it is my understanding. The example was given to me a number of years ago by a prof. during my bachelor  degree but his definition might differ from what is being used in the literature.


text:
Insect with Mohawk-style back in Mexico City
About 5mm long. Any idea what it is?


text:
Can any one identify this insect from Lokhandwala, Mumbai India?

I found this insect on my bed. I have never seen such creature before. Can any one identify this?

It's looks like a Leaf-Footed Bug (Homoeocerus Sp., Coreidae).

Source: https://www.flickr.com/photos/itchydogimages/17774939209

Source: https://www.flickr.com/photos/itchydogimages/6211603956/


text:
Large spider identification, Kentucky USA

What kind of spider is this I live in KY and it was found on my stairs.

It's not a widow, false black widow,  or a brown recluse, and you're in Kentucky, so it is not a spider that could be a medical threat to a human. Since all I can do is rule that out, I'm not posting this as an answer.


text:
Is there a feasible way to create a large number of long random DNA strands?
Suppose I want to create a large number of random DNA strands (maybe a million, or a billion, or even something close to all $4^N$ possible sequences of $N$ base pairs).  Is there an experimental way to do this?

Please do not add inappropriate tags to attract the attention of more people. It is abusing the system. I have removed both them and your aplpologia.

I'm curious, why do you want to do this?

Chemical DNA synthesis has you covered for short DNA strands.
It's possible to just use an equimolar mixture of all 4 bases when you do chemical synthesis, which results in random sequences. (This is most often used to generate barcoded primers).
The main problem with this approach is that:

chemical synthesis is not super efficient, anything above ~1-2kb will likely not be possible
If you work with a fully randomised sequence it becomes much harder to do quality control of the product (you can't sequence it).

You can also easily even calculate the probability of generating all possible sequences for a given strand length and yield.


text:
What type of fish is this- Cabo San Lucas, Gulf of California side

Can anybody tell me what this fish is?  Caught in Cabo last week, actually closer to San Jose, with a Joe's Flies 1/4oz spinner.  Cool looking fish for sure, just can't seem to find it online of what it is??

We need a picture...

That is a giant hawkfish, Cirrhitus rivulatus. It is identified by its unique markings from other species in the same region. This individual looks slightly young to me from the size, however it is most certainly this species. Giant hawkfish on mexican-fish.com

Cannot thank you enough!  You look to be exactly right!

@BrettNelson No problem. If you think the answer is correct you can also accept the answer but no need to.


text:
In what fluid does the sperm swim in the oviduct?
We know that after sexual intercourse, sperm enters the female body and continues to pass through the oviduct by swimming. "Swimming" implies the presence of fluid.
I want to know what that fluid is called. Also could you please tell me the color of that fluid? Is it yellow/off-white?

Specifically in the fallopian tubes, the fluid is called tubal fluid, and is produced by the innermost mucosal layer of the tubes (specifically, the peg cells in the epitelium)

In the follicles, there is the follicular fluid, liquor folliculi.
In the uterus, the endometrial fluid.
In the cervix, cervical fluid.

I don't know about the color. For what it's worth, cervical fluid varies from white to yellowish, but it's transparent when it's best for spermatozoa to swim.