source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-1844 | 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.
What is a combination of two or more substances in any proportions called? | [
"structure",
"mixture",
"mix",
"Combination"
] | B | A mixture is a combination of two or more substances in any proportions. The substances in a mixture do not combine chemically, so they retain their physical properties. |
SciQ | SciQ-1845 | geophysics, plate-tectonics, earth-history, continent
Title: Why Do Supercontinents Form? It would seem, on the face of it, improbable that the continental land-masses would accumulate into a single composite, yet it has happened numerous times, and is expected to again in the future.
There must likely then be some aspect of plate tectonics which favors these arrangements.
Can anyone provide an explanation?
EDIT: This is not, as I see it, a duplicate of the 'What are the causes of the supercontinent cycle?' question. This question goes to what process drives the formation of any & all supercontinent formations, which I assert should be improbable, made more improbable by their recurrence, not so much the cycle itself. The other question did not address this more fundamental aspect, or in any case receive a pertinent account of its resolution. If anyone wants to engage on this, or doesn't see the distinction, please do so in the comments or a chat. I think the mechanisms that you're looking for are subduction, paired with the "stickiness" of continental crust.
The subduction of oceanic crust under continental crust inevitably creates a net movement of crustal material toward a continental plate. Any oceanic plate that is carrying continental material will therefore always drag that continent toward the continental plate that it is subducting underneath, always resulting in eventual collision.
If an oceanic plate has subduction occurring on both sides, the ocean will inevitably narrow until it closes, thereby causing the continental plates on either side to collide.
In every case, subduction inevitably pulls continents together.
Furthermore, once continental plates collide, they have a tendency to stick together for long periods of time, increasing the likelihood that all continental material will eventually accumulate there.
The following is multiple choice question (with options) to answer.
What does subduction of a plate lead to? | [
"swell and volcanism",
"bending and volcanism",
"melting and volcanism",
"pressure and volcanism"
] | C | Subduction of a plate leads to melting and volcanism. |
SciQ | SciQ-1846 | earth-history
Common elements in space, such as CO2, H20, CH4 and NH3 are gaseous at Earth's distance from the sun and as a result, are unlikely to stick to anything in the Earth's formation region. This is true for all 4 inner planets and likely all rocky worlds. Rocky planets likely can only form close to their star, just as gas giants, ice giants or other icy abundant bodies like comets and low-density moons, can only form further out.
Gases like the 4 above can begin to be retained around a planet after it reaches a sufficiently large mass with low enough surface temperature to retain those gases by gravity.
The boundaries where CO2, H20, CH4, NH3 and other gases can be found in the protoplanetary disk is called the frost line. Different gases have different frost lines depending on their freezing point.
It's thought that much of Earth's water, CO2, CH4 and NH3 came to the Earth by comet after the planet formed. There's still some uncertainty on the percentages, as some of those elements could have been trapped during formation.
Just to add, hydrogen and helium are obviously abundant, but will only begin to accrue around a planet of a certain mass. In our solar-system, only Jupiter and Saturn are massive enough to accrue hydrogen and helium. That's why Uranus and Neptune are relatively low on hydrogen and helium compared to the universal abundance.
Argon is in Earth's atmosphere because it forms from gradual radioactive decay of Potassium-40. Earth's Helium is also present as a result of radioactive decay.
The following is multiple choice question (with options) to answer.
The mixture of gases that surrounds the planet and makes up the atmosphere is known as ________. | [
"energy",
"vaccum",
"air",
"fuel"
] | C | The atmosphere is a mixture of gases that surrounds the planet. We also call it air. The gases in the atmosphere include nitrogen, oxygen, and carbon dioxide. Along with water vapor, the atmosphere allows life to survive. Without it, Earth would be a harsh, barren world. |
SciQ | SciQ-1847 | 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.
What system protects the soft organs of the body? | [
"nervous system",
"skeletal system",
"Cardiovascular system",
"digestive system"
] | B | The skeletal system protects the soft organs of the body. For example, the skull surrounds and protects the brain. The ribs protect the heart and lungs. |
SciQ | SciQ-1848 | atmosphere, planetary-science
With no plate tectonics, there was no mechanism to bury carbon inside of Venus. Plate tectonics developed fairly early on in Earth's history. By the time the Sun became hot enough (the early Sun was faint), the Earth had already started the process of sequestering away carbon into the lithosphere.
Life. Life loves carbon. It is one of the key agents by which atmospheric carbon is transferred to the lithosphere. Life apparently never had a chance on Venus.
References
Bercovici D. and Ricard Y., "Plate tectonics, damage and inheritance," Nature 508, 513-516 (2014)
Fei et al., "Small effect of water on upper-mantle rheology based on silicon self-diffusion coefficients," Nature 498, 213–215 (2013)
Mian Z. and Tozer D., "No water, no plate tectonics: convective heat transfer and the planetary surfaces of Venus and Earth," Terra Nova 2:5, 455-459 (1990)
The following is multiple choice question (with options) to answer.
Before the atmosphere became oxygenated, the planet was subjected to what harmful energy source, meaning the first organisms would have flourished where they were more protected? | [
"convection",
"conduction",
"radiation",
"evaporation"
] | C | Before the atmosphere became oxygenated, the planet was subjected to strong radiation; thus, the first organisms would have flourished where they were more protected, such as in ocean depths or beneath the surface of Earth. At this time, too, strong volcanic activity was common on Earth, so it is likely that these first organisms—the first prokaryotes—were adapted to very high temperatures. These are not the typical temperate environments in which most life flourishes today; thus, we can conclude that the first organisms that appeared on Earth likely were able to withstand harsh conditions. Microbial mats may represent the earliest forms of life on Earth, and there is fossil evidence of their presence, starting about 3.5 billion years ago. A microbial mat is a large biofilm, a multi-layered sheet of prokaryotes (Figure 13.3a), including mostly bacteria, but also archaea. Microbial mats are a few centimeters thick, and they typically grow on moist surfaces. Their various types of prokaryotes carry out different metabolic pathways, and for this reason, they reflect various colors. Prokaryotes in a microbial mat are held together by a gummy-like substance that they secrete. The first microbial mats likely obtained their energy from hydrothermal vents. A hydrothermal vent is a fissure in Earth’s surface that releases geothermally heated water. With the evolution of photosynthesis about 3 billion years ago, some prokaryotes in microbial mats came to use a more widely available energy source—sunlight—whereas others were still dependent on chemicals from hydrothermal vents for food. |
SciQ | SciQ-1849 | fluid-dynamics, conventions, flow, turbulence, models
$\frac{\Delta p}{\rho U^2}=f(Re)$, where $f$ is some function of Reynolds number.
In a turbulent flow it so happens that pressure drop is determined primarily by processes other than viscous dissipation (mixing of momentum by advection of fluid elements rather than by molecular diffusion), so to a good approximation viscosity is unimportant, in which case there cannot be dependence on $Re$ i.e. $\frac{\Delta p}{\rho U^2} \approx$ constant, which means for a turbulent flow, $\Delta p~\alpha~ U^2~\alpha~Q^2$. I think those who call $K_2$ turbulent flow factor are drawing upon this resemblance. But it is only a resemblence, may be it helps the person remember which factor is which.
If we write out $\Delta p$ as a polynomial series of $Q$, then for small enough $Q$, we may neglect higher powers of $Q$ and we thus have $\Delta p~\alpha~Q$. This is laminar flow regime, and calling $K_1$ laminar flow factor is again only by way of resemblance.
The following is multiple choice question (with options) to answer.
Turbulent sounds, at the onset of blood flow when the cuff pressure becomes sufficiently small are called? | [
"whooping sounds",
"korotkoff sounds",
"pinworm sounds",
"choanocyte sounds"
] | B | 12.5 The Onset of Turbulence Sometimes we can predict if flow will be laminar or turbulent. We know that flow in a very smooth tube or around a smooth, streamlined object will be laminar at low velocity. We also know that at high velocity, even flow in a smooth tube or around a smooth object will experience turbulence. In between, it is more difficult to predict. In fact, at intermediate velocities, flow may oscillate back and forth indefinitely between laminar and turbulent. An occlusion, or narrowing, of an artery, such as shown in Figure 12.17, is likely to cause turbulence because of the irregularity of the blockage, as well as the complexity of blood as a fluid. Turbulence in the circulatory system is noisy and can sometimes be detected with a stethoscope, such as when measuring diastolic pressure in the upper arm’s partially collapsed brachial artery. These turbulent sounds, at the onset of blood flow when the cuff pressure becomes sufficiently small, are called Korotkoff sounds. Aneurysms, or ballooning of arteries, create significant turbulence and can sometimes be detected with a stethoscope. Heart murmurs, consistent with their name, are sounds produced by turbulent flow around damaged and insufficiently closed heart valves. Ultrasound can also be used to detect turbulence as a medical indicator in a process analogous to Doppler-shift radar used to detect storms. |
SciQ | SciQ-1850 | biochemistry, plant-physiology, plant-anatomy
Title: Why do plants store energy as carbohydrates and not as fats? In my introductory biology class, we are learning about biomolecules. The textbook says fats are a more efficient energy store than carbohydrates.
So my question is - why would plants store their energy as carbohydrates and not as fats, if fats are a more efficient energy store? There are quite some reasons for why plants prefer carbohydrates for energy storage rather than fats. I will reach some of them one at a time.
The following is multiple choice question (with options) to answer.
What is the simple sugar that living things us to store energy? | [
"glucose",
"brown",
"nicotine",
"chloride"
] | A | simple sugar that all living things use to store and transport energy. |
SciQ | SciQ-1851 | chromosome, meiosis
Title: Is there random assortment in metaphase II? First, a little notation. Call a the first chromosome from my mother and A its homologous partner from my father. b and B would be the second pair, c and C the third, and so on, down to w and W (the 23rd).
The tetrads in interphase would be expressed as aa AA...ww WW (so, for example, AA are sister chromatids). Finally, use the notation a' and A' to express that those two chromatids have crossed over via recombination.
Ok: I understand that in Metaphase I, there's a random assortment of chromosomes at the equator, so that we might end up with a division like so:
aA' Aa'
bB' b'B
CC' c'C
...
wW' Ww'
Which pair ends up on the right or left is random, and there are therefore $2^{23}$ possible arrangements.
My question is whether an analogous shuffle happens during metaphase II? I visualize metaphase II as taking one of the columns above and turning it on its side, so that for instance taking the right column you have:
a' B C ... w'
A b' c' W
These "rows" are then split to become 2 of the 4 gametes.
The question is whether at this stage, before this final split, there is an analogous shuffling possible whereby, say, the A and a' could switch sides?
My intuition is yes, of course, but in all the accounts of meiosis I can find online, the "random assortment" and shuffling is all described as happening in metaphase I.
(I think whether the shuffling between this particular A and a' happens in metaphase I or metaphase II is inconsequential in terms of which one ends up in which daughter cell... but I'd still like to have a sense for what's literally physically happening.) Metaphase I
Your understanding of the metaphase I is not entirely correct. In normal (human) metaphase I homologous chromosomes separate. Therefore, sister chromatides go together. More precisely sister chromatides are kept together at centromere. You have only two possibilities for each chromosome:
<-AA aa->
The following is multiple choice question (with options) to answer.
Reversing the orientation of a chromosomal segment is called what? | [
"spontaneous mutation",
"volatiles",
"inversions",
"occurrences"
] | C | Inversions are reversing the orientation of a chromosomal segment. |
SciQ | SciQ-1852 | 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.
What does the clitellum secrete, while the sperm received are stored temporarily? | [
"cocoon of mucus",
"amoeba of mucus",
"pathogen of mucus",
"discharge of mucus"
] | A | |
SciQ | SciQ-1853 | physical-chemistry, aqueous-solution, gas-laws, vapor-pressure
An example of this situation playing out in the environment can be seen in the growth of water and ice particles in clouds. The vapor pressure of one particle can differ from that of another due to solute concentration, particle size (small droplets have a greater vapor pressure than larger droplets) and phase (supercooled water droplets have a greater vapor pressure than ice particles at the same temperature). Regardless of the cause of the vapor pressure difference, whether it's solute concentration or one of the other factors, the situation is the same as depicted in your question. And the result is the same; the particles having greater vapor pressure will end up evaporating and then condensing onto the particles having lower vapor pressure (of course we're talking about vapor pressure of water/ice only, not any solute). This is generally referred to as the Wegener–Bergeron–Findeisen process, although this technically only refers to water-to-ice vapor transfer.
The following is multiple choice question (with options) to answer.
What forms when water vapor condenses around particles in the air? | [
"wind",
"humididty",
"clouds",
"storms"
] | C | Clouds form when water vapor condenses around particles in the air. The particles are specks of matter, such as dust or smoke. Billions of these tiny water droplets come together to make up a cloud. If the air is very cold, ice crystals form instead of liquid water. |
SciQ | SciQ-1854 | inorganic-chemistry, acid-base, redox, halogens
$\ce{4 Cu/ 2 Fe/ 2 Co/ 2 Cr + O2 + 2 H+ -> 4 Cu+/ 2 Fe++/ 2 Co++/ 2 Cr++ + 2 OH- }$
Interesting and supportive, the above noted electrolysis reaction with copper can also be derived from a series of radical chemistry reactions. Namely, per a 2013 radical reaction supplement, "Impacts of aerosols on the chemistry of atmospheric trace gases: a case study of peroxides radicals", I cite the following reactions:
R24: $\ce{O2 + Cu+ → Cu++ + •O2− (k = 4.6*10^5) }$
R27: $\ce{ •O2− + Cu+ + 2 H+ → Cu++ + H2O2 (k = 9.4*10^9) }$
R25 $\ce{H2O2 + Cu+ → Cu++ + •OH + OH− (k= 7.0*10^3 ) }$
R23 $\ce{•OH + Cu+ → Cu++ + OH- ( k = 3.0×E09 ) }$
Where the implied net reaction, in the case of copper, confirms the claim reaction above, namely, a net reaction of:
$\ce{O2 + 4 Cu+ + 2 H+ → 4 Cu++ + 2 OH- }$
where the reactions above clearly suggest again the need for a soluble cuprous presence.
The mechanics of the etching of copper with $\ce{H2O2}$, $\ce{NaCl}$ and a acid source would not be likely complete without noting the role of radicals created via a Fenton-type reaction with copper:
$\ce{Cu+ + H2O2 + H+ → Cu++ + .OH + H2O }$
$\ce{H2O2 + .OH -> .HO2 + H2O }$
The following is multiple choice question (with options) to answer.
The cycle of copper reacting is a good example of what principle? | [
"conservation of mass",
"conservation of momentum",
"conservation of energy",
"law of inertia"
] | A | A series of chemical reactions where an initial amount of copper reacts with nitric acid, goes into solution, and disappears. Then a series of reactions proceed, only to have the copper metal recovered. The copper cycle is a good illustration of how mass is conserved in a given chemical reaction. |
SciQ | SciQ-1855 | homework-and-exercises, newtonian-mechanics, forces
Title: Friction on a box being pulled up a ramp
A box with mass $25$ kg on a ramp at an angle of inclination $30^\circ$ to the horizontal is pulled with a force of $75$ N at an angle of $20^\circ$ to the ramp. What is the frictional force if it is pulled up the ramp at constant speed?
I've constructed a free-body diagram:
The following is multiple choice question (with options) to answer.
A ramp is an example of what? | [
"change plane",
"inclined plane",
"level plane",
"move plane"
] | B | A ramp like the one in the Figure below is another example of an inclined plane. Inclined planes make it easier to move objects to a higher elevation. The sloping surface of the inclined plane supports part of the weight of the object as it moves up the slope. As a result, it takes less force to move the object uphill. The trade-off is that the object must be moved over a greater distance than if it were moved straight up to the higher elevation. You can see several other examples of inclined planes at this URL:. |
SciQ | SciQ-1856 | 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.
What kind of muscle is responsible for hollow organs contracting? | [
"tough muscle",
"micro muscle",
"rough muscle",
"smooth muscle"
] | D | Smooth muscles and cardiac muscles are not attached to bone. Recall that these types of muscles are under involuntary control. Smooth muscle is responsible for the contractility of hollow organs, such as blood vessels, the gastrointestinal tract, the bladder, or the uterus. Like skeletal muscles, smooth muscle fibers do contract together, causing the muscle to shorten. Smooth muscles have numerous functions, including the following. |
SciQ | SciQ-1857 | botany, plant-physiology, plant-anatomy
Title: How do plants grow year after year even though they die? How do plants grow, die, and then grow again? For instance, when my plants die during the winter, how do they grow again next year? Does it have something to do with the root system? Or do they even die? It depends on the type of plant, but basically not all of the plant dies. Plants have evolved a number of strategies for winter* dormancy. These are common ones, but probably not an exhaustive list.
Deciduous trees and bushes simply drop their leaves in the fall, and so may look "dead" to the unskilled eye - though with practice, it's usually easy to distinguish between dead and dormant. Then when the weather warms in the spring, new leaves grow.
Other perennial plants may lose some or all of their top growth, even dying back to ground level, but the roots will be alive, and will start growing when the ground warms.
Still other plants have developed specialized underground structures like bulbs & rhizomes - think daffodils, tulips, irises, and similar. The rest of the plant dies, only to grow again from the bulb when conditions are right.
It's worth noting that most, if not all, of these are used for propagation as well, often naturally, and frequently with a bit of human help. Bulbs and rhizomes multiply: the daffodil bulb you planted a few years ago may now be a dozen bulbs, each of which can be moved to grow new ones. Many perennials can be increased by dividing the root mass into pieces, each of which will become a new plant. And cuttings from many trees & bushes can be induced to form new root systems, and become new plants.
Or summer, dry season, &c. For simplicity, I'll just say "winter".
The following is multiple choice question (with options) to answer.
In vascular plants, do primary roots grow downward or to the side? | [
"to the side",
"neither",
"it depends",
"downward"
] | D | Roots are important organs in all vascular plants. Most vascular plants have two types of roots: primary roots that grow downward and secondary roots that branch out to the side. Together, all the roots of a plant make up a root system . |
SciQ | SciQ-1858 | visible-light, electromagnetic-radiation, radiation
Blue light is potentially more harmful if it has enough energy (depending how blue) to affect chemical bonds. Ultraviolet (very blue) light has enough energy to break molecules apart and so can be dangers, which is why you get sunburn. Light of longer wavelengths can only damage you by the heating effect so you need a lot more light to cause any harm. So the infrared light from your stove doesn't harm you, but an industrial cutting laser at the same wavelength can cut you in half.
I don't know what wavelength the 'therapy' uses, but if it is ultraviolet then a small amount of power could be harmful (ie sunburn), if it is visible blue then they would need to have very high levels of power to do any harm - by simply cooking you (like cell phones!).
Of course if the light is too long a wavelength and too low a power to have any effect on you - then exactly what is the point of the treatment?
The following is multiple choice question (with options) to answer.
What type of light has shorter wavelengths than visible light and has enough energy to kill bacteria? | [
"infrared",
"ultraviolet",
"luminescence",
"reflected light"
] | B | Mid-wavelength electromagnetic waves are called light. Light consists of visible, infrared, and ultraviolet light. Humans can see only visible light. Infrared light has longer wavelengths than visible light and is perceived as warmth. Ultraviolet light has shorter wavelengths than visible light and has enough energy to kill bacteria. It can also harm the skin. |
SciQ | SciQ-1859 | ## 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 characteristic of the endothelium structure minimizes resistance to the flow of blood? | [
"transition surface",
"liquid surface",
"smooth surface",
"uneven surface"
] | C | |
SciQ | SciQ-1860 | bond
Title: Types of bonds in a molecule For example in dinitrogen pentoxide, $\ce{N2O5}$, covalent as well as coordinate bonds (type of covalent bonds) are present, but it appears that it contains only covalent bond.
What is a proper method to find out which type of bonds are present in a molecule? Electrovalent bonds are easiest to identify. If a compound is made up of a metal and non-metal/non-metallic radical (like carbonate), then, 99.99% times, it contains electovalent bond. If a compound is made up of 2 or more non-metals/non-metallic radicals, then it contains covalent bond. Coordinate covalent bonds appear mostly with compounds containing Hydrogen element. To identify the coordinate covalent bonds, you can draw the branched structural formula of the compound and see if the shared pair of electrons are coming from the same molecule.
The following is multiple choice question (with options) to answer.
What type of bonds contain atoms that possess either a partial positive or a partial negative charge? | [
"geologic bonds",
"hot bonds",
"polar bonds",
"ionic bonds"
] | C | Polar bonds contain atoms that possess either a partial positive or a partial negative charge. |
SciQ | SciQ-1861 | human-anatomy
Title: Why is a penis an organ? According to Wikipedia an "An organ is a group of tissues with similar functions". I don't know anything about anatomy but it doesn't seem to me that a penis can be delimited somewhere to form a "group". Therefore I do not understand why a penis is considered an organ.
Can you explain it to me ? Frankly, that's a terrible definition by Wikipedia.
Merriam-Webster defines an organ as:
a differentiated structure (such as a heart, kidney, leaf, or stem) consisting of cells and tissues and performing some specific function in an organism
or
bodily parts performing a function or cooperating in an activity
The important defining feature of an organ is not that the tissues have similar functions but that, together, the tissues comprise a functional whole that achieves some end goal.
For the penis, it consists of multiple tissues with different functions:
(from https://www.ncbi.nlm.nih.gov/books/NBK525966/figure/article-20668.image.f1/ - original from Gray's Anatomy)
The different tissues pictured here: the fibrous envelope, the corpora cavernosa, the septum pectiniforme, the urethra and blood vessels, the nervous tissue in the skin: all of these tissues have different individual functions: structural, erectile, carrying urine or semen, etc.
The key that unifies them into an organ is that the functions of the penis at the organism level (principally sexual function) are not served by any of these tissues alone, but rather by their combination in a full structure: an organ.
Ultimately, organ definitions are somewhat opinion-based: people are lumpers and splitters, so you might find conflicting definitions for which groupings of tissues reflect distinct organs, but I think by most standards you would find the penis to be considered a distinct organ, affiliated with but distinct from the primary sex organs and associated glands.
The following is multiple choice question (with options) to answer.
The body contains how many types of muscle tissue? | [
"two",
"three",
"four",
"seven"
] | B | 38.4 Muscle Contraction and Locomotion The body contains three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. Skeleton muscle tissue is composed of sarcomeres, the functional units of muscle tissue. Muscle contraction occurs when sarcomeres shorten, as thick and thin filaments slide past each other, which is called the sliding filament model of muscle contraction. ATP provides the energy for cross-bridge formation and filament sliding. Regulatory proteins, such as troponin and tropomyosin, control cross-bridge formation. Excitation–contraction coupling transduces the electrical signal of the neuron, via acetylcholine, to an electrical signal on the muscle membrane, which initiates force production. The number of muscle fibers contracting determines how much force the whole muscle produces. |
SciQ | SciQ-1862 | evolution, zoology, eyes
Title: Do other animals suffer from myopia or hypermetropia? Mammals have eyes similar to humas and many other animals like octopuses have a lens in the eye. So do they have such eye defects? If yes, how do they overcome it? Do they feel selection pressure against them in such cases?
do they have such eye defects?
Yes, eye defect is not specific to humans of course. Cases of eye defect are very common in animals. It is most often witnessed in domestic animals and they are the ones we observe the most (see The physiology of domestic animals)
Eye defects have typically been observed in tree shrews, monkeys (incl. macaques), cats, dogs, horses, rats, elephant and a Cape buffalo.
You should have a look at the wikipedia article Myopia in animals
howw do they overcome it?
They don't wear glasses obviously!
Humans uses the sense of vision a lot. Many animals uses smell (and taste), hearing or touch much more than humans do. For such non-visual animal, having a slight eye defect is not too big of a deal.
Do they feel selection pressure against them in such cases?
That is a bit of an awkward question. Nobody can feel a selection pressure on themselves. A selection pressure is a fitness differential associated with genotypes. A selection pressure is therefore defined at the population level. There is no such thing as a fitness pressure against a single individual.
Let me rephrase this last question to something that makes more sense. I am not sure I will address the specific question that was of interest to you though.
Are non-humans animals that have an eye defect aware that they have an eye defect?
It is unlikely that any animal would have the cognitive abilities to notice that they see more poorly than another animal of the same species. Doing so, would at least require having the ToM and only few species do.
The following is multiple choice question (with options) to answer.
The eyes of all vertebrates possess a single one of these structures? | [
"sty",
"lens",
"stalk",
"vessel"
] | B | |
SciQ | SciQ-1863 | pregnancy, children
Title: What happens to the umblical cord inside the mother? After giving birth to a child, the umblical cord is cut (and stored if they want). The end connected to the child's navel will fell off eventually but what happens to the end inside the mother?
Will it be removed right after birth by doctors or what happens? Labor is typically divided into 3 stages:
Stage 1: From the onset of contractions (true labor pains) to full dilatation of the cervix (which is about 10 cm) - this takes about 12 to 18 hours
Stage 2: From full dilatation of cervix to expulsion of fetus - This takes about ~ 30 minutes
Stage 3. From expulsion of fetus to expulsion of placenta - this takes about ~ 15 minutes. During the third stage, the umblical cord which is attached to placenta is expelled along with the placenta. This would be the answer to your question.
Source:Hympath.com
The following is multiple choice question (with options) to answer.
The final stage of labor is delivery of the what? | [
"umbilical cord",
"placenta",
"embryo",
"uterus"
] | B | |
SciQ | SciQ-1864 | protein-structure
Title: What is a "monomeric polypeptide"? In the sentence: "Bacteriophage (viral) polymerases are typically monomeric polypeptides".
I know that polypeptides are chains of amino acids monomers. But what is a "monomeric polypeptide" and what other kinds of polypeptides are there? Monomer in this context means the protein has only one polypeptide chain. In some proteins, after the individual chains have folded into their 3D or tertiary structure, they associate (generally non-covalently) into a higher order or quaternary structure. A protein with a quaternary structure containing two copies of the same chain would be called a homo-dimer. One with one copy of each of two different chains is a hetero-dimer.
Haemoglobin is a well-known example of a protein with quaternary structure — it has two copies of the alpha- and two of the beta- chain. Further elementary treatment can be found in Berg et al. and explanation of the nomenclature in this Wikipedia page.
Monomeric polypeptide is somewhat misleading in the sentence quoted. Monomeric protein would have probably been better as you wouldn't be likely to say ‘dimeric polypeptide’, given that polypeptide implies a single chain.
The following is multiple choice question (with options) to answer.
All proteins are made of monomers called what? | [
"peptides",
"aminotides",
"monotides",
"amino acids"
] | D | Proteins are molecules that have many different functions in living things. All proteins are made of monomers called amino acids ( Figure below ) that connect together like beads on a necklace ( Figure below ). There are only 20 common amino acids needed to build proteins. These amino acids form in thousands of different combinations, making about 100,000 or more unique proteins in humans. Proteins can differ in both the number and order of amino acids. It is the number and order of amino acids that determines the shape of the protein, and it is the shape (structure) of the protein that determines the unique function of the protein. Small proteins have just a few hundred amino acids. The largest proteins have more than 25,000 amino acids. |
SciQ | SciQ-1865 | 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.
What system consists of all the muscles of the body? | [
"endocrine",
"vascular",
"digestive",
"muscular"
] | D | The muscular system consists of all the muscles of the body. Does the word muscle make you think of the bulging biceps of a weightlifter, like the man in Figure below ? Muscles such as biceps that move the body are easy to feel and see, but they aren’t the only muscles in the human body. Many muscles are deep within the body. They form the walls of internal organs such as the heart and stomach. You can flex your biceps like a body builder but you cannot control the muscles inside you. It’s a good thing that they work on their own without any conscious effort your part, because movement of these muscles is essential for survival. |
SciQ | SciQ-1866 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
Photoautotrophs and chemoautotrophs are two basic types of what? | [
"consumers",
"autotrophs",
"decomposers",
"plants"
] | B | Producers are organisms that produce food for themselves and other organisms. They use energy and simple inorganic molecules to make organic compounds. The stability of producers is vital to ecosystems because all organisms need organic molecules. Producers are also called autotrophs . There are two basic types of autotrophs: photoautotrophs and chemoautotrophs. |
SciQ | SciQ-1867 | human-biology, genetics, human-genetics
Title: Are all genetic disorders inherited? I know that genetic diseases such as cystic fibrosis are often passed down through generations and are therefore classified as genetic disorders, but if a mutation occurs spontaneously, which for example leads to cancer, is this then classified as a genetic disorder?
Are all genetic disorders inherited?
Not all individuals with a genetic disorder inherited that disorder. Some genetic disorders are caused by spontaneous mutations.
Is cancer a genetic disorder?
Yes. The seminal paper by Hanahan and Weinberg, the Hallmarks of Cancer, is a good place to go to get a sense of what we understand cancer to be. This paper is quite influential and has its own wikipedia page. These authors wrote an updated review in 2011. Re: your question as it relates to cancer, yes, genetic changes result in tumorigenesis. Cancer is a genetic disorder of cell populations. One can view cancer diagnosis and treatment from the framework of cancer as a metabolic disease, but this adds to, rather than subtracts from the framework of cancer as a genetic disease.
Are other diseases caused by spontaneous mutations genetic disorders?
Yes. Achondrodysplasia is one illuminating example. It is a form of dwarfism caused by a mutation in the FGFR3 gene. It does follow mendelian autosomal dominant inheritance patterns, but in 80% of cases, the mutation is, in fact, acquired spontaneously (that is, not present in either parent). As noted by @Eff in the comments, Down syndrome, Trisomy 21 (and other chromosomal abnormalities, e.g., Turner, Kleinfelter, Patau, Edwards) are other common examples.
The following is multiple choice question (with options) to answer.
Many genetic disorders are caused by mutations in one or a few of? | [
"lesions",
"genes",
"blood cells",
"organs"
] | B | Many genetic disorders are caused by mutations in one or a few genes. |
SciQ | SciQ-1868 | human-biology, physiology, endocrinology, autonomic-nervous-system
Title: Can stress and arousal be independent? I'm trying to figure out if it's possible to have a stress response without being initially, or simultaneously aroused. I'm defining stress to be physiological stress (ie. release of cortisol) and arousal to be activation of the sympathetic nervous system.
Every example I can think of, these two are not independent. In the case of "fight-or-flight," one initially activates the sympathetic nervous system, which is then followed by the release of cortisol. Or in individuals with major depressive disorder, their sympathetic nervous systems are constantly activated while cortisol is being secreted.
So, is it possible to experience cortisol release without activation of the sympathetic nervous system? Stress response has 2 main components:
Quick response, within minutes, is by the Sympathomedullary Pathway (SAM): hypothalamus > sympathetic nervous system > release of adrenaline and noradrenaline from the adrenal medulla > stimulation of the heart, dilation of the muscle arteries, constriction of the gut and skin arteries, glcogenolysis (the breakdown of glycogen into glucose) > more glucose available as a fuel
Delayed response, within hours, is by the The Hypothalamic Pituitary-Adrenal (HPA) System: hypothalamus > pituitary gland > ACTH > release of cortisol from the adrenal cortex > gluconeogenesis (formation of glucose in the body from other substances) > more glucose available as a fuel
The following is multiple choice question (with options) to answer.
In some cases, the nervous system directly stimulates endocrine glands to release hormones, which is referred to as what? | [
"functional stimuli",
"neural stimuli",
"active stimuli",
"brain stimuli"
] | B | Neural Stimuli In some cases, the nervous system directly stimulates endocrine glands to release hormones, which is referred to as neural stimuli. Recall that in a short-term stress response, the hormones epinephrine and norepinephrine are important for. |
SciQ | SciQ-1869 | genetics
Additional response added as requested:
I see what you are getting at - why do children seem like such individual and unique things sometimes?
In sexual reproduction, the offspring are the product of the shuffling of the parent's genomes through meiosis, where the pairs of chromosomes we have are combined to make a single chromosome that will be half of the children genome.
This process can result in completely novel combinations of genes while conveying many likenesses from the parent. I would guesstimate that this is the major cause of the uniqueness of offspring/children.
Also in mammals there are some cell lines which splice families of genes which will cause offspring to be potentially quite different from either parent. Immune genes for instance are created from scratch from a bunch of genes that the parents give. Making each offspring unique but also the product of the parent's genetic repertoire. This can be significant as it affects health and also to some extent attraction - studies have shown that people who smell attractive to us are immunologically distinct from us.
@David mentions epigenetic variation, which is a more recent significant development. During our life, the germline (sperm/egg) DNA may be chemically labelled depending upon environmental conditions we experience. A famous example is experiencing famine conditions, which caused the children to be born on the small side amongst other effects. More recent studies have shown that this is a widespread mechanism to control cells in our body during our lifetime as well as communicate to our offspring how life is. It is expected that this labeling does not affect us forever - the epigenetic labels change over the course of a generation quite often (we believe).
The following is multiple choice question (with options) to answer.
What kind of reproduction results in offspring that are generally all genetically different? | [
"asexual",
"sexual",
"perceptual",
"individual"
] | B | Sexual reproduction is typically slower. However, it also has an advantage. Sexual reproduction results in offspring that are all genetically different. This can be a big plus for a species. The variation may help it adapt to changes in the environment. |
SciQ | SciQ-1870 | waves, vacuum
Title: Mechanical waves edge between material and vacuum I have been thinking about the propagation of EM waves vs. mechanical waves and some of their odd cases. One such case that I haven't been able to puzzle out is what happens when a mechanical wave reaches the end of a medium (such as the outer layer of the atmosphere) and the beginning of a vacuum - outer space itself.
Edit: for clarity, I created a simple image demonstrating what I thought should happen:
Basically, my theory was that the "edge" particles (or particles with a large amount of space between them) would continue into space with perpetual motion as the force applied to them is not counteracted by particles in front of them.
My question is, after the wave has affected the last molecules on the edge of a vacuum, what happens to it, and, do the molecules on the very edge continue to move indefinitely (or do they return to equilibrium)? the materials are elastic, so when it reaches the end it would reflect, because the last layer won't have other layer to collide and the elastic properties of the material would make it bounce back, making the wave reflect back. Unless the wave energy is sooo large that would break the material and in that case the particles would indeed leave the material. if you have a bucket of water and drop a tiny piece of something, it would make a wave, but no water would separate, now if you drop something really big, some part of the water would separate from the other part.
The following is multiple choice question (with options) to answer.
When traveling through space what do mechanical waves lose? | [
"Force",
"Speed",
"energy",
"Mass"
] | C | An electromagnetic wave is a transverse wave that can travel across space as well as through matter. When it travels through space, it doesn’t lose energy to a medium as a mechanical wave does. |
SciQ | SciQ-1871 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
How many types of major tissues do modern plants have? | [
"seven",
"three",
"two",
"four"
] | B | A tissue is a group of specialized cells of the same kind that perform the same function. Modern plants have three major types of tissues. They're called dermal, ground, and vascular tissues. |
SciQ | SciQ-1872 | electric-circuits, home-experiment, electrical-resistance
Title: Measuring human resistance with a DMM When I attach a Digital Multimeter (DMM) to read the resistance between my right and left hands, the resistance starts off high and reduces over time. It appears almost like "RC-type" behavior. Can someone explain to me what it is that I am seeing on the DMM in some detail? It has nothing to do with any capacitance. It's all about skin resistance. The resistivity inside your body is much lower than that of the skin. As a result, your measurement is really showing you the sum of two resistances thru the skin.
The main reason skin has higher resistance than the body internally is because the skin is dry. However, the skin can get moister by sweating and external blocking of evaporation. When you grip the probes, evaporation is blocked in the immediate vicinity, so moisture builds up. Your body may also produce a bit more sweat when you grip hard.
Try licking your fingers before touching the probes and you will see the resistance reduced substantially. You can also reduce the resistance by gripping harder. That increases the contact area and also makes better contact.
The following is multiple choice question (with options) to answer.
How does a reduced sweating ability affect elderly people? | [
"extreme tiredness",
"less energy",
"loss of mental ability",
"extreme heat intolerance"
] | D | The accessory structures also have lowered activity, generating thinner hair and nails, and reduced amounts of sebum and sweat. A reduced sweating ability can cause some elderly to be intolerant to extreme heat. Other cells in the skin, such as melanocytes and dendritic cells, also become less active, leading to a paler skin tone and lowered immunity. Wrinkling of the skin occurs due to breakdown of its structure, which results from decreased collagen and elastin production in the dermis, weakening of muscles lying under the skin, and the inability of the skin to retain adequate moisture. Many anti-aging products can be found in stores today. In general, these products try to rehydrate the skin and thereby fill out the wrinkles, and some stimulate skin growth using hormones and growth factors. Additionally, invasive techniques include collagen injections to plump the tissue and injections of BOTOX® (the name brand of the botulinum neurotoxin) that paralyze the muscles that crease the skin and cause wrinkling. |
SciQ | SciQ-1873 | fruit, alcohol, fermentation
http://www.plantphysiol.org/content/100/1/1.full.pdf+html
During the early hours of germination [...] seeds rapidly generate high respiratory quotients and exhibit increased ADH2 activities and active alcoholic fermentation.
The following is multiple choice question (with options) to answer.
What substance do developing seeds produce which promotes fruit growth? | [
"xenon",
"pepsin",
"interferon",
"auxin"
] | D | |
SciQ | SciQ-1874 | atmosphere, clouds, fluid-dynamics
Title: What affects the surface characteristics of cumulus clouds? I love looking at clouds. I love trying to describe them and compare what I see day to day.
I have dozens of questions about the things I’ve observed and I would really like to understand the physics of the world around me. Today I would like to focus on the surface dynamics of cumulus clouds.
Why do some cumulus clouds have distinct textured surface while others are softer and wispy at the edge?
I imagine it probably comes down to temperature and pressure. It may also be an effect of direct sunlight, I’m not sure. I notice the soggy cotton clouds are more common in the evening and the billowy ice cream clouds are more common mid-day.
Do clouds have surface tension like liquid water?
Does the flow of water either into or out of a cloud affect its surface characteristics? No, clouds don't really have a 'surface' that could have tension like a body of water. The different looks in these two examples (left Cumulonimbus Calvus and right Cumulus Humilis) are greatly dependent on how they have formed and how are they evolving now.
The large Cumulonimbus is still growing in a relatively rapid speed. The cloud is reaching higher and higher upwards carrying moist air. The moist air due to turbulent flows and expanding of the rising air gets mixed with the cold air and instantly forms/extends cloud as it reaches saturation (saturation is reached with less water in colder air and air is colder in higher altitudes). If there wasn't the expansion then flows of dry air to the cloud would desaturate the cloud and more small scale variation could be seen as in the Cumulus Humilis. Also the Cumulonimbus being much larger and further away looks different just due to distance. The steady state like situation of the Cumulus Humilis where it isn't growing (perhaps a little on the top) and the fact that the lower atmosphere has stronger turbulent motions equals to the appearance where more cotton candy pieces 'drift' from the cloud.
The following is multiple choice question (with options) to answer.
Different clouds are associated with different types of what? | [
"biomes",
"zodiac signs",
"weather conditions",
"magnetic fields"
] | C | |
SciQ | SciQ-1875 | 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.
The testes produce sperm and secrete what? | [
"testosterone",
"thyroxine",
"melanin",
"estrogen"
] | A | The testes produce sperm and secrete testosterone. |
SciQ | SciQ-1876 | newtonian-mechanics, forces, energy, work
Title: Energy transfer and Negative work Is energy always transferred from the source to the object when positive work is done by the source on the object ?
If so, what energy is transferred from the earth to a freely falling body ?
The potential energy is converted to kinetic energy in the process. But I see no transfer of energy between the earth and the body.
And how does energy transfer takes place in case of negative work ?
When a body is moved across a surface which has friction, the friction does negative work. Does it mean that a sort of energy transfer occurs between the surface (source) and the body (object) ?
If so, how ? Is energy always transferred from the source to the object when positive work is done by the source on the object ?
Yes, but be careful. If something else simultaneously does an equal amount of negative work on the object, the net work on the object will be zero.
If so, what energy is transferred from the earth to a freely falling body ?
Gravitational potential energy of the earth/body system is transferred to the freely falling body. Gravity does positive work giving the object kinetic energy per the work energy theorem.
The potential energy is converted to kinetic energy in the process. But I see no transfer of energy between the earth and the body.
Energy transfer to the body comes from the gravitational potential energy of the earth/body system. It does not come from just the earth, but from the earth/body system. Neither the body alone nor the earth alone has gravitational potential energy. It is a property of the earth/body system.
And how does energy transfer takes place in case of negative work ?
In the case of negative work, the force is in the opposite direction as the displacement. The thing doing negative work takes energy away from the thing it does work on, as discussed in the next answer.
When a body is moved across a surface which has friction, the friction does negative work. Does it mean that a sort of energy transfer occurs between the surface (source) and the body (object) ? If so, how ?
Yes. When friction does negative work it takes energy away from the object it does work on. What makes friction interesting, however, is that it involves both energy transfer to the stationary surface upon which the body slides from the object, and energy transfer from the stationary surface to the object.
The following is multiple choice question (with options) to answer.
Friction does negative work and removes some of the energy the person expends and converts it to which kind of energy? | [
"erosion",
"hydro",
"evaporation",
"thermal"
] | D | Discussion for (a) This value is the net work done on the package. The person actually does more work than this, because friction opposes the motion. Friction does negative work and removes some of the energy the person expends and converts it to thermal energy. The net work equals the sum of the work done by each individual force. Strategy and Concept for (b) The forces acting on the package are gravity, the normal force, the force of friction, and the applied force. The normal force and force of gravity are each perpendicular to the displacement, and therefore do no work. Solution for (b) The applied force does work. |
SciQ | SciQ-1877 | evolution, genetics, natural-selection
Genetic Adaptation During Lifetime of a multicellular organism
For a beginner in evolutionary biology, saying that a multicellular individual's genome does not change during its lifetime might be considered satisfying. In reality it is slightly more complicated. Two elements that are mostly influent very early in the lifetime of an individual have to be considered.
While most mutations occurs during reproduction, some mutations does also occurs during body growth or stated differently during cell reproduction (Mitosis). In consequence, some pairs of your cells share exactly the same genome while other pairs of cells have a sligthly different genome.
Moreover, once some mutations had occurred within the development of an individual, these mutations might influence the fitness of the cells and therefore some alleles (variant of a gene) might raise in frequency while others decrease in frequency (Natural selection). It is important to understand that this process of natural selection select for cells that have a higher fitness and therefore do not necessarily select for the cells that allows the individual to increase its own fitness.
I don't fully understand what you mean when saying: "But does evolution work by some primitive genetics-engineering too?" Could you try to rephrase this question?
Please, let me know if I answered your question!
Note:
Here is a good way to understand the difference between "gene" and "allele". A gene might be a called the "eyes color" gene for example, while the three alleles of the "eyes color" gene might be callsed "blue eyes", "brown eyes" and "green eyes". In this sense, the alleles are the different variants of a gene. Mutations increase the number of alleles and natural selection reduces the number of alleles by selecting for the allele that cause its holder to have the greatest fitness. If you understood that, it is already good!
Note: Natural selection does not necessarily reduce the number of alleles, several alleles might be kept (polymorphism) in certain "types" of natural selection (frequency dependent selection and overdominance (heterozygote advantage), fitness varies in space and/or time, selection acts on different levels). The "type" of Natural selection that reduces the number of alleles after some time is called directional selection.
The following is multiple choice question (with options) to answer.
What happens when forces of evolution work over a long period of time? | [
"developmental evolution",
"macroevolution",
"substantial evolution",
"Microevolution"
] | B | What happens when forces of evolution work over a long period of time? The answer is macroevolution. An example is the evolution of a new species. |
SciQ | SciQ-1878 | humidity, water-vapour
Title: Water vapor content versus specific humidity I am wondering the difference between water vapor content and specific humidity to determine the moisture availability in the atmosphere. Which one is more acceptable variable to determine the moisture availability in the atmosphere?
I need to show the moisture availability in the atmosphere in my study. So should I explain it through water vapor content or through specific humidity? I will explain the rainfall deficiency over a region For a study relating to rainfall, I would be inclined to look at total column water vapour (TCWV), also known as integrated water vapour (IWV) or precipitable water. They're all (more or less) the same thing.
The company Remote Sensing Systems describes it as:
Total column water vapor is a measure of the total gaseous water contained in a vertical column of atmosphere. It is quite different from the more familiar relative humidity, which is the amount of water vapor in air relative to the amount of water vapor the air is capable of holding. Atmospheric water vapor is the absolute amount of water dissolved in air. When measured in linear units (millimeters, mm), it is the height (or depth) the water would occupy if the vapor were condensed into liquid and spread evenly across the column. Using the density of water, we can also report water vapor in kg/m2 = 1 mm or g/cm2 = 10 mm.
For rain to form, clouds need to form first. Clouds need cloud condensation nuclei, but crucially, for clouds to form, the water vapour partial pressure needs to reach the saturation vapour pressure. The latter is strongly dependent on temperature (Clausius-Clapeyron relation), so a profile of relative humidity is not the most directly useful quantity. The total column water vapour describes how much liquid water might form, which is why it is sometimes even described as precipitable water.
You can get this product either from reanalysis (like ERA-5) or retrieved from hyperspectral infrared sounders, such as IASI, AIRS, or CrIS. Depending on where and when in the world you're looking at, there may also exist products from geostationary instruments.
The following is multiple choice question (with options) to answer.
What measurement is used to describe the amount of water vapor in the air? | [
"heat",
"humidity",
"precipitation",
"barometric pressure"
] | B | Humidity is the amount of water vapor in the air. Relative humidity is the percent of water vapor in the air relative to the total amount the air can hold. The total amount depends on temperature. |
SciQ | SciQ-1879 | everyday-chemistry, metal, transition-metals, smell
Also, it turns out that $\ce{Fe^{2+}}$ ions (but not $\ce{Fe^{3+}}$) are capable of oxidizing substances present in oils produced by the skin, namely lipid peroxides. A small amount of $\ce{Fe^{2+}}$ ions are produced when iron comes into contact with acids in sweat. These then decompose the oils releasing a mixture of ketones and aldehydes with carbon chains between 6 and 10 atoms long. In particular, most of the smell of metal comes from the unsaturated ketone 1-octen-3-one, which has a fungal/metallic odour even in concentrations as low as $1\ \mu g\ m^{-3}$ . In short:
Sweaty skin corrodes iron metal to form reactive $\ce{Fe^{2+}}$ ions that are oxidized within seconds to $\ce{Fe^{3+}}$ ions while simultaneously reducing and decomposing existing skin lipid peroxides to odorous carbonyl hydrocarbons that are perceived as a metallic odor.
In the supporting information for the article (also free-access), the authors describe experiments performed with other metals, including copper:
The following is multiple choice question (with options) to answer.
Sebaceous glands produce an oily substance called what? | [
"ear wax",
"synovial fluid",
"sebum",
"pus"
] | C | Sebaceous glands produce an oily substance called sebum . Sebum is secreted into hair follicles and makes its way to the skin surface. It waterproofs the hair and skin and helps prevent them from drying out. Sebum also has antibacterial properties, so it inhibits the growth of microorganisms on the skin. |
SciQ | SciQ-1880 | dna, codon
Title: Will a Codon result in same amino acid across organisms Will all organisms with the same 3 nucleotide sequence in the codon produce the same exact same amino acid. I read that the three nucleotide sequence will code for a particular amino acid. I did not understand if that is the case across organisms. Can someone explain this in simple terms. Although the answer to this question may be found in Mitochondrial Genetic code, because that answer is primarily about mitochondrial genetic codes, I shall give a more directed answer here.
Because the same genetic code that was elucidated in bacteria was found to apply to higher eukaryotes, it was initially assumed that the genetic code was universal, and was referred to as such. Subsequently it was discovered that mitochondria did not generally employ this ‘universal’ code, which is now usually referred to as the ‘standard’ code — indeed different mitochondrial codes were found in different organisms.
However the question seems to be more concerned with the genetic codes of bacteria and the nuclear genetic codes of eukaryotes. Here also there are deviations from the standard genetic code, which can be found listed either on this Wikipedia page or at NCBI.
Below are some examples from the NCBI list (where references may be found) with the standard coding in parentheses:
Mycoplasma
UGA Trp (Ter)
Ciliates, Dasycladacean and Hexamita
UAA Gln (Ter)
UAG Gln (Ter)
Euplotidae
UGA Cys (Ter)
Candidate Division SR1, Gracilibacteria
UGA Gly (Ter)
Pachysolen tannophilus
CUG Ala (Leu)
Finally, tRNAs for the ‘additional’ amino acids, selenocysteine and pyrrolysine recognize, respectively, the UGA and UAG stop codons in specific contexts.
The following is multiple choice question (with options) to answer.
In what kind of a series does the genetic code work? | [
"three-letter codes",
"four-letter codes",
"universal codes",
"nine letter-codes"
] | A | The genetic code works as a series of three-letter codes. Each sequence of three letters, called a triplet, corresponds to one of the twenty common amino acids. The triplets are read by the cell, one after the other, in the process of protein synthesis. The Table below shows all of the possible triplets and the amino acids that result from each three-letter code. |
SciQ | SciQ-1881 | energy, electricity, heat
Title: Electricity directly from heating a material I am looking for some more information about how to obtain electricity from heat directly. This e.g. involves the Seebeck effect, as I have found it is called, where a material produces a voltage across when heated in one end and having the other end slightly cooler. This should be the princip in measuring instruments etc., since just a small voltage is created.
This Wikipedia link explains what the phenomenon is about. But it is not well explained in an understandable language (for me at least). And it doesn't dive deep enough into the reason.
Are there someone who can in a down-to-earth way explain how and why a voltage can be measured between the ends of a bar of a certain material, when it is heated in one end? My question regards what happens on the atomic scale - can heat push electrons or what?
Thanks. The electrons in a metal are whizzing around due to thermal energy. Lattice vibrations excite the electrons, the electrons travel some distance then scatter off the lattice again and transfer energy back to the lattice. Just like a gas, the electrons have some average mean free path, and this depends on the temperature. You would think the mean free path would increase with temperature, because the lattice transfers more energy to the electrons, but the rate of scattering off the lattice also increases with temperature. How the mean free path behaves with temperature depends on the trade-off between these two effects, and the varation with temperature can be positive or negative.
Anyhow, if you heat one end of a metal rod and cool the other then the mean free path will be different at the two ends, and the electrons at the end with the higher mean free path will tend to diffuse into the end with the lower mean free path. The result is a net charge movement, and this creates the potential difference.
The following is multiple choice question (with options) to answer.
Free-flowing electrons enable what materials to conduct electricity and heat very well? | [
"metals",
"acids",
"noble gases",
"alloys"
] | A | This model for metallic bonding explains some of the physical properties of metals. Metals conduct electricity and heat very well because of their free-flowing electrons. As electrons enter one end of a piece of metal, an equal number of electrons flow outward from the other end, allowing an electrical current to pass through the material with minimal resistance. Additionally, because the electron "glue" that holds the metal atoms together is very easy to deform and reshape, bulk metals can be easily hammered, bent, and pulled without breaking apart. |
SciQ | SciQ-1882 | electric-circuits, electric-current, electrical-resistance, voltage, batteries
Title: Voltage drop across battery with internal resistance Consider a battery with internal resistance connected to an external voltage source; there is a voltage difference along the battery
The voltage source is not drawn in the picture
The voltage difference is $\ V= E ± Ir$ where ± is determined by the direction of the current flow. The symbols have their usual meanings
V is the total voltage difference through the battery. As per the definition of resistance ; the resistance of some component is equal to the total voltage difference through that component divided by the total current that flows through it.
Accordingly, it would follow that $\frac{V}{r}=I$ Which is in contradiction to the aforementioned. E would be zero, which is clearly wrong
The second method implicitly assumes that the total voltage drop is only caused by the resistance alone. However to my knowledge resistance is defined as the ratio between the total voltage difference and the current that flows through it.
What is the correct definition of resistance of a component, if it is different from the above? Or is there something wrong in my reasoning?
Reading the answer I now consider the contexts where V=IR can be used as a definition for the resistance of a component.
https://en.m.wikipedia.org/wiki/Electrical_resistance_and_conductance The wiki article uses “object” implying, some sort of a generality. $V$-$I$ linear OR $V=IR$ is statement of Ohm's law? Too stresses how resistance is defined.
Where have I gone wrong?
You've gone wrong here:
the resistance of some component is equal to the total voltage
difference through that component divided by the total current that
flows through it.
It's not some component that Ohm's law applies to, it's specifically (ideal) resistors.
To model a physical cell, one starts by putting an ideal resistor in series with an ideal voltage source. You'll note that the voltage across the resistor is given by Ohm's law but the voltage across the voltage source is what it is regardless of the current through, i.e., the ideal voltage source does not obey Ohm's law.
Thus, the voltage across the series combination of the voltage source and resistor will not, and should not be expected to, obey Ohm's law.
The following is multiple choice question (with options) to answer.
What is the difference in voltage across a resistor or other electrical devices called? | [
"power drop",
"volt effect",
"voltage drop",
"falling voltage"
] | C | The name electric current is the name given to the phenomenon that occurs when an electric field moves down a wire at close to the speed of light. Voltage is the electrical energy density that causes the electric current. Resistance is the amount a device in the wire resists the flow of current by converting electrical energy into other forms of energy. A device, the resistor, could be a light bulb, transferring electrical energy into heat and light or an electric motor that converts electric energy into mechanical energy. The difference in Voltage across a resistor or other electrical device is called the voltage drop. |
SciQ | SciQ-1883 | evolution
Title: In this representation of the tree of life, what are the lateral connections?
I found this simple representation of the tree of life in a wikipedia article, and I was curious what these horizontal connections shown here are supposed to be, like the ones between plants and protists, or bacteria and protists going to plants. Do they represent things like lateral gene transfer or potential endosymbiotic origin relationships? (like the theory that eucaryotes came from a merging of a bacteria with an archae). Yes, pretty much! Lateral branches here indicate endosymbiotic events and major horizontal gene transfers.
I'd warn though that the diagram is not very accurate, and additions I'd make would complicate it further as a bush (rather than a tree). Each branch root itself is an instance of cladogenesis, and for this reason the diagram is not very accurate (e.g. fungi and metazoans seem to arise within the same "branch"), and also misses a few lateral branches that otherwise exist. My favorite example of atypical horizontal gene transfer is that of prokaryote-insect transfers which occur frequently. This has been known for some time; many insects contain genes of Wolbachia origin and some (not all) are definitively functional, and are understood to facilitate obligate (fully-dependent) mutualisms.
The following is multiple choice question (with options) to answer.
What is the science that describes the ancestral and descendant connections between organisms? | [
"experimentally",
"organic science",
"phylogeny",
"polygamy"
] | C | Building Phylogenetic Trees with Analysis of DNA Sequence Alignments All living organisms display patterns of relationships derived from their evolutionary history. Phylogeny is the science that describes the relative connections between organisms, in terms of ancestral and descendant species. Phylogenetic trees, such as the plant evolutionary history shown in Figure 26.7, are tree-like branching diagrams that depict these relationships. Species are found at the tips of the branches. Each branching point, called a node, is the point at which a single taxonomic group (taxon), such as a species, separates into two or more species. |
SciQ | SciQ-1884 | energy, collision
Title: Why can't collisions be elastic? I understand that in inelastic collisions thermal energy is given out, but why does that happen? Why can't they simply rebound without giving off energy? Also, why in some collisions more heat is given out than in others (i.e. what determines that one collision is more inelastic than the other)? Thanks. Given your comments, I shall attempt an answer. This obviously depends on how you model the interaction between the two particles/masses.
First, let us see what happens if we bounce two particles off each other in a simple theoretical model where the particles don’t have any internal structure. To simplify things, we assume one dimension and use the following Hamiltonian:
$$ H = \frac{1}{2 } m_1 v_1^2 + \frac{1}{2 } m_2 v_2^2 + U(x_1,x_2) $$
where we define $v_i$ ($m_i$) to be the speed (mass) of the $i$-th particle and $U(x_1,x_2)$ is the interaction potential which describes how the particles interact. Usually, we want something like
$$ U(x_1,x_2) = \{ \infty\textrm{ if }x_1 - x_2 < d \quad,\quad 0\textrm{ otherwise }\}$$
So the two particles can only get within distance $d$ of each other, because otherwise the potential energy $U$ is infinite (corresponding to a physically impossible state). If you try to solve the system given by the above Hamiltonian you will notice that it only describes elastic collisions. This can be linked to the fact that it is a microscopic view: We know where each particle is and even if we tried to introduce something like ‘heat’, it would only manifest itself in a different speed for a given particle.
So in order to get an inelastic collision (and in lieu of more complicated microscopic systems which sometimes, especially in quantum mechanics, define special operators to model interactions which can also result in inelastic collisions), we need a different model: A macroscopic one.
The following is multiple choice question (with options) to answer.
According to collision theory, particles that lack what kind of energy may collide, but the particles will simply bounce off one another unchanged? | [
"kinetic energy",
"viscosity energy",
"residual energy",
"elastic energy"
] | A | The behavior of the atoms, molecules, or ions that comprise the reactants is responsible for the rates of a given chemical reaction. Collision theory is a set of principles that states that the reacting particles can form products when they collide with one another provided those collisions have enough kinetic energy and the correct orientation. Particles that lack the necessary kinetic energy may collide, but the particles will simply bounce off one another unchanged. The figure below illustrates the difference. In the first collision, the particles bounce off one another and no rearrangement of atoms has occurred. The second collision occurs with greater kinetic energy, and so the bond between the two red atoms breaks. One red atom bonds with the other molecule as one product, while the single red atom is the other product. The first collision is called an ineffective collision , while the second collision is called an effective collision . |
SciQ | SciQ-1885 | marine-biology, vestigial
Title: Modern Whales with Vestigial legs Myth? Is it a myth that modern whales have been found with hind legs sticking out of their sides and full formed tibias, fibias, and toe bones? I keep finding assertions, but no citations. For example, the wikipedia page has no citation for it.
http://en.wikipedia.org/wiki/Whales#Appendages The link you give doesn't mention limbs sticking out of the body wall, but only vestigial hind limb elements. Many whales do retain pelves and femora, as this page at the Bergen Museum shows. Given the variation in limb development across vertebrates, it would not be surprising to find more distal elements (but I would be very surprised if they extended past the body wall).
The following is multiple choice question (with options) to answer.
Muscles that move what long bone originate on the pelvic girdle? | [
"tibia",
"femur",
"patella",
"sacrum"
] | B | Gluteal Region Muscles That Move the Femur Most muscles that insert on the femur (the thigh bone) and move it, originate on the pelvic girdle. The psoas major and iliacus make up the iliopsoas group. Some of the largest and most powerful muscles in the body are the gluteal muscles or gluteal group. The gluteus maximus is the largest; deep to the gluteus maximus is the gluteus medius, and deep to the gluteus medius is the gluteus minimus, the smallest of the trio (Figure 11.29 and Figure 11.30). |
SciQ | SciQ-1886 | quantum-mechanics, homework-and-exercises, atoms, hydrogen
The second part of the question is a bit more subtle, because it's asking what spherical shell is most likely to contain the electron. The point of the question is that the volume of the spherical shell of radius $r$ and thickness $dr$ is $dV = 4 \pi r^2 dr$, so the probability of finding the electron in this shell is given by:
$$ P = \psi^2 dV = A e^{-2r/a_0} 4 \pi r^2 dr $$
You need to find the value of $r$ at which this function is a maximum.
The following is multiple choice question (with options) to answer.
In an atom, what is determined by electron distribution in shells? | [
"covalence",
"electromagnetism",
"ionic bonds",
"chemical behavior"
] | D | |
SciQ | SciQ-1887 | EXPONENTS
Exponents are a "shortcut" method of showing a number that was multiplied by itself several times. For instance, number $$a$$ multiplied $$n$$ times can be written as $$a^n$$, where $$a$$ represents the base, the number that is multiplied by itself $$n$$ times and $$n$$ represents the exponent. The exponent indicates how many times to multiple the base, $$a$$, by itself.
Exponents one and zero:
$$a^0=1$$ Any nonzero number to the power of 0 is 1.
For example: $$5^0=1$$ and $$(-3)^0=1$$
$$a^1=a$$ Any number to the power 1 is itself.
Powers of zero:
If the exponent is positive, the power of zero is zero: $$0^n = 0$$, where $$n > 0$$.
If the exponent is negative, the power of zero ($$0^n$$, where $$n < 0$$) is undefined, because division by zero is implied.
Powers of one:
$$1^n=1$$ The integer powers of one are one.
Negative powers:
$$a^{-n}=\frac{1}{a^n}$$
Powers of minus one:
If n is an even integer, then $$(-1)^n=1$$.
If n is an odd integer, then $$(-1)^n =-1$$.
Operations involving the same exponents:
Keep the exponent, multiply or divide the bases
$$a^n*b^n=(ab)^n$$
$$\frac{a^n}{b^n}=(\frac{a}{b})^n$$
$$(a^m)^n=a^{mn}$$
$$a^m^n=a^{(m^n)}$$ and not $$(a^m)^n$$
The following is multiple choice question (with options) to answer.
What term is defined as a way of writing very large or small numbers that uses exponents? | [
"quadratic notation",
"certain notation",
"scientific notation",
"exponential notation"
] | C | Quantities in science may be very large or very small. This usually requires many zeroes to the left or right of the decimal point. Such numbers can be hard to read and write accurately. That’s where scientific notation comes in. Scientific notation is a way of writing very large or small numbers that uses exponents. Numbers are written in this format:. |
SciQ | SciQ-1888 | electrons, energy-conservation, atomic-physics, orbitals
Title: The unanswered question: Where do electrons get their ever-lasting circulating energy? This question has been asked by many others like me, and in so many forums as well as here, and answered by many as well, and I still do not find the answer. The question is "Where do electrons get their ever-lasting circulating energy?". All answers somehow start explaining about the descreet energy levels of the electrons (BUT not how these emerged at the first place), the theories about why electrons do not crash into the nucleus, and the uncertainty principle etc. But no one so far really answers the main question - where the electrons get their initial energy from, the energy they need to start operating at all? Is it the energy they got at the beginning, by the proposed Big Bang of the Universe, or how? Is this a question that is still unanswered by science? Well, we don't know how the universe got started, so a valid answer would just be that there's some amount of energy available and distributed throughout all physical systems, and we can't say where it came from.
(If we take into account the expansion of the universe then the total energy isn't constant, but it changes in a predictable way.)
However, for the specific case of an atom I can be a bit more useful: an electron in an atom has less energy than an electron by itself. This makes sense: things generally tend towards a state of lower energy, so if an atom had positive energy (instead of negative) it would break apart. If you start with a proton and an electron separated from each other, they will attract thanks to the electromagnetic force, and end up together in a state of lower energy. The difference will be radiated away as electromagnetic waves, and will disperse through the universe.
The following is multiple choice question (with options) to answer.
Electrons are always added to which energy level first? | [
"the lowest",
"the major",
"the second",
"the highest"
] | A | Electrons are always added to the lowest energy level first until it has the maximum number of electrons possible, and then electrons are added to the next higher energy level until that level is full, and so on. The maximum number of electrons at a given energy level depends on its number of orbitals. There are at most two electrons per orbital. |
SciQ | SciQ-1889 | organic-chemistry, stereochemistry, isomers, chirality, erratum
Title: Planes of Symmetry and Chirality I am trying to identify whether the following objects possess planes of symmetry or not, but my answers seem different, from the textbook solutions (Klein Organic Chemistry 2e, Page 220, Question 23). Some of them I am unsure of and would like to make sure I know the proper reasoning for. Can someone please clarify?
(b) The correct response is yes. Is the plane of symmetry I have drawn acceptable?
(c) The correct response is no, but I thought it is possible to have a plane of symmetry like the one I have drawn.
(e) The correct response is yes, which I think I understand. I think this has three planes of symmetry.
(f) The correct response is no, which I agree with. However, it doesn't seem to concur with the response for the follow-up question.
Follow-up: Which image has three planes of symmetry? The correct answer is apparently, (f). My response would have been (e). Let us address the elephant in the room first and foremost. All of these objects do not have any symmetry if you wanted to get real technical about it. However, let us just assume certain things for this useful exercise to be relevant.
b.) The teacup has a vertical plane of symmetry splitting the teacup in half along the handle axis and intersecting with the centroid of the cup and saucer. I would say that your guess is correct though it would be useful to have drawn in a plane rather than simply a line (for all examples).
c.) At first glance the pliers have a couple planes of symmetry BUT upon further thought it may not due to the way the rotating JOINT is constructed. See the example below:
The following is multiple choice question (with options) to answer.
What type of symmetry do echinoderms show? | [
"parallel",
"lateral",
"radial",
"mirrored"
] | C | As mentioned earlier, echinoderms show radial symmetry. Other key echinoderm features include an internal skeleton and spines, as well as a few organs and organ systems. Although echinoderms look like they have a hard exterior, they do not have an external skeleton. Instead, a thin outer skin covers an internal skeleton made of tiny plates and spines. This provides rigid support. Some groups of echinoderms, such as sea urchins ( Figure below ), have spines that protect the organism. Sea cucumbers use these spines to help them move. |
SciQ | SciQ-1890 | ### Show Tags
16 Jan 2019, 08:15
As we are dealing with two numbers 3 & 4 .... lets take the LCM of them i.e.,12 .
Cost price for 12 nails = $0.25*12/4=$0.75 & Selling price for 12 nails = $0.22*12/3=$0.88
Profit made per 12 nails = $0.88 -$0.75 = $0.13 So total '12 units' sold =$2.60/$0.13 =20 Total nails sold = 20*12 = 240 .... Thus Ans would be option B. _________________ Please let me know if I am going in wrong direction. Thanks in appreciation. Director Joined: 12 Feb 2015 Posts: 863 Re: How many nails did Rudy buy if he purchased them at a price of$0.25 [#permalink]
### Show Tags
25 Feb 2019, 09:26
Nums99 wrote:
How many nails did Rudy buy if he purchased them at a price of $0.25 per four nails, sold them at$0.22 per three nails, and made a profit of $2.60? A. 300 B. 240 C. 180 D. 160 E. 120 LCM approach is good in such questions:- Rudy purchased nails at a price of$0.25 per four nails, or $0.75 per 12 nails sold them at$0.22 per three nails, or $0.88 per 12 nails and made a profit of$2.60 (total) or $(0.88-0.75) =$ 0.13 per 12 nails
(2.60 * 12)/0.13 = 240 nails (Ans)
_________________
"Please hit +1 Kudos if you like this post"
_________________
Manish
The following is multiple choice question (with options) to answer.
Nails cover the tips of what? | [
"fingers and toes",
"fingers and lips",
"ribs and nerves",
"lips and teeth"
] | A | Nails are similar to claws in other animals. They cover the tips of fingers and toes. Fingernails and toenails both grow from nail beds. As the nail grows, more cells are added at the nail bed. Older cells get pushed away from the nail bed and the nail grows longer. There are no nerve endings in the nail. Otherwise cutting your nails would hurt a lot!. |
SciQ | SciQ-1891 | biochemistry, transition-metals, oxidation-state, proteins
15. Goddard, W. A., III; Olafson, B. D. Ozone Model for Bonding of an O2 to Heme in Oxyhemoglobin. Proc. Natl. Acad. Sci. 1975, 72 (6), 2335–2339. DOI: http://10.1073/pnas.72.6.2335.
16. Chen, H.; Ikeda-Saito, M.; Shaik, S. Nature of the Fe−O2 Bonding in Oxy-Myoglobin: Effect of the Protein. J. Am. Chem. Soc. 2008, 130 (44), 14778–14790. DOI: 10.1021/ja805434m.
17. Grinstaff, M. W.; Hill, M. G.; Labinger, J. A.; Gray, H. B. Mechanism of catalytic oxygenation of alkanes by halogenated iron porphyrins. Science 1994, 264 (5163), 1311–1313. DOI: 10.1126/science.8191283.
18. Wilson, S. A.; Kroll, T.; Decreau, R. A.; Hocking, R. K.; Lundberg, M.; Hedman, B.; Hodgson, K. O.; Solomon, E. I. Iron L-Edge X-ray Absorption Spectroscopy of Oxy-Picket Fence Porphyrin: Experimental Insight into Fe–O2 Bonding. J. Am. Chem. Soc. 2013, 135 (3), 1124–1136. DOI: 10.1021/ja3103583
19. Wilson, S. A.; Green, E.; Mathews, I. I.; Benfatto, M.; Hodgson, K. O.; Hedman, B.; Sarangi, R. X-ray absorption spectroscopic investigation of the electronic structure differences in solution and crystalline oxyhemoglobin. Proc. Natl. Acad. Sci. 2013, 110 (41), 16333–16338. DOI: 10.1073/pnas.1315734110.
The following is multiple choice question (with options) to answer.
Which carrier molecule becomes less effective at binding oxygen as temperature increases? | [
"hydrogen",
"helium",
"water",
"hemoglobin"
] | D | |
SciQ | SciQ-1892 | botany, anatomy, plant-anatomy
Title: Plant anatomy, what are these stem like filaments growing under the flower The picture below shows what I am talking about. Each flower has one and I am just wondering what they are? Looking at this, it looks like a spur. A quite overbreed one, though.
The following is multiple choice question (with options) to answer.
What is found at the top of the stamen? | [
"pistil",
"pollen",
"petals",
"fungi"
] | B | The next structure is the stamen , consisting of the stalk-like filament that holds up the anther , or pollen sac. The pollen, which is found at the top of the stamen, is the male gametophyte. |
SciQ | SciQ-1893 | terminology
Title: Is AI entirely a part of Computer Science? Both AI and Computer Science are Sciences, as I understood from Wikipedia, Computer Science is everything that has any relation to computers. And AI is commonly defined as
Study of machines that take the prerogative of humans (creating musical pieces e.t.c
But recently, when I was reading, I read this sentence : "In Computer Science, AI is [...]"
So my question is really : Is there a part of AI studies that do not refer to Computer Science? AI is an amalgamation of many fields, Computer Science plays a major role in imparting "Intelligence" to the machine. Following is a quote from the best selling AI book Artificial Intelligence: A Modern Approach by
Stuart J. Russell and Peter Norvig.
Artificial Intelligence (AI) is a big field, and this is a big book.
We have tried to explore the full breadth of the field, which
encompasses logic, probability, and continuous mathematics;
perception, reasoning, learning, and action; and everything from
microelectronic devices to robotic planetary explorers.
So, the answer to your question is yes, there are other fields that AI depends including mathematics (to optimize AI algorithms), electronic components (sensors, microprocessors, etc.), mechanical actuators (hydraulic, pneumatic, electric, etc.)
I highly recommend the book if you are looking for a starting point.
The following is multiple choice question (with options) to answer.
What field of study is called the language of science? | [
"physics",
"linguistics",
"logic",
"mathematics"
] | D | The field of science has gotten so big that it is common to separate it into more specific fields. First, there is mathematics, the language of science. All scientific fields use mathematics to express themselves—some more than others. Physics and astronomy are scientific fields concerned with the fundamental interactions between matter and energy. Chemistry, as defined previously, is the study of the interactions of matter with other matter and with energy. Biology is the study of living organisms, while geology is the study of the earth. Other sciences can be named as well. Understand that these fields are not always completely separate; the boundaries between scientific fields are not always readily apparent. Therefore, a scientist may be labeled a biochemist if he or she studies the chemistry of biological organisms. Finally, understand that science can be either qualitative or quantitative. Qualitative implies a description of the quality of an object. For example, physical properties are generally qualitative descriptions: sulfur is yellow, your math book is heavy, or that statue is pretty. A quantitative description represents the specific amount of something; it means knowing how much of something is present, usually by counting or measuring it. As such, some quantitative descriptions would include 25 students in a class, 650 pages in a book, or a velocity of 66 miles per hour. Quantitative expressions are very important in science; they are also very important in chemistry. |
SciQ | SciQ-1894 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
What is the term for tough, flexible connective tissue that contains the protein collagen? | [
"muscle",
"membrane",
"cartilage",
"cuticle"
] | C | Cartilage is a tough, flexible connective tissue that contains the protein collagen. It covers the ends of bones where they meet. The gray tissue in Figure below is cartilage. |
SciQ | SciQ-1895 | thermodynamics, water, phase-transition, evaporation, gas
Title: Why does water turn into water vapor? I read an article lately and it said that water turns into steam when it reaches its boiling point. But it led me to another question.
Why does water boil and why does the water turn into gas when it boils? Water molecules have attractive forces between them and form the liquid state.
First of all start with a container with water liquid and a vacuum above the water liquid.
This container and the water within it is kept at a constant temperature.
Some the water liquid molecules will have enough kinetic energy to overcome the attraction of their neighbouring water liquid molecules and escape from water liquid surface and become water vapour.
There is a net migration with water liquid molecules becoming water vapour molecules.
As time goes on and the number of water vapour molecules increases but some of those water vapour molecules will hit the water surface and become part of water liquid.
Eventually there are sufficient water vapour molecules and a dynamic equilibrium will be set up where the rate at which water liquid is converted into water vapour is exactly the same as the rate at which water vapour is converted into water liquid.
The pressure of the water vapour when this condition is satisfied is called the saturated vapour pressure.
Increasing the temperature means that the average kinetic energy of the water molecules increases and so the probability of a water liquid escaping from the surface of the liquid is increased.
So the rate at which water liquid turns to into water vapour increases.
For a time there is a net migration from water liquid to water vapour until the increase in the density of water vapour is sufficient for a new dynamic equilibrium to be set up.
The saturated vapour pressure increases as the temperature increases.
Raising the temperature will thus increase the saturated vapour pressure until there comes a temperature when the density of the vapour is the same as the density of the liquid.
The boundary (surface) between the liquid and the vapour disappears and you have just one phase.
That temperature is called the critical temperature and here is one video showing this effect.
Water liquid does not exist above the its critical temperature of $374\,^\circ \rm c$
The following is multiple choice question (with options) to answer.
Liquid water changing to water vapor is called? | [
"respiration",
"transpiration",
"oxidation",
"evaporation"
] | D | |
SciQ | SciQ-1896 | everyday-chemistry
Vinegar is used by many DIY people, but it is not a popular commercial product because it smells kind of bad, it's not very effective, and if it is mixed with bleach (WARNING) it can cause a serious health hazard. Also, 5% acetic acid is not extremely germicidal (it will work to kill bacteria in food after a few days); many spores will survive for hours in acetic acid. Vinegar is most effective against non-spore forming (gram negative) bacteria- which are often the more nasty kinds of bacteria (Salmonella, E. coli, Serratia, Pseudomona, etc.)... but it's less effective against spore forming (gram positive) bacteria (Candida, Bacillus, Streptococcus, Micrococcus, etc.). Again, it is an effective preservative in food... as is 5% ethanol (ie., beer). 50% acetic acid is much more effective and it works faster... as does 50% ethanol. pH is a factor, so vinegar is a bit more effective than ethanol, but in general, a high pH is much more effective than a low pH. So, ammonia or lye solutions are more effective than organic acids.
70% isopropanol and 60% ethanol are a common hand and wound disinfectants. They are fairly antimicrobial and antiviral, but again, spores (and other gram positive bacteria) can survive in dilute alcohols (for a little while).
The following is multiple choice question (with options) to answer.
What is used to prevent some infectious diseases? | [
"radiation",
"pesticides",
"pathogens",
"vaccines"
] | D | Vaccines are available for some infectious diseases. For example, there are vaccines to prevent measles, mumps, whooping cough, and chicken pox. These vaccines are recommended for infants and young children. |
SciQ | SciQ-1897 | evolution, human-evolution
Title: Can there be significant new changes in physical features of Humans due to evolution in 10000 years of span? Humans migrated from Africa about 60000 years. And in these years humans physical features undergone significantly in terms of skin color, hair, eye color and facial features.
So, with this we can say that given 10000 years of span we can see a significant noticeable new changes in physical features of humans? like some humans with new skin color (apart from today's white, black and brown), new color eye balls, big heads etc.? Yes & perhaps (or probably?) no, depending on what you define as significant changes.
Less than 10,000 years ago everyone in the british isles & the rest of europe were dark skinned so the answer if (unlike me) you consider the change in skin color a significant change is obviously a resounding yes.
Here's what English people looked like 10,000 years ago
Darker skinned than you were expecting perhaps.
If as suggested in this article white skin arrived in Europe around 5,000 years ago that only leaves 2,000 years before early Greek & Roman art we have available which shows it as ubiquitous, so it perhaps took only 2,000 years or so (maybe less) to become dominant in europe, that's fast.
Using 20 years as the measure of a generation that's only 100 generations, so, very fast.
Timeline of human prehistory
The first reconstruction in the link below is a reconstruction of a Neanderthal woman found in a cave in Gibraltar. She died at least 30,000 years ago.
Here she is, the skin tone may not be accurate but we do know from gene's recovered from Neanderthal remains that they were relatively light skinned.
Personally I don't consider her appearance to be significantly different from modern humans.
29 Reconstructed Faces Of Ancient People
So my answer based on what I consider significant changes would be no.
But for you or others the answer may well be yes.
And of course a mutation for a new eye colour could appear at any time in one individual & spread like wildfire practically overnight just because we think it's unusual & 'cool' (aka sexual selection) so if eye color ticks your boxes it's a very definite yes.
The following is multiple choice question (with options) to answer.
The change in the characteristics of living things over time is known as _________ | [
"generation",
"evolution",
"spontaneous mutation",
"variation"
] | B | Evolution is a change in the characteristics of living things over time. Evolution occurs by a process called natural selection. In natural selection, some living things produce more offspring than others, so they pass more genes to the next generation than others do. Over many generations, this can lead to major changes in the characteristics of living things. Evolution explains how living things are changing today and how modern living things have descended from ancient life forms that no longer exist on Earth. |
SciQ | SciQ-1898 | structural-engineering
Title: Rammed Earth Building I am estimating the amount of materials required to make a rammed earth building and I can't find anything related with the foundation of rammed earth building and about two-storeyed rammed earth building. Can you tell me about how the foundations are constructed on rammed earth building and what should be done to make two storeyed rammed earth building? I would suggest the safest way is to build the foundation with reinforced concrete and leave dowels out to bond with the rebars of the rammed earth wall.
In the middle east, they have build adobe houses for centuries by combining clay and straw as a wall material. This system has proved to have excellent thermal properties, but not sufficient strength for earthquakes.
They used to mix lime with sand and silt and clay as primitive concrete for the foundation.
There is no code for the rammed earth construction. So every individual needs to hire an engineer to do the calculations and prepare the plans for them. here are some photos that were taken during the construction.
source
The following is multiple choice question (with options) to answer.
What provides building materials for the body? | [
"heat",
"food",
"energy",
"water"
] | B | Food provides building materials for the body. The body needs building materials for growth and repair. |
SciQ | SciQ-1899 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
What is the term for animals that eat producers to get energy? | [
"carnivores",
"secondary consumers",
"herbivores",
"predators"
] | C | Herbivores are animals that eat producers to get energy. For example, rabbits and deer are herbivores that eat plants. The caterpillar pictured below ( Figure below ) is a herbivore. Animals that eat phytoplankton in aquatic environments are also herbivores. |
SciQ | SciQ-1900 | optics, visible-light, vision
Title: How does nearsightedness know what's near versus far? If I wear a VR headset, I still have to wear my glasses, because the image arriving on the surface of my eye is still arriving as if it were actually far away. But how does that work? Why does the image from a distant object arrive at the surface of the eye differently than a near object? Let's start by discussing how the eye works.
As you look around, light rays from objects around you are traveling into your eye. They enter through your pupil, are refracted (i.e. bent) by the cornea and lens in your eye, and finally strike the retina, as shown in this image borrowed from here:
The blue lines represent light rays coming in from a faraway object, the object pointed to by the $P_{small}$ label is the lens, and the surface where the light rays converge on the back of the eye is the retina. The photoreceptors - the cells in the eye that sense light and send it to your brain - are all on the retina, so it's important that the image be fully focused there in order for you to see it sharply.
In this image, we assumed that the object was infinitely far away - in this case, the light rays are parallel to each other. But let's see what happens when we consider objects closer to the eye:
The following is multiple choice question (with options) to answer.
Farsightedness, or hyperopia, is the condition in which distant objects are seen clearly, but nearby objects are? | [
"invisible",
"darker",
"inverted",
"blurry"
] | D | Farsightedness, or hyperopia, is the condition in which distant objects are seen clearly, but nearby objects are blurry. It occurs when the eyeball is shorter than normal. This causes images to be focused in back of the retina. Hyperopia can be corrected with convex lenses. The lenses focus images farther forward in the eye, so they are on the retina instead of behind it. |
SciQ | SciQ-1901 | phase-transition, biophysics, medical-physics, glass, amorphous-solids
313 6003 pp573-5 (1985).
This outcome was identified as early as the 1960s by electron microscopy of thawed cells, which revealed many puncture holes in the membrane.
Both freezing and rethawing are opportunities for damage, as recrystallization can occur during the latter regardless of how carefully the former was performed.
Freezing into the crystalline phase of ice (and many other materials) produces sharp dendrites because some crystal orientations exhibit very fast growth kinetics. This issue doesn't arise with amorphous freezing.
For an early discussion, see, for example, Mazur's "Cryobiology: the freezing of biological systems" Science 168 3934
pp939-49 (1970) and the references within.
The following is multiple choice question (with options) to answer.
Melting ice and grinding wood into sawdust are examples of what? | [
"chemical changes",
"unpredictable changes",
"physical changes",
"reversible changes"
] | C | Melting ice and grinding wood into sawdust are examples of physical changes. |
SciQ | SciQ-1902 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
In humans and other multicellular organisms, different types of what basic structures are specialized for specific jobs? | [
"lipids",
"organs",
"cells",
"proteins"
] | C | Different types of cells in the human body are specialized for specific jobs. Do you know the functions of any of the cell types shown here?. |
SciQ | SciQ-1903 | visible-light, polarization
Title: Will 2 polarizing filters at 90° with the distance of the wavelength of the light between them let it through? So what I have been taught is, that if you have a polarizing filter which is just 1 vertical slit, you will only get light which is travelling at that angle, turning a 3-dimensional beam of light into a (more or less) 2-dimensional ribbon of light (Now I am not sure if it is a ribbon, I'd guess multi-coloured light will be a ribbon while one-coloured light will more or less be just the oscillating sine-like curve, if there is only one light source)
So, if I put 2 slits behind each other, so looking at them from the front they will be a +
Now, if the first and the second one are exactly a multiple of the wavelength of any colour apart from each other, shouldn't exactly that colour pass through that polarizing filter (of course only those that are 90° to the vertical allignment of the filter, happen to be precisely centered and happen to enter the 1st polarizing filter exactly at the beginning of a wave in the exact middle)?
That would probably be a very small amount of light, but wouldn't it mean that it's wrong to say that no light passes through them?
Here, i illustrated what I mean right here. I know that n×480nm would also let other wavelengths through which are a multitude of that, like 960nm, but let's just ignore that.
if you have just 1 vertical slit, you will only get light which is travelling at that angle, turning a 3-dimensional beam of light into a (more or less) 2-dimensional ribbon of light ...
You must be aware that behind edges light gets deflected and instead of a ribbon one get a wavelike intensity distribution (source) behind edges and slits.
... while one-coloured light will more or less be just the oscillating sine-like curve, if there is only one light source
A common light source isn’t spatial coherent for the outgoing light. Instead of a beam with periodically increasing and decreasing intensity one get a continuous stream of light with a quantum noise.
You get an oscillating beam with a wave generator for radio waves:
The following is multiple choice question (with options) to answer.
How much unpolarized light does a polarized filter block? | [
"100%",
"50%",
"40 %",
"60 %"
] | B | Polarized filters block 50% of unpolarized light. If two filters are oriented so that their polarization axes are aligned, how much light is transmitted? What about if their axes are oriented perpendicular to each other? Draw two diagrams below to support your answers. |
SciQ | SciQ-1904 | entomology, parasitology, parasitism
The male (microgametocytes) and female (macrogametocytes) gametocytes are ingested by a female Anopheles mosquito during a blood meal (8) - only female mosquitoes (of pretty much any species) drink blood. The parasites' multiplication in the mosquito is known as the sporogonic cycle (stage C). While in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes (9). The zygotes in turn become motile and elongated (ookinetes) (10) which invade the midgut wall of the mosquito where they develop into oocysts (11). The oocysts grow, rupture, and release sporozoites (12), which make their way to the mosquito's salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle (1).
Sources
The following is multiple choice question (with options) to answer.
What is the term for cellular eating? | [
"Pinocytosis",
"consumption",
"ancylosis",
"phagocytosis"
] | D | Phagocytosis , or cellular eating, occurs when the dissolved materials enter the cell. The plasma membrane engulfs the solid material, forming a phagocytic vesicle. |
SciQ | SciQ-1905 | genetics, gene-expression, mrna, protein-expression, microarray
You can think of the microarray and RNASeq approaches as a fishing expeditions. If you find mRNAs that are only present after the cell receives a stimulus or an insult, expression of the mRNA has occurred (whether or not the amounts are directly proportional to the rate of synthesis). If the mRNA is synthesised you can assume it is translated into the protein it encodes. In the case of gamma irradiation you might assume any mRNA that shows a large increase in quantity encodes a protein that involved in protecting the cell from the radiation. This will be of scientific interest, especially if it is not what one anticipated.
The following is multiple choice question (with options) to answer.
Genes are used to make mrna by the process of transcription; mrna is used to synthesize proteins by the process of what? | [
"moderation",
"translation",
"production",
"modification"
] | B | 9.4 Translation The central dogma describes the flow of genetic information in the cell from genes to mRNA to proteins. Genes are used to make mRNA by the process of transcription; mRNA is used to synthesize proteins by the process of translation. The genetic code is the correspondence between the three-nucleotide mRNA codon and an amino acid. The genetic code is “translated” by the tRNA molecules, which associate a specific codon with a specific amino acid. The genetic code is degenerate because 64 triplet codons in mRNA specify only 20 amino acids and three stop codons. This means that more than one codon corresponds to an amino acid. Almost every species on the planet uses the same genetic code. The players in translation include the mRNA template, ribosomes, tRNAs, and various enzymatic factors. The small ribosomal subunit binds to the mRNA template. Translation begins at the initiating AUG on the mRNA. The formation of bonds occurs between sequential amino acids specified by the mRNA template according to the genetic code. The ribosome accepts charged tRNAs, and as it steps along the mRNA, it catalyzes bonding between the new amino acid and the end of the growing polypeptide. The entire mRNA is translated in three-nucleotide “steps” of the ribosome. When a stop codon is encountered, a release factor binds and dissociates the components and frees the new protein. |
SciQ | SciQ-1906 | cell-signaling, chemical-communication
Title: How many molecules are generally required for cell signallng processes for given cases? I know its really a broad topic but I am interested in just few cases:
Quorum sensing
neurotransmitters for the communication of images/ general information
hormones/pheromones
I actually want to know that does a single or hundreds of molecules are needed to communicate information from one cell to another.
I searched but approx number of molecules, I can't find anywhere. A cell can interact with other cells in zillions of ways. You can send information from one cell to other cells via neurotransmitters, hormones, pheromones, electric signals, magnetic resonance ,leukotrines etc.
In general a single type of molecule is enough to send such information. Like you require only Acetylcholine(Ach) as neurotransmitter to transmit various nerve impulses.
But, even for a single type, you require thousands of molecules. Like 1 molecule of Ach can do almost nothing and would immediately be broken by Acetylcholinesterase. You require 1000s of such molecules.
You can modify the communicating information via different types of transmitters. You can use GABA or glycine to supress any information exchange or use dopamine to enhance it. But again you will need many molecules of GABA or Glycine.
For visual pathway, you can use no. of types of transmitters like glutamate, glycine, gaba, dopamine, acetylcholine, substance P etc.
Neurotransmitters for visual pathway.
Hormones are transmitters that are required in small quantities. But, again you require certain concentration. There is normal blood concentration of various hormones like 80 pg/ml for calcitonin.
Quorum sensing use transmitters like AHLs. Again a certain threshold value is required for them to act.
Again, to produce these transmitters you have to go through a rigorous process of transcription, translation and post-translational modifications.
So, for cell to communicate a rigorous process is used.
The following is multiple choice question (with options) to answer.
What is the most important way that humans communicate? | [
"instinct",
"painting",
"inheritance",
"language"
] | D | The most important way that humans communicate is with language. Language is the use of symbols to communicate. In human languages, the symbols are words. Words may stand for things, people, actions, feelings, or ideas. By combining words in sentences, language can be used to express very complex thoughts. |
SciQ | SciQ-1907 | neuroscience, neuroanatomy
Likewise, the spinal chord is structured into sensory and motor regions. In summary, the spinal chord consists of: 1) cell bodies (motor, sensory, inter; grey in the picture), 2) ascending axons (blue), 3) descending axons (red). Similar to nerves, axons going up or down the spinal chord are bundled into "tracts". Sensory axons are never bundled with motor axons, making it possible to create a map of the spinal chord in cross-section.
The tracts' names might be a bit confusing at first, but on second look are actually pretty self-explanatory. They usually contain where the axons come from and where they are going in order to synapse with other neurons. E.g. the spinocerebellar tract is formed of axons coming from the spine and going to the cerebellum. Given that the cerebellum is near the brain and the spine is further down, this is obviously an ascending tract - and ascending tracts are always sensory (because sensory information never needs to be carried downwards due to the brain being at the top).
Where it gets blurry
The sensory/motor separation isn't always as clear as I've described above. In fact, nerves (bundles of axons anywhere in the body outside of the CNS) will usually contain both sensory and motor pipelines. In particular, the cranial nerves (12 of the most important nerves) all include sensory and motor components for the respective part of the body that they manage. E.g. the facial nerve contains both the sensory connections for parts of the tongue and the motor connections that control facial muscles.
Another more complex example is pain sensation, where interneurons in the spinal chord can feed back onto sensory neurons and inhibit their signals, or axons can inhibit those packed in the same nerve bundle simply due to electrical effects.
The following is multiple choice question (with options) to answer.
Somatic, autonomic, and enteric structures are part of what system? | [
"circulatory system",
"circulatory system",
"nervous system",
"adrenal system"
] | C | Figure 12.6 Somatic, Autonomic, and Enteric Structures of the Nervous System Somatic structures include the spinal nerves, both motor and sensory fibers, as well as the sensory ganglia (posterior root ganglia and cranial nerve ganglia). Autonomic structures are found in the nerves also, but include the sympathetic and parasympathetic ganglia. The enteric nervous system includes the nervous tissue within the organs of the digestive tract. |
SciQ | SciQ-1908 | species-identification, botany, ecology
Title: Algae or Lichen identification. Coastal BC, Canada I have tried all books and internet resources I know of, but I still have no idea what this might be — a lichen or something else.
At first glimpse, I thought it was something man-made and unnatural, but then I looked closer and saw how it appears to be attached and growing. It grows on exposed rocks well above the high tide. The photo is taken in late March, on northern Vancouver Island. It's loosely attached to the rock.
It was somewhat abundant around the general area (within of a few km), but I haven't seen it elsewhere - although I'm not from BC so there might be a lot of this around.
The water droplet in the lower right corner give a rough sense of scale.
Edit:
Adding another photo in which I just noticed a streak of white, which I included in original resolution. I want to propose you expand your search to a broader taxonomic scope. Specifically, I think you might be looking at a species of "red" green algae (family: Trentepohliaceae).
From Nelson et al. (2011):
All Trentepohliaceae have filamentous growth forms and often contain large amounts of carotenoid pigments (ß-carotene and hematochrome), causing the algae to appear yellow orange in color (Thompson and Wujek 1997, Lo´pez-Bautista et al. 2002).
The Trentepohliaceae contains five genera: (Trentepohlia, Printzina, Phycopeltis, Cephaleuros and Stomatochroon) and 70+ species worldwide.
For example, the following algae (picture from England) looks fairly similar to your specimen:
Trentepohlia aurea
Source: David Fenwick
If your specimen is a species in this family of algae, it is most likely in the Trentepohlia genus (or possibly Printzina genus).
Trentepohlia is a genus of filamentous chlorophyte green algae in the family Trentepohliaceae.
Typically orange or yellow in color.
Live on tree trunks and wet rocks or symbiotically in lichens.
Here's a picture of a free-living Trentepohlia species from coastal Oregon, USA:
Source: Richard C. Hoyer (2015)
The following is multiple choice question (with options) to answer.
Duckweed and cattails serve what role in the food chain in freshwater biomes? | [
"secondary consumer",
"primary producer",
"tertiary consumer",
"primary consumer"
] | B | Duckweed: Jonathan Jordan; Cattails: User:JoJan/Wikimedia Commons. Duckweed and cattails are respectively the primary producers in standing and running freshwater biomes . Duckweed: CC BY 2.0; Cattails: CC BY 3.0. |
SciQ | SciQ-1909 | hybridization
Title: Determine percentage of crow hybrids We had in class following question which I had no idea how to get to the correct answer:
The carrion crow and the hooded crow are fertile together, but their
reproductive success is reduced by 50%. In a certain region exist
two populations of both species of roughly the same size. Thus,
mixed couples occur in about 10% of all cases. What is the percentage of
hybrids in the F1-generation?
(Translated from German.)
I thought it would be something like 5/95 = 5,3% but apparently the answer is 1%. Why? In order to make your reasoning clearer, you should use more formal notations and explain your thinking step by step. Here's a proposition.
Let's use the following notations :
$C$: the total number of couples (mixed and not mixed)
$r$: the reproductive success
$F1_h$: the number of hybrids in the F1 generation
$F1_{nh}$: the number of non hybrids in the F1 generation
You are looking for the percentage of hydrids in the F1 generation, which is:
$x = \frac{F1_h}{F1_h + F1_{nh}}$
You know that $10~\%$ of the couples are mixed couples and that their reproductive success is reduced by $50~\%$. This can be written:
$\begin{cases} 0.9\cdot C \cdot r = F1_{nh} \\ 0.1\cdot C\cdot \frac{r}{2} = F1_h \end{cases}$
Thus: $\displaystyle x = \frac{F1_h}{F1_h + F1_{nh}} = \frac{0.05\cdot C\cdot r}{C\cdot r\cdot 0.95} = \frac{0.05}{0.95}$
This is indeed the result you suggested. So the correction you were given might not be correct. Or maybe there was some more information in your homework that you ignored...
The following is multiple choice question (with options) to answer.
If humans were to artificially intervene and fertilize the egg of a bald eagle with the sperm of an african fish eagle and a chick did hatch, that offspring, called a hybrid (a cross between two species), would probably be this? | [
"fertile",
"nonviable",
"infertile",
"mutated"
] | C | In other cases, individuals may appear similar although they are not members of the same species. For example, even though bald eagles (Haliaeetus leucocephalus) and African fish eagles (Haliaeetus vocifer) are both birds and eagles, each belongs to a separate species group (Figure 18.10). If humans were to artificially intervene and fertilize the egg of a bald eagle with the sperm of an African fish eagle and a chick did hatch, that offspring, called a hybrid (a cross between two species), would probably be infertile—unable to successfully reproduce after it reached maturity. Different species may have different genes that are active in development; therefore, it may not be possible to develop a viable offspring with two different sets of directions. Thus, even though hybridization may take place, the two species still remain separate. |
SciQ | SciQ-1910 | electricity, everyday-life, atmospheric-science, lightning
Title: What causes the color difference of lightning flashes? Some flashes of lightning are seen in a blue shade while some have a yellowish/orange appearance .What is the possible cause of colour difference? First I thought to point to an old answer but I have then realised that it is not really a duplicate. However it does support what I was thinking to write (I am not a specialist of atmosphere physics), at least for the part concerning
what causes the lighting to, as for its name, emit light.
The visible part of the lightning, that we can consider as a spark of very big length size happening in not well controlled conditions, is a tiny ribbon of plasma surrounded by a hot and thermally ionized atmosphere envelope that the plasma itself generates.
Thus, a lightning does emit light both
thermally, which leads to a continuum and T dependent spectrum of the black body type
and
via emission by plasma recombination and by the radiative relaxations of the species excited by the plasma itself.
The following is multiple choice question (with options) to answer.
What causes lightning during a thunderstorm? | [
"difference in elevation",
"difference in temperature",
"difference in wind",
"difference in charge"
] | D | During a thunderstorm, some parts of a thunderhead become negatively charged. Other parts become positively charged. The difference in charge creates lightning. Lightning is a huge release of electricity. Lightning can jump between oppositely charged parts of the same cloud, between one cloud and another, or between a cloud and the ground. You can see lightning in Figure below . Lightning blasts the air with energy. The air heats and expands so quickly that it explodes. This creates the loud sound of thunder . |
SciQ | SciQ-1911 | human-biology, physiology, cardiology, anatomy
Title: Can humans live without their right atrium? The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated blood from the superior and inferior venae cavae, the coronary sinus, and the anterior and smallest cardiac veins, and pumps it into the right ventricle through the tricuspid valve.
Can humans survive without right atrium? In this condition blood would fill the right ventricle directly, comparable to some animals like frogs, toads, snakes and lizards. What advantages does the normal human heart have to this anatomy ? If we had this anatomy, where would the best place for pacemakers be, like the sinus node? This is an interesting theoretical question, but several things would need to be clarified:
Does removing the R atrium relocate the SA node to the R ventricle or remove it completely from the picture?
Does the remaining R ventricle have a tricuspid valve?
Technically, the R atrium is the home of the sino-atrial node, which provides natural pacing of the human heart between 60-80 beats/min. Without this natural pacing, our hearts would rely on back-up pacer systems such as atrioventricular node, His-Purkinje systems or the intrinsic but ectopic pacing of individual atrial or ventricular cells.
The following is multiple choice question (with options) to answer.
The human heart is located within what cavity? | [
"pelvic",
"spinal",
"thoracic",
"abdominal"
] | C | Location of the Heart The human heart is located within the thoracic cavity, medially between the lungs in the space known as the mediastinum. Figure 19.2 shows the position of the heart within the thoracic cavity. Within the mediastinum, the heart is separated from the other mediastinal structures by a tough membrane known as the pericardium, or pericardial sac, and sits in its own space called the pericardial cavity. The dorsal surface of the heart lies near the bodies of the vertebrae, and its anterior surface sits deep to the sternum and costal cartilages. The great veins, the superior and inferior venae cavae, and the great arteries, the aorta and pulmonary trunk, are attached to the superior surface of the heart, called the base. The base of the heart is located at the level of the third costal cartilage, as seen in Figure 19.2. The inferior tip of the heart, the apex, lies just to the left of the sternum between the junction of the fourth and fifth ribs near their articulation with the costal cartilages. The right side of the heart is deflected anteriorly, and the left side is deflected posteriorly. It is important to remember the position and orientation of the heart when placing a stethoscope on the chest of a patient and listening for heart sounds, and also when looking at images taken from a midsagittal perspective. The slight deviation of the apex to the left is reflected in a depression in the medial surface of the inferior lobe of the left lung, called the cardiac notch. |
SciQ | SciQ-1912 | botany, plant-physiology, ecology, virology, host-pathogen-interaction
Note about symbiosis - comes in reaction to @Gerhard's comment
Different authors use the word symbiosis differently. From wikipedia:
The definition of symbiosis is controversial among scientists. Some believe symbiosis should only refer to persistent mutualisms, while others believe it should apply to any type of persistent biological interaction (i.e. mutualistic, commensalistic, or parasitic).4 After 130+ years of debate,5 current biology and ecology textbooks now use the latter "de Bary" definition or an even broader definition (i.e. symbiosis = all species interactions), with the restrictive definition no longer used (i.e. symbiosis = mutualism)
The following is multiple choice question (with options) to answer.
What is the name of the symbiotic relationship in which one species benefits while the other species is not affected? | [
"differentiation",
"pollenation",
"mutualism",
"commensalism"
] | D | Commensalism is a symbiotic relationship in which one species benefits while the other species is not affected. One species typically uses the other for a purpose other than food. For example, mites attach themselves to larger flying insects to get a “free ride. ” Hermit crabs use the shells of dead snails for homes. |
SciQ | SciQ-1913 | metabolism, ecology, photosynthesis
Title: Why isn't phosphorus or nitrogen a limiting nutrient for animals? Nitrogen and Phosphorus are usually the limiting nutrient for plants, especially for algae. Phosphorus is used for DNA, ATP and phospholipids, and Nitrogen is used for pretty much every protein a cell might want to produce. That is, their need for biological processes is not tied specifically to photosynthesis: anything that lives is going to need them, pretty much for anything it might want to do. It would make sense for them to be a limiting nutrient for almost anything that's trying to grow, plant or animal.
Yet for animals the limiting "nutrient" seems to always be energy, ie: food. Why aren't animals limited by lack of nutrients in the same way that plants are? Obviously animals need these nutrients, too. Or to reverse the question, why do plants need so much more phosphorus/nitrogen than animals do?
My best guess is that an animal's digestion of plant material is relatively inefficient energy-wise but relatively efficient nutrient-wise. So for an animal to eat enough food to have sufficient energy to survive, it's probably eaten more than enough Nitrogen and Phosphorus for its needs. But I'm just guessing and I can't find any data that would back up that guess. Phosphorus
Your suggestion that if we are meeting our calorific requirement we will be getting enough is true for phosphorus.
Most foods contain lots of phosphorus. The maximum dietary requirement occurs during adolescent growth, estimated at 1250 mg per day. Assuming a calorie intake of 2500 kcal we can calculate a 2500 kcal equivalent phosphorus content for various foods:
skimmed milk contains 7,400 mg phosphorus per 2500 kcal
roasted chicken breast contains 7,500 mg phosphorus per 2500 kcal
cooked white rice contains 3840 mg per 2500 kcal
(Calculations are based upon values obtained via this site.)
Nitrogen
Our requirement for nitrogen is met by our protein intake: inadequate protein intake manifests as kwashiorkor which is essentially due to a dietary deficiency of essential amino acids. In other words, the only way to achieve a nitrogen-deficient diet is to not eat protein, and this would not be alleviated by any inorganic source of nitrogen, even if we could consume enough of such a N source.
The following is multiple choice question (with options) to answer.
Living things need to take in nutrients so that they can grow and create what? | [
"protein",
"plasma",
"energy",
"hydrogen"
] | C | |
SciQ | SciQ-1914 | thermodynamics, visible-light
Title: Is heat always associated with Light? I have found that light always produces heat. The only cases I think heat is absent with light is Fluorescence and Phosphorescence (maybe because they emit low energy but maybe the heat is still present?). So my question is: Is heat energy always present when light is emitted, specially for bright light(more energy)?
If some example or any links can be provided, then it will be very helpful. Thermal radiation is emitted by any surface having a temperature higher than absolute zero. So the short answer to your question is yes. Light (electromagnetic radiation) of any frequency will heat surfaces that absorb it. In case of Fluorescence, the emitted light has a longer wavelength (lower frequency), and therefore lower energy, so that's why you feel the heat is absent.
The following is multiple choice question (with options) to answer.
Common forms of what include light, chemical and heat, along with kinetic and potential? | [
"energy",
"pressure",
"reactions",
"fuel"
] | A | Energy can take several different forms. Common forms of energy include light, chemical, and heat energy. Other common forms are kinetic and potential energy. |
SciQ | SciQ-1915 | hematology
Title: Is Hemoglobin binding to oxygen the same as Adsorption I have recently been reading about Hemoglobin and came across how it binds to oxygen. This seems very similar to Adsorption. Is the process of Hemoglobin binding to oxygen through Adsorption ? From the Wikipedia article you cite the answer to your question is clearly NO. They seem very different: absorption is described as a surface phenomenon, whereas oxygen binding occurs in a single internal pocket in each globin subunit and forms a specific bond to an Fe(II) atom. The chemical nature of this pocket is quite different from that of the surface of the protein.
The Wikipedia article states:
Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface.[1] This process creates a film of the adsorbate on the surface of the adsorbent.
and
Similar to surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent, or metallic) of the constituent atoms of the material are filled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates.
However if you consult a text-book which describes the biochemistry of haemoglobin, such as Berg et al. you will find the specific chemical nature of the binding clearly described, as indicated by this extract:
The iron atom lies in the center of the protoporphyrin, bonded to the four pyrrole nitrogen atoms. Under normal conditions, the iron is in the ferrous (Fe2+) oxidation state. The iron ion can form two additional bonds, one on each side of the heme plane. These binding sites are called the fifth and sixth coordination sites. In hemoglobin, the fifth coordination site is occupied by the imidazole ring of a histidine residue from the protein. In deoxyhemoglobin, the sixth coordination site remains unoccupied...The binding of the oxygen molecule at the sixth coordination site of the iron ion substantially rearranges the electrons within the iron so that the ion becomes effectively smaller, allowing it to move into the plane of the porphyrin (Figure 10.19).
The following is multiple choice question (with options) to answer.
What is the job of hemoglobin in the body? | [
"transports neurons",
"become scabs",
"transports oxygen",
"infects oxygen"
] | C | Hemoglobin is a protein that transports oxygen throughout the body. Source: Image from the RCSB PDB (www. org) of PDB ID 1I3D (R. Kidd, H. Baker, A. Mathews, T. Brittain, E. Baker (2001) Oligomerization and ligand binding in a homotetrameric hemoglobin: two high-resolution crystal structures of hemoglobin Bart's (gamma(4)), a marker for alpha-thalassemia. Protein Sci. 1739– 1749). Figure 18.8 Levels of Structure in Proteins Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-1916 | biochemistry
Title: educational sources for learning biochemistry I just finished high school and am going into a biology undergraduate degree, I'm getting into biochemistry too and would like to learn more about it through online platforms or even non-fiction books to use my time effectively this summer. So far I've been using online flash cards to learn more about the jargon and would like to hear some suggestions of platforms or books to read that teach concepts strongly tied to biochemistry beyond what a basic high school curriculum would teach. There are several reference books for biochemistry, some more readable than others. I personally recommend two of them: (1) Lehninger et al. Principles of Biochemistry and (2) Voet, D., Voet, J., et al. Fundamentals of Biochemistry: Life at the molecular level. Both books contain the most important and basic features of each subject. The chapters are generally well written. I have to say that, from my own experience, I consider that Voet's book is more enjoyable, given that some of the sections of Lehninger's can be a bit tricky. Whichever book you choose, make sure you get relatively new editions. Good luck!
As a side note, even though biochemistry is one the first proper biology classes one takes in undergrad, there are some background requirements. Taking organic and inorganic chemistry courses before is important and some understanding of thermodynamics will certainly come in handy.
The following is multiple choice question (with options) to answer.
What are the most numerous and diverse biochemical compounds? | [
"proteins",
"vitamins",
"acids",
"lipids"
] | A | Proteins are the most numerous and diverse biochemical compounds. They have many different functions. |
SciQ | SciQ-1917 | zoology, ecology, population-biology, ecosystem, predation
Title: Predator prey interaction I went through a line in my textbook which read:
"But for predators, prey species could achieve very high population densities and cause ecosystem instability."
I was not able to understand the meaning 'but for predators'. Can anyone please help me to interpret it's meaning?link to page where this line is mentioned
Edit: In terms of biology, I was unable to understand the meaning of the sentence, and I wanted to make sure that I don't misunderstand things... And this is why I posted the question.. I feel that the answer given is correct and in case, you find better explanation, please do post. I disagree with GForce's explanation; the meaning is not that growth of prey populations causes instability in predator species.
The sentence is merely saying that without predation, prey population growth is more likely to be at a level which leads to ecosystem instability. The term "but for predation" means "if it wasn't for the effects of predation". In other words:
"Ecosystem instability can occur when population growth of some species goes unchecked by predation."
See here for more explanation, where this example comes from in which it says that running a red light caused a crash:
"but for running the red light, the collision would not have occurred"
Biologically this makes sense in the sentence you show; without predators a species is limited by its supply of resources, and it can use these resources at an unsustainable level, whereas if you add predators to the mix there is additional extrinsic effects on population size, not determined by ecosystem properties such as space or nutrients.
The following is multiple choice question (with options) to answer.
Loss of what eventually threatens other species not impacted directly, because of their interconnectedness; as species disappear from an ecosystem others are threatened by changes in available resources? | [
"technology",
"oxygen",
"climate",
"biodiversity"
] | D | Community Dynamics Community dynamics are the changes in community structure and composition over time. Sometimes these changes are induced by environmental disturbances such as volcanoes, earthquakes, storms, fires, and climate change. Communities with a stable structure are said to be at equilibrium. Following a disturbance, the community may or may not return to the equilibrium state. Succession describes the sequential appearance and disappearance of species in a community over time. In primary succession, newly exposed or newly formed land is colonized by living things; in secondary succession, part of an ecosystem is disturbed and remnants of the previous community remain. Primary Succession and Pioneer Species Primary succession occurs when new land is formed or rock is exposed: for example, following the eruption of volcanoes, such as those on the Big Island of Hawaii. As lava flows into the ocean, new land is continually being formed. On the Big Island, approximately 32 acres of land is added each year. First, weathering and other natural forces break down the substrate enough for the establishment of certain hearty plants and lichens with few soil requirements, known as pioneer species (Figure 45.32). These species help to further break down the mineral rich lava into soil where other, less hardy species will grow and eventually replace the pioneer species. In addition, as these early species grow and die, they add to an ever-growing layer of decomposing organic material and contribute to soil formation. Over time the area will reach an equilibrium state, with a set of organisms quite different from the pioneer species. |
SciQ | SciQ-1918 | units, history, si-units, metrology
Title: Is the definition of the meter arbitrary? From Wikipedia, the definition of the meter is
The meter is defined as the distance traveled by light in a vacuum in 1/299792458 seconds.
Why is this number of seconds chosen? Is there a motivation for this choice? Yes and no.
Yes - because one can pick any distance one wants, and call it a meter (originally, it was 1/40,000,000th of the circumference of Earth measured over the poles; then the distance between a pair of lines on a standard platinum rod, then...).
But no - it is specifically chosen to be that value because
a) we believe the speed of light to be an absolute constant in the universe
b) by defining distance in terms of speed of light (a constant) and time (something we can measure precisely) we no longer need to maintain two separate standards.
The number was chosen such that the speed of light (which was previously known to be approximately 299,792,458 m/s) will henceforth be exactly that number.
Much detail on this can be found in this question and the associated answers. Note that that question asks the converse of this one - namely, "why does the speed of light have no uncertainty". This is the other half of that question.
The following is multiple choice question (with options) to answer.
How many centimeters are in a meter? | [
"200",
"1000",
"50",
"100"
] | D | 500. mm is equivalent to 0.5 m. |
SciQ | SciQ-1919 | solutions, vapor-pressure
Title: If some particles of liquid in a solution convert to vapour then why can't some liquid particles convert to solid? I was reading about the vaporisation of liquid when I came across the following statement.
The average energy of the particles in a liquid is governed by the
temperature. The higher the temperature, the higher the average
energy. But within that average, some particles have energies higher
than the average, and others have energies lower than the average.Some
of the more energetic particles on the surface of the liquid can be
moving fast enough to escape from the attractive forces holding the
liquid together. They evaporate.
Now if some particles have energies lower than the average, then why don't they convert into solids in the same way the particles with higher energies convert to gases.
If we cover a vessel filled with water with a plate, after some time, we observe droplets of water accumulated at the plate because of vaporisation of water. Why don't we observe any changes that show liquid particles converting to solid? If water molecules go into the gas phase from the liquid then they are in a different phase. But water molecules go into the gas phase one at a time. If there are the same number of water molecules leaving the liquid as coming into it then the atmosphere above the liquid would have 100% humidity and be in equilibrium with the liquid.
Now if some small number molecules of water happen to line up to form an ice crystal within the water itself what happens? Such an ice crystal is thermodynamically unstable and then "melts" within the liquid phase. Since the whole process takes place in the liquid phase it is virtually undetectable.
Now you also have to realize that form ice crystals big enough to detect visually requires more than a handful of molecules. You'd need billions of billions of molecules. That is just a statistical impossibility.
The following is multiple choice question (with options) to answer.
What is the term of a phase change if solid water has it's average kinetic energy increased to change it to liquid water? | [
"boiling",
"melting",
"freezing",
"evaporation"
] | B | Problem-Solving Strategies for the Effects of Heat Transfer 1. Examine the situation to determine that there is a change in the temperature or phase. Is there heat transfer into or out of the system? When the presence or absence of a phase change is not obvious, you may wish to first solve the problem as if there were no phase changes, and examine the temperature change obtained. If it is sufficient to take you past a boiling or melting point, you should then go back and do the problem in steps—temperature change, phase change, subsequent temperature change, and so on. Identify and list all objects that change temperature and phase. Identify exactly what needs to be determined in the problem (identify the unknowns). A written list is useful. Make a list of what is given or what can be inferred from the problem as stated (identify the knowns). Solve the appropriate equation for the quantity to be determined (the unknown). If there is a temperature change, the transferred heat depends on the specific heat (see Table 14.1) whereas, for a phase change, the transferred heat depends on the latent heat. See Table 14.2. Substitute the knowns along with their units into the appropriate equation and obtain numerical solutions complete with units. You will need to do this in steps if there is more than one stage to the process (such as a temperature change followed by a phase change). Check the answer to see if it is reasonable: Does it make sense? As an example, be certain that the temperature change does not also cause a phase change that you have not taken into account. |
SciQ | SciQ-1920 | zoology, behaviour, mammals, rodents
Title: Why do Guinea Pigs chirp / sing? Ok, so this appears to be quite a mystery. Me and my girlfriend have 2 Guinea Pigs, 1 male and 1 female.
My girlfriend once picked up the female one and took her outside into our garden. The Guinea got scared for some unknown reason and jumped out of my girlfriend's arms and fell down hard.. That night, the female Guinea woke us up with some very strange sounds. She sounded like a chirping bird.
Since then, she sometimes repeats these sounds (most often at night, but not always). Mostly, we are puzzled as to why as there is often no apparent reason for her sounds. Also, when she makes the sounds, she appears to be in a trance-like state, making no movements at all.
Looking for the answer online I found many discussions on the subject like this one or this one. Mostly, the sounds (and the often mentioned trance like behavior) appear to be interpreted as either (1) alarm sounds, (2) loneliness sounds or (3) happiness sounds.
There are also recordings of it one Youtube, like this one.
What I was wondering:
Does anybody know about some actual research that has been committed on this subject? If so, what were the results?
I'm just so very curious to find out! I found this question very interesting so I did some research. Here's a brief summary of what I've found:
Researchers have found that there are 11 different call types. Some of these include a "sharp alarm cry", "sociable clucking", chutter, whining, purring etc. Using body position and behaviour, researchers attempted to associate these vocalizations with behaviour. Some vocalizations had no apparent associated action including what researchers designated the "chirrup" ( I think this is similar to what your guinea pig might have emitted.)
For more information you can read the results section of this paper by Berryman. You can find a full description of each of the 11 calls and their assumed cause or purpose. Some involve social interaction, reproduction, and distress. Much of the research regarding Guinea pig vocalization involves communication and response between mothers and pups.
In short, it seems as though this chirping behaviour your Guinea pig is exhibiting is normal, but not of any known cause.
The following is multiple choice question (with options) to answer.
What type of animals are known for being playful and frisky? | [
"sea otters",
"snakes",
"cows",
"giant tortoises"
] | A | Sea otters are known for being playful and frisky. They are serious eaters, however! A major part of a sea otter's diet are echinoderms, such as sea urchins. They manage to eat the soft part of the sea urchins while avoiding the huge sea urchin spines. |
SciQ | SciQ-1921 | evolution
Not that I can think of or find easily. While there are detriments associated with being born prematurely, and some evidence that women waiting until they're late 30's and men until they're 60 or older can negatively affect their gametes and consequently the development of any children born from them - it's been such a short time since the introduction of hormonal contraception and modern medicine that we may not see results tangible results for hundreds of years. Although condoms have been around for several hundred years, and there's been no associations with condom use that I can think of.
In the short term, what it has done is affect the ethnic diversity of countries. For the first time ever, Hispanic births have outnumbered Caucasian births in 2012 in the United States. Other countries, mostly European countries, are seeing declines in birth rates - which means their populations will decline with age or be compensated for by immigration. Higher birth rates, however, are associated with lower income brackets or very religious communities - both of which are associated with ethnic Minorities, at least in the United States. So while minority populations have more kids, they do so on fewer resources which may negatively affect their children in the long-term, whereas higher-earning segments of the population might have fewer children later in their lives, but can provide a much more stable environment and opportunities to continue that success.
One thing that hormone-centered birth control has done, however, is eliminate rape as a viable form of passing on one's genes. As gruesome as it might be to consider, pregnancies as a result of rape can produce "fit" offspring. It is a legitimate reproductive strategy in nature, and is in humans... unless the woman is using contraception. In the long-term this will probably show some interesting results (nominally an enhanced "Female Choice" effect - which is already evident in human evolution), but nothing right now.
The following is multiple choice question (with options) to answer.
Virtually all of the effects of pregnancy can be attributed in some way to the influence of what? | [
"enzymes",
"acids",
"proteins",
"hormones"
] | D | Effects of Hormones Virtually all of the effects of pregnancy can be attributed in some way to the influence of hormones—particularly estrogens, progesterone, and hCG. During weeks 7–12 from the LMP, the pregnancy hormones are primarily generated by the corpus luteum. Progesterone secreted by the corpus luteum stimulates the production of decidual cells of the endometrium that nourish the blastocyst before placentation. As the placenta develops and the corpus luteum degenerates during weeks 12–17, the placenta gradually takes over as the endocrine organ of pregnancy. The placenta converts weak androgens secreted by the maternal and fetal adrenal glands to estrogens, which are necessary for pregnancy to progress. Estrogen levels climb throughout the pregnancy, increasing 30-fold by childbirth. Estrogens have the following actions: • They suppress FSH and LH production, effectively preventing ovulation. (This function is the biological basis of hormonal birth control pills. ) • They induce the growth of fetal tissues and are necessary for the maturation of the fetal lungs and liver. • They promote fetal viability by regulating progesterone production and triggering fetal synthesis of cortisol, which helps with the maturation of the lungs, liver, and endocrine organs such as the thyroid gland and adrenal gland. • They stimulate maternal tissue growth, leading to uterine enlargement and mammary duct expansion and branching. Relaxin, another hormone secreted by the corpus luteum and then by the placenta, helps prepare the mother’s body for childbirth. It increases the elasticity of the symphysis pubis joint and pelvic ligaments, making room for the growing fetus and allowing expansion of the pelvic outlet for childbirth. Relaxin also helps dilate the cervix during labor. |
SciQ | SciQ-1922 | we can discover the conditions under which it performs simple harmonic motion, and we can derive an interesting expression. Intuitively, we know that the double pendulum has four configurations in which the segments will remain stationary if placed there carefully and not disturbed. if P α l a g b. A pendulum is considered to be a simple harmonic motion. The period of a pendulum or any oscillatory motion is the time required for one complete cycle, that is, the time to go back and forth once. Testimonials. It is represented using the aphabet ( l ). The purpose of this experiment was to measure the acceleration due to gravity in the. IBDP PHYSICS Internal Assessment – The Simple Pendulum 9 INTRODUCTION The original aim for this invesigation was to “investigate the simple pendulum”. A simple pendulum's period is: In order to find the angle for the amplitude, we used trigonometry: The "tape" is the distance from the mass to where half of an oscillation would extend to. Carrying out the experiment Load settings. It is independent of the mass of the bob. squareroot(L/g) where L is the length of the string and g is the acceleration due to gravity. This activity demonstrates how potential energy (PE) can be converted to kinetic energy (KE) and back again. The resulting pendulum period using this method was 3. Simply put, the problem is to drive the robot base forward or backward in such a manner as to prevent the inverted pendulum design from falling over. Box 04455, 70919-970, Brasilia-DF, Brazil P. I lost the pendulum capability and I'd like to find a simple circuit that would move the pendulum with the same speed as in a normal clock. The E ects of Mass, Length, and Amplitude on the Period of a Simple Pendulum Phil Rubin September 26, 2004 Abstract The e ects of bob mass, length, and amplitude on the period of a simple pendulum are investigated. Derivation of the equation of motion of the simple pendulum with a linear drag force is trivial, however, we present it here for completeness of the discussion. P-3 SIMPLE PENDULUM. Suppose you must be made part of this experiment. Notice that it is typed and spell checked, and should not contain errors such as interchanging “affect “ and “effect”. The percent different between these ratios is 3. Discussion of Principles A particle that
The following is multiple choice question (with options) to answer.
A mass suspended by a wire is a simple type of what and undergoes simple harmonic motion for amplitudes less than about 15 degrees? | [
"weight",
"pendulum",
"gravity",
"variation"
] | B | 16.4 The Simple Pendulum • A mass m suspended by a wire of length L is a simple pendulum and undergoes simple harmonic motion for amplitudes less than about 15º. The period of a simple pendulum is. |
SciQ | SciQ-1923 | acid-base, lewis-structure
Title: Why is carbon dioxide a Lewis acid? I know this has been asked before, but can anyone explain me in simpler terms? Why is $\ce{CO2}$ a Lewis acid? The carbon atom doesn't have any vacant orbitals to accept a lone pair. How can it be a Lewis acid? Suppose one of the doublets of one C=O bond moves to one of these two atoms. It will not be to the Carbon atom. The Oxygen atom is a better choice. And now this Oxygen atom would be negatively charged. As a consequence the Carbon atom is positively charged and has a vacant orbital able to accept a lone pair, for example from an $\ce{OH-}$ ion or from water. This will produce the ion $\ce{HCO3^-}$ (from $\ce{OH-}$) or $\ce{H2CO3}$ (from $\ce{H2O}$).
The following is multiple choice question (with options) to answer.
The structure of the gas carbon dioxide consists of one atom of carbon and two atoms of what? | [
"sulfur",
"methane",
"Helium",
"oxygen"
] | D | Another example is carbon dioxide. This gas is produced from a variety of reactions, often by the burning of materials. The structure of the gas consists of one atom of carbon and two atoms of oxygen. Carbon dioxide production is of interest in many areas, from the amount we breather out to the amount of the gas produced by burning wood or fossil fuels. By knowing the exact composition of carbon dioxide, we can make predictions as to the effects of different chemical processes. |
SciQ | SciQ-1924 | The exact value of 0.3 + -0.29 is 0.01.
Compute the following:
(float approx of 0.3) + (float approx of -0.29) =
(2.8125) + -0.28125) =
0
Then compare the approximate value (0) to the exact value (0.1) for the number of significant figures of $$z = float(x_1) + float(x_2)$$
1.0 - 0.0 = 1.0
The result has zero significant figures of accuracy.
Note that your textbook's definition of significant figures is probably different than mine. In your homework, explain to your teacher what definition you used. The concept of significant figures is more important that the details. Knowing roughly how many digits of the approximation are correct is more important than knowing exactly how to compute the number of significant figures.
The following is multiple choice question (with options) to answer.
What type of numerical figure is important in considering the precision and accuracy of a number? | [
"component",
"insignificant",
"exponent",
"significant"
] | D | Next, we identify the least precise measurement: 13.7 kg. This measurement is expressed to the 0.1 decimal place, so our final answer must also be expressed to the 0.1 decimal place. Thus, the answer is rounded to the tenths place, giving us 15.2 kg. Significant Figures in this Text In this text, most numbers are assumed to have three significant figures. Furthermore, consistent numbers of significant figures are used in all worked examples. You will note that an answer given to three digits is based on input good to at least three digits, for example. If the input has fewer significant figures, the answer will also have fewer significant figures. Care is also taken that the number of significant figures is reasonable for the situation posed. In some topics, particularly in optics, more accurate numbers are needed and more than three significant figures will be used. Finally, if a number is exact, such as the two in the formula for the circumference of a circle, c = 2πr , it does not affect the number of significant figures in a calculation. |
SciQ | SciQ-1925 | homework-and-exercises, newtonian-mechanics, forces, torque
Title: A rod with a ball attached is balanced?
An object is made by hanging a ball of mass $M$ from one end of a plank having the same mass and length $L$. The object is then pivoted at a point a distance $L/4$ from the end of the plank supporting the ball, as shown.
I would like to know why the above is true.
Since $\tau= \mid r \mid \mid F \mid \sin \theta$, given that $\sin \theta$ is when $\theta=90^{\circ}$. The torque should then be $\tau= rF$ when assuming the axis to be a standard xy-plane. Am I supposed to figure out how $F_g= \tau$ where the some of the variables cancel? I don't really see it. How should I approach this problem to gain further understanding?
thanks in advance! Please note that the rod is not massless. The gravitational force can be effectively applied to the centre of gravity.
Hope this gives you some direction.
Some additional hint: center of gravity of an uniform rod is located at its midpoint. Thus the opposing torque could come from the weight of the rod itself.
The following is multiple choice question (with options) to answer.
What rod provides stiffness to counterbalance the pull of muscles? | [
"mesoderm",
"spinal cord",
"vertebrae",
"notochord"
] | D | The notochord lies between the dorsal nerve cord and the digestive tract. It provides stiffness to counterbalance the pull of muscles. |
SciQ | SciQ-1926 | 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.
What type of cell does the sperm cell fertilize? | [
"fat",
"egg",
"bacteria",
"protein"
] | B | Together with random fertilization, more possibilities for genetic variation exist between any two people than the number of individuals alive today. Sexual reproduction is the random fertilization of a gamete from the female using a gamete from the male. In humans, over 8 million (2 23 ) chromosome combinations exist in the production of gametes in both the male and female. Essentially, when the homologous pairs of chromosomes line up during metaphase I and then are separated at anaphase I, there are (2 23 ) possible combinations of maternal and paternal chromosomes. During random fertilization, a sperm cell, with over 8 million possible chromosome combinations, fertilizes an egg cell, which also has over 8 million possible chromosome combinations. Together, there are over 64 trillion unique combinations, not counting the additional variation produced by crossing-over during prophase I. In other words, each human couple could produce a child with over 64 trillion unique chromosome combinations!. |
SciQ | SciQ-1927 | climate-change
What this means is that the traditional monsoon dynamics i.e. cool Indian ocean and warm continental land mass has been disturbed by human influenced climate change as well as the natural geography of the land and ocean mass. One significant ISM phenomenon the tropical easterly jet stream has shown a weakening trend over the last few decades. A significant fall out of this could be mid latitude atmospheric dynamics could come into play during the ISM(one can think of this as the weather during a break in monsoons where upper level subtropical westerlies come into play) and a disturbing trend has been noted in recent times with increasing frequency of hail storms.
The following is multiple choice question (with options) to answer.
Where does the most important monsoon in the world occur? | [
"southern asia",
"eastern aisa",
"the atlantic ocean",
"northern africa"
] | A | Monsoons are like land and sea breezes, but on a larger scale. They occur because of seasonal changes in the temperature of land and water. In the winter, they blow from land to water. In the summer, they blow from water to land. In regions that experience monsoons, the seawater offshore is extremely warm. The hot air absorbs a lot of the moisture and carries it over the land. Summer monsoons bring heavy rains on land. Monsoons occur in several places around the globe. The most important monsoon in the world is in southern Asia ( Figure below ). These monsoons are important because they carry water to the many people who live there. |
SciQ | SciQ-1928 | evolution, herpetology, dinosaurs
Title: Evolution of dinosaurs What did dinosaurs evolve from? Was it the reptiles that evolved from amphibians? I have been researching this but am very confused with who their direct predecessor was. Amphibians evolved from fish...reptiles from amphibians...dinosaurs from reptiles (?)...and birds from dinosaurs. That is my understanding, but it could be wrong. How are dinosaurs related to reptiles? And if they did evolve from reptiles, which kind of reptiles (such as lizards, crocodiles, or turtles for example)? Source of information
See the post The best free and most up to date phylogenetic tree on the internet? for info about how to find such information.
Generally speaking, you might be interested in an intro to phylogenetics such as the one provided in this answer for example.
Where are dinosaurs in the tree of life?
Dinosaurs fall within the Reptiliomorpha clade. Please note that Reptiliomorpha does not quite correspond to what we today call reptiles. Please see the post If dinosaurs could have feathers, would they still be reptiles?
Reptiliomorpha is the sister clade to Amphibia (from here) which contain all living amphibians.
If you look within the Amniota, you will find all of the following
Here, you see that turtles and mammals are an off-shoot of Diapsida. So dinosaurs are not mammals and there are not closely related to turtles. Now if you click on Diapsida you will find ...
the Archosauromorpha which contains all crocodiles, birds and dinosaurs. You can keep going to find Therapoda which contains many dinosaurs and birds. You can keep going like this for yourself and discover the entire tree of life!
Reacting to your sentences
What did dinosaurs evolve from?
When asking this question, please do not forget that no species evolved from an extant species. If this is unclear to you, you should have a look at this post.
Was it the reptiles that evolved from amphibians?
Well... the term reptile is a mess because it does not represent a monophyletic group (see this post). If you do not understand the term monophyletic, then you should have a look at this answer.
Amphibians evolved from fish...
The following is multiple choice question (with options) to answer.
What is the earliest reptile? | [
"pliosaur",
"staurikosaurus",
"hylonomus",
"sporozoans"
] | C | Earliest Reptile: Hylonomus. The earliest known reptile is given the genus name Hylonomus. It was about 20 to 30 centimeters (8 to 12 inches) long, lived in swamps, and ate insects and other small invertebrates. |
SciQ | SciQ-1929 | 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.
Which side of the heart does blood from the lungs enter into? | [
"left ventricle",
"right ventricle",
"left atrium",
"right atrium"
] | C | Blood from the lungs enters the left atrium of the heart. The left atrium pumps the blood to the left ventricle, which pumps it to the body. This loop is represented by the red arrows in Figure above . |
SciQ | SciQ-1930 | electromagnetic-radiation, visible-light, vision
Title: If an object emits radiation, is that object visible to us? I learned that all material objects emit electromagnetic (light) radiation. But, we can only "see" visible light. I'm aware that non-visible light is 'invisible' to us; however, I was wondering about this. Doesn't the sun emit UV light, and isn't it visible to us? Rather, I should ask, isn't the source of the UV light (the sun) visible?
If an object emits any type of EM radiation, will it be technically visible? Thank you. Yes, any object that emits any form of radiation is visible to us. However, since humans are capable of directly observing, only the visible light wavelengths, so, we'll ofcourse need special devices to observe said radiation. The sun emits UV radiation, as well as visible light and other forms of radiation. We are just able to see the visible light part of it. I can provide the link to a youtube video, that shows how the world would appear from an ultraviolet lens, if you want.
Snakes for example, can see infrared, and butterflies can see ultraviolet, if I'm not wrong.
The following is multiple choice question (with options) to answer.
Smog is a visible form of what? | [
"condensation",
"oxidation",
"air pollution",
"water pollution"
] | C | Smog clouds the city of Los Angeles, California. Visible air pollution in the form of smog is a sign that the air is unhealthy. |
SciQ | SciQ-1931 | virology, retrovirus, treatment, gene-therapy
Title: Using viruses to treat altered or misconfigured DNA Consider how a Retrovirus can modify existing cell DNA to 'execute instructions' on its behalf.
I wondered: Why can we not utilize lab-generated viruses to infect sick patients with a 'healthy' virus that would rewrite bad segments of DNA with something either correct or non-malus? This of course is assuming that we have a solid understanding of the relationship between genomes and precise viral functions, additionally that we had some sort of gene replacement functionality.
Consider how a Retrovirus can modify existing cell DNA to 'execute instructions' on its behalf.
Not only retroviruses do that. Actually, pretty much all viruses use the machinery of the host cell on its behalf.
Why can we not utilize lab-generated viruses to infect sick patients with a 'healthy' virus that would rewrite bad segments of DNA with something either correct or non-malus?
We actually do that. We use viruses (incl. retrovirus but not only) to insert DNA segments into eukaryote genome. See vectors in gene therapy > viruses
Retrovirus to reverse another retrovirus
Note that I don't really understand your title so, I ignored it a bit focusing on the content of the post.
The following is multiple choice question (with options) to answer.
Which therapy uses viruses to genetically modify diseased cells and tissues? | [
"chemotherapy",
"oxygen therapy",
"digestive therapy",
"viral therapy"
] | D | In a similar fashion, viral therapy uses viruses to genetically modify diseased cells and tissues. Viral therapy shows promise as a method of gene therapy and in the treatment of cancer. Gene therapy is the insertion of genes into a person’s cells and tissues to treat a disease. In the case of a genetic disease, the defective gene is replaced with a working gene. Although the technology is still new, it has been used with some success. |
SciQ | SciQ-1932 | dna, radiation
Title: How do electrons destroy DNA bonds in radiation? Malignant tumors can be treated by radiation therapy. Most commonly it's radiotherapy with photons, or protons and so on. The common denominator for both types is that the radiation creates electrons inside the body via different effects.
What I haven't quite understood is how these electrons destroy the DNA bonds in the tumor and how this aids in killing off the cancer cells? Is it due to the generation of heat, or otherwise? I think you have a fundamental misunderstanding of the chemical reactions involved in radiation therapy. Neither photon based or proton based therapies "create electrons", but they do cause ionization by adding enough energy to existing electrons around atoms so that the electron is ejected from the atom, creating an ion or free radical, which can then undergo chemical reaction.
Photons, typically gamma rays, X-rays, and high energy UV, typically interact with water molecules and produce free radicals, including the dangerous hydroxyl radical. The hydroxyl radical can interact with proteins and DNA and damage those molecules, but has a very short half-life. Molecular oxygen can help increase the damage by reacting with the hydroxyl radical to produce Reactive Oxygen Species, ROS, which can also damage DNA or protein. However, many tumors have low oxygen concentration that reduces the effectiveness of photon based radiation therapy.
To overcome this, many patients receive proton based radiation therapy. Protons are much heavier than photons (I guess infinitely heavier than a photon, since photons have no mass) and therefore scatter to a much smaller extent. They just sort of plow through tissue and knock electrons out of orbitals as they collide with molecules such as DNA or protein. They don't rely so much on free radical generation or ROS, so low oxygen levels don't reduce their effectiveness.
The goal is damage the DNA to induce double strand breaks which are hard to repair in fast growing cancer cells. Because they grow so quickly, they are already stressed and their DNA repair machinery is less effective than in healthy cells. If their DNA can be sufficiently damaged, the cell will die.
For more information about these processes, please see these wikipedia articles on Radiation Therapy, Radiolysis, Linear Energy Transfer, and Free Radical Damage to DNA.
The following is multiple choice question (with options) to answer.
Radiotherapy is effective against cancer because cancer cells reproduce rapidly and, consequently, are more sensitive to this? | [
"UV light",
"radiation",
"separation",
"destruction"
] | B | Radiotherapy is effective against cancer because cancer cells reproduce rapidly and, consequently, are more sensitive to radiation. The central problem in radiotherapy is to make the dose for cancer cells as high as possible while limiting the dose for normal cells. The ratio of abnormal cells killed to normal cells killed is called the therapeutic ratio, and all radiotherapy techniques are designed to enhance this ratio. Radiation can be concentrated in cancerous tissue by a number of techniques. One of the most prevalent techniques for well-defined tumors is a geometric technique shown in Figure 32.13. A narrow beam of radiation is passed through the patient from a variety of directions with a common crossing point in the tumor. This concentrates the dose in the tumor while spreading it out over a large volume of normal tissue. The external radiation can be x-rays, 60 Co γ rays, or ionizing-particle beams produced by accelerators. Accelerator-produced beams of neutrons, π-mesons , and heavy ions such as nitrogen nuclei have been employed, and these can be quite effective. These particles have larger QFs or RBEs and sometimes can be better localized, producing a greater therapeutic ratio. But accelerator radiotherapy is much more expensive and less frequently employed than other forms. |
SciQ | SciQ-1933 | 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 type of cells are multiple small spaces located in the right and left sides of the ethmoid bone? | [
"amniotic sacs",
"ethmoid air cells",
"alveoli",
"ethmoid vacuoles"
] | B | Figure 7.18 Paranasal Sinuses The paranasal sinuses are hollow, air-filled spaces named for the skull bone that each occupies. The most anterior is the frontal sinus, located in the frontal bone above the eyebrows. The largest are the maxillary sinuses, located in the right and left maxillary bones below the orbits. The most posterior is the sphenoid sinus, located in the body of the sphenoid bone, under the sella turcica. The ethmoid air cells are multiple small spaces located in the right and left sides of the ethmoid bone, between the medial wall of the orbit and lateral wall of the upper nasal cavity. |
SciQ | SciQ-1934 | thermodynamics, heat, visible-light, photons, everyday-life
That is more or less how I see it.
What steps are ok ?
And the main question , why is there light involved ?
I mean why cant we just have kinetic energy of the electrons and a changing magnetic field ? Why are there photons ?
If the electrons are in a high energy state why cant they just move faster instead of emitting a photon ???
Why is the light usually visible ? is that because of our structure of air ?
If the light is an electromagnetic wave why does the flame go up ? does that imply all electromagnetic waves go up ?? But electromagnetic waves are not influanced by gravity or buoyancy are they ??
What is the final destiny of the electrons and photons if the heat is gone ??
I am puzzled by this. You should take some time to read the links zhermes suggests. As a starting point:
Fire, or more accurately a flame, is a gas phase reaction. When you look at wood burning you are actually seeing wood heated by the flame giving off gas, and the flame is this gas reacting with oxygen.
When a molecule of combustible gas reacts with a molecule of oxygen the reaction products fly away with more energy than the original molecules had. This extra energy comes from the energy of reaction. The increased velocity of the reaction products corresponds to an increase in temperature according to the Maxwell-Boltzmann distribution.
The light comes from two sources. Firstly, the typical red/orange /yellow glow comes from particles of unburnt carbon in the flame. These are heated by collisions with the rapidly moving reaction products and glow by black body radiation. Secondly the most energetic reaction products collide hard enough to excite electronic transitions or even ionise gas molecules. As the excited molecules relax they may give off light that is characteristic of the transition. That's why you get specific colours e.g. green from copper, yellow from sodium etc.
The flame is not a plasma. Only a tiny tiny fraction of molecules and/or atoms in the flame are ionised.
The following is multiple choice question (with options) to answer.
When what element - whose name means "light bringing" - was first isolated, scientists noted that it glowed in the dark and burned when exposed to air? | [
"oxygen",
"phosphorus",
"mercury",
"neon"
] | B | Phosphorus The name phosphorus comes from the Greek words meaning light bringing. When phosphorus was first isolated, scientists noted that it glowed in the dark and burned when exposed to air. Phosphorus is the only member of its group that does not occur in the uncombined state in nature; it exists in many allotropic forms. We will consider two of those forms: white phosphorus and red phosphorus. White phosphorus is a white, waxy solid that melts at 44.2 °C and boils at 280 °C. It is insoluble in water (in which it is stored—see Figure 18.24), is very soluble in carbon disulfide, and bursts into flame in air. As a solid, as a liquid, as a gas, and in solution, white phosphorus exists as P4 molecules with four phosphorus atoms at the corners of a regular tetrahedron, as illustrated in Figure 18.24. Each phosphorus atom covalently bonds to the other three atoms in the molecule by single covalent bonds. White phosphorus is the most reactive allotrope and is very toxic. |
SciQ | SciQ-1935 | biochemistry, cell-biology, proteins, enzymes, digestive-system
So, while maybe something like $\ce{H2SO4}$ or $\ce{HNO3}$ could work too, hydrochloric acid is just more convenient to use? Parietal cells use ion pumps to expel protons and chlorine ions into the lumen, which create the necessary acidic environment to denature pepsinogen into pepsin.
It is the low pH environment that reconfigures or denatures pepsinogen into pepsin. The acid used does not matter. For example, one experiment in classifying properties of pepsinogen used a 3.5 pH solution of 0.5 N sulfuric acid to activate pepsin.
We evolved stomachs with parietal cells that use an energetically expensive process to maintain the acidic gradient necessary for digestion and protection from pathogens.
It may be that biochemical pathways to generate other acids did not evolve, because it is either energetically cheaper for these cells to make HCl, compared with other pathways that would generate other acids of sufficient strength; or the relevant chemical components involved are more abundant than others in what we eat and drink, and thus easier to make in quantities needed for digestion and defense. Chloride ions also serve a role in maintaining intra- and extracellular fluid pressure and thus play a larger part as electrolytes in the normal function of the body — they are available and cells use them.
But to answer your main question, an acidic environment activates pepsin, and it is not chemically necessary for this to be created by hydrochloric acid.
The following is multiple choice question (with options) to answer.
Digestive enzymes secreted in the acidic environment (low ph) of the stomach help break down what? | [
"particles",
"molecules",
"proteins",
"cells"
] | C | Digestive enzymes secreted in the acidic environment (low pH) of the stomach help break down proteins into smaller molecules. The main digestive enzyme in the stomach is pepsin , which works best at a pH of about 1.5. These enzymes would not work optimally at other pHs. Trypsin is another enzyme in the digestive system, which breaks protein chains in food into smaller parts. Trypsin works in the small intestine, which is not an acidic environment. Trypsin's optimum pH is about 8. |
SciQ | SciQ-1936 | elementary-particles
A textbook on solid state physics can help elucidate further properties of solids for you.
A textbook on the Standard Model of particle physics would be useful to catalog the known point-particles like electrons, muons, gluons, etc.
Finally, you mentioned "elements". By this, I believe you mean the different types of atoms, e.g., the element hydrogen, the element copper, etc. The different elemental atoms have different properties due to their differing number of protons, e.g. hydrogen has 1 proton, copper has 29 protons. In this matter, too, a textbook on chemistry will be useful to you.
Cheers.
The following is multiple choice question (with options) to answer.
The majority of solids are what in nature? | [
"crystalline",
"complex",
"gases",
"liquids"
] | A | The majority of solids are crystalline in nature. A crystal is a substance in which the particles are arranged in an orderly, repeating, three-dimensional pattern. Particles of a solid crystal may be ions, atoms, or molecules, depending on the type of substance. The three-dimensional arrangement of a solid crystal is referred to as the crystal lattice . Different arrangements of the particles within a crystal cause them to adopt several different shapes. |
SciQ | SciQ-1937 | species-identification, botany, ecology
Title: Algae or Lichen identification. Coastal BC, Canada I have tried all books and internet resources I know of, but I still have no idea what this might be — a lichen or something else.
At first glimpse, I thought it was something man-made and unnatural, but then I looked closer and saw how it appears to be attached and growing. It grows on exposed rocks well above the high tide. The photo is taken in late March, on northern Vancouver Island. It's loosely attached to the rock.
It was somewhat abundant around the general area (within of a few km), but I haven't seen it elsewhere - although I'm not from BC so there might be a lot of this around.
The water droplet in the lower right corner give a rough sense of scale.
Edit:
Adding another photo in which I just noticed a streak of white, which I included in original resolution. I want to propose you expand your search to a broader taxonomic scope. Specifically, I think you might be looking at a species of "red" green algae (family: Trentepohliaceae).
From Nelson et al. (2011):
All Trentepohliaceae have filamentous growth forms and often contain large amounts of carotenoid pigments (ß-carotene and hematochrome), causing the algae to appear yellow orange in color (Thompson and Wujek 1997, Lo´pez-Bautista et al. 2002).
The Trentepohliaceae contains five genera: (Trentepohlia, Printzina, Phycopeltis, Cephaleuros and Stomatochroon) and 70+ species worldwide.
For example, the following algae (picture from England) looks fairly similar to your specimen:
Trentepohlia aurea
Source: David Fenwick
If your specimen is a species in this family of algae, it is most likely in the Trentepohlia genus (or possibly Printzina genus).
Trentepohlia is a genus of filamentous chlorophyte green algae in the family Trentepohliaceae.
Typically orange or yellow in color.
Live on tree trunks and wet rocks or symbiotically in lichens.
Here's a picture of a free-living Trentepohlia species from coastal Oregon, USA:
Source: Richard C. Hoyer (2015)
The following is multiple choice question (with options) to answer.
What are the most abundant unicellular algae in the oceans? | [
"sporozoans",
"chlorella",
"staurikosaurus",
"chryosophytes"
] | D | 22.11.4 Chryosophytes Chryosophytes are the most abundant unicellular algae in the oceans. They are also one of the biggest components of plankton, a free-floating collection of microorganisms, eggs, and larvae. As photosynthetic organisms, they produce a significant amount of atmospheric oxygen. The reproduction cycle of chryosophytes is particularly interesting. Note that diatoms reproduce both asexually and sexually. Since diatoms have a rigid cell wall with an outer layer of silica (found in sand and glass), the daughter cells produced by mitosis must fit inside the original cell wall. Therefore, each generation of diatoms is smaller than the one before. The reduction in size continues until the diatoms produce sexually, producing a zygote which eventually grows to the original size as it matures. |
SciQ | SciQ-1938 | cell-biology, proteins, mitosis
Title: Purpose of intensive protein synthesis in G1 phase of mitosis What is the purpose of intensive protein synthesis in G1 phase of mitosis, and what purposes do these synthesized proteins serve? Why are lipids and carbohydrates not synthesized intensively as well? The G1 phase of eukaryotic cell cycle is part of interphase, which is when the cell is replicating its DNA ready for division. To understand the need for intense protein synthesis, we first need to understand how DNA is organised during mitosis.
Before DNA is condensed into chromosomes ready for nuclear division it is in the form of chromatin, a long fiber-like structure inside the nucleus. In order to condense into chromosomes, this chromatin must undergo a process of coiling and folding in order to create the chromosome 'X' structure we are familiar with.
A major part of this DNA 'miniaturization' is the folding of the double helix around proteins called Histones - this creates new structures called nucleosomes.
In order to fully condense the roughly 3 meters of DNA in the average human cell down to a singular chromosome, millions upon millions of these Histone proteins are required.
And that answers your question; intense protein synthesis during the G1 phase is required in order to produce the extremely large amount of Histone proteins that are needed for packaging DNA into chromosomes ready for cellular division.
As for carbohydrates, these are constantly being processed by the body in order for the production of ATP for use as energy. The use of said energy for mitosis is a just another constantly required use of ATP within the body. Therefore there isn't any noticeable increase in carbohydrate processing/production, as it is happening regardless of the cell's stage in its cycle.
-See the image below (from shmoop.com) that explains the process of getting DNA into a chromosome.
The following is multiple choice question (with options) to answer.
What term is used to describe the cellular structures responsible for protein synthesis? | [
"chromosomes",
"ribosomes",
"nuclei",
"chloroplasts"
] | B | Ribosomes Ribosomes are the cellular structures responsible for protein synthesis. When viewed through an electron microscope, free ribosomes appear as either clusters or single tiny dots floating freely in the cytoplasm. Ribosomes may be attached to either the cytoplasmic side of the plasma membrane or the cytoplasmic side of the endoplasmic reticulum (Figure 3.7). Electron microscopy has shown that ribosomes consist of large and small subunits. Ribosomes are enzyme complexes that are responsible for protein synthesis. Because protein synthesis is essential for all cells, ribosomes are found in practically every cell, although they are smaller in prokaryotic cells. They are particularly abundant in immature red blood cells for the synthesis of hemoglobin, which functions in the transport of oxygen throughout the body. |
SciQ | SciQ-1939 | mass, astrophysics, astronomy, sun
Title: How massive is the Sun compared to other stars? I was just reading "Rare Earth" by Peter Ward and Donald Brownlee and they claim that $95\%$ of stars are less massive than the Sun. But, I was always told the Sun is an average star. Which is it? The notion that the sun is an 'average' star, is a popular notion, not a scientific one. It is to my knowledge based on the spectral colour-classification (OBAFGKM..) of stars, where the sun (G2-class) hits about the center of this classification, depending how many classes one adds at the end.
However by number, the sun is not average, it is on the rarer end of the mass distribution function. See also this graphic, provided by the University of Colorado:
This has to do with two effects:
1. Heavier stars burn through their fuel much faster than low-mass stars.
The lifetime $t_{\rm life}$ of a star on the main sequence goes like $$t_{\rm life} \sim 10^{10}yrs \left(\frac{M}{M_{\odot}}\right)^{-2.5}$$ so you can do the math yourself how short more massive stars live.
2. Lower mass stars are formed more frequently.
In star-forming environments it is the 3D-turbulence that clumps gas together at smaller and smaller scales (as opposed to larger and larger scales). It is because of this, that there are more small clumps that become gravitationally unstable than large clumps, which then form stars of a given clump mass.
The following is multiple choice question (with options) to answer.
What is the sun classified as on the main sequence? | [
"shrinking star",
"red dwarf",
"yellow dwarf",
"gas giant"
] | C | Producers create food energy. They are the base of all life on Earth. Most producers use photosynthesis but a very small number use chemosynthesis. |
SciQ | SciQ-1940 | • @flea, the French word is "poisson" (same spelling as that mathematician, if it helps). This undermines your assertion a wee bit. Aug 19, 2016 at 8:54
The following is multiple choice question (with options) to answer.
The term science comes from a latin word that means? | [
"were knowledge",
"only knowledge",
"having knowledge",
"having information"
] | C | Understanding the "hows" and "whys" of the world is the goal of science. The term science comes from a Latin word that means "having knowledge. " But science is as much about adding to knowledge as it is about having knowledge. Science is a way of thinking as well as a set of facts. Science can be defined as a way of learning about the natural world that is based on evidence and logic. |
SciQ | SciQ-1941 | circulatory-system, lymphatic-system, veins
Title: How does most of lymph get back into the blood stream? (I don't mean the lymphatic system) I once read that it was because of osmotic pressure that it returns to the blood stream, by entering the venules. But why? If lymph originated as plasma how come that the solute concentration is higher in the venule? Doesn't plasma contain solutes such as salts, nutrients, oxygen, etc. ? Technically 'lymph' is used to refer to the fluid found within the lymphatic system. If it's not in the lymphatic system, it is not lymph fluid. Thus, your question is really asking about interstitial fluid or the plasma that was filtered out of blood capillaries.
The answer to your question is based on the Starling equation. Normally fluid leaves a capillary due to a net pressure that favors the interstitium. This net pressure is based on the hydrostatic pressure within the capillary being greater than the interstitial pressure of the surrounding tissues, and the oncotic pressure of the capillary (that draws fluid in) being weaker than the hydrostatic pressure of the capillary (that pushes fluid out). At the venule end of this system, the capillary oncotic pressure is stronger than the capillary hydrostatic pressure, drawing fluid back into the circulatory system.
Remember that albumin is the most important component which establishes the oncotic pressure within a vessel, and that this protein is normally NOT released out of a vessel during filtration. Thus, it passes from the capillary into its corresponding venule directly.
The following is multiple choice question (with options) to answer.
Lymph vessels, like veins, have what objects that prevent the backflow of fluid? | [
"pumps",
"fibers",
"pores",
"valves"
] | D | |
SciQ | SciQ-1942 | anatomy, liver
The figure below is a picture of the intestinal veins from Gray's Anatomy (wikipedia) that form the hepatic portal vein, the superior and inferior mesenteric as well as the splenic vein. In the figure the older term lienal vein is used instead of splenic vein. The latin word for spleen is lineal.
The picture below is a schematic of the hepatic lobule that receives its blood from a portal triad. In the center of the lobule is the "central vein". The blood flows from the portal triad to the central vein, and then the central veins coalesce to form the hepatic veins (which then drain into the inferior vena cava). The picture below is available from this website, along with some other text and picture for more information.
And another nice picture from wikipedia on "hepatic lobules".
.
As for a "freely available review" that you asked for, I can't find any with better pictures from PubMed that what is already in this answer.
The following is multiple choice question (with options) to answer.
Veins subdivide repeatedly and branch throughout what? | [
"stroma",
"mesophyll",
"periosteum",
"epidermis"
] | B | |
SciQ | SciQ-1943 | thermodynamics, energy, terminology
You are absolutely correct. Heat is not a form of energy. It is a mechanism by which energy is transferred from one substance, object, etc., to another due solely to temperature difference.
When I was learning about thermodynamics I found a particular description that, at least for me, help differentiate between the energy of something and the transfer of energy (by work or heat) from one thing to another. In this case the transfer of energy by heat. I'd like to share it with you in case it might be helpful. For simplicity, the description is for heat conduction.
Consider two solid objects, one having a higher temperature than the other. Which means the molecules of the higher temperature object 1 have a higher average translational kinetic energy than the molecules of the lower temperature object 2.
The objects are placed in contact with each other. At the interface between the objects the molecules of the higher temperature object collide with the molecules of the lower temperature object. On average, this results in the transfer of kinetic energy from the molecules of the higher temperature object to molecules of the lower temperature object causing the temperature of the higher temperature object to decrease, and the temperature of the lower temperature object to increase.
This transfer of kinetic energy from the molecules of the higher temperature object to the molecules of the lower temperature object is what we mean by heat. But the increase in the average kinetic energy of the molecules of the lower temperature object and decrease in the average kinetic energy of the molecules of the higher temperature object is what we mean by a change in the internal (kinetic) energy of the two objects. Thus the difference between the transfer of energy and the energy itself.
Hope this helps.
The following is multiple choice question (with options) to answer.
What is the term for heat being transferred from molecule to molecule? | [
"conduction",
"decomposition",
"oxidation",
"convection"
] | A | In conduction, heat is transferred from molecule to molecule by contact. Warmer molecules vibrate faster than cooler ones. They bump into the cooler molecules. When they do they transfer some of their energy. Conduction happens mainly in the lower atmosphere. Can you explain why?. |
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