source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-2744 | solid-state-physics, crystals, glass, amorphous-solids
Title: Which factors determine whether a substance will be amorphous or crystalline on solidification? What decides whether a substance will be crystalline or amorphous when it solidifies?
I heard various folklores that the method of condensation of a liquid (fast or slow cooling) can be a factor which decides whether the resulting solid will be amorphous or crystalline. If this is true, is it possible that substances which are usually crystalline such as metals can end up being amorphous due to fast cooling? Seems no. Conversely, a substance such as glass which is usually amorphous can become crystalline due to slow enough cooling? Seems no. Then what decides? You are right, here are the details.
In forming crystals in a metal after solidification from the melt, the material is seeking to minimize the energy invested in the bonds between adjacent atoms, giving rise to nanocrystals in the bulk which then grow at the expense of the higher-energy regions without long-range order. It is possible to "outrun" the kinetics of the crystallization process by quenching the metal from the melt so fast that nanocrystalline phases don't have enough time to form, giving rise to an amorphous solid galled a metallic glass instead of a crystalline metal. The quench rates required are heroic; on the order of ~millions of degrees per second. Metallic glasses are metastable; if subsequently heated to between 1/3 and 1/2 the melt temperature, they promptly crystallize.
It is also possible to get long-range order in ceramic glasses by cooling them extremely slowly, but note that the reason we get ceramic glass in the first place is the presence of substances in the glass mix which are added in order to interfere with crystal growth. These substances are called glass formers.
Finally, note that it is also possible to promote the formation of a metallic glass by including alloy constituents in the melt which interfere with crystallization; these alloy metals are also called glass formers in this context.
The following is multiple choice question (with options) to answer.
Many glasses eventually crystallize, rendering them brittle and this? | [
"powdered",
"molten",
"opaque",
"soft"
] | C | Many glasses eventually crystallize, rendering them brittle and opaque. Modifying agents such as TiO 2 are frequently added to molten glass to reduce their tendency to crystallize. Why does the addition of small amounts of TiO2 stabilize the amorphous structure of glass?. |
SciQ | SciQ-2745 | magnetic-fields
Further explanation:
It has been experimentally observed that all magnetic fields are produced by currents*. Straight currents produce circular magnetic fields (see diagram below) and circular currents produce straight magnetic fields (see diagram below). The direction of magnetic field around a straight current is given by one of the right hand thumb rules "Point thumb towards current; curl your fingers. The fingers now give the direction of curling om magnetic field." A current loop produces a magnetic field similar to a hypothetical "short magnetic dipole" with "north and south poles". (Please remember that all magnetic field are produced by currents and thus the poles are imaginary. No magnetic [mono]pole has been found. (at least till now)). The direction of poles of a current loop is given by the right hand thumb rule "curl fingers towards current; thumb points north". So since a single current loop produces a field like a short magnetic dipole, we might expect a solenoid with lots of current loops to produce a field like a bar magnet, and this expectation is correct. But since I said that all magnetic fields are due to current, you might wonder why a magnet produces a magnetic field. Does the magnet have currents flowing in it? The answer is yes, all atoms in a magnet have unpaired electrons spinning** and thus they all behave like permanent current loops.
Now the thing is that we define direction of current to be "direction of motion of positive charges". So if the electron rotates** anticlockwise, the current is clockwise (opposite to direction of motion of electron). So the right hand thumb rule now says "curl fingers opposite to direction of motion of electron; thumb points north." So I hope you have now understood both the mechanism by which magnetic fields are created by a magnet, and the right hand thumb rule(s).
Diagrams to help understanding:
Magnetic field of a current loop
*Actually changing electric field can also produce a magnetic field but right now I'm talking about magnetostatics only.
**An electron does not actually rotate or spin according to Quantum Mechanics, but you can think that it is rotating both about its axis and in its "orbit".
The following is multiple choice question (with options) to answer.
What is magnetism produced by an electrical current? | [
"exomagnetism",
"strong magnetism",
"hydromagnetism",
"electromagnetism"
] | D | Electromagnetism is magnetism produced by an electric current. Current flowing through a wire creates a magnetic field that surrounds the wire in concentric circles. |
SciQ | SciQ-2746 | electrostatics
Title: Why isn't electrostatic attraction cancelled out by electrostatic repulsion? Van der Waals interactions involve two molecules, when they are very close together, exhibiting attraction to each other as a result of instantaneous and very brief shifts in their polarities (e.g. consider molecule A on the right side of molecule B; the electron cloud briefly shifts to create a positive polar charge on the left of A and a negative charge on the right of B resulting in attraction).
However, why aren't these interactions also instantaneously cancelled out by repulsions that arise for the same reason? So, for one moment A is positive and B is negative, but the next moment A is positive and B is also positive and they repulse with the same strength that they interacted. What gives? It is not canceled out because it is advantageous from an energy perspective to have the electron clouds shifted to cause attraction. This means, on average, the molecules will be in an attractive configuration more often than a repulsive configuration.
The following is multiple choice question (with options) to answer.
A weak and temporary dipole that influences nearby atoms through electrostatic attraction and repulsion is known as what? | [
"an incomplete dipole",
"an debased dipole",
"a fused dipole",
"an instantaneous dipole"
] | D | The electron cloud of a helium atom contains two electrons, which can normally be expected to be equally distributed spatially around the nucleus. However, at any given moment the electron distribution may be uneven, resulting in an instantaneous dipole. This weak and temporary dipole subsequently influences neighboring helium atoms through electrostatic attraction and repulsion. It induces a dipole on nearby helium atoms (see Figure below ). |
SciQ | SciQ-2747 | statistical-mechanics, physical-chemistry, ideal-gas, molecules
Title: Difficulty in understanding Maxwell Boltzmann distribution in case on ions in a field I learned that the velocity of molecules obey Maxwell Boltzmann (MB) distribution at a Temperature T. If I have ions of mass 'M' accelerated to 2eV in a specific region. As the ions are not "internally excited", it is in room temperature right? In this case how the velocity distribution along each axis(x,y and z)?
Here the velocity I would calculate from: (1/2)Mv^2 = E; From here I get the average velocity.
But MB says the average or mean velocity is sqrt(3kT/M), where the energy of the ions (here 2eV) is not taken into account! I am confused here. I believe, I did not get the right concept of MB distribution
In this case how should I assume the distribution of energy along different axis?
But MB says the average or mean velocity is sqrt(3kT/M), where the energy of the ions (here 2eV) is not taken into account! I am confused here.
The following is multiple choice question (with options) to answer.
The motion of molecules in a gas is random in magnitude and direction for individual molecules, but a gas of many molecules has a predictable distribution of what, which is called the maxwell-boltzmann distribution? | [
"molecular shape",
"molecular rate",
"molecular size",
"molecular speeds"
] | D | Distribution of Molecular Speeds The motion of molecules in a gas is random in magnitude and direction for individual molecules, but a gas of many molecules has a predictable distribution of molecular speeds. This distribution is called the Maxwell-Boltzmann distribution, after its originators, who calculated it based on kinetic theory, and has since been confirmed experimentally. (See Figure 13.23. ) The distribution has a long tail, because a few molecules may go several times the rms speed. The most probable speed v p is less than the rms speed. |
SciQ | SciQ-2748 | telomere
Title: Why don't all cells have active telomerase? If telomere degeneration plays a role in aging, and extending them is biologically possible with telomerase, why isn't it active in all cells? Humans use it in their germ cells, so why not all somatic cells too? We don't want all body cells dividing indefinitely. When that happens we call it "cancer".
Telomeres are one of many ways to regulate cell division and prevent runaway growth in a last-ditch manner where a cell becomes non-viable after dividing too many times without telomeres. From Wikipedia:
With telomerase activation some types of cells and their offspring become immortal (bypass the Hayflick limit), thus avoiding cell death as long as the conditions for their duplication are met. Many cancer cells are considered 'immortal' because telomerase activity allows them to live much longer than any other somatic cell, which, combined with uncontrollable cell proliferation[46] is why they can form tumors. A good example of immortal cancer cells is HeLa cells, which have been used in laboratories as a model cell line since 1951.
and:
Telomerase activation has been observed in ~90% of all human tumors,[48] suggesting that the immortality conferred by telomerase plays a key role in cancer development. Of the tumors without TERT activation,[49] most employ a separate pathway to maintain telomere length termed Alternative Lengthening of Telomeres (ALT).[50] The exact mechanism behind telomere maintenance in the ALT pathway is unclear, but likely involves multiple recombination events at the telomere.
The following is multiple choice question (with options) to answer.
What helps the cell continually renew itself? | [
"vacuole",
"lymphocytes",
"lysosomes",
"centrosome"
] | C | |
SciQ | SciQ-2749 | mathematics, theory-of-everything, laws-of-physics
Title: What is fundamentally physically impossible? Mathematical logic defines quite clearly what is true or false in math, and also that some theorems are impossible to prove. This resulted in some clear definitions of axioms set like Peano, ZF or ZFC, which are proved (or strongly believed) to be consistent, i.e do not allow to demonstrate both a theorem and its negation.
In physics, the distinction between axioms, postulates, principles and laws isn't clear at all. Some laws are linked to others, however not by simple derivation. For example the first law of thermodynamics is related to conservation of energy, which in turn is equivalent to the invariance by time translation by by Noether's theorem, which means (to me) it depends on the (perfect) cosmological principle.
We consider as "impossible" anything that violates any of those laws or principles, but are some violations "more impossible" than others because some laws are "stronger"?
For example thermodynamics or energy conservation are definitely unquestionable at our scale, but since they're connected to the cosmological principle at large scale (which can be criticized), are we sure they're "absolutely true"?
Are we sure the principles of physics are consistent, or might we end up with contradictions between, say, Einstein's principles and quantum mechanics?
And do we have something approaching Gödel's theorem in physics to assert that some things that we observe (dark matter?) are impossible to describe with our current laws, but that we need some more?
Well, I realize my question is actually several. Please answer with just a link or book reference if you think I should just read more. This is a question of philosophy of science.
Some philosophers have held that generic principles, such as conservation laws, are more conventional than really true (neither true or false e.g. Wittgenstein viewed the principle of causality and perhaps all scientific laws as a 'fishnet' for apprehending reality. Something that does not follow the principle of causality, he assumed, is not thinkable which does not entail that this principle belongs to the world itself) Poincaré also held conventionalist thesis.
The following is multiple choice question (with options) to answer.
One of the fundamental laws of chemistry deals with the fact that we cannot create or destroy what? | [
"stars",
"matter",
"protein",
"time"
] | B | One of the fundamental laws of chemistry deals with the fact that we cannot (using chemical means) create or destroy matter. When a reaction is run, the number of atoms of each specific type must be the same on both sides of the equation. For some materials, it turns out that one element can combine with a second element in more than one ratio. Carrying out mass ratio calculations helped establish the law of multiple proportions. |
SciQ | SciQ-2750 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
What are the tiny, tube-shaped structures found inside a kidney called? | [
"jejunum",
"nephrons",
"neurons",
"dendrites"
] | B | There are many blood vessels in the kidneys ( Figure above ). The kidneys remove urea and other wastes from the blood through tiny filtering units called nephrons. Nephrons ( Figure below ) are tiny, tube-shaped structures found inside each kidney. Each kidney has up to a million nephrons. Each nephron collects a small amount of fluid and waste from a small group of capillaries. |
SciQ | SciQ-2751 | genetics, cell-biology, embryology, meiosis, gamete
Title: Fertilization of the human egg- where does our centrosome come from? Is there a centrosome in a human egg cell? Is the reason why the egg cell remains paused before meiosis 2 because there isn't a centrosome, and it only divides when the sperm fertilizes it thus it can have a centrosome? If this is so, then how did oogenesis happen? ? To answer the first part of your question. The sperm actually introduces two centrosomes. The centrosome then nucleates the new microtubule assembly to form the sperm aster — a step essential for successful fertilization. You can visit these sites Simerly, et al as well as Paweltz, et al
The following is multiple choice question (with options) to answer.
How many sperm does it take to fertilize an egg? | [
"two",
"one",
"ten",
"five"
] | B | 85 million sperm per day are produced. per testicle. That's 170,000,000 every day. This means that a single male may produce more than a quadrillion (1,000,000,000,000) sperm cells in his lifetime! But it only takes one to fertilize an egg. |
SciQ | SciQ-2752 | the-sun, solar-system, earth, temperature, weather
That Wikipedia quote mentioned that "change in day length is another factor". I have some info and graphs about that here.
The distance from the Earth to the Sun does have an effect on the climate, but it's fairly minor. Currently, the Earth is closest to the Sun (perihelion) in early January, around 10 days after the December solstice, during the northern hemisphere winter and southern hemisphere summer. That makes the southern summer a bit hotter than the northern summer. It also makes the southern summer a bit shorter, because the orbital speed is fastest near the perihelion. However, the climate in the southern hemisphere is strongly affected by the strong circumpolar ocean current around Antarctica, which keeps the southern oceans cold all year round. In the southern hemisphere, not many people live at higher latitudes than 40° because it's just too cold, but that latitude in the northern hemisphere is quite heavily populated.
I have some info about the perihelion here and here.
For what it's worth, here's a graph of the distance from the Earth to Sun and to the SSB, for 2022, with a 7 day timestep between the data points.
Plotting script from https://astronomy.stackexchange.com/a/49823/16685
Here's a plot spanning 1700 to 2200 (the same timespan as my Sun-SSB plot in the answer linked above), also with a 7 day timestep.
The following is multiple choice question (with options) to answer.
What type of climate is found mostly near the equator? | [
"warm subtropical",
"warm tropical",
"cool tropical",
"hot dessert"
] | B | Climate is found in zones around the planet. Warm tropical climates are mostly found near the Equator. Glaciers are mostly found nearer the poles. Wegener assumed that these things were true in the ancient past. |
SciQ | SciQ-2753 | 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.
Metabolism is the collection of what that occur in an organism? | [
"mineral reactions",
"chemical reactions",
"mechanical reactions",
"growth reactions"
] | B | |
SciQ | SciQ-2754 | biochemistry, physiology, muscles, bioenergetics
Title: Location of t tubule in muscle Why do mammalian skeletal muscles have t-tubules at the junction of the anisotropic and isotropic band, whereas non-mammalian muscles and cardiac muscles have it at Z-line? What could have been the functional significance?
If skeletal muscle would have it at the Z-line then I think it would have been more effective in contraction of muscle fibre. So which arrangement is more efficient?
Also, why is a common arrangement (the more efficient one) not seen in all those muscle types? Interesting question. Indeed it is related to the working of cardiac muscles. First of all, lets have a look at the structure of a sarcomere of a cardiac muscle from here:
Here, what we can see is that the t-tubule is a depression formed in myocyte. It is important to know this fact here. Why? See this:
In contrast to skeletal muscle, cardiac muscle requires extracellular calcium ions for contraction to occur. Like skeletal muscle, the initiation and upshoot of the action potential in ventricular cardiomyocytes is derived from the entry of sodium ions across the sarcolemma in a regenerative process. However, an inward flux of extracellular calcium ions through L-type calcium channels sustains the depolarization of cardiac muscle cells for a longer duration. The reason for the calcium dependence is due to the mechanism of calcium-induced calcium release (CICR) from the sarcoplasmic reticulum that must occur during normal excitation-contraction (EC) coupling to cause contraction.
First, cardiac muscles don't work by external action potentials, they work on a cycle governed by themselves, known as the cardiac cell cycle.
Second, as is clear from above paragraph, these cells depend on extracellular Ca2+ ions for initiating contraction, a clear difference from skeletal muscles which need Ca2+ stored in SR. Hence, they require t-tubule at a place where a sarcomere ends. Obviously, having a depression in the middle of a sarcomere (i.e. between I- and A-band) would not work here.
Also, the structure of t-tubules is also different between the two. Compare my first image with the image below from here:
The following is multiple choice question (with options) to answer.
What is the arrangement of a t-tubule with the membranes of sr on either side called? | [
"triad",
"acid",
"aracnid",
"orchid"
] | A | As the membrane depolarizes, another set of ion channels called voltage-gated sodium channels are triggered to open. Sodium ions enter the muscle fiber, and an action potential rapidly spreads (or “fires”) along the entire membrane to initiate excitation-contraction coupling. Things happen very quickly in the world of excitable membranes (just think about how quickly you can snap your fingers as soon as you decide to do it). Immediately following depolarization of the membrane, it repolarizes, re-establishing the negative membrane potential. Meanwhile, the ACh in the synaptic cleft is degraded by the enzyme acetylcholinesterase (AChE) so that the ACh cannot rebind to a receptor and reopen its channel, which would cause unwanted extended muscle excitation and contraction. Propagation of an action potential along the sarcolemma is the excitation portion of excitation-contraction coupling. Recall that this excitation actually triggers the release of calcium ions (Ca++) from its storage in the cell’s SR. For the action potential to reach the membrane of the SR, there are periodic invaginations in the sarcolemma, called T-tubules (“T” stands for “transverse”). You will recall that the diameter of a muscle fiber can be up to 100 μm, so these T-tubules ensure that the membrane can get close to the SR in the sarcoplasm. The arrangement of a T-tubule with the membranes of SR on either side is called a triad (Figure 10.7). The triad surrounds the cylindrical structure called a myofibril, which contains actin and myosin. |
SciQ | SciQ-2755 | sequence-alignment, phylogenetics, genome, phylogeny
Title: What is the most appropriate way to find the most recent common ancestor between two distantly related species I want to specifically find the common ancestor between a lobster and a humans. I suspect it was an aquatic worm of some description. But I want to know about the nervous system of this common ancestor. Because I've now posted several comments, I'll just roll them all up.
For background on the approaches used to identify most recent common ancestors and a high-level look at how animal taxonomy has been inferred, I suggest Lynch 1999.
I think that there are 2 interpretations of this question. If you are interested in just looking up a single MRCA of well-defined clades, such as lobster and human, here are some approaches:
Easy way:
Look at a tree diagram, e.g. this:
Find the tips that correspond to your species of interest (arthropods for lobster, chordata for humans).
Find where they join together in the diagram (the branch labeled "true coelom").
You have your answer, the MRCA is the group of organisms with a true coelom, coelomates.
A more involved way using a database
Go to this website.
Find the group of species 1 (arthropods, protostomes, etc. for lobster, chordata, deuterostomes etc. for human)
navigate around until you see the group containing the two groups (in this case listed as "bilateria"). In this case you are looking for the bilaterian common ancestor.
another database
Go to this website.
Point and click your way to a view where you see your 2 clades of interest (arthropods, chordates in this case). See figure.
Find where they join (in this case, it is less certain about the existence of a coelomate common ancestor, so it just says "bilaterians").
The following is multiple choice question (with options) to answer.
What is the name of the order that salamanders belong to? | [
"aneuploid",
"platyhelminth",
"urodela",
"oronthalic"
] | C | Salamanders belong to a group of approximately 500 species of amphibians. The order Urodela, containing salamanders and newts, is divided into three suborders:. |
SciQ | SciQ-2756 | 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 tough tissue that contains collagen? | [
"cartilage",
"fiber",
"muscle",
"membrane"
] | A | Another distinguishing feature of vertebrates is an endoskeleton made of bone or cartilage. Cartilage is a tough tissue that contains a protein called collagen. Bone is a hard tissue that consists of a collagen matrix, or framework, filled in with minerals such as calcium. Bone is less flexible than cartilage but stronger. An endoskeleton made of bone rather than cartilage allows animals to grow larger and heavier. Bone also provides more protection for soft tissues and internal organs. |
SciQ | SciQ-2757 | human-anatomy
Atraumatic dislocation.
This occurs when the shoulder dislocates with minimal force such as reaching up for an object or turning over in bed. Usually it will 'pop' back in itself or with a little help. Normally this type of dislocation does not need reducing in A&E. It can occur regularly throughout the day and will be associated with certain positions the arm is placed into. This type of dislocation is associated with people that have 'lax' joints, for example people who hyper-extend their knees and elbows and can get the palms of both hands onto the floor with ease. This joint laxity is normal for these people and the onset of dislocation can be associated with a change in how the muscles around the shoulder are interacting with each other or a change in posture/ position of the arm. This can produce an imbalance in the control of the joint. Referral for appropriate physiotherapy is the initial form of management. The physiotherapist should look at the way in which the muscles and shoulder joint is moving and posture aiming to restore the balance. Treatment can 'cure' the problem as long as the exercises and advice is continued, but in some cases there is only minimal or nil benefit. At this point surgical intervention is indicated.
Positional Non-traumatic dislocations.
This group of people can dislocate their shoulders without any form or history of trauma. Some may have started out dislocating their shoulder as a party trick; others may have always had shoulders that just 'fall' out of joint. This type of dislocation is usually painless and can be put back in easily. Both shoulders are typically involved. The cause of this type of dislocation is usually a result of what we call 'abnormal muscle patterning' which means the strong muscles around the shoulder joint are not working in the correct order causing them to pull the shoulder out of joint with active movement in the particular direction such as lifting the arm forward above the head or out to the side and above the head. The main treatment for this is physiotherapy that looks at re-sequencing the muscles in order to prevent further dislocations. Occasionaly surgery in the form of thermal capsular shrinkage or plication may be neccessary.
The following is multiple choice question (with options) to answer.
What common ailment is typically caused by tense muscles in the shoulders, head and neck? | [
"pollution",
"disturbances",
"fever",
"headache"
] | D | A headache is a very common nervous system problem. Headaches may be a symptom of serious diseases, but they are more commonly due to muscle tension. A tension headache occurs when muscles in the shoulders, neck, and head become too tense. This often happens when people are “stressed out. ” Just trying to relax may help relieve this type of headache. Mild pain relievers such as ibuprofen may also help. |
SciQ | SciQ-2758 | 2. Solve the formula for $$V$$ in terms of $$r\text{.}$$
1. 339.39 cubic in
2. $$\displaystyle V=12.57r^3$$
##### 22.
In order for a windmill to generate $$P$$ watts of power, the velocity of the wind, in miles per hour, must be
\begin{equation*} v=\sqrt[3]{\dfrac{P}{0.015}} \end{equation*}
1. How much power will a wind speed of 30 mph generate?
2. Solve the formula for $$P$$ in terms of $$v\text{.}$$
##### Exercise Group.
For Problems 23–26, solve the formula for the indicated variable.
###### 23.
$$c=\sqrt{a^2-b^2},~$$ for $$b$$
$$b= \pm \sqrt{a^2-c^2}$$
###### 24.
$$x=a-\sqrt{h(2r-h)},~$$ for $$r$$
###### 25.
$$D=S\sqrt[3]{1-\dfrac{v}{W}},~$$ for $$W$$
$$W=\dfrac{v}{1-(\dfrac{D}{S})^3}$$
$$R=\dfrac{T}{1-\sqrt[3]{1-K}},~$$ for $$K$$
The following is multiple choice question (with options) to answer.
How many watts equals a horse power? | [
"375",
"904",
"695",
"745"
] | D | Sometimes power is measured in a unit called the horsepower. For example, the power of car engines is usually expressed in horsepowers. One horsepower is the amount of work a horse can do in 1 minute. It equals 745 watts of power. Compare the horsepowers in the Figure below to the other Figure below . |
SciQ | SciQ-2759 | bacteriology
Title: Extract bacteria from compost? I'm working on a project where I need to find certain cellulolytic bacteria. I was looking at this list : http://webcache.googleusercontent.com/search?q=cache:CrtQ9T6K7m8J:www.wzw.tum.de/mbiotec/cellmo.htm+&cd=1&hl=nl&ct=clnk&gl=be
How could I selectively separate one of the bacteria types that I had in mind from that list?
So how would I have to extract the bacteria from the compost? A first (and obvious) approach is the use of cellulose agar in order to isolate all the celluloltic bacteria in the sample. Be careful, however, since the nutrient requirements of some of those microbes may be higher and then they won't grow with only cellulose (they may need some other compounds, like a nitrogen source). Be careful with fungi, too.
If you have the proper equipment, it would be ideal to extract DNA and analyze the environmental rRNA 18s sequences. With this, you should be able to know if your bacteria is present in your sample. If so, proceed with the previous steps.
Once you had a set of suspected colonies, you must proceed with more specific culture media (wich would depend of the exact bacteria you're looking for. For example, if you're looking for Clostridium, you should try to grow your sample in an anaerobic jar and test the ability to reduce sulphur). With this approach, you may reach a point where you can't differenciate similar species. At this point, mollecular characterization is the best option, with the use of rRNA 18s again. Note that the mollecular approach, while relative expensive, can be performed in every step, so you can combine cultures and DNA analyses at will.
Lastly, if you're looking for an specific bacteria, it would be useful to know wich one is, so the community can give you more accurate responses.
The following is multiple choice question (with options) to answer.
Some microorganisms can digest cellulose, breaking it down into what? | [
"fructose polymers",
"fructose monomers",
"gluclose polymers",
"glucose monomers"
] | D | |
SciQ | SciQ-2760 | natural-satellites
Title: Are moons geologically active? Are there natural satellites in the Solar System that are geologically active? This includes volcanism, existence and motion of tectonic plates, et cetera.
Is it a common or a rather rare feature among such bodies? Yes. Moons around Jupiter (Io, Europa and Ganymede), Saturn (Titan and Enceladus) and Neptune (Triton) all have some form of geological activity. Charon also may have geological activity, being in a binary system with Pluto. However, while Earth's geological activity is caused by internal heating and tectonic plates, the geological activity of the moons around Jovian planets comes in the form of tidal forces. Io is the most iconic instance of tidal stress, because Io's plumes are frequent, volatile and make the world look extremely chaotic, with its surface frequently being altered and renewed by its non stop volcanic activity. (Because it is chaotic)
As for tectonic plates, Europa is the closest you get to tectonic plates with moons in our star system. Water replaces lava when it comes to ice worlds. Ice worlds being worlds that have ice instead of rock for their crust. This means that water mantles are a frequent occurrence, with the core of ice worlds being mineral rich stone. This is the case for Triton as well, which has cyro-volcanism from the sheer tidal stress Neptune exerts on the captured dwarf planet.
Enceladus and Titan have water mantles, Enceladus being the world notable for its massive plumes, high albedo and tiger stripe surface fractures. Titan may also have tectonic activity for similar reasons to Europa.
The following is multiple choice question (with options) to answer.
Where does most geological activity take place? | [
"plate waves",
"plate buildings",
"plate boundaries",
"plate medians"
] | C | Most geological activity takes place at plate boundaries. This activity includes volcanoes, earthquakes, and mountain building. The activity occurs as plates interact. Giant slabs of lithosphere moving around can create a lot of activity! The features seen at a plate boundary are determined by the direction of plate motion and by the type of crust found at the boundary. |
SciQ | SciQ-2761 | experimental-chemistry
Pouring the copper sulfate solution into the beaker resulted in a vigorous reaction and quite a bit of heat. I stirred the reaction mixture and let it go to completion. The magnet still stuck strongly to the bottom of the beaker, indicating that there was still substantial powdered iron remaining.
The mixture was decanted to another beaker, with some mostly useless filtering (no good filter paper at hand), and allowed to settle for about an hour. The copper particles produced in the reaction are very small and settle out very slowly. Some of the supernatant solution was transferred to a sample cell, illuminated from the left via an LED flashlight and photographed. This is shown in the next figure:
Despite the light scattering, the green color of the ferrous sulfate solution is evident. The photo will be updated after more particulate has settled out.
The following is multiple choice question (with options) to answer.
What can be used to mechanically separate the two elements by attracting the iron filings out of the mixture and leaving the sulfur behind? | [
"centrifuge",
"magnet",
"graduated cylinder",
"laser"
] | B | When iron filings and sulfur powder are mixed together in any ratio, they form a mixture. No chemical reaction occurs, and both elements retain their individual properties. A magnet can be used to mechanically separate the two elements by attracting the iron filings out of the mixture and leaving the sulfur behind. |
SciQ | SciQ-2762 | aqueous-solution, solubility, phase
Whereas the IUPAC Gold Book defines a chemical reaction as:
A process that results in the interconversion of chemical species.
One aspect of solvation vs. reaction that may seem confusing is the solubility of ionic species. Even though $\ce{NaCl}$ becomes $\ce{Na+}$ and $\ce{Cl-}$ in an aqueous solution, this does not constitute a chemical reaction as defined above, and we say that $\ce{NaCl}$ is soluble in water. The same is true of your example of $\ce{H2SO4}$; even though it dissociates in water, it is not converted to a new chemical compound. One way to think of this is if you remove the solvent, the solute should typically resume to it's original form. From our previous example, if we evaporate the water from our aqueous solution of $\ce{Na+}$ and $\ce{Cl-}$, we just get the solid $\ce{NaCl}$ back.
Your examples of solubility in hydrochloric acid are a bit complex because that is a two-component system of water and $\ce{HCl}$. All of the compounds you discuss are water soluble and it doesn't matter if the $\ce{HCl}$ is there or not. One slight exception in your examples is ethylamine. Ethylamine itself is miscible with water, but many higher molecular weight amines are not water soluble, but are soluble in hydrochloric acid. In this case, the $\ce{H+}$ from $\ce{HCl}$ protonates the amine, making the hydrochloride salt. This is still an example of solubility however, as once you remove the solvent, you are left with the original compound, in this case the amine.
The following is multiple choice question (with options) to answer.
What forms when a solute dissolves in a solvent? | [
"liquid",
"chemical",
"solution",
"gas"
] | C | A solution forms when a solute dissolves in a solvent. The rate of dissolving is faster with stirring, a higher temperature, or greater surface area. Many solutes are soluble in water because water is polar. |
SciQ | SciQ-2763 | human-biology, neuroscience, peripheral-nervous-system
Title: Are spinal nerves myelinated and unmyelinated at the same time? I was trying to answer this question when I remembered that the somatic axon is myelinated, while both sympathetic and parasympathetic preganglionic axons are also myelinated. Are they only myelinated or are they both myelinated and unmyelinated? Thanks
Edit:
This is a question from an old lecture quiz (previous year) and unfortunately I do not have the answers for the questions. The wording of the question was
Spinal Nerves are
a.) myelinated
b.) unmyelinated
c.) answers a and b
d) none of the above" Spinal nerves are mixed nerves containing afferent and efferent neurons of various types. Anatomically, they protrude from the spinal column bilaterally at each vertebral level. They contain both myelinated fibers (e.g., A fibers) and unmyelinated fibers (e.g., C fibers).
The answer is (c): both myelinated and unmyelinated.
Please note that spinal nerves are NOT located in the spinal cord, despite the fact that neurons in each spinal nerve will either originate or terminate there. A spinal nerve is a peripheral structure. It starts at the point where the dorsal and ventral root converge (See April's Clinical Anatomy, Ch. 1). If you have the opportunity to observe back surgery or dissect a human cadaver, you can see and touch a spinal nerve. They are cable like structures containing bundles of many many many axons, but no neuron in its entirety. A nerve is not a neuron. This is a common misconception.
Just to add, the details here may seem like trivia, but they are not. Similar questions (and questions that require you to understand the distinction between a nerve and a neuron) are often asked on US medical licensing exams. This is because they are relevant to understanding and interpreting neurological symptoms and physical exam findings.
The following is multiple choice question (with options) to answer.
The enteric nervous system provides intrinsic innervation, and the autonomic nervous system provides this? | [
"arise innervation",
"autonomic innervation",
"complex innervation",
"extrinsic innervation"
] | D | layers: mucosa, submucosa, muscularis, and serosa. The enteric nervous system provides intrinsic innervation, and the autonomic nervous system provides extrinsic innervation. |
SciQ | SciQ-2764 | biophysics, theoretical-biology, ecosystem
Systems ecology, especially with regard to energy and nutrient flow.
This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem Ecology: Understanding Element Cycles by Ågren & Bosatta (Ågren was originally a physicist)
Physical limitations to growth and transport
This can include for instance mechanical contraints on plant growth (see e.g. the book Plant Physics by Nicklas & Spatz), water transport in trees (see e.g. this BioSE question) or the biomechanics of movement (see e.g. Hudson et al (2012) on the speed and movement of cheetahs or Wikipedia: Biomechanics).
Allometric relationships between organisms, e.g. with regard to metabolism
To explain these types of relationships knowledge in physics is useful. See e.g. Kleiber's law for more.
MAXENT as a general approach to ecological patterns or to model species distributions
This is basically a tool lifted from physics that can be applied to ecological problems. There are many papers to look at, but Harte & Newman (2014) (Harte is another previous physicist) and Elith et al (2010) are two good starting points.
Dynamical modelling of populations and communities
This field use many of the same tools for analysis as physics, e.g. systems of differential equations. One of the pioneers in this field (among many) were Robert May (also started with a PhD in physics), and his classical book Theoretical Ecology: Principles and Applications is still a good starting point.
Energy harnessing and conversion by organisms
This can refer both to how organsims convert prey to energy (e.g. conversion efficiencies) and the physics of photosynthesis (which is an interesting intersection between physics and molecular biology). See Jang et al (2004) and O'Reilly & Olaya-Castro (2013) for examples of the how quantum mechanics can inform us about photosynthesis.
Hopefully this will give you a sense of some different ways that knowledge in physics can be useful for biology.
The following is multiple choice question (with options) to answer.
Virtually all aquatic organisms depend directly or indirectly on what for food? | [
"protists",
"growths",
"prokaryotes",
"ground beef"
] | A | Figure 23.30 Virtually all aquatic organisms depend directly or indirectly on protists for food. (credit “mollusks”: modification of work by Craig Stihler, USFWS; credit “crab”: modification of work by David Berkowitz; credit “dolphin”: modification of work by Mike Baird; credit “fish”: modification of work by Tim Sheerman-Chase; credit “penguin”: modification of work by Aaron Logan). |
SciQ | SciQ-2765 | ions, solvents, aqueous-solution
Title: What is the exact definition of Salinity? I am a bit unclear on the definition of salinity. I have always thought of it as simply total dissolved ions.
Wikipedia seems to agree "saltiness or dissolved salt content" but many other sources seem to suggest that only certain ions contribute.
So is there a list of specific anions and cations that contribute to salinity and is there an underlying logic involved in their selection or is it simply arbitrary? Is the definition dependent on the solute in question? The term 'salinity' is measure of 'saltiness', particularly used in reference to sea water.
The exact scientific definition has evolved over time to incorporate our ever growing understanding of physics and chemistry.
In 1889 the International Council for the Exploration of the Sea (ICES) used a measure of salinity based on the total dissolved solids of salt (g/kg) found in seawater after evaporation and drying at 480$^{o}$C.
By taking samples of ocean water from around the world and at different depths, oceanographers have determined that whilst the concentration of salts varies, the relative ionic composition remains essentially constant. The average salinity of the world's ocean water is usually stated as 35 g/kg, with the relative ionic composition of this "average sea water" made up as follows:
The major cations present in 1 kg of sea water are Na$^{+}$ (10.7653 g), Mg$^{2+}$ (1.2942 g), Ca$^{2+}$ (0.4117 g), K$^{+}$ (0.3991 g) and Sr$^{2+}$ (0.0079 g).
The following is multiple choice question (with options) to answer.
Saltwater is a homogeneous mixture, another term for what? | [
"lipid",
"element",
"structure",
"solution"
] | D | Solution 1. Saltwater acts as if it were a single substance even though it contains two substances—salt and water. Saltwater is a homogeneous mixture, or a solution. Soil is composed of small pieces of a variety of materials, so it is a heterogeneous mixture. Water is a substance; more specifically, because water is composed of hydrogen and oxygen, it is a compound. Oxygen, a substance, is an element. |
SciQ | SciQ-2766 | brain
Title: When a thought 'crosses your mind', does it literally cross between left and right cerebral hemispheres? I've heard that part of cognitive processing is information passing between left and right cerebral hemispheres.
This is what happens in the Cerebral Cortex which is divided into two hemispheres,
left brain and right brain connected by a thick layer of nerve fibers called the corpus callosum. These nerve fibers allow messages to pass between the left and right brain
hemispheres
My question is When a thought 'crosses your mind', does it literally cross between left and right cerebral hemispheres?
Assumptions:
I'm making a big leap from 'electronic impulses of neurons' to 'thoughts'. Neuroscience doesn't really have a clear model for what a "thought" consists of exactly. Certain processes that are involved in thought have begun to be mapped--for example, this recent paper talks about a model for how the brain associates location in space with it's own mental map (http://www.ncbi.nlm.nih.gov/pubmed/24462102, I'll try to find something related that's not behind a paywall...). This one doesn't address your particular problem though, they only measured activity on one side of the brain. So basically, it might be possible to partially answer your question for more specific brain processes, but different kinds of "thoughts" are processed in different ways.
And of course I am also conflating impulses crossing the corpus callosum with the thoughts themselves, but I don't think this is really accurate. The most popular models in the labs I'm familiar with suggest that a "thought" is composed of a bunch of neural activity taken together rather than the activities of a few neurons on their own. But that might ultimately just be arguing semantics.
The following is multiple choice question (with options) to answer.
What connects the two hemispheres of the brain? | [
"holy callosum",
"disruption callosum",
"corpus callosum",
"The brain stem"
] | C | The Brain The brain is the part of the central nervous system that is contained in the cranial cavity of the skull. It includes the cerebral cortex, limbic system, basal ganglia, thalamus, hypothalamus, cerebellum, brainstem, and retinas. The outermost part of the brain is a thick piece of nervous system tissue called the cerebral cortex. The cerebral cortex, limbic system, and basal ganglia make up the two cerebral hemispheres. A thick fiber bundle called the corpus callosum (corpus = “body”; callosum = “tough”) connects the two hemispheres. Although there are some brain functions that are localized more to one hemisphere than the other, the functions of the two hemispheres are largely redundant. In fact, sometimes (very rarely) an entire hemisphere is removed to treat severe epilepsy. While patients do suffer some deficits following the surgery, they can have surprisingly few problems, especially when the surgery is performed on children who have very immature nervous systems. In other surgeries to treat severe epilepsy, the corpus callosum is cut instead of removing an entire hemisphere. This causes a condition called split-brain, which gives insights into unique functions of the two hemispheres. For example, when an. |
SciQ | SciQ-2767 | 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.
Cells like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes, but a eukaryotic cell is typically larger than a prokaryotic cell, has a true nucleus (meaning its dna is surrounded by a membrane), and has other membrane-bound organelles that allow for what? | [
"replicating of functions",
"compartmentalization of functions",
"scrobipalpa of functions",
"misuse of functions"
] | B | 4.3 Eukaryotic Cells Like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes, but a eukaryotic cell is typically larger than a prokaryotic cell, has a true nucleus (meaning its DNA is surrounded by a membrane), and has other membrane-bound organelles that allow for compartmentalization of functions. The plasma membrane is a phospholipid bilayer embedded with proteins. The nucleus’s nucleolus is the site of ribosome assembly. Ribosomes are either found in the cytoplasm or attached to the cytoplasmic side of the plasma membrane or endoplasmic reticulum. They perform protein synthesis. Mitochondria participate in cellular respiration; they are responsible for the majority of ATP produced in the cell. Peroxisomes hydrolyze fatty acids, amino acids, and some toxins. Vesicles and vacuoles are storage and transport compartments. In plant cells, vacuoles also help break down macromolecules. Animal cells also have a centrosome and lysosomes. The centrosome has two bodies perpendicular to each other, the centrioles, and has an unknown purpose in cell division. Lysosomes are the digestive organelles of animal cells. Plant cells and plant-like cells each have a cell wall, chloroplasts, and a central vacuole. The plant cell wall, whose primary component is cellulose, protects the cell, provides structural support, and gives shape to the cell. Photosynthesis takes place in chloroplasts. The central vacuole can expand without having to produce more cytoplasm. |
SciQ | SciQ-2768 | evolution
bacteria
cyanobacteria
archaea
protists
fungi
algae
plants
nematodes
arthropods
vertebrates
Bacterial and archaean colonisation
The first evidence of life on land seems to originate from 2.6 (Watanabe et al., 2000) to 3.1 (Battistuzzi et al., 2004) billion years ago. Since molecular evidence points to bacteria and archaea diverging between 3.2-3.8 billion years ago (Feng et al.,1997 - a classic paper), and since both bacteria and archaea are found on land (e.g. Taketani & Tsai, 2010), they must have colonised land independently. I would suggest there would have been many different bacterial colonisations, too. One at least is certain - cyanobacteria must have colonised independently from some other forms, since they evolved after the first bacterial colonisation (Tomitani et al., 2006), and are now found on land, e.g. in lichens.
Protistan, fungal, algal, plant and animal colonisation
Protists are a polyphyletic group of simple eukaryotes, and since fungal divergence from them (Wang et al., 1999 - another classic) predates fungal emergence from the ocean (Taylor & Osborn, 1996), they must have emerged separately. Then, since plants and fungi diverged whilst fungi were still in the ocean (Wang et al., 1999), plants must have colonised separately. Actually, it has been explicitly discovered in various ways (e.g. molecular clock methods, Heckman et al., 2001) that plants must have left the ocean separately to fungi, but probably relied upon them to be able to do it (Brundrett, 2002 - see note at bottom about this paper). Next, simple animals... Arthropods colonised the land independently (Pisani et al, 2004), and since nematodes diverged before arthropods (Wang et al., 1999), they too must have independently found land. Then, lumbering along at the end, came the tetrapods (Long & Gordon, 2004).
Note about the Brundrett paper: it has OVER 300 REFERENCES! That guy must have been hoping for some sort of prize.
References
The following is multiple choice question (with options) to answer.
Colonial organisms were probably one of the first evolutionary steps towards which type of organisms? | [
"fetus",
"multicellular",
"mutated",
"double cellular"
] | B | Colonial organisms were probably one of the first evolutionary steps towards multicellular organisms. Algae of the genus Volvox are an example of the bridge between colonial organisms and multicellular organisms. Each Volvox , shown in Figure above , is a colonial organism. It is made of up to 50,000 photosynthetic flagellate algae that are grouped together into a hollow sphere. Volvox live in a variety of freshwater habitats, and were first reported by Antonie van Leeuwenhoek in 1700. |
SciQ | SciQ-2769 | biophysics, diffusion
We also need expressions for the pressure change inside the tissue for each of the gases. We could formulate other criteria from biology or thermodynamics arguments, but the simplest case is when these functions are constant and equal to the pressure difference between the boundaries:
$$\frac{dP_{O_2}}{dx} = const = \frac{P^{out}_{O_2} - P^{in}_{O_2}}{d_t} = \beta_{O_2} = 30 {\rm Pa/\mu m}$$
$$\frac{dP_{{CO}_2}}{dx} = const = \frac{P^{out}_{{CO}_2} - P^{in}_{{CO}_2}}{d_t} = \beta_{{CO}_2} = -0.87 {\rm Pa/\mu m}$$ where $d_t$ is the tissue thickness.
It should be noted how the sign of the $\beta$ corresponds to the convention chosen: positive for pressure gradients in the outwards direction (towards the water) and negative for pressure gradients inwards. This convention affects also the influx/outflux of the gases.
This is a system of linear differential equations fully determined due to the knowledge of the concentrations on the boundaries. There are documented methods for their solution. I am not sure if you also want the solution.
The following is multiple choice question (with options) to answer.
What do you call accumulation of excess water in the tissues? | [
"edema",
"gout",
"asthma",
"diuretic"
] | A | Fluid Balance: Edema Edema is the accumulation of excess water in the tissues. It is most common in the soft tissues of the extremities. The physiological causes of edema include water leakage from blood capillaries. Edema is almost always caused by an underlying medical condition, by the use of certain therapeutic drugs, by pregnancy, by localized injury, or by an allergic reaction. In the limbs, the symptoms of edema include swelling of the subcutaneous tissues, an increase in the normal size of the limb, and stretched, tight skin. One quick way to check for subcutaneous edema localized in a limb is to press a finger into the suspected area. Edema is likely if the depression persists for several seconds after the finger is removed (which is called “pitting”). Pulmonary edema is excess fluid in the air sacs of the lungs, a common symptom of heart and/or kidney failure. People with pulmonary edema likely will experience difficulty breathing, and they may experience chest pain. Pulmonary edema can be life threatening, because it compromises gas exchange in the lungs, and anyone having symptoms should immediately seek medical care. In pulmonary edema resulting from heart failure, excessive leakage of water occurs because fluids get “backed up” in the pulmonary capillaries of the lungs, when the left ventricle of the heart is unable to pump sufficient blood into the systemic circulation. Because the left side of the heart is unable to pump out its normal volume of blood, the blood in the pulmonary circulation gets “backed up,” starting with the left atrium, then into the pulmonary veins, and then into pulmonary capillaries. The resulting increased hydrostatic pressure within pulmonary capillaries, as blood is still coming in from the pulmonary arteries, causes fluid to be pushed out of them and into lung tissues. Other causes of edema include damage to blood vessels and/or lymphatic vessels, or a decrease in osmotic pressure in chronic and severe liver disease, where the liver is unable to manufacture plasma proteins (Figure 26.9). A decrease in the normal levels of plasma proteins results in a decrease of colloid osmotic pressure (which counterbalances the hydrostatic pressure) in the capillaries. This process causes loss of water from the blood to the surrounding tissues, resulting in edema. |
SciQ | SciQ-2770 | physiology, ichthyology
Salmon use to deal with the NaCl fluxes driven by the gradients between the salmon and its surroundings. In their gill epithelial cells, salmon have a special enzyme that hydrolyzes ATP and uses the released energy to actively transport both Na+ and Cl- against their concentration gradients. In the ocean, these Na+-Cl- ATPase molecules 'pump' Na+ and Cl- out of the salmon's blood into the salt water flowing over the gills, thereby causing NaCl to be lost to the water and offsetting the continuous influx of NaCl. In fresh water, these same Na+-Cl- ATPase molecules 'pump' Na+ and Cl- out of the water flowing over the gills and into the salmon's blood, thereby offsetting the continuous diffusion-driven loss of NaCl that the salmon is subject to in fresh water habitats with their vanishingly low NaCl concentrations.
Reference
Reference
The following is multiple choice question (with options) to answer.
Transport epithelia that function in maintaining water balance also often function in disposal of what? | [
"bacteria",
"metabolic wastes",
"organisms wastes",
"absorption wastes"
] | B | |
SciQ | SciQ-2771 | electromagnetism, electricity, magnetic-fields
Title: Why does electricity flowing through a copper coil generate a magnetic field? Can some one please explain to me why electricity flowing though a copper coil generates a magnetic field or where I could possibly find that information? Are there other materials that produce a magnetic field when a current is run through them in a different shape? Thanks!
Can some one please explain to me why electricity flowing though a
copper coil generates a magnetic field or where I could possibly find
that information?
An electric current (a flow of electric charge) has an associated magnetic field regardless of the material (or space) the flow occurs in. This is a fundamental part of electromagnetism, rooted in observation, and quantified in Ampere's Law.
I wish to emphasize that this phenomenon is considered fundamental in nature, which means there cannot be a "more" fundamental explanation (if there were, electromagnetism would not be fundamental).
The following is multiple choice question (with options) to answer.
What is magnetism produced by electricity called? | [
"excitation",
"momentum",
"electrical attraction",
"electromagnetism"
] | D | Electricity can be used to produce a magnetic field. Magnetism produced by electricity is called electromagnetism. |
SciQ | SciQ-2772 | terminology, meteorology
I've tried to illustrate the relationships with insolation and temperature here:
There are some other ways too:
Ecological. Scientists who study the behaviour of organisms (hibernation, blooming, etc.) adapt to the local climate, sometimes using 6 seasons in temperature zones, or only 2 in polar and tropical ones.
Agricultural. This would centre around the growing season and therefore, in North America and Europe at least, around frost.
Cultural. What people think of as 'summer', and what they do outdoors (say), generally seems to line up with local weather patterns. In my own experience, there's no need for these seasons to even be 3 month long; When I lived in Calgary, summer was July and August (hiking), and winter was December to March (skiing). Here's another example of a 6-season system, and a 3-season system, from the Aboriginal people of Australia, all based on weather.
Why do systems with later season starting dates prevail today? Perhaps because at mid-latitudes, the seasonal lag means that the start of seasonal weather is weeks later than the start of the 'insolation' period. In a system with no heat capacity, there would be no lag. In systems with high heat capacity, like the marine environment, the lag may be several months (Ibid.). Here's what the lag looks like in three mid-latitude cities:
The exact same effect happens on a diurnal (daily) basis too — the warmest part of the day is often not midday (or 1 pm in summer). As with the seasons, there are lots of other factors too, but the principle is the same.
These aren't mutually exclusive ways of looking at it — there's clearly lots of overlap here. Cultural notions of season are surely rooted in astronomy, weather, and agriculture.
The following is multiple choice question (with options) to answer.
What is an area that is saturated with water or covered by water for at least one season of the year? | [
"a bog",
"a peat",
"a wetland",
"a valley"
] | C | A wetland is an area that is saturated with water or covered by water for at least one season of the year. The water may be freshwater or salt water. Wetlands are extremely important biomes for several reasons:. |
SciQ | SciQ-2773 | machine-learning, image-classification, computer-vision, image-recognition
Title: Machine learning algorithms for identification and classification of Microorganisms https://www.google.com/search?q=Viruses+images&tbm=isch&ved=2ahUKEwiB9-fsoL3sAhUJyHMBHWRZB-sQ2-cCegQIABAC&oq=Viruses+images&gs_lcp=ChJtb2JpbGUtZ3dzLXdpei1pbWcQA1AAWABgo_sCaABwAHgAgAEAiAEAkgEAmAEAwAEB&sclient=mobile-gws-wiz-img&ei=HL6LX4H5DImQz7sP5LKd2A4&bih=592&biw=360&client=ms-android-lava&prmd=inv
https://www.google.com/search?q=bacteria+images&client=ms-android-lava&prmd=inv&sxsrf=ALeKk00Z4XiPIbFDVbfDqZyuAOCSzt6Izw:1602994167858&source=lnms&tbm=isch&sa=X&ved=2ahUKEwj4xs7Por3sAhW-7HMBHav0ChEQ_AUoAXoECCQQAQ&biw=360&bih=592&dpr=2
https://bio.libretexts.org/Bookshelves/Microbiology/Book%3A_Microbiology_(Boundless)/1%3A_Introduction_to_Microbiology/1.2%3A_Microbes_and_the_World/1.2A_Types_of_Microorganisms
Can machine learning classification, computer vision, image processing algorithms assist in identification & segregation of viruses & bacteria microorganisms?
Input Dataset : Images of all viruses and bacteria in gif, jpg formats.
Output : Virus or Bacteria identification with the name, short description.
New updates :
Modify the existing images of all seven types of microorganisms database by adding proper label name with Adobe Photoshop web designing software or any other image editing software.
Examples : COVID-19 virus, Tuberculosis bacteria etc
The following is multiple choice question (with options) to answer.
How are bacteria identified and classified? | [
"by there cell count",
"by their shape",
"by there movement",
"by their color"
] | B | Bacteria are so small that they can only be seen with a microscope. When viewed under the microscope, they have three distinct shapes ( Figure below ). Bacteria can be identified and classified by their shape:. |
SciQ | SciQ-2774 | newtonian-mechanics, forces, free-body-diagram
Title: Newton's Second Law and External Forces I was reading about Newton's Second Law, and I saw that only external forces can move a body. However, when animals and people walk, when rockets launch, and cars drive, isn't it an internal force that causes a change? How do these things fit into Newton's Second Law? One has to be careful how to define what is the system under consideration so as to know what is internal and external. When animals and people walk, they are acted on by an external force - the friction between their feet and the ground. With rockets, hot gases are forced out the back. They exert an equal and opposite, now external, force on the rocket.
The following is multiple choice question (with options) to answer.
What do we call forces that act on the system from outside? | [
"internal",
"material",
"external",
"static"
] | C | External forces are forces that act on the system from outside. In our previous example, external forces include the force of gravity acting on both cars (because the other part of the force pair, the pull of gravity the Earth experiences coming from the cars, is not included in the system) and the forces of friction between the tires and the road. |
SciQ | SciQ-2775 | physiology, hematology
Title: What is the function of clot retraction? I am thinking how clot retraction and fibrinolysis work together.
I think that clot retraction is a process that gets clot towards fibrinolysis process.
Fibrinolysis process then lyses the clot.
However, I am not sure if it is so simple.
Some seems to be discussing about how to differentiate start of fibrinolysis from clot retraction morphologically.
So they probably seem to be at this stage similar processes visually, but not functionally.
What is the function of clot retraction? The platelets in the clot contain contractile proteins. They bring the edges of the wound together, which also reduces the chance of further bleeding. The contraction process also supports the wound healing process as it brings the ends of the wound together.
For more information see this article: "Mechanics and contraction dynamics of single platelets and implications for clot stiffening"
The following is multiple choice question (with options) to answer.
Prostaglandins also help regulate the aggregation of platelets, one step in the formation of what? | [
"blood clots",
"acne",
"cysts",
"bloats"
] | A | |
SciQ | SciQ-2776 | newtonian-mechanics, forces, acceleration, inertia, jerk
Title: Bidirectional jerk motion on a stopping vehicle A stopping vehicle (say a car) has an apparent retardation (which may/may not be constant in magnitude) when force via brakes is applied.
I travel by subway trains, and I noticed an odd phenomenon. The thing about such trains (might be irrelevant) is that, being light-weight, their motion somewhat mimics that of cars, and the effects of motion are more apparent as one usually stands in such trains. The thing I noticed was that I could feel a force pulling me in the initial direction of motion, as the train slowed down. That obviously is the inertia. But as soon as the train halted, I noticed a secondary jerk...this time in the opposite direction, and it was kind of short lasting.
I'm curious to know, what causes this secondary jerk backwards as soon as a vehicle comes to rest. I'm guessing it has something to do with the reaction force by the brakes which overcome the forward motion and provide an impulse backwards. But then it has to have a proper force 'mirror' as per the third law of motion. Also, there never is any intentional backwards motion here (the drivers are precise, I guess).
So what could it really be? "Jerk" is indeed the correct term to describe both the experience and the cause, which is a (sudden) change in acceleration.
If the car decelerates at a constant rate, there is a constant force on you from the safety belt, to prevent you hitting the windscreen. If the car were to maintain the same deceleration when it had reached zero velocity then it would immediately start going backwards. However, the car does not move backwards. The deceleration changes from a constant value to zero in a very short time. But there is still a force on you from the springiness in the safety belt, which is under tension, throwing you back into the seat, which is no longer accelerating backwards. The force on you from the safety belt changes suddenly as you are flung back into the seat, as it did if the braking also started suddenly; the sudden change in the force on you is what causes the discomfort.
The following is multiple choice question (with options) to answer.
Deceleration is the opposite of what? | [
"stimulation",
"stopping",
"acceleration",
"vibration"
] | C | Discussion The minus sign indicates that acceleration is to the left. This sign is reasonable because the train initially has a positive velocity in this problem, and a negative acceleration would oppose the motion. Again, acceleration is in the same direction as the change in velocity, which is negative here. This acceleration can be called a deceleration because it has a direction opposite to the velocity. |
SciQ | SciQ-2777 | cell-biology, hematology, red-blood-cell
Title: Why are red blood cells considered to be cells? Wikipedia states that a cell is
the basic structural, functional and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently.
It then goes on to state that
All cells (except red blood cells which lack a cell nucleus and most organelles to accommodate maximum space for hemoglobin) possess DNA.
Then why are red blood cells still considered cells, while they can't replicate? Is the definition on Wikipedia just a bad definition? Or are red blood cells wrongly considered cells, but remain so for historical reasons? Or are they considered cells for some other reason, such as this answer which states that red blood cells do contain a nucleus at some point? A very good question, and it is most likely because of the last option. It had a nucleus for part of its life. After the RBC jettisons its nucleus, it still remains very metabolically active for approximately 3 months. It maintains its cell membrane integrity, it metabolizes glucose, it interacts constantly with its environment, numerous cellular functions and structure remain intact... It is extremely specialized for a primary purpose, and no longer requires the nucleus to provide more proteins. It has limited capacity to heal from injury, so it has a limited life span.
Speculation: I wonder if it might lose the nucleus early on so that when it is destroyed in the spleen at the end of its life as RBCs are, the spleen macrophages are not overwhelmed with additional processing of nucleic acids? Macrophage type cells are already working hard in there to clear infectious agents and some immune cells from the blood.
The following is multiple choice question (with options) to answer.
Each cell and every living thing requires what? | [
"calcium",
"salt",
"potassium",
"energy"
] | D | All living things need energy. You can often see energy at work in living things. Look at the hummingbird and jellyfish in Figure below . Both of them are obviously using energy. Living things constantly use energy in less obvious ways as well. Inside every cell, all living things need energy to carry out life processes. Life runs on chemical energy. Where does this chemical energy come from?. |
SciQ | SciQ-2778 | breathing
Title: Why does the pulmonary artery have higher glucose concentration than the pulmonary vein? If the pulmonary artery have higher glucose concentration than the pulmonary vein, does it mean glucose will be consumed during gas exchange?
That confused me because gas exchange is something like diffusion and shouldn't consume any glucose Gas exchange doesn't but the cells of the tissue it occurs in do consume glucose, even the cells in the walls of the artery will consume some. The cells in the lungs still need to be fed and only one of those two vessels has flow going into the tissue so it is the one that has to carry that glucose into the tissue.
The following is multiple choice question (with options) to answer.
In the human body, what do you call the intersection where the paths for air and food cross.? | [
"esophagus",
"cloaca",
"larynx",
"pharynx"
] | D | |
SciQ | SciQ-2779 | cooling, air
Title: is it possible to use copper coil instead of pads in air cooler The pads are used in air coolers to cool the air but make it more humid.
Is it possible to use copper / aluminum coils instead of pads to get cold and dry air? Reverse cycle air conditioners, heat pumps by another name, are closed system coolers whereby heat is transferred form one side of a divide to another, ie from inside a room to outside the building, when cooling.
Evaporative air coolers operate on a totally different principle. Water is evaporated and dispersed into the air to cool the air by absorbing heat. In doing so they increase the humidity of the air inside the room. Because of this, such coolers are not suited to environments with humid air, such as tropical regions and coastal regions. They are best suited to areas with dry air, such as deserts.
If the pads of an evaporative air cooler were to be replaced with a coil, as you ask, there is nothing to evaporate. The only way for such a system to work is to turn the evaporative air cooler into a refrigerative air conditioner (also known as a reverse cycle air condition or a heat pump). This defeats the purpose of having an evaporative air cooler. You may as well just acquire a reverse cycle air conditioner.
The following is multiple choice question (with options) to answer.
Air conditioning systems can incubate certain bacteria and what else? | [
"wood",
"Cancer",
"mold",
"root"
] | C | Air conditioning systems that can incubate certain bacteria and mold. |
SciQ | SciQ-2780 | evolution, ornithology, palaeontology
One thing those many, many bird and proto-bird fossils also made clear is that the traits of modern birds (feathers, wings, toothless beaks, etc) didn't evolve in a simple line from non-bird to bird. Many of those traits evolved convergently in several lineages, were lost in some, maybe regained in others, and feathers in particular turn out to be a widespread dinosaur feature that cannot be considered a uniquely bird trait anymore (unless we want to call T-rexes "birds"). Still, saying "beaks evolved several times" or "feathers evolved several times" doesn't mean that birds, let alone modern birds, evolved from several different ancestors. It can mean that the common ancestor of birds had lots of variously bird-like more-or-less distant cousins living around the same time.
The following is multiple choice question (with options) to answer.
The toothlessness of modern birds, which serves to trim the weight of the head, is an example of what? | [
"adaptation",
"genetic drift",
"mutation",
"variety"
] | A | |
SciQ | SciQ-2781 | cell-biology, molecular-biology
Title: Intracellular lipid transport I know that lipids are carried around the body in the blood either as micelles or by lipid-binding proteins which allow them to be solved.
Lipids can't always be integrated in a membrane though, the phospholipids used in membranes have to be synthesised somewhere from a precursor which will also by hydrophobic.
Consequently, at some point there will have to be transport of lipids within the cell where the lipids will need to be in solution. How is this facilitated? Like in the blood, intracellular lipid trafficking is facilitated by vesicular transport and lipid carriers like fatty acid binding proteins. In addition, intracellular membranes are densely packed and they can exchange lipids by collision and transient hemifusion. If you have access to Cell, a good review is from Prinz W. 2010 Lipid Trafficking sans vesicles, Where, Why, How?
The following is multiple choice question (with options) to answer.
What are the active transport mechanisms by which molecules enter and leave the cell inside vesicles? | [
"dielectric and exocytosis",
"oxidation and exocytosis",
"endocytosis and oxidation",
"endocytosis and exocytosis"
] | D | Endocytosis and exocytosis are active transport mechanisms in which large molecules enter and leave the cell inside vesicles. |
SciQ | SciQ-2782 | human-biology, physiology, endocrinology, vitamins, homeostasis
Title: Counterintuitive action of Vitamin D? Vitamin D acts in a way which to me is counterintuitive. It functionally supplemets Parathormone. It in the intestinal tract steps up calcium absorption by altering nuclear gene expression and also prevents calcium excretion in kidneys. All of this is understandable. But it also, like parathormone, steps up osteoclast action in bone (actually steps up both osteoclast and osteoblast, but the osteoclast action is increased more to result in net bone resorption). This means that Vitamin D increases blood calcium level by increasing bone resorption.
Then how does Vitamin D help in improving bone density, bone strength and prevent rickets or osteoporosis? All of these would require bone deposition rather than resorption. There are two pieces to this question:
a) How does bone resorption (movement of Ca/Phos out of bone into the blood) result in net improvement in bone structure?
Bones are constantly remodeling, primarily in response to mechanical stressors. Although you clearly already realize this, I will make it explicit: osteoblasts are the cells that create new bone; osteoclasts break down (resorb) bone.
Quoting Harrison’s Internal Medicine1:
Radioisotope studies indicate that as much as 18% of the total skeletal calcium is deposited and removed each year. Thus, bone is an active metabolizing tissue.…The cycle of bone resorption and formation is a highly orchestrated process carried out by the basic multicellular unit, which is composed of a group of osteoclasts and osteoblasts
The following is multiple choice question (with options) to answer.
Fractures, rickets, and osteoarthritis all affect what part(s) of the body? | [
"bones",
"animals",
"fossils",
"Heart"
] | A | Despite their hardness and strength, bones can suffer from injury and disease. Bone problems include fractures, osteoarthritis, and rickets. |
SciQ | SciQ-2783 | sequence-alignment, phylogenetics, genome, phylogeny
Title: What is the most appropriate way to find the most recent common ancestor between two distantly related species I want to specifically find the common ancestor between a lobster and a humans. I suspect it was an aquatic worm of some description. But I want to know about the nervous system of this common ancestor. Because I've now posted several comments, I'll just roll them all up.
For background on the approaches used to identify most recent common ancestors and a high-level look at how animal taxonomy has been inferred, I suggest Lynch 1999.
I think that there are 2 interpretations of this question. If you are interested in just looking up a single MRCA of well-defined clades, such as lobster and human, here are some approaches:
Easy way:
Look at a tree diagram, e.g. this:
Find the tips that correspond to your species of interest (arthropods for lobster, chordata for humans).
Find where they join together in the diagram (the branch labeled "true coelom").
You have your answer, the MRCA is the group of organisms with a true coelom, coelomates.
A more involved way using a database
Go to this website.
Find the group of species 1 (arthropods, protostomes, etc. for lobster, chordata, deuterostomes etc. for human)
navigate around until you see the group containing the two groups (in this case listed as "bilateria"). In this case you are looking for the bilaterian common ancestor.
another database
Go to this website.
Point and click your way to a view where you see your 2 clades of interest (arthropods, chordates in this case). See figure.
Find where they join (in this case, it is less certain about the existence of a coelomate common ancestor, so it just says "bilaterians").
The following is multiple choice question (with options) to answer.
Name the closest living relatives of tetrapods? | [
"spinefishes",
"lumpfishes",
"lungfishes",
"shrimp"
] | C | |
SciQ | SciQ-2784 | meteorology, tornado, coriolis
And then conversely, Australia doesn't have a lot of land Poleward yet is still a reasonably busy tornado spot.
Mountain ranges Poleward also generally aren't a big deal... even pretty large ones; one of the biggest tornado areas is Bangladesh\India, despite the disruption the Himalayas presents. Because enough cold air can filter into the region in spite of the blockage.
The only thing that would be a real large scale geographic issue to the needed cold air would be a warm sea Poleward that modifies the incoming cold air significantly.
But that's pretty tough to have geographically. Perhaps more possible in the Autumn... maybe the Great Lakes serves as a slight dampener on fall season tornadoes in parts of the US? Though their effect is still mostly pretty small overall. Bring too near any large body of water, in any direction, is really a downer on supercellular tornadoes, as it modifies temperature gradients and instability.
To your direct question... there actually is a very good example of what Tornado Alley would look like in the Southern Hemisphere already: the Pampas Lowlands of Argentina.
It has that big mountain range to the west, in the midlatitudes, and does have fairly warm water a ways northward.
But it doesn't have quite as large of a region east of the mountains to have the tornadoes in, the cold air (and storm system strength) is probably modified due to the closed nature of the Antarctic vortex and the widespread oceans of the SH modifying air masses, and the source water isn't probably as well located being so far north (and is it warm?).
But even still, Pampas area might be the second most consistent tornado region on Earth. Such that some US storm chasers have traveled down there in our winter.
In the end, local effects play a huge role too, creating mesoscale ingredients (seabreezes\temperature boundaries, upsloping, local vortex flow, etc) to add plenty of rotation to the ledger (see Florida, one of highest tornadoes per square mile in US, in large part due to seabreeze water spouts and hurricanes). But all things equal, being east of mountains in the midlatitudes is a jackpot ingredient to climatological tornado formation (regardless of hemisphere).
The following is multiple choice question (with options) to answer.
What type of air may get stuck on the windward side of a mountain range? | [
"steady air",
"brisk air",
"maritime air",
"live air"
] | C | Maritime air may become stuck on the windward side of a mountain range. For this reason it is unable to bring cooler air farther inland. |
SciQ | SciQ-2785 | evolution
bacteria
cyanobacteria
archaea
protists
fungi
algae
plants
nematodes
arthropods
vertebrates
Bacterial and archaean colonisation
The first evidence of life on land seems to originate from 2.6 (Watanabe et al., 2000) to 3.1 (Battistuzzi et al., 2004) billion years ago. Since molecular evidence points to bacteria and archaea diverging between 3.2-3.8 billion years ago (Feng et al.,1997 - a classic paper), and since both bacteria and archaea are found on land (e.g. Taketani & Tsai, 2010), they must have colonised land independently. I would suggest there would have been many different bacterial colonisations, too. One at least is certain - cyanobacteria must have colonised independently from some other forms, since they evolved after the first bacterial colonisation (Tomitani et al., 2006), and are now found on land, e.g. in lichens.
Protistan, fungal, algal, plant and animal colonisation
Protists are a polyphyletic group of simple eukaryotes, and since fungal divergence from them (Wang et al., 1999 - another classic) predates fungal emergence from the ocean (Taylor & Osborn, 1996), they must have emerged separately. Then, since plants and fungi diverged whilst fungi were still in the ocean (Wang et al., 1999), plants must have colonised separately. Actually, it has been explicitly discovered in various ways (e.g. molecular clock methods, Heckman et al., 2001) that plants must have left the ocean separately to fungi, but probably relied upon them to be able to do it (Brundrett, 2002 - see note at bottom about this paper). Next, simple animals... Arthropods colonised the land independently (Pisani et al, 2004), and since nematodes diverged before arthropods (Wang et al., 1999), they too must have independently found land. Then, lumbering along at the end, came the tetrapods (Long & Gordon, 2004).
Note about the Brundrett paper: it has OVER 300 REFERENCES! That guy must have been hoping for some sort of prize.
References
The following is multiple choice question (with options) to answer.
Most protists are aquatic organisms and need what kind of environment to survive? | [
"warm",
"cold",
"moist",
"dry"
] | C | Most protists are aquatic organisms. They need a moist environment to survive. They are found mainly in damp soil, marshes, puddles, lakes, and the ocean. Some protists are free-living organisms. Others are involved in symbiotic relationships. They live in or on other organisms, including humans. |
SciQ | SciQ-2786 | biochemistry, molecular-biology, cell-biology, cell-membrane
Once you have a firm grasp on that, consider that in order for a hydrophobic molecule to reach a plasma membrane, it must already be solvated by water. The transfer of a hydrophobe from one hydrophillic environment (water) to another (head groups of the phospholipids in the plasma membrane) should be energetically negligible. The limiting step for passive diffusion across a membrane is transfer from the hydrophillic environment of the phospholipid head groups to the hydrophobic environment of their tails. In fact, the rate of diffusion across a plasma membrane increases with hydrophobicity.
The following is multiple choice question (with options) to answer.
The help with diffusion comes from special proteins in the membrane known as what? | [
"lazy proteins",
"navigation proteins",
"transport proteins",
"installation proteins"
] | C | Water and many other substances cannot simply diffuse across a membrane. Hydrophilic molecules, charged ions, and relatively large molecules such as glucose all need help with diffusion. The help comes from special proteins in the membrane known as transport proteins . Diffusion with the help of transport proteins is called facilitated diffusion . There are several types of transport proteins, including channel proteins and carrier proteins. Both are shown in Figure below . |
SciQ | SciQ-2787 | cell-biology
Title: Are There Exceptions to Animal Cells not Having Cell Walls? In the January Issue of SciAm (discussing Haemophilia):
When damage occurs to blood vessels, exposure of the blood to collagen in the cell walls and material released by the cells triggers the activation of clotting factors.
I read the original in print, but it is available online here.
This seems to imply that animal cells (in this example, those of humans) have cell walls. I sometimes see similar implications in other resources. However, in elementary biology, one is taught that animal cells never have cell walls.
Therefore, my question: Are references to animal cell cell walls (such as the above, for human animal cells) simple mistakes--or are they exceptions to a generalization? Humans, as well as the rest of the metazoans (i.e. animals), absolutely do not have cell walls. What humans do have is extracellular matrix (ECM), which is the sort of fibrous, sort of gel-like material in which cells in many of the tissues are embedded. Collagen is a major component of ECM.
From the old copy of Alberts that is hosted on the NCBI website:
Tissues are not made up solely of cells. A substantial part of their volume is extracellular space, which is largely filled by an intricate network of macromolecules constituting the extracellular matrix (Figure 19-33). This matrix is composed of a variety of proteins and polysaccharides that are secreted locally and assembled into an organized meshwork in close association with the surface of the cell that produced them...
Two main classes of extracellular macromolecules make up the matrix: (1) polysaccharide chains of the class called glycosaminoglycans (GAGs), which are usually found covalently linked to protein in the form of proteoglycans, and (2) fibrous proteins, including collagen, elastin, fibronectin, and laminin, which have both structural and adhesive functions.
The following is multiple choice question (with options) to answer.
The extracellular matrix of most animal cells contains abundant amounts of what protein, which helps hold things together? | [
"collagen",
"keratin",
"elastin",
"actin"
] | A | Extracellular Matrix of Animal Cells Most animal cells release materials into the extracellular space. The primary components of these materials are proteins, and the most abundant protein is collagen. Collagen fibers are interwoven with carbohydrate-containing protein molecules called proteoglycans. Collectively, these materials are called the extracellular matrix (Figure 4.27). Not only does the extracellular matrix hold the cells together to form a tissue, but it also allows the cells within the tissue to communicate with each other. How can this happen?. |
SciQ | SciQ-2788 | species-identification, marine-biology
Title: help identify this fish
I came across this washed up fish in Panama City, Florida in November 2015. I'm guessing it's a puffer fish but I can't find anything like it online.
Thanks. This is a kind of trunkfish. (They have different names, this could be a smooth or spotted trunkfish.). It's really a lovely and comical little fish when observed alive in coral reefs. It has the ability to change its coloration depending on whether it's excited or calm, or to minimize its contrast to the background. It is related to puffer fish.
It has a boxy, triangular body shape, and propels itself with relatively tiny, delicate fins. Like pufferfish, they are toxin producers.
In death, the body shape and coloration are different, of course. Never saw a dead one before; sad. The juveniles are adorable:
Members of this family occur in a variety of different colors, and are notable for the hexagonal or "honeycomb" patterns on their skin. - Wikipedia
The following is multiple choice question (with options) to answer.
What are two types of lobe finned fish? | [
"piranha and pike",
"coelacanths and lungfish",
"sharks and piranha",
"moles and lungfish"
] | B | Lobe-fined fish are currently far fewer in number than ray-finned fish. Their fins, like the one shown in Figure above , contain a stump-like appendage of bone and muscle. There are two groups of lobe-finned fish still alive today: coelacanths and lungfish. |
SciQ | SciQ-2789 | units, notation, unit-conversion
These are just a few examples where electrical engineering is chock full of "A rate of something happening in a time period of one second" is basically defined as that something multiplied by time, as opposed to divided by time as in the case of velocity.
As far as I can tell the phrasing is effectively equivalent, but mathematically, the difference is profound, and very, very confusing. Can someone explain the difference between the two? Velocity, $m/s$, is a measure of the rate at which something moves. I guess you could define displacement as velocity-seconds, a measure of how far something moves at a given rate over a second. In your examples, it is not rates being defined, but the effect of going at a certain rate over a period of time. Amps are Coulombs per second, so you can define Coulombs as the amount of charge moved over a second at a rate of one amp. If you multiply the rate at which something happens by how long that something happens, you will get how much of that something happened.
The following is multiple choice question (with options) to answer.
What is the rate of change of velocity called? | [
"transmission",
"vibration",
"acceleration",
"speed"
] | C | Acceleration is the rate of change of velocity. So in other words, acceleration tells you how quickly the velocity is increasing or decreasing. An acceleration of indicates that the velocity is increasing by in the positive direction every second. |
SciQ | SciQ-2790 | 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 is the main organ required for respiration in mammals? | [
"the lungs",
"the heart",
"the brain",
"the diaphragm"
] | A | Respiration is the process in which gases are exchanged between the body and the outside air. |
SciQ | SciQ-2791 | organic-chemistry, nomenclature, notation
Title: Symbol to denote a group which is either an oxygen atom or NH group I'm drawing the generic structure of several different organic molecules in my thesis. They share some features, one of which is a carbonyl carbon attached to either an oxygen atom (i.e. ester) or an $\ce{-NH}$ (i.e. amide).
My first instinct was to draw it like this†: $\ce{R-X-C(=O)-R'}$
But I wonder if X wrongly implies that it's a halogen? In which case, what would be the correct letter or symbol to use? I've seen Z used sometimes when X is used elsewhere, would that be more appropriate? Or perhaps Q for heteroatom, as in Reaxys? Or A for 'any'?
† I'm actually drawing in ChemDraw, this is simplified for the sake of the question
Edit: corrected mistake (nitrogen atom -> $\ce{-NH}$ group) Oxygen and nitrogen have different valencies, so you can't use the same letter to denote literally an $\ce{O}$ or an $\ce{N}$ atom, as they can't be directly substituted for one another.
You should use the same letter to denote $\ce{O}$ or $\ce{NH}$, for example. It's perfectly permissible to write $\ce{R-X-C(O)-R'}$ and say $\ce{X} = \ce{O}, \ce{NH}$. This approach is commonly used in the literature. If your amide is tertiary then write something like $\ce{X} = \ce{O}, \ce{NH}, \ce{NR}$. The same applies to structures drawn in ChemDraw.
Beyond that, the choice of letter is arbitrary (as long as you define it!) so $\ce{X}$ is perfectly fine, although you should obviously avoid letters which already represent a chemical element (e.g. $\ce{B}$, $\ce{C}$, ...).
The following is multiple choice question (with options) to answer.
Molecules are represented by symbols that all who agree on? | [
"physics",
"chemists",
"geologists",
"astrologists"
] | B | This passage from a Bach cello suite could be played by any trained musician from any country, because there is agreement as to what the symbols on the page mean. In the same way, molecules are represented using symbols that all chemists agree upon. |
SciQ | SciQ-2792 | time, dimensional-analysis, quantum-computer, adiabatic
Title: What are the units of time in the Quantum Adiabatic Theorem? To preface my question, I'm coming to adiabatic quantum computing from a background in classical computer science with little knowledge of quantum physics, so simple, step-by-step explanations or references to helpful literature on this subject would be greatly appreciated.
A folk theorem of adiabatic quantum computation states that the minimum time $T$ required to track the ground state of a time-dependent Hamiltonian $H(t)$ evolving from $t=0$ to $t=1$ is on the order of $\frac{\mathcal{E}}{\gamma^2}$, where $\mathcal{E}$ is usually the magnitude of an eigenvalue of $H(t)$ and $\gamma$ is the minimum spectral gap (i.e., the difference between the two smallest eigenvalues) of $H(t)$ for $t \in [0,1]$. My question is, what are the units of time for the quantity $T$? Is $T$ measured in seconds, is it a measurement of "computation steps" in the classical complexity theory sense, or is it somehow dimensionless? And if $T$ has no dimension, then how is it supposed to be understood as a quantity, and more practically, is there some way to convert it to more natural units of time?
I've checked the Physics Stack Exchange for similar questions, and the closest thing I could find was What are the units of time when planck's constant is equal to 1? I'm sorry to say that I couldn't quite follow the answer to that question, and in any event, I'm not sure if it addresses precisely this subject. Use dimensional analysis to restore the missing power of $\hbar$, remembering that it has the dimensions of energy times time. In normal units, $T$ is on the order of $\hbar\mathcal{E}/\gamma^2$. For example, you could measure the energies $\mathcal{E}$ and $\gamma$ in joules and the time in seconds if you like SI units.
The following is multiple choice question (with options) to answer.
What is the smallest unit of time commonly based on? | [
"minute",
"millimeter",
"hour",
"second"
] | D | |
SciQ | SciQ-2793 | energy, nuclear-physics, mass-energy, fusion
Title: Can the fusion and fission of a group of atoms occur infinitely? Is it possible to split a nucleus and put it back together? If so, is it feasible to do it an indefinite number of times, i.e. without them wearing out or failing to stick together once again? That is a 'what if' multi-layered question, so let's start with building the hypotheses to make this work until we can arrive at a conclusion. So what can we do to make aforementioned process to work?
The following is multiple choice question (with options) to answer.
Atoms cannot be subdivided, created, or what? | [
"contaminated",
"contained",
"destroyed",
"observed"
] | C | Atoms cannot be subdivided, created, or destroyed. |
SciQ | SciQ-2794 | physical-chemistry, phase
Title: How does the process of nucleation work for boiling liquids? I have a somewhat clear picture how (on the molecular level) a gas turns into a liquids as it cools. When a gas has a certain temperature, its molecules on average have a high enough kinetic energy so that electromagnetic interactions cannot hold the molecules together and they are essentially free. When the gas cools, the kinetic energies are smaller and thus electromagnetic interactions between molecules start to pull the molecules together and the process of turning into a liquid begins. As more molecules lose kinetic energy, initially small numbers of molecules start to cluster up, forming "lumps" that continue growing as more molecules gather up into these clusters. I believe this process is called "nucleation".
I found this video that helps visualize the effect:
https://www.youtube.com/watch?v=wFT6G4CIL1o
But how does the reverse take place? Let's say I'm boiling water. I have a textbook that specifically states:
During nucleation, small droplets of liquid form in gases or gas bubbles form in water as it starts to boil.
The following is multiple choice question (with options) to answer.
What process changes a liquid to a gas without boiling? | [
"absorption",
"evaporation",
"bubbling",
"melting"
] | B | Vaporization is easily confused with evaporation, but the two processes are not the same. Evaporation also changes a liquid to a gas, but it doesn’t involve boiling. Instead, evaporation occurs when particles at the surface of a liquid gain enough energy to escape into the air. This happens without the liquid becoming hot enough to boil. |
SciQ | SciQ-2795 | sensation, senses, peripheral-nervous-system
Title: Any nerves/fibers in foot similar to ulnar nerve in elbow? I just noticed that when I gently run my fingers along the top of my right foot, I get the same exact "funnybone" sensation in my toes that I get when I hit the ulnar nerve in my elbow.
So I ask: are there similar nerves/fibrous structures running along the top of your foot as whatever is going on in your elbow with the ulnar nerve?
Not medical advice; just curious about the anatomy here. Why would peripheral anatomy determine subjective sensation? In the end, the cerebral cortex determines the sensation associated with peripheral input. Rewired hamsters can have visual sensations in their auditory cortex (Frost et al., 2000) and visual sensations through tactile stimulation have been reported in man (Ortiz et al., 2011).
The sensations you describe are related to tactile stimulation of peripheral nerves. Peripheral nerves are pretty homogenous, and typically carry a bunch of afferent nerve fibers up to the somatosensory cortex.
References
- Frost et al., PNAS (2000); 97(20): 11068–73
- Ortiz et al., PLOSone (2011)
The following is multiple choice question (with options) to answer.
Every peripheral nerve is connected directly or indirectly to what? | [
"the spinal cord",
"the functional cord",
"the umbilical chord",
"the optimal cord"
] | A | The blue lines in this drawing represent nerves of the peripheral nervous system. Every peripheral nerve is connected directly or indirectly to the spinal cord. Notice the thick sciatic nerve. It is the longest (and thickest) nerve in the body, running from the lower region of the spinal cord to just above the knee. |
SciQ | SciQ-2796 | genetics, cell-biology, chromosome, meiosis, mitosis
https://www.khanacademy.org/science/biology/cellular-molecular-biology/meiosis/a/phases-of-meiosis
So, during metaphase I, homologue pairs—not individual
chromosomes—line up at the metaphase plate for separation.
The following is multiple choice question (with options) to answer.
The four phases of mitosis are prophase, metaphase, anaphase and what? | [
"spirogyra",
"telophase",
"trichina",
"postphase"
] | B | Mitosis occurs in four phases, called prophase, metaphase, anaphase, and telophase. |
SciQ | SciQ-2797 | pathology
Title: Are all diseases caused by organisms (microorganisms)? Are there other causes? Or is it correct to say that all diseases are in fact caused by organisms (microorganisms)? It is not correct to say that all diseases are caused by foreign organisms. Counterexamples are:
Cancer is caused by random genetic mutations in the cells of our body. The mutations can be caused by many factors such as ionizing radiation, smoking, chemical toxins etc.
Diseases such as stroke or heart attack are caused by blood clots blocking the blood flow to essential organs.
Autoimmune diseases are caused by the immune system falsely recognizing cells of the body as foreign and attacking that tissue leading to a wide variety of symptoms.
Alzheimer's disease is caused by chronic neurodegeneration, meaning that the cells in the brain die. The causes are not quite understood but as Alzheimer's usually appears late in life it is likely related to ageing. Also, it is known that some genetic defects can lead to early-onset Alzheimers.
Prion proteins can cause diseases such as Creutzfeldt–Jakob disease also known as mad-cow disease.
Hereditary diseases such as early-onset Alzheimers or ALS are cause by gene defects inherited from the parents.
Toxins can cause chronic diseases such as lead poisoning.
The list probably goes on...
Please note that the first two on the list are the most common cause of death in developed countries.
The following is multiple choice question (with options) to answer.
Pathogenic prokaryotes usually cause illness by producing what? | [
"poisons",
"ions",
"insects",
"organisms"
] | A | |
SciQ | SciQ-2798 | development
Title: How detachment/separation works in biology? It might be a strange question, but I'm interested in the mechanics of separation/detachment during asexual reproduction, for example when an organism reproduces by budding (I don't mean cellular budding like baker's yeast). When the newly formed body is fully matured it detaches itself from the parent / original body.
It might not be caused by a specific tissue, as animals with not so differentiated bodies are (also) capable of such, but I could easily be wrong. Is this (the detachment) triggered by changes in the cell membrane? I can't really think of other explanations. Reproductive budding and what you call 'cellular budding' are really highly related processes. Budding as a form of reproduction essentially partitions protein aggregates and damaged cellular components into the host or mother and builds fresh or 'young' cells on the opposite side of a partition. To begin understanding this look at Saccharomyces cerevisiae (budding yeast) which forms protein rings (from the septin proteins) at the membrane, around the bud neck which separates the mother and daughter cells Hartwell 1971. This ring acts a partition that in part, withholds protein aggregates and certain proteins from diffusing from the mother to the daughter. This protein ring is an example of how cells limit diffusion of proteins and cellular components to the daughter cell. Another good example that comes to mind is Linder 2007, though it is done in E Coli, not budding yeast, where mother cells maintain protein aggregates and age, while the daughter cells are given fresh components and are therefore more fresh and 'young'.
Now like you mention, imagine this process in a multicellular organism to be fundamentally the same. At some point the multicellular organism will start an outgrowth of cells, while restricting what materials are given to the daughter cells to maintain their youth. And eventually a new organism will have been created. Some of the details will be different, but the fundamental process is is quite similar. In that you start with an old cell that creates a new cell from scratch, but rather than splitting all cellular components equally between mother and daughter, the daughter cells is made in peak condition while the mother cell retains much of the cell 'junk' like protein aggregates.
Hopefully that starts to answer your question.
The following is multiple choice question (with options) to answer.
Once cells _______, they can no longer divide | [
"differentiate",
"mature",
"migrate",
"propagate"
] | A | Most plants continue to grow throughout their lives. Like other multicellular organisms, plants grow through a combination of cell growth and cell division. Cell growth increases cell size, while cell division (mitosis) increases the number of cells. As plant cells grow, they also become specialized into different cell types through cellular differentiation. Once cells differentiate, they can no longer divide. How do plants grow or replace damaged cells after that?. |
SciQ | SciQ-2799 | inorganic-chemistry, nomenclature, solutions, phase, notation
Title: Phase description for a substance dissolved in a solvent other than water? I'm trying to write an equation for which I have $\ce{CuI}$ dissolved in acetonitrile. Usually if you have a salt dissolved in water you can denote that using $\ce{(aq)}$, but is there a notation for substances dissolved in a solvent other than water? IUPAC “Green Book” recommends to use $\mathrm{sln}$ for denoting a solution in general [1, p. 54], referring to earlier Recommendations 1981. Appendix No. IV to Manual of Symbols and Terminology for Physicochemical Quantities and Units [2, pp. 1240–1242].
This has been extensively covered in the following posts:
What is the standard way to denote physical states in a chemical reaction? (Meta)
Phase abbreviations for non-aqueous solutions
On the contrary, abbreviation $\mathrm{sol}$ is used to denote a process (typically a sub- or superscript to a symbol for a thermodynamic quantity), not state of matter [1, pp. 59–60]:
2.11.1 Other symbols and conventions in chemical thermodynamics
(i) Symbols used as subscripts to denote a physical chemical process or reaction
These symbols should be printed in Roman (upright) type, without a full stop (period).
$$
\begin{array}{ll}
\ldots \\
\text{solution (of solute in solvent)} & \mathrm{sol} \\
\ldots
\end{array}
$$
Another reason not to use $\mathrm{sol}$ for denoting a state of aggregation is its ambiguity: $\mathrm{sol}$ is often used as an abbreviation for “solid”, as listed in Appendix 10-2 Abbreviations, Acronyms, and Symbols in ACS Style Guide [3, p. 197]
$$
\begin{array}{ll}
\ldots \\
\text{sol} & \text{solid} \\
\text{soln} & \text{solution} \\
\ldots
\end{array}
$$
The following is multiple choice question (with options) to answer.
Phase labels - and even special conditions - are sometimes included for the substances that are part of what? | [
"carbon equations",
"solid equations",
"chemical equations",
"toxic equations"
] | C | Many chemical equations also include phase labels for the substances: (s) for solid, (ℓ) for liquid, (g) for gas, and (aq) for aqueous (i. , dissolved in water). Special conditions, such as temperature, may also be listed above the arrow. For example, 2NaHCO. |
SciQ | SciQ-2800 | earthquakes, waves, scale
Title: If a very huge Earthquake occured anywhere on Earth could waves emerge to come together again on the opposite side? Suppose that a super-powerful earthquake occurred anywhere on Earth, say one with the value 10 on Richter's scale. The quake can have any value but as can be read in a comment below the highest value ever measured was 32 on a superdense star. In that case, it's much more difficult to tear the star apart. The Earth, in contrast, could be torn apart by a quake with value 10 because she is highly less massive.
Suppose the quake was mainly transversal (in a vertical direction). Could it be that correspondingly waves emerged from the center of the quake, traveling the Earth around to come together and reinforced again on the opposite side of the center, with the effect that the quake was felt more strongly on the opposite side of the center than at places halfway from the center (or halfway to the opposite side of the center), to say it in one long breath? Or would too much energy be absorbed from the waves by the Earth to reach the opposite side? It is called "antipodal focusing". See for example Antipodal focusing of seismic waves observed with the USArray.
We present an analysis of the M-w = 5.3 earthquake that occurred in the Southeast Indian Ridge on 2010 February 11 using USArray data. The epicentre of this event is antipodal to the USArray, providing us with an opportunity to observe in details the antipodal focusing of seismic waves in space and time. We compare the observed signals with synthetic seismograms computed for a spherically symmetric earth model
The above paper deals with "body waves" that travel through the interior of the Earth.
There are also Rayleigh waves that travel on the surface and can travel around the Earth several times before dissipating (Wikipedia). Antipodal focusing of seismic waves due to large meteorite impacts on Earth does numerical simulations of surface waves at the antipode of the Chicxulub impact. The waves do not arrive at the antipode at the same time because of Earth’s ellipsoidal shape and different rock properties along their paths.
Isosurfaces of the norm of the peak displacement vector after a vertical impact for the impact hemisphere (left-hand side) and antipodal hemisphere (right-hand side).
The following is multiple choice question (with options) to answer.
Body waves travel through the earth and arrive at seismograms before what? | [
"surface waves",
"function waves",
"velocity waves",
"sound waves"
] | A | Body waves travel through the Earth and arrive at seismograms before surface waves. |
SciQ | SciQ-2801 | human-physiology, digestion, stomach
The stomach accomplishes much of its function by mechanically breaking down the swallowed food particles and mixing them with acid and enzymes into a sort of slurry. To do this, there are three major layers of muscle surround the stomach - from the outside, the longitudinal layer, the circular layer, and the oblique layer. The stomach also has two holes in it - the gastroesophageal opening, coming from the esophagus with the swallowed food/saliva mix, and the pylorus, where the food/acid/enzyme slurry exits into the duodenum, which is the beginning of the small intestine.
Due to the three layers of (rather strong) muscle, the stomach doesn't have a lot of expansion capability once it is filled completely to capacity. Fortunately, this almost never occurs (despite how we may feel after a large meal) because material is always leaving the stomach on its way to enzymatic digestion in the intestines. Additionally, once the stomach is filled to a certain extent, hormones such as leptin are secreted that give you the feeling of being sated, or full, triggering the brain to make you stop eating.
Of course, as we can see with the current epidemic of obesity around the world, the stomach can change its size over time. However, this is a rather slow process (weeks to months to years) of adapting to continuously consuming large meals.
But what would happen if you completely ignored these internal warnings, or were being force-fed, or whatever? Instead of rupturing (the biological equivalent of "exploding"), food would most likely be expelled either into the small intestine or back into the esophagus and back up the way it came down, i.e. causing vomiting.
The following is multiple choice question (with options) to answer.
What are the outpocketings of the digestive tract that remove nitrogenous wastes and function in osmoregulation? | [
"intestinal tubules",
"malpighian tubules",
"olivary tubules",
"integumentary tubules"
] | B | |
SciQ | SciQ-2802 | evolution, biochemistry, life-history
Title: Was iron important for the first life on Earth? Some ions or compounds are thought not to have become involved or important in the metabolism of living organisms until some time after certain mutations took place. For instance, early life is thought to selectively allow calcium ions through its membrane, but eventually also evolved the ability to selectively allow sodium ions, specifically through a mutation that lead to a change in the composition of a channel protein from glutamine to lysine.
Currently, iron is involved in oxidations involving molecular oxygen, such as in cytochromes and clearly holds a key role in modern life, despite that free iron or even ferric compounds are rarely accessible. From my understanding, iron most likely became incorporated into the metabolism of microbes after during/after aerobic organisms had developed, but this does not rule out the possibility that iron was involved earlier on. So, I am wondering if iron was involved in early life, and details on how would be appreciated. Cyanobacteria require iron for photosynthesis and can be found as fossil stromatolites dating back to 3.5 billion years ago. Stromatolites are layered structures made up of cyanobacteria and sediment.
Source: https://en.wikipedia.org/wiki/Stromatolite
Modern stromatolites can be found at Shark Bay in Australia, Chetumal Bay in Belize, and Laguna Bacalar in the Yucatan Peninsula.
Cyanobacteria are also believed to have evolved into the first microbes to produce oxygen by photosynthesis, which was a catalyst for the Great Oxygenation Event which occurred around 2.45 billion years ago.
The following is multiple choice question (with options) to answer.
What were the first photosynthetic organisms on earth? | [
"mosses",
"bacteria",
"trees",
"fungi"
] | B | Plants aren't the only organisms that use the energy of the sun to make food. Some bacteria can also perform photosynthesis. In fact, the first photosynthetic organisms on Earth were bacteria. Photosynthesis is just one of many ways that bacteria can obtain energy. |
SciQ | SciQ-2803 | inorganic-chemistry, thermodynamics, melting-point
Title: Chemical reaction between dichloromethane and solid carbon dioxide I studied heat transfer liquids with low melting point (coolants), and how fast their temperature decreases when they are contacting with solid carbon dioxide. Nearly all liquids (brines, glycols etc.) that I studied have similar behavior, except dichloromethane.
When I put solid carbon dioxide grains into dichloromethane, the temperature of the liquid dropped nearly immediately! At first, the temperature was $\pu{20^\circ C}$, and after just $\pu{5 s}$ the temperature of the liquid was $\pu{-70^\circ C}$! Do you know why is it possible? When I freezed $\ce{KCl}$-brine, the temperature had been decreasing from $\pu{20^\circ C}$ to $\pu{-40^\circ C}$ for more than $\pu{5 min}$!
This property of dichloromethane may be very useful. I think it is due to its low viscosity.
Can you help me and explain this phenomenon? In brine cooling happens only on the surface of the solid carbon dioxide and causes the water to freeze there, forming an insulating layer (the same happens with ethylene glycol). In dichloromethane, which freezes below $-97$ degrees, no freezing occurs. Moreover, carbon dioxide is well soluble in dichloromethane, which makes the heat transfer more efficient. The latter property may cause you problems if you want to use your coolant in closed installations, because after warming the solution may release the excess of carbon dioxide.
The following is multiple choice question (with options) to answer.
What do you call the substance in a cooling system that has a low boiling point and changes between liquid and gaseous states? | [
"byproduct",
"coolant",
"emission",
"refrigerant"
] | D | The key to how a refrigerator or other cooling system works is the refrigerant. A refrigerant is a substance with a low boiling point that changes between liquid and gaseous states as it passes through the refrigerator. |
SciQ | SciQ-2804 | evolution, terminology, natural-selection, computational-model, definitions
A variation exists between some fitness related hereditary material as regards their final causal effect on the degree of their fitness in a common environment $E$. Mathematically speaking, this is:
$\exists E, g_1, g_2( E \text { is an environment } \wedge g_1,g_2 \text { are fitness related hereditary material } \wedge g_1 \neq g_2 \wedge fit_E(g_1) \neq fit_E(g_2))$
In English: There exists an environment $E$ and $g_1, g_2$ where both are fitness related hereditary material such that $g_1$ is different from $g_2$ and fitness of $g_1$ in enviornment $E$ is different from fitness of $g_2$ in environment $E$.
Two fitness related hereditary material that have the same final effect on the degree of their fitness (even if through different causal mechanisms) in a common environment $E$, are said to be isofit$_E$, while those that differ are said to be anisofit$_E$. Formally:
$g_1 \ isofit_E \ g_2 \iff fit_E(g_1)=fit_E(g_2)$
$g_1 \ anisofit_E \ g_2 \iff fit_E(g_1) \neq fit_E(g_2)$
Of course anisofit fitness related hereditary material might even have a difference in the direction of their effect on fitness, so a positive direction means that "the causal relationship from the hereditary material to its fitness, is towards increasing its fitness"; while the opposite is for negative direction.
Now for every hereditary material $g$ the population of all individuals in environment $E$ that harbour $g$, is to be called the "$g$ population in $E$".
There is an environment $E$ that has two anisofit$_E$ fitness related hereditary material populations living in $E$.
The following is multiple choice question (with options) to answer.
Certain characteristics are frequently inherited together because of what? | [
"correlation",
"linkage",
"genetic combination",
"mitosis"
] | B | Linkage explains why certain characteristics are frequently inherited together. For example, genes for hair color and eye color are linked, so certain hair and eye colors tend to be inherited together, such as blonde hair with blue eyes and brown hair with brown eyes. What other human traits seem to occur together? Do you think they might be controlled by linked genes?. |
SciQ | SciQ-2805 | 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.
Which organ protects the body from injury, water loss, and microorganisms? | [
"kidney",
"liver",
"stomach",
"skin"
] | D | Skin protects the body from injury, water loss, and microorganisms. It also plays a major role in maintaining a stable body temperature. |
SciQ | SciQ-2806 | geology, rocks, sedimentology, geomorphology, terminology
Title: What do you call boulders of non sedimentary rock that were lithified into sandstone? I'm convinced there is a word for this. I was in the Hoodoos at Writing on Stone this weekend and kept noticing what looked like reddish quartzite boulders laying around in the sand, or sometimes sticking partially out of the hoodoos.
When a non-sedimentary rock gets washed out into silt which later lithifies, what's it called? It's kind of like a conglomerate, except there's only a couple of really big rocks, which eventually fall out out the rock because all the sandstone around them eroded away. The technical term for a sedimentary rock that has a lithified fine-grained sediment with larger pieces of rocks suspended in it upon lithification is a conglomerate. The fine-grained interstitial part is called the matrix, and the large pieces suspended in it are called clasts. Clasts can range from gravel- to boulder-size. These are technical terms used by sedimentologists.
It is tempting to refer to these fragments as xenoliths but as that word has a very specific meaning in igneous petrology, it is best to avoid it to remove any confusion.
The following is multiple choice question (with options) to answer.
What is the term for the sudden movement of large blocks of rock and soil down a slope? | [
"sludge",
"torrent",
"hurricane",
"slump"
] | D | Less dramatic types of mass wasting move Earth materials slowly down a hillside. Slump is the sudden movement of large blocks of rock and soil down a slope. ( Figure below ). All the material moves together in big chunks. Slumps may happen when a layer of slippery, wet clay is underneath the rock and soil on a hillside. Or they may occur when a river (or road) undercuts a slope. Slump leaves behind crescent-shaped scars on the hillside. |
SciQ | SciQ-2807 | I assume you have two samples of categorical data and want to know if they were taken from the same distribution. Perhaps most commonly, to compare nominal categorical samples, one can use a chi-squared test.
For the fictitious data below, levels of the categorical variables are denoted by $$1$$ through $$5,$$ but those are not ordered labels.
Suppose we have populations with two different probability distributions $$p_1$$ and $$p_2$$ as follows:
p1 = c(.1,.1,.1,.2,.5) # heavy emphasis on last category
p2 = c(.1,.2,.2,.2,.3) # less heavy
Use R to sample data vectors x1 and x2 (of different sizes) both from population with probabilities $$p_1.$$
set.seed(2021)
x1 = sample(1:5,1000,rep=T,prob=p1)
t1 = tabulate(x1, nbins=5); t1
[1] 105 99 85 196 515 # tabulation of first sample
x2 = sample(1:5,1500,rep=T,prob=p1)
t2 = tabulate(x2, nbins=5); t2
[1] 157 154 132 289 768 # tabulation of second
Then take a sample 'y from the population with probabilities $$p_2.$$
y = sample(1:5,1500,rep=T,prob=p2)
t = tabulate(y, nbins=5); t
[1] 155 287 320 309 429
Use a chi-squared test to compare samples x1 and x2, using the appropriate table TABs of counts:
TBLs = rbind(t1,t2); TBLs
TBLs
[,1] [,2] [,3] [,4] [,5]
t1 105 99 85 196 515
t2 157 154 132 289 768
With P-value above 5% the test finds no difference between these two samples from the same population.
chisq.test(TBLs)
Pearson's Chi-squared test
The following is multiple choice question (with options) to answer.
What is the comparison of two factors within a population? | [
"variable",
"hypothesis",
"curve",
"correlation"
] | D | Correlation is a comparison of two factors within a population. Correlation does not imply causation. |
SciQ | SciQ-2808 | nitrogen
Step three is when plants and the animals that live of the plants die and breaks down into ammonia and other waste products (this is where many explanations of the nitrogen cycle usually starts). The waste products gets converted into ammonia by bacteria and the ammonia gets converted to nitrite and the entire cycle starts all over again.
Legumes have a symbiotic relationship with some bacteria that can fixate nitrogen (N2) https://aces.nmsu.edu/pubs/_a/A129/
sources:
https://science.howstuffworks.com/life/biology-fields/nitrogen-cycle.htm
https://www.britannica.com/science/denitrifying-bacteria
The rest is from my memory.
The following is multiple choice question (with options) to answer.
What process is the opposite of nitrogen fixation? | [
"denitrification",
"respiration",
"digestion",
"percolation"
] | A | When plants and other organisms die, decomposers break down their remains. In the process, they release nitrogen in the form of ammonium ions. This process is called ammonification. Nitrifying bacteria change the ammonium ions into nitrites and nitrates. Some of the nitrates are used by plants. The process of converting ammonium ions to nitrites or nitrates is called nitrification. Still other bacteria, called denitrifying bacteria, convert some of the nitrates in soil back into nitrogen gas in a process called denitrification. The process is the opposite of nitrogen fixation. Denitrification returns nitrogen gas back to the atmosphere, where it can continue the nitrogen cycle. |
SciQ | SciQ-2809 | microbiology, bacteriology, photosynthesis
2H+ + 2e– → H2
So that the overall reaction becomes:
2H2O + hν → 2H2 + O2
(Of course, this will be at the expense of energy and reducing power for carbohydrate synthesis.)
Using Hydrogenase for the Catalysis
The enzyme, hydrogenase, can catalyse the reduction of hydrogen ions shown above. This enzyme is rare in eukaryotes and absent from higher plants. It is thought to be very ancient, and may have originally been involved in energy generation from hydrogen in early evolution. One of the roles it plays in contemporary organisms is in reoxidizing NADH generated during certain fermentations in bacteria such as the Clostridium family — hydrogen is the gas produced in gas gangrene caused by Clostridium perfringens.
Certain photosynthetic organisms — notably the microalga, Chlamydomonas reinhardtii, and the photosynthetic cyanobacteria — also contain a hydrogenase in their chloroplasts. The activity of this is generally low, but appears to be coupled to photosynthesis in certain circumstances. This is through the reduced ferredoxin produced at PSI transferring its electron to the iron or iron–nickel centre of the hydrogenase:
The following is multiple choice question (with options) to answer.
Plant-like protists produce oxygen through which process? | [
"photosynthesis",
"metamorphosis",
"respiration",
"glycolysis"
] | A | Plant-like protists are essential to the ecosystem. They are the base of the marine food chain, and they produce oxygen through photosynthesis for animals to breathe. They are classified into a number of basic groups ( Table below ). |
SciQ | SciQ-2810 | h. Evaluate C.
i. Compute Q(7), the amount of glucose produced during the day.
Exercise 10.3.5 “Based on studies using isolated animal pancreas preparations
maintained in vitro, it has been determined that insulin is secreted in a biphasic manner in response to a marked increase in blood glucose. There is an initial burst of insulin secretion that may last 5-15 minutes, a result of secretion of preformed insulin secretory granules. This is followed by more gradual and sustained insulin secretion that results largely from biosynthesis of new insulin molecules. ” (Rhoades and Tanner, P 710)
a. A student eats a candy bar at 10:20 am. Draw a graph representative of the rate of insulin secretion between 10:00 and 11:00 am.
b. Draw a graph representative of the amount of serum insulin between 10:00 and 11:00. Assume that insulin is degraded throughout 10 to 11 am at a rate equal to insulin production before the candy is eaten, and that serum insulin at 10:00 was Iq.
CHAPTER 10. THE FUNDAMENTAL THEOREM OF CALCULUS
468
c. Write an expression for the amount of serum insulin, I(t), for t between 10:00 and 11:00 am.
Exercise 10.3.6 Equal quantities of gaseous hydrogen and iodine are mixed resulting in the reaction
which runs until I 2 is exhausted [H 2 is also exhausted). The rate at which I 2 disappears is ^°’^ 2 gm/sec. How much I 2 was initially introduced into the mixture?
a. Sketch the graph of the reaction rate, r(t) = jp^yi-
b. Approximately how much I 2 combined with H 2 during the first second?
c. Approximately how much I 2 combined with H 2 during the second second?
d. Let Q(x) be the amount of I 2 that combines with H 2 during time 0 to 2; seconds. Write an integral that is Q(x).
e. What is Q\x)l
f. Compute W'{x) for W(x) = =^.
g. Show that there is a number, C, for which Q(x) = W(x) + C.
h. Show that C = 0.2 so that Q(x) = 0.2 – g.
The following is multiple choice question (with options) to answer.
Insulin is produced by what part of the body? | [
"thyroid",
"kidneys",
"pancreas",
"liver"
] | C | 17.9 The Endocrine Pancreas The pancreas has both exocrine and endocrine functions. The pancreatic islet cell types include alpha cells, which produce glucagon; beta cells, which produce insulin; delta cells, which produce somatostatin; and PP cells, which produce pancreatic polypeptide. Insulin and glucagon are involved in the regulation of glucose metabolism. Insulin is produced by the beta cells in response to high blood glucose levels. It enhances glucose uptake and utilization by target cells, as well as the storage of excess glucose for later use. Dysfunction of the production of insulin or target cell resistance to the effects of insulin causes diabetes mellitus, a disorder characterized by high blood glucose levels. The hormone glucagon is produced and secreted by the alpha cells of the pancreas in response to low blood glucose levels. Glucagon stimulates mechanisms that increase blood glucose levels, such as the catabolism of glycogen into glucose. |
SciQ | SciQ-2811 | orbitals, electronic-configuration, elemental-analysis, ceramics
As for why they are "bright", that is simply related to the selection rules. For transitions between atomic states, the requirements are
$$\Delta S = 0; \Delta l = \pm 1; \Delta L = 0, \pm 1; \Delta J = 0, \pm 1 \text{ except }J = 0 \not\leftrightarrow 0$$
and for centrosymmetric systems like atoms there is an additional constraint that
$$\mathrm{g} \not\leftrightarrow \mathrm{g}; \mathrm{u} \not\leftrightarrow \mathrm{u}; \mathrm{g} \leftrightarrow \mathrm{u}$$
which is the Laporte selection rule. The bottom line is that these "f-f transitions" (I am using this term to loosely refer to the collective set of electronic transitions) are parity-conserving and therefore Laporte-forbidden. Vibronic coupling, which is the pathway which allows this selection rule can be relaxed, is not of consequence in the lanthanide ions because of the lack of covalency; the colours are not intense, and therefore typically a pale colour is observed. (Compare $\ce{KMnO4}$ which has a fully parity-allowed LMCT transition; its dark purple colour is exactly the opposite of pale.)
Much greater discussion of the electronic spectra of lanthanides can be found in ref 3.
References
Oxford lecture notes.
Aspinall, H. C. Chemistry of the f-Block Elements; p 35.
Cotton, S. Lanthanide and Actinide Chemistry; pp 61 onwards.
The following is multiple choice question (with options) to answer.
What color is the brittle metalloid tallurium? | [
"brownish black",
"silvery white",
"yellowish green",
"purplish blue"
] | B | Tellurium is a silvery white, brittle metalloid. It is toxic and may cause birth defects. Tellurium can conduct electricity when exposed to light, so it is used to make solar panels. It has several other uses as well. For example, it makes steel and copper easier to work with and lends color to ceramics. |
SciQ | SciQ-2812 | physical-chemistry, reaction-mechanism, everyday-chemistry, experimental-chemistry
Title: Need reactants for a rocket I am doing a project in chemistry at the moment to build a rocket out of materials that can be easily bought and that react strongly to create thrust.
I was wondering if anyone knew a good chemical formula for my rocket fuel? I know lots of good fuels and reactants used in amateur rocketry however commercial fuels have been banned from the project.
Any help would be appreciated. Put some potassium nitrate $\ce{KNO3}$ plus powdered charcoal and sulfur in a mortar. Wet it carefully and grind the whole until you get a black homogeneous paste. Let it dry overnight in the mortar. The obtained black gun powder may be detached from the mortar with a wooden spoon. It is a safe rocket fuel. The proportions of the powders are defined by stoichiometry. They must allow the chemical reaction : $$\ce{2 KNO3 + 3 C + S -> K2S + 3 CO2 + N2}$$
I have done it many times with my students. It's a good exercice of stoichiometry. Never had an accident ! And remember : Never ! Never grind dry powders ! Grind as wet powders as possible ! In case of doubt add more water ! Pastes are even a better choice for grinding purposes !
The following is multiple choice question (with options) to answer.
What compounds, which serve as fuels and are used in manufacturing, are called the driving force of western civilization? | [
"gas",
"fossils",
"forests",
"hydrocarbons"
] | D | It is hard to overstate the importance of hydrocarbons to modern life. Hydrocarbons have even been called the driving force of western civilization. You saw some ways they are used in Figure above . Several other ways are illustrated in Figure below . Their most important use is as fuels. Gasoline, natural gas, fuel oil, diesel fuel, jet fuel, coal, kerosene, and propane are just some of the hydrocarbon compounds that are burned for fuel. Hydrocarbons are also used to manufacture many products, including plastics and synthetic fabrics such as polyester. |
SciQ | SciQ-2813 | biochemistry, biophysics, bioenergetics
Title: Are there known life forms that are able to transform mechanical energy into chemical energy? Are there known life forms that are able to transform mechanical energy into chemical energy?
This question asks a similar subject, but more specific and has no answers.
The background of this question are thoughts about hypothetical life on tidally locked exoplanets of red dwarf stars, where light for photosynthesis is scarce but mechanical energy (storms and/or water currents) aplenty. There are no known life forms that use mechanical energy as a primary form of metabolic energy (i.e., for generic cellular functions). Many life forms are sensitive to mechanical disruption in some way, so they do utilize mechanical energy, but in a very limited fashion (@David's answer touches on this), and of course many organisms have life cycles that somehow depend on mechanical transportation (seed/spore dispersal, traveling on the wind or ocean currents, etc).
I think the main physical problem is that mechanical energy just isn't available to biological cells in a form that can be converted to substantial chemical energy. They are small, and tend to have other great benefits for being small.
To use an ocean wave as an example, there is very little or no perceptible movement for a cell in that wave, besides an apparent increase and decrease in the force of gravity. The top and bottom of the cell are moving together with the flow of water, so there is no differential to operate on.
An E. coli weighs about 1 picogram. If it could capture all of the energy from falling from 1km in the air on earth, assuming no uncaptured aerodynamic drag, that would be about 10-11 joules.
If there are ~3000 kJ/mol of energy available from burning glucose, that means about 5 × 10-21 joules per molecule of glucose, so about 20 billion glucose molecules, which sounds like a lot but it is only 1 femtogram, 0.1% the weight of the cell.
The following is multiple choice question (with options) to answer.
What is the main type of organism that gets its energy directly from the sun? | [
"plants",
"carnivores",
"animals",
"consumers"
] | A | This tiny plant can use the energy of the sun to make its own food. You can't make food by just sitting in the sun. Plants are not the only organisms that can get energy from the sun, however. Some protists, such as algae, and some bacteria can also use the energy of the sun to make their own food. |
SciQ | SciQ-2814 | fluid-dynamics, pressure, bernoulli-equation
But the secondary effects are more interesting. In conductors, charge tends to pile up on the edge of the box: so the center of the box now has a much lower density, the outside has a much higher density, and so we roughly would expect that the added "push" of the system outwards manifests as a higher total pressure. Repulsive particle interactions increase pressure, attractive particle interactions reduce it. You can similarly imagine that the attractive interaction means that when you increase volume, you get a "bump" from kinetic energy but you have to "tear apart" the potential energy holding these guys together, if that helps you visualize why the force on the external world is weaker.
Finally, it's worth considering diatomic compounds like $O_2$. These things can be treated a lot like ideal gases, but they have an internal energy (rotational kinetic energy) which doesn't tend to contribute to the pressure. This is to encourage you to forget the fallacy "average internal energy per unit volume" or some such; it's a rate-of-change, not an average.
Example: van der Waals equation of state
Probably the most famous example of the effects of particle-interactions on pressure is the so-called van der Waals equation. This is a simple, early heuristic to capture the non-ideal effects of a changing volume and pressure on a real fluid. It turns out that it contains a liquid-gas phase transition at a certain temperature, so it is our first stop also when we want to introduce phase transitions to our students. Actual fluids have been fitted to the following equation for parameters $(a, b)$:$$
\left( p + a~\left(\frac {n}{V}\right)^2\right)~\big(V - b~n\big) = n~R~T.
The following is multiple choice question (with options) to answer.
What are the two factors that affect the pressure of fluids? | [
"viscosity and gravity",
"momentum and density",
"depth and decrease",
"depth and density"
] | D | Two factors that affect the pressure of fluids are depth and density. This explains why water pressure is greater deeper in the ocean and air pressure is greatest at sea level. Denser fluids, such as water, exert more pressure than less dense fluids, such as air. |
SciQ | SciQ-2815 | inorganic-chemistry
$$\ce{H2O + B(OH)3 <=>H2OB(OH)3 <=>H+(aq) + B(OH)4^- (aq)}$$
The following is multiple choice question (with options) to answer.
What consists of four major components: inorganic mineral matter, organic matter, water and air, and living matter? | [
"nitrogen",
"soil",
"rocks",
"color"
] | B | 31.2 The Soil Plants obtain mineral nutrients from the soil. Soil is the outer loose layer that covers the surface of Earth. Soil quality depends on the chemical composition of the soil, the topography, the presence of living organisms, the climate, and time. Agricultural practice and history may also modify the characteristics and fertility of soil. Soil consists of four major components: 1) inorganic mineral matter, 2) organic matter, 3) water and air, and 4) living matter. The organic material of soil is made of humus, which improves soil structure and provides water and minerals. Soil inorganic material consists of rock slowly broken down into smaller particles that vary in size, such as sand, silt, and loam. Soil formation results from a combination of biological, physical, and chemical processes. Soil is not homogenous because its formation results in the production of layers called a soil profile. Factors that affect soil formation include: parent material, climate, topography, biological factors, and time. Soils are classified based on their horizons, soil particle size, and proportions. Most soils have four distinct horizons: O, A, B, and C. |
SciQ | SciQ-2816 | thermodynamics, statistical-mechanics
Title: Why do particles of an ideal gas move in random motion? Suppose we imagine that the particles (no molecules) of a helium gas are all initially moving horizontally at the same speed.(there is no interaction among them, and the container is ideal, in the sense that the particles scatter horizontally when they hit it) Would at least some later be moving vertically?
If they were completely organized in the beginning, would they get sprayed around at all angles, and then would the sprayed ones get sprayed some more, and sprayed some more, and sprayed some more?
What would be the origin of the random motion of the particles of a helium gas , for example, in a perfect box? Uncertainty principle? You could design initial conditions for a gas for which it doesn't move in brownian motion, just like you described. It's just that that takes some really particular initial conditons, and life is way too messy for that to happen frequently. Not only that, considering that there are on the order of $~10^{23}$ particles in a macroscopic object, the word "infrequently" here becomes "so rare that it has most likely never happened anywhere in the visible universe".
For example, start with your suggestion, and imagine you trap the particles in a box. They will hit a wall, ricochet off at different angles, collide into each other, and soon you will once again have a mess of particles moving unpredictable directions. This kind of thing is very typical and that's why any gas you see in real life will have random motion with probability which is unfathomably close to 100%.
The following is multiple choice question (with options) to answer.
What is the term for the movement of substances due to random thermal molecular motion? | [
"diffusion",
"Transfusion",
"condensation",
"convection"
] | A | 12.7 Molecular Transport Phenomena: Diffusion, Osmosis, and Related Processes Diffusion There is something fishy about the ice cube from your freezer—how did it pick up those food odors? How does soaking a sprained ankle in Epsom salt reduce swelling? The answer to these questions are related to atomic and molecular transport phenomena—another mode of fluid motion. Atoms and molecules are in constant motion at any temperature. In fluids they move about randomly even in the absence of macroscopic flow. This motion is called a random walk and is illustrated in Figure 12.20. Diffusion is the movement of substances due to random thermal molecular motion. Fluids, like fish fumes or odors entering ice cubes, can even diffuse through solids. Diffusion is a slow process over macroscopic distances. The densities of common materials are great enough that molecules cannot travel very far before having a collision that can scatter them in any direction, including straight backward. It can be shown that the average distance x rms that a molecule travels is proportional to the square root of time:. |
SciQ | SciQ-2817 | phase
"Which elements form the most phases?" is an impossible question to give and absolute answer as we are limited to certain pressures and temperatures with which to experiment. The way experimentation is done is likely to bias any verifiable answer toward more practical materials.
The following is multiple choice question (with options) to answer.
Most metals exist in which form at room temperature? | [
"solids",
"gases",
"oils",
"liquids"
] | A | Matter typically exists in one of three states: solid, liquid, or gas. The state of a given substance is a physical property. Some substances exist as gases at room temperature (such as oxygen and carbon dioxide), while others (like water and mercury metal) exist as liquids. Most metals exist as solids at room temperature. All substances can exist in any of these three states. |
SciQ | SciQ-2818 | cancer, stem-cells, telomere
Title: Why do tumours need stem cells, when they can generate their own telomerase? In the molecular biology of the cell (6th ed), it is stated that:
Some cancers seem to be organized in a similar way: they consist of
rare cancer stem cells capable of dividing indefinitly, toghether with
much lager numbers of dividing transit amplifying cells that are
derived from the ancer stem cells but haave a limited capacity for
self-renewal. These non-stem cells appear to constitute the great
majority of the cell population of some tumorus (p.1121).
Although in an earlier segment, however, we can read that:
Human cancer cells avoid replicative cell senescense in one of two
ways. They can maintain the activity of telomerase as they
proliferate, so that their telomeres do not shorten or become
uncapped, or they can evolve an alternate mechamism based on
homologous recombination (called ALT) for elongating their chromosome
ends. Regardless of strategy usedd, the result is that the cancer
cells continue to proliferate under conditions when normal cells would
stop (p.1100).
How do we interpret these two passages? Are some cancer cells incapable of lenghtening their telomeres, and is it these types of tumours that can't persist without cancer stem cells? Or are cancer stem cells beneficial in some other way to the tumour (such that a tumour stem cell might differentiate into several types of tumour cells, which might be suitable for different environments)?
I understand that having cancer stem cells that proliferate at a slower pace than regular cancer cells might be beneficial for withstanding things like chemotherapy. But what's being emphaphized is not their capacity for survival, but their greater ability at self renewal? This is like asking why there are multiple forms/mechanisms of dementia when "one would suffice".
To save this from being just a trivial comment, note that the mechanism of elongation differs between cancer types, likely depending on the types of cells involved:
The following is multiple choice question (with options) to answer.
A stem cell is an unspecialized cell that can divide without limit as needed and can, under specific conditions, differentiate into these? | [
"specialized cells",
"germ cells",
"clones",
"infectious cells"
] | A | Stem Cells A stem cell is an unspecialized cell that can divide without limit as needed and can, under specific conditions, differentiate into specialized cells. Stem cells are divided into several categories according to their potential to differentiate. The first embryonic cells that arise from the division of the zygote are the ultimate stem cells; these stems cells are described as totipotent because they have the potential to differentiate into any of the cells needed to enable an organism to grow and develop. The embryonic cells that develop from totipotent stem cells and are precursors to the fundamental tissue layers of the embryo are classified as pluripotent. A pluripotent stem cell is one that has the potential to differentiate into any type of human tissue but cannot support the full development of an organism. These cells then become slightly more specialized, and are referred to as multipotent cells. A multipotent stem cell has the potential to differentiate into different types of cells within a given cell lineage or small number of lineages, such as a red blood cell or white blood cell. Finally, multipotent cells can become further specialized oligopotent cells. An oligopotent stem cell is limited to becoming one of a few different cell types. In contrast, a unipotent cell is fully specialized and can only reproduce to generate more of its own specific cell type. Stem cells are unique in that they can also continually divide and regenerate new stem cells instead of further specializing. There are different stem cells present at different stages of a human’s life. They include the embryonic stem cells of the embryo, fetal stem cells of the fetus, and adult stem cells in the adult. One type of adult stem cell is the epithelial stem cell, which gives rise to the keratinocytes in the multiple layers of epithelial cells in the epidermis of skin. Adult bone marrow has three distinct types of stem cells: hematopoietic stem cells, which give rise to red blood cells, white blood cells, and platelets (Figure 3.34); endothelial stem cells, which give rise to the endothelial cell types that line blood and lymph vessels; and mesenchymal stem cells, which give rise to the different types of muscle cells. |
SciQ | SciQ-2819 | reproduction, endocrinology, pregnancy, ovulation
The decline of the corpus luteum is correlated with a decline in serum levels of ovarian hormones including progesterone, estradiol, and inhibin A. Release from negative feedback provided by these hormones at the level of the hypothalamus and pituitary permits FSH to rise, and the cycle begins again.
You should now be able to see that:
Around the time of ovulation, the uterine lining is not fully developed and is stable due to the hormonal milieu. Menstruation does not occur.
Around the time of menstruation, FSH and LH are suppressed in a way that is not conducive to ovulation.
In theory, yes, of course there would be a lower chance of initiating a viable pregnancy (implantation rather than conception is the most obvious problem) were the endometrial lining to be unstable at the time of ovulation. The problem of luteal phase deficiency is along these lines. In this condition, the corpus luteum does not produce adequate progesterone during the luteal phase to develop the endometrial lining in such a way as to support a healthy pregnancy. However, ovulation and menstruation are still time-separated events for the reasons outlined above.
*Note that the first term is with respect to the endometrium; the second is with respect to the ovary.
Abbreviations:
GnRH - Gonadotropin Releasing Hormone; LH - Luteinizing Hormone; FSH - Follicule Stimulating Hormone
References
1. Anatomy & Physiology, Connexions Web site. Illustration is also from here.
2. Jerome Strauss, Robert Barbieri. Yen & Jaffe's Reproductive Endocrinology. September, 2013. Saunders.
The following is multiple choice question (with options) to answer.
What monthy cycle causes changes in the ovaries and uterus? | [
"water cycle",
"the menstrual cycle",
"tides",
"sleep-wake cycle"
] | B | The menstrual cycle is a monthly cycle of changes in the ovaries and uterus. |
SciQ | SciQ-2820 | evolution
bacteria
cyanobacteria
archaea
protists
fungi
algae
plants
nematodes
arthropods
vertebrates
Bacterial and archaean colonisation
The first evidence of life on land seems to originate from 2.6 (Watanabe et al., 2000) to 3.1 (Battistuzzi et al., 2004) billion years ago. Since molecular evidence points to bacteria and archaea diverging between 3.2-3.8 billion years ago (Feng et al.,1997 - a classic paper), and since both bacteria and archaea are found on land (e.g. Taketani & Tsai, 2010), they must have colonised land independently. I would suggest there would have been many different bacterial colonisations, too. One at least is certain - cyanobacteria must have colonised independently from some other forms, since they evolved after the first bacterial colonisation (Tomitani et al., 2006), and are now found on land, e.g. in lichens.
Protistan, fungal, algal, plant and animal colonisation
Protists are a polyphyletic group of simple eukaryotes, and since fungal divergence from them (Wang et al., 1999 - another classic) predates fungal emergence from the ocean (Taylor & Osborn, 1996), they must have emerged separately. Then, since plants and fungi diverged whilst fungi were still in the ocean (Wang et al., 1999), plants must have colonised separately. Actually, it has been explicitly discovered in various ways (e.g. molecular clock methods, Heckman et al., 2001) that plants must have left the ocean separately to fungi, but probably relied upon them to be able to do it (Brundrett, 2002 - see note at bottom about this paper). Next, simple animals... Arthropods colonised the land independently (Pisani et al, 2004), and since nematodes diverged before arthropods (Wang et al., 1999), they too must have independently found land. Then, lumbering along at the end, came the tetrapods (Long & Gordon, 2004).
Note about the Brundrett paper: it has OVER 300 REFERENCES! That guy must have been hoping for some sort of prize.
References
The following is multiple choice question (with options) to answer.
Chytridiomycota are considered the most primitive of what kingdom? | [
"protists",
"plants",
"animals",
"fungi"
] | D | 24.2 Classifications of Fungi Chytridiomycota (chytrids) are considered the most primitive group of fungi. They are mostly aquatic, and their gametes are the only fungal cells known to have flagella. They reproduce both sexually and asexually; the asexual spores are called zoospores. Zygomycota (conjugated fungi) produce non-septated hyphae with many nuclei. Their hyphae fuse during sexual reproduction to produce a zygospore in a zygosporangium. Ascomycota (sac fungi) form spores in sacs called asci during sexual reproduction. Asexual reproduction is their most common form of reproduction. Basidiomycota (club fungi) produce showy fruiting bodies that contain basidia in the form of clubs. Spores are stored in the basidia. Most familiar mushrooms belong to this division. Fungi that have no known sexual cycle were classified in the form phylum Deuteromycota, which the present classification puts in the phyla Ascomycota and Basidiomycota. Glomeromycota form tight associations (called mycorrhizae) with the roots of plants. |
SciQ | SciQ-2821 | inorganic-chemistry, acid-base, ph
Title: What alkali and alkaline earth metal oxides will turn moist red litmus blue and finally white?
How many of the following will turn moist red litmus blue and finally white?
$\ce{Li2O}$, $\ce{KO3}$, $\ce{RbO2}$, $\ce{Cs2O2}$, $\ce{BeO}$, $\ce{MgO}$, $\ce{BaO2}$, $\ce{SrO}$.
Since bleach convert moist red litmus blue and then white, but how we can identify which compound will act as bleach ? The standard oxides $\ce{Li2O, MgO}$ and $\ce{SrO}$ are water soluble and hydrolyse to form hydroxides and a basic solution. $\ce{BeO}$ is insoluble in water.
$\ce{RbO2}$ is a superoxide which in aqueous solution undergoes disproportionation to $\ce{O2}$ and $\ce{OH-}$ so will give a blue litmus test.
The peroxides $\ce{Cs2O2}$ and $\ce{BaO2}$ react with water to give hydrogen peroxide and the hydroxides, so again a basic solution(source). The hydrogen peroxide produced will bleach the litmus paper.
$\ce{KO3}$(Potassium Ozonide) is highly unstable, decomposes in water to $\ce{O2}$ and $\ce{KOH}$
The oxides which will NOT decolorize litmus are $\ce{Li2O, MgO, BeO}$ and $\ce{SrO}$. The peroxides ($\ce{Cs2O2}$ and $\ce{BaO2}$), the superoxide($\ce{RbO2}$) and the ozonide($\ce{KO3}$) will decolorize litmus.
The following is multiple choice question (with options) to answer.
What is a soft, gray, nontoxic alkaline earth metal? | [
"magnesium",
"calcium",
"potassium",
"pewter"
] | B | For a better understanding of alkaline Earth metals, let’s take a closer look at two of them: calcium (Ca) and strontium (Sr). Calcium is a soft, gray, nontoxic alkaline Earth metal. Although pure calcium doesn’t exist in nature, calcium compounds are very common in Earth’s crust and in sea water. Calcium is also the most abundant metal in the human body, occurring as calcium compounds such as calcium phosphate and calcium carbonate. These calcium compounds are found in bones and make them hard and strong. The skeleton of the average adult contains about a kilogram of calcium. Because calcium—like barium—absorbs x-rays, bones show up white in x-ray images. Calcium is an important component of a healthy human diet. Good food sources of calcium are pictured in Figure below . |
SciQ | SciQ-2822 | 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.
In many polychaetes, the parapodia are richly supplied with blood vessels and also function as what? | [
"pores",
"gills",
"scales",
"tails"
] | B | |
SciQ | SciQ-2823 | soil
Caliche generally forms when minerals leach from the upper layer of the soil (the A horizon) and accumulate in the next layer (the B horizon), at depths around 3 to 10 feet under the surface. It generally consists of carbonates in semiarid regions—in arid regions, less-soluble minerals form caliche layers after all the carbonates have been leached from the soil. The deposited calcium carbonate accumulates—first forming grains, then small clumps, then a discernible layer, and finally, a thicker, solid bed. As the caliche layer forms, the layer gradually becomes deeper, and eventually moves into the parent material, which lies under the upper soil horizons.
However, caliche also forms in other ways. It can form when water rises through capillary action. In an arid region, rainwater sinks into the ground very quickly. Later, as the surface dries out, the water below the surface rises, carrying up dissolved minerals from lower layers. This water movement forms a caliche that tends to grow thinner and branch out as it nears the surface. Plants can contribute to the formation of caliche, as well. Plant roots take up water through transpiration, and leave behind the dissolved calcium carbonate, which precipitates to form caliche. It can also form on outcrops of porous rocks or in rock fissures where water is trapped and evaporates. In general, caliche deposition is a slow process, but if enough moisture is present in an otherwise arid site, it can accumulate fast enough to block a drain pipe.
(photo from http://www.naturephoto-cz.com/karst-cave-photo-24442.html)
The following is multiple choice question (with options) to answer.
What is formed when plant bodies are lithified? | [
"coal",
"fossils",
"methane",
"copper"
] | A | The bodies of organisms can make a sedimentary rock. Plant bodies are lithified to become coal. When shells are cemented together they make a type of limestone. So limestone can be considered chemical or organic. |
SciQ | SciQ-2824 | molecular-biology, synthetic-biology
Source: https://web.archive.org/web/20161212170103/http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/TransgenicAnimals.html
Now, depending on how you inject your gene you can distinguish between transgenics and knock-in mice. In a transgenic mouse you insert the gene somewhere in the genome and, although there are method to understand where it ended up you generally do not know.
Knock-in animals, instead, target a specific region of the genome. This is usually used in order to change an existing gene, to improve its function or to remove its function (knock-out animals). This process, called gene targeting relies on the biological process called homologous recombination.
So, why don't we just synthesize a new genome each time?
Aside from Venter's dream, the process would:
have incredibly high cost
be extremely complicated technically
be extremely long (mostly for reason 2)
suffer from the problem that there is so much we do not know about genome regulation in a bacteria, let alone in a mouse! You have to think that the genome is not just a series of genes one after another: there is a big part of regulatory regions that define things like the 3D form of the genome, which determines when and how much genes are accessible for transcription, when and where they are activated and so on. Also, more and more attention is now drawn to something called epigenetics marks, modifications of the DNA, or its associated proteins that can also modulate its transcription.
What is the cheapest experiment you can perform at your own home without access to a biology lab which involves changing the genome of a living organism in a way that's functionally visible? (An arbitrary example: Can you create an apple that's blue in color with a budget of $500? By create, I mean you should be able to hold the blue apple in your hand.)
Quick answer: no you cannot.
The following is multiple choice question (with options) to answer.
What is the term for the direct manipulation of genes for practical purposes? | [
"genetic cloning",
"genetic testing",
"manual engineering",
"genetic engineering"
] | D | |
SciQ | SciQ-2825 | homework-and-exercises, newtonian-mechanics, collision
Title: Equations for Perfect Collisions I have two bodies of known mass $m_0$ and $m_1$. $m_0$ is at constant velocity of $v_0$ on a level friction-less plane surface, and $m_1$ is moving across the same plane at constant velocity $v_1$ towards $m_0$; the assumption is that $v_1$ > $v_0$ so they will collide at some point.
When the two bodies perfectly collide (no energy transformed) I know that kinetic energy is conserved (as I believe is momentum), but I am at a loss as to how to calculate the new velocities of $m_0$ and $m_1$ after the collision.
I think if $m_0$ and $m_1$ are the same mass and $v_0$ is initially zero, then the only solution is that $m_0$ will move at velocity $v_1$ and that $m_1$ will stop, but apart from that I can't seem to get my head around the math where $m_0$ and $m_1$ are different. This is a elastic collision described above in which the kinetic energy is conserved. The momentum will always be conserved in the cases of collisions as no external force acts.
I will use these two facts - momentum conservation and kinetic energy conservation to derive the final velocities of the masses.
Let the final velocities be $v_0'$ and $v_1'$ of $m_0$ and $m_1$ respectively.
Using the first fact;
$$m_0v_0 + m_1v_1 = m_0v_0' + m_1v_1' ....(i)$$
And from the second fact;
$$\frac{1}{2}m_0v_0^2 + \frac{1}{2}m_1v_1^2 = \frac{1}{2}m_0v_0'^2 + \frac{1}{2}m_1v_1'^2 ...(ii)$$
The following is multiple choice question (with options) to answer.
When both momentum and kinetic energy are conserved in a closed system, the collision is called what? | [
"a spontaneous collision",
"an elastic collision",
"an accidental collision",
"a static collision"
] | B | For all collisions in a closed system, momentum is conserved. In some collisions in a closed system, kinetic energy is conserved. When both momentum and kinetic energy are conserved, the collision is called an elastic collision. Most collisions are inelastic because some amount of kinetic energy is converted to potential energy, usually by raising one of the objects higher (increasing gravitation PE) or by flexing the object. Any denting or other changing of shape by one of the objects will also be accompanied by a loss of kinetic energy. The only commonly seen elastic collisions are those between billiard balls or ball bearings, because these balls do not compress. And, of course, collisions between molecules are elastic if no damage is done to the molecules. |
SciQ | SciQ-2826 | evolution, human-evolution
Apes
The split between the line leading to modern humans and the line leading to modern chimpanzees occured somewhere around 4 to 7 million years ago. The clade is called Hominini. The split between those and the line leading to modern gorillas occured around 8 to 19 million years ago (yes, the dates are getting fuzzier). A fossil coming close to this ancestor may be Nakalipithecus nakayamai, however, we only have a fossil jaw from that species.
Going back, we get to the split between modern-day humans/chimpanzees/gorillas and modern-day orang-utans. This is the "ape" family, Hominidae. The largest ape that we know of, Gigantopithecus, that grew to about 3 meters, is classified as an orang-utan. Note that this is not a direct ancestor of humans. Even if our ancestors were larger than modern humans at this point it's unlikely that we are talking about anything larger than a big gorilla.
Primates
Going a bit in the reverse order here: The first true primates evolved around 55 million years ago. Fossils from that time are about the size of squirrels. Humans are "old world monkeys" who first appeared around 40 million years ago - the fossils from that clade we know, for example Apidium or Aegyptopithecus are a bit larger, some as large as a dog.
Primate-like mammals
The first primate-like mammals, called Plesiadapiformes appeared around 60 million years ago. We don't know all that much about them, but the most famous Purgatorius was the size of a rat or mouse.
Mammals / placenta mammals
Going back even further, things become even murkier, but early mammals were small. Placentalia, placental mammals appeared around 90 million years ago. They were small, arboreal (tree-dwelling) animals. Early mammals appeared around 160 million years ago and fossils we have from that time place them around the size of a shrew.
Now, is it possible that there were larger mammals in there somewhere, that then "shrunk" again? Sure. Just unlikely.
Therapsid
The following is multiple choice question (with options) to answer.
What are the two groups of therian mammals? | [
"monotremes and mollusks",
"felines and canines",
"placental mammals and marsupials",
"dolphins and whales"
] | C | Therian mammals are viviparous. They give birth to an embryo or infant rather than laying eggs. The female reproductive system of a therian mammal includes a uterus and a vagina. There are two groups of therian mammals: placental mammals and marsupials. |
SciQ | SciQ-2827 | telescope, space, space-telescope
Title: Which space telescope is the most distant? From the earth, and from the sun. Only interested in active, operational ones. Currently New Horizions is temporarily hibernating; it's last activity was two months ago. So I'm going to post a supplementary answer here because it is "operational" in the sense that it still works and will be used again, even though it is not "active" at the moment.
The most recent and farthest-from-earth telescopic observations that I know of are from the New Horizons spacecraft and it's Long-Range Reconnaissance Imager (LORRI), a 208 mm (8.2 inch) diameter Ritchey–Chretien telescope equipped with silicon-carbide optics and a cooled silicon CCD imager with a resolution of about 1 arcsecond:
The Long-Range Reconnaissance Imager (LORRI) is a long-focal-length imager designed for high resolution and responsivity at visible wavelengths. The instrument is equipped with a 1024×1024 pixel by 12-bits-per-pixel monochromatic CCD imager giving a resolution of 5 μrad (~1 arcsec)] The CCD is chilled far below freezing by a passive radiator on the antisolar face of the spacecraft. This temperature differential requires insulation, and isolation from the rest of the structure. The 208.3 mm (8.20 in) aperture Ritchey–Chretien mirrors and metering structure are made of silicon carbide, to boost stiffness, reduce weight, and prevent warping at low temperatures. The optical elements sit in a composite light shield, and mount with titanium and fiberglass for thermal isolation. Overall mass is 8.6 kg (19 lb), with the optical tube assembly (OTA) weighing about 5.6 kg (12 lb), for one of the largest silicon-carbide telescopes flown at the time (now surpassed by Herschel).
In December 2017 LORRI captured the images below of two Kuiper belt objects. From the February 9, 2018 NASA News item New Horizons Captures Record-Breaking Images in the Kuiper Belt:
The following is multiple choice question (with options) to answer.
What is the name of the spacecraft that has performed the closest flyby of uranus? | [
"Zodiac 4",
"voyager 2",
"Mercury 7",
"centaur 2"
] | B | Uranus is so far away that there has been relatively little exploration of the planet. The closest approach was a flyby by Voyager 2 in 1986. Great images have also been taken by the Hubble Space Telescope. |
SciQ | SciQ-2828 | cell-biology, microbiology
Title: Are there any organisms that are made of more than one (~5-12) cell? Prokaryotes and eukaryotes are unicellular, made of one cell. Great. Eukaryotes are unicellular or multicellular. But the typical examples of multicellular eukaryotes we have are made of, often, trillions of cells, like us humans. Ants must still be made of many millions of cells. Are there known eukaryotes with very few cells that make them up? Like, 5, or something? Or maybe a dozen cells making up the whole organism in its fully developed state? There's Trichoplax adhaerens, a Placozoa, made of a few thousand cells. Then there is Dicyema japonicum, a simple mesozoan, made up of 9 to 41 cells. Arguably, the simplest multicellular organism is the algae Tetrabaena socialis, whose body consists of 4 cells. Then, there's the parasitic Myxozoa which have 7 cells.
The following is multiple choice question (with options) to answer.
What is the group of all the eukaryotes that are not fungi, animals, or plants called? | [
"lizards",
"filamentous",
"protists",
"arthropods"
] | C | Protists are a group of all the eukaryotes that are not fungi, animals, or plants. As a result, it is a very diverse group of organisms. The eukaryotes that make up this kingdom, Kingdom Protista , do not have much in common besides a relatively simple organization. Protists can look very different from each other. Some are tiny and unicellular, like an amoeba , and some are large and multicellular, like seaweed . However, multicellular protists do not have highly specialized tissues or organs. This simple cellular-level organization distinguishes protists from other eukaryotes, such as fungi, animals, and plants. There are thought to be between 60,000 and 200,000 protist species, and many have yet to be identified. Protists live in almost any environment that contains liquid water. Many protists, such as the algae , are photosynthetic and are vital primary producers in ecosystems. Other protists are responsible for a range of serious human diseases, such as malaria and sleeping sickness. |
SciQ | SciQ-2829 | ecology, mycology
Title: Is there an antagonistic association between Penicillium and Aspergillus? Some Aspergillus species appear to like walnuts. My question concerns the association of Penicillium and Aspergillus. No sooner does Aspergillus colonize a walnut (or some other challenging carbon source) than Penicillium seems to move in, eventually killing the Aspergillus colony.
A totally unscientific guess is that Aspergillus is a good colonizer and Penicillium a good opportunist and that this is a common pattern with these two species. Is there any science in this direction? I do recall a sort of well-known picture from an old text in which Penicillium is shown more or less strangling a species of Aspergillus. I didn't think about it much at the time.
The image attached is not very incriminating but the theme is the same. Penicillium are the green hand-like structures strewn about the clover-like Aspergillus. Foot-cell of the latter cropped.
This seems like a simple question but a quick search doesn't reveal a lot, I think in part because this would generally come up as a contamination issue. It is hard to find any articles on the association between Penicillium and Aspergillus species, although they are both considered two of the most common mold species found indoors.
In this study, the most prevalent spore types detected in both the indoor and outdoor air samples were generally from the Penicillium/Aspergillus group [...] these findings are qualitatively similar to those observed in other geographical locations, confirming the ubiquitous nature of these fungi.
Although these genera seem to be found commonly, it also has to do with environmental factors, and the relative humidity of the area as well.
Geographical location, climate, and short-term meteorological
conditions are responsible for outdoor types and levels of fungal
spores.
As for the association and apparently colonization/opportunistic behaviour of the genera, it seems like there are not any associations between the two, unless perhaps environmental conditions are subject to changing, and different mold species have different moisture/temperature thresholds, although again these mold groups tend to be generalists and do well at a wider range of environmental conditions than other fungi.
The following is multiple choice question (with options) to answer.
What have a symbiotic relationship between a fungus and a photosynthetic organism? | [
"crustaceans",
"sponges",
"amphibians",
"lichens"
] | D | farm fungi as a supply of food. Lichens are a symbiotic relationship between a fungus and a photosynthetic organism, usually an alga or cyanobacterium. The photosynthetic organism provides energy derived from light and carbohydrates, while the fungus supplies minerals and protection. Some animals that consume fungi help disseminate spores over long distances. |
SciQ | SciQ-2830 | newtonian-mechanics, kinematics
Title: Are there only 2 types of motion -- Translational & Rotational? When searching up the different types of motion, results show circular motion, translational motion, oscillatory motion, rotational motion, periodic motion, etc. But just to clear things up in my head, all types of motion can be described as either translational or rotational right? To me it seems like an object either moves its position or moves its orientation(rotation), and things like circular motion and oscillatory motion are just used to describe specific patterns of translational motion. Thanks. There is only one kind of 3D motion at any instant. This is the so called Chasles' theorem.
This motion is that of a rotation about some arbitrary axis, and a parallel translation along the axis. This motion is often called the screw motion, and it is the basis for Screw Theory in the study of rigid body motions, kinematics, and robotics.
Any instantaneous motion of a rigid body can be decomposed into a screw motion defined by the rotation axis direction, a point somewhere along the axis of rotation, the magnitude (speed) of the rotation and the pitch which represents the ratio of translation to rotation.
The general screw motion has two special cases
Pure rotation is when the pitch is zero and there is no translation
Pure translation has its axis of rotation at infinity and zero pitch, or just a translational velocity (zero rotation) which means the pitch is infinite. Both interpretations are equally valid.
When looking at 2D motion, then the axis of rotation must be out of plane if it exists. You might have heard of the term for "centre of rotation". This designates the point where the rotation axis intersects the plane of motion.
The following is multiple choice question (with options) to answer.
Define motion. | [
"speed of objects",
"gravitational pull",
"change of position",
"distance traveled"
] | C | Motion is defined as a change of position. |
SciQ | SciQ-2831 | 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.
Most tissues regulated by the autonomic nervous system receive both sympathetic and parasympathetic input from? | [
"peristaltic neurons",
"Chemosensory center",
"parasympathetic neurons",
"postganglionic neurons"
] | D | |
SciQ | SciQ-2832 | evolution, mutations, antibiotic-resistance
Title: If bacterial resistance randomly occur, then why limit broad-spectrum antibiotic use? If there is importance to study some discipline, then one of the main matters is its applications, so besides the primary goal of knowing the truth of the matter regarding what that discipline is investigating, applicability or usefulness of that study in other fields or in the field itself is a very important matter. I'll direct my attention here to Evolution, and its mechanisms. So accordingly if something that I personally want to come up with is application of that knowledge to the field of my work.
In reality we don't study evolution extensively at college level in medicine, since it doesn't have a direct clinical impact on the diagnosis and treatment of patients in most of the cases. However, one possible area of interaction is "bacterial resistance to antibiotics", since this is related to "mutations", and generally viewed as a mechanism whereby the bacterium adapts to its environment.
Now all of my life in medicine from college through specialty and academic teaching, we've never ceased being reminded about not dispensing antibiotics liberally, and the main concern outlined is "emergence of resistant strains of bacteria" due to this liberal use of antibiotics itself. There are other reasons of course, like side effects and cost, but they are not the main concern most of the times.
During my recent review of Evolution, looking at the introductory courses that were cited to me by many participants here, in particular this page of Evo101 titled "Mutations are Random" I was really shocked to know that even the mutations that resulted in bacterial resistance were not "directed mutations", i.e. it is not the case that the exposure to the antibiotic caused the bacteria to have that mutation in the first place, actually the page mentions Esther and Joshua Lederberg experiments showing that those resistant bacteria were already there before the population was exposed to the antibiotics?
So why have we been always reminded by bacteriologists of limiting our antibiotic usage if emergence of drug resistance is not due to exposure to it?
The following is multiple choice question (with options) to answer.
What is responsible for the development of antibiotic-resistant strains of bacteria? | [
"flu shots",
"bacterial mutations",
"mosquitoes",
"negative mutations"
] | B | Mutations in many bacteria that allow them to survive in the presence of antibiotic drugs. The mutations lead to antibiotic-resistant strains of bacteria. |
SciQ | SciQ-2833 | human-biology, cancer, medicine
Title: Why are only few cigarette smokers prone to cancer? It's tacit that only a few populace of smokers get cancer. What spares the others from it or what specifically cause cancer in those populace? See this Washington Post Article Cigarette smokers are most certainly prone to cancer. See Cecil Medicine, Chapter 183, on the epidemiology of cancer, exposure to tobacco is the most important environmental risk factor for cancer development, at least in the US:
Exposure to tobacco is the single largest cause of cancer in the United States... All forms of tobacco can cause cancer. Cigarette smoking causes cancer of the lip, oral cavity, nasal cavity, paranasal sinuses, pharynx (nasal, oral, and hypopharnyx), larynx, lung, esophagus (squamous cell and adenocarcinoma), stomach, colorectum, pancreas, liver, kidney (adenocarcinoma and renal pelvis), urinary bladder, uterine cervix, and myeloid leukemia.
Cancer may be identified or the cause of death in fewer smokers than might be expected, though, because smoking is an even greater risk factor for cardiovascular disease, and death due to cardiovascular disease.
Cancer is an unlikely phenomenon in an individual cell, but becomes more likely at the organism level, and even more likely over time. Though tobacco may be the most important environmental risk factor for cancer, age is actually a stronger predictor of cancer (see again, Cecil Chapter 183. Autopsy studies give us a quite remarkable example, this one shows incidental prostate cancer in nearly 60% of men over 80 who died from other causes. That figure is not out of the ordinary. Live long enough and you are likely to develop cancer.
Death due to heart disease may account for the lower than expected rates of cancer diagnoses and deaths in smokers. Nothing prevents cancer as well as dying from something else. And as discussed in the blog in the Washington Post you linked to, up to 2/3 of smokers die from smoking related causes
The following is multiple choice question (with options) to answer.
Many cancers, as well as autism, are thought to have what component, which is certainly a factor in asthma? | [
"emotional",
"ecological",
"critical",
"environmental"
] | D | Does everyone who smokes develop lung cancer? No, of course not. Is it possible to get lung cancer without smoking? Sadly, yes it is. That's not to say there is no relationship between the two: smoking is still the leading cause of lung cancer. But it does suggest that a person's genetic background has a role in this process. Apart form true single gene disorders, environmental factors, or environmental triggers , may determine the development of disease in individuals genetically predisposed to a particular condition. Environmental triggers may include stress, physical and mental abuse, diet, exposure to toxins, pathogens, and radiation. Many cancers are thought to have an environmental component. It has been suggested that environmental factors play a role in autism as well. Asthma is obviously triggered under certain environmental conditions. |
SciQ | SciQ-2834 | evolution
bacteria
cyanobacteria
archaea
protists
fungi
algae
plants
nematodes
arthropods
vertebrates
Bacterial and archaean colonisation
The first evidence of life on land seems to originate from 2.6 (Watanabe et al., 2000) to 3.1 (Battistuzzi et al., 2004) billion years ago. Since molecular evidence points to bacteria and archaea diverging between 3.2-3.8 billion years ago (Feng et al.,1997 - a classic paper), and since both bacteria and archaea are found on land (e.g. Taketani & Tsai, 2010), they must have colonised land independently. I would suggest there would have been many different bacterial colonisations, too. One at least is certain - cyanobacteria must have colonised independently from some other forms, since they evolved after the first bacterial colonisation (Tomitani et al., 2006), and are now found on land, e.g. in lichens.
Protistan, fungal, algal, plant and animal colonisation
Protists are a polyphyletic group of simple eukaryotes, and since fungal divergence from them (Wang et al., 1999 - another classic) predates fungal emergence from the ocean (Taylor & Osborn, 1996), they must have emerged separately. Then, since plants and fungi diverged whilst fungi were still in the ocean (Wang et al., 1999), plants must have colonised separately. Actually, it has been explicitly discovered in various ways (e.g. molecular clock methods, Heckman et al., 2001) that plants must have left the ocean separately to fungi, but probably relied upon them to be able to do it (Brundrett, 2002 - see note at bottom about this paper). Next, simple animals... Arthropods colonised the land independently (Pisani et al, 2004), and since nematodes diverged before arthropods (Wang et al., 1999), they too must have independently found land. Then, lumbering along at the end, came the tetrapods (Long & Gordon, 2004).
Note about the Brundrett paper: it has OVER 300 REFERENCES! That guy must have been hoping for some sort of prize.
References
The following is multiple choice question (with options) to answer.
The first plants probably evolved from what? | [
"mould",
"aquatic green algae",
"moss",
"dry green algae"
] | B | The first plants probably evolved from aquatic green algae. They had male and female reproductive organs. However, they lacked true stems, roots, and leaves. |
SciQ | SciQ-2835 | units, si-units, metrology
Title: How units were defined? I was wondering how we humans can be sure that one meter is one meter and that one second is one second. Nowadays, except for the Kilogram, all other units are well defined using highly accurate techniques (frequency of atoms vibrations or stuff like that). But at the end all units are kind of related to each other and the definition of each unit is based on a combination of other units. There must be some viable sources that have constant measurable values that we used to define the basic units. What is those sources?
To explain more let's start with the meter. From wikipedia, the definition is: The metre is the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second. So here it is clear that the definition of a meter relies on the accuracy of how we define a second.
Now let's look at the second:
the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.
How is this period calculated? The sensor has probably some equations that imply transformations using other units like Kg etc...
Where does this loop stops?
EDIT:
I think I was a little bit mistaken. Not all units are directly related and there is 3 totally independent units which are : Time (second), Temperature (kelvin) and Mass (kilogram). Time and Temperature are well defined but Kilogram is still unclear. Every existing unit can be transformed into a combination of those three. It means that all units based on Kilogram are not absolute. In short, up until now, the $kg$ was arbitrary, but now people are trying to define it based on universal constants
There is a ongoing process to try and link all the units to universal constants.
This has been done already for the second (using Cesium) and the meter (using the speed of light in a vacuum)
However, the kilogram is a little less straightforward. An interesting read is SI units revision proposal.
It proposes to link the kg to the Plank constant $h$, but also to link Kelvin $K$ to the Stefan-Boltzman constant $k$ and more of these constructions.
The following is multiple choice question (with options) to answer.
What is the unit of liquid measurement in the metric system? | [
"pint",
"liter",
"cylinder",
"gallon"
] | B | Transition metal ions often involve rearrangements of both d and s electrons. |
SciQ | SciQ-2836 | electromagnetism, waves, electromagnetic-radiation, electric-fields, frequency
Title: How is the frequency of a wave defined if it propagates on three different directions? Let's consider a wave which propagates on 2 or three directions, like for instance an electromagnetic wave inside a rectangular waveguide totally closed on two ideal conductor surfaces:
The following is multiple choice question (with options) to answer.
Wavelength and frequency are defined in the same way for electromagnetic waves as they are for which other waves? | [
"mechanical",
"sonar",
"light",
"gravitational"
] | A | Wavelength and frequency are defined in the same way for electromagnetic waves as they are for mechanical waves. Both properties are illustrated in Figure below . |
SciQ | SciQ-2837 | fluid-dynamics, kinematics, momentum
Title: Could a fish in a sealed ball, move the ball? If you had a glass ball filled with water, completely sealed and containing a fish, could the fish move the ball? Yes, with gravity and a generous definition of "moving".. it would be the same principle as the toys where you can control a sphere using a radio control (or using your iphone). The fish swims along the edge and gravity pulls it back down, which starts a rotation of the water and by friction to the sphere starts the rolling motion of the sphere on the ground or other surface. Obviously the water/sphere friction will probably be miniscule, but at least it is possible in theory :)
A follow-up question would of course be if it's possible to move a hermetically sealed sphere freefloating in vacuum and without gravity or any other appreciable fields intersecting it. If you solve this, I'm pretty sure NASA will want to talk to you (or the fish)!
The following is multiple choice question (with options) to answer.
What covers the body of a fish to help the move their body to swim? | [
"scales",
"gelatin",
"skin",
"hairs"
] | A | Fish are covered with scales. Scales are overlapping tissues, like shingles on a roof. They reduce friction with the water. They also provide a flexible covering that lets fish move their body to swim. |
SciQ | SciQ-2838 | bond, electrons, lewis-structure, valence-bond-theory
Title: Why do unbonded electrons exist in pairs? Basically the term which we use to refer them is lone pair. In Lewis structure why we represent those unbonded electron in pairs. Like here (structure of SO2)
Here if we assume both the unbonded electrons to be existing in pairs then it's geometry will be different from what we would observe in case when both electrons exists freely (without pair).
So why we basically consider those electrons to be existing in pair? Is it any kind of observation or any theory or both?
Why unbonded electrons exits in pair
Unbonded, non-bonded or lone pair electrons are terms used to describe electrons that surround an atom, but don't play a direct role in bond formation. Importantly, these electrons do not always exist as lone pairs where the electrons reside in a common orbital. Sometimes they exist as single non-bonding electrons residing in separate orbitals.
Let's compare the non-bonding electrons in water to those in molecular oxygen. Here is an illustration of the molecular orbital arrangement for water. As we fill the orbitals with electrons according to the Aufbau Principle we arrive at the point where we have two electrons remaining and the next available molecular orbital is the $\ce{1b_1}$ orbital. According to Hund's Rule, we must place these two electrons into this orbital with their spins paired. The result is that we have two non-bonding electrons paired up in the same orbital - a lone pair of electrons.
The following is multiple choice question (with options) to answer.
What type of bond forms by unpaired electrons from two atoms "matching up"? | [
"covalent bond",
"reactive bond",
"accretion bond",
"magnetic bond"
] | A | You have learned that a covalent bond forms when the electron clouds of two atoms overlap with each other. In a simple H 2 molecule, the single electron in each atom becomes attracted to the nucleus of the other atom in the molecule as the atoms come closer together. An optimum distance, equal to the bond length, is eventually attained, and the potential energy reaches a minimum. A stable, single covalent bond has formed between the two hydrogen atoms. Other covalent bonds form in the same way as unpaired electrons from two atoms “match up” to form the bond. In a fluorine atom, there is an unpaired electron in one of the 2p orbitals. When a F 2 molecule forms, the 2p orbitals from each of the two atoms overlap to produce the F−F covalent bond. The overlapping orbitals do not have to be of the same type. In a molecule of HF, the 1s orbital of the hydrogen atom overlaps with the 2p orbital of the fluorine atom (see Figure below ). |
SciQ | SciQ-2839 | homework-and-exercises, thermodynamics, work
Title: Doubt in thermodynamics pressure volume work done derivation Please tell me where i got wrong with my understanding here:
Consider a cylinder fitted with a frictionless and weightless piston having area of cross section $A$. Let it contain gas of volume $V$ and let the pressure of gas inside the cylinder be $P_{int} $. Let the pressure outside be $P_{ext} $.
Now if the external pressure is greater than internal pressure an unbalanced force will try to compress the piston, in the general derivation we take for small compression the force as $P_{ext} \cdot A$ which gives us the final small work done as $P \cdot dV$ but isn't this just due to outside force, the piston moves because of net unbalance force because of pressure from both sides and that means net force should be $F=(P_{ext}-P_{int}) \cdot A$ which gives us small work done as $\Delta P \cdot dV$, $\Delta P$ being the pressure difference between external and internal. The work done by the gas is given by $W= \int F \cdot dl$, which is $\int PA \cdot dl =\int P dV$. The reason it is not what you have stated is because you are using the net force acting on the piston, when in actuality the work done by the gas is just the product of the force exerted by the gas on the piston and the displacement of the piston in the direction of the force. What happens is that $P_{ext}$ does work given by $P_{ext} dV$. The gas, on the other hand, only does work $-P_{int} dV$.
The following is multiple choice question (with options) to answer.
When gas pressure-forces are used to move an object the work is done on the object by? | [
"expanding gas",
"contracting gas",
"kinetic energy",
"gravitational pull"
] | A | When gas pressure-forces are used to move an object then work is done on the object by the expanding gas. Work can be done on the gas in order to compress it. |
SciQ | SciQ-2840 | immunology, cancer, immunosuppression
Title: Normal cells and the immune system Normal or healthy cells have a natural ability to avoid being attacked by the immune system.
So if a cancer cell has all inherited 'strategies' for avoiding the immune system (that are from their earlier pre-cancerous states) does this make them hard to detect or be affected by the immune system. The development of cancer has various reasons. For example in more than 50% of tumors, p53 is mutated. p53 among other things regulates mitosis and forces the cell to arrest in a specific growth state if other systems detected a mutation in the DNA.
But in your special case we have to look at major histocompatibility complexes (MHCs) and NLRC5. There are two types of MHC, namely MHC class I and class II. MHC II presents mostly bacterial peptides to CD4+ T cells causing a immune response. However, MHC I presents viral peptides and peptides from your own body. These peptides are detected by CD8+ T cells which are cytotoxic T cells initializing apoptosis. Without these own peptides natural killer (NK) cells are activated because of a missing-self signal causing apoptosis, too.
The following is multiple choice question (with options) to answer.
A lymphocyte is the type of which cell involved in an immune system response? | [
"red blood cell",
"white blood cell",
"white brain cell",
"white immunity cell"
] | B | A lymphocyte is the type of white blood cell involved in an immune system response. You can see what a lymphocyte looks like, greatly magnified, in Figure below . Lymphocytes make up about one quarter of all white blood cells, but there are trillions of them in the human body. Usually, fewer than half of the body’s lymphocytes are in the blood. The majority are in the lymph, lymph nodes, and lymph organs. |
SciQ | SciQ-2841 | evolution, species
Title: Reasons why living fossils exist?
A living fossil is a living species (or clade) that
appears to be similar to another species otherwise known only from fossils,
typically with no close living relatives.
A living fossil is considered as a successful organism, which has made its way through many major extinction events. Also, the morphology of living fossils resemble some species of organisms which we know only through their fossil remains.
What is the reason for a particular type of species to become a living fossil; is the engineering of this particular species extraordinary, in that it can survive any selection process encountered thus far?
Is there not enough selection pressure exerted on this species in order to force it to change morphologically?
Have these organisms modified themselves, so that currently their morphology seems to be similar to a fossil organism? One part of your question betrays a serious error:
Is there not enough selection pressure exerted on this species in order to force it to change morphologically?
Actually the reverse is true; constancy of form can only be maintained in the presence of continuous selective pressure. It's just that this is stabilising selection that acts to maintain the existing form rather than push the organism to new morphologies. In fact, most selection acts in this manner. This shouldn't surprise you: organisms are typically well adapted to their environments so changes are more likely to reduce fitness than increase fitness.
It's also worth noting that although living fossils show little morphological change they can continue to show change at the molecular level at rates as high as, or higher than, other organisms - e.g. (May et al 2007; Cao et al 2013).
The following is multiple choice question (with options) to answer.
Most fossils form when a dead organism is buried in what? | [
"ash",
"soil",
"sediment",
"sand"
] | C | Most fossils form when a dead organism is buried in sediment. Layers of sediment slowly build up. The sediment is buried and turns into sedimentary rock. The remains inside the rock also turn to rock. The remains are replaced by minerals. The remains literally turn to stone. Fossilization is illustrated in Figure below . |
SciQ | SciQ-2842 | magnetic-fields, ferromagnetism
Title: Technical Term for Material That is Only Magnetic Next to A Magnet I was wondering what the technical term is for some metal(like a refrigerator door) that is not magnetic on its own like neodymium but when there is a magnet in its vicinity, it attracts to the magnet. Neodymium has a polarity but these metals don't have one, they just stick to a magnet. Is it called ferromagnetism? As far as I know there is no single term to refer to a material that is attracted by magnetism but not a magnet. Rather, there are terms that describe a material's magnetic behaviour regardless of its magnetized state.
There are a few versions. Ferromagnetic, paramagnetic, and diamagnetic.
Ferromagnetic is like iron it will be attracted to other magnets, but can also be magnetized and turned into a permanent magnet.
Paramagnetic and diamagnetic materials can't be turned into permanent magnets. The difference might be considered nitty gritty and I'm not qualified to comment.
But it sounds like you're asking for a specific term for a material that is ferromagnetic, but not currently magnetized. I don't know of one.
The following is multiple choice question (with options) to answer.
What do you call an object that attracts certain materials such as iron? | [
"electron",
"magnet",
"antenna",
"neutron"
] | B | A magnet is an object that attracts certain materials such as iron. All magnets have two magnetic poles and a magnetic field over which they exert force. Opposite magnetic poles attract each other, and like magnetic poles repel each other. |
SciQ | SciQ-2843 | 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.
Coral and the algae living inside of them have what type of relationship, since the algae relies on the coral to stay close to the water's surface? | [
"competitive",
"parasitic",
"symbiotic",
"peculiar"
] | C | Corals form large colonies in shallow tropical water. They are confined to shallow water because they have a symbiotic relationship with algae that live inside of them. The algae need sunlight for photosynthesis, so they must stay relatively close to the surface of the water to get enough light. Corals exist only as polyps. They catch plankton with their tentacles. |
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