source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-4344 | nuclear-engineering, gamma-rays, medical-physics
Title: X-ray shielding X-ray shielding, why is lead used to shield us when taking X-ray images?
As far as I remember (but can't find it on wikipedia ... ), the deflection on (high energy) photons increases the more heavier the nuclei are. (Don't remember and don't find if it's really the mass or rather the proton number.)
In either case, there are heavier, more dense materials with higher proton numbers.
The material is not consumed nor altered by exposure to X-rays. So why don't we use gold or depleted uranium (just to name some alternatives)?
(Not sure about tags, if anyone knows better, please feel free to suggest/add some others.)
Edit: as the answers and comments here helped me to clear my mind to change the question, but the new question is sufficiently different, I've asked a follow-up here: Formula for scattering and energy change of photons on (naked) nuclei I pulled out my notes from a shielding class and found that the absorption cross section per atom follows a rule: $$\sigma_a\sim\frac{Z^p}{E^3},$$
where $z$ is the atomic number of the absorber atom, $E$ is the energy of the photon, and $p$ is an energy dependent value between 3 and 5. For most x-rays, $p\simeq 4$.
While the cross-section per atom does indeed get larger for increasing $Z$, the density of the material is important, too. The density peaks at osmium ($Z=76$), then drops off, then climbs again in the actinides, but never reaches densities near osmium and iridium ($Z=77$).
When considering the effectiveness of an shield/absorber, one must consider the combined effects of cross-section per atom and density. The result of this is a quantity known as the linear attenuation coefficient, $\mu$, which is typically quoted in $\mathrm{cm}^{-1}$. This is used to calculated the intensity of radiation after travelling through a thickness, $x$ of a material: $$I(x)=I_0 e^{-\mu x}.$$
The following is multiple choice question (with options) to answer.
What aspect of beryllium allows it to absorb x-rays? | [
"low atomic number",
"high atomic number",
"relative atomic number",
"magnetism"
] | A | TiCl4(l) + 2Mg(s) → Ti(s) + 2MgCl2(s) The only other alkaline earth that is widely used as the metal is beryllium, which is extremely toxic. Ingestion of beryllium or exposure to beryllium-containing dust causes a syndrome called berylliosis, characterized by severe inflammation of the respiratory tract or other tissues. A small percentage of beryllium dramatically increases the strength of copper or nickel alloys, which are used in nonmagnetic, nonsparking tools (such as wrenches and screwdrivers), camera springs, and electrical contacts. The low atomic number of beryllium gives it a very low tendency to absorb x-rays and makes it uniquely suited for applications involving radioactivity. Both elemental Be and BeO, which is a high-temperature ceramic, are used in nuclear reactors, and the windows on all x-ray tubes and sources are made of beryllium foil. Millions of tons of calcium compounds are used every year. As discussed in earlier chapters, CaCl 2 is used as “road salt” to lower the freezing point of water on roads in cold temperatures. In addition, CaCO 3 is a. |
SciQ | SciQ-4345 | nuclear-physics, nuclear-engineering
Title: What is the origin of radioactivity that appears *sometimes* in rivers close to a nuclear plant? What is the origin of radioactivity that appears sometimes in rivers close to a nuclear plant? (due to nuclear plant activity) ?
In particular, is it due to primary circuit that would contaminate the tertiary circuit ?
Or is it due to nuclear waste that is sent on purpose to the river once its radioactivity is lower to the maximum threshold authorized by authorities ? Thank you for providing the link to the article, which discusses measured tritium contamination in a French river.
Tritium can come from many different places/reactions, but in a PWR it is usually from boron absorption and decay in the primary loop. Tritium is a very light nuclei and is very difficult to contain, it can even pass through steel piping. The tritium is produced in the primary loop, but then it can go to cleanup loops and escape into the environment, which is usually groundwater. From groundwater, it can get to the river.
Tritium is very difficult to contain, but it is also very benign biologically (meaning no measured adverse affects). The body quickly rejects tritium, so it doesn't stay in the body long enough to do much damage. It is interesting that the news article had a quote a "'flagrant' lack of data on the carcinogenic effects of tritium". The reason for the lack of data is that it is very difficult to show that tritium has a carcinogenic effect!
Since there is not much data showing the carcinogenic effect of tritium, international standards vary considerably. The article implies that the environmental limits in France are 100 Bq/L, which means you can measure 100 tritium decays in a liter of water. In the US, the limit is 740 Bq/L (20,000 picoCuries per liter). The values measured were 310 Bq/L.
Additional information about tritium can be found on the NRC website.
In summary, tritium is very hard to contain, easy to measure, and relatively harmless.
The following is multiple choice question (with options) to answer.
What are drilled to monitor groundwater pollution? | [
"test wells",
"sewers",
"draining wells",
"aquifers"
] | A | Test wells are drilled to monitor groundwater pollution. |
SciQ | SciQ-4346 | organic-chemistry, acid-base, hydrogen-bond
Title: Which dicarboxylic acid has the most acidic hydrogen?
Which of the following acids (maleic, fumaric, succinic, or malonic) has the most acidic hydrogen?
The following is multiple choice question (with options) to answer.
The two smallest carboxylic acids are formic acid and what else? | [
"acetic acid",
"ascorbic acid",
"ethylene acid",
"carbonates acid"
] | A | The two smallest carboxylic acids are formic acid (found in the stingers of ants) and acetic acid (found in vinegar). Many organic compounds are considerably more complex than the examples described here. Many compounds, such as cholesterol discussed in the chapter-opening essay, contain more than one functional group. The formal names can also be quite complex. In http://catalog. flatworldknowledge. com/bookhub/reader/2547 - gobch12through http://catalog. flatworldknowledge. com/bookhub/reader/2547 - gob-ch15, we will examine the characteristics and chemistry of other important organic compounds and functional groups. |
SciQ | SciQ-4347 | earth-history, mass-extinction, geobiology, evolution, ecology
Title: Why haven't weeds overtaken the entire planet? Given how rapidly weed plants spread and grow, choking out all other plant life, how come after millions of years we haven't ended with forests full of thistle or pokeweed, as opposed to pines or oak trees? A weed is just a plant where you do not want it. Totally a matter of context. Tumbleweeds are non-native, introduced centuries ago. I assume you mean the invasive species of plants that have been spread by humans and are disrupting ecologies throughout most of the world
Until recently, these plants we consider weeds were limited in their range to home environments simply by geographic barriers and surrounding unfriendly environments. And the natural consumers, parasites and competitors in the home environments had adjusted to these plants and kept them in check.
When non-native plants are introduced into a new environment by humans, most of them do not thrive, but occasionally a plant is wildly successful. Eventually the potential consumers, parasites and competitors in that new environment will adjust through evolution. But the tragedy is that many or most of the original species will be destroyed before that balance is restored in a new, way more simplified form. The landscape itself may be totally changed. Removal of a key original species can cause great change too: How Wolves Change Rivers.
Not only will many ecologies be reduced to much simpler versions, even if they eventually conquer the invasive plant, those simplified ecologies will closely resemble each other, if their geography is similar, even if on the other side of the world. If humans were to totally stop transplanting invasive species (collapse of civilization?), diversity would return after millions of years. We know this from Extinction Events.
So to answer you question, weeds before human intervention generally did not take over in their home environments because the potential weeds and their natural consumers, parasites and competitors all evolved together in a quasi-equilibrium. Now, however, most ecologies throughout the world are out of equilibrium because of environmental change and/or invasive species. This will inevitably lead to simplified, usually less robust, weedy ecologies throughout the world. That reduction in diversity might as well be considered a permanent situation compared to the timescale of civilization.
The following is multiple choice question (with options) to answer.
What incredibly successful species has quickly colonized almost all of earth’s terrestrial habitats, but also impacted earth, its climate, and its environment? | [
"birds",
"fish",
"chimpanzees",
"humans"
] | D | The human species has been incredibly successful. In a relatively short period of time, it has colonized almost all of Earth’s terrestrial habitats. Unfortunately, human beings have also impacted Earth, its climate, and its environment. Human actions threaten Earth’s valuable biodiversity. |
SciQ | SciQ-4348 | human-anatomy
Taken from here such people would be able to dislocate then get their hands in front and relocate.
The body can be trained to be quite flexible through training like gymnastics etc...
The following is multiple choice question (with options) to answer.
What prepares the body for fight or flight during emergencies? | [
"sympathetic division",
"metabolic response",
"abnormal division",
"adrenal mechanism"
] | A | The sympathetic division controls internal organs and glands during emergencies. It prepares the body for fight or flight ( Figure below ). For example, it increases the heart rate and the flow of blood to the legs, so you can run away from danger. |
SciQ | SciQ-4349 | evolution, trees
Title: How related are trees? I was surprised to see how far apart macadamia and hazelnuts are from each other. I always thought all trees had a common ancestor that was also a tree. But that doesn't seem to be the case? Did wood evolve multiple times? The word "tree" is a not a taxonomic classification, but a human perceptual clustering based on form and size. The word "fish" has a similar problem, covering a vast collection of taxa, some of which are less closely related to one another than they are to us.
Becoming tree-like often has a strong evolutionary value, because plants compete for sunlight and taller plants shade shorter plants. Thus, we should not be surprised that "tree" forms have evolved independently in a number of different lineages.
The common evolutionary lineage for all of these, however, is tracheophyta, the vascular plants. These are plants that have differentiated xylem (which is the wood of a tree) and phloem tissues for transport of water and minerals. Most such plants are not trees, of course, but these tissues provide an effective means of vertical transport and the basis for hard woody material, which appears to have been the key differentiator between plants capable of evolving into trees and plants that are not able do to so.
The following is multiple choice question (with options) to answer.
Gymnosperms have evolved to include what? | [
"cells",
"flowers",
"seeds",
"stems"
] | C | Gymnosperms evolved to have seeds but do not have flowers. Examples of gymnosperms include the Redwood, Fir, and Cypress trees. Gymnos means "naked" in Greek; the seeds of gymnosperms are naked, not protected by flowers. |
SciQ | SciQ-4350 | botany, plant-physiology, plant-anatomy
Title: Sporophyte and gametophyte
My textbook says that in both groups of seedless plants (vascular plants, non-vascular plants) the gametophyte is a free-living plant, independent of the sporophyte.
I don't understand this statement and am now wondering if the sporophyte and gametophyte are stages in a plant's lifecycle, or are they individual parts of the plant, or are the sporophyte and the gametophyte different plants altogether? Secondly, does this differ depending on the organism?
Different plants or different structures that make up the same organism? The sporophtye is the diploid stage in the life cycle. In comparison, with humans, you and I would be sporophytes.
The Gametophyte is the haploid stage in the life cycle. In comparison, with humans, spermatozoids and ovules are gametophytes.
The following is multiple choice question (with options) to answer.
How do gametophyte plants form haploid gametes? | [
"through mitosis",
"during after mitosis",
"during omniosis",
"during after omniosis"
] | A | Plants in the haploid generation are called gametophytes . They form from haploid spores. They have male and/or female reproductive organs and reproduce sexually. They produce haploid gametes by mitosis. Fertilization of gametes produces diploid zygotes. Zygotes develop into the diploid generation. |
SciQ | SciQ-4351 | inorganic-chemistry, coordination-compounds, crystal-structure
Title: Why is Polonium the only metal to crystallize forming Simple Cubic Cell? I have read that Polonium is the only metal that crystallizes forming SCC. I searched for a concrete explanation but all they were saying is the stability of Polonium at STP. I can't really comprehend their explanation.
The inorganic crystal structure database (ICSD), by specifying that
the structure contains only a single element, you can reduce the
number of hits to 55. Structure examples are Cr, Po, Mn, Sb, Se, P,
Ca, Li, As. Some are specific phases occurring at different
temperature or pressures.
So Po is not the ONLY metal to have a simple cubic structure, but
the other cases require special conditions.
The origin of the stabilized simple-cubic (SC) structure in Po is
explored by using the first-principles band calculations. We have
found that the prime origin is the inherent strong spin-orbit (SO)
interaction in Po, which suppresses the Peierls-type structural
instability, as usually occurs in p-bonded systems. Based on the
systematic analysis of electronic structures, charge densities, Fermi
surfaces, and susceptibilities of Se, Te, and Po, we have proven that
the stable crystal structure in VIA elements is determined by the
competition between the SO splitting and the crystal-field splitting
induced by the low-symmetry structural transition. Our study suggests
that the large SO interaction would suppress the Peierls instability
which is generally expected to occur in one-dimensional conductors.
In fact, Po becomes airborne with ease: if a sample is heated in air
to 55 °C (131 °F), 50% of it is vaporized in 45 hours to form diatomic
Po2 molecules. (The melting point of polonium is 254 °C and its
boiling point is 962 °C.)
Putting it all together, Po is in the column with Se and Te, and just to the right of Bi, none of which are typical of "normal" metals. The formation of $\ce{Po2}$ molecules at near ambient temperatures suggests that the outer electrons of Po form bonds of a highly covalent nature.
But it is indeed unusual and fascinating, and if Po were not 5000 times more radioactive than radium, I might be tempted to do a little chemistry.
References
The following is multiple choice question (with options) to answer.
What french chemist discovered the radioactive elements polonium and radium? | [
"louis pasteur",
"pascal curie",
"margaret curie",
"marie curie"
] | D | Another scientist, who worked with Becquerel, actually came up with the term radioactivity . The other scientist was the French chemist Marie Curie. She went on to discover the radioactive elements polonium and radium. She won two Nobel Prizes for her discoveries. You can learn more about Marie Curie at this URL: http://nobelprize. org/nobel_prizes/physics/laureates/1903/marie-curie-bio. html. |
SciQ | SciQ-4352 | homework-and-exercises, newtonian-mechanics, kinematics
rearranging the equation $s=ut+{1 \over 2}at^2$ we get $u = {s - {1 \over 2}at^2 \over t}$
so
$$u_t= {h/2 - {1 \over 2}(-g){h \over g} \over \sqrt {h \over g}} \\
= {h/2 + {1 \over 2}{h} \over \sqrt {h \over g}} \\
= \sqrt {h g}$$
Thus, the equations tell us that $u_t = v_d$ - always, for the three conditions listed at the top.
Finally, it is easy to show that $v_t$ the final velocity of the thrown ball must be zero. I am not going to prove it mathematically, but it is not difficult to do from here.
Now thinking about it the dropped ball starts at zero and ends up with some velocity... whereas the thrown ball ends up with zero velocity because the distance, time and acceleration are the same (except the acceleration is negative for the thrown ball).
If you plot a distance time graph for the two objects you will find that they have similar (similar here = identical) parabolic shapes(, but sort of reflected in the y-axis. )
Hope this is helpful...
The following is multiple choice question (with options) to answer.
What is another term for the parabolic motion of a thrown object? | [
"regular motion",
"simple motion",
"projectile motion",
"newtonian motion"
] | C | In this chapter, we aim to understand and explain the parabolic motion of a thrown object, known as projectile motion. Motion in one direction is unrelated to motion in other perpendicular directions. Once the object has been thrown, the only acceleration is in the (up/down) direction. The (right/left) direction velocity remains unchanged. |
SciQ | SciQ-4353 | human-biology, immunology, infection, immune-system
Question 3: there is no mechanism for directly transfering information between lymphocytes. Lymphocytes cannot read and write their DNA at will, and they are not able to simply copy sequences from each other. Rather, their diversity comes from first randomly re-shuffling their immunoglobulin-coding DNA, followed by selection of the successful cells --- this is a brute-force, random-search method, like evolution itself. Also, lymphocytes from unrelated individuals will generally interpret each other as invaders, causing an immune response. However, it is possible to experimentally "edit" the "memory" of lymphocytes extracted from blood using genetic techniques. This has for example recently been explored to "train" cancer patients own lymphocytes to attack cancer cells, in some cases with remarkably good results.
The following is multiple choice question (with options) to answer.
Passive immunity arises from the transfer of what to an individual, without requiring them to mount their own active immune response? | [
"viruses",
"bacteria",
"parasites",
"antibodies"
] | D | Passive immunity arises from the transfer of antibodies to an individual without requiring them to mount their own active immune response. Naturally acquired passive immunity is seen during fetal development. IgG is transferred from the maternal circulation to the fetus via the placenta, protecting the fetus from infection and protecting the newborn for the first few months of its life. As already stated, a newborn benefits from the IgA antibodies it obtains from milk during breastfeeding. The fetus and newborn thus benefit from the immunological memory of the mother to the pathogens to which she has been exposed. In medicine, artificially acquired passive immunity usually involves injections of immunoglobulins, taken from animals previously exposed to a specific pathogen. This treatment is a fast-acting method of temporarily protecting an individual who was possibly exposed to a pathogen. The downside to both types of passive immunity is the lack of the development of immunological memory. Once the antibodies are transferred, they are effective for only a limited time before they degrade. |
SciQ | SciQ-4354 | reaction-mechanism, thermodynamics, equilibrium, chemical-engineering
Title: Thermodynamics - Series Reaction - Estimating mols of reactants based on Free Energy of Rxn Question
Three reactions occur simulteneously (assume ideal) at $\pu{T = 0^\circ C}$.
$$\ce{A<=>B<=>C<=>D}$$
a) With $\Delta_r G^\circ_\text{AB} = \pu{400 J/mol}$, $\Delta_r G^\circ_\text{BC} = \pu{-100 J/mol}$, and $\Delta_r G^\circ_\text{CD} = \pu{-200 J/mol}$. If you start with 10 moles of A, calculate how many moles of B, C, and D you have when the system reaches equilibrium. Show all your work. (Hint: mass can neither be created nor destoyed)
b) Order the equilibrium concentrations from largest to smallest. Explain how you might be able to intuitively guess this ranking.
I know that given deltaG_RxN, one can calculate Keq, and use Keq to find the moles at equilibrium of reactants and products. Since the products at the end of one reaction became the reactants of the second, I fed in the mol amount of the first equation into the second equation.
Confused because in discussion - we went over how to do part B. and I don't think my math lines up.
positive delta G_RXN = more reactants than products, and vice versa
thus in the first rxn there should be more [A] than [B] @ equilibrium
in the second rxn there should be more [C] than [B]
and the third rxn there should be more [D] than [C].
The following is multiple choice question (with options) to answer.
At equilibrium reactants and what are equally abundant? | [
"products",
"proactives",
"minerals",
"results"
] | A | Reactants and products are equally abundant at equilibrium. |
SciQ | SciQ-4355 | evolution, dna, mitochondria, plasmids, prokaryotes
Title: Why don't mitochondria have plasmids? According to the endosymbiotic theory, mitochondria are descended from specialised bacteria (probably purple nonsulfur bacteria) that somehow survived endocytosis by another species of prokaryote or some other cell type, and became incorporated into the cytoplasm [ref].
And plasmids naturally exist in bacterial cells, and they also occur in some eukaryotes [ref].
I was however taught that mitochondria have no plasmid and only have circular DNA. If the endosymbiotic theory is true, then how come mitochondria have no plasmid? The mitochondrial genome is highly reduced; many mitochondrial genes have been transferred to the nuclear genome (see endosymbiotic gene transfer) and therefore the mitochondria are fully dependent on the nucleus to function.
Bacteria need not necessarily have a plasmid. Usually, all the important genes are present in the chromosomal DNA. Since the mitochondria have lost most of their genes and retain only a few genes that are highly essential for their function, the likelihood of retention of any plasmid DNA is very low. However, there are some reports of plasmid-like DNA in mitochondria (mostly in plants).
Handa (2008): in Brassica
Robison et al., (2005): in carrots
Collins et al., (1981): in Neurospora (a fungus)
Likewise, chloroplasts also harbour plasmid-like DNA (google-scholar hits).
The following is multiple choice question (with options) to answer.
Mitochondria are thought to have evolved from what kind of cells? | [
"ancient ribosome",
"ancient prokaryotic",
"ancient matrix",
"ancient phosphorylation"
] | B | Mitochondria are thought to have evolved from ancient prokaryotic cells. |
SciQ | SciQ-4356 | human-biology, human-genetics, skin
Stratum corneum represents the "skin cells that becomes the dust in our homes and it always grows back to full thickness". It is lost during a physiological process called desquamation [2]. The cells that are lost are non living corneocytes. Their only purpose is to from a protection barrier [3].
Basement membrane holds the germinativum layer of the epidermis. Injuries that do not affect it are repaired by complete regeneration of all destroyed layers. However, if the injury destroys membrane continuity, the germinative cells on the edges will fail to "reconnect" with each other, thus the layers derived from them will follow the same rule. A process of fibrosis is triggered. The result of extensive fibrosis is a scar, containing collagen secreted by the granulation tissue with dermal origins. Yet, the germinative layer tends to join back together [6], but probably the excess collagen production, without the limiting basement membrane, bulges into the epidermis and limits germinative layer extension. That's why keeping the edges of the tissue close to each other reduces excessive fibrosis and allows germinative layer regeneration, thus resulting in none to small, barely visible scars.
How deep should an injury be in order not to affect basement membrane? No more than 0.06 to 0.08 mm [5].
What about skin transplants ?
Skin grafts contain at least a part of dermis [4], which will allow granulation tissue formation thus permitting revascularisation and making the graft stick. Otherwise it would fall off and/or be lost by necrosis.
References:
The following is multiple choice question (with options) to answer.
An acellular, external cuticle protects the _________. | [
"lungs",
"epidermis",
"dermis",
"stomach"
] | B | Anatomy The epidermis is protected by an acellular, external cuticle, but this is much thinner than the cuticle found in the ecdysozoans and does not require periodic shedding for growth. Circular as well as longitudinal muscles are located interior to the epidermis. Chitinous hairlike extensions, anchored in the epidermis and projecting from the cuticle, called setae/chaetae are present in every segment. Annelids show the presence of a true coelom, derived from embryonic mesoderm and protostomy. |
SciQ | SciQ-4357 | population mean and population standard deviation are represented by the Greek letters µ and σ, respectively. On the other hand, the standard deviation of the return measures deviations of individual returns from the mean. Population Standard Deviation. It measures the typical distance between each data point and the mean. Standard deviation is a term in statistics and probability theory used to quantify the amount of dispersion in a numerical data set, that is - how far from the normal (average) are the data points of interest. This means that the sample variance is 30/4 = 7.5. Donate or volunteer today! Input is always welcome (no pun intended! It should be noted that the standard deviation value can never be negative. In our first calculation, we will treat our data as if it is the entire population. Population standard deviation. Since population variance is given by ???\sigma^2?? 2. in ophthalmology, strabismus. A sample is a part of a population that is used to describe the characteristics (e.g. Deviation just means how far from the normal. In statistics, the standard deviation in a population affects the standard error for that population. Looking for a way to calculate Population Standard Deviation in R -- using greater than 10 samples. The deviations are found by subtracting the mean from each value: We now add these squared deviations and see that their sum is 9 + 4 + 0 + 1 + 16 = 30. The Standard Deviation is a measure of how spread out numbers are.. You might like to read this simpler page on Standard Deviation first.. There are a total of 100 pirates on the ship. σ (Greek letter sigma) is the symbol for the population standard deviation. More than likely, this sample of 10 turtles will have a slightly different mean and standard deviation, even if they’re taken from the same population: Now if we imagine that we take repeated samples from the same population and record the sample mean and sample standard deviation … Solution for A population has a standard deviation ? A sample dataset contains a part, or a subset, of a population.The size of a sample is always less than the size of the population from which it is taken. Standard deviation is a term in statistics and probability theory used to quantify the amount of dispersion in a numerical data set, that is - how far from the normal (average) are the data points of interest. Population standard deviation takes into account
The following is multiple choice question (with options) to answer.
The average number of individuals per unit of area or volume is referred to as a population's what? | [
"output",
"increase",
"density",
"diameter"
] | C | Population density is the average number of individuals per unit of area or volume. |
SciQ | SciQ-4358 | human-biology, genetics, human-genetics
Title: Are all genetic disorders inherited? I know that genetic diseases such as cystic fibrosis are often passed down through generations and are therefore classified as genetic disorders, but if a mutation occurs spontaneously, which for example leads to cancer, is this then classified as a genetic disorder?
Are all genetic disorders inherited?
Not all individuals with a genetic disorder inherited that disorder. Some genetic disorders are caused by spontaneous mutations.
Is cancer a genetic disorder?
Yes. The seminal paper by Hanahan and Weinberg, the Hallmarks of Cancer, is a good place to go to get a sense of what we understand cancer to be. This paper is quite influential and has its own wikipedia page. These authors wrote an updated review in 2011. Re: your question as it relates to cancer, yes, genetic changes result in tumorigenesis. Cancer is a genetic disorder of cell populations. One can view cancer diagnosis and treatment from the framework of cancer as a metabolic disease, but this adds to, rather than subtracts from the framework of cancer as a genetic disease.
Are other diseases caused by spontaneous mutations genetic disorders?
Yes. Achondrodysplasia is one illuminating example. It is a form of dwarfism caused by a mutation in the FGFR3 gene. It does follow mendelian autosomal dominant inheritance patterns, but in 80% of cases, the mutation is, in fact, acquired spontaneously (that is, not present in either parent). As noted by @Eff in the comments, Down syndrome, Trisomy 21 (and other chromosomal abnormalities, e.g., Turner, Kleinfelter, Patau, Edwards) are other common examples.
The following is multiple choice question (with options) to answer.
What is the medical term for a condition caused by abnormalities, such as mutations, in your genes or chromosomes? | [
"nervous disorder",
"radiation disorder",
"genetic disorder",
"mutations disorder"
] | C | Mutations , changes in the DNA or RNA sequence, can have significant phenotypic effects or they can have no effects. What are possible outcomes of some of those mutations. Some can produce genetic disorder . A genetic disorder is a condition caused by abnormalities, such as mutations, in your genes or chromosomes. Genetic disorders are usually present from conception. These disorders include chromosomal abnormalities, in which the individual has too few or too many chromosomes or chromosomes with large alterations, or diseases due to a mutation in a specific gene. These defective genes are usually inherited from the parents, hence the term hereditary disease or genetic disorder. Genetic disorders can be inherited in a dominant or recessive manner ( Figure below and Figure below ). Recessive disorders require the inheritance of a defective gene from each parent. The parents are usually unaffected and are healthy carriers of the defective gene. |
SciQ | SciQ-4359 | biochemistry, microbiology, growth
Plot $\frac{1}{V}$ vs $\frac{1}{[S]}$; find the slope and intercept of this plot.
Depending on what you consider as primary substrate (glucose??) measure the concentrations using appropriate assays. Glucose sensors (based on glucose oxidase) are available or you can do conventional biochemical assays (DNSA) for glucose and other reducing sugars. To find the growth rate, measure OD at different time-points and get the differences of OD in a time interval. A better method would be to make a scatter-plot of OD and time and fit a polynomial function. Get rate by taking the tangent of the curve at that time-point.
The following is multiple choice question (with options) to answer.
What is glucose used for the bacteria? | [
"reproduction",
"food",
"fuel",
"energy"
] | B | Photosynthetic bacteria use the energy of the sun to make their own food. In the presence of sunlight, carbon dioxide and water are turned into glucose and oxygen. The glucose is then turned into usable energy. Glucose is like the "food" for the bacteria. An example of photosynthetic bacteria is cyanobacteria, as seen in the opening image. |
SciQ | SciQ-4360 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
What do carnivores eat? | [
"animals",
"plants",
"ice",
"algae"
] | A | Carnivores consume animals. Examples include lions, polar bears, hawks, frogs, salmon, and spiders. Carnivores that are unable to digest plants and must eat only animals are called obligate carnivores. Other carnivores can digest plants but do not commonly eat them. |
SciQ | SciQ-4361 | botany
All
142
45.01± 5.23
2306
45.64± 4.95
18 124
46.85± 3.98
3754
47.88± 3.49
For an algal estimate, see here:
Carbon is obtained from the post-carbon-capture flow and compressed to 1 MPa for transport and supply to the growth volume (requiring 248 kJ/kg of gas). Carbon uptake efficiency is 79%. The algal biomass productivity is 82.5 t/ha-yr (23.8 g/m2-d) with an elemental composition consisting of 48% carbon, 6.3% nitrogen, and 0.6% phosphorus (Huntley et al., 2015).
The following is multiple choice question (with options) to answer.
What is algae easier to covert into that corn is currently used for? | [
"fuel",
"oil",
"sugar",
"food"
] | A | Research is being done into alternative crops for biofuels. A very promising alternative is algae. Algae appears to be a better biofuel than corn. Algae is much easier to convert to a usable fuel. Growing algae requires much less land and energy than crops. Algae can be grown in locations that are not used for other things. For example, they can be grown in desert areas where food crops are not often grown. Corn must be grown where food crops are grown. This can reduce the land and water available for growing food. Algae can be fed agricultural and other waste, so valuable resources are not used. Much research is being done to bring these alternative fuels to market. |
SciQ | SciQ-4362 | homework-and-exercises, newtonian-mechanics, forces, free-body-diagram, string
Title: Does $m$ in this problem refer to the total mass of the system or just the mass of a single body? I am trying to figure something out in this problem:
I am having trouble with these types of problems because often I don't understand which forces I need to consider when setting up $F=ma$.
Here is what I have got so far:
I separated the force of gravity $m_1 g$ and $m_2 g$ acting on the relative bodies into the horizontal and vertical components. Because I can assume there is no friction the vertical component doesn't matter. For the forces along the plane I get:
The following is multiple choice question (with options) to answer.
Dividing net force by total mass yields what? | [
"energy",
"movement",
"acceleration",
"transmission"
] | C | Solution: The force acting to move the system is the weight of box B, and the force resisting the movement is the force of friction between the table and box A. The mass of the system is the sum of the masses of both boxes. The acceleration of the system can be found by dividing the net force by the total mass. |
SciQ | SciQ-4363 | evolution, botany, development, fruit, seeds
What is the point of fruit if not to be eaten? It’s my understanding that organisms will adapt to survive and thrive. I understand that being eaten can spread seeds, but this just seems like too much of a risky tactic to rely on.
Following on from part one: If being eaten is the best way to spread seed, why do some plants avoid this (such as by being poisonous or thorny)? Seeds are spread by many mechanisms
Wind dispersal: When air currents used to spread seeds. Often these plants have evolved features to facilitate wind catching, for example dandelions. Aka, anemochory.
Propulsion & bursting: When seeds are propelled from the plant in an such as in these videos. This is called Ballochory.
Water: Similarly to wind dispersal plants can spread seeds by water movement/currents, aka Hydrochory. This is used by many algae and water living plants.
Sticky Seeds: There are many ways a seed can attach to the outside of an animal - by using hooks, barbs, sticky excretions, hairs. Seeds then get carried by an animal and fall off later. This is epizoochory.
Fruiting: Plants can use seed-bearing fruit to encourage animals to eat the seeds. They will then be spread when the waste is excreted after digestion. This is a process of endozoochory.
More than one way to spread a seed
The following is multiple choice question (with options) to answer.
What ensures that seeds germinate only when conditions for seedling survival are optimal? | [
"survival dormancy",
"seed dormancy",
"germination dormancy",
"seed forcing"
] | B | |
SciQ | SciQ-4364 | computer-algebra
A quirk of the Latin alphabet is that if you represent the four nucleotides in alphabetical order and assign a two-bit code to them, the complement of a nucleotide is its the logical "not".
00 A Adenosine
01 C Cytosine
10 G Guanine
11 T Thymine
The following is multiple choice question (with options) to answer.
The a in atp is short for what? | [
"acetic",
"acid",
"amino",
"adenosine"
] | D | Let’s take a closer look at a molecule of ATP. Although it carries less energy than glucose, its structure is more complex. “A” in ATP refers to the majority of the molecule – adenosine – a combination of a nitrogenous base and a five-carbon sugar. “T” and “P” indicate the three phosphates, linked by bonds which hold the energy actually used by cells. Usually, only the outermost bond breaks to release or spend energy for cellular work. |
SciQ | SciQ-4365 | human-anatomy
[source]
And now, follow along with your own hand!
finger (4 DOF): each finger has 2 interphalangeal joints between the distal, middle and proximal phalanges that allow for flexion/extension (2 DOF); each finger also has a metacarpophalangeal joint between the proximal phalanx and the metacarpal that allows for flexion/extension as well as abduction/adduction (2 DOF)
thumb (5 DOF): an interphalangeal joint between the distal and proximal phalanges allowing flexion/extension (1 DOF); a metacarpophalangeal joint between the proximal phalanx and metacarpal allowing flexion/extension and abduction/adduction (2 DOF); a carpometacarpal joint between the metacarpal and trapezium allowing flexion/extension and abduction/adduction (2 DOF)
wrist (6 DOF): between the carpals and radius allowing flexion/extension, abduction/adduction and supination/pronation (3 DOF); I think when the authors refer to translation of the wrist, they are simply saying that hand can be moved in all planes of 3D space (ie up/down, side to side, forward/backward - 3 DOF)
Since we have 4 fingers, they give 16 DOF. Adding the 5 DOF of the thumb and 6 of the wrist, we get 27. Please nobody question my reasoning. Thank you.
The following is multiple choice question (with options) to answer.
How many fingers do apes have on each hand? | [
"seven",
"five",
"six",
"four"
] | B | Humans and apes have five fingers they can use to grasp objects. Do you think these are analogous or homologous structures? Explain. |
SciQ | SciQ-4366 | electromagnetism, electrostatics, charge
Title: Conservation of a specific type of charge The Law of Conservation of Charge states that 'the total charge in an isolated system is conserved.' Can we say that total negative and positive charges (individually) in an isolated system is conserved? No, the positive and negative charges are not conserved separately.
There are many processes in particle physics
where positive and negative charges are created newly,
or where positive and negative charges are annihilated.
Some examples:
The radioactive decay of a free neutron
$$n \to p^+ + e^- + \bar{\nu}$$
The annihilation of an electron-positron pair
$$e^- + e^+ \to \gamma + \gamma$$
The creation of an electron-positron pair
$$\gamma + \text{nucleus} \to e^- + e^+ + \text{nucleus}$$
The creation of particles in high-energy collisions
(like for example in the Large Hadron Collider)
$$p^+ + p^- \to \text{many positive and negative particles}$$
So, in general only the total charge (positive + negative) is conserved.
The following is multiple choice question (with options) to answer.
Which atomic particle has a positive charge? | [
"the proton",
"the electron",
"the neutron",
"the nucleus"
] | A | A proton is one of three main particles that make up the atom. The other two particles are the neutron and electron. Protons are found in the nucleus of the atom. This is a tiny, dense region at the center of the atom. Protons have a positive electrical charge of one (+1) and a mass of 1 atomic mass unit (amu), which is about 1.67 × 10 -27 kilograms. Together with neutrons, they make up virtually all of the mass of an atom. For an excellent video on protons and other fundamental particles in atoms, go to this URL:. |
SciQ | SciQ-4367 | species-identification, zoology, marine-biology, ichthyology, bone
Title: Identification of a strange skull My father is a fisherman in the Baltic sea, and he has found this very strange skull. I would like to know to which animal it belonged. Can someone help identify it? Looks like this is a neurocranium of a tuna or a similar species (dorsal view on this site).
I've also found a very similar picture of Atlantic blue tuna from USA, which seems to support that this is indeed a neurocranium.(source of the picture).
Thank you all for your help!
The following is multiple choice question (with options) to answer.
What does the presence of gill slits suggest about humans and fish? | [
"Shared History",
"Same evolutionary chain",
"Common Cells",
"common ancestor"
] | D | Some unexpected traits can appear in animal embryos. For example, human embryos have gill slits just like fish! In fish they develop into gills, but in humans they disappear before birth. The presence of the gill slits suggests that a long time ago humans and fish shared a common ancestor. |
SciQ | SciQ-4368 | ornithology
Title: How do birds learn their tunes in isolation from their own species? I wonder what a bird would sing if it didn't have its parents around (or any other birds for that matter) to learn its chirping sounds from.
I'm interested in how a bird would sing...
in complete isolation from creatures communicating through sound;
in isolation from its own species, but with other birds;
in isolation from all birds (other animals and creatures are there for it)
For example,
Would a bird even feel the need to speak up if there wasn't any other vocalizing creature around?
Would a bird learn other species' signals? Would it only learn from one species, the one which it would think of a fitting mate?
Would a bird try to mimic a non-flying creature's signals?
These are similar questions, but if you think they should be separated, let me know in the comments. Birds have to learn their song patterns.
They are able to chirp, but the songs with "meaning" are learned from their parents or whatever they learned to be their "parent".
Here is a paper that related bird song learning to human learning (of speech, for example).
Birds brought up by parents from another species learned to sing their songs.
There are many birds that learn to imitate other animals or sounds, so in isolation from all birds they will probably do this.
I can't recall where, but I read a paper once, where little finches brought up by humans developed a song resembling the "Hello there, now there's food", their caretaker always greeted them with. (Not the speech, but the overall sound pattern.) They might not understand the signals, but they try to communicate nevertheless. Some birds use sound from other species to mock others, scare them off or lure them into thinking they might be more powerful than they are.
Birds brought up in total isolation do sing, but not the typical songs you know from their species. Deaf birds who can't hear themselves, though, do not (always) sing.
The following is multiple choice question (with options) to answer.
What was first discovered in songbirds that produce new neurons while learning songs? | [
"homeostasis",
"Brain Cord",
"neurogenesis",
"proteins"
] | C | Neurogenesis At one time, scientists believed that people were born with all the neurons they would ever have. Research performed during the last few decades indicates that neurogenesis, the birth of new neurons, continues into adulthood. Neurogenesis was first discovered in songbirds that produce new neurons while learning songs. For mammals, new neurons also play an important role in learning: about 1,000 new neurons develop in the hippocampus (a brain structure involved in learning and memory) each day. While most of the new neurons will die, researchers found that an increase in the number of surviving new neurons in the hippocampus correlated with how well rats learned a new task. Interestingly, both exercise and some antidepressant medications also promote neurogenesis in the hippocampus. Stress has the opposite effect. While neurogenesis is quite limited compared to regeneration in other tissues, research in this area may lead to new treatments for disorders such as Alzheimer’s, stroke, and epilepsy. How do scientists identify new neurons? A researcher can inject a compound called bromodeoxyuridine (BrdU) into the brain of an animal. While all cells will be exposed to BrdU, BrdU will only be incorporated into the DNA of newly generated cells that are in S phase. A technique called immunohistochemistry can be used to attach a fluorescent label to the incorporated BrdU, and a researcher can use fluorescent microscopy to visualize the presence of BrdU, and thus new neurons, in brain tissue (Figure 16.20). |
SciQ | SciQ-4369 | evolution, molecular-biology, molecular-evolution
DNA. Why only 4 bases? Why the bases that we have (ACTG)? Researchers are able to create organisms with expanded DNA alphabets even here on earth (1). Even if you believe that some form of molecular mechanism of heredity is a requirement for life, there is no reason it need be DNA. And while there has been plenty of controversy about arsenic-based life here on Earth, I don't see why there couldn't be arsenic-based life elsewhere.
Ribosomes. Why a combination of RNA and protein? There is a lot in the overall architecture of ribosomes that is locked in due to historical/evolutionary contingency, not any necessary feature of life.
The Central Dogma. Biology as we know it has certainly made great use of the ability to make temporary copies of messages, but I don't see why life orbiting Alpha Centauri would have to have arrived at a similar solution.
Phospholipid membranes. You could make the argument that some degree of compartmentalization is necessary for life to occur (to reduce complexity and allow evolution via drift and small-number effects to generate change), but I don't think they need to be phospholipids. I can also imagine all life on another planet contained within viral-like particles with purely protein (or some other alien polymer) coats.
Genes. Depending on the level one is arguing I can see this going either way. If a gene is just a modular set of instructions for a limited number of components, then perhaps this will show up everywhere---life on our planet is surprisingly modular, and it is hard to imagine life on another planet being able to get by without some modularity (though of course it is possible in principle). But certainly nothing is inevitable about the details of gene organization into promoters, coding regions (why a 3-base code?), introns and exons (I'm still surprised these exist on our own planet), operons, etc.
The following is multiple choice question (with options) to answer.
Whether focused on ancient life, the life of bacteria, or how humans could live on the moon, four unifying principles form the basis of what branch of science? | [
"geology",
"biology",
"electronics",
"chemistry"
] | B | Four unifying principles form the basis of biology. Whether biologists are interested in ancient life, the life of bacteria, or how humans could live on the moon, they base their overall understanding of biology on these four principles:. |
SciQ | SciQ-4370 | tropical-cyclone, barometric-pressure
Also, a figure from Stull showing the difference in temperature within the hurricane core relative to surroundings:
That perhaps makes it more sensible that the warmer core air cannot continue subsiding down to the near-sea surface low at base of the core, where the air is very moist, but at lower temperature (might consider this to be a high stopping on encounter with a low).
The following is multiple choice question (with options) to answer.
What do we call the center of a hurricane where the air is calm and clear? | [
"epicenter",
"neck",
"eye",
"nose"
] | C | At the center of a hurricane is a small area where the air is calm and clear. This is the eye of the hurricane. The eye forms at the low-pressure center of the hurricane. You can see the eye of a hurricane in Figure below . |
SciQ | SciQ-4371 | black-holes, event-horizon
Title: Destroying a black hole Is there any (known? theoretical?) way to destroy a black-hole?
"Destroy" means forcing it to disappear - before it evaporates through Hawking radiation.
"Disappear" means that it stops being a black-hole: no more event horizon, no more impossibility for light to escape it, etc - it becomes just a "regular" object of mass or loses the mass completely. (i.e. releases its mass to energy or loses its properties in some other way)
"Before" means any time before it would fizzle away through Hawking radiation. Even if it's achieved a split-second earlier, it's a win. The standard definition of a black hole in classical GR is that it has an event horizon. By that definition, there is no way to convert the stuff that has fallen into the hole to other stuff that can then be observed from infinity. That would just mean that the spacetime never met the definition of being a black hole spacetime.
If you had something that formed a singularity by gravitational collapse, but the singularity was observable from infinity (at any time, even much later), then that might be somewhat like what you're describing, although it wouldn't be a black hole by the standard definition. However, the statement that that doesn't happen is the cosmic censorship conjecture. (What Aslan Monahov's answer describes sounds like the kinds of scenarios that have been cooked up in attempts to find counterexamples to cosmic censorship.)
The following is multiple choice question (with options) to answer.
Mass can be destroyed to release what? | [
"acceleration",
"energy",
"velocity",
"mass"
] | B | Mass can be destroyed to release energy. • We do not ordinarily notice the increase or decrease in mass of an object because the change in mass is so small for a large increase in energy. • The relativistic work-energy theorem is W net = E − E 0 = γmc 2 − mc 2 = ⎛⎝γ − 1⎞⎠mc 2 . • Relativistically,. |
SciQ | SciQ-4372 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
Name the organ located behind the nasal cavity in which both food and air pass through? | [
"medulla",
"diaphragm",
"sinus",
"pharynx"
] | D | Behind the nasal cavity, air passes through the pharynx , a long tube. Both food and air pass through the pharynx. |
SciQ | SciQ-4373 | cell-biology, meiosis, mitosis
Title: Is the cell cycle applicable to meiosis as well, or just mitosis? All the diagrams I can find, show the cell cycle as having G1 phase (growth 1), S phase (DNA replication), G2 (growth 2) before the Mitotic phase (mitosis + cytokinesis).
Is there an equivalent "cell cycle" for meiosis, since the chromosomes in parent cell in meiosis also having "double" the genetic material prior to cell division (presumably from DNA replication too)?
Is it simply the same cell cycle as mitosis but with a Meiotic phase instead of Mitotic?
If so, would appreciate if anyone had a diagram :) Thanks! The cell cycle is only associated with mitosis. The cell cycle is the normal process of cell division with which cells can indefinitely increase their number by cyclically repeating the process. When a cell goes through the cycle, the result is two cells that are genetically identical.
Meiosis is a special type of cell division (which can occur only in eukaryotes) that produces cells that are not genetically identical to the initiating cell. The number of chromosomes in each of the resulting cells is half the number that were in the initial cell. (These haploid cells can later participate in fertilization, producing a cell with the original number of chromosomes.) Many of the steps of meiosis are similar to the steps involved in mitosis, but overall the process is more complex. Since meiosis reduces the number of chromosomes, it cannot be repeated and so does not take part in a cell division cycle.
The following is multiple choice question (with options) to answer.
Both mitosis and meiosis result in eukaryotic cells doing what? | [
"multiplication",
"dividing",
"friction",
"limiting"
] | B | Both mitosis and meiosis result in eukaryotic cells dividing. So what is the difference between mitosis and meiosis? The primary difference is the differing goals of each process. The goal of mitosis is to produce two daughter cells that are genetically identical to the parent cell, meaning the new cells have exactly the same DNA as the parent cell. Mitosis happens when you want to grow, for example. You want all your new cells to have the same DNA as the previous cells. The goal of meiosis, however, is to produce sperm or eggs, also known as gametes . The resulting gametes are not genetically identical to the parent cell. Gametes are haploid cells, with only half the DNA present in the diploid parent cell. This is necessary so that when a sperm and an egg combine at fertilization , the resulting zygote has the correct amount of DNA—not twice as much as the parents. The zygote then begins to divide through mitosis. |
SciQ | SciQ-4374 | biochemistry
Now we can go on to explain the action potential in the neuron, which is not something I originally wanted to go into, but since the original question has been edited I feel that I have to address this now. Even though the original question now makes no reference to the action potential, it is describing exactly those events that occur during an action potential.
The inside and the outside of the neuron is separated by a cell membrane, which is selectively permeable to ions such as $\ce{Na+}$, $\ce{K+}$, $\ce{Ca^2+}$, and $\ce{Cl-}$. Of these four, sodium and potassium ions are the most important as they are directly involved in depolarisation and repolarisation when an action potential is generated.
The distribution of ions is not symmetrical across the membrane. When at rest, the extracellular concentration of $\ce{Na+}$ is much higher than the intracellular concentration of $\ce{Na+}$; the converse is true for $\ce{K+}$. Due to the membrane having different permeabilities to $\ce{Na+}$ and $\ce{K+}$ (for details of this, one can consult a neuroscience text), the resting membrane potential is -70 mV. Conventionally, the membrane potential is described as the intracellular potential with respect to the potential of the extracellular potential; this means that the inside of the cell is more negative.
Neurons react to certain stimuli by having $\ce{Na+}$ enter the cell, via various means which are not important to the current discussion. Since positively charged ions are entering the cell, this causes the membrane potential to rise. Once the membrane potential has risen to roughly -55 mV, voltage-gated $\ce{Na+}$ channels open, making the membrane permeable to $\ce{Na+}$.
At this stage, we have to consider the two factors that influence the diffusion of $\ce{Na+}$:
Since the potential difference is still negative, it favours influx of $\ce{Na+}$.
Since the extracellular concentration of $\ce{Na+}$ is larger than the intracellular concentration, the concentration gradient also favours influx of $\ce{Na+}$.
The following is multiple choice question (with options) to answer.
In resting neurons, the plasma membrane has many open potassium channels but few open of which other channels? | [
"sodium",
"oxygen",
"sulfur",
"silicon"
] | A | |
SciQ | SciQ-4375 | evolution
Title: How to define "evolution"? The standard answer found in intro course to evolutionary biology to the question:
what is evolution?
is:
It is a change in allele frequency over time!
I believe a complete definition should encompass the following concepts:
mutations
copy number variation (CNV)
codon usage
chromosome numbers
phenotypic change (whether heritable or not)
Complex phenotypic trait such as plasticity and developmental noise
maybe some other things...
My questions are:
Would it be worth it to talk about phenotype in a definition of evolution?
What are the alternative definitions that have been proposed?
What is your definition?
Note: I would rather talk about genetic evolution, but if you think it is worth making one definition for genetic and cultural (and some other stuff maybe) evolution, you're free to suggest it! What is evolution?
In a non-biological sense, evolution means change:
"a process of [...] change"
Biological evolution (seeing as this is Biology stack exchange) then needs to be tweaked to give a biologically specific context. Many textbooks etc. give definitions of evolution and here are a few good ones from across the history of evolutionary biology:
Charles Darwin:
"Descent with modification".
Mark Ridley1:
"Evolution means change, change in the form and behaviour of organisms between generations. ... When members of a population breed and produce the next generation we can imagine a lineage of populations, made up of a series of populations through time. Each population is ancestral to the descendant population in the next generation: a lineage is an ancestor-descendent series of populations. Evolution is then change between generations within a population lineage."
Brian and Deborah Charlesworth2:
"Evolution means cumulative change over time in the characteristics of a population of living organisms. ... All evolutionary changes require initially rare genetic variants to spread among the members of a population, rising to high frequency..."
All of these have a common theme. Biological information is moving through time, descending with a degree of directionality (e.g. parent $\rightarrow$ offspring), and the information is modified with time.
Personally I would define evolution as:
The following is multiple choice question (with options) to answer.
The theory of evolution by what (and other processes) explains both the diversity of organisms and how populations of organisms change over time? | [
"natural selection",
"genocide",
"characteristic selection",
"natural evolution"
] | A | Biology has only a few over arching theories. One of these, the Cell Theory of Life, explains the historic continuity of organisms, while the Theory of Evolution by Natural Selection (and other processes), explains both the diversity of organisms and how populations of organisms change over time. Finally, the Physicochemical Theory of Life explains how it is that organisms can display their remarkable properties without violating the laws that govern all physical and chemical systems.40 What is life, exactly? Clearly, if we are going to talk about biology, and organisms and cells and such, we have to define exactly what we mean by life. This raises a problem peculiar to biology as a science. We cannot define life generically because we know of only one type of life. We do not know whether this type of life is the only type of life possible or whether radically different forms of life exist elsewhere in the universe or even on Earth, in as yet to be recognized forms. While you might think that we know of many different types of life, from mushrooms to whales, from humans to the bacterial communities growing on the surfaces of our teeth (that is what dental plaque is, after all), we will discover that the closer we look the more these different “types of life” are in fact all versions of a common underlying motif, they represent versions of a single type of life. Based on their common chemistry, molecular composition, cellular structure, and the way that they encode, read, and use hereditary information in the form of molecules of deoxyribonucleic acid (DNA), all topics we will consider in depth later on, there is no reasonable doubt that all organisms are related, they are descended from a common ancestor. We cannot currently answer the question of whether the origin of life is a simple, likely, and predictable event given the conditions that existed on the Earth when life first arose, or whether it is an extremely rare and unlikely event. In the absence of empirical data, one can question whether scientists are acting scientifically or more as lobbyists for their own pet projects when they talk about doing astrobiology or speculating on when and where we will discover alien life forms. That said, asking seemingly silly questions, provided that empirically-based answers can be generated, has often been the critical driver of scientific progress. Consider, for example, current searches for life on Earth, almost all of which are based on what we already know about life. Specifically, most of the methods used rely on the fact that all known organisms use DNA to encode their genetic information; these methods would not be expected to recognize dramatically different types of life; they certainly would not detect organisms that used a non-DNA method to encode genetic information. If we could generate living systems de novo in the laboratory we would have a better understanding of what functions are necessary for life and how to look for possible “non-standard” organisms using better methods. It might even lead to the discovery of alternative forms of life right here on Earth, assuming they exist.41 That said, until someone manages to create or identify such non-standard forms of life, it seems quite reasonable to concentrate on the characteristics of life as we know them. |
SciQ | SciQ-4376 | biochemistry
Another important difference with respect to resulting polymers formed from these bonds - polysaccharides, in contrast to proteins and nucleic acids, form branched as well as linear polymers
α-Amylose is a linear polymer of several thousand glucose residues linked by α(1 >4) bonds. Note that although α-amylose is an isomer of cellulose, it has very different structural properties. This is because cellulose’s β-glycosidic linkages cause each successive glucose residue to flip 180° with respect to the preceding residue, so that the polymer assumes an easily packed, fully extended conformation.
Peptide bond
The resulting linkage formed when α-amino acids polymerize, through the elimination of a water molecule is known as a peptide bond (sometimes called an amide bond):
Peptide bond (shown in red)
Glycosidic bonds between monosaccharide units are the basis for the formation of oligosaccharides and polysaccharides.
The glycosidic bond is therefore the carbohydrate analog of the peptide bond in proteins. (The bond in a nucleoside linking its ribose residue to its base is also a glycosidic bond)
The following is multiple choice question (with options) to answer.
What is formed when a monomer of glucose and a monomer of fructose are joined in a dehydration reaction to form a glycosidic bond? | [
"sulfate",
"sucrose",
"chloride",
"fructose"
] | B | Figure 3.7 Sucrose is formed when a monomer of glucose and a monomer of fructose are joined in a dehydration reaction to form a glycosidic bond. In the process, a water molecule is lost. By convention, the carbon atoms in a monosaccharide are numbered from the terminal carbon closest to the carbonyl group. In sucrose, a glycosidic linkage is formed between carbon 1 in glucose and carbon 2 in fructose. |
SciQ | SciQ-4377 | cancer, mutations
Here is another great paper that specifically addresses your question, linking increased cell division with the accumulation of both significant and insignificant mutations, which over time, lead to an accumulation of mutations needed for cancer to develop.
The following is multiple choice question (with options) to answer.
What is the spread of cancer cells beyond their original site called? | [
"scattering",
"metastasis",
"mutations",
"apoptosis"
] | B | |
SciQ | SciQ-4378 | parasitology
Title: Tapeworms and their effect on humans I've read that some people in some countries actually use tapeworms as a form of losing weight. What are the dangers to these people? I haven't really found much on this topic (besides popular sites) but I can summarize it here:
There are quite some tapeworms (or cestoda), I found numbers of up to 3500 species. They attach to the intestinal wall of the humans and then start to take up predigested food through their skin. With that, they reduce food from their host and start to grow, some get as long as 15 meters!
Some of the worms seem to be relatively harmless (besides stealing food), but this is more true for the first world. In poor countries, where there is not enough food, tapeworms can cause severe malnutrition.
Some tapeworms can migrate into the blood stream and from there into other tissues or organs like muscles, eye and brain. There they can cause cysts which can lead to organ failure and death.
For more information see this CDC webpage and this article: "Biochemistry and physiology of tapeworms.". This popular article is probably also interesting.
The following is multiple choice question (with options) to answer.
What is another name for flatworms such as tapeworms and flukes? | [
"polychaetes",
"trematodes",
"platyhelminthes",
"epiphytes"
] | C | Platyhelminthes are flatworms such as tapeworms and flukes. |
SciQ | SciQ-4379 | geophysics, plate-tectonics, earth-history, continent
Title: Why Do Supercontinents Form? It would seem, on the face of it, improbable that the continental land-masses would accumulate into a single composite, yet it has happened numerous times, and is expected to again in the future.
There must likely then be some aspect of plate tectonics which favors these arrangements.
Can anyone provide an explanation?
EDIT: This is not, as I see it, a duplicate of the 'What are the causes of the supercontinent cycle?' question. This question goes to what process drives the formation of any & all supercontinent formations, which I assert should be improbable, made more improbable by their recurrence, not so much the cycle itself. The other question did not address this more fundamental aspect, or in any case receive a pertinent account of its resolution. If anyone wants to engage on this, or doesn't see the distinction, please do so in the comments or a chat. I think the mechanisms that you're looking for are subduction, paired with the "stickiness" of continental crust.
The subduction of oceanic crust under continental crust inevitably creates a net movement of crustal material toward a continental plate. Any oceanic plate that is carrying continental material will therefore always drag that continent toward the continental plate that it is subducting underneath, always resulting in eventual collision.
If an oceanic plate has subduction occurring on both sides, the ocean will inevitably narrow until it closes, thereby causing the continental plates on either side to collide.
In every case, subduction inevitably pulls continents together.
Furthermore, once continental plates collide, they have a tendency to stick together for long periods of time, increasing the likelihood that all continental material will eventually accumulate there.
The following is multiple choice question (with options) to answer.
The lithosphere-asthensophere divisions are based on what? | [
"elemental properties",
"constant properties",
"mechanical compounds",
"mechanical properties"
] | D | The lithosphere-asthensophere divisions are based on mechanical properties. |
SciQ | SciQ-4380 | electrons, atoms, orbitals
Title: How can an electron shell hold more than two electrons? The Pauli Exclusion principle states
in an atom or molecule, no two electrons can have the same four electronic quantum numbers. As an orbital can contain a maximum of only two electrons, the two electrons must have opposing spins.
So how can some electron shells have up to 6 electrons or more? Take the electron configuration of Magnesium. The 2p shell holds 6 electrons. How is this possible? Can you have multiple orbitals in a single electron shell? A "shell" is the term for all states with the same principal quantum number $n$, but in each shell there are also possible different values for the angular momentum quantum number $0\leq \ell \leq n$, the magnetic quantum number $-\ell \leq m_\ell \leq \ell$ and the spin quantum number $m_s\in\{-1/2,1/2\}$.
So for $n>1$, 6 electrons in a shell do not violate the Pauli exclusion principle.
The following is multiple choice question (with options) to answer.
The second shell holds a maximum of how many electrons? | [
"8",
"12",
"9",
"6"
] | A | |
SciQ | SciQ-4381 | human-biology, senses
Olfaction (smell, as carried out by neurons in the nasal epithelium; e.g. smell of vanilla, and smell of bad food)
Gustation (taste, as carried out by neurons on the tongue; e.g. salt, sugar)
Antigen chemosensing (chemical sensing, as carried out by, for instance, immune antigen receptors on B cells)
Hormonal signaling chemosensing (chemical sensing of hormones such as insulin, as carried out for instance by myocytes)
Starch sensing? (amylase in saliva can be used as a test for digestable starch)
Visual system, at the retina?
Visible light (sensing electromagnetic radiation on the order of a few hundred nanometers in wavelength)
Internal methanol sensing (the visual system as a sensor for methanol, which disproportionately affects myelin surrounding the optic nerve)
Pressure sensing (see phosphenes)
The vestibular system
Gravity sensing
Balance
Coordination
Motion sensor
Head position sensor
Spatial orientation
Skin
thermosensation (touching a hot kettle!)
Nociception (pain sensing)
allergen sensing
sensor for gamma rays, X-rays and UV light (indicated by radiation burns, development of skin cancer, sunburns, etc.)
Bones and muscles?
Kinesthetic and bodily proprioception
Brain/mind/mental/social senses?
mental pain
boredom
mental or spiritual distress
sense of self and other, including friendship, power, place in social hierarchy, reputation, companionship
motivation and love (oxytocin, dopamine, etc. in limbic systems and other neural correlates)
I'm sure some would agree, and some would disagree about the specific cases I provide. Thus the definition of senses, or sensing, seems to be opinion-based or at the very least very sensitive to an agreed-upon operational definition, for which there is none.
The following is multiple choice question (with options) to answer.
Olfaction refers to which of the five senses? | [
"touch",
"sight",
"taste",
"smell"
] | D | Olfaction is not the pre-eminent sense, but its loss can be quite detrimental. The enjoyment of food is largely based on our sense of smell. Anosmia means that food will not seem to have the same taste, though the gustatory sense is intact, and food will often be described as being bland. However, the taste of food can be improved by adding ingredients (e. , salt) that stimulate the gustatory sense. Testing vision relies on the tests that are common in an optometry office. The Snellen chart (Figure 16.7) demonstrates visual acuity by presenting standard Roman letters in a variety of sizes. The result of this test is a rough generalization of the acuity of a person based on the normal accepted acuity, such that a letter that subtends a visual angle of 5 minutes of an arc at 20 feet can be seen. To have 20/60 vision, for example, means that the smallest letters that a person can see at a 20-foot distance could be seen by a person with normal acuity from 60 feet away. Testing the extent of the visual field means that the examiner can establish the boundaries of peripheral vision as simply as holding their hands out to either side and asking the patient when the fingers are no longer visible without moving the eyes to track them. If it is necessary, further tests can establish the perceptions in the visual fields. Physical inspection of the optic disk, or where the optic nerve emerges from the eye, can be accomplished by looking through the pupil with an ophthalmoscope. |
SciQ | SciQ-4382 | thermodynamics, energy, electricity, efficient-energy-use
Title: Cutting down on power by bypassing mechanical to electrical conversions: Why not? The only answer to this I can think of is energy portability issues.
Another modern-world insanity is converting mechanical energy to electrical, only to turn it back into mechanical. The example I like to use is a refrigerator's reciprocating compressor.
If we directly attach a steam turbine's axle to the crankshaft of the compressor, we will not need to suffer losses in heat in our conversion of mechanical to electrical (at the power plant) then back to mechanical energy (in our appliance). Long ago, a primitive factory used one big engine or turbine or water wheel to rotate a set of overhead shafts, from which leather belts were suspended at intervals to power small pieces of machinery scattered throughout the factory. This arrangement was inflexible in that when the single big engine stopped, so did the entire factory, and when electricity came into common use, this overhead shafting arrangement fell quickly out of favor.
The power losses in long-distance electrical power transmission are more than made up for by the ease with which it is performed and the flexibility it affords. This makes "local power generation" as you describe it impractical because a hundred small steam turbines are much more wasteful of heat energy than one large turbine.
The only practical exception is integrated co-generation in which a small engine running on, for example, natural gas powers a generator while also spinning the shaft of a heat pump. The waste heat from the engine's cooling system makes residential hot water, the waste heat from its exhaust goes through a heat exchanger to provide hot air for space heating, the heat pump furnishes air conditioning (or pulls heat from outside the dwelling) and the electricity from the generator powers up your small appliances in the home while also charging a set of batteries.
Overall thermodynamic efficiency of such a device can exceed 95%, and examples of this technology are just now coming onto the market.
The following is multiple choice question (with options) to answer.
What devices convert mechanical energy to electric energy? | [
"kinetic generators",
"transformation generators",
"electric generators",
"mechanical generators"
] | C | Electric generators convert mechanical energy to electric energy. |
SciQ | SciQ-4383 | hematology
Title: Is Hemoglobin binding to oxygen the same as Adsorption I have recently been reading about Hemoglobin and came across how it binds to oxygen. This seems very similar to Adsorption. Is the process of Hemoglobin binding to oxygen through Adsorption ? From the Wikipedia article you cite the answer to your question is clearly NO. They seem very different: absorption is described as a surface phenomenon, whereas oxygen binding occurs in a single internal pocket in each globin subunit and forms a specific bond to an Fe(II) atom. The chemical nature of this pocket is quite different from that of the surface of the protein.
The Wikipedia article states:
Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface.[1] This process creates a film of the adsorbate on the surface of the adsorbent.
and
Similar to surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent, or metallic) of the constituent atoms of the material are filled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates.
However if you consult a text-book which describes the biochemistry of haemoglobin, such as Berg et al. you will find the specific chemical nature of the binding clearly described, as indicated by this extract:
The iron atom lies in the center of the protoporphyrin, bonded to the four pyrrole nitrogen atoms. Under normal conditions, the iron is in the ferrous (Fe2+) oxidation state. The iron ion can form two additional bonds, one on each side of the heme plane. These binding sites are called the fifth and sixth coordination sites. In hemoglobin, the fifth coordination site is occupied by the imidazole ring of a histidine residue from the protein. In deoxyhemoglobin, the sixth coordination site remains unoccupied...The binding of the oxygen molecule at the sixth coordination site of the iron ion substantially rearranges the electrons within the iron so that the ion becomes effectively smaller, allowing it to move into the plane of the porphyrin (Figure 10.19).
The following is multiple choice question (with options) to answer.
When oxygen is not bound to heme and the partial pressure of oxygen is low, hemoglobin readily binds to what? | [
"carbon",
"iron",
"carbon dioxide",
"sulfur"
] | C | to within the alveoli. As a result, carbon dioxide dissociates readily from hemoglobin and diffuses across the respiratory membrane into the air. In addition to the partial pressure of carbon dioxide, the oxygen saturation of hemoglobin and the partial pressure of oxygen in the blood also influence the affinity of hemoglobin for carbon dioxide. The Haldane effect is a phenomenon that arises from the relationship between the partial pressure of oxygen and the affinity of hemoglobin for carbon dioxide. Hemoglobin that is saturated with oxygen does not readily bind carbon dioxide. However, when oxygen is not bound to heme and the partial pressure of oxygen is low, hemoglobin readily binds to carbon dioxide. |
SciQ | SciQ-4384 | periodic-trends, periodic-table
Title: How long the block starting with element 121 will be? I remember from my chemistry classes that (after the initial irregularities) a new block of elements starts every two periods. After the initial s-block and p-block following it shortly, we have d-block starting at period IV, and f-block starting at period VI.
Now that Element 118 has been discovered, we're about to open period VIII and we're two elements short of a new block.
What block will it be? How many groups, what name etc? As you noted, this is a very appropriate question in light of the IUPAC announcement that we have just finished filling Period 7!
The names of the subshells s, p, d, and f are named after the old spectroscopic terms sharp, principal, diffuse, and fundamental. We ran out of fancy names after that, so the subsequent subshells are named in alphabetical order - g, h, and so on - which means that after the 8s block is filled, we would theoretically have a 5g block.
The orbitals in the g subshell would be labelled with the quantum number $l = 4$, so $m_l$ would take integer values between $-4$ and $4$ (inclusive) giving a total of nine g-orbitals. Each g-orbital could hold two electrons with opposite spins, so the g-block would have $18$ electrons.
However, it is worth noting that the electronic configurations may or may not obey the aufbau principle fully. Whether the 5g orbitals will actually be filled or not will certainly not be easy to determine, considering how short the half-lives of those elements are likely to be.
Wikipedia has an article which talks about it.
The following is multiple choice question (with options) to answer.
What is group 16 of the periodic table referred to? | [
"sulfur group",
"acid group",
"dioxide group",
"oxygen group"
] | D | Group 16 of the periodic table is also called the oxygen group. The first three elements—oxygen (O), sulfur (S), and selenium (Se)—are nonmetals. They are followed by tellurium (Te) ( Figure below ), a metalloid, and polonium (Po), a metal. All group 16 elements have six valence electrons and are very reactive. Oxygen is a gas at room temperature, and the other elements in the group are solids. |
SciQ | SciQ-4385 | soil
An analogous hypothesis proposed by RUSSEL3 for increases in the number of bacteria after partial sterilization by heat, frost, or other means is that by such partial sterilization the protozoa are killed, thus permitting the unhindered development of bacteria which under normal conditions is held in check by protozoa.
BROWN and SMITH (loc. cit.) in their investigations dealt mainly with the physiological activities of bacteria under conditions of low temperature and frost, although they also made some determinations of the number of bacteria in frozen soil. Their principal conclusions regarding the ammonifying, nitrifying, denitrifying, and nitrogen fixing powers of frozen soils are as follows: (1) that "frozen soils possess a much greater ammonifying power than unfrozen soils"; (2) that "during the fall season, the ammonifying power of the soil increases until the temperature of the soil almost reaches zero, when a decrease occurs, and this is followed by a gradual increase and the ammonifying power of the soil reaches a maximum at the end of the frozen period"; (3) that "the nitrifying power of frozen soils is weak and shows no tendency to increase with extension of the frozen period"; (4) that "frozen soils possess a decided denitrifying power which seems to diminish with the continuance of the frozen period"; (5) that "during the fall season, the denitrifying power of the soil increases until the soil freezes, after which a decrease occurs"; (6) that "frozen soils possess a nitrogen fixing power which increases with the continuance of the frozen period, being independent of moderate changes in the moisture conditions, but restricted by large decreases in moisture"; and (7) that "in the fall, the nitrogen fixing power of the soil increases until the soil becomes frozen, which in almost ceases, after which a smaller nitrogen fixing power is established."
The following is multiple choice question (with options) to answer.
Restoring nitrogen to the soil is one reason for what agricultural practice? | [
"sowing",
"irrigation",
"crop rotation",
"plowing"
] | C | |
SciQ | SciQ-4386 | evolution
Title: How to define "evolution"? The standard answer found in intro course to evolutionary biology to the question:
what is evolution?
is:
It is a change in allele frequency over time!
I believe a complete definition should encompass the following concepts:
mutations
copy number variation (CNV)
codon usage
chromosome numbers
phenotypic change (whether heritable or not)
Complex phenotypic trait such as plasticity and developmental noise
maybe some other things...
My questions are:
Would it be worth it to talk about phenotype in a definition of evolution?
What are the alternative definitions that have been proposed?
What is your definition?
Note: I would rather talk about genetic evolution, but if you think it is worth making one definition for genetic and cultural (and some other stuff maybe) evolution, you're free to suggest it! What is evolution?
In a non-biological sense, evolution means change:
"a process of [...] change"
Biological evolution (seeing as this is Biology stack exchange) then needs to be tweaked to give a biologically specific context. Many textbooks etc. give definitions of evolution and here are a few good ones from across the history of evolutionary biology:
Charles Darwin:
"Descent with modification".
Mark Ridley1:
"Evolution means change, change in the form and behaviour of organisms between generations. ... When members of a population breed and produce the next generation we can imagine a lineage of populations, made up of a series of populations through time. Each population is ancestral to the descendant population in the next generation: a lineage is an ancestor-descendent series of populations. Evolution is then change between generations within a population lineage."
Brian and Deborah Charlesworth2:
"Evolution means cumulative change over time in the characteristics of a population of living organisms. ... All evolutionary changes require initially rare genetic variants to spread among the members of a population, rising to high frequency..."
All of these have a common theme. Biological information is moving through time, descending with a degree of directionality (e.g. parent $\rightarrow$ offspring), and the information is modified with time.
Personally I would define evolution as:
The following is multiple choice question (with options) to answer.
What is the term for evolution over geologic time above the level of the species? | [
"microevolution",
"mutation",
"macroevolution",
"speciation"
] | C | Macroevolution is evolution over geologic time above the level of the species. One of the main topics in macroevolution is how new species arise. The process by which a new species evolves is called speciation . How does speciation occur? How does one species evolve into two or more new species?. |
SciQ | SciQ-4387 | thermodynamics, equilibrium, entropy
[A] option is incorrect since the system is losing heat and hence $$ \Delta S\lt0$$
[B] Lets assume we have an endothermic reaction $$\ce { A <=> B - Heat} $$
Now if we increase the temperature, the reaction will shift to the product side and hence the entropy of the surroundings will decrease more as compared to the initial conditions. Therefore the Unfavourable change in entropy(decrease in entropy) should increase.
[C] Though the reaction is endothermic, since we are supplying heat to the system, the net change in entropy of the system is positive.
[D] Lets assume another exothermic reaction $$ \ce{A<=>B + Heat}$$.
When we increase the temperature, the reaction will shift to the left side and hence less heat will be given off to the surroundings. Therefore, favourable change in entropy(increase in entropy) decreases.
Hence, according to me, the correct answer should only be [D], but [B] option is also given correct. What is the error in my explanation? The key point is that the entropy of the surroundings changes, not that of the system (at least for a small change in $T$), so only [B] and [D] are relevant, as you correctly determined.
You can write
$$\log(K)=-\frac{\Delta H}{RT}+\frac{\Delta S}R$$
This of course is one form of van 't Hoff's equation. It tells you, assuming $\Delta H$ and $\Delta S$ are constant, that the temperature dependence is due to $\Delta H-$ the heat transferred to/from the surroundings (entropy increase/loss of the surroundings):
$$\log(K)\propto-\frac{\Delta H}{RT}=\frac{\Delta S_\text{surr}}R$$
Now increasing $T$ makes the change in the entropy of the surroundings smaller.
The following is multiple choice question (with options) to answer.
Is the heat of reaction positive or negative for an endothermic reaction? | [
"Neither",
"Negative",
"positive",
"Both"
] | C | Because the heat is absorbed by the system, the 177.8 kJ is written as a reactant. The heat of reaction is positive for an endothermic reaction. |
SciQ | SciQ-4388 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
The superior nasal concha and middle nasal concha are parts of which bone? | [
"nasal bone",
"ethmoid bone",
"nostril bone",
"gastrulation bone"
] | B | Figure 7.13 Lateral Wall of Nasal Cavity The three nasal conchae are curved bones that project from the lateral walls of the nasal cavity. The superior nasal concha and middle nasal concha are parts of the ethmoid bone. The inferior nasal concha is an independent bone of the skull. |
SciQ | SciQ-4389 | physical-chemistry, bond, energy, covalent-compounds
Title: Where does the energy of formation of covalent bonds come from? Consider two $\ce{H}$ atoms. Since the proton in one attracts the electron in another, they attract each other, and form a covalent bond ($\ce{H-H}$). Bond forming requires energy (436 kJ/mol for an $\ce{H-H}$ bond) – where does that energy come from?
If I put two $\ce{H}$ atoms in a container, would they form an $\ce{H-H}$ bond by themselves, or would I need to add energy to the system in order for them to bond? Your view of bonding is a little simplified and confused. For the details it is worth reading the great answer referred to in some comments already: Fundamental forces behind covalent bonding .
I'll stick with a simpler view that focusses just on the energy involved and not the mechanism of chemical bonding. Firstly, you are wrong that boding two hydrogen atoms needs an input of energy. It actually releases energy. This is a thermodynamic view of the reaction. This tells us whether there is more or less energy in the product of the reaction being described than in the chemicals being combined to create the product.
The following is multiple choice question (with options) to answer.
The energy a chemical reaction needs to get started is called what kind of energy? | [
"fusion",
"function",
"conduction",
"activation"
] | D | All chemical reactions, even exothermic reactions, need a certain amount of energy to get started. This energy is called activation energy . For example, activation energy is needed to start a car. Turning the key causes a spark that activates the burning of gasoline in the engine. The combustion of gas won’t occur without the spark of energy to begin the reaction. |
SciQ | SciQ-4390 | electromagnetism
Title: Crossed fields : Finding the charge to mass ratio So, we are discussing the crossed field (JJ Thompson's) experiment in which the $q/m$ ratio of charged particles were produced.
Deflection due to the electric field is given by-
$$y=\frac{qEL^2}{2mv^2}$$
Now, if we adjust the $\vec E$ and $\vec B$ so that the net force is $0$ we get,$v=\frac{E}{B}$. Now, thus the crossed field can act as a velocity selector. Thus particles with velocity $E/B$ are undeflected as net force on them=$0$.
Now, my book says, we can substitute this value of $v$ in the previous equation to get-
$$\frac{m}{q}=\frac{B^2L^2}{2yE}$$
I don't understand how this works because $y$ would be $0$ when $v=E/B$. So, why don't we directly replace $y$ by $0$ in that equation. Shouldn't $y$ be $0$ when $v=E/B$? The experiment is in two parts.
With crossed electric (E) and magnetic (B) fields you adjust the electric field and/or the magnetic field to get zero deflection from which you can find the spreed of the electrons.
Then the magnetic field is switched off and the deflection of the electrons $y$ due to only the electric field is measured from which the specific charge of the electron can be found using you second equation.
The following is multiple choice question (with options) to answer.
Crossing charges is one method for obtaining what? | [
"superscripts",
"notations",
"subscripts",
"hybrids"
] | C | Crossing charges. One method for obtaining subscripts in the empirical formula is by crossing charges. When crossing charges, you will sometimes find it necessary to reduce the subscripts to their simplest ratio to write the empirical formula. Consider, for example, the compound formed by Mg2+ and O2−. Using the absolute values of the charges on the ions as subscripts gives the formula Mg2O2:. |
SciQ | SciQ-4391 | You collected some data, the results weren’t conclusive, so now what you want to do is collect more data until the the results are conclusive. In one sense, that’s true. By way of comparison, imagine that you had used the following strategy. Bayesian Data Analysis (3rd ed.). You are not allowed to use the data to decide when to terminate the experiment. This book is based on over a dozen years teaching a Bayesian Statistics course. Also it does incorporate some humour into the bundle like Bayesian Statistics… And as a consequence you’ve transformed the decision-making procedure into one that looks more like this: The “basic” theory of null hypothesis testing isn’t built to handle this sort of thing, not in the form I described back in Chapter 11. Most of the examples are simple, and similar to other online sources. It describes how a learner starts out with prior beliefs about the plausibility of different hypotheses, and tells you how those beliefs should be revised in the face of data. Welcome to Applied Statistics with R! All we do is change the subscript: \[ The result is significant with a sample size of $$N=50$$, so wouldn’t it be wasteful and inefficient to keep collecting data? What this table is telling you is that, after being told that I’m carrying an umbrella, you believe that there’s a 51.4% chance that today will be a rainy day, and a 48.6% chance that it won’t. Edinburgh, UK: Oliver; Boyd. I mean, it sounds like a perfectly reasonable strategy doesn’t it? You can type ?ttestBF to get more details.↩, I don’t even disagree with them: it’s not at all obvious why a Bayesian ANOVA should reproduce (say) the same set of model comparisons that the Type II testing strategy uses. 1.1 About This Book This book was originally (and currently) designed for use with STAT 420, Methods of Applied Statistics, at the University of Illinois at Urbana-Champaign. Bayes Bayes Bayes Bayes Bayes. Jeffreys, Harold. All you have to do is be honest about what you believed before you ran the study, and then report what you learned from doing it. Afterwards, I provide a brief overview of how you can do Bayesian versions of chi-square tests
The following is multiple choice question (with options) to answer.
What do scientists collect to test a hypothesis? | [
"books",
"arguements",
"beilefs",
"evidence"
] | D | Scientists collect evidence to test a hypothesis. The evidence may refute the hypothesis. In that case, it will be thrown out. The evidence may support the hypothesis. The scientists will then gather more evidence. The scientists will accept the hypothesis if: (1) There is no significant evidence to refute the hypothesis. (2) There is an enormous amount of evidence to support the hypothesis. The hypothesis may then become a theory. |
SciQ | SciQ-4392 | neuroscience, brain, pain
Let's take stabbing as another cause of pain. One stab in a less dangerous place missing all important structures may be not that harmful but may be painful. However multiple small stabs into important structures like arteries or spinal cord could be horribly destructive.
Then let's look at headaches or nerve pain. Here it is only the pain and usually there isn't any destructive or harmful process. Most individuals would take one really, really bad headache followed by never having a headache then chronic daily "tension" headaches.
Psychologically though usually the chronic daily pain is the worst. Particularly as without adequate pain management from the start, it is less responsive to painkillers (analgesia). It frequently adds to depression if it does not cause it itself and can lead to suicide. Also painkillers themselves may cause chronic pain which does not help.
In summary, acute severe pain suggests something is seriously wrong and needs to be dealt with immediately biologically as there is likely a damaging process underlying it. However if this event is survived, it may be linked with high disability from any biological process that underpinned the pain. Chronic daily pain suggests a long continuing process. The cause of this may be life threatening, such as cancers, but is usually less dangerous at least compared to acute severe pain biologically. However the psychological aspects of this pain are seriously important as they can be particularly detrimental.
The following is multiple choice question (with options) to answer.
Fatal swelling of what organ can result from both encephalitis and meningitis, which typically cause a severe headache and a fever? | [
"liver",
"brain",
"heart",
"kidney"
] | B | Encephalitis and meningitis aren’t very common, but they can be extremely serious. They may cause swelling of the brain, which can be fatal. That’s why it’s important to know the symptoms of these diseases. Both encephalitis and meningitis typically cause a severe headache and a fever. Meningitis also causes a stiff neck. Both require emergency medical treatment. |
SciQ | SciQ-4393 | diffusion
The reverse process is also happening with molecules diffusing from right to left at a rate proportional to their concentration in the right side solution. As the concentration on the right side increases to be equal to the concentration on the left, so the diffusion rates become equal and there is zero nett diffusion and the system approaches equilibrium.
Note that this assumes a "perfect" system where there is no chemical reaction occurring between the solutes or between the solutes and the membrane. In practice this means that either the interaction between solutes A and B is the same as the interaction between the solutes and the solvent or that the solute molecules are so greatly outnumbered by the solvent molecules that the solute-solute interactions are not significant.
The rate of diffusion of solute A may be different from B (i.e. the proportionality constant between rate and concentration may be different). This means that before reaching equilibrium the relative concentrations of A and B may change but at equilibrium, the relative concentration will be the same as initially.
If we define "reaching equilibrium" as having some fraction (say 99.99%) of the final concentration then increasing the initial global concentration will increase the lag for both solutes equally and will not change their relative concentrations.
The following is multiple choice question (with options) to answer.
Gases can undergo diffusion, or the opposite, which is what? | [
"dissipation",
"infusion",
"effusion",
"defusion"
] | C | Define diffusion and effusion and how they relate to other properties of gases. |
SciQ | SciQ-4394 | genetics, epidemiology, biostatistics
That is the denominator.
Taking that group of people, we can then ask:
Of those people that have the disease, what proportion of this affected group has a full sibling that also has the disease?
That is the numerator.
So if we have a population of 100 people, say 10 people have the disease. The denominator is then $0.1$. We might then observe that 4 of those cases are two pairs of siblings (and there are no other siblings). So
$$risk\ in\ sibling = Pr(sib\_has\_disease | person\_has\_disease) = \frac{4}{10} = 0.4$$
And thus
$$ \lambda_s = \frac{\text{risk of sibling}}{\text{risk in population}} \
= \frac{0.4}{0.1} = 4$$
It's worth pointing out that we are not controlling for environment or for pedigree or anything like that here. The null hypothesis of what $\lambda_s$ should be without any genetic risk is a complex function of prevalence and family structure (what if everyone is an only child, or the whole population is all siblings?). So it's not even clear how to interpret it, except to say that you might intuitively guess that a disease that strikes purely randomly might have $lambda_s = 1$. But I'm not even sure that that's true! All that this ratio is measuring is a rough estimate of how clustered the disease is within families within a population.
The following is multiple choice question (with options) to answer.
What science is the study of the occurrence, distribution, and determinants of health and disease in a population? | [
"toxicology",
"epidemiology",
"physiology",
"histology"
] | B | Epidemiologist Epidemiology is the study of the occurrence, distribution, and determinants of health and disease in a population. It is, therefore, related to public health. An epidemiologist studies the frequency and distribution of diseases within human populations and environments. Epidemiologists collect data about a particular disease and track its spread to identify the original mode of transmission. They sometimes work in close collaboration with historians to try to understand the way a disease evolved geographically and over time, tracking the natural history of pathogens. They gather information from clinical records, patient interviews, and any other available means. That information is used to develop strategies and design public health policies to reduce the incidence of a disease or to prevent its spread. Epidemiologists also conduct rapid investigations in case of an outbreak to recommend immediate measures to control it. Epidemiologists typically have a graduate-level education. An epidemiologist often has a bachelor’s degree in some field and a master’s degree in public health (MPH). Many epidemiologists are also physicians (and have an MD) or they have a PhD in an associated field, such as biology or epidemiology. |
SciQ | SciQ-4395 | cell-biology, development
Title: What determines the fate of a cell with respect to differentiation? I have been reading about Townes and Holtfreter's work in 1955, in which cells are dissociated from a blastocyst in an alkaline solution then mixed together and spontaneously reaggregates based on type, so epidermal cells around the outside and neural plate cells in the middle.
I understand enough about cell adhesion to understand why the cells will seem to attract cells of their own type, but would like to know how they can initially detect what to become and where they are needed in a specialised form, without something acting like a brain telling them what to become and where to go.
If the selection from the available types is random, as I suspect, what happens to blastocysts with too much epidermal tissue or vice versa? I'm struggling to imagine how organisms like this can develop without something taking the lead and actively coordinating what goes where. Cell differentiation, cell fate and cell mapping is an interplay of accessible evolutionary strategies/programmes and responses to dynamic environmental cues such as specialized hormones (e.g. morphogens) and physical parameters and constraints. That is putting it very broadly. It is a complex issue, if L. Wolpert's PLOS assays are any indication. I compiled a few links to get you started.
Specifically, reappraising the topic of your cited classical experiment are R.Moore et al:
The classical cell sorting experiments undertaken by Townes and
Holtfreter described the intrinsic propensity of dissociated embryonic
cells to self-organize and reconcile into their original embryonic
germ layers with characteristic histotypic positioning. Steinberg
presented the differential adhesion hypothesis to explain these
patterning phenomena.....
The following is multiple choice question (with options) to answer.
Amphibian larvae go through what process to change into the adult form? | [
"metamorphosis",
"parthenogenesis",
"morphing",
"merging"
] | A | Amphibian larvae go through metamorphosis to change into the adult form. |
SciQ | SciQ-4396 | climate-change, co2, greenhouse-gases, geoengineering, methane
Title: What potential geoengineering technologies could help a country "achieve its Paris (agreement) targets"? CNN's China to expand weather modification program to cover area larger than India ends with the following sentence:
"While China has not yet shown signs of 'unilaterally' deploying geoengineering projects on the ground, the scale of its weather modification and other massive engineering projects, including mega-dam projects (such as the Three Gorges), suggests China is willing to deploy large-scale geoengineering schemes to tackle the impacts of climate change and achieve its Paris targets."
and the scope of my question is limited to the Earth Science aspects of geoengineering projects that could "..tackle the impacts of climate change and achieve... Paris (agreement) targets".
To my knowledge the Paris Agreement primarily focuses on the reduction of greenhouse gas emission itself, so I would think that geoengineering solutions might involve removing gases already emitted in the form of new biomass or as gas in geological sequestration sites, or by producing energy with a technology having a lower greenhouse emission rate.
Is that so? If so, what are specific examples?
Since the same article discusses both cloud seeding for precipitation induction and the dispersal of reflective particles to reduce global warming earlier, could there be some atmospheric dispersal technology that could help a country "...achieve its Paris targets"? I think the third paragraph of the article hints at what might be the thinking.
In the next five years, the total area covered by artificial rain or snowfall will reach 5.5 million sq km, while over 580,000 sq km (224,000 sq miles) will be covered by hail suppression technologies. The statement added that the program will help with disaster relief, agricultural production, emergency responses to forest and grassland fires, and dealing with unusually high temperatures or droughts.
The following is multiple choice question (with options) to answer.
Reducing the production of what gas, or removing it from the air, are practices that could reduce global warming? | [
"carbon dioxide",
"hydrogen",
"helium",
"oxygen"
] | A | Efforts to reduce future global warming mainly involve energy use. We need to use less energy, for example, by driving more fuel-efficient cars. We also need to switch to energy sources that produce less carbon dioxide, such as solar and wind energy. At the same time, we can increase the amount of carbon dioxide that is removed from air. We can stop destroying forests and plant new ones. |
SciQ | SciQ-4397 | organic-chemistry, nomenclature
Title: Why derived name of nomenclature is used for Alkanes and alcohols only? My chemistry textbook says derived system of nomenclature of organic compounds is only limited to alkanes and alcohols!
What is the reason behind it? Is it chemical or like a ritualistic/cultural? The derived system is really, really old. Even my textbook from the 20th century has IUPAC naming. My recommendation would be to just find IUPAC naming online, or just get a new textbook.
I can't seem to find much on the derived system, but here's another question about it; LINK
I tried searching about, and there really isn't much about it. I don't see why you'd want to learn about it though, as history of nomenclature isn't very useful or interesting. Besides, if you try to use the derived system, no one else is going to know what compound you're describing.
The following is multiple choice question (with options) to answer.
There are a series of rules for naming branched alkanes (and, ultimately, for all organic compounds). these rules make up the system of nomenclature for naming what? | [
"oxygen molecules",
"typical molecules",
"non-organic molecules",
"organic molecules"
] | D | Not all hydrocarbons are straight chains. Many hydrocarbons have branches of C atoms attached to a chain. These branched alkanes are isomers of straight-chain alkanes having the same number of C atoms. However, they are different compounds with different physical and chemical properties. As such, they need different names. How do we name branched hydrocarbons? There are a series of rules for naming branched alkanes (and, ultimately, for all organic compounds). These rules make up the system of nomenclature for naming organic molecules. Worldwide, the International Union of Pure and Applied Chemistry (IUPAC) has developed the system of nomenclature for organic compounds. So these rules are sometimes called the IUPAC rules of nomenclature. By learning and applying these rules, you can name any organic compound when given its structure or determine the unique structure of a molecule from its name. You have already learned the basics of nomenclature—the names of the first 10 normal hydrocarbons. Here, we will add some steps to the procedure so you can name branched hydrocarbons. First, given the structure of an alkane, identify the longest continuous chain of C atoms. Note that the longest chain may not be drawn in a straight line. The longest chain determines the parent name of the hydrocarbon. For example, in the molecule. |
SciQ | SciQ-4398 | machine-learning, classification, decision-trees, information-theory
Weather and Wind both produce only one incorrect label hence have the same accuracy of 16/17. However, given this data, we would assume that weak winds (75% YES) are more predictive for a positive outcome than sunny weather (50% YES). That is, wind teaches us more about both outcomes. Since there are only few data points for positive outcomes we favor wind over weather, because wind is more predictive on the smaller label set which we would hope to give us a rule that is more robust to new data.
The entropy of the outcome is $ -4/17*log_2(4/17)-14/17*log_2(14/17)) =0.72$. The entropy for weather and outcome is $14/17*(-1/14*log_2(1/14)-13/14*log_2(13/14)) = 0.31$ which leads to an information gain of $0.41$. Similarly, wind gives a higher information gain of $0.6$.
The following is multiple choice question (with options) to answer.
Which theory helps predict future events in weather? | [
"carbon change theory",
"expected change theory",
"climate change theory",
"future weather theory"
] | C | The theory of climate change is very new. In fact, scientists don't even call it a theory. But it meets the requirements. These are the things we know: (1) average global temperatures are rising, (2) greenhouse gases trap heat in the atmosphere, (3) CO 2 is released into the atmosphere when fossil fuels are burned, (4) CO 2 is a greenhouse gas, (5) more CO 2 in the atmosphere traps more heat so global temperature is rising. No information contradicts this theory, although some details have not been worked out. The theory is very effective at predicting future events, which are already taking place. This idea will be explored in detail in the chapter Atmospheric Processes . |
SciQ | SciQ-4399 | virus, life, philosophy-of-science
Title: Is there any definition of life which makes viruses undeterminable? There are many different definitions of life (RNA, something that comes through evolution) but not one I have seen which could not determine wheter viruses are living things (even though there are many definitions both for YES and NO). Are there any such definitions (I'm looking for cases where it's really fundamental debate, not only struggling for the correct dictionary definition)?
Thank you. Your last sentence is the key: defining life really is just finding a dictionary definition that we can agree upon. Biology is something that defies discrete definitions at times: "What is it to be alive?" "What is a species?" maybe even "What is the wild type allele of a gene?"
I would recommend not looking at viruses as a challenge to determine if they are alive or not so much as an excellent opportunity to discuss what we think are important characteristics of life.
Life can alternately be described as:
"Comprised of self-replicating cells" (a paraphrase of the "Cell Theory of Life"
or
As things that embody at least most of the following characteristics:
1. Self-Replicating
2. Metabolizing
3. Growing
4. Showing signs of adaptation
5. Being organized
6. Respond to their environment
7. Being comprised of cells
I like to think that we should focus on extraterrestrial forms when we define life. i.e. what would we want to see in an extraterrestrial in order to call it 'life'? While some are troubled by calling viruses alive here on earth, the same people might be willing to say that we have found extraterrestrial life on another planet if it was similar (granted, it's hard to imagine this kind of life existing without a host...)
as an aside: You might also ask whether this question is fit for this stack as it can not be supported by literature references (at least none that would actually support a conclusion). So should this be posted as 'Biology' or 'Philosophy'?
The following is multiple choice question (with options) to answer.
What is defined as a group of living and nonliving things and their environment? | [
"degradation",
"habitat",
"ecosystem",
"degradation"
] | C | An ecosystem is a group of living things and their environment. It is made up of both living and nonliving things. |
SciQ | SciQ-4400 | cancer, mutations
Here is another great paper that specifically addresses your question, linking increased cell division with the accumulation of both significant and insignificant mutations, which over time, lead to an accumulation of mutations needed for cancer to develop.
The following is multiple choice question (with options) to answer.
Cancer is caused by mutations, which can be caused by pathogens, chemicals, or what else? | [
"radiation",
"diseases",
"evaporation",
"convection"
] | A | Cancer is caused by mutations, which can be caused by pathogens, chemicals, or radiation. |
SciQ | SciQ-4401 | botany, plant-physiology, ecology, virology, host-pathogen-interaction
Note about symbiosis - comes in reaction to @Gerhard's comment
Different authors use the word symbiosis differently. From wikipedia:
The definition of symbiosis is controversial among scientists. Some believe symbiosis should only refer to persistent mutualisms, while others believe it should apply to any type of persistent biological interaction (i.e. mutualistic, commensalistic, or parasitic).4 After 130+ years of debate,5 current biology and ecology textbooks now use the latter "de Bary" definition or an even broader definition (i.e. symbiosis = all species interactions), with the restrictive definition no longer used (i.e. symbiosis = mutualism)
The following is multiple choice question (with options) to answer.
What is the term for a mutually beneficial relationship in which one organism lives inside the other? | [
"parasite",
"endosymbiosis",
"symbiosis",
"parthenogenesis"
] | B | Endosymbiosis We have mentioned that both mitochondria and chloroplasts contain DNA and ribosomes. Have you wondered why? Strong evidence points to endosymbiosis as the explanation. Symbiosis is a relationship in which organisms from two separate species depend on each other for their survival. Endosymbiosis (endo- = “within”) is a mutually beneficial relationship in which one organism lives inside the other. Endosymbiotic relationships abound in nature. We have already mentioned that microbes that produce vitamin K live inside the human gut. This relationship is beneficial for us because we are unable to synthesize vitamin K. It is also beneficial for the microbes because they are protected from other organisms and from drying out, and they receive abundant food from the environment of the large intestine. Scientists have long noticed that bacteria, mitochondria, and chloroplasts are similar in size. We also know that bacteria have DNA and ribosomes, just as mitochondria and chloroplasts do. Scientists believe that host cells and bacteria formed an endosymbiotic relationship when the host cells ingested both aerobic and autotrophic bacteria (cyanobacteria) but did not destroy them. Through many millions of years of evolution, these ingested bacteria became more specialized in their functions, with the aerobic bacteria becoming mitochondria and the autotrophic bacteria becoming chloroplasts. The Central Vacuole Previously, we mentioned vacuoles as essential components of plant cells. If you look at Figure 4.8b, you will see that plant cells each have a large central vacuole that occupies most of the area of the cell. The central vacuole plays a key role in regulating the cell’s concentration of water in changing environmental conditions. Have you ever noticed that if you forget to water a plant for a few days, it wilts? That’s because as the water concentration in the soil becomes lower than the water concentration in the plant, water moves out of the central vacuoles and cytoplasm. As the central vacuole shrinks, it leaves the cell wall unsupported. This loss of support to the cell walls of plant cells results in the wilted appearance of the plant. |
SciQ | SciQ-4402 | genetics, dna
Title: How do mutations come to be shared by all cells? It's my understanding that various hazards can damage the DNA in our cells, causing mutations.
But whenever I picture this, I see the damage being done to one of our tissues (for example, our lungs due to smoking, or our skin due to UV rays).
When I think about this, I see that... many cells in a smoker's lungs, or many cells on the back of a beach-goer's neck, may have mutations in their DNA. But only the cells in that tissue have these mutations... the other cells in our body would not have the same mutations.
In particular, sperm and egg cells would not have the same mutations, so the mutations due to smoking and UV rays shouldn't pass on to children.
Are there instances where mutations that occur over the course of our life are spread to every cell, including sperm and egg cells, so that every cell reflects the mutation, and the mutation is passed onto our offspring? Goods question! Only mutations that occurred when we were in the early stages of development will affect all cells. That's why pregnant mothers shouldn't smoke. The reason for this is that one cell goes on to divide and become all our cells so any mutations in that cell are passed on to cells formed when it divides. That same principle explains your smoker example. In the lung we have two types of cells which are called Type 1 and Type 2. Type 1 cells are constantly dying as they get old and they get replaced by type 2 cells whose job it is to divide continuously to replace Type 1 cells. So we have lots of type 1 and few type 2. When type 2 divide they make one type 1 cell and one type 2 cell, so type 2 cells never run out. If smoke causes a mutation in type 1 cells generally they're okay because they'll die before enough mutations occur. Of course something that causes lots of mutations could make it cancerous before it dies but that's rare. Now if it occurs in Type 2 cells every subsequent type 1 or type 2 cell that cell makes is mutated.
The following is multiple choice question (with options) to answer.
All new alleles are formed by what types of mutations? | [
"systemic",
"random",
"ordinary",
"chaotic"
] | B | |
SciQ | SciQ-4403 | genetics, botany, food, ethnobiology, seeds
Title: How are oranges in the US or anywhere made seedless? How are oranges in the US or anywhere made seedless? Please explain the broad principles and not the technicalities. Oranges and other fruits are generally not actively made seedless. Rather, seeds may fail to develop due to either lack of fertilization (pollination) or a natural tendency. The natural production of unfertilized and thus seedless fruit is called Parthenocarpy.
To quote the Scientific American article (3) mentioned by Oreotrephes:
Fruit development normally begins when one or more egg cells in the
ovular compartment of the flower are fertilized by sperm nuclei from
pollen. In some plants, however, fruit develops without fertilization,
a phenomenon known as parthenocarpy. Parthenocarpic fruit has
advantages over seeded fruit: longer shelf life and greater consumer
appeal.
The most frequent reasons for lack of seed development are pollination
failure, or nonfunctional eggs or sperm. In many plants,
self-incompatibility genes limit successful fertilization to
cross-pollination between genetically different male and female
parents. This property is exploited by citrus farmers who grow
seedless fruits, such as navel oranges and clementines. Because these
cultivars are self-incompatible, they fail to set seed when they are
planted in orchards of identical plants (clones). These plants have a
high frequency of parthenocarpy, however, so they still produce fruit.
Parthenocarpic varieties may arise from a lack of pollinators. From the Wikipedia page on Parthenocarpy:
Plants moved from one area of the world to another may not always be
accompanied by their pollinating partner and the lack of pollinators
has spurred human cultivation of parthenocarpic varieties. Some
parthenocarpic varieties have been developed as genetically modified
organisms.
To preserve the seedless trait, parthenocarpic trees can be propagated by grafting. It is possible that more kinds of seedless fruits will be engineered in the future (3):
Plant biologists have learned that if the plant hormone auxin is
produced early in ovule development, parthenocarpic fruit can grow on
plants that do not usually exhibit this property. Thus, genetic
engineering will most likely give consumers parthenocarpic fruit in
many other species in the near future.
The following is multiple choice question (with options) to answer.
What are seeds plants that produce naked seeds in cones called? | [
"gymnosperms",
"cytoplasm",
"lipids",
"angiosperms"
] | A | Gymnosperms are seed plants that produce naked seeds in cones. There are about 1000 species of gymnosperms. Conifers are the most common group of gymnosperms. The spruce tree in Figure below is an example of a conifer. |
SciQ | SciQ-4404 | aqueous-solution
A final point is that some dissolved species can, in fact, be solvents on their own. In this case, the definition of whether the species is aqueous or liquid is not well-defined and usually depends on the context. For example, a 1:4 mixture of $\ce{MeOH}$ and $\ce{H_2O}$ is typically written as $\ce{MeOH{(l)} + {H_2O{(l)}}}$, but a solution where a small amount of $\ce{MeOH}$ (maybe used as a reactant) would be denoted $\ce{MeOH{(aq)}}$. This has to do with the definition of the thermodynamic activities of the species and if you have questions about this, there's probably someone else on here who is a better expert than I to explain.
The following is multiple choice question (with options) to answer.
Water is the solvent in solutions called acids and? | [
"proteins",
"alkalines",
"nutrients",
"bases"
] | D | Water is the solvent in solutions called acids and bases. To understand acids and bases, it is important to know more about pure water, in which nothing is dissolved. In pure water (such as distilled water), a tiny fraction of water molecules naturally breaks down, or dissociates, to form ions. An ion is an electrically charged atom or molecule. The dissociation of pure water into ions is represented by the chemical equation:. |
SciQ | SciQ-4405 | thermodynamics, statistical-mechanics, temperature
Air is not an ideal gas. The most important factor is that air usually contains a non negligible amount of water vapor, the presence of which can greatly change its thermodynamic properties
In the atmosphere, wind is actually a large mass of air moving from regions of higher pressure to regions of lower pressure. Such a mass of air can be colder than the surrounding air, so the presence of wind can actually be linked to a decrease in temperature. The discussion becomes much more complicated in this cases, and a full understanding of it would require some knowledge of atmospheric science.
The following is multiple choice question (with options) to answer.
What two gases are the main components of air? | [
"carbon and oxygen",
"nitrogen and oxygen",
"hydrogen and helium",
"oxygen and helium"
] | B | A: Other examples of liquid mixtures include salt water and salad dressing. Air is a mixture of gases, mainly nitrogen and oxygen. The rock pictured in the Figure below is a solid mixture. |
SciQ | SciQ-4406 | evolution, biochemistry, plant-physiology, plant-anatomy, life
Title: Plants without bacteria? is it theoretically possible? I know from school, that all live on the Earth need bacteria as low-level "machines" that break down/extract/convert/produce chemical elements and combinations, other high-level organisms needed. But it is a natural way.
But is it possible to have a world with plants (without mammals or microorganisms and without bacteria) that could exist in the long term. Saying the atmosphere of these world has already enough nitrogen, oxygen and CO2, and of course there is water.
What could break this artificially created world with such conditions (say the world created not from low-level living structures)?
Could bacteria emerge in the world? This is the sort of question that should be considered from more than one perspective. Since this is speculation, take it as a given that there is a lot of 'what if' here.
I doubt most animals and plants can do entirely without bacteria - as you say most of the essential nutrients come from bacteria, who fix nitrogen. If only plants were left on earth, eventually the plants would use up all the nitrogen and they would have to find a way to fix more.
Can bacteria emerge from just a world of plants? I don't think viruses arise spontaneously, but since genomes often have viruses embedded in them, over the course of a billion years or so, its possible since bacteria and viruses continue to be impressed upon our genomes. Would it happen in time? Most would be skeptical whether that timing could work out.
In practice it would be hard to create a world like this. I would be interested to see whether you could sterilize the microorganisms off of seeds without killing the plant for instance. If you're asking about a small sterile environment with only plants, you could do it by adding the nutrients the plants need and giving them sunlight. Such self sustaining systems have been made with cyanobacteria and i'd be surprised if plants could not be included. But these are closed systems and judged by limited amounts of time, so whether this is an answer to your question is not clear. Here it looks like some water plants and fish have been done. If there was a plant that created CO₂ at an adequate rate its possible.
The following is multiple choice question (with options) to answer.
Anaerobic prokaryotes can live without what compound in their environment (it's a compound that people do need to live)? | [
"oxygen",
"carbon",
"nitrogen",
"Hydrogen"
] | A | Aerobic prokaryotes live in habitats with oxygen. Anaerobic prokaryotes live in habitats without oxygen. Prokaryotes may also be adapted to habitats that are hot, moderate, or cold in temperature. |
SciQ | SciQ-4407 | computer-vision, rangefinder
Title: Why do robots need rangefinders while animals don't? Will vision based system eventually prevail rangefinders based systems given that the most successful autonomous agents in the world like animals use primarily visions to navigate? Animals and robots both need to understand something about the 3D structure of the world in order to thrive. Because it's so important, animals have evolved a huge number of strategies to estimate depth based on camera-like projective sensors (eyes). Many make use of binocular disparity -- the fact that the distance between the same scene point in two different views is inversely proportional to depth. A mantis moves its head sideways to do this, a dragonfly makes very precise forward motion, birds move their heads forward and backwards, we use the fact that our eyes are widely spaced on our heads and have overlapping fields of view. Stereo vision is a computer vision technique that mimics this.
However disparity is not the only trick we use, there are lots of others including proprioceptive signals from the muscles in our eyes (focus and vergence), observing how things in the world move as we move (optical flow), our knowledge about the world (the tree looks small, we know trees are big, therefore it must be far away), haziness, texture density, occlusion (thing A blocks thing B, therefore A must be closer). Each technique (or cue) is imperfect, but mostly in a different way, and each operates across a different range of distances. Our brain stitches (fuses) all that together to give a result that is mostly pretty robust.
Checkout the wikipedia page for more details. I like this (old) article
How the eye measures reality and virtual reality.
JAMES E. CUTTING, Cornell University, Ithaca, New York.
Behavior Research Methods, Instruments, & Computers 1997, 29 (1), 27-36
which gives a good insight into this issue.
There are now deep-learnt networks now that can take a monocular (single) image and output estimated depth. We can never know for sure but my theory is that they are encoding some of the cues that we use for depth estimation such as texture and apparent size.
The following is multiple choice question (with options) to answer.
What part of earth do many animals use for navigation? | [
"atmosphere",
"magnetic field",
"molten core",
"oceans"
] | B | Another benefit of Earth’s magnetic field is its use for navigation. People use compasses to detect Earth’s magnetic north pole and tell direction. Many animals have natural “compasses” that work just as well. For example, the loggerhead turtle in the Figure below senses the direction and strength of Earth’s magnetic field and uses it to navigate along migration routes. Many migratory bird species can also sense the magnetic field and use it for navigation. Recent research suggests that they may have structures in their eyes that let them see Earth’s magnetic field as a visual pattern. You can learn more at this URL: http://www. smithsonianmag. com/science-nature/How-Do-Birds-Find-Their-Way-Home. html. |
SciQ | SciQ-4408 | biochemistry, cell-biology, neurotransmitter, membrane-transport, synapses
Title: Exocytosis of synaptic vesicles I'm reading the following paper:
http://jcs.biologists.org/content/123/6/819
The part I am really confused about is when they say:
Exocytosis appears to use two alternative pathways: clathrin-mediated endocytosis (CME), which is well established by numerous lines of evidence, and the more controversial ‘kiss-and-run’ pathway, which involves direct retrieval of a vesicle at the site of fusion
My question is .. How can exocytosis (contents inside of cell are transported to outside of cell) use clathrin mediated endocytosis?
I thought endocytosis is the opposite of exocytosis, so why do synaptic vesicles use clathrin mediated endocytosis as a method of exocytosis? That sentence is located in a paragraph titled "Stages 5-7: Endocytosis and recycling": it's talking about recycling exocytosed membrane which is necessary for making vesicles for further exocytosis.
The sentences before the part you quoted are:
Synapses possess highly efficient mechanisms for retrieving SVs from the plasma membrane of the presynaptic terminal after exocytosis. Fast regeneration of functional SVs is a prerequisite for synapses to function during prolonged activity.
I think the passage is just somewhat confusingly worded, in that "exocytosis" is used as the subject of the sentence which is strange in this context. You could rewrite that sentence:
There appear to be two alternative pathways to recycle membrane for exocytosis: clathrin-mediated...
The following is multiple choice question (with options) to answer.
Endocytosis and exocytosis are types of vesicle transport that carry very large molecules across what structure? | [
"cell membrane",
"dermis",
"cell substrate",
"the heart"
] | A | Illustration of the two types of vesicle transport, exocytosis and endocytosis. Endocytosis and exocytosis are types of vesicle transport that carry very large molecules across the cell membrane. |
SciQ | SciQ-4409 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
What are biochemical compounds that living things use to store energy and make cell membranes? | [
"carbohydrates",
"nucleic acid",
"lipids",
"proteins"
] | C | Lipids are biochemical compounds that living things use to store energy and make cell membranes. Types of lipids include fats, oils, and phospholipids. |
SciQ | SciQ-4410 | home-experiment, density, experimental-technique
Edit to describe updated method:
Having recovered from my embarrassment at failing to do this properly the first time, some may be interested in a repeat of the experiment which has yielded a much better result:
I cut the valve out of a bicycle inner tube and glued it into the lid of a 2 litre pop bottle, having first drilled a suitable hole in the lid through which to poke the valve.
This enabled me to pump the bottle up to about 25 psi with a bicycle pump.
This time, unlike the balloon, the bottle stretches only very slightly under pressure, so the extra weight really is the extra weight of the air.
We collected the weighed extra air over water as before to measure its volume. 2.65 g air had a volume of 2.4 l.
The density came out as 1100 g/m3, which isn't too far from the accepted value of 1225. Your method is the problem,
Imagine for an instant trying to measure the density of helium by the same method, your balance would measure a negative weight (the balloon rise), and hence a negative density. Which isn't the case.
Archimede's fault really
As @akhmeteli pointed out, pressure look like a far better explanation, if the pressure inside is 10% more ($1.1$ atm which seems realistic), the mass would also increase by 10%, and lead to the kind of mass difference you are expecting.
My first explanation involved CO2, but this gas does not represent a sufficiently large portion of breathed air to explain anything.
The following is multiple choice question (with options) to answer.
What happens to the volume of a balloon when you add moles of gas to it by blowing up? | [
"increases",
"changes randomly",
"decreases",
"stays the same"
] | A | where is the number of moles of gas and is a constant. Avogadro’s law is in evidence whenever you blow up a balloon. The volume of the balloon increases as you add moles of gas to the balloon by blowing it up. |
SciQ | SciQ-4411 | biochemistry, bioenergetics
Having got those out of the way, I can now attempt to answer your question (slightly rephrased). Can a reaction in a metabolic pathway be at equilibrium?
To be extremely pedantic, if there is a flux through the pathway (net conversion of first substrate to end product) then the answer is no (Newsholme & Start, 1973, p 11). That is, if there is a flux through the pathway, ΔG' cannot be exactly zero for any individual reaction. However, reactions in a metabolic pathway may be very close to equilibrium (Newsholme & Start, 1973, chapter 1).
Let’s (once again) rephrase your question. Are there any examples of reactions in metabolic pathways that are close to equilibrium, and how can we determine this?
To again quote Newsholme & Start (1973, p11) “In a series of reactions that constitute a metabolic pathway, a few may be displaced far from equilibrium, whereas the majority of reactions may be close to equilibrium”.
So how can this be determined? One way would be to measure the ratio of products to substrates (or the ratio of product to substrate pairs) in the cell, and compare this with the equilibrium constant. Note that it is only the ratio of substrate/product pairs we are interested in, not the absolute concentrations. We might be interested in the NAD+/NADH ratio in the cell, for example.
That is, we measure the mass action ratio and compare this with the equilibrium constant.
Such measurements are fraught with difficulties, but let’s agree that they can be made. We could rapidly freeze the tissue sample to -190°C (using liquid nitrogen), for example, and then measure the ratio of metabolites. Finally, it should be pointed out that comparison of mass-action ratio with the equilibrium constant is not the only way of deducing that a reaction is near equilibrium, and agreement between alternative methods is highly desirable before any firm conclusions are drawn.
Let’s consider glycolysis as an example. It is generally agreed that the reactions catalyzed by phosphoglucoisomerase, phosphoglycerate mutase and enolase are all close to equilibrium: the mass action ratios and the equilibrium constants are about the same (see Newsholme & Start, 1973, p 98).
The following is multiple choice question (with options) to answer.
The addition of starting materials and the removal of end products prevent metabolism from reaching what state? | [
"imbalance",
"constant",
"equilibrium",
"inequality"
] | C | |
SciQ | SciQ-4412 | genetics, homework, hardy-weinberg
Title: calculate the number of heterozygotes The ability to taste PTC is due to a single dominant allele "T". You sampled 215 evolution students, and determined that 150 could detect the bitter taste of PTC and 65 could not. Assuming this trait is in Hardy-Weinberg equilibrium in this population and that there are only two alleles, calculate the number of heterozygotes for this trait there are in the population. Hardy-Weinberg law gives the frequencies of genotypes from allele frequencies: $p^2 + 2pq + q^2$
Because the allele "T" is dominant, the frequency you're directly measuring through the experiment is the addition of $p^2$ and $2pq$.
$$p^2 + 2pq = 150/215 ≈ 0.6976$$
solving for $p$ (and replacing $q$ by $1-p$) gives:
$$p = 1 - \sqrt{\frac{13}{42}} ≈ 0.45 $$
The frequency of heterozygotes is given by:
$$2p(1-p) ≈ 0.4950 $$
And the number of heterozygotes in a population of 215 individuals is given by:
$$215 \cdot 0.4950 = 106.43$$
That sounds very alike what you wrote in the comments!
The following is multiple choice question (with options) to answer.
In what year was the hardy-weinberg theorem formulated? | [
"1901",
"1928",
"1938",
"1908"
] | D | Evolution occurs in a population when allele frequencies change over time. What causes allele frequencies to change? That question was answered by Godfrey Hardy and Wilhelm Weinberg in 1908 (see the Hardy-Weinberg Theorem concept). |
SciQ | SciQ-4413 | gene-expression, transcription, gene-regulation
Title: Transcription of Genes: Are Specific Transcription Factors + Enhancers Necessary? I learned about transcription in my AP Biology class and we discussed how transcription occurs, but I was wondering whether transcription always requires the enhancers, activators (specific transcription factors), DNA-bending proteins, etc. to be present, or if this is only used for higher-level production of RNA transcripts?
Can transcription occur if only the RNA Polymerase (I, II, or III) and the General Transcription Factors are present?
Thanks! enhancers, activators, silencers, repressors are necessary in controlling of the transcriptional process. Utilization of enhancers/silencers plays a part in differentiation of developmental processes (i.e. maturation, growth)
https://en.wikipedia.org/wiki/Enhancer_(genetics)
The following is multiple choice question (with options) to answer.
The regulation of gene expression is extremely important during the development of what? | [
"protein",
"tissues",
"organism",
"cells"
] | C | 3. Name and describe the division of gymnosperms. |
SciQ | SciQ-4414 | virology, infection
Title: Why don't viruses cause wounds? A simple mental model of a viral infection is that an infected cell emits a lot of virions and eventually dies. The emitted virions have a chance of infecting other cells. Nearby cells are at a higher risk of infection.
Based on this model, if one cell in my nose gets infected, I would expect a large part of my nose to be destroyed, as the infection spreads and destroys more and more cells in the same area.
This does not happen! I survived a number of infections and still have my nose. Why?
I know there are "flesh eating" bacteria. Why isn't this the norm for infections? Does a common cold virus or SARS-CoV-2 not infect a lot of cells within the same area? A virus does not destroy that many cells before it is exterminated by the immune system or before the host dies.
Perhaps even more crucially, viruses typically target a very specific type of cell — those on the inner mucal surface of the nose in the case of cold or flu, those of the gastrointestinal tract in the case of stomach viruses, CD4 immune cells in the case of HIV, etc.
Update
As an example of how much time it takes for a virus to eat a noticeable wound, one could take the extermination of the immune cells by HIV - although it does not look as a physical wound, it is one, in the sense that enough of the specific tissue is destroyed to cause a life-threatening condition. It takes about a decade(!) - from the initial infection to the immune system failure.
On the other hand, the lethal effect of typical respiratory viruses is typically via obstructions of the respiratory ways due to inflammation or secretions resulting from the immune response, or via creating suitable conditions for a more serious bacterial infection.
The following is multiple choice question (with options) to answer.
What does a virus inject into the host cell? | [
"cells acid",
"proteins acid",
"Acetic acid",
"nucleic acid"
] | D | 22.2.1 Lytic Cycle 1. Attachment: The virus binds to specific receptors on the host cell. Entry: There are two ways in which a virus can enter cells. Firstly, the virus can inject its nucleic acid into the host cell. Secondly, if a virus is contained in an envelope, the host cell can phagocytosise the entire virus particle into a vacuole. When the virus breaks out of the vacuole, it then releases its nucleic acid into the cell. Replication: The virus's nucleic acid instructs the host cell to replicate the virus's DNA or RNA. Assembly: New virus particles are assembled. Lysis and Release: The virus directs the production of an enzyme which damages the host cell wall, causing the host cell to swell and burst. The newly formed virus particles are now released. |
SciQ | SciQ-4415 | cancer, mutations
Here is another great paper that specifically addresses your question, linking increased cell division with the accumulation of both significant and insignificant mutations, which over time, lead to an accumulation of mutations needed for cancer to develop.
The following is multiple choice question (with options) to answer.
Mutations in regulatory genes that normally control the cell cycle cause what? | [
"illness",
"anxiety",
"tumors",
"cancer"
] | D | Mutations in regulatory genes that normally control the cell cycle cause cancer. |
SciQ | SciQ-4416 | cell-biology
Title: Are there human cells, apart from red blood cells and platelets, without a nucleus? I know that blood platelets and erythrocytes do not have a nucleus. Are there more cells in the human body without a nucleus, such as pancreas, cartilage, or lung cells? Short answer
As far as I know, red blood cells and blood platelets are the only human cells in our body without a nucleus.
Background
Erythrocytes and thrombocytes are the only human cells without a nucleus, as far as I know. However, if you count the gut as being part of the human body (in essence it is a continuation of the skin and as such it can be considered to be on our outside), then we are loaded with cells lacking a nucleus, namely all the bacteria that live in our intestines such as E. coli. Bacteria, being prokaryotes, lack a nucleus. In fact, there are ten times more bacteria than human cells in our gut (Wenner, 2007).
Reference
Wenner, Sci Am 2007
The following is multiple choice question (with options) to answer.
Blood is made up of red blood cells, white blood cells, platelets, and what else? | [
"pathogens",
"potassium",
"hemoglobin",
"plasma"
] | D | Did you know that blood is a tissue? Blood is a fluid connective tissue that is made up of red blood cells, white blood cells, platelets, and plasma. The cells that make up blood are pictured below ( Figure below ). The different parts of blood have different roles. |
SciQ | SciQ-4417 | biophysics, theoretical-biology, ecosystem
Systems ecology, especially with regard to energy and nutrient flow.
This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem Ecology: Understanding Element Cycles by Ågren & Bosatta (Ågren was originally a physicist)
Physical limitations to growth and transport
This can include for instance mechanical contraints on plant growth (see e.g. the book Plant Physics by Nicklas & Spatz), water transport in trees (see e.g. this BioSE question) or the biomechanics of movement (see e.g. Hudson et al (2012) on the speed and movement of cheetahs or Wikipedia: Biomechanics).
Allometric relationships between organisms, e.g. with regard to metabolism
To explain these types of relationships knowledge in physics is useful. See e.g. Kleiber's law for more.
MAXENT as a general approach to ecological patterns or to model species distributions
This is basically a tool lifted from physics that can be applied to ecological problems. There are many papers to look at, but Harte & Newman (2014) (Harte is another previous physicist) and Elith et al (2010) are two good starting points.
Dynamical modelling of populations and communities
This field use many of the same tools for analysis as physics, e.g. systems of differential equations. One of the pioneers in this field (among many) were Robert May (also started with a PhD in physics), and his classical book Theoretical Ecology: Principles and Applications is still a good starting point.
Energy harnessing and conversion by organisms
This can refer both to how organsims convert prey to energy (e.g. conversion efficiencies) and the physics of photosynthesis (which is an interesting intersection between physics and molecular biology). See Jang et al (2004) and O'Reilly & Olaya-Castro (2013) for examples of the how quantum mechanics can inform us about photosynthesis.
Hopefully this will give you a sense of some different ways that knowledge in physics can be useful for biology.
The following is multiple choice question (with options) to answer.
What is the term for the study of how living things interact with each other and with their environment? | [
"ecology",
"anthropology",
"biology",
"radiology"
] | A | Ecology is the study of how living things interact with each other and with their environment. It is a major branch of biology, but has areas of overlap with geography, geology, climatology, and other sciences. This lesson introduces fundamental concepts in ecology, beginning with organisms and the environment. |
SciQ | SciQ-4418 | biochemistry, mitochondria, bioenergetics, chloroplasts
A hypothesis is an assumption made before any research has been done.
It is formed so that it can be tested to see if it might be true. A
theory is a principle formed to explain the things already shown in
data. Because of the rigors of experiment and control, it is much more
likely that a theory will be true than a hypothesis.
But is this dogmatism justified, and how does it apply to the current problem? Mitchell’s proposal was made to be tested (as in a hypothesis) but it was intended to explain the observed phenomenon (as in a theory) of oxidative phosphorylation.
An extensive article in Wikipedia begins with a more modest statement:
A hypothesis (plural hypotheses) is a proposed explanation for a
phenomenon.
And chemi-osmosis is a proposed explanation for the phenomenon of ATP synthesis in double-membrane systems; so by this token Mitchell’s choice of words seems justified.
Major dictionaries record how words are or were used in practice. In some contexts there are sharp distinctions in usage of particular words, where in others the same words are used interchangeably. In modern biological science, unlike philosophy, logic or the numerical sciences, laws, theories and hypotheses are generally of no great concern, and the writers quoted may merely feel that the word ‘theory’ (‘Einstein’s’ theory, ‘Darwin’s theory’) has more gravitas than ‘hypothesis’, a word they perhaps use to describe ideas about relatively humble scientific problems of their own.
…or they may just find it easier to spell.
The following is multiple choice question (with options) to answer.
What takes place directly after developing a hypothesis in the scientific method process? | [
"testing the hypothesis",
"gathering materials",
"making a conclusion",
"independent variables"
] | A | Scientific method is a process consisting of making observations, developing a hypothesis, and testing that hypothesis. |
SciQ | SciQ-4419 | optics, visible-light, vision, absorption, laboratory-safety
Title: Why are UV protective eyeware Orange? Many industrial processes use uv as a curing agent. When one uses such a process, one must protect one's eyes from the radiation. Most uv protective gear I have seen is tinted orange?
Does this orange color come from the actual uv blocking chemicals, or is that color added for some user related reason (like being confident you picked up the right glasses) For typical laser goggles the color of lens is the color of light that is transmitted through the lens. Thus if the lens is red, it will not protect you from laser beams that are in the red portion of the spectrum.
The color you are looking for will be, in some sense, the complementary color; since red-orange-pink are far from blue-violet-ultraviolet, these are the lens colors you would expect to work for UV light.
I have often worked with high power, class 3B and class 4, UV lasers, from 405 nm, which is UVA, down to 264 nm, which is beyond the UVB. The typical goggles which cover these ranges are orange to pink.
Your hypothesis is correct: the color comes from an absorptive dye which is incorporated into the plastic or glass.
It is also possible to apply multi-layer optical coatings to the lenses of spectacles which will preferentially reflect in the UV; this is a more expensive approach (hence dyes), and relies on destructive interference for the transmitted waves. The goal is to make make it transparent in the visible spectrum.
The following is multiple choice question (with options) to answer.
What should you use to protect your eyes from chemicals? | [
"certain goggles",
"your hands",
"eye goggles",
"contacts"
] | C | |
SciQ | SciQ-4420 | neuroscience, brain
When $m$ synapses simultaneously generate an EPSP of size $u$, these EPSPs will sum up at the axon hillock to
$$ U = m\times u\times 10^{-\alpha r}$$
Only if $U \geq \theta$ an action potential will be generated, that is, the minimal number of simultaneously active synapses to generate an action potential is
$$ n = 10^{\alpha r}\ \frac{\theta}{u}$$
With this we can estimate the excitability $E = \log\frac{N}{n} = \log 10^{-\alpha r}\frac{N\ u}{\theta}$ by
$$E = -\alpha r + \log(N) + \log \frac{u}{\theta} $$
$\alpha$, $u$ and $\theta$ are more physical constants (more or less the same for all types of neurons?), $r$ and $N$ depend heavily on the arbitrary geometry/morphology of the neuron (especially do longer and more strongly branched dendrites have more synapses).
My specific questions are (please feel free to answer only with "yes" or "no"):
Has the property of excitability (in the operational sense above) been investigated a) for single neurons, b) for morphological types of
neurons?
Is there an observed significant correlation between morphological type and excitability? Note that larger dendritic trees have larger
$r$ (decreasing $E$) but also larger $N$ (increasing $E$).
The following is multiple choice question (with options) to answer.
Because action potentials are so brief, a neuron can produce hundreds per what? | [
"minute",
"day",
"lifetime",
"second"
] | D | |
SciQ | SciQ-4421 | evolution
Title: Which of this 2 affirmations is more close to the explanation of evolution? I am almost secure that this affirmation aren't exactly true but I want to know which of these statements is more near to a description of how evolution works:
The evolution has an exactly target and always progress to it, each generation the childs are more close to make complete a certain task, that is beacuse evolution is like "directional".
For example: The task is be 10cm taller. Each generation the race become 1mm taller up to complete the task.
The evoultion is random but the specie (or natual selection) try to reach a target, each generation has random traits but only benefical traits tends to "survive" and get offpring.
For example: In order to survive the task is be 10cm taller. Some childs are half cm taller and other childs are half cm smaller, the last ones die naturally and only the taller ones survive enough to get offspring. The second is marginally better because it mentions randomness and emphasizes differential survivorship, but the parts about "trying to reach a target" and specifying a particular "task" are misleading at best. I would rewrite the statement as follows (I have edited for grammar, spelling and style as well, but emphasize more substantive deviations with strikeout for omitted parts and boldface for added parts). The substantive edits change the meaning of the statement significantly: most evolutionary biologists would be very uncomfortable with the second statement as written above (setting aside any grammatical issues).
Evolution is has a random component but the species (or natural selection) tries to reach a target, may result in directional change: each generation has some random variation in traits but only individuals with beneficial traits tends to are more likely to survive and produce offspring. For example, In order to survive the task is be 10cm taller. taller individuals survive better than smaller ones. Some offspring are a half cm taller and other children are a half cm smaller; the latter die naturally and only the taller ones survive long enough to produce offspring.
I would probably say "offspring" rather than "children" in a technical context.
Note also that this emphasizes evolution by natural selection; broadly speaking, there are many non-adaptive processes (vicariance, drift ...) that also lead to evolution (change in gene frequencies between generations).
The following is multiple choice question (with options) to answer.
Darwin coined what term to refer to an organism’s relative ability to survive and produce fertile offspring? | [
"metabolism",
"fitness",
"strength",
"momentum"
] | B | Darwin coined the term fitness to refer to an organism’s relative ability to survive and produce fertile offspring. Nature selects the variations that are most useful. Therefore, he called this type of selection natural selection. |
SciQ | SciQ-4422 | air, molecules
Title: If you compress air to a large enough pressure do new molecules form that have a large activation energy? If you compress air to a large enough pressure do new molecules form that have a large activation energy? The average speed of the molecules depends on the temperature, not the pressure. That drives the energy available from collisions. On average, there is no more energy available at high pressure than at low pressure. At higher pressures, there will be more collisions, so ones at the top end of the energy spectrum become more common (as do all the others). That might help with reactions that just need a bit more energy. You also shift the equilibrium of reactions to the side that has fewer molecules, because driving that direction reduces the pressure.
The following is multiple choice question (with options) to answer.
At high pressures, how are the molecules of a gas crowded? | [
"few together",
"small together",
"further apart",
"closer together"
] | D | Particles of a hypothetical ideal gas have no significant volume and do not attract or repel each other. In general, real gases approximate this behavior at relatively low pressures and high temperatures. However, at high pressures, the molecules of a gas are crowded closer together, and the amount of empty space between the molecules is reduced. At these higher pressures, the volume of the gas molecules themselves becomes appreciable relative to the total volume occupied by the gas (Figure 9.36). The gas therefore becomes less compressible at these high pressures, and although its volume continues to decrease with increasing pressure, this decrease is not proportional as predicted by Boyle’s law. |
SciQ | SciQ-4423 | inorganic-chemistry, molecular-orbital-theory
Below is a drawing of the five occupied orbitals where you can see that the $\sigma$ ones have become $sp$-like and that the carbon contribution is greater in the HOMO. C is on the left and N on the right.
The following is multiple choice question (with options) to answer.
The number of possible isomers increases tremendously as carbon skeletons increase in what? | [
"size",
"variation",
"mass",
"weight"
] | A | |
SciQ | SciQ-4424 | 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.
What are vascular plants that produce seeds in cones called? | [
"gymnosperms",
"deciduous",
"evergreen",
"angiosperms"
] | A | Gymnosperms are vascular plants that produce seeds in cones. Examples include conifers such as pine and spruce trees. The gymnosperm life cycle has a very dominant sporophyte generation. Both gametophytes and the next generation’s new sporophytes develop on the sporophyte parent plant. Figure below is a diagram of a gymnosperm life cycle. |
SciQ | SciQ-4425 | photosynthesis, botany
Title: Photosynthesis - Light Intensity Say I was conducting an experiment for photosynthesis. If I moved light closer to the plant, what effect would this have on the process of photosynthesis? The rate of photosynthesis varies from plant to plant. Some plants require more light and some require less. If you move light closer to the plant, in most scenarios the rate of photosynthesis is likely to be increased. For some plants a minimal light is enough for their photosynthesis, so for those plants, moving light source closer or further will have less effect.
The following is multiple choice question (with options) to answer.
What does photosynthesis change light energy into? | [
"carbon energy",
"electrical energy",
"radiation energy",
"chemical energy"
] | D | Photosynthesis changes light energy to chemical energy. The chemical energy is stored in the bonds of glucose molecules. Glucose, in turn, is used for energy by the cells of almost all living things. Photosynthetic organisms such as plants make their own glucose. Other organisms get glucose by consuming plants (or organisms that consume plants). |
SciQ | SciQ-4426 | neurotransmitter, addiction
Title: Are endorphins addictive? Endorphins are among the brain chemicals known as neurotransmitters, which function to transmit electrical signals within the nervous system. Stress and pain are the two most common factors leading to the release of endorphins. I wanted to know if they are addictive, and found some contradicting answers:
If people can get addicted to risky sports just for the thrills they
provide, they can also get addicted to painful activities where
endorphins provide relief, "despite the harm to self and/or others,"
says Dr. Anna Lembke, chief of addiction medicine at Stanford
University School of Medicine in an email interview. "For example,
someone who compulsively cuts herself for the endorphin release is
causing self-harm. Someone who compulsively runs, even to the point of
causing musculoskeletal injury, is causing self-harm."
Source:
https://science.howstuffworks.com/life/inside-the-mind/human-brain/can-be-addicted-to-endorphins.htm
In contrast to the opiate drugs, however, activation of the opiate receptors by the body's endorphins does not lead to addiction or dependence.
The following is multiple choice question (with options) to answer.
Addiction affects what type of chemical receptors within the brain? | [
"bind receptors",
"dopamine receptors",
"mitochondria receptors",
"serotonin receptors"
] | B | Figure above shows the accumulation of radioactive compounds that bind to dopamine receptors. The non-addicted individuals have large numbers of receptors for dopamine. The addicted persons show less binding to these receptors, indicating that fewer receptors are present. |
SciQ | SciQ-4427 | particle-physics, nuclear-physics
Title: Can a gamma ray photon transfer it's energy to an atom, not an electron of the atom? I know that due to the photoelectric effect, when you shoot a gamma ray at an atom, it causes an electron to absorb that energy. However, can the nucleus of an atom take in that energy, instead of the electrons? The answer is yes, but at common gamma-ray energies it's not very probable. At typical energies, the final state of the nucleus would be bound, and the density of available excited states would be quite low. In the photoelectric effect, you're scattering the electron into the continuum, so there are guaranteed to be states with the right energy.
Coulomb excitation is a process in which a nucleus scatters inelastically from another nucleus and excites it through electromagnetic interactions. This can be considered as excitation by a virtual gamma ray. Coulomb excitation is a very common process, often with a huge cross-section.
The following is multiple choice question (with options) to answer.
What is the ability of an atom to emit, or give off, charged particles and energy from the nucleus? | [
"electrolysis",
"magnetism",
"radioactivity",
"electromagnetism"
] | C | Radioactivity is the ability of an atom to emit, or give off, charged particles and energy from the nucleus. The charged particles and energy are called by the general term radiation . Only unstable nuclei emit radiation. When they do, they gain or lose protons. Then the atoms become different elements. (Be careful not to confuse this radiation with electromagnetic radiation, which has to do with the light given off by atoms as they absorb and then emit energy. ). |
SciQ | SciQ-4428 | jupiter, planetary-atmosphere, astrochemistry
There are more polar molecules than non-polar, but outside of the somewhat odd CF2CL2, all polar gases are relatively light, SO2 being the most massive, molecular weight of 64.
You mentioned Methylamine which is basically ammonia (NH3) where one of the hydrogens is replaced by a methyl (CH3) group. NH2CH3.
DiMethylamine (CH3)2NH is also a gas at about 7 degrees C and up (boiling point).
Playing around with temperature and variations on the gas molecules (replacing H with CH3, replacing H with NH2, replacing H with OH, but remember, Oxygen tends to be spoken for, like a perfect 10 at a dance, so that's not a good one, unless there's life and a source of oxygen (photosynthesis).
Similarly the "Ane" series, more accurately called the Group 14 hydrides. Group 14: carbon, silicon, germanium, tin, and lead, and the hydrides, Methane, Silane, Germane, Stanane, Plumbane. All of these are polar and all are gas molecules. Most are very reactive with Oxygen. Methane requires a flame, but the other 4 react with Oxygen quite easily.
And as temperature goes up, you add new gases, but heat tends to destroy complex chemistry, so there's a bit of a trade-off. There's no easy answer as to what could be a gas and what couldn't, but starting with the building blocks and swaping might be a place to start. That doesn't always work though. CO2 is non polar and a gas. SO2, even though Silicon is in the carbon group, is polar and bent. It's not a gas (it's closer to sand) with a very high melting point.
The following is multiple choice question (with options) to answer.
What group of gases are unusually unreactive? | [
"noble gases",
"greenhouse gases",
"volcanic gases",
"halogens"
] | A | Nonmetals tend to gain electrons in chemical reactions and have a high attraction to electrons within a compound. The most reactive nonmetals reside in the upper right portion of the periodic table. Since the noble gases are an unusually unreactive group, the element fluorine is the most reactive nonmetal. It is also not found in nature as a free element. Fluorine gas reacts explosively with many other elements and compounds and is considered to be one of the most dangerous known substances. |
SciQ | SciQ-4429 | crystal-structure, organometallic-compounds
8th parameter is occupancy (_atom_site_occupancy).
These both examples were for not disordered atoms. If they are disordered then it looks like this:
shelx-ins/res
O1 4 0.297097 -0.198418 -0.064164 10.50000 0.34896 0.34935 =
^ occup. 1/2
or
FVAR 0.22777 0.51340 0.51266
...
O1 4 0.551971 0.536866 0.295322 21.00000 0.03100 0.03031 =
^ occup. bound to 2nd free variable
here 51%
cif-file:
O1_20 O 0.6673(9) 0.3140(7) 0.1724(3) 0.0434(14) Uani 0.513(3) 1 d PDU C 1
^
The following is multiple choice question (with options) to answer.
A point defect can be an atom missing from a site in the crystal known as a what? | [
"vacuum",
"deficiency",
"vacancy",
"void"
] | C | Summary Real crystals contain large numbers of defects. Defects may affect only a single point in the lattice (a point defect), a row of lattice points (a line defect), or a plane of atoms (a plane defect). A point defect can be an atom missing from a site in the crystal (a vacancy) or an impurity atom that occupies. |
SciQ | SciQ-4430 | neuroscience, brain, neurophysiology, development, synapses
Title: How do neurons find each other? Neurons form complicated networks in brains, but their connections can't be random (at least not entirely). Brains function similarly among all members of individual species, and that functionality is largely dependent on neuron organization. Furthermore, various brain regions have predictable functions, and there are even parts of the brain where specific cells carry out specialized functions (place cells are an interesting example).
Great! We know neurons can organize into very complex networks, but how? They need to find each other, somehow.
The best I can guess is that either:
Neurons find other target neurons with specific chemical signals.
Neurons don't "find" each other, exactly, but grow in predetermined shapes from from set locations. In this case, the connections would simply be due to neurons bumping into each other as they grow in their predetermined paths.
Or both.
In the first case, there would be a mechanism for searching each other out. In the second, there would be a mechanism for staying in one spot (and growing from there). What are the names of said mechanisms? How do I find out more about them? Q: We know neurons can organize into very complex networks, but how?
The answer is your first guess: Neurons find other target neurons with specific chemical signals.
Q: What are the names of said mechanisms?
This process is called axon guidance, by which the growth cones of developing axons are directed to reach their targets. This process depends upon a slew of cellular and molecular cues. The first axons to grow in any particular brain region are called pioneer axons and are the most dependent upon these cues. Later axons are able to follow (and diverge from) previous axons by the interaction of cell adhesion molecules on their surfaces. Dendritic development is also important for your question, but dendrites tend not to travel as far.
Here are some of the molecules that we know to participate in axon guidance:
Cell adhesion molecules and substrate adhesion molecules, including IgSF CAMs and cadherins
Some chemokines, e.g. CXCL12
Netrins, ephrins, and semaphorins
Slits, via the Slit-Robo cell signaling pathway
Developmental morphogens, e.g. Wnts and Hedgehog
The following is multiple choice question (with options) to answer.
What is the place called where the axon of one neuron meets the dendrite of another? | [
"uptake",
"apoptosis",
"synapse",
"neurotransmitter"
] | C | The place where the axon of one neuron meets the dendrite of another is called a synapse . Synapses are also found between neurons and other types of cells, such as muscle cells. The axon of the sending neuron does not actually touch the dendrite of the receiving neuron. There is a tiny gap between them, the synaptic cleft ( Figure below ). |
SciQ | SciQ-4431 | organic-chemistry, inorganic-chemistry, physical-chemistry
Title: What are the main axis of research in Chemistry? I would like to know what are the main problems currently studied in Chemistry.
For some reason, it seems that there is far less vulgarisation in chemistry than the other fields, and it's hard to find an overview of the field accessible to a layman (compared to math or physics for instance).
I only found this wikipedia page, but I have no idea how relevant it is. Even though I voted to close this question as not constructive, these are among the most important unsolved problems in chemistry:
The following is multiple choice question (with options) to answer.
Organic chemistry is the study of the chemistry of what? | [
"hydrogen",
"metals",
"oxidation",
"carbon compounds"
] | D | Organic chemistry is the study of the chemistry of carbon compounds. |
SciQ | SciQ-4432 | 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.
Gastropods, cephalopods, and bivalves are examples of what class? | [
"cetaceans",
"invertebrates",
"mollusks",
"animals"
] | C | Mollusks are divided into ten living classes, including the familiar gastropods, cephalopods, and bivalves. |
SciQ | SciQ-4433 | cholesterol
Some LDL cholesterol circulating through the bloodstream tends to deposit in the walls of arteries. This process starts as early as childhood or adolescence.
White blood cells swallow and try to digest the LDL, possibly in to digest the LDL, possibly in an attempt to protect the blood vessels.
In the process, the white blood cells convert the LDL to a toxic (oxidized) form.
More white blood cells and other cells migrate to the area, creating steady low steady low-grade inflammation in the artery wall.
Over time, more LDL cholesterol and cells collect in the area. The ongoing process creates a bump in the artery wall called a plaque. The plaque is made of cholesterol, cells, and debris.
The process tends to continue, growing the plaque and slowly blocking the artery.
There is a good overview of the general physiology here in Robbins The Pathologic Basis of Disease. Chapter 5, Genetic Disorders, reviews the physiology, and the relevance to disease, in the section on Familial Hypercholesterolemia. The review is relevant to hypercholesterolemia in general.
The following is multiple choice question (with options) to answer.
What type of cholesterol is commonly referred to as bad? | [
"hdl",
"unsaturated",
"ldl",
"insulin"
] | C | When you get your cholesterol tested, they are measuring not only the total amount of cholesterol in the blood, but also whether it is being transported by LDL or HDL. All of these values are important for assessing the likelihood of a heart attack. Total cholesterol gives an idea of the overall cholesterol load in the body. The LDL cholesterol (sometimes referred to as “bad” cholesterol) is more likely to be incorporated into a cell or a plaque, so it is important that these levels below. Conversely, since cholesterol being carried by HDL (“good” cholesterol) is being transported away from the rest of the body and into the liver for disposal, higher HDL levels are generally considered beneficial. |
SciQ | SciQ-4434 | fracking, clathrates
Title: Do we know how large deposits of methane clathrates were formed in permafrost regions? We can see that there are large buildups of methane clathrates in permafrost regions. This seems different to the buildups of natural gas which fracking releases, which appear to have just come from escaped gases from oil/coal deposits.
My question is: Do we know how large deposits of methane clathrates were formed in permafrost regions? Rotting vegetation generates methane, or marsh gas as it is sometimes called. The most obvious method by which clathrates were formed in Arctic regions is that many years ago during summer and autumn, rotting vegetation produced methane, which combined with water at cold temperatures to produce methane ice, otherwise known as clathrates. Extremely cold temperatures are not necessary to form clathrates. They form at the bottom of deep seas, where the temperature even in the tropics is a constant 4 or 5 C. There are huge deposits of clathrates on the deep ocean floor, and there has been talk of exploiting them commercially.
A theory to explain the Permo-Triassic extinction event of 250 million years ago hypothesises that super-eruptions in the Siberian Traps super-volcano raised temperatures enough to release vast quantities of methane from tundras and ocean beds, so that with the additional greenhouse gas the average temperature rose by about 10 C, causing the extinction of nearly 90 percent of all large animals, a greater mass extinction than the better known event at the end of the Cretaceous.
The following is multiple choice question (with options) to answer.
Where does most natural gas come from? | [
"oceans",
"recycled cooking oil",
"wells that produce petroleum",
"alchemy"
] | C | Most natural gas comes from the wells that produce petroleum. An increasing amount comes from a new method. Hydraulic fracturing, called fracking , is very much in the news lately. Fracking makes it easier and quicker to get natural gas from the rock ( Figure below ). |
SciQ | SciQ-4435 | endocrinology, pathology, experimental, diabetes-mellitus
Title: Growth Hormone and diabetes Growth hormone and insulin like growth factors are diabetogenic, so I assume that people with high growth hormone (say due to pituitary tumor) may be at high risk for diabetes. Has any correlation been established between these two? I know that diabetes is a multifactorial disorder and so only a correlation may be established. Yes:
That GH has an effect on glycaemic control is most evident from the abnormal glucose tolerance seen in acromegalics...
acromegaly is defined as abnormal growth of the hands, feet, and face, caused by overproduction of growth hormone by the pituitary gland.
Such an effect has been known for decades, which makes sense given how interrelated the axes are. Although I think the best evidence is the fact that the side effects of growth hormone therapy says that Some patients have developed diabetes mellitus...
The following is multiple choice question (with options) to answer.
Medical problems associated with the body responding poorly to insulin are commonly associated with what disease? | [
"diabetes",
"colitis",
"AIDS",
"pertussis"
] | A | In some cases, an endocrine gland secretes a normal amount of hormone, but target cells do not respond to the hormone. Often, this is because target cells have become resistant to the hormone. Type 2 diabetes is an example of this type of endocrine disorder. In type 2 diabetes, body cells do not respond to normal amounts of insulin. As a result, cells do not take up glucose and the amount of glucose in the blood becomes too high. This type of diabetes is usually treated with medication and diet. The addition of extra insulin to the treatment can help some patients. |
SciQ | SciQ-4436 | 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.
The pancreatic hormones insulin and glucagon maintain glucose homeostasis by tightly regulating the synthesis and breakdown of what? | [
"lipids",
"enzyme",
"pathway",
"glycogen"
] | D | |
SciQ | SciQ-4437 | homework, embryology
Title: Why are Birds and Reptiles with abundant yolk sac polyspermic? I was given an explanation that birds and reptiles are polyspermic because they have an abundant yolk sac. But how does it explain the thing?
Chicken as an adult is not using in my opinion yolk as an energy source.
Yolk is used during embryogenesis as the primary energy source with blastula and gastrula -stages and during organogenesis, since the embryo needs proteins and energy somewhere.
How does abundant yolk sac make birds and reptiles polyspermic? My professor says that
The yolk sac is not connected to the mechanism of polyspermy or
monospermy. [Amount of yolk inside the oocyte is then again.] The
oocytes of reptiles and birds are yolk rich - polylecithal for instance.
where
lecithal = yolk containing and some pieces of information about here.
The following is multiple choice question (with options) to answer.
The marsupial embryo is nourished inside the uterus with food from a yolk sac instead of through a what? | [
"placenta",
"stomach",
"ovum",
"umbilical cord"
] | A | The marsupial embryo is nourished inside the uterus with food from a yolk sac instead of through a placenta. The yolk sac stores enough food for the short period of time the embryo remains in the uterus. After the embryo is born, it moves into the mother’s pouch, where it clings to a nipple. It remains inside the pouch for several months while it continues to grow and develop. Even after the offspring is big enough to leave the pouch, it may often return to the pouch for warmth and nourishment. Eventually, the offspring is mature enough to remain outside the pouch on its own. |
SciQ | SciQ-4438 | acid-base, analytical-chemistry, experimental-chemistry, extraction
Title: Separation of Binary mixture? I will be given a binary mixture containing two unknown compounds(the mixture could be either liquid or solid- I don't know yet). The plan of the experiment is to identify the two compounds. So my primary concern is to separate the binary mixture and purify the individual compounds(then the subsequent classification tests/NMR/IR analysis should be straightforward). I am thinking of doing an acid-base extraction but don't know how to since I don't know any physical properties of the compounds. Any suggestions would be appreciated. N.B.: the advice below mostly applies to organic compounds. If you're dealing with inorganic salts, or solutions thereof, the approach will be very different.
For a solid mixture, I would take an IR first. That should allow you to rule out potentially useless chemical tests by identifying the functional groups present in your mixture without wasting any of the sample. This would also give you some indication whether acid/base extraction is likely to be of any use. After that, it seems logical to test solubility in a wide range of solvents and at different temperatures. If you can find one that dissolves your mixture only partially at low temperature, but completely at high temperature, then you can likely separate the components immediately by recrystallization. Judicious use of a centrifuge can help if the crystals form a fine suspension.
In the case of a liquid mixture, I would again take an IR initially. In some cases, one component of the mixture can be chemically separated, and IR results would again be useful in determining the viability of that approach. Ketones and aldehydes, for example, will react to form semicarbazones that can be recrystallized and then identified by melting point. As far as physical methods of separation, standard are distillation and fractional freezing.
The following is multiple choice question (with options) to answer.
The substances that comprise heterogeneous mixtures can also be separated by what means? | [
"atmospheric",
"physical",
"thermal",
"chemical"
] | B | The substances that comprise heterogeneous mixtures can also be separated by physical means. We will discuss separation techniques in the following lesson. |
SciQ | SciQ-4439 | evolution, botany, development, fruit, seeds
What is the point of fruit if not to be eaten? It’s my understanding that organisms will adapt to survive and thrive. I understand that being eaten can spread seeds, but this just seems like too much of a risky tactic to rely on.
Following on from part one: If being eaten is the best way to spread seed, why do some plants avoid this (such as by being poisonous or thorny)? Seeds are spread by many mechanisms
Wind dispersal: When air currents used to spread seeds. Often these plants have evolved features to facilitate wind catching, for example dandelions. Aka, anemochory.
Propulsion & bursting: When seeds are propelled from the plant in an such as in these videos. This is called Ballochory.
Water: Similarly to wind dispersal plants can spread seeds by water movement/currents, aka Hydrochory. This is used by many algae and water living plants.
Sticky Seeds: There are many ways a seed can attach to the outside of an animal - by using hooks, barbs, sticky excretions, hairs. Seeds then get carried by an animal and fall off later. This is epizoochory.
Fruiting: Plants can use seed-bearing fruit to encourage animals to eat the seeds. They will then be spread when the waste is excreted after digestion. This is a process of endozoochory.
More than one way to spread a seed
The following is multiple choice question (with options) to answer.
What type of organism has spores that are spread by water and wind? | [
"Plants",
"yeast",
"fungi",
"Trees"
] | C | Spores may be dispersed by moving water, wind, or other organisms. Some fungi even have “cannons” that “shoot” the spores far from the parent organism. This helps to ensure that the offspring will not have to compete with the parents for space or other resources. You are probably familiar with puffballs, like the one in Figure below . They release a cloud of spores when knocked or stepped on. Wherever the spores happen to land, they do not germinate until conditions are favorable for growth. Then they develop into new hyphae. |
SciQ | SciQ-4440 | parasitology
Title: Tapeworms and their effect on humans I've read that some people in some countries actually use tapeworms as a form of losing weight. What are the dangers to these people? I haven't really found much on this topic (besides popular sites) but I can summarize it here:
There are quite some tapeworms (or cestoda), I found numbers of up to 3500 species. They attach to the intestinal wall of the humans and then start to take up predigested food through their skin. With that, they reduce food from their host and start to grow, some get as long as 15 meters!
Some of the worms seem to be relatively harmless (besides stealing food), but this is more true for the first world. In poor countries, where there is not enough food, tapeworms can cause severe malnutrition.
Some tapeworms can migrate into the blood stream and from there into other tissues or organs like muscles, eye and brain. There they can cause cysts which can lead to organ failure and death.
For more information see this CDC webpage and this article: "Biochemistry and physiology of tapeworms.". This popular article is probably also interesting.
The following is multiple choice question (with options) to answer.
Through which organ do hookworm larvae enter the human body? | [
"through the rectum",
"through the mouth",
"through the lungs",
"through the skin"
] | D | Parasitic roundworms may have plant, vertebrate, or invertebrate hosts. Several species have human hosts. For example, hookworms, like the one in Figure below , are human parasites. They infect the human intestine. They are named for the hooks they use to grab onto the host’s tissues. Hookworm larvae enter the host through the skin. They migrate to the intestine, where they mature into adults. Adults lay eggs, which pass out of the host in feces. Then the cycle repeats. |
SciQ | SciQ-4441 | thermodynamics
In your question you talk about heating up the gas, the gas losing energy by doing work on the piston and its pressure dropping - for that case the piston must reduce its pressure on the gas, otherwise the piston would compress the gas.
The best example I can think of to relate directly to your question is if the cylinder is in a heat bath that keeps it at constant temperature and the piston is free to move. Then the volume, $V$, can increase and the pressure, $P$, will drop and heat will go into the gas, which will be converted into work done in pushing back the cylinder. The temperature of the gas will be constant.
The following is multiple choice question (with options) to answer.
Inside a cylinder, thermal energy is converted to what type of energy of the moving piston? | [
"residual energy",
"kinetic energy",
"horsepower",
"electrochemical energy"
] | B | Thermal energy is converted to the kinetic energy of the moving piston inside the cylinder. The moving piston, in turn, can be used to turn a turbine or do other useful work. |
SciQ | SciQ-4442 | 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.
To the extent that behaviors are controlled by what, they may evolve through natural selection? | [
"rna",
"dna",
"mutation",
"genes"
] | D | To the extent that behaviors are controlled by genes, they may evolve through natural selection. If behaviors increase fitness , they are likely to become more common over time. If they decrease fitness, they are likely to become less common. |
SciQ | SciQ-4443 | human-anatomy, muscles
Title: Contracting muscles in humans I study biology at school, and unfortunately for me, my program skips the muscles in humans chapter.
I know (and mainly, feel) that the movement in one direction isn't created by the same muscle as the movement in the opposite direction, e.g the Triceps ("front") and Biceps ("back").
I know that the triceps straightens the elbow, while the biceps contracts the elbow.
I also know that, instead of actually moving the arm, I can contract these two muscles (when I show off, for example...) without actually moving the arm. That area becomes hard. Both muscles, as I feel, are contracting. I cannot statically contract only one of them.
My question is whether this action is something "special", or simply both muscles working against each other, resulting in zero movement? The situation you are describing where muscles are situated on opposites sides of a joint and produce opposing movements is called "antagonism." Most joints are set up where one or more muscles on either sides will produce such movements (e.g., flexors vs. extensors). Here's a question about muscles without antagonists.
When you contract all the muscles crossing a joint (i.e., when you are "showing off"), the muscles balance each other. If not, the bones would move and the joint angles would change. So taking the elbow as an example, in the image below, Arnold is contracting the elbow flexors (biceps brachii, brachialis) as well as the elbow extensors (triceps brachii). In order for the bones to remain static, the forces must be equal and opposite.
The following is multiple choice question (with options) to answer.
What kind of muscle relationship generally produces back-and-forth movement of a body part? | [
"synchronized muscles",
"complementary muscles",
"cooperative muscles",
"antagonistic muscles"
] | D |
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