source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-5944 | meteorology, tornado
Title: Why does the so called "tornado alley" exist? 75% of the world's tornadoes occur in the USA, and within the USA these tornadoes are most likely to occur in particular regions of the country, such as the well known "tornado alley". The diagram below shows tornado activity in various parts of the USA, from 1950 to 1998. It can be seen from the diagram below that most tornadoes occur on the Eastern half of the country. Within this half of the country, there are regions with much greater tornado activity than others, highlighted in dark red in the diagram below, and includes the so called "tornado alley". Why is there a higher frequency of tornadoes in these regions compared to other regions of the USA and around the world? The kind of tornadoes "tornado alley" refers to are associated with supercell thunderstorms. To first figure out why this region exists, we need to explore why this is a hotspot for supercells.
Thunderstorms require energy and this energy comes in the form of convective available potential energy (CAPE). This is simply the vertically integrated buoyancy of a parcel from its level of free convection (LFC) to its equilibrium level (EL). Thunderstorms need CAPE but CAPE is not a great predictor of what kind of storm we get, that falls to vertical windshear. Supercells form in environments with a 0-6 km shear (this measure if just a vector difference of the winds at these levels) greater than 20 m/s.
CAPE is going to be maximized where you have warm, moist air at the surface and cold air aloft. The Gulf of Mexico has plenty of water and it is common to find strong southerlies advecting this moisture into the US. With a particularly strong low level jet, this moisture can be advected as far north as the Dakotas. As warm air is typically found toward the equator, this is also advecting warm air northward. This results in a tongue of warm, moist air extending northward out of the gulf.
The following is multiple choice question (with options) to answer.
At what time of the year can tornadoes occur? | [
"spring",
"summer",
"any",
"winter"
] | C | |
SciQ | SciQ-5945 | volcanoes, pyroclastic-flows
Edit: In a research* it is suggested that a turbidite current can flow over barriers, if the thickness of the flow exceeds %65 of the barrier. One may interpret this that, after a pyroclastic current dives to shallow water it may come back to the surface again.
The following is multiple choice question (with options) to answer.
How is sediment transported? | [
"winds",
"currents",
"landslides",
"storms"
] | B | The shore may have a lot of sediment washed from land or eroded from cliffs. The sediment is transported by currents. |
SciQ | SciQ-5946 | metabolism, human-anatomy, pharmacology, liver
For drugs introduced through an injection, for example, metabolism occurs throughout the circulatory system and in the liver. Remember that it's all the same blood supply, but the first-pass effect just refers to the blood that goes to the liver before entering the systemic circulation (by which it can travel to its target).
The following is multiple choice question (with options) to answer.
Where are all hormones secreted into before entering the circulatory system? | [
"Amniotic fluid",
"interstitial fluid",
"blood stream",
"Cerebrospinal fluid"
] | B | |
SciQ | SciQ-5947 | 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.
Vertebrates have tissues which are organized into organs which in turn are organized into what? | [
"organ systems",
"artificial systems",
"information systems",
"maturation systems"
] | A | 24.4 Subphylum Vertebrata (Vertebra from Latin vertere, to turn). Characterized by separate bones or cartilage blocks firmly joined as a backbone. The backbone supports and protects a dorsal nerve cord. Vertebrates have tissues which are organized into organs which in turn are organized into organ systems. All vertebrates share the following characteristics: - segmentation - a true coelom - bilateral symmetry - cephalization - a backbone - a bony skull - a closed circulatory system - chambered heart - two pairs of jointed appendages - tissues organized into organs Vertebrate Organ Systems: - Nervous System - Circulatory System - Digestive System Respiratory System - Reproductive System - Excretory System • Vertebral column: Not present in higher vertebrate adults. (In humans, the gel-like, spongy core of the vertebral column is the only remainder. Ruptured or herniated disc is an injury to this. ) • Cranium: Composite structure of bone/cartilage. Two functions: 1. Supports sensory organs of head and 2. Encloses or partially encloses the brain. What evolutionary relationship could we imagine between sessile echinoderms and the higher chordate animals? Paedomorphic (child-form) hypothesis: basically, evolution of sexual reproduction in what had previously been a larval life stage, or the retention of at least one juvenile characteristic into the adult (adult = sexually reproducing) stage. Some scientists believe that this occurred in a proto-chordate animal lineage. Maybe chordates (and vertebrates) arose from sessile (attached) ancestors. Selection in these proto-chordates maybe began to favor more time in the larval stage, as feeding was more successful or mortality lower in this stage. As larvae got bigger physics shows that the cilia become less efficient for locomotion, favoring the undulating motion allowed by a notochord. Is this hypothesis crazy? A similar example of this today is Epemeroptera, the mayfly, which has almost abandoned its adult stage. Its one-year lifespan is mostly larval with just a brief day of reproduce-and-die as an adult, which doesn’t even have usable mouthparts. Tunicate (sea squirt) larva has all four chordate characteristics, although adult sessile (“attached”). |
SciQ | SciQ-5948 | resources, soil
Title: Is soil a renewable resource? My geology textbook tells me that soil is not renewable, and I agree with this, but there was some question in my class as to whether this is true.
Some soils take more than a human lifetime to regenerate. However, in crop production, it seems as if soil can be regenerated with additives.
In the scientific community of soil scientists, is soil considered a renewable resource by most of those scientists? Is there strong evidence to support this? Soil is an interesting case because although it is non-renewable (at any useful rate) as a 'bulk material' once removed from the ground, the nutrient content of soil can be renewed with fertilizers.
What a soil-scientist would understand as 'soil' is ultimately produced from the physical and chemical breakdown of solid bedrock at the base of the soil horizon. The rate at which this happens for natural soil production can vary substantially depending on the climatic conditions and other factors, but typically could range from 0.1 to 2.0 mm/yr.
In many intensively farmed regions, (top)soil is being removed by erosion much faster than it is being replaced by natural process. Removal of vegetation cover is enough to expose bare soil to rainsplash erosion at rates much greater than it is renewed. Once soil is bare, it becomes much more susceptible to erosion.
I think the additives you are referring to replenish the nutrient content of the soil, and not the the bulk material that would be produced by bedrock decomposition. With careful management, the fertility of existing soil can be maintained. But if the soil is allowed to be washed off or erode, for all practical purposes, the rate of replenishment is not fast enough for it to be classed as renewable in that sense.
This site has links to more aspects surrounding this issue.
The following is multiple choice question (with options) to answer.
What can renewable resources can be replaced by? | [
"natural processes",
"fossil fuels",
"human processes",
"change processes"
] | A | Renewable resources can be replaced by natural processes as quickly as they are used. |
SciQ | SciQ-5949 | meteorology, temperature, barometric-pressure
Title: Why do tropical areas have low air pressure? From the question Why are pressure levels raised on warm days?, my understanding is that the air pressure at surface level is not affected by temperature, as the mass of the imagined air column stays the same (even though it's extended higher due to lower density). Then, at any given true altitude, warmer temperatures would correspond to higher pressure. The air column analogy makes a lot of sense to me.
However, I was reading NOAA's explanation of atmospheric circulations, which says "This region would become very hot, with hot air rising into the upper atmosphere. This would create a constant belt of low pressure around the equator". That seems to contradict the concept above.
My guess is, in the air column analogy, when the air column is extended higher, it's "leveled out" with the surrounding air, just like water. So we end up with the column with the same original height but lower density, meaning that the total weight at the bottom is lower than before (which means lower pressure). However, if this is true, then the pressure would be lower at any altitude, not just at the surface.
I'm confused now. Please help, thank you! Your guess is correct. As the column of air gets heated, it expands, and that results in a higher pressure in the upper troposphere.
As a result, the air from this warm column flows outwards along the tropopause. This outflow of air is what causes a reduction in the net air mass within the column, and a subsequent reduction in the surface pressure. Therefore at the surface, the air will flow towards the column; so the air moves in a cyclonic sense:
However, if this is true, then the pressure would be lower at any altitude, not just at the surface.
The surface pressure has indeed reduced, but so has the pressure lapse rate (since the air has expanded upwards). Therefore, in the upper atmosphere, the pressure will actually be higher above the warm surface (as can be seen in the first image).
(Images source: Meteorology by Oxford)
The following is multiple choice question (with options) to answer.
When warm air rises up to the tropopause, where does it flow? | [
"east or west",
"west or south",
"east or north",
"north or south"
] | D | Earth is hottest at the equator and gets cooler toward the poles. The differences in heating create huge convection currents in the troposphere. At the equator, for example, warm air rises up to the tropopause. It can’t rise any higher, so it flows north or south. |
SciQ | SciQ-5950 | neuroscience, brain
Davis, Z. W., Muller, L., Martinez-Trujillo, J., Sejnowski, T., & Reynolds, J. H. (2020). Spontaneous travelling cortical waves gate perception in behaving primates. Nature, 1-5.
Harris, K. D. (2005). Neural signatures of cell assembly organization. Nature Reviews Neuroscience, 6(5), 399-407.
Liu, X., Ramirez, S., Pang, P. T., Puryear, C. B., Govindarajan, A., Deisseroth, K., & Tonegawa, S. (2012). Optogenetic stimulation of a hippocampal engram activates fear memory recall. Nature, 484(7394), 381-385.
Luczak, A., McNaughton, B. L., & Harris, K. D. (2015). Packet-based communication in the cortex. Nature Reviews Neuroscience, 16(12), 745-755.
The following is multiple choice question (with options) to answer.
What kind of messages do neurons send? | [
"digestive messages",
"minor messages",
"Neurotic messages",
"electrical messages"
] | D | Nervous tissue consists of nerve cells, or neurons, which can send and receive electrical messages. Nervous tissue makes up the brain, spinal cord, and other nerves that run throughout the body. |
SciQ | SciQ-5951 | thermodynamics, pressure, surface-tension, stability, bubbles
Title: Why is there a limited range of possible soap bubble size? Soap bubbles are never "too small" or "too large". What defines the range of possible diameters of a soap bubble?
Related questions:
Why do steam bubbles increase in size as they rise,
Why is the pressure inside a soap bubble higher than on the outside,
What is the physics behind a soap bubble At the lower limit, if the bubble is very small the pressure inside will be so large that the gas inside can dissolve into the shell of the bubble, and from there diffuse out to the atmosphere. That limits the life time of small bubbles.
On the large side, huge bubbles (several meters diameter) are certainly possible. These tend to be unstable because they require extremely low surface tension, and thus they don't "keep their shape" very well. Over time they evaporate, or the soap molecules migrate causing an uneven distribution of surface tension along the surface. With insufficient surface tension in some places the bubble will once again burst.
In the absence of evaporation and instability, the ultimate size limit of a bubble may have to do with gravity: the film somehow needs to support the "column of soap bubble" above it, and if you think about hanging a soap film from a thread, you can see that it would be thinner at the top (which is supporting more weight) and thicker at the bottom. There will be a limit beyond which the film cannot support its own weight - I don't know how to compute it.
The following is multiple choice question (with options) to answer.
What forces in liquids are strong enough to keep them from expanding significantly when heated? | [
"intermolecular forces",
"gravitational forces",
"particles forces",
"outermolecular forces"
] | A | Thermal Expansion The intermolecular forces in liquids are strong enough to keep them from expanding significantly when heated (typically only a few percent over a 100°C temperature range). Thus the volumes of liquids are somewhat fixed. Notice from Table 11.1 "The Density of Water at Various Temperatures" that the density of water, for example, changes by only about 3% over a 90-degree temperature range. Table 11.1 The Density of Water at Various Temperatures. |
SciQ | SciQ-5952 | neuroscience, pathology, human-genetics, neurology
Presumably, genes in the first category contribute most to the shared phenotype of Down syndrome, and genes in the second category contribute most to the variation. Perhaps alleles that produce mRNA transcripts at the low end of normal for those genes are less susceptible to the effects of chromosome duplication.
A case study: Amyloid precursor protein
One protein of interest in particular is the amyloid precursor protein, APP, which is also associated with Alzheimer's disease (which shares some phenotypic characteristics with Down syndrome). APP expression varies widely among tissue types and individuals. Therefore, although APP mRNA levels are significantly elevated in Down syndrome individuals, the distributions between controls and Down syndrome are very overlapping; for example, see Figure 2B from the Antonarakis 2016 review.
3. Interactions with genes on other chromosomes
The third contributor to the variation of symptoms is the interaction of duplicated chromosome 21 genes with alleles located on other chromosomes. Just for an example where some of the genetic basis is understood, Down syndrome individuals are susceptible to certain leukemias, which are also associated with specific alleles on other chromosomes (Antonarakis, 2016). It seems that trisomy 21 affects histone modification in the areas of those alleles (Lane et al., 2014) and promotes proliferation of B-cells. Therefore, Down syndrome interacts with those other oncogenes to produce a greater combined risk. Individual with Down syndrome but not possessing the other alleles are less susceptible to the increased risk of leukemia
Similar interactions are likely with other systems that are influenced by Down syndrome, though the full molecular basis of all of those interactions are not fully understood. The Down Syndrome Genomes Project aims to, among other things, discover these other alleles outside of chromosome 21 that contribute to Down syndrome symptoms, which may also help understanding of the contribution of those alleles to other disorders (Antonarakis, 2016).
The following is multiple choice question (with options) to answer.
Which chromosome is associated with cri du chat syndrome? | [
"spore 5",
"genome 5",
"chromosome 5",
"collagen 5"
] | C | Chromosomal disorders also occur when part of a chromosome becomes damaged. For example, if a tiny portion of chromosome 5 is missing, the individual will have cri du chat (cat’s cry) syndrome. These individuals have misshapen facial features, and the infant’s cry resembles a cat’s cry. |
SciQ | SciQ-5953 | organic-chemistry
Title: Use of concentrated sulfuric acid in Fischer esterification Concentrated sulfuric acid is often used as a catalyst in Fischer esterification reactions. To my knowledge, the role it plays in the reaction is not as a reducing agent or dehydrating agent but only serves the role of creating an acidic environment, as seen in the mechanism.
Thus, dilute sulfuric acid would be sufficient. In fact, it would be better since it ionises to give an even more acidic solution. However, chemists choose to use the concentrated one instead, suggesting that the role of sulfuric acid is more of a reducing agent. Is there a reason for this? In fact, sulfuric acid is not a must. Many other H-acids, as well as Lewis acids and their combinations would be sufficient.
The trick here is not to get concentrated acid, but to reduce amount of water in the system. Consider the simpliest transformation, which is typically performed with a large excess of methanol and trace amounts of acid:
$$\ce{R-C(O)OH + CH3OH_{(excess)} <=>>[HCl] R-C(O)OCH3 + H2O}$$
This is an equilibrium reaction. The catalyst allows us significantly faster achieve the equilibrium state, but it does not shift it. Catalyst is equally promoting both direct and reverse reactions. A large excess of alcohol, in accordance with the law of mass action, shifts the equilibrium toward the formation of the ether and thus increases the degree of conversion of the acid into ether.
But if water is not eliminated from the system, or is initially present, hydrolysis occurs:
$$\ce{R-C(O)OCH3 + H2O_{(excess)} <=>>[HCl] R-C(O)OH + CH3OH }$$
Hydrolysis of ether will happen even faster, if a strong base is present, as in this case reaction equilibrium shifts further to the right due to the salt formation.
The bottom line is, in order for the reaction to go to the end, you either add an excess of acid (or alcohol), or remove water as it is produced. Starting with concentrated or water-free acid you are not only simplifying your life, but you are also getting better yield.
The following is multiple choice question (with options) to answer.
The strong affinity of concentrated sulfuric acid for water makes it a good agent of what? | [
"diluting",
"hydrating",
"concentrating",
"dehydrating"
] | D | The strong affinity of concentrated sulfuric acid for water makes it a good dehydrating agent. It is possible to dry gases and immiscible liquids that do not react with the acid by passing them through the acid. Sulfuric acid is a strong diprotic acid that ionizes in two stages. In aqueous solution, the first stage is essentially complete. The secondary ionization is not nearly so complete, and HSO 4 − is a moderately strong acid (about 25% ionized in solution of a HSO 4 − salt: Ka = 1.2 × 10−2). Being a diprotic acid, sulfuric acid forms both sulfates, such as Na2SO4, and hydrogen sulfates, such as NaHSO4. Most sulfates are soluble in water; however, the sulfates of barium, strontium, calcium, and lead are only slightly soluble in water. Among the important sulfates are Na2SO4⋅10H2O and Epsom salts, MgSO4⋅7H2O. Because the HSO 4 − ion is an acid, hydrogen sulfates, such as NaHSO4, exhibit acidic behavior, and this compound is the primary ingredient in some household cleansers. Hot, concentrated sulfuric acid is an oxidizing agent. Depending on its concentration, the temperature, and the strength of the reducing agent, sulfuric acid oxidizes many compounds and, in the process, undergoes reduction to SO2, HSO 3 −, SO 3 2−, S, H2S, or S2−. Sulfur dioxide dissolves in water to form a solution of sulfurous acid, as expected for the oxide of a nonmetal. Sulfurous acid is unstable, and it is not possible to isolate anhydrous H2SO3. Heating a solution of sulfurous acid expels the sulfur dioxide. Like other diprotic acids, sulfurous acid ionizes in two steps: The hydrogen sulfite ion, HSO 3 −, and the sulfite ion, SO 3 2−, form. Sulfurous acid is a moderately strong acid. Ionization is about 25% in the first stage, but it is much less in the second (Ka1 = 1.2 × 10−2 and Ka2 = 6.2 × 10−8). In order to prepare solid sulfite and hydrogen sulfite salts, it is necessary to add a stoichiometric amount of a base to a sulfurous acid solution and then evaporate the water. These salts also form from the reaction of SO2 with oxides and hydroxides. Heating solid sodium hydrogen sulfite forms sodium sulfite, sulfur dioxide, and water: Δ. |
SciQ | SciQ-5954 | reproduction
Excerpts from the references that lead to the short answer above:
In the developing female fetus, oogonia become primary oocytes that begin the first division of meiosis. However, this division is not completed and the primary oocytes remain “frozen” in the prophase stage of the first meiotic division.
At birth, oogonia are no longer present. Each primary oocyte is surrounded by a single layer of squamous epithelial cells called follicular cells. The primary oocyte together with its follicular cells is called a primordial follicle. There are about two million primordial follicles with their primary oocytes in the ovaries at birth suspended in the first division of meiosis.
As the female grows, primary oocytes begin to die and disappear with their follicular cells. This process continues until puberty when there are only about 400,000 primordial follicles left in the ovaries. The primary oocytes continue the process of oogenesis after puberty begins.[Source]
The total number of primary oocytes at birth is estimated to vary from 700,000 to2 million. During childhood most oocytes become atretic; only approximately400,000 are present by the beginning of puberty, and fewer than 500 will be ovulated.[Source]
Primary oocytes reach their maximum development at ~20[6] weeks of gestational age, when approximately seven million primary oocytes have been created; however, at birth, this number has already been reduced to approximately 1-2 million.Recently, however, two publications have challenged the belief that a finite number of oocytes are set around the time of birth.[Source]
In the human embryo, the thousand or so oogonia divide rapidly from the second to the seventh month of gestation to form roughly 7 million germ cells.[Source]
REFERENCES:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0008772
The following is multiple choice question (with options) to answer.
Where in the female body does egg production take place? | [
"ovaries",
"testes",
"endometrium",
"uterus"
] | A | Egg production takes place in the ovaries. It occurs in several steps:. |
SciQ | SciQ-5955 | physical-chemistry, biochemistry, heat, combustion, fuel
Title: Is incineration of a solid fuel complete or incomplete? If I have some solid material like biomass and incinerate it at 1000 Celsius degrees for 15 minutes in an oxidized atmosphere within an incineration oven. As an output it gives me ash. Is the incineration complete or incomplete? Like for example we have incomplete combustion (lack of oxygen) and complete combustion (enriched oxygen medium). What about this incineration? The comment by Maurice is perfectly good for analytical purposes.
For commercial use, in practical applications, the ash residue is not the only product of combustion that must be completely oxidized. The gaseous products should be $CO_2$, $H_2O$ and $N_2$, maybe a little $SO_2$ - but sometimes organic compounds volatilize before burning and escape. In backyard leaf-burning, or in fireplace fires, this escape is mostly innocuous (except for creosote buildup in chimneys), but when tons of garbage are pyrolyzed, the gaseous products can be obnoxious. In some cases, extra fuel is added to a pyrolytic garbage treatment to raise the temperature of burning and reduce noxious emissions, but that increases the cost.
So if you are going to ask about complete combustion, you might analyze for $CO$, nitrogen oxides, and other volatiles that may have escaped.
The following is multiple choice question (with options) to answer.
What is the amorphous form of carbon prepared by the incomplete combustion of natural gas? | [
"dioxide black",
"dark black",
"carbon black",
"liquid black"
] | C | Atoms within a graphite layer are bonded together tightly by the σ and π bonds; however, the forces between layers are weak. London dispersion forces hold the layers together. To learn more, see the discussion of these weak forces in the chapter on liquids and solids. The weak forces between layers give graphite the soft, flaky character that makes it useful as the so-called “lead” in pencils and the slippery character that makes it useful as a lubricant. The loosely held electrons in the resonating π bonds can move throughout the solid and are responsible for the electrical conductivity of graphite. Other forms of elemental carbon include carbon black, charcoal, and coke. Carbon black is an amorphous form of carbon prepared by the incomplete combustion of natural gas, CH4. It is possible to produce charcoal and coke by heating wood and coal, respectively, at high temperatures in the absence of air. Recently, new forms of elemental carbon molecules have been identified in the soot generated by a smoky flame and in the vapor produced when graphite is heated to very high temperatures in a vacuum or in helium. One of these new forms, first isolated by Professor Richard Smalley and coworkers at Rice University, consists of icosahedral (soccerball-shaped) molecules that contain 60 carbon atoms, C60. This is buckminsterfullerene (often called bucky balls) after the architect Buckminster Fuller, who designed domed structures, which have a similar appearance (Figure 18.22). |
SciQ | SciQ-5956 | genetics, botany, seeds
Title: What DNA does a self-fertile plant's seedling have? Some plants are said to be self-fertile. An example is Prunus tomentosa.
Assuming that no cross-pollination happened with other plants, if a self-fertile plant such as prunus tomentosa produces a seedling, what DNA will the seedling have? Is the seedling's DNA an exact copy of the parent plant's DNA, or do the genes get rearranged? Selfing (aka self-fertilizing) differs from cloning. When selfing occurs, the offspring is not an exact copy of the parent. When cloning occurs, the offspring is an exact copy (except for a few mutations) of the parent.
Selfing implies that an individual will produce two gametes (typically a spermatozoid and an ovule but that might be a bit more complicated) and these two gametes are fusing to give the zygote (egg or offspring if you prefer).
As a consequence, when selfing, meiosis is occurring (and therefore segregation and recombination) so that the offspring is not an exact clone of the parent but rather some kind of a rearrangement of the parent genome (with a few mutations of course).
The following is multiple choice question (with options) to answer.
What do gametes undergo to produce many additional copies of themselves? | [
"angiogenesis",
"mitosis",
"prophase",
"cytokinesis"
] | B | Life Cycles of Algae: Zygotic Meiosis (A), Gametic Meiosis (B) and Sporic Meiosis (C). In life cycle A (left), diploid (2n) zygotes result from fertilization and then undergo meiosis to produce haploid (n) gametes. The gametes undergo mitosis and produce many additional copies of themselves. How are life cycles B and C different from life cycle A?. |
SciQ | SciQ-5957 | thermodynamics, solar-system, atmospheric-science, climate-science, meteorology
Title: Is the atmospheric pressure the cause of a planet's surface temperature or is it the temperature the cause of a planet's atmospheric pressure? I heard a climatologist on a talk show saying that one of the widely known arguments used by climate scientists to exemplify what a runaway greenhouse effect could cause to Earth's temperature and climate (a comparison with Venus' atmosphere) is basically a farce.
He argued that Venus' high surface temperature (which is over 400ºC) is caused mainly by its high surface pressure (which is over 90x greater than Earth's) and that the so-called "greenhouse effect contribution" to this temperature was "negligible" or simply "non-existent". He mentioned the ideal gas law in order to "prove" his argument, saying that temperature grows proportionally with pressure (which, of course, is true for an ideal gas). And this pretty much settled his train of thought.
This made me wonder and I'm trying to come up with a reasoning that debunks his argument. At first, I thought one could not simply apply the ideal gas law to Venus' atmosphere, since the molar density at the surface is too high and that one should use more terms of the virial expansion to account for the behavior of the pressure near the surface. However, even if that is true, his argument remains undisputed, since the leading term of the expansion is still the "ideal gas" term.
Then I realized his oversight may have been the cause-effect relationship he tried to establish between pressure and temperature. As a matter of fact, an equation of state doesn't tell us anything about causality: it only states the relationship between different state variables that describe a system. This takes us back to my question: Is it the really the high pressure of Venus' at surface the agent responsible for its high surface temperature, or is it the other way around or maybe even a mix of the two?
The following is multiple choice question (with options) to answer.
The greenhouse effect on earth is caused by an increase in what in the atmosphere? | [
"phosphorous",
"vapor",
"satellites",
"carbon"
] | D | Burning of fossil fuels, such as oil, releases carbon into the atmosphere. This carbon must be cycled - removed from the atmosphere - back into living organisms, or it stays in the atmosphere. Increased carbon in the atmosphere contributes to the greenhouse effect on Earth. |
SciQ | SciQ-5958 | physical-chemistry, energy, heat, temperature
Title: Can we define a new unit instead of specific heat that is constant with temperature rise? Specific heat plays an important role in calculating energy and thus, heat, enthalpy and etc.
But as I sighted the definition for calorie, I was surprised.
A calorie is the amount of heat needed to alter the temperature of 1 gram of 14.5 °C water to 15.5 °C water in the pressure of one atmosphere.
The following is multiple choice question (with options) to answer.
What is the term for the quantity of heat required to raise the temperature of 1 gram of a substance by 1 degree celsius? | [
"thermal heat capacity",
"heat requirement",
"specific heat capacity",
"transferable heat"
] | C | The specific heat capacity (c) of a substance, commonly called its “specific heat,” is the quantity of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius (or 1 kelvin): q c= mΔT Specific heat capacity depends only on the kind of substance absorbing or releasing heat. It is an intensive property—the type, but not the amount, of the substance is all that matters. For example, the small cast iron frying pan has a mass of 808 g. The specific heat of iron (the material used to make the pan) is therefore: c iron =. |
SciQ | SciQ-5959 | evolution, embryology, chromosome, polyploidy
Unfortunately, whilst the first two points are valid facts about polyploids, the third point is incorrect. A major flaw with Muller's explanation is that it only applies to animals with chromosomal ratio-based sex determination, which we have since discovered is actually relatively few animals. In 1925 there was comparatively little systematic study of life, so we really didn't know what proportion of plant or animal taxa showed polyploidy. Muller's answer doesn't explain why most animals, e.g. those with Y-dominant sex determination, exhibit relatively little polyploidy. Another line of evidence disproving Muller's answer is that, in fact, polyploidy is very common among dioecious plants (those with separate male and female plants; e.g. Westergaard, 1958), while Muller's theory predicts that prevalence in this group should be as low as in animals.
The 'complexity' answer...
Another answer with some historical clout is the one given by Daniel Standage in his answer, and has been given by various scientists over the years (e.g. Stebbins, 1950). This answer states that animals are more complex than plants, so complex that their molecular machinery is much more finely balanced and is disturbed by having multiple genome copies.
This answer has been soundly rejected (e.g. by Orr, 1990) on the basis of two key facts. Firstly, whilst polyploidy is unusual in animals, it does occur. Various animals with hermaphroditic or parthenogenetic modes of reproduction frequently show polyploidy. There are also examples of Mammalian polyploidy (e.g. Gallardo et al., 2004). In addition, polyploidy can be artificially induced in a wide range of animal species, with no deleterious effects (in fact it often causes something akin to hybrid vigour; Jackson, 1976).
The following is multiple choice question (with options) to answer.
In animals, how many sets of chromosomes do gametes have? | [
"2",
"zero",
"23",
"one"
] | D | |
SciQ | SciQ-5960 | ph, titration
Title: Experimental determination of pH I am trying to determine the experimental pKa for two weak acids that were titrated against 0.20M NaOH.
I have read elsewhere that you can take the point where the graph becomes steep and divide the value of base added by two the corresponding pH value would then be the pKa, but how do i choose which value since it may not be obvious which point the graph becomes steep.
Below I can see that the pka for acetic acid should be close to the theoretical value calculated of 4.76 and the Tris-HCl pka should be approximately 8.3 but there must be a better way than just guessing from a graph.
My textbook doesn't explain how to experimentally find pH just that it's the point where $[A^-]/ [HA]$. I am hoping someone can give me an equation to work with or guide me in the right direction.
Thank you, So I think what you heard is about the right idea. The flat region is your buffering region, and isn't super helpful to deduce the pKa. Adding base consumes the weak acid, and because it is weak, you know you are mostly consuming the [HA] form, and equilibrating back to around the pKa. This is why your pH doesn't change much around the pKa.
As an example, if you had 10 mmol of HA to start, then at the pKa point you would have 5 mmol of HA and 5 mmol of A-. Now, if you keep adding base, at some point you will essentially consume the remaining 5 mmol of HA. Then, there will be negligible amount left and it can't buffer anymore - i.e. your pH will change rapidly because you are adding strong base. Here you will have ~0 mmol of HA, and ~10 mmol of A-. Note that you have twice the amount of A- now. The pKa will have been at the point where you had half of this.
Experimentally, I know two simple ways. Using a pH meter and no indicator, you have to measure the sharp region more carefully (i.e., drop by drop), because you want to be able to find the exact point where the pH changes the fastest. By approximating the derivative, i.e.
The following is multiple choice question (with options) to answer.
What scale measures acidity? | [
"frequency scale",
"ph scale",
"richter scale",
"salinity scale"
] | B | Note that Earth's axis of rotation is tilted. The axis is not perpendicular to the plane of the ecliptic. This plane is the one that solar system bodies are mostly lined up in. |
SciQ | SciQ-5961 | reaction-mechanism, ions, raman
Title: Compound formed from concentrated sulfuric acid and sulfur In the reaction below, I know what A and B are, but I'm not sure what compound C is.
All I know about it is the following:
Deep yellow solid
Dication contains only sulfur
Raman and infra-red spectra of the dication show no common features
I think that the dication might be $\ce{[S4]^{2+}}$ since I think that this would be square planar and therefore have $D_{\mathrm{4h}}$ symmetry, which has no irreps that are both Raman and IR active, but I don't know what the anion would be.
The other likely options for the sulfur dication would be $\ce{[S8]^{2+}}$ or $\ce{[S19]^{2+}}$ but I think the fact that it's yellow would make it $\ce{[S4]^{2+}}$. The reaction is given here.
$$\ce{S + 2H2SO4 → 3SO2 + 2H2O}$$
Sulfur react with sulfuric acid to produce sulfur dioxide and water. Sulfuric acid should be concentrated solution. The reaction takes place in a boiling solution.
$\ce{[S4]^2+}$, $\ce{[S8]^2+}$ or $\ce{[S19]^2+}$ is formed when sulfur is dissolved in oleum. The following is a paraphrase of an inorganic textbook.
The following is multiple choice question (with options) to answer.
What is sulfur trioxide dissolved in to form sulfuric acid? | [
"silver",
"water",
"mercury",
"lead"
] | B | Sulfuric acid is produced in extremely large quantities in the United States (about 40 million tons/year). This material is manufactured by oxidizing sulfur to form sulfur trioxide. The SO 3 is then dissolved in water to form the sulfuric acid. Most of the sulfuric acid produced is used in fertilizers. This acid is also found in lead-acid car batteries. |
SciQ | SciQ-5962 | genetics
So the modern definition of a phenotype is the observable characteristics of an organism, anatomical, physiological or behavioral. The first 2 points are easily accepted and uncontroversial. But there is debate about what exactly should be included in "behavior". I'm going to ignore behavior for now.
An important point, and I think this is where there is disagreement between Remi.b and me, is that a phenotype must have a genetics basis. I realize this is not explicitly mentioned in any definition, but that is very much the way people mean it. And if not, the definition is totally meaningless. Take the example of a monkey missing a finger congenitally. This is a phenotype, it is due to its genes. If the monkey is missing a finger due to a fight, this is not a phenotype because genes have nothing to do with it (again, ignoring behavior for now).
So, in my opinion, what would not be a phenotype is something that you could conclusively prove to have no genetics basis whatsoever. That's an extremely (impossible) hard case to make. But in retrospect I was perhaps to quick to include behavior in the definition, and this is due to my own biases as a behavioral neuroscientist.
I think this is the narrow definition of phenotype and I don't think anyone would disagree up to that point. You might notice that there has been no mention of evolution so far. It is because genetics and evolution have been developed independently, and even though everybody was quite aware they must be 2 sides of the same coin evolution is not directly relevant to the genotype/phenotype distinction.
The following is multiple choice question (with options) to answer.
Mendelian inheritance has its physical basis in the behavior of what? | [
"chromosomes",
"animals",
"ribosomes",
"prokaryotes"
] | A | 15.1 Mendelian inheritance has its physical basis in the behavior of chromosomes. |
SciQ | SciQ-5963 | terminology, definition, non-linear-systems, complex-systems, stochastic-processes
Title: Stochastic system vs. stochastic process I work on a project on stochastic diffusive systems described by stochastic differential equations (SDEs).
My background is from dynamical systems, so I tend to call the system under consideration a stochastic system. However my collaborator has a statistics background, and they naturally name the systems under consideration a stochastic process.
Since we are currently finishing our article, there are parts of the text where we refer to systems and parts where we refer to processes.
So I was wondering whether I can use these two terms interchangeably, or whether there are some subtle formalities that I have to consider?
Or is stochastic system equivalent to stochastic process in every respect? TL;DR: "Stochastic system" is probably best, but either one is fine.
First, one can investigate a deterministic (non-stochastic) system using statistical tools that treat the variables as random (even though they aren't) so, since your system truly contains a random element, this fact is made more clear by using the term "stochastic system", which makes it arguably preferable to "stochastic process".
Besides, a given system can be described by different models, and a given model can yield different measurements (variables) — hence, one can ascribe different stochastic processes to the same system: So, calling it "system" highlights it's the focus of the work and the "process" is just being used to study it.
Now, that's of course a very fine distinction, and these terms often remain loosely defined, so it's also OK to just add a remark in the beginning of the paper along the lines of "the terms 'stochastic system' and 'stochastic process' are used interchangeably", or even to choose either term and stick to it throughout the text.
Here are some excerpts that, besides my own experience, might support my statements above:
Book chapter:
Variables that fluctuate randomly in time are called stochastic processes or random functions.
Lecture notes:
The following is multiple choice question (with options) to answer.
The parasympathetic system can also be referred to as the what? | [
"craniosacral system",
"digestive system",
"badolato system",
"lentivirus system"
] | A | Parasympathetic Division of the Autonomic Nervous System The parasympathetic division of the autonomic nervous system is named because its central neurons are located on either side of the thoracolumbar region of the spinal cord (para- = “beside” or “near”). The parasympathetic system can also be referred to as the craniosacral system (or outflow) because the preganglionic neurons are located in nuclei of the brain stem and the lateral horn of the sacral spinal cord. The connections, or “circuits,” of the parasympathetic division are similar to the general layout of the sympathetic division with a few specific differences (Figure 15.4). The preganglionic fibers from the cranial region travel in cranial nerves, whereas preganglionic fibers from the sacral region travel in spinal nerves. The targets of these fibers are terminal ganglia, which are located near—or even within—the target effector. These ganglia are often referred to as intramural ganglia when they are found within the walls of the target organ. The postganglionic fiber projects from the terminal ganglia a short distance to the target effector, or to the specific target tissue within the organ. Comparing the relative lengths of axons in the parasympathetic system, the preganglionic fibers are long and the postganglionic fibers are short because the ganglia are close to—and sometimes within—the target effectors. The cranial component of the parasympathetic system is based in particular nuclei of the brain stem. In the midbrain, the Edinger–Westphal nucleus is part of the oculomotor complex, and axons from those neurons travel with the fibers in the oculomotor nerve (cranial nerve III) that innervate the extraocular muscles. The preganglionic parasympathetic fibers within cranial nerve III terminate in the ciliary ganglion, which is located in the posterior orbit. The postganglionic parasympathetic fibers then project to the smooth muscle of the iris to control pupillary size. In the upper medulla, the salivatory nuclei contain neurons with axons that project through the facial and glossopharyngeal nerves to ganglia that control salivary glands. Tear production is influenced by parasympathetic fibers in the facial nerve, which activate a ganglion, and ultimately the lacrimal (tear) gland. Neurons in the dorsal nucleus of the vagus nerve and the nucleus ambiguus project through the vagus nerve (cranial nerve X) to the terminal ganglia of the thoracic and abdominal cavities. Parasympathetic preganglionic fibers primarily influence the heart, bronchi, and esophagus in the thoracic cavity and the stomach, liver, pancreas, gall bladder, and small intestine of the abdominal cavity. The postganglionic fibers from the ganglia activated by the vagus nerve are often incorporated into the structure of the organ, such as the mesenteric plexus of the digestive tract organs and the intramural ganglia. |
SciQ | SciQ-5964 | endocrinology, glucose, homeostasis, insulin, hypothalamus
Title: Role of the Hypothalmus in the control of Blood Sugar In homeostatic regulation of blood glucose, the receptor and effector is the Pancreas, but how does the control centre — the Hypothalamus — connect and link into this process? Your question doesn’t make it clear whether you think that the pancreas must be under the control of the hypothalmus, or whether you are asking whether it has an influence on the pancreas in relation to the secretion of insulin and glucagon, which control the concentration of blood glucose.
First, it has been long known that secretion of insulin can be influenced by the concentration of glucose in isolated pancreatic islets in vitro, so it can not be true that the effects must involve the hypothalmus. This is implicit in most book or general information articles you might find on the web, but for an original reference a review by W.J. Malaisse in Diabetologia 9, 167–173 (1973) seems highly cited.
I know almost nothing about physiology, but on searching the web for the role of the hypothalmus in glucose homeostasis, found a most readable prize-winning postgraduate essay on the topic by Syed Hussein of Imperial College London. I trust that it is in order to append an edited extract of this:
The following is multiple choice question (with options) to answer.
Negative feedback controls insulin secretion by what organ? | [
"uterus",
"thyroid",
"pancreas",
"liver"
] | C | Negative feedback also controls insulin secretion by the pancreas. You can interact with a feedback loop of this process at the link below. http://www. abpischools. org. uk/page/modules/hormones/horm6. cfm?coSiteNavigation_allTopic=1. |
SciQ | SciQ-5965 | asteroids, comets, extinction
This is somewhat doable, but quickly get complex (different populations, orbits are not actually evenly distributed, etc.) A better approach may simply be to look at the past impacts causing extinctions! Depending on how you count, there has been one known mass extinction due to impacts since the Cambrian 538.8 mya, so the rate might be on the order of $2\cdot 10^{-9}$ per year. But that likely leaves out a fair number of minor extinctions. If we assume all Big 5 were due to impacts the rate becomes $9\cdot 10^{-9}$ per year.
Incidentally, to get these values in the above formula for the assumed values, $N$ should be in the range 0.2 to 1.
Obviously this can be improved: we can use statistical modelling to get error bars, we can use the known size distribution of asteroids (a power law) to estimate the fraction of Earth-crossers and long-periodic comets that could be bad and their inflow rate, and so on. But that misses the Drake equation approach of trying to find a quick-and-dirty model that shows the key variables we care about and might want to estimate.
The following is multiple choice question (with options) to answer.
In the past, what colliding with planet earth has caused many organisms to die off? | [
"asteroids",
"acid rain",
"the Sun",
"meteorites"
] | A | Near-Earth asteroids have orbits that cross Earth’s orbit. This means that they can collide with Earth. There are over 4,500 known near-Earth asteroids. Small asteroids do sometimes collide with Earth. An asteroid about 5–10 m in diameter hits about once per year. Five hundred to a thousand of the known near-Earth asteroids are much bigger. They are over 1 kilometer in diameter. When large asteroids hit Earth in the past, many organisms died. At times, many species became extinct. Astronomers keep looking for near-Earth asteroids. They hope to predict a possible collision early so they can to try to stop it. |
SciQ | SciQ-5966 | molecular-genetics, human-genome
Title: Criteria for the numbering of human chromosomes What were the criteria devised for the numbering convention employed in human chromosomes? When was it fixed?
Correct me if I am wrong; it appears that chromosome pairs 1 to 22 were originally ordered in terms of perceived structural size, which ended up fitting neatly with the quantity of base pairs (but not with the quantity of genes).
The sex chromosomes in turn were arbitrarily assigned as "pair 23".
Is this sound?
Thanks in advance. Why do you think it was "fixed?" Here's a nice review of the history of human cytogenetics, which included not only the original image from 1956 but points out a report which comments on the standardization of chromosome number. The autosomes were indeed numbered by length, and the sex chromosomes are traditionally put at the end as they are "numbered" 23 but clearly function quite differently. Gene content was decades away from being known at the time, and honestly isn't even known now. It's also just as arbitrary; simple size is easy enough and makes for rather nice pictures.
The following is multiple choice question (with options) to answer.
The number, size, shape, and banding pattern of chromosomes make them easily identifiable in a what? | [
"karyogram",
"nanocyte",
"spirogyra",
"xerophyte"
] | A | 13.2 Chromosomal Basis of Inherited Disorders The number, size, shape, and banding pattern of chromosomes make them easily identifiable in a karyogram and allows for the assessment of many chromosomal abnormalities. Disorders in chromosome number, or aneuploidies, are typically lethal to the embryo, although a few trisomic genotypes are viable. Because of X inactivation, aberrations in sex chromosomes typically have milder phenotypic effects. Aneuploidies also include instances in which segments of a chromosome are duplicated or deleted. Chromosome structures may also be rearranged, for example by inversion or translocation. Both of these aberrations can result in problematic phenotypic effects. Because they force chromosomes to assume unnatural topologies during meiosis, inversions and translocations are often associated with reduced fertility because of the likelihood of nondisjunction. |
SciQ | SciQ-5967 | zoology, organs, vestigial
Title: Is the appendix a vestigial structure in all vertebrates? In humans the Appendix is a vestigial organ. Does it serve no apparent purpose in all the vertebrates that have one? Smith et al. (2009) provide a survey of the morphology of the cecal appendix. One current hypothesis is that the appendix provides "safe harbor" for symbiotic gut bacteria. Among mammals, there is a vast array of cecal appendices:
In summary:
A comparative anatomical approach reveals three apparent morphotypes
of the cecal appendix, as well as appendix-like structures in some
species that lack a true cecal appendix. Cladistic analyses indicate
that the appendix has evolved independently at least twice (at least
once in diprotodont marsupials and at least once in Euarchontoglires),
shows a highly significant (P < 0.0001) phylogenetic signal in its
distribution, and has been maintained in mammalian evolution for 80
million years or longer.
The following is multiple choice question (with options) to answer.
What are the egg shaped organs on either side of the uterus? | [
"ovaries",
"lungs",
"kidneys",
"testes"
] | A | The two ovaries are small, egg-shaped organs that lie on either side of the uterus. They produce eggs and secrete estrogen. Each egg is located inside a structure called a follicle. Cells in the follicle protect the egg and help it mature. |
SciQ | SciQ-5968 | electrochemistry, ions
Title: Can the Galvanic cell use a different ionic solution? It makes sense that
water-soluble salt when dissolved in water, they conduct electricity. Then when using the old method of the Volta Battery(using copper and zinc) with a different water-soluble salt dissolved in water, can it make electricity too?
Plus, If I use a ammeter to check its current, then does all of the water-soluble salts do not go to zero?
Can the Volta Battery use a different ionic solution?
Yes you can use any soluble salt as long as it does not react with electrodes, and certainly such a battery would be able to produce current. My chemistry high school teacher had a clock which ran on salt water. See for example, https://science.howstuffworks.com/environmental/green-tech/sustainable/water-powered-clock2.htm. This technology is at least 400 years old. volta used common salt as well for zinc and copper.
Now the problem is that you can generate voltage by using copper/ zinc and salt water however one cannot predict the voltage by using the Nernst equation. It requires that the electrode dip in its own ions. Hence such batteries are theoretically difficult to deal with.
The following is multiple choice question (with options) to answer.
A voltaic cell uses what type of reaction to generate an electric current | [
"instantaneous redox",
"chemical reaction",
"spontaneous catalyst",
"spontaneous redox"
] | D | A voltaic cell uses a spontaneous redox reaction to generate an electric current. It is also possible to do the opposite. When an external source of direct current is applied to an electrochemical cell, a reaction that is normally nonspontaneous can be made to proceed. Electrolysis is the process in which electrical energy is used to cause a nonspontaneous chemical reaction to occur. Electrolysis is responsible for the appearance of many everyday objects such as gold-plated or silver-plated jewelry and chrome-plated car bumpers. |
SciQ | SciQ-5969 | inorganic-chemistry, ions, identification
Title: Identifying a quadruply charged anion containing three carbon atoms
This linear polyatomic ion containing three atoms of carbon has a negative four charge and is only found bonded with lithium and magnesium.
Could anyone identify this for me? It's from a quiz bowl clue that doesn't have the answer with it.
Sesquicarbide
A quick Google search suggests that $\ce{Li4C3}$ is a real compound, but based on what I saw in the links, it probably is not ionic in the same way that lithium acetylide $\ce{Li2C2}$ is.
$\ce{Mg2C3}$ appears to be the formula for magnesium carbide, or at least a magnesium carbide.
A carbide is a binary compound of carbon and a less electronegative element, usually a metal or metalloid. Carbide is also a generic name for mono- and polyatomic anions containing only carbon. The following ions would all carbide ions: $\ce{C^{4-}, C2^2-, C2^{4-}, C2^{6-}, C3^{4-}, C3^{6-1}, C3^{8-}}$, etc.
The special name of three of these carbide ions are:
$\ce{C^{4-}}$ - Methide
$\ce{C2^{2-}}$ - Acetylide
$\ce{C3^{4-}}$ - Sesquicarbide
The following is multiple choice question (with options) to answer.
Binary compounds of carbon with less electronegative elements are called what? | [
"carbides",
"alkaloids",
"oxides",
"carborane"
] | A | Note the Pattern Pi bonds between carbon and the heavier chalcogenides are weak due to poor orbital overlap. Binary compounds of carbon with less electronegative elements are called carbides. The chemical and physical properties of carbides depend strongly on the identity of the second element, resulting in three general classes: ionic carbides, interstitial carbides, and covalent carbides. The reaction of carbon at high. |
SciQ | SciQ-5970 | pathology
Title: Why are some bodily fluids more of an infection risk than others? Whilst on a recent refresher course it was highlighted that when considering risk of exposure to infection from bodily fluids we should be aware of two distinct risk levels:
High Risk:
Blood
Semen
Vaginal Secretions
Diarrhea
Low Risk:
Saliva
Vomit
Urine
CSF (Cerebrospinal fluid)
Why is it that some bodily fluids are a greater infection risk than others? Is it related to the fluids themselves or the species of pathogen that are located within them? This is just about where the pathogens can be found that are dangerous to people.
Vomit is highly acidic and less accommodating to microbe growth. Similarly saliva has many immune components in it as well as digestive enzymes that keep most microorganisms down.
Urine and CSF are actually quite sterile as they come from environments that are highly filtered - the kidney is an osmotic processor that essentially is a molecular filter and does not allow cells to pass, the spine is highly insulated from the blood and other direct exposure to microorganisms.
Compare that with the 'dangerous' list and you have organs that are open to human pathogens. Venerial disease like HPV is so common that what - about 1 in 5 people under a certain age carry it. That is a pretty high expectation of a biohazard. most infections and viruses are blood bourne - influenza, cold, as well as any bacterial infections.
Feces is always a dangerous thing to handle as the digestive tract is rich in nutrients and essentially directly open to external bacteria and fungi. (and its not acidified like the stomach). Also parasites like tape worms and other multicelled animals! yum!
Diarrhea is often caused by an infection of some sort, so its just more likely a hazard, but feces is always a place where you might find a pathogen.
This is not to say that the 'safe' list is totally safe. Its just less likely to bear disease causing agents.
The following is multiple choice question (with options) to answer.
What makes viral stis more dangerous than other types? | [
"they are more severe",
"they are more contagious",
"they are larger",
"they are incurable"
] | D | This is the Human Papilloma Virus, which causes a viral STI. Viral STIs can be especially dangerous, as they cannot be cured. Once you get one, it's yours for life. And also, it's the person's you give it to. |
SciQ | SciQ-5971 | fluid-dynamics, water, entropy, air
Title: Fluid Dynamics - Water Bottle Drink Mix: Air or No Air? If you take an ordinary sized plastic water bottle full of water and pour a packet of powdered (or liquid) drink mix into it, Will shaking the bottle with the cap screwed on to dissolve the mix into the water work better if there is a small amount of air inside the bottle? Or does it not make a difference at all and will shaking work just as well with no air bubbles at all in the bottle? Within reasonable limits, the more air in the bottle the better the mixing.
This isn't to do with air bubbles. To get good mixing you need turbulent flow, and for that you need high flow velocities. If the bottle is completely full it's hard to get a high flow velocity started because for water to move it has to push other water out of the way. If the bottle is only half full the moving water only has to push air out of the way, and air is both much more compressible and much less viscous than water. For any given amount of shaking effort you'll get higher flow velocities and therefore better mixing if there is a substantial amount of air in the bottle.
The following is multiple choice question (with options) to answer.
What flows like taffy or hot wax? | [
"molten rock",
"sand dunes",
"water",
"gas"
] | A | Magma forms deep beneath the Earth’s surface. Rock melts below the surface under tremendous pressure and high temperatures. Molten rock flows like taffy or hot wax. Most magmas are formed at temperatures between 600 o C and 1300 o C ( Figure below ). |
SciQ | SciQ-5972 | units, history, si-units, metrology
Title: Is the definition of the meter arbitrary? From Wikipedia, the definition of the meter is
The meter is defined as the distance traveled by light in a vacuum in 1/299792458 seconds.
Why is this number of seconds chosen? Is there a motivation for this choice? Yes and no.
Yes - because one can pick any distance one wants, and call it a meter (originally, it was 1/40,000,000th of the circumference of Earth measured over the poles; then the distance between a pair of lines on a standard platinum rod, then...).
But no - it is specifically chosen to be that value because
a) we believe the speed of light to be an absolute constant in the universe
b) by defining distance in terms of speed of light (a constant) and time (something we can measure precisely) we no longer need to maintain two separate standards.
The number was chosen such that the speed of light (which was previously known to be approximately 299,792,458 m/s) will henceforth be exactly that number.
Much detail on this can be found in this question and the associated answers. Note that that question asks the converse of this one - namely, "why does the speed of light have no uncertainty". This is the other half of that question.
The following is multiple choice question (with options) to answer.
What unit of measurement determines how far something travels in a given amount of time? | [
"density",
"distance",
"volume",
"speed"
] | D | How fast or slow something moves is its speed . Speed determines how far something travels in a given amount of time. The SI unit for speed is meters per second (m/s). Speed may be constant, but often it varies from moment to moment. |
SciQ | SciQ-5973 | resonance
Title: Resonance and modes I use a metal body (let's say cooking pot) in which I induce eddy current via induction at certain frequency which I can change as I wish.
Every object has it's own accustic resonant frequency. If exciting frequency is the same as the accustic resonant frequency of the body, then the sound produced by eddy currents will also be strong at that frequency.
If I drive the coil at half the frequency (or 1/4th the frequency) of an accustic resonance of the cooking pot), then the sound will still be loud at the resonant frequency.
But does the same effect happen if I drive it with double frequency of the cooking pot accustic resonant frequency? Do I still hear loud frequency at the accustic resonant frequency, or does this only apply if the exciting frequency is lower(half, one fourth...) of the accustic resonant frequency? This is a bit complicated and it depends on the details of the driving. If you are driving with a pure sinewave and there are no nonlinear aspects that introduce overtones, then the pot will only resonate at its resonant frequencies (which are many, not just one). Driving at 1/2 or at double will not excite a resonance.
But you may be driving with something other than a pure sinewave or there may be nonlinearity which effectively makes it not a sinewave. If the cooking pot is resting on a surface, then it will respond differently to a push than to a pull, and this non-linearity introduces overtones of the driving frequency. This is similar to what you hear when part of a speaker has come loose and it buzzes. Harmonics (multiples of the frequency) not present in the original are being generated. So in your case, if you drive the pot at 1/4 of a resonant frequency, there may easily be some nonlinearity that will create a harmonic of 4 times the driving frequency. That harmonic is what makes the pot resonate.
But nonlinearities don't create subharmonics, so I would not expect you to be able to excite a particular resonance by driving it at say 3x that resonant frequency.
The following is multiple choice question (with options) to answer.
What happens do the sound during a resonance? | [
"it dissipates",
"it becomes quieter",
"it echoes",
"amplified, it becomes louder"
] | D | Most musical instruments use resonance to amplify the sound waves and make the sounds louder. Resonance occurs when an object vibrates in response to sound waves of a certain frequency. In a musical instrument such as a guitar, the whole instrument and the air inside it may vibrate when a single string is plucked. This causes constructive interference with the sound waves, which increases their amplitude. |
SciQ | SciQ-5974 | evolution, taxonomy, ornithology
Title: Birds and Dinosaurs This came up in an argument with some friends. I know that birds are direct descendants of dinosaurs, shown pretty clearly through the fossil record. However, is it proper to say that birds are dinosaurs, or is there an actual distinction? I bet you'll be interested about the concept monophyly. Any human-made group of species (or taxon) like birds dinosaurs, primate, bacteria, angiosperm, reptiles, … are either monophyletic, polyphyletic or paraphyletic. This picture explain the concept When the taxon is monophyletic it is called a clade.
Monophyletic taxon are those groups of species that can be considered to be objective in the sense that it represents a group of species where each species in the taxon is more related (in terms of time to common ancestor, not according to their genetic similarity) to any other species within the same taxon than to any other species outside this taxon. This is obviously not the case for paraphyletic or polyphyletic taxon.
Typically, we do not consider a parrot or a deer to be reptiles. Therefore, the ususal understanding of "reptiles" makes this taxon paraphyletic. Now, one should not confound the common understanding (what is a reptile in our everyday life) with the strict definition of the taxon Reptilia, which is a monophyletic taxon (or a clade in other words). Probably the best source for exploring the tree of life is tolweb.org. Here, you will find the clade Reptilia (who include birds, snakes, turtles and lizards). Note: Mammals are within the Reptiliomorpha, not the Reptilia.
It is exactly the same issue with the dinosaurs. When we talk about dinosaurs in our everyday life we do not mean birds. But there is a clade called Dinosauria, which include both dinosaurs and birds.
In short, I would say that a bird is a Dinosauria (monophyletic taxon) but is not a dinosaur (paraphyletic taxon). But this little play on word is not a scientific issue but an issue of english usage.
You will also find in this post an introduction to phylogeny
The following is multiple choice question (with options) to answer.
With a diet of live animals such as birds, small mammals and fish, all crocodilians are considered what? | [
"symbiotes",
"omnivores",
"predators",
"carnivores"
] | D | All crocodilians are carnivores. They feed on live animals such as birds, small mammals and fish. Crocodilians use several methods of attack when pursuing live prey. One approach is that of the ambush. The crocodilian lies motionless beneath the water's surface with only their nostrils above the water line. This keeps them concealed while they watch for prey that approaches the water's edge. The crocodilian then lunges out of the water, taking their prey by surprise and dragging it from the shoreline into deep water where the prey is killed. |
SciQ | SciQ-5975 | organic-chemistry, bond, biochemistry, covalent-compounds
Title: Are bulkier molecules more likely to react? I have heard a theory from someone and just wanted to confirm if its true or not. Is it true that more bulkier an organic compound is, more likely it is to react? So does this mean that higher the molecular weight of an organic compound, more will be the probability of it to react? The relative rates are going to depend not on molecular weight so much but the structure of the molecule.
The specific reaction is also very important.
Nucleophilic substitution reactions (some of the first reactions most students learn about in an organic chemistry course).
Let us compare 1-chlorobutane and 2-chloro-2-methylpropane, both $\ce{C4H9Cl}$. However, the 1-chlorobutane is a primary alkyl halide (not very bulky) and 2-chloro-2-methylpropane is a tertiary alkyl halide (bulky).
The bulkier compound reacts faster in a solvolysis reaction:
$$\ce{(CH3)3CCl ->[\ce{H2O}] (CH3)3COH}\ \ \mathrm{fast}$$
$$\ce{CH3CH2CH2CH2Cl ->[\ce{H2O}] CH3CH2CH2CH2OH}\ \ \mathrm{slow\approx no\ reaction}$$
The reason that the tertiary halide reacts faster in this reaction is that its mechanism involves the formation of a carbocation intermediate and the extra carbon groups at the tertiary center provide more inductive stabilization to that carbocaion than the single alkyl group attached to a primary position. In general, in reactions that generate carbocation intermediates, tertiary substrates will react faster.
However, in many reactions bulkier molecules have steric interactions that negatively effect the rate. In a nucleophilic displacement with $\ce{NaI}$ in acetone, 1-chlorobutane will react faster.
$$\ce{(CH3)2CCl ->[\ce{NaI}][\mathrm{acetone}](CH3)3CI}\ \ \mathrm{slow\approx no\ reaction}$$
The following is multiple choice question (with options) to answer.
Which types of compounds are more likely to burn easily? | [
"chlorophyll",
"salty",
"covalent",
"hydroxyl"
] | C | Many covalent compounds, especially those containing carbon and hydrogen, burn easily. In contrast, many ionic compounds do not burn. |
SciQ | SciQ-5976 | newtonian-mechanics, forces, mass, acceleration
Title: Force, Newtons second law In the book "An Introduction to Mechanics - Second edition" by Kleppner D., Kolenkow R, I came across a paragraph:
pg. 54 , sec 2.5.2(force)
It is worth emphasizing that force is not merely a matter of definition. For instance, if we observe that an air track rider of mass $m$ starts to accelerate at rate $\vec a$, it might be tempting to conclude that we have just observed a force $\vec F=m\vec a$. Tempting, but wrong. The reason is that forces always arise from real physical interactions between systems. Interactions are scientifically significant: accelerations are merely their consequence. Consequently, if we eliminate all interactions by isolating a body sufficiently from its surroundings —an inertial system— we expect it to move uniformly.
I can not understand why it is wrong. Please explain to me the reason author gave. Yes, the author's statement is weirdly worded to say the least. Unless Newton's laws are incorrect, you can obviously conclude that if an object is accelerating, then the net force acting on it is mass times acceleration (assuming you're in the inertial frame).
However, what the author is trying to convey is the theoretical structure of our model of the world in Newtonian mechanics. That is that we ought to think of acceleration as the consequence of the forces acting on the particle rather than the other way around. In other words, you have to have a formalism where you can calculate forces acting on a particle independently of the acceleration of the particle (say, for example, as a function of the charges of the particles and the distances between them) and then you should verify if the acceleration produced due to this force according to the formula $F=ma$ matches with the experimentally observed acceleration of the particle. If you don't have an independent way of deducing what the force acting on a particle is independent of just observing the acceleration of the particle then you'd have learnt nothing about the world. Because you'd just see some acceleration and just define a force as $ma$ but you'd have no predictive power because you didn't really say anything about how this acceleration is arising.
The following is multiple choice question (with options) to answer.
Which of newton's law shows that there is a direct relationship between force and acceleration? | [
"first",
"second",
"third",
"none of the above"
] | B | Newton’s second law shows that there is a direct relationship between force and acceleration. The greater the force that is applied to an object of a given mass, the more the object will accelerate. For example, doubling the force on the object doubles its acceleration. The relationship between mass and acceleration, on the other hand, is an inverse relationship. The greater the mass of an object, the less it will accelerate when a given force is applied. For example, doubling the mass of an object results in only half as much acceleration for the same amount of force. |
SciQ | SciQ-5977 | human-biology, digestive-system, immune-system, microbiome
All of these immune cells also respond to diffused chemical signals called cytokines. These molecules are secreted by some cells and are received by receptors on the host cells. Sometimes the secretion is by another immune cell, sometimes it is from a non-immune system host cell, and sometimes these molecules can be secreted by the bacteria, fungi, or worms themselves.
Depending on the chemical signals that are secreted, and how the cells are interacting at the time of the message, and which cells are receiving the message, will determine the response to the message. It is contextual. Think of the phrase "You're killing me." If someone says it, while laughing, to a good friend who is telling jokes, it means one thing. If it is screamed as someone is being choked by an attacker, it means something very different.
To summarize, the immune cells are surveilling the environment and trying to pick up what is friend and what is foe and they try to respond accordingly.
Over time and coevolution, our microbiomes have developed ways of communicating with our immune system to let it know that these microbes do not mean any harm. They are able to "train" the immune cells using chemical signaling to temper the immune systems response to them (15), and this is how they are able to coexist within our body and with an immune system that is constantly on seek an destroy missions. Also because of the mucus, our microbiome usually isn't in direct contact with our cells, so it is a different kind of interaction than if an infecting pathogen were to breech the barriers and gain access to sterile areas where no bacteria or fungi should be found, and as a result, the immune system reacts differently.
The following is multiple choice question (with options) to answer.
Which proteins recognize and combine with harmful materials, including both toxic chemicals and invasive microorganisms? | [
"enzymes",
"essential amino acids",
"collagen",
"antibodies"
] | D | Antibodies – These proteins recognize and combine with harmful materials, including both toxic chemicals and invasive microorganisms (such as bacteria and viruses). When an antibody binds to its target, it is tagged for destruction. This tag is recognized by white blood cells, which complete the process. Some antibodies also partially or completely deactivate their targets while waiting for further help from white blood cells. |
SciQ | SciQ-5978 | terminology, meteorology
I've tried to illustrate the relationships with insolation and temperature here:
There are some other ways too:
Ecological. Scientists who study the behaviour of organisms (hibernation, blooming, etc.) adapt to the local climate, sometimes using 6 seasons in temperature zones, or only 2 in polar and tropical ones.
Agricultural. This would centre around the growing season and therefore, in North America and Europe at least, around frost.
Cultural. What people think of as 'summer', and what they do outdoors (say), generally seems to line up with local weather patterns. In my own experience, there's no need for these seasons to even be 3 month long; When I lived in Calgary, summer was July and August (hiking), and winter was December to March (skiing). Here's another example of a 6-season system, and a 3-season system, from the Aboriginal people of Australia, all based on weather.
Why do systems with later season starting dates prevail today? Perhaps because at mid-latitudes, the seasonal lag means that the start of seasonal weather is weeks later than the start of the 'insolation' period. In a system with no heat capacity, there would be no lag. In systems with high heat capacity, like the marine environment, the lag may be several months (Ibid.). Here's what the lag looks like in three mid-latitude cities:
The exact same effect happens on a diurnal (daily) basis too — the warmest part of the day is often not midday (or 1 pm in summer). As with the seasons, there are lots of other factors too, but the principle is the same.
These aren't mutually exclusive ways of looking at it — there's clearly lots of overlap here. Cultural notions of season are surely rooted in astronomy, weather, and agriculture.
The following is multiple choice question (with options) to answer.
What type of behavioral rhythms are linked to the yearly cycle of seasons? | [
"biannual",
"monthly",
"annual",
"circannual"
] | D | |
SciQ | SciQ-5979 | telescopes, exoplanets, imaging, space-mission
Title: Exoplanet detection via space-based parasol I remember from watching Cosmos years ago, Carl Sagan suggested an interesting hypothetical method for directly seeing exoplanets. He proposed that in the 'future' we could launch a satellite designed to block the light from distant stars, effectively eclipsing them, perhaps by unfolding a large circular parasol, allowing a powerful telescope to directly detect the light from nearby orbiting planets. Based on this notion I have two questions:
Has or is this idea being seriously considered?
Would it be possible to position a space based telescope to take advantage of objects that are already in space to eclipse light from a star, perhaps a moon or asteroid?
Related:
Lack of exoplanet missions in the decadal survey, and Given a photo of the Moon, taken from Earth, is it possible to calculate the position of the photographer's site? Scientists can image exoplanets today, using coronagraphs and other techniques:
The major difference from Sagan's speculation are the advances in adaptive optics that allow terrestrial observatories to perform in ways that vastly exceed the expectations of Sagan's time.
Space-based observatories are awesome, but the sheer size of these instruments is daunting. This is Gemini Observatory's Near-Infrared Coronograph Imager (NICI), which is just the instrument (never mind the 8M primary mirror). You can get a sense of the scale from the railings and instrument panels:
Exoplanets are, of course, a very exciting area and all the major observatories are bringing even better instruments online. At Gemini (at which I work, but do not speak for), we are very excited about bringing online next-generation instruments that will allow even greater science to be done.
The following is multiple choice question (with options) to answer.
What type of scientist uses earth-orbiting telescopes? | [
"biologist",
"astrologer",
"anthropologist",
"astronomer"
] | D | Astronomers use many tools to study things in space. Earth-orbiting telescopes view stars and galaxies from the darkness of space ( Figure below ). They may have optical and radio telescopes to see things that the human eye can't see. Spacecraft travel great distances to send back information on faraway places. |
SciQ | SciQ-5980 | taxonomy
Title: Why are sponges sometimes not considered multicellular? I read somewhere (I can't find where) that there is no scientific consensus whether sponges should be considered multicellular organisms.
It seems I don't understand where is the line between unicellular and multicellular life.
I am not able to find a more elaborate explanation of that doubt. What are the reasons for it? Sponges are generally considered as colonial organisms because there is little cell specialization and little separation of function/role. All cells do pretty much the same thing; it looks more like a pile of individual cells than an actual multicellular organism. In reality it is a little bit in between.
In any case, what one wants to call multicellular or unicellular is a matter of definition and preferences. You cannot find the line between unicellular and multicellular because there is no such line that would not be very arbitrary and filled with special cases.
You can study a little more the physiology of sponges and then decide for yourself if it looks sufficiently like a multicellular organism or more like a colony of cells (a colonial organism).
The following is multiple choice question (with options) to answer.
Sponges possess an internal skeleton called what? | [
"hydrostatic skeleton",
"fluid skeleton",
"exoskelton",
"endoskeleton"
] | D | Sponges have an internal skeleton that gives them support and protection. An internal skeleton is called an endoskeleton . A sponge endoskeleton consists of short, sharp rods called spicules (see Figure below ). Spicules are made of silica, calcium carbonate, or spongin, a tough protein. They grow from specialized cells in the body of the sponge. |
SciQ | SciQ-5981 | standard-model, quarks, protons
Title: What's inside a proton? What constitutes protons? When I see pictures, I can't understand. Protons are made of quarks, but some say that they are made of 99% empty space. Also, in this illustration from Wikipedia, what's between the quarks? Ah, I know this one!
What's in a proton?
A proton is really made of excitations in quantum fields (kind of like localized waves). Remember that. Any time you hear any other description of the composition of a proton, it's just some approximation of the behavior of quantum fields in terms of something people are likely to be more familiar with. We need to do this because quantum fields behave in very nonintuitive ways, so if you're not working with the full mathematical machinery of QCD (which is hard), you have to make some kind of simplified model to use as an analogy.
One of the more confusing things about quantum field excitations is that they react differently depending on how they are observed. More specifically, the only way to measure the properties of an excitation in a quantum field is to make it interact with another excitation and see how the excitations affect each other. Or in particle language, you have to hit the particle with another particle (the "probe") and see what comes out. Depending on the charge, energy, momentum and other properties of the probe, you can get various results.
The following is multiple choice question (with options) to answer.
A fundamental particle of matter, protons and neutrons are made of these? | [
"quarks",
"neutrinos",
"atoms",
"particles"
] | A | Protons and neutrons are made up of fundamental particles of matter called quarks. Electrons are another type of fundamental particles of matter called leptons. Bosons are fundamental particles that carry forces between fundamental particles of matter. |
SciQ | SciQ-5982 | protein-structure
Title: What is a "monomeric polypeptide"? In the sentence: "Bacteriophage (viral) polymerases are typically monomeric polypeptides".
I know that polypeptides are chains of amino acids monomers. But what is a "monomeric polypeptide" and what other kinds of polypeptides are there? Monomer in this context means the protein has only one polypeptide chain. In some proteins, after the individual chains have folded into their 3D or tertiary structure, they associate (generally non-covalently) into a higher order or quaternary structure. A protein with a quaternary structure containing two copies of the same chain would be called a homo-dimer. One with one copy of each of two different chains is a hetero-dimer.
Haemoglobin is a well-known example of a protein with quaternary structure — it has two copies of the alpha- and two of the beta- chain. Further elementary treatment can be found in Berg et al. and explanation of the nomenclature in this Wikipedia page.
Monomeric polypeptide is somewhat misleading in the sentence quoted. Monomeric protein would have probably been better as you wouldn't be likely to say ‘dimeric polypeptide’, given that polypeptide implies a single chain.
The following is multiple choice question (with options) to answer.
What is the name of the smaller molecules that make up proteins? | [
"DNA acids",
"amino acids",
"rna acids",
"fundamental acids"
] | B | Proteins are nutrients made up of smaller molecules called amino acids. The digestive system breaks down proteins in food to amino acids, which are used for protein synthesis. Proteins synthesized from the amino acids in food serve many vital functions. They make up muscles, control body processes, fight infections, and carry substances in the blood. |
SciQ | SciQ-5983 | rotational-dynamics, rotation
Question From OP
Is there a possibility to help explain this at a high-school (i suppose, I'm 15) level? We haven't been introduced to shear force yet and have just finished Newton's Laws and Inertia
I'm guessing that the notion of pressure and shear force is the most mysterious to you. The way we measure the way dollops of fluid interact with their neighbors is through the stress tensor. This is a slightly frightening word, but bear with me. You are to imagine a small polyhedron of fluid and we wish to calculate the forces on the faces from the neighboring fluid. You specify the face by a vector pointing in a direction normal to the face and whose length is proportional to the face's area. Then the tensor is a matrix - a linear function - that takes this vector and returns another vector - the force on the face. You multiply the face vector by the matrix to get the force.
In general, you probably know that matrices change the directions of the vectors they multiply. The component of force in the direction of the face vector, i.e. normal to the face, is called the pressure; that along the face's plane is called the shear.
The definition of a fluid is that it cannot withstand shear unless the neighbors are in motion relative to one another. Any shear shifts the fluid until it finds an equilibrium. At equilibrium the stress tensor matrix multiplies the any face vector, no matter what its direction may be, and returns another vector in the same direction, i.e. normal to the face. The only matrix that has this property is a constant times the identity matrix. It is for this reason that we know the pressure p acting towards the center of rotation on the little triangle is equal to the pressure thrusting up to support the triangle's weight. So the weight gives the pressure, which can then be used to find the nett force towards the center of rotation.
Alternatively, one can imagine, instead of a fluid, a tight packing of identical steel cubes with fantastic lubrication between them; pressure is then the force normal to the cubes' faces, shear is the friction between the faces. Perfectly lubricated cubes can only push normal to each others' faces, there is no force transmission associated with any tendency to relative sideways motion - no friction.
The following is multiple choice question (with options) to answer.
What is the term for a state of matter that yields to sideways or shearing forces? | [
"solid",
"gravity",
"plasma",
"fluid"
] | D | Section Summary 11.1 What Is a Fluid? • A fluid is a state of matter that yields to sideways or shearing forces. Liquids and gases are both fluids. Fluid statics is the physics of stationary fluids. |
SciQ | SciQ-5984 | evolution, dna, natural-selection
It seems plausible to me that we (advanced life) could have a biological mechanism to "write" needed alterations into either our own DNA or our reproductive DNA over time, triggering the very specific evolutionary developments necessary to our survival without relying on random mutation.
My question:
Is this possible? Does any similar mechanism exist that we know of? If not, how can so many specific (advanced) evolutionary leaps be otherwise explained? This entire answer will be long, so read the short part first, then read the rest if you (or anyone else) is curious. Citations are included in the long section. I can include additional citations in the short section if needed.
Long Story Short
Your question touches on some common misconceptions about how the evolutionary process. Organisms don't "want" to evolve traits. Traits evolve through the biological processes of random mutation and natural selection.
Organisms do not "want" to evolve traits. (Well, OK, I'd love to evolve an extra pair of hands but that is not possible.) Natural selection works by modifying existing traits. Your turtle can stare all she wants at food out of reach but she will not evolve a longer neck. Instead, natural variation exists among neck lengths of the turtles because of variation of the genes that determine features related to overall boxy size. Those individuals with longer necks may be able to get a bit more food, live a little longer, and reproduce a little more. They will pass along their genes to their offspring, so perhaps more of their offspring will also have longer necks. Over many generations, the turtles may have somewhat longer necks.
A common misconception is that the traits of organisms are precisely adapted for a specific need. They are not, for a few reasons. First, natural selection occurs relative to the current environment. Adaptations that work well in one environment may not be so useful in another environment. Environments are rarely stable over evolutionary time so traits are subject to constant change.
Next, as mentioned above, natural selection can only work on what traits are present. While an extra set of arms would be handy, I am a tetrapod. My four appendages, along with the appendages of all other tetrapods, trace back to our common ancestor. The appendages of all tetrapods are modifications of that ancestral trait.
The following is multiple choice question (with options) to answer.
Many structures in fish are adaptations for what type of lifestyle? | [
"asexual",
"aquatic",
"carnivorous",
"symbiotic"
] | B | Many structures in fish are adaptations for their aquatic lifestyle. Several are described below and shown in Figure below . |
SciQ | SciQ-5985 | thermodynamics, geophysics
With supercooled water, this effect is even more pronounced - a water at -30 °C has about the same density as water at 60 °C.
Oceans cool mostly by evaporation - the surface layers of water "spontaneously" changing state from liquid to gaseous. You get a balancing act between energy lost to evaporation, and incoming sunlight. However, there's a huge gap between the surface and the deeps, a lot of water mass - the incoming sunlight is nowhere near enough to warm ocean waters throughout. So you get warm surface waters, then a gradient of cooler and cooler water, and finally about 0-3 °C in the deep. To illustrate how big this gap is, about 90% of the worldwide ocean water is in the 0-3 °C range (hence the "nowhere near enough sunlight to heat the whole thing through").
Of course, a 4 °C body of water is great for cooling systems running at 40 °C and more. Air is actually a pretty good insulator, so air cooling gets tricky with large systems. Water, on the other hand, is pretty thermally conductive, and it easily convects, so cooling a huge data centre becomes almost trivial.
EDIT:
Let me address the Sun part, since there seems to be some confusion there as well.
Nuclear fusion is something that happens very infrequently. Two nuclei must come very close together to fuse, and they need enough kinetic energy to overcome the repulsion between each other (since both have the same electric charge).
The first problem is solved by increasing density. The more nuclei you have in the same volume, the higher the likelihood of close contact. This is where pressure comes in - that's how you get a higher density. Stars are made of plasma, and plasma is easily compressible, similar to a gas, so as pressure increases, so does density. How compressed is it? Well, the Sun's core, where the fusion reactions are actually happening, contains 34% of the Sun's mass, in only 0.8% of the Sun's volume. In the centre, the density is around 150 times the density of liquid water. The pressure is about 100 000 times the pressure in the Earth's core, and about 100 000 000 times the pressure of the water on the bottom of the Mariana trench.
The following is multiple choice question (with options) to answer.
What takes place at some coastlines or along the equator and brings cool, nutrient-rich water to the surface? | [
"red tide",
"high tide",
"upwelling",
"flooding"
] | C | Upwelling takes place at some coastlines or along the Equator. Upwelling brings cool, nutrient-rich water to the surface. |
SciQ | SciQ-5986 | sequence-alignment, phylogenetics, genome, phylogeny
Title: What is the most appropriate way to find the most recent common ancestor between two distantly related species I want to specifically find the common ancestor between a lobster and a humans. I suspect it was an aquatic worm of some description. But I want to know about the nervous system of this common ancestor. Because I've now posted several comments, I'll just roll them all up.
For background on the approaches used to identify most recent common ancestors and a high-level look at how animal taxonomy has been inferred, I suggest Lynch 1999.
I think that there are 2 interpretations of this question. If you are interested in just looking up a single MRCA of well-defined clades, such as lobster and human, here are some approaches:
Easy way:
Look at a tree diagram, e.g. this:
Find the tips that correspond to your species of interest (arthropods for lobster, chordata for humans).
Find where they join together in the diagram (the branch labeled "true coelom").
You have your answer, the MRCA is the group of organisms with a true coelom, coelomates.
A more involved way using a database
Go to this website.
Find the group of species 1 (arthropods, protostomes, etc. for lobster, chordata, deuterostomes etc. for human)
navigate around until you see the group containing the two groups (in this case listed as "bilateria"). In this case you are looking for the bilaterian common ancestor.
another database
Go to this website.
Point and click your way to a view where you see your 2 clades of interest (arthropods, chordates in this case). See figure.
Find where they join (in this case, it is less certain about the existence of a coelomate common ancestor, so it just says "bilaterians").
The following is multiple choice question (with options) to answer.
The major classes of living members of this phylum include gastropods, bivalves, and cephalopods? | [
"mollusks",
"invertebrates",
"insects",
"crustaceans"
] | A | There are approximately 160,000 living species and probably 70,000 extinct species of mollusks. They are typically divided into ten classes, of which two are extinct. The major classes of living mollusks include gastropods, bivalves, and cephalopods ( Figure below ). |
SciQ | SciQ-5987 | cell-biology, molecular-biology
Title: Intracellular lipid transport I know that lipids are carried around the body in the blood either as micelles or by lipid-binding proteins which allow them to be solved.
Lipids can't always be integrated in a membrane though, the phospholipids used in membranes have to be synthesised somewhere from a precursor which will also by hydrophobic.
Consequently, at some point there will have to be transport of lipids within the cell where the lipids will need to be in solution. How is this facilitated? Like in the blood, intracellular lipid trafficking is facilitated by vesicular transport and lipid carriers like fatty acid binding proteins. In addition, intracellular membranes are densely packed and they can exchange lipids by collision and transient hemifusion. If you have access to Cell, a good review is from Prinz W. 2010 Lipid Trafficking sans vesicles, Where, Why, How?
The following is multiple choice question (with options) to answer.
What is the thin coat of phospholipids that surrounds the cell and controls what enters and leaves? | [
"plasma",
"blood",
"cell membrane",
"myelin"
] | C | The cell membrane is a thin coat of phospholipids that surrounds the cell. It’s like the “skin” of the cell. It forms a physical boundary between the contents of the cell and the environment outside the cell. It also controls what enters and leaves the cell. The cell membrane is sometimes called the plasma membrane. |
SciQ | SciQ-5988 | evolution
Not that I can think of or find easily. While there are detriments associated with being born prematurely, and some evidence that women waiting until they're late 30's and men until they're 60 or older can negatively affect their gametes and consequently the development of any children born from them - it's been such a short time since the introduction of hormonal contraception and modern medicine that we may not see results tangible results for hundreds of years. Although condoms have been around for several hundred years, and there's been no associations with condom use that I can think of.
In the short term, what it has done is affect the ethnic diversity of countries. For the first time ever, Hispanic births have outnumbered Caucasian births in 2012 in the United States. Other countries, mostly European countries, are seeing declines in birth rates - which means their populations will decline with age or be compensated for by immigration. Higher birth rates, however, are associated with lower income brackets or very religious communities - both of which are associated with ethnic Minorities, at least in the United States. So while minority populations have more kids, they do so on fewer resources which may negatively affect their children in the long-term, whereas higher-earning segments of the population might have fewer children later in their lives, but can provide a much more stable environment and opportunities to continue that success.
One thing that hormone-centered birth control has done, however, is eliminate rape as a viable form of passing on one's genes. As gruesome as it might be to consider, pregnancies as a result of rape can produce "fit" offspring. It is a legitimate reproductive strategy in nature, and is in humans... unless the woman is using contraception. In the long-term this will probably show some interesting results (nominally an enhanced "Female Choice" effect - which is already evident in human evolution), but nothing right now.
The following is multiple choice question (with options) to answer.
Because conditions are not ideal, most populations grow ____________. | [
"historically",
"SOCIALLY",
"mathematically",
"logistically"
] | D | Most populations do not live under ideal conditions and grow logistically instead. |
SciQ | SciQ-5989 | mitochondria
Title: Are porins on the inner or on the outer membrane of mitochondria? I've looked at multiple resources and they are saying different things. This is not my field, but The Transporter Classification Database would appear to be a reliable source and states that:
The best characterized members of the MPP family are the voltage-dependent anion-selective channel (VDAC) porins in the mitochondrial outer membrane.
Searching through the Protein Data Bank one can find a crystal structure for human voltage-dependent anion channel 1 and the associated paper also states that it is in the outer mitochondrial membrane, so you would imagine that they should know.
The following is multiple choice question (with options) to answer.
Besides the inner membrane, where are many respiratory enzymes found? | [
"the matrix",
"alveoli",
"golgi apparatus",
"cytoplasm"
] | A | |
SciQ | SciQ-5990 | phase
"Which elements form the most phases?" is an impossible question to give and absolute answer as we are limited to certain pressures and temperatures with which to experiment. The way experimentation is done is likely to bias any verifiable answer toward more practical materials.
The following is multiple choice question (with options) to answer.
The most common elements have the most tightly bound __________. | [
"membrane",
"atoms",
"nuclei",
"quarks"
] | C | There are some noticeable spikes on the BE / A graph, which represent particularly tightly bound nuclei. These spikes reveal further details of nuclear forces, such as confirming that closed-shell nuclei (those with magic numbers of protons or neutrons or both) are more tightly bound. The spikes also indicate that some nuclei with even numbers for Z and N , and with Z = N , are exceptionally tightly bound. This finding can be correlated with some of the cosmic abundances of the elements. The most common elements in the universe, as determined by observations of atomic spectra from outer space, are hydrogen, followed by 4 He , with much smaller amounts of 12 C and other elements. It should be noted that the heavier elements are created in supernova explosions, while the lighter ones are produced by nuclear fusion during the normal life cycles of stars, as will be discussed in subsequent chapters. The most common elements have the most tightly bound nuclei. It is also no accident that one of the most tightly bound light nuclei is 4 He , emitted in α decay. |
SciQ | SciQ-5991 | forces, relativity
Weak force:
there are no experiments currently, that would measure the strength of the weak force. I do not know of any such experiment that would measure it at 0.9c speeds at all.
Strong force:
It is the strong force that holds quarks together to form a neutron or proton, and it is the residual strong force, or nuclear force that holds the neutrons and protons together in a nucleus. Now if you take a composite object, like a proton or neutron, and try to measure the strong force, there is no experiment for that, but you can try to calculate it theoretically, and at rest you would get the same measurement as if the proton or neutron would travel at speed 0.9c.
There are exotic atoms, like the pionic atom, where the electrons are replaced by pions, and then the pions are held to the nucleus by the strong force. They use these to measure the strong force between the pions and the nucleus.
But anyway, the speed of the object will not change the strong force inside it.
Please see here:
https://tel.archives-ouvertes.fr/tel-01674426/document
The following is multiple choice question (with options) to answer.
What are particles that feel the strong nuclear force called? | [
"baryons",
"hadrons",
"bosons",
"mesons"
] | B | Hadrons and Leptons Particles can also be revealingly grouped according to what forces they feel between them. All particles (even those that are massless) are affected by gravity, since gravity affects the space and time in which particles exist. All charged particles are affected by the electromagnetic force, as are neutral particles that have an internal distribution of charge (such as the neutron with its magnetic moment). Special names are given to particles that feel the strong and weak nuclear forces. Hadrons are particles that feel the strong nuclear force, whereas leptons are particles that do not. The proton, neutron, and the pions are examples of hadrons. The electron, positron, muons, and neutrinos are examples of leptons, the name meaning low mass. Leptons feel the weak nuclear force. In fact, all particles feel the weak nuclear force. This means that hadrons are distinguished by being able to feel both the strong and weak nuclear forces. Table 33.2 lists the characteristics of some of the most important subatomic particles, including the directly observed carrier particles for the electromagnetic and weak nuclear forces, all leptons, and some hadrons. Several hints related to an underlying substructure emerge from an examination of these particle characteristics. Note that the carrier particles are called gauge bosons. First mentioned in Patterns in Spectra Reveal More Quantization, a boson is a particle with zero or an integer value of intrinsic spin (such as s = 0, 1, 2, . ), whereas a fermion is a particle with a half-integer value of intrinsic spin (. |
SciQ | SciQ-5992 | aqueous-solution, kinetics
Title: Diffusion of CO2 and O2 in Water/Atmosphere System Consider the following experiment:
One reservoir of pure water is interfacing the atmosphere at standard condition.
Both are at rest and at the same temperature.
Both have no internal gradients (ie: constant concentrations, temperature, ...)
The interface between them is a perfect flat surface (for sake of simplicity).
The dissolved $\ce{CO2}$ in the water has a concentration somewhere between 0-50ppm.
The dissolved $\ce{O2}$ in the water has a concentration somewhere between 0-11ppm.
Questions
in order of importance
How to mathematically model the $\ce{CO2}$ and $\ce{O2}$ rate of change per unit area (flux) in the water and in the atmosphere considering only diffusion?
Suppose the atmosphere is at constant velocity relative to the water reservoir. How this would change the mathematical model above?
The following is multiple choice question (with options) to answer.
Aquatic producers need nutrients and what dissolved gas, which is more abundant near the surface of water? | [
"methane",
"oxygen",
"helium",
"nitrogen"
] | B | In addition to sunlight, aquatic producers also need dissolved oxygen and nutrients. Water near the surface generally contains more dissolved oxygen than deeper water. Many nutrients enter the water from the land. Therefore, water nearer shore usually contains more dissolved nutrients than water farther from shore. |
SciQ | SciQ-5993 | orbitals, atoms
Title: Why are atoms with eight electrons in the outer shell extremely stable? Atoms that have eight electrons in their outer shell are extremely stable. It can't be because both the $s$ and the $p$ orbitals are full, because then an atom with 13 or 18 valence electrons would be extremely stable. ($d$ has 10, and 5 is also stable).
Why is it that atoms with eight electrons in the outer shell are extremely stable? First, this isn't quite true. It is true for the first row of the periodic chart (from lithium to neon). It is almost true for the second row (from sodium to argon. But there are exceptions there. Beyond that it really isn't true at all for the elements beyond the first two columns.
The reason for the increased stability for the first two rows lies in quantum mechanics. Classically we can note that there are no $d$ electrons there. Another ways of looking at it from a classical point of view is that the early elements are too small to allow too many other atoms or groups of atoms around them. That tends to go away as you go down the periodic chart and the atoms get "fatter". A typical example is chloroplatinic acid which has six chlorines around it.
Most transition metals also can have more than four groups around them as well.
I suspect that this isn't an exceptionally useful explanation. As I said, the answer really lies in quantum mechanics. In looking up "molecular orbital theory", one reference can be found here.
The following is multiple choice question (with options) to answer.
All elements are most stable when their outermost shell is filled with electrons according to which rule? | [
"string rule",
"octet rule",
"coupling rule",
"quartet rule"
] | B | Chemical Reactions and Molecules All elements are most stable when their outermost shell is filled with electrons according to the octet rule. This is because it is energetically favorable for atoms to be in that configuration and it makes them stable. However, since not all elements have enough electrons to fill their outermost shells, atoms form chemical bonds with other atoms thereby obtaining the electrons they need to attain a stable electron configuration. When two or more atoms chemically bond with each other, the resultant chemical structure is a molecule. The familiar water molecule, H2O, consists of two hydrogen atoms and one oxygen atom; these bond together to form water, as illustrated in Figure 2.9. Atoms can form molecules by donating, accepting, or sharing electrons to fill their outer shells. |
SciQ | SciQ-5994 | water
You get the same effect heating distilled water in a microwave oven. If you use pure water and a clean glass bowl there is nothing to act as a nucleus for the steam bubbles and the water can superheat. Sadly you often discover this as you remove the bowl as the vibration can induce nucleation and an explosion of steam - hopefully not in your face!
The following is multiple choice question (with options) to answer.
What do you need to do to water to make it steam? | [
"freeze it",
"cool it",
"stir it",
"heat it"
] | D | Energy in a body of water can be gained or lost depending on conditions. When water is heated above a certain temperature steam is generated. The increase in heat energy creates a higher level of disorder in the water molecules as they boil off and leave the liquid. |
SciQ | SciQ-5995 | evolution, natural-selection, speciation
Title: Have scientists ever produce a new species in laboratory by means of natural selection? I was wondering, if scientists ever produce a more complex species from a less complex species by means of natural selection? I imagine something like, bacteria which can't photosynthesis and oxygen (chemoautotrophs) to bacteria that can photosynthesis and oxygen like cyanobacteria.
If scientists have never done this, is this theoretically possible to be done in lab by means of natural selection? There are a few issues your question brings up. First, the idea that species evolve from simple to complex is actually not a prediction or inevitable consequence of evolution by natural selection. The terms "simple" and "complex" themselves are ill-defined. For instance, if you defined "complex" to be size of the genome, the most complex organism found to date is probably a flowering plant from Japan. This idea of arranging organisms from simple to complex hearkens back to a pre-Darwinian idea of the Great Chain of Being.
You may be thinking that since multicellular life, for example, evolved from single-celled organisms, mutlticellular life is more complex than single celled life. The fallacy is that modern single celled organisms also evolved from the same single-celled ancestor. In no evolutionary sense is modern multicellular life more evolved than modern single celled organisms. You can, of course, defined notions of complexity to make multicellular life more complex than single celled life, but such definitions have no evolutionary significance.
We can, of course, say that organisms evolved from earlier organisms. So the second issue your question brings up is have scientists seen large evolutionary changes in a laboratory setting. The example you bring up is whether we could observe the evolution of photosynthesis in a lab.
The following is multiple choice question (with options) to answer.
When scientists work in natural settings rather than a lab, it is called what? | [
"extracurricular activity",
"exploratory",
"outside work",
"fieldwork"
] | D | Some life scientists mainly do lab research. Other life scientists, like the botanist in Figure below , work in natural settings. This is called fieldwork . Whether in the lab or the field, research in life science can be dangerous. It’s important to be aware of the risks and how to stay safe. |
SciQ | SciQ-5996 | meteorology, atmosphere, carbon, co2, rain
Bear in mind that this assumes an enormous rainfall intensity, 100% CO2 saturation of the water and equilibrium chemical dynamics. After the raindrops hit the ground at least half of it will immediately re-evaporate back into the air, leaving, at absolute most, about 3% of the atmospheric CO2 leached out of the atmosphere that will be available to react with the soil, rock or biosphere. Also consider that this is but one of several important processes affecting CO2 transience, such as photosynthesis, respiration, volcanism, industrial pollution, etc. So the CO2 estimates that you read about are average values. Advection and turbulent air mixing should ensure that the CO2 regains approximately normal concentration within an hour or two after rainfall.
The following is multiple choice question (with options) to answer.
What is released into the atmosphere when fossil fuels are burned? | [
"hydrogen dioxide",
"hydrogen monoxide",
"ferris oxide",
"carbon dioxide"
] | D | Major reservoirs of carbon include sedimentary rocks, fossil fuels, and the ocean. Sediments from dead organisms may form carbon-containing sedimentary rocks. Alternatively, the sediments may form carbon-rich fossil fuels, which include oil, natural gas, and coal. Carbon can be stored in these reservoirs for millions of years. However, if fossil fuels are extracted and burned, the stored carbon enters the atmosphere as carbon dioxide. Natural processes, such as volcanic eruptions, can also release underground carbon from rocks into the atmosphere. |
SciQ | SciQ-5997 | species-identification, botany
Title: What is this plant's scientific name? This is the picture of a tree in my college's botanical garden.
First I thought it to be a banana tree for its leaves but then seeing its lower part, I don't think it is a banana tree. So what is it's scientific name? I am just curious. Is it any hybrid or something like that plant?
Edit: This tree is from Bangladesh in South Asia. This tree is approximately 9-10 feet (I think, I cannot go near the tree). This picture is from Spring season. The name of this plant is:
Ravenala madagascariensis
Check: wikipedia
The following is multiple choice question (with options) to answer.
The leaf chameleon (brookesia micra) was discovered in northern madagascar in 2012. at just over one inch long, it is what? | [
"first known chameleon",
"hottest known chameleon",
"largest chameleon",
"smallest known chameleon"
] | D | Figure 27.1 The leaf chameleon (Brookesia micra) was discovered in northern Madagascar in 2012. At just over one inch long, it is the smallest known chameleon. (credit: modification of work by Frank Glaw, et al. , PLOS). |
SciQ | SciQ-5998 | electricity, electric-current, electrical-resistance
Title: Is the resistivity of all (conducting) alloys more than that of all (conducting) metals? Is the resistivity of all (conducting) alloys more than that of all (conducting) metals?
I have read it in some places but then I thought of solder. Lead is an elemental metal. Its resistivity is about $1.9\times10^{-7}\ \Omega m$.
${\rm Sn_{96.5} Ag_3 Cu_{0.5}}$ is a commonly used solder alloy (usually called "SAC305" when used as a solder), and its resistivity is about $1.3\times10^{-7}\ \Omega m$. (source)
So there's one example of an alloyed metal and an elemental metal with higher resistivity.
If you meant to ask, do all metallic alloys have higher resistivity than their component elemental metals, then consider lead ($\rho=1.9\times10^{-7}\ \Omega m$) and ${\rm Sn_{63}Pb_{37}}$ with resistivity of about $1.45\times10^{-7}\ \Omega m$.
The following is multiple choice question (with options) to answer.
Water and many metals are materials that have low resistance to electric currents and are therefore known as what? | [
"electric conductors",
"electromagnets",
"good insulators",
"radioactive"
] | A | Materials that have low resistance to electric current are called electric conductors . Many metals—including copper, aluminum, and steel—are good conductors of electricity. Water that has even a tiny amount of impurities in it is an electric conductor as well. |
SciQ | SciQ-5999 | nomenclature, research-process
I suspect the reason that most materials don't discuss how this process really works is because it is really, really complicated and often pretty dry. You'll see plenty of examples of new names being coined in journals like Taxon. But doing taxonomy is often conceived as not very glamorous, so doesn't receive that much attention, even though it underpins most comparative fields like ecology and evolution.
As a final note, the reasons that a species will be included in a given genus, or split into its own genus, or several genera will be lumped together into one large genus, are more murky, and related to phylogeny, morphology, final size, etc. These decisions are often also left up to the discretion of the author, unless of course they conflict with the code.
The following is multiple choice question (with options) to answer.
What is the name of the science that is concerned with naming and grouping organisms? | [
"geology",
"biology",
"methodology",
"taxonomy"
] | D | Carolus (Carl) Linnaeus (1707-1778) ( Figure below ) built on Aristotle’s work to create his own classification system. He invented the way we name organisms today, with each organism having a two word name. Linnaeus is considered the inventor of modern taxonomy , the science of naming and grouping organisms. |
SciQ | SciQ-6000 | analytical-chemistry, identification, isomers
Title: Does knowing the ratio of masses of the elements in a compound lead to the unique chemical identity of the compound? I was posed this question from a friend, however I am not necessarily sure. I think: yes, because a molecule of any compound is composed of a whole-number ratio of atoms of its elements, per the law of definite proportions. However, I feel as if I am wrong. No, knowing the mass ratios is not sufficient by itself. In the absence of additional information (for example, molar mass) that would only be enough information to determine the empirical formula, which is the formula that contains the smallest integral ratios of atoms. (E.g., the empirical formula of $\ce{C2H6}$ would be $\ce{CH3}$.) There are (theoretically) infinitely many molecules with the same atomic and mass ratios, yet differing in the actual molecular formula.
Further, even given the additional information of molar mass (so that the molecular formula can be determined), the existence of isomers precludes identification of a singular, specific compound without more sophisticated analysis. For example, $\ce{C3H6}$ could be either cyclopropane or propene. $\ce{C3H6O}$ could be as innocuous as acetone, or it could be highly carcinogenic epoxypropane. With more atoms, the number of possible isomers grows very rapidly. There's a nice table giving the number of isomers of alkanes of different lengths in this article. By the time you get to $\ce{C30H62}$, the number is $4111846763$. (Note, this is only considering structural isomers; accounting for stereoisomerism, the number would be even more astronomical.)
The following is multiple choice question (with options) to answer.
What substance can be identified by their atomic number and mass number? | [
"solutions",
"compounds",
"structures",
"elements"
] | D | Elements can be identified by their atomic number and mass number. |
SciQ | SciQ-6001 | human-biology, evolution, immunology
Title: In which order did the cells of the immune system evolve? Thinking about how complex the interactions between different types of immune system cells (T-helpers, T-Killers, Phagocytes, B-Cells etc.) are, it's fascinating how they all combine to get the desired effect.
However, I assume that they didn't all evolve simultaneously! Is there any way to tell which immune cell developed first or any theories to that effect? Perhaps that question is too specific, in which case was it humoral or cell mediated immunity that developed first?
You may find this paper helpful - unfortunately I'm still months off a campus so can't access it. As I'm lucky enough to have access to that article, I'm going to extract whatever I can find to answer your question.
To begin with, innate immunity must have evolved first - we can see it at almost all stages of evolution. According to Cooper & Herrin, ever since aerobic respiration gave rise to multicellular organisms which in turn needed protection from invasion by single-cell organisms.
They state that around 500 million years ago, the first adaptive immune systems evolved in vertebrates, but do not explain how although they attempt to. Instead, they explain why we are not able to discern at the moment how this evolution came about. The main reason given is that it is unknown when some key cells evolved (namely natural killer cells and dendritic cells) Additionally, mice and humans evolved two different kinds of natural killer cell receptors relatively recently while sharing a common ancestor only quite a long time ago.
Apparently jawed and jawless vertebrates have also evolved two different kinds of adaptive immune systems. They both seem to rely on the same mechanisms but on a different molecular and genetic basis. Cooper & Herrin conclude that at the current level of research, we are not able to determine the evolution of our immune system.
Source: How did our complex immune system evolve?
The following is multiple choice question (with options) to answer.
What do you call the first cell of a new organism? | [
"starter cell",
"egg",
"embryo",
"zygote"
] | D | Cells divide repeatedly to produce an embryo. Previously the one-celled zygote (the first cell of a new organism) divided to make two cells (a). Each of the two cells divides to yield four cells (b), then the four cells divide to make eight cells (c), and so on. Through cell division, an entire embryo forms from one initial cell. |
SciQ | SciQ-6002 | natural-satellites
Title: Are moons geologically active? Are there natural satellites in the Solar System that are geologically active? This includes volcanism, existence and motion of tectonic plates, et cetera.
Is it a common or a rather rare feature among such bodies? Yes. Moons around Jupiter (Io, Europa and Ganymede), Saturn (Titan and Enceladus) and Neptune (Triton) all have some form of geological activity. Charon also may have geological activity, being in a binary system with Pluto. However, while Earth's geological activity is caused by internal heating and tectonic plates, the geological activity of the moons around Jovian planets comes in the form of tidal forces. Io is the most iconic instance of tidal stress, because Io's plumes are frequent, volatile and make the world look extremely chaotic, with its surface frequently being altered and renewed by its non stop volcanic activity. (Because it is chaotic)
As for tectonic plates, Europa is the closest you get to tectonic plates with moons in our star system. Water replaces lava when it comes to ice worlds. Ice worlds being worlds that have ice instead of rock for their crust. This means that water mantles are a frequent occurrence, with the core of ice worlds being mineral rich stone. This is the case for Triton as well, which has cyro-volcanism from the sheer tidal stress Neptune exerts on the captured dwarf planet.
Enceladus and Titan have water mantles, Enceladus being the world notable for its massive plumes, high albedo and tiger stripe surface fractures. Titan may also have tectonic activity for similar reasons to Europa.
The following is multiple choice question (with options) to answer.
What planet in our solar system has a moon with volcanic activity? | [
"Venus",
"Saturn",
"jupiter",
"Mars"
] | C | Earth is not the only active planetary body in the solar system. Io, one of Jupiter’s moons, is home to fantastic volcanic eruptions. Volcanism is much hotter than on Earth. Lava curtains and fountains are common. In this color image, the Galileo spacecraft spotted two volcanic plumes. One is spewing high above the planet on the horizon. The second is near he boundary between day and night. Besides being hotter than Earth’s volcanism, eruptions on Io have a different composition. They are mostly sulfur!. |
SciQ | SciQ-6003 | zoology, marsupials
Title: Do male marsupials have a pouch? Do male marsupials have a pouch, or is it a female organ only (like the womb)? In most marsupials, only the females have a pouch. However, males of the water opossum and the extinct tasmanian tiger (or thylacine) also have a pouch. The males of both the thylacine and water opposum used/use their pouch to keep their genitalia from getting entangled in vegetation.
The following is multiple choice question (with options) to answer.
Kangaroos, koalas, and opossums are examples of what type of mammals? | [
"marsupials",
"carnivorous",
"cephalopods",
"monotremes"
] | A | By giving birth to tiny embryos, marsupial mothers are at less risk. However, the tiny newborn marsupial may be less likely to survive than a newborn placental mammal. The marsupial embryo completes its growth and development outside the mother’s body in a pouch. It gets milk by sucking on a nipple in the pouch. There are very few living species of marsupials. They include kangaroos, koalas, and opossums. You can see a baby koala peeking out of its mother’s pouch in Figure below . |
SciQ | SciQ-6004 | nomenclature, elements
0 = nil, 1 = un, 2 = bi, 3 = tri, 4 = quad, 5 = pent, 6 = hex, 7 = sept, 8 = oct, 9 = enn
(Pure & Appl. Chem. 51, 1979, 381-384, open access)
Thus it was until specific agreement that unnilunium ($\ce{_{101}Unu}$) eventually was named mendelevium ($\ce{_{101}Md}$), and IUPAC continues to publish how to name the new elements (example).
Despite this report, however, the roots are neither pure Latin, nor Greek, but convention. Because there no tenners (like decem, vīgintī), or hundreds (like centum, ducentī), etc. Even spelling the numeri only by position, you would expect unus, duo, tres, quattuor, quinque, sex, septem, octo, novem for $1\dots9$ for the former.
For the names eventually adopted, IUPAC set the rules that these
"In keeping with tradition, elements are named after
a mythological concept or character (including an astronomical object);
a mineral, or similar substance;
a place or geographical region;
a property of the element; or
a scientist.
[...] The names of all new elements should have an ending that reflects and maintains historical and chemical consistency. This would be in general “-ium” for elements belonging to groups 1–16, “-ine” for elements of group 17 and “-on” for elements of group 18. N.B. The present recommendation is here more specific than that
written in the 2002 document."
(Pure & Appl. Chem., 88, 2016, 401-505, open access)
The following is multiple choice question (with options) to answer.
Fe for iron and pb for lead are examples of elements known since ancient times, which have symbols based on their name in what language? | [
"spanish",
"arabic",
"latin",
"italian"
] | C | The figure below shows the most commonly used form of the periodic table. Each square shows the chemical symbol of the element along with its name. Notice that several of the symbols seem to be unrelated to the name of the element: Fe for iron, Pb for lead, etc. Most of these are the elements that have been known since ancient times and have symbols based on their Latin names. The atomic number of each element is written above the symbol. |
SciQ | SciQ-6005 | physiology
Title: Why does dehydration lead to low blood pressure I understand that the two leading causes of death from dehydration is imbalance in electrolytes and loss of blood pressure. I'm trying to understand what role water is playing in these cases and how the loss of it causes these imbalances, focusing for now on the blood pressure angle.
While I understand that blood is made up heavily of water, I'm still a little confused why dehydration so quickly leads to drop in blood pressure. Why can't the body continue to pump the already existing blood through the body, where is it using the water to keep the blood pressure up and what vital function is no longer being performed that causes that pressure to drop? The blood pressure is the exertion of force upon the blood vessels by the blood fluids. Thus having less fluids will results in decreased pressure.
The following is multiple choice question (with options) to answer.
Referring to low what, hypovolemia may be caused by bleeding, dehydration, vomiting, severe burns, or some medications used to treat hypertension? | [
"blood volume",
"brain volume",
"Secretion Volume",
"heart volume"
] | A | Blood Volume The relationship between blood volume, blood pressure, and blood flow is intuitively obvious. Water may merely trickle along a creek bed in a dry season, but rush quickly and under great pressure after a heavy rain. Similarly, as blood volume decreases, pressure and flow decrease. As blood volume increases, pressure and flow increase. Under normal circumstances, blood volume varies little. Low blood volume, called hypovolemia, may be caused by bleeding, dehydration, vomiting, severe burns, or some medications used to treat hypertension. It is important to recognize that other regulatory mechanisms in the body are so effective at maintaining blood pressure that an individual may be asymptomatic until 10–20 percent of the blood volume has been lost. Treatment typically includes intravenous fluid replacement. Hypervolemia, excessive fluid volume, may be caused by retention of water and sodium, as seen in patients with heart failure, liver cirrhosis, some forms of kidney disease, hyperaldosteronism, and some glucocorticoid steroid treatments. Restoring homeostasis in these patients depends upon reversing the condition that triggered the hypervolemia. |
SciQ | SciQ-6006 | mycology
Title: How do fairy rings propagate? It was somewhat new to me that mushrooms usually aren't individual organisms, but are merely the visible bodies of a bunch of fungi living in the soil. I know that mushrooms emit spores to reproduce, but what has been bizarre to me is how fairy rings form. Why do the fruiting bodies arrange themselves in a more or less circular shape, as opposed to the random scattering one would expect from wind-borne spores? When a fungal spore germinates in a suitable location, the growing mycelium will spread underground in all directions. In the ideal situation, the result is that the mycelium will become circular. Over time, the center of the mycelium will die out whereas the newly formed mycelium (underground) will develop the familiar mushrooms above ground and this will result in a fairy ring.
The following is multiple choice question (with options) to answer.
What particles allow fungi to reproduce through unfavorable conditions? | [
"atoms",
"quarks",
"bosons",
"spores"
] | D | How about both? That would suggest that fungi can produce both diploid and haploid cells, which they can. Shown above are fungi mycelia and haploid spores. Spores allow fungi to reproduce through unfavorable conditions. |
SciQ | SciQ-6007 | hydrology, mountains, rivers
Title: Why do rivers have 'wells' in mountains? Why/how can rivers have sources in places high above the sea level? The presence of water underground has nothing to do with sea level in mountainous country.
When rain fails on a mountain, or snow falls on a mountain and the snow eventually melts, the water from the rain or snow melt mostly travels downhill via rivers to the sea.
In getting to a river some of the water will fall on the ground. In places where the ground is covered by soil, water can travel through the soil via the pore spaces between the grains of soil. Similarly if porous rock, such as sandstone lies beneath the soil water can travel through the pores in the rock.
If a layer of impervious rock lies under the porous rock or soil, the water cannot move downwards, due to gravity, any further. This can lead to water accumulating in the soil or porous rock and saturating the soil or rock. In such situations an aquifer can form. The top of the saturated zone in an aquifer is called a water table.
The ground beneath a river is saturated and the surface of the river shows the water table exposed to atmosphere. Thus in mountainous regions the ground beneath rivers will be saturated and capable of supporting a well developed from the bank of a river.
The following is multiple choice question (with options) to answer.
What is the term for an underground layer of rock that is saturated with groundwater? | [
"aquifer",
"bason",
"river",
"delta"
] | A | An underground layer of rock that is saturated with groundwater is called an aquifer . A diagram of an aquifer is shown in Figure below . Aquifers are generally found in porous rock, such as sandstone. Water infiltrates the aquifer from the surface. The water that enters the aquifer is called recharge. |
SciQ | SciQ-6008 | botany, ecology, energy
Title: Why do plants create enough energy for the entire ecosystem? In my environmental class, we were recently learning about the $10\%$ law that basically says only $10\%$ of the energy goes from one trophic level to the next.
This got me thinking about why energy flows from one level to the next. Specifically, why do plants create enough energy for the entire ecosystem? Wouldn't they do fine without us, and wouldn't that save them the work of creating all that excess energy? Plants collect energy for themselves via photosynthesis, not for others.
It is used for it's own growth and survival.
It's energy is then redistributed to other organisms when either the plant dies and decomposes or when it is consumed. Many organism cannot collect their energy like plants do, and thus must feed on organisms (like plants) that are able to collect and store energy. This is in many cases detrimental to the plant (it should be intuitive why being eaten might be bad), and many, many plants do have traits to discourage other organisms from eating them (plants with toxins, thorns, etc.).
The following is multiple choice question (with options) to answer.
Where do most ecosystems get energy from? | [
"forests",
"sunlight",
"oceans",
"precipitation"
] | B | Ecosystems need a constant input of energy to supply the needs of their organisms. Most ecosystems get energy from sunlight. A few ecosystems get energy from chemical compounds. |
SciQ | SciQ-6009 | energy, energy-conservation, biophysics
Title: How efficient is the human body? This question sort of comes to mind when hearing how efficient an internal combustion engine is turning chemical energy in mechanical energy (something like 20-40%) with lots of excess heat. As an analog, how efficient is (or potentially) the human body at turning food into energy? Please bare with me, I realise there LOTS of different variables (how much the person weighs vs mass, metabolism, diet, etc). But I would imagine that there shouldn't be much margin of error given that most people maintain the same constant temperature (98 F +/- 1 degree). The MET (Metabolic Equivalent Task) readout on your gym equipment is your body doing 1Kcal/kg/h = 4184 J/kg/h and can be reasonably accurately measured by how much oxygen a test victim uses.
Sitting still is roughly 1 met and cycling at 100 Watts is around 5.5 Mets.
So taking a man of 75kg, cycling at 100Watts (100J/s) he is having to do 5.5 * 4184 * 75 / 3600s = 480Watts so an efficency of 20%
Remember though that the person is spending 80-100Watts just staying alive doing nothing - unlike your car. There is an interesting experimental fit to how much energy you need to just stay alive, calculated about 100 years ago, the Harris-Benedict equation
The following is multiple choice question (with options) to answer.
Maintaining a high metabolic rate takes a lot of what? | [
"energy",
"food",
"fuel",
"calories"
] | A | Maintaining a high metabolic rate takes a lot of energy. The energy must come from food. Therefore, mammals need a nutritious and plentiful diet. The diets of mammals are diverse. Except for leaf litter and wood, almost any kind of organic matter may be eaten by mammals. |
SciQ | SciQ-6010 | electrons, charge, quasiparticles, leptons
Title: How do electrons get a charge? Electrons belong to a group of elementary particles called leptons. There are charged and neutral leptons. And electron is the charged one. But how come it got charged?
The negative or positive charges were assigned by convention. But it is a fact that electrons are charged. My question is why electrons? and not neutrons?
Also while reading http://en.wikipedia.org/wiki/Electron, I saw that "Independent electrons moving in vacuum are termed free electrons. Electrons in metals also behave as if they were free. In reality the particles that are commonly termed electrons in metals and other solids are quasi electrons, quasiparticles, which have the same electrical charge, spin and magnetic moment as real electrons but may have a different mass ( or Effective mass - extra mass that a particle seems to have while interacting with some force )."
What does this mean? Your question touches the question of ontology in particle physics. Historically we are used to be thinking of particles as tiny independent entities that behave according to some laws of motion. This stems from the atomistic theory of matter, which was developed some two thousand years ago from the starting point of what would happen if we could split matter in ever smaller parts. The old Greeks came to the conclusion that there had to be a limit to that splitting, hence the atom hypothesis was born.
This was just a philosophical idea, of course, until around the beginning of the 19th century we learned to do chemistry so well that it became obvious that the smallest chunks that matter can be split into seemed to be the atoms of the periodic table. A hundred years later we realized that atoms can be split even further into nuclei and electrons. What didn't change was this idea that each chunk had its own independent existence.
This idea ran into a deep crisis during the early 20th century when we discovered the first effects of quantum mechanics. It turns out that atoms and nuclei and electrons do not, at all, behave like really small pieces of ordinary matter. Instead, they are behaving radically different, so different, indeed, that the human imagination has a hard time keeping up with their dynamic properties.
The following is multiple choice question (with options) to answer.
Electrons can move from one atom to another; when they do, specimens called what, with overall electric charges, are formed? | [
"atoms",
"ions",
"molecules",
"cations"
] | B | So far, we have discussed elements and compounds that are electrically neutral. They have the same number of electrons as protons, so the negative charges of the electrons is balanced by the positive charges of the protons. However, this is not always the case. Electrons can move from one atom to another; when they do, species with overall electric charges are formed. Such species are called ions. Species with overall positive charges are termed cations, while species with overall negative charges are called anions. Remember that ions are formed only when electrons move from one atom to another; a proton never moves from one atom to another. Compounds formed from positive and negative ions are called ionic compounds. Individual atoms can gain or lose electrons. When they do, they become monatomicions. When atoms gain or lose electrons, they usually gain or lose a characteristic number of electrons and so take on a characteristic overall charge. Table 3.6 "Monatomic Ions of Various Charges" lists some common ions in terms of how many electrons they lose (making cations) or gain (making anions). There are several things to notice about the ions in Table 3.6 "Monatomic Ions of Various Charges". First, each element that forms cations is a metal, except for one (hydrogen), while each element that forms anions is a nonmetal. This is actually one of the chemical properties of metals and nonmetals: metals tend to form cations, while nonmetals tend to form anions. Second, most atoms form ions of a single characteristic charge. When sodium atoms form ions, they always form a 1+ charge, never a 2+ or 3+ or even 1− charge. Thus, if you commit the information in Table 3.6 "Monatomic Ions of Various Charges"to memory, you will always know what charges most atoms form. (In Chapter 9 "Chemical Bonds", we will discuss why atoms form the charges they do. ) Table 3.6 Monatomic Ions of Various Charges H+ Na+ K+ Ions formed by losing a single electron. |
SciQ | SciQ-6011 | reaction-mechanism
It is generally said that reactants react so that they can achieve a
lower energy state. Then why does a reversible reaction occur in the
first place?
Good question. Remember that we can always add energy to make an unfavorable reaction proceed. For example, the sodium ion, which is isoelectronic with neon, is stable with a full octet of electrons. However, we can still take away more electrons. It just takes a rather sizable application of energy.
The following is multiple choice question (with options) to answer.
Energy is absorbed as reactants are converted to products in what kind of chemical reaction? | [
"anaphoric",
"hydrostatic",
"synthesis",
"endothermic"
] | D | For an endothermic chemical reaction, energy is absorbed as reactants are converted to products. Exothermic and endothermic reactions can be thought of as having energy as either a product of the reaction or a reactant. Exothermic reactions give off energy, so energy is a product. Endothermic reactions require energy, so energy is a reactant. |
SciQ | SciQ-6012 | evolution, natural-selection, mutations, sexual-reproduction
The testis seems to be the Oven in which genetic variation is baked. The rapid turnover of spermatogenesis, whereby each primary spermatocyte finally results in 4 sperms (Compared to One Ovum resulting from each primary Oogonia), that's beside the very large number of sperms produced daily, that continues for years and year. While with the Oogenesis everything really finishes at the foetal life, the remaining is just maturation steps, nothing is new as far as change of genetic material inside the Oocytes is concerned, this is the state throughout most of the female's life.
When I look at the seminiferous tubules, and see all those layers of spermatocytes leading to sperms, I tend to think that there is even some small scale natural selection, that bad mutated germline cells would die off, and only the ones with good genomes would survive all the stages of spermatogensis, and possibly the ones with beneficial mutation might have an advantage in survival in that milieu and even might have better chances of fertilizing the ovum?
Not only that, the testis seems to be more exposed to stressors inside the body and even to direct external environmental stressors, while the Ovaries lying deep inside, seem to be more protected. The Oocyte actually "selects" one sperm, so it's rule is selective rather than productive of change.
All of that makes one think that it is the male germline cells that could mediate high mutation rate in response to stressors, or even without stressors by virtue of the very high production rate of germline cells for very long periods of time. It seems that this is the real source of beneficial mutations that would ultimately drive evolution.
The following is multiple choice question (with options) to answer.
What is the permanent prevention of gamete production or release called? | [
"sterilization",
"fertilization",
"insemination",
"restoration"
] | A | |
SciQ | SciQ-6013 | immunology, bacteriology
S. epidermidis is considered part of the of the normal human microbial flora, while S. aureus is usually regarded as a transient member. Colonization by either species usually does not lead to adverse events. However, when these organisms or their extracellular products are allowed to breach the epithelial layer, serious disease can result (1). S. aureus has many cell surface virulence factors (such as protein A and clumping factor) and secreted exotoxins and enzymes that allow strains to cause a myriad of infections. These diseases range from relatively benign furuncles and subcutaneous abscesses to scalded skin syndrome, sepsis, necrotizing pneumonia, and toxic shock syndrome (TSS). While no single cell surface virulence factor has been shown to be uniquely required for mucous membrane attachment, once colonization occurs, numerous secreted exotoxins, including the pyrogenic toxin superantigens and exfoliative toxins, definitively cause serious human disease. Other secreted exotoxins, such as the four hemolysins (α, β, δ, and γ) and Panton-Valentine leukocidin have also been suggested to contribute to significant illnesses. S. epidermidis does not possess the array of extracellular toxins that S. aureus does, and its primary virulence factor is considered to be its ability to form biofilms.
To improve their ability to cause this variety of human disease and to occupy numerous niches within the host, staphylococci have developed quorum-sensing systems that enable cell-to-cell communication and regulation of numerous colonization and virulence factors.
The following is multiple choice question (with options) to answer.
Because pathogenic bacteria typically cause disease by releasing exotoxins or endotoxins, they have potential use as what type of weapon? | [
"radioactive",
"pandemic",
"nuclear missile",
"bioterrorism"
] | D | |
SciQ | SciQ-6014 | nitrogen
Step three is when plants and the animals that live of the plants die and breaks down into ammonia and other waste products (this is where many explanations of the nitrogen cycle usually starts). The waste products gets converted into ammonia by bacteria and the ammonia gets converted to nitrite and the entire cycle starts all over again.
Legumes have a symbiotic relationship with some bacteria that can fixate nitrogen (N2) https://aces.nmsu.edu/pubs/_a/A129/
sources:
https://science.howstuffworks.com/life/biology-fields/nitrogen-cycle.htm
https://www.britannica.com/science/denitrifying-bacteria
The rest is from my memory.
The following is multiple choice question (with options) to answer.
What cycle vital to plants includes a process called denitrification? | [
"sedimentation cycle",
"nitrogen cycle",
"photosynthesis",
"carbon cycle"
] | B | 3.4 NITROGEN: RUNNING IN CYCLES Introduction: In the previous assignment, you studied the carbon cycle. In a previous unit, you described the water cycle. Carbon and water are matter. As you learned in the first unit, matter cycles. Nitrogen is another form of matter that cycles. Like water and carbon, nitrogen is essential to life. Also, like water and carbon, its cycles affect you. Therefore it is important that you learn about the nitrogen cycle, how it affects you, and how you affect it. Assignment: There are three parts to this assignment. You must complete all three parts to receive credit for the assignment. Be sure to turn in all three parts at the same time. I will not correct partial assignments. THANKS! PART ONE: 1. Describe the nitrogen cycle. Describe how nitrogen goes from the atmosphere to a form usable to plants, how it is used and excreted by animals, and how it returns to the atmosphere. In your description be sure to explain the words: * decay * denitrification. |
SciQ | SciQ-6015 | pathology
Title: Are all diseases caused by organisms (microorganisms)? Are there other causes? Or is it correct to say that all diseases are in fact caused by organisms (microorganisms)? It is not correct to say that all diseases are caused by foreign organisms. Counterexamples are:
Cancer is caused by random genetic mutations in the cells of our body. The mutations can be caused by many factors such as ionizing radiation, smoking, chemical toxins etc.
Diseases such as stroke or heart attack are caused by blood clots blocking the blood flow to essential organs.
Autoimmune diseases are caused by the immune system falsely recognizing cells of the body as foreign and attacking that tissue leading to a wide variety of symptoms.
Alzheimer's disease is caused by chronic neurodegeneration, meaning that the cells in the brain die. The causes are not quite understood but as Alzheimer's usually appears late in life it is likely related to ageing. Also, it is known that some genetic defects can lead to early-onset Alzheimers.
Prion proteins can cause diseases such as Creutzfeldt–Jakob disease also known as mad-cow disease.
Hereditary diseases such as early-onset Alzheimers or ALS are cause by gene defects inherited from the parents.
Toxins can cause chronic diseases such as lead poisoning.
The list probably goes on...
Please note that the first two on the list are the most common cause of death in developed countries.
The following is multiple choice question (with options) to answer.
Cerebral palsy is a disease caused by injury to what organ as it is developing? | [
"brain",
"liver",
"heart",
"skin"
] | A | Cerebral palsy is a disease caused by injury to the developing brain. The injury occurs before, during, or shortly after birth. Cerebral palsy is more common in babies that have a low weight at birth. But the cause of the brain injury is not often known. The disease usually affects the parts of the brain that control body movements. Symptoms range from weak muscles in mild cases to trouble walking and talking in more severe cases. There is no known cure for cerebral palsy. |
SciQ | SciQ-6016 | metabolism, human-anatomy, pharmacology, liver
Title: Circulation through the liver in light of drug metabolism I have a lingering question which stems from an answer that I gave to What hydrolyses aspirin within the digestive tract and blood stream?
When a drug or any other substance is absorbed into the bloodstream in the stomach or small intestine, it ultimately passes through the hepatic portal vein and into the liver sinusoids, where it is processed by hepatocytes and introduced into the general circulation via the vena cava. In terms of metabolism, this is what causes a "first-pass" effect for drugs that are ingested.
For drugs that are delivered either by intravenous, intramuscular, or sub-lingually (as in the other Biology.SE question), this first-pass effect is avoided, and the drug is introduced into the general circulation without being metabolized by the liver first.
Even though the first pass is avoided, the blood in the body still makes its way back through the liver eventually via the hepatic artery, which is a branch off of the celiac artery.
The issue I still have is, does the incoming blood from the hepatic artery merge with the blood from the hepatic portal vein? If not, does the blood from the hepatic artery still interact with the hepatocytes in some way? (it makes sense that it does, and I have also read that one of the main functions of the hepatic artery was to deliver blood supply for the liver's metabolic needs) If this is not the case, where in the body would these drugs that were introduced via IV, etc., be metabolized? Yes, the blood from the hepatic artery (proper) and the portal vein mix in the sinusoids of the liver. The hepatic vein supplies about 75% of the blood to the liver, and the hepatic artery the remaining 25%. Because the portal vein provides such a large part of the blood supply to the liver, then any disease that causes the blood to build up can cause portal hypertension.
The hepatic artery carries oxygen-rich blood from the heart. The portal vein is part of the portal system and connects the capillary beds of the gastrointestinal tract to those of the liver. Because of the larger volume through the portal vein, I think that each vessel carries about half the oxygen supply to the liver.
The following is multiple choice question (with options) to answer.
What substance is removed from waste as it passes through the large intestine? | [
"nutrients",
"air",
"blood",
"water"
] | D | Food waste enters the large intestine from the small intestine in a liquid state. As the waste moves through the large intestine, excess water is absorbed from it. The remaining solid waste is called feces. After a certain amount of feces have collected, a sphincter relaxes to let the feces pass out of the body through the anus. This is elimination. |
SciQ | SciQ-6017 | solid-state-physics, crystals
that seems to derive the interplanar distance, namely $\displaystyle d=(\mathbf{R}_{n'}-\mathbf{R}_n)\cdot\frac{\mathbf{G}_m}{|\mathbf{G}_m|}$, where $\mathbf{R}_{n'}$ and $\mathbf{R}_n$ are two arbitrary direct lattice vectors satisfying $\mathbf{R}_{n'} \cdot \mathbf{G}_m = 2\pi (Z+1)$ and $\mathbf{R}_{n} \cdot \mathbf{G}_m = 2\pi Z$.
This can't be right, since the theorem requires the shortest vector in the direction of $\mathbf{G}_m$, and not $\mathbf{G}_m$ itself. Where is the mistake? Each reciprocal lattice vector $\mathbf{G}$ defines a set of equally-spaced, parallel planes via
$$
\mathbf{G}\cdot\mathbf{R}=2\pi m\,,
$$
one for every integer $m$. Nearest-neighbor planes have $|\Delta m| =1$. Your calculation indeed shows that the distance between consecutive planes is exactly $2\pi/G$. For completeness, I'll sketch the proof here.
Let $\mathbf{r}_1$ and $\mathbf{r}_2$ be points in consecutive planes, i.e. they satisfy
$$
\mathbf{G}\cdot\mathbf{r}_1=2\pi m\,,~~~~~~~
\mathbf{G}\cdot\mathbf{r}_2=2\pi (m+1)\,.
$$
The following is multiple choice question (with options) to answer.
The distance between two consecutive z discs or z lines is called what? | [
"contractile",
"sarcomere",
"radius",
"ligule"
] | B | When a sarcomere shortens, some regions shorten whereas others stay the same length. A sarcomere is defined as the distance between two consecutive Z discs or Z lines; when a muscle contracts, the distance between the Z discs is reduced. The H zone—the central region of the A zone—contains only thick filaments and is shortened during contraction. The I band contains only thin filaments and also shortens. The A band does not shorten—it remains the same length—but A bands of different sarcomeres move closer together during contraction, eventually disappearing. Thin filaments are pulled by the thick filaments toward the center of the sarcomere until the Z discs approach the thick filaments. The zone of overlap, in which thin filaments and thick filaments occupy the same area, increases as the thin filaments move inward. |
SciQ | SciQ-6018 | bioinformatics, phylogenetics
Title: How to get taxonomic specific ids for kingdom, phylum, class, order, family, genus and species from taxid? I have a list of taxids that looks like this:
1204725
2162
1300163
420247
I am looking to get a file with taxonomic ids in order from the taxids above:
kingdom_id phylum_id class_id order_id family_id genus_id species_id
I am using the package "ete3". I use the tool ete-ncbiquery that tells you the lineage from the ids above. (I run it from my linux laptop with the command below)
ete3 ncbiquery --search 1204725 2162 13000163 420247 --info
The result looks like this:
# Taxid Sci.Name Rank Named Lineage Taxid Lineage
2162 Methanobacterium formicicum species root,cellular organisms,Archaea,Euryarchaeota,Methanobacteria,Methanobacteriales,Methanobacteriaceae,Methanobacterium,Methanobacterium formicicum 1,131567,2157,28890,183925,2158,2159,2160,2162
1204725 Methanobacterium formicicum DSM 3637 no rank root,cellular organisms,Archaea,Euryarchaeota,Methanobacteria,Methanobacteriales,Methanobacteriaceae,Methanobacterium,Methanobacterium formicicum,Methanobacterium formicicum DSM 3637 1,131567,2157,28890,183925,2158,2159,2160,2162,1204725
420247 Methanobrevibacter smithii ATCC 35061 no rank root,cellular organisms,Archaea,Euryarchaeota,Methanobacteria,Methanobacteriales,Methanobacteriaceae,Methanobrevibacter,Methanobrevibacter smithii,Methanobrevibacter smithii ATCC 350611,131567,2157,28890,183925,2158,2159,2172,2173,420247
The following is multiple choice question (with options) to answer.
What is the largest taxonomic rank? | [
"sublet",
"core",
"top",
"domain"
] | D | Coming up with a scientific naming method may not seem like a big deal, but it really is. Prior to Linnaeus, there was no consistent way to name species. Names given to organisms by scientists were long and cumbersome. Often, different scientists came up with different names for the same species. Common names also differed, generally from one place to another. A single, short scientific name for each species avoided a lot of mistakes and confusion. |
SciQ | SciQ-6019 | human-biology, neuroscience, peripheral-nervous-system
Title: Are spinal nerves myelinated and unmyelinated at the same time? I was trying to answer this question when I remembered that the somatic axon is myelinated, while both sympathetic and parasympathetic preganglionic axons are also myelinated. Are they only myelinated or are they both myelinated and unmyelinated? Thanks
Edit:
This is a question from an old lecture quiz (previous year) and unfortunately I do not have the answers for the questions. The wording of the question was
Spinal Nerves are
a.) myelinated
b.) unmyelinated
c.) answers a and b
d) none of the above" Spinal nerves are mixed nerves containing afferent and efferent neurons of various types. Anatomically, they protrude from the spinal column bilaterally at each vertebral level. They contain both myelinated fibers (e.g., A fibers) and unmyelinated fibers (e.g., C fibers).
The answer is (c): both myelinated and unmyelinated.
Please note that spinal nerves are NOT located in the spinal cord, despite the fact that neurons in each spinal nerve will either originate or terminate there. A spinal nerve is a peripheral structure. It starts at the point where the dorsal and ventral root converge (See April's Clinical Anatomy, Ch. 1). If you have the opportunity to observe back surgery or dissect a human cadaver, you can see and touch a spinal nerve. They are cable like structures containing bundles of many many many axons, but no neuron in its entirety. A nerve is not a neuron. This is a common misconception.
Just to add, the details here may seem like trivia, but they are not. Similar questions (and questions that require you to understand the distinction between a nerve and a neuron) are often asked on US medical licensing exams. This is because they are relevant to understanding and interpreting neurological symptoms and physical exam findings.
The following is multiple choice question (with options) to answer.
Which system is divided into the somatic and autonomic nervous systems? | [
"peripheral nervous system",
"central nervous system",
"auxiliary nervous system",
"local nervous system"
] | A | The motor division of the PNS carries nerve impulses from the central nervous system to muscles and glands throughout the body. The nerve impulses stimulate muscles to contract and glands to secrete hormones. The motor division of the peripheral nervous system is further divided into the somatic and autonomic nervous systems. |
SciQ | SciQ-6020 | 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.
The composition of the magma determines if the rock is mafic, felsic, or what? | [
"porous",
"intermediate",
"variable",
"magnetic"
] | B | The composition of the magma determines if the rock is mafic, felsic, or intermediate. |
SciQ | SciQ-6021 | kinematics, projectile, curvature
As you can see, the sides of the parabola are pretty flat, whereas its vertex and the surrounding region (i.e.: at $x=0$) have a relatively sharp corner.
So the question is how to mathematically describe this property?
Well, one way to do it is to use circles. The part of the curve that is pretty flat can be considered to be a section of a really large circle(as shown in the picture), this circle has large radius, and hence we say this part of the curve has large radius of curvature, that is, it's very flat.
On the other hand, the vertex of the parabola and the surrounding region are relatively sharp and pointy, hence you'll notice it takes a circle with small radius to fit it on this edgy section of the parabola, we say this region has small radius of curvature.
You'll also note that, the radius of curvature for a curve, changes from one point on the curve to another, you'll further notice that, when the region is flat, the rate of change of the radius of curvature is small(you can use small number of huge circles to describe a flat region), whereas it takes a lot of circles with small radii to describe a sharp corner, and hence the rate of change of the radius of curvature is great at these regions.
How can a parabola have a center from which radius is to be measured?
No, it does not, but every point on the parabola and and the surrounding region can be regarded as a part of a circle with certain radius.
Does the radius of curvature changes with the position of body(in projectile motion)?
Yes, as stated earlier, the radius of curvature changes from point to point on a curve, since the path of the projectile can be modeled as its position on a parabola, hence the radius of curvature will change with the change of position of the projectile.
The following is multiple choice question (with options) to answer.
The shape of the path of an object undergoing projectile motion is called? | [
"linear",
"a triangle",
"spherical",
"a parabola"
] | D | The shape of the path of an object undergoing projectile motion is a parabola. |
SciQ | SciQ-6022 | infection, amphibians
Title: What is this toad suffering from? Myiasis or chytridiomycosis? I found this toad on Aug. 29th at this location: position on osm
I think it is a bufo bufo, approx. 10 cm long. The nostrils seemed to be completely filled with a grey matter and from the activity of the floor of the mouth it apparently tried to breathe againgst this obstruction. It probably had enough oxygen via its skin though.
I tried to remove the obstruction using a blade of grass but this seemed to produce some pain as the toad closed its eyes on contact, so I stopped. The skin looked fairly normal and the toad was able to walk away after a while.
I can think of two causes for this condition.
Batrachochytrium dendrobatidis infestation
Lucilia bufonivora larvae
I could not see properly, if there were any larvae or unhatched eggs inside the nostrils, but as the rest of the skin seemed unharmed I assume the latter.
Is my assumption valid or is there even a third possibility? It is a female Bufo Bufo and you are right, there are toad fly (Lucilia bufonivora) larvae/eggs inside her nostrills. These flies lay their eggs inside toads' nostrills (specifically on Bufo Bufos) and the larvae start eating them. Sadly this disease ends up by the death of toad. They slowly eat nostrills, then mouth, eyes, and all the head.
Here's a photo of a male bufo bufo, without a head. Someone found it walking around at this situation. https://i.stack.imgur.com/I6twl.jpg
The following is multiple choice question (with options) to answer.
What type of animals breathe with gills as larvae and with lungs as adults? | [
"mammals",
"insects",
"reptiles",
"amphibians"
] | D | Amphibians breathe with gills as larvae and with lungs as adults. They have a three-chambered heart and relatively complex nervous system. |
SciQ | SciQ-6023 | human-biology, biochemistry, hematology, red-blood-cell, human-physiology
Title: Besides hemoglobin, what proteins are present in red blood cells? I knew that mature red blood cells (RBCs) lacked nuclei, but I wasn't aware until just now that they also lacked ribosomes and mitochondria. Most cells in the human body all contain a common laundry list of housekeeping proteins and RNAs (including mitochondrial proteins and ribosomal RNAs), but I guess RBCs lack a number of them. Do they still have all of the other organelles? Obviously hemoglobin (and to a lesser extent carbonic anhydrase) makes up a large portion of the dry weight of RBCs, but are other proteins still present? If so, what are their relative abundances?
For example, do red blood cells have any of the normal metabolic (i.e. ATP producing) proteins? Obviously they don't have any of the TCA cycle proteins, but do they still have the glycolysis ones? Reticulocyte stage is when the ribosomes are still present and after that no new protein synthesis occurs. However RBCs have a lot of proteins and major proteins other than haemoglobin are cytoskeletal proteins and ion channels/pumps (In fact, cytoskeletal proteins are more abundant than haemoglobin). It is the Na+-K+-ATPase that consumes most ATP. As you correctly identified the RBCs produce ATP via glycolysis and glycolytic enzymes are also present. Note that deficiency of pyruvate kinase leads to haemolytic anaemia.
For a detail on the proteins present in human RBSs, see this paper. They have studied the RBC proteome by ion-trap MS. The top 5 proteins (from Table-1) are:
No. Protein description Molecular mass (Da) Gi Number Sequence No. of identified
coverage(%) peptides
1 Spectrin α chain, erythrocyte 279,916.5 1174412 48.0 77*
2 Spectrin β chain, erythrocyte 246,468.1 17476989 48.0 76*
3 Ankyrin 1, splice form 2 206,067.9 105337 45.0 55
The following is multiple choice question (with options) to answer.
The most abundant formed elements in blood, erythrocytes are red, biconcave disks packed with an oxygen-carrying compound called this? | [
"pus",
"hemoglobin",
"hydrogen",
"plasma"
] | B | 18.3 Erythrocytes The most abundant formed elements in blood, erythrocytes are red, biconcave disks packed with an oxygen-carrying compound called hemoglobin. The hemoglobin molecule contains four globin proteins bound to a pigment molecule called heme, which contains an ion of iron. In the bloodstream, iron picks up oxygen in the lungs and drops it off in the tissues; the amino acids in hemoglobin then transport carbon dioxide from the tissues back to the lungs. Erythrocytes live only 120 days on average, and thus must be continually replaced. Worn-out erythrocytes are phagocytized by macrophages and their hemoglobin is broken down. The breakdown products are recycled or removed as wastes: Globin is broken down into amino acids for synthesis of new proteins; iron is stored in the liver or spleen or used by the bone marrow for production of new erythrocytes; and the remnants of heme are converted into bilirubin, or other waste products that are taken up by the liver and excreted in the bile or removed by the kidneys. Anemia is a deficiency of RBCs or hemoglobin, whereas polycythemia is an excess of RBCs. |
SciQ | SciQ-6024 | ph, titration
Title: Experimental determination of pH I am trying to determine the experimental pKa for two weak acids that were titrated against 0.20M NaOH.
I have read elsewhere that you can take the point where the graph becomes steep and divide the value of base added by two the corresponding pH value would then be the pKa, but how do i choose which value since it may not be obvious which point the graph becomes steep.
Below I can see that the pka for acetic acid should be close to the theoretical value calculated of 4.76 and the Tris-HCl pka should be approximately 8.3 but there must be a better way than just guessing from a graph.
My textbook doesn't explain how to experimentally find pH just that it's the point where $[A^-]/ [HA]$. I am hoping someone can give me an equation to work with or guide me in the right direction.
Thank you, So I think what you heard is about the right idea. The flat region is your buffering region, and isn't super helpful to deduce the pKa. Adding base consumes the weak acid, and because it is weak, you know you are mostly consuming the [HA] form, and equilibrating back to around the pKa. This is why your pH doesn't change much around the pKa.
As an example, if you had 10 mmol of HA to start, then at the pKa point you would have 5 mmol of HA and 5 mmol of A-. Now, if you keep adding base, at some point you will essentially consume the remaining 5 mmol of HA. Then, there will be negligible amount left and it can't buffer anymore - i.e. your pH will change rapidly because you are adding strong base. Here you will have ~0 mmol of HA, and ~10 mmol of A-. Note that you have twice the amount of A- now. The pKa will have been at the point where you had half of this.
Experimentally, I know two simple ways. Using a pH meter and no indicator, you have to measure the sharp region more carefully (i.e., drop by drop), because you want to be able to find the exact point where the pH changes the fastest. By approximating the derivative, i.e.
The following is multiple choice question (with options) to answer.
What is the scale on which acidity is measured? | [
"μg",
"hp",
"ph",
"μm"
] | C | The concentration of hydronium ions in a solution is known as acidity. In pure water, the concentration of hydronium ions is very low; only about 1 in 10 million water molecules naturally breaks down to form a hydronium ion. As a result, pure water is essentially neutral. Acidity is measured on a scale called pH , as shown in Figure below . Pure water has a pH of 7, so the point of neutrality on the pH scale is 7. |
SciQ | SciQ-6025 | mycology
Title: How do fairy rings propagate? It was somewhat new to me that mushrooms usually aren't individual organisms, but are merely the visible bodies of a bunch of fungi living in the soil. I know that mushrooms emit spores to reproduce, but what has been bizarre to me is how fairy rings form. Why do the fruiting bodies arrange themselves in a more or less circular shape, as opposed to the random scattering one would expect from wind-borne spores? When a fungal spore germinates in a suitable location, the growing mycelium will spread underground in all directions. In the ideal situation, the result is that the mycelium will become circular. Over time, the center of the mycelium will die out whereas the newly formed mycelium (underground) will develop the familiar mushrooms above ground and this will result in a fairy ring.
The following is multiple choice question (with options) to answer.
Almost all fungi reproduce asexually by producing what? | [
"roots",
"atoms",
"ions",
"spores"
] | D | Almost all fungi reproduce asexually by producing spores. A fungal spore is a haploid cell produced by mitosis from a haploid parent cell. It is genetically identical to the parent cell. Fungal spores can develop into new haploid individuals without being fertilized. |
SciQ | SciQ-6026 | potential-energy, many-body, biology, models
cmap_cool = plt.get_cmap('cool')
#plot initial and final positions only
fig, ax = plt.subplots(1, figsize=(15,12))
theta = np.linspace(0, 2*np.pi, 200)
ax.plot(expected_radius*np.cos(theta), expected_radius*np.sin(theta), 'black', label="Expected radius")
ax.plot(X_pos[:, 0], Y_pos[:, 0], 'o', label="Initial position", color=cmap_cool(0)) #initial position in blue
ax.plot(X_pos[:, -1], Y_pos[:, -1], 'o', label="Final position", color=cmap_cool(0.99)) #final position in purple
ax.axis("scaled")
ax.set_xlim(left=-24, right=24)
plt.legend(loc='best')
#plot trajectories too
fig, ax = plt.subplots(1, figsize=(15,12))
theta = np.linspace(0, 2*np.pi, 200)
ax.plot(expected_radius*np.cos(theta), expected_radius*np.sin(theta), 'black', label="Expected radius")
ax.plot(X_pos[:, 0], Y_pos[:, 0], 'o', label="Initial position", color=cmap_cool(0)) #initial position in blue
ax.plot(X_pos[:, -1], Y_pos[:, -1], 'o', label="Final position", color=cmap_cool(0.99)) #final position in purple
ax.axis("scaled")
ax.set_xlim(left=-24, right=24)
The following is multiple choice question (with options) to answer.
Thomson’s plum pudding model shows the structure of what? | [
"DNA",
"cell",
"atom",
"nucleus"
] | C | Following the discovery of the electron, J. J. Thomson developed what became known as the “ plum pudding ” model in 1904. Plum pudding is an English dessert similar to a blueberry muffin. In Thomson’s plum pudding model of the atom, the electrons were embedded in a uniform sphere of positive charge like blueberries stuck into a muffin. The positive matter was thought to be jelly- like or a thick soup. The electrons were somewhat mobile. As they got closer to the outer portion of the atom, the positive charge in the region was greater than the neighboring negative charges and the electron would be pulled back more toward the center region of the atom. |
SciQ | SciQ-6027 | organic-chemistry, reaction-mechanism, analytical-chemistry, halides, alkali-metals
Carbon tetraiodide ($\ce{CI4}$): 519.628/5 = 103.9 u/atom; density = 6.36 g/$\text{cm}^3$ (m.p. = 168$^\circ$C, so it's solid at room temperature)
Mercury ($\ce{Hg}$): 200.592/1 = 200.6 u/atom; density = 13.534 g/$\text{cm}^3$
The following is multiple choice question (with options) to answer.
What type of carbons may be gases, liquids, or solids at room temperature? | [
"hydrocarbons",
"amorphous",
"graphites",
"diamonds"
] | A | Hydrocarbons vary greatly in size, which influences properties such as melting and boiling points. At room temperature, hydrocarbons may be gases, liquids, or solids. They are generally nonpolar and do not dissolve in water. |
SciQ | SciQ-6028 | arduino, sensors
Title: Is it possible to use HC-SR04 ultrasonic range sensor to indicate thickness of a material The HC-SR04 is directly connected to an Arduino board with the receiver end(echo) connected to analog pin 2 and the transmitter (trigger) connected to digital pin 4.
I am wondering if I can use the sensor to sense the change in saturation from when object block its path. The receiver and transmitter will be positioned like this
The line in the middle is supposed to be a paper. I'll be using it to see the difference between one paper and two paper when they travel trough the two.
Now I'm not sure if this is possible but the way I see it working is kind of similar to an IR LED Arduino program connected to an LED, where when one paper passes trough the light gets a little bit weaker and with two it takes a heavier hit.
Is this possible? The short answer is "no, a sonic range sensor can't do it".
It might "work" under very controlled conditions, but relying on only the attenuation of the returned signal to determine thickness may leave you open to incorrect results due to multipath propagation effects.
The more traditional way to measure thickness with sound is called profiling. The following is excerpted from a USGS Woods Hole Science Center page on Seismic Profiling systems:
reflection profiling is accomplished by [emitting] acoustic energy in timed intervals [...]. The transmitted acoustic energy is reflected from boundaries between various layers with different acoustic impedances [i.e. the air and the paper]. Acoustic impedance is defined by the bulk density of the medium times the velocity of the sound within that medium. The reflected acoustic signal is received [by one or more microphones]. The receiver converts the reflected signal to an analog signal [which is digitized and heavily processed to determine the makeup of the materials].
Rather than just measuring the time of the incoming pulse, you'd need to analyze both the time and frequency domain of the recovered signal to solve for the acoustic properties necessary to transform your transmitted pulse into the received pulse.
So the long answer is that it can be done sonically, although a sonic range sensor is generally insufficient for this purpose.
The following is multiple choice question (with options) to answer.
What diagnostic technology uses high-frequency vibrations transmitted into any tissue in contact with the transducer? | [
"ultrasound",
"radiation",
"laser",
"sonar"
] | A | Ultrasound in Medical Diagnostics When used for imaging, ultrasonic waves are emitted from a transducer, a crystal exhibiting the piezoelectric effect (the expansion and contraction of a substance when a voltage is applied across it, causing a vibration of the crystal). These highfrequency vibrations are transmitted into any tissue in contact with the transducer. Similarly, if a pressure is applied to the crystal (in the form of a wave reflected off tissue layers), a voltage is produced which can be recorded. The crystal therefore acts as both a transmitter and a receiver of sound. Ultrasound is also partially absorbed by tissue on its path, both on its journey away from the transducer and on its return journey. From the time between when the original signal is sent and when the reflections from various boundaries between media are received, (as well as a measure of the intensity loss of the signal), the nature and position of each boundary between tissues and organs may be deduced. Reflections at boundaries between two different media occur because of differences in a characteristic known as the acoustic impedance Z of each substance. Impedance is defined as. |
SciQ | SciQ-6029 | human-biology, cancer
Title: Why do most breast cancers occur in women? According to Korde et al. (2010):
Male breast cancer accounts for less than 1% of all cancers in men and less than 1% of breast cancers.
This raises the question: Why do most breast cancers occur in women?
Two plausible explanations I can think of:
A male is less likely to get breast cancer for anatomical reasons (such as a smaller quantity of breast tissue, or breast tissue that is less susceptible to cancer),
Women have higher significantly levels of estrogen, which is linked to mutations that cause breast cancer (see Cavalieria et al. (2006)).
Although, I have no evidence to suggest that either of these is predominant factor. Yes, this is mostly about estrogen. Most breast cancers rely on endogenous estrogen to sustain proliferation.
Some general reading: Cancer Medicine, Chapter 18
More in-depth reading: Endogenous Hormones as a Major Factor in Human Cancer
Requested summary of mentioned readings:
First of all, there is an established link between breast cancer cell proliferation and concentration of estrogens and progesterone, which is logical, because normal breast cells divide in response to those hormones (e.g. puberty, pregnancy, even luteal phase of the menstrual cycle). Secondly, the incidence of breast cancer in women correlates with major changes in their hormonal profile - girls and elderly women (i.e. women with lower levels of sex hormones) don't get breast cancer.
Many factors, that influence the risk of developing breast cancer are in fact tightly connected to the hormones' levels. For example - early age of menarche (or, more importantly, first ovulation, because physical activity at young age disturbs ovulation AND is protective against breast cancer) and Hormone Replacement Therapy raise the risk, early age of first full-term pregnancy or any form of artificial menopause (such as preventive oophorectomy for women with mutations in BRCA1 or 2) reduce the risk.
The first table from the book chapter lists known risk and preventive factors. The review article explains the same ideas, but connects them to other types of cancer (e.g. ovarian cancer) and suggests mechanisms, which might be the cause of those risk changes.
The following is multiple choice question (with options) to answer.
At what time of life does menopause occur? | [
"old age",
"adolescence",
"young adulthood",
"in middle adulthood"
] | D | The menstrual cycle includes events that take place in the ovary, such as ovulation. It also includes changes in the uterus, including menstruation. Menopause occurs when menstruation stops occurring, usually in middle adulthood. |
SciQ | SciQ-6030 | electricity
Title: How much of current flows through a bird sitting on a power line? I've been googling for hours and went through over a hundred answers. Now, some say the bird doesn't form a closed loop, some say the current is so small that it doesn't kill the bird. From as much as I understand electricity, I'm sure the bird does make a parallel connection to the wire, so there must be some electrons moving through it's body.
Could someone please explain which is the right answer and why? And if it's the case that a parallel circuit is formed, how can I calculate the current going through the birds body? The copper cable inside the telephone wire has some finite resistance per unit length, call it $\alpha$. If current $I_0$ is flowing through the wire, then the voltage drop across a length $L$ of cable is $V=I_0\alpha L$. Here $L$ is the distance between the bird's feet. The bird forms a parallel branch whose resistance $R$ is probably almost entirely due to the resistance of the insulator on the wire under the bird's feet, not the bird's body itself. The current though the bird is $I_B=V/R=I_0\alpha L/R$. Because $\alpha$ is small and $R$ is large, this current is extremely small compared to $I_0$.
The people who tell you $I_B$ is zero are basically right. They're applying approximations that are excellent in most situations and that are excellent in this situation. Specifically, we normally take $\alpha\approx0$ for a wire, so there is no voltage drop between any two points on the same wire.
The following is multiple choice question (with options) to answer.
What type of current carries warm air from surrounding rocks to an animal's body? | [
"electric",
"convection",
"ventilation",
"radiation"
] | B | Heat Transfer to an Ectothermic Reptile. This crocodile is being warmed by the environment in three ways. Heat is radiating directly from the sun to the animal’s back. Heat is also being conducted to the animal from the rocks it rests on. In addition, convection currents are carrying warm air from surrounding rocks to the animal’s body. |
SciQ | SciQ-6031 | acoustics, air
The net result of all this is that the resonant frequencies of the entire instrument (mouthpiece + horn + bell) are now tuned into the ratio $2 f'_0, 3 f'_0, 4f'_0, ...$ for a different frequency than one would assume from the length of the tube. For example, a trombone is approximately 270 cm (9 feet) long. An open tube of this length would have a fundamental frequency of about $f_0 = 31$ Hz; but for a standard trombone, all of the resonant frequencies are multiples of B♭1, with $f'_0 = 58$ Hz.
The most interesting part about the acoustics of the brass family is that they can "play" the fundamental frequency $f'_0$, even though it is not a resonance of the tube! These are called pedal tones, and they rely on a psychoacoustical trick. When most musical instruments play a note, the signal they produce doesn't just contain the fundamental frequency of the note $f$, but also contains frequencies at integer multiples $2f, 3f, 4f, ...$. This "mixture" of the base frequency with other frequencies at integer multiples of the fundamental is what gives musical notes their timbre; different amounts of these different overtones are what makes a violin (say) sound different from a clarinet even when playing the same note. A brass instrument playing a pedal tone actually only produces the overtones of the fundamental $2f'_0, 3f'_0, ...$ without playing the fundamental $f'_0$ itself. Your ear and your brain then fill in the rest, making you think that you're actually hearing a note at the frequency $f'_0$.
The following is multiple choice question (with options) to answer.
What quality of sound makes a tuba and a piccolo very different to a listener? | [
"wavelength",
"curve",
"pitch",
"tune"
] | C | A piccolo and a tuba sound very different. One difference is the pitch of their sounds. |
SciQ | SciQ-6032 | evolution, botany, proteins
tl;dr: the egg contains more proteins than the seed because the chicken that made the egg ate a whole lot of seeds, and all the protein in those seeds ended up concentrated in that one egg.
EDIT: running into this much later I realized I missed a pretty vital half of the question, because there is a difference between fruits and seeds. The difference is the following: nitrogen is precious for plants so they'll try and use it for very important things. Seeds are very important to the plant, so while a seed has less protein than an egg it will still have lots of protein by plant standards. Fruits now, that's another story. Like the sugary nectar, fruits are a bribe for animals, a bit of food offered to them so that they'll spread the plant's seeds. And like with the sugary nectar, the plant has every incentive to pack that bribe full of cheap carbohydrates and as few precious proteins as it can manage.
The following is multiple choice question (with options) to answer.
Where is the food supply and embryo stored in a seed? | [
"tegmen",
"epicotyl",
"plumule",
"hull"
] | D | reproductive structure produced by a seed plant that contains an embryo and food supply enclosed within a hull. |
SciQ | SciQ-6033 | evolution, zoology, anatomy, species
Title: Examples of animals with 12-28 legs? Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list:
snakes have 0
Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs)
Most mammals, reptiles, amphibians have 4 legs
Echinoderms (e.g., sea stars) typically have 5 legs.
Insects typically have 6 legs
Octopi and arachnids have 8 legs
decapods (e.g., crabs) have 10 legs
....But I can't really think of many examples of animals containing more legs until you reach 30+ legs in centipedes and millipedes. Some millipedes even have as many as 750 legs! The lone example I am aware of, the sunflower sea star, typically has 16-24 (though up to 40) limbs.
So my question is: what are some examples of animals with 12-28 legs? As a couple of counterexamples, species in the classes Symphyla (Pseudocentipedes) and Pauropoda within Myriapoda have 8-11 and 12 leg pairs respectively, so between 16 to 24 legs (sometimes with one or two leg pair stronlgy reduced in size).
(species in Symphyla, from wikipedia)
Another common and species-rich group with 14 walking legs (7 leg pairs) is Isopoda.
(Isopod, picture from wikipedia)
You also need to define 'legs' for the discussion to be meaningful. As you say, decapods have 10 legs on their thoracic segments (thoracic appendages), but they can also have appendages on their abdomens (Pleopods/swimming legs), which will place many decapods in the 10-20 leg range.
(Decapod abdominal appendages/legs in yellow, from wikipedia)
So overall, in Arthropoda, having 12-28 legs doesn't seem all that uncommon. There are probably other Arthropod groups besides those mentioned here that also have leg counts in this range.
However, for a general account, the most likely answer (if there is indeed a relative lack of 12-28 legged animals) is probably evolutionary contingencies and strongly conservative body plans within organism groups.
The following is multiple choice question (with options) to answer.
Most arthropods are insects. the phylum also includes spiders, centipedes, and what? | [
"coral",
"amphibians",
"crystals",
"crustaceans"
] | D | Most arthropods are insects. The phylum also includes spiders, centipedes, and crustaceans. |
SciQ | SciQ-6034 | 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.
A cartilaginous joint where the bones are joined by fibrocartilage is called a what? | [
"mitosis",
"symphysis",
"Testes",
"vesicles"
] | B | Symphysis A cartilaginous joint where the bones are joined by fibrocartilage is called a symphysis (“growing together”). Fibrocartilage is very strong because it contains numerous bundles of thick collagen fibers, thus giving it a much greater ability to resist pulling and bending forces when compared with hyaline cartilage. This gives symphyses the ability to strongly unite the adjacent bones, but can still allow for limited movement to occur. Thus, a symphysis is functionally classified as an amphiarthrosis. The gap separating the bones at a symphysis may be narrow or wide. Examples in which the gap between the bones is narrow include the pubic symphysis and the manubriosternal joint. At the pubic symphysis, the pubic portions of the right and left hip bones of the pelvis are joined together by fibrocartilage across a narrow gap. Similarly, at the manubriosternal joint, fibrocartilage unites the manubrium and body portions of the sternum. The intervertebral symphysis is a wide symphysis located between the bodies of adjacent vertebrae of the vertebral column. Here a thick pad of fibrocartilage called an intervertebral disc strongly unites the adjacent vertebrae by filling the gap between them. The width of the intervertebral symphysis is important because it allows for small movements between the adjacent vertebrae. In addition, the thick intervertebral disc provides cushioning between the vertebrae, which is important when carrying heavy objects or during high-impact activities such as running or jumping. |
SciQ | SciQ-6035 | botany, terminology, fruit
Title: What is the name of this part in plants, fruits, vegetables? What is the name of this part of the plant, fruit, vegetable? The thing that the plant is connected with the tree and gets nutrients with? The part we usually cut out when eat fruit.
Examples below
Papaya
Banana
Mango 'Stalk' or 'pedicel' would be an appropriate term (see, for example, this paper or this one). Specifically, you could say 'terminal part of the stalk/pedicel', though I don't know if there is a word for that.
Note that the term pedicel is commonly used for the stalk of a flower; it makes sense to use it for fruits too as they are derived from flowers.
The following is multiple choice question (with options) to answer.
The horizontal stems on strawberry plants are called what? | [
"stolons",
"glands",
"buds",
"nodules"
] | A | User:DrU/Wikipedia. Strawberry plants have horizontal stems called stolons that can form new plants. . Public Domain. |
SciQ | SciQ-6036 | botany, species-identification, mycology
Title: What are those huge plants / fungi on trees called? I've seen them in Scotland in August 2015:
The plants / fungi were quite high (over 2m) on the tree. They are almost circular if you view them from the top, I guess (except for the part where they are connected to the tree). I guess the diameter of them might be over 14cm.
What are they called? Well I will agree with fileunderwater, it is a Fomes fomentarious. For more info check this: Fomes fomentarius is a tough perennial polypore that usually becomes hoof-shaped with age; it is found on standing and fallen hardwoods. Its woody upper surface develops grayish zones, and its brown pore surface features tiny round pores. When sliced open (no easy task, given its toughness) it is usually composed more of vaguely layered tubes than flesh.
Along with Piptoporus betulinus, Fomes fomentarius is one of two mushrooms that the Tyrolean Iceman was carrying around 5000 years ago. He apparently used Fomes fomentarius as tinder.
Description:
Ecology: Parasitic and saprobic on the wood of hardwoods (especially birches and beech); causing a white rot; growing alone or gregariously; perennial; fairly widely distributed in northern and north-temperate North America
Cap: Up to about 20 cm across; shell-shaped to hoof-shaped; with a dull, woody upper surface that is zoned with gray and brownish gray.
Pore Surface: Brownish; 2-5 round pores per mm; tube layers indistinct, brown, becoming stuffed with whitish material.
Stem: Absent.
Flesh: Brownish, thin, hard.
The following is multiple choice question (with options) to answer.
What are the newest, outer layers of secondary xylem called? | [
"bark",
"fibrous",
"vascular",
"sapwood"
] | D | |
SciQ | SciQ-6037 | infection, amphibians
Title: What is this toad suffering from? Myiasis or chytridiomycosis? I found this toad on Aug. 29th at this location: position on osm
I think it is a bufo bufo, approx. 10 cm long. The nostrils seemed to be completely filled with a grey matter and from the activity of the floor of the mouth it apparently tried to breathe againgst this obstruction. It probably had enough oxygen via its skin though.
I tried to remove the obstruction using a blade of grass but this seemed to produce some pain as the toad closed its eyes on contact, so I stopped. The skin looked fairly normal and the toad was able to walk away after a while.
I can think of two causes for this condition.
Batrachochytrium dendrobatidis infestation
Lucilia bufonivora larvae
I could not see properly, if there were any larvae or unhatched eggs inside the nostrils, but as the rest of the skin seemed unharmed I assume the latter.
Is my assumption valid or is there even a third possibility? It is a female Bufo Bufo and you are right, there are toad fly (Lucilia bufonivora) larvae/eggs inside her nostrills. These flies lay their eggs inside toads' nostrills (specifically on Bufo Bufos) and the larvae start eating them. Sadly this disease ends up by the death of toad. They slowly eat nostrills, then mouth, eyes, and all the head.
Here's a photo of a male bufo bufo, without a head. Someone found it walking around at this situation. https://i.stack.imgur.com/I6twl.jpg
The following is multiple choice question (with options) to answer.
Most amphibians breathe with these as larvae? | [
"nostrils",
"lungs",
"gills",
"pores"
] | C | Amphibian skin contains keratin, a protein that is also found in the outer covering of most other four-legged vertebrates. The keratin in amphibians is not too tough to allow gases and water to pass through their skin. Most amphibians breathe with gills as larvae and with lungs as adults. However, extra oxygen is absorbed through the skin. |
SciQ | SciQ-6038 | human-biology, nutrition
Title: Do we know a complete list of nutrients that humans must ingest to live? When the people who are making "nutritionally complete" foods like Soylent are developing their product, how do they know that they've covered all their bases? You need to have protein, carbohydrates, fats etc., but what about vitamins or minerals?
Has science produced a commonly accepted list of all the nutrients that humans need to live? For babies there is certainly a formula available for a complete menu for survival: formula*
Here are the nutrition facts from Nestlé's "Good Start":
Formula nutrition facts. source: Nestlé
Comparable lists are available for people that cannot eat normally (e.g. people in a comatose state) and are fed enteral or parenteral nutrition.
*. Remember though, breast is best :)
The following is multiple choice question (with options) to answer.
Defined as a substance in foods and beverages that is essential to human survival, what term encompasses water, energy-yielding and body-building substances, and vitamins and minerals? | [
"nutrients",
"calories",
"molecules",
"sustenance"
] | A | Nutrients A nutrient is a substance in foods and beverages that is essential to human survival. The three basic classes of nutrients are water, the energy-yielding and body-building nutrients, and the micronutrients (vitamins and minerals). The most critical nutrient is water. Depending on the environmental temperature and our state of health, we may be able to survive for only a few days without water. The body’s functional chemicals are dissolved and transported in water, and the chemical reactions of life take place in water. Moreover, water is the largest component of cells, blood, and the fluid between cells, and water makes up about 70 percent of an adult’s body mass. Water also helps regulate our internal temperature and cushions, protects, and lubricates joints and many other body structures. The energy-yielding nutrients are primarily carbohydrates and lipids, while proteins mainly supply the amino acids that are the building blocks of the body itself. You ingest these in plant and animal foods and beverages, and the digestive system breaks them down into molecules small enough to be absorbed. The breakdown products of carbohydrates and lipids can then be used in the metabolic processes that convert them to ATP. Although you might feel as if you are starving after missing a single meal, you can survive without consuming the energy-yielding nutrients for at least several weeks. Water and the energy-yielding nutrients are also referred to as macronutrients because the body needs them in large amounts. In contrast, micronutrients are vitamins and minerals. These elements and compounds participate in many essential chemical reactions and processes, such as nerve impulses, and some, such as calcium, also contribute to the body’s structure. Your body can store some of the micronutrients in its tissues, and draw on those reserves if you fail to consume them in your diet for a few days or weeks. Some others micronutrients, such as vitamin C and most of the B vitamins, are water-soluble and cannot be stored, so you need to consume them every day or two. |
SciQ | SciQ-6039 | pathology
Title: Are all diseases caused by organisms (microorganisms)? Are there other causes? Or is it correct to say that all diseases are in fact caused by organisms (microorganisms)? It is not correct to say that all diseases are caused by foreign organisms. Counterexamples are:
Cancer is caused by random genetic mutations in the cells of our body. The mutations can be caused by many factors such as ionizing radiation, smoking, chemical toxins etc.
Diseases such as stroke or heart attack are caused by blood clots blocking the blood flow to essential organs.
Autoimmune diseases are caused by the immune system falsely recognizing cells of the body as foreign and attacking that tissue leading to a wide variety of symptoms.
Alzheimer's disease is caused by chronic neurodegeneration, meaning that the cells in the brain die. The causes are not quite understood but as Alzheimer's usually appears late in life it is likely related to ageing. Also, it is known that some genetic defects can lead to early-onset Alzheimers.
Prion proteins can cause diseases such as Creutzfeldt–Jakob disease also known as mad-cow disease.
Hereditary diseases such as early-onset Alzheimers or ALS are cause by gene defects inherited from the parents.
Toxins can cause chronic diseases such as lead poisoning.
The list probably goes on...
Please note that the first two on the list are the most common cause of death in developed countries.
The following is multiple choice question (with options) to answer.
Genetic disorders are diseases caused by what? | [
"environment",
"traits",
"lesions",
"mutations"
] | D | Sequencing the human genome has increased our knowledge of genetic disorders. Genetic disorders are diseases caused by mutations. Many genetic disorders are caused by mutations in a single gene. Others are caused by abnormal numbers of chromosomes. |
SciQ | SciQ-6040 | 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.
Transgenic animals are animals that have incorporated a gene from another species into their what? | [
"enemies",
"habitats",
"genome",
"food"
] | C | DNA technology has proved very beneficial to humans. Transgenic animals are animals that have incorporated a gene from another species into their genome. They are used as experimental models to perform phenotypic tests with genes whose function is unknown, or to generate animals that are susceptible to certain compounds or stresses for testing purposes. Other applications include the production of human hormones, such as insulin. Many times these animals are rodents, such as mice, or fruit flies ( Drosophila melanogaster ). Fruit flies are extremely useful as genetic models to study the effects of genetic changes on development. GloFish are the first genetically modified animal to be sold as a pet and are transgenic zebrafish transfected with a natural fluorescence gene. Watch these fish at http://www. youtube. com/watch?v=6cQLGKH2ojY or in the video below. |
SciQ | SciQ-6041 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
What structure of a cell is enclosed by a membrane and contains most of the cell’s dna? | [
"nucleus",
"vacuole",
"ribosome",
"epidermis"
] | A | Besides the four parts listed above, many cells also have a nucleus. The nucleus of a cell is a structure enclosed by a membrane that contains most of the cell’s DNA. Cells are classified in two major groups based on whether or not they have a nucleus. The two groups are prokaryotic cells and eukaryotic cells. |
SciQ | SciQ-6042 | meteorology, temperature, barometric-pressure
Title: Why do tropical areas have low air pressure? From the question Why are pressure levels raised on warm days?, my understanding is that the air pressure at surface level is not affected by temperature, as the mass of the imagined air column stays the same (even though it's extended higher due to lower density). Then, at any given true altitude, warmer temperatures would correspond to higher pressure. The air column analogy makes a lot of sense to me.
However, I was reading NOAA's explanation of atmospheric circulations, which says "This region would become very hot, with hot air rising into the upper atmosphere. This would create a constant belt of low pressure around the equator". That seems to contradict the concept above.
My guess is, in the air column analogy, when the air column is extended higher, it's "leveled out" with the surrounding air, just like water. So we end up with the column with the same original height but lower density, meaning that the total weight at the bottom is lower than before (which means lower pressure). However, if this is true, then the pressure would be lower at any altitude, not just at the surface.
I'm confused now. Please help, thank you! Your guess is correct. As the column of air gets heated, it expands, and that results in a higher pressure in the upper troposphere.
As a result, the air from this warm column flows outwards along the tropopause. This outflow of air is what causes a reduction in the net air mass within the column, and a subsequent reduction in the surface pressure. Therefore at the surface, the air will flow towards the column; so the air moves in a cyclonic sense:
However, if this is true, then the pressure would be lower at any altitude, not just at the surface.
The surface pressure has indeed reduced, but so has the pressure lapse rate (since the air has expanded upwards). Therefore, in the upper atmosphere, the pressure will actually be higher above the warm surface (as can be seen in the first image).
(Images source: Meteorology by Oxford)
The following is multiple choice question (with options) to answer.
Does air temperature increase or decrease as it rises higher in the atmosphere? | [
"neither",
"increase",
"both",
"decrease"
] | D | The rising air cools as it goes higher in the atmosphere. If it is moist, the water vapor may condense. Clouds may form, and precipitation may fall. |
SciQ | SciQ-6043 | genetics, cell-biology, chromosome, meiosis, mitosis
https://www.khanacademy.org/science/biology/cellular-molecular-biology/meiosis/a/phases-of-meiosis
So, during metaphase I, homologue pairs—not individual
chromosomes—line up at the metaphase plate for separation.
The following is multiple choice question (with options) to answer.
During what do homologous chromosomes separate and go to different daughter cells? | [
"birth",
"electrolysis",
"mitosis",
"meiosis"
] | D | Overview of Meiosis. During meiosis, homologous chromosomes separate and go to different daughter cells. This diagram shows just the nuclei of the cells. Notice the exchange of genetic material that occurs prior to the first cell division. |
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