source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-344 | waves, acoustics, frequency
Low frequencies really only get attenuated according to the inverse square law, but higher frequencies are attenuated more strongly.
3 - detecting sound
In order to detect sound, a membrane needs to be moved. This motion then has to somehow be conveyed to the nervous system, which is water-based and therefore has a very different acoustic impedance than air ($z_0 = \rho c$ - so when density increases by 1000x and speed of sound by 4x, you have a mismatch...). The mechanisms in the ear (tympanic membrane, malleus, incus, stapes, oval window, cochlea) is a beautiful piece of engineering to create something of an acoustic match, and works quite well over a range of frequencies. Unfortunately, for very low or very high frequencies, bit of that mechanism stop working so well - the finite mass (inertia) of the components makes them more reluctant to move at high frequencies. This again puts an upper limit on the frequency we can hear. However, the "amplification" that the entire organ provides is exquisite - as I computed in the answer linked above this means you can hear tiny, tiny vibrations.
4 - evolution
The human body is a wonderful machine, refined by aeons of evolution - "she who hears the approaching predator lives to procreate another day". The combination of "everything disturbs the air around it" and "we are designed to detect the slightest sound" is the answer to your question.
The following is multiple choice question (with options) to answer.
Which part of the ear amplifies the sound waves? | [
"cochlea",
"middle ear",
"ear canal",
"eardrum"
] | B | The outer ear catches sound waves and funnels them to the middle ear. The middle ear amplifies the sound waves and passes them to the inner ear. The inner ear changes the sound waves to electrical signals. The signals travel to the brain, which interprets the sounds. |
SciQ | SciQ-345 | virology, protein-interaction
Negative-stain transmission electron micrographs of the C. crescentus phage phiCbK and five phiCbK-like phages. All five exhibit Siphoviridae morphology and prolate heads. Scale bars are 100 nm.
The conical capsids of lentiviruses like HIV have a similar geometry to these corndog phage, except the two endcaps are asymmetric; with 7 pentons at one end and 5 at the other. If HIV was like many large icosahedral viruses and encoded different proteins for the pentons, arranging them correctly would be difficult. However, the current theory is that the overall geometry is imposed on the maturing HIV capsid, and CA protein simply changes into a pentameric arrangement where the local curvature of the immature lattice is too great for hexameric arrangement. From Unclosed HIV-1 Capsids Suggest a Curled Sheet Model of Assembly, referencing Nonequilibirum Assembly, Retroviruses, and Conical Structures:
Levandovsky and Zandi used tapered triangular prisms to represent CA units and were able to recapitulate spherical, conical, and tubular shapes.26 Tapering caused growing sheets to curve, and as the curved sheets grew, inclusion of pentamers became necessary to relieve accumulated stress. Opposing edges of the growing sheets eventually curled around toward each other and connected and then the top and bottom ends sealed. Conical shapes therefore emerged not as a result of template interactions or membrane enclosures but through simple nonequilibrium growth of elastic sheets.
The overall shape of the CA immature lattice before the conical core forms is guided by two forces that mimic the "scaffold" proteins used by other viruses. These are the outer membrane and the inner RNA payload, to which CA is stuck via the MA and NC subunits of the Gag polyprotein, respectively. This figure from Assembly and Architecture of HIV illustrates how the constraints of the membrane and RNA leave the Gag units organized in a way that allows the CA units to organize into the required shape once they are cleaved free:
The following is multiple choice question (with options) to answer.
The shape of a virus is determined by the type and arrangement of proteins in its what? | [
"anode",
"nuclei",
"capsid",
"enamel"
] | C | 22.1 Introduction Viruses are the smallest biological particle (the tiniest are only 20 nm in diameter). However, they are not biological organisms so they are not classified in any kingdom of living things. They do not have any organelles and cannot respire or perform metabolic functions. Viruses are merely strands of DNA or RNA surrounded by a protective protein coat called a capsid. Viruses only come to life when they have invaded a cell. Outside of a host cell, viruses are completely inert. Since first being identified in 1935, viruses have been classified into more than 160 major groups. Viruses are classified based on their shape, replication properties, and the diseases that they cause. Furthermore, the shape of a virus is determined by the type and arrangement of proteins in its capsid. Viruses pathogenic to humans are currently classified into 21 groups. Viruses can also attack bacteria and infect bacterial cells. Such viruses are called bacteriophages. |
SciQ | SciQ-346 | density, air, buoyancy
Title: Feeling of coldness in heights We know that due to buoyancy the cold air sinks and warm air floats above it due to it being less dense than cold air. Then why do we feel cold as we go to greater heights/hill stations and feel hot when we are in the normal surface of earth? This is because the air pressure changes significantly with height, and compression or expansion of a gas causes it to warm or cool. In a convective atmosphere, temperature differences cause air to rise in some places and descend in others. When it rises, it expands, and that causes it to cool. When air descends, it is compressed, and that causes it to warm.
(The compressive warming/cooling of gases is also why a bicycle tyre air pump gets hot when you use it, and how a refrigerator works.)
This warming and cooling effect stabilises the atmosphere against heat rising. If the rate of temperature change with height is less than a particular value called the adiabatic lapse rate (ALR), then the atmosphere is stable and warm air won't rise. ('Adiabatic' means that we assume there is no heat gained or lost from an air packet by radiation or conduction.) If the gradient exceeds the adiabatic lapse rate, then convection suddenly starts up again, the heat rises and reduces the gradient back down until, usually in a matter of minutes to a few hours, it once again equals the adiabatic lapse rate.
The adiabatic lapse rate in dry air is about $9.8$ K/km, so for every $1$ km you rise, the temperature drops $1$ K (= $1^\circ$C). However, in the presence of water vapour, there is an additional heating and cooling effect from the condensation or evaporation of water droplets (latent heat of condensation). This reduces the lapse rate down to around $6.5$ K/km, called the moist adiabatic lapse rate (MALR). This is the value the International Standard Atmosphere assumes for aviation purposes, and is generally a pretty accurate approximation, but there are variations from it depending on humidity and weather conditions. (In particular, at night or in the polar winters you can get temperature inversions when surface heating stops and cold air pools near the surface.)
The following is multiple choice question (with options) to answer.
What is the rising and sinking of warm and cooler material called? | [
"convection",
"diffusion",
"conveyance",
"depression"
] | A | Hot lower mantle material rises upward ( Figure below ). As it rises, it cools. At the top of the mantle it moves horizontally. Over time it becomes cool and dense enough that it sinks. Back at the bottom of the mantle, it travels horizontally. Eventually the material gets to the location where warm mantle material is rising. The rising and sinking of warm and cooler material is called convection . |
SciQ | SciQ-347 | neuroscience, brain, neurophysiology, development, synapses
Title: How do neurons find each other? Neurons form complicated networks in brains, but their connections can't be random (at least not entirely). Brains function similarly among all members of individual species, and that functionality is largely dependent on neuron organization. Furthermore, various brain regions have predictable functions, and there are even parts of the brain where specific cells carry out specialized functions (place cells are an interesting example).
Great! We know neurons can organize into very complex networks, but how? They need to find each other, somehow.
The best I can guess is that either:
Neurons find other target neurons with specific chemical signals.
Neurons don't "find" each other, exactly, but grow in predetermined shapes from from set locations. In this case, the connections would simply be due to neurons bumping into each other as they grow in their predetermined paths.
Or both.
In the first case, there would be a mechanism for searching each other out. In the second, there would be a mechanism for staying in one spot (and growing from there). What are the names of said mechanisms? How do I find out more about them? Q: We know neurons can organize into very complex networks, but how?
The answer is your first guess: Neurons find other target neurons with specific chemical signals.
Q: What are the names of said mechanisms?
This process is called axon guidance, by which the growth cones of developing axons are directed to reach their targets. This process depends upon a slew of cellular and molecular cues. The first axons to grow in any particular brain region are called pioneer axons and are the most dependent upon these cues. Later axons are able to follow (and diverge from) previous axons by the interaction of cell adhesion molecules on their surfaces. Dendritic development is also important for your question, but dendrites tend not to travel as far.
Here are some of the molecules that we know to participate in axon guidance:
Cell adhesion molecules and substrate adhesion molecules, including IgSF CAMs and cadherins
Some chemokines, e.g. CXCL12
Netrins, ephrins, and semaphorins
Slits, via the Slit-Robo cell signaling pathway
Developmental morphogens, e.g. Wnts and Hedgehog
The following is multiple choice question (with options) to answer.
What is a group of connected cells that have a similar function within an organism called? | [
"organ",
"colony",
"tissue",
"nucleus"
] | C | A tissue is a group of connected cells that have a similar function within an organism. More complex organisms such as jellyfish, coral, and sea anemones have a tissue level of organization. For example, jellyfish have tissues that have separate protective, digestive, and sensory functions. |
SciQ | SciQ-348 | atomic-physics
This question was also asked on chem.SE so I reposted my answer here. I'm sure someone will correct any mistake I made.
The following is multiple choice question (with options) to answer.
The number of what subatomic particles can vary between atoms of the same element? | [
"protons",
"neurons",
"electrons",
"neutrons"
] | D | As stated earlier, not all atoms of a given element are identical. Specifically, the number of neutrons in the nucleus can vary for many elements. As an example, naturally occurring carbon exists in three forms, which are illustrated in Figure below . |
SciQ | SciQ-349 | atmosphere, geophysics, water, magnetosphere
Title: How much water is the atmosphere losing to space? Up until recently, I was under a (wrong) impression that the amount of planetary cumulative water resources was finite as I believed its escape from the atmosphere was impossible. I believed that, unlike other planetary resources, it was impossible to "waste" water as any waste would simply recycle itself in nature, i.e. municipal waste would be treated and get into the oceans from where it would eventually evaporate and precipitate back into continental waters renewing our water supply.
Recently, I learned I was wrong and that there is such a phenomenon called sequestration and that it is indeed possible for the total water resources on the planet to vary.
I am curious if there are metrics on how much water the planet has been losing (or gaining in case of a reverse phenomenon). Additionally, is there anything we can do to reduce this effect?
This article says that we've lost a quarter of our water total but I was looking for more granular statistics. It is not actual water what is lost to space, because in the high atmosphere water usually dissociate into other molecules or ions. The oxygen ion outflow is frequently assumed to be a proxy for the loss of water from the planetary atmosphere. In terms of global outflow rates for the Earth the rate varies from $10^{25}$ to $10^{26} s^{-1}$, depending on geomagnetic activity (reference).
On the poster of the reference (sent to me by the author) we can read:
If we assume oxygen corresponds to water loss (self-regulation, Hunten
and McElroy [1970]), then an oxygen loss rate of ~$10^{25} s^{-1}$
corresponds to ~300 $\text{g s}^{-1}$ of water loss. Over the age of the
solar system (4.5 billion years ~ $1.4 \times 10^{17}$ s) this loss
rate gives $4.2 \times 10^{19}$ g of water.
The following is multiple choice question (with options) to answer.
Water is recycled constantly through which system? | [
"the habitat",
"the troposphere",
"the hydropshere",
"the ecosystem"
] | D | Water is recycled constantly through the ecosystem. That means any water you drank today has been around for millions of years. You could be drinking water that was once drunk by George Washington, the first humans, or even the dinosaurs. |
SciQ | SciQ-350 | 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.
The process in which organ systems work to maintain a stable internal environment is called what? | [
"homeostasis",
"consciousness",
"ketosis",
"thrombosis"
] | A | The process in which organ systems work to maintain a stable internal environment is called homeostasis . Keeping a stable internal environment requires constant adjustments. Here are just three of the many ways that human organ systems help the body maintain homeostasis:. |
SciQ | SciQ-351 | planets
Title: What is Venus's core made of? As we all know Venus's surface is so hot that it can probably melt lead.
What would be in it's in core?
Is it in the liquid or solid state?
What would be it's temperature?
How many cores does it have? Scientists think that Venus' internal structure is somewhat like Earth's, as shown below:
In other words, a crust, mantle, and core. The evidence points to Venus not having plate tectonics like Earth or a magnetic field. Venus also probably has a partially molten core, like Earth, as it has been cooling at the same rate.
Honestly, we don't know much else. We can tell you the atmosphere composition, but we don't know what the core is made up of. The Venus Wikipedia page (here) is very helpful and has more information and explanations of why we don't know these things.
The following is multiple choice question (with options) to answer.
What do scientist's believe mercury's core is mostly made of? | [
"helium gas",
"melted iron",
"water",
"quicksilver"
] | B | Figure below shows a diagram of Mercury’s interior. Mercury is one of the densest planets. Scientists think that the interior contains a large core made mostly of melted iron. Mercury's core takes up about 42% of the planet's volume. Mercury's highly cratered surface is evidence that Mercury is not geologically active. |
SciQ | SciQ-352 | the-sun, solar-system, earth, star-formation, planetary-formation
Earth Composition
Iron 32.1%
Oxygen 30.1%
Silicon 15.1%
Magnesium 13.9%
Sulfur 2.9%
Nickel 1.8%
Calcium 1.5%
Aluminum 1.4%
Other 1.2%
A couple things I notice. The sun is quite homogenous compared to earth! It is mostly composed of just two elements whereas on earth no single element makes up more than 32% of the planet's mass.
Also, there is extremely little overlap in the elements: hydrogen and helium are the only game in town on the sun, but are nearly nonexistent on earth.
This makes me very curious! What aspect of the process of the formation of the solar system was responsible for essentially segregating these elements? Is it simply that the heavier elements were "burned" away in the hotter environment of the sun, or is there some other explanation? The composition of the Sun is close to the composition of the universe as a whole. It's the Earth that's the outlier. If you look up the elemental composition of the universe as a whole, you'll see numbers for hydrogen and helium almost identical with the ones for the Sun. Theory can predict the elemental ratios. The universe started out as entirely hydrogen, and helium and a few light elements like lithium were created in the big bang. Heavier elements like oxygen and iron were made in stars, and elements heavier than iron are largely from supernovae. But enough background, let's answer your question.
Earth, along with the other planets, formed from the same cloud of dust and gas as the Sun. The cloud started out with the same elemental composition as the Sun. The cloud collapsed under the force of gravity, and somehow chunks of material (called planetesimals) started to coalesce into planets (nobody is really certain how this process worked). The proto-Sun started to emit light and warm up the surroundings. The regions closer to the Sun, where the Earth was forming, got hot enough that light elements like hydrogen evaporated from the planetesimals. Left behind were heavier elements like oxygen, silicon (which make up most rocks) and iron. The lighter elements ended up further out, which is why Jupiter has a hydrogen-rich atmosphere.
The following is multiple choice question (with options) to answer.
What material comprises the sun and other stars, as well as lightning and the northern lights? | [
"plasma",
"gas",
"gamma",
"aurora"
] | A | The sun and other stars consist of plasma. Plasma is also found naturally in lightning and the northern and southern lights. Human-made plasma is found in fluorescent lights, plasma TV screens, and plasma spheres. |
SciQ | SciQ-353 | blood-circulation, kidney
Title: Why does glomerulus don't allow white blood cells to leave? The glomerulus in nephrons are just a ball of capillaries, so why can't it allow the white blood cells to squeeze though the epithelial cells into Bowman's capsule just like the formation of tissue fluid in other capillaries by filtration? Red blood cells, White blood cells, platelets and proteins with large molecular weight cannot pass through the podocyte and fenestrations in glomerular capillary, but small molecules like water, salts and sugars are filtered out as part of urine.
As these cells and proteins are large to cross through this filter, they remain in the capillary and create osmotic pressure within the capillary. Bowman’s space has osmotic pressure approximately zero. So, only hydrostatic pressure works in this state and help in movement of fluid across the capillary wall.
Via: https://opentextbc.ca/anatomyandphysiology/chapter/25-5-physiology-of-urine-formation/
The following is multiple choice question (with options) to answer.
The function of which organ is to filter blood and form urine? | [
"gallbladder",
"kidneys",
"lungs",
"liver"
] | B | |
SciQ | SciQ-354 | newtonian-mechanics, newtonian-gravity, celestial-mechanics
Title: Attraction between two objects in the universe. The resulting number of forces between them Right now I am studying Newton's Law of Universal Gravitation and I already learned his Third Law. It is said that there is an action-reaction pair between the falling apple and the Earth which results in the apple being attracted to the Earth and Earth to the apple at the same time and with the same force. But if we imagine bigger objects like Earth and Mars in the close distance, will it mean that Earth attracts to Mars and Mars is being attracted to the Earth with the gravitational force of Earth and at the same time Mars attracts to Earth and Earth to Mars because of Mars gravitational force. So as a result I counted 4 forces between two objects. Is it correct or not, and please explain why :) There's only the one gravitational interaction. You can describe it however many ways you like, but the physical interaction is only happening once.
If you want to know how two objects will move because of a force between them, relative to a distant inertial observer, calculate the change of their relative velocity by picking whatever frame measures the acceleration due to gravity that you want to integrate over time, then conserve momentum in the distant inertial frame.
For example: Bob and Alice are standing together on some frictionless ice. Bob (mass $m_B$) pushes on Alice (mass $m_A$) such that Alice has a velocity of $v$ relative to Bob. Conserve momentum $P_0$ in the frame in which you want to measure Alice's and Bob's velocity. (If this is the frame in which Alice and Bob were initially standing still, $P_0 = 0$.)
$P_0 = m_A v_a + m_Bv_b$
$v = v_a - v_b$
Solve for $v_a$ and $v_b$ in terms of $v, m_A, m_B, P_0$.
The following is multiple choice question (with options) to answer.
The attraction between all objects in the universe is known as ______. | [
"variation",
"magnetism",
"electricity",
"gravity"
] | D | All objects in the universe have an attraction to each other. This attraction is known as gravity ( Figure below ). The strength of the force of gravity depends on two things. One is the mass of the objects. The other is the distance between the objects. As an object's mass increases, the attraction increases. As the distance between the objects increases, the attraction decreases. |
SciQ | SciQ-355 | fluid-dynamics, friction, drag, flow, viscosity
Title: Friction in a fluid when an object is moving in a fluid(air for example), the air will resist the object's movement: molecules of the air will collide with the surface of the object (no slip condition) and then we will have many layers of fluid "above" the surface of the object due to viscosity of the fluid. My question is: are the layers responsible for the friction between the air and the solid or it is just to the molecules that collide at the surface of the object or both? Tried to comment on question, need 50 rep. (why??)
I believe what you are referring to is viscosity in laminar flow. If I recall correctly, non-laminar flow is a precondition for turbulence, but I believe you can have viscosity which is not turbulent.
Is this the direction you had in mind?
EDIT:
Fluid molecules far away from the object will feel nothing.
Fluid molecules in the object's path will be pushed aside (and exert an equal and opposite force on the object).
As fluid molecules are pushed aside, they come into interaction with fluid close to the object path, and secondary interactions ensue.
So I think the answer to your question is: Both. Particles not in the object's path affect it indirectly, by causing those molecules directly in its path to escape less quickly. Imagine how the fluid density and molecular mass will affect the situation.
The following is multiple choice question (with options) to answer.
Friction causes the molecules on rubbing surfaces to move faster, which produces what? | [
"precipitation",
"life",
"cold",
"heat"
] | D | You know that friction produces heat. That’s why rubbing your hands together makes them warmer. But do you know why the rubbing produces heat? Friction causes the molecules on rubbing surfaces to move faster, so they have more heat energy. Heat from friction can be useful. It not only warms your hands. It also lets you light a match (see Figure below ). On the other hand, heat from friction can be a problem inside a car engine. It can cause the car to overheat. To reduce friction, oil is added to the engine. Oil coats the surfaces of moving parts and makes them slippery so there is less friction. |
SciQ | SciQ-356 | 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 cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents what? | [
"exhaustion",
"dehydration",
"extinction",
"Respiration"
] | B | Most prokaryotes have a peptidoglycan cell wall and many have a polysaccharide capsule (Figure 4.5). The cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration. The capsule enables the cell to attach to surfaces in its environment. Some prokaryotes have flagella, pili, or fimbriae. Flagella are used for locomotion. Pili are used to exchange genetic material during a type of reproduction called conjugation. Fimbriae are used by bacteria to attach to a host cell. |
SciQ | SciQ-357 | evolution, zoology
Title: Why are hens so different from other birds? Hens lay many eggs during their lifetime (at least, I don't know of one which can lay more eggs) and they can't fly. Compared to other domestic animals it seems to me they are the least capable of defending themselves or escape if it comes to be left alone in open wild. What is their evolutionary story? Domestic organisms are bred to serve specific purposes for humans. Sheep are bred to produce wool; Cows are bred to provide meat and milk for human consumption; dogs are bred for service and companionship. Since domestic animal do need to survive in the wild in order to reproduce (ignoring feral animals, which is an interesting topic by itself), most of the other aspects of that animal relevant to its survival tend to be minimized.
So one could just as easily point out that there is no other animal that produces as much wool as a sheep, and yet producing copious amounts of wool isn't particularly useful to the animal itself (i.e. other than the fact that humans will tend to select good wool producers for breeding). So sheep are not particularly good at surviving in the wild, and yet they are incredibly successful as a species and are widely distributed, thanks to humans.
In short, domestic hens evolved to produce many eggs in their lifetime because over the past millennia since humans have started keeping them as livestock, humans tended to preferentially breed those individuals which produced more eggs and to eat those individuals which did not. Chickens tended to be kept in pens and guarded by humans or other animals, so the ability to defend themselves or flee from danger was not important to their survival, and in fact, those that did attack their handlers or escape were probably less likely to be bred.
This process is known as selective breeding or artificial selection.
The following is multiple choice question (with options) to answer.
What's another term for egg-laying mammals? | [
"amphibians",
"monotremes",
"herbivores",
"viviparus"
] | B | There are very few living species of monotremes, or egg-laying mammals. They include the echidna and platypus, both pictured in Figure below . Monotremes are found only in Australia and the nearby island of New Guinea. |
SciQ | SciQ-358 | evolution, terminology, classification
Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time.
Any node in a (fully bifurcating) tree that is an ancestor to more than two tips will necessarily contain tips that are also descended from some other node.
OP is correct that "there is a common ancestor at some point," and there is strong evidence that all cellular life arose by common descent from our most recent common ancestor.
In practice, the term is usually limited by context. For example, many more relevant comparisons can be made between roses and apples, than between roses and dogs, even though the ancestor of animals and plants did once exist. In a conversation about energy procurement it wouldn't make sense to reference the common descent between roses and dogs; but in a conversation about, say mitosis, it might.
The term "related" suffers similar ambiguity.
As the figure shows, two species can share many "common ancestors," so it may be necessary to specify the "most recent common ancestor." In the figure, both A and B are common ancestors of 1 and 2, but A is their most recent common ancestor.
B is the most recent common ancestor of 1,3, 2,3, and 1,2,3.
The thick black line coming down from B in the figure represents the connection to B's ancestors. All of those ancestors are common ancestors of 1,2,3, but none are the most recent common ancestor of 1,2,3.
The most recent common ancestor of cellular life is the last universal common ancestor.
OP may want to review the term clade for a slightly more precise way to talk about related species. A clade is a group composed of an ancestor plus all and only its descendants.
In the figure:
1 and 2 form a clade with A.
1, 2, 3, A, and B form a clade.
1 and 3 (excluding 2) do not form a clade.
The following is multiple choice question (with options) to answer.
What code is the same in all living things and shows that all organisms are related by descent from a common ancestor? | [
"descendant",
"intrinsic",
"genetic",
"biochemical"
] | C | The genetic code is the same in all living things. This shows that all organisms are related by descent from a common ancestor. |
SciQ | SciQ-359 | cellular-respiration
Title: Do cold blooded animals generate any heat? In explaining energy and work to an 8 year-old I said that all conversion of energy generates heat as a by-product. For example, cars generate heat in their engines and running generates heat in our bodies. Then the 8 year-old said, except for cold-blooded animals.
So my question is, do cold-blooded animals generate any heat in their conversion of stored energy (food, fat, etc) into motion? If they generate heat, why are they cold-blooded? They do generate heat. They just do not SPEND energy specifically on heating their bodies by raising their metabolisms. This is a form of energy conservation. The metabolic rate they need to live is not nearly enough to heat their bodies.
An example of spending energy to heat the body is seen in humans shivering. Here muscle is activated not for its usual purpose, but to function as a furnace. "Warm-blooded" and "cold-blooded" is somewhat a misnomer. The correct way to think of it is...
Endotherm or ectotherm. Does the heat primarily come from within (endo) or from the surroundings (ecto). Endothermic animals include mammals. Most of their body heat is generated by their own metabolisms. Ectothermic animals include reptiles and insects. They absorb most of their body heat from the surroundings. This is not the same as saying they let their body temperature fluctuate with their surroundings, some avoid this by moving around to accomodate themselves.
Homeotherm or poikilotherm. Homeotherms want to maintain homeostasis for their body temperatures. They don't want it to change. Poikilotherms do not exhibit this behaviour, instead their body temperatures vary greatly with the environment.
We can have endotherm poikilotherms, such as squirrels, who let their body temperature drop while hibernating. Endotherm homeotherms, such as humans, where temperature is constant by means of complex thermoregulation. Ectotherm homeotherms, such as snakes (moving into shadow or into the sun to regulate temperature), and ectotherm poikilotherms, such as maggots.
The following is multiple choice question (with options) to answer.
All animals that derive energy from food are classified as what? | [
"paleotrophs",
"heterotrophs",
"heliotrophs",
"lifeforms"
] | B | Figure 15.2 All animals that derive energy from food are heterotrophs. The (a) black bear is an omnivore, eating both plants and animals. The (b) heartworm Dirofilaria immitis is a parasite that derives energy from its hosts. It spends its larval stage in mosquitos and its adult stage infesting the hearts of dogs and other mammals, as shown here. (credit a: modification of work by USDA Forest Service; credit b: modification of work by Clyde Robinson). |
SciQ | SciQ-360 | enzymes, biotechnology
Title: Can any enzyme be produced? After reading about how recombinant insulin is produced, the following question occured to me. Does the current level of technology allow any enzyme to be produced in a similar way?
As I see, producing amino acid sequences is not an issue. A possible difficulty I can think of is modifying the amino acid chains. In the case of insulin the problem has been solved. Are there some generally applicable solutions available to this problem, or do they have to be researched on a case-by-case basis?
Are there any other limitations to producing enzymes?
EDIT: As pointed out by P. Jay, the question might seem to suggests that insulin is an enzyme which it is not. No, not all enzymes (or other proteins for that matter) can be obtained in functional form by recombinant expression with today's methods. As you suspect, problems arise when complex post-translational modifications are necessary to obtain the correct function.
Direct modifications to peptide is one potential problem. Some of these can be resolved by expression the recombinant protein in the right cell type: for example, expression in a bacteria may not provide the right modification, but expression in yeast or a mammalian cell might. CHO cells are a common mammalian cell type used in such cases; antibody production in hybridomas is another well-known example. But there are plenty of posttranslational modifications that are poorly understood, and most likely there are still many completely unknown types; new ones are still being discovered.
Another posttranslational event is association with cell membranes. Membrane proteins (including membrane-embedded enzymes, for example in lipid metabolism) can be very difficult to express properly, as not only the peptide but some surround membrane structure must be reproduced in the expression system to obtain correct function. This is also a major hurdle in obtaining structures for membrane proteins, notably many cell surface receptors. This article is a summary of the current challenges and unsolved problems in this area. And you can imagine the problems with proteins that need to form large superstructures to be functional --- large protein polymers, respiratory chain complexes, ribosomes, DNA replication forks ...
So there is no universal method; all proteins are different, some are easy to express, some are extremely hard.
The following is multiple choice question (with options) to answer.
Through which process is the human gene for insulin placed into bacteria? | [
"transformation",
"absorption",
"migration",
"mutation"
] | A | Through the process of transformation, the human gene for insulin is placed into bacteria. The bacteria then use that gene to make a protein. The protein can be separated from the bacteria and then used to treat patients. The mass production of insulin by bacteria made this medicine much more affordable. |
SciQ | SciQ-361 | botany, plant-physiology, ecology, virology, host-pathogen-interaction
Note about symbiosis - comes in reaction to @Gerhard's comment
Different authors use the word symbiosis differently. From wikipedia:
The definition of symbiosis is controversial among scientists. Some believe symbiosis should only refer to persistent mutualisms, while others believe it should apply to any type of persistent biological interaction (i.e. mutualistic, commensalistic, or parasitic).4 After 130+ years of debate,5 current biology and ecology textbooks now use the latter "de Bary" definition or an even broader definition (i.e. symbiosis = all species interactions), with the restrictive definition no longer used (i.e. symbiosis = mutualism)
The following is multiple choice question (with options) to answer.
What is a symbiotic relationship in which both species benefit? | [
"inorganic",
"mutualism",
"parasitism",
"detrimental"
] | B | Mutualism is a symbiotic relationship in which both species benefit. An example of mutualism involves goby fish and shrimp (see Figure below ). The nearly blind shrimp and the fish spend most of their time together. The shrimp maintains a burrow in the sand in which both the fish and shrimp live. When a predator comes near, the fish touches the shrimp with its tail as a warning. Then, both fish and shrimp retreat to the burrow until the predator is gone. From their relationship, the shrimp gets a warning of approaching danger. The fish gets a safe retreat and a place to lay its eggs. |
SciQ | SciQ-362 | biochemistry
Another important difference with respect to resulting polymers formed from these bonds - polysaccharides, in contrast to proteins and nucleic acids, form branched as well as linear polymers
α-Amylose is a linear polymer of several thousand glucose residues linked by α(1 >4) bonds. Note that although α-amylose is an isomer of cellulose, it has very different structural properties. This is because cellulose’s β-glycosidic linkages cause each successive glucose residue to flip 180° with respect to the preceding residue, so that the polymer assumes an easily packed, fully extended conformation.
Peptide bond
The resulting linkage formed when α-amino acids polymerize, through the elimination of a water molecule is known as a peptide bond (sometimes called an amide bond):
Peptide bond (shown in red)
Glycosidic bonds between monosaccharide units are the basis for the formation of oligosaccharides and polysaccharides.
The glycosidic bond is therefore the carbohydrate analog of the peptide bond in proteins. (The bond in a nucleoside linking its ribose residue to its base is also a glycosidic bond)
The following is multiple choice question (with options) to answer.
What is the term for longer chains of monosaccharides ? | [
"proteins",
"hydrocarbons",
"polysaccharides",
"oligosaccharides"
] | C | Longer chains of monosaccharides are referred to as polysaccharides . Starch, glycogen, and cellulose are three extremely common polysaccharides made entirely out of glucose molecules. The differences lie in the types of bonds between the glucose units and the extent of branching in the carbohydrate chain. Starch is found in plants and is consumed as part of our diet. Glycogen is made by the body and is a storage form of glucose for when the cells need extra energy. Cellulose is another long-chain polysaccharide found in plants. Unlike starch and glycogen, the human body cannot break cellulose down into molecules of glucose. Although cellulose does not have any nutritional value in terms of calories, it is a major component of dietary fiber, which has other digestive benefits. |
SciQ | SciQ-363 | electrostatics, charge, potential, potential-energy, voltage
Title: When should I use $U=QV$ as opposed to $U=\frac{QV}2$? In my electricity course, I am having trouble understanding the difference in between $U=QV$ and $U=\frac{QV}2$ when talking about energy stored in a system.
My idea was that when the potential is created by the charges arriving to the system, we would use $U=\frac{QV}2$, as the charges themselves are building the system potential as they arrive; on the other hand, when a potential is imposed from the outside, we would use $U=QV$. You use $U=QV$ when V is being supplied by charges other than the one in your formula (we call these "external"). When you're talking about the the amount of energy stored in charges and the voltage is supplied by the same charges your asking about, then you use $U=\frac{QV}{2}$.
In either case, the correct formula is $U=\int_0^Q V \operatorname{d}q$. This is just a mathematical way of saying, "Add up the energy from building up the charge piece by piece (each piece is $\operatorname{d}q$)." When $V$ isn't changed by the charges you're adding, then it's a constant that can come outside of the integral, giving you $U=QV$. When you're adding charges to a capacitor, on the other hand, then the voltage and charge are related by $V= q/C$, and when you put that into the formula and do the integral, you get $U=\frac{Q^2}{2C} = \frac{QV}{2}$. For another example, if you can set up the situation somehow to make $V=kq^2$ then the energy would be $U=k \frac{Q^3}{3}$.
The following is multiple choice question (with options) to answer.
Electrical potential energy can be described by the equation pe = qv, where q is the electric charge and v is what? | [
"voltage",
"wavelength density",
"frequency",
"amplitude"
] | A | This equation is based on the conservation of energy and conservation of charge. Electrical potential energy can be described by the equation PE = qV , where q is the electric charge and V is the voltage. Thus the energy supplied by the source is qV , while that dissipated by the resistors is. |
SciQ | SciQ-364 | lo.logic, ds.data-structures, circuit-complexity, randomized-algorithms, db.databases
Next, one of the traditional principles of logic is ex falso quodlibet: that is, $\bot \to A$ holds for all propositions $A$ — if you assume false, everything follows. If you are thinking about the possibility of believing false things (for example, someone has lied to you, or you have a database with errors in it), this is potentially disastrous. In practical reasoning, you don't want to derive a contradiction and then happily believe everything — you want to find a contradiction, and deduce that you have made an error.
The study of what happens to logic when you drop ex falso is called relevance logic, so named because the idea is that you should only make inferences from hypotheses that are relevant to the conclusion. Again, see the SEP article on relevance logic for more. Also, you might wish to tolerate contradictions in your logic system. In this case, the thing to look at is paraconsistent logic.
Next, you mentioned a worry that individual inferential steps might not be completely reliable. In traditional logic we accept the unrestricted use of modus ponens. That is, inside a proof, if we know $A \to B$ and $A$ hold, we can conclude $B$ holds, any number of times. If you start to consider the idea that individual inferential steps might not be completely reliable, then you might think that proofs depending on long chains of inferential steps are "less reliable" than short ones.
It's a bit tricky to formalize this, but it is one of the (several) motivations for ultrafinitism. See Mannucci and Cherubin's draft Model Theory of Ultrafinitism I: Fuzzy Initial Segments of Arithmetic, for an exploration of this idea (and some explanation of its connection to fuzzy logic).
The following is multiple choice question (with options) to answer.
What are broad explanations that are widely accepted as true? | [
"informal theories",
"scientific theories",
"scientific hypotheses",
"scientific experiments"
] | B | Scientific theories are broad explanations that are widely accepted as true. This is because they are supported by a great deal of evidence. |
SciQ | SciQ-365 | thermodynamics, evaporation, gas, liquid-state
On the water surface, knowing the temperature, we can estimate the vapor pressure and vapor mixture fraction. Then there will be an diffusion process for the water vapor to move out and for the ambient air to move in. Because the water surface doesn't allow the air to further move, a circulation forms. When the water vapor moves out, the water vapor pressure drops, so more liquid water evaporates to fill up the loss of water vapor. The evaporation associates latent heat so water surface area temperature drops (you may see dew on the bowl wall). Then a heat transfer process starts which may initiate water circulation as well.
As this is complex, doing test might be a quick way to get the K value if you assume it is a constant, which is questionable.
The following is multiple choice question (with options) to answer.
What process is at work when warm air or water rises, and cool air or water sinks? | [
"convection",
"evaporation",
"moisture",
"radiation"
] | A | Warmer, lighter air is more buoyant than the cooler air above it. So the warm air rises. The cooler air is denser than the air beneath it. So it sinks down. This is convection: warm air rises, and cool air sinks. Warm fluids can undergo convection as well. This is described in the chapter Plate Tectonics . |
SciQ | SciQ-366 | newtonian-mechanics, forces, rotational-dynamics, reference-frames, torque
Title: What is the explanation of greater torque having greater "rotatory effect" on a stationary body? Why does moving a constant force further from center of mass (and thus increasing torque) increase angular acceleration? I know that the explanation for my question is that during the same angular displacement the same amount of force would be exerted over longer (linear) displacement, hence doing more work, and since conservation of energy is a thing the angular acceleration would increase, but it (at least for me) doesn't explain why moving a weight on a balanced beam makes it move (because when it is not yet moving, no work is being done and I can't mathematically prove that it would move). I used to ask myself a similar question: How does a load at one end of a lever know how far away along the lever another force is being exerted? Forgive the anthropomorphic phrasing, but I hope you get my drift.
I solved my problem by realising that the lever had to have some internal structure. I considered the case of a lever of length 6$a$, pivoted at a point one third of the way along. I envisaged a lever in the form of a pin-jointed lattice of thin weightless struts and ties. The bottom of the lever is a thin horizontal rod of length 6$a$, resting on the pivot. A distance $a$ above the bottom rod is another thin horizontal rod. Between the two rods are 6 rods of length $\sqrt 2 a$, angled at 45°, each at 90° to its neighbour(s), to form a lattice running from one end of the bottom rod to the other. Two of the angled rods are one side of the pivot; the other four are on the other side; the top horizontal rod needs to be only $4a$ long.
You will find simply by applying force resolution at each joint that if a force $W$ is applied downwards at the end of the long arm of the lever, a force $2W$ is needed at the end of the short arm, in order to have equilibrium.
I then convinced myself that this result is independent of the particular internal structure chosen. This is almost certainly a very eccentric method of establishing the law of the lever (principle of moments) but I found it instructive and convincing!
The following is multiple choice question (with options) to answer.
If force is applied further away from a pivot point, than what kind of acceleration will be greater? | [
"parameters",
"rectangular",
"angular",
"circular"
] | C | 10.3 Dynamics of Rotational Motion: Rotational Inertia If you have ever spun a bike wheel or pushed a merry-go-round, you know that force is needed to change angular velocity as seen in Figure 10.10. In fact, your intuition is reliable in predicting many of the factors that are involved. For example, we know that a door opens slowly if we push too close to its hinges. Furthermore, we know that the more massive the door, the more slowly it opens. The first example implies that the farther the force is applied from the pivot, the greater the angular acceleration; another implication is that angular acceleration is inversely proportional to mass. These relationships should seem very similar to the familiar relationships among force, mass, and acceleration embodied in Newton’s second law of motion. There are, in fact, precise rotational analogs to both force and mass. |
SciQ | SciQ-367 | kinetic-theory
Title: What is the kinetic energy of one molecule of a polyatomic gas? According to Kinetic theory, the kinetic energy of one molecule of gas is 3/2kT. Is this true for diatomic and polyatomic gases as well?
I've read that a diatomic gas has 5 degrees of freedom (3 translational +2 rotational), and according to the Law of Equipartition of Energy, each degree of freedom contributes an energy of 1/2kT. So, shouldn't the kinetic energy of a diatomic gas like Chlorine actually be 5/2kT?
Or maybe the equation K.E. = 3/2kT only takes traslation motion into account and the K.E. they are talking about is actually translation one. Please tell me. Kinetic theory assigns a degree of freedom to every quadratic term involving momentum (linear, rotational/angular, vibrational) and every quadratic term involving the cartesian co-ordinates appearing in the expression for the total energy for a molecule.
The Equipartition of Energy theorem then says that for a system in thermal equilibrium, each degree of freedom has an average energy of $k_BT/2$, where $T$ is the absolute temperature and $k_B$ is Boltzmann's constant.
If a molecule has $f$ degrees of freedom then the total energy of a molecule
is
$$E_{molecule} = \frac{f}{2}k_BT\,.
$$
However, there is a problem since each degree of freedom a molecule can possibly possess does not always contribute to its energy. This is because the contribution by the degrees of freedom to the energy of a molecule depends on the temperature of the gas.
The following is multiple choice question (with options) to answer.
The kinetic-molecular theory as it applies to gases has how many basic assumptions? | [
"two",
"five",
"seven",
"four"
] | B | The kinetic-molecular theory as it applies to gases has five basic assumptions. |
SciQ | SciQ-368 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
During photosynthesis, what is energy from the sun converted to after entering a plant? | [
"Carbon",
"Proteins",
"chloride",
"glucose"
] | D | Cellular respiration and photosynthesis are direct opposite reactions. Energy from the sun enters a plant and is converted into glucose during photosynthesis. Some of the energy is used to make ATP in the mitochondria during cellular respiration, and some is lost to the environment as heat. |
SciQ | SciQ-369 | organic-chemistry, acid-base, hydrogen-bond
Title: Which dicarboxylic acid has the most acidic hydrogen?
Which of the following acids (maleic, fumaric, succinic, or malonic) has the most acidic hydrogen?
The following is multiple choice question (with options) to answer.
Formic acid is found in the secretions of? | [
"acid rain",
"sweat glands",
"stinging ants",
"stomach acid"
] | C | where R can be an alkyl group, an aryl group, or a hydrogen atom. The simplest example, HCO2H, is formic acid, so called because it is found in the secretions of stinging ants (from the Latin formica, meaning “ant”). Another example is acetic acid(CH3CO2H), which is found in vinegar. Like many acids, carboxylic acids tend to have sharp odors. For example, butyric acid (CH3CH2CH2CO2H), is responsible for the smell of rancid butter, and the characteristic odor of sour milk and vomit is due to lactic acid [CH3CH(OH)CO2H]. Some common carboxylic acids are shown in Figure 2.21 "Some Common Carboxylic Acids". where R can be an alkyl group, an aryl group, or a hydrogen atom. The simplest example, HCO2H, is formic acid, so called because it is found in the secretions of stinging ants (from the Latin formica, meaning “ant”). Another example is acetic acid(CH3CO2H), which is found in vinegar. Like many acids, carboxylic acids tend to have sharp odors. For example, butyric acid (CH3CH2CH2CO2H), is responsible for the smell of rancid butter, and the characteristic odor of sour milk and vomit is due to lactic acid [CH3CH(OH)CO2H]. Some common carboxylic acids are shown in Figure 2.21 "Some Common Carboxylic Acids". |
SciQ | SciQ-370 | stereochemistry, history-of-chemistry, drugs, medicinal-chemistry, pharmacology
The difference between two enantiomers of a drug is illustrated below using a hypothetical interaction between a chiral drug and its chiral binding site. In this case, one enantiomer is biologically active while the other enantiomer is not. The portions of the drug labeled A, B, and C must interact with the corresponding regions of the binding site labeled a, b, and c for the drug to have its pharmacologic effect. The active enantiomer of the drug has a 3-dimensional structure that can be aligned with the binding site to allow A to interact with a, B to interact with b, and C to interact with c. In contrast, the inactive enantiomer cannot bind in the same way no matter how it is rotated in space. Although the inactive enantiomer possesses all of the same groups A, B, C, and D as the active enantiomer, they cannot all be simultaneously aligned with the corresponding regions of the binding site:
Here is another example of epinephrine:
A postulated fit to epinephrine’s receptor can explain why (-)-epinephrine exhibits 12 to 15 times more vasoconstrictor activity than (+)-epinephrine.
This is the classical three-point attachment model. For epinephrine, the benzene ring, benzylic hydroxyl, and protonated amine must have the stereochemistry seen with the (-) isomer to match up with the hydrophobic or aromatic region, anionic site, and a hydrogen-bonding center on the receptor. The (+) isomer (the mirror image) will not align properly on the receptor.
ii. Another possibility
It is difficult to conclude that one isomer is superior to the other. For instance, S-verapamil is a more active pharmacological stereoisomer than R-verapamil, but the former is more rapidly metabolized by the first-pass effect. First-pass refers to orally administered drugs that are extensively metabolized as they pass through the liver.
The following is multiple choice question (with options) to answer.
What do hydrophilic substances have an affinity for? | [
"air",
"soil",
"heat",
"water"
] | D | |
SciQ | SciQ-371 | human-anatomy
Title: Why is a penis an organ? According to Wikipedia an "An organ is a group of tissues with similar functions". I don't know anything about anatomy but it doesn't seem to me that a penis can be delimited somewhere to form a "group". Therefore I do not understand why a penis is considered an organ.
Can you explain it to me ? Frankly, that's a terrible definition by Wikipedia.
Merriam-Webster defines an organ as:
a differentiated structure (such as a heart, kidney, leaf, or stem) consisting of cells and tissues and performing some specific function in an organism
or
bodily parts performing a function or cooperating in an activity
The important defining feature of an organ is not that the tissues have similar functions but that, together, the tissues comprise a functional whole that achieves some end goal.
For the penis, it consists of multiple tissues with different functions:
(from https://www.ncbi.nlm.nih.gov/books/NBK525966/figure/article-20668.image.f1/ - original from Gray's Anatomy)
The different tissues pictured here: the fibrous envelope, the corpora cavernosa, the septum pectiniforme, the urethra and blood vessels, the nervous tissue in the skin: all of these tissues have different individual functions: structural, erectile, carrying urine or semen, etc.
The key that unifies them into an organ is that the functions of the penis at the organism level (principally sexual function) are not served by any of these tissues alone, but rather by their combination in a full structure: an organ.
Ultimately, organ definitions are somewhat opinion-based: people are lumpers and splitters, so you might find conflicting definitions for which groupings of tissues reflect distinct organs, but I think by most standards you would find the penis to be considered a distinct organ, affiliated with but distinct from the primary sex organs and associated glands.
The following is multiple choice question (with options) to answer.
What is a structure that consists of two or more types of tissues that work together to do the same job? | [
"cell",
"organ",
"organism",
"organ system"
] | B | After tissues, organs are the next level of organization of the human body. An organ is a structure that consists of two or more types of tissues that work together to do the same job. Examples of human organs include the brain, heart, lungs, skin, and kidneys. Human organs are organized into organ systems, many of which are shown in Figure below . An organ system is a group of organs that work together to carry out a complex overall function. Each organ of the system does part of the larger job. |
SciQ | SciQ-372 | biochemistry, synthesis, proteins, amino-acids
Also, assume a constant amount of amino acids always being added to the resin to couple. If only the so far correctly built sequences are available, these will ‘see’ a higher ‘concentration per site’ of their coupling partners maybe resulting in slightly increased yield, too. (Note that this paragraph used layman’s terminology.)
The following is multiple choice question (with options) to answer.
What is formed when amino acids are linked together in a long chain? | [
"protein",
"amino acid",
"water molecule",
"hormones"
] | A | Many amino acids can be linked together to form a long chain known as a protein . These linkages are formed when the carboxylic acid of one amino acid reacts with the amine of another to produce an amide (see Figure below ). |
SciQ | SciQ-373 | diffusion
$$
\langle \vec{x}^2\rangle = \frac{2dT}{m\eta_D}\, t.
$$
Comparing to the mean square deviation from the diffusion equation $\partial_0n-D\nabla^2 n=0$ I get
$$
D =\frac{T}{m\eta_D}
$$
independent of $d$. This is the Einstein relation.
The second ingredient is to use the drag force predicted by Stokes drag. This is the drag on a sphere/disk in a viscous fluid in the limit of small Reynolds number. In 3d this is the well known result
$$
\eta_D = \frac{6\pi\eta a}{M}
$$
and in 2d it is the more subtle result (due to Oseen)
$$
\eta_D = \frac{4\pi\eta}{M}\frac{1}{\log(4/Re)}
$$
where $Re=ua\rho/\eta$. Here $u$ is the relative velocity of the disk and the fluid, and $\rho$ is the density of the fluid.
Comments: The result in 3d is simple and intuitive. $D\sim T/(\eta a)$, so diffusion is faster if the temperature is higher, the viscosity of the solvent is smaller, and the particles are smaller. The 2d result is unusual, because even though we find the same dependence on $T/\eta$, the diffusion constant is only weakly (logarithmically) dependent on the particle size $a$.
We could have guessed this on purely dimensional grounds. There is no formula for the drag force that scales as $\eta a$. Indeed, if instead of diffusion of macroscopic particles (experiencing drag) I study microscopic particles experiencing quantum mechanical scattering with scattering length $a_s$ I find a power law $D\sim \frac{T}{n}\frac{1}{\sqrt{mT}a_S^2}$ in 3d, and log dependence $D\sim \frac{T}{n}\log(\frac{1}{mTa_s^2})$ in 2d.
The following is multiple choice question (with options) to answer.
Both diffusion and effusion are related to the speed at which what objects move? | [
"electricity",
"solids",
"copper molecules",
"gas molecules"
] | D | A related process to diffusion is the effusion. Effusion is the process of a confined gas escaping through a tiny hole in its container. Effusion can be observed by the fact that a helium-filled balloon will stop floating and sink to the floor after a day or so. This is because the helium gas effuses through tiny pores in the balloon. Both diffusion and effusion are related to the speed at which various gas molecules move. Gases that have a lower molar mass effuse and diffuse at a faster rate than gases that have a higher molar mass. |
SciQ | SciQ-374 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
Baroreceptors in the aortic arch and carotid sinuses monitor what level in the body? | [
"air intake",
"temperature",
"hunger",
"blood pressure"
] | D | 25.9 Regulation of Fluid Volume and Composition The major hormones regulating body fluids are ADH, aldosterone and ANH. Progesterone is similar in structure to aldosterone and can bind to and weakly stimulate aldosterone receptors, providing a similar but diminished response. Blood pressure is a reflection of blood volume and is monitored by baroreceptors in the aortic arch and carotid sinuses. When blood pressure increases, more action potentials are sent to the central nervous system, resulting in greater vasodilation, greater GFR, and more water lost in the urine. ANH is released by the cardiomyocytes when blood pressure increases, causing Na+ and water loss. ADH at high levels causes vasoconstriction in addition to its action on the collecting ducts to recover more water. Diuretics increase urine volume. Mechanisms for controlling Na+ concentration in the blood include the renin–angiotensin–aldosterone system and ADH. When Na+ is retained, K+ is excreted; when Na+ is lost, K+ is retained. When circulating Ca++ decreases, PTH stimulates the reabsorption of Ca++ and inhibits reabsorption of HPO 24 − . pH is regulated through buffers, expiration of CO2, and excretion of acid or base by the kidneys. The breakdown of amino acids produces ammonia. Most ammonia is converted into less-toxic urea in the liver and excreted in the urine. Regulation of drugs is by glomerular filtration, tubular secretion, and tubular reabsorption. |
SciQ | SciQ-375 | physical-chemistry, electrochemistry
Electronegativity has nothing to do with electrochemistry.
Electronegativity is the attraction an atom has for a pair of electrons in a covalent bond.
Electrochemistry is about controlling the electron transfer that accompanies a redox reaction. Usually this involves ionic species, and so electronegativity is not the relevant quantity to compare. In this case, we care about the energy change that occurs when copper and zinc lose electrons (ionization energy) and the stability of the resulting ions in solution. Ionization data mined from this NIST publication.
For zinc:
$$\ce{Zn->Zn+ + e-} \ \ \ \ \ \Delta H= 9.585\times 10^2 \text{ kJ/mol}$$
$$\ce{Zn+->Zn}^{2+}\ce{ + e-} \ \ \ \ \ \Delta H= 1.733\times 10^3 \text{ kJ/mol}$$
$$\ce{Zn->Zn}^{2+} \ce{+ 2e-} \ \ \ \ \ \Delta H= 2.692\times 10^3 \text{ kJ/mol}$$
For copper:
$$\ce{Cu->Cu+ + e-} \ \ \ \ \ \Delta H= 7.454\times 10^2 \text{ kJ/mol}$$
$$\ce{Cu+->Cu}^{2+}\ce{ + e-} \ \ \ \ \ \Delta H= 1.958\times 10^3 \text{ kJ/mol}$$
$$\ce{Cu->Cu}^{2+} \ce{+ 2e-} \ \ \ \ \ \Delta H= 2.703\times 10^3 \text{ kJ/mol}$$
Why is zinc oxidized and copper reduced?
The following is multiple choice question (with options) to answer.
The electronegativity of an element increases with increasing of what state? | [
"oxidation",
"conduction",
"isolation",
"evaporation"
] | A | Oxides As with the halides, the nature of bonding in oxides of the transition elements is determined by the oxidation state of the metal. Oxides with low oxidation states tend to be more ionic, whereas those with higher oxidation states are more covalent. These variations in bonding are because the electronegativities of the elements are not fixed values. The electronegativity of an element increases with increasing oxidation state. Transition metals in low oxidation states have lower electronegativity values than oxygen; therefore, these metal oxides are ionic. Transition metals in very high oxidation states have electronegativity values close to that of oxygen, which leads to these oxides being covalent. The oxides of the first transition series can be prepared by heating the metals in air. These oxides are Sc2O3, TiO2, V2O5, Cr2O3, Mn3O4, Fe3O4, Co3O4, NiO, and CuO. Alternatively, these oxides and other oxides (with the metals in different oxidation states) can be produced by heating the corresponding hydroxides, carbonates, or oxalates in an inert atmosphere. Iron(II) oxide can be prepared by heating iron(II) oxalate, and cobalt(II) oxide is produced by heating cobalt(II) hydroxide:. |
SciQ | SciQ-376 | evolution, mammals
Title: Why haven't land animals evolved beyond urination? It occurred to me (while urinating) that this would seem to be selected against because water is a scarce resource. Why are we constantly losing water we don't need to through urination? What is it about the chemistry of urine and the waste products eliminated that make urination necessary as opposed to eliminating them through defecation and recovering the water on the way out? It is probably true that toilets and other resting-ish area are always a great place to think about biology, I agree $\ddot \smile$.
Why do we urinate?
In short, urine contains the waste from our blood while defecation is just the stuff that we haven't digested. Kidneys are the organs responsible for draining wastes (mostly nitrogen-containing, or nitrogenous, wastes) from our blood.
Trade-off: energy cost vs. water loss
You're correct that the loss of water through urination is a considerable cost for an organism (especially those living in dry environments). But the amount of water used to excrete nitrogenous wastes is negatively correlated with the energy it costs to perform this excretion. In other words, there is a trade-off between water and energy loss during nitrogen excretion. Also, the question of toxicity is important.
Three ways to excrete nitrogenous wastes
Animals basically have three choices to excrete nitrogenous wastes:
Uric acid (excreted by uricotelic organisms)
Solid (crystal) with low water solubility
Low toxicity
Little water is needed
Lots of energy is needed
Ammonia (excreted by aminotelic organisms)
Highly soluble in water
High toxicity
Lots of water is needed to dilute it because of the toxicity
Not much energy is needed
Urea (excreted by ureotelic organisms)
Solid but highly soluble in water
"medium" amount of water is needed
"medium" toxicity
"medium" amount of energy is needed
The following is multiple choice question (with options) to answer.
Animals require air, water, and what in order to live and survive? | [
"time",
"shade",
"mates",
"food?"
] | D | |
SciQ | SciQ-377 | quantum-spin, standard-model, fermions, bosons
Title: How can multiple fermions combine to form a boson? I understand that composite particles with integer spin form a boson. For example a helium nucleus is a boson because it has 2 protons and 2 neutrons.
If all of the components on their own are fermions, which mean they can not occupy the same space, how can combining them allow them to now occupy the same space?
I guess my question is: Is there an "intuitive" explanation for this behavior, or is the answer just the integer spin always equals boson? The Pauli exclusion principle applies to the constituent fermions of the composite bosons. For example, many atoms of helium can be in the same lowest energy state forming a superfluid. However, they cannot be squeezed to a zero volume, because the Pauli exclusion principle holds for protons and neutrons, as well as for their constituent quarks.
The following is multiple choice question (with options) to answer.
How many types of bosons are there? | [
"one",
"five",
"three",
"four"
] | D | There are four known types of bosons, which are force-carrying particles. Each of these bosons carries a different fundamental force between interacting particles. In addition, there is a particle which may exist, called the "Higgs Boson", which gives objects the masses they have. Some types of bosons have mass; others are massless. Bosons have an electric charge of +1, -1, or 0. |
SciQ | SciQ-378 | radiation, solar-system, radioactivity, asteroids
Title: How to estimate the minimum radius of asteroid the rocky portion of which melted due to radioactive decay? One of the mechanisms for the heating of asteroids in the early history of the Solar System is believed to be decay of the isotope ${}^{26}\mathrm{Al}$. This was created by the supernova that produced the dust cloud from which the asteroids formed. For example in this paper the astrophysicist G. Jeffrey Taylor wrote:
${}^{26}\mathrm{Al}$ was present when meteorites were forming (see PSRD article Using Aluminum-26 as a Clock for Early Solar System Events). It is a radioactive isotope with a half-life of only 700 thousand years, so its presence means that the solar system formed within a few half-lives of the formation of ${}^{26}\mathrm{Al}$ in an exploding star. It decayed by emitting a beta particle (an electron), creating ${}^{26}\mathrm{Mg}$ (magnesium-26) and releasing energy. The energy released is considerable. If ${}^{26}\mathrm{Al}$ made up only $5 \times 10^{-5}$ ($0.005\%$) of all the aluminum in a chondrite (most is aluminum-27, which is not radioactive), it would release enough energy to melt asteroids a few kilometers across and larger. Lower amounts of ${}^{26}\mathrm{Al}$ cause less melting.
The following is multiple choice question (with options) to answer.
What astronomical phenomenon, formed of split asteroids or planetary rocks, provides clues about our solar system? | [
"comets",
"meteorites",
"stars",
"galaxies"
] | B | Meteorites provide clues about our solar system. Many were formed in the early solar system ( Figure below ). Some are from asteroids that have split apart. A few are rocks from nearby bodies like Mars. For this to happen, an asteroid smashed into Mars and sent up debris. A bit of the debris entered Earth’s atmosphere as a meteor. |
SciQ | SciQ-379 | quantum-mechanics, wave-particle-duality
Title: Question on de Broglie hypothesis I have read about de Broglie hypothesis that matter like light can also exhibit wave particle duality. This gave rise to the following questions in my mind.
The wavelength for electrons is significant. So does that mean that electrons are both particles and waves at the same time or they show different behaviour in different experiments. Or they are only waves.
I cannot understand why only moving objects will possess a wavelength.
What kind of waves will electrons be like light is an electromagnetic wave.
If electrons behave like waves then will the electric current flowing in wires also be considered as waves.
Please provide me the explanation. Thank you very much de Broglie hypothesis is a historically significant development that has very little bearing on what is happening now. IMHO it is only relevant for historians.
The following is multiple choice question (with options) to answer.
An electron possesses both particle and these? | [
"surging properties",
"wave properties",
"land properties",
"shock properties"
] | B | An electron possesses both particle and wave properties. CONCEPTUAL PROBLEMS 1. |
SciQ | SciQ-380 | dna, gene-expression
Title: Complexity in creating transgenic animals (e.g., mice) Many papers I have seen describing transgenic rodent models (and presumably applicable to other model organisms) involve the knock-in, or modification to, a single gene, possibly two genes. With respect to recombineering techniques, what prevents targeting multiple genes in a single organism? For instance, if I wanted to simultaneously knock-in some genes and knock-out others within the same mouse, would I be forced to generate individually modified transgenic lines and then do some "fancy" breeding to generate the multiple-modified mice? One reason is the low likelihood of success. Modifying a gene almost always involves a recombination event of plasmid DNA with a target site in the genome (and I say almost just because there may be some method that I don't know about, but all the ones I'm familiar with do). The likelihood of that decreases exponentially with the number of genes you're trying to modify. If you're trying to make several mutants of individual genes the likelihood of success decreases only linearly.
Another reason is having more knowledge and experimental power. You can learn little from a double mutant if you don't also have the individual mutants to compare. In fact, most reviewers would ask for individual mutant data if you've made a double mutant in your paper. This is especially true with flies and worms, as crosses take less time with them.
Also, the more mutant genes you have, the weaker the animal. Your mutants may not be viable at all with too many mutations.
The following is multiple choice question (with options) to answer.
What are mutant versions of normal genes called? | [
"antecedent - oncogenes",
"extinction - oncogenes",
"anti-oncogenes",
"proto-oncogenes"
] | D | |
SciQ | SciQ-381 | human-anatomy
Title: Why is a penis an organ? According to Wikipedia an "An organ is a group of tissues with similar functions". I don't know anything about anatomy but it doesn't seem to me that a penis can be delimited somewhere to form a "group". Therefore I do not understand why a penis is considered an organ.
Can you explain it to me ? Frankly, that's a terrible definition by Wikipedia.
Merriam-Webster defines an organ as:
a differentiated structure (such as a heart, kidney, leaf, or stem) consisting of cells and tissues and performing some specific function in an organism
or
bodily parts performing a function or cooperating in an activity
The important defining feature of an organ is not that the tissues have similar functions but that, together, the tissues comprise a functional whole that achieves some end goal.
For the penis, it consists of multiple tissues with different functions:
(from https://www.ncbi.nlm.nih.gov/books/NBK525966/figure/article-20668.image.f1/ - original from Gray's Anatomy)
The different tissues pictured here: the fibrous envelope, the corpora cavernosa, the septum pectiniforme, the urethra and blood vessels, the nervous tissue in the skin: all of these tissues have different individual functions: structural, erectile, carrying urine or semen, etc.
The key that unifies them into an organ is that the functions of the penis at the organism level (principally sexual function) are not served by any of these tissues alone, but rather by their combination in a full structure: an organ.
Ultimately, organ definitions are somewhat opinion-based: people are lumpers and splitters, so you might find conflicting definitions for which groupings of tissues reflect distinct organs, but I think by most standards you would find the penis to be considered a distinct organ, affiliated with but distinct from the primary sex organs and associated glands.
The following is multiple choice question (with options) to answer.
The heart and a network of blood vessels that run throughout the body make up what organ system? | [
"respiratory system",
"immune system",
"cardiovascular system",
"lymphatic system"
] | C | The organs that make up the cardiovascular system are the heart and a network of blood vessels that run throughout the body. The blood in the cardiovascular system is a liquid connective tissue. Figure below shows the heart and major vessels through which blood flows in the system. The heart is basically a pump that keeps blood moving through the blood vessels. |
SciQ | SciQ-382 | zoology, ecology, population-biology, ecosystem, predation
Title: Predator prey interaction I went through a line in my textbook which read:
"But for predators, prey species could achieve very high population densities and cause ecosystem instability."
I was not able to understand the meaning 'but for predators'. Can anyone please help me to interpret it's meaning?link to page where this line is mentioned
Edit: In terms of biology, I was unable to understand the meaning of the sentence, and I wanted to make sure that I don't misunderstand things... And this is why I posted the question.. I feel that the answer given is correct and in case, you find better explanation, please do post. I disagree with GForce's explanation; the meaning is not that growth of prey populations causes instability in predator species.
The sentence is merely saying that without predation, prey population growth is more likely to be at a level which leads to ecosystem instability. The term "but for predation" means "if it wasn't for the effects of predation". In other words:
"Ecosystem instability can occur when population growth of some species goes unchecked by predation."
See here for more explanation, where this example comes from in which it says that running a red light caused a crash:
"but for running the red light, the collision would not have occurred"
Biologically this makes sense in the sentence you show; without predators a species is limited by its supply of resources, and it can use these resources at an unsustainable level, whereas if you add predators to the mix there is additional extrinsic effects on population size, not determined by ecosystem properties such as space or nutrients.
The following is multiple choice question (with options) to answer.
When a predator kills and eats its prey, what sort of predation is this referred to as? | [
"true",
"just",
"predestined",
"false"
] | A | True predation is when a predator kills and eats its prey. Some predators of this type, such as jaguars, kill large prey. They tear it apart and chew it before eating it. Others, like bottlenose dolphins or snakes, may eat their prey whole. In some cases, the prey dies in the mouth or the digestive system of the predator. Baleen whales, for example, eat millions of plankton at once. The prey is digested afterward. True predators may hunt actively for prey, or they may sit and wait for prey to get within striking distance. Certain traits enable organisms to be effective hunters. These include camouflage, speed, and heightened senses. These traits also enable certain prey to avoid predators. |
SciQ | SciQ-383 | physical-chemistry, thermodynamics, gas-laws, gas-phase-chemistry
Title: Why is volume inversely proportional to pressure? If temprature is directly proportional to volume (Charles's law) and
temperature is directly proportional to pressure (Gay-Lussac's law), then why is pressure and volume are inversely proportional? Given you know and understand Charles' and Gay-Lussac's laws, it's not about chemistry, rather, simple ratios:
$$
\begin{cases}
T \propto V\\
T \propto p
\end{cases}
\implies
p \propto \frac 1 V
$$
which, as Zenix commented, is a math form of Boyle's law.
The following is multiple choice question (with options) to answer.
Pressure, volume, and temperature are related by which law? | [
"gas law",
"Law of Conservation",
"Murphy's Law",
"law of inertia"
] | A | Pressure, volume, and temperature are related by the combined gas law. |
SciQ | SciQ-384 | crystal-structure, carbon-allotropes
Title: Why is the buckminsterfullerene the purest form of carbon? Other websites say that $\ce{C60}$ doesn't have surface bonds that are attracted by other atoms as in graphite and diamond.
I understand that graphite may be attracted by other atoms because of its dangling electron. But why diamond? Each carbon in diamond is covalently bonded to $4$ other carbon atoms in a tetrahedral fashion. Diamond has dangling bonds on the outer surface of the crystal for pretty much the same reason as graphite. If you understood graphite differently, then you understood it wrong.
See, a molecule of oxygen contains 2 atoms, a molecule of sulfur has 8; but how many atoms are there in a "molecule" of diamond or graphite? Try drawing one to the end, so as to count them. You won't be able to do that. There is no end. The thing is infinite. But the real-world objects are finite, which means that at some point you have to say "Enough" and crop your ideal structure, and in doing so, you leave dangling bonds which attract other atoms. Fullerene lacks those, and hence is "more pure".
There is an altogether different dimension to the problem. Our thought experiment implied that we are able to produce a huge crystal without defects except maybe some on the surface. This is not true. Real-world compounds always contain impurities, and once you have a wrong atom built into the crystal lattice of graphite or diamond, it is stuck there forever. You'll never remove it, short of destroying the entire crystal. Fullerenes, on the other hand, are molecular compounds. They can be dissolved. They can be put through chromatography, sublimation, and other purification techniques. We can always remove any impurity (not that we can remove all of them, because nothing is ideal).
Either way, fullerenes win.
The following is multiple choice question (with options) to answer.
Different forms, or allotropes, of carbon are diamond, graphite, and what? | [
"ligands",
"vesicles",
"carbonite",
"fullerenes"
] | D | Different forms, or allotropes, of carbon are diamond, graphite, and fullerenes. |
SciQ | SciQ-385 | reproduction, asexual-reproduction
Title: can self-fertilization in flowers be called asexual reproduction? Suppose a flower having both male and female reproductive parts is self-fertilized then can this be called asexual reproduction...?I'm quite confused cause in this case the fusion of male and female gametes do take place but again the gametes are from the same parent....please help. According to this article from Berkeley, asexual reproduction is:
Any reproductive process that does not involve meiosis or syngamy
Using this definition of asexual reproduction and knowing self-fertilization involves meiosis and syngamy, it is not asexual.
The following is multiple choice question (with options) to answer.
What is the process in which organisms reproduce sexually by joining gametes called? | [
"fertilization",
"migration",
"propagation",
"stimulation"
] | A | Organisms that reproduce sexually by joining gametes , a process known as fertilization , must have a mechanism to produce haploid gametes. This mechanism is meiosis , a type of cell division that halves the number of chromosomes. Meiosis occurs only in gamete producing cells within the gonads. During meiosis the pairs of chromosomes separate and segregate randomly to produce gametes with one chromosome from each pair. Meiosis involves two nuclear and cell divisions without an interphase in between, starting with one diploid cell and generating four haploid cells ( Figure below ). Each division, named meiosis I and meiosis II, has four stages: prophase, metaphase, anaphase, and telophase. These stages are similar to those of mitosis, but there are distinct and important differences. |
SciQ | SciQ-386 | newtonian-mechanics, newtonian-gravity, celestial-mechanics
Title: Attraction between two objects in the universe. The resulting number of forces between them Right now I am studying Newton's Law of Universal Gravitation and I already learned his Third Law. It is said that there is an action-reaction pair between the falling apple and the Earth which results in the apple being attracted to the Earth and Earth to the apple at the same time and with the same force. But if we imagine bigger objects like Earth and Mars in the close distance, will it mean that Earth attracts to Mars and Mars is being attracted to the Earth with the gravitational force of Earth and at the same time Mars attracts to Earth and Earth to Mars because of Mars gravitational force. So as a result I counted 4 forces between two objects. Is it correct or not, and please explain why :) There's only the one gravitational interaction. You can describe it however many ways you like, but the physical interaction is only happening once.
If you want to know how two objects will move because of a force between them, relative to a distant inertial observer, calculate the change of their relative velocity by picking whatever frame measures the acceleration due to gravity that you want to integrate over time, then conserve momentum in the distant inertial frame.
For example: Bob and Alice are standing together on some frictionless ice. Bob (mass $m_B$) pushes on Alice (mass $m_A$) such that Alice has a velocity of $v$ relative to Bob. Conserve momentum $P_0$ in the frame in which you want to measure Alice's and Bob's velocity. (If this is the frame in which Alice and Bob were initially standing still, $P_0 = 0$.)
$P_0 = m_A v_a + m_Bv_b$
$v = v_a - v_b$
Solve for $v_a$ and $v_b$ in terms of $v, m_A, m_B, P_0$.
The following is multiple choice question (with options) to answer.
What is the force of attraction between things that have mass | [
"gravity",
"momentum",
"motion",
"friction"
] | A | Gravity has traditionally been defined as a force of attraction between things that have mass. The strength of gravity between two objects depends on their mass and their distance apart. |
SciQ | SciQ-387 | cell-biology, meiosis, mitosis
Title: Is the cell cycle applicable to meiosis as well, or just mitosis? All the diagrams I can find, show the cell cycle as having G1 phase (growth 1), S phase (DNA replication), G2 (growth 2) before the Mitotic phase (mitosis + cytokinesis).
Is there an equivalent "cell cycle" for meiosis, since the chromosomes in parent cell in meiosis also having "double" the genetic material prior to cell division (presumably from DNA replication too)?
Is it simply the same cell cycle as mitosis but with a Meiotic phase instead of Mitotic?
If so, would appreciate if anyone had a diagram :) Thanks! The cell cycle is only associated with mitosis. The cell cycle is the normal process of cell division with which cells can indefinitely increase their number by cyclically repeating the process. When a cell goes through the cycle, the result is two cells that are genetically identical.
Meiosis is a special type of cell division (which can occur only in eukaryotes) that produces cells that are not genetically identical to the initiating cell. The number of chromosomes in each of the resulting cells is half the number that were in the initial cell. (These haploid cells can later participate in fertilization, producing a cell with the original number of chromosomes.) Many of the steps of meiosis are similar to the steps involved in mitosis, but overall the process is more complex. Since meiosis reduces the number of chromosomes, it cannot be repeated and so does not take part in a cell division cycle.
The following is multiple choice question (with options) to answer.
Mitosis and meiosis are two types of what process, with dramatically different products? | [
"cell diffusion",
"cell solution",
"cell division",
"cell transition"
] | C | Mitosis and meiosis are two types of cell division, with dramatically different products. Mitosis begins with a diploid somatic cell and ends with two genetically identical diploid cells. Meiosis begins with a diploid cell and produces four haploid genetically unique cells that form gametes. |
SciQ | SciQ-388 | electrochemistry
Title: Redox Mg+Copper(II) If I put solid magnesium in a solution of Copper(II) sulfate, what reaction occurs that causes the bubbles?
Looking at the Potential tables the only reaction that theoretically occurs is the reduction of copper and oxidation of magnesium...so why there are bubbles?
https://www.youtube.com/watch?v=LkUX5vhLjJ0 Copper (II) sulfate hydrolyzes in water and makes the solution slightly acidic. Then the magnesium is reacting with the weak acid, displacing hydrogen, as well as displacing the copper.
Magnesium displaces hydrogen only slowly with pure water, partly because the magnesium hydroxide product is only sparingly soluble. Just a little acid, even from an ammonium salt or (as here) hydrolysis of a transition metal salt, is enough to dissolve the hydroxide and launch the hydrogen displacement.
The following is multiple choice question (with options) to answer.
Zinc reacting with hydrochloric acid produces bubbles of which gas? | [
"helium",
"mustard",
"hydrogen",
"carbon"
] | C | Zinc reacting with hydrochloric acid produces bubbles of hydrogen gas. |
SciQ | SciQ-389 | climate-change, geography, rivers, rainfall, agriculture
Today Climate change and its consequences are some of the biggest challenges facing Humanity, with water scarcity being the big factor in Sub-Sahara Africa.
By Ultimately raising the Rainfall in the entire Southern Africa, through the managed and controlled filling and utilization of the Natural 30 000 - 60 000 square km of evaporation pans more regularly, will this not lower the extreme temperatures (day and night temperatures due to water absorbing much of the daytime heat and releasing it during the night) and drought patterns Southern Africa has experienced, and by all predictions are bound to worsen and could become more extreme?
In effect, creating a second Okavango Delta, but considerably bigger - large parts of Chobe.
A study of such a magnitude will need large amounts of research in multidisciplinary sciences, from Archaeology to Agriculture to Economics, and a much broader field of expertise - the biggest being Politics!
Could such a mammoth project not be but one small answer to a much bigger Climate Change challenge facing the Earth? (and ultimately send a bit of rain to my little piece of land in the Waterberg in the long dry winter months when we receive those dry West Winds - and fires become a serious hazard - simply by adding a bit of moisture from the vast pans Botswana are so blessed with!)
My mind has been going in circles as to the feasibility of such a mammoth, yet so cheap and easily implementable idea?
Any ideas? We agree that additional evaporation enhances energy transport from the surface to the atmosphere and intensifies the hydrological cycle and cloud formation, and that some of the most serious climate change issues such as:
The following is multiple choice question (with options) to answer.
Water gains and loses what more slowly than does land, affecting seasonal conditions inland and on the coast? | [
"humidity",
"heat",
"minerals",
"volume"
] | B | Temperature falls from the equator to the poles. Therefore, major temperature zones are based on latitude. They include tropical, temperate, and arctic zones (see Figure below ). However, other factors besides latitude may also influence temperature. For example, land near the ocean may have cooler summers and warmer winters than land farther inland. This is because water gains and loses heat more slowly than does land, and the water temperature influences the temperature on the coast. Temperature also falls from lower to higher altitudes. That’s why tropical zone mountain tops may be capped with snow. |
SciQ | SciQ-390 | physical-chemistry, electrochemistry, aqueous-solution, solutions
Title: What is the interaction between dissolved ions of opposite valence in a solution at rest? NaCl is dissolved in water. Ions sodium and chloride are sufficiently free from each other so that they may occupy different regions of the solution after an active transport process through a membrane, or a mere electric field is in place.
They still act upon each other, and a membrane voltage is set by oppositely charged ions lining its interior and exterior surfaces.
So my question is this: how free are those ions in a uniform solution at equilibrium? Aren't they actually forming pairs of watered ions, although weakly bound? Can they form even bigger clusters, be them of short lifetime?
Note: I originally asked this on Physics SE but after several weeks I have received no answer nor any other kind of reaction, so I am trying Chemistry SE now. The answer is: it depends. Dissolution of a salt implies that the entropy gained exceeds the cost of breaking lattice interactions (the solution enthalpy, assuming it is positive). Electrostatic interactions compete with kT (thermal jostling). Under physiological conditions, long range interactions are strongly screened by intervening solvent molecules and other ions. At best ions are subject to an effective potential due to distant ions, in particular between segregated charges as in the cases you present (e.g. on opposite sides of a membrane).
However, ionic solutions are generally regarded as "non-ideal". This means that interactions between the ions and with the solvent cannot be dismissed. At high salt concentration ion pairing will be encouraged. Above the solubility limit salt precipitation will occur, preceded by formation of clusters (seeds). If an ion has multiple charges, then electrostatic interactions will be stronger and pairing will be encouraged. Some metal ions form permanent ligand complexes that can attenuate the overall charge or distribute it over the complex, and the ligands can form a "cage" about the central ion, altering the interaction potential with solvent and other ions. The effect of temperature is complex. The entropic cost of association increases with T, but the dielectric constant of the solvent tends to decrease also.
If you are interested in reading on ion-pairing in NaCl solutions you may want to start with Ref. 1. It explains that association is negligible in dilute solutions:
The following is multiple choice question (with options) to answer.
Covalent solutes separate into what when dissolved? | [
"true molecules",
"second molecules",
"new molecules",
"individual molecules"
] | D | Ionic solutes separate into individual ions when they dissolve. Covalent solutes separate into individual molecules. |
SciQ | SciQ-391 | acid-base, aqueous-solution, ph
As regards the matter of adding molarities, in some instances that is allowed.
Say we add $n_1$ moles of $X$ to $V\ \mathrm{L}$, that would give a molarity $M_1=\frac{n_1}{V}$. At a later stage we add $n_2$ moles of $X$, that molarity would be $M_2=\frac{n_2}{V}$.
The total molarity would be:
$$M=M_1+M_2=\frac{n_1}{V}+\frac{n_2}{V}=\frac{n_1+n_2}{V}$$
But if we were to mix volumes of solutions it would be:
$$M=\frac{M_1V_1+M_2V_2}{V_1+V_2}$$
Now they are no longer simply additive.
The following is multiple choice question (with options) to answer.
What term indicates moles per liter, whereas molality is moles per kilogram of solvent? | [
"kilocalorie",
"molarity",
"abundance",
"pollenation"
] | B | A N SW E R S 1. Molarity is moles per liter, whereas molality is moles per kilogram of solvent. |
SciQ | SciQ-392 | endocrinology
Excitement or stress response, including fast heart rate and breathing and anxiety: short term response: adrenaline; long-term response: cortisol
Appetite: ghrelin, leptin, adiponectin, cholecystokinin, insulin, glucagon-like peptide, gastrointestinal peptide...
Sexual drive: sex hormones, mainly testosterone and estradiol
Sleepiness: melatonin, cortisol
Depression: cortisol, sex hormones (mainly in women)
The point of this answer is to show that some of your feelings can be simply affected by hormones, which are note some ultimate forces, and that being aware of that can help you to control them to some extent.
The following is multiple choice question (with options) to answer.
Many of the hormones are secreted in response to what signals of the body? | [
"heart system signals",
"nose system signals",
"skeletal system signals",
"nervous system signals"
] | D | may be located in organs or tissues that have functions in addition to hormone production. Hormones circulate throughout the body and stimulate a response in cells that have receptors able to bind with them. The changes brought about in the receiving cells affect the functioning of the organ system to which they belong. Many of the hormones are secreted in response to signals from the nervous system, thus the two systems act in concert to effect changes in the body. |
SciQ | SciQ-393 | vision, human-eye, transplantation
Title: Retina Transplant Difficulties Why is retina transplant not as easy as the normal eye donation and transplant (I think the latter involves the cornea ) ?
This says that a new method has come up but why isnt the process similar and simple as the normal transplant ?
What are the difficulties in retina transplant ? This is a diagram of a cross-section of the cornea:
It is an amazing but relatively simple structure, the shape of which is responsible for about 60% of our focusing power, and the clarity of which allows light to enter. It is avascular (no blood vessels), and the non-mylenated nerve endings are very tiny and present in the epithelium.
Transplanting this relatively simple tissue is easy (well, not do-it-at-home easy, but easy.) The only problem with cutting all those nerve endings is that the new cornea will feel nothing if there's dust in the eye, etc. This is a problem, but nothing compared to blindness.
This is a diagram of a cross section of the retina:
As you can see, it is not nearly as simple as the cornea. The nerves (to the left: yellow, light blue, medium blue and darker blue), which collect information from the rods and cones (pink and purple) are very numerous, and absolutely vital to the ability of the brain to interpreting information from these photoreceptors. Therefore, a cut piece of retina immediately loses the ability to send any information to the brain. To transplant it into an eye with a damaged retina would do nothing to improve vision. Also, it is not easy surgery. It's very difficult.
What has been called "retinal transplants" in the recent past have been tiny pieces of embryonic retina, about...
4 millimetre square of retinal tissue, complete with retinal progenitor cells and the retinal pigment epithelium that nourishes them. The tissues were placed in the sub-retinal space beneath the fovea, the area of the retina responsible for sharp central vision.
The following is multiple choice question (with options) to answer.
What are two of the most common vision problems? | [
"myopia and nearsightedness",
"cross-eye and blindness",
"nearsightedness and farsightedness",
"blindness and astigmatism"
] | C | Many people have vision problems. Often, the problem is due to the shape of the eyes and how they focus light. Two of the most common vision problems are nearsightedness and farsightedness. |
SciQ | SciQ-394 | acid-base, reaction-mechanism
I got a result (about $\pu{1671.524g}$ 30% hydrochloric acid), which I verified this way:
Let $p$ be the number of dissolved $\ce{CaCO3}$ moles, which is about $\mathrm{605.5/100.0869 = 6.05}$
$\ce{HCl = 1671.524g * 0.3}$
$\ce{H_2O = 1671.524g * 0.7}$
$\ce{HCl_{end} = HCl - 2 * (p * M(HCl)}$)
$\ce{H2O_{end} = H2O + p * M(H2O)}$
$\ce{CaCl_{2end} = p * M(CaCl2)}$
$c_{end}$ = $\ce{\frac{HCl_{end}}{HCl_{end} + H2O_{end} + CaCl_{2end}} = 0.03}$
But my solution is claimed to be incorrect. Am I missing something here? We'll assume the reaction loses only $\ce {CO2}$ from the system (although it is a exothermic reaction, we'll assume $\ce{H2O}$ produced would not be lost as vapors):
$$\ce{CaCO3 + 2 HCl -> CaCl2 + H2O + CO2}$$
The following is multiple choice question (with options) to answer.
Hydrochloric acid is formed when hcl is dissolved into what? | [
"blood",
"water",
"sodium",
"plasma"
] | B | When HCl is dissolved into water, it is called hydrochloric acid. Ionic compounds and some polar compounds are completely broken apart into ions and thus conduct a current very well. A strong electrolyte is a solution in which a large fraction of the dissolved solute exists as ions. |
SciQ | SciQ-395 | atoms
Title: Why is the atomic mass unit less than the mass of both a neutron and a proton? The atomic mass unit is $1.6605 \times 10^{-27}$ kg.
This is less than the mean of the masses of 6 protons and 6 neutrons.
How do we account for the lower mass ?
My understanding is that some of the mass is in the form of energy somewhere, in the bonding maybe or in the kinetic energy.
Can someone clarify where this mass is please ? The source of the discrepancy is the mass defect, which is described in the article below as :
The difference between the sum of the masses of the components and the measured atomic mass is called the mass defect of the nucleus. Just as a molecule is more stable than its isolated atoms, a nucleus is more stable (lower in energy) than its isolated components. Consequently, when isolated nucleons assemble into a stable nucleus, energy is released. According to Equation 4, this release of energy must be accompanied by a decrease in the mass of the nucleus.
The equation four referenced is just E=mc^2. When these nucleons form carbon-12, which is the reference isotope for the definition of the amu, the mass defect appears, as you mentioned, by conversion to binding energy.
https://chem.libretexts.org/Courses/Grand_Rapids_Community_College/CHM_120_-_Survey_of_General_Chemistry/2%3A_Atomic_Structure/2.07_Mass_Defect_-_The_Source_of_Nuclear_Energy
The following is multiple choice question (with options) to answer.
Atoms of the same element that have different masses are called what? | [
"radioactive",
"isotopes",
"mutations",
"variations"
] | B | Isotopes are atoms of the same element that have different masses. |
SciQ | SciQ-396 | forces, potential-energy, conventions, vector-fields, conservative-field
Of course, this is all a convention -- if you'd like, you can define a "potential schmenergy" function $\tilde{V} = -V$, and then $\vec{F} = + \nabla \tilde{V}$. None of the physics would be changed, except that objects would fall from low to high potential schmenergy, which might go against the grain of your intuition.
The following is multiple choice question (with options) to answer.
What term is used to describe potential energy due to an object’s shape? | [
"elastic potential energy",
"kinetic energy",
"stimulated potential energy",
"flexible energy"
] | A | Irrigation is the single biggest use of water. Overhead irrigation wastes a lot of water. Drip irrigation ( Figure below ) wastes a lot less. Water pipes run over the surface of the ground. Tiny holes in the pipes are placed close to each plant. Water slowly drips out of the holes and soaks into the soil around the plants. Very little of the water evaporates or runs off the ground. |
SciQ | SciQ-397 | thermodynamics, fluid-dynamics, thermal-conductivity, navier-stokes
I am not too familiar with this and would appreciate any guidence/help.
Thank you in advance! As a crude and quite simple approximation you could try the following.
The following is multiple choice question (with options) to answer.
What property is characterized by eddies and swirls that mix layers of fluid together, unlike laminar flow? | [
"turbulence",
"compression",
"evaporation",
"combustion"
] | A | 12.4 Viscosity and Laminar Flow; Poiseuille’s Law • Laminar flow is characterized by smooth flow of the fluid in layers that do not mix. • Turbulence is characterized by eddies and swirls that mix layers of fluid together. • Fluid viscosity η is due to friction within a fluid. Representative values are given in Table 12.1. Viscosity has units of. |
SciQ | SciQ-398 | homework-and-exercises, electrostatics, experimental-physics, charge
Title: Electric charges separation I know that any electric charge (Millikan) is always an integer multiple $n\in \Bbb Z$ of the electron charge $e$ i.e.
$$\boxed{Q=ne} \tag 1$$
Assuming by induction or contact or by friction to separate an electric charge $Q$ that has an excess of protons ($6$ to be exact) near two other neutral charges of the same size,
there is after contact the charge equipartes, obtaining three charges of $Q/3$.
So from the $(1)$ every charged sphere $q$ is:
$$\boxed{q=\frac n3 e}$$ Is the subdivision by $N$, with $N\in \Bbb N$ charges verified experimentally with a leaf electroscope, or is there a physical law that confirms the subdivision in relation to the number of spheres? I had never actually read Millikan's paper until earlier this year. It is a real tour de force of experimental technique and science communication, and I recommend it highly. But the very short version (expounded upon in the linked answer) is that, because the electronic charge is so small, measuring single-electron charge effects requires you to worry about many nitty-gritty experimental details that ordinary people are free to forget or ignore. I described some in an answer to a similar question.
The experiment you are describing is almost certainly impossible. (Not the least problem: any three-body interaction is, under the hood, a sequence of two-body interactions.) Let's think about a simpler one: imagine a sphere with charge $Ne$ comes into contact with an identical uncharged sphere, so that the charges should redistribute:
$$
\Big(Ne\Big) + \Big(0\Big) \to \Big(\frac N2e\Big) + \Big( \frac N2 e \Big)
$$
Some issues you'd have to deal with:
Suppose that $N$ is odd. Now it's impossible for them to share their charge equally. One of the spheres is going to have more charge than the other. You might expect this to happen randomly.
The following is multiple choice question (with options) to answer.
What process refers to a separation of charge within an atom or molecule? | [
"convection",
"diffusion",
"rotation",
"polarization"
] | D | material, and is intimately related to the polarizability of the material. Things Great and Small The Submicroscopic Origin of Polarization Polarization is a separation of charge within an atom or molecule. As has been noted, the planetary model of the atom pictures it as having a positive nucleus orbited by negative electrons, analogous to the planets orbiting the Sun. Although this model is not completely accurate, it is very helpful in explaining a vast range of phenomena and will be refined elsewhere, such as in Atomic Physics. The submicroscopic origin of polarization can be modeled as shown in Figure 19.18. |
SciQ | SciQ-399 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
What is the largest cartilaginous fish? | [
"whale shark",
"dolphin",
"sturgeon",
"blue whale"
] | A | Mike Johnston. Whale sharks are the largest cartilaginous fish . CC BY 2.0. |
SciQ | SciQ-400 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
Capillaries in the chorionic villi filter fetal wastes out of the blood and return clean, oxygenated blood to the fetus through what? | [
"skin vein",
"umbilical vein",
"Back Vein",
"separates vein"
] | B | The placenta develops throughout the embryonic period and during the first several weeks of the fetal period; placentation is complete by weeks 14–16. As a fully developed organ, the placenta provides nutrition and excretion, respiration, and endocrine function (Table 28.1 and Figure 28.12). It receives blood from the fetus through the umbilical arteries. Capillaries in the chorionic villi filter fetal wastes out of the blood and return clean, oxygenated blood to the fetus through the umbilical vein. Nutrients and oxygen are transferred from maternal blood surrounding the villi through the capillaries and into the fetal bloodstream. Some substances move across the placenta by simple diffusion. Oxygen, carbon dioxide, and any other lipid-soluble substances take this route. Other substances move across by facilitated diffusion. This includes water-soluble glucose. The fetus has a high demand for amino acids and iron, and those substances are moved across the placenta by active transport. Maternal and fetal blood does not commingle because blood cells cannot move across the placenta. This separation prevents the mother’s cytotoxic T cells from reaching and subsequently destroying the fetus, which bears “non-self” antigens. Further, it ensures the fetal red blood cells do not enter the mother’s circulation and trigger antibody development (if they carry “non-self” antigens)—at least until the final stages of pregnancy or birth. This is the reason that, even in the absence of preventive treatment, an Rh− mother doesn’t develop antibodies that could cause hemolytic disease in her first Rh+ fetus. Although blood cells are not exchanged, the chorionic villi provide ample surface area for the two-way exchange of substances between maternal and fetal blood. The rate of exchange increases throughout gestation as the villi become thinner and increasingly branched. The placenta is permeable to lipid-soluble fetotoxic substances: alcohol, nicotine, barbiturates, antibiotics, certain pathogens, and many other substances that can be dangerous or fatal to the developing embryo or fetus. For these reasons, pregnant women should avoid fetotoxic substances. Alcohol consumption by pregnant women, for example, can result in a range of abnormalities referred to as fetal alcohol spectrum disorders (FASD). These include organ and facial malformations, as well as cognitive and behavioral disorders. |
SciQ | SciQ-401 | genetics, human-genetics, population-genetics, molecular-evolution, genomes
Title: Is genetic purging based on random shuffling of the genes of an individual or is it more intentional way of removing deleterious recessive alleles? Inbreeding depression may be reduced by selection against deleterious alleles, which eliminates, or purges, them from the population. I have two questions:
Is genetic purging based on random shuffling of the genes of an individual or is it more intentional way of removing deleterious recessive alleles?
Do the individuals/couple with deleterious alleles that breed together, pass down the purged genes EACH AND EVERY TIME they produce offspring? Does it happen every time they mate or just some times?
Is genetic purging based on random shuffling of the genes of an individual or is it more intentional way of removing deleterious recessive alleles?
There is no intention in evolution. Purging refer to the action of selection at removing deleterious alleles. This term is specifically used when a population goes through a demographic change under which purifying selection becomes more efficient (such as an increase in inbreeding coefficient).
Do the individuals/couple with deleterious alleles that breed together, pass down the purged genes EACH AND EVERY TIME they produce offspring? Does it happen every time they mate or just some times?
Purging is a population-level process so your second question does not make much sense
Rephrasing the above a bit differently, purging refers to the reduction in frequency of deleterious alleles in the populations. Individuals will transmit whatever allele they can transmit.
The following is multiple choice question (with options) to answer.
What is the term for a random change in allele frequencies that occurs in a small population? | [
"speciation",
"mutation",
"evolution",
"genetic drift"
] | D | Genetic drift is a random change in allele frequencies that occurs in a small population. When a small number of parents produce just a few offspring, allele frequencies in the offspring may differ, by chance, from allele frequencies in the parents. |
SciQ | SciQ-402 | physiology, muscles
Title: Does muscle get bigger by increase in size of individual cells or increase in number? Somewhere in the back of my mind, I have the claim that a muscle never increases its amount of cells but, if the muscle gets bigger, it's simply because individual cells get bigger.
The book Anatomy Trains on page 36 cites "Changes in sarcomere length and physiological properties in immobilized muscle by Williams et al" when it makes the claim :
Stretched, a muscle will attempt to recoil back to its
resting length before giving up and adding more cells
and sarcomeres to bridge the gap.
Is that true? Do muscles increase the number of their cells in that way? The "back of your mind" is correct: "if the muscle gets bigger, it's simply because individual cells get bigger."
Growth of muscle can occur in three ways:
by an increase in muscle cell numbers
by an increase in muscle fiber diameter
by an increase in fiber length.
However, growth in cell numbers is limited to the prenatal and immediately postnatal period, with the animals and man being born with or soon reaching their full complement of muscle cells.
[G]rowth occurs by either hypertrophy of the existing muscle fibers by adding additional myofibrils to increase the muscle mass or by adding new sarcomeres to the ends of the existing muscle fibers to increase their length. Both of these mechanisms occur during the growth process. Growth in the girth of the muscle fibers... may be stimulated by development of stress creating an unequal pressure with splitting at the Z-band and development of additional SR and T-tubule systems. This adds to the diameter or girth of myofibers without any hyperplasia. The growth in length occurs at either end of the fibers and results in addition of new sarcomeres. In both cases, new myofibrillar protein must be synthesized and deposited in the muscle cells.
The following is multiple choice question (with options) to answer.
Aerobic exercise helps improve the cardiovascular system, while what exercise causes muscles to get bigger and stronger? | [
"anaerobic",
"skeletal",
"enzymatic",
"endurance"
] | A | Aerobic exercise helps improve the cardiovascular system, while anaerobic exercise causes muscles to get bigger and stronger. |
SciQ | SciQ-403 | classical-mechanics, elasticity, stress-strain
The internal stress comes from the bending $$ \sigma(\theta) = \frac{|M| y}{I} \approx \frac{y ( F a \left( \frac{2}{\pi}-\frac{5 \epsilon^2}{6\pi} \right) + F b \sin \theta)}{I}$$ where $y$ is the half width of the section.
Maximum stress is at $\theta=\frac{\pi}{2}$ with $$\sigma_{max} \approx \frac{F\, y}{I} \left( \frac{b (6 \pi+13)}{6 \pi} - \frac{b^3}{6 \pi a^2} \right)$$
The following is multiple choice question (with options) to answer.
An excessive posterior curvature of the thoracic region is also known as what? | [
"babesiosis",
"osmosis",
"kyphosis",
"lordosis"
] | C | Vertebral Column Developmental anomalies, pathological changes, or obesity can enhance the normal vertebral column curves, resulting in the development of abnormal or excessive curvatures (Figure 7.21). Kyphosis, also referred to as humpback or hunchback, is an excessive posterior curvature of the thoracic region. This can develop when osteoporosis causes weakening and erosion of the anterior portions of the upper thoracic vertebrae, resulting in their gradual collapse (Figure 7.22). Lordosis, or swayback, is an excessive anterior curvature of the lumbar region and is most commonly associated with obesity or late pregnancy. The accumulation of body weight in the abdominal region results an anterior shift in the line of gravity that carries the weight of the body. This causes in an anterior tilt of the pelvis and a pronounced enhancement of the lumbar curve. Scoliosis is an abnormal, lateral curvature, accompanied by twisting of the vertebral column. Compensatory curves may also develop in other areas of the vertebral column to help maintain the head positioned over the feet. Scoliosis is the most common vertebral abnormality among girls. The cause is usually unknown, but it may result from weakness of the back muscles, defects such as differential growth rates in the right and left sides of the vertebral column, or differences in the length of the lower limbs. When present, scoliosis tends to get worse during adolescent growth spurts. Although most individuals do not require treatment, a back brace may be recommended for growing children. In extreme cases, surgery may be required. Excessive vertebral curves can be identified while an individual stands in the anatomical position. Observe the vertebral profile from the side and then from behind to check for kyphosis or lordosis. Then have the person bend forward. If scoliosis is present, an individual will have difficulty in bending directly forward, and the right and left sides of the back will not be level with each other in the bent position. |
SciQ | SciQ-404 | biochemistry, neuroscience, brain, neuroanatomy
Title: The human brain in numbers I: neurons Even though knowing the number of neurons in a functional unit or with the same function is not of main importance, it may be interesting to know their orders of magnitude, especially in the human brain. For example:
|------------------|------------------|
| cerebellum | 100,000,000,000 |
| cortex | 20,000,000,000 |
| telencephalon | 10,000,000,000 |
| brainstem | 1,000,000,000 |
| sensory neurons | |
| haptic | 500,000,000 |
| visual | 100,000,000 |
| auditory | 2,000 |
| limbic system | |
| amygdala | 10,000,000 |
|------------------|------------------|
The following is multiple choice question (with options) to answer.
What are the two main divisions of the human nervous system? | [
"central and identical",
"somatic and autonomic",
"central and peripheral",
"left and right"
] | C | The two main divisions of the human nervous system are the central nervous system and the peripheral nervous system. The peripheral nervous system has additional divisions. |
SciQ | SciQ-405 | dna, terminology
Title: Is a DNA molecule a single strand of polynucleotide or two of them linked together? Our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds. The thing is, until now, I always thought a DNA molecule was composed of two strands, those being polynucleotides, both of them being linked together. I can't find a link which is saying the same as my teacher, even if it seems technically correct to call a double helix a dimer of two DNA molecules.
I was curious to know what was the exact terminology. As you pointed out, though this may be basic biology, seeking clarification when receiving conflicting information is a good thing. Don't feel embarrassed for asking. :)
.. our molecular biology teacher told us that a double helix of DNA was composed of two DNA molecules linked together by hydrogen bonds.
Respectfully, your teacher is incorrect. A single, double-stranded DNA molecule is comprised of two helical shaped polynucleotides, and are connected together via hydrogen bonding.
Highlight of each polynucleotide
Highlight of hydrogen bonding
And just for further validation, according to Molecular Biology of the Cell, 4th ed., by Alberts B, Johnson A, Lewis J, et al.:
A DNA molecule consists of two long polynucleotide chains composed of four types of nucleotide subunits. Each of these chains is known as a DNA chain, or a DNA strand. Hydrogen bonds between the base portions of the nucleotides hold the two chains together.
So, it would seem that your teacher is referring to each polynucleotide, a.k.a. DNA strand, as a DNA molecule. Instead, she should use the verbiage: a single DNA molecule is composed of two DNA strands, which are helical-shaped polynucleotides.
The following is multiple choice question (with options) to answer.
What is composed of two strands of nucleotides in a double-helical structure? | [
"bacteria",
"molecule",
"dna",
"RNA"
] | C | DNA Double-Helical Structure DNA has a double-helical structure (Figure 2.23). It is composed of two strands, or polymers, of nucleotides. The strands are formed with bonds between phosphate and sugar groups of adjacent nucleotides. The strands are bonded to each other at their bases with hydrogen bonds, and the strands coil about each other along their length, hence the “double helix” description, which means a double spiral. |
SciQ | SciQ-406 | human-anatomy
Title: Why is a penis an organ? According to Wikipedia an "An organ is a group of tissues with similar functions". I don't know anything about anatomy but it doesn't seem to me that a penis can be delimited somewhere to form a "group". Therefore I do not understand why a penis is considered an organ.
Can you explain it to me ? Frankly, that's a terrible definition by Wikipedia.
Merriam-Webster defines an organ as:
a differentiated structure (such as a heart, kidney, leaf, or stem) consisting of cells and tissues and performing some specific function in an organism
or
bodily parts performing a function or cooperating in an activity
The important defining feature of an organ is not that the tissues have similar functions but that, together, the tissues comprise a functional whole that achieves some end goal.
For the penis, it consists of multiple tissues with different functions:
(from https://www.ncbi.nlm.nih.gov/books/NBK525966/figure/article-20668.image.f1/ - original from Gray's Anatomy)
The different tissues pictured here: the fibrous envelope, the corpora cavernosa, the septum pectiniforme, the urethra and blood vessels, the nervous tissue in the skin: all of these tissues have different individual functions: structural, erectile, carrying urine or semen, etc.
The key that unifies them into an organ is that the functions of the penis at the organism level (principally sexual function) are not served by any of these tissues alone, but rather by their combination in a full structure: an organ.
Ultimately, organ definitions are somewhat opinion-based: people are lumpers and splitters, so you might find conflicting definitions for which groupings of tissues reflect distinct organs, but I think by most standards you would find the penis to be considered a distinct organ, affiliated with but distinct from the primary sex organs and associated glands.
The following is multiple choice question (with options) to answer.
The body is made up of how many types of tissue? | [
"six",
"seven",
"four",
"five"
] | C | As for all animals, your body is made of four types of tissue: epidermal, muscle, nerve, and connective tissues. Plants, too, are built of tissues, but not surprisingly, their very different lifestyles derive from different kinds of tissues. All three types of plant cells are found in most plant tissues. Three major types of plant tissues are dermal, ground, and vascular tissues. |
SciQ | SciQ-407 | 10
The Sloan Digital Sky Survey Data Release 15 contains over 4 million spectra of both galactic and extra-galactic origin from the multi-fiber spectrographs. Of these spectra, 0.7 million came from the original spectrographs during the SDSS-I/II Legacy Survey and the remainder from the upgraded spectrographs as part of the BOSS survey during SDSS-III (see SDSS ...
9
So where are these measurements of galaxies moving faster than light? They're redshift measurements. Check out the Wikipedia redshift article. It's good stuff. "we can actually observe galaxies that are moving away from us at >c" It's true. You might think it cannot be, but it can. Um, I think I missed the groundbreaking headline that said ...
8
The Hubble parameter is defined as the rate of change of the distance between two points in the universe, divided by the distance between those two points. The Hubble parameter is getting smaller because the denominator is getting bigger more quickly than the numerator. In the future, the cosmological constant, $\Lambda$ could result in an exponential ...
8
The Hubble law gives the velocity of a distant galaxy right now. A galaxy at a distance $d$ recedes at a velocity $v = H_0\,d$ right now$^\dagger$. However, the relation between $d$ and the redshift — which is the quantity that we observe — is a non-trivial function of the expansion history of the Universe, obtained by integrating the (inverse) scale factor ...
8
The following is multiple choice question (with options) to answer.
The great astronomer edwin hubble discovered that all distant galaxies are receding from our milky way galaxy with velocities proportional to their what? | [
"distances",
"paths",
"dimensions",
"masses"
] | A | (a) A jet airplane flying from Darwin, Australia, has an air speed of 260 m/s in a direction 5.0º south of west. It is in the jet stream, which is blowing at 35.0 m/s in a direction 15º south of east. What is the velocity of the airplane relative to the Earth? (b) Discuss whether your answers are consistent with your expectations for the effect of the wind on the plane’s path. (a) In what direction would the ship in Exercise 3.57 have to travel in order to have a velocity straight north relative to the Earth, assuming its speed relative to the water remains 7.00 m/s ? (b) What would its speed be relative to the Earth? 60. (a) Another airplane is flying in a jet stream that is blowing at 45.0 m/s in a direction 20º south of east (as in Exercise 3.58). Its direction of motion relative to the Earth is 45.0º south of west, while its direction of travel relative to the air is 5.00º south of west. What is the airplane’s speed relative to the air mass? (b) What is the airplane’s speed relative to the Earth? 61. A sandal is dropped from the top of a 15.0-m-high mast on a ship moving at 1.75 m/s due south. Calculate the velocity of the sandal when it hits the deck of the ship: (a) relative to the ship and (b) relative to a stationary observer on shore. (c) Discuss how the answers give a consistent result for the position at which the sandal hits the deck. The velocity of the wind relative to the water is crucial to sailboats. Suppose a sailboat is in an ocean current that has a velocity of 2.20 m/s in a direction 30.0º east of north relative to the Earth. It encounters a wind that has a velocity of 4.50 m/s in a direction of 50.0º south of west relative to the Earth. What is the velocity of the wind relative to the water? 63. The great astronomer Edwin Hubble discovered that all distant galaxies are receding from our Milky Way Galaxy with velocities proportional to their distances. It appears to an observer on the Earth that we are at the center of an expanding universe. Figure 3.64 illustrates this for five galaxies lying along a straight line, with the Milky Way Galaxy at the center. Using the data from the figure, calculate the velocities: (a) relative to galaxy 2 and (b) relative to galaxy 5. The results mean that observers on all galaxies will see themselves at the center of the expanding universe, and they would likely be aware of relative velocities, concluding that it is not possible to locate the center of expansion with the given information. |
SciQ | SciQ-408 | rotational-dynamics
Title: Friction due to pure rolling on an inclined plane When a body is executing pure rolling we know that the point of contact of the body with the ground is at rest with respect to the ground. If that's the case no friction should act as it is stationary.So when a body is rolling down an inclined plane its point of contact is stationary , then how does friction act to cause a torque, as static friction only acts when there is a tendency of relative motion with respect to the ground.
When a body is executing pure rolling we know that the point of contact of the body with the ground is at rest with respect to the ground.
This is true.
If that's the case no friction should act as it is stationary
This is false. Static friction is a friction force that can act on an object that is not sliding relative to the surface it is touching.
So when a body is rolling down an inclined plane its point of contact is stationary , then how does friction act to cause a torque, as static friction only acts when there is a tendency of relative motion with respect to the ground?
Gravity is attempting to accelerate the body down the incline. The static friction force opposes this. Since the friction is applied at the edge of the body and tangent to it friction has a torque about the center of the body and it starts to roll.
Contrast this with a body rolling on a flat surface. If there are no other horizontal forces then there is nothing for friction to oppose. Therefore, there is no static friction force, hence no torque. The body will continue to roll at a constant speed. However if I then apply a horizontal force, static friction now wants to oppose this. Hence we now have a torque and a change in speed (this problem, discussed here and here, is actually not trivial. You can get different magnitudes and directions of friction depending on the body and the the location and strength of the applied force if you want rolling without slipping).
The following is multiple choice question (with options) to answer.
What is friction that acts on objects while it is rolling over a surface called? | [
"surface friction",
"rolling friction",
"opposing friction",
"blowing friction"
] | B | Rolling friction is friction that acts on objects when they are rolling over a surface. Rolling friction is much weaker than sliding friction or static friction. This explains why most forms of ground transportation use wheels, including bicycles, cars, 4-wheelers, roller skates, scooters, and skateboards. Ball bearings are another use of rolling friction. You can see what they look like in the Figure below . They let parts of a wheel or other machine roll rather than slide over on another. |
SciQ | SciQ-409 | 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.
Traditionally, mammals were divided into groups based on what? | [
"their colors",
"their sizes",
"their characteristics",
"their behaviors"
] | C | Traditionally, mammals were divided into groups based on their characteristics. Scientists took into consideration their anatomy (body structure), their habitats, and their feeding habits. Mammals are divided into three subclasses and about 26 orders. Some of the groups of mammals include:. |
SciQ | SciQ-410 | bond
Title: Types of bonds in a molecule For example in dinitrogen pentoxide, $\ce{N2O5}$, covalent as well as coordinate bonds (type of covalent bonds) are present, but it appears that it contains only covalent bond.
What is a proper method to find out which type of bonds are present in a molecule? Electrovalent bonds are easiest to identify. If a compound is made up of a metal and non-metal/non-metallic radical (like carbonate), then, 99.99% times, it contains electovalent bond. If a compound is made up of 2 or more non-metals/non-metallic radicals, then it contains covalent bond. Coordinate covalent bonds appear mostly with compounds containing Hydrogen element. To identify the coordinate covalent bonds, you can draw the branched structural formula of the compound and see if the shared pair of electrons are coming from the same molecule.
The following is multiple choice question (with options) to answer.
What type of bonds do alkanes only contain? | [
"carbon-hydrogen bonds",
"hydrogen-carbon bonds",
"carbon-carbon single bonds",
"hydrogen bonds"
] | C | Alkanes contain only carbon-carbon single bonds. |
SciQ | SciQ-411 | optics, electromagnetic-radiation, refraction
Title: Why does change in speed of a wave make it refract? When a light wave enters a medium with a higher refractive index (e.g. from air to standard glass) and its speed decreases, why does that make it refract/bend?
I understand that wavelength decreases and frequency stays the same and therefore its speed decreases, but I can't find anywhere whatsoever why the speed decrease cause the wave to refract. So could someone please explain this? The wave only refracts if it enters the medium at an angle. Follow a single wavecrest; if the wave is entering the medium at an angle, then part of the wavecrest enters the medium first, and starts to slow down, while the other part of the wavecrest is still going fast, and therefore the wavecrest must bend. If the wave enters at a right angle, then the entire wavecrest is slowed down simultaneously and no refraction occurs.
The following is multiple choice question (with options) to answer.
Which part of the wave helps make the wave bend and cause refraction? | [
"shallow part",
"bright part",
"dense part",
"heavy part"
] | A | Lymph that collects in tissues slowly passes into tiny lymph vessels. Lymph then travels from smaller to larger lymph vessels. Muscles around the lymph vessels contract and squeeze the lymph through the vessels. The lymph vessels also contract to help move the lymph along. Eventually, lymph reaches the main lymph vessels, which are located in the chest. From these vessels, lymph drains into two large veins of the cardiovascular system. This is how lymph returns to the blood. |
SciQ | SciQ-412 | human-biology, evolution
Humans are off the charts in the amount of resources we invest in our children - our lives are 1/4 to 1/3 over before we sometimes leave our parents household (in some societies of course they never leave the house, but step into an extended family). This may be one of the reasons we are so successful as a species - we live in practically every place we possibly could and have no danger of competition from any other living thing excepting ourselves.
The grandmother effect is essentially the idea that if women, who are more attached to the offspring in more cases than fathers, continue to live and help support the grandchildren and make them more successful, then this will allow post menopausal women to have a longer lifespan (which they do).
The evolutionary biologist Sara Hrdy, emeritus UC Davis, has written quite a bit about the nuances of the evolution of the role of motherhood - reading some of her articles or books might give you a deeper sense of how profoundly filial love has shaped human beings.
--- more answer this stuff may or may not be worth reading depending on how broadly you want to understand this question...
Its important to say that many of the expansions of human average human lifespan have not been genetic. Its commonly cited that sewer systems, clean water, antibiotics and plentiful food are the three most important factors in human lifespan - and before modern developed world nations, the average lifespan of human beings was somewhere in the 30s. And there are significant lifespan differences in regions where these factors and others (education of women, access to prenatal and early care etc) are available.
Studies continue to be published that examine environmental and lifestyle factors compared to genetics and it seems that environment and lifestyle can make an astounding difference.
But genetics undoubtedly has a role to play here too. There are probably some individual humans and animals which have evolved to live longer. This has been found to be genetically related in some humans by demographics and family lines.
The following is multiple choice question (with options) to answer.
What are passed from one generation to the next so species can survive? | [
"selections",
"fluctuations",
"mutations",
"adaptatioins"
] | D | |
SciQ | SciQ-413 | optics, waves, diffraction
Title: Interference in diffraction gratings I am currently studying the Wikipedia article for diffraction grating, and am having difficulty understanding some of the information in the theory of operation section of the article.
An idealised grating is made up of a set of slits of spacing $d$, that must be wider than the wavelength of interest to cause diffraction. Assuming a plane wave of monochromatic light of wavelength $\lambda$ with normal incidence (perpendicular to the grating), each slit in the grating acts as a quasi point-source from which light propagates in all directions (although this is typically limited to a hemisphere). After light interacts with the grating, the diffracted light is composed of the sum of interfering wave components emanating from each slit in the grating. At any given point in space through which diffracted light may pass, the path length to each slit in the grating varies. Since path length varies, generally, so do the phases of the waves at that point from each of the slits. Thus, they add or subtract from each other to create peaks and valleys through additive and destructive interference. When the path difference between the light from adjacent slits is equal to half the wavelength, $\dfrac{\lambda}{2}$, the waves are out of phase, and thus cancel each other to create points of minimum intensity. Similarly, when the path difference is $\lambda$, the phases add together and maxima occur. The maxima occur at angles $\theta_m$, which satisfy the relationship $d \sin(\theta_m) = |m|$, where $\theta_m$ is the angle between the diffracted ray and the grating's normal vector, and $d$ is the distance from the center of one slit to the center of the adjacent slit, and $m$ is an integer representing the propagation-mode of interest.
(By Vigneshdm1990 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=58383485.)
The following is multiple choice question (with options) to answer.
What kind of lines does a diffraction grating produce? | [
"evenly spaced lines",
"randomly spaced lines",
"nearly spaced lines",
"properly spaced lines"
] | A | 27.5 Single Slit Diffraction Light passing through a single slit forms a diffraction pattern somewhat different from those formed by double slits or diffraction gratings. Figure 27.21 shows a single slit diffraction pattern. Note that the central maximum is larger than those on either side, and that the intensity decreases rapidly on either side. In contrast, a diffraction grating produces evenly spaced lines that dim slowly on either side of center. |
SciQ | SciQ-414 | plant-anatomy
Title: Are bryophyte sporangia multicellular? My research on the matter can be summarized in a sentence: "It [sporangium] can be composed of a single cell or can be multicellular" (Source: https://en.wikipedia.org/wiki/Sporangium). Yet there shouldn't be a reply placed between "They are" and "They aren't" test options, speaking of "Are bryophyte sporangia multicellular?". A link to the source where I could ascertain whether the bryophyte sporangia is multicellular (if I could ascertain) is highly appreciated. In Embryophyta (land plants), including bryophytes, the sporangium is usually a multicellular structure.
Perhaps you meant to ask about the number of spore mother cells (SMCs) in each sporangium? That varies across groups. In bryophytes, each sporangium has many SMCs, and accordingly produces a large number of spores. (Contrast this with angiosperms, where a megasporangium [called an ovule] has only one megaspore mother cell.)
References and further reading:
https://courses.lumenlearning.com/boundless-biology/chapter/bryophytes/
https://www.britannica.com/science/plant-development
Image attribution:
By LadyofHats. (Public domain;
https://commons.wikimedia.org/wiki/File:Hornwort_structures.jpg)
The following is multiple choice question (with options) to answer.
Which type of ferns have yellow sporangia and no leaves? | [
"Hothouse fern",
"whisk ferns",
"Boston fern",
"Ostrich fern"
] | B | Forest and Kim Starr/Starr Environmental. Whisk ferns have yellow sporangia and no leaves . CC BY 3.0. |
SciQ | SciQ-415 | fluid-dynamics, pressure, water, ice, oceanography
Title: Does water turn solid under deep ocean because of high pressure? I know that we can make water solid with high pressure, so I think water will be solid in the deep ocean?
If that is true, the depth of the ocean would be limited because water will become ice? Anyone know that maximum depth? You are mistaken. Actually, you can melt ice by applying pressure. This is why ice is so slippery; when you step on a frozen lake, you are melting the very first layer of water, and thus creating a very good instant lubricant for you to slide on. It is a common knowledge false fact, see comments.
Ok, granted, at very high pressures water does become solid. From the phase diagram, to get solid at around 0 °C you need around 650 MPa. How much is that? Pressure depends with depth as:
$$P = \rho g h$$
Assuming constant density, you need a column of water of $66\ \mathrm{km}$ for ice to be formed. That is about six times the depth of Challenger Deep, in Mariana trench.
So the answer is no – on Earth. You will not find enormous amounts of more or less pure liquid water anywhere else in the Solar System, but if you are happy with hydrogen, helium, and other gases, you may find it around Jupiter's core. Definitely, liquid H and He.
When water is mixed with other elements, the phase diagram is perturbed. For example, salt in the sea at atmospheric pressure lowers the freezing point about a couple of degrees (depending on the concentration). If water is mixed with hydrogen, helium, methane, and company as in a gas giant, the diagram will be drastically changed, so more detailed computations would be needed.
The following is multiple choice question (with options) to answer.
Ice masses, acquifers, and the deep ocean are examples of water what? | [
"seas",
"lakes",
"reservoirs",
"fields"
] | C | The atmosphere is an exchange pool for water. Ice masses, aquifers, and the deep ocean are water reservoirs. |
SciQ | SciQ-416 | thermodynamics, energy, electricity, efficient-energy-use
Title: Cutting down on power by bypassing mechanical to electrical conversions: Why not? The only answer to this I can think of is energy portability issues.
Another modern-world insanity is converting mechanical energy to electrical, only to turn it back into mechanical. The example I like to use is a refrigerator's reciprocating compressor.
If we directly attach a steam turbine's axle to the crankshaft of the compressor, we will not need to suffer losses in heat in our conversion of mechanical to electrical (at the power plant) then back to mechanical energy (in our appliance). Long ago, a primitive factory used one big engine or turbine or water wheel to rotate a set of overhead shafts, from which leather belts were suspended at intervals to power small pieces of machinery scattered throughout the factory. This arrangement was inflexible in that when the single big engine stopped, so did the entire factory, and when electricity came into common use, this overhead shafting arrangement fell quickly out of favor.
The power losses in long-distance electrical power transmission are more than made up for by the ease with which it is performed and the flexibility it affords. This makes "local power generation" as you describe it impractical because a hundred small steam turbines are much more wasteful of heat energy than one large turbine.
The only practical exception is integrated co-generation in which a small engine running on, for example, natural gas powers a generator while also spinning the shaft of a heat pump. The waste heat from the engine's cooling system makes residential hot water, the waste heat from its exhaust goes through a heat exchanger to provide hot air for space heating, the heat pump furnishes air conditioning (or pulls heat from outside the dwelling) and the electricity from the generator powers up your small appliances in the home while also charging a set of batteries.
Overall thermodynamic efficiency of such a device can exceed 95%, and examples of this technology are just now coming onto the market.
The following is multiple choice question (with options) to answer.
This heat is used to convert water into steam, which is then used to turn a turbine, thus generating what? | [
"radiation power",
"electrical power",
"solar power",
"heating power"
] | B | The generation of electricity is critical for the operation of nearly all aspects of modern society. The following diagram illustrates the types of fuels used to generate electrical power in the Unites States. In 2009, almost 45% of the power generated in the U. S. was derived from coal, with natural gas making up another 23% of the total. The third primary source of electrical energy is nuclear power, which accounts for approximately 20% of the total amount generated. All of these fuels give off energy in the form of heat. This heat is used to convert water into steam, which is then used to turn a turbine, thus generating electrical power. |
SciQ | SciQ-417 | atmosphere, clouds, thermodynamics, air-currents
Title: Elevation of Atmosphere differ? Does the atmosphere depth (or how high the air molecules from the ground) of Earth or Mars differ gradually or can there be plumes of atmosphere that reaches into space? If I were able to travel a perfect circle around the equator would the atmosphere differ in elevation? The atmosphere, as a whole, is approximately in hydrostatic equilibrium. This means that the gravity of the earth holds the atmosphere to the earth, preventing its escape, though few molecules may escape every so often.
Mathematically, this can be described by $$\frac{dP}{dr}=-\rho g$$ where P is the pressure, $\rho$ is the density, and $g$ is gravity. Using the Ideal Gas Law $$P=\rho R T$$, where $T$ is temperature and $R$ is the gas constant for air. Assuming that the temperature in the height of a column of the atmosphere is averaged ($\bar{T}$) an equation for the average height of the atmosphere can be found $$P(r,\phi,\lambda)=P_0(\phi,\lambda)exp(-\frac{(r-r_0)g}{R\bar{T}(\phi,\lambda)})=P_0(\phi,\lambda)exp(-\frac{gz}{R\bar{T}(\phi,\lambda)})$$
where $r_0$ is the radius of the earth,$P_0$ is the surface pressure, $r=z+r_0$, where $z$ is the height above the earth's surface, $\phi$ is the latitude, and $\lambda$ is the longitude.
To Summarize:
As the average temperature of the atmosphere increases, the height of the atmosphere will generally increase. This means that the height of the atmosphere will generally be the lowest near the poles, but highest near the equator. There are certainly exceptions to this rule, but this generally works. If you were to go around the equator, it will likely not be a "perfect circle" since the average temperature would have to be exactly the same.
The following is multiple choice question (with options) to answer.
What atmospheric layer lies above the highest altitude an airplane can go and below the lowest altitude a spacecraft can orbit? | [
"mesosphere",
"stratosphere",
"troposphere",
"thermosphere"
] | A | Not so fast. The mesosphere is the least known layer of the atmosphere. The mesosphere lies above the highest altitude an airplane can go. It lies below the lowest altitude a spacecraft can orbit. Maybe that's just as well. If you were in the mesosphere without a space suit, your blood would boil! This is because the pressure is so low that liquids would boil at normal body temperature. |
SciQ | SciQ-418 | neuroscience, sensation, perception, neurophysiology, receptor
Title: How precisely can we sense temperature differences? We have thermoreceptors, thus we can sense temperature (both warm and cold). I'm interested in the sensitivity of our thermoreceptors - What is the smallest temperature difference that we can sense? I assume that different parts / organs may have different sensitivity (eg. lips vs fingers), thus I'd like to narrow my focus on the palms / fingers. But if someone has comparative data, that is welcomed too. Short answer
Temperature differences of 0.02 degrees Celcius can be distinguished, dependent on various factors including experimental conditions and bodily location.
Background
The ability to discriminate temperature differences depends on whether it is a cooling or heating pulse, the skin temperature, the duration of the temperature stimulus, age, bodily location among other factors. Unfortunately I cannot access the primary literature other than a few isolated smaller studies. However, Scholarpedia has a very nice entry and associated references, and I quote:
The thermal sensory system is extremely sensitive to very small changes in temperature and on the hairless skin at the base of the thumb, people can perceive a difference of 0.02-0.07 °C in the amplitudes of two cooling pulses or 0.03-0.09 °C of two warming pulses delivered to the hand. The threshold for detecting a change in skin temperature is larger than the threshold for discriminating between two cooling or warming pulses delivered to the skin. When the skin at the base of the thumb is at 33 °C, the threshold for detecting an increase in temperature is 0.20 °C and is 0.11 °C for detecting a decrease in temperature.
The rate that skin temperature changes influences how readily people can detect the change in temperature. If the temperature changes very slowly, for example at a rate of less than 0.5 °C per minute, then a person can be unaware of a 4-5 °C change in temperature, provided that the temperature of the skin remains within the neutral thermal region of 30-36 °C. If the temperature changes more rapidly, such as at 0.1 °C/s, then small decreases and increases in skin temperature are detected. [...]
The following is multiple choice question (with options) to answer.
Where are sensors for thermoregulation concentrated in the brain? | [
"pituitary gland",
"thyroid",
"medulla",
"the hypothalamus"
] | D | |
SciQ | SciQ-419 | biochemistry, metabolism
The second system, glycolysis, simply refers to the breakdown of carbohydrates (e.g. glucose) to resynthesize ATP from the energy stored in those carbohydrates. Your muscles contain a buffer of glycogen, approx. 300~ gr for the average Joe (give or take). The glycogen can be broken down to glucose-6-phosphate, which can then enter glycolysis. The glucose-6-phosphate is broken down to 2 pyruvate and yields 3 ATP netto (2 when derived from glucose, rather than glycogen, due to a first enzymatic step which requires 1 ATP). The enzymatic steps of glycolysis are controlled by ATP, AMP, ADP and other factors, factually integrating the energy status of the muscle (primarly through allosteric regulation of enzymes, especially phosphofructokinase).
The third system, the oxidative system, refers to the breakdown of carbohydrates and fatty acids, requiring oxygen to 'burn' them (citric acid cycle). The yield of this is much higher than for glycolysis, but the process is way slower.
In essence, all are regulated by the concentration of substrates and products, as well as through allosteric regulation (binding of a molecule at a different site, inhibiting or activating the enzyme, often by intermediates of the pathways themselves). Additionally, there is some long-term regulation through gene expression (e.g. up- or down-regulating expression of genes involved in these pathways), mostly by hormones.
Edit:
Well, I guess this is described in any basic biochemistry book (I'm very fund of the book 'Fundamentals of Biochemistry: Life at the Molecular Level'). If you want to see a description of these energy systems in a more exercise related context (since you were aiming at myocytes) I suggest reading Strength and Condition: Biological Principles and Practical Applications from Marco Cardinale et al., and the NSCA book Essentials of Strength and Conditioning.
The following is multiple choice question (with options) to answer.
What is the first step in the breakdown of glucose to extract energy for cellular metabolism? | [
"photosynthesis",
"mutation",
"glycolysis",
"mitosis"
] | C | 7.2 | Glycolysis By the end of this section, you will be able to: • Describe the overall result in terms of molecules produced in the breakdown of glucose by glycolysis • Compare the output of glycolysis in terms of ATP molecules and NADH molecules produced You have read that nearly all of the energy used by living cells comes to them in the bonds of the sugar, glucose. Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism. Nearly all living organisms carry out glycolysis as part of their metabolism. The process does not use oxygen and is therefore anaerobic. Glycolysis takes place in the cytoplasm of both prokaryotic and eukaryotic cells. Glucose enters heterotrophic cells in two ways. One method is through secondary active transport in which the transport takes place against the glucose concentration gradient. The other mechanism uses a group of integral proteins called GLUT proteins, also known as glucose transporter proteins. These transporters assist in the facilitated diffusion of glucose. Glycolysis begins with the six carbon ring-shaped structure of a single glucose molecule and ends with two molecules of a three-carbon sugar called pyruvate. Glycolysis consists of two distinct phases. The first part of the glycolysis pathway traps the glucose molecule in the cell and uses energy to modify it so that the six-carbon sugar molecule can be split evenly into the two three-carbon molecules. The second part of glycolysis extracts energy from the molecules and stores it in the form of ATP and NADH, the reduced form of NAD. |
SciQ | SciQ-420 | particle-physics, charge, standard-model, elementary-particles
Title: How do particles get their charge?
How does an electron get its charge?
And how can it maintain that charge for very long (infinite) periods of time?
And how come a neutron has no charge since and a proton does? They are both made of the same type of quarks and they both have no movement.
1 How does an electron get its charge?
This is the elementary particle table . The electron is an elementary particle and its charge is an observable attribute that , together with its other quantum numbers and mass, classify it as an electron.
And how can it maintain that charge for very long (infinite) periods of time?
Observations gathered over a century have not shown the decay of an electron, i.e. of losing charge and thus becoming another particle. So it is by construction of Nature.
And how come a neutron has no charge since and a proton does? They are both made of the same type of quarks and they both have no movement.
Look at the quarks on the table. The exact quark content has to be added up, and the charge added.
Proton is up+ up +down =+1 , and neutron is down+ down +up =0.
So the general answer to
How do particles get their charge?
is, it depends on the particles, if they are elementary or composite. Composite one get their charge by the addition of the charges of the elementary ones they are made out of. Elementary particles have been defined by the study of the results of innumerable experiments, over more than a century. A minimal mathematical model called the standard model of particle physics assigns them as a basis for describing the underlying quantum mechanical level of nature. This model has been very successful in describing all known interactions and predicting new observations.
The following is multiple choice question (with options) to answer.
What charge do atoms carry? | [
"negative",
"neutral",
"positive",
"static"
] | B | Atoms, which are always neutral in electric charge, contain electrons as well as protons and neutrons. An electron has an electrical charge of -1. If an atom has three electrons, infer how many protons it has. |
SciQ | SciQ-421 | homework, cell-membrane, human-physiology, lungs
Title: How many cell membranes are oxygen and carbon dioxide diffuse through in the lungs? In the lungs, oxygen and carbon dioxide pass through cell membranes by diffusion.
Which row is correct?
The correct answer is D, but I think it should be B. I can only think about three layers as maximum which are; epithelium of alveolus, endothelium of capillaries and the membrane of red blood cell. I don't know what are remainings.
Any help would be much appreciated! Oxigen goes from the alveolar's lumen to the cytoplasm of the erythrocyte, and that's 5 membranes:
the "top" of the alveolar epithelial cell
the "bottom" of such cell
the "top" of the endothelial cell (capillary)
the "bottom" of such cell
the erythrocyte membrane
You got all the cells right, but your only problem was this: oxygen diffuses through the cell membrane entering the cell, moves through the cytoplasm, and diffuses through the membrane again exiting the cell. So, for each cell, you have to count 2 membranes. For the last one, the erythrocyte, you have only 1 membrane (because it is $\ce{O2}$ final destination).
For the $\ce{CO2}$ the situation is a little bit more tricky. We have the same 4 membranes (2x epithelial cell and 2x capillary), but $\ce{CO2}$ can come from 2 locations:
from the erythrocyte, where it is formed from $\ce{H2CO3}$ (by the reaction $\ce{H2CO3 -> H2O + CO2}$) or released from the N-terminal group of proteins, like haemoglobin (where it has previously bound)
from the plasma (around 9% of the $\ce{CO2}$).
In the first case we have 5 membranes, and in the second case just 4.
So, the correct answer is D.
The following is multiple choice question (with options) to answer.
The pleura that surrounds the lungs consists of how many layers? | [
"four",
"three",
"one",
"two"
] | D | The pleura that surrounds the lungs consists of two layers, the ________. visceral and parietal pleurae. mediastinum and parietal pleurae. visceral and mediastinum pleurae. none of the above 14. Which of the following processes does atmospheric pressure play a role in? a. pulmonary ventilation b. production of pulmonary surfactant c. resistance d. surface tension 15. A decrease in volume leads to a(n) ________ pressure. |
SciQ | SciQ-422 | evolution, biochemistry, plant-physiology, plant-anatomy, life
Title: Plants without bacteria? is it theoretically possible? I know from school, that all live on the Earth need bacteria as low-level "machines" that break down/extract/convert/produce chemical elements and combinations, other high-level organisms needed. But it is a natural way.
But is it possible to have a world with plants (without mammals or microorganisms and without bacteria) that could exist in the long term. Saying the atmosphere of these world has already enough nitrogen, oxygen and CO2, and of course there is water.
What could break this artificially created world with such conditions (say the world created not from low-level living structures)?
Could bacteria emerge in the world? This is the sort of question that should be considered from more than one perspective. Since this is speculation, take it as a given that there is a lot of 'what if' here.
I doubt most animals and plants can do entirely without bacteria - as you say most of the essential nutrients come from bacteria, who fix nitrogen. If only plants were left on earth, eventually the plants would use up all the nitrogen and they would have to find a way to fix more.
Can bacteria emerge from just a world of plants? I don't think viruses arise spontaneously, but since genomes often have viruses embedded in them, over the course of a billion years or so, its possible since bacteria and viruses continue to be impressed upon our genomes. Would it happen in time? Most would be skeptical whether that timing could work out.
In practice it would be hard to create a world like this. I would be interested to see whether you could sterilize the microorganisms off of seeds without killing the plant for instance. If you're asking about a small sterile environment with only plants, you could do it by adding the nutrients the plants need and giving them sunlight. Such self sustaining systems have been made with cyanobacteria and i'd be surprised if plants could not be included. But these are closed systems and judged by limited amounts of time, so whether this is an answer to your question is not clear. Here it looks like some water plants and fish have been done. If there was a plant that created CO₂ at an adequate rate its possible.
The following is multiple choice question (with options) to answer.
Organisms that obtain food from outside themselves (i.e. they don't make their own food) are known as what? | [
"zygotes",
"fungi",
"heterotrophs",
"autotrophs"
] | C | Fungi are heterotrophs, meaning they obtain food from outside themselves. |
SciQ | SciQ-423 | where do I start
in a large restaurant an average of every 7 customers ask for water with the their meal. A random sample of 12 customers is selected, find the probability that exactly 6 ask for water with their meal
any body with idea
Rufai
conditional probability
Ramesh
Rufai
iam really sorry. it's been long since I used these things. I just gave you a hint though
Ramesh
ok
Rufai
this follows binomial distribution. p(X=6)=12C6*(0.6)^6*0.4^6 use this formula n find.
syeda
can you explain the cosidered variable in the formula
Divya
x is variable wich is exactly 6 costumers
syeda
n is number of customers
syeda
ncx*p^X*q^X?
Divya
q^n-x
syeda
oh right !!! thanks yaar
Divya
I agree with Seyda too
Hoshyar
I agree with Syeda too
Hoshyar
7/12 =0.58is it?
yousaf
.
yousaf
r8
khalid
what is descriptive statistic
Descriptive statistics are brief descriptive coefficients that summarize a given data set, which can be either a representation of the entire or a sample of a population. Descriptive statistics are broken down into measures of central tendency and measures of variability (spread).
Divya
are you getting this ?
Divya
if so let me know
Divya
yes m getting
Ramesh
fine
Divya
what's taking place can l join u
Anest
yeah !!why not? sure
Divya
okey thanks
Anest
where are statistics used
hello
Giannis
Hi
Makhosi
how u doing
Muhid
the upper quartile of the population 10,12,14,16,18,20,25,15,11,11,17,is................?
Gach
The probability range is 0 to 1... but why we take it 0 to 1....
because in probability 1 means success and 0 means failure and it cnnt be more or less than 1 and 0.
syeda
b/c v hv mazimum probibliy 1 and minimum which is.no.probiblity is 0.so.v hv the range from 0 to 1
khalid
the size of a set is greeter than its subset
The following is multiple choice question (with options) to answer.
In scientific investigations, descriptive statistics are useful for summarizing the characteristics of large what? | [
"organisms",
"questions",
"samples",
"tissues"
] | C | The girls in the picture above make up a small sample—there are only four of them. In scientific investigations, samples may include hundreds or even thousands of people or other objects of study. Especially when samples are very large, it’s important to be able to summarize their overall characteristics with a few numbers. That’s where descriptive statistics come in. Descriptive statistics are measures that show the central tendency, or center, of a sample or the variation in a sample. |
SciQ | SciQ-424 | 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.
The process of the cytoplasm splitting apart and the cell pinching in two is known as what? | [
"cytokinesis",
"electrolysis",
"mitosis",
"budding"
] | A | The cell wall grows toward the center of the cell. The cytoplasm splits apart, and the cell pinches in two. This is called cytokinesis . |
SciQ | SciQ-425 | geomorphology
Title: What causes these mound-like ground formations? Whilst riding on Mam Tor in Castleton, England I came across this scene (not my photo) and I would like to know what causes the formations which I have ringed in red. They look like piles of earth have been deposited a long time ago, but clearly that can't be the case, so what causes them?
Another image of these mounds They're landslide deposits; Mam Tor gets its name, which translates as "mother hill", from the regular landslides that come off the higher slopes and form hillocks further down into the valley.
The following is multiple choice question (with options) to answer.
What kind of mountainous formation can often be found near trenches? | [
"caves",
"craters",
"volcanoes",
"earthquakes"
] | C | deep sea trenches : Trenches are found in the sea. Some are near the edges of continents. Trenches are found near chains of active volcanoes. An example is the line of the very deepest blue, off of western South America. |
SciQ | SciQ-426 | molecular-biology, neurotransmitter, muscles, receptor
Is the membrane continuous along these tubules, or does the tubule just end somewhere inside the muscle fiber?
The membranes are continuous.
When the muscle is twitching... is this neurological of nature, or is it related to a molecular cause in the muscle itself?
Most things you'd call a muscle twitch are at the whole-muscle-group scale, involving the coordinated contraction of many individual motor units, so it's basically neurological.
When the muscle is cramping... I'm almost certain this arises in the muscle. What causes it? A malfunction with regard to the calcium ions?
A muscle cramp is a colloquialism for a couple of things that are quite different from each other. Overall, as with the previous question, if someone's experiencing a muscle cramp that means it's a fairly macroscopic phenomenon and it likely involves a whole group of muscle filaments, so it's neurological. Most spasms and cramps are neurologically mediated.
The connections with electrolyte balances (cramps from low sodium, potassium, magnesium, or calcium) also hint at the neurological basis because neurons act on each other (and on muscles) by forming or dissipating ion gradients. You may know that low dietary calcium can lead to muscle cramps; if this was relevant to the calcium release within the myocyte (from the sarcoplasmic reticulum) then the calcium-starved muscles wouldn't be expected to chronically contract (which requires calcium) but to chronically relax.
That being said, there's a lot of room for feedback mechanisms. So, let's say a person experiences a muscle tear; the tear is small enough that it doesn't compromise the function of the entire muscle group. In this case it's adaptive for the local damage to 'signal' to the rest of the muscle group to initiate spasm so as to stabilize the damaged structures as they're repaired. In this scenario the local damage would 'inform' a neurological (and/or endocrine) response that actually effects the spasm.
Lastly, and on a slightly different subject, what are the microlesions in the muscles that occur during strength training, and what is the overcompensation that happens?
The following is multiple choice question (with options) to answer.
Because it can be controlled intentionally, skeletal muscle is also called what type of muscle? | [
"automatic",
"involuntary",
"necessary",
"voluntary"
] | D | Skeletal muscle tissue forms skeletal muscles, which attach to bones and sometimes the skin and control locomotion and any other movement that can be consciously controlled. Because it can be controlled intentionally, skeletal muscle is also called voluntary muscle. When viewed under a microscope, skeletal muscle tissue has a striped or striated appearance. This appearance results from the arrangement of the proteins inside the cell that are responsible for contraction. The cells of skeletal muscle are long and tapered and have multiple nuclei on the periphery of each cell. Smooth muscle tissue occurs in the walls of hollow organs such as the intestines, stomach, and urinary bladder, and around passages such as in the respiratory tract and blood vessels. Smooth muscle has no striations, is not under voluntary control, and is called involuntary muscle. Smooth muscle cells have a single nucleus. Cardiac muscle tissue is only found in the heart. The contractions of cardiac muscle tissue pump blood throughout the body and maintain blood pressure. Like skeletal muscle, cardiac muscle is striated, but unlike skeletal muscle, cardiac muscle cannot be consciously controlled and is called involuntary muscle. The cells of cardiac muscle tissue are connected to each other through intercalated disks and usually have just one nucleus per cell. |
SciQ | SciQ-427 | gravity, water, space, planets
The only detail left is how to get a surface temperature that's in the right range for the surface to be liquid. This depends on the distance from the star, but also on the composition of the atmosphere. On Earth, the atmosphere's composition is mostly due to the action of the biosphere, which keeps the temperature regulated in just the right range for water to be liquid. Perhaps it's possible to imagine life on such a water world, in the form of photosynthesising algae-like organisms, which might play a similar role.
The following is multiple choice question (with options) to answer.
What effect in the atmosphere ensures that the earth maintains the correct temperature to support life? | [
"greenhouse effect",
"coriolis effect",
"smog effect",
"ozone effect"
] | A | When sunlight heats Earth’s surface, some of the heat radiates back into the atmosphere. Some of this heat is absorbed by gases in the atmosphere. This is the greenhouse effect , and it helps to keep Earth warm. The greenhouse effect allows Earth to have temperatures that can support life. |
SciQ | SciQ-428 | mineralogy, petrology
Title: How do you use the streckeisen (QAPF) classification ternary diagram to identify igneous rocks based on chemical rock composition? I have been given the following diagrams:
and
and a database that is structured like this:
ROCK NAME |SIO2 |TIO2| AL2O3| CR2O3| FEOT| CAO| MGO| MNO| K2O| NA2O| P2O5|
WEHRLITE |45.42| 0.17| 2.57| 0.32| 11.3384| 7.54| 31.93| 0.17| 0.01| 0.24| 0.01|
I want to know how to normalize the data and use these diagrams to identify the rock name based on the IUGS specification. I then am tasked to write a program that will do this automatically meaning that I have to come up with some semi-mathematically-based process to identify these rocks. Any ideas? Why you should not do it
The QAPF and related diagrams are intended for classification of rocks in the field, or preliminary classification with modal proportions as seen in the optical microscope. They are not designed with the chemical composition of the rocks in the mind. Furthermore, these diagrams are merely descriptive and not genetic. They do not take into account many factors affecting the various characteristics of the rocks. While doing something like this may be interesting for homework exercise, it is not something I would expect to see in a recent research article.
If you want to do it anyway
Your solution should consist of two steps.
The following is multiple choice question (with options) to answer.
Felsic, intermediate, mafic, and ultramafic are types of composition of what rock group? | [
"igneous",
"asteroids",
"metamorphic",
"Sedimentary"
] | A | Igneous rocks are classified by composition and texture. The composition can be felsic, intermediate, mafic, or ultramafic. The composition depends on the minerals the rock includes. A felsic rock will contain felsic minerals. |
SciQ | SciQ-429 | organic-chemistry
Title: What are the minimal chemical requirements for a food which we all can eat? I've been puzzled by the following though experiment for the past few days:
I want to make my own food from scratch, but I do not know where to start from.
I want to be 100% sure that what I eat will never contains something that can damage my body. For example: If you buy something from the local market you can not be 100% sure that it's safe to eat. (99.9 % maybe... but that's not 100%)
I want to ask you to tell me, how can I make a food that I can eat, or should I say - live on it, for the rest of my life, that's 100% safe, I can control every aspect of it's creation and has many combinations of taste because I love diversity.
Thank you for your time : )
Edit:
Because I realized my question is very broad and indeed is a little... too much scientific I want to close it. But before I do so, here's what I had in mind:
I wanted to take some chemical elements, put them in a jar, run some electricity, heat, whatever through it, filter it, do some additional processing and eat it.
I wanted to know if the stomach can take it, because I was going to eat food that's not hard to digest. Considering the three basic biomolecules used by the body are carbohydrates, lipids, and proteins, you would need to consume these three molecules only. Now we can choose three substances.
Glucose, one of the most basic carbohydrates, is needed for ATP production, so that would be a food choice there.
Any oil or butter will provide lipids.
Protein comes from a variety of sources. Meat is typically though of as the best, but nuts are a pretty good source too.
Since nuts satisfy proteins and lipids, I'd say honey roasted peanuts are the most basic food you could live off of, if you replace pure glucose for the honey.
The following is multiple choice question (with options) to answer.
What is the base of nearly all food chains on earth? | [
"synthesis",
"glycolysis",
"photosynthesis",
"atherosclerosis"
] | C | Photosynthesis is the base of nearly all food chains on Earth. This is true of marine food chains, too. |
SciQ | SciQ-430 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
The skull is a part of a vertebrate endoskeleton that encloses and protects what organ? | [
"nervous system",
"heart",
"lung",
"brain"
] | D | part of a vertebrate endoskeleton that encloses and protects the brain; also called the skull. |
SciQ | SciQ-431 | climate-change
What this means is that the traditional monsoon dynamics i.e. cool Indian ocean and warm continental land mass has been disturbed by human influenced climate change as well as the natural geography of the land and ocean mass. One significant ISM phenomenon the tropical easterly jet stream has shown a weakening trend over the last few decades. A significant fall out of this could be mid latitude atmospheric dynamics could come into play during the ISM(one can think of this as the weather during a break in monsoons where upper level subtropical westerlies come into play) and a disturbing trend has been noted in recent times with increasing frequency of hail storms.
The following is multiple choice question (with options) to answer.
The global pattern of precipitation is influenced by movements of what? | [
"air masses",
"air valleys",
"pollution masses",
"clouds"
] | A | The global pattern of precipitation is influenced by movements of air masses. For example, there is a global belt of dry air masses and low precipitation at about 30° N and 30° S latitude. |
SciQ | SciQ-432 | electromagnetism
Title: Region of most and least intense magnetic field
It's a unmagnetized iron screw placed in the north pole of a U shaped magnet. I believe the region of least intense magnetic field is at the far left of the board. From what I understand the screw becomes magnetized and it's south pole is where it's touching the north of the magnetic, is it correct to assume the most intense magnetic field will be where the screw is touching the magnet due to there being direct contact between them?
Consider these images showing the magnetic field lines of a horse-shoe magnet. Magnetic intensity at any point in its field is directly proportional to its magnetic flux.So the region where the field lines are more densely packed have a higher intensity than where the field lines are loosely packed. If possible, draw the field lines for your own case and you will realize where the magnetic intensity is most and least.
The following is multiple choice question (with options) to answer.
What is the name of the region of a magnet that has the most pull? | [
"grid",
"pole",
"tail",
"center"
] | B | Imagine a huge bar magnet passing through Earth’s axis, as in the Figure below . This is a good representation of Earth as a magnet. Like a bar magnet, Earth has north and south magnetic poles. A magnetic pole is the north or south end of a magnet, where the magnet exerts the most force. |
SciQ | SciQ-433 | genetics, evolution, population-genetics, theoretical-biology, natural-selection
Title: Why does the slope of parent-offspring regression equals the heritability in the narrow sense? Background
---- Notations and assumptions ----
let $W_{ij}$ be the fitness associated to the genotype $AiAj$. $x$ is the frequency of the allele $A1$ in the population. The frequency of the allele $A2$ is $1-x$ because we'll consider only the case of a bi-allelic locus. Also, we consider that only one locus influence the random variable $W$ (the fitness). We will assume that the environment does not influence the fitness. We also assume random mating in order to use hardy-Weinberg equilibrium.
---- calculations ----
The mean fitness is:
$$\bar W = x^2W_{11} + 2x(1-x)W_{12} + (1-x)^2W_{22}$$
The variance of fitness is:
$$\sigma^2 = x^2(W_{11}-\bar W)^2 + 2x(1-x)(W_{12}-\bar W)^2 + (1-x)^2(W_{22}-\bar W)^2$$
We then want to calculate the covariance between father and son with respect to fitness.
Suppose first that the father is $A_1A_1$ Then the son will be $A_1A_1$ if the mother transmits an $A_1$ gene to him, an event with probability x. Similarly the son will be $A_1A_2$ with probability $1-x$. The father himself will be $A_1A_1$ with probability $x^2$. Continuing this wa it is possible to draw up a table of the probabilities of the various father-son combinations in genotype and hence fitness.
Therefore, assuming no change in frequency of $A1$ between the two generations, the covariance father-son is:
The following is multiple choice question (with options) to answer.
How many major forces of elevation cause allele frequencies to change? | [
"three",
"four",
"one",
"five"
] | B | There are four major forces of evolution that cause allele frequencies to change. They are mutation, gene flow, genetic drift, and natural selection. |
SciQ | SciQ-434 | particle-physics, nuclear-physics, neutrons
Title: Are neutrons and protons stable inside atomic nuclei? Some people naturally assume that atomic nuclei are made of protons and neutrons. That is, they are basicly clumps of protons and neutrons that each maintain its separate existence, like pieces of gravel maintain their existence if you mold them together in a ball with mud for a binding force.
How come neutrons in a nucleus don't decay?
This is a natural assumption. A hydrogen nucleus can have one proton as its nucleus. Nuclei can absorb neutrons to become other isotopes. It's natural to assume that nuclei are clumps of protons and neutrons.
Sometimes if an atomic nucleus gets broken by application of large amounts of energy, typically applied with a fast-moving subatomic particle, they might release a neutron or a proton. So for example, smash an alpha particle into a beryllium nucleus and a neutron comes out. Doesn't that imply that the neutron was in there all along, waiting to get out?
But that reasoning implies that electrons, positrons, muons etc are also inside the nucleus all the time, waiting to get out.
There's an idea that protons and neutrons inside a nucleus swiftly transfer charges. This is analogous to a theory from organic chemistry, where sometimes single and double bonds switch back and forth, increasing stability. We could have quarks getting exchanged rapidly between protons and neutrons, increasing stability. I can see that as increasing stability for the nucleus, but I just don't see it as making the protons and neutrons more stable. If ten Hollywood couples get repeated divorces and marry each other's exes, you wouldn't say that the original marriages are stable.
In the extreme, the quarks might just wander around in a nuclear soup, and the protons and neutrons have no more identity than a bunch of used computers disassembled with the parts on shelves for resale. Maybe you could collect enough parts to take a working computer out of the store with you, but it probably won't be one of the old computers.
The following is multiple choice question (with options) to answer.
Where in the atom is a neutron found? | [
"orbit",
"the nucleus",
"electron",
"proton"
] | B | A neutron is one of three main particles that make up the atom. It is found in the nucleus and is neutral in electric charge. It has about the same mass and diameter as a proton. Neutrons are found in all atoms except for most atoms of hydrogen. |
SciQ | SciQ-435 | special-relativity, terminology, definition
The first term in the expansion above is the rest mass (energy) and the second is the "kinetic" energy. If a particle's total kinetic energy is much larger than its rest mass energy, you should be able to see that this means the particle is "relativistic".
Given that the average kinetic energy of a system of particles is simply related to the temperature, this basically means that (in units where $c = 1$ and the Boltzmann constant $k_B = 1$) when $T \gg m$, a massive particle can be considered to be relativistic, and when $T \ll m$ a massive particle can be considered to be non-relativistic. In other words, as a system of particles cools, $T \sim m$ is a rough threshold for the particle to be "non-relativistic".
The following is multiple choice question (with options) to answer.
In physics, what is defined as the average kinetic energy of the particles of matter? | [
"friction",
"density",
"temperature",
"magnetism"
] | C | No doubt you already have a good idea of what temperature is. You might say that it’s how warm or cool something feels. In physics, temperature is defined as the average kinetic energy of the particles of matter. When particles of matter move more quickly, they have more kinetic energy, so their temperature is higher. With a higher temperature, matter feels warmer. When particles move more slowly, they have less kinetic energy on average, so their temperature is lower. With a lower temperature, matter feels cooler. |
SciQ | SciQ-436 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
What organelles are known as the "power plants" of the cell? | [
"mitochondria",
"golgi body",
"flagella",
"plastid"
] | A | They have lots of mitochondria. Mitochondria are called the power plants of the cell, as these organelles are where most of the cell's energy is produced. Cells that need lots of energy have lots of mitochondria. |
SciQ | SciQ-437 | physical-chemistry, thermodynamics, solubility, solutions, ideal-gas
Title: Confusion in solubility expressions in Henry's Law While reading about Henry's law and solubility I frequently come across two relations:
$C = k_{h}P$ (c = concentration of a dissolved gas)
$P = k_{h}x$ (x = solubility/mole_fraction)
What is the difference in these two expressions, do they seem to contradict each other? I am not able to decide whether a gas with higher $k_{h}$ would be more soluble or less soluble.
Please help me out with the same I am new to this topic Sander (Ref. 1) has compiled a useful review of Henry's law constants in water that includes an introduction showing notation and conversions.
There are two types of Henry's law constants:
Solubility constants convert from pressure to concentration in solution (solubility):
$$c=Hp$$
Volatility constants convert from concentration in solution (solubility) to pressure:
$$p=Kc$$
Usually it is possible to determine which constant is reported by inspecting the units.
References
R. Sander. Compilation of Henry’s law constants (version 4.0) for water as solvent. Atmos. Chem. Phys., 15, 4399–4981, 2015.
www.atmos-chem-phys.net/15/4399/2015/doi:10.5194/acp-15-4399-2015
The following is multiple choice question (with options) to answer.
Dalton's law and henry's law both describe aspects of what type of exchange? | [
"gas",
"liquid",
"electron",
"energy"
] | A | 22.4 Gas Exchange The behavior of gases can be explained by the principles of Dalton’s law and Henry’s law, both of which describe aspects of gas exchange. Dalton’s law states that each specific gas in a mixture of gases exerts force (its partial pressure) independently of the other gases in the mixture. Henry’s law states that the amount of a specific gas that dissolves in a liquid is a function of its partial pressure. The greater the partial pressure of a gas, the more of that gas will dissolve in a liquid, as the gas moves toward equilibrium. Gas molecules move down a pressure gradient; in other words, gas moves from a region of high pressure to a region of low pressure. The partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries. As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood. In contrast, the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli. Therefore, carbon dioxide diffuses across the respiratory membrane from the blood into the alveoli. The amount of oxygen and carbon dioxide that diffuses across the respiratory membrane is similar. Ventilation is the process that moves air into and out of the alveoli, and perfusion affects the flow of blood in the capillaries. Both are important in gas exchange, as ventilation must be sufficient to create a high partial pressure of oxygen in the alveoli. If ventilation is insufficient and the partial pressure of oxygen drops in the alveolar air, the capillary is constricted and blood flow is redirected to alveoli with sufficient ventilation. External respiration refers to gas exchange that occurs in the alveoli, whereas internal respiration refers to gas exchange that occurs in the tissue. Both are driven by partial pressure differences. |
SciQ | SciQ-438 | evolution, neuroscience
Several types of molecules are used as neurotransmitters; their evolutionary deployment in different synapse types across animals is fascinating and still poorly understood. Many are used widely in eukaryotes for intercellular communication, but some of the biogenic amines may be present in animals as a result of the late horizontal transfer of synthesis enzymes from bacteria(Iyer et al. 2004). For instance, epinephrine and norepinephrine are important neurotransmitters in vertebrates but not in protostomes (but see Bauknecht & Jekely 2017), whereas the opposite is true of octopamine and tyramine (Figure 4). Cnidarians make a set of neurotransmitters similar to those in vertebrates (Kass-Simon & Pierobon 2007), but Nematostella expresses most nonpeptide types in the endoderm near the pharynx and testes—only peptide transmitters are found in neurons(Oren et al. 2014)
Intriguingly, ctenophores seem to use a much more restricted set, as glutamate is the only well-validated neurotransmitter (Moroz et al. 2014). This is consistent with the theory that neurons arose independently in ctenophores and planulozoans because vertebrates and most protostomes use acetylcholine at the NMJ [neuromuscular junction I assume -my edit]. However, arthropods use glutamate at the NMJ, just as ctenophores do ( Jan & Jan 1976), and cnidarians probably use neuropeptides (Oren et al. 2014). Although sponges do not have true synapses, they use γ-aminobutyric acid (GABA), glutamate, and nitric oxide to coordinate contractions (Elliott & Leys 2010). Trichoplax individuals also lack synapses,but their secretory flask cells label for FMRFamide, suggesting a conserved role in transmission for this peptide class (Smith et al. 2014).
The following is multiple choice question (with options) to answer.
What vesicles store neurotransmitters? | [
"hydrophobic",
"Golgi apparatus",
"dendritic",
"synaptic"
] | D | Secretory Vesicles contain materials that are to be excreted from the cell, such as wastes or hormones . Secretory vesicles include synaptic vesicles and vesicles in endocrine tissues. Synaptic vesicles store neurotransmitters. They are located at presynaptic terminals in neurons. When a signal reaches the end of an axon, the synaptic vesicles fuse with the cell membrane and release the neurotransmitter. The neurotransmitter crosses the synaptic junction, and binds to a receptor on the next cell. Some cells also produce molecules, such as hormones produced by endocrine tissues, needed by other cells. These molecules are stored in secretory vesicles and released when needed. Secretory vesicles also hold enzymes needed to make extracellular structures, such as the extracellular matrix of animal cells. |
SciQ | SciQ-439 | shown for illustrative purposes.Anders Celsius ( °C ) the CIPM formally adopted degree to... Is an absolute absence of any thermal energy temperatures from Celsius to kelvin-K = °C... Is 273.15 K − 273.15 Celsius = 0° C. what is the temperature value can be converted Celsius... To degrees Celsius the Celsius temperature is -273.15ºC 273 in Kelvin Units independently formula. Sciences, but is often used to measure temperature in order to obtain the required Celsius is... Celsius … the unit of temperature and a unit of Kelvin is the temperature the! Let us now study in detail about Kelvin to Celsius, is 1 Celsius is C = 0 as! 273 Kelvin -273.15 Kelvin - celsius.The equation is simple use 273 kelvin to celsius formula temperature in Kelvin … Kelvin ( )... ) is equal to the nearest hundredth formula is used instead of 273.15 °C = 273.15 + Celsius and scales... Vice versa the time example problem illustrates the method to convert temperatures from to... A common System International ( SI ) temperature conversion above Units independently of Units ) an.: Celsius, which equals 273 Kelvin ( K ) = T [ °C ] +.! Formula, an equation, or both used to measure the temperature in order obtain... This 273 means and why is this 273 and not any other value shown... -273.15ºc = 0 ºC as T = 1 ºC as T = 273 + 0 =273 K. 1ºC to formula! Of Largs, who described the need for an absolute … Celsius Kelvin. This formula to convert degree to Kelvin numbers are always exactly 273.15 apart Celsius degree now in! Equation is simple lowest possible temperature definíciója alapján és sok kísérlet tanulsága alapján kimondható hogy... = °C + 273 °C = K - 273.15 Mutasd a folyamatot nearest hundredth Réaumur the... 273 is used, T [ K ] = T [ K ] = [. In Kelvin ( K ) to Celsius conversion formula: Kelvin = 273.15.. Freezes at 0 degrees Kelvin is often used to convert
The following is multiple choice question (with options) to answer.
What temperature scale is obtained by adding 273 degrees from the corresponding celsius temperature? | [
"whittle scale",
"kelvin scale",
"ph scale",
"seismic scale"
] | B | The Celsius scale is the standard SI temperature scale. It is equal to the Kelvin scale if you minus 273 from the Celsius reading. Water has a boiling point of and a freezing point of . |
SciQ | SciQ-440 | hematology
Title: Is Hemoglobin binding to oxygen the same as Adsorption I have recently been reading about Hemoglobin and came across how it binds to oxygen. This seems very similar to Adsorption. Is the process of Hemoglobin binding to oxygen through Adsorption ? From the Wikipedia article you cite the answer to your question is clearly NO. They seem very different: absorption is described as a surface phenomenon, whereas oxygen binding occurs in a single internal pocket in each globin subunit and forms a specific bond to an Fe(II) atom. The chemical nature of this pocket is quite different from that of the surface of the protein.
The Wikipedia article states:
Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface.[1] This process creates a film of the adsorbate on the surface of the adsorbent.
and
Similar to surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent, or metallic) of the constituent atoms of the material are filled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates.
However if you consult a text-book which describes the biochemistry of haemoglobin, such as Berg et al. you will find the specific chemical nature of the binding clearly described, as indicated by this extract:
The iron atom lies in the center of the protoporphyrin, bonded to the four pyrrole nitrogen atoms. Under normal conditions, the iron is in the ferrous (Fe2+) oxidation state. The iron ion can form two additional bonds, one on each side of the heme plane. These binding sites are called the fifth and sixth coordination sites. In hemoglobin, the fifth coordination site is occupied by the imidazole ring of a histidine residue from the protein. In deoxyhemoglobin, the sixth coordination site remains unoccupied...The binding of the oxygen molecule at the sixth coordination site of the iron ion substantially rearranges the electrons within the iron so that the ion becomes effectively smaller, allowing it to move into the plane of the porphyrin (Figure 10.19).
The following is multiple choice question (with options) to answer.
Hemoglobin is a large molecule made up of proteins and iron. it consists of four folded chains of a protein called this? | [
"globin",
"peptide",
"histone",
"insulin"
] | A | Hemoglobin Hemoglobin is a large molecule made up of proteins and iron. It consists of four folded chains of a protein called globin, designated alpha 1 and 2, and beta 1 and 2 (Figure 18.7a). Each of these globin molecules is bound to a red pigment molecule called heme, which contains an ion of iron (Fe2+) (Figure 18.7b). |
SciQ | SciQ-441 | evolution, definitions, artificial-selection
It does not lead to new species
In short, 1) it does lead to new species 2) the concept of species is often meaningless as poorly defined 3) evolution > speciation. In more details, below..
It does lead to new species. Different lineages of cabbage are considered different species. Cows and ox are different species. Pigs and boars are often considered different species. While wolves and dogs are considered same species, some lineages within this species (such as a Chihuahua and a Great Dane) are, I think, reproductively isolated. You might also want to have a look at the post Have we ever observed two drosophila lineages that evolved reproductive isolation in labs?
The question of whether selective breeding lead to speciation or not does not matter much on the question of whether it leads to evolution. Speciation is one outcome of evolution but is definitely not the same as evolution. Evolution does not need to lead to speciation. For example, evolution of the lactase gene in humans (see this post) did not lead to any speciation. It is still an evolutionary process.
The concept of species is mainly arbitrary. If you want to understand the concept of species, have a look at the post How could humans have interbred with Neanderthals if we're a different species?.
It decreases, rather than increases, the size of the gene pool (is this actually true?)
The following is multiple choice question (with options) to answer.
A new species is said to have evolved if separated members of a species evolve genetic differences that prevent what from occurring with the original members?? | [
"re-population",
"extinction",
"evolution",
"interbreeding"
] | D | Assume that some members of a species become geographically separated from the rest of the species. If they remain separated long enough, they may evolve genetic differences. If the differences prevent them from interbreeding with members of the original species, they have evolved into a new species. Speciation that occurs in this way is called allopatric speciation . An example is described in the Figure below . |
SciQ | SciQ-442 | human-biology, human-anatomy, terminology, anatomy, etymology
Title: Why is the opposite of plantar flexion called "dorsiflexion"? Why is the action of flexing the foot so that the toes move anteriorly/superiorly (i.e. in the direction opposite that which they move during plantar flexion) described as "dorsiflexion?" In the same vein, why is the top surface of the foot called the "dorsal surface?"
If anything, the action opposite to plantar flexion moves the foot in the ventral direction, doesn't it? And surely if you've ever seen a human in the anatomical position, you can see that there's nothing dorsal about the top surface of the foot - it's superior, perhaps, but by no means dorsal. Anatomical terms must be able to fit a wide variety of organisms, from insects to fish, dogs, horses, chimpanzees to humans. That's why the terms are sometimes confusing to people who are thinking only of bipedal humans.
In anatomy, the dorsum is the upper side of animals that typically run fly, swim or crawl in a horizontal position. In vertebrates the dorsum contains the backbone. In such an animal the "ground side" is the ventrum.
Due to varied orientation on quadrupedal mammals (where the term is more appropriately used) the "back"-side of the hand, the "top"-side of the foot and the upper surface of the tongue are referred to by the term dorsum.
Does this picture help? Note the dorsal surfaces of the body, muzzle, feet.
In anatomy, the sole of the foot is called the plantar surface. The top of the foot is called the dorsum of the foot. (Imagine us walking on all fours like apes.) Therefore when you extend your foot, it's called plantar flexion; when you flex your foot upwards towards your head, it's called dorsiflexion.
Similarly, the arteries feeding the bottom of your foot form the plantar arch. Those feeding the top are the dorsal artery (or the dorsalis pedis).
Because anatomy must describe other animals than ourselves with other orientations, it must be consistent. In a quadruped, the dorsum of the tongue and the feet do actually point to it's "back" surface. See the picture below:
The following is multiple choice question (with options) to answer.
What term describes the orientation of a body lying face-down? | [
"Under",
"Supine",
"prone",
"Diagnal"
] | C | A body that is lying down is described as either prone or supine. Prone describes a face-down orientation, and supine describes a face up orientation. These terms are sometimes used in describing the position of the body during specific physical examinations or surgical procedures. |
SciQ | SciQ-443 | energy, visible-light, photons, atomic-physics, absorption
Why is it that the electron loses energy when it jumps to the next energy level
Let's take the common usage of the word jump as upwards. So in this above case, the electron gains energy. It loses energy when it falls back down to a lower level.
I have to admit that I don't like using words like jump and fall, because they are based on the Bohr model of the atom, which is not correct in almost every aspect.
So let me give you two pictures, one of the old model, which your question is based on, and one of the more modern picture.
The Bohr model (of 100 years ago)
The Orbital Distribution Density model
The electron will tend to lose energy if it can, by emitting a photon of the correct wavelength, that enables it to transition to a lower energy level, but if that lower level is already occupied to the maximum amount, then the electron is forced to stay at a higher level.
The difference between the pictures is the the Bohr model assumes a particle structure, whereas we now think in terms of the probability of finding an electron in a certain region, so we cannot be as definite as in the earlier model. Also, when the transition from one level to another occurs, it is not a smooth transfer like a car changing lanes, it is for a time a more chaotic operation, with the electron (or rather its' likelyhood of being found) bouncing around the place until it settles into a lower orbit.
In the first example the electrons moving with current gives energy to the electron in the atom. So the electron in the atom absorbs the moving electron? If so how is this possible because they are both negative?
There is no question of an electron absorbing another electron. Instead, by means of photon emission, momentum can be transferred between electrons, bearing in mind the conservation laws regarding energy and momentum.
An example of this is a Feynman Diagram:
Where the wavy line represents energy and momentum being transferred by means of a photon.
The following is multiple choice question (with options) to answer.
What happens to energy when an atom gains an electron? | [
"it increases",
"it is used",
"it is released",
"it is folded"
] | C | A: Energy is released when an atom gains an electron. Halogens release the most energy when they form ions. As a result, they are very reactive elements. |
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