source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-1244 | human-biology, endocrinology, organs
Title: Is there a blood panel lab test that measures all the hormone-producing glands? I understand that there are gland-specific hormone tests, such as:
Secretin: for the pancreas; and
Prolactin/ACTH: for the pituitary; and
PTH: for the payathyroid, etc.
However, are there any "composite" blood panels that test the "entire gamut/spectrum" of organs/glands, similar to what composite metabolic panels do for your cell counts? There are no composite tests that measure all the clinically important hormone producing glands. There are too many hormones produced by too many hormone producing cells/tissues in the body to test for all of them all at once (i.e. in a panel).
For illustrative purposes only... if you go to wikipedia they have a list of all hormones in the human body which is definitely far from complete! But it gives you an indication of just "how many" hormones there are and why testing for all of them is impossible in a panel.
Even with regard only to pancreatic hormones, there are several hormones produced (e.g. insulin, glucagon, somatostatin) that aren't necessarily a marker of the glands overall function (because they are not necessarily involved in the same function). Each of these hormones has different functions even though they are produced by the same gland.
Regardless, from a medical perspective you would never have a reason to test for all of them anyway. If you tested enough of them you'd find at least one of them that would - by chance - be abnormal.
Additionally, if you asked a handful of scientists to name fifty hormones there would be a lot of different hormones on each of their lists. The definition of hormone is vague, and we are learning more about new hormones every day. In the last decade we have learned that bile acids - chemicals predominately produced by the liver that are involved in dietary fat absorption - also act as hormones. There aren't clinical reasons to study all of these molecules just yet, but this demonstrates that it would be impossible to measure all of them all at the same time in one particular "panel".
The following is multiple choice question (with options) to answer.
The molecule pictured above is thyroxine, a compound produced by which gland? | [
"gallbladder",
"thyroid",
"stomach",
"kidney"
] | B | The molecule pictured above is thyroxine, a compound produced by the thyroid gland. This molecule regulates how the body uses energy. In a condition known as hypothyroidism, the thyroid makes less thyroxine than normal. A person with this disease feels tired all the time and often puts on weight. Treatment with thyroid hormone supplements takes care of the problem. |
SciQ | SciQ-1245 | species-identification, ornithology
Why would a mother do that to her young? Does she hates the little one? Not at all. It’s just that those little birds were made to fly, and they don’t know it, so she is going to push them out of the nest. She never lets them hit bottom, but she does let them fall, because they have to learn something they don’t know.
The next time the mother bird comes back she decides to clean house, and so she stands on the edge of the nest. The first things to go are the feathers inside; she drops them over the edge. Then the leaves go over the edge—heave ho! While this is going on, she’s not very talkative, either. ("Mom, what are you doing?") She pays no attention. Since she built the house, she knows how to take it apart.
Next she decides to take the sticks out of the middle of the nest, and with her great strong beak and feet, she’s able to break them off and stand them straight up. ("Mom, it’s not comfortable in here anymore.") Then she takes certain key sticks out of the nest and throws them over the edge. ("What are you doing, Mom? You are wrecking my room.")
She seemingly pays no attention to the concerns of her young as she prepares to pull the nest apart, for she is determined that those little ones will fly, and she knows something they don’t. She knows they will never fly as long as they remain in the nest.
The following is multiple choice question (with options) to answer.
Birds generally practice what kind of relationship, with both parents helping to care for the young? | [
"synonomous",
"monogamous",
"homologous",
"carnivorous"
] | B | Birds generally are monogamous, and both parents help to care for the young. |
SciQ | SciQ-1246 | botany
Title: Do any plants exhibit hormonal changes similar to puberty? Just what the title states.
Are there any plants/trees that exhibit a growth spurt at a definite interval after the shoot appears? In flowering plants (the angiosperms) there are several developmental transitions in the life of the plant. I won't list the plants, because the list includes pretty much all of them (although the magnitude in the change of developmental pace differs widely between taxa and environments).
First there is seed germination, which is controlled hormonally. Absence of germination is usually imposed by abscisic acid, whilst germination is caused at the appropriate time by gibberellic acid and ethylene (among other things; Holdsworth, Bentsink & Soppe, 2008).
Next, in many herbaceous species there is a transition between a spreading growth stage (e.g. rosette growth) and the flowering stage. The 'growth spurt' here is the differentiation and elongation of the flowering stem, and then subsequently the sudden flowering of buds. The transition is also controlled hormonally, by a variety of hormones including auxin (Zhao, 2010), gibberellic acid, ethylene (Schaller, 2012), and the long anticipated, recently confirmed florigen (Choi, 2012). Ethylene and abscisic acid then play important roles in the next developmental transition when seeds and fruits are produced and dehisced.
Small RNAs are also now being revealed to play a large role in controlling the timing of developmental, but they are upstream of the hormonal changes. In particular some key miRNAs are involved in auxin-based regulation of branching, and in embryogenesis (Nodine & Bartel, 2010), and RNA silencing is involved in the switch from rosette growth to flowering growth (reviewed in Poethig, 2009 and Baurle & Dean 2006).
The following is multiple choice question (with options) to answer.
Gravitropism ensures that roots grow into the soil and that shoots grow toward what? | [
"trees",
"the south pole",
"the north pole",
"sunlight"
] | D | Plant Responses to Gravity Whether or not they germinate in the light or in total darkness, shoots usually sprout up from the ground, and roots grow downward into the ground. A plant laid on its side in the dark will send shoots upward when given enough time. Gravitropism ensures that roots grow into the soil and that shoots grow toward sunlight. Growth of the shoot apical tip upward is called negative gravitropism, whereas growth of the roots downward is called positive gravitropism. Amyloplasts (also known as statoliths) are specialized plastids that contain starch granules and settle downward in response to gravity. Amyloplasts are found in shoots and in specialized cells of the root cap. When a plant is tilted, the statoliths drop to the new bottom cell wall. A few hours later, the shoot or root will show growth in the new vertical direction. The mechanism that mediates gravitropism is reasonably well understood. When amyloplasts settle to the bottom of the gravity-sensing cells in the root or shoot, they physically contact the endoplasmic reticulum (ER), causing the release of calcium ions from inside the ER. This calcium signaling in the cells causes polar transport of the plant hormone IAA to. |
SciQ | SciQ-1247 | mole
Title: How to calculate the mass of a single atom? If we know the molar mass of a certain element and Avogadro's constant, how can we calculate the mass of a single atom? Do we need to multiply the molar mass with Avogadro's constant? For most atoms it's around Ryan's answer.
E.g. Carbon-12:
$$\frac{\ce{12 g}~\ce{C}}{\pu{1 mol}~\ce{C}} \times
\frac{\pu{1 mol}~\ce{C}}{\pu{6.022E23 atoms}} =
\pu{1.993E-23 g//atom} = \pu{1.993E-27 kg//atom}.$$
That was the molar mass $M$ multiplied by $1/N_\mathrm{A}$, where $N_\mathrm{A}$ is Avagadro's constant.
Thus $M/N_\mathrm{A}$ gives you a calculation for mass of an atom for the specific element.
The following is multiple choice question (with options) to answer.
What is the mass of one mole of any given substance? | [
"molar mass",
"protons mass",
"atomic mass",
"solute mass"
] | A | Molar mass is the mass of one mole of any given substance. |
SciQ | SciQ-1248 | exoplanet, space-telescope
Title: Why use a large separate starshade instead of an occulting disk? The New Worlds Mission proposal has a large occulter on a different spacecraft from the space telescope to block glare from a star to reveal its planets. What is its advantage compared to a disk on an arm such as on the Solar and Heliospheric Observatory (SOHO)?
I can understand that on Earth, a coronagraph suffers from atmospheric scattering, but why would it matter in space? TL;DR: The Sun is well-resolved in small telescopes so a focal plane occulter works well. Other stars are not resolved (except in a few exciting cases using interferometry) so an internal blocking disk would be useless.
Local blocking disks for telescope coronagraphs are placed inside the instrument at a focal plane, usually the first focal plane. That way they have sharp edges and can block the Sun (or star) but allow light nearby to reach a detector.
A blocking disk "on an arm" some short distance in front of a telescope would be way way out of focus and so act like a "fuzzy blob" at best. SOHO does not have one of these.
It does have a small disk on a small arm inside the telescope.
The disk of the Sun is huge compared to the resolution of the telescope, roughly 2000 arcseconds compared to order 1 arcsecond resolution (depending on wavelength). So a disk at the focal plane is sufficient to block the Sun and allow the larger corona to still reach the focal plane.
However a star's angular size is way, way, way smaller than the resolution of a modern space telescope. There's no hope of blocking the star and letting light from nearby orbiting exoplanets to reach the focal plane.
So the only alternative is to move the disk so far from the telescope that it appears as small as the star itself, and blocks the light.
The following is multiple choice question (with options) to answer.
The corona surrounds which major object in our solar system? | [
"the sun",
"Earth's moon",
"Jupiter",
"Neptune"
] | A | The corona is the halo around the Sun. |
SciQ | SciQ-1249 | respiration
Here is what happens at the molecular level.
The $\rm CN^-$ ions diffuse into the mitochondria. They have high affinity to the ferrous ion of the mitochondrial enzyme cytochrome c oxidase involved in the electron transport chain (ETC), one of the phases of cellular respiration where $\rm ATP$ is generated from $\rm NADH$ and $\rm FADH_2$. And it is this process that actually requires oxygen. The inhibited cytochrome c oxidase is of no good in transporting electrons, thus no $\rm ATP$ molecules are generated. The oxygen molecules waiting for those electrons remain empty handed resulting in the increase in the concentration of molecular oxygen. Remember, ETC occurs in almost all living cells except a few like RBC which get their major share of ATP from the highly inefficient anaerobic glycolysis. Also, $\rm ATP$ is the energy currency of our body and is required in a wide variety of bodily processes like osmotic balance, nerve impulse transmission, muscle contraction etc. With no $\rm ATP$ your heart and respiratory muscles can't contract, your medulla can't regulate breathing, your kidneys can't concentrate urine and the list goes on. Death is imminent if a high concentration of cyanide gets into your blood.
The symptoms of panic like tachypnea and tachycardia (that result due to low oxygen in blood) are not usually seen unless the victim himself knows he is poisoned. The end effects like cardiac and respiratory arrest, seizures and coma, however, are similar to those of suffocation.
For further read:
The Mechanism of Cyanide Intoxication and its Antagonism
The following is multiple choice question (with options) to answer.
Respiration that occurs in the cells is called? | [
"cellular respiration",
"electromagnetic respiration",
"biological respiration",
"plasma respiration"
] | A | Another kind of respiration takes place within body cells. This kind of respiration is called cellular respiration. It’s the process in which cells obtain energy by “burning” glucose. Both types of respiration are connected. Cellular respiration uses oxygen and produces carbon dioxide. Respiration by the respiratory system supplies the oxygen needed for cellular respiration. It also removes the carbon dioxide produced by cellular respiration. |
SciQ | SciQ-1250 | evolution, molecular-biology, molecular-evolution, abiogenesis
The issue isn't actually as clear-cut as it may seem, since there is a very wide unknown space between what we consider the most archaic forms of life, and any entity that could plausibly arise via purely abiotic processes; every theory of abiogenesis does assume that a lot of the features we consider essential to life must have arisen after some kind of replication appeared, meaning those features would have evolved. So there definitely is some evolutionary biology involved in investigating abiogenesis, and maybe if we ever solve abiogenesis it will be folded into the ToE (like I said, the ToE is actually a complex set of theories and observations, not one single thing. So while our understanding of what the theory says and can say currently excludes abiogenesis, our understanding and definition of the theory could evolve). But we haven't, and it currently isn't.
You need to edit your question however, because it is completely unclear from the title or text that you are asking about abiogenesis. Your question sounds like it's about embryonic development or biochemistry. Those are the current instances we have of organisms forming; whatever processes were at work in creating the very first life, well for one thing maybe we wouldn't want to call whatever that was an "organism", but more to the point those processes cannot happen today. The atmosphere is wrong and too full of oxygen, there are organisms everywhere vaccuuming up whatever resources those original biochemical processes might have used, basically there is likely no chemical environment on modern Earth that's anything like the chemical environment life originated in.
To answer your question though, abiogenesis is currently an unsolved question, so no, Science does not have an explanation of how the first organisms formed. But if you want to have an idea of how things could have happened, what the challenges are in figuring things out, and what things Science currently considers likely or impossible, there is a lot of active research in the field and many different hypotheses. The Wikipedia page for Abiogenesis has a fairly comprehensive rundown on this.
This video describes one of them (my favorite and the first I've found actually convincing, I have no expertise whatsoever to base this on but I plug it anyway; if nothing else it gives an appreciation for what kind of things the researchers in this field look at when thinking abiogenesis) :
The following is multiple choice question (with options) to answer.
Metabolism is an emergent property of life that arises from orderly interactions between what? | [
"molecules",
"nutrients",
"tissues",
"body systems"
] | A | |
SciQ | SciQ-1251 | biochemistry
Alright so this is the oxidation of one mole of glucose equation (Without the ATPs) but till now I don't exactly know the correct answer for this question, but to not create any confusion this question is related to the Aerobic respiration (Glycolysis, Krebs Cycle and Electron transport chain).
Here's how I approached this question:
(a) is obviously not correct because the products of glycloysis are 2 pyruvate molecules and 2 ATP molecules so I checked off this choice.
(b) However seems correct because the products of 2 Krebs cycle is 4 CO2 and there is already 2CO2 when the pyruvate acid formed the 2 acetyl CoA molecules so in total that's 6CO2, but still what about the 6 Water molecules?
(c) is a very debating choice because when there is a "Complete occurrence of oxidative phosphorylation process" so that means 2 Krebs cycles had already occurred and formed the 6CO2, and during the oxidative phosphorylation process Water molecules are formed. and ATPs too? I don't exactly know about the ATPs, but aren't they supposed to be in the equation's products in order for this choice to be correct?
(d) This choice indicates to Krebs cycle but the water molecules only are formed during oxidative phosphorylation only.
So basically all the choices seems very debating and confusing and if I were to choose then I'll go with (C) because it's the only choice that makes sense for the water molecules (and the question asks for water), but I want someone to please answer this question with a brief explanation to why he chose this answer,
Thanks :) This reaction only means complete oxidation of glucose to 6 molecules of carbon dioxide and 6 molecules of water.
Reaction presented in question is very generalized, but the presence of six water molecules only means complete cellular respiration. Check out the actual biochemical pathways which take place to oxidize one glucose molecule.
And other options do not represent the complete cellular respiration, so there will not be formation of six water molecules, only option C means complete oxidation of glucose.
The following is multiple choice question (with options) to answer.
During cellular respiration, carbons from the glucose molecule are changed back into what gas? | [
"deformation dioxide",
"carbon dioxide",
"carbon monoxide",
"liquid dioxide"
] | B | In biological systems, matter is continuously changing states as well. For example, carbon in the form of the gas carbon dioxide is changed into glucose, a solid. This change, of course, occurs during photosynthesis. During cellular respiration, carbons from the glucose molecule are changed back into the carbon dioxide gas. |
SciQ | SciQ-1252 | universe, relativity, space-expansion
If you're interested I talk about how we calculate $a$ in How does the Hubble parameter change with the age of the universe?.
But to get back to your question:
I would guess that when you say mass increases you mean the fact that relativistic mass increases as you approach the speed of light. So if distant galaxies are speeding away from us their mass must be increasing. However those distance galaxies are (approximately) stationary with respect to us just like $A$ and $B$ in my discussion above. All that is happening is that the distance between us and the distant galaxies is increasing with time. So the distant galaxies aren't getting more massive, and for completeness they aren't suffering any relativitic time dilation either.
But there is a sense in which you are correct that mass could stop the expansion, though in our universe it doesn't appear this will happen. The way the scale factor changes with time depends on the average density of the universe. If the density is lower or equal to the critical density then $a$ just increases smoothly with time and the universe keeps getting bigger. If the average density is higher than the critical density then $a$ increases at first, but then peaks and starts to decrease again, which means the expansion of the universe slows to a stop then reverses.
As far as we can tell the density of our universe is too low for the expansion to reverse. In fact the presence of dark energy means the expansion will keep getting faster and in the far future the scale factor will increase exponentially with time.
The following is multiple choice question (with options) to answer.
How does the distance between galaxies change as the universe expands? | [
"it increases",
"it decreases",
"it is unchanged",
"it becomes irrelevant"
] | A | Figure below shows a simple diagram of the expanding universe. Imagine a balloon covered with tiny dots. When you blow up the balloon, the rubber stretches. The dots slowly move away from each other as the space between them increases. In an expanding universe, the space between galaxies is expanding. We see this as the other galaxies moving away from us. We also see that galaxies farther away from us move away faster than nearby galaxies. |
SciQ | SciQ-1253 | meteorology, atmosphere, carbon, co2, rain
Bear in mind that this assumes an enormous rainfall intensity, 100% CO2 saturation of the water and equilibrium chemical dynamics. After the raindrops hit the ground at least half of it will immediately re-evaporate back into the air, leaving, at absolute most, about 3% of the atmospheric CO2 leached out of the atmosphere that will be available to react with the soil, rock or biosphere. Also consider that this is but one of several important processes affecting CO2 transience, such as photosynthesis, respiration, volcanism, industrial pollution, etc. So the CO2 estimates that you read about are average values. Advection and turbulent air mixing should ensure that the CO2 regains approximately normal concentration within an hour or two after rainfall.
The following is multiple choice question (with options) to answer.
Rainwater absorbs carbon dioxide (co 2 ) as it falls. the co 2 combines with water to form what? | [
"methane gas",
"nitrate acid",
"carbonic acid",
"carbon monoxide"
] | C | Rainwater absorbs carbon dioxide (CO 2 ) as it falls. The CO 2 combines with water to form carbonic acid. The slightly acidic water is especially good at dissolving the rock limestone. Groundwater creates landforms by dissolving away rock. |
SciQ | SciQ-1254 | states-of-matter, elements
Title: At what temperature are the most elements of the periodic table liquid? For elements where 'liquid', is relatively easy to define, at which temperature are the most elements liquid, and which ones?
Assume 1 atm We take the natural elements (atomic numbers $1$ to $92$) to have well-defined melting and boiling points. Additionally, all figures are quoted at the standard $1\text{ atm}$ pressure. Here's some quick Python code that fetches the number of elements in the liquid state at various temperatures (note that it relies on the values of the melting and boiling points of elements defined in the mendeleev package, however it is straightforward to instead use your own dataset).
from mendeleev import element
elements = [element(i) for i in range(1, 92 + 1)] # Hydrogen to Uranium
n_liquid_list = [sum(element.melting_point < temp < element.boiling_point for element in elements) for temp in range(0, 5000)]
n_liquid_max = max(n_liquid_list)
temperature = n_liquid_list.index(n_liquid_max)
print(n_liquid_max, "elements are in the liquid state at", temperature, "K")
prints 38 elements are in the liquid state at 2161 K
For the full list, just add in
for elem in elements:
if elem.melting_point < temperature < elem.boiling_point:
print(elem.name, end=", ")
which gives you
Beryllium, Aluminum, Silicon, Scandium, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Gallium, Germanium, Yttrium, Zirconium, Palladium, Silver, Indium, Tin, Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Lutetium, Platinum, Gold, Actinium, Thorium, Protactinium, Uranium
The following is multiple choice question (with options) to answer.
Most molecular compounds that have a mass similar to water are in what state of matter at room temperature? | [
"solid",
"vapor",
"liquid",
"gas"
] | D | The hydrogen bonding that occurs in water leads to some unusual, but very important properties. Most molecular compounds that have a mass similar to water are gases at room temperature. Because of the strong hydrogen bonds, water molecules are able to stay condensed in the liquid state. The Figure below shows how the bent shape and two hydrogen atoms per molecule allows each water molecule to be able to hydrogen bond to two other molecules. |
SciQ | SciQ-1255 | biochemistry, cell-biology, metabolism, photosynthesis
Title: How are ions 'pumped' across a membrane during electron transport? A number of sites (including this one) that provide descriptions of photosynthesis state that high energy electrons 'pump' ions across a membrane. What is the actual 'pumping' mechanism? I've looked at Wikipedia and at a number of YouTube lectures/tutorials but so far have only found statements as to the where and when but not the how of this important process. Short answer:
Electrons flow through membranes by floating through kind of channels made out of iron-sulfur clusters.
Long answer:
Let's take a look at the electron transport chain in the inner mitochodrial membrane. There is a proton gradient across the membrane building up a potential difference by pumping protons across the membrane as electeons flow through the respiratory chain. They (electrons) like to flow throught the respiratory chain because they can go from enzyme to enzyme each with a lower standart free energy. These enymes together form one big complex within the inner membrane with Fe-S clusters enabeling electrons to flow through the membrane by giving them a kind of a power stroke (see here).
This as an simplyfied answer on a example.
The following is multiple choice question (with options) to answer.
What do you call the movement of molecules across a membrane without the input of energy? | [
"passive transport",
"reactive transport",
"obvious transport",
"active transport"
] | A | Recall that the cell membrane is semipermeable. It does not allow everything to pass through. Some molecules can pass easily through your cell membranes, while others have more difficulty. Sometimes molecules need the help of special transport proteins to move across the cell membrane. Some molecules even need an input of energy to help get them across the cell membrane. The movement of molecules across a membrane without the input of energy is known as passive transport . When energy (ATP) is needed, the movement is known as active transport . Active transport moves molecules against their concentration gradient, from an area of low concentration to an area of high concentration. |
SciQ | SciQ-1256 | electrostatics, charge
Title: Will charges attract or repel? If the universe consist of only two particles namely electron and proton, and if they are separated away by huge distance, they will still attract each other.
Can we prove it without using Coulomb's law?
Can we find out why they attract or what causes them to attract?
What really happens there that makes the both particles move towards each other? Physics does not answer why questions, except with how from postulates and mathematical models one can describe the data. The how is Coulombs law.
Physics is about fitting experimental observations with mathematical models. The answer to the "why attraction" in this case, is, data dictates so. There is no other answer except that Coulomb's law fits the data. Our present theories of physics incorporate this law in more inclusive mathematical models, because of this experimental fact.
The following is multiple choice question (with options) to answer.
Opposite charges attract and like charges do what? | [
"nothing",
"rebound",
"repulse",
"impede"
] | C | Opposite charges attract and like charges repulse. |
SciQ | SciQ-1257 | inorganic-chemistry, solubility, analytical-chemistry
Title: Solubility and wetting of substances in water We have seen that, when we pour salt in water then it gets dissolved, that means it is soluble in water. But when we pour sand into water then it doesn't dissolve in water, that means it is insoluble, but still sand gets wet. But there are certain substances which doesn't get wet by water for example, sulfur particles don't get wet by water but wet in oil, as I was studying about froth floatation method.
My question is that:
What is the difference between solubility and wetting in water ?
What is the reason that the sulfur particle doesn't get wet by water? Polar/hydrophilic soluble substances get dissolved, like table salt or sugar.
Polar/hydrophilic insoluble substances get wet, as they attract water, like sand, or limestone.
Nonpolar/hydrophobic insoluble substances do not get wet, as they repulse water, like wax, teflon or silanized glass.
The following is multiple choice question (with options) to answer.
What molecules are usually insoluble in water? | [
"acids",
"ions",
"non-polar",
"polar"
] | C | Non-polar molecules are usually insoluble in water. |
SciQ | SciQ-1258 | electricity
Title: Static Electricity I just took a flannel shirt off and it crackled with static. I threw it on a metal chair and I hear it crackle some more. I played with a stray string with my hand, watching it rise to meet my hand and fall when I move it away. But this leaves me with a question to which I cant find an answer on Google. I know later I will pick up the shirt and the static will be gone. Where does static electricity go if its not grounded? Does it dissipate into the air? Or into the object its on? The charges on your shirt will disappear due to discharging through the small conductivity of air and the conductivity of the object where you have put your shirt on.
The following is multiple choice question (with options) to answer.
What occurs when there is a sudden discharge of static electricity between a cloud and the ground? | [
"wind",
"updraft",
"lightning",
"rain"
] | C | Lightning occurs when there is a sudden discharge of static electricity between a cloud and the ground. |
SciQ | SciQ-1259 | respiration
Title: Relation between respiration and concentration of citric acid
A and B are 2 reactions.
If there is an excess availability of citrate, then which of the above reactions will prevail?
I know that citric acid is formed when oxaloacetic acid reacts with acetyl coA. But how does concentration of citric acid influence the above reactions This image is a bit misleading since both ways seem to be the reversion of each other, but in fact they are not (although the same metabolites are used).
Reaction A takes only place in gluconeogenesis which makes glucose from other metabolites (coming from the metabolism of fatty acids for example) and this pathway is only active when there is an abundance of energy present in the cell. Citrate activates the Fructose-1,6-bisphosphatase. The gluconeogenesis takes only place in liver and kidney.
Reaction B takes place in glycolysis and is the rate limiting for the whole pathway. It takes place when glucose is taken up and then used for the production of energy. The Phosphofructokinase (PFK) is inhibited by signals of excess energy as ATP (which is an allosteric inhibitor of PFK) as well as citrate and NADH/H+. While citrate is a weak allosteric inhibitor on its own, it acts as a strong inhibitor together with ATP. This makes sense since both molecules are indicators of free energy metabolites in the cell.
See these two publications for details:
"Allosteric regulatory properties of muscle phosphofructokinase."
Effect of citrate on the activities of 6-phosphofructokinase from
nervous and muscle tissues from different animals and its
relationships to the regulation of glycolysis.
If there is an excess of AMP/ADP then the enzyme is activated and phosphorylates Fructose-1-phosphate.
The following is multiple choice question (with options) to answer.
If citrate accumulates in mitochondria, some of it passes into where and inhibits phosphofructokinase? | [
"pores",
"cytosol",
"Golgi apparatus",
"epidermis"
] | B | |
SciQ | SciQ-1260 | astrophysics, stars, stellar-evolution
Title: Death of Stars and Red Giants As a matter of fact, I was learning stellar astrophysics where I couldn't understand the chain of events at the time of death of stars,
Once the hydrogen fuel core is exhausted, the stars start shrinking until the helium nuclei starts fusing under immense gravitational pressure. Due to powerful radiation pressure the star starts expanding. Like our sun is expected to stretch 200 times it current radius, gobbling up the Mercury and Venus planets.
Here I couldn't understand that helium fusion starts when star is shrinking, but after star starts expanding, so how could star sustain fusion $?$ I mean helium fusion requires even more pressure or temperature than hydrogen, but once star starts expanding, it become cooler and less denser, which should make fusion impossible. And during this phase of Red giant, not only helium, but more heavier nuclei are formed like oxygen which should require even more pressure and temperature.
Is there any flaw in my understanding,then please tell$!$ Please help and thanks in advance $!$ As the hydrogen fuel is exhausted, the core heat that resists gravity diminishes, so gravity takes over and compresses the star. If the star was big enough to start with, then the extra pressure from the compression is enough to enable helium fusion and the heat generated by that is enough to blow parts of the outer envelope off the star and expand it into an immense but cooler sphere. Meanwhile, the remaining inner core of the star continues to fuse helium and remains very hot, and all the heavier elements you mention get fused there as well.
The following is multiple choice question (with options) to answer.
For most of a star’s life, hydrogen atoms fuse to form what? | [
"helium atoms",
"gas atoms",
"neon atoms",
"ionic atoms"
] | A | For most of a star’s life, hydrogen atoms fuse to form helium atoms. A star like this is a main sequence star . The hotter a main sequence star is, the brighter it is. A star remains on the main sequence as long as it is fusing hydrogen to form helium. |
SciQ | SciQ-1261 | neuroscience, neurotransmitter
Most often, chloride-based channels fit into the second statement: their reversal potential is less than the spike threshold.
How Shunting Inhibition Works:
Any time you open a channel, you will shift the membrane potential towards the reversal potential for that channel. The amount of current that flows through a channel depends on the 'driving force': the difference in voltage from the reversal potential.
Let's consider a fairly typical textbook cell, with a spike threshold at -50mV, a resting potential of -65mV, and a chloride reversal at -60mV.
If the cell is at rest, and you open chloride channels (such as with GABA via GABA-A receptors), the resulting flow of current will tend to push the membrane potential towards -60mV, so the cell 'depolarizes'. However, no matter how big of a chloride conductance you open, you will never pass -60mV, so you will never reach spike threshold.
If, in that same cell, you instead opened AMPA channels, with a reversal of around 0mV, you also get depolarization, but in this case as you open more AMPA channels you can potentially depolarize the cell all the way to 0mV. Of course, unless you have blocked sodium channels you will get an action potential before you reach that point, but that's the key: you will cross threshold, therefore we call it excitatory.
Now let's consider a third case where we open both AMPA channels and GABA-A channels. As long as the membrane potential is <-60mV, both channels contribute to depolarization. However, as soon as the membrane potential is >-60mV, chloride ions will start flowing into the cell. We call this "shunting" inhibition because if you look at the sum current flow in the cell, it will look small, because you have chloride ions coming in at the same time as sodium ions, resulting in little change of the membrane potential despite lots of ions moving.
The result is that GABA-A channels, even if they can depolarize a cell that is at rest, will act to prevent the cell from depolarizing far enough to reach threshold. It's important to consider the dynamics of the membrane potential, rather than thinking of the membrane potential as something that is simply added or subtracted to instantaneously.
The following is multiple choice question (with options) to answer.
What two ways do channels respond during membrane depolarization? | [
"independently and sequentially",
"independently and typically",
"typically and sequentially",
"sequentially and identically"
] | A | |
SciQ | SciQ-1262 | organic-chemistry, physical-chemistry, biochemistry, alcohols
Title: Storage of Urine Not all may be favorable to this project, but I will explain what I am trying to do. I work at home, and instead of walking a moderate distance to the bathroom and loosing my focus, I've been, at times, peeing in a 3 Quart Poland Springs water bottle. If you take offense at this, please do not continue reading except to be helpful in the scientific goal. I know this subject won't suit many types of people, so just ignore it if that is your case.
I noticed first of all that urine is not at all as sterile as people say that it is. The rate of growth of bacteria is relatively slow, but as a precaution, I found the need to use additional measures to prevent the growth of bacteria. I settled on the following method: I have two bottles and I add to each bottle about enough salt as can be soluble in the urine and sometimes maybe a little more. The one bottle then fills up throughout the day and is emptied, washed, and refilled with salt. The salt helps to kill the bacteria which would be lingering in the empty bottle. The next day, the bottle stays empty and the other is used.
I would add that I discovered that the bacteria (without the salt) does not usually grow unless the bottle is left with urine for two days. After this, however, that same bottle (without the salt) would retain the bacteria and immediately grow, if used again.
This system works relatively well, so long as it is done every day. It will even withstand 2 days with only moderate growth. (If I should leave it by mistake for longer it can get ugly). Nevertheless, I am still looking to improve upon this. One reason is that, if I drink less water or relieve myself normally, the bottle does not fill in one day. I am looking for someone with knowledge of chemistry to help me find a substance that can be added to this solution which fits a number of common sense criteria. I will also add a list of the substances that I have tried or already considered.
Necessary qualities
The following is multiple choice question (with options) to answer.
What kind of compound, contained in coffee and alcohol, increases urine volume? | [
"additive",
"anabolic",
"acid",
"diuretic"
] | D | Diuretics and Fluid Volume A diuretic is a compound that increases urine volume. Three familiar drinks contain diuretic compounds: coffee, tea, and alcohol. The caffeine in coffee and tea works by promoting vasodilation in the nephron, which increases GFR. Alcohol increases GFR by inhibiting ADH release from the posterior pituitary, resulting in less water recovery by the collecting duct. In cases of high blood pressure, diuretics may be prescribed to reduce blood volume and, thereby, reduce blood pressure. The most frequently prescribed anti-hypertensive diuretic is hydrochlorothiazide. It inhibits the Na+/ Cl– symporter in the DCT and collecting duct. The result is a loss of Na+ with water following passively by osmosis. Osmotic diuretics promote water loss by osmosis. An example is the indigestible sugar mannitol, which is most often administered to reduce brain swelling after head injury. However, it is not the only sugar that can produce a diuretic effect. In cases of poorly controlled diabetes mellitus, glucose levels exceed the capacity of the tubular glucose symporters, resulting in glucose in the urine. The unrecovered glucose becomes a powerful osmotic diuretic. Classically, in the days before glucose could be detected in the blood and urine, clinicians identified diabetes mellitus by the three Ps: polyuria (diuresis), polydipsia (increased thirst), and polyphagia (increased hunger). |
SciQ | SciQ-1263 | immunology, reproduction, development
Title: How do Sertoli cells protect sperms? I was reading Developmental biology by Gilbert and stumbled upon a fact that Sertoli cells provide protection to the developing sperms with no futher explanation.
I googled it and found a few books mentioning that it protects sperms from cell mediated immunity and antisperm antibodies. Yet I found a website called fertilitypedia that said:
Sertoli cells do not only control the process of spermatogenesis, but they are also responsible for creating so called immunologically privileged area in the testicles. It means, that Sertoli cell manage to keep blood separated from seminiferous tubules through the connection between them, called tight junction. Tight junction keeps bloodborne substances from reaching germ cells, so all stages of germ cells are protected from the body immunity. Tight junction also keeps surface antigens found on developing germ cells from eluding into the bloodstream so no autoimmune reaction could happen. Since Sertoli cells form the block between the blood and lumen of seminiferous epithelium, they are also in control of the entry and exit of nutrients, hormones and other chemicals into the tubules of the testis.
I'm unable to verify this explanation from the cited sources as none contain the mentioned information.
So my question, how does it actually protect the sperms? The Wikipedia pages on Blood-testis barrier and Sertoli cells have some information relevant to your question, with some academic references included.
You could also search for reviews on Sertoli cells on Google Scholar - several of the first returned results seem relevant, if you are able to access them.
The following is multiple choice question (with options) to answer.
In mammals what does the zona pellucida protect? | [
"egg",
"sperm",
"fetus",
"testes"
] | A | Fertilization Fertilization, pictured in Figure 43.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. The egg and sperm each contain one set of chromosomes. To ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. In mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. When a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. In placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma. |
SciQ | SciQ-1264 | cellular-respiration
Title: Do cold blooded animals generate any heat? In explaining energy and work to an 8 year-old I said that all conversion of energy generates heat as a by-product. For example, cars generate heat in their engines and running generates heat in our bodies. Then the 8 year-old said, except for cold-blooded animals.
So my question is, do cold-blooded animals generate any heat in their conversion of stored energy (food, fat, etc) into motion? If they generate heat, why are they cold-blooded? They do generate heat. They just do not SPEND energy specifically on heating their bodies by raising their metabolisms. This is a form of energy conservation. The metabolic rate they need to live is not nearly enough to heat their bodies.
An example of spending energy to heat the body is seen in humans shivering. Here muscle is activated not for its usual purpose, but to function as a furnace. "Warm-blooded" and "cold-blooded" is somewhat a misnomer. The correct way to think of it is...
Endotherm or ectotherm. Does the heat primarily come from within (endo) or from the surroundings (ecto). Endothermic animals include mammals. Most of their body heat is generated by their own metabolisms. Ectothermic animals include reptiles and insects. They absorb most of their body heat from the surroundings. This is not the same as saying they let their body temperature fluctuate with their surroundings, some avoid this by moving around to accomodate themselves.
Homeotherm or poikilotherm. Homeotherms want to maintain homeostasis for their body temperatures. They don't want it to change. Poikilotherms do not exhibit this behaviour, instead their body temperatures vary greatly with the environment.
We can have endotherm poikilotherms, such as squirrels, who let their body temperature drop while hibernating. Endotherm homeotherms, such as humans, where temperature is constant by means of complex thermoregulation. Ectotherm homeotherms, such as snakes (moving into shadow or into the sun to regulate temperature), and ectotherm poikilotherms, such as maggots.
The following is multiple choice question (with options) to answer.
What type of vertebrates control body temperature to just a limited extent from the outside by changing behavior? | [
"endothermic",
"mimetic",
"ectothermic",
"etheric"
] | C | Early vertebrates were ectothermic. Ectothermy means controlling body temperature to just a limited extent from the outside by changing behavior. For example, an ectotherm might stay in the shade to keep cool on a hot, sunny day. On a cold day, an ectotherm might bask in the sun to warm up, like the snake in Figure below . Almost all living fish, amphibians, and reptiles are ectothermic. They can raise or lower their body temperature by their behavior but not by very much. In cold weather, an ectotherm cools down. As its body temperature drops, its metabolism slows down and it becomes inactive. |
SciQ | SciQ-1265 | human-biology, cancer, hematology
Donor-related tumors in transplant patients occur in immunosuppressed patients, but are still rare. The low frequency of transmission seems to be due, in part, to screening. The fact that we see this at all demonstrates the significance of transmission route and immune escape.
Maternal-fetal, and in utero twin-twin seem to be exceedingly rare, but have occurred, again, demonstrating the existence, but poor efficiency of transmission. Here, the fetus has an undeveloped immune system. I would not consider this case to be cancer cells causing cancer in a healthy person.
Inoculation of volunteers with tumor cells in a problematic series of experiments at Sloan Kettering in the 50s, transplantation of tumor cells into patients with other cancers, resulted in growth, recurrence after excision, and death in some cases. Transplantation into healthy volunteers (yes, they did this) resulted in nodules that spontaneously regressed. This experiment has since been interpreted as evidence for immune system control of transplanted tumor system in healthy individuals, as compared to growth and progression in a receptive niche in a cancer patient.
So person-to-person transmission of cancer cells is rare and requires an immunosuppressed or undeveloped host, or a host who already has cancer. There are no documented cases of person-to-person transmission to a healthy individual, and documented cases of failed transmission despite a surgical attempt. This is because, unlike an infectious microbe, in a healthy individual, there is not a suitable receptor for adhesion at an exposed or accessible site, a suitable environment for replication, and adaptations for immune escape by tumor cells in the original host are not effective in a new host.
As a side note, there are contagious cancers in other species, but this doesn't seem to be particularly relevant to a question about whether cancer can be transmitted between two humans. Many cancers have transmissible risk factors (e.g., human herpesvirus-8, hepatitis B and C viruses, human papilloma virus 16 and 18, and others)
The following is multiple choice question (with options) to answer.
Worldwide, viruses seem to play a role in what percentage of the cases of human cancer? | [
"15%",
"+.15 %",
"5%",
"20 %"
] | A | |
SciQ | SciQ-1266 | organic-chemistry, mixtures
Title: Would Oxygen Gas and Ozone be a pure substance together? If I have oxygen gas and ozone ($\ce{O2 + O3}$) together would it be considered a pure substance or a mixture?
And would pure substances always have the same molecular structure? Ozone is highly reactive and unstable, while dioxygen is stable. There do not combine to form a compound. So, clearly it is a mixture.
To answer the second part of the question, "And would pure substances always have the same molecular structure?", first a Wikipedia definition on substances, to quote:
A chemical substance is a form of matter having constant chemical composition and characteristic properties.[1][2]...
Chemical substances can be simple substances[4], chemical compounds, or alloys. Chemical elements may or may not be included in the definition, depending on expert viewpoint.[4]
Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water...
However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical.
And further:
A chemical substance may well be defined as "any material with a definite chemical composition" in an introductory general chemistry textbook.[5] According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. But, there are exceptions to this definition; a pure substance can also be defined as a form of matter that has both definite composition and distinct properties.[6] The chemical substance index published by CAS also includes several alloys of uncertain composition.[7] Non-stoichiometric compounds are a special case (in inorganic chemistry) that violates the law of constant composition, and for them, it is sometimes difficult to draw the line between a mixture and a compound, as in the case of palladium hydride. Broader definitions of chemicals or chemical substances can be found, for example: "the term 'chemical substance' means any organic or inorganic substance of a particular molecular identity, including – (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature".[8]
The following is multiple choice question (with options) to answer.
Elements are pure substances that make up what? | [
"Objects",
"Solids",
"all matter",
"some matter"
] | C | Elements are pure substances that make up all matter, so each one is given a unique name. The names of elements are also represented by unique one-, two-, or three- letter symbols. |
SciQ | SciQ-1267 | reproduction, digestion, sexual-reproduction
Hazardous components of pollen:
Trace amounts of hepatotoxic pyrrolizidine alkaloids were found in pollen of Echium vulgare, E. plantagineum, Senecio jacobaea, S. ovatus, and Eupatorium cannabinum (Boppre et al., 2008). In Middle and Northern Europe these pollens are not among the main pollen grains gathered by bees, however in Southern Europe the two Echium plants are more diffused and are gathered by bees in larger amounts (Campos et al., 1994; Serra Bonvehi, 1997). [Source 1] (Page 5)
Therefore, it should undergo tests to approve it's purity as allergies can be caused.
References:
1 : Future of bee pollen(Research gate)
2 : Pollen composition and standardisation of analytical methods(Research gate)
3 : Hollow pollen shells to enhance drug delivery(NCBI)
4 : Bee pollen: chemical composition and therapeutic application(NCBI)
5 : Biological activities of commercial bee pollens: antimicrobial, antimutagenic, antioxidant and anti-inflammatory(NCBI)
6 : Biological and therapeutic properties of bee pollen: a review(NCBI)
The following is multiple choice question (with options) to answer.
What reproductive part is stored in a plant's pollen? | [
"the egg",
"the sperm",
"the gamete",
"the mimic"
] | B | Plants can also reproduce sexually, but their reproductive organs are different from animals’ gonads. Plants that have flowers have their reproductive parts in the flower. The sperm is contained in the pollen, while the egg is contained in the ovary, deep within the flower. The sperm can reach the egg two different ways:. |
SciQ | SciQ-1268 | star, luminosity, helium
Title: What is the most appropriate way to estimate the helium composition of a star? Say we have to estimate the helium content in Proxima Centauri.
We begin by calculating the content of helium in the Sun (source): $24.85$% of $2.10^{30}$ kg.
Mostly all the energy is generated due to the product of nuclear fusion of hydrogen into helium by way of the proton–proton (PP) chain mechanism and the luminosity of Proxima Centauri is $0.00005\ L_☉$.
Thus, would it be a good approximation to say that the helium content is $0.00005 * 0.2485 * 2 * 10^{30}$?
Would you suggest a better way of estimating the helium content? Nearly all the helium in the photosphere of the sun comes from the helium in the interstellar gas that collapsed to form the sun. That helium was produced shortly after the Big Bang (in about the first 20 minutes) while the universe was hot and dense enough for hydrogen to fuse to helium. That produces a universe in which ordinary matter is about 25% helium and 75% hydrogen. (by mass) Over the eons, the gas is enriched in helium somewhat by previous stars to about 27% helium.
The outer layers of the sun still have this 25%-75% composition. Some of the helium has settled under gravity, reducing the composition of the photosphere to your 24.85% helium. The core is enriched in helium by fusion reactions. It isn't constant. The outer core is about 30% helium. The inner core has as much as 65% helium. The average composition is about 28% helium, only slightly more than what it started with.
Proxima Centauri is fully convective, which means that helium from the core gets mixed up through the whole star. But it is such a dim candle that it has hardly produced any more helium than when it formed: about 27%.
So for any star, no matter how bright or dim (with a few exceptions) the helium composition is about 25%, or a little more.
The following is multiple choice question (with options) to answer.
Atoms of what element ultimately form in a red supergiant? | [
"steel",
"iron",
"coal",
"gold"
] | B | In a red supergiant, fusion does not stop. Lighter atoms fuse into heavier atoms. Eventually iron atoms form. |
SciQ | SciQ-1269 | organic-chemistry, food-chemistry, fats
Title: Saturated vs unsaturated fats - Structure in relation to room temperature state? I'm sure most of us have heard that saturated fats are solid at room temperature, and unsaturated fats are liquid at room temperature. I'm wondering how this relates to their chemical structure -- saturated fats contain only single bonds between carbons, yet to qualify as an unsaturated fat a C=C double bond must exist.
Since a double bond is stronger than a single bond, and the length of the C=C double bond is shorter than that of the single bond, why is it that the fat containing a double bond is a liquid and saturated fats are solids at room temperature? Seems like the double bond would inhibit movement and the resulting substance would be less like olive oil and more like butter. In the solid state, the individual triacylglycerol molecules are interacting with each other primarily through Van der Waals interaction. These weak bonds between molecules are broken at the solid-liquid transition. The amount of energy needed to disrupt these interactions (which determines the melting point of the fat or oil) is determined by the energy associated with all of these bonds added together. In a saturated fat, the acyl chains are able to align perfectly right along their length, maximizing intermolecular interactions. This effect is reflected in the fact that the melting temperature of a pure triacylglycerol increases as the chain length increases.
You can see this effect clearly in the melting temperatures of individual fatty acids. (C18:0 means an 18 carbon molecule with zero double bonds in the acyl chain):
C18:0 (stearic acid) 70°C
C16:0 (palmitic acid) 63°C
C14:0 (myristic acid) 58°C
So the addition of a single -CH2- group in the acyl chain increases melting temperature by a few degrees.
When a cis double bond is introduced into the acyl chain this creates a kink in the structure. Because of this, the acyl chains cannot align completely along their length - they don't pack together as well. Because of this, the sum of the energy associated with intermolecular Van der Waals interactions is reduced. Again this is seen clearly in the melting temperatures of fatty acids:
stearic acid C18:0 70°C
oleic acid C18:1 16°C
The following is multiple choice question (with options) to answer.
What are the two types of fats? | [
"full and empty",
"saturated and unsaturated",
"liquid and solid",
"thick and thin"
] | B | Fats may be either saturated or unsaturated. A saturated fat is a fat that consists of triglycerides whose carbon chains consist entirely of carbon-carbon single bonds. Therefore, the carbon chains are saturated with the maximum number of hydrogen atoms possible. An unsaturated fat is a fat that consists of triglycerides whose carbon chains contain one or more carbon-carbon double bonds . A fat with one double bond is called monounsaturated, while a fat with multiple double bonds is called polyunsaturated (see Figure below ). |
SciQ | SciQ-1270 | embryology
Title: Is endoderm visible in the germ layer? This picture is my drawing about germ layer - not embryonic folding as I wrote initially.
Where exactly is the endoderm here in the picture?
The known things
Ectoderm
Neural tube
Notochord
Endoderm - Where is this?
Somite
Somite leg
Intraembryonic coelom
Embryonic somatopleura
Embryonic splanchopleura (lateral mesoderm)
Endoderm
Mesoderm (intraembryonic) I think you're going for a view of tube formation, in which case, here's a good image:
Lateral plate mesoderm
Intermediate mesoderm
Somite mesoderm
Chorda
Endoderm
(Reference)
Again in your drawing I think you correctly have it labeled as 10, and don't really need to put it twice.
The following is multiple choice question (with options) to answer.
What structure consists of an outer layer of cells called the trophoblast and an inner cell mass called the embryoblast? | [
"nucleus",
"cell wall",
"cytoplasm",
"blastocyst"
] | D | Blastocyst. The blastocyst consists of an outer layer of cells called the trophoblast and an inner cell mass called the embryoblast. The blastocyst fluid-filled cavity is also known as the blastocoel or blastocoele. |
SciQ | SciQ-1271 | biochemistry
This explanation provides a somewhat agreement of Le Chatlier’s principle. (i.e. where a dynamic equilibrium is affected by changing conditions, the position of equilibrium moves to counteract the change)
Consider this simple hypothesis:
J = vf – vr
Since a metabolic pathway is a series of enzyme-catalysed reactions,
it is easiest to describe the flux of metabolites through the pathway
by considering its reaction steps individually. The flux of
metabolites, J, through each reaction step is the rate of the forward
reaction, vf, less that of the reverse reaction, vr:
At equilibrium, by definition, there is no flux (J=0), although vf and
vr may be quite large. At the other extreme, in reactions that are far
from equilibrium, vf>> vr, so that the flux is essentially equal to
the rate of the forward reaction, J~vf.
The flux throughout a steady-state pathway is constant and is set (generated) by the pathway’s rate determining step (or steps).
Consequently, control of flux through a metabolic pathway requires:
that the flux through this flux-generating step vary in response to the organism’s metabolic requirements and
that this change in flux be communicated throughout the pathway to maintain a steady state
The following is multiple choice question (with options) to answer.
Metabolic pathways are a series of reactions catalyzed by multiple what? | [
"enzymes",
"particles",
"vitamins",
"hormones"
] | A | Figure 4.11 Metabolic pathways are a series of reactions catalyzed by multiple enzymes. Feedback inhibition, where the end product of the pathway inhibits an upstream process, is an important regulatory mechanism in cells. |
SciQ | SciQ-1272 | 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.
What causes eutrophication to occur? | [
"excess of carbonate and other nutrients",
"excess of increased and other nutrients",
"excess of decreased and other nutrients",
"excess of fertilizers and other nutrients"
] | D | Fertilizer in runoff leads to algal blooms and dead zones in bodies of water. This type of pollution is called nonpoint-source pollution. Point-source pollution includes waste water from factories and sewage treatment plants. Hot water discharge causes thermal pollution. |
SciQ | SciQ-1273 | mechanical-engineering, thermodynamics, heat-transfer, chemistry, heat
Title: In case of solvation , Who converts gaseous ions to aqueous ? Why do we even have gaseous but not solid ions? We take Nacl and dissolve it in water. There is formation of $Na^+$ and $Cl^-$ gaseous ions along with 2H+ and $Cl^{2-}$ aqueous ions.
Then , Na+ is attracted towards $Cl^{2-}$ and 2H+ is attracted towards $Cl^-$ ions.
Energy required by water molecules to separate the NaCl molecules is knows as Lattice enthalpy.
Energy required to form aqueous NaCl molecule is called hydration enthalpy.
My questions are:
Who is the one that converts gaseous ions of NaCl to aqueous ions?
During the dissolution of NaCl, why is there no formation of solid ions first but directly, it states that gaseous ions of NaCl are formed?
Also We define reactions uniquely depending on the reactants and products. Here are examples related to your question.
Formation: Na(s) + (1/2)Cl$_2$(g) $\rightarrow$ NaCl(s)
Lattice Formation: Na$^+$(g) + Cl$^-$(g) $\rightarrow$ NaCl(s)
Solution: NaCl(s) $\rightarrow$ NaCl(aq)
Hydration: Na$^+$(g) $\rightarrow$ Na$^+$(aq)
Atomization: Na(s) $\rightarrow$ Na(g)
A significant observation here is that the STATE of the reactants and products is also required because it is a unique identifier.
As to your questions ...
Who is the one that converts ...
We can convert NaCl(s) to gaseous ions experimentally through processes that may involve multiple steps, including vaporization and ionization.
During the dissolution of NaCl(s), why is there no formation of solid ions first but directly, it states that gaseous ions of NaCl are formed?
The following is multiple choice question (with options) to answer.
What do you call the separation of ions that occurs when a solid ionic compound dissolves? | [
"dissolution",
"decomposition",
"deformation",
"dissociation"
] | D | An ionic crystal lattice breaks apart when it is dissolved in water. Dissociation is the separation of ions that occurs when a solid ionic compound dissolves. It is important to be able to write dissociation equations. Simply undo the crisscross method that you learned when writing chemical formulas of ionic compounds. The subscripts for the ions in the chemical formulas become the coefficients of the respective ions on the product side of the equation. Shown below are dissociation equations for NaCl, Ca(NO 3 ) 2 , and (NH 4 ) 3 PO 4 . |
SciQ | SciQ-1274 | optics, visible-light, wavelength
Title: Why we can't see objects smaller than wave length of light? I would like to ask, why we can't see objects smaller than wave length of light under traditional microscope. I know that there is some way to see them and the scientists who discover this.
Why we can't see objects smaller than wave length of light?
And who were these scientists?
I would like to ask, why we can't see objects smaller than wave length of light under traditional microscope.
The wavelength of light is any wavelength. There's visible light (which is what I think you mean) and then there's every possible wavelength above and below that.
Our eyes don't detect light (electromagnetic radiation) outside of the visible region (hence the name :-)) but we can use and do machines to detect these wavelengths and you've probably experienced them : X-ray machines, UV lights for security purpose, infra-red lights for remote controls.
Whatever wavelength you use is going to diffraction limited for resolution. As this detailed article explains, the limit for resolution (and that's assuming everything else is optimal) is about half the wavelength used.
Optical microscopes are designed for the visible wavelengths of light and focus light outside of this region well. You can use special optics designed for that purpose if your interest is outside of visible light.
The development and use of microscopes, not just visible light microscopes, is called Microscopy. That link should provide you with enough information to start with.
I know that there is some way to see them and the scientists who discover this.
Beyond light microscopes, scientists developed the electron microscope and later the scanning tunneling microscope. The principles of these devices are explained at those links.
The 1986 Nobel prize for Physics was shared between three people for their work on these inventions. Another man, Hans Busch, had made a major contribution to the design of the electron microscope but died in 1984 and the Nobel Prize is never awarded posthumously, so even if the committee had thought it appropriate to award him, the rules would have forbidden it.
The following is multiple choice question (with options) to answer.
What is light with wavelengths shorter than visible light called? | [
"radio waves",
"ultraviolet light",
"weathering light",
"infrared light"
] | B | Light with wavelengths shorter than visible light is called ultraviolet light . The term ultraviolet means “above violet. ” Ultraviolet light is the range of light waves that have shorter wavelengths and higher frequencies than violet light in the visible range of light. With higher frequencies than visible light, ultraviolet light has more energy. It can be used to kill bacteria in food and to sterilize surgical instruments. The human skin also makes vitamin D when it is exposed to ultraviolet light. Vitamin D, in turn, is needed for strong bones and teeth. You can learn more about ultraviolet light and its discovery at this URL: http://www. youtube. com/watch?v=QW5zeVy8aE0. |
SciQ | SciQ-1275 | radiation, material-science, radioactivity
Title: Working out the penetration of radioactive decay products From my understanding of the products of radioactive decay (alpha particles, beta particles, and gamma are all I know of), the particles (or energy I guess?) are stopped by a medium according to it's density, and the atomic size of the atoms that make it up (I could quite easily be wrong). Without conducting an experiment, how would you calculate how far the three types of radioactive decay can travel through a certain material, knowing only the material's density (or any other documentable property)? We take into account the inelastic interactions that take place between the respective type of particle and the material, i.e. interaction that can consume part of the energy of the radiation particle, and calculate the mean-free path of the respective type of particle in the material. In this calculus we also consider the density and the structure of the material. In general, for particles with rest-mass, the higher is the velocity, the lower is the cross section of interaction with the material, and longer the free path in it. But the charge of the particle and mass are also relevant. For instance, $\alpha$ particles although very energetic, have low velocities, are highly ionizing and can travel only a few centimeters in air.
The opposite example are $\gamma$ rays. The higher is their energy the harder is to stop them. Before being finally being absorbed by some photoelectric event or pair production (for energy > 1.02Mev), they can interact a lot on the way by Compton scattering. Thick walls of concrete are needed to stop them, or isolation by lead layers. $\beta$ radiation has intermediate properties.
The following is multiple choice question (with options) to answer.
How much distance can beta particles travel through air? | [
"inches",
"density",
"meter",
"centimeters"
] | C | Beta particles can travel up to a meter through air. They can pass through paper and cloth but not through a sheet of aluminum. They can penetrate and damage tissues beneath the skin. |
SciQ | SciQ-1276 | 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 is created when the warm air at the cold front rises and creates a low pressure cell, causing winds to rush into the low pressure? | [
"rising air column",
"Hurricane",
"Wind pressure",
"Tornado"
] | A | The warm air at the cold front rises and creates a low pressure cell. Winds rush into the low pressure. This creates a rising column of air. The air twists, rotating counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Since the rising air is moist, rain or snow falls. |
SciQ | SciQ-1277 | human-biology, physiology, endocrinology, vitamins, homeostasis
Title: Counterintuitive action of Vitamin D? Vitamin D acts in a way which to me is counterintuitive. It functionally supplemets Parathormone. It in the intestinal tract steps up calcium absorption by altering nuclear gene expression and also prevents calcium excretion in kidneys. All of this is understandable. But it also, like parathormone, steps up osteoclast action in bone (actually steps up both osteoclast and osteoblast, but the osteoclast action is increased more to result in net bone resorption). This means that Vitamin D increases blood calcium level by increasing bone resorption.
Then how does Vitamin D help in improving bone density, bone strength and prevent rickets or osteoporosis? All of these would require bone deposition rather than resorption. There are two pieces to this question:
a) How does bone resorption (movement of Ca/Phos out of bone into the blood) result in net improvement in bone structure?
Bones are constantly remodeling, primarily in response to mechanical stressors. Although you clearly already realize this, I will make it explicit: osteoblasts are the cells that create new bone; osteoclasts break down (resorb) bone.
Quoting Harrison’s Internal Medicine1:
Radioisotope studies indicate that as much as 18% of the total skeletal calcium is deposited and removed each year. Thus, bone is an active metabolizing tissue.…The cycle of bone resorption and formation is a highly orchestrated process carried out by the basic multicellular unit, which is composed of a group of osteoclasts and osteoblasts
The following is multiple choice question (with options) to answer.
People with osteoporosis have an increase risk of what? | [
"cancer",
"weight loss",
"bone fractures",
"muscle loss"
] | C | People with osteoporosis have an increased risk of bone fractures. A bone fracture is a crack or break in bone. Even if you have healthy bones, you may fracture a bone if too much stress is placed on it. This could happen in a car crash or while playing a sport. Wearing a seatbelt when you ride in a motor vehicle and wearing safety gear when you play sports may help prevent bone fractures. |
SciQ | SciQ-1278 | zoology, circulatory-system, heart-output, amphibians
I would add to this my notes from when I was a biochem student (but studied Zoology), mentioning the arterial cone and a spiral valve. This is better described in Britannica:
The conus arteriosus is muscular and contains a spiral valve. Again, as in lungfishes, this has an important role in directing blood into the correct arterial arches. In the frog, Rana, venous blood is driven into the right atrium of the heart by contraction of the sinus venosus, and it flows into the left atrium from the lungs. A wave of contraction then spreads over the whole atrium and drives blood into the ventricle, where blood from the two sources tends to remain separate. Separation is maintained in the spiral valve, and the result is similar to the situation in lungfishes. Blood from the body, entering the right atrium, tends to pass to the lungs and skin for oxygenation; that from the lungs, entering the left atrium, tends to go to the head. Some mixing does occur, and this blood tends to be directed by the spiral valve into the arterial arch leading to the body.
The following is multiple choice question (with options) to answer.
What is the main artery of the systematic circulation called? | [
"femoral",
"aorta",
"carotid",
"subclavian"
] | B | Blood Vessels The blood from the heart is carried through the body by a complex network of blood vessels (Figure 16.12). Arteries take blood away from the heart. The main artery of the systemic circulation is the aorta; it branches into major arteries that take blood to different limbs and organs. The aorta and arteries near the heart have heavy but elastic walls that respond to and smooth out the pressure differences caused by the beating heart. Arteries farther away from the heart have more muscle tissue in their walls that can constrict to affect flow rates of blood. The major arteries diverge into minor arteries, and then smaller vessels called arterioles, to reach more deeply into the muscles and organs of the body. Arterioles diverge into capillary beds. Capillary beds contain a large number, 10’s to 100’s of capillaries that branch among the cells of the body. Capillaries are narrow-diameter tubes that can fit single red blood cells and are the sites for the exchange of nutrients, waste, and oxygen with tissues at the cellular level. Fluid also leaks from the blood into the interstitial space from the capillaries. The capillaries converge again into venules that connect to minor veins that finally connect to. |
SciQ | SciQ-1279 | special-relativity
Title: Rearrangement of length contraction formula I have just learnt that an object appears shorter in length when viewed by an observer in relative motion with respect to the object. We can derive this with Lorentz transformation formulas, and that's where my doubt lies. If a rod is moving with velocity $v$ with respect to a frame $S$, and another frame $S'$ is moving in the same direction as the rod with respect to $S$ with the same velocity $v$, then the length measured by an observer in frame $S'$ will be the proper length, as the observer is at rest with respect to the rod. Let $x',y' and\,z'$ be the coordinate axis of $S'$ and $ x,y\,and\, z$ be the coordinate axis of the frame $S$. Therefore, we can write the proper length $L_\circ = x_2' - x_1'$. We can also find the value of length as seen from the frame $S$, i.e., $L=x_2 - x_1$, if we put the values of $x_2'\, and \, x_1'$ from the formula $x'=\gamma(x-vt)$ (Inverse Lorentz Transformation) in $L_\circ=x_2' - x_1'$, as the term containing the variables $t_1 \,and \,t_2$ will cancel out because $t_1=t_2$. The result will come out to be $L_\circ=\gamma L$ or simply $L= \frac{L_\circ}{\gamma}$. My question is that when we put the value of $x$ directly in the formula $L=x_2 - x_1$ as $ x= \gamma(x' + vt')$, and then calculate, the result comes out to be $L=\gamma L_\circ$, quite the opposite of what we got earlier. Is there something that I am doing wrong here? It is important to keep in mind that $S$ can determine the length of the moving rod only when he measures the two end points of the rod at the same time in his reference frame : this is why we take
The following is multiple choice question (with options) to answer.
The length that an object has travelled in one or multiple directions can also be called what? | [
"velocity",
"axis",
"distance",
"range"
] | C | The length traveled by an object moving in any direction or even changing direction is called distance. |
SciQ | SciQ-1280 | biochemistry, physiology, cell-biology
Title: What triggers meiosis in gonadal cells? What specific biochemical processes are involved in inducing meiosis rather than mitosis? Why are gonadal cells the only cells in the human body which do undergo meiosis?
What specific biochemical processes are involved in inducing meiosis rather than mitosis?
It's a difficult question because every step in the development of a germ cell is ultimately necessary for the final differentiation, which includes a meiotic division. Meiosis requires a lot of specialized components to pair and segregate homologues, to induce and resolve recombination, etc. What starts it all is still largely unknown. There are plenty of mutants that halt the process, but these are required along the way, so damaging the pathway ultimately stops it from progressing. At least one study has been able to initiate the program of meiosis in yeast:
Induction of meiosis in Saccharomyces cerevisiae depends on conversion of the transcriptional represssor Ume6 to a positive regulator by its regulated association with the transcriptional activator Ime1. I Rubin-Bejerano, S Mandel, K Robzyk, and Y Kassir
Basically, they turned on a transcription factor, which activated an entire suite of downstream genes necessary for meiosis. In essence, they turned on the "meiosis pathway." Bear in mind this is yeast, so does't have separate germ cells, but the concept is probably the same.
Why are gonadal cells the only cells in the human body which do undergo meiosis?
All other cells are diploid. Only in germ cells does the organism induce reductional divisions (to make haploid gametes for ultimate fusion in the zygote of the next generation). Creation of haploid somatic cells would uncover recessive lethal mutations and cells would die. In sperm and eggs, which do not express any genes until after fertilization and karyogamy, this is not a problem.
The following is multiple choice question (with options) to answer.
In animals, what process occurs only in germ cells, which are in the ovaries or testes? | [
"mitosis",
"electrolysis",
"reproduction",
"meiosis"
] | D | |
SciQ | SciQ-1281 | aromatic-compounds, molecular-orbital-theory
Title: How are the electrons of benzene actually configurated? I found this diagram:
According to it, it is not true that the six electrons of carbons in the pi-orbitals above the ring are all identical.
But, how can it be the case, seeing that this molecule should have an order-6 rotational symmetry? So, as I told you in chat what you have here is the orbitals of something which looks like, but which is not, benzene. It is the orbitals of one the all its two mesomeric form, it is so a static view.
Now let me show you the orbitals which are in the benzene. I only draw with the p-orbitals, I won't do the hybridation with the hydrogen it will be too difficult for me two draw and it will not be more effective.
How to draw a molecular diagram when the molecule has a lot of atoms?
First draw the diagram like if in the molecule there is just its squeleton (atoms which interact to create the shape of the molecule, for example with benzene only for the carbon atoms) and do like if these atoms were hydrogen atoms.
Second draw the correct orbitals with the same symetry of what you got with hydrogen just before.
You are obviously not obliged to do it but it is easier to see which orbitals in the fragments have the same symetry or not.
First step
Here for the benzene I will draw the MO's diagram of benzene with $\ce{H_6}$ first, with a molecule which is a rectangle of hydrogen atoms and the other fragment is a longer dihydrogen molecule than the original one. After seeing which of them have the good symetries I get this
Second step
Here we want the same but with the p-orbital of the carbons so keeping the same symetries or antisymetries you get this
And then here you have the correct orbitals.
Be careful
The color on the orbitals represent the sign of the wave function which has no meaning in the reality. So you can make the black and the white anywhere you want if you obviously respect the molecule symetries.
In this example I draw exactly the same orbital.
The following is multiple choice question (with options) to answer.
Which theory describes the benzene molecule and other planar aromatic hydrocarbon molecules as hexagonal rings of sp2-hybridized carbon atoms with the unhybridized p orbital of each carbon atom perpendicular to the plane of the ring? | [
"hybrid orbital theory",
"molecular orbital theory",
"valence bond theory",
"covalent bond theory"
] | C | Valence bond theory describes the benzene molecule and other planar aromatic hydrocarbon molecules as hexagonal rings of sp2-hybridized carbon atoms with the unhybridized p orbital of each carbon atom perpendicular to the plane of the ring. Three valence electrons in the sp2 hybrid orbitals of each carbon atom and the valence electron of each hydrogen atom form the framework of σ bonds in the benzene molecule. The fourth valence electron of each carbon atom is shared with an adjacent carbon atom in their unhybridized p orbitals to yield the π bonds. Benzene does not, however, exhibit the characteristics typical of an alkene. Each of the six bonds between its carbon atoms is equivalent and exhibits properties that are intermediate between those of a C–C single bond and a C = C double bond. To represent this unique bonding, structural formulas for benzene and its derivatives are typically drawn with single bonds between the carbon atoms and a circle within the ring as shown in Figure 20.11. |
SciQ | SciQ-1282 | climate-change, sea-level
Here you can clearly see how, with some ups and downs, the rate of sea level rise have been increasing over the last few centuries. And notably the current rate, about 20 years after the end of this plot is already out of the scale, and around 3.2 mm/year as pointed also by other answers.
I would highlight the following from their abstract:
Sea level rose by 6 cm during the 19th century and 19 cm in the 20th
century.Superimposed on the long-term acceleration are quasi-periodic
fluctuations with a period of about 60 years. If the conditions that
established the acceleration continue,then sea level will rise 34 cm
over the 21st century. Longtime constants in oceanic heat content and
increased ice sheet melting imply that the latest
Intergovernmental Panel on Climate Change (IPCC) estimates of sea
level are probably too low.
Regarding to whether this is caused by humans or not, I rather stay out of that argument and point that our best science and models suggest that lowering $\text{CO}_2$ emissions can make a significant impact in slowing down sea level rise in the upcoming centuries, so we should ACT NOW, and stop arguing whether it was or not our fault in the first place.
The following is multiple choice question (with options) to answer.
What type of carbon dioxide levels have been rising for the past several decades? | [
"magnetic",
"atmospheric",
"subatomic",
"aqueous"
] | B | Atmospheric carbon dioxide levels have been rising for the past several decades. |
SciQ | SciQ-1283 | meteorology, precipitation, clouds, snow, severe-weather
Title: Snow from Fire: Could graupel, or even snow, fall from pyrocumulus clouds? Pyrocumulus clouds often form in areas that experience prolonged fire conditions, particularly forest fires, but are also associated with volcanic eruptions and even nuclear explosions. This question focuses on forest fire origins.
An example of what one looks from above, is below:
Caption: Pyrocumulus cloud, above the Oregon Gulch fire in Oregon & California, 2014. Aircraft is a F-15C Eagle. Image source
The general idea of how pyrocumulus clouds are formed is quite well known, and its relationship with a 'firestorm' is, in a simplistic way, is shown below:
Caption: Firestorm: fire (1), updraft (2), strong gusty winds (3) (A) pyrocumulonimbus cloud.Image source
Pyrocumulus and related pyroconvective clouds have been known to have caused severe hail to fall. An example reported in the Earth Observatory: Russian Firestorm: Finding a Fire Cloud from Space, from the Canberra, Australia fires:
Called pyrocumulonimbus clouds, the clouds are capable of dangerous lightning, hail, and strong winds. One such firestorm in 2003 pelted Canberra, Australia, with large, soot-darkened hail, produced a damaging tornado
The following is multiple choice question (with options) to answer.
Freezing rain that falls from the sky is also called? | [
"snowfall",
"hail",
"sleet",
"fog"
] | C | |
SciQ | SciQ-1284 | newtonian-mechanics, waves, interference
Title: Interaction of two sound emitting particles in a medium Consider a free particle at rest suspended in an infinite medium.
If the particle becomes the source of a sound wave in one direction, will the particle start to move in the opposite direction due to an opposing force from the produced wave?
If the particle instead produces that wave in all directions, will the particle stay at rest because of the cancellation of the forces?
If a similar particle (i.e., producing a sound wave in all directions) is placed in the vicinity of the original particle, I want to know if there will be any kind of interaction between the two particles because of interference of the two waves. Specifically, will the particles repel each other, or attract each other, or absolutely nothing will happen and they’ll continue to stay at rest? Our source particle is unique. Its driving the medium. It is the origin of the vibrations that have now spread out in the medium. It decides its state.
Consider the unidirectional case. Since it acts on the medium, the medium pushes back. For sound waves, this means that as the particle moves to compress its surroundings, it increases the pressure in the medium in its neighborhood. The increased pressure then pushes back. Similarly for rarefaction.
This is similar to the movement of air in a half-pipe being driven at the closed end. There is clearly pressure variation from the vibrating air at the closed end.
For the omnidirectional case, I fail to see how a single point particle can generate omnidirectional sound waves.
Lets say the particle isn't really a point particle but has some size. The net force due to the surrounding air on such a 'throbbing' particle is zero by isotropy, but the pressure isn't. So its sound would still have the characteristics of the unidirectional case, without any motion of the particle's center of mass, though I won't characterise it as "not moving". (remember that in the unidirectional case, the particle moves).
So the net motion of the source particle is determined by the reaction of the medium and the force driving it. In this, it acts as a driven oscillator. I think the sound waves will show resonance.
The following is multiple choice question (with options) to answer.
Do waves move faster when particles are close to each other or far away? | [
"open",
"unaffected",
"far away",
"close"
] | D | The speed of most waves depends on the medium through which they are traveling. Generally, waves travel fastest through solids and slowest through gases. That’s because particles are closest together in solids and farthest apart in gases. When particles are farther apart, it takes longer for the energy of the disturbance to pass from particle to particle. |
SciQ | SciQ-1285 | entomology, ant
Title: In an ant (or bee) colony, what is the very approximate ratio of new breeders to workers? For example, out of every 1000 eggs laid, X mature into drones and/or virgin queens. That seems impossibly precise but it illustrates the kind of number I want well. I'll accept answers for any species and any number of species, even one, with any amount of precision or lack thereof, because right now I can't even feel confident saying that there are more workers or more breeders, though I obviously suspect more workers.
I would also be ecstatic to have any live count just before the nuptial flight, i.e. for this colony in this study there were X workers, Y drones, and Z virgin queens just before the nuptial flight, or X workers and (Y+Z) breeders, or X% of the colony was breeders, or for this species on average X% are breeders just before the nuptial flight.
Anything. Any one thing and I can accept it as an answer.
I can find any number of studies that talk about the sex ratio between drones and virgin queens, so I know someone is counting. Maybe I'm not reading closely enough, but they always seem to slip away from giving all the numbers I need to figure this out for myself. So.
This answer is specific to the western honeybee, Apis mellifera, as there are massive amounts of data on them; more, possibly, than any other insect species. There has certainly been more data collected about them than any other hymenopteran.
At around the time of the nuptial flight, there may be as many as 60,000 workers in the hive, though likely number is more like 15,000 - 20,000. There will be either one (virgin) or two (one mated, one virgin) queens (the old queen will stay with the hive, if she is alive). There may be as many as 400 drones from the original colony (though usually the number is less, around 150 is typical; 10 - 50 of them will actually mate with the queen), and an equal number may join in the flight drawn from other colonies, especially in commercial beekeeping operations. Somewhere between 1000 - 6000 workers will take part in the nuptial flight with the virgin queen and the drones.
The following is multiple choice question (with options) to answer.
Adult bees include workers, a queen and what other type? | [
"soldiers",
"drones",
"builders",
"laborers"
] | B | Look at the honeybees in Figure below . Honeybees live in colonies that may consist of thousands of individual bees. Generally, there are three types of adult bees in a colony: workers, a queen, and drones. |
SciQ | SciQ-1286 | geology, paleontology, dating, history-of-science
Title: Did geologists determine the age of rocks and fossils before the advent of modern scientific dating methods? Did geologists determine the age of rocks and fossils before the advent of modern scientific dating methods such as radiometric, electron spin resonance and thermoluminescence?
If they did, does anyone know how they went about it? The approach adopted by Charles Lyell (and other writers in a similar timeframe), in his book 'Principles of Geology' which was first published in the 1830s was to look at processes in the modern landscape where the rate of change could be determined by observation or from historical evidence, and assuming that similar processes operated at similar rates in the geological past. So, for instance, if you measure the amount of sediment transported by a river today, and you measure the volume of sediment in that river's delta, you can estimate how long that delta took to form. If you see a similar delta in the geological record, you can assume it took a similar time to form. Lyell's estimates of the age of the earth were low, but as the concept of plate tectonics, with it's progressive recycling of rocks through subduction wasn't recognised, it was remarkably prescient.
The following is multiple choice question (with options) to answer.
Name the law that determines as to which rock layers are younger or older than others. | [
"law of apposition",
"geologic theory",
"law of gravity",
"law of superposition"
] | D | In this lesson, you read how scientists determine the relative ages of sedimentary rock layers. The law of superposition determines which rock layers are younger or older than others. |
SciQ | SciQ-1287 | electromagnetism, electrostatics, electric-fields, conventions, point-particles
Title: Direction of the electric field of a negative point charge? How can the direction of the electric field of a negative point charge be going in towards itself (radially), when the charge itself is generating the electric field? Is it generated at infinity then? Because if it's generated by the charge then it cannot go further in towards itself?
In case of positive charge, it is understandable that the field is being generated at the charge (at it's surface to be precise) and is going outwards radially. There is no "going" going on in field-line diagrams. The direction of the field lines indicates, by convention, the direction of the electrostatic force experienced by a positive test charge at that location.
Field lines do not indicate the 'flow' of any physical quantity, and there is nothing being 'generated'; instead, all you have is a force field, and ways to study and analyze it. This extends to the concept of electric flux (i.e. for a given surface $S$, the integral $\iint_S\mathbf E\cdot\mathrm d\mathbf S$): we call it 'flux' by analogy, but there's nothing at all actually 'flowing'; instead, it is just one more tool to understand and analyze the force field and the laws that govern it.
For more on field lines, see Why does the density of electric field lines make sense, if there is a field line through every point?.
The following is multiple choice question (with options) to answer.
Since the electric field lines point radially away from the charge, they are perpendicular to what? | [
"equipotential lines",
"archetypical lines",
"singularity lines",
"magnetic field lines"
] | A | 19.4 Equipotential Lines We can represent electric potentials (voltages) pictorially, just as we drew pictures to illustrate electric fields. Of course, the two are related. Consider Figure 19.8, which shows an isolated positive point charge and its electric field lines. Electric field lines radiate out from a positive charge and terminate on negative charges. While we use blue arrows to represent the magnitude and direction of the electric field, we use green lines to represent places where the electric potential is constant. These are called equipotential lines in two dimensions, or equipotential surfaces in three dimensions. The term equipotential is also used as a noun, referring to an equipotential line or surface. The potential for a point charge is the same anywhere on an imaginary sphere of radius r surrounding the charge. This is true since the potential for a point charge is given by V = kQ / r and, thus, has the same value at any point that is a given distance r from the charge. An equipotential sphere is a circle in the two-dimensional view of Figure 19.8. Since the electric field lines point radially away from the charge, they are perpendicular to the equipotential lines. |
SciQ | SciQ-1288 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
What are in leaves that function as solar collectors and food factories? | [
"fibroblasts",
"chloroplasts",
"cellulose",
"vacuoles"
] | B | Leaves are rich in chloroplasts that function as solar collectors and food factories. The first leaves were very small, but leaves became larger over time. |
SciQ | SciQ-1289 | reproduction
Excerpts from the references that lead to the short answer above:
In the developing female fetus, oogonia become primary oocytes that begin the first division of meiosis. However, this division is not completed and the primary oocytes remain “frozen” in the prophase stage of the first meiotic division.
At birth, oogonia are no longer present. Each primary oocyte is surrounded by a single layer of squamous epithelial cells called follicular cells. The primary oocyte together with its follicular cells is called a primordial follicle. There are about two million primordial follicles with their primary oocytes in the ovaries at birth suspended in the first division of meiosis.
As the female grows, primary oocytes begin to die and disappear with their follicular cells. This process continues until puberty when there are only about 400,000 primordial follicles left in the ovaries. The primary oocytes continue the process of oogenesis after puberty begins.[Source]
The total number of primary oocytes at birth is estimated to vary from 700,000 to2 million. During childhood most oocytes become atretic; only approximately400,000 are present by the beginning of puberty, and fewer than 500 will be ovulated.[Source]
Primary oocytes reach their maximum development at ~20[6] weeks of gestational age, when approximately seven million primary oocytes have been created; however, at birth, this number has already been reduced to approximately 1-2 million.Recently, however, two publications have challenged the belief that a finite number of oocytes are set around the time of birth.[Source]
In the human embryo, the thousand or so oogonia divide rapidly from the second to the seventh month of gestation to form roughly 7 million germ cells.[Source]
REFERENCES:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0008772
The following is multiple choice question (with options) to answer.
What is the process of producing eggs in the ovary is called? | [
"morphogenesis",
"oogenesis",
"meiosis",
"gametogenesis"
] | B | The process of producing eggs in the ovary is called oogenesis. Eggs, like sperm, are haploid cells, and their production occurs in several steps that involve different types of cells, as shown in Figure below . You can follow the process of oogenesis in the figure as you read about it below. |
SciQ | SciQ-1290 | human-biology, reproduction, reproductive-biology
Also condom is not a modern mechanism it was used in ancient times, but the usage was to protect oneself from sexually transmitted diseases, but an unknown chemical used which is a spermicide and this resulted in contraception.
Records of condom use dates back to 3000 B.C. where King Minos of Crete, son of Zeus and Europa, utilized the bladders of goats to protect himself during intercourse.
In the 1500s, a syphilis epidemic spread across Europe. It was at this time that Gabriel Fallopius,created a linen
condom as a means to protect from the continuing spread of disease . This proved especially effective when soaked in an unknown chemical solution acting as a spermicide.
Reference
The medieval contraception methods includes,
Condoms
Female Barrier Methods
Herbs and Rituals
Intrauterine devices
Male methods
The Pill
These methods are widely described in this article.
The following is multiple choice question (with options) to answer.
What term refers to the deliberate prevention of pregnancy? | [
"reproduction",
"abortion",
"contraception",
"cessation"
] | C | |
SciQ | SciQ-1291 | genetics, cell-biology, chromosome, meiosis, mitosis
https://www.khanacademy.org/science/biology/cellular-molecular-biology/meiosis/a/phases-of-meiosis
So, during metaphase I, homologue pairs—not individual
chromosomes—line up at the metaphase plate for separation.
The following is multiple choice question (with options) to answer.
Homologous chromosomes move toward what poles? | [
"interior",
"parallel",
"opposite",
"octogonal"
] | C | Homologous chromosomes move toward opposite poles of a dividing cell during. |
SciQ | SciQ-1292 | species-identification, botany, ecology, trees
Title: Identifying a shrub with unusual "many shoots" growth behavior While recently hiking in the southern mountains of New Hampshire, we came across a plant, and some of them were exhibiting what we interpreted to be a disease, or least unusual growth. On some of the nodes, there were a large number of extra stalks:
On each plant, the number and locations of these things varied, and not all of them had it. And we first assumed it was some ivy, or parasite, or separate plant, but it seemed pretty clear to us that it was coming right from the same branch.
We soon saw there were dead versions of this plant, and all of them had this "extra shoot" variation:
So we reasoned that no matter what this thing was -- natural variation or some kind of disease -- it was killing the plants.
Google image search was no help. It possibly identified the plant as a "viburnum", but was unable to help with the growth.
Anyone know what plant this is, or what this growth behavior is the result of? Possibly an example of a "Witch's Broom."
Witch's Broom is a deformity in plants (typically woody species) which typically causes dense patches of stems/shoots to grow from a single point on the plant. The name comes from the broom-like appearance of the stems.1
Witch's broom may be caused by many different types of organisms, including fungi, oomycetes, insects, mistletoe, dwarf mistletoes, mites, nematodes, phytoplasmas, or viruses.2
Sources:
1. Wikipedia
2. Book of the British Countryside. Pub. London : Drive Publications, (1973). p. 519
Image1. Gardeningknowhow.com
Image2. Iowa state University
The following is multiple choice question (with options) to answer.
Why are the stems of many xerophytes fleshy? | [
"stores water",
"pressures water",
"drains water",
"collects water"
] | A | |
SciQ | SciQ-1293 | pathology
Title: Why are some bodily fluids more of an infection risk than others? Whilst on a recent refresher course it was highlighted that when considering risk of exposure to infection from bodily fluids we should be aware of two distinct risk levels:
High Risk:
Blood
Semen
Vaginal Secretions
Diarrhea
Low Risk:
Saliva
Vomit
Urine
CSF (Cerebrospinal fluid)
Why is it that some bodily fluids are a greater infection risk than others? Is it related to the fluids themselves or the species of pathogen that are located within them? This is just about where the pathogens can be found that are dangerous to people.
Vomit is highly acidic and less accommodating to microbe growth. Similarly saliva has many immune components in it as well as digestive enzymes that keep most microorganisms down.
Urine and CSF are actually quite sterile as they come from environments that are highly filtered - the kidney is an osmotic processor that essentially is a molecular filter and does not allow cells to pass, the spine is highly insulated from the blood and other direct exposure to microorganisms.
Compare that with the 'dangerous' list and you have organs that are open to human pathogens. Venerial disease like HPV is so common that what - about 1 in 5 people under a certain age carry it. That is a pretty high expectation of a biohazard. most infections and viruses are blood bourne - influenza, cold, as well as any bacterial infections.
Feces is always a dangerous thing to handle as the digestive tract is rich in nutrients and essentially directly open to external bacteria and fungi. (and its not acidified like the stomach). Also parasites like tape worms and other multicelled animals! yum!
Diarrhea is often caused by an infection of some sort, so its just more likely a hazard, but feces is always a place where you might find a pathogen.
This is not to say that the 'safe' list is totally safe. Its just less likely to bear disease causing agents.
The following is multiple choice question (with options) to answer.
Most body fluids that you release from your body contain chemicals that kill pathogens. for example, mucus, sweat, tears, and saliva contain enzymes called? | [
"enzymes",
"lipids",
"sporozoans",
"lysozymes"
] | D | Most body fluids that you release from your body contain chemicals that kill pathogens. For example, mucus, sweat, tears, and saliva contain enzymes called lysozymes that kill pathogens. These enzymes can break down the cell walls of bacteria to kill them. |
SciQ | SciQ-1294 | meteor
Title: Trying to identify something I saw in the sky I'm trying to identify something I saw in the sky. This occurred in central Virginia (Louisa county), US on Sunday at around 2:15 AM EST. It started as a ring of what looked like smoke, high in the sky. The ring got gradually larger. Then a small light moved out of it. The light looked like a star but it was moving about the 'relative' speed of an airplane viewed from the ground. I say relative because I think this was higher up than an airplane and so it was probably moving faster. The light had a puff behind it which was much larger than the light (so it was much bigger than the entrails of a jet plane). When I say 'big' or 'small' I mean it relative to the view of someone standing on the ground. I kept observing this light moving across the sky until I lost it in the trees.
I have not seen anything like this before. If I had to guess, I'd say it was possibly a military plane at high altitude moving at high speed. I guess it could also be a meteor that caused the ring when it hit the atmosphere and moved off at a strange angle. However, I have never seen a meteor move that slow. They usually zip fast across the sky. Maybe it's a meteor that hit the atmosphere at an angle that slowed it down? Anyone know what it could have been?
Edit: I saw this photo submitted to the american meteorologic society. It's about the same time and looks exactly like what I saw. It was from someone in PA at 2:30am.
The following is multiple choice question (with options) to answer.
What is at the top of the mesosphere? | [
"mesopause",
"Mesosphere",
"Troposphere",
"Stratosphere"
] | A | At the top of the mesosphere is the mesopause. Temperatures here are colder than anywhere else in the atmosphere. They are as low as -100° C (-212° F)! Nowhere on Earth’s surface is that cold. |
SciQ | SciQ-1295 | food, biotechnology
Title: How to increase the shelf life of yogurt without refrigeration? When we make yogurt at home and do not refrigerate it, it will become sour because of conversion of lactose into lactic acid by Lactobacillus bacteria, but this does not happen in case of Nestle's yogurt or any other brand until it remains air tight.
I wonder though bacteria is still present in it and continue to convert lactose into lactic acid then why does not packed yogurt becomes sour? How these companies increase the shelf life of yogurt..? This article gives an excellent review on yogurt manufacturing, but to summarize:
-Raw milk goes through centrifugation to remove somatic cells and other solid impurities.
-Thermalization is conducted at "60–69 °C for 20–30 s, aiming at the killing of many vegetative microorganisms and the partial inactivation of some enzymes."
After this point, the milk may be inoculated with lactic acid bacteria or other microfloras.
-Then, standardization occurs which for milk refers to the standardization of fat and solid-non-fat content (SNF). This in short affects the fermentation process ("an increase of SNF increases the duration of the fermentation process").
-The next step is homogenization, which prevents milk fat from rising to the top of the liquid. This has an effect on the stability of the emulsion.
-I think this step is where "sterility" comes into play, "heat treatment of milk reduces the number of pathogenic microorganisms to safe limits for the consumer’s health. Various heat treatments can be applied, which are classified based on the duration and the temperature. The most common are known as thermalization, low and high pasteurization, sterilization and UHT (Ultra Heat Treatment)." The review goes into more detail about each type and what they eliminate or don't eliminate (spores, vegetative bacteria, etc.).
The following is multiple choice question (with options) to answer.
Yogurt is made from milk fermented with what type of organism? | [
"bacteria",
"algae",
"yeast",
"viruses"
] | A | Mom the Barbarian. Yogurt is made from milk fermented with bacteria . CC BY 2.0. |
SciQ | SciQ-1296 | senescence, telomere
So its not clear if the telomeres are protected in hydrae and other immortal animals. I would guess they probably don't have active telomerase if they are truly immortal, though its possible the telomeres are shortened and are repaired.
There are other factors which are supposed to be important for immortality. Yeast and single eukaryotes are not individually immortal; an individual mother cell can only divide a limited number of times. While hydrae are not a popular focus of research, there has been a concerted effort in trying to understand yeast mortality and there are more than one mechanism being pointed to.
Since there is no germline in single celled organisms, (they only have one copy of their genome to reproduce from) telomeric shortening would not be a useful mechanism for aging; Calorie restriction has been shown to prolong fission and budding yeast by activating pathways which slow aging by protecting against stress, and slowing down reproduction. All of these findings have strong parallels in work in aging in animals which is a hot topic now.
Finding these pathways is encouraging strong thought that aging and senescence are an evolutionary adaptation rather than a biological necessity.
Our current knowledge suggests that an apoptotic program has evolved in microorganisms as a survival strategy beneficial to the group. This program is dependent on cellular pathways like the Sch9, Tor1, and Ras/PKA pathways and its activation reduces cell protection and maintenance and raises the level of superoxide production, which in turn contributes to cell damage and death. Superoxide also elevates DNA damage and mutation frequency in the aging cultures ... Aging and apoptosis are intrinsically related in yeast and the mechanisms that cause them have just begun to be elucidated. ... will provide important information to understand the fundamental biology of aging in other species and investigate the controversial hypothesis that an “aging program” might be conserved in higher eukaryotes.
The following is multiple choice question (with options) to answer.
What happens to an animal's telomeres as it ages? | [
"shorten",
"divide",
"multiply",
"lengthen"
] | A | As cells divide, their chromosomes get shorter. This is because the telomeres, the DNA sequences at both ends of a chromosome, lose material every time the DNA is replicated. The older the animal is, the shorter its telomeres will be, because of the number of cell cycles the cells have been through This is a natural part of aging. So, what happens to the clone if its transferred nucleus is already fairly old? Will the shortened telomeres affect its development or lifespan? The answer is still unclear. But starting a new organisms with "old" DNA with shortened telomeres is bound to have some effects, at least in some clones. Some cloned animals may be affected, others may not. Dolly the sheep's chromosomes did have shorter telomere lengths than normal. This means that Dolly's cells were aging faster than the cells from a normal sheep. |
SciQ | SciQ-1297 | cancer
Title: do tumour cells begin with abnormal characteristics? At what point in the cell cycle do cells start to become tumorous? Do they have abnormal characteristics to begin with; if so what are they? Cancer cells don't start to become cancerous at a specific stage of the cell cycle; you will find that while uncontrolled proliferation is a hallmark of cancer, different cancers acquire alterations in different phases of the cell cycle. BRCA-deficient cancers for example have a compromised G2-M checkpoint [1], while Rb deficient cancers have a compromised G1-S [2] checkpoint in the cell cycle.
The cell cycle is simply a property of proliferating cells and the same broad phases of the cell cycle are universal to both normal and malignant cells.
As for when abnormally growing cells actually become a cancer - this has nothing to do with phases of the cell cycle, and everything to do with the ability to break through the basement membrane of the original site (indicating the potential to be invasive/spread), because the ability to invade is a hallmark of cancer [3]
References
[1] http://cancerres.aacrjournals.org/content/67/13/6286
[2] https://www.ncbi.nlm.nih.gov/pubmed/16936740
[3] https://www.ncbi.nlm.nih.gov/pubmed/21376230
The following is multiple choice question (with options) to answer.
Characterized by uncontrolled growth, cancerous cells are also called what? | [
"malignant",
"benign",
"toxic",
"abnormal"
] | A | Cancer is the uncontrolled growth of abnormal cells in the body. Cancerous cells are also called malignant cells. There are over 200 different known cancers that afflict humans. |
SciQ | SciQ-1298 | evolution
An Immune Basis for Malaria Protection by the Sickle Cell Trait
Sickle Cell Anaemia and Malaria
If you look further, you will find a number of different examples, where evolution is present after humans went through a genetic bottleneck (meaning the number of humans was drastically reduced).
The following is multiple choice question (with options) to answer.
Historically, malaria has rivaled what as the leading cause of human death by infectious disease? | [
"heart attack",
"cancer",
"tuberculosis",
"hepatitis"
] | C | Alloys can be one of two general types. In one type, called a substitutional alloy, the various atoms simply replace each other in the crystal structure. In another type, called an interstitial alloy, the smaller atoms such as carbon fit in between the larger atoms in the crystal packing arrangement. |
SciQ | SciQ-1299 | atoms, terminology
Title: What is a neutral atom? I was told that an atom's atomic number is defined as follows:
The number of electrons or protons present in a neutral atom is called atomic number. It is represented by Z.
What does neutral mean here? Why isn't it just "..present in an atom..."? Electrons and protons are charged particles. The electrons have negative charge, while protons have positive charge. A neutral atom is an atom where the charges of the electrons and the protons balance. Luckily, one electron has the same charge (with opposite sign) as a proton.
Example: Carbon has 6 protons. The neutral Carbon atom has 6 electrons. The atomic number is 6 since there are 6 protons.
The following is multiple choice question (with options) to answer.
When the number of electrons and the number of protons are equal, the object is what? | [
"Positive",
"neutral",
"Negative",
"static"
] | B | When the number of electrons and the number of protons are equal, the object is neutral. |
SciQ | SciQ-1300 | waves, refraction, approximations, complex-numbers
Title: Index of Refraction in Metal: Approximating Complex Perturbation If you consider waves in a metal, you can write the index of refraction for the metal as,
$$ n^2 = 1 - \frac{\omega_p^2}{\omega^2} $$
I am interested in what will happen if the index is perturbed by some small complex quantity,
$$ n^2 = 1 - \frac{\omega_p^2}{\omega^2} - i\epsilon $$
In the low frequency limit, this usually corresponds to an attenuation. To compute quantities that depend on $n$ (such as absorption), I would like to expand $n$ since $\epsilon$ is small.
The function is,
$$ n = \sqrt{1 - \frac{\omega_p^2}{\omega^2}-i\epsilon} $$
So I write,
$$ n = \sqrt{1 - \frac{\omega_p^2}{\omega^2}}\sqrt{1 - i \frac{\epsilon}{1 - \omega_p^2/\omega^2}} $$
For this problem $\omega_p > \omega$, so I rewrite,
$$ n = i \sqrt{\frac{\omega_p^2}{\omega^2}-1}\sqrt{1 + i \frac{\epsilon}{\omega_p^2/\omega^2 - 1}} $$
And, since $\epsilon << 1$, I tried to expand this:
$$ \approx i \sqrt{\frac{\omega_p^2}{\omega^2}-1}\left(1 + i \frac{\epsilon}{2(\omega_p^2/\omega^2-1)} \right) = \sqrt{\frac{\omega_p^2}{\omega^2}-1}\left(i - \frac{\epsilon}{2(\omega_p^2/\omega^2-1)} \right)$$
The following is multiple choice question (with options) to answer.
The angle of refraction depends on the index of what? | [
"vibration",
"frequency",
"refraction",
"reflection"
] | C | Refraction is responsible for dispersion in rainbows and many other situations. The angle of refraction depends on the index of refraction, as we saw in The Law of Refraction. We know that the index of refraction n depends on the medium. But for a given medium, n also depends on wavelength. (See Table 25.2. Note that, for a given medium, n increases as wavelength decreases and is greatest for violet light. Thus violet light is bent more than red light, as shown for a prism in Figure 25.23(b), and the light is dispersed into the same sequence of wavelengths as seen in Figure 25.21 and Figure 25.22. Making Connections: Dispersion Any type of wave can exhibit dispersion. Sound waves, all types of electromagnetic waves, and water waves can be dispersed according to wavelength. Dispersion occurs whenever the speed of propagation depends on wavelength, thus separating and spreading out various wavelengths. Dispersion may require special circumstances and can result in spectacular displays such as in the production of a rainbow. This is also true for sound, since all frequencies ordinarily travel at the same speed. If you listen to sound through a long tube, such as a vacuum cleaner hose, you can easily hear it is dispersed by interaction with the tube. Dispersion, in fact, can reveal a great deal about what the wave has encountered that disperses its wavelengths. The dispersion of electromagnetic radiation from outer space, for example, has revealed much about what exists between the stars—the so-called empty space. |
SciQ | SciQ-1301 | thermodynamics, statistical-mechanics
Title: In Boltzmann distribution, why is the system at the same temperature as the reservoir? Consider a boltzmann distribution where the total energy of the reservoir and the system is $E$. The energy of the system can be $\epsilon_i$ and the energy of the reservoir is $E-\epsilon_i$.
Now if the system can take on different energies of $\epsilon_i$, why can one say that the system is at equilibirum with the reservoir and has a fixed temperature $T$ which is same as that of the reservoir?
At one second the system can have energy $\epsilon_1$ and at the next second the system can have energy $\epsilon_2$, with good probability of it happening. There is thus a net flow of energy between the system and the reservoir. How can then one say that the system and reservoir is at equilibirum and have the same temperature? The reservoir is taken to be large enough to provide the system with a very well-defined probability distribution for its energy $\epsilon_i$. For the theorists, this means of course that the reservoir is actually infinitely large.
A system is said to be in thermal equilibrium with the reservoir if its energy is found to obey the expected probability distribution provided by the heat reservoir. This means that one should measure the energy of the system over some longer period of time, since one is considering the probability distribution of the energy, not the value of the energy at any single instant. If the system is not in thermal equilibrium with the bath, the distribution of energies will be very different than expected. For instance, if the system is initially colder than the reservoir, its energy will be found to be smaller than expected until the system has equilibrated.
The following is multiple choice question (with options) to answer.
Systems are in thermal equilibrium when they have the same of what measurement? | [
"temperature",
"density",
"mass",
"oxygen"
] | A | T ºF = 9 T ºC + 32 5 5 T ºC = ⎛⎝T ºF − 32⎞⎠ 9 T K = T ºC + 273.15 T ºC = T K − 273.15 • Systems are in thermal equilibrium when they have the same temperature. • Thermal equilibrium occurs when two bodies are in contact with each other and can freely exchange energy. • The zeroth law of thermodynamics states that when two systems, A and B, are in thermal equilibrium with each other, and B is in thermal equilibrium with a third system, C, then A is also in thermal equilibrium with C. 13.2 Thermal Expansion of Solids and Liquids • Thermal expansion is the increase, or decrease, of the size (length, area, or volume) of a body due to a change in temperature. • Thermal expansion is large for gases, and relatively small, but not negligible, for liquids and solids. • Linear thermal expansion is. |
SciQ | SciQ-1302 | condensed-matter
Title: If a liquid is compressed enough, would it become solid? If a liquid were to be compressed so tensely that the particles had no room to move, would it then become a solid?
Also, would the same happen with a gas? It depends on the substance. It is easy to work out though from the relevant phase diagram.
Isothermally increasing the pressure of liquid CO$_2$ will create a solid phase (dry ice). But increasing the pressure of liquid water will not create ice.
A gas-to-solid transition with increasing pressure is a process called deposition. It will happen with most substances if the temperature is sufficiently low.
The following is multiple choice question (with options) to answer.
What needs to be increased to change a solid into a liquid or gas? | [
"pressure",
"temperature",
"oxygen",
"volume"
] | B | In the last lesson, we studied the characteristics of liquids and solids at a macroscopic level and at the molecular level. Increasing the temperature of a solid transforms the particles from a rigid arrangement to a fluid (a liquid or gas). Conversely, decreasing the temperature of a liquid or gas slows the particles down, going back from free movement to a fixed arrangement. In this section, we will further explore how temperature and pressure affect the characteristics and behavior of matter. Pressure has a larger effect on gases, which are very compressible, than liquids and solids. However, changes in pressure are still relevant to solids and liquids. For example, Figure above shows ice skates on ice. Because your entire weight is all concentrated on a thin blade, ice skates exert quite a bit of pressure on the ice below them. An interesting property of water is that increasing the pressure on its solid form (ice) will eventually convert it to liquid water. The pressure exerted by ice skates makes small amounts of liquid water on the surface, allowing the skates to glide smoothly. |
SciQ | SciQ-1303 | identification, minerals
Title: How can chemists distinguish pure chemical element specimens that look almost "the same" as well as what deposit is what in a multimineral mined rock? As a non chemist I am most often charmed when visiting Wikipedia articles of chemical elements and see images of very pure specimens of element after element, proton by proton, and often also metal cube specimen made from smithing similar pure deposits.
The wiki article Periodic table allows me to do so easily; here are some elements I found looking almost the same and don't think I personally could distinguish between them without some instrument:
molybdenum and manganase
titanium and chromium
rutenium and cadmium
sodium and aluminium
silicone and germanium
The following is multiple choice question (with options) to answer.
Minerals that are not compounds consist of a single what? | [
"gas",
"proton",
"electron",
"element"
] | D | Minerals that are not just a single element are made of chemical compounds. For example, the mineral quartz is made of the compound silicon dioxide, or SiO 2 . This compound has one atom of the element silicon for every two atoms of the element oxygen. |
SciQ | SciQ-1304 | biochemistry, structural-biology
This looks complicated, but its not. you move the probe sphere along the surface of the molecule in the XY plane until it just touches the vdW radius of the protein, keeping the center of the sphere as the surface, all the way around the molecule. If you like, you can color the surface by the charge of the position too, which is useful for discussing solvent interactions.
Then you translate along the z axis and do another contour until you run out of protein. Apparently jmol and other packages will do this for you.
Wikipedia references a more mathematical method LCPO, which I am not so familiar with.
Is this accurate? As usual with such calculations its more of a guess than an answer. You can do the calculation on any structure or any ensemble of structures (like NMR gives). It doesn't understand how the molecule might be flexible or dynamic. If you read up on your physical chemistry you see that proteins breathe and can allow diffusion into the core rather readily. If I recall right, you can get rather large molecules quenching heme flouresence in hemoglobin at room temperature.
If you are looking to dock 2 proteins, SAS might be more useful. Its an important piece of information, but not an ultimate answer. I'm afraid with proteins that doesn't happen so easily.
@bobthejoe asked about SAS for which no structure exists.
This is an extremely difficult thing to even guess at. The non helpful answer is that the surface of the protein goes as the cube root of the molecular weight of the protein.
By getting a solution of the protein and shooting it in a syhcrotron, you can get a mean radius of gyration pretty easily which will give you an ellipsoidal volume (and surface area) for a protein. Again most of the particulars would be lost and this could easily be off by 25% for an irregularly shaped protein. For a regular globular protein it might give an answer similar to the power law above.
I have seen physical chemistry experiments that look for changes in osmotic pressure when the salt concentration in a solution of the protein changes substantially (Adrian Parsegian's work at NIH in the late 80s).
The following is multiple choice question (with options) to answer.
What globular protein is used in the construction of the hollow tube? | [
"actin",
"cyclin",
"tubulin",
"keratin"
] | C | |
SciQ | SciQ-1305 | substance can be converted to other forms of energy by a chemical reaction. The full name of this effect is gravitational potential energy because it relates to the energy which is stored by an object as a result of its vertical position or height. ATOMIC PHYSICS — 10% (such as properties of electrons, Bohr model, energy quantization, atomic structure, atomic spectra, selection rules, black-body radiation, x-rays, atoms in electric and magnetic fields) SPECIAL RELATIVITY — 6%. Here are some practice questions that you can try. Output in Joules (J, kJ, MJ), Watt-hours (Wh, kWh), calories (Cal, kCal) and foot-pounds (ft-lbs). Engineering Physics Resources. 8 m//s^(2)). Can you calculate the energy needed to increase the temperature of 100kg of iron by 40°C? Extension. In physics , energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat , the object. Learn more Accept. KINETIC ENERGY CALCULATOR. 6x10^6 js / 18x10^3 js. If wavelength is measured in centimeters, then Planck's constant is 6. KE = 1/2*m*v^2. Physics Calculator is available here for free use. Energy can be in many forms! Here we look at Potential Energy (PE) and Kinetic Energy (KE). A particle in the lower energy state absorbs a photon and ends up in the upper energy state. This chemical energy in the cyclist is then converted to kinetic energy on the bike pedal due to the cyclist applying a downward force upon the bike pedal. ATOMIC PHYSICS — 10% (such as properties of electrons, Bohr model, energy quantization, atomic structure, atomic spectra, selection rules, black-body radiation, x-rays, atoms in electric and magnetic fields) SPECIAL RELATIVITY — 6%. To +W From -W - Constant force: F x ma x d v v v v axd ax 2 2 2 0 2 2 0 2 Work done by the force = Energy. Exothermic reactions release energy by transferring heat to their surroundings. In older works, power is sometimes called activity. the bungee cord has more potential energy when it is stretched out than when it is slack. , green plants convert solar energy to chemical energy (commonly of
The following is multiple choice question (with options) to answer.
Two important types of energy that can be converted to one another include potential and what? | [
"magnetic",
"thermal",
"kinetic",
"physical"
] | C | Give examples of energy conversions between potential and kinetic energy. |
SciQ | SciQ-1306 | diffusion
The reverse process is also happening with molecules diffusing from right to left at a rate proportional to their concentration in the right side solution. As the concentration on the right side increases to be equal to the concentration on the left, so the diffusion rates become equal and there is zero nett diffusion and the system approaches equilibrium.
Note that this assumes a "perfect" system where there is no chemical reaction occurring between the solutes or between the solutes and the membrane. In practice this means that either the interaction between solutes A and B is the same as the interaction between the solutes and the solvent or that the solute molecules are so greatly outnumbered by the solvent molecules that the solute-solute interactions are not significant.
The rate of diffusion of solute A may be different from B (i.e. the proportionality constant between rate and concentration may be different). This means that before reaching equilibrium the relative concentrations of A and B may change but at equilibrium, the relative concentration will be the same as initially.
If we define "reaching equilibrium" as having some fraction (say 99.99%) of the final concentration then increasing the initial global concentration will increase the lag for both solutes equally and will not change their relative concentrations.
The following is multiple choice question (with options) to answer.
What is the diffusion of water through a semipermeable membrane according to the concentration gradient of water across the membrane | [
"Gravity",
"nutrients",
"osmosis",
"mirrors"
] | C | Osmosis Osmosis is the diffusion of water through a semipermeable membrane according to the concentration gradient of water across the membrane. Whereas diffusion transports material across membranes and within cells, osmosis transports only water across a membrane and the membrane limits the diffusion of solutes in the water. Osmosis is a special case of diffusion. Water, like other substances, moves from an area of higher concentration to one of lower concentration. Imagine a beaker with a semipermeable membrane, separating the two sides or halves (Figure 3.21). On both sides of the membrane, the water level is the same, but there are different concentrations on each side of a dissolved substance, or solute, that cannot cross the membrane. If the volume of the water is the same, but the concentrations of solute are different, then there are also different concentrations of water, the solvent, on either side of the membrane. |
SciQ | SciQ-1307 | human-biology, digestive-system, immune-system, microbiome
The next level of defense comes from the cells of the innate immune system (14). In innate immunity, specialized cells monitor the area they are in for Pathogen-Associated Molecular Patterns (PAMPs). PAMPs can be sugars that make up the cell walls of the microbe or proteins that get expressed on the surface of the organism, such as Flagellin, a protein only found in the flagella of certain pathogen. The innate immune cells have pattern recognition receptors (PRR) that have a general specificity for recognizing and responding to the PAMPs. Our cells even have PRRs for DNA and Double Stranded RNA's, however those are usually found in vesicles on the inside of the cell. These interactions are very general, however once PRRs bind to the PAMP, they are able to signal into the cytoplasm, which can lead to the production of proteins, among other possible responses.
Here you can think of PRRs like a motion detector in a security system; the dog, or your two year old, or an intruder are going to set off the alarm just the same. It is not specific. The motion sensor "knows" that something that it is supposed to recognize, i.e. a moving object larger than a mouse passed by and it triggered the response, but it cannot tell you which moving object triggered it, only that it was triggered.
The innate immune cells are also able to respond by "eating" the pathogen in a process called phagocytosis. Here, they break up the bacteria, yeast, or the remnants of other dead host cells or large pathogens, things like worms, and put the broken up pieces on protein molecules on their surface.
When innate immune cells do this, they are presenting molecules to specialized immune cells (adaptive immune cells (14)), B-Cells and T-Cells, that are highly specific as to what they will react to. These cells can also cause a lot of damage to the host, so they are tightly regulated. Think of the interactions as keys and locks. A protein from a bacteria should turn a few of these cells on, but a protein from the host should not fit the lock.
The following is multiple choice question (with options) to answer.
What are the key cells of an immune response? | [
"erythrocytes",
"histiocytes",
"lymphocytes",
"keratinocytes"
] | C | Courtesy of Dr. Triche and the National Cancer Institute. Lymphocytes are the key cells of an immune response . Public Domain. |
SciQ | SciQ-1308 | evolution
Title: Why similarities among organisms led scientists to believe that organisms are evolved? Theory of evolution states that organisms are evolved into other more advanced ones over time because there are some traits in modern organisms resemble with organisms existing before (from fossil record). But it might be possible that each organism has created independently of each other. why similarities mean evolutionary relationship? I will answer by explaining some misconceptions in your original question:
Theory of evolution states that organisms are evolved into other more advanced ones over time
Nope that's not what the theory of evolution is stating, mainly because the expression "more advanced" does not mean much and also is a loaded expression. You might want to start with an intro course to evolutionary biology to understand what the theory of evolution says. Understanding Evolution is a very introductory course you might like
@Remi.b Alright I will have a look at what theory of evolution states but the basic thing is humans are thought to have evolved from chimpanzees. What I want to know is chimpanzees might resemble to humans but why chimpanzees are considered ancestor of humans? It might be possible that humans and chimpanzees created individually?
The following is multiple choice question (with options) to answer.
Darwin found that, since all species are related to each other and some of them evolve together, so they develop similar what? | [
"systems",
"appearance",
"language",
"adaptations"
] | D | It's rare for a biologist to predict the discovery of a new species. For his prediction, Kavanaugh drew inspiration from Darwin's own 1862 prediction. When Darwin observed an orchid from Madagascar with a foot-long nectar, he predicted that a pollinator would be found with a tongue long enough to reach the nectar inside the orchid's very thin, elongated nectar ‘‘pouch’’, though he had never seen such a bird or insect. Darwin's prediction was based on his finding that all species are related to each other and that some of them evolve together, developing similar adaptations . Darwin's prediction came true in 1903, when a moth was discovered in Madagascar with a long, thin proboscis, which it uncurls to reach the nectar in the orchid's nectar. In the process of feeding from the orchid, the moth serves as its pollinator. The moth was given the scientific name Xanthopan morganii praedicta , in honor of Darwin’s prediction. |
SciQ | SciQ-1309 | c++, multithreading
Title: C++ Improved ThreadGroup Implementation After the amazing feedback from these questions; I have prepared a third version of the original posted code.
The Idea is the same: An std::size_t variable threads_ready is increased to threads.size() until all threads are finished with the payload, and then back to 0 when all threads are ready to execute again.
I eliminated all busy waiting that I could find
made the class more generic by making the class use of variadic templates.
The Best solution would be to have a lambda capture the required context, but unfortunately I couldn't find a way to deter thread related parameters comfortably from a generic lambda. The best I could manage was to reduce the used parameters to "thread index", so each thread would have an idea about the relevant regions in the inputs.
I made a better use-case to better test the implementation
#include <iostream>
#include <functional>
#include <tuple>
#include <vector>
#include <thread>
#include <mutex>
#include <iomanip>
#include <numeric>
#include <atomic>
#include <condition_variable>
#include <algorithm>
#include <cassert>
#include <chrono>
#include <cmath>
using std::atomic;
using std::vector;
using std::function;
using std::tuple;
using std::thread;
using std::mutex;
using std::unique_lock;
using std::lock_guard;
using std::condition_variable;
using std::size_t;
template<typename First, typename ...T>
class ThreadGroup{
public:
ThreadGroup(int number_of_threads, function<void(tuple<First, T...>&, int)> function)
: worker_function(function)
, state(Idle)
{
for(int i = 0; i < number_of_threads; ++i)
threads.emplace_back(thread(&ThreadGroup::worker, this, i));
}
The following is multiple choice question (with options) to answer.
Newly formed what aggregates into threads that form the framework of the clot? | [
"fibrin",
"collagen",
"plasma",
"blood"
] | A | |
SciQ | SciQ-1310 | proteins, amino-acids, classification
Title: Classifying Polypeptides (and/or Proteins) Since polypeptides are a linear chain of twenty amino acids, each having a single letter abbreviation (e.g. Alanine = A). So can a polypeptide be represented as just the sequence (say: ADN for an Alanine, Aspartic acid, Asparagine polypeptide)?
This method of classifying polypeptides would lead to a possible 8000 (20**3) variations just for 3-amino-acid-polypetides (3200000 for 5-amino-acid-polypeptides, etc.) and that there would be many variations; and for longer polypeptides - that is, proteins - there would be even more variations.
Or are only the important polypeptides and proteins named, since not every variation of polypeptides and proteins are found in the body? I would've thought that many proteins (and enzymes, etc.) are incredibly specific and so they could be classified in some methodological way, as opposed to just 'lipase' or 'carbohydrase' which provides no structural information (though it would have a long methodological name). You can certainly refer to short peptides by their sequence. I don't know of any exact boundaries, but I've seen tripeptides referred to by either their three letter codes (Ala-Asp-Asn) or even the chemical name (alanylaspartylasparagine) although obviously that gets ridiculous pretty quickly.
As the largest known protein, titin also has the longest IUPAC name of
a protein. The full chemical name of the human canonical form of
titin, which starts methionyl... and ends ...isoleucine, contains
189,819 letters and is sometimes stated to be the longest word in the
English language, or any language. However, lexicographers regard generic names of chemical compounds as verbal formulae rather than English words
The following is multiple choice question (with options) to answer.
The general term peptide refers to an amino acid chain of what? | [
"incomplete length",
"unspecified length",
"large length",
"small length"
] | B | The general term peptide refers to an amino acid chain of unspecified length. However, chains of about 50 amino acids or more are usually called proteins or polypeptides. In its physiologically active form, a protein may be composed of one or more polypeptide chains. For peptides and proteins to be physiologically active, it is not enough that they incorporate certain amounts of specific amino acids. The order, or sequence, in which the amino acids are connected is also of critical importance. Bradykinin is a nine-amino acid peptide produced in the blood that has the following amino acid sequence: arg-pro-pro-gly-phe-ser-pro-phe-arg This peptide lowers blood pressure, stimulates smooth muscle tissue, increases capillary permeability, and causes pain. When the order of amino acids in bradykinin is reversed, arg-phe-pro-ser-phe-gly-pro-pro-arg the peptide resulting from this synthesis shows none of the activity of bradykinin. Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-1311 | atmosphere, climate-change, climate
Title: Why is the temperature *still* rising? 2015 is the hottest year on record, and the average temperature continues to rise.
I don't understand why this continues, as (over the past twenty years) so much work was put into reducing Global Warming over the past 40 years, yet not only does the temperature not fall, it continues to rise more than it did between 1870-1960.
I don't understand something. The amount of industry went through the roof (literally) between 1870 to 1960, and no one cared about the environment
Now that we do care about it, and (at least somewhat) legislate cleaner cars, factories, etc, I would expect the temperature to even out, yet it doesn't
Why not? "So much work"? Actually, compared to the global rate of greenhouse gas emissions, it's a case of "so little work"! From a scientific perspective the 'economists' solution' of carbon trading was always unlikely to achieve the required carbon cuts, as has been verified by their ineffectiveness over the last decade or so. As farrenthorpe points out, the rate of increase of CO2 is largely population-driven, and hence there is still an inexorable rise in mean atmospheric CO2. The acid test of human efforts to limit global warming is whether the Hawaiian CO2 monitoring graph is flattening off:
It clearly isn't going to flatten anytime soon. In fact, if anything, it is getting steeper. So all the hot air from 'Paris', and previous talkfests, is evidently too little, too late. Realistically, limiting the average temperature rise to less than 2 °C, is now effectively unattainable. We have yet to see what 'all this work' can achieve. So far, almost nothing.
The following is multiple choice question (with options) to answer.
Average global temperature has been doing what for the past several decades? | [
"falling",
"fluctuating",
"rising",
"stabilizing"
] | C | Average global temperature has been rising for the past several decades. |
SciQ | SciQ-1312 | botany, entomology
Title: What is this small white insect on my plants? Environment
I have a large amount of plants in an old industrial loft apartment.
I live in Rochester, New York.
I ship plants in from across the US, often exotic ones.
Observations
A few months ago, I noticed that two of my Sarracenia plants in my carnivorous plant bog were not growing anymore. Upon cutting them out as to not disrupt the live sphagnum moss grow medium, I noted that one of the insects in question had burrowed its way down into the core of the plant. I assume this to be the cause of the growing issue.
Today I noticed that one of my grape plants and Colocasia plants were covered in these bugs at different stages of growth. They range from white specs to ~3mm with the tail thing.
These insects appear sedentary. I have never seen one move, except when I cut the one out of the center of the plant.
Here is a picture of the bug, which was difficult to get due to the size.
Research
I looked through a variety of different "common insect" sites as well as some insect identification sites but I was unable to find anything remotely similar.
I have only elementary knowledge of insects. Any pointers in the right direction would be appreciated. Mealybug; don't know much about them.
The following is multiple choice question (with options) to answer.
What disease is caused when the oomycete plasmopara viticola parasitizes grape plants? | [
"alkaline mildew",
"toxic mildew",
"dainty mildew",
"downy mildew"
] | D | Plant Parasites Protist parasites of terrestrial plants include agents that destroy food crops. The oomycete Plasmopara viticola parasitizes grape plants, causing a disease called downy mildew (Figure 23.33). Grape plants infected with P. viticola appear stunted and have discolored, withered leaves. The spread of downy mildew nearly collapsed the French wine industry in the nineteenth century. |
SciQ | SciQ-1313 | genetics, dna-sequencing, human-genetics, genomics, biotechnology
Yes, it is counted on the haploid genome. I would not make any sense to count it on the diploid genome. When looking at my last paragraph you might see why: Remember, we are looking at (i) fixed differences (both copies of a diploid human genome differ from both copies of a diploid chimpanzee genome) or (ii) at variable sites. Assume you find one site in one haploid genome that fulfills either (i) or (ii). If you then look at the same site in the other copy of the genome you already know that the position is either (i) or (ii). This means that it has already been counted as a difference. If you counted it again, in the worst case, over the complete genome, you would count everything twice. In general, you would strongly overestimate the absolute difference.
Also ,I'm not sure that about one percent difference is calculated on one base pair or one nucleotide every thousand base pairs or nucleotides .Because he mentioned the both.
I do not understand this. I had a brief look at the video and heard him talking of one nucleotide per thousand. He compares the sequence difference between human-chimpanzee (98.8% overlap, approx. 1 per 100, about 1.2% fixed differences and SNPS) and human-human (99.9% overlap, approx. 1 per 1000, 0.1% SNP), pairs. Note that in the last case we cannot look at fixed differences as there are no fixed differences between human populations. The 0.1% difference are the percentage of SNP in the human genome.
The following is multiple choice question (with options) to answer.
What is the diploid number for fruit flies? | [
"9",
"8",
"7",
"10"
] | B | |
SciQ | SciQ-1314 | thermodynamics
Title: Physics of boiling an egg - what am I missing? (heat capacity and coagulation question) Update:
1) I originally posted this because the numbers seemed to make no sense to me (seemed very counterintuitive to only need 60-100ml of water to cook an egg when you usually have to boil it continuously in a saucepan of water...). I expected that perhaps the "latent heat" (activation energy, rather) of denaturing will contribute significantly to why it might not work. Well, I ended up just trying it out and it actually worked - I put a 63g egg with about 100ml of water in a thermos flask for one and a half hours and it turned out perfectly. You can see the process and results in this photo album - https://i.stack.imgur.com/Z5QOI.jpg
This is consistent with what tom10 said in the reply, which is that the denaturing would be negligible. I did some of my own calculations too, which agreed with that. I couldn't believe that it would really be negligible, but well here we go...
2) That said, I must admit I still don't -really- understand this whole denaturing process and how it works, but I'm trying to understand it better, so I'd still appreciate more replies! I'm quite sure the way I'm analyzing it isn't completely right, but at least I know now that it's a good-enough approximation for cooking.
The following is multiple choice question (with options) to answer.
An example of irreversible denaturation of what substance occurs to the liquid albumin when an egg is fried? | [
"bacterial",
"acids",
"liquid",
"protein"
] | D | Denaturation and Protein Folding Each protein has its own unique sequence and shape that are held together by chemical interactions. If the protein is subject to changes in temperature, pH, or exposure to chemicals, the protein structure may change, losing its shape without losing its primary sequence in what is known as denaturation. Denaturation is often reversible because the primary structure of the polypeptide is conserved in the process if the denaturing agent is removed, allowing the protein to resume its function. Sometimes denaturation is irreversible, leading to loss of function. One example of irreversible protein denaturation is when an egg is fried. The albumin protein in the liquid egg white is denatured when placed in a hot pan. Not all proteins are denatured at high temperatures; for instance, bacteria that survive in hot springs have proteins that function at temperatures close to boiling. The stomach is also very acidic, has a low pH, and denatures proteins as part of the digestion process; however, the digestive enzymes of the stomach retain their activity under these conditions. Protein folding is critical to its function. It was originally thought that the proteins themselves were responsible for the folding process. Only recently was it found that often they receive assistance in the folding process from protein helpers known as chaperones (or chaperonins) that associate with the target protein during the folding process. They act by preventing aggregation of polypeptides that make up the complete protein structure, and they disassociate from the protein once the target protein is folded. |
SciQ | SciQ-1315 | biophysics, theoretical-biology, ecosystem
Systems ecology, especially with regard to energy and nutrient flow.
This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem Ecology: Understanding Element Cycles by Ågren & Bosatta (Ågren was originally a physicist)
Physical limitations to growth and transport
This can include for instance mechanical contraints on plant growth (see e.g. the book Plant Physics by Nicklas & Spatz), water transport in trees (see e.g. this BioSE question) or the biomechanics of movement (see e.g. Hudson et al (2012) on the speed and movement of cheetahs or Wikipedia: Biomechanics).
Allometric relationships between organisms, e.g. with regard to metabolism
To explain these types of relationships knowledge in physics is useful. See e.g. Kleiber's law for more.
MAXENT as a general approach to ecological patterns or to model species distributions
This is basically a tool lifted from physics that can be applied to ecological problems. There are many papers to look at, but Harte & Newman (2014) (Harte is another previous physicist) and Elith et al (2010) are two good starting points.
Dynamical modelling of populations and communities
This field use many of the same tools for analysis as physics, e.g. systems of differential equations. One of the pioneers in this field (among many) were Robert May (also started with a PhD in physics), and his classical book Theoretical Ecology: Principles and Applications is still a good starting point.
Energy harnessing and conversion by organisms
This can refer both to how organsims convert prey to energy (e.g. conversion efficiencies) and the physics of photosynthesis (which is an interesting intersection between physics and molecular biology). See Jang et al (2004) and O'Reilly & Olaya-Castro (2013) for examples of the how quantum mechanics can inform us about photosynthesis.
Hopefully this will give you a sense of some different ways that knowledge in physics can be useful for biology.
The following is multiple choice question (with options) to answer.
In an environment, symbiosis, competition, and relying on other organisms for food are examples of what? | [
"interaction",
"collaboration",
"commensalism",
"adaptation"
] | A | All living things depend on their environment to supply them with what they need, including food, water, and shelter. Their environment consists of physical factors—such as soil, air, and temperature—and also of other organisms. An organism is an individual living thing. Many living things interact with other organisms in their environment. In fact, they may need other organisms in order to survive. For example, living things that cannot make their own food must eat other organisms for food. Other interactions between living things include symbiosis and competition. |
SciQ | SciQ-1316 | behaviour
References
Shimada M, Watanabe H, Komine Y, Kigawa R, Sato Y. New records of Ctenolepismacalvum (Ritter,1910) (Zygentoma, Lepismatidae) from Japan. Biodivers Data J. 2022 Nov 3;10:e90799. doi: 10.3897/BDJ.10.e90799. PMID: 36761636; PMCID: PMC9836529.
Kulma M, Bubová T, Davies MP, Boiocchi F, Patoka J. Ctenolepisma longicaudatum Escherich (1905) Became a Common Pest in Europe: Case Studies from Czechia and the United Kingdom. Insects. 2021 Sep 10;12(9):810. doi: 10.3390/insects12090810. PMID: 34564251; PMCID: PMC8471186.
Querner P, Szucsich N, Landsberger B, Erlacher S, Trebicki L, Grabowski M, Brimblecombe P. Identification and Spread of the Ghost Silverfish (Ctenolepisma calvum) among Museums and Homes in Europe. Insects. 2022 Sep 19;13(9):855. doi: 10.3390/insects13090855. PMID: 36135556; PMCID: PMC9505982.
The following is multiple choice question (with options) to answer.
What is another term for ghost sharks? | [
"chimaera",
"anascea",
"litoria",
"aurea"
] | A | The 1,000 or so species of cartilaginous fish are subdivided into two subclasses: the first includes sharks, rays, and skates; the second includes chimaera, sometimes called ghost sharks. Fish from this group range in size from the dwarf lanternshark, at 6.3 inches, to the over 50-foot whale shark. Sharks obviously have jaws, as do the other cartilaginous fish. These fish evolved from the jawless fish. So why did fish eventually evolve to have jaws? Such an adaptation would allow fish to eat a much wider variety of food, including plants and other organisms. |
SciQ | SciQ-1317 | evolution, mammals, marine-biology
The question remains: why? The most likely explanation is that cetaceans evolved to exploit an unfilled ecological niche or adapted to new niches that formed as a result of plate tectonics or other types of environmental changes that occurred 50-55 million years ago. The niche describes all of the living and non-living resources needed by an organism to survive. Although land-based mammals were increasing in diversity, few or none were present in the oceans. The basic hypothesis is that the early whale-like artiodactyls, like Indohyus and Pakicetus were land-based (terrestrial) mammals that spent most of their time near the water's edge. Over time, they adapted to the niches in the ocean. Fossils like Ambulcetus and Rodhocetus showed clear evidence of swimming ability, with flattened tails and the enlarged rear feet. In addition, the nostrils shifted from the front of the face to the top of the head, which we recognize as the blowhole.
The shift to the aquatic habitat allowed these species to exploit resources that were not available to land-based mammals, thereby reducing competition for the resources. Reduced competition allows more individuals to survive and reproduce.
Similar scenarios are very likely for other marine mammals, such as seals or manatees. They evolved to take advantage of ecological niches that were not filled by other organisms. This basic concept, evolving to fill available niches, is a common outcome of the evolutionary process.
The of adaptation of cetaceans and other mammals to the oceans may be similar to that of the hippopotamus. Hippos spend most of their time in the water, and they show many adaptations that allow them to live in the aquatic environment. The eyes and nostrils of the hippo are high on the head, which allows them to remain almost entirely submerged but still see and smell, as shown below.
(Hippo photo by Johannes Lunberg, Flickr Creative Commons.)
Hippos feed underwaters, they are heavy enough to walk on the bottom of the river, and the mate and give birth underwater. The young can suckle underwater. Clearly, hippos seem to be another mammal that is "returning to water." Similar types of processes must have occurred in cetaceans for them to adapt to the marine habitat.
The following is multiple choice question (with options) to answer.
What makes the realized niche of chthamalus much smaller than its fundamental niche? | [
"asexual competition",
"instantaneous competition",
"microscopic competition",
"interspecific competition"
] | D | |
SciQ | SciQ-1318 | star, astrophysics
Title: Why are blue stars the hottest? I know that blue stars are the hottest and youngest (according to Universe Today). But what makes them blue, instead of other colors like purple? Our eyes and brains make them blue.
Stars are (close to) a black body, they emit a broad band of radiation. The hottest stars will emit most of their radiation in the ultraviolet but they will still be very bright in visible light.
As they get hotter, they emit even more ultraviolet, and more visible light but the mixture of wavelengths in visible light doesn't change much.
This mixture is interpreted by our brains as being a sort of light blue. No matter how hot the star gets, it will still be emitting lots of visible light in a mixture that looks "light blue". It will never look purple.
Purple can only be seen if either a single short-wavelength visible light is being emitted, or a mixture of short and long wavelengths (red and blue). Neither of the mixtures can occur in light emitted from a black body.
So stars can appear red, orange, yellow, white or light blue, but never green or purple.
The following is multiple choice question (with options) to answer.
Red stars are the coolest; which are the hottest? | [
"giant",
"white",
"yellow",
"blue"
] | D | Stars are classified by color, which correlates with temperature. Red stars are the coolest and blue are the hottest. |
SciQ | SciQ-1319 | human-anatomy, muscles
Title: Contracting muscles in humans I study biology at school, and unfortunately for me, my program skips the muscles in humans chapter.
I know (and mainly, feel) that the movement in one direction isn't created by the same muscle as the movement in the opposite direction, e.g the Triceps ("front") and Biceps ("back").
I know that the triceps straightens the elbow, while the biceps contracts the elbow.
I also know that, instead of actually moving the arm, I can contract these two muscles (when I show off, for example...) without actually moving the arm. That area becomes hard. Both muscles, as I feel, are contracting. I cannot statically contract only one of them.
My question is whether this action is something "special", or simply both muscles working against each other, resulting in zero movement? The situation you are describing where muscles are situated on opposites sides of a joint and produce opposing movements is called "antagonism." Most joints are set up where one or more muscles on either sides will produce such movements (e.g., flexors vs. extensors). Here's a question about muscles without antagonists.
When you contract all the muscles crossing a joint (i.e., when you are "showing off"), the muscles balance each other. If not, the bones would move and the joint angles would change. So taking the elbow as an example, in the image below, Arnold is contracting the elbow flexors (biceps brachii, brachialis) as well as the elbow extensors (triceps brachii). In order for the bones to remain static, the forces must be equal and opposite.
The following is multiple choice question (with options) to answer.
Which type of muscle is most common in the human body? | [
"skeletal",
"hormonal",
"digestive",
"smooth"
] | A | Skeletal muscle is attached to the bones of the skeleton. It is striated like cardiac muscle because its muscle fibers are arranged in bundles. Contractions of skeletal muscle are voluntary. This means that they are under conscious control. Whether you are doing pushups or pushing a pencil, you are using skeletal muscles. Skeletal muscles are the most common type of muscles in the body. You can read more about them below. |
SciQ | SciQ-1320 | history-of-chemistry
Title: Any false chemical element in history of chemistry? Was there any false chemical element introduced in history of chemistry? I mean a substance that after a while proved that it was not an element. The example that comes to mind is didymium, which turned out to be a mixture of praesodymium and neodymium. The term is still used, as far as I know, to refer to glass doped with a mixture of these lanthanides. This is discussed in one of the 'Chemistry in its element' podcast episodes.
As it turns out, wikipedia has a category called 'Misidentified Chemical Elements'. Especially notable are illmenium, dianium and pelopium, which were all likely mixtures of niobium and tantalum, two rather similar elements.
The following is multiple choice question (with options) to answer.
What is the name for a combination of elements that acts as a different substance? | [
"mixture",
"contrast",
"compound",
"solution"
] | C | An element is a fundamental chemical part of a substance; there are about 115 known elements. A compound is a combination of elements that acts as a different substance; there are over 50 million known substances. |
SciQ | SciQ-1321 | exoplanet
It's probably possible to have volcanic eruptions even though dozens or maybe even hundreds of miles of exotic ice because the heat has to go somewhere, eventually, assing it's likely to build up over time, so either by circulation of eruption, the heat has push through at some point. This even happens on so called "dead" planets like Mars or even the Moon. Mars still has the occasional volcanic eruption, just not very often.
But water worlds certainly can have plate tectonics. There's nothing in the water that would prevent it from happening. Plate Tectonics is, as I understand it, primarily a factor of the size of the planet. Gas planets - different story, but planets with a hard surface, Earth sized, a tiny bit smaller to a fair bit but not much bigger are good candidates for plate tectonics (I think). There's some debate on how large, I think, still going on. But I remember reading that ocean/water worlds might even be more likely to have plate tectonics. Plate tectonics is definitely something we'd look for if we ever get a close enough look at other planets in different solar-systems (exoplanets).
Just my thoughts on this. Not meant to be complete or definitive.
The following is multiple choice question (with options) to answer.
Volcanoes can be active, dormant, or what else? | [
"extinct",
"still",
"burgeoning",
"remnant"
] | A | Volcanoes can be active, dormant, or extinct. |
SciQ | SciQ-1322 | biochemistry, cell-biology, neurotransmitter, membrane-transport, synapses
Title: Exocytosis of synaptic vesicles I'm reading the following paper:
http://jcs.biologists.org/content/123/6/819
The part I am really confused about is when they say:
Exocytosis appears to use two alternative pathways: clathrin-mediated endocytosis (CME), which is well established by numerous lines of evidence, and the more controversial ‘kiss-and-run’ pathway, which involves direct retrieval of a vesicle at the site of fusion
My question is .. How can exocytosis (contents inside of cell are transported to outside of cell) use clathrin mediated endocytosis?
I thought endocytosis is the opposite of exocytosis, so why do synaptic vesicles use clathrin mediated endocytosis as a method of exocytosis? That sentence is located in a paragraph titled "Stages 5-7: Endocytosis and recycling": it's talking about recycling exocytosed membrane which is necessary for making vesicles for further exocytosis.
The sentences before the part you quoted are:
Synapses possess highly efficient mechanisms for retrieving SVs from the plasma membrane of the presynaptic terminal after exocytosis. Fast regeneration of functional SVs is a prerequisite for synapses to function during prolonged activity.
I think the passage is just somewhat confusingly worded, in that "exocytosis" is used as the subject of the sentence which is strange in this context. You could rewrite that sentence:
There appear to be two alternative pathways to recycle membrane for exocytosis: clathrin-mediated...
The following is multiple choice question (with options) to answer.
Vesicular transport includes exocytosis and what? | [
"endocytosis",
"phagocytosis",
"metastasis",
"meiosis"
] | A | There are four main ways that molecules can pass through a phospholipid membrane. The first way requires no energy input by the cell and is called simple diffusion. This type of transport includes passive diffusion and osmosis. No assistance by a transport is necessary in simple diffusion. Facilitated diffusion, does involve the assistance of transport proteins. The third way, called active transport , requires that the cell uses energy to pull in or pump out certain molecules and ions. Active transport involves proteins known as pumps. The fourth way is through vesicle transport , in which large molecules are moved across the membrane in bubble-like sacks that are made from pieces of the membrane. Vesicular transport includes exocytosis and endocytosis. |
SciQ | SciQ-1323 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
What supports the scapula, transmits the weight and forces from the upper limb to the body trunk, and protects the underlying nerves and blood vessels? | [
"bladder",
"clavicle",
"cranium",
"pelvis"
] | B | end is also anchored to the first rib by the costoclavicular ligament. The acromial end of the clavicle articulates with the acromion of the scapula at the acromioclavicular joint. This end is also anchored to the coracoid process of the scapula by the coracoclavicular ligament, which provides indirect support for the acromioclavicular joint. The clavicle supports the scapula, transmits the weight and forces from the upper limb to the body trunk, and protects the underlying nerves and blood vessels. The scapula lies on the posterior aspect of the pectoral girdle. It mediates the attachment of the upper limb to the clavicle, and contributes to the formation of the glenohumeral (shoulder) joint. This triangular bone has three sides called the medial, lateral, and superior borders. The suprascapular notch is located on the superior border. The scapula also has three corners, two of which are the superior and inferior angles. The third corner is occupied by the glenoid cavity. Posteriorly, the spine separates the supraspinous and infraspinous fossae, and then extends laterally as the acromion. The subscapular fossa is located on the anterior surface of the scapula. The coracoid process projects anteriorly, passing inferior to the lateral end of the clavicle. |
SciQ | SciQ-1324 | thermodynamics, material-science, phase-transition, states-of-matter
Title: Why does matter exist in 3 states (liquids, solid, gas)? Why does matter on the earth exist in three states? Why cannot all matter exist in only one state (i.e. solid/liquid/gas)? The premise is wrong. Not all materials exist in exactly three different states; this is just the simplest schema and is applicable for some simple molecular or ionic substances.
Let's picture what happens to a substance if you start at low temperature, and add ever more heat.
Solid
At very low temperatures, there is virtually no thermal motion that prevents the molecules sticking together. And they stick together because of various forces (the simplest: opposite-charged ions attract each other electrostatically). If you picture this with something like lots of small magnets, it's evident enough that you get a solid phase, i.e. a rigid structure where nothing moves.
Actually though:
Helium won't freeze at any temperature: its ground state in the low-temperature limit at atmospheric pressure is a superfluid. The reason is that microscopically, matter does not behave like discrete magnets or something, but according to quantum mechanics.
There is generally not just one solid state. In the magnet analogy, you can build completely different structures from the same components. Likewise, what we just call “ice” is actually just one possible crystal structure for solid water, more precisely called Ice Ih. There are quite a lot of other solid phases.
Liquid
Now, if you increase temperature, that's like thoroughly vibrating your magnet sculpture. Because these bonds aren't infinitely strong, some of them will release every once in a while, allowing the whole to deform without actually falling apart. This is something like a liquid state.
Actually though:
The following is multiple choice question (with options) to answer.
What are the three fundamental phases of matter? | [
"big, small. and medium",
"fast, slow, normal",
"solid, liquid, and gas",
"air, water, and land"
] | C | is the phase (or state) of matter. The three fundamental phases of matter are solid, liquid, and gas (see Figure 1.1 "The Phases of Matter"). Chemical properties are characteristics of matter that describe how matter changes form in the presence of other matter. Does a sample of matter burn? Burning is a chemical property. Does it behave violently when put in water? This reaction is a chemical property as well (Figure 1.2 "Chemical Properties"). In the following chapters, we will see how descriptions of physical and chemical properties are important aspects of chemistry. If matter always stayed the same, chemistry would be rather boring. Fortunately, a major part of chemistry involves change. A physical change occurs when a sample of matter changes one or more of its physical properties. For example, a solid may melt (Figure 1.3 "Physical Changes"), or alcohol in a thermometer may change volume as the temperature changes. A physical change does not affect the chemical composition of matter. A chemical change is the process of demonstrating a chemical property, such as the burning match in Figure 1.2 "Chemical Properties". As the matter in the match burns, its chemical composition changes, and new forms of matter with new physical properties are created. Note that chemical changes are frequently accompanied by physical changes, as the new matter will likely have different physical properties from the original matter. |
SciQ | SciQ-1325 | cell-biology, hematology, red-blood-cell
Title: Why are red blood cells considered to be cells? Wikipedia states that a cell is
the basic structural, functional and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently.
It then goes on to state that
All cells (except red blood cells which lack a cell nucleus and most organelles to accommodate maximum space for hemoglobin) possess DNA.
Then why are red blood cells still considered cells, while they can't replicate? Is the definition on Wikipedia just a bad definition? Or are red blood cells wrongly considered cells, but remain so for historical reasons? Or are they considered cells for some other reason, such as this answer which states that red blood cells do contain a nucleus at some point? A very good question, and it is most likely because of the last option. It had a nucleus for part of its life. After the RBC jettisons its nucleus, it still remains very metabolically active for approximately 3 months. It maintains its cell membrane integrity, it metabolizes glucose, it interacts constantly with its environment, numerous cellular functions and structure remain intact... It is extremely specialized for a primary purpose, and no longer requires the nucleus to provide more proteins. It has limited capacity to heal from injury, so it has a limited life span.
Speculation: I wonder if it might lose the nucleus early on so that when it is destroyed in the spleen at the end of its life as RBCs are, the spleen macrophages are not overwhelmed with additional processing of nucleic acids? Macrophage type cells are already working hard in there to clear infectious agents and some immune cells from the blood.
The following is multiple choice question (with options) to answer.
What system in the human body makes white blood cells that protect the body from diseases? | [
"renal system",
"lymphatic system",
"reproductive system",
"cardiovascular system"
] | B | The lymphatic system also plays an important role in the immune system. For example, the lymphatic system makes white blood cells that protect the body from diseases. Cells of the lymphatic system produce two types of white blood cells, T cells and B cells, that are involved in fighting specific pathogens. Lymph nodes, which are scattered throughout the lymphatic system, act as filters or traps for foreign particles and are important in the proper functioning of the immune system. The role of the lymphatic system in the immune response is discussed in additional concepts. |
SciQ | SciQ-1326 | forces, newtonian-gravity, planets, centrifugal-force
Title: Why are planets not torn apart? There are two forces we know, Centripetal force (or Gravity) and Centrifugal force. Both are applied to all the planets including earth. Planets are kind of spherical due to gravitational force but also not perfectly round due to this centrifugal force (or any other force idk) applied.
I read a lil before asking this question here and found, centrifugal force (or whatever) is not really great on earth but obviously it's enough to cause bend to it. But, I found this about Altair
A significant percentage of stars in the sky rotate much faster and
bulge noticeably at their equators. Like
Altair is notable for spinning very, very rapidly and completes a
full rotation on its axis every 10.4 earth hours. Accordingly,
astronomers estimate that Altair is at least 14 percent wider at the
equator than it is from pole to pole.
I'm sure there must be many stars and planets with greater centrifugal force on them like Altair. But why then none of the planet or star is torn apart till now ? I mean less or more a force is applied and that force is making an impact and huge impact maybe in many cases. Then why none of such planet is torn apart till now ?
If you say Gravity or centripetal force keeping it together and maybe canceling out other forces then why even this bend ? that means other forces have an impact (if i understood it correctly).
I'm not a physicist but have interest in physics. Would be thankful if someone can explain in simple words.
Then why none of such planet is torn apart till now ?
The following is multiple choice question (with options) to answer.
Which process or force pulls rocks apart? | [
"composition stress",
"friction stress",
"tension stress",
"tactile stress"
] | C | Tension stress pulls rocks apart. Tension causes rocks to lengthen or break apart. Tension is the major type of stress found at divergent plate boundaries. |
SciQ | SciQ-1327 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
What rigid layer surrounds the cell membrane of a plant cell? | [
"cuticle",
"epidermis",
"cell wall",
"bark"
] | C | The cell wall is a rigid layer that surrounds the cell membrane of a plant cell. It’s made mainly of the complex carbohydrate called cellulose. The cell wall supports and protects the cell. The cell wall isn’t solid like a brick wall. It has tiny holes in it called pores. The pores let water, nutrients, and other substances move into and out of the cell. |
SciQ | SciQ-1328 | electromagnetism, optics, quantum-optics
Title: What exactly happens when total internal reflection takes place at a quantum level? What happens when light interacts with the boundary between 2 mediums at a quantum level? Why is it totally reflected back when it is travelling from an optically denser to a less dense medium? How does the quantum of light know that its going through such a boundary?
"How does the quantum of light know that its going through such a boundary?"
By obeying the quantum mechanical solution of the boundary value problem "photon scattering off boundary"
Here is the light phenomenon:
Total internal reflection is a phenomenon which occurs when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is greater than the critical angle, the wave cannot pass through and is entirely reflected.
The refractive index is a collective measure of the atoms/molecules of the lattice on which the light is incident and depends on the collective fields built up by them. This is the field on which each individual photon will be scattering and partakes of the boundary conditions of the problem.The fields must be such that the individual photons from that angle on are scattered in only a backward direction .
The following is multiple choice question (with options) to answer.
When does internal reflection occur? | [
"when light goes from a fast medium to another fast medium",
"when light goes from a slow medium to another slow medium",
"when light goes from a slow medium to a fast",
"when light goes from a fast medium to a slow"
] | C | Total internal reflection occurs when light goes from a slow (high index of refraction) medium to a fast (low index of refraction) medium. With total internal reflection, light refracts so much it actually refracts back into the first medium. This is how fiber optic cables work: no light leaves the wire. |
SciQ | SciQ-1329 | solar-system, exoplanet
Title: Are the planets Trappist-1 in the solar system? I'm an Astronomy noob, but I'm interested in learning how stars and planets work. Everything started with the Trappist-1. I read about it, and it's fascinating. However, it's impossible for me to localize it with my current state of knowledge. Therefore, I would like to ask some general questions here.
First of all, during high school, I have learned that we are in the solar system and there are some planets orbiting the sun. Easy to remember and imagine, but there are stars, planets, constellations, etc. which I can't manage to relate to this basic system that I learned about.
And what confused me a lot are these two pictures:
and
And this definition of an exoplanet:
An exoplanet or extrasolar planet[...]
From the pictures, I can see that Trappist is in fact in the solar system. Is this right? And if this is right, why in the world did it take us so many years to find it? We have one Voyager that is almost out from the solar system. Couldn't it find it before? And is it possible to find more planets in our solar system? Is it because Voyager went only in the x-y direction, and not "perpendicular" to the orbits?
I'm sorry for asking these stupid questions, but I simply can't build new knowledge on my current low-level understanding of the solar system. This is my current knowledge:
Can you please help me to answer the above questions?
During high school, I have learned that we are in the solar system and there are some planets orbiting the Sun.
Yes that is correct. According to current definitions of what counts as a planet, there are 8 planets orbiting our Sun $-$ Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. There are also a collection of smaller "Dwarf Planets" which include (in no particular order): Pluto, Ceres, Eris, and Makemake. There's also a lot of other minor solar system bodies out there like asteroids, comets, etc.
but there are stars, planets, constellations
The following is multiple choice question (with options) to answer.
What is the fourth planet from the sun? | [
"Pluto",
"mars",
"Mercury",
"Saturn"
] | B | Mars is the fourth planet from the Sun. It has two small, irregular moons. Mars is red because of rust in its soil. Mars has the largest mountain and the largest canyon in the solar system. |
SciQ | SciQ-1330 | genetics, dna, molecular-genetics, gene
and that employed by the ENCODE project is defined by Gerstein et al. as:
The gene is a union of genomic sequences encoding a coherent set of potentially overlapping functional products
a gene is a genomic sequence (DNA or RNA) directly encoding functional product molecules, either RNA or protein.
In the case that there are several functional products sharing overlapping regions, one takes the union of all overlapping genomic
sequences coding for them.
This union must be coherent — i.e., done separately for final protein and RNA products — but does not require that all products necessarily
share a common sub-sequence
(It is supplemented by an ontological diagram that I shall not reproduce here.)
This is complex, but in relation to the poster’s concern one thing is clear, at no time are the authors concerned with strandedness, and there is no proposal that a gene is confined to a single strand.
Two simple arguments
One might argue that nobody mentions strandedness because everyone assumes a gene is on only one strand. Really? Anyway, I‘ll finish with a couple of mundane arguments that strandedness has no place in defining genes, overlapping or not.
The Transcription Factor/RNA polymerase binding site — the TATA box — is regarded as an integral part of a gene. Both strands of the TATA box are required for binding. Likewise other transcription factor binding sites. Hence the gene cannot be on only one strand.
Single-stranded DNA viruses are found with what are called ‘positive sense’ and ‘negative sense‘ genomes. So clearly among these genomes there are heredity units which read ‘anti-sense’ as well as some that are ‘anti-sense’. On the ‘one-stranded gene’ thesis one of these could not be called genes. One would have to devise some term from them as progenitors of the gene in the complementary strand in the replicative DNA form!
The following is multiple choice question (with options) to answer.
Which region of dna consists of one or more genes that encode the proteins needed for a specific function? | [
"antigen",
"mRNA",
"operon",
"chromosome"
] | C | Regulation of transcription in prokaryotes typically involves operons. An operon is a region of DNA that consists of one or more genes that encode the proteins needed for a specific function. The operon also includes a promoter and an operator. The operator is a region of the operon where regulatory proteins bind. It is located near the promoter and helps regulate transcription of the operon genes. |
SciQ | SciQ-1331 | immunology, parasitology
Title: Why is untreated trypanosomiasis invariably fatal in humans? If left untreated, African trypanosomiasis will invariably kill the patient. The human immune system is unable to clear the infection.
I am aware of a few other infectious diseases with this property and I have a rudimentary understanding of the reason why. For example, I'm told that rabies has evolved to be uniquely good at attacking the brain because that's the only way it can spread to other hosts, and the neuroimmune system, being quite different from the peripheral immune system, is not capable of dealing with a virus that has this property.
I do not understand why the human immune system is ineffective against trypanosomiasis. One explanation I was offered is that the human immune system is just not very good at fighting parasitic infections (compared to viral and bacterial infections). However, this can't be the full answer, because there are other parasitic infections that may go away on their own without treatment. African trypanosomiasis, or sleeping sickness, is caused by the protozoan Trypanosoma brucei, a single-celled eukaryote. Being eukaryotic, it has a cell nucleus and a larger genome than most bacteria; it also has a flagellum with which it can propel itself. Infection with T. brucei occurs via the bite of a blood-sucking fly, one of several species of tsetse fly.
The mammalian immune system has a difficult time with T. brucei because of an effective set of adaptations. The protozoan's surface maintains a dense coat of a particular glycoprotein on its surface which generally hide other necessary surface features such as chemical receptors and ion channels. Since it is this glycoprotein that the adaptive immune system will encounter, that molecule is the one which it will develop antibodies to recognize.
The following is multiple choice question (with options) to answer.
Members of the genus trypanosoma are flagellate protozoa that cause what? | [
"cancer",
"hypertension",
"sleeping sickness",
"mutations"
] | C | Members of the genus Trypanosoma are flagellate protozoa that cause sleeping sickness , which is common in Africa. They also cause Chagas disease , which is common in South America. The parasites are spread by insect vectors. The vector for Chagas disease is shown in Figure below . Trypanosoma parasites enter a person’s blood when the vector bites. Then they spread to other tissues and organs. The diseases may be fatal without medical treatment. |
SciQ | SciQ-1332 | human-biology, cell-biology
Title: What kinds of cells does human saliva contain? I have heard that our saliva contains cells. What cell types can be found in human saliva? It contains white blood cells (leukocytes) and cells from the inner lining of the mouth (buccal epithelial cells). The DNA obtained from these cells is the basis of DNA profiling based on saliva samples.
Source: Salimetrics
The following is multiple choice question (with options) to answer.
The major salivary enzyme is called? | [
"amylase",
"mucosa",
"sucrase",
"synthase"
] | A | The mouth is the first digestive organ that food enters. The sight, smell, or taste of food stimulates the release of digestive enzymes by salivary glands inside the mouth. The major salivary enzyme is amylase. It begins the chemical digestion of carbohydrates by breaking down starch into sugar. |
SciQ | SciQ-1333 | astronomy, orbital-motion, history
1. For $p$ in Earth years and $r$ in Earth orbital radii (today's AU).
2. Applying trigonometry to the observed angular extent of the moons' orbits and the distance to Jupiter.
3. Ganymede produces a slightly different value. No. Johannes Kepler published what is now known as his third law of planetary motion in 1619 (in his treatise Harmonices Mundi), but discovered it already on May 15, 1618. He simply related mean distance of a planet from the Sun to its mean angular motion, without a word about a mass, I think. He did write on gravity and mass (not the precise physical term) in a foreword to his earlier book Astronomia Nova.
Thanks to people (Rafael Gil Brand, Roger Ceragioli and R. H. van Gent) from H-ASTRO discussion forum I have the following update #1:
1, The original form of the third law (formulated for planets), freely traslated to English reads approximately:
"...it is absolutely certain and perfectly correct, that the ratio which exists between the periodic times of any two planets is precisely 3/2 of the ratio of the mean distances, i.e. of the spheres themselves, bearing in mind, however, that the arithmetic mean between both diameters of the elliptic orbit is slightly less than the longer diameter"
2, Although (as far as I know from my own experience with early observations of double stars by Galileo) it is virtually impossible to prove that an earlier observation/idea didn't exist, it seems that the first application of Kepler's Third Law to the Jovian satellite system, is found in Newton's Philosophiae Naturalis Principia Mathematica (2nd ed. of 1713), lib. III, prop. 8, resulting in 1/1033 solar mass.
It is possible that Riccioli had something about the topic in one of his monumental treatises published around the middle of the 17th century.
Update #2
Riccioli seem to discuss relation between elongation of Galilean satellites of Jupiter and their orbital periods both in his Almagestum Novum and Astronomia Reformata, and cites Vendelinus (Godefroy_Wendelin). The Wikipedia entry for him states:
"In 1643 he recognized that Kepler's third law applied to the satellites of Jupiter."
The following is multiple choice question (with options) to answer.
Who first discovered the moons of jupiter in 1610? | [
"galileo",
"darwin",
"Socrates",
"Newton"
] | A | Jupiter has lots of moons. As of 2011, we have discovered over 60 natural satellites of Jupiter. Four are big enough and bright enough to be seen from Earth using a pair of binoculars. These four moons were first discovered by Galileo in 1610. They are called the Galilean moons . Figure below shows the four Galilean moons and their sizes relative to Jupiter’s Great Red Spot. These moons are named Io, Europa, Ganymede, and Callisto. The Galilean moons are larger than even the biggest dwarf planets, Pluto and Eris. Ganymede is the biggest moon in the solar system. It is even larger than the planet Mercury!. |
SciQ | SciQ-1334 | paleontology
Title: How to start studying dinosaurs and pre-historic mammals/sea creatures I'm kind new to this hole thing of dinosaurs that I'm really interested in, are there any good books/websites/webpages to study the biology of pre-historic creatures? Dinosaurs, mammals, fishes, anything that is not alive anymore. Also, any good books about the history of how these species evolved and the history behind them would be appreciated. Here's what it takes to really study this: you need to go through the whole bachelor program for geoscientists, that includes fundamental geodynamics like plate tectonics, magmatism, volcanism, volcanic and metamorphic rocks and generally the cycles that make up earth's internal dynamics.
Then there is the huge field of external factors, like sediment geology (that's really complicated stuff), weathering and transport and how soils come to being, diagenesis and the structures sediments can form and their classifications. Role of the ocean (that's where it starts, before all) and the atmosphere, of course.
When through that, usually 4 semesters or so, you can start to specialize. For paleontolgy you need knowledge of earth history, of course, it's subdivision, and the conditions at certain times as far as they are known. Once that's done, then comes real paleontology: Animals (invertebrates and vertebrates), plants, and their development, biological evolution (that's frequently underrated, I find), taphonomy, ... For a sturdy base count another 2-4 semesters.
You may see that even a bunch of websites, maybe all of them together, cannot replace actual study. I am not aware of any site that even gives a reasonable overview of the field. Geoscience, and thus paleontology, touch many fields of natural science.
That said, when asked "How to learn about animal paleontology ?" I allways mention Micheal Benton, Vertebrate Paleontology. It needs a basic understanding of geoscience, evolution and skeleton anatomy. Functional morphology, phylogeny and an overview over sediment geology and earth history also won't harm, but you could give it a try. Some things are explained in between.
The following is multiple choice question (with options) to answer.
Fossil records show that what process may occur in "fits and starts"? | [
"evolution",
"isolation",
"generation",
"variation"
] | A | Millions of fossils have been found since Darwin’s time. They show that evolution may occur in fits and starts. Long period of little or gradual change may be interrupted by bursts of rapid change. The rate of evolution is influenced by how the environment is changing. Today, Earth’s climate is changing rapidly. How do you think this might affect the rate of evolution?. |
SciQ | SciQ-1335 | 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 part of the ear is often described as a bony labyrinth? | [
"embedded ear",
"outer ear",
"inner ear",
"solid ear"
] | C | The inner ear is often described as a bony labyrinth, as it is composed of a series of canals embedded within the temporal bone. It has two separate regions, the cochlea and the vestibule, which are responsible for hearing and balance, respectively. The neural signals from these two regions are relayed to the brain stem through separate fiber bundles. However, these two distinct bundles travel together from the inner ear to the brain stem as the vestibulocochlear nerve. Sound is transduced into neural signals within the cochlear region of the inner ear, which contains the sensory neurons of the spiral ganglia. These ganglia are located within the spiral-shaped cochlea of the inner ear. The cochlea is attached to the stapes through the oval window. The oval window is located at the beginning of a fluid-filled tube within the cochlea called the scala vestibuli. The scala vestibuli extends from the oval window, travelling above the cochlear duct, which is the central cavity of the cochlea that contains the sound-transducing neurons. At the uppermost tip of the cochlea, the scala vestibuli curves over the top of the cochlear duct. The fluid-filled tube, now called the scala tympani, returns to the base of the cochlea, this time travelling under the cochlear duct. The scala tympani ends at the round window, which is covered by a membrane that contains the fluid within the scala. As vibrations of the ossicles travel through the oval window, the fluid of the scala vestibuli and scala tympani moves in a wave-like motion. The frequency of the fluid waves match the frequencies of the sound waves (Figure 14.6). The membrane covering the round window will bulge out or pucker in with the movement of the fluid within the scala tympani. |
SciQ | SciQ-1336 | equilibrium, enzyme-kinetics
[OP] I based the kinetics for these reactions on Michaelis-Menten kinetics, so every enzyme has a $V_{max}$ and $K_M$, and has velocity $v=V_{max}x /(K_M+x)$
The product $P$ has a maximum rate of $r_\mathrm{P,max}$, not the enzyme. This value is obtained when the substrate is so abundant that $[S] \gg K_\mathrm{M}$.
[OP] I use the Reaction Quotient $Q$ at any point in time to determine in which direction a reaction would proceed. E.g. would (net/overall) $A$ be converted to $B$ or vice versa. Each reaction is defined with a reaction energy which is used to calculate Equilibrium constant $K_e$.
You have as many reaction quotients $Q$ as reversible chemical reactions. You can do this for $\text{R1}$ because this step is reversible. However, you cannot do this for $\text{R2}$, because for the M-M mechanism this step is irreversible. Thus, once any quantity of $\ce{ES}$ complex has been formed, $\text{R2}$ will proceed, independently if you had a lot of $\pu{P}$ at $t=0$.
My understanding is that Miachelis-Menten kinetics only describe the case in which $Q<<K_e$. What happens if $Q→K_e$?
A reaction quotient is not defined for irreversible reactions.
Intuitively I would assume that the overall reaction velocity slows down as $Q$ approaches $K_e$. Is there a term that I can add to the Michaelis-Menten equation which would describe this decreasing $v$?
The following is multiple choice question (with options) to answer.
Enzymes speed up the rate of a specific chemical reaction and is therefore known as what? | [
"biochemical catalysts",
"genetic catalysts",
"protein catalysts",
"characteristic catalysts"
] | A | Enzymes are biochemical catalysts, which means that they speed up the rate of a specific chemical reaction. A process that might take weeks in the absence of an enzyme can occur in milliseconds if the proper enzyme is present. A generic enzyme-catalyzed reaction could be represented as follows:. |
SciQ | SciQ-1337 | bond
Title: Breaking bonds with energy I'm learning about breaking molecular bonds currently and I'm wondering what are the methods to actually use the amount of bond energy to break the bond. What I'm saying is, knowing the bond energy, how can you actually use this information to break the bond? Do you heat it up the equivalent amount as the Kj/mol or something similar to that? Yes, the energy showed that is needed to break bonds is usually in the form of heat. I don't believe there is another common way to do it, but don't quote me on it. I haven't learned about lasers and other such technologies :). Keep in mind that as bonds are broken, they release energy themselves. As bonds are created, they take in energy on their own. Often, you will just need to start a reaction with some outside energy source (A bunsen burner for example) and it will be able to continue on its own because it produces energy from breaking bonds. If you look at the formation of Magnesium Oxide, all you really have to do is light a small end of a piece of Magnesium ribbon, and the whole thing burns because it creates energy as it reacts. I hope that helps!
The following is multiple choice question (with options) to answer.
What is required to break bonds in reactants? | [
"protein",
"energy",
"gas",
"food"
] | B | Why is activation energy needed? A reaction won’t occur unless atoms or molecules of reactants come together. This happens only if the particles are moving, and movement takes energy. Often, reactants have to overcome forces that push them apart. This takes energy as well. Still more energy is needed to start breaking bonds in reactants. The graphs in Figure below show the changes in energy in endothermic and exothermic reactions. Both reactions need the same amount of activation energy in order to begin. |
SciQ | SciQ-1338 | organs, lifespan
Title: Organs lifespan out of the body What organ can be conserved outside of the body for the longest time and still function when reimplanted? Depends what you consider an organ. Typically though it's the cells which require the most metabolic activity which have the shortest life span. The kidney is the most of the major internal organs with up to 36 hours with liver coming second at up to 16 hours.
The following is multiple choice question (with options) to answer.
Organs are made up of two or more types of what? | [
"fluids",
"tissues",
"muscles",
"bones"
] | B | Bones come in many different shapes and sizes, but they are all made of the same materials. Bones are organs, and recall that organs are made up of two or more types of tissues. |
SciQ | SciQ-1339 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
During what type of reproduction do two haploid gametes join in the process of fertilization to produce a diploid zygote? | [
"asexual reproduction",
"sexual reproduction",
"essential reproduction",
"internal reproduction"
] | B | During sexual reproduction, two haploid gametes join in the process of fertilization to produce a diploid zygote. |
SciQ | SciQ-1340 | botany, homework, terminology, plant-anatomy, tissue
Interfascicular cambium differentiates from parenchyma or collenchyma cells located between the vascular bundles (mainly in stem)
The following is multiple choice question (with options) to answer.
What does the ground tissue consist mostly of in the stems of both monocots and eudicots? | [
"hinterrhein cells",
"eudiocotic cells",
"parenchyma cells",
"epenthesis cells"
] | C | |
SciQ | SciQ-1341 | waves, electromagnetic-radiation, visible-light
Title: Questions regarding light being depicted as a sine wave Light waves are often depicted as sine waves...
Why is it so?
What's actually waving?
And what does the sine wave signify and represent?
What does wavelength of light mean/signify? and how is it calculated for specific colors?
Thank you! :) The picture is very missleading. What is waving is an electric field and a magnetic field, therefor we call it an electromagnetic wave. the different colors have different wavelength, which is the distance of two consecutive maxima of the electric field. but the wavelength is so short, one can not really depict it, it is less than $\frac{1}{100000}mm$ but the kind of wave is just the same as the radio waves .
The following is multiple choice question (with options) to answer.
What type of wave is visible light? | [
"static",
"electromagnetic",
"radio",
"acoustic"
] | B | Many kinds of waves exist, such as sound waves and water waves. Visible light is also a wave. It is a specific type of a more general phenomenon called an electromagnetic wave. All waves can be described in terms of the basic physical properties frequency and wavelength . These two properties are related to the speed of a wave by the following equation:. |
SciQ | SciQ-1342 | biochemistry
Title: Numbering amino acid residues While reading about primary structures of protein, I came across the following image.
What do the numberings $n-1, n, n+1$ in the below image refer to?
I thought about it : The amino acid residues are numbered from 1 to n starting from the N-terminus to the C-terminus .
But the image below shows only a part of the protein.. so why is the last residue numbered $n+1$ instead of $n$ also, why is this shown as termination?
I looked out few papers.. but they seem to be very technical and beyond the scope of my understanding. This question is a bit hard to answer for me without more context.
However, it is clear that the n refers to the tyrosine which is highlighted in the figure as well (especially the interaction of its phenol). The other positions (n+1, n-1) are shown relative to the tyrosine.
I'm unsure about the role of tyrosine in the primary structure of proteins, but maybe this is more clearly explained where you found the figure. I'm also unsure if the glutamic acid is terminal.
The following is multiple choice question (with options) to answer.
What catalyzes the hydrolysis of amino acids from the n-terminal end of a protein? | [
"synthase",
"nucleic acid",
"testosterone",
"aminopeptidase"
] | D | Pepsinogen is an inactive form of pepsin; pepsin is the active form of the enzyme. Both enzymes catalyze the hydrolysis of peptide bonds. Chymotrypsin catalyzes the hydrolysis of peptide bonds following aromatic amino acids, while trypsin catalyzes the hydrolysis of peptide bonds following lysine and arginine. Aminopeptidase catalyzes the hydrolysis of amino acids from the N-terminal end of a protein, while carboxypeptidase catalyzes the hydrolysis of amino acids from the Cterminal end of a protein. |
SciQ | SciQ-1343 | evolution, terminology, history, species, definitions
Title: Was Darwin aware of the difficulties behind the concept of species? Introduction
The concept of species is a very old concept that suffers from not being a natural category. There exists no single definition that would categorize living beings into groups and that would fit our intuitions of what a species should be.
Many of such problems in definitions are revealed in the field of evolutionary biology. For more information about the difficulties behind the definition of the concept of species, have a look at
How could humans have interbred with neanderthals if were a different species?
This post on ring species.
Question
Did Charles Darwin comment on this problem?
If yes, did Charles Darwin comment on the reason why he chose to keep using the term "species" instead of simply "lineage"? The whole point of Darwin's theory was that transition from one species to another is extremely slow and gradual. There are plenty of quotes in "Origin of Species" stating this, and also affirming that there is no clear boundary between species and subspecies, or "races".
Quotes from Origin of Species > Variation under Nature (Chapter 2)
Quote 1
Nevertheless, no certain criterion can possibly be given by which variable forms, local forms, sub species and representative species can be recognised
Quote 2
Several experienced ornithologists consider our British red grouse as only a strongly marked race of a Norwegian species, whereas the greater number rank it as an undoubted species peculiar to Great Britain. A wide distance between the homes of two doubtful forms leads many naturalists to rank them as distinct species; but what distance, it has been well asked, will suffice if that between America and Europe is ample, will that between Europe and the Azores, or Madeira, or the Canaries, or between the several islets of these small archipelagos, be sufficient?
Quote 3
It is here the most definitive quote I managed to find and partially answers to your second question.
From these remarks it will be seen that I look at the term species as one arbitrarily given, for the sake of convenience, to a set of individuals closely resembling each other, and that it does not essentially differ from the term variety, which is given to less distinct and more fluctuating forms. The term variety, again, in comparison with mere individual differences, is also applied arbitrarily, for convenience sake.
The following is multiple choice question (with options) to answer.
Which group of species is defined as having moist skin without scales? | [
"mammals",
"amphibians",
"fish",
"reptiles"
] | B | Amphibians have moist skin without scales. The skin is kept moist by mucus, which is secreted by mucous glands. In some species, the mucous glands also secrete toxins that make the animal poisonous to predators. The blue poison-dart frogs in Figure below are a good example. The toxin in their mucus is used by native people in South America to poison the tips of their hunting arrows. |
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