source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-6044 | photosynthesis
Title: Photosystem I and the ETC In the light reactions of photosynthesis, Photosystem I receives electrons from the ETC after Photosystem II sends them to the ETC. Then, when Photosystem I receives light, the electron becomes excited and passes the electron back to the ETC. This leads me to my question: In the following question, are both $B$ and $E$ correct?
Which of the following are directly associated with photosystem I?
$A)$ harvesting of light energy by ATP
$B)$ receiving electrons from the thylakoid membrane electron transport chain
$C)$ generation of molecular oxygen
$D)$ extraction of hydrogen electrons from the splitting of water
$E)$ passing electrons to the thylakoid membrane electron transport chain It appears the author of the question is trying to use "thylakoid electron transport chain" in an overly specific way. The chain from which PS I receives electrons has far more components and is different from the shorter chain to which PS I passes its electrons. But according to my copy of Biology, Campbell & Reece 7th edition, both are called "electron transport chains" and both reside in, or on, the thylakoid membrane. Perhaps the "directly" in the question refers to the fact that PS I's electron is first captured by a "primary receptor" before being passed to ferredixon, the first member of the chain to which PS I passes electrons. But, again according to Campbell, this primary acceptor is considered part of the photosystem.
I used to teach this stuff. I'd toss out the question.
The following is multiple choice question (with options) to answer.
The light reactions take place in which membranes? | [
"the phospholipid",
"the cell membranes",
"the stroma",
"the thylakoid"
] | D | Both stages of photosynthesis take place in chloroplasts. The light reactions take place in the thylakoid membranes, and the Calvin cycle takes place in the stroma. |
SciQ | SciQ-6045 | evolution, species
Title: Reasons why living fossils exist?
A living fossil is a living species (or clade) that
appears to be similar to another species otherwise known only from fossils,
typically with no close living relatives.
A living fossil is considered as a successful organism, which has made its way through many major extinction events. Also, the morphology of living fossils resemble some species of organisms which we know only through their fossil remains.
What is the reason for a particular type of species to become a living fossil; is the engineering of this particular species extraordinary, in that it can survive any selection process encountered thus far?
Is there not enough selection pressure exerted on this species in order to force it to change morphologically?
Have these organisms modified themselves, so that currently their morphology seems to be similar to a fossil organism? One part of your question betrays a serious error:
Is there not enough selection pressure exerted on this species in order to force it to change morphologically?
Actually the reverse is true; constancy of form can only be maintained in the presence of continuous selective pressure. It's just that this is stabilising selection that acts to maintain the existing form rather than push the organism to new morphologies. In fact, most selection acts in this manner. This shouldn't surprise you: organisms are typically well adapted to their environments so changes are more likely to reduce fitness than increase fitness.
It's also worth noting that although living fossils show little morphological change they can continue to show change at the molecular level at rates as high as, or higher than, other organisms - e.g. (May et al 2007; Cao et al 2013).
The following is multiple choice question (with options) to answer.
Fossils themselves and the order in which they appear in are generally collectively called what? | [
"fossil record",
"fuel cycle",
"fossil magnitude",
"coal record"
] | A | There are many layers of rock in the Earth's surface. Newer layers form on top of the older layers; the deepest rock layers are the oldest. Therefore, you can tell how old a fossil is by observing in which layer of rock it was found. The fossils and the order in which fossils appear is called the fossil record . The fossil record provides evidence for when organisms lived on Earth, how species evolved, and how some species have gone extinct. Geologists use a method called radiometric dating to determine the exact age of rocks and fossils in each layer of rock. This technique, which is possible because radioactive materials decay at a known rate, measures how much of the radioactive materials in each rock layer have broken down ( Figure below ). |
SciQ | SciQ-6046 | biochemistry, endocrinology, cell-signaling
Title: Effect of steroid hormone on specific cells? As steroid hormones can pass through the plasma membrane by simple diffusion because they are lipid derived hormones, it means that they are capable of passing through every cell of our body, BUT why are only specific cells responsive against steroid hormones?
For example, all of our body cells almost contains the genes for the development of secondary sexual characters but why do only specific cells show a response against these steroid hormones because the development of secondary sexual characters occur only in specific region of our body, that is, beard formation occur only in a specific region of the face, etc.
IN SUMMARY: When steroid hormones can pass through every cell of our body then why do they show only a localized response? Unlike other types of hormones, steroid hormones do not have to bind to plasma membrane receptors. Instead, they can interact with intracellular receptors that are themselves transcription activators. Steroid hormones too hydrophobic to dissolve readily in the blood travel on specific carrier proteins from their point of release to their target tissues. In the target tissue, the hormone passes through the plasma membrane by simple diffusion and binds to its specific receptor protein in the cytoplasm. The receptor-hormone complex then translocates into the nucleus where it acts by binding to highly specific DNA sequences called hormone response elements (HREs), thereby altering gene expression.
Hormone binding triggers changes in the conformation of the receptor proteins so that they be- come capable of interacting with additional transcription factors. The bound hormone-receptor complex can either enhance or suppress the expression of adjacent genes.
The DNA sequences (HREs) to which hormone- receptor complexes bind are similar in length and arrangement, but differ in sequence, for the various steroid hormones. Each receptor has a consensus HRE sequence to which the hormone-receptor complex binds well, with each consensus consisting of two six-nucleotide sequences, either contiguous or separated by three nucleotides,
The ability of a given hormone to act through the hormone-receptor complex to alter the expression of a specific gene depends on the exact sequence of the HRE, its position relative to the gene, and the number of HREs associated with the gene.
The following is multiple choice question (with options) to answer.
Hormones send what through your body? | [
"nutrients",
"proteins",
"signals",
"cells"
] | C | Good record keeping is very important in scientific research. |
SciQ | SciQ-6047 | evolution, biochemistry, physiology, speculative, bioinorganic-chemistry
While iron skeletons might seem to be an advantage, they are electrochemically unstable - oxygen and water will tend to oxidize (rust) them quickly and the organism would have to spend a lot of energy keeping it in working form. Electrical conductivity sounds useful, but the nervous system favors exquisite levels of control over bulk current flow, even in cases like electric eels, whose current is produced by gradients from acetylcholine.
What's more, biological materials actually perform as well as or better than metal when they need to. Spider silk has a greater tensile strength than steel (along the direction of the thread). Mollusk shells are models for tank armor - they are remarkably resistant to puncture and breakage. Bone is durable for most purposes and flexible in addition.
The time it would take for metallized structures to evolve biologically are likely too long. By the time the metalized version of an organ or skeleton got started, the bones, shells and fibers we know probably have a big lead and selective advantage.
The following is multiple choice question (with options) to answer.
What does the armor including spines in some species offer? | [
"protection from predators",
"energy",
"nutrition",
"protection from cold"
] | A | |
SciQ | SciQ-6048 | dna, terminology
Title: Is a DNA molecule a single strand of polynucleotide or two of them linked together? Our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds. The thing is, until now, I always thought a DNA molecule was composed of two strands, those being polynucleotides, both of them being linked together. I can't find a link which is saying the same as my teacher, even if it seems technically correct to call a double helix a dimer of two DNA molecules.
I was curious to know what was the exact terminology. As you pointed out, though this may be basic biology, seeking clarification when receiving conflicting information is a good thing. Don't feel embarrassed for asking. :)
.. our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds.
Respectfully, your teacher is incorrect. A single, double-stranded DNA molecule is comprised of two helical shaped polynucleotides, and are connected together via hydrogen bonding.
Highlight of each polynucleotide
Highlight of hydrogen bonding
And just for further validation, according to Molecular Biology of the Cell, 4th ed., by Alberts B, Johnson A, Lewis J, et al.:
A DNA molecule consists of two long polynucleotide chains composed of four types of nucleotide subunits. Each of these chains is known as a DNA chain, or a DNA strand. Hydrogen bonds between the base portions of the nucleotides hold the two chains together.
So, it would seem that your teacher is referring to each polynucleotide, a.k.a. DNA strand, as a DNA molecule. Instead, she should use the verbiage: a single DNA molecule is composed of two DNA strands, which are helical-shaped polynucleotides.
The following is multiple choice question (with options) to answer.
Individual nucleotides can be linked together through their phosphate groups to form? | [
"dna",
"nucleic acid polymers",
"nitrous acid polymers",
"atoms"
] | B | Individual nucleotides can be linked together through their phosphate groups to form nucleic acid polymers. Once constructed, DNA generally exists as two strands that are linked together by hydrogen bonds, producing a double-helical structure (see Figure below ). |
SciQ | SciQ-6049 | redox, oxides
Special methods are needed to generate semiconductor-grade silicon. These actually do not use silica as the silicon source; instead, volatile compounds that can be pre-purified by fractional distillation, such as $\ce{SiCl4}$, are employed. Additional purification by zone melting is needed to get the purity needed for semiconductor use.
The following is multiple choice question (with options) to answer.
The name silicon is derived from the latin word for flint? | [
"silk",
"simple",
"pelea",
"silex"
] | D | The name silicon is derived from the Latin word for flint, silex. The metalloid silicon readily forms compounds containing Si-O-Si bonds, which are of prime importance in the mineral world. This bonding capability is in contrast to the nonmetal carbon, whose ability to form carbon-carbon bonds gives it prime importance in the plant and animal worlds. |
SciQ | SciQ-6050 | biochemistry, proteins, enzymes, digestive-system, digestion
Title: Betaine HCl stomach pH It seems betaine HCL is often recommended for those suffering from "low stomach acid" -- which, as I understand, is having too high stomach pH for proper digestion (especially for proteolysis via pepsin). However, I have a few questions then -- though I'm not sure if my reasoning is correct here:
Understandably, one wouldn't want to drink pure or highly concentrated HCl by itself to increase stomach acid! But then, what role does the betaine play?
I'm guessing betaine HCl probably does not dissolve in water to give the same pH as just straight (or concentrated) hydrochloric acid -- since then it would seem just as dangerous as drinking plain HCl!
In that case, if it doesn't decrease the pH as much, making it safe for oral consumption, what value does it bring for "lowering stomach pH" anyway? I mean, one could just drink a little vinegar or citric acid for the same effect?
Or, perhaps, is betaine-HCl just a means of some "delayed release" of HCl to lower stomach pH without hurting the mouth and esophagus during its initial consumption? Betaine may just be a useful carrier here, given it's quaternary ammonium and carboxylic acid groups (e.g., a zwitterionic carrier)
Alternatively, could the value of betaine HCl simply be in providing a source of Cl- anions, possibly for increased pepsin activity? (I'm not sure if pepsin requires merely low pH or specifically also needs Cl- anions as well) Betaine-HCl does seem to be often formulated with additional pepsin enzyme(s) as well... Betaine HCl (trimethylglycine) was present in over the counter "stomach acidifiers" but the US FDA says there is no evidence for its efficacy and has banned its use for this indication (source: US FDA) - it may be freely available elsewhere, I am unaware of the regulatory status in other jurisdictions.
The following is multiple choice question (with options) to answer.
What two types of juices help digestion within the small intestine? | [
"amniotic fluid, bile",
"intestinal and pancreatic",
"bile and lymph",
"chyme and phloem"
] | B | Chemical Digestion in the Small Intestine The digestion of proteins and carbohydrates, which partially occurs in the stomach, is completed in the small intestine with the aid of intestinal and pancreatic juices. Lipids arrive in the intestine largely undigested, so much of the focus here is on lipid digestion, which is facilitated by bile and the enzyme pancreatic lipase. Moreover, intestinal juice combines with pancreatic juice to provide a liquid medium that facilitates absorption. The intestine is also where most water is absorbed, via osmosis. The small intestine’s absorptive cells also synthesize digestive enzymes and then place them in the plasma membranes of the microvilli. This distinguishes the small intestine from the stomach; that is, enzymatic digestion occurs not only in the lumen, but also on the luminal surfaces of the mucosal cells. For optimal chemical digestion, chyme must be delivered from the stomach slowly and in small amounts. This is because chyme from the stomach is typically hypertonic, and if large quantities were forced all at once into the small intestine, the resulting osmotic water loss from the blood into the intestinal lumen would result in potentially life-threatening low blood volume. In addition, continued digestion requires an upward adjustment of the low pH of stomach chyme, along with rigorous mixing of the chyme with bile and pancreatic juices. Both processes take time, so the pumping action of the pylorus must be carefully controlled to prevent the duodenum from being overwhelmed with chyme. |
SciQ | SciQ-6051 | immunology, bacteriology
Title: How do infectious bacteria determine when their numbers are high enough to attack a host? When you get sick, you generally don't contract enough bacteria at once for them to succeed in battling your immune system, right? Their numbers must gradually increase in the host's body before they know that they can attack. How does that work? I think the current answer to this for bacterial infections is quorum sensing. Quorum sensing is a signalling pathway in bacteria which senses a molecule that the bacteria themselves secrete. When the concentration of the quorum signal reaches a certain level, the bacteria interpret this as their population density reaching some threshhold.
Bacteria are always around - even infectious Staph, as described in the other answer, the bacteria are always being cleared out by the immune system, but when they find the right place where they can get critical mass, they dig in, form a biofilm and secrete toxins, which can help them divide more successfully.
This is a description of the process from a paper on Staph infection, a common bacterial infection in humans.
The following is multiple choice question (with options) to answer.
Cells in a biofilm secrete what to recruit nearby cells? | [
"signaling molecules",
"harnessing molecules",
"signaling neurons",
"signaling proteins"
] | A | |
SciQ | SciQ-6052 | waves, harmonics
Title: Standing waves confusion Its just so confusing as to why the antinodes are formed from the constructive interference by superposition of the wave formed by the incident wave and the reflected wave... The phase difference is clearly 180° and not 0°, so shouldn't the reflected wave and incident wave superpose to destructive interference? which would then make it a node.. but not the antinode.. similarly.. with the node.. the phase difference is 0°.. so how come it does not oscillate at that point?.. Honestly, I think how standing waves arise itself is confusing me.. Standing wave animation and see that at a node the phase difference between the two travelling waves is always $180^\circ$ and at an antinode the phase between the two travelling waves is $0^\circ$.
The following is multiple choice question (with options) to answer.
A standing wave is created when what type of wave interferes with the original wave? | [
"translated wave",
"realized wave",
"refracted wave",
"reflected wave"
] | D | When a wave meets a barrier, it reflects and travels back the way it came. The reflected wave may interfere with the original wave. If this occurs in precisely the right way, a standing wave can be created. The types of standing waves that can form depend strongly on the speed of the wave and the size of the region in which it is traveling. |
SciQ | SciQ-6053 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
The kidneys are a pair of bean-shaped structures that are located just below and posterior to the liver in this? | [
"peritoneal cavity",
"cerebral cavity",
"stomach cavity",
"mantle cavity"
] | A | Kidneys: The Main Osmoregulatory Organ The kidneys, illustrated in Figure 41.4, are a pair of bean-shaped structures that are located just below and posterior to the liver in the peritoneal cavity. The adrenal glands sit on top of each kidney and are also called the suprarenal glands. Kidneys filter blood and purify it. All the blood in the human body is filtered many times a day by the kidneys; these organs use up almost 25 percent of the oxygen absorbed through the lungs to perform this function. Oxygen allows the kidney cells to efficiently manufacture chemical energy in the form of ATP through aerobic respiration. The filtrate coming out of the kidneys is called urine. |
SciQ | SciQ-6054 | human-biology, senses
Olfaction (smell, as carried out by neurons in the nasal epithelium; e.g. smell of vanilla, and smell of bad food)
Gustation (taste, as carried out by neurons on the tongue; e.g. salt, sugar)
Antigen chemosensing (chemical sensing, as carried out by, for instance, immune antigen receptors on B cells)
Hormonal signaling chemosensing (chemical sensing of hormones such as insulin, as carried out for instance by myocytes)
Starch sensing? (amylase in saliva can be used as a test for digestable starch)
Visual system, at the retina?
Visible light (sensing electromagnetic radiation on the order of a few hundred nanometers in wavelength)
Internal methanol sensing (the visual system as a sensor for methanol, which disproportionately affects myelin surrounding the optic nerve)
Pressure sensing (see phosphenes)
The vestibular system
Gravity sensing
Balance
Coordination
Motion sensor
Head position sensor
Spatial orientation
Skin
thermosensation (touching a hot kettle!)
Nociception (pain sensing)
allergen sensing
sensor for gamma rays, X-rays and UV light (indicated by radiation burns, development of skin cancer, sunburns, etc.)
Bones and muscles?
Kinesthetic and bodily proprioception
Brain/mind/mental/social senses?
mental pain
boredom
mental or spiritual distress
sense of self and other, including friendship, power, place in social hierarchy, reputation, companionship
motivation and love (oxytocin, dopamine, etc. in limbic systems and other neural correlates)
I'm sure some would agree, and some would disagree about the specific cases I provide. Thus the definition of senses, or sensing, seems to be opinion-based or at the very least very sensitive to an agreed-upon operational definition, for which there is none.
The following is multiple choice question (with options) to answer.
What term means anything that is detected either through human senses or with instruments and measuring devices that extend human senses? | [
"observation",
"evacuation",
"variation",
"evaluation"
] | A | Science rests on evidence and logic, so it deals only with things that can be observed. An observation is anything that is detected either through human senses or with instruments and measuring devices that extend human senses. Things that cannot be observed or measured by current means—such as supernatural beings or events—are outside the bounds of science. Consider these two questions about life on Earth:. |
SciQ | SciQ-6055 | materials
Title: Making Lyophilized Cake Lookalike using household ingredients I'm working on a machine learning model to identify flaws in vaccines in lyophilized cake form. To train the model, I need a number of samples that look something like this:
I have vials, but I'm having trouble making a suitable cake – I need something that will stick to itself when dried...
What I've tried so far:
Salt dissolved in water/isopropyl alcohol
Baking soda dissolved in water/isopropyl alcohol
Both of these turned back into powder (instead of caking) when dry.
Next, I'm considering using powdered detergent, adding water, then letting it dry...
How would you recommend making this using common household ingredients? You may want to consider whey. Looks like Karen Smith, Dairy Processing Technologist at the Wisconsin Center for Dairy Research, already did some of the work for you. The result depends on the specific type of whey (a high score of 4 or 5 on the caking test means the material cakes readily, forming a gummy crust):
Whey – (Scored 2-5) – whey exhibited a wide range of caking scores. How the whey is processed has a very large effect on the tendency of the resulting powder to cake as evident in this result. Clearly, two of the samples had large amounts of amorphous lactose and without the presence of significant amounts of protein the samples readily caked.
The following is multiple choice question (with options) to answer.
The white fluffy part of popcorn is also what? | [
"phosphor",
"jiffy",
"endosperm",
"membrane"
] | C | |
SciQ | SciQ-6056 | EDIT: I just wanted to add that the only method simpler than the recipe above is when there exists a zero component in $$\mathbf{u}$$. When $$u_i=0$$, then a vector $$\mathbf{v}$$ with only one non-zero component $$v_i$$ (e.g. $$v_i=1$$) is perpendicular to $$\mathbf{u}$$.
The following is multiple choice question (with options) to answer.
What change can you expect in vectors that are perpendicular to each other? | [
"Molecular Reaction",
"no effect",
"Chemical reaction",
"Large Effect"
] | B | Vectors that are perpendicular to each other have no effect on each other. |
SciQ | SciQ-6057 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
Where is roughage fermented and digested in pseudo-ruminants? | [
"in their pancreas",
"in their ileum",
"in their appendix",
"in their cecum"
] | D | Pseudo-ruminants Some animals, such as camels and alpacas, are pseudo-ruminants. They eat a lot of plant material and roughage. Digesting plant material is not easy because plant cell walls contain the polymeric sugar molecule cellulose. The digestive enzymes of these animals cannot break down cellulose, but microorganisms present in the digestive system can. Therefore, the digestive system must be able to handle large amounts of roughage and break down the cellulose. Pseudo-ruminants have a threechamber stomach in the digestive system. However, their cecum—a pouched organ at the beginning of the large intestine containing many microorganisms that are necessary for the digestion of plant materials—is large and is the site where the roughage is fermented and digested. These animals do not have a rumen but have an omasum, abomasum, and reticulum. |
SciQ | SciQ-6058 | theoretical-biology, population-dynamics, population-biology
\frac{dN_C}{dt} = \nu_B N_B(t - \tau_B) - \gamma_C N_C \\
$$
So constants $\beta, \gamma, \nu, \tau$ represent constants for the birth rate, death rate, migration-maturation rate, and time lag. In my actual model I have 2 species that compete, but this model above gives a flavor of the dynamics. I would like to include some carrying capacity constraints too, but that can come later.
Like I said, it is easy enough to express this model in a discrete form as well. But I was hoping someone might be able to reference articles or something that shows someone analyzing discete multi-generational models--so that I can see a flavor of how they deal with the nondimensionalization, bifurcations, chaotic dynamics, etc.
I was hoping to see if other biologists or ecologists had studied this kind of continuous system, and how they had analyzed it. It seems like the first thing to do is nondimensionalize it, as I have way too many parameters. But I am not sure of a good scheme or equilibrium condition to use to do that. You use the word "evolution" here to mean "change in populations over time", as is typical in (say) astrophysics (or, I guess, economics?). My initial comments and suggestions were based on a misreading of "evolution" having its biological meaning, i.e. change of genetic make-up of a population over time.
With that out of the way: delay differential equations are slightly less common than ordinary DEs in population biology, but still very common. I wouldn't say there are any special mathematical tricks that aren't also used by mathematical analysts or people studying dynamics in other fields ...
The following is multiple choice question (with options) to answer.
How quickly a population changes in size over time is known as what? | [
"population direction rate",
"population impact rate",
"population multiplication rate",
"population growth rate"
] | D | The population growth rate is how quickly a population changes in size over time. The rate of growth of a population may be positive or negative. A positive growth rate means that the population is increasing in size because more people are being added than lost. A negative growth rate means that the population is decreasing in size because more people are being lost than added. |
SciQ | SciQ-6059 | electromagnetism, thermodynamics, energy, work, radiation
Title: Is energy only transmitted through electromagnetic and particle radiations? Which are the other ways of transmission if any? If energy does not require any medium for transmission(as for sunlight reaching earth, the heat too), is it transmitted in quanta in particle radiation too? Energy transfer can be thought to occur via the exchange of a 'virtual particle'. In nature, there are 4 fundamental forces, namely:
1. Electromagnetic force
2. Gravitational force
3. Strong force
4. Weak force
Each of these forces have a different exchange particle:
For instance, the exchange particle for EM is a photon whereas that for the strong force is the gluon. The nature of the interaction is characterised by the properties of the exchange particle.
Now if you want to connect this rather abstract idea to a bigger picture of the more 'real world', you just have to carefully think about what the process you are considering actually involved on a deeper level.
For example: suppose you are pushing a box across your room. What you are actually doing is repelling the electrons on the box by the electrons on your hands, thus causing it to move. Therefore, you the interaction is an electromagnetic interaction and hence the exchange particles involved are photons.
If you think of energy transfer in this way, then indeed all energy transfers occur via 'particle exchanges' or radiation (since you a particle is essentially a wave packet [wave particle duality]).
The following is multiple choice question (with options) to answer.
Electromagnetic waves transfer energy across space as well as through what? | [
"filtering",
"osmosis",
"matter",
"plasma"
] | C | Electromagnetic waves transfer energy across space as well as through matter. They vary in their wavelengths and frequencies, and higher-frequency waves have more energy. The full range of wavelengths of electromagnetic waves, shown in the Figure below , is called the electromagnetic spectrum. |
SciQ | SciQ-6060 | human-biology, biochemistry, red-blood-cell
Title: Can excessive carbonated drink consumption lead to elevated red blood cell levels? I've recently had a blood test and the results displayed elevated levels of erythrocytes as well as hemoglobin. (As a result my hematocrit levels were also above average)
At my workplace there is a water cooler which also has an option to dispense carbonated water (this is just regular ol' carbonated tap water) and usually over the course of the day I tend to drink quite a lot of the stuff.
Since erythrocytes/hemoglobin deals with O2 and CO2 transport, I was wondering if my daily consumption of carbonated water is a plausible cause for the additional erythrocytes that are being pumped out? The main regulatory input into erythrocyte production is hypoxia. The response to elevated CO2 levels in the blood (hypercapnia) is mainly to increase ventilation (i.e. more and/or deeper breaths) so that the excess can be "blown off".
I think that some carbon dioxide could pass into the bloodstream from the stomach since gases tend to be quite good at diffusing across membranes, but this would be easily dealt with by the physiological mechanism described above.
The following is multiple choice question (with options) to answer.
What is the term for abnormally low blood levels of carbon dioxide? | [
"spirogyra",
"hepatitis",
"trichina",
"hypocapnia"
] | D | The chemical reactions that regulate the levels of CO2 and carbonic acid occur in the lungs when blood travels through the lung’s pulmonary capillaries. Minor adjustments in breathing are usually sufficient to adjust the pH of the blood by changing how much CO2 is exhaled. In fact, doubling the respiratory rate for less than 1 minute, removing “extra” CO2, would increase the blood pH by 0.2. This situation is common if you are exercising strenuously over a period of time. To keep up the necessary energy production, you would produce excess CO2 (and lactic acid if exercising beyond your aerobic threshold). In order to balance the increased acid production, the respiration rate goes up to remove the CO2. This helps to keep you from developing acidosis. The body regulates the respiratory rate by the use of chemoreceptors, which primarily use CO2 as a signal. Peripheral blood sensors are found in the walls of the aorta and carotid arteries. These sensors signal the brain to provide immediate adjustments to the respiratory rate if CO2 levels rise or fall. Yet other sensors are found in the brain itself. Changes in the pH of CSF affect the respiratory center in the medulla oblongata, which can directly modulate breathing rate to bring the pH back into the normal range. Hypercapnia, or abnormally elevated blood levels of CO2, occurs in any situation that impairs respiratory functions, including pneumonia and congestive heart failure. Reduced breathing (hypoventilation) due to drugs such as morphine, barbiturates, or ethanol (or even just holding one’s breath) can also result in hypercapnia. Hypocapnia, or abnormally low blood levels of CO2, occurs with any cause of hyperventilation that drives off the CO2, such as salicylate toxicity, elevated room temperatures, fever, or hysteria. |
SciQ | SciQ-6061 | evolution, zoology, adaptation
One answer that came to mind is domestic animals - the horse and dog in prehistory, the cat in ancient Egypt, etc. That seems too obvious on one hand, and on the other hand may not really be an answer, as there seems to be no indication that pre-domestic animals were endangered by humans in any meaningful way. Are there animals that have significantly adapted themselves to surviving as wild animals in human-influenced environments? Note: This is an answer to the last line of your question.
A classical example of animals adapting to the influence of humans on their environment is the adaption of the Peppered Moth.
Here is a brief summary:
The peppered moth was originally a mostly unpigmented animal (<1800). During the industrial revolution in the southern parts of the UK a lot of coal was burned. This led to soot blackening the countryside. Soon afterwards, a fully pigmented variety was first observed. Only a hundred years later, in 1895, this pigmented variety almost completely displaced the unpigmented variety.
It has been shown that the pigmentation is under strong selective pressure as birds hunt these moths. Since birds rely on their visual system to detect their prey, the variety that blends in with its environment (=camouflage) has a selective advantage over the variety that stands out.
As pointed out by Tim in the comments, since the 1970s there has been a rapid reversal with unpigmented animals being more abundant. As far as I understand, it is accepted that this reversal is due to a decrease in human induced air pollution leading to less sooty barks on trees which makes the unpigmented variety harder to prey upon.
Addendum: genetic basis of adaption
In a beautiful recent study, the causal mutation for the pigmented, or melanic, variety was identified: A ~9kb transposon insertion in the first intron of the gene cortex. The authors calculate that this mutation happened in the year 1819, a few years after the industrial revolution was in full swing. The interpretation is that due to sooty tree bark this mutation, causing pigmented moth, was under strong selection.
The following is multiple choice question (with options) to answer.
The vivid colors of flowers are an adaptation designed to encourage what by animals such as insects and birds? | [
"pollination",
"flowering",
"eating",
"consumption"
] | A | Figure 26.13 These flowers grow in a botanical garden border in Bellevue, WA. Flowering plants dominate terrestrial landscapes. The vivid colors of flowers are an adaptation to pollination by animals such as insects and birds. (credit: Myriam Feldman). |
SciQ | SciQ-6062 | entomology, parasitology, parasitism
The male (microgametocytes) and female (macrogametocytes) gametocytes are ingested by a female Anopheles mosquito during a blood meal (8) - only female mosquitoes (of pretty much any species) drink blood. The parasites' multiplication in the mosquito is known as the sporogonic cycle (stage C). While in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes (9). The zygotes in turn become motile and elongated (ookinetes) (10) which invade the midgut wall of the mosquito where they develop into oocysts (11). The oocysts grow, rupture, and release sporozoites (12), which make their way to the mosquito's salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle (1).
Sources
The following is multiple choice question (with options) to answer.
Arthropods change into the adult form in a process called what? | [
"metamorphosis",
"parthenogenesis",
"spontaneous mutation",
"budding"
] | A | Arthropods have a life cycle with sexual reproduction. Most species go through larval stages after hatching. The larvae are very different from the adults. They change into the adult form in a process called metamorphosis . This may take place within a cocoon. A familiar example of metamorphosis is the transformation of a caterpillar (larva) into a butterfly (adult). Other arthropod species, in contrast, hatch young that look like small adults. These species lack both larval stages and metamorphosis. |
SciQ | SciQ-6063 | biochemistry, neuroscience, brain, neuroanatomy
Title: The human brain in numbers I: neurons Even though knowing the number of neurons in a functional unit or with the same function is not of main importance, it may be interesting to know their orders of magnitude, especially in the human brain. For example:
|------------------|------------------|
| cerebellum | 100,000,000,000 |
| cortex | 20,000,000,000 |
| telencephalon | 10,000,000,000 |
| brainstem | 1,000,000,000 |
| sensory neurons | |
| haptic | 500,000,000 |
| visual | 100,000,000 |
| auditory | 2,000 |
| limbic system | |
| amygdala | 10,000,000 |
|------------------|------------------|
The following is multiple choice question (with options) to answer.
What is the largest part of the brain? | [
"limbic system",
"cerebellum",
"stem",
"cerebrum"
] | D | The cerebrum is the largest part of the brain. It controls conscious functions such as reasoning, language, sight, touch, and hearing. It is divided into two hemispheres, or halves. The hemispheres are very similar but not identical to one another. They are connected by a thick bundle of axons deep within the brain. Each hemisphere is further divided into the four lobes shown in Figure below . |
SciQ | SciQ-6064 | geology, mineralogy, minerals, weathering
To me, supergene has a specific meaning, it may be part of the weathering process in some locations, but weathering involves the breaking down of rocks due to: reactions with atmospheric gasses, water (usually rain), changes brought on by plants, bacteria wind and temperature.
My suggestion to use the term weathering or weathered.
The following is multiple choice question (with options) to answer.
What type of weathering breaks rock into smaller pieces? | [
"mechanical weathering",
"fluid weathering",
"chemical weathering",
"chemical erosion"
] | A | Mechanical weathering breaks rock into smaller pieces. These smaller pieces are just like the bigger rock; they're just smaller! The rock has broken without changing its composition. The smaller pieces have the same minerals in the same proportions. You could use the expression “a chip off the old block“ to describe mechanical weathering! The main agents of mechanical weathering are water, ice, and wind. |
SciQ | SciQ-6065 | inorganic-chemistry, acid-base, aqueous-solution, coordination-compounds, transition-metals
Simply, a complex metal ion has a metal ion at its center with a number of other molecules (e.g., $\ce{H2O}$) or ions (e.g., $\ce{CN-}$) surrounding it. When you start learning complex ions (or molecules) you must learn why complex ions of the type $\ce{[M(H2O)6]^n+}$ (hexaaqua ions) are acidic. Examples are, $\ce{[Fe(H2O)6]^2+}$, $\ce{[Fe(H2O)6]^3+}$, $\ce{[Cu(H2O)6]^2+}$, $\ce{[Co(H2O)6]^2+}$, $\ce{[Ni(H2O)6]^2+}$, $\ce{[V(H2O)6]^2+}$, etc. The first thing you need to know is the solutions of hexaaqua ions with equal concentrations have varying range of acidity (pH of solution), which depend a lot on type of metal's charge, ionic radius, etc. See the following graph extracted from the web page, Complex Metal Ions - The Acidity of the Hexaaqua Ions.
Let's take the hexaaquairon(III), $\ce{[Fe(H2O)6]^3+}$ as typical complex ion. The structure of the ion (octahedral) is given in the diagram A below and an explanation for its acidity is given in the diagram B (From Complex Metal Ions - The Acidity of the Hexaaqua Ions):
The following is multiple choice question (with options) to answer.
The coordination sphere consists of the central metal ion or atom plus its attached what? | [
"subunits",
"ligands",
"molecules",
"strands"
] | B | The coordination sphere consists of the central metal ion or atom plus its attached ligands. Brackets in a formula enclose the coordination sphere; species outside the brackets are not part of the coordination sphere. The coordination number of the central metal ion or atom is the number of donor atoms bonded to it. The coordination number for the silver ion in [Ag(NH3)2]+ is two (Figure 19.14). For the copper(II) ion in [CuCl4]2−, the coordination number is four, whereas for the cobalt(II) ion in [Co(H2O)6]2+ the coordination number is six. Each of these ligands is monodentate, from the Greek for “one toothed,” meaning that they connect with the central metal through only one atom. In this case, the number of ligands and the coordination number are equal. |
SciQ | SciQ-6066 | evolution, biochemistry, physiology, speculative, bioinorganic-chemistry
While iron skeletons might seem to be an advantage, they are electrochemically unstable - oxygen and water will tend to oxidize (rust) them quickly and the organism would have to spend a lot of energy keeping it in working form. Electrical conductivity sounds useful, but the nervous system favors exquisite levels of control over bulk current flow, even in cases like electric eels, whose current is produced by gradients from acetylcholine.
What's more, biological materials actually perform as well as or better than metal when they need to. Spider silk has a greater tensile strength than steel (along the direction of the thread). Mollusk shells are models for tank armor - they are remarkably resistant to puncture and breakage. Bone is durable for most purposes and flexible in addition.
The time it would take for metallized structures to evolve biologically are likely too long. By the time the metalized version of an organ or skeleton got started, the bones, shells and fibers we know probably have a big lead and selective advantage.
The following is multiple choice question (with options) to answer.
What functions like a flexible coat of armor, preventing the protist from being torn or pierced without compromising its range of motion? | [
"fimbriae",
"biofilm",
"pellicle",
"endothelium"
] | C | Cell Structure The cells of protists are among the most elaborate of all cells. Most protists are microscopic and unicellular, but some true multicellular forms exist. A few protists live as colonies that behave in some ways as a group of free-living cells and in other ways as a multicellular organism. Still other protists are composed of enormous, multinucleate, single cells that look like amorphous blobs of slime, or in other cases, like ferns. In fact, many protist cells are multinucleated; in some species, the nuclei are different sizes and have distinct roles in protist cell function. Single protist cells range in size from less than a micrometer to three meters in length to hectares. Protist cells may be enveloped by animal-like cell membranes or plant-like cell walls. Others are encased in glassy silica-based shells or wound with pellicles of interlocking protein strips. The pellicle functions like a flexible coat of armor, preventing the protist from being torn or pierced without compromising its range of motion. |
SciQ | SciQ-6067 | meteorology, geomorphology, climatology, atmospheric-circulation
Source Commons Wikipedia.
The cold waters near the ocean surface results in a cool, stable coastal atmosphere. In this region, evaporation from the ocean is reduced and produces extremely low rainfall over land. Precipitation is limited to morning fog and produces some of the driest ecosystems on Earth. The Atacama desert is the best example of such environment with average rainfalls of 15 mm/year (the driest non-polar region). In some areas, they are trying to take advantage of the little moisture the fog (Camanchaca) brings to establish some agricultural zones. The fog droplets are too small (1-40 micrometers) to form water drops and precipitate, so they use fog-catchers to collect moisture from the fog.
Source: newatlas.com
The following is multiple choice question (with options) to answer.
The marine west coast climate gets lots of rain because of what being nearby? | [
"the ocean",
"highways",
"the Sun",
"the mountains"
] | A | The marine west coast climate gets lots of rain from the nearby ocean. |
SciQ | SciQ-6068 | energy
Title: Why are more energetic events less likely So I was watching this very interesting video by DoS and noticed all the downward sloping lines in his Doomsday graph, and started wondering what is the fundamental reason behind those expected trends. I mean, it seems obvious that bigger hurricanes are rarer than smaller ones but I couldn't quite point out what law of physics/postulate implies this. Is it entropy, the second law in some way? Or just because we assume the energy in a semi-isolated system if finite therefore more energetic events are necessarily less common? But that doesn't really explain other curves for climate change or resistant bacteria. Or even why the volcanoes one is a plateau. I'm not sure if this is even the most appropriate SE to post this on, or if I'm grasping at straws, but I couldn't help getting annoyed that as a physics grad I couldn't explain the shape of those curves by anything else than an intuition. Thanks More energetic events require more energy to get started. The "activation energy" is higher. It is less likely to get that activation energy, hence the events themselves are also less likely.
You might be familiar with plots such as this one, which shows how catalysis works. You might also remember plots of quantum tunneling. The higher the barrier, the less likely it is to tunnel through.
The following is multiple choice question (with options) to answer.
What determines whether a volcanic eruption will be explosive or not? | [
"magma velocity",
"curve of magma",
"thickness of magma",
"lava temperature"
] | C | Volcanic eruptions can be non-explosive or explosive depending on the thickness of the magma. |
SciQ | SciQ-6069 | inorganic-chemistry
Title: Usage of platinum in flame test Why should we use platinum wire or loop in flame test, can we use any other material ? Why can't we use glass it something? Platinum is chemically inert ("noble") meaning it resists forming oxides or other compounds. This stability is desirable when doing a flame test because it ensures that we only see the spectrum of what we are burning. (Think how much noise we would have in our spectrum if we used a Magnesium wire to hold our sample)
Of the chemically inert metals (e.g. Au, Ag, Pd, Pt), Platinum has the highest melting point (2041º C), so it's the most useful for holding in a flame.
Glass, on the other hand, melts at a temperatures ~500º C lower than Platinum.
The following is multiple choice question (with options) to answer.
Platinum and gold are useful materials for constructing circuits because of their ability to resist what? | [
"decomposition",
"oxidation",
"Electricity",
"nitrogen"
] | B | If something is MULTIcolored, it has many colors. |
SciQ | SciQ-6070 | human-genetics
Title: In our 23 chromosome pairs, do the 2 members of the pair have distinct or virtually identical sequences? I understand that we have 46 DNA molecules in the nucleus of our cells, arranged in 23 pairs: 22 autosomal and 1 sex chromosome pairs.
I have read in different sources that the pairs contain nearly identical members, excluding any mutations. I have also read that the pairs contain 1 member we inherited from our mothers and 1 we inherited from our fathers, which are different due to inheritance.
This seems contradictory, given that genealogical companies match up on the differences on these chromosomes.
My understanding was that meiosis creates sperm and egg cells that each carry 23 chromosomes - they are haploids. During the first steps of meiosis that creates the reproductive cells we have a combining of the parent's chromosome pair from their parents to create 4 daughter cells, each independently viable, where the recombination of the chromosome pair has occurred at somewhat predictable spots (for you perhaps :-) ) and that these spots can be related to genes. It is this step that give us our genetic variation between siblings for example. A new person's DNA is partially formed from any one of these highly varied daughter cell possibilities.
Fertilization combines the reproductive cells to produce the 46 chromosome zygote with is again diploid.
I think this understanding supports the second interpretation that our chromosome pairs are not 2 nearly identical DNA molecules but are distinct.
Have I got this right? Is there a missing process or a misunderstanding in my interpretation? Homologous chromosomes (those that are paired up), excluding the sex pair are almost identical in size, shape and genes (members as you called them) present in them.
Genes determine traits and each homologous chromosome controls the same traits. The level of identity of a gene inside a population varies between genes. There are very conserved ones that do not change even between humans and yeast and others that vary alot event inside a species. This changes can be small in sequence length, a simple base (letter) swap or one deletion, and have a huge effect on the traits. This is how chimps and humans are very different but share 98.6% of their genome and humans are very similar and share 99.9% of their genome.
In summary, on the bigger scale homologous chromosomes are very similar (size, shape, traits inside), on the smaller scale homologous chromosomes have small changes that affect greatly.
The following is multiple choice question (with options) to answer.
How many set of chromosomes do moss have? | [
"triple set",
"double set",
"none",
"single set"
] | D | That may depend on the plant. Start with moss. The typical nonvascular plant. But such a simple plant has a very interesting life cycle. Whereas most kinds of plants have two sets of chromosomes in their vegetative cells, mosses have only a single set of chromosomes. So, how does meiosis occur?. |
SciQ | SciQ-6071 | electromagnetism, electricity, magnetic-fields, electromagnetic-induction
Title: What is meant by “changing magnetic field” At first I thought it was the consequence of an object moving from an area of high to low or low to high flux density, but that doesn’t help understand what is meant by “a changing magnetic field” inducing a voltage on a transformers secondary coil. So what is a changing magnetic field? Now that I understand that you're referring to transformers, and that you're a GCSE student, I think I have a more appropriate answer to your question, in a way I would have understood when I did my GCSE.
In the case of a transformer the changing magnetic field is due to the fact that the current in the primary coil is an alternating current. In AC systems both the current and the voltage change over time. Indeed they have a sinusoidal wave pattern. If you haven't already done so in GCSE, you will derive this in A-Level physics and see exactly why this is the case, but it's everything to do with how electricity is generated (by a spinning magnet). Below I've linked a plot of DC current (top) and voltage against AC (bottom).
DC current and voltage and AC current and voltage.
I take it that you have learned that charge carrying wires produce magnetic fields. The alternating current in the primary wire then induces a magnetic field in the iron that also alternates, i.e. changes over time, like the current. It is this changing magnetic field that then induces a current in the secondary coil, this time with a lower voltage.
The following is multiple choice question (with options) to answer.
When you change a magnetic field through electromagnetic induction what do you create? | [
"electric current",
"microwave current",
"cooling current",
"Light Current"
] | A | The process of generating electric current with a changing magnetic field is called electromagnetic induction . It occurs whenever a magnetic field and an electric conductor, such as a coil of wire, move relative to one another. As long as the conductor is part of a closed circuit, current will flow through it whenever it crosses magnetic field lines. One way this can happen is pictured in Figure below . It shows a magnet moving inside a wire coil. Another way is for the coil to move instead of the magnet. |
SciQ | SciQ-6072 | evolution, natural-selection, ornithology
Title: The evolutionary process in bird wings, especially with regard to winglets In this answer on aviation.SE a comparison is made between the shapes of airplanes wings and the shapes of birds wings. It concludes with the following remark:
After all, no bird has winglets. Not a single one.
In addition to be a disputable assertion (the wing tips such as the eagle's could be considered akin to a "winglet" of the fanned type) this has stricken me as based on a quite wrong assumption of how evolution works.
I tried to make my point in the comments only to reach this point:
So you consider evolved wings as not mature. The winglet modification is just waiting to happen? Nature never tried it, in >100 million years of biological flight? Could be, yes. But is extremely unlikely. That settles it for me.
Am I correct in identifying this in a wrong interpretation of the evolutionary process?
As I understand the evolutionary process, the current bird wings are not necessarily perfect, are simply the version that so far has given the best advantage. The lack of "winglets" in birds cannot then be explained simply by assuming that they do not improve the wing, but it could also be that there has never been an evolutionary pressure to evolve them or that since birds flap their wings they would be detrimental instead of beneficial or whatever other reason.
Is my understanding of the evolutionary process correct? if not, where am I at fault?
As a small addendum, another user cited the "Spandrels" in comparison to the above debate, could someone explain what could have been the meaning of the comparison? I looked up winglets so I had context for this answer. I'm interpreting winglets as the vertical tips at the end of airplane wings. If so, then you are correct. The spread primary feathers of soaring birds like eagles function as winglets (Tucker 1993). Airbus has a biomimicry web page devoted to some of the biological designs, including winglets, they incorporated into their airplane designs. Some studies suggest airplant winglets do increase efficiency (e.g., Hossain et al. 2011), but there is still some debate.
From the aviation.se answer:
The following is multiple choice question (with options) to answer.
Morphological and molecular data indicate that wings evolved how many times in insects? | [
"twice",
"never",
"once",
"many times"
] | C | |
SciQ | SciQ-6073 | bond
Title: Types of bonds in a molecule For example in dinitrogen pentoxide, $\ce{N2O5}$, covalent as well as coordinate bonds (type of covalent bonds) are present, but it appears that it contains only covalent bond.
What is a proper method to find out which type of bonds are present in a molecule? Electrovalent bonds are easiest to identify. If a compound is made up of a metal and non-metal/non-metallic radical (like carbonate), then, 99.99% times, it contains electovalent bond. If a compound is made up of 2 or more non-metals/non-metallic radicals, then it contains covalent bond. Coordinate covalent bonds appear mostly with compounds containing Hydrogen element. To identify the coordinate covalent bonds, you can draw the branched structural formula of the compound and see if the shared pair of electrons are coming from the same molecule.
The following is multiple choice question (with options) to answer.
Nonmetal structures contain what type of bonds? | [
"gravitational",
"covalent",
"polymeric",
"prevalent"
] | B | Structures of the Nonmetals The structures of the nonmetals differ dramatically from those of metals. Metals crystallize in closely packed arrays that do not contain molecules or covalent bonds. Nonmetal structures contain covalent bonds, and many nonmetals consist of individual molecules. The electrons in nonmetals are localized in covalent bonds, whereas in a metal, there is delocalization of the electrons throughout the solid. The noble gases are all monatomic, whereas the other nonmetal gases—hydrogen, nitrogen, oxygen, fluorine, and chlorine—normally exist as the diatomic molecules H2, N2, O2, F2, and Cl2. The other halogens are also diatomic; Br2 is a liquid and I2 exists as a solid under normal conditions. The changes in state as one moves down the halogen family offer excellent examples of the increasing strength of intermolecular London forces with increasing molecular mass and increasing polarizability. Oxygen has two allotropes: O2, dioxygen, and O3, ozone. Phosphorus has three common allotropes, commonly referred to by their colors: white, red, and black. Sulfur has several allotropes. There are also many carbon allotropes. Most people know of diamond, graphite, and charcoal, but fewer people know of the recent discovery of fullerenes, carbon nanotubes, and graphene. Descriptions of the physical properties of three nonmetals that are characteristic of molecular solids follow. |
SciQ | SciQ-6074 | mechanical-engineering, pressure, piping
Title: How to seal a pressure vessel I'm trying to construct a stainless steel high pressure containment vessel (pressure reactor) (2000 psi or so). Yes I realize that this is a don't try this at home type of thing, and I plan to put some lexan in front of it before I do any testing.
I'm looking at 2" stainless pipe with a wall thickness of .148"(rated 4000 psi), and I'm trying to figure out the best way to seal the ends. I plan on welding one end cap on, but the other end needs to be removable. I'm not certain how to calculate how much pressure a threaded pipe end would be able tolerate, or if perhaps some sort of high pressure triclamp. I've seen some industrial pressure reactor vessels, but they are rates for something like 13,000 psi, way overkill, they are also super expensive. Looking for a DIY lower cost alternative. Any info would be appreciated. I have done this before so would like to share some of what I know. Super critical CO2 has some unique properties, for one it is extremely difficult to keep in a closed container since it has near zero surface tension. As such, if a standard threaded fitting is used and the fluid comes into contact with it you can be fairly certain it will leak (and usually badly).
Welding stainless of this thickness properly requires a powerful TIG welder, this in turn calls for a certain level of skill in the operator. If you have both of these then please disregard this comment.
Another option all together is carbon steel. It is inexpensive (compared to your stainless piece), comes in a variety of sizes (DOM is a good place to start), welds nicely with a basic MIG, and is easier to machine.
Regardless sizing and material type are critical, although engineering this piece with an adequate factor of safety will keep things together. Once again this requires a certain level of skill, if you don't have it then this is not a safe project to tackle.
Next you will need correctly rated and calibrated pressure gauges. Installation is straightforward although their importance can not be under estimated. Two is the minimum in case one is not reading properly (stuck needle for example).
Calibrated pressure relief valves are also essential, and once again two is the minimum in case of failure.
The following is multiple choice question (with options) to answer.
Gas lines should be made of what so they do not rupture? | [
"Hard material",
"typically material",
"flexible material",
"adjustment material"
] | C | Check to see that gas lines are made of flexible material so they do not rupture. Any equipment that uses gas should be well secured. |
SciQ | SciQ-6075 | neurophysiology
Title: Why myelin sheat does not cover the whole axon? Is there an optimal lenght for myelin sheats to be effective and lead potential across the nerve cell? This has always bugged me. The nodes of Ranvier (the gaps between myelin sheath segments) speed up the action potential because the electric current can jump from node to node (or gap to gap). If the myelin covered the entire axon, the signal wouldn't have the gaps to speed up the signal. As for optimal length, the gap is 1μm long, but can be longer, on the order of millimeters depending on the type of cell. The length of the myelin doesn't matter so much as the length of the nodes of Ranvier because they are where the Na+/K+ channels are found so the ion exchange can occur. This is how an action potetial can occur, so the myelin not covering the entire axon is crucial for the ability of neurons to propagate a signal.
The following is multiple choice question (with options) to answer.
What is the lipid-rich sheath that surrounds the axon and facilitates the transmission of electrical signals along the axon? | [
"myelin sheath",
"axon sheath",
"neural sheath",
"receptors sheath"
] | A | Myelin The insulation for axons in the nervous system is provided by glial cells, oligodendrocytes in the CNS, and Schwann cells in the PNS. Whereas the manner in which either cell is associated with the axon segment, or segments, that it insulates is different, the means of myelinating an axon segment is mostly the same in the two situations. Myelin is a lipid-rich sheath that surrounds the axon and by doing so creates a myelin sheath that facilitates the transmission of electrical signals along the axon. The lipids are essentially the phospholipids of the glial cell membrane. Myelin, however, is more than just the membrane of the glial cell. It also includes important proteins that are integral to that membrane. Some of the proteins help to hold the layers of the glial cell membrane closely together. The appearance of the myelin sheath can be thought of as similar to the pastry wrapped around a hot dog for “pigs in a blanket” or a similar food. The glial cell is wrapped around the axon several times with little to no cytoplasm between the glial cell layers. For oligodendrocytes, the rest of the cell is separate from the myelin sheath as a cell process extends back toward the cell body. A few other processes provide the same insulation for other axon segments in the area. For Schwann cells, the outermost layer of the cell membrane contains cytoplasm and the nucleus of the cell as a bulge on one side of the myelin sheath. During development, the glial cell is loosely or incompletely wrapped around the axon (Figure 12.13a). The edges of this loose enclosure extend toward each other, and one end tucks under the other. The inner edge wraps around the axon, creating several layers, and the other edge closes around the outside so that the axon is completely enclosed. |
SciQ | SciQ-6076 | human-biology
Title: Is urine dirty as soon as it leaves the human body? Human urine is sterile as long as it is in the human body. But is it dirty after leaving the human body? Could you get sick from it, if you drink it or don't wash your hands, for example? It was believed for a long time that urine stored in the urinary bladder is sterile. However, Wolfe et al(1). recently found evidence of bacterial presence in the urine extracted from bladders of healthy women. In an article just published, Hilt et al. found that at least some bacteria found in the bladder of healthy women are viable and can be grown in a laboratory after extraction from the bladder).2 (Paywall). They expect that the same is the case for men.
From the Hilt et al. paper:
Thirty-five different genera and 85 different species were identified
by EQUC. The most prevalent genera isolated were Lactobacillus (15%),
followed by Corynebacterium (14.2%), Streptococcus (11.9%),
Actinomyces (6.9%), and Staphylococcus (6.9%). Other genera commonly
isolated include Aerococcus, Gardnerella, Bifidobacterium, and
Actinobaculum.
Note that these species for the most part (Actinobaculum being one exception, as a possible uropathogen) appear to be part of the normal microbiome (collection of microorganisms) in healthy people in the same way as bacteria inhabit other parts of healthy persons. Additionally, the recovered organisms required special care to achieve growth:
Most of the bacteria isolated required either increased CO2 or
anaerobic conditions for growth, along with prolonged incubation, and
they often were present in numbers below the threshold of detection
used in routine diagnostic urine culture protocols.
The following is multiple choice question (with options) to answer.
Where is urine formed in the body? | [
"the lungs",
"the kidneys",
"the liver",
"the pancreas"
] | B | Urine is a liquid that is formed by the kidneys when they filter wastes from the blood. Urine contains mostly water, but it also contains salts and nitrogen-containing molecules. The amount of urine released from the body depends on many things. Some of these include the amount of fluid and food a person consumes and how much fluid they have lost from sweating and breathing. Urine ranges from colorless to dark yellow but is usually a pale yellow color. Light yellow urine contains mostly water. The darker the urine, the less water it contains. |
SciQ | SciQ-6077 | water, ph, environmental-chemistry
Title: Difference in pH of water and rainwater In my textbook (Olmsted and Williams 4th ed) it is given that pH of pure water is 7, pH of unpolluted rain water is between 5-6 and pH of acid rain is between 4-5.
It is obvious that pH for acid rain would be low. But how is it acidic, even slightly, for unpolluted rain water? Shouldn't unpolluted mean without any solutes or dust in water? Shouldn't it be similar to pH of pure water (7)? At first thought, it might seem that rainwater should be clean like distilled water, as it evaporated, condensed, then fell back to earth. It sounds like a condenser or distillation apparatus in a laboratory. But in reality, the process is very different.
To start with, every raindrop must have a particle to condense upon, called a cloud condensation nucleus. According to this Wikipedia article:
Cloud condensation nuclei or CCNs (also known as cloud seeds) are
small particles typically 0.2 µm, or 1/100th the size of a cloud
droplet on which water vapor condenses. Water requires a
non-gaseous surface to make the transition from a vapor to a liquid;
this process is called condensation. In the atmosphere, this surface
presents itself as tiny solid or liquid particles called CCNs.
Furthermore, the composition of CCN is frequently very acidic, having formed from sulfuric acid or sometimes weak organic acids. These types of CCN form in both polluted as well as pristine environments. Both natural and man-made sources of sulfur emissions result in the photochemical oxidation to sulfuric acid, which forms new CCN which are very hygroscopic (water absorbing).
The type of CCN described above are most commonly formed over land. In marine environments, there are natural sources of sulfur gases, but most CCN form from evaporated sea spray, which is of course much more pH neutral.
However, regardless of how the cloud drop was originally formed, they all have another source of acidity from the atmosphere; they absorb carbon dioxide, which is rapidly converted to carbonic acid when dissolved in a cloud droplet. It is this absorption of naturally occurring, acidic carbon dioxide that is the primary reason that essentially all rain is somewhat acidic.
The following is multiple choice question (with options) to answer.
What is the term for rain consisting of water with a ph below 5? | [
"carbon rain",
"produce rain",
"acid rain",
"Hot Rain"
] | C | Acid rain is rain that has a pH less than 5 ( Figure below ). Acidity is measured on the pH scale . Lower numbers are more acidic, and higher numbers are less acidic (also called more alkaline ). An acid has a pH of less than 7. The pH of normal rain is 5.6. It’s slightly acidic because carbon dioxide in the air dissolves in rain. This forms carbonic acid, a weak acid. |
SciQ | SciQ-6078 | ocean, glaciology, ice, ecology, cryosphere
Title: Do icebergs have any impact on ecology? Are icebergs neutral actors in the environment, or do they have any impact on the local ecology. Do they have any environmental impacts that might influence any part of the biosphere? Yes, they have many impacts:
They provide a substrate for algae to grow and they can have whole ecosystems under them. You might think that such substrate is transient because it is melting, but Arctic and Antarctic waters are often below zero degrees Celsius, therefore, freshwater ice doesn't melt. You can find many articles about such ecosystems (here is one).
They transport sediments and nutrients into the ocean.
They provide safe rest areas for animals like seals, birds and penguins.
They impact the temperature of surface waters, specially in fjords.
They stir the sea floor in shallow waters
And there must be more ways they impact the environment and ecosystems but those are the ones I can think about right now.
The following is multiple choice question (with options) to answer.
What type of ecosystem do polar bears live in? | [
"natural",
"oceanic",
"arctic",
"tropical"
] | C | Polar Bears. Thick fur and a layer of blubber keep polar bears warm in their Arctic ecosystem. Why do you think their fur is white? Why might it be an adaptation in an Arctic biome?. |
SciQ | SciQ-6079 | marine-biology, vestigial
Title: Modern Whales with Vestigial legs Myth? Is it a myth that modern whales have been found with hind legs sticking out of their sides and full formed tibias, fibias, and toe bones? I keep finding assertions, but no citations. For example, the wikipedia page has no citation for it.
http://en.wikipedia.org/wiki/Whales#Appendages The link you give doesn't mention limbs sticking out of the body wall, but only vestigial hind limb elements. Many whales do retain pelves and femora, as this page at the Bergen Museum shows. Given the variation in limb development across vertebrates, it would not be surprising to find more distal elements (but I would be very surprised if they extended past the body wall).
The following is multiple choice question (with options) to answer.
Pseudopods are false what? | [
"teeth",
"feet",
"fingers",
"eyes"
] | B | What is a cell? Gradient Physical difference between two regions of space, in such a way that the molecules tend to move in response to the gradients. Diffusion Movement of the molecules in a fluid, from the regions of high concentration to those of low concentration. Passive transport Movement of substances in a membrane that doesn’t need to use energy. Simple diffusion Diffusion of water, gases or molecules across the membrane. Facilitated diffusion Diffusion of molecules across the membranes with the participation of proteins. Osmosis Diffusion of the water across a membrane with differential permeability. Transport that needs energy Movement of substances across a membrane generally in opposition to a gradient of concentration with the requirement of energy. Active transport Movement of small molecules using energy (ATP). Endocytosis Movement of big particles towards the interior of the cell using energy. The cells enclose particles or liquids. Pinocytosis (Literally cell drinking) Form in which the cell introduces liquids. Phagocytosis Way of eating of the cells. It feeds in this case of big particles or entire microorganisms. Pseudopods False feet (the amoeba). Exocitosis Movement of materials out of the cell with the use of energy. It throws waste material. Isotonic The cytoplasm fluid of the interior of the cells is the same that the outer. Hypertonic solution. |
SciQ | SciQ-6080 | bond, atoms, molecules, valence-bond-theory
So the short answer to your first question is: "Molecular orbitals hold atoms together in covalent bonds, and those are a result of electrostatic interactions and the quantum nature of electrons."
Yes, ionic compounds are large collections of ions, and you can't really define "molecules" for them - instead we talk about "formula units" which are the lowest possible whole-number ratio of elements that represent the compound. Groups of covalently bonded atoms are also held together by electrostatic interactions, but since the covalent bonds are so much stronger, a molecular compound can exist "on its own" as a single molecule. Collectively, the forces that hold collections of molecules together are called van der Waals forces if they don't involve ions. In any atom or molecule, there is never a completely uniform charge density on the surface. For some molecules, this is extreme (water is a good example) and we say it is very polar, or that it has a large dipole moment. This is just another way of saying that one part has a negative charge and the other has a positive charge. In water it looks like this (from wikipedia):
In this picture, red means "more electrons" and blue means "less electrons." Water can form hydrogen bonds, which are very strong electrostatic interactions. Some atoms and molecules have an almost uniform charge density on the surface. We call these "non-polar" molecules - noble gases are good examples. However, even noble gases have what is called an induced dipole due to statistically correlated fluctuations in electron density when the atoms are near each other. As a result, even noble gases can be cooled to the point where they become liquid - the very, very weak electrostatic interactions will hold them together at low temperature, when they are not moving very fast. These forces are called London Dispersion Forces - after the guy who first described them. London dispersion forces are important, because they are found in all molecules - polar or not. In fact, this is what makes most plastics solid. Polyethylene, for example, is made of very long chains of essentially non-polar molecules (from wikipedia):
The following is multiple choice question (with options) to answer.
Ionic bonds are what kind of attraction between ions? | [
"magnetic",
"nuclear",
"electrostatic",
"kinetic"
] | C | Ionic bonding. Ionic bonds result from electrostatic attractions between positively and negatively charged side chains of amino acids. For example, the mutual attraction between an aspartic acid carboxylate ion and a lysine ammonium ion helps to maintain a particular folded area of a protein (part (a) of http://catalog. flatworldknowledge. com/bookhub/reader/2547 - gob-ch18_s04_s01_f05). Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-6081 | solutions, phase, evaporation
Title: What is the relationship between solutions and changes to states of matter? For example, when liquid water evaporates, my instinct is to say that of course it's become gas, but I'm a bit unsure because, if I understand correctly, evaporation occurs because air dissolves the water, and it's not clear to me whether that counts as a phase change. Intuitively it seems like it should should water dissolves in the air or salt dissolved in water, etc. have different properties before and after being dissolved. And yet, the way I've always heard it explained, phase changes are specifically due to changes in temperature and/or pressure, not due to chemical interactions with another another substance.
On the other hand, from what I remember from chem 101 and 102, when we considered chemical reactions occuring between solids dissolved in a liquid (usually acids and bases dissolved in water), we usually just labeled them as aqueous, meaning "in solution", whereas for non-aqueous substances, we'd label them with the relevant state of matter, solid, liquid, or gas. Does that mean dissolved substances constitute their own state of matter? Or that it's simply not meaningful to talk about the state of the solute independent of the solvent?
I also saw this thread, Is it appropriate to say "solid-in-gas solution" and "liquid-in-gas solution"?, where someone says, "Whenever there is only one phase, but there are two or more chemical species, then you have a solution", which heavily implies there's a fundamental relationship between phase changes and solutions, but it also doesn't seem quite right Water vapour in air is a solution, but not in the same sense as solutions in water.
Water vapour in air is solution in sense of homogenous mixture, where molecules move freely and independently.
Salts in water dissociate (are dissociated by water) to ions. Having a net charge, they form a nonhomogeneous electrostatic gradient.Ions are hydrated by water molecules that have an electric dipole and therefore attracted to the center of such a gradient. So here we see strong interaction and dependent motion.
The following is multiple choice question (with options) to answer.
What type of change occurs when matter changes chemically into an entirely different substance with different chemical properties? | [
"chemical",
"material",
"genetic",
"physical"
] | A | Did you ever make a "volcano," like the one in Figure below , using baking soda and vinegar? What happens when the two substances combine? They produce an eruption of foamy bubbles. This happens because of a chemical change. A chemical change occurs when matter changes chemically into an entirely different substance with different chemical properties. When vinegar and baking soda combine, they form carbon dioxide, a gas that causes the bubbles. It’s the same gas that gives soft drinks their fizz. |
SciQ | SciQ-6082 | zoology, marsupials
Title: Do male marsupials have a pouch? Do male marsupials have a pouch, or is it a female organ only (like the womb)? In most marsupials, only the females have a pouch. However, males of the water opossum and the extinct tasmanian tiger (or thylacine) also have a pouch. The males of both the thylacine and water opposum used/use their pouch to keep their genitalia from getting entangled in vegetation.
The following is multiple choice question (with options) to answer.
Australia is home to many endemic species. the (a) wallaby (wallabia bicolor), a medium-sized member of the kangaroo family, is a pouched mammal, or this? | [
"placental",
"marsupial",
"rodent",
"primate"
] | B | Throughout Chemistry, you will find features that draw the students into scientific inquiry by taking selected topics a step further. Students and educators alike will appreciate discussions in these feature boxes. Chemistry in Everyday Life ties chemistry concepts to everyday issues and real-world applications of science that students encounter in their lives. Topics include cell phones, solar thermal energy power plants, plastics recycling, and measuring blood pressure. How Sciences Interconnect feature boxes discuss chemistry in context of its interconnectedness with other scientific disciplines. Topics include neurotransmitters, greenhouse gases and climate change, and proteins and enzymes. Portrait of a Chemist features present a short bio and an introduction to the work of prominent figures from history and present day so that students can see the “face” of contributors in this field as well as science in action. |
SciQ | SciQ-6083 | marine-biology, vestigial
Title: Modern Whales with Vestigial legs Myth? Is it a myth that modern whales have been found with hind legs sticking out of their sides and full formed tibias, fibias, and toe bones? I keep finding assertions, but no citations. For example, the wikipedia page has no citation for it.
http://en.wikipedia.org/wiki/Whales#Appendages The link you give doesn't mention limbs sticking out of the body wall, but only vestigial hind limb elements. Many whales do retain pelves and femora, as this page at the Bergen Museum shows. Given the variation in limb development across vertebrates, it would not be surprising to find more distal elements (but I would be very surprised if they extended past the body wall).
The following is multiple choice question (with options) to answer.
What do you call structures like a whale's pelvic bones, which were once attached to legs, or wings that cannot be used for flight? | [
"distinctive",
"primitive",
"vestigial",
"primordial"
] | C | Penguins do not use their wings, known as flippers, to fly in the air. However, they do use them to move in the water. The theory of evolution suggests that penguins evolved to use their wings for a different purpose. A whale’s pelvic bones, which were once attached to legs, are also vestigial structures. Whales are descended from land-dwelling ancestors that had legs. |
SciQ | SciQ-6084 | inorganic-chemistry, coordination-compounds, hybridization
Title: Hybridisation of complex compound having octahedral geometry $$\ce{K[Co(NH3)2Cl4]}$$
I have problem finding the hybridisation of this compound. The strong field ligand $\ce{NH3}$ forms the minority among the ligands, so do I consider the hybridisation to be $\ce{sp^3d^2}$ ? Next, in this compound, $\ce{[Co(NH3)Cl3]}$, the number of strong field ligands is equal to the number of weak field ones. Can someone please explain the basis on which I can find out the hybridisation using crystal field splitting. If you calculate the oxidation state of the central metal atom in both of these cases, you'll find it to be $+3$. With $\ce{Co^3+}$, all ligands behave as strong field ligands except in the cases of $\ce{[CoF6]^3-}$ and $\ce{[Co(H2O)3F3]}$. Thus, in both of the cases you've mentioned, the ligands will cause pairing of electrons, the complex will be of a diamagnetic nature and the hybridization will be $\ce{d^2sp^3}$.
The following is multiple choice question (with options) to answer.
What type of hybridization does ammonia undergo? | [
"nh3 hybridization",
"h2O hybridization",
"sp 3 hybridization",
"ionic hybridization"
] | C | The methane and ammonia examples illustrate the connection between orbital hybridization and the VSEPR model. The electron domain geometry predicted by VSEPR leads directly to the type of hybrid orbitals that must be formed to accommodate that geometry. Both methane and ammonia have tetrahedral electron domain geometries and thus both undergo sp 3 hybridization. |
SciQ | SciQ-6085 | thermodynamics, energy, temperature, energy-conservation
Yes, but it is important to realize that the KE and PE components of the internal energy $U$ is the KE and PE associated with the motion and position of the molecules of the system, i.e., KE and PE at the microscopic level. The motion and positions you cannot observe directly. That is why they call it "internal" energy.
It is not the mechanical KE and PE of the system as a whole due to its velocity or position relative to an external frame of reference. I like to call this the "external" KE and PE of the system because they are associated with an external (to the system) frame of reference. These are the $\Delta KE$ and $\Delta PE$ in the general equation of the first law given in @Chet Miller answer.
Additionally, temperature is determined only by translational KE.
This statement can be misleading. Although the kinetic temperature doesn't take into account vibrational and rotational forms of molecular kinetic energy, the specific heats do take them into account, and the specific heats determine the temperature change for a given amount of heat transfer in the absence of work.
However, exercises in my textbook make it out to seem that an increase
in $U$ (whether via work or heat energy) always results in an increase
in temperature as well.
I'm not sure what those exercises are, but an increase in internal energy does not always result in an increase in temperature. For example, adding heat to cause a phase change from a solid to a liquid (e.g, melting of ice) increases internal energy with no change in temperature. That's because the heat addition only increases the internal PE, not KE of the water molecules. On the other hand, heating an ideal gas results in only an increase in translational KE.
How can work done on an object (e.g. accelerating it with a constant
force over some distance in a vacuum) increase the random
translational KE of its atoms?
The following is multiple choice question (with options) to answer.
What does increased temperature do to a substance's kinetic energy? | [
"increases",
"decreases",
"generates",
"nothing"
] | A | Entropy increases as temperature increases. An increase in temperature means that the particles of the substance have greater kinetic energy. The faster moving particles have more disorder than particles that are moving more slowly at a lower temperature. |
SciQ | SciQ-6086 | cell-biology, apoptosis, autophagy
Apoptosis: A Review of Programmed Cell Death
Apoptosis vs. Necrosis
Cell death by necrosis: towards a molecular definition
Review Necrosis: a specific form of programmed cell death?
The following is multiple choice question (with options) to answer.
What natural process is associated with the death of cells? | [
"dissolving",
"cooling",
"reducing",
"aging"
] | D | 6. Aging is associated with the death of cells. Give two reasons why cells die. |
SciQ | SciQ-6087 | atmosphere, clouds, fluid-dynamics
Title: What affects the surface characteristics of cumulus clouds? I love looking at clouds. I love trying to describe them and compare what I see day to day.
I have dozens of questions about the things I’ve observed and I would really like to understand the physics of the world around me. Today I would like to focus on the surface dynamics of cumulus clouds.
Why do some cumulus clouds have distinct textured surface while others are softer and wispy at the edge?
I imagine it probably comes down to temperature and pressure. It may also be an effect of direct sunlight, I’m not sure. I notice the soggy cotton clouds are more common in the evening and the billowy ice cream clouds are more common mid-day.
Do clouds have surface tension like liquid water?
Does the flow of water either into or out of a cloud affect its surface characteristics? No, clouds don't really have a 'surface' that could have tension like a body of water. The different looks in these two examples (left Cumulonimbus Calvus and right Cumulus Humilis) are greatly dependent on how they have formed and how are they evolving now.
The large Cumulonimbus is still growing in a relatively rapid speed. The cloud is reaching higher and higher upwards carrying moist air. The moist air due to turbulent flows and expanding of the rising air gets mixed with the cold air and instantly forms/extends cloud as it reaches saturation (saturation is reached with less water in colder air and air is colder in higher altitudes). If there wasn't the expansion then flows of dry air to the cloud would desaturate the cloud and more small scale variation could be seen as in the Cumulus Humilis. Also the Cumulonimbus being much larger and further away looks different just due to distance. The steady state like situation of the Cumulus Humilis where it isn't growing (perhaps a little on the top) and the fact that the lower atmosphere has stronger turbulent motions equals to the appearance where more cotton candy pieces 'drift' from the cloud.
The following is multiple choice question (with options) to answer.
What color and shape are cumulus clouds? | [
"dark and wispy",
"dark and tall",
"white and puffy",
"white and wispy"
] | C | Cumulus clouds are white and puffy. Convection currents make them grow upward, and they may grow very tall. When they produce rain, they are called cumulonimbus. |
SciQ | SciQ-6088 | geology, atmosphere, climate-change, planetary-science, paleoclimatology
Title: Is there any evidence for higher air pressures in the geological past? I was curious about how the Earth's overall air pressure has varied over time, and tried to take a look around the internet. However, Google pops up a lot of sites with questionable science proposing that the air pressure was much higher in the past. The more outrageous claims (such as those by David Esker) are dealt with on Skeptics.SE.
However, there are more reasonable claims that air pressure was perhaps 4 or 5 times higher in the Mesozoic, thus allowing pterosaurs to fly more effectively, etc. The websites making such claims do heavily set off my pseudoscience alarms, but then some are published by the American Chemical Society by reputable sounding scientists with references to papers.
There is evidence that in the far distant past, air pressures were lower than they are currently. But after the changes to the atmosphere wrought by photosynthetic life, is there any evidence supporting the various theories of higher air pressures? Yes, there is.
But the data is still very sparse and errors are large.
Past atmospherics pressures have been estimated by at least three different methods:
Isotopic composition of fluid inclusions trapped hydrothermal quartz ( Nishizawa ey al 2007; Goldblatt et al 2009; Marty et al, 2013)
Image from Fig. 2 of Nishizawa et al 2007.
Size distribution of gas bubbles in basaltic lava flows (Som et al 2016)
Figure 3c of Som et al (2016): Beasley River geologic context and flow detail (scale bar, 1 cm)
Size distribution of fossilised raindrop imprints (Som et al, 2012; Kavanagh & Goldblat, 2015)
The following is multiple choice question (with options) to answer.
During the early paleozoic, the amount of carbon dioxide in the atmosphere compared to today was? | [
"much lower",
"the same",
"much greater",
"none"
] | C | During the early Paleozoic, the amount of carbon dioxide in the atmosphere was much greater than it is today. This may have begun to change later, as land plants became more common. As the roots of land plants began to infiltrate rock and soil began to form, carbon dioxide was drawn out of the atmosphere and became trapped in the rock. This reduced the levels of carbon dioxide and increased the levels of oxygen in the atmosphere, so that by the end of the Paleozoic, atmospheric conditions were similar to those of today. As plants became more common through the latter half of the Paleozoic, microclimates began to emerge and ecosystems began to change. As plants and ecosystems continued to grow and become more complex, vertebrates moved from the water to land. The presence of shoreline vegetation may have contributed to the movement of vertebrates onto land. One hypothesis suggests that the fins of aquatic vertebrates were used to maneuver through this vegetation, providing a precursor to the movement of fins on land and the development of limbs. The late Paleozoic was a time of diversification of vertebrates, as amniotes emerged and became two different lines that gave rise, on one hand, to mammals, and, on the other hand, to reptiles and birds. Many marine vertebrates became extinct near the end of the Devonian period, which ended about 360 million years ago, and both marine and terrestrial vertebrates were decimated by a mass extinction in the early Permian period about 250 million years ago. |
SciQ | SciQ-6089 | computability, turing-machines, physics
Title: Can normal physics laws be simulated in Digital physics? Physics is defined as the study of an object {matter or energy} with its interaction with other objects:
Physics is the study of matter, energy, and the interaction between them.
On the other hand, Digital physics is based on computations and information.
Digital physics is a collection of theoretical perspectives based on the premise that the universe is, at heart, describable by information, and is therefore computable.
The following is multiple choice question (with options) to answer.
Physical science is defined as the study of what? | [
"matter & elements",
"biology & light",
"light & matter",
"matter & energy"
] | D | Look at the topographic map of Stowe, Vermont ( Figure below ). There is a steep hill rising just to the right of the city of Stowe. You can tell this because the contour lines there are closely spaced. The contour lines also show that the hill has a sharp rise of about 200 feet. Then the slope becomes less steep toward the right. |
SciQ | SciQ-6090 | electromagnetism
Title: Region of most and least intense magnetic field
It's a unmagnetized iron screw placed in the north pole of a U shaped magnet. I believe the region of least intense magnetic field is at the far left of the board. From what I understand the screw becomes magnetized and it's south pole is where it's touching the north of the magnetic, is it correct to assume the most intense magnetic field will be where the screw is touching the magnet due to there being direct contact between them?
Consider these images showing the magnetic field lines of a horse-shoe magnet. Magnetic intensity at any point in its field is directly proportional to its magnetic flux.So the region where the field lines are more densely packed have a higher intensity than where the field lines are loosely packed. If possible, draw the field lines for your own case and you will realize where the magnetic intensity is most and least.
The following is multiple choice question (with options) to answer.
What do you call the two ends of a magnet where the magnetic effect is strongest? | [
"magnetos",
"opposites",
"poles",
"plates"
] | C | Any magnet has two ends called poles where the magnetic effect is strongest. |
SciQ | SciQ-6091 | acoustics
Title: Is there a non-relative unit of measurement for the volume of sound? I understand dB to be the main unit of measurement of the volume of a sound, but (to the best of my limited knowledge), dB only gives a measurement of the volume of a sound relative to the volume of another sound. Is there such thing as a universal scale for simply measuring volume non-relatively? If not, could someone explain why there has never been a need for such a unit of measurement? Yes, you can use the pressure generated by the sound wave or the energy it transmits. For example zero decibels is $10^{-12}$ W/m$^2$.
I suspect the dB scale originated because the preception of volume in human hearing is logarithmic i.e. we perceive each successive doubling as a linear volume increment. The dB scale is also logarithmic and maps well onto human perception of volume. It's also very convenient for expressing signal to noise ratios as these tend to span many orders of magnitude.
The following is multiple choice question (with options) to answer.
The scale that is used to measure the loudness of sound measures their loudness in what? | [
"decibels",
"waves",
"centimeters",
"weight"
] | A | The most common cause of hearing loss is exposure to loud sounds. Loud sounds can damage hair cells inside the ears. Hair cells change sound waves to electrical signals that the brain can interpret as sounds. Louder sounds, which have greater intensity than softer sounds, can damage hair cells more quickly than softer sounds. You can see the relationship between sound intensity, exposure time, and hearing loss in the following Figure below . The intensity of sounds is measured in decibels (dB). |
SciQ | SciQ-6092 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
What are located on either side of the pharynx in the throat? | [
"wrinkles",
"lymph nodes",
"tonsils",
"testicles"
] | C | The tonsils are located on either side of the pharynx in the throat. They trap pathogens, which are destroyed by lymphocytes in the tonsils. |
SciQ | SciQ-6093 | reproduction, asexual-reproduction
Title: can self-fertilization in flowers be called asexual reproduction? Suppose a flower having both male and female reproductive parts is self-fertilized then can this be called asexual reproduction...?I'm quite confused cause in this case the fusion of male and female gametes do take place but again the gametes are from the same parent....please help. According to this article from Berkeley, asexual reproduction is:
Any reproductive process that does not involve meiosis or syngamy
Using this definition of asexual reproduction and knowing self-fertilization involves meiosis and syngamy, it is not asexual.
The following is multiple choice question (with options) to answer.
What kind of reproduction requires the fusion of male and female gametes? | [
"subject reproduction",
"sexual reproduction",
"autonomous reproduction",
"asexual reproduction"
] | B | |
SciQ | SciQ-6094 | human-biology, cancer, systems-biology
Title: How does cancer of the larynx (laryngeal cancer) affect the respiratory system? The larynx is part of the respiratory system and is responsible for producing sound (our voices). My question is how cancer in the larynx (voice box) affect the respiratory system overall? I appreciate any answer, but if it's not too inconvenient, please don't use too complex terminology (I'm in grade 10 Canada).
Thanks According to this website:
http://www.spirometry.guru/fvc.html
it causes difficulty with inhalation but exhalation is normal...
"Typically the expiratory part of the F/V-loop is normal: the
obstruction is pushed outwards by the force of the expiration."
"During inspiration the obstruction is sucked into the trachea with
partial obstruction and flattening of the inspiratory part of the
flow-volume loop."
the exact symptoms of a laryngeal tumor depends on where it is located on the larynx... above the vocal cords, on the vocal cords, or below the vocal cords...
but more generally:
anatomy:
mouth/nose-->pharynx-->larynx-->trachea-->bronchi-->lungs
a tracheostomy may be necessary... basically the surgeon makes a connection between the skin outside the throat and the trachea... this bypasses the larynx (as well as pharynx and nose/mouth)...
The following is multiple choice question (with options) to answer.
Diseases of the lungs, bronchial tubes, trachea, nose, and throat affect what organ system? | [
"digestive",
"respiratory",
"skin",
"heart"
] | B | Respiratory diseases are diseases of the lungs, bronchial tubes, trachea, nose, and throat ( Figure below ). These diseases can range from a mild cold to a severe case of pneumonia. Respiratory diseases are common. Many are easily treated, while others may cause severe illness or death. Some respiratory diseases are caused by bacteria or viruses, while others are caused by environmental pollutants, such as tobacco smoke. Some diseases are genetic and, therefore, are inherited. |
SciQ | SciQ-6095 | human-biology, human-anatomy, human-genetics
Title: Are males taller than females in humans? Is there any scientific evidence that in humans males are taller than females? And if so, what is the reason that they are taller (please include genes or hormones that accounts for human growth and how they are affected in males and females)? Are males taller than females?
Best data I could find come from the Statistical Abstract of the United States (1999) > Section 3. Here is a table reporting the percentage of the male and female population which height is lower than a given threshold
Note that this data collection was done among students in US universities and is therefore not representative of the whole world or even the whole country.
Does height follow a bimodal distribution?
A difference in height between males and females is often used as a classical example in introductory statistic class to exemplify a bimodal distribution as seen in this picture
and on these (a priori fake) data
However, Schilling et al. 2002 argued that while the difference in mean height between the sexes is real, this difference is too small relative to the variance in height within each sex to be clearly depicted on a graph.
Note that I found this non-peer-reviewed paper which shows real data that display a truly bimodal distribution of height.
Genetics of height
The question why are they taller? is very broad. I will just focus to give you some hints about the genetics of height in humans. First, you want to make sure you understand the concept of heritability.
Evoy and Vissher 2009 report a heritability coefficient of 0.8. This estimate is impressively high - only a few phenotypic traits have such high heritability. They also review articles discussing that 50 loci are correlated with variation in height (actually, today, more than 500 loci are known to contribute to height, see the link in AlexDeLarge's comment to this answer). However, these loci are not sufficient to explain the whole heritability observed (common missing heritability issue). Yang et al. 2010 provide evidence that the remaining heritability is due to incomplete linkage
disequilibrium between causal variants and loci of weak effects. In short, height is a highly polygenic trait.
Related post
You should have a look at Is there a genetic reason explaining the difference of the height of male and female? for more information.
The following is multiple choice question (with options) to answer.
What factor other than genes is important in determining adult height? | [
"nutrition",
"intelligence",
"relaxation",
"cultivation"
] | A | Genes play an important part in determining our adult height. However, factors such as poor nutrition can prevent us from achieving our full genetic potential. |
SciQ | SciQ-6096 | inorganic-chemistry
Title: Wood burning and carbon dioxide or monoxide? I am building greenhouse and i want to operate greenhouse at winter time. For heating i ll use wood. And also i am thinking to give back carbon monoxide which ll come from burning process of wood. There is a question, how can avoid to get carbon monoxide from burning wood, do i must give more air flow (or oxygen flow) to burning process? Or when you burn wood there is just one gas output that is carbon dioxide? A good reference to read is Laboratory and field investigations of particulate and carbon monoxide emissions from traditional and improved cookstoves Atmospheric Environment February 2009, Pages 1170–1181.
Unforntunately, there is a significant amount of carbon monoxide, from 29 to 118 grams of CO per kg of wood.
They find that the drier the wood, the less CO, but don't expect to completely eliminate CO.
The following is multiple choice question (with options) to answer.
What does burning wood release into the atmosphere? | [
"helium",
"hydrogen chloride",
"oxygen",
"carbon dioxide"
] | D | Forests are also being destroyed. Trees may be cut down for their wood, or they may be burned to clear the land for farming. Burning wood releases more carbon dioxide into the atmosphere. You can see how a tropical rainforest was cleared for farming in Figure below . With forests shrinking, there are fewer trees to remove carbon dioxide from the air. This makes the greenhouse effect even worse. |
SciQ | SciQ-6097 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
The largest region of each of the palatine bone is the what? | [
"big plate",
"abnormal plate",
"magnetic plate",
"horizontal plate"
] | D | Palatine Bone The palatine bone is one of a pair of irregularly shaped bones that contribute small areas to the lateral walls of the nasal cavity and the medial wall of each orbit. The largest region of each of the palatine bone is the horizontal plate. The plates from the right and left palatine bones join together at the midline to form the posterior quarter of the hard palate (see Figure 7.8a). Thus, the palatine bones are best seen in an inferior view of the skull and hard palate. |
SciQ | SciQ-6098 | intermolecular-forces, viscosity
Title: Why doesn't the viscosity of water change much with temperature like it does for other substances? I would like to know why water doesn't ever become like syrup before it freezes when many other liquids, such as hydrocarbons, seem to have a more gradual change from becoming more viscous and then turning solid.
As I understand it, the more viscous a material is, the stronger the inter-molecular forces are. When the liquid is heated up, the molecules have more kinetic energy and so they can more easily break free of these forces--the liquid will become less viscous.
Why doesn't water have the same spectrum of viscosity as other materials? It seems like it is either solid, or it has very low viscosity. This is something I spent a lot of time thinking about during my PhD, so let me see if I can explain it.
What you are talking about is the relationship between macroscopically observable properties (like viscosity), the relaxation time spectrum (which is a way of looking at the time scales involved in molecular movements), and the structure of the molecules themselves. It's kind of complicated, but I think I can explain it in way that will make sense.
You know that as we increase the temperature, molecules have more kinetic energy and can more easily break free of the forces holding them together. I have some other answers here and here that explain this in more detail. With something like viscosity, however, there is more to the picture.
The first thing you need to know is:
Viscosity is a measure of momentum transfer in a fluid
The following is multiple choice question (with options) to answer.
What does viscosity do to liquids? | [
"condusive to flowing",
"resistant to flowing",
"salinity to flowing",
"responsive to flowing"
] | B | Viscosity is a liquid’s resistance to flowing. You can think of it as friction between particles of liquid. Thicker liquids are more viscous than thinner liquids. For example, the honey pictured in the Figure below is more viscous than the vinegar. You can learn more about viscosity at this URL: http://chemed. chem. wisc. edu/chempaths/GenChem-Textbook/Viscosity-840. html . |
SciQ | SciQ-6099 | history, autoimmune, diabetes-mellitus
Title: When was it determined that Type 1 Diabetes is an autoimmune disease? I just found out today that type 1 diabetes is an autoimmune disease. When was this discovered? This question has two answers: The difference was first described in 1936 by Harold Percival Himsworth, which described it in this article.
At this time it was established that there are two forms of Diabetes, one sensitive to insuline while the other is not.
The terms Diabetes type 1 and 2 where established somewhere between 1974 and 1976, for details see the review "The discovery of type 1 Diabetes".
The following is multiple choice question (with options) to answer.
What system is involved in diseases that include type 1 diabetes, rheumatoid arthritis and multiple sclerosis? | [
"immune system",
"circulatory system",
"digestion system",
"nervous system"
] | A | One example is type 1 diabetes . In this disease, the immune system attacks cells of the pancreas. Other examples are multiple sclerosis and rheumatoid arthritis. In multiple sclerosis , the immune system attacks nerve cells. This causes weakness and pain. In rheumatoid arthritis , the immune system attacks the cells of joints. This causes joint damage and pain. |
SciQ | SciQ-6100 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
What are are organisms that feed on small pieces of organic matter? | [
"waste feeders",
"bottom feeders",
"difference feeders",
"deposit feeders"
] | D | Deposit feeders, which are organisms that feed on small pieces of organic matter, usually in the top layer of soil. Sea cucumbers are deposit feeders, living on the ocean floor. They eat the tiny scrap particles that are usually abundant in the environments that they inhabit. |
SciQ | SciQ-6101 | evolution, dna, natural-selection
It seems plausible to me that we (advanced life) could have a biological mechanism to "write" needed alterations into either our own DNA or our reproductive DNA over time, triggering the very specific evolutionary developments necessary to our survival without relying on random mutation.
My question:
Is this possible? Does any similar mechanism exist that we know of? If not, how can so many specific (advanced) evolutionary leaps be otherwise explained? This entire answer will be long, so read the short part first, then read the rest if you (or anyone else) is curious. Citations are included in the long section. I can include additional citations in the short section if needed.
Long Story Short
Your question touches on some common misconceptions about how the evolutionary process. Organisms don't "want" to evolve traits. Traits evolve through the biological processes of random mutation and natural selection.
Organisms do not "want" to evolve traits. (Well, OK, I'd love to evolve an extra pair of hands but that is not possible.) Natural selection works by modifying existing traits. Your turtle can stare all she wants at food out of reach but she will not evolve a longer neck. Instead, natural variation exists among neck lengths of the turtles because of variation of the genes that determine features related to overall boxy size. Those individuals with longer necks may be able to get a bit more food, live a little longer, and reproduce a little more. They will pass along their genes to their offspring, so perhaps more of their offspring will also have longer necks. Over many generations, the turtles may have somewhat longer necks.
A common misconception is that the traits of organisms are precisely adapted for a specific need. They are not, for a few reasons. First, natural selection occurs relative to the current environment. Adaptations that work well in one environment may not be so useful in another environment. Environments are rarely stable over evolutionary time so traits are subject to constant change.
Next, as mentioned above, natural selection can only work on what traits are present. While an extra set of arms would be handy, I am a tetrapod. My four appendages, along with the appendages of all other tetrapods, trace back to our common ancestor. The appendages of all tetrapods are modifications of that ancestral trait.
The following is multiple choice question (with options) to answer.
What process would be impossible without some variation in the inherited traits of organisms within a species? | [
"environmental selection",
"natural selection",
"characteristic selection",
"darwin's selection"
] | B | There is some variation in the inherited traits of organisms within a species. Without this variation, natural selection would not be possible. |
SciQ | SciQ-6102 | botany, terminology
Title: Definitions of hermaphroditism, dioecious and monoecious? What is the difference between these terms "monoecious","Hermaphrodite".
my lecturer says hermaphrodite is a zoological term and monoecious is botanical term, but in contrary to it, in my textbook both of these terms are used both botany and zoology.
So what is the actual difference? Below are definitions that I've seen; there may be less strict definitions under which monoecy (the noun form of 'monoecious'). and hermaphroditism would be the same thing.
Dioecious: Although rarely used for animals, one could say that human are dioecious because each individual produces only one type of gamete. In a dioecious species, some individuals are males and others are females.
Monoecious: In monoecious plants, individuals carry both males and female flowers but not flowers that can produce both female and male gametes.
Hermaphrodite: Hermaphroditic plants have flowers that can produce both male and female gametes.
Then, there are many other fancy terms such as dichogamous, gynomonoecious, subandroecious, heterostyly or androgynomonoecious! Plant mating systems are fantastically diverse and complex!
More information
Some of these terms are defined in The Evolution of Sex Determination, which is very pleasant to read. For shorter articles, consider Barrett 2002 or just Wikipedia > plant reproductive morphology or Wikipedia > dioecy (the noun form of 'dioecious').
The following is multiple choice question (with options) to answer.
Monoecious flowers are also known as “perfect” flowers because they contain both types of what organ? | [
"sex organ",
"phloem",
"vascular organ",
"respiratory organ"
] | A | groups of angiosperms: the monocots and the eudicots. Seed food reserves are stored outside the embryo, in the form of complex carbohydrates, lipids or proteins. The cotyledons serve as conduits to transmit the broken-down food reserves from their storage site inside the seed to the developing embryo. The seed consists of a toughened layer of integuments forming the coat, the endosperm with food reserves, and at the center, the well-protected embryo. Most flowers are monoecious or bisexual, which means that they carry both stamens and carpels; only a few species selfpollinate. Monoecious flowers are also known as “perfect” flowers because they contain both types of sex organs (Figure 26.14). Both anatomical and environmental barriers promote cross-pollination mediated by a physical agent (wind or water), or an animal, such as an insect or bird. Cross-pollination increases genetic diversity in a species. |
SciQ | SciQ-6103 | human-biology, evolution
Humans are off the charts in the amount of resources we invest in our children - our lives are 1/4 to 1/3 over before we sometimes leave our parents household (in some societies of course they never leave the house, but step into an extended family). This may be one of the reasons we are so successful as a species - we live in practically every place we possibly could and have no danger of competition from any other living thing excepting ourselves.
The grandmother effect is essentially the idea that if women, who are more attached to the offspring in more cases than fathers, continue to live and help support the grandchildren and make them more successful, then this will allow post menopausal women to have a longer lifespan (which they do).
The evolutionary biologist Sara Hrdy, emeritus UC Davis, has written quite a bit about the nuances of the evolution of the role of motherhood - reading some of her articles or books might give you a deeper sense of how profoundly filial love has shaped human beings.
--- more answer this stuff may or may not be worth reading depending on how broadly you want to understand this question...
Its important to say that many of the expansions of human average human lifespan have not been genetic. Its commonly cited that sewer systems, clean water, antibiotics and plentiful food are the three most important factors in human lifespan - and before modern developed world nations, the average lifespan of human beings was somewhere in the 30s. And there are significant lifespan differences in regions where these factors and others (education of women, access to prenatal and early care etc) are available.
Studies continue to be published that examine environmental and lifestyle factors compared to genetics and it seems that environment and lifestyle can make an astounding difference.
But genetics undoubtedly has a role to play here too. There are probably some individual humans and animals which have evolved to live longer. This has been found to be genetically related in some humans by demographics and family lines.
The following is multiple choice question (with options) to answer.
Human beings depend on learned behaviors more than any other? | [
"Organisms",
"Beings",
"mammals",
"species"
] | D | Human beings depend on learned behaviors more than any other species. Think about some of the behaviors you have learned. They might include making a bed, riding a bicycle, using a computer, and playing a sport, to name just a few. You may have learned each of the behaviors in different ways. There are several different ways in which animals learn. They include habituation, observational learning, conditioning, learning through play, and insight learning. |
SciQ | SciQ-6104 | water, elements
Title: Chemical composition of seawater Is it true that the sea water is composed of about $86\%$ oxygen, $11\%$ hydrogen and $3\%$ of minerals? The chemical formula of water is $\ce{H2O}$ (two hydrogen and one oxgen) that shows that the number of hydrogen is greater than that of oxygen.
If the number of hydrogen is greater, then why does the sea water consist of $11\%$ hydrogen and $86\%$ oxygen, which is lesser than the oxygen?
The book which I am reading says which is confusing me:
... Seawater is composed of about $86\%$ oxygen, $11\%$ hydrogen and $3\%$ of minerals, consisting mainly of sodium and chlorine. The book that you're reading is measuring by mass.
If you have pure water then you would expect oxygen to make up $\frac{16}{16 + 2}\times 100\% \approx 89 \% $ by mass. Likewise, hydrogen would make up $\frac{2}{16 + 2}\times 100\% \approx 11 \% $ by mass.
The following is multiple choice question (with options) to answer.
Oxygen, carbon, hydrogen and what other element make up approximately 96% of living matter? | [
"helium",
"calcium",
"silicon",
"nitrogen"
] | D | |
SciQ | SciQ-6105 | electromagnetism, electrons, electric-current, causality
Title: How do electrons know which path to take in a circuit? The current is maximum through those segments of a circuit that offer the least resistance. But how do electrons know beforehand that which path will resist their drift the least? This is really the same as Adam's answer but phrased differently.
Suppose you have a single wire and you connect it to a battery. Electrons start to flow, but as they do so the resistance to their flow (i.e. the resistance of the wire) generates a potential difference. The electron flow rate, i.e. the current, builds up until the potential difference is equal to the battery voltage, and at that point the current becomes constant. All this happens at about the speed of light.
Now take your example of having let's say two wires (A and B) with different resistances connected between the wires - lets say $R_A \gt R_B$. The first few electrons to flow will be randomly distributed between the two wires, A and B, but because wire A has a greater resistance the potential difference along it will build up faster. The electrons feel this potential difference so fewer electrons will flow through A and more electrons will flow through wire B. In turn the potential along wire B will build up and eventually the potential difference along both wires will be equal to the battery. As above this happens extremely rapidly.
So the electrons don't know in advance what path has the least resistance, and indeed the first few electrons to flow will choose random paths. However once the current has stabilised electron flow is restricted by the electron flowing ahead, and these are restricted by the resistance of the paths.
To make an analogy, imagine there are two doors leading out of a theatre, one small door and one big door. The first person to leave after the show will pick a door at random, but as the queues build up more people will pick the larger door because the queue moves faster.
The following is multiple choice question (with options) to answer.
What type electrical circuits have multiple paths the current may take? | [
"parallel",
"perpendicular",
"serial",
"single loop"
] | A | Parallel electrical circuits have multiple paths the current may take. |
SciQ | SciQ-6106 | ionic-compounds
As ionic solids are added to water, water molecules proceed to surround each ion on the surface of the solid, forming a sphere of hydration. In the process, ions are separated from each other.
The $\delta^-$ charge on the oxygen atoms of water are attracted to cations and inversely, repels the $\delta^+$ hydrogen atoms. Thus, for cations, the oxygens of water point inward, and for anions, the hydrogens face inward respectively. The most important thing is that the ion-dipole interactions and separation of ions with little change in energy.
We can relate the potential energy of the ions to the two partial charges of a polar molecule like water:
$$ E_p \propto - \frac{|z|\mu}{r^2}$$
Z is the charge number of the ion and $\mu$ is the dipole moment of the polar molecule. Potential energy is lowered by the interaction between the solvent molecules and the ion. The $r^2$ term indicates that the interaction between ions and dipoles depends more on distance than the charges between two ions.
Thus, for hydration to occur, ion-dipole interactions must occur at the surface of the ion, and thus, ion-dipole interactions are strong for small, highly charged ions such as $\ce{Mg^{2+}}$, $\ce{Li^{2+}}$ etc.
$\ce{AgCl}$ is very slightly soluble in water and will not dissociate into it's ions. $\ce{HF}$ is a weak acid thus it does not deprotonate easily.
The following is multiple choice question (with options) to answer.
Hydrophobic interactions arise because water molecules engage in what type of bonding with other water molecules? | [
"helium bonding",
"hydrogen bonding",
"aquatic bonding",
"oxygen bonding"
] | B | high proportion of amino acids in the protein have nonpolar side chains. The term hydrophobic interaction is often misused as a synonym for dispersion forces. Hydrophobic interactions arise because water molecules engage in hydrogen bonding with other water molecules (or groups in proteins capable of hydrogen bonding). Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-6107 | human-biology, cancer, medicine
Title: Why are only few cigarette smokers prone to cancer? It's tacit that only a few populace of smokers get cancer. What spares the others from it or what specifically cause cancer in those populace? See this Washington Post Article Cigarette smokers are most certainly prone to cancer. See Cecil Medicine, Chapter 183, on the epidemiology of cancer, exposure to tobacco is the most important environmental risk factor for cancer development, at least in the US:
Exposure to tobacco is the single largest cause of cancer in the United States... All forms of tobacco can cause cancer. Cigarette smoking causes cancer of the lip, oral cavity, nasal cavity, paranasal sinuses, pharynx (nasal, oral, and hypopharnyx), larynx, lung, esophagus (squamous cell and adenocarcinoma), stomach, colorectum, pancreas, liver, kidney (adenocarcinoma and renal pelvis), urinary bladder, uterine cervix, and myeloid leukemia.
Cancer may be identified or the cause of death in fewer smokers than might be expected, though, because smoking is an even greater risk factor for cardiovascular disease, and death due to cardiovascular disease.
Cancer is an unlikely phenomenon in an individual cell, but becomes more likely at the organism level, and even more likely over time. Though tobacco may be the most important environmental risk factor for cancer, age is actually a stronger predictor of cancer (see again, Cecil Chapter 183. Autopsy studies give us a quite remarkable example, this one shows incidental prostate cancer in nearly 60% of men over 80 who died from other causes. That figure is not out of the ordinary. Live long enough and you are likely to develop cancer.
Death due to heart disease may account for the lower than expected rates of cancer diagnoses and deaths in smokers. Nothing prevents cancer as well as dying from something else. And as discussed in the blog in the Washington Post you linked to, up to 2/3 of smokers die from smoking related causes
The following is multiple choice question (with options) to answer.
What is the second most common skin cancer? | [
"precancerous cell carcinoma",
"melanoma",
"basal cell carcinoma",
"squamous cell carcinoma"
] | D | Squamous Cell Carcinoma Squamous cell carcinoma is a cancer that affects the keratinocytes of the stratum spinosum and presents as lesions commonly found on the scalp, ears, and hands (Figure 5.19). It is the second most common skin cancer. The American Cancer Society reports that two of 10 skin cancers are squamous cell carcinomas, and it is more aggressive than basal cell carcinoma. If not removed, these carcinomas can metastasize. Surgery and radiation are used to cure squamous cell carcinoma. |
SciQ | SciQ-6108 | evolution, speciation
Lastly, I consider whether primary and secondary sympatric speciation represent a mechanistic dichotomy, I suggest that primary and secondary contact can leave a similar genomic signature, when speciation is driven by tightly clustered or large effect loci. Arguably, the advent of affordable population genomic studies should place less focus on whether study systems result from primary or secondary contact and instead focus on the mechanistic aspects of the genomic architecture and making progress in identifying the conditions and processes under which natural and sexual selection can drive speciation, without extrinsic barriers to gene flow. TLDR
Sympatric speciation and allopatric speciation with later migration into the same habitat were historically diffucult to distinguish without looking at palaeo-biological data. The paper argues that while palaeo-genetics has made this easier, it is still difficult to distinguish pure sympatric speciation (which it calls primary) and sympatric speciation with a geneflow from an geographically separated (allopatrically speciated?) subpopulation (which it terms "secondary sympatric speciation" or "speciation with secondary gene flow", "...with secondary contact" etc.).
Speciation
Speciation is the divergence of one species (with one gene pool) into two different species (with different gene pools). It is obvious that this will happen if subpolulations are geographically separated and continue to adapt to their local conditions (allopatric speciation).
However, Mayr suggested (back in the 1940s) that there is another type of speciation that happens while the speciating populations share a habitat, and, consequently, while gene flow between these subpopulations is maintained until the speciation process is complete. This requires strong selection pressure towards two different ecological niches each with their associated adaptations.
Empirical examples have been discussed and called into question again. One cool and frequently discussed example is that of the apple maggot in North America that has developed from the hawthorn maggot after the introduction of apples in North America.
Debate
The following is multiple choice question (with options) to answer.
Species divergence often, but not always, occurs because of what type of barrier between species? | [
"emotional",
"visible",
"physical",
"language"
] | C | Sympatric Speciation Can divergence occur if no physical barriers are in place to separate individuals who continue to live and reproduce in the same habitat? The answer is yes. The process of speciation within the same space is called sympatric speciation; the prefix “sym” means same, so “sympatric” means “same homeland” in contrast to “allopatric” meaning “other homeland. ” A number of mechanisms for sympatric speciation have been proposed and studied. One form of sympatric speciation can begin with a serious chromosomal error during cell division. In a normal cell division event chromosomes replicate, pair up, and then separate so that each new cell has the same number of chromosomes. However, sometimes the pairs separate and the end cell product has too many or too few individual chromosomes in a condition called aneuploidy (Figure 18.14). |
SciQ | SciQ-6109 | bioinformatics, phylogenetics
Title: How to get taxonomic specific ids for kingdom, phylum, class, order, family, genus and species from taxid? I have a list of taxids that looks like this:
1204725
2162
1300163
420247
I am looking to get a file with taxonomic ids in order from the taxids above:
kingdom_id phylum_id class_id order_id family_id genus_id species_id
I am using the package "ete3". I use the tool ete-ncbiquery that tells you the lineage from the ids above. (I run it from my linux laptop with the command below)
ete3 ncbiquery --search 1204725 2162 13000163 420247 --info
The result looks like this:
# Taxid Sci.Name Rank Named Lineage Taxid Lineage
2162 Methanobacterium formicicum species root,cellular organisms,Archaea,Euryarchaeota,Methanobacteria,Methanobacteriales,Methanobacteriaceae,Methanobacterium,Methanobacterium formicicum 1,131567,2157,28890,183925,2158,2159,2160,2162
1204725 Methanobacterium formicicum DSM 3637 no rank root,cellular organisms,Archaea,Euryarchaeota,Methanobacteria,Methanobacteriales,Methanobacteriaceae,Methanobacterium,Methanobacterium formicicum,Methanobacterium formicicum DSM 3637 1,131567,2157,28890,183925,2158,2159,2160,2162,1204725
420247 Methanobrevibacter smithii ATCC 35061 no rank root,cellular organisms,Archaea,Euryarchaeota,Methanobacteria,Methanobacteriales,Methanobacteriaceae,Methanobrevibacter,Methanobrevibacter smithii,Methanobrevibacter smithii ATCC 350611,131567,2157,28890,183925,2158,2159,2172,2173,420247
The following is multiple choice question (with options) to answer.
The chytrids the only class in the phylum chytridiomycota is the chytridiomycetes. the chytrids are the simplest and most primitive eumycota, or true this? | [
"fungi",
"organisms",
"proteins",
"acids"
] | A | Chytridiomycota: The Chytrids The only class in the Phylum Chytridiomycota is the Chytridiomycetes. The chytrids are the simplest and most primitive Eumycota, or true fungi. The evolutionary record shows that the first recognizable chytrids appeared during the late preCambrian period, more than 500 million years ago. Like all fungi, chytrids have chitin in their cell walls, but one group of chytrids has both cellulose and chitin in the cell wall. Most chytrids are unicellular; a few form multicellular organisms and hyphae, which have no septa between cells (coenocytic). They produce gametes and diploid zoospores that swim with the help of a single flagellum. The ecological habitat and cell structure of chytrids have much in common with protists. Chytrids usually live in aquatic environments, although some species live on land. Some species thrive as parasites on plants, insects, or amphibians (Figure 24.10), while others are saprobes. The chytrid species Allomyces is well characterized as an experimental organism. Its reproductive cycle includes both asexual and sexual phases. Allomyces produces diploid or haploid flagellated zoospores in a sporangium. |
SciQ | SciQ-6110 | botany, plant-physiology, plant-anatomy
*No others are known, but could definitely exist.
Bibliography
Crafts, A. S. “Phloem Anatomy, Exudation, and Transport of Organic Nutrients in Cucurbits.” Plant Physiology 7, no. 2 (1932): 183–225.
Fischer, A. “Das Siebröhrensystem von Cucurbita.” Berichte Deutsche Botanische Gesell 1 (1883): 276–279.
Fischer, A. “Neue Beiträge Zur Kenntniss Der Siebröhren.” Berichte Über Die Verhandlungen Der Königlich-Sächsischen Gesellschaft Der Wissenschaften Zu Leipzig, Mathematisch-Physische Klasse 38 (1886): 291–336.
Fischer, A. Untersuchungen Über Das Siebröhren System Der Cucurbitaceen. Berlin, 1884.
Turgeon, R. and Oparka, K. “The Secret Phloem of Pumpkins.” Proceedings of the National Academy of Sciences 107, no. 30 (2010): 13201 –13202.
Walz, C. and Giavalisco, P. and Schad, M. and Juenger, M. and Klose, J. and Kehr, J. “Proteomics of Curcurbit Phloem Exudate Reveals a Network of Defence Proteins.” Phytochemistry 65, no. 12 (2004): 1795–1804.
Zhang, B. and Tolstikov, V. and Turnbull, C. and Hicks, L. M. and Fiehn, O. “Divergent Metabolome and Proteome Suggest Functional Independence of Dual Phloem Transport Systems in Cucurbits.” Proceedings of the National Academy of Sciences 107, no. 30 (2010): 13532.
The following is multiple choice question (with options) to answer.
Almost all vascular plants have mycorrhizae and rely on their fungal partners for what? | [
"nutrients",
"air",
"sunlight",
"respiration"
] | A | |
SciQ | SciQ-6111 | mountains, rainfall
Title: Could a waterfall lashing onto a road lead to a landslide? Here is a video of a waterfall lashing on to a mountain road, with vehicles driving under it.
https://youtu.be/cHaguj--YBc
There appears to be a big hole carved out right next to the road, possibly by the force of the waterfall.
Is this a ticking time bomb for a landslide? Potentially, a landslide could occur. Whether it would be a minor slip or a major fall depends on the geological conditions at the site, the force of the water and the duration that the site is impacted by the water.
In the video in question, the rock face above the road appears competent, but there are not guarantees. The main issue would be is the water undermining the road which could cause a slip and the road to slide.
The more loose the geological material is, the easier it is to dislodge it. Once one item moves a chain of events can occur where additional items are dislodged and a slide occurs.
In addition to high pressure water dislodging material, water acts as a lubricant, making it easier for rocks and regolith to be dislodged.
To minimise the potential for a slide to occur in such a situation, the surface of the road would need to be sealed very well and a very good drainage system installed that would move the water away from the road and the slope below the road
The following is multiple choice question (with options) to answer.
What occurs when there is a sudden and large falling of rocks down a slope? | [
"earthquake",
"landslide",
"avalanche",
"tsunami"
] | B | Landslides are sudden and massive falls of rock down a slope. Landslides may be very destructive or even deadly. Slump and creep are slower types of mass wasting. |
SciQ | SciQ-6112 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
What are gymnosperms lacking compared to most angiosperms? | [
"vessel elements",
"use elements",
"muscle elements",
"vascular elements"
] | A | |
SciQ | SciQ-6113 | concentration, notation, units
Title: Conversion from a PPB value to µg/m3 of Isobutylene I have a quite simple problem, found a lot of information about it, but I am not sure anymore if I do my calculations right.
I own a sensor, which reports measurements in isobutylene units as PPB. So if I understand this right, the measurement would be the number of isobutylene molecules per one billion (x/1'000'000'000).
Therefore to convert this value into the more common µg/m3 unit, I would just use this formula:
$$ \text{Concentration}\ \frac{µg}{m3} = \frac{\text{Concentration}\ \text{PPB}\times\text{Molecular Mass}\ \frac{g}{mol}}{\text{MolarVolume}\ l} $$
Therefore to convert 400 PPM of isobutylene, with a molecular mass of 56.106 g/mol or 0.0005879 g/l, in the molar volume of a gas at STP with 22.4 l, the calculation would be:
$$ \frac{400\times56.106}{22.4} = 1001.9 \frac{µg}{m^3} $$
This seemed very high to me, and the Range of the sensor is 0-1056 PPM.
Is this the correct formula for the conversion? This is much simpler than you think, even though the value you've obtained looks reasonable to me.
Part per billion ($\pu{1 ppb} = \pu{1e-9}$) on its own is meaningless.
Based on a context, it can refer to anything: mass fraction, mole fraction, particles etc.
The thing is, for gaseous mixtures $\pu{ppb}$ always refers to the volume fraction $\phi_i$:
$$\varphi_i = \frac{V_i}{V}$$
where $V_i$ is the volume of the $i$th gas (here, isobutylene) and $V$ is the total volume.
In order to convert volume fraction expressed in $\pu{ppb}$ to desired mass concentration $\rho_i$ expressed as
The following is multiple choice question (with options) to answer.
Calculations are described showing conversions between molar mass and what for gases? | [
"length",
"density",
"volume",
"weight"
] | B | Calculations are described showing conversions between molar mass and density for gases. |
SciQ | SciQ-6114 | newtonian-mechanics, estimation
Would the rock have created a seismic event of its own (if so, how large)?
Would the rock have created a crater? The energy of the rock at the time of hitting the earth is mgh.
No rock we know of is going to be able to survive this collision with out breaking into pieces.
Non the less it will be a big impact and depending on the geology of the location it hits a variety of reactions scenarios can happen.
If the soil is aggregate of silt and sand and gravel, it would part into several shear rupture sections which look like slices of shell pattern surfaces starting from the bottom surface of the rock and turning up exiting the earth surface a few hundred yards outside of the impact zone and probably even eject some material out like a bomb crater. This scenario will have shakes that could be recorded miles away.
The calculation of how much of the momentum of rock will be shared with the shear material and accelerating them will be involved but not impossible.
If the geology of the impact area is of very low bearing like mostly silt and loose clays, the rock my lose most of its kinetic energy by just sinking into the dirt mostly with a giant humph with a cloud of dust rising.
If the geology is hard or rocky with the 'optimal' amount of mass and resilience it could create a substantial earthquake by resonating with the impact.
The following is multiple choice question (with options) to answer.
What sudden ground movement is caused by the sudden release of the energy stored in rocks, which is transmitted in seismic waves? | [
"eruption",
"sandstorm",
"earthquake",
"quicksand"
] | C | An earthquake is sudden ground movement. This movement is caused by the sudden release of the energy stored in rocks. An earthquake happens when so much stress builds up in the rocks that the rocks break. An earthquake’s energy is transmitted by seismic waves. |
SciQ | SciQ-6115 | the-sun, earth
Title: If the Sun got larger, but maintained its luminosity, would the Earth get hotter or colder? A recent question If the Sun were bigger but colder, Earth would be hotter or colder? asked - if the Sun got bigger and cooler, would the Earth heat up or cool down. I think the answer to that is mainly that it depends on the final luminosity.
However, what I want to know here (hypothetically), is if the Sun got larger and it's effective temperature decreased such that it's luminosity was unchanged; how would that affect the equilibrium temperature of the Earth? I suspect the answer may involve the wavelength dependence of the albedo, emissivity and atmospheric absorption of the Earth.
Another, less hypothetical, way of asking this is, if you put an Earth-like planet at different distances from stars with a variety of temperatures, such that the total flux incident at the top of the atmosphere was identical, how would the temperatures of those planets compare? The key issue is the opacity of the atmosphere, because I presume the question is about the temperature at the solid surface of the Earth. The atmospheric opacity can be seen from https://physics.stackexchange.com/questions/135260/can-someone-explain-to-me-the-concept-of-atmosphere-opacity, where you can see that the "rainbow" of maximum heat flux from the Sun happens to hit a kind of hole in atmospheric opacity. That has a significant warming effect on the Earth, and is exacerbated by the Greenhouse effect. If sunlight was further into the infrared, the graph shows that much more of it would be intercepted in the atmosphere. That would make the surface significantly colder, though certainly not a factor of 2 colder.
No doubt the question is of more than passing interest, because M dwarfs are the most numerous main-sequence stars and are therefore interesting for life. To have life near an M dwarf, the planet would need to be closer than Earth is to the Sun, but the effect of moving the planet closer and shrinking and cooling the star would be similar to leaving Earth where it is and making the star cooler and larger. So the nature of atmospheric opacity for wet atmospheres must be of great significance for understanding the prospects for life around M dwarfs.
The following is multiple choice question (with options) to answer.
What is the name for the cooler, darker areas on the sun’s surface? | [
"aurora borealis",
"corona",
"sunspots",
"anomalies"
] | C | The most noticeable magnetic activity of the Sun is the appearance of sunspots. Sunspots are cooler, darker areas on the Sun’s surface ( Figure below ). Sunspots occur in an 11 year cycle. The number of sunspots begins at a minimum. The number gradually increases to the maximum. Then the number returns to a minimum again. |
SciQ | SciQ-6116 | botany, plant-physiology, plant-anatomy
It made me wonder if we are simulating the sun in a dark room for growing the plants with the help of red, blue, and a little bit of far-red light, what will happen to the plants if we keep the ideal conditions for which the plants carry out photosynthesis whole day? Does it affect its yield or the plants die out quick?
I am an engineering student working on indoor farming, my knowledge of botany is the same as a high school student. So if I am wrong please tell me. Ideal conditions for photosynthesis
You mention ideal conditions to carry out photosynthesis, I would just like to point out that this includes carbondioxide levels, temperature, and nutrients as well as light.
Flowering
As anongoodnurse mentions performance might be measured by blooming which, in most flowering plants, has a day-light related component. However, for general growth increasing daylight over the 'natural' day length can often increase yield.
Daylight Cycles
The important point to note is that plants do 'ramp up' at dawn getting ready to start photosynthesizing (for some plants with temporal photosynthesis mechanisms (see CAM photosynthesis) this can be even more important). The reason plants do this is because plants can suffer from 'photobleaching' which can be considered similar to sunburn in humans, if they are not ready for sunlight. Getting 'ready' can involve lots of things including opening stomata (pores) to let CO2 in, changing which metabolic pathways are active, and moving about chloroplasts inside cells. Plants 'figure out' how and when to ramp up based on circadian rhythms which work well on 24 hour clocks and slight changes over time. Thus 12 hrs to 16 hrs can be a big change, particularly if the change happens by lights coming on earlier. Additionally, the 24 hour 'clock' means that plants will do better with 18hr light then 6hrs dark cycles than 36hrs light 6 hrs dark, because the total cycle length should be about 24hrs.
Photosynthesis Side Effects
The following is multiple choice question (with options) to answer.
Plants need sunlight for what process? | [
"cyclogenesis",
"photosynthesis",
"glycolysis",
"metamorphosis"
] | B | The water in a large lake may be so deep that sunlight cannot penetrate all the way to the bottom. Without sunlight, water plants and algae cannot live on the bottom of the lake. That’s because plants need sunlight for photosynthesis. |
SciQ | SciQ-6117 | plate-tectonics, mountains, tectonics
Title: What is the impact of divergent tectonic plates on old mountain ranges? I found this question, which is similar to what I'm wondering, but my question is slightly different:
What happens if a new divergent boundary forms in a way that bisects a mountain range, especially one formed by converging plates -- and is that even possible?
Purely for the sake of example, if a divergent rift somehow formed on the North American plate, dividing the Appalachians [ETA: apparently I circled a valley, please pretend I'm not a geography-illiterate dork and that it's actually some old mountains.]:
What would happen to the circled area? Anything? Would the mountain range be recognizable after an ocean formed between them? Considering the timescale involved, perhaps an older range would be unrecognizably eroded? I've tried to find examples in the real world, but my Google-fu fails me.
Somewhere I picked up the idea that the Appalachian and Welsh coal seams were once connected or formed together (I think it may have been from an offhand comment in a movie about Welsh miners, so a] maybe I understood wrong and b] who knows how accurate it was), so I initially wondered if that might be an example of what I'm curious about. Unfortunately, some light research seems to indicate that's not the case (if I'm understanding this and this correctly, the connection ends at "both formed, at least partially, during the Carboniferous.)
I'm most interested in what the effects (if any) would be on older mountain ranges such as the Urals or Appalachians, but if anyone knows what kind of effects it might have on younger, taller ranges, I'd love to hear about it.
If anyone has sources I could look into for a deeper understanding, I'd love to have those as well! My lack of knowledge is distressing me to no end. The example of the East African Rift was given in a different answer.
Splitting of mountain ranges in two becomes even more apparent as you go up north from there.
The Red Sea between Egypt and Saudi Arabia is a young new spreading ocean, that cuts through Precambrian mountains.
The following is multiple choice question (with options) to answer.
The vast majority of what phenomena occurs along one of three types of plate boundaries? | [
"earthquake",
"volcanoes",
"hurricane",
"tornados"
] | A | Nearly 95% of all earthquakes take place along one of the three types of plate boundaries. As you learned in the Plate Tectonics chapter, scientists use the location of earthquakes to draw plate boundaries. |
SciQ | SciQ-6118 | meteorology, atmosphere, wind, air-currents
Title: Where does wind come from? Wind is (according to Wikipedia) the flow of gases on a large scale.On the surface of the Earth, wind consists of the bulk movement of air.
What forces would cause such a mass movement of air? Wind is caused by pressure differences. Think of a balloon full of air; poke a hole in it and the air comes out. Why? Because the pressure in the balloon is higher than outside, and so to regain equal pressure, mass moves and that is the wind.
There is a bit more to this in the atmosphere as the Earth rotates and near the surface friction also plays a role. The equation of motion is the Navier-Stokes and in vector form in Cartesian space is:
$$\dfrac{\partial\mathbf u}{\partial t} = - \mathbf u \cdot \nabla \mathbf u -\dfrac{1}{\rho}\nabla p-2 \mathbf \Omega \times \mathbf u + \mathbf g + \mathbf F$$
In this equation, $\mathbf u$ is the vector wind, $(\mathbf u \cdot \nabla)$ is the advection operator, $\rho$ is density, $\mathbf \Omega$ is the vector rotation of the Earth, $\mathbf g$ is effective gravity and $\mathbf F$ is friction.
The LHS is the time rate of change of the wind at a point in space (as opposed to following the parcel). The RHS represent a number of factors that produce a change in the wind. From left to right:
Advection of momentum (non-linear)
Pressure gradient force (this is wind blowing from high to low pressure)
Coriolis force (this turns wind to the right in the NH and left in the SH and causes the wind to flow parallel to isobars)
gravity (provides hydrostatic balance with the PGF in the vertical)
Friction (in the boundary layer you may see this as $\nu\nabla^2\mathbf u$)
The following is multiple choice question (with options) to answer.
What weather events move with the prevailing winds and originate in the trade winds in the northern hemisphere? | [
"tsunamis",
"hurricanes",
"earthquakes",
"droughts"
] | B | Hurricanes move with the prevailing winds. In the Northern Hemisphere, they originate in the trade winds and are blown to the west. When they reach the westerlies, they switch direction. So they travel toward the north or northeast. You can look at a map of hurricane tracks to see this happen ( Figure below ). Hurricanes may cover 800 km (500 miles) in one day. |
SciQ | SciQ-6119 | human-anatomy
Title: Why is a penis an organ? According to Wikipedia an "An organ is a group of tissues with similar functions". I don't know anything about anatomy but it doesn't seem to me that a penis can be delimited somewhere to form a "group". Therefore I do not understand why a penis is considered an organ.
Can you explain it to me ? Frankly, that's a terrible definition by Wikipedia.
Merriam-Webster defines an organ as:
a differentiated structure (such as a heart, kidney, leaf, or stem) consisting of cells and tissues and performing some specific function in an organism
or
bodily parts performing a function or cooperating in an activity
The important defining feature of an organ is not that the tissues have similar functions but that, together, the tissues comprise a functional whole that achieves some end goal.
For the penis, it consists of multiple tissues with different functions:
(from https://www.ncbi.nlm.nih.gov/books/NBK525966/figure/article-20668.image.f1/ - original from Gray's Anatomy)
The different tissues pictured here: the fibrous envelope, the corpora cavernosa, the septum pectiniforme, the urethra and blood vessels, the nervous tissue in the skin: all of these tissues have different individual functions: structural, erectile, carrying urine or semen, etc.
The key that unifies them into an organ is that the functions of the penis at the organism level (principally sexual function) are not served by any of these tissues alone, but rather by their combination in a full structure: an organ.
Ultimately, organ definitions are somewhat opinion-based: people are lumpers and splitters, so you might find conflicting definitions for which groupings of tissues reflect distinct organs, but I think by most standards you would find the penis to be considered a distinct organ, affiliated with but distinct from the primary sex organs and associated glands.
The following is multiple choice question (with options) to answer.
What is the name for the male reproductive organs or gonads? | [
"anus",
"nucleus",
"testes",
"ovaries"
] | C | Testes The testes (singular = testis) are the male gonads—that is, the male reproductive organs. They produce both sperm and androgens, such as testosterone, and are active throughout the reproductive lifespan of the male. Paired ovals, the testes are each approximately 4 to 5 cm in length and are housed within the scrotum (see Figure 27.3). They are surrounded by two distinct layers of protective connective tissue (Figure 27.4). The outer tunica vaginalis is a serous membrane that has both a parietal and a thin visceral layer. Beneath the tunica vaginalis is the tunica albuginea, a tough, white, dense connective tissue layer covering the testis itself. Not only does the tunica albuginea cover the outside of the testis, it also invaginates to form septa that divide the testis into 300 to 400 structures called lobules. Within the lobules, sperm develop in structures called seminiferous tubules. During the seventh month of the developmental period of a male fetus, each testis moves through the abdominal musculature to descend into the scrotal cavity. This is called the “descent of the testis. ” Cryptorchidism is the clinical term used when one or both of the testes fail to descend into the scrotum prior to birth. |
SciQ | SciQ-6120 | human-biology, immunology, antibody
Title: Transfer of antibodies in breast milk of humans Why isn't the IgA secreted in breast milk digested due to proteases of the digestive system in the baby?
Wikipedia says:
The secretory component of sIgA protects the immunoglobulin from being
degraded by proteolytic enzymes, thus sIgA can survive in the harsh
gastrointestinal tract environment and provide protection against
microbes that multiply in body secretions.
But what exactly does the secretory component do? What is the secretory component? Is IgA absorbed in the circulation of fetus? I remember reading it somewhere that it is not absorbed, at least in humans. Please answer these questions focusing more on humans. Though, information about other animals will be appreciated as well. It is! Here is an amazing review from 2011 that literally has all the answers. I'm not kidding, all of them. I would marry this review if I could.1 It also includes information on other animals.
The main takeaway is that IgA from milk is not readily absorbed by the infant body. Secreted IgA is mainly to provide a protective coating for the mucosa while the infant is developing its own nascent immune system. IgG passed along from the placenta (your other question) provides the main source of absorbed antibodies. As it says in the review:
Milk sIgA is not taken up by the infant’s intestinal mucosa. In fact, gut closure in humans occurs before birth and little immunoglobulin is absorbed intact in the intestine after birth. However, the presence of sIgA in the intestinal lumen is part of the protective function of the epithelial barrier in the intestine... Secretory IgA is considered to be the primary immunoglobulin responsible for immune protection of mucosal surfaces such as the intestine.
In terms of enzymatic activity, the digestive system will in indeed chomp up the antibodies; that's part of the reason breast feeding should continue as needed. That's okay, because there's plenty to go around:
Much of the immunoglobulin consumed in an immune milk can be expected to be partially or completely digested, however some portion of the immunoglobulin will remain intact or at least partially intact and capable of binding to an antigen.
The following is multiple choice question (with options) to answer.
What glands in the breast secrete milk? | [
"mammary glands",
"fetal glands",
"primordial glands",
"adrenal glands"
] | A | The breasts are not directly involved in reproduction, but they nourish a baby after birth. Each breast contains mammary glands, which secrete milk. The milk drains into ducts leading to the nipple. A suckling baby squeezes the milk out of the ducts and through the nipple. |
SciQ | SciQ-6121 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
Sutures, gomphoses, and syndesmoses are types of what, which are found where adjacent bones are strongly united by connective tissue? | [
"cartilage",
"ligaments",
"metallic joints",
"fibrous joints"
] | D | 9.2 Fibrous Joints Fibrous joints are where adjacent bones are strongly united by fibrous connective tissue. The gap filled by connective tissue may be narrow or wide. The three types of fibrous joints are sutures, gomphoses, and syndesmoses. A suture is the narrow fibrous joint that unites most bones of the skull. At a gomphosis, the root of a tooth is anchored across a narrow gap by periodontal ligaments to the walls of its socket in the bony jaw. A syndesmosis is the type of fibrous joint found between parallel bones. The gap between the bones may be wide and filled with a fibrous interosseous membrane, or it may narrow with ligaments spanning between the bones. Syndesmoses are found between the bones of the forearm (radius and ulna) and the leg (tibia and fibula). Fibrous joints strongly unite adjacent bones and thus serve to provide protection for internal organs, strength to body regions, or weight-bearing stability. |
SciQ | SciQ-6122 | equilibrium, water
Title: Can water synthesis and decomposition be in a dynamic equilibrium? When heated at extreme temperatures, water can spontaneously decompose.
According to Wikipedia (https://en.wikipedia.org/wiki/Water_splitting):
In thermolysis, water molecules split into their atomic components hydrogen and oxygen. For example, at 2200 °C about three percent of all H2O are dissociated into various combinations of hydrogen and oxygen atoms, mostly H, H2, O, O2, and OH. Other reaction products like H2O2 or HO2 remain minor. At the very high temperature of 3000 °C more than half of the water molecules are decomposed, but at ambient temperatures only one molecule in 100 trillion dissociates by the effect of heat.[15] The high temperatures and material constraints have limited the applications of this approach.
The following is multiple choice question (with options) to answer.
Heat, electricity, or light might provide what necessary input to the process of decomposition? | [
"food",
"energy",
"material",
"source"
] | B | Most decomposition reactions require an input of energy in the form of heat, light, or electricity. |
SciQ | SciQ-6123 | cell-biology, terminology
Title: What is the difference between cytosol and cytoplasm? I've generally seen cytosol defined as the solution inside cells minus the organelles, cytoskeleton, etc and cytoplasm as the cytosol plus the organelles, cytoskeleton, etc. This naturally leads to the impression that cytosol is the cytoplasm minus all the solids. The problem here is that there are all sorts of other large molecules in the cells which could be thought of as solid. Are they also part of the cytosol or are they suspended in it? (I.e. are they part of the cytosol or are they non-cytosol components of the cytoplasm?)
Basically, I'm asking if the precise definition of cytosol is just anything in the cell that's not behind an endomembrane (save the exoskeleton) or if the dividing line is something else.
Subquestion: things can get even more terminologically confused because the cytosol is sometimes called the matrix. What the heck is the preferred terminology with this stuff? IMO, the definitive answer to this question is given in a paper by J. S Clegg. He traced the origin of the term cytosol to a book chapter by H. A. Lardy, and confirmed by email that Lardy had indeed coined the term. Their definition of cytosol is as follows:
... that portion of the cell which is found in the supernatant fraction after centrifuging the homogenate at 105 000 x g for 1 hour.
The following is multiple choice question (with options) to answer.
What is made up of a watery substance called cytosol and contains other cell structures such as ribosomes? | [
"cytoplasm",
"rna",
"plasma",
"cytoskeleton"
] | A | Cytoplasm refers to all of the cellular material inside the plasma membrane. Cytoplasm is made up of a watery substance called cytosol and contains other cell structures such as ribosomes. |
SciQ | SciQ-6124 | bond
Title: Is energy required to form bonds [phase change] My question is if any energy is required to form bonds, for instance when there is a phase change?
If I am correct, energy might be required in the beginning, to make the reaction start and then release a bigger amount of energy than it was putted in. However, in terms of molecular behaviour in a phase change, I think there should not be any energy required to make the molecules to form bonds, if they are placed in a system which has a lower temperature than the molecules. Would they not lose the kinetic energy after a specific time? Bond formation always lowers the energy of the system (or bond formation is a consequence of lower energy, take your pick.)
Indeed, you may have to add energy, because presumably certain bonds must break in order to rearrange the atoms.
Adding energy won't guarantee formation of much higher energy isomers, because the atoms have a large amount of kinetic energy, and so they can just as easily turn around and go back whence they came.
Sometimes the kinetic energy can be dissipated by solvent, collisions with inert gasses, etc. and then you may end up with a measurable quantity of the higher energy species.
The following is multiple choice question (with options) to answer.
What type of energy is required in all chemical reactions? | [
"activation",
"function",
"solar",
"conduction"
] | A | All chemical reactions require activation energy, which is the energy needed to get a reaction started. |
SciQ | SciQ-6125 | optics, reflection, geometric-optics
Title: Reflection of light rays A set of light rays emitted from a point of an orange hits a smooth and flat surface. My question is: The angles of incidence are different, light rays are reflected towards different directions, why is a distorted image not formed? Why is this not an example of diffuse reflection? That's precisely why a single sharp image is formed. Extend all three reflected rays back below the surface to see where the light seems to come from. If your drawing is precise enough, you'll find that they intersect at a single point, which is precisely the mirror image of the object.
The point of specular reflection is that the light seems to come from the mirror image. You already get divergent rays from each point even from the original object, and the mirror image does the same. You'll only get parallel rays, if the incident rays were parallel (e.g. from an object that is effectively infinitely far away).
The following is multiple choice question (with options) to answer.
What type of image is formed when light rays diverge in front of a mirror? | [
"fake",
"large",
"reversed",
"virtual"
] | D | When light rays diverge in front of a mirror, a virtual image is formed. A virtual image is formed by your brain tracing diverging rays backwards and is kind of a trick, like the person you see “behind” a mirror’s surface when you brush your teeth (there's obviously no real light focused behind a mirror!). Since virtual images aren’t actually “anywhere,” you can’t place photographic film anywhere to capture them. |
SciQ | SciQ-6126 | osmosis, prokaryotes
Title: Does osmosis take place in prokaryotic cells? As far as I know, osmosis occurs in Eukaryotic cells, and I'm wondering if it could take place in prokaryotic cells too. Osmosis works across every cell membrane along a concentration gradient as its a physico-chemical principle. Water can cross the membrane (or cell wall), while the substance dissolved in it (for example salts) can not. Because eukaryotic cells only have a cell membrane, they will burst eventually, while bacteria (and also plant cells) have a more rigid cell wall, which will mostly prevent bursting. However the influx (or outflux) of water creates a pressure which is called turgor pressure. How this works is shown below (figure from here), bacterial cells and plant cells work pretty much the same way:
The following is multiple choice question (with options) to answer.
What is the condition of a plant in which the fluid in a cell exerts a pressure against the cell wall? | [
"tumor",
"turgor",
"hydration",
"constriction"
] | B | called the relative osmotic pressure if neither solution is pure water, and it is called the osmotic pressure if one solution is pure water. Osmotic pressure can be large, depending on the size of the concentration difference. For example, if pure water and sea water are separated by a semipermeable membrane that passes no salt, osmotic pressure will be 25.9 atm. This value means that water will diffuse through the membrane until the salt water surface rises 268 m above the pure-water surface! One example of pressure created by osmosis is turgor in plants (many wilt when too dry). Turgor describes the condition of a plant in which the fluid in a cell exerts a pressure against the cell wall. This pressure gives the plant support. Dialysis can similarly cause substantial pressures. |
SciQ | SciQ-6127 | evolution, natural-selection, population-dynamics, adaptation
Title: Genetic Diversity and Adaptation I am somewhat new to evolutionary biology, having studied it on my free time as a computer science student. There is one particular thing that has always bothered me for which I have not seen a good treatment, relating to adaptations to the environment with respect to genetic diversity. If it is possible for a population to adapt to rapid environmental changes, and they don't have an adaptation for dealing with change directly (such as a complex brain), it seems to me that every generation must have present within them almost every possible environmental adaptation that the population is capable of expressing (including many irrelevant ones and a few relevant to the particular environmental challenge). Otherwise, it may take too many generations to deal with a change, which may be disastrous for the population.
So my question would be: how does an evolutionary biologist explain the mechanics behind the ability for a population to adapt quickly? Are most environmental changes slow or gradual enough that the population has a few generations to happen upon the mutations that will allow it to survive, and have generally been successful in this regard for 3.5 billion years? Or, are a large majority of possible adaptations present in almost every generation, and just serve no purpose or advantage for most of the population if the provided "benefit" is unneeded (i.e., are effectively neutral)? Or something in between? It is a good question. The question is hard to answer though because
The answer is not completely resolved
There are many influential parameters hidden behind this question.
Your question, as I understand it, can be formulated as
Do natural populations have enough genetic variance to directly respond to an environmental change or do they have to wait for this variance to be created through mutations?
To address this question, I will have to assume you have some intermediate level of knowledge in evolutionary biology.
How do we call these two alternatives?
Adaptation can occur through selection on:
Standing genetic variance
De novo mutations
How can we tell them apart?
This section is mainly inspired from Barrett and Schluter (2008).
Adaptation from standing genetic variance and from de novo mutations tend to yield different genetic signature.
In comparison to de novo mutations, adaptation from standing genetic variation is likely to lead to
Faster evolution
Because there the respond to the new environmental is immediate, there is no need to wait for more mutations.
Because the fitness variance associated with the trait under selection is very low even when the first mutation occurs.
Fixation of more alleles of small effects.
The following is multiple choice question (with options) to answer.
What phenomenon, crucial for evolution, creates new genetic variation in a gene pool and is how all new alleles first arise? | [
"natural selection",
"mutation",
"adaptation",
"radiation"
] | B | Mutation creates new genetic variation in a gene pool. It is how all new alleles first arise. In sexually reproducing species, the mutations that matter for evolution are those that occur in gametes. Only these mutations can be passed to offspring. For any given gene, the chance of a mutation occurring in a given gamete is very low. Thus, mutations alone do not have much effect on allele frequencies. However, mutations provide the genetic variation needed for other forces of evolution to act. |
SciQ | SciQ-6128 | molecular-biology, molecular-genetics, development, sex
Quote from a Review (Yao 2005):
We have just begun to glimpse into the mechanisms underlying ovarian development. Convincing evidence challenges us to reconsider the existing paradigm that describes ovarian development as a default system. The default concept was first proposed in the early 1950s when Jost performed the groundbreaking experiments to demonstrate mechanisms of sex differentiation of reproductive tracts (Jost, 1947, 1953, 1970). The term “default” was not originally intended to describe the developmental status of the ovary. Instead, it is referred to the female reproductive tract or the Mullerian duct based on the fact that the female reproductive tract forms in both XX and XY individuals in the absence of gonads. Indeed, now it has become evident that early ovarian development is an active process involving intrinsic cell fate decisions and complex crosstalks between germ cells and somatic cells. Most intriguingly, the appearance of testicular structures in XX individuals where Sry and its downstream components are absent further raises the improbable question: Could the testicular development be default after all?
The following is multiple choice question (with options) to answer.
What is the name of the stage of life when a child becomes sexually mature? | [
"reproductive stage",
"puberty",
"pre-adolescence",
"adulthood"
] | B | Puberty is the stage of life when a child becomes sexually mature. Puberty begins when the pituitary gland tells the testes to secrete testosterone in boys, and in girls the pituitary gland signals the ovaries to secrete estrogen. Changes that occur during puberty are discussed in the Male Reproductive Development and Female Reproductive Development concepts. |
SciQ | SciQ-6129 | statistical-mechanics, atmospheric-science, density
A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which dissolved carbon dioxide (CO2) suddenly erupts from deep lake waters, forming a gas cloud that can suffocate wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water. Scientists believe earthquakes, volcanic activity, or explosions can be a trigger for such phenomenon. Lakes in which such activity occurs may be known as limnically active lakes or exploding lakes.
Picture 1: one of a number of cattle killed by a limnic eruption at Lake Nyos, Cameroon.
We can occasionally prevent the buildup of carbon dioxide by degassing the body of water.
Picture 2: a siphon used by French scientists to de-gas Lake Nyos. The carbon dioxide emerges from its deposits and bubbles into the water, floating to the top.
The following is multiple choice question (with options) to answer.
A man made lake is known as what? | [
"Lake",
"resevoirs",
"Pond",
"Lagoon"
] | B | Many lakes are not natural, but are human-made. People dam a stream in a suitable spot. Water backs up behind the dam, creating a lake. These lakes are "reservoirs" ( Figure below ). |
SciQ | SciQ-6130 | inorganic-chemistry, solubility, metallurgy
Any insights would be much appreciated! Let me give an extreme example of chemical analysis. It is an anecdote. Some analytical chemists were using a very sensitive technique to analyze metals in blood. It is called neutron activation analysis. What they saw was that a very small quantity of molybdenum (Mo) was present in small quantities persistently. Nobody expected that. It turned out after a lot of hard work that Mo was coming from the stainless steel syringe needle used for drawing blood. Lesson of the story: There is nothing which is perfectly insoluble in water. It all depends on the analytical technique. If you try to weigh a hair on a "weighing machine" it will tell you that the mass is zero kg, but if you use a fine analytical balance it will tell you that hair has a mass.
The same goes for lead pipes. Natural water has plenty of minerals, dissolved oxygen anions, cations and don't forget the microorganisms. The bacteria do a lot of chemical transformations in water. As a result, Pb would slowly leach into the water at parts per million or parts per billion levels. Don't assume that Romans were drinking lead salt solutions in high concentration ranges. Not only water lead was present in water, it was also present in alcoholic beverages.
Read more here Lead in ancient Rome’s city waters
Lead in water is still a serious problem in several areas of the modern world. It is not an ancient problem.
The following is multiple choice question (with options) to answer.
Alchemy helped improve the study of metallurgy and the extraction of metals from what? | [
"wood",
"ores",
"water",
"air"
] | B | However, out of all this secrecy came several contributions to modern-day chemistry. Early acids and bases were discovered. Glassware for running chemical reactions was developed. Alchemy helped improve the study of metallurgy and the extraction of metals from ores. More systematic approaches to research were being developed, although the idea of orderly scientific experimentation had not become well-established yet. But the groundwork was laid to the development of chemistry as a foundational science. |
SciQ | SciQ-6131 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
What are the two types of vascular tissues? | [
"ganglia and phloem",
"ectoderm and phloem",
"xylem and phloem",
"epidermis and phloem"
] | C | Vascular tissue runs through the ground tissue inside a plant. It transports fluids throughout the plant. Vascular tissue actually consists of two types of tissues, called xylem and phloem. The two types of vascular tissue are packaged together in bundles. You can see them in the celery in Figure below . |
SciQ | SciQ-6132 | neuroscience, cancer
Title: Can neurons become cancerous? I've been reading about brain cancer lately, and something I've noticed is that the tumors seem to start in all tissues, except neural tissue. Am I missing something, or is there an explanation? Short answer
Neuronal tumors are rare, but they do exist. These cancers develop from neuroblast cells, a population of undifferentiated, dividing precursor cells that will eventually fully differentiate into functional neuronal cells.
Background
Most neuronal cell types have lost their ability to divide, because of their progressed state of differentiation. There are but a few regions in the brains that generate new nerve cells in adulthood, for example in the hippocampus where neuro-regeneration is believed to be involved in memory formation. Because of the rarity of cell division of neuronal cells in adulthood, neural cancers are rare.
The point where neuronal cells actively divide is during development. These cells are basically still stem cells. A prime example here are retinoblastomas. These are tumors in the photosensitive part of the eye, namely the retina. During early development stem cells actively divide to lay down a layered structure in the back of the eye eventually forming the rods and cones and other visual cells. If this division process goes out of control, tumors can develop. Retinoblasomas can now be diagnosed in utero (Paquette et al., 2012).
Tumors with a neuronal origin developing post natally are rare, but do exist. Neuroblastoma being a prime example. This is a rare cancer (prevalence of 1:100,000) most commonly found in children younger than age 5. It affects the sympathetic nervous system, which regulates involuntary bodily functions such as heart rate, blood pressure, breathing, and digestion. Neuroblastoma typically begins in the nerve tissues of the adrenal glands but may also begin in the nerves that are located anywhere along the spinal cord, including the neck, chest, or abdomen. The cancer can metastasize (spread) to other organs.
The following is multiple choice question (with options) to answer.
The spinal cord develops, cells making up the wall of the neural tube proliferate and differentiate into what? | [
"neurons and glia",
"membrane and glia",
"jelly and glia",
"muscles and glia"
] | A | Spinal Cord Development While the brain is developing from the anterior neural tube, the spinal cord is developing from the posterior neural tube. However, its structure does not differ from the basic layout of the neural tube. It is a long, straight cord with a small, hollow space down the center. The neural tube is defined in terms of its anterior versus posterior portions, but it also has a dorsal–ventral dimension. As the neural tube separates from the rest of the ectoderm, the side closest to the surface is dorsal, and the deeper side is ventral. As the spinal cord develops, the cells making up the wall of the neural tube proliferate and differentiate into the neurons and glia of the spinal cord. The dorsal tissues will be associated with sensory functions, and the ventral tissues will be associated with motor functions. |
SciQ | SciQ-6133 | development
Title: How detachment/separation works in biology? It might be a strange question, but I'm interested in the mechanics of separation/detachment during asexual reproduction, for example when an organism reproduces by budding (I don't mean cellular budding like baker's yeast). When the newly formed body is fully matured it detaches itself from the parent / original body.
It might not be caused by a specific tissue, as animals with not so differentiated bodies are (also) capable of such, but I could easily be wrong. Is this (the detachment) triggered by changes in the cell membrane? I can't really think of other explanations. Reproductive budding and what you call 'cellular budding' are really highly related processes. Budding as a form of reproduction essentially partitions protein aggregates and damaged cellular components into the host or mother and builds fresh or 'young' cells on the opposite side of a partition. To begin understanding this look at Saccharomyces cerevisiae (budding yeast) which forms protein rings (from the septin proteins) at the membrane, around the bud neck which separates the mother and daughter cells Hartwell 1971. This ring acts a partition that in part, withholds protein aggregates and certain proteins from diffusing from the mother to the daughter. This protein ring is an example of how cells limit diffusion of proteins and cellular components to the daughter cell. Another good example that comes to mind is Linder 2007, though it is done in E Coli, not budding yeast, where mother cells maintain protein aggregates and age, while the daughter cells are given fresh components and are therefore more fresh and 'young'.
Now like you mention, imagine this process in a multicellular organism to be fundamentally the same. At some point the multicellular organism will start an outgrowth of cells, while restricting what materials are given to the daughter cells to maintain their youth. And eventually a new organism will have been created. Some of the details will be different, but the fundamental process is is quite similar. In that you start with an old cell that creates a new cell from scratch, but rather than splitting all cellular components equally between mother and daughter, the daughter cells is made in peak condition while the mother cell retains much of the cell 'junk' like protein aggregates.
Hopefully that starts to answer your question.
The following is multiple choice question (with options) to answer.
Eventually the parent cell will pinch apart to form two identical types of what cells? | [
"son cells",
"father cells",
"brother cells",
"daughter cells"
] | D | Cell division is relatively simple in prokaryotic cells. The two cells divide by binary fission. Green and orange lines indicate old and newly-generated bacterial cell walls, respectively. Eventually the parent cell will pinch apart to form two identical daughter cells. Left, growth at the center of bacterial body, such as in Bacillus subtilis and E. coli . Right, apical growth from the ends of the bacterial body, such as in Corynebacterium diphtheriae . |
SciQ | SciQ-6134 | endocrinology, glucose, homeostasis, insulin, hypothalamus
Title: Role of the Hypothalmus in the control of Blood Sugar In homeostatic regulation of blood glucose, the receptor and effector is the Pancreas, but how does the control centre — the Hypothalamus — connect and link into this process? Your question doesn’t make it clear whether you think that the pancreas must be under the control of the hypothalmus, or whether you are asking whether it has an influence on the pancreas in relation to the secretion of insulin and glucagon, which control the concentration of blood glucose.
First, it has been long known that secretion of insulin can be influenced by the concentration of glucose in isolated pancreatic islets in vitro, so it can not be true that the effects must involve the hypothalmus. This is implicit in most book or general information articles you might find on the web, but for an original reference a review by W.J. Malaisse in Diabetologia 9, 167–173 (1973) seems highly cited.
I know almost nothing about physiology, but on searching the web for the role of the hypothalmus in glucose homeostasis, found a most readable prize-winning postgraduate essay on the topic by Syed Hussein of Imperial College London. I trust that it is in order to append an edited extract of this:
The following is multiple choice question (with options) to answer.
The body cells cannot use insulin properly in which type of diabetes? | [
"type 2 diabetes",
"type 3 diabates",
"type 1 diabetes",
"type 4 diabetes"
] | A | In type 2 diabetes, the body cells cannot use insulin properly. |
SciQ | SciQ-6135 | evolution, ornithology, palaeontology, herpetology, dinosaurs
A few words about pterosaurs
Along with birds and bats, pterosaurs are the other clade of vertebrates capable of powered, flapping flight. Pterosaurs fall within Reptilia (and Diapsida and Archosauria) along with Dinosauria, which includes birds. There are a lot of other extinct lineages in the tree that are not shown, e.g., ornithodirans that are not dinosaurs and not pterosaurs. Pterosaurs and birds share anatomical features that all reptiles, diapsids, archosaurs, and ornithodirans have, which is how we know that they are more closely related to each other than to other groups, like crocodiles. But their flight structures evolved independently and are anatomically distinct fro one another. So pterosaurs are flying reptiles but not flying dinosaurs.
These images might help you understand the above explanation.
The following is multiple choice question (with options) to answer.
Birds belong to a group of diapsids called the what? | [
"mammals",
"conifers",
"aviators",
"archosaurs"
] | D | Evolution of Birds The evolutionary history of birds is still somewhat unclear. Due to the fragility of bird bones, they do not fossilize as well as other vertebrates. Birds are diapsids, meaning they have two fenestrations or openings in their skulls. Birds belong to a group of diapsids called the archosaurs, which also includes crocodiles and dinosaurs. It is commonly accepted that birds evolved from dinosaurs. Dinosaurs (including birds) are further subdivided into two groups, the Saurischia (“lizard like”) and the Ornithischia (“bird like”). Despite the names of these groups, it was not the bird-like dinosaurs that gave rise to modern birds. Rather, Saurischia diverged into two groups: One included the long-necked herbivorous dinosaurs, such as Apatosaurus. The second group, bipedal predators called theropods, includes birds. This course of evolution is suggested by similarities between theropod. |
SciQ | SciQ-6136 | evolution, zoology, anatomy, species
Title: Examples of animals with 12-28 legs? Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list:
snakes have 0
Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs)
Most mammals, reptiles, amphibians have 4 legs
Echinoderms (e.g., sea stars) typically have 5 legs.
Insects typically have 6 legs
Octopi and arachnids have 8 legs
decapods (e.g., crabs) have 10 legs
....But I can't really think of many examples of animals containing more legs until you reach 30+ legs in centipedes and millipedes. Some millipedes even have as many as 750 legs! The lone example I am aware of, the sunflower sea star, typically has 16-24 (though up to 40) limbs.
So my question is: what are some examples of animals with 12-28 legs? As a couple of counterexamples, species in the classes Symphyla (Pseudocentipedes) and Pauropoda within Myriapoda have 8-11 and 12 leg pairs respectively, so between 16 to 24 legs (sometimes with one or two leg pair stronlgy reduced in size).
(species in Symphyla, from wikipedia)
Another common and species-rich group with 14 walking legs (7 leg pairs) is Isopoda.
(Isopod, picture from wikipedia)
You also need to define 'legs' for the discussion to be meaningful. As you say, decapods have 10 legs on their thoracic segments (thoracic appendages), but they can also have appendages on their abdomens (Pleopods/swimming legs), which will place many decapods in the 10-20 leg range.
(Decapod abdominal appendages/legs in yellow, from wikipedia)
So overall, in Arthropoda, having 12-28 legs doesn't seem all that uncommon. There are probably other Arthropod groups besides those mentioned here that also have leg counts in this range.
However, for a general account, the most likely answer (if there is indeed a relative lack of 12-28 legged animals) is probably evolutionary contingencies and strongly conservative body plans within organism groups.
The following is multiple choice question (with options) to answer.
How many limbs to birds have? | [
"six",
"four",
"ten",
"five"
] | B | Birds are four-limbed, endothermic vertebrates with wings and feathers. They produce amniotic eggs and are the most numerous class of vertebrates. |
SciQ | SciQ-6137 | fluid-dynamics, pressure, aerodynamics, aircraft, lift
Title: Why does the higher pressure of air underneath an aeroplane wing keep it flying? With aeroplane flight, the wings are shaped so that the air that goes over the top of the wing has to travel faster than the air that goes below the wing. This means that the air below the wing has higher pressure than the air above it (as the air above is moving much faster), keeping it in the air.
Why is it that lower pressure above the wing and higher pressure below stops the plane from falling? First thing, that's a common misconception that the plane flies due to the Bernoulli effect.
See the these questions: What really allows airplanes to fly? Why does the air flow faster over the top of an airfoil? for the correct explanation.
Assuming that the bernoulli effect does explain flight, the answer to your question is:
Pressure of a fluid is force exerted by a fluid on a unit area of a neighboring body (the force exists inside the fluid as well, but it is balanced). So, if there is more pressure underneath, the upward force is greater (area if top and bottom of wings are approximately the same)
If the upward force is greater, the net force due to pressure is upwards. This force is called 'lift', and it balances gravity, helping the plane fly.
Read http://enwp.org/Pressure for more info.
The following is multiple choice question (with options) to answer.
Planes fly in what layer of the atmosphere because there is less friction and turbulence? | [
"stratosphere",
"mesosphere",
"ozone layer",
"crust"
] | A | Sure we can! If you've ever flown on a jet airplane, you've been in the stratosphere. Airplanes fly in the stratosphere, because there is less friction. They get better gas mileage and so costs are lower. There is also less turbulence, so passengers are happier. Can you identify the bottom of the stratosphere in the photo? It's where the clouds begin. Remember that all weather is in the troposphere. |
SciQ | SciQ-6138 | ecology, biogeography
Edit in response to comments
Comment about biome scale
The reason behind the scale comment is that typically we observe succession for a given habitat. Part of this stems from the origin of the succession ideas, where Frederic Clements posited that climate was the major driving factor of successional trajectories (Clements 1916). This would actually fit well with the biome view of succession, however in order for this model to explain all the variation we see in the world (eg. why a tree grows in location X but not location Y 4 metres away), you devolve into splitting the world into infinitesimally small micro-climates. Henry Gleason proposed a more individualistic model, which suggested that climate was just one influence, and that each plant species responds to a myriad of different environmental cues (Gleason 1927). The sum of these responses results in the community at a given location. This seems to fit better with our current understanding of succession but is not without problems. In a Gleasonian model, any variation can be expected to result in a different community. Since it would be strange for the pampas region to be homogeneous over 1.2 million km2, there are likely distinct communities within the biome, each developing as a result of factors like soil moisture, soil chemistry, climate, wind exposure, and herbivore use. One can still talk about succession at a biome scale, but at that scale we would be thinking about what factors lead the pampas region to become a grassland, rather than what factors lead grass X, tree Y and forb Z to coexist next to each other.
Factors maintaining grassland type ecosystems are fairly uniform globally. You need some sort of event that will kill woody vegetation but not kill grasses and forbs. Fire and grazing are natural examples (Briggs et al. 2002), but mowing would also maintain grassland (Fidelis et al. 2012). Earthquakes are unlikely to maintain grassland as trees and shrubs are likely to survive earthquakes.
Comment about global pampas
The following is multiple choice question (with options) to answer.
What is a group of similar ecosystems with the same general abiotic factors and primary producers? | [
"taxon",
"ecoregion",
"biome",
"family"
] | C | The two photos in Figure above represent two different biomes. A biome is a group of similar ecosystems with the same general abiotic factors and primary producers. Producers are organisms that produce food for themselves and other organisms. Biomes may be terrestrial or aquatic. |
SciQ | SciQ-6139 | human-biology, digestive-system, immune-system, microbiome
All of these immune cells also respond to diffused chemical signals called cytokines. These molecules are secreted by some cells and are received by receptors on the host cells. Sometimes the secretion is by another immune cell, sometimes it is from a non-immune system host cell, and sometimes these molecules can be secreted by the bacteria, fungi, or worms themselves.
Depending on the chemical signals that are secreted, and how the cells are interacting at the time of the message, and which cells are receiving the message, will determine the response to the message. It is contextual. Think of the phrase "You're killing me." If someone says it, while laughing, to a good friend who is telling jokes, it means one thing. If it is screamed as someone is being choked by an attacker, it means something very different.
To summarize, the immune cells are surveilling the environment and trying to pick up what is friend and what is foe and they try to respond accordingly.
Over time and coevolution, our microbiomes have developed ways of communicating with our immune system to let it know that these microbes do not mean any harm. They are able to "train" the immune cells using chemical signaling to temper the immune systems response to them (15), and this is how they are able to coexist within our body and with an immune system that is constantly on seek an destroy missions. Also because of the mucus, our microbiome usually isn't in direct contact with our cells, so it is a different kind of interaction than if an infecting pathogen were to breech the barriers and gain access to sterile areas where no bacteria or fungi should be found, and as a result, the immune system reacts differently.
The following is multiple choice question (with options) to answer.
Interferons are produced in virally infected cells and cause them to secrete signals for surrounding cells to make what? | [
"resist proteins",
"Raising Proteins",
"overwhelm proteins",
"antiviral proteins"
] | D | Chapter 21 1 The three main components are the lymph vessels, the lymph nodes, and the lymph. 3 The bacterium is digested by the phagocyte’s digestive enzymes (contained in its lysosomes). 5 B 7 C 9 A 11 D 13 C 15 B 17 B 19 D 21 D 23 B 25 C 27 B 29 C 31 D 33 A 35 B 37 B 39 The lymph enters through lymphatic capillaries, and then into larger lymphatic vessels. The lymph can only go in one direction due to valves in the vessels. The larger lymphatics merge to form trunks that enter into the blood via lymphatic ducts. 41 Interferons are produced in virally infected cells and cause them to secrete signals for surrounding cells to make antiviral proteins. C-reactive protein is induced to be made by the liver and will opsonize certain species of bacteria. 43 Antigen-specific clones are stimulated as their antigen receptor binds to antigen. They are then activated and proliferate, expanding their numbers. The result is a large number of antigen-specific lymphocytes. 45 IgM is an antigen receptor on naïve B cells. Upon activation, naïve B cells make IgM first. IgM is good at binding complement and thus has good antibacterial effects. IgM is replaced with other classes of antibodies later on in the primary response due to class switching. 47 Tuberculosis is caused by bacteria resistant to lysosomal enzymes in alveolar macrophages, resulting in chronic infection. The immune response to these bacteria actually causes most of the lung damage that is characteristic of this life-threatening disease. 49 Antibody response to the cell walls of β-Streptococcus cross-reacts with the heart muscle. Complement is then activated and the heart is damaged, leading to abnormal function. Tolerance is broken because heart myosin antigens are similar to antigens on the β- Streptococcus bacteria. |
SciQ | SciQ-6140 | geophysics, sedimentology
Title: Does dirt compact itself over time? If so, how does this happen? If I were to bury something 10 feet (~3 metres) underground, with loose soil on top, would the ground naturally compact itself over time, until whatever I had buried has dirt tightly pressing against it on all sides?
What if I buried it 50 feet (~15 metres) underground?
If it exists, what is this compaction process called and how does it happen? Soil is a collection of various sized minerals grains, of various types of minerals produced by the weathering of rock. Typical soil minerals are clays, silts and sands.
The properties and behavior of different soil types depends of the composition of the soil: the proportion of clays, silts and sand in a soil. Sandy soils are well draining and clayey soils are sticky.
Between the grains of minerals that comprise a soil are spaces, called pores or pore spaces. The pores can be filled with either water or air, depending the location of water tables and wetting events like rain, snow melts or other forms of water inundation.
The density of a soil is dependent on the degree of compaction of the soil. For to a soil to be compacted, a stress has to be applied to the soil to realign the grains of soil which reduces the total volume of the pores and reduces the amount of air within the pores.
Consolidation of a soil occurs when pore space is reduced and water in a soil is displaced due to an applied stress.
Regarding having something buried and soil compacting around it over time, yes that will occur but it is a question of how much stress the soil experiences, the duration of time and the nature of the soil - sandy or clayey. Something buried for a day without any stresses not much will happen. But, something buried for thousands of years with people and animals walking over it, rain falling on the soil, vibrations from nearby human activity and an occasional earthquake all add to the stresses the soil will experience and increases the degree of compaction or consolidation over time.
The following is multiple choice question (with options) to answer.
What slow process is required for formation of soil? | [
"weathering",
"digestion",
"fossilization",
"leaching"
] | A | Soil formation requires weathering. Where there is less weathering, soils are thinner. However, soluble minerals may be present. Where there is intense weathering, soils may be thick. Minerals and nutrients would have been washed out. Soil development takes a very long time. It may take hundreds or even thousands of years to form the fertile upper layer of soil. Soil scientists estimate that in the very best soil forming conditions, soil forms at a rate of about 1mm/year. In poor conditions, it may take thousands of years!. |
SciQ | SciQ-6141 | electrostatics
Title: Inducing positive charge on a Sphere(Metallic) Sorry if this question is asked already. I want to know that while inducing positive charge on a neutral body, at the time of earthing why the electrons move out so easily from the neutral body to the ground.I wonder Is it that easy to remove the electrons from a body. And aren't there a lots of electrons already in the ground so that if electrons are moving through earthing to ground will be repelled back to the body. Hope I will get a reply soon Thanks! The potential of earth is consider to be zero so charge can easily flow into earth as charge flow from body at higher potential to lower potential.Also the earth is so large that the addition of electrons dont increase the charge of earth they will simply lost in the earth.
The following is multiple choice question (with options) to answer.
What is defined as superheated gas with a positive electrical charge? | [
"greenhouse gas",
"supernova",
"ion",
"plasma"
] | D | The Sun is made mostly of plasma. Plasma is superheated gas with a positive electrical charge. |
SciQ | SciQ-6142 | magnetic-fields, ferromagnetism
Title: Technical Term for Material That is Only Magnetic Next to A Magnet I was wondering what the technical term is for some metal(like a refrigerator door) that is not magnetic on its own like neodymium but when there is a magnet in its vicinity, it attracts to the magnet. Neodymium has a polarity but these metals don't have one, they just stick to a magnet. Is it called ferromagnetism? As far as I know there is no single term to refer to a material that is attracted by magnetism but not a magnet. Rather, there are terms that describe a material's magnetic behaviour regardless of its magnetized state.
There are a few versions. Ferromagnetic, paramagnetic, and diamagnetic.
Ferromagnetic is like iron it will be attracted to other magnets, but can also be magnetized and turned into a permanent magnet.
Paramagnetic and diamagnetic materials can't be turned into permanent magnets. The difference might be considered nitty gritty and I'm not qualified to comment.
But it sounds like you're asking for a specific term for a material that is ferromagnetic, but not currently magnetized. I don't know of one.
The following is multiple choice question (with options) to answer.
Materials, such as iron, that exhibit strong magnetic effects are labeled what? | [
"superconducting",
"paramagnetic",
"ferromagnetic",
"ultramagnetic"
] | C | Magnetic poles always occur in pairs of north and south—it is not possible to isolate north and south poles. All magnetism is created by electric current. Ferromagnetic materials, such as iron, are those that exhibit strong magnetic effects. The atoms in ferromagnetic materials act like small magnets (due to currents within the atoms) and can be aligned, usually in millimeter-sized regions called domains. • Domains can grow and align on a larger scale, producing permanent magnets. Such a material is magnetized, or induced to be magnetic. • Above a material’s Curie temperature, thermal agitation destroys the alignment of atoms, and ferromagnetism disappears. • Electromagnets employ electric currents to make magnetic fields, often aided by induced fields in ferromagnetic materials. |
SciQ | SciQ-6143 | ornithology, kidney
Back to worrying about the mammal-centric thinking: there is a causal implication in both the original and my edited version that is not warranted, which is that the anatomy of the loops of Henle is somehow determining the nitrogen excretion strategy that birds use. It's equally reasonable to presume that birds don't need long loops of Henle since they evolved an alternative excretion mechanism that makes it unnecessary to concentrate urine to a great degree.
The "trick" of that alternative excretion mechanism is using uric acid and excreting a paste. Because uric acid crystalizes and comes out of solution, it doesn't "count" toward osmolarity of the urine, it's excreted as a solid. Birds don't need to remove water to crystalize uric acid, and don't need to use water to flush it out at all, it falls out of solution on its own because it's not very soluble. You could add a bunch of extra water and it would still stay mostly solid rather than dissolving.
So back to your original question: how do birds concentrate their urine? Well, pretty much the same way we do as far as the kidney goes. They also pull some water back in through the cloaca before urine is released, similar to how mammals pull water in from stool in the large intestine. The important difference is not how birds concentrate their urine (because urine concentration isn't a goal/need in itself), but rather how birds excrete nitrogen waste. By not flushing soluble nitrogenous waste with water in the first place, they don't have as much urine to concentrate, so it's less important for them to be very efficient in doing so.
The following is multiple choice question (with options) to answer.
Like birds, most other reptiles excrete their nitrogenous wastes as what acid? | [
"hydrochloric",
"uric",
"lactic",
"sulphuric"
] | B |
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