source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-5044 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
What is the name of the outer layer of skin? | [
"hypodermis",
"endodermis",
"the epidermis",
"the dermis"
] | C | The epidermis is the outer layer of skin, consisting of epithelial cells and little else (see Figure below ). For example, there are no nerve endings or blood vessels in the epidermis. The innermost cells of the epidermis are continuously dividing through mitosis to form new cells. The newly formed cells move up through the epidermis toward the skin surface, while producing a tough, fibrous protein called keratin . The cells become filled with keratin and die by the time they reach the surface, where they form a protective, waterproof layer called the stratum corneum . The dead cells are gradually shed from the surface of the skin and replaced by other cells. |
SciQ | SciQ-5045 | humidity, water-vapour
Title: Water vapor content versus specific humidity I am wondering the difference between water vapor content and specific humidity to determine the moisture availability in the atmosphere. Which one is more acceptable variable to determine the moisture availability in the atmosphere?
I need to show the moisture availability in the atmosphere in my study. So should I explain it through water vapor content or through specific humidity? I will explain the rainfall deficiency over a region For a study relating to rainfall, I would be inclined to look at total column water vapour (TCWV), also known as integrated water vapour (IWV) or precipitable water. They're all (more or less) the same thing.
The company Remote Sensing Systems describes it as:
Total column water vapor is a measure of the total gaseous water contained in a vertical column of atmosphere. It is quite different from the more familiar relative humidity, which is the amount of water vapor in air relative to the amount of water vapor the air is capable of holding. Atmospheric water vapor is the absolute amount of water dissolved in air. When measured in linear units (millimeters, mm), it is the height (or depth) the water would occupy if the vapor were condensed into liquid and spread evenly across the column. Using the density of water, we can also report water vapor in kg/m2 = 1 mm or g/cm2 = 10 mm.
For rain to form, clouds need to form first. Clouds need cloud condensation nuclei, but crucially, for clouds to form, the water vapour partial pressure needs to reach the saturation vapour pressure. The latter is strongly dependent on temperature (Clausius-Clapeyron relation), so a profile of relative humidity is not the most directly useful quantity. The total column water vapour describes how much liquid water might form, which is why it is sometimes even described as precipitable water.
You can get this product either from reanalysis (like ERA-5) or retrieved from hyperspectral infrared sounders, such as IASI, AIRS, or CrIS. Depending on where and when in the world you're looking at, there may also exist products from geostationary instruments.
The following is multiple choice question (with options) to answer.
What is the major source of water vapor in the atmosphere? | [
"streams",
"sea",
"drift",
"ocean"
] | D | Oceans are the major source of water vapor in the atmosphere. Sunlight heats water near the sea surface ( Figure below ). As the water warms, some of it evaporates. The water vapor rises into the air, where it may form clouds and precipitation. Precipitation provides the freshwater needed by plants and other living things. |
SciQ | SciQ-5046 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
The release of mature eggs that occurs at the midpoint of each cycle is called? | [
"induction",
"fertilization",
"ovulation",
"semination"
] | C | |
SciQ | SciQ-5047 | transcription, translation
Ralston, A. (2008) Operons and prokaryotic gene regulation. Nature Education
From Genes to Genomes: Concepts and Applications of DNA Technology
Molecular cell biology
Analysis of Genes and Genomes
The following is multiple choice question (with options) to answer.
What are the three ways to control the transcription of an operon? | [
"repressive, activator, inducible",
"transparent , activator , inducible",
"hormonal, repressive, activator,",
"repressive, activator, spontaneous"
] | A | 16.2 Prokaryotic Gene Regulation The regulation of gene expression in prokaryotic cells occurs at the transcriptional level. There are three ways to control the transcription of an operon: repressive control, activator control, and inducible control. Repressive control, typified by the trp operon, uses proteins bound to the operator sequence to physically prevent the binding of RNA polymerase and the activation of transcription. Therefore, if tryptophan is not needed, the repressor is bound to the operator and transcription remains off. Activator control, typified by the action of CAP, increases the binding ability of RNA polymerase to the promoter when CAP is bound. In this case, low levels of glucose result in the binding of cAMP to CAP. CAP then binds the promoter, which allows RNA polymerase to bind to the promoter better. In the last example—the lac operon—two conditions must be met to initiate transcription. Glucose must not be present, and lactose must be available for the lac operon to be transcribed. If glucose is absent, CAP binds to the operator. If lactose is present, the repressor protein does not bind to its operator. Only when both conditions are met will RNA polymerase bind to the promoter to induce transcription. |
SciQ | SciQ-5048 | organic-chemistry, redox
As you can see, the ketone gets oxidised, more precisely the carbonyl carbon gets oxidised as increases its oxidation state. On the other side, the peroxide oxygens get reduced as they decrease their oxidation state.
The following is multiple choice question (with options) to answer.
Peroxisomes carry out oxidation reactions that break down what acids? | [
"fatty acids and amino acids",
"stomach acids",
"acetic acids",
"nitric acids"
] | A | Peroxisomes Peroxisomes are small, round organelles enclosed by single membranes. They carry out oxidation reactions that break down fatty acids and amino acids. They also detoxify many poisons that may enter the body. Alcohol is detoxified by peroxisomes in liver cells. A byproduct of these oxidation reactions is hydrogen peroxide, H2O2, which is contained within the peroxisomes to prevent the chemical from causing damage to cellular components outside of the organelle. Hydrogen peroxide is safely broken down by peroxisomal enzymes into water and oxygen. |
SciQ | SciQ-5049 | difference of two vectors is still a vector. Since mass is a scalar quantity and velocity is a vector quantity, we can derive that momentum must therefore be a vector quantity as the product of a vector with a scalar is a vector. Linear momentum is a vector quantity. Just checking; you are saying it can be either, depending on whether the index is "up" or "down"? Here we will demonstrate the power of 4-vector thinking by deriving the momentum 4-vector, of which the momentum 3-vector is a part. Momentum is a vector because it is the product of a scalar and a vector. But, we can also think of momentum as the product of mass with 4-velocity, which is a 4-vector. The teacher quickly inverts the can containing boiling water into a bowl of cold water, as shown in the diagram. Momentum of an object is the product of its mass and velocity (p=m x v). Get the first item in a sequence that matches a condition, How does one maintain voice integrity when longer and shorter notes of the same pitch occur in two voices, How to \futurelet the token after a space. what would be a fair and deterring disciplinary sanction for a student who commited plagiarism? Momentum is a vector: It has a direction as well as a magnitude. ⃗⃗⃗ = m ∙ Momentum is a vector quantity that has the same direction as the velocity of the object and a magnitude m times the velocity. Momentum is in the same direction as velocity. In situations like this the momentum is usually stated to be positive to the right, and negative to the left. Momentum is frequently expressed as ##p=mv##, where ##p## is momentum, ##m## is mass, and ##v## is the velocity. Thanks for contributing an answer to Physics Stack Exchange! Momentum is a vector quantity. When the can is inverted in the cold water, the can collapses. It collides with a car (m2) traveling east at 22 m/s. African sleeping sickness is due to (a) Plasmodium vivax transmitted by Tsetse fly (b) Trypanosoma lewsii transmitted by Bed Bug (c) Trypanosoma gambiense transmitted by Glossina palpalis (d) Entamoeba gingivalis spread by Housefly. *Response times vary by subject and question
The following is multiple choice question (with options) to answer.
The magnitude of the momentum vector is the product of what two properties? | [
"acceleration and speed",
"volume and speed",
"mass and speed",
"work and speed"
] | C | Momentum is a vector that points in the direction of the velocity vector. The magnitude of this vector is the product of mass and speed. |
SciQ | SciQ-5050 | evolution, biochemistry, physiology, speculative, bioinorganic-chemistry
While iron skeletons might seem to be an advantage, they are electrochemically unstable - oxygen and water will tend to oxidize (rust) them quickly and the organism would have to spend a lot of energy keeping it in working form. Electrical conductivity sounds useful, but the nervous system favors exquisite levels of control over bulk current flow, even in cases like electric eels, whose current is produced by gradients from acetylcholine.
What's more, biological materials actually perform as well as or better than metal when they need to. Spider silk has a greater tensile strength than steel (along the direction of the thread). Mollusk shells are models for tank armor - they are remarkably resistant to puncture and breakage. Bone is durable for most purposes and flexible in addition.
The time it would take for metallized structures to evolve biologically are likely too long. By the time the metalized version of an organ or skeleton got started, the bones, shells and fibers we know probably have a big lead and selective advantage.
The following is multiple choice question (with options) to answer.
Hydrostatic skeletons are well suited for life in what kind of environments? | [
"bacterial",
"pelagic",
"surface",
"aquatic"
] | D | |
SciQ | SciQ-5051 | 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.
How do prokaryotic organisms reproduce asexually? | [
"mitosis",
"kinetic fission",
"residual fission",
"binary fission"
] | D | Prokaryotic organisms reproduce asexually by binary fission , a process that produces identical offspring ( Figure below ). In asexual reproduction , a single parent produces genetically identical offspring. As prokaryotes do not have a nucleus, and have only one circular chromosome, they do not need to reproduce by the same mechanism as eukaryotic cells; mitosis does not exist in prokaryotic cells . Prokaryotic cell division is a much simpler process. In prokaryotic cell division, after the single chromosome is copied, the cell grows larger. Eventually the two chromosomes separate and move to opposite ends of the cell. Newly formed cell membrane then grows into the center of the cell, separating the two chromosomes, and forming two genetically identical daughter cells. Some eukaryotic organelles, such as mitochondria and chloroplasts, also divide by binary fission. |
SciQ | SciQ-5052 | evolution, zoology, adaptation
One answer that came to mind is domestic animals - the horse and dog in prehistory, the cat in ancient Egypt, etc. That seems too obvious on one hand, and on the other hand may not really be an answer, as there seems to be no indication that pre-domestic animals were endangered by humans in any meaningful way. Are there animals that have significantly adapted themselves to surviving as wild animals in human-influenced environments? Note: This is an answer to the last line of your question.
A classical example of animals adapting to the influence of humans on their environment is the adaption of the Peppered Moth.
Here is a brief summary:
The peppered moth was originally a mostly unpigmented animal (<1800). During the industrial revolution in the southern parts of the UK a lot of coal was burned. This led to soot blackening the countryside. Soon afterwards, a fully pigmented variety was first observed. Only a hundred years later, in 1895, this pigmented variety almost completely displaced the unpigmented variety.
It has been shown that the pigmentation is under strong selective pressure as birds hunt these moths. Since birds rely on their visual system to detect their prey, the variety that blends in with its environment (=camouflage) has a selective advantage over the variety that stands out.
As pointed out by Tim in the comments, since the 1970s there has been a rapid reversal with unpigmented animals being more abundant. As far as I understand, it is accepted that this reversal is due to a decrease in human induced air pollution leading to less sooty barks on trees which makes the unpigmented variety harder to prey upon.
Addendum: genetic basis of adaption
In a beautiful recent study, the causal mutation for the pigmented, or melanic, variety was identified: A ~9kb transposon insertion in the first intron of the gene cortex. The authors calculate that this mutation happened in the year 1819, a few years after the industrial revolution was in full swing. The interpretation is that due to sooty tree bark this mutation, causing pigmented moth, was under strong selection.
The following is multiple choice question (with options) to answer.
Many species use their body shape and coloration to avoid what? | [
"detection by predators",
"sunlight",
"exposure",
"human contact"
] | A | Many species use their body shape and coloration to avoid being detected by predators. The tropical walking stick is an insect with the coloration and body shape of a twig which makes it very hard to see when stationary against a background of real twigs (Figure 45.20a). In another example, the chameleon can change its color to match its surroundings (Figure 45.20b). Both of these are examples of camouflage, or avoiding detection by blending in with the background. |
SciQ | SciQ-5053 | biochemistry, ecology, marine-biology, climate-change
So... raising temps can cause less mixing of water due to more stratification (layering), which results in less water in the ocean available to absorb and hold the CO2. This means that as atmospheric CO2 continues to increase, the non-mixing surface layer of ocean water (which will become saturated with CO2 at some point) won't be able to keep up with more and more and more CO2 in the air. As a result, the ocean will decline (and eventually potentially fail) in its ability to "buffer" the ever increasing CO2 in the air. This would mean that the rate of CO2 in the air will start increasing more rapidly (since less and less of it is being absorbed by the oceans).
As for the phytoplankton (which are in this top layer of water), this stratification will not directly result in less CO2 availability to them. As atmospheric CO2 increases, so will the amount in this top layer of water. The rate of increase in CO2 concentration will just slow until a saturation point is reached, but absolute levels will not decline.
Though, note, however, that phytoplankton tend to thrive in areas of high nutrients (i.e., upwelling zones). Less mixing of waters will decrease the upwelling of nutrient-rich, cooler subsurface water. So less mixing (i.e., more stratification) likely would lead to declines in phytoplankton abundance due to decreased nutrients availability. (See here). Perhaps this decreased nutrient availability (which would include loss of carbon sources) is related to what you're referring to?
Read here for some more thoughts: https://earthobservatory.nasa.gov/features/OceanCarbon
Raising Temperatures may decrease CO2 solubility
However, given all this, the solubility of CO2 in water does decline with increasing temperature (see here for raw data). This suggests that some rise in global temps may impact CO2 concentration in ocean waters.
The following is multiple choice question (with options) to answer.
What property of ocean water increases rapidly as the water gets deeper? | [
"pressure",
"salt content",
"speed",
"visability"
] | A | The pressure of ocean water increases rapidly as the water gets deeper. |
SciQ | SciQ-5054 | electrons, charge, conventions, history
Title: What would have happened if electron was considered positive? We always keep on telling that current flows opposite to electron, since electron is negatively charged. And old people didn't knew, that it is electron which actually flows..
So, now if we correct them and change the convention. And consider electron as positive, what will happen?
Will our laws get mutated?
Is there a reason of taking electron negative and proton positive? Obviously our laws have to change. Because we redefine the direction of current and leave the direction of magnetism unaffected, the result must be that right-hand rule changes into a left-hand rule. After all, reality does not change. Electrons moving in a given direction still cause the same magnetic fields.
The following is multiple choice question (with options) to answer.
Remember electrons are negatively charged, so ions with a positive charge have lost what? | [
"electron",
"proton",
"neutron",
"atom"
] | A | Solution First, write out the electron configuration for each parent atom. We have chosen to show the full, unabbreviated configurations to provide more practice for students who want it, but listing the coreabbreviated electron configurations is also acceptable. Next, determine whether an electron is gained or lost. Remember electrons are negatively charged, so ions with a positive charge have lost an electron. For main group elements, the last orbital gains or loses the electron. For transition metals, the last s orbital loses an electron before the d orbitals. (a) Na: 1s22s22p63s1. Sodium cation loses one electron, so Na+: 1s22s22p63s1 = Na+: 1s22s22p6. (b) P: 1s22s22p63s23p3. Phosphorus trianion gains three electrons, so P3−: 1s22s22p63s23p6. (c) Al: 1s22s22p63s23p1. Aluminum dication loses two electrons Al2+: 1s22s22p63s23p1 = Al2+: 1s22s22p63s1. (d) Fe: 1s22s22p63s23p64s23d6. Iron(II) loses two electrons and, since it is a transition metal, they are removed from the 4s orbital Fe2+: 1s22s22p63s23p64s23d6 = 1s22s22p63s23p63d6. Sm: 1s22s22p63s23p64s23d104p65s24d105p66s24f6. Samarium trication loses three electrons. The first two will be lost from the 6s orbital, and the final one is removed from the 4f orbital. Sm3+: 1s22s22p63s23p64s23d104p65s24d105p66s24f6 = 1s22s22p63s23p64s23d104p65s24d105p64f5. |
SciQ | SciQ-5055 | biochemistry, bioenergetics, lipids
Title: Why is hydrogen to oxygen ratio used to compare energy storage efficiency? I came across an article that says that lipids are more efficient energy storage molecules compared to starch because lipids have higher “hydrogen to oxygen ratio”.
I do not understand how “hydrogen to oxygen ratio” equates to more efficient energy storage.
I am guessing that since energy production have to do with reducing NAD+, so “hydrogen to oxygen ratio” is a measure of the ability to reduce NAD+. And since NADH is then later used in oxidative phosphorylation in mitochondria to produce energy currency ATP, “hydrogen to oxygen ratio” is a measure of the potential amount of ATP the molecule is able to produce. And thus it is a measure of energy storage efficiency.
Is this correct? Answer
In my opinion:
The original poster’s overall interpretation of the statement in the article (as
reported) is most likely correct.
Problems with original statement
Although the statement may be clear in context, I would rephrase it because of two specific objections I have to it. These are:
“Energy storage efficiency” in isolation is ambiguous. It is not clear whether it refers to storage per unit mass or per unit volume, both of which may be considerations for living organisms.
“Hydrogen to oxygen ratio” is an imperfect heuristic for the reduction state of the carbon backbone.
I would also be specific in naming the lipids involved in ‘energy storage‘ — there are other lipids (e.g. steroids) that are not used as energy stores.
So my restatement (adapted from Berg et al. ‘Biochemistry’) would be:
Triacylglycerols are more concentrated stores of metabolic energy than
polysaccharides such as starch or glycogen because they are more
highly reduced. The energy yield per gram from the complete oxidation
of triacylglycerol is over twice that from polysaccharides (38 kJ/g
cf. 17 kJ/g).
Comments on restatement
The following is multiple choice question (with options) to answer.
What type of starch is used for long-term energy storage in animal cells? | [
"rigid",
"enzyme",
"glycogen",
"fructose"
] | C | Starches are one of the more common polysaccharides. Starch is made up of a mixture of amylose (15–20%) and amylopectin (80–85%). Amylose consists of a linear chain of several hundred glucose molecules and amylopectin is a branched molecule made of several thousand glucose units. Starches can be digested by hydrolysis reactions , catalyzed by enzymes called amylases , which can break the glycosidic bonds. Humans and other animals have amylases, so they can digest starches. Potato, rice, wheat, and maize are major sources of starch in the human diet. The formations of starches are the ways that plants store glucose. Glycogen is sometimes referred to as animal starch. Glycogen is used for long-term energy storage in animal cells. Glycogen is made primarily by the liver and the muscles. |
SciQ | SciQ-5056 | cell-biology, nutrition, blood-circulation, liver
Title: How do nutrients get to the cells they need to get to? I understand the basics of digestion. I know that nutrients get absorbed by the microvilli, enter the bloodstream and travel to the liver but after all that, what is the biological mechanism that guides these nutrients to the proper receiving location? Broadly speaking, nutrients that enter the blood from the gut, and those that are released into the blood by the liver, are available to any cells that require them. So there is no "guiding to the correct location" in the sense that you suggest.
Lipids for example are present in the various lipoproteins and can be acquired from these by all cells. Iron is bound to transferrin, and any cell with transferrin receptors can internalise the transferrin and take the iron. Glucose is available in solution in the plasma, and free fatty acids are bound to serum albumin in the blood. During starvation the liver produces ketones ("ketone bodies") which are taken up by many different tissues/cell types.
The following is multiple choice question (with options) to answer.
What contracts to move food throughout the gastrointestinal tract? | [
"nerves",
"vessels",
"fluids",
"muscles"
] | D | waves of muscle contractions in the organs of the gastrointestinal tract that keep food moving through the tract. |
SciQ | SciQ-5057 | newtonian-mechanics, electromagnetism, forces, free-body-diagram
Title: Forces acting on a magnet and paper clip Suppose a paper clip is stuck to a surface, with tape for example. A magnet is placed close to the clip, and starts moving towards it. Now, there is a force acting on the clip from the magnet, but is there a force acting on the magnet from the clip? Does Newton's third law apply literally here? Absolutely yes, third Newton's law is satisfied in this case too. Maybe when you think in a magnet heavier than the clip you may think that there are no forces acting in the magnet, but you can think in a little magnet close to a heavy metal object, the object doesn't move and the magnet moves in the object's direction. Because of the magnetic field the clip gets magnetized, that means that the clip gets a magnetic induction field in the direction of the magnet's field and that creates a new magnetic field that attracts other magnetic objects, included the initial magnet.
The following is multiple choice question (with options) to answer.
A magnet can exert force on objects without touching them, as long as they are within what? | [
"gravitational field",
"audio field",
"molecular field",
"magnetic field"
] | D | A familiar example may help you understand the vibrating electric and magnetic fields that make up electromagnetic waves. Consider a bar magnet, like the one in the Figure below . The magnet exerts magnetic force over an area all around it. This area is called a magnetic field. The field lines in the diagram represent the direction and location of the magnetic force. Because of the field surrounding a magnet, it can exert force on objects without touching them. They just have to be within its magnetic field. |
SciQ | SciQ-5058 | human-biology, evolution
Humans are off the charts in the amount of resources we invest in our children - our lives are 1/4 to 1/3 over before we sometimes leave our parents household (in some societies of course they never leave the house, but step into an extended family). This may be one of the reasons we are so successful as a species - we live in practically every place we possibly could and have no danger of competition from any other living thing excepting ourselves.
The grandmother effect is essentially the idea that if women, who are more attached to the offspring in more cases than fathers, continue to live and help support the grandchildren and make them more successful, then this will allow post menopausal women to have a longer lifespan (which they do).
The evolutionary biologist Sara Hrdy, emeritus UC Davis, has written quite a bit about the nuances of the evolution of the role of motherhood - reading some of her articles or books might give you a deeper sense of how profoundly filial love has shaped human beings.
--- more answer this stuff may or may not be worth reading depending on how broadly you want to understand this question...
Its important to say that many of the expansions of human average human lifespan have not been genetic. Its commonly cited that sewer systems, clean water, antibiotics and plentiful food are the three most important factors in human lifespan - and before modern developed world nations, the average lifespan of human beings was somewhere in the 30s. And there are significant lifespan differences in regions where these factors and others (education of women, access to prenatal and early care etc) are available.
Studies continue to be published that examine environmental and lifestyle factors compared to genetics and it seems that environment and lifestyle can make an astounding difference.
But genetics undoubtedly has a role to play here too. There are probably some individual humans and animals which have evolved to live longer. This has been found to be genetically related in some humans by demographics and family lines.
The following is multiple choice question (with options) to answer.
What field of science seeks to explain how traits are passed on from one generation to the next? | [
"genetics",
"quantum physics",
"zoology",
"biochemistry"
] | A | Genetics is the study of inheritance. The field of genetics seeks to explain how traits are passed on from one generation to the next. |
SciQ | SciQ-5059 | organic-chemistry, nomenclature, hydrocarbons
Title: Preferred IUPAC names for branched unsaturated hydrocarbons (polyenes)?
What are the preferred IUPAC names for the following three compounds?
Compound 1 is 3-ethenylhexa-1,5-diene. 2 is 3-methylidenehexa-1,5-diene.
But I am still not sure about 3. I have narrowed it down to two choices: 3-ethylidenehexa-1,5-diene or 4-ethenylhexa-1,4-diene.
How do I decide which two of the three double bonds should be in the parent chain, considering that both choices of parent chain have the same number of complex and double bonds?
The information I used is from the following Q&As:
How is a side-group that contains a double bond named?
How do you name an alkene using IUPAC rules if the longest carbon chain in this alkene does not include the double bond? According to the general methodology described in the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), a double bond is expressed by changing the ending ‘ane’ of the name of the corresponding saturated parent structure to ‘ene’.
P-31.1.1.1 The presence of one or more double or triple bonds in an otherwise saturated parent hydride (…) is denoted by changing the ending ‘ane’ of the name of a saturated parent hydride to ‘ene’ or ‘yne’. Locants as low as possible are given to multiple bonds as a set, even though this may at times give ‘yne’ endings lower locants than ‘ene’ endings. If a choice remains, preference for low locants is given to the double bonds. In names, the ending ‘ene’ always precedes ‘yne’, with elision of the final letter ‘e’ in ‘ene’. Only the lower locant for a multiple bond is cited, except when the numerical difference between the two locants is greater than one, in which case the higher locant is enclosed in parentheses.
(…)
For example:
The following is multiple choice question (with options) to answer.
Saturated hydrocarbons get their name because they are saturated with what atoms? | [
"helium",
"nitrogen",
"hydrogen",
"oxygen"
] | C | Saturated hydrocarbons have only single bonds between carbon atoms, so the carbon atoms are bonded to as many hydrogen atoms as possible. In other words, they are saturated with hydrogen atoms. |
SciQ | SciQ-5060 | optics, vision
Title: Insides of eyelids and light People commonly see the insides of their eyelids and see a little amount of light and no amount of light of the insides of their eyelids depending on what environment they're in, What's the difference of seeing the amount of light of the insides of their eyelids? Your eyelids are partially transparent to light. In the presence of a strong light source, even with eyes closed some light will make it through. Usually it will be reddish after passing through the skin filled with blood vessels.
You may also see greenish, yellowish, magenta, or purplish images that fade after closing your eyes. These are called after-images and are the result of the chemicals in your retina resetting themselves after light is removed. They typically consist of cyan, magenta, and yellow which are are opposite colors of your cone receptors: red, green, and blue.
The following is multiple choice question (with options) to answer.
What is the name of the black opening in the eye that lets light enter? | [
"pupil",
"inlet",
"cornea",
"iris"
] | A | Next, light passes through the pupil. The pupil is a black opening in the eye that lets light enter the eye. |
SciQ | SciQ-5061 | organic-chemistry, everyday-chemistry, experimental-chemistry, biochemistry, food-chemistry
Title: How Bread is made with yeast, sugar and luke warm milk? Materials and Apparatus:
wheat flour
sugar
dry yeast
glass bowl
covering plate
milk
Procedure:
Lukewarm milk is taken in the glass bowl and sugar is added to it. Then, yeast is added to the same.
The mixture is left undisturbed for 10-12 minutes to activate the yeast
3 cups of wheat flour are added to the bowl containing the milk mixture.
The mixture is mixed thoroughly with 100ml of added water and the dough is kneaded well
The dough is placed in a bowl, covered with a plate and left undisturbed for 2 hours.
My query/confusion:
Why is milk needed?
"activated yeast"- what's the difference?
Can yeast work without sugar or milk.
Detail out the stages of the anaerobic oxidative process which takes place as a common first step in both aerobic and anaerobic respiration.
Finally, feel free to share anything I may be missing which should be here.
If you have any confusion regarding what I want to ask, please ask in the comments. Please upvote if you are curious about it too
milk is not needed, 'pure' bread is without milk
yeast is a fungus, therefore, it is alive. Its best to work with fresh yeast, which you find as small cubes in the refrigerated section. This one does not have to be activated. non-fresh yeast is dried, so in order for it to work properly, it has to be undried by adding water, which is called activation.
and 4. As said before, milk is not needed. Sugar however is the food for the yeast, without it, it does nothing. In aerobic breathing, the yeast metabolizes the sugar as we would: sugar + oxygen -> water + CO2. Without oxygen, the yeast resorts to ethanol fermentation: sugar -> alcohol + CO2 (this is, why it is used to make beer or wine). For making bread, we have a mixture of both respirations, which does not really matter, since we are only interested in the CO2, which makes the dough fluffy =) But without sugar, there is no CO2.
The following is multiple choice question (with options) to answer.
Enzymes in saliva help bread down and digest what? | [
"starches and water",
"starches and fats",
"fiber and minerals",
"water and fiber"
] | B | Figure 16.5 (a) Digestion of food begins in the mouth. (b) Food is masticated by teeth and moistened by saliva secreted from the salivary glands. Enzymes in the saliva begin to digest starches and fats. With the help of the tongue, the resulting bolus is moved into the esophagus by swallowing. (credit: modification of work by Mariana Ruiz Villareal). |
SciQ | SciQ-5062 | 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.
What comes first in the life cycle of a plant? | [
"pair",
"garden",
"flower",
"seed"
] | D | |
SciQ | SciQ-5063 | photosynthesis, chloroplasts
Title: Chloroplasts in an animal cell What would happen if we inject a chloroplast organelle into an animal cell?
Will the animal cell destroy it? Or is it possible that the chloroplast will somehow survive, and even replicate? Could there be photosynthesis in such a cell, or will some of the necessary mechanisms be missing? To answer your bigger question:
Yes, most of this is possible - under some conditions -, and animals and animal cells can acquire chloroplasts, and use them.
E.g.: see Elysia chlorotica whose cells actively take up chloroplasts and use them, and keep them alive (though not replicating). - Though some genes of algae are also contained in the Elysia chlorotica genome - which may be considered as partial replication.
Also there are salamanders that have replicating algae within them (since embryogenesis) - even algae (with chloroplasts) within animal cells - though here the algae might be rather understood as symbionts or "cell types", and the animal cells don't have the chloroplasts by themselves.
The following is multiple choice question (with options) to answer.
Within the chloroplast, synthesis of what takes place in the fluid inside the inner membrane called the stroma? | [
"sugar",
"fructose",
"wheat",
"glucose"
] | A | Figure 4.17 The chloroplast has an outer membrane, an inner membrane, and membrane structures called thylakoids that are stacked into grana. The space inside the thylakoid membranes is called the thylakoid space. The light harvesting reactions take place in the thylakoid membranes, and the synthesis of sugar takes place in the fluid inside the inner membrane, which is called the stroma. Chloroplasts also have their own genome, which is contained on a single circular chromosome. |
SciQ | SciQ-5064 | dna, gene-expression
Title: Complexity in creating transgenic animals (e.g., mice) Many papers I have seen describing transgenic rodent models (and presumably applicable to other model organisms) involve the knock-in, or modification to, a single gene, possibly two genes. With respect to recombineering techniques, what prevents targeting multiple genes in a single organism? For instance, if I wanted to simultaneously knock-in some genes and knock-out others within the same mouse, would I be forced to generate individually modified transgenic lines and then do some "fancy" breeding to generate the multiple-modified mice? One reason is the low likelihood of success. Modifying a gene almost always involves a recombination event of plasmid DNA with a target site in the genome (and I say almost just because there may be some method that I don't know about, but all the ones I'm familiar with do). The likelihood of that decreases exponentially with the number of genes you're trying to modify. If you're trying to make several mutants of individual genes the likelihood of success decreases only linearly.
Another reason is having more knowledge and experimental power. You can learn little from a double mutant if you don't also have the individual mutants to compare. In fact, most reviewers would ask for individual mutant data if you've made a double mutant in your paper. This is especially true with flies and worms, as crosses take less time with them.
Also, the more mutant genes you have, the weaker the animal. Your mutants may not be viable at all with too many mutations.
The following is multiple choice question (with options) to answer.
When referring to genes, what term describes the property of having multiple phenotypic effects? | [
"xerophyte",
"prototype",
"pleiotrophy",
"archetype"
] | C | Many genes have multiple phenotypic effects, a property called pleiotropy. |
SciQ | SciQ-5065 | gazebo, rviz, urdf, ros-kinetic, solidworks
<link name="link1">
<inertial>
<mass value="0.11529" />
<inertia ixx="1.2008E-05" ixy="-4.262E-05" ixz="-2.59095E-05" iyy="2.743395E-05" iyz="4.1807E-05" izz="2.794303E-05" />
</inertial>
<visual>
<origin xyz="0.001 -0.038 0.02" rpy="-1.7 0 0" />
<geometry>
<mesh filename="package://ros_as/meshes/link1.STL" />
</geometry>
<material name="">
<color rgba="0.77647 0.75686 0.73725 1" />
</material>
</visual>
</link>
<link name="link2">
<inertial>
<mass value="0.11529" />
<inertia ixx="3.46069E-05" ixy="-7.86556E-05" ixz="-1.295125E-05" iyy="7.548495E-05" iyz="1.42141E-05" izz="7.410357E-05" />
</inertial>
<visual>
<origin xyz="0.001 -0.066 0.05" rpy="-1.7 0 0" />
<geometry>
<mesh filename="package://ros_as/meshes/link2.STL" />
</geometry>
<material name="">
<color rgba="0.77647 0.75686 0.73725 1" />
</material>
</visual>
</link>
The following is multiple choice question (with options) to answer.
What are intervertebral discs made of? | [
"intercartilage",
"fibrotissue",
"connective cartilage",
"fibrocartilage"
] | D | Figure 9.3 Intervertebral Disc An intervertebral disc unites the bodies of adjacent vertebrae within the vertebral column. Each disc allows for limited movement between the vertebrae and thus functionally forms an amphiarthrosis type of joint. Intervertebral discs are made of fibrocartilage and thereby structurally form a symphysis type of cartilaginous joint. |
SciQ | SciQ-5066 | atmosphere, atmospheric-chemistry, atmospheric-radiation, upper-atmosphere, air
You're completely right. If you simulate light scattering only, you'll get exactly this result: a sandy-colored sky, with a bit redder belt of Venus, and a gray shadow of the Earth:
But our stratosphere contains a small amount of ozone, which absorbs in the orange region of the spectrum in what is known as Chappuis band:
At daytime the solar light propagates at a small angle to the atmosphere, crossing a low amount of ozone, so the color of the sky is not affected (see also the question at Chemistry.SE: What exact color does ozone gas have?). But at twilight the sunlight goes through a large layer of atmosphere horizontally, thus the Chappuis absorption is very prominent.
The same simulation as above, but with ozone included (and with a bit higher exposure), will look like this:
Why is the shadow more blue (less orange) than the other parts of the sky? It's because in the shadow, there's no light from the single scattering: a ray from the Sun must be scattered at least twice to get to the earthly observer. This makes the Rayleigh scattering multiplier $\propto\lambda^{-4}$ apply twice, thus increasing the blue component of the inscattered light relatively to the red component. OTOH, the other atmosphere parts being not in the shadow, means that they do have contribution from the light scattered once, which has only a first power of this multiplier.
The following is multiple choice question (with options) to answer.
What harmful light does ozone reduce in the upper atmospheres? | [
"ultraviolet light",
"visible light",
"infrared light",
"specific light"
] | A | The ozone in smog is also harmful to human health. The image below shows the levels of ozone to watch out for ( Figure below ). Some people are especially sensitive to ozone. They can be harmed by levels of ozone that would not affect most other people. These people include those with lung or heart problems. |
SciQ | SciQ-5067 | earthquakes, seismology, instrumentation, in-situ-measurements, diy
Title: Using accelerometer as a seismograph I'm using ADXL345 accelerometer with Raspberry Pi to build a seismograph. I've successfully hooked it up and can plot the accelerometer data in three axis. Is there any way to express these data in the form of the magnitude of an earthquake, of course, at the point of sensing? I know that it might be imprecise, but any representation would be helpful (e.g. Richter scale), and how to accomplish that. The magnitude of an earthquake is related to the total energy released, therefore to estimate it from a seismogram you need to know the distance to the source. In the case of the Richter scale for example, the relationship between magnitude and seismogram amplitude is defined for a standard distance.
If you have only one seismograph, you can not triangulate the location of the source (hypocenter). Therefore, you can not estimate the magnitude of a seismic event (Richter or moment magnitude).
But you can estimate the local seismic intensity of the event at the particular location of your instrument. With the accelerometer data you can easily measure the peak ground acceleration, that can be used to estimate the intensity in any of the existing scales. For example, the peak ground accelerations associated to each intensity level in the commonly used Mercalli intensity scale are:
Those g values would be easy to calculate with the accelerometer data and proper calibration constants.
Table taken from the Wikipedia page for peak ground acceleration
You might want to have a look at this question. There are some nice answers and references that you might find useful.
The following is multiple choice question (with options) to answer.
What device detects and measuresee earthquake waves? | [
"stenograph",
"seismograph",
"polygraph",
"sphygmomanometer"
] | B | Although the idea that Earth is a magnet is centuries old, the discovery of why Earth is a magnet is a relatively new. In the early 1900s, scientists started using seismographic data to learn about Earth’s inner structure. A seismograph detects and measure earthquake waves. Evidence from earthquakes showed that Earth has a solid inner core and a liquid outer core (see the Figure below ). The outer core consists of molten metals, mainly iron and nickel. Scientists think that Earth’s magnetic field is generated by the movement of charged particles through these molten metals in the outer core. The particles move as Earth spins on its axis. The video at the URL below takes a closer look at how this occurs. |
SciQ | SciQ-5068 | meteorology, severe-weather
The lack of rich low-level moisture is due in large part to the lack of accessibility from warmer moisture sources, particularly the Gulf of Mexico; the Rockies provide a barrier to much of the moisture reaching further west.
As you note, parts of Wyoming and Montana do see supercells and tornadoes a bit more often... but on a good topographic map, fair parts of those states are east of the Continental Divide, and so still on an "upsloping" area and thereby not blocked by sinking regions which prevent full moisture progress. They're still less-tornado prone due to elevation and increased distance from moisture, but it does happen.
The desert southwest also does manage to get monsoon moisture sneaking around the terrain further south... but further north that monsoon moisture sees additional blocking by the more elevated terrain across Nevada and Utah. (And in the southwest, a different key ingredient in tornadic supercell development is typically missing in the summer monsoon: upper-air winds sufficient for supercell development)
The Pacific Coast does see a few occasional tornadoes. But from what I've seen, they typically form from smaller storms with much less classical and intense mesocyclones. As you mention, they're a bit more in line with cold-core setups, which usually produce weaker short-lived tornadoes than classic supercells of the Plains and on east. If you plug in the events you speak of into SPCs Severe Weather Events archive, [pick the date, then click Obs and Mesoanalysis on the left, then use the dropdowns to find various parameters]
you can see that CAPE was typically very meager (well short of 1000 J/kg) and the storm structure quite weak in reflectivity in comparison to a classic supercell, more indicative of such cold-core setups.
Capping inversions may be helpful to "keep the lid on the pot" if you have strong CAPE (and therefore quality moisture) and intense updrafts to erode the cap during the day. But as it is, there isn't enough moisture typically for the cap to be a positive factor.
The following is multiple choice question (with options) to answer.
While some climate regions have multiple layers, arid regions are poor for development of what? | [
"plants",
"minerals",
"soil",
"rain"
] | C | Not all climate regions develop soils. Arid regions are poor at soil development. Not all regions develop the same soil horizons. Some areas develop as many as five or six distinct layers. Others develop only a few. |
SciQ | SciQ-5069 | botany, plant-physiology, plant-anatomy
It made me wonder if we are simulating the sun in a dark room for growing the plants with the help of red, blue, and a little bit of far-red light, what will happen to the plants if we keep the ideal conditions for which the plants carry out photosynthesis whole day? Does it affect its yield or the plants die out quick?
I am an engineering student working on indoor farming, my knowledge of botany is the same as a high school student. So if I am wrong please tell me. Ideal conditions for photosynthesis
You mention ideal conditions to carry out photosynthesis, I would just like to point out that this includes carbondioxide levels, temperature, and nutrients as well as light.
Flowering
As anongoodnurse mentions performance might be measured by blooming which, in most flowering plants, has a day-light related component. However, for general growth increasing daylight over the 'natural' day length can often increase yield.
Daylight Cycles
The important point to note is that plants do 'ramp up' at dawn getting ready to start photosynthesizing (for some plants with temporal photosynthesis mechanisms (see CAM photosynthesis) this can be even more important). The reason plants do this is because plants can suffer from 'photobleaching' which can be considered similar to sunburn in humans, if they are not ready for sunlight. Getting 'ready' can involve lots of things including opening stomata (pores) to let CO2 in, changing which metabolic pathways are active, and moving about chloroplasts inside cells. Plants 'figure out' how and when to ramp up based on circadian rhythms which work well on 24 hour clocks and slight changes over time. Thus 12 hrs to 16 hrs can be a big change, particularly if the change happens by lights coming on earlier. Additionally, the 24 hour 'clock' means that plants will do better with 18hr light then 6hrs dark cycles than 36hrs light 6 hrs dark, because the total cycle length should be about 24hrs.
Photosynthesis Side Effects
The following is multiple choice question (with options) to answer.
Some plants open their leaves during the day to collect what? | [
"precipitation",
"moisture",
"energy",
"sunlight"
] | D | Plants also detect and respond to the daily cycle of light and darkness. For example, some plants open their leaves during the day to collect sunlight and then close their leaves at night to prevent water loss. |
SciQ | SciQ-5070 | digestive-system
Title: Energetics and Products of Pepsin/HCl Protein Digestion What are the energetics of protein digestion during which the enzyme pepsin is "activated" (whatever that means) by HCl? I've looked and been unable to find anything like a chemical equation that includes an energy term.
Of course, pepsin, being an enzyme, is not used up in that sought-for equation. Is HCl used up? If so, what are the products? How and in what form is the chlorine removed, assuming the HCl is consumed in the equation? This is well-explained on the Wikipedia page for pepsin. You are misinterpreting the use of the word activated. The protein is secreted by chief cells in the gastric glands in the form of pepsinogen, an inactive pro- form which has an extra ~40 amino acids at its N-terminus (the propeptide). The propeptide binds at the catalytic site of the enzyme and keeps it inactive. At low pH (this is where the HCl comes in - HCl secreted by parietal cells of the gastric glands acidifies the stomach) the protein is able to cleave off its own propeptide, making it fully active.
The following is multiple choice question (with options) to answer.
What secretion initiates chemical digestion while also protecting the oral cavity? | [
"saliva",
"lymph",
"mucus",
"stomach acid"
] | A | |
SciQ | SciQ-5071 | zoology, ichthyology, marine-biology
Switek goes on to to talk about exceptions in some marine mammals:
At this point some of you might raise the point that living pinnipeds like seals and sea lions move in a side-to-side motion underwater. That may be true on a superficial level, but pinnipeds primarily use their modified limbs (hindlimbs in seals and forelimbs in sea lions) to move through the water; they aren’t relying on propulsion from a large fluke or caudal fin providing most of the propulsion with the front fins/limbs providing lift and allowing for change in direction. This diversity of strategies in living marine mammals suggests differing situations encountered by differing ancestors with their own suites of characteristics, but in the case of whales it seems that their ancestors were best fitted to move by undulating their spinal column and using their limbs to provide some extra propulsion/direction.
The following is multiple choice question (with options) to answer.
What makes echinoderms force water into the feet and move forward? | [
"muscle contractions",
"spring contractions",
"field contractions",
"vacuum contractions"
] | A | A unique feature of echinoderms is their water vascular system . This is a network of canals that extend along each body part. In most echinoderms, the canals have external projections called tube feet (see Figure below ). The feet have suckers on the ends. Muscle contractions force water into the feet, causing them to extend outward. As the feet extend, they attach their suckers to new locations, farther away from their previous points of attachment. This results in a slow but powerful form of movement. The suckers are very strong. They can even be used to pry open the shells of prey. |
SciQ | SciQ-5072 | human-biology, red-blood-cell
Title: How do people who have lost both of their legs produce red blood cells? As far as I know, just leg bones produce red blood cells. So, how people who lost their both legs produce red blood cells? Red blood cells are produced in the red marrow which...
"is found mainly in the flat bones, such as the pelvis, sternum,
cranium, ribs, vertebrae and scapulae, and in the cancellous
("spongy") material at the epiphyseal ends of long bones such as the
femur and humerus." - Wikipedia
So you are partly right; the femur is associated with red blood cell production, or Erythropoiesis to give it it's technical name, but there are other bones within the human body that also do this job. The process of erythropoiesis is stimulated when the kidneys detect low levels of oxygen in the blood stream and stimulate production of the hormone erythropoietin. Further, the role of the tibia and femur in erythropoiesis also decreases with age whereas...
"the vertebrae, sternum, pelvis and ribs, and cranial bones continue
to produce red blood cells throughout life." - again from the wiki page
So I'd suggest it is unlikely that loss of the legs would have a major impact on the production of red blood cells in adults. I imagine that with the loss of legs comes some reduction in functionality of erythropoiesis but also a lower requirement of red blood cell production (less blood capacity = less blood cells needed = less blood cells need to be produced). I can't find any studies which explore the ability or needs of amputees and non-amputees with regards to red blood cell production.
The following is multiple choice question (with options) to answer.
Red blood cells, white blood cells, and platelets are all produced where? | [
"in collagen",
"in red marrow",
"in synovial fluid",
"in yellow marrow"
] | B | energy. Red marrow is where hematopoiesis—the production of blood cells—takes place. Red blood cells, white blood cells, and platelets are all produced in the red marrow. |
SciQ | SciQ-5073 | geology, oceanography, geochemistry, mineralogy
Title: Will the sea get saltier forever? The sea wasn't always salty. It's been getting saltier over millions of years as minerals dissolve.
Is there a natural limit to this process, or the will the sea keep getting saltier forever?
Is there a natural process which removes salt from the sea at a significant rate?
How long would it take for the sea to get too salty to support life as we know it? No there are natural processes that remove salt as well.
as sea level changes water gets trapped in basins and evaporates leaving the salt behind, this is where many of the salt formation on earth came from. whenever sea levels fall the salinity of the ocean drops. Tectonically isolated basin can remove salt in the same way. The process can even happen repeatedly in the same basin as sea level changes.
There are biological processes that remove it as well the formation of shells and limestone remove some of the ocean salts.
Can it increase yes, but it can also decrease, over earths history there have been saltier and less salty periods.
The following is multiple choice question (with options) to answer.
Fine-grained mud in the deep ocean comes from silts and clays brought from the land by? | [
"waves",
"water",
"wind",
"fire"
] | C | Fine-grained mud in the deep ocean comes from silts and clays brought from the land by wind. The particles are deposited on the sea surface. they slowly settle to the deep ocean floor, forming brown, greenish, or reddish clays. Volcanic ash may also settle on the seafloor. |
SciQ | SciQ-5074 | 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.
Pseudopods are temporary extensions of what? | [
"cytopods",
"the cell wall",
"the cytoplasm",
"the mucus"
] | C | Almost all protozoa can move. They have special appendages for this purpose. You can see different types in Figure below . Cilia (cilium, singular) are short, hair-like projections. Pseudopods are temporary extensions of the cytoplasm. Flagella are long, whip-like structures. Flagella are also found in most prokaryotes. |
SciQ | SciQ-5075 | fluid-dynamics, states-of-matter
Title: Why does sweetness of coke change after freezing completely I freeze my coke in a freezer completely to solid and then keep it out to melt and as it melts portion by portion I starts to drink, initially It will be very sweet and later it wont be sweet at all. why does this happen?
We know that all sugar in coke will be dissolved (Solid solution) but how a major portion of this melts faster than water in the juice their by getting more sweet? How these sucrose can escape through the crystals formed by the ice and join in the water.
I measured the sweetness (Brix) and found it varies. Substances in solution have the effect of decreasing the temperature of the freezing point of the liquid they are dissolved in. This is called freezing-point depression. This is one of the reasons why adding salt to ice helps it melt.
Your coke is a complicated solution + colloid and sugar is one of the main substances dissolved in it.
During freezing:
What happens is that during the freezing process, as the coke cools a lot of sugar is pushed out of solution which allows the less-saturated water to freeze first. The last bit of liquid to freeze has much more sugar in it and takes a while to freeze because it is a concentrated solution and the freezing point has been lowered a lot.
During melting:
The last portion of the coke to freeze has the bulk of the sugar and the lowest freezing point and will melt first when warmed. When you allow the coke to start melting the most saturated portions melt the fastest and you consume most of the sugar in this stage. Later when the drink continues to warm the rest of the water starts melting with much less sugar in it, thereby making the remaining portion less sweet.
More information about sugar solubility:
One common way to grow sugar crystals is by slowly cooling the solution to push the sugar out of solution. There is some information about this here and they provide a nice sugar (sucrose) solubility versus temperature graph too:
As you can see the temperature dependence for solubility is dramatic. I haven't been able to find a curve for fructose (the primary sugar in coke in the United States) but I suspect the curve is very similar.
The following is multiple choice question (with options) to answer.
Ice cubes in cola cause the cola to lose what? | [
"thermal energy",
"mechanical energy",
"kinetic energy",
"gravity"
] | A | Simon Cousins. Ice cubes in cola cause the cola to lose thermal energy . CC BY 2.0. |
SciQ | SciQ-5076 | species-identification, microbiology, microscopy
Title: Identification of protozoa under microscope I observed maybe Protozoa from standing FRESH water and from slowly flowing FRESH water. I am complete dilettante. Can you tell what these creatures are?
https://www.youtube.com/watch?v=6D5ck3zNJzA&t=474s
Thank you.
Added picture for to be more specific At first glance, the organisms may hold the appearance of protozoans like ciliates. However, I am of the belief that these 'totally tubular' micro organisms are in fact diatoms.
The diatoms are a diverse range of eucaryotic microalgae which comprise a large percentage of the phytoplankton group. (Diatomaceous earth is the residual remains of their calcareous walls)
They are likely diatoms because of their apparent hard membrane, and slight brown-green pigment, typical of heterokont diatoms.
I would be unable to specify the organism to family level. However, you may wish to complete your investigation by looking under the order 'Pennales'.
For general information regarding the Diatoms, you may visit https://en.wikipedia.org/wiki/Diatom
Morphology and description available from: https://books.google.co.uk/books?id=xhLJvNa3hw0C&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
Good luck
The following is multiple choice question (with options) to answer.
How are protists traditionally classified? | [
"animal-like, plant-like, or fungi-like",
"carnivorous or herbivorous",
"sponges, fungi and bacteria",
"organic and inorganic"
] | A | Protists are traditionally classified as animal-like, plant-like, or fungi-like. You will read more about each of these types of protists in the next lesson. |
SciQ | SciQ-5077 | climate-change, climate, paleoclimatology, carbon-cycle
Title: Did climate cool down when underground hydrocarbons stocks formed? As far as I understand, the dominant theory of modern climate change says that recent warming is mainly caused by the massive burning of hydrocarbons that used to be stored in solid form mostly underground as petroleum, coal, etc.
This suggests that the reverse process should contribute to a cooling of the climate (or to a slowed down warming if other processes are at play at the same time).
In particular, a cooling should have occurred throughout the period when the stocks of underground hydrocarbons were formed by the "pilling" of organic remains.
My questions:
The following is multiple choice question (with options) to answer.
Coal is a solid hydrocarbon formed from what type of decaying material? | [
"insects",
"mammals",
"soil",
"plant"
] | D | Coal is a solid hydrocarbon formed from decaying plant material over millions of years. |
SciQ | SciQ-5078 | paleontology
Title: How to start studying dinosaurs and pre-historic mammals/sea creatures I'm kind new to this hole thing of dinosaurs that I'm really interested in, are there any good books/websites/webpages to study the biology of pre-historic creatures? Dinosaurs, mammals, fishes, anything that is not alive anymore. Also, any good books about the history of how these species evolved and the history behind them would be appreciated. Here's what it takes to really study this: you need to go through the whole bachelor program for geoscientists, that includes fundamental geodynamics like plate tectonics, magmatism, volcanism, volcanic and metamorphic rocks and generally the cycles that make up earth's internal dynamics.
Then there is the huge field of external factors, like sediment geology (that's really complicated stuff), weathering and transport and how soils come to being, diagenesis and the structures sediments can form and their classifications. Role of the ocean (that's where it starts, before all) and the atmosphere, of course.
When through that, usually 4 semesters or so, you can start to specialize. For paleontolgy you need knowledge of earth history, of course, it's subdivision, and the conditions at certain times as far as they are known. Once that's done, then comes real paleontology: Animals (invertebrates and vertebrates), plants, and their development, biological evolution (that's frequently underrated, I find), taphonomy, ... For a sturdy base count another 2-4 semesters.
You may see that even a bunch of websites, maybe all of them together, cannot replace actual study. I am not aware of any site that even gives a reasonable overview of the field. Geoscience, and thus paleontology, touch many fields of natural science.
That said, when asked "How to learn about animal paleontology ?" I allways mention Micheal Benton, Vertebrate Paleontology. It needs a basic understanding of geoscience, evolution and skeleton anatomy. Functional morphology, phylogeny and an overview over sediment geology and earth history also won't harm, but you could give it a try. Some things are explained in between.
The following is multiple choice question (with options) to answer.
Many disciplines within the study of biology contribute to understanding how past and present life evolved over time; these disciplines together contribute to building, updating, and maintaining this? | [
"tree of life",
"amount of life",
"root of life",
"forests of life"
] | A | The diagrams above can serve as a pathway to understanding evolutionary history. The pathway can be traced from the origin of life to any individual species by navigating through the evolutionary branches between the two points. Also, by starting with a single species and tracing back towards the "trunk" of the tree, one can discover that species' ancestors, as well as where lineages share a common ancestry. In addition, the tree can be used to study entire groups of organisms. Another point to mention on phylogenetic tree structure is that rotation at branch points does not change the information. For example, if a branch point was rotated and the taxon order changed, this would not alter the information because the evolution of each taxon from the branch point was independent of the other. Many disciplines within the study of biology contribute to understanding how past and present life evolved over time; these disciplines together contribute to building, updating, and maintaining the “tree of life. ” Information is used to organize and classify organisms based on evolutionary relationships in a scientific field called systematics. Data may be collected from fossils, from studying the structure of body parts or molecules used by an organism, and by DNA analysis. By combining data from many sources, scientists can put together the phylogeny of an organism; since phylogenetic trees are hypotheses, they will continue to change as new types of life are discovered and new information is learned. |
SciQ | SciQ-5079 | units, notation, unit-conversion
These are just a few examples where electrical engineering is chock full of "A rate of something happening in a time period of one second" is basically defined as that something multiplied by time, as opposed to divided by time as in the case of velocity.
As far as I can tell the phrasing is effectively equivalent, but mathematically, the difference is profound, and very, very confusing. Can someone explain the difference between the two? Velocity, $m/s$, is a measure of the rate at which something moves. I guess you could define displacement as velocity-seconds, a measure of how far something moves at a given rate over a second. In your examples, it is not rates being defined, but the effect of going at a certain rate over a period of time. Amps are Coulombs per second, so you can define Coulombs as the amount of charge moved over a second at a rate of one amp. If you multiply the rate at which something happens by how long that something happens, you will get how much of that something happened.
The following is multiple choice question (with options) to answer.
A flow of one coulomb per second is called one ampere, which is a measure of what? | [
"Direct current",
"performance current",
"powered current",
"electric current"
] | D | The electric current is measured in coulombs per second. A flow of one coulomb per second is called one ampere, A, of current. |
SciQ | SciQ-5080 | sexual-reproduction
So when it's not maintained -- when there's no selection pressure on two populations -- inevitably there will be genetic drift that will randomly disrupt this fine-tuned system. If a population of, say, voles is isolated on an island, they will continue to have pressure to be able to interbreed with other voles on the island, but if they can't interbreed with those on the mainland there won't be any consequences, and so over long enough time they'll drift and lose that ability -- just as many apes, not suffering any consequences from not synthesizing vitamin C, gradually lost that ability from random drift.
There's another side to it. Two populations in the same location may be positively selected to not be able to interbreed. Think about two groups of finches, one with small fine beaks that eat tiny seeds deep inside pine cones, and one with heavy beaks that crush and eat thick-shelled nuts. They each do fine, but they can interbreed and produce offspring that have intermediate beaks -- too thick to reach the fine seeds that one parent eats, but too delicate to crush the nuts that the other parent eats. Those intermediate offspring will die off, and both parents will have wasted their resources raising them. Both parents would be better off not breeding with each other, but only breeding with their own kind to produce specialized and efficient offspring. There is now selection pressure on the birds to recognize their own kind (perhaps through songs or mating displays) and ultimately to be inter-sterile, so they never waste resources on the un-fit offspring. There's a gradation of separation over time, in which the different populations become more and more distinct. Eventually, at some arbitrary point, humans start calling them "species", but that's just us, not biology.
"Species" is an important concept, but it's not special in evolution; speciation is just one aspect of natural selection, there's nothing magical about it.
The following is multiple choice question (with options) to answer.
What might eventually happen to a species if it is unable to reproduce? | [
"migration",
"natural selection",
"extinction",
"adaptation"
] | C | |
SciQ | SciQ-5081 | 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 do muscles need to contract? | [
"stress",
"tendons",
"stimulus",
"pressures"
] | C | Muscles cannot contract on their own. They need a stimulus from a nerve cell to “tell” them to contract. Let’s say you decide to raise your hand in class. Your brain sends electrical messages to nerve cells, called motor neurons, in your arm and shoulder. The motor neurons, in turn, stimulate muscle fibers in your arm and shoulder to contract, causing your arm to rise. Involuntary contractions of cardiac and smooth muscles are also controlled by nerves. |
SciQ | SciQ-5082 | newtonian-mechanics, newtonian-gravity, orbital-motion
Title: Is the shape of an orbit unique for a given energy? Consider a body at a given distance from a star. If we project it perpendicular to the radius vector at the correct velocity, the body can undergo circular motion about the star. However, if we project it at an angle to the radius vector with the same velocity, I would expect it to undergo an elliptical orbit; however, will this orbit devolve into the circular orbit, i.e. for a given energy, is the orbit of the body unique? No.
For any given energy, there is a continuum of keplerian orbits that range from a fully circular orbit to more highly elliptical motions, all the way up to the limiting case of an almost-linear motion (extremely elliptical orbit) that whips around the focus infinitely sharply. These correspond to storing more or less energy in radial vs angular motion, i.e. to the angular momentum of the orbit.
There is also, of course, a three-dimensional degeneracy in the orientation of the orbit (usually given by three orbital elements such as the inclination, ascending node, and argument of periapsis) but dynamically speaking that is less interesting than the 'shape' degeneracy that comes from the variability in angular momentum.
And, for clarity, in a two-body problem, keplerian elliptical orbits are completely stable, and none of them "devolves" into any of the others. If there is a third body present then this changes (often quite dramatically) but then the space of possibilities becomes impossibly large to describe here.
The following is multiple choice question (with options) to answer.
What is considered to be a unique feature of echinoderms? | [
"oil vascular system",
"iron vascular system",
"air vascular system",
"water vascular system"
] | D | A unique feature of echinoderms is their water vascular system. This is a network of canals that extends along each body part. In most echinoderms, the canals have external projections called tube feet (see Figure below ). The feet have suckers on the ends. Muscle contractions force water into the feet, causing them to extend outward. As the feet extend, they attach their suckers to new locations, farther away from their previous points of attachment. This results in a slow but powerful form of movement. The suckers are very strong. They can even be used to pry open the shells of prey. |
SciQ | SciQ-5083 | pathology
Title: Are all diseases caused by organisms (microorganisms)? Are there other causes? Or is it correct to say that all diseases are in fact caused by organisms (microorganisms)? It is not correct to say that all diseases are caused by foreign organisms. Counterexamples are:
Cancer is caused by random genetic mutations in the cells of our body. The mutations can be caused by many factors such as ionizing radiation, smoking, chemical toxins etc.
Diseases such as stroke or heart attack are caused by blood clots blocking the blood flow to essential organs.
Autoimmune diseases are caused by the immune system falsely recognizing cells of the body as foreign and attacking that tissue leading to a wide variety of symptoms.
Alzheimer's disease is caused by chronic neurodegeneration, meaning that the cells in the brain die. The causes are not quite understood but as Alzheimer's usually appears late in life it is likely related to ageing. Also, it is known that some genetic defects can lead to early-onset Alzheimers.
Prion proteins can cause diseases such as Creutzfeldt–Jakob disease also known as mad-cow disease.
Hereditary diseases such as early-onset Alzheimers or ALS are cause by gene defects inherited from the parents.
Toxins can cause chronic diseases such as lead poisoning.
The list probably goes on...
Please note that the first two on the list are the most common cause of death in developed countries.
The following is multiple choice question (with options) to answer.
Noninfectious diseases can't be passed from one person to another. instead, these types of diseases are caused by factors such as environment, genetics and what? | [
"education",
"age",
"weight",
"lifestyle"
] | D | Noninfectious diseases can't be passed from one person to another. Instead, these types of diseases are caused by factors such as the environment, genetics, and lifestyle. Examples of inherited noninfectious conditions include cystic fibrosis and Down syndrome. If you're born with these conditions, you must learn how to manage the symptoms. Examples of conditions caused by environmental or lifestyle factors include heart disease and skin cancer. We can't change our genetic codes, but there are plenty of ways to prevent other noninfectious diseases. For example, cutting down on exposure to cigarette smoke and the sun's rays will prevent certain types of cancer. |
SciQ | SciQ-5084 | radioactivity, gamma-rays
Title: how close to radioactive material to be detected I am not expert on this but we have a project to detect radioactive material, we have found an off-the-shelf devise where its sensitivity for gamma rays starts from 20 KeV. My question is if you have very small traces of a radioactive material, how close this devise should be in order to pick any gamma ray? There are various radioactivity kinds. Take for example two kinds: alpha and gamma. While gamma are electromagnetic particles, photons, with rather big energy, it can travel a long way in open air, and even penetrate not so dense barriers like wood, glass or even concrete depending on photons energy, material structure and thickness. Of course it is absorbed in heavy metals like lead.
On the other side alpha rays are just helium nuclei. It may be very energetic but usually they get absorbed even in air in short lengths - for example 0.5 m - in practice typical alpha get absorbed after several cm ( say 10cm) but there are exceptions. But they are very dangerous as they ionise matter with high efficiency, and they will be absorbed by the skin when you are close enough to the source. Absorption means here energy transfer, so basically skin will be just burned!
Detectors usually used one or another kind of radioemission of electrons caused by radiation absorption in semiconductor or on various electrodes. After amplification, electric current of such electrons is measured.
So - what is the correct answer? It depends both on energy of the radioactivity radiation and kind of the radiation, and radioactive material you are expecting to measure, detect etc. Probably you should focus on measure of gamma or beta radiation ( electrons) as they can be detected far from the source.
The following is multiple choice question (with options) to answer.
What 'counting' instrument is used to measure radioactivity? | [
"ellie counter",
"pryor counter",
"Liquid Counter",
"geiger counter"
] | D | prepared. A student measures the radioactivity of this source with a Geiger counter and observes 1500 counts per minute. She notices that the source was prepared 120 days before her lab. What fraction of the decays is she observing with her apparatus? (b) Identify some of the reasons that only a fraction of the α s emitted are observed by the detector. Armor-piercing shells with depleted uranium cores are fired by aircraft at tanks. (The high density of the uranium makes them effective. ) The uranium is called depleted because it has had its 235 U removed for reactor use and is. |
SciQ | SciQ-5085 | ecology
I have tried to find explanatory texts both in this and other books without any success so my question is how's this balanced state achieved in both types of successions (the answer is hinted in the first paragraph which I don't quite understand)?
Related to my last post. The author is saying that 1) Mature ecosystems tend to have a balance between production (=P) and use (=R, respiration) of biomass. This is actually tautological because the author would probably define a mature ecosystem as one where this is true (P=R).
If it starts out P > R, the autotrophs are dominant: more biomass is being produced than used up. It is possible, for a time, that P will increase as, for example, plants grow more leaves, but R is growing too, and there is an eventual limit on P, which at maximum depends on the light available to the ecosystem. As biomass grows, so does the amount of biomass to potentially decay, so eventually R will always catch up to P, until there is balance.
If it starts out P < R, that means you are using up biomass faster than you are creating it. This case is even simpler: you will gradually run out of biomass, and R will decrease.
In either case, when the author is talking about P = R, this is going to be in relative terms; there might still be variations between them, for example seasonal variation, but on average over years or decades you would expect P = R in a mature, stable ecosystem.
The following is multiple choice question (with options) to answer.
Often primary producers, what term describes species considered the “base” or “bedrock” of a community, having the greatest influence on its overall structure? | [
"fundamental",
"primary",
"foundation",
"consumable"
] | C | Foundation Species Foundation species are considered the “base” or “bedrock” of a community, having the greatest influence on its overall structure. They are often primary producers, and they are typically an abundant organism. For example, kelp, a species of brown algae, is a foundation species that forms the basis of the kelp forests off the coast of California. Foundation species may physically modify the environment to produce and maintain habitats that benefit the other organisms that use them. Examples include the kelp described above or tree species found in a forest. The photosynthetic corals of the coral reef also provide structure by physically modifying the environment (Figure 19.24). The exoskeletons of living and dead coral make up most of the reef structure, which protects many other species from waves and ocean currents. |
SciQ | SciQ-5086 | oceanography, tropical-cyclone
Title: Would hurricanes on an ocean planet continue indefinitely? Hurricanes seem to run out of steam when they make landfall.
If our planet were entirely covered by ocean, would hurricanes continue indefinitely? Would they keep gathering energy and increasing in intensity until...? No. As it is, many hurricanes never make landfall. In an oceanic world I could see three fates happening:
Hurricanes that dissipate due to dynamical features or climatological features.
By dynamical features, I mean things like two hurricanes that shear each other out or produce an environment that can't be sustained. An example of the latter is upwelling, which generates cooler water that saps the energy from the hurricane. A climatological feature that might prevent a hurricane from developing indefinitely might be the Azores high. As it is, there are places that hurricanes don't seem to go.
Hurricanes that undergo extratropical transition.
Notice in the figure above, the hurricanes just disappear near the poles? As they come closer to the poles, the temperature difference becomes larger. Eventually they no longer look like tropical cyclones/hurricanes (little to no temperature difference), but rather look like an extratropical cyclone (see this link for some differences). This process is called Extratropical transition.
Chavas and Reed (2019)
While looking up papers for this question, I stumbled upon this paper. It implies that we would get longer lived hurricanes spreading the entire planet. I'd be a little skeptical of this result though, since it ignores the fact that the earth is heated unevenly, which drives most of the climate.
On a side note, such simulations do exist. These are called Aquaplanet simulations. Some studies I found include:
Li et al. (2011)
Merlis and Held (2019)
Chavas and Reed (2019)
Viale and Merlis (2017)
And for kicks and giggles, if you want to consider what the worst-case scenario for a hurricane could be, such a thing has been named a "Hypercane" (see here, too).
The following is multiple choice question (with options) to answer.
Hurricanes that form in the tropics are called what? | [
"tornados",
"caribbean cyclones",
"tropical cyclones",
"rain cyclones"
] | C | Hurricanes are cyclones. Since they form in the tropics, they are called tropical cyclones. These storms form over very warm ocean water in summer and autumn. The temperature of the sea surface must be 28 o C (82 o F) or higher. The air above the water warms and rises. This forms a low pressure cell. The air begins to rotate around the low pressure cell. Water vapor condenses. If conditions are right, the storm will build into a hurricane in two to three days. |
SciQ | SciQ-5087 | mapping
Title: Software to draw maps based on Earth I am looking for a tool to sketch changes to Earth. It should start with a geoid or an Earth model, rise/lower/flood selected areas. "Heal" boardersk: if an island is added in an ocean height shouldn't abruptly change from 0 $m$ to $-$1000 $m$. It should also measure distances between points, allow labeling and export maps of selected images as raster graphics (jpg image).
So far I could do two things:
Start with Google Earth, prepare necessary shapes using flooding, paste results as layers in Gimp/Photoshop [fast and ugly]
Import data in Matlab, define rules for modified regions, export [manual rule definitions is slow, no way to smart select, drag and drop regions]
What is the standard approach to do this? For instance, how people display flood plains, draft a channel or a new island project?
Windows/Mac/Linux/doesn't_matter? Windows preferred, Linux is OK.
GUI or also command line? GUI, or GUI+CLI batching. CLI only is undesired.
Go you want to use a GIS? I didn't know about GIS. Looking into in. The most common software for creating and modifying maps is ArcGIS (commercial but you can get free trial for a month) or QGIS (open source).
The following is multiple choice question (with options) to answer.
What types of flat maps show users changes in land elevation? | [
"atlases",
"surveyor maps",
"elliptical maps",
"topographic maps"
] | D | Topographic maps are flat maps that show the three-dimensional surface features of an area. Topographic maps help users see the how the land changes in elevation. |
SciQ | SciQ-5088 | meiosis
Title: Aneuploidy in meiosis I am quite confused about nondisjuction in anaphase II. If the double chromosome is not segregated, isn't it double. On pictures they are drawn as single but I don't understand why, and if they are double do they duplicate themselves in the S phase?
What is confusing me in picture above is cell (n+1) , why are all chromosomes single? I thought, after end of division in the third cell (labeled as n+1) there should be 3 chromosomes with single chromatid, and 1 chromosome with 2 chromatid joined at centromeric region, as it is drawn in picture above that show nondisjunction in cell during anaphase ii . When and how do these 2 chromatids get physically separated? From Study.com >>
On the off chance that nondisjunction happens amid anaphase II of meiosis II, it implies that no less than one set of sister chromatids did not isolate.
In this situation, two cells will have the typical haploid number of chromosomes. Additionally, one cell will have an additional chromosome (n + 1) and one will miss a chromosome (n - 1) due to the nondisjunction of the chromosomes.
Here is a picture reference taken from Google.ca >>
In the image provided in the question, the chromosomes are not indicated clear and concisely, so it is very hard to follow through the logic of segregation of the daughter cells to (n + 1) and (n - 1) chromosomes.
As you can see from the updated image reference in the answer, we can notice that the cell that underwent nondisjunction in anaphase 2 gives rise to 2 daughter cells, in which, one cell receives the non-segregated chromosome plus one copy of a sister chromatid which makes it (n + 1) and the other daughter cell receives one segregated sister chromatid ONLY which makes it (n - 1).
On an additional note, from Biology Exams 4 U >>
The following is multiple choice question (with options) to answer.
Sister chromatids separate as part of anaphase in what process? | [
"mitosis",
"vesicles",
"osmosis",
"angiogenesis"
] | A | |
SciQ | SciQ-5089 | evolution, herpetology, dinosaurs
Title: Evolution of dinosaurs What did dinosaurs evolve from? Was it the reptiles that evolved from amphibians? I have been researching this but am very confused with who their direct predecessor was. Amphibians evolved from fish...reptiles from amphibians...dinosaurs from reptiles (?)...and birds from dinosaurs. That is my understanding, but it could be wrong. How are dinosaurs related to reptiles? And if they did evolve from reptiles, which kind of reptiles (such as lizards, crocodiles, or turtles for example)? Source of information
See the post The best free and most up to date phylogenetic tree on the internet? for info about how to find such information.
Generally speaking, you might be interested in an intro to phylogenetics such as the one provided in this answer for example.
Where are dinosaurs in the tree of life?
Dinosaurs fall within the Reptiliomorpha clade. Please note that Reptiliomorpha does not quite correspond to what we today call reptiles. Please see the post If dinosaurs could have feathers, would they still be reptiles?
Reptiliomorpha is the sister clade to Amphibia (from here) which contain all living amphibians.
If you look within the Amniota, you will find all of the following
Here, you see that turtles and mammals are an off-shoot of Diapsida. So dinosaurs are not mammals and there are not closely related to turtles. Now if you click on Diapsida you will find ...
the Archosauromorpha which contains all crocodiles, birds and dinosaurs. You can keep going to find Therapoda which contains many dinosaurs and birds. You can keep going like this for yourself and discover the entire tree of life!
Reacting to your sentences
What did dinosaurs evolve from?
When asking this question, please do not forget that no species evolved from an extant species. If this is unclear to you, you should have a look at this post.
Was it the reptiles that evolved from amphibians?
Well... the term reptile is a mess because it does not represent a monophyletic group (see this post). If you do not understand the term monophyletic, then you should have a look at this answer.
Amphibians evolved from fish...
The following is multiple choice question (with options) to answer.
Vertebrates evolved from primitive forms of which creature? | [
"humanoids",
"chordates",
"cephalopods",
"arthropods"
] | B | Vertebrates evolved from primitive chordates. This occurred about 550 million years ago. The earliest vertebrates may have been jawless fish, like the hagfish in Figure below . Vertebrates evolved a backbone to replace the notochord after the embryo stage. They also evolved a cranium , or bony skull, to enclose and protect the brain. |
SciQ | SciQ-5090 | acid-base
Title: What is called a salt? While I was doing experiments in my school days, they gave me different substances with the combination of base and acid radicals, for example ammonium nitrate and zinc chloride and they seldom called it a salt.
But actually a salt is a NaCl as far as I know.
So My Question is: Actually, what is called a salt?
Why do they call the acid and basic radical a salt? I think what confuses you is that 'salt' has two meanings: In the every day sense it means table salt (which has the formula NaCl) but in the chemical sense it means a certain way for particles to hold together and form a tangible substance.
I'd define the latter as any periodic arrangement/lattice (see e.g. here ) of particles held together by ionic bonds.
The positive ion is almost always a metal, the negative one can be anything (so usually either a halogen (those lack only one valence electron to have a full shell, see e.g. Cl) or a (smallish) molecule-ion like SO4^2−)
base and acid radicals
I really don't see much connection between salts and either bases/acids and radicals. Do consider that not all ions are bases/acids and all radicals are highly reactive. It would rather be an edge case to have a salt with a radical in it; most salts have ions with energetically favourable number of electrons (as a rough rule this means all "electron shells" are either full or empty.)
NaCl is a good example.
Because different sized salt crystals still have extremely similar behaviour, the salt formulas express only the ratio of anions and cations. Realize that on the whole salts are neutral.
Why do they call the acid and basic radical a salt?
A single kind of particle is never called a salt, salt means an arrangement of two ions of different polarity. I guess some lab 'recipes' have sloppy language if something is provided as a salt, but only one component is important for the reaction.
Perhaps I can give a better answer I understood what you mean by radical in this context.
The following is multiple choice question (with options) to answer.
Another name for table salt is? | [
"carbon chloride",
"hydrogen chloride",
"dioxide chloride",
"sodium chloride"
] | D | The table salt pictured in the Figure below contains two elements that are so reactive they are rarely found alone in nature. Instead, they undergo chemical reactions with other elements and form compounds. Table salt is the compound named sodium chloride (NaCl). It forms when an atom of sodium (Na) gives up an electron and an atom of chlorine (Cl) accepts it. When this happens, sodium becomes a positively charged ion (Na + ), and chlorine becomes a negatively charged ion (Cl - ). The two ions are attracted to each and join a matrix of interlocking sodium and chloride ions, forming a crystal of salt. |
SciQ | SciQ-5091 | oceanography, rivers, satellite-oddities
Title: What are these river/canyon-like carvings in the ocean? Browsing around Google Maps, I came across this off the south-west coast of Ireland
It looks very consistent with the shape rivers and their tributaries might make, but it has me puzzled since it's all underwater!
The main, most "river-like" one is in the middle-left of the picture but there are more (which look more like fjords) at the bottom.
What caused this feature? The carvings are submarine canyons, a part of the continental slope leading from the continental shelf to the continental rise and ultimately the Abyssal plains. They are a product of :
erosion through currents and
slumping of the continental shelf
Like other erosive or slumping effects, they can be self-reinforcing, leading to canyon-like structures. The highlighted canyon here is the Gollum Channel system, seen here.
The following is multiple choice question (with options) to answer.
In iceland, the mid-atlantic ridge is above sea what? | [
"level",
"bottom",
"atmosphere",
"tide"
] | A | In Iceland, the Mid-Atlantic Ridge is above sea level. It's the only place we can see a mid-ocean ridge out of the water. The Midlina Bridge connects two plates. On the west side is the North American plate. On the east side is the Eurasian plate. A mid-ocean ridge is where new crust is created. Eventually this spot will be beneath the Atlantic Ocean. |
SciQ | SciQ-5092 | atmosphere, geography
Title: How much atmoshphere is there compared to land and water We know our earth has 71% water and 29% land, but compared to that land and water, how much air do we have in our atmosphere?
I mean:
How big is our atmosphere
Is there any increase or decrease in the amount of atmosphere over time
Is there any change in percentage of oxygen over time 71% of Earth's surface is covered with water and 29% land.
Thinking in that regard, that's saying that on 29% of Earth's "surface" locations you have land below your feet, and in 71% of the locations, you have water. So to continue in such terms, you'd then ask... ok, what percentage of Earth's surface locations would have air above them!?! Well that's all of them. So to if you're comparing it with those percentages, I guess you'd have to say it's another 100%. Or, if we put them together into a full 3-dimensional surroundings at the surface, well it'd basically be 50% air, 36% water, 14% land.
But to compare how much of each there REALLY is, you need to include depth, getting some sort of 3 dimensional understanding of it. But the picture that reveals is certainly not the picture we are used to from daily experience. From the values I was able to find:
In terms of the room each takes up, the volume:
Surface water (oceans+lakes+rivers, glaciers, etc) is 1.4 billion km³
The inside of the Earth is about 1 trillion = 1000 billion km³
For the atmosphere, as mentioned in comments, it's a little more difficult, as the gases only gradually give way to space. You find less and less gas as you go up, but there's no set spot where there is none, as some tiny amount is always floating off into space. So where do you draw the line? A commonly used boundary between the atmosphere and space is the Karman line. This would lead to a volume of 53 billion km³ (using Earth's radius = 6371 km). Note that only about half of that is in the troposphere and stratosphere, which are perhaps the familiar zones of the atmosphere where weather and the ozone layer (and 95% of air molecules) reside.
The following is multiple choice question (with options) to answer.
The earth's atmosphere, climate, and living things are effected by what feature that covers more than 70 percent of earth's surface? | [
"continents",
"oceans",
"rivers",
"mountains"
] | B | Oceans cover more than 70 percent of Earth's surface and hold 97 percent of its surface water. It’s no surprise that the oceans have a big influence on the planet. The oceans affect the atmosphere, climate, and living things. |
SciQ | SciQ-5093 | zoology
Title: Why Egg shell is not called a cell wall? Egg is a single cell and has a outer hard covering outside inside which there is a cell membrane. Then why isn't the egg shell a cell wall?
Is it because no exchange of materials take place through it? Egg shells are actually porous so that the organism inside can aquire oxygen and get rid of carbon dioxide as it develops (http://www.scientificamerican.com/article/bring-science-home-chick-breathe-inside-shell/).
Although gametes (eggs and sperm) are single cells, an egg shell (or "wall" if you like) is created by the mother (therefore external to the egg cell) and contains many compartments separated by protein membranes:
https://www.exploratorium.edu/cooking/eggs/eggcomposition.html
The initial egg cell is a tiny fraction of a size of the egg visualised here, so it would therefore be incorrect to call the egg shell a "cell wall" as it is a structure independent of the egg cell itself.
The following is multiple choice question (with options) to answer.
What is the nest of cell an egg rests in called? | [
"follicle",
"mitochondria",
"epidermis",
"pod"
] | A | After puberty, an egg develops in an ovary about once a month. As you can see in Figure below , the egg rests in a nest of cells called a follicle. The follicle and egg grow larger and go through other changes. |
SciQ | SciQ-5094 | waves
Title: If two waves on a string have the same amplitude but different frequencies, does the wave with greater frequency also have more energy? I'm trying to better understand the dependency of mechanical wave energy on amplitude and frequency. From what I understand, mechanical wave energy depends on both but many of the examples that I have read about focus on amplitude and not frequency. Sound in air would be a good analogy for your question because we can have both frequency and amplitude in the air. There are 2 variables here, the size of the pulse (volume) and the frequency (pitch). Any combination is possible at any energy level. (The speed of sound is fixed in the air at constant conditions.)
In many environments it is easier to control amplitude, like water wave experiments. So it is more common to talk about waves and amplitude. Another variable is the duration of the wave/signal ... more energy is in a sound that lasts a longer time.
The following is multiple choice question (with options) to answer.
The energy of a wave depends on time as well as what other property of the wave? | [
"power",
"force",
"amplitude",
"frequency"
] | C | The energy effects of a wave depend on time as well as amplitude. For example, the longer deep-heat ultrasound is applied, the more energy it transfers. Waves can also be concentrated or spread out. Sunlight, for example, can be focused to burn wood. Earthquakes spread out, so they do less damage the farther they get from the source. In both cases, changing the area the waves cover has important effects. All these pertinent factors are included in the definition of intensity I as power per unit area:. |
SciQ | SciQ-5095 | evolution, natural-selection, theoretical-biology
Title: Probability of Extinction under Genetic Drift Here is the Wright-Fisher model of genetic drift:
$$\frac{(2N)!}{k!(2N-k)!}p^kq^{2N-k} \Leftrightarrow \binom{2N}{k}p^kq^{2N-k}$$
where $\binom{2N}{k}$ is the binomial coefficient.
This formula gives the probability of obtaining $k$ copies of an allele at generation $t+1$ given that there are $p$ copies of this allele at generation $t$. $N$ is the population size and $2N$ is the number of copies of each gene (this model applies to diploid population only).
From this formula, how can we calculate the probability of extinction of an allele in say 120 generations starting at a given frequency, let's say 0.2?
and
How can we calculate the probability of extinction rather than fixation of an allele present at frequency $p$ if we wait an infinite amount of time? update
The answer is here!
The following is multiple choice question (with options) to answer.
Genetic equilibrium occurs when what process doesn't exist within the population? | [
"variation",
"evolution",
"movement",
"reproduction"
] | B | The Hardy-Weinberg model describes how a population can remain at genetic equilibrium , referred to as the Hardy-Weinberg equilibrium. Genetic equilibrium occurs when there is no evolution within the population. In other words, the frequency of alleles (variants of a gene) will be the same from one generation to another. At genetic equilibrium, the gene or allele frequencies are stable — they do not change. For example, let's assume that red hair is determined by the inheritance of a gene with two alleles— R and r . The dominant allele, R , encodes for non-red hair, while the recessive allele, r , encodes for red hair. If a population's gene pool contains 90% R and 10% r alleles, then the next generation would also have 90% R and 10% r alleles. However, this only works under a strict set of conditions. |
SciQ | SciQ-5096 | biochemistry, physiology, cell-biology
Title: What triggers meiosis in gonadal cells? What specific biochemical processes are involved in inducing meiosis rather than mitosis? Why are gonadal cells the only cells in the human body which do undergo meiosis?
What specific biochemical processes are involved in inducing meiosis rather than mitosis?
It's a difficult question because every step in the development of a germ cell is ultimately necessary for the final differentiation, which includes a meiotic division. Meiosis requires a lot of specialized components to pair and segregate homologues, to induce and resolve recombination, etc. What starts it all is still largely unknown. There are plenty of mutants that halt the process, but these are required along the way, so damaging the pathway ultimately stops it from progressing. At least one study has been able to initiate the program of meiosis in yeast:
Induction of meiosis in Saccharomyces cerevisiae depends on conversion of the transcriptional represssor Ume6 to a positive regulator by its regulated association with the transcriptional activator Ime1. I Rubin-Bejerano, S Mandel, K Robzyk, and Y Kassir
Basically, they turned on a transcription factor, which activated an entire suite of downstream genes necessary for meiosis. In essence, they turned on the "meiosis pathway." Bear in mind this is yeast, so does't have separate germ cells, but the concept is probably the same.
Why are gonadal cells the only cells in the human body which do undergo meiosis?
All other cells are diploid. Only in germ cells does the organism induce reductional divisions (to make haploid gametes for ultimate fusion in the zygote of the next generation). Creation of haploid somatic cells would uncover recessive lethal mutations and cells would die. In sperm and eggs, which do not express any genes until after fertilization and karyogamy, this is not a problem.
The following is multiple choice question (with options) to answer.
During meiosis, each parent synthesizes gametes that contain only half of their complement of what? | [
"chromosomes",
"neutrons",
"receptors",
"atoms"
] | A | The Chromosomal Theory of Inheritance was consistent with Mendel’s laws and was supported by the following observations: • During meiosis, homologous chromosome pairs migrate as discrete structures that are independent of other chromosome pairs. • The sorting of chromosomes from each homologous pair into pre-gametes appears to be random. • Each parent synthesizes gametes that contain only half of their chromosomal complement. • Even though male and female gametes (sperm and egg) differ in size and morphology, they have the same number of chromosomes, suggesting equal genetic contributions from each parent. • The gametic chromosomes combine during fertilization to produce offspring with the same chromosome number as their parents. |
SciQ | SciQ-5097 | 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 evolution that occurs over a long period of time called? | [
"spontaneous mutation",
"macroevolution",
"introgression",
"catabolism"
] | B | Evolution that occurs over a long period of time is called macroevolution . It might take place over millions of years. This scale of evolution occurs above the level of the species. Fossils provide evidence for evolution at this scale. The evolution of the horse family, shown in Figure below , is an example of macroevolution. |
SciQ | SciQ-5098 | biophysics, cell-membrane
Title: Why doesn't the cell membrane just...break apart? Forgive me if this is a silly question. I can't understand the basics. Why doesn't the cell membrane just break apart? What's keeping the layers in the phospholipid bilayer together? I know that the membrane is embedded with proteins and lipids, but I still can't wrap my head around the "why". Are the hydrophobic interactions in the middle "stronger" than the hydrophilic interactions on the outside? What's keeping the individual phosphate heads together instead of, say, one of them just drifting away due to a nearby water molecule? The membrane bilayer is held together by hydrophobic forces. This is an entropy driven process. When a greasy or hydrophobic molecule is suspended in water, the water molecules form an organized "cage" around the hydrophobic molecule. When two hydrophobic molecules come into contact, they force the water between them out. This increases the entropy because the freed waters don't need to be organized into the cage. Lipid bilayers have many many many hydrophobic lipids that squeeze out a lot of water and greatly increase entropy. The polar phosphates allow the water to interact with the surface of the membrane, without a polar head group the lipids would form a spherical blob instead of a membrane.
Read this section on wikipedia for more.
The following is multiple choice question (with options) to answer.
What is the plasma membrane formed by? | [
"a cytoplasm bilayer",
"single lipid layer",
"cholesterol byproduct",
"a phospholipid bilayer"
] | D | The plasma membrane is formed by a phospholipid bilayer. |
SciQ | SciQ-5099 | electrons, metal, electronic-configuration
Title: Can a metal be forced to form an anion theoretically? I know that metals have the capability to lose electrons and form cations, but is it also theoretically possible to supply an electron to a metal so that it forms an anion?
If so, has it ever been done?
I referred this question (Can two metals combine to form a compound?) but could not get a satisfactory solution from that. Absolutely! You will find these mostly in electride systems and off these, mostly in alkali metals.
Here is an example research paper:
"Superakali-Alkalide Interactions and Ion Pairing in Low-Polarity Solvents, J. Am. Chem. Soc., 2021, 143(10), 3934–3943 (https://pubs.acs.org/doi/10.1021/jacs.1c00115)
Remember, metals have a positive charged when ionized because it is energetically more favorable to lose electrons than to gain them, this being of course an oversimplified version of electron orbitals and shells. If you have a situation in which this is reverse or not possible, you will get a negative metal ion
The following is multiple choice question (with options) to answer.
What is formed when an element gains one or more electrons? | [
"neutron",
"cation",
"ion",
"anion"
] | D | When an element gains one or more electrons, an anion is formed. Nonmetals typically become anions when they interact with other chemical species. |
SciQ | SciQ-5100 | soil, minerals, terminology, soil-science
Title: "Down wash" as a source for mineral particles in the soil In a previous IGCSE examination paper$^1$, the following question was asked and answer provided:
State one source of mineral particles in soil.
Marking Scheme:
Accept any one of:
rock;
down wash;
What's "down wash" and how is it responsible for providing minerals to soil? Googling the term lead me to an aerodynamics definition, which I doubt is the one referred to by the marking scheme.
$^1$ UCLES. Environmental Management, 0680/12, Paper 1. Cambridge International General Certificate of Secondary Education, February/March 2017. Downwash can be part of some erosion environments where minerals are moved down from their host rock environment to another location.
Black Snake Range - Granite Slopes, Victoria, Australia
The crest of the divide rises to almost 400 metres and at this site there are numerous exposed granite slopes and large boulders near the ridge crest. The lower slopes have a cover of granite downwash and the minor valleys have become partly infilled with this granitic sand wash, and hence they are swampy
Southdowns, UK, page 4
Overlying the bedrock geology are drift deposits of alluvium (along the numerous
streams) and ‘head’ (downwash deposits at the base of the Greensand Hills around
Liss and Petersfield).
In the Discussion section of Slope Stability and Slope Formation in the Flysch Zone of the Vienna Forest (Austria)
The downwash of the basal clays and marls, uncovering the solid bedrock, has to be regarded as the main aspect of this phase
The following is multiple choice question (with options) to answer.
What is the term for the slow wearing down of rocks on earth’s surface? | [
"evaporation",
"experiencing",
"slipping",
"weathering"
] | D | Weather makes life interesting. Weather also causes weathering. Weathering is the slow wearing down of rocks on Earth’s surface. Wind-blown sand scours rocks like sandpaper. Glaciers of ice scrape across rock surfaces like a file. Even gentle rain may seep into rocks and slowly dissolve them. If the water freezes, it expands. This eventually causes the rocks to crack. Without the atmosphere, none of this weathering would happen. Rocks at the surface would be pristine and unaltered. |
SciQ | SciQ-5101 | sequence-alignment, phylogenetics, genome, phylogeny
Title: What is the most appropriate way to find the most recent common ancestor between two distantly related species I want to specifically find the common ancestor between a lobster and a humans. I suspect it was an aquatic worm of some description. But I want to know about the nervous system of this common ancestor. Because I've now posted several comments, I'll just roll them all up.
For background on the approaches used to identify most recent common ancestors and a high-level look at how animal taxonomy has been inferred, I suggest Lynch 1999.
I think that there are 2 interpretations of this question. If you are interested in just looking up a single MRCA of well-defined clades, such as lobster and human, here are some approaches:
Easy way:
Look at a tree diagram, e.g. this:
Find the tips that correspond to your species of interest (arthropods for lobster, chordata for humans).
Find where they join together in the diagram (the branch labeled "true coelom").
You have your answer, the MRCA is the group of organisms with a true coelom, coelomates.
A more involved way using a database
Go to this website.
Find the group of species 1 (arthropods, protostomes, etc. for lobster, chordata, deuterostomes etc. for human)
navigate around until you see the group containing the two groups (in this case listed as "bilateria"). In this case you are looking for the bilaterian common ancestor.
another database
Go to this website.
Point and click your way to a view where you see your 2 clades of interest (arthropods, chordates in this case). See figure.
Find where they join (in this case, it is less certain about the existence of a coelomate common ancestor, so it just says "bilaterians").
The following is multiple choice question (with options) to answer.
Lobsters are what kind of food source? | [
"arthropod",
"sauropod",
"combination",
"mollusc"
] | A | Lobsters are one kind of arthropod food source. |
SciQ | SciQ-5102 | acoustics, rotational-dynamics
Title: The sound of rotating helicopter blades Why do helicopter blades make this pulsing, oscilating, slapping(?) sound?
Since their movement is smooth, shouldn't the sound be a similar, constant shush, perhaps increasing or decreasing in frequency as the speed of the blades changes?
update: Won't the sound heard depend on the location of the listener? Perhaps a person standing below (or above;) the helicopter would hear a more constant and uniform sound wave, while a listener standing to the side will hear the mentioned pulsing sound? In start-up and hover each blade produces more or less constant sound. But the sound is attenuated by distance and may not be the same in all directions. Therefore you hear it differently depending on the blade's position relative to you. So as the blades rotate, the sound you hear pulsates because the blades alternately get to positions where you hear them more or less strongly. In this video showing helicopter start-up from cockpit you can clearly hear the swish of each blade as it passes overhead with the pulsing increasing in frequency as the rotor spins up.
The blade tips also move quite fast, often more than half of speed of sound, so Doppler effect is adding more variation to the sound if you are standing to the side.
In cruise flight additionally the advancing blade moves faster relative to air than the retreating one, so even the generated sound changes as the rotor turns.
This effect increases as the helicopter accelerates. If it overspeeds, blade tips on the advancing side may (depending on helicopter type) get close to the speed of sound and shockwaves start to form on that side that add even more pulsating sound.
In some cases (turns at high speed, descent) the blades may also be hitting the wake vortex shed by the previous blade resulting in sharp increase in the puslating sound called "blade slapping". The reason is the blades only hits the vortex when it passes one particular place on the rotor disk, usually on the advancing side. Apparently it is rather complex; I found there is a paper about it (not read it; it is behind paywall).
The following is multiple choice question (with options) to answer.
Helicopters store large amounts of rotational energy of what type in their blades? | [
"kinetic",
"magnetic",
"seismic",
"thermal"
] | A | Figure 10.18 The first image shows how helicopters store large amounts of rotational kinetic energy in their blades. This energy must be put into the blades before takeoff and maintained until the end of the flight. The engines do not have enough power to simultaneously provide lift and put significant rotational energy into the blades. The second image shows a helicopter from the Auckland Westpac Rescue Helicopter Service. Over 50,000 lives have been saved since its operations beginning in 1973. Here, a water rescue operation is shown. (credit: 111 Emergency, Flickr). |
SciQ | SciQ-5103 | waves
Title: Is there a specific branch of physics that studies waves? Is there a branch of physics that studies waves and how they propagate through air, wires etc.? Acoustic physic deals with mechanical waves. But as CuriousOne says, many areas of physics uses waves in some way, so it's hard to pinpoint a "wave-only" physics.
The following is multiple choice question (with options) to answer.
What branch of science is the study of matter and energy? | [
"Chemistry",
"Thermodynamics",
"environmental science",
"physical science"
] | D | Physical science is the study of matter and energy. It includes the sciences of chemistry and physics. Most careers in physical science require a 4-year college degree in one of these fields. Some careers require more advanced education as well. For example, an astronaut might have a master’s degree or even a doctoral degree. |
SciQ | SciQ-5104 | photosynthesis
Title: Photosynthesis in oxygen free enviornment If a plant is grown in an oxygen free enviornment would it live longer in light or darkness?
It is evident that oxygen would compete with carbon dioxide during various processes like competing with carbon dioxide for reducing power, also oxygen quenches the excited electron of chlorophyll etc.
But all these effects to me don't give any sense of the extent of oxygen on these reactions. What does the absense of oxygen have on the system? Except ofcourse the plant not being able to respire properly. If that "environment" is a closed vessel or bell-jar; certainly the plant would survive in light (when it simultaneously perform respiration and photosynthesis), and in darkness (when it can perform only the respiration) it would survive upto certain time due to the oxygen it accumulated. But should die at prolonged darkness when the plant would finish all the oxygen.
(as suggested by Priestley's classic 1870 experiment * there was enough oxygen to keep a mouse for certain time)
(image link)
However, if we look the effect of various concentration of O2 on photosynthesis rate without altering the CO2 concentration; yes the photosynthesis rate get affected; one known effect is called Warburg effect or Inhibition of photosynthesis by O2.
In this effect, photosynthesis rate only decrease if O2 concentration is increased. And in vice-versa, with O2 concentration decrease, photosynthesis rate only increase. (source: this, this, this and this)
This take place due to mainly 2 causes: 1. O2 work in competitive way with CO2 for binding with the enzyme RuBisCO, the key enzyme for CO2 fixation in plants. 2. And that induces photorespiration (in C3 plants). (Wikipedia shows reference to here). (However this old paper also tells other hypotheses)
The following is multiple choice question (with options) to answer.
Plants and algae maintain the atmosphere. during photosynthesis, they add oxygen and remove what? | [
"carbon dioxide",
"water",
"nitrogen",
"methane"
] | A | Plants and algae maintain the atmosphere. During photosynthesis, they add oxygen and remove carbon dioxide. |
SciQ | SciQ-5105 | electromagnetism, electric-circuits, electromagnetic-induction, induction
Consider a series circuit which consists of an alternating voltage source and an ideal inductor.
The alternating voltage source is trying to change the current in the circuit by varying the electric field in the circuit.
The inductor is trying to oppose any change to the current and hence the magnetic flux by producing a non-conservative electric field in opposition to the field produced by the voltage source.
The strength of the non-conservative field which will oppose the electric field trying to change the current in the circuit is determined by the rate of change of current in the circuit.
The following is multiple choice question (with options) to answer.
Electric substations have what devices, which use electromagnetic induction to increase or decrease the voltage of the current? | [
"generators",
"transistors",
"transformers",
"tubes"
] | C | Electric substations have several functions. Many substations distribute electricity from a few high-voltage lines to several lower-voltage lines. They have electric transformers, which use electromagnetic induction to change the voltage of the current. Some transformers increase the voltage; others decrease the voltage. In the Figure below , you can see how both types of transformers are used in an electrical grid. |
SciQ | SciQ-5106 | physiology, respiration
Title: Why does a worm's skin need to be wet for oxygen to diffuse across it? Pages I've read about worms' respiratory systems says that the skin needs to be wet (covered in mucus) or oxygen won't diffuse across the skin. Why? If there is more oxygen outside the worm's skin than inside, what prevents it from diffusing across the skin, even if the skin is dried out? The quick answer: When the skin dries, the lipids in the cell membranes of the skin tissue undergo a phase transition which makes the membranes less permeable for oxygen.
Explanation: The lipids of the cell membrane can exist in different phase states. In the liquid disordered phase the lipids are relatively flexible and mobile, making this phase more oxygen permeable compared to the liquid ordered phase, in which the lipids are more rigidly packed.
The phase transition temperature of lipids increases upon dehydration (another reference), meaning that at the same ambient temperature, a dry lipid membrane is in the liquid ordered state and a wet lipid membrane is in the liquid disordered state.
Therefore, a dry cell membrane is less oxygen permeable than a wet one.
The following is multiple choice question (with options) to answer.
By what process does oxygen enter the pores of flatworms? | [
"permeation",
"absorption",
"filtration",
"diffusion"
] | D | Flatworms do not have a respiratory system. Instead, they have pores that allow oxygen to enter through their body. Oxygen enters the pores by diffusion. |
SciQ | SciQ-5107 | neuroscience, history, synapses, literature
Title: What is the full name of E. G. Gray? E. G. Gray is Neuro scientist who found and described first the two major morphologically defined synapse types (Gray Type I (asymmetric) and II (symmetric)) in his work
E G Gray (Oct. 1959). “Axo-somatic and axo-dendritic synapses of the cerebral cortex: an electron microscope study”. In: Journal of Anatomy 93.4, pp. 420–433
However I am unable to find his full name nor further information about his life. Edward George Gray went by the first name of George, which isn't evident from his initials (he was born Edward George), but I happened to stumble upon the Wikipedia article below. From there, I found his obituary.
From his obituary:
GEORGE GRAY was a pioneer in the study of brain ultrastructure. He was Professor of Cytology in the anatomy department at University College London from 1967 to 1977 and then headed the Laboratory of Biological Ultrastructure at the National Institute for Medical Research.
From the Wikipedia article for synaptosome:
In a collaborative study with the electron microscopist George Gray from University College London, Victor P. Whittaker eventually showed that the acetylcholine-rich particles derived from guinea-pig cerebral cortex were synaptic vesicle-rich pinched-off nerve terminals. Whittaker coined the term synaptosome to describe these fractionation-derived particles and shortly thereafter synaptic vesicles could be isolated from lysed synaptosomes
The following is multiple choice question (with options) to answer.
The iconic gray mantle of the human brain, which appears to make up most of the mass of the brain, is called? | [
"brain stem",
"thrombus",
"cerebrum",
"lobes"
] | C | The Cerebrum The iconic gray mantle of the human brain, which appears to make up most of the mass of the brain, is the cerebrum (Figure 13.6). The wrinkled portion is the cerebral cortex, and the rest of the structure is beneath that outer covering. There is a large separation between the two sides of the cerebrum called the longitudinal fissure. It separates the cerebrum into two distinct halves, a right and left cerebral hemisphere. Deep within the cerebrum, the white matter of the corpus callosum provides the major pathway for communication between the two hemispheres of the cerebral cortex. |
SciQ | SciQ-5108 | mantle, crystallography, crystals, pressure, diamond
That’s because the Botswana diamond also contained a high-pressure form of ice as well as another high-pressure mineral known as wüstite (SN: 3/8/18). The presence of those inclusions helped narrow down the rough pressures at which the davemaoite might have formed: somewhere between 24 billion pascals and 35 billion pascals, Tschauner says. It’s hard to say exactly what depth that corresponds to, he adds. But the discovery directly links heat generation (the radioactive materials), the water cycle (the ice) and the carbon cycle (represented by the formation of the diamond itself), all in the deep mantle, Tschauner says.
From the article I think that I'm being told that the diamond is preserving enough pressure to keep both the "davemaoite" and " a high-pressure form of ice" and the wüstite stable as well.
Am I understanding this correctly?
Question: When diamonds "migrate" from deep underground to the surface, do they maintain pressure inside when there is no more pressure outside? If so, how?
I would think that as the diamond rises to the surface and the pressure relaxes outside it would relax and expand uniformly and the pressure would relax inside as well. If that's not the case, why not?
The following is multiple choice question (with options) to answer.
What kind of rocks form as an existing rock is altered by high temperature or pressure? | [
"basaltic",
"metamorphic",
"igneous",
"sedimentary"
] | B | Metamorphic rocks form as an existing rock is altered by high temperature or pressure. |
SciQ | SciQ-5109 | adaptation
Title: How do longleaf pine trees adapt to the florida keys rainforest? I know that longleaf pine trees can be found in rainforests, but I can't find anything. This is sort of a too broad question but here are a few ideas. The second most fragile part of plants are the leaves. In the latitudes and elevations that experience freezing, plants have learned to abscise their leaves and go dormant for the winter season. Conifers have thick, waxy, very thin leaves that most conifers do not need to shed.
In a rainforest there is no danger of too cold temperatures. That is why there is an abundance of broadleaf trees and plants in the rainforest. Most of our indoor plants are tropical rainforest species.
There is also an awful lot of rain in a rainforest. There is a problem with leaves covered with water, as it inhibits the absorption of CO2. Beneath the leaf, O2 is released as a by-product of photosynthesis. Broad leafed plants that have adapted to an environment with lots of rain, little wind, and being crowded together have leaves designed to 'wick' the rain water off the leaf to run down the midrib and off the pointy tip or lobed or curled under leaf margins. This clears off the water and allows the plant to take up CO2, or it would not be able to do photosynthesis to make its own food for energy.
The other cool thing I can remember, is that broad leafs of plants are able to 'adjust' to the light. Similar to a 'solar sail' in outer space. If in full sun, those leaves get thick and stay smaller. If in shade, very normal in a rainforest, those leaves can thin and get larger in order to capture as much light as possible.
A better wording for your question would be, 'why is there an abundance of broad leaf species versus conifers in a rainforest'? If I've been able to translate your question correctly?
Hope this helps.
The following is multiple choice question (with options) to answer.
What kind of water are cattails adapted for with narrow, strap-like leaves? | [
"moving water",
"stagnant water",
"saline water",
"turbulent water"
] | A | Living in water does present challenges to plants, however. For one thing, pollination by wind or animals isn’t feasible under water, so aquatic plants may have adaptations that help them keep their flowers above water. For instance, water lilies have bowl-shaped flowers and broad, flat leaves that float. This allows the lilies to collect the maximum amount of sunlight, which does not penetrate very deeply below the water's surface. Plants that live in moving water, such as streams and rivers, may have different adaptations. For example, cattails have narrow, strap-like leaves that reduce their resistance to the moving water (see Figure below ). |
SciQ | SciQ-5110 | habitable-zone
Title: Better than Earth habitability Earth undoubtly has very good conditions for supporting life. Although it is expected that many other planets on the outer space have conditions at least as good as Earth, the vast majority doesn't, making them unhospitable to life or probably being able to support only very simple lifeforms. Earth itself for some billions of years until the Ediacaran or Cambrian could only support very simple lifeforms.
There are many parameters that may influence the habitability of a planet and its ability to support complex life: Star type; star temperature; star luminosity; stellar activity; stellar stability; star age; planet age; planet composition; planet size; orbital excentricity; orbital length; rotation axis inclination; planet tectonics; planet magnetosphere; presence and influence of satellites; abundance of water; planet atmosphere; interactions with other planets; presence or absence of asteroids, comets and minor planets planets belts and their position, distribution and composition; galactic orbit; galactic neighborhood; mass-extinction events rate, probability and intensity; and hundred of other possible variables including some based on pure luck and random chance.
Many of the parameters are modeled after Earth itself, since Earth is the only place so far that we know that life exists, and even if we found some alien life somewhere, it will probably be limited only to very simple forms of life.
But, what combinations of those parameters could lead to a planet with better life support than Earth itself?
Ok, you may argue that the question is too broad, so by "good life support" we could say something that allows the planet to evolve plenty biodiverse multicellular life ranging from simple microscopic creatures to complex dozens-meters long creatures with many body-differentiated parts and organs in a short timespan. So, a planet that has an environment which allows the development of richly-diverse and complex plant-like and animal-like creatures in a billion years after formation and stay like this for another 10 billion years is expected to be more life-friendly than Earth.
Further, lets restrict the biochemistry to what we know: water-based and carbon-based life, but not necessarily oxygen-breathing.
By the way, I am not asking anything about intelligent life or humans, just complex multicellular and biodiverse life.
The following is multiple choice question (with options) to answer.
What is the most abundant living thing on earth that can be found in almost any environment? | [
"pathogens",
"viruses",
"bacteria",
"pests"
] | C | Bacteria are the most abundant living things on Earth. They live in almost all environments. They are found in the air, ocean, soil, and intestines of animals. They are even found in rocks deep below Earth's surface. Any surface that has not been sterilized is likely to be covered with bacteria. The total number of bacteria in the world is amazing. It's estimated to be about 5 million trillion trillion. If you write that number in digits, it has 30 zeroes!. |
SciQ | SciQ-5111 | inorganic-chemistry
Title: How do I derive metallic aluminum without electricity? I'm laying the foundation for a project called 21st Century steampunk, where I figure out what the world would look like if electricity was never discovered.
I'm wondering if it's possible to derive usable metallic aluminum from naturally occurring substances without using the Hall–Héroult process. One method, which would also require a non-electrical heating source, involves reduction with carbon. Given a high enough temperature -- meaning over 2000°C -- carbon carries off the oxygen as carbon monoxide and leaves the aluminum behind. See Ref. [1](https://doi.org/10.1016/j.energy.2007.06.002), which includes the equilibrium composition calculation below.
Reference
M.Halmann, A.Frei, A.Steinfeld (2007)."Carbothermal reduction of alumina: Thermochemical equilibrium calculations and experimental investigation". Energy 32, Issue 12, December 2007, Pages 2420-2427. https://doi.org/10.1016/j.energy.2007.06.002
The following is multiple choice question (with options) to answer.
Oxidation does not necessarily require heating. which is the common and natural method of oxidation? | [
"rusting",
"boiling",
"ageing",
"fermentation"
] | A | Oxidation does not necessarily require heating. Iron that is exposed to air and water slowly oxidizes in a process commonly known as rusting. Bleaches contain various compounds such as sodium hypochlorite (NaClO), which release oxygen that oxidizes stains. Hydrogen peroxide (H 2 O 2 ) releases oxygen as it spontaneously decomposes. It acts as a bleach and an antiseptic that kills bacteria by oxidizing them. |
SciQ | SciQ-5112 | cardiology, embryology, pain, central-nervous-system
Title: At what stage is the nervous system developed enough to interpret neuronal signals as 'pain'? According to this article in Live Science, one of the reasons the fetus can't feel pain until 19 weeks is because the nervous system isn't fully developed.
But according to this article, the heart starts beating at day 16.
And according to this article, the nervous system controls the rate beating of the heart.
Then my question is, **how can it be assured that the nervous system isn't developed until 19 weeks, when the nervous system controls the heart beating rate since day 16? First, there is some confusion on your part about heart cells and pain perception. Heart cells generate an action potential intrinsically; they do not need the central nervous system to beat (your second article explains this; read the part about the importance of calcium.) So yes, long before a fetus can feel pain, the heart is beating, because there must be circulation of nutrients throughout the embryo.
Secondly, the vagus nerve and sympathetic nerves can affect heart rate (the former by slowing it down when firing). These nerves start to reach their endpoints late in week 4 of development. So 19 days is not correct.
Cardiac sympathetic system
Although the primitive human heart starts to beat at 21 to 22 d, heart development continues to day 50, and it is near the end of this period, during the fifth week, that thoracic neural crest cells migrate from the neural tube through the somites and form aggregations (ganglia) near the dorsal aorta. [emphasis mine]
To experience pain, however, requires maturation of certain parts of the brain, most importantly, part of the thalamus and the cerebral cortex:
Current theories of pain consider an intact cortical system to be both necessary and sufficient for pain experience. In support are functional imaging studies showing that activation within a network of cortical regions correlate with reported pain experience. Furthermore, cortical activation can generate the experience of pain even in the absence of actual noxious stimulation. These observations suggest thalamic projections into the cortical plate are the minimal necessary anatomy for pain experience. These projections are complete at 23 weeks' gestation. [emphasis mine]
The following is multiple choice question (with options) to answer.
Toward the late stages of pregnancy, a drop in progesterone and stretching forces from the fetus lead to increasing uterine irritability and prompt labor. contractions serve to dilate the cervix and expel this? | [
"blood",
"newborn",
"uteris",
"tissues"
] | B | Toward the late stages of pregnancy, a drop in progesterone and stretching forces from the fetus lead to increasing uterine irritability and prompt labor. Contractions serve to dilate the cervix and expel the newborn. Delivery of the placenta and associated fetal membranes follows. |
SciQ | SciQ-5113 | optics, visible-light, everyday-life, diffraction
Title: How does light bend around my finger tip? When I close one eye and put the tip of my finger near my open eye, it seems as if the light from the background image bends around my finger slightly, warping the image near the edges of my blurry fingertip.
What causes this? Is it the heat from my finger that bends the light? Or the minuscule gravity that the mass in my finger exerts? (I don't think so.) Is this some kind of diffraction?
To reproduce: put your finger about 5 cm from your open eye, look through the fuzzy edge of your finger and focus on something farther away. Move your finger gradually through your view and you'll see the background image shift as your finger moves.
For all the people asking, I made another photo. This time the backdrop is a grid I have on my screen (due to a lack of grid paper). You see the grid deform ever so slightly near the top of my finger. Here's the setup:
Note that these distances are arbitrary. It worked just as well with my finger closer to the camera, but this happens to be the situation that I measured.
Here are some photos of the side of a 2 mm thick flat opaque plastic object, at different aperture sizes. Especially notice how the grid fails to line up in the bottom two photos. OK, it seems that user21820 is right; this effect is caused by both the foreground and the background objects being out of focus, and occurs in areas where the foreground object (your finger) partially occludes the background, so that only some of the light rays reaching your eye from the background are blocked by the foreground obstacle.
To see why this happens, take a look at this diagram:
The following is multiple choice question (with options) to answer.
Light bends when it passes in from what to what? | [
"product to water",
"air to water",
"water to air",
"air to ground"
] | B | Refraction is another way that waves interact with matter. Refraction occurs when waves bend as they enter a new medium at an angle. You can see an example of refraction in Figure below . Light bends when it passes from air to water. The bending of the light causes the pencil to appear broken. |
SciQ | SciQ-5114 | photosynthesis, cellular-respiration, energy, sugar
Basically, points 4-7 convey that Calvin-Benson cycle not only produces sugar but what it actually does is fix inorganic carbon (as CO2) to organic form (in the form of sugar). So, most (practically all) of the carbon that a photosynthetic plant has, comes from this carbon fixation process and that's how plants are photoautotrophic.
The following is multiple choice question (with options) to answer.
Photosynthesis uses solar energy, carbon dioxide, and water to produce energy-storing carbohydrates.what is produced as a waste product? | [
"calcium",
"sulfur",
"oxygen",
"methane"
] | C | Figure 8.4 Photosynthesis uses solar energy, carbon dioxide, and water to produce energy-storing carbohydrates. Oxygen is generated as a waste product of photosynthesis. |
SciQ | SciQ-5115 | memory-access
Title: What is an addressable cell size? This question started with a quiz question from my university:
Consider a big-endian computer system with an addressable cell size of one byte. The values in memory cells 372 to 375 are shown in the table below. What 16-bit two's complement value (expressed as a decimal number) is stored at address 374?
Address Value
372 0xC5
372 0x5E
374 0x7F
375 0x23
One thing I'm not clear about is what exactly does "addressable cell size of one byte" mean? Addressable cell size of one byte, in this context, means that every cell in memory contains one byte. Variables which take up more than one byte are spread across several contiguous cells.
The following is multiple choice question (with options) to answer.
What is the basic unit of computer memory? | [
"Bit",
"byte",
"Teraybte",
"Megabyte"
] | B | Multiplicative prefixes are used for other units as well, such as computer memory. The basic unit of computer memory is the byte (b). What is the unit for one million bytes?. |
SciQ | SciQ-5116 | human-anatomy
Title: Difference between Appendix and the Cecum? What's the difference between an appendix and a cecum, and what are their functions? In herbivores the Cecum is an area that stores plant matter and helps digest it via symbiotic bacteria. Carnivores have smaller Cecums because meat is easier to digest than plant matter. In humans the Cecum is also an anatomical landmark that delineates the change from small intestine (a digesting organ) to the large intestine (mostly a capacity/storage organ).
The Appendix is a small, previously thought "superfluous" fleshy worm-shaped organ at the junction between the small and large intestines. Recent research posits that the appendix is sort of a harbor for a person's gut flora that can re-populate the intestines should the existing bacteria die or get removed (diarrhea being the most common cause). It can also become infected, inflamed, and require surgery to remove (Appendicitis).
The following is multiple choice question (with options) to answer.
What is the first part of the large intestine, where wastes enter from the small intestine? | [
"bowel",
"stomach",
"esophagus",
"the cecum"
] | D | The cecum is the first part of the large intestine, where wastes enter from the small intestine. The wastes are in a liquid state. As they passes through the colon, which is the second part of the large intestine, excess water is absorbed. The remaining solid wastes are called feces . Feces accumulate in the rectum, which is the third part of the large intestine. As the rectum fills, the feces become compacted. After a certain amount of feces accumulate, they are eliminated from the body. A sphincter controls the anus and opens to let feces pass through. |
SciQ | SciQ-5117 | energy, fuel, environmental-chemistry
Title: Effect of coal and natural gas burning on particulate matter pollution I sometimes hear people talking about how we should replace coal burning plants with natural gas ones, to alleviate the case of particulate matter pollution. What exactly is the difference between coal fuel and natural gas that makes the latter seem "cleaner"?
At the same energy outcome, natural gas produces less carbon dioxide than coal. In a way, natural gas is half way between coal and hydrogen.
Coal produces smelly smoke, solid particles, sulfur dioxide and minor or trace heavy metal pollutants.
It is less known to common people, but power plants burning coal are more significant source of radioactive pollution than nuclear plants. This pollution is very diluted, but rather significant in absolute amount. Coal ash, used in past as a filler for some construction materials, has lead in some cases to significantly increased content of radium-226 in building walls. This radium is a product of long term decay of natural uranium. It further decays while producing radioactive gaseous radon-222, which is dangerous in long term inhalation because of lung cancer. As it stays in lungs as polonium-218 and its decay products.
See e.g. Uranium produced from coal ash
... the uranium concentration in the ash pile is about 150-180 parts per million, about 1/4th of the concentration often thought of as commercially viable for ISL[In Situ Leaching] mining. However, coal ash piles have some physical characteristics that might help overcome that disadvantage since they may be easier to drill and it might be easier to protect the local groundwater from contamination. ...
See Radon in building materials by Czech government agency for radiation protection.
The following is multiple choice question (with options) to answer.
Burning fossil fuels produces air pollution and what? | [
"carbon dioxide",
"liquid dioxide",
"oxygen",
"acid rain"
] | A | Fossil fuels—including oil, natural gas, and coal—provide most of the energy used in the world today. Burning fossil fuels produces air pollution as well as carbon dioxide that causes global climate change. |
SciQ | SciQ-5118 | human-biology, biochemistry, metabolism, food
Which seem to go in different, rather contradictory directions.
Also, Studies partially supporting either viewpoint can be found:
Study considering hemoglobin A1c levels
Study considering peak glucose levels
Study considering snacking
Which leaves the non-biologist asking themselves which is the "major effect" (certainly, there will be some truth to each position, but the question is which one(s) got the "main point"), and if there are any other important effects to be considered, hence this broad question here, so I understand, from a biological standpoint, what happens to the carbohydrates when I eat them, so I can conclude for myself how to adapt my diet for "optimal" health. Scope of Answer
The original poster provided ample context for his question, which related to health considerations. It was perhaps for this reason, among others, that the question had not received an answer at the time of writing: questions relating to medical or health advice are off-topic here. However, his actual question is primarily biochemical:
What are the biological differences between the digestion of sugar and
different types of carbs as constituents of different types of food in
humans?
Although this might be answered with a little internet search, I felt it would be hospitable if someone offered him an answer to this — and this only.
Definitions
The basic sugar unit is a mono-saccharide, those of relevance to this question being hexoses or pentoses, having six or five carbon atoms, respectively.
What in non-technical language is called sugar, refers to a specific molecule, sucrose, which is a disaccharide of covalently-bonded glucose and fructose.
What in non-technical language are referred to as dietary carbohydrates generally refers to the storage polysaccharide of plants such as potato and other root vegetables, rice, and other cereal crops used to make bread. This is a homo-polymer composed solely of glucose units.
Summary of the differences in metabolism
Arising from these definitions, the following differences in metabolism emerge:
Different enzymes (amylase for these polysaccharides, sucrase for saccharose) are used to catalyse the hydrolysis of the linkages between the monomeric units.
Absorption in the gut is different for glucose and fructose, as is transport into cells.
The following is multiple choice question (with options) to answer.
Monosaccharides, particularly glucose, are major nutrients for what? | [
"photosynthesis",
"lipids",
"proteins",
"cells"
] | D | |
SciQ | SciQ-5119 | molecular-structure, covalent-compounds
Title: How to know it when I see a covalent network? This is a well-known (better said: well-discussed) question in the internet. When you look for answers for popular questions, you usually see them with a variable degree of reliability and complexity. Unfortunately, for this one, I only observed very very crude and general rules of thumb. So let's get a real answer:
A network solid or covalent network solid is a chemical compound (or element) in which the atoms are bonded by covalent bonds in a continuous network extending throughout the material. In a network solid there are no individual molecules, and the entire crystal may be considered a macromolecule. Formulas for network solids, like those for ionic compounds, are simple ratios of the component atoms represented by a formula unit. Covalent network, wikipedia
Diamond and SiO$_2$ are really great examples of covalent networks-lattices. So enough with stories:
If you face a new chemical formula, how would you assume it's a covalent network? (In case it is) Is it somehow done by drawing the Lewis structure? Is there a rule for this? Or is it only possible to know such thing with experimental data?
The following is multiple choice question (with options) to answer.
Covalent solids are formed by networks or chains of atoms or molecules held together by what? | [
"gravitational bonds",
"bail bonds",
"covalent bonds",
"ionic bonds"
] | C | Covalent Solids Covalent solids are formed by networks or chains of atoms or molecules held together by covalent bonds. A perfect single crystal of a covalent solid is therefore a single giant molecule. For example, the structure of diamond, shown in part (a) in , consists of sp3hybridized carbon atoms, each bonded to four other carbon atoms in a tetrahedral array to create a giant network. The carbon atoms form six-membered rings. Figure 12.19 The Structures of Diamond and Graphite. |
SciQ | SciQ-5120 | ichthyology, homeostasis, osmoregulation
Pillans, R.D. and C.E. Franklin, 2004. Plasma osmolyte concentrations and rectal gland mass of bull sharks Carcharhinus leucas, captured along a salinity gradient. Comparative Biochemistry and Physiology, Part A 138: 363-371.
The following is multiple choice question (with options) to answer.
In response to high blood osmolarity, which can occur during dehydration or following a very salty meal, the osmoreceptors signal the posterior pituitary to release this? | [
"adrenaline",
"oxygen",
"antidiuretic hormone (adh)",
"salt"
] | C | Antidiuretic Hormone (ADH) The solute concentration of the blood, or blood osmolarity, may change in response to the consumption of certain foods and fluids, as well as in response to disease, injury, medications, or other factors. Blood osmolarity is constantly monitored by osmoreceptors—specialized cells within the hypothalamus that are particularly sensitive to the concentration of sodium ions and other solutes. In response to high blood osmolarity, which can occur during dehydration or following a very salty meal, the osmoreceptors signal the posterior pituitary to release antidiuretic hormone (ADH). The target cells of ADH are located in the tubular cells of the kidneys. Its effect is to increase epithelial permeability to water, allowing increased water reabsorption. The more water reabsorbed from the filtrate, the greater the amount of water that is returned to the blood and the less that is excreted in the urine. A greater concentration of water results in a reduced concentration of solutes. ADH is also known as vasopressin because, in very high concentrations, it causes constriction of blood vessels, which increases blood pressure by increasing peripheral resistance. The release of ADH is controlled by a negative feedback loop. As blood osmolarity decreases, the hypothalamic osmoreceptors sense the change and prompt a corresponding decrease in the secretion of ADH. As a result, less water is reabsorbed from the urine filtrate. Interestingly, drugs can affect the secretion of ADH. For example, alcohol consumption inhibits the release of ADH, resulting in increased urine production that can eventually lead to dehydration and a hangover. A disease called diabetes insipidus is characterized by chronic underproduction of ADH that causes chronic dehydration. Because little ADH is produced and secreted, not enough water is reabsorbed by the kidneys. Although patients feel thirsty, and increase their fluid consumption, this doesn’t effectively decrease the solute concentration in their blood because ADH levels are not high enough to trigger water reabsorption in the kidneys. Electrolyte imbalances can occur in severe cases of diabetes insipidus. |
SciQ | SciQ-5121 | neuroscience, physiology, human-physiology, reflexes
Title: Are there neuron mediated reactions faster than reflexes? I'm interested in how fast the human body can respond to a stimulus. I know the fastest reflex, the blink reflex, operates around 100ms from stimulus to reaction. I also know that the blink reflex is known as the fastest reflex in the human body. My interest is in the fastest responses to stimuli I can find in the body.
Are there any faster responses to stimuli within the human body which use neurons but are not categorized as a reflex (due to some technicality), meaning they could be faster than the fastest reflex? To the best of my understanding a reflex is defined by the use of neurons to convey the information, I'm just wondering if there are any grey areas which don't qualify as a reflex but may be faster. I don't want to potentially write off an entire class of neurological behavior in my research simply because I stopped at the blink reflex. A reflex as fast as the blink in a neural circuit:
I would consider suppression of outer hair cells in the cochlea to be a reflex; the faster component of this reflex is about the same as the blink reflex, around 100 ms. The hair cells themselves aren't considered neurons, but the pathway that suppresses their motility certainly is.
A much much faster non-neuronal "reflex":
That said, the outer hair cells themselves also dance along quite fast in response to sensory input, even faster than the typical hearing range for humans, faster than 20kHz! In some ways, this is a reflex because you are taking sensory (specifically, auditory) information and turning it into a motor response, but all the "action" is taking place within one cell, and it isn't a neuron.
A more classical reflex that is substantially faster than 100 ms
Reflexes in the periphery can be much faster than 100 ms. The myotatic reflex, or stretch reflex, can be as fast as 30 ms in the knee - this is the reflex that is tested when a physician smacks you on the knee with a hammer (used as a test of spinal and peripheral nerve function, not as a punishment). It's likely there are other stretch reflexes that are faster just because distances to the spinal cord are shorter, but these might be more difficult to test (in this paper they report latencies as fast as 20 ms).
The following is multiple choice question (with options) to answer.
The grasp reflex in humans is an example of what kind of behavior? | [
"habit",
"innate",
"inclination",
"trait"
] | B | One of the few innate behaviors in human beings is the grasp reflex. It occurs only in babies. |
SciQ | SciQ-5122 | virus, antibiotics
Title: What are the positive effects of wrongful antibiotic use on a viral infection? I categorically accept that bacteria differ from viruses; so antibiotics DON'T help in viral infections. I also read this and this; so no need to explain this. I've read about the negative effects (eg exacerbation of antibiotic resistance); I ask only about the positive effects here, and NOT for reasons to exploit antibiotics for infections not due bacteria.
Yet I myself have witnessed that some people with viral infections feel better after wrongly taking antibiotics? and so asked about this first on Cognitive Sciences SE.
Initially, I suspected only some placebo effect, but this enlightened me on the side benefits of antibiotic consumption for a viral infection and motivated this question, now that my original question on psychology has revealed the relevance of biology. There are indeed antibiotics which have immunomodulatory side-effects, these are mostly from the class of macrolide antibiotics (erythromycin, clarithromycin, roxithromycin, azithromycin) and to some degree from the tetracyclines. Beta-lactam antibiotics (as Penicillin or Ampicillin) have not been shown to be immunomodulatory, but they are among the most commonly used. See reference 1 for more details.
The biggest effect has been shown on pulmonary diseases such as cystic fibrosis or diffuse panbrochiolitis (see reference 2).
Although the exact mechanism of action is not known, Macrolides are know to downregulate the inflammatory cascade and that the reduce the strong cytokine expression of some viral infections. However, these regulatory effects are relatively weak if you compare them to the anti-inflammatory properties of corticosteroids. So the question here is if the advantages are really sufficient compared to the problems, which an unnecessary use of antibiotics may cause. See reference 3 and the references in the paper for more details here.
Antibiotics may be useful to fight bacterial secondary or superinfections which accompany a virus infection.
References:
Immunomodulatory Properties of Antibiotics
Macrolide activities beyond their antimicrobial effects: macrolides
in diffuse panbronchiolitis and cystic fibrosis
Macrolide Therapy in Respiratory Viral Infections
The following is multiple choice question (with options) to answer.
Antibiotics can cure most infections that are caused by what? | [
"bile",
"bacterium",
"bacteria",
"algae"
] | C | Health care has been improving over the most recent centuries. Vaccines were developed that could prevent many diseases ( Figure below ). Antibiotics were discovered that could cure most infections caused by bacteria. Together, these two advances saved countless lives. |
SciQ | SciQ-5123 | interstellar-medium, astrochemistry
The new work may also solve another longstanding puzzle. Carbon chains with more than nine atoms are unstable, the team explains. Yet observations have detected more complex carbon molecules in interstellar space. How nature builds these complex carbon molecules from simpler carbon molecules has been a mystery for many years.
Buseck explained, "Longer carbon chains are stablized by the addition of iron clusters." This opens a new pathway for building more complex molecules in space, such as polyaromatic hydrocarbons, of which naphthalene is a familiar example, being the main ingredient in mothballs.
Said Timmes, "Our work provides new insights into bridging the yawning gap between molecules containing nine or fewer carbon atoms and complex molecules such as C60 buckminsterfullerene, better known as 'buckyballs.'" On Earth we don't see a big difference between hydrocarbon chains with lengths below and above 9 (think kerosene, wax...), why is there such a cutoff in stability in interstellar space? What is it about hydrocarbon chains longer than 9 atoms that makes them unstable there but not here? Unlike the saturated hydrocarbons in kerosene, carbynes are unsaturated carbon chains with alternating single and triple bonds.
Molecules containing such chains are called polyynes, e.g. the short cyanopolyyne HC5N:
H−C≡C−C≡C−C≡N
Those carbon atoms readily interact, and long chains (if they form; see comments) are more likely to crosslink or form cycles than to remain linear.
Tarakeshwar et al. suggest that iron clusters in "pseudocarbynes" inhibit this by bonding to some of the carbons.
Loomis et al. 2016 looked for cyanopolyynes in radio spectra of Taurus molecular cloud 1.
They got a good HC9N signal but did not detect the HC11N lines Travers et al. 1996 observed in the lab.
The following is multiple choice question (with options) to answer.
Hydrocarbons are made up of carbon and what else? | [
"hydrogen",
"silicon",
"helium",
"nitrogen"
] | A | Hydrocarbons are compounds that contain only carbon and hydrogen. The carbon atoms in hydrocarbons may share single, double, or triple covalent bonds. Unsaturated hydrocarbons contain at least one double or triple bond between carbon atoms. They are classified on the basis of their bonds as alkenes, aromatic hydrocarbons, or alkynes. |
SciQ | SciQ-5124 | cell-biology
Title: Are There Exceptions to Animal Cells not Having Cell Walls? In the January Issue of SciAm (discussing Haemophilia):
When damage occurs to blood vessels, exposure of the blood to collagen in the cell walls and material released by the cells triggers the activation of clotting factors.
I read the original in print, but it is available online here.
This seems to imply that animal cells (in this example, those of humans) have cell walls. I sometimes see similar implications in other resources. However, in elementary biology, one is taught that animal cells never have cell walls.
Therefore, my question: Are references to animal cell cell walls (such as the above, for human animal cells) simple mistakes--or are they exceptions to a generalization? Humans, as well as the rest of the metazoans (i.e. animals), absolutely do not have cell walls. What humans do have is extracellular matrix (ECM), which is the sort of fibrous, sort of gel-like material in which cells in many of the tissues are embedded. Collagen is a major component of ECM.
From the old copy of Alberts that is hosted on the NCBI website:
Tissues are not made up solely of cells. A substantial part of their volume is extracellular space, which is largely filled by an intricate network of macromolecules constituting the extracellular matrix (Figure 19-33). This matrix is composed of a variety of proteins and polysaccharides that are secreted locally and assembled into an organized meshwork in close association with the surface of the cell that produced them...
Two main classes of extracellular macromolecules make up the matrix: (1) polysaccharide chains of the class called glycosaminoglycans (GAGs), which are usually found covalently linked to protein in the form of proteoglycans, and (2) fibrous proteins, including collagen, elastin, fibronectin, and laminin, which have both structural and adhesive functions.
The following is multiple choice question (with options) to answer.
Archaeal cell walls contain a variety of polysaccharides and proteins but lack what? | [
"S-layers",
"RNA",
"DNA",
"peptidoglycan"
] | D | |
SciQ | SciQ-5125 | neurophysiology
Title: Why myelin sheat does not cover the whole axon? Is there an optimal lenght for myelin sheats to be effective and lead potential across the nerve cell? This has always bugged me. The nodes of Ranvier (the gaps between myelin sheath segments) speed up the action potential because the electric current can jump from node to node (or gap to gap). If the myelin covered the entire axon, the signal wouldn't have the gaps to speed up the signal. As for optimal length, the gap is 1μm long, but can be longer, on the order of millimeters depending on the type of cell. The length of the myelin doesn't matter so much as the length of the nodes of Ranvier because they are where the Na+/K+ channels are found so the ion exchange can occur. This is how an action potetial can occur, so the myelin not covering the entire axon is crucial for the ability of neurons to propagate a signal.
The following is multiple choice question (with options) to answer.
What are lipids' function in relation to nerves? | [
"protection",
"conservation",
"reproduction",
"transportation"
] | A | Lipids are nutrients, such as fats that store energy. Lipids also have several other roles in the body. For example, lipids protect nerves and make up the membranes that surround cells. |
SciQ | SciQ-5126 | organic-chemistry, acid-base, ph
The usual rule that "$\mathrm{pH}$ of 7 is neutral" comes from solutions in water: Water has the property that it can be converted into, and self-converts between ("auto-ioniziation") separate $\mathrm{H}^{+}$ and $\mathrm{OH}^{-}$ ions and its usual molecular form, $\mathrm{H}_2\mathrm{O}$. When one is dealing with pure water with no adulterants present, there is always, due to this process, around $10^{-7}\ \mathrm{\frac{mol}{dm^3}}$ of $\mathrm{H}^{+}$ present (though actually, this depends on temperature, but around room temp, it is around this much). Decimal logarithm of $10^{-7}$ is -7, hence the $\mathrm{pH}$ is 7. When you throw some acid in and it releases its protonic payload, the concentration of $\mathrm{H}^{+}$ rises by that amount, thus the $\mathrm{pH}$ drops.
The following is multiple choice question (with options) to answer.
What's the name for the point reached at a ph of 7? | [
"equivalence point",
"acidic point",
"constriction point",
"analogous point"
] | A | As base is added to acid at the beginning of a titration, the pH rises very slowly. Nearer to the equivalence point, the pH begins to rapidly increase. If the titration is a strong acid with a strong base, the pH at the equivalence point is equal to 7. A bit past the equivalence point, the rate of change of the pH again slows down. A titration curve is a graphical representation of the pH of a solution during a titration. The Figure below shows two different examples of a strong acid-strong base titration curve. On the left is a titration in which the base is added to the acid and so the pH progresses from low to high. On the right is a titration in which the acid is added to the base. In this case, the pH starts out high and decreases during the titration. In both cases, the equivalence point is reached when the moles of acid and base are equal and the pH is 7. This also corresponds to the color change of the indicator. |
SciQ | SciQ-5127 | thermodynamics, mixtures
As the temperature increases the enthalpy increases as does T$\Delta S$, but $\Delta G$ remains largely constant and remains positive, see sketch below. This suggest that water and oil will not easily mix.
The following is multiple choice question (with options) to answer.
Crystallization separates mixtures based on differences in what, which usually increases with temperature? | [
"density",
"viscosity",
"solubility",
"humidity"
] | C | Crystallization separates mixtures based on differences in solubility, a measure of how much solid substance remains dissolved in a given amount of a specified liquid. Most substances are more soluble at higher temperatures, so a mixture of two or more substances can be dissolved at an elevated temperature and then allowed to cool slowly. Alternatively, the liquid, called the solvent, may be allowed to evaporate. In either case, the least soluble of the dissolved substances, the one that is least likely to remain in solution, usually forms crystals first, and these crystals can be removed from the remaining solution by filtration. Figure 1.9 "The Crystallization of Sodium Acetate from a Concentrated Solution of Sodium Acetate in Water" dramatically illustrates the process of crystallization. Most mixtures can be separated into pure substances, which may be either elements or compounds. An element, such as gray, metallic sodium, is a substance that cannot be broken down into simpler ones by chemical changes; a compound, such as white, crystalline sodium chloride, contains two or more elements and has chemical and physical properties that are usually different from those of the elements of which it is composed. With only a few exceptions, a particular compound has the same elemental composition (the same elements in the same proportions) regardless of its source or history. The chemical composition of a substance is altered in a process called achemical change. The conversion of two or more elements, such as sodium and chlorine, to a chemical compound, sodium chloride, is an example of a chemical change, often called a chemical reaction. Currently, about 115 elements are known, but millions of chemical compounds have been prepared from these 115 elements. The known elements are listed in the periodic table (see Chapter 32 "Appendix H: Periodic Table of Elements"). In general, a reverse chemical process breaks down compounds into their elements. For example, water (a compound) can be decomposed into hydrogen and oxygen (both elements) by a process called electrolysis. In electrolysis, electricity provides the energy needed to separate a compound into its constituent elements (Figure 1.10 "The Decomposition of Water to Hydrogen and Oxygen by Electrolysis"). A similar technique is used on a vast scale to obtain pure aluminum, an element, from its ores, which are mixtures of compounds. Because a great deal of energy is required for electrolysis, the cost of electricity is by far the greatest expense incurred in manufacturing pure aluminum. Thus recycling aluminum is both cost-effective and ecologically sound. |
SciQ | SciQ-5128 | organic-chemistry, mixtures
Title: Would Oxygen Gas and Ozone be a pure substance together? If I have oxygen gas and ozone ($\ce{O2 + O3}$) together would it be considered a pure substance or a mixture?
And would pure substances always have the same molecular structure? Ozone is highly reactive and unstable, while dioxygen is stable. There do not combine to form a compound. So, clearly it is a mixture.
To answer the second part of the question, "And would pure substances always have the same molecular structure?", first a Wikipedia definition on substances, to quote:
A chemical substance is a form of matter having constant chemical composition and characteristic properties.[1][2]...
Chemical substances can be simple substances[4], chemical compounds, or alloys. Chemical elements may or may not be included in the definition, depending on expert viewpoint.[4]
Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water...
However, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical.
And further:
A chemical substance may well be defined as "any material with a definite chemical composition" in an introductory general chemistry textbook.[5] According to this definition a chemical substance can either be a pure chemical element or a pure chemical compound. But, there are exceptions to this definition; a pure substance can also be defined as a form of matter that has both definite composition and distinct properties.[6] The chemical substance index published by CAS also includes several alloys of uncertain composition.[7] Non-stoichiometric compounds are a special case (in inorganic chemistry) that violates the law of constant composition, and for them, it is sometimes difficult to draw the line between a mixture and a compound, as in the case of palladium hydride. Broader definitions of chemicals or chemical substances can be found, for example: "the term 'chemical substance' means any organic or inorganic substance of a particular molecular identity, including – (i) any combination of such substances occurring in whole or in part as a result of a chemical reaction or occurring in nature".[8]
The following is multiple choice question (with options) to answer.
Pure substances have a constant composition and can only be changed through what? | [
"dissolution",
"heating",
"chemical reactions",
"liquid reactions"
] | C | When studying the different states that matter exhibits, we have been looking at pure substances . Pure substances have a constant composition and can only be changed through chemical reactions. Constant composition indicates that a sample of a pure substance always contains the same elements in the same proportions. There are two main types of pure substances:. |
SciQ | SciQ-5129 | ocean, thermohaline-circulation, salinity
Title: Thermohaline Circulation in the Oceans I'm slightly confused by how thermohaline circulation works in the Earth's oceans. Is it different for surface water as opposed to deep water? I thought that warm water from the equator is transported to the poles, cools down, and then returns to lower latitudes. Is my thinking incorrect? Isn't water denser near the equator because of higher salinity? How does this impact the ocean circulation?
Thanks! Salinity and temperature both affects the density of sea water. When water with a fixed salinity cools down, it becomes heavier and sinks. In the same way, when vapor or ice removes water from sea water, the remains is more saline and heavier.
Thermohaline circulation can work as you describe. Surface water in the tropics is saline, due to evaporation, but warm due to high temperature in the atmosphere and therefor low density. As it reach colder climate (less solar energy per area), it cools down and the high salinity makes it sink. Surface water in polar regions also get heavier as ice is formed of water and leave the salt behind in the sea.
This is very simplified model, you can read more on the topic here and here.
The following is multiple choice question (with options) to answer.
Which water from the equator mixes with cold water from the poles? | [
"ice water",
"hot",
"warm",
"spring water"
] | C | Water flows through all the world’s oceans. Warm water from the Equator mixes with cold water from the poles. The mixing of warm and cold water makes the water temperature moderate. |
SciQ | SciQ-5130 | organic-chemistry, stoichiometry, elemental-analysis
Title: How to determine the molecular formula based on molecular weight, amount of substance, and partial masses of some, but not all contained elements? I am working on a chemistry assignment and can’t figure out part of the problem.
$\pu{0.2 mol}$ of a compound with a molecular weight of $82$ contain $\pu{9.6 g}$ of carbon, $\pu{1.2 g}$ of hydrogen and the rest is nitrogen.
The question is asking for the empirical and molecular formula which I can solve, but how do you determine the amount of nitrogen?
First I assumed a $\pu{100 g}$ sample but that didn't get me anywhere. The empirical formula answer is supposed to be $\ce{C2H3N}$ but I couldn’t achieve that. Unless the book is wrong. If you have $0.2\ \mathrm{mol}$ of a compound with $M_\mathrm{r}=82$, then you have $16.4\ \mathrm{g}$ of material. If there is only carbon, hydrogen and nitrogen present, and the carbon and hydrogen total up to $10.8\ \mathrm{g}$, then the amount of nitrogen must be $16.4\ \mathrm{g}-10.8\ \mathrm{g}=5.6\ \mathrm{g}$.
The following is multiple choice question (with options) to answer.
In order to determine its molecular formula, it is necessary to know what about the compound? | [
"lipid mass",
"protons mass",
"molar mass",
"polar mass"
] | C | Empirical formulas can be determined from the percent composition of a compound. In order to determine its molecular formula, it is necessary to know the molar mass of the compound. Chemists use an instrument called a mass spectrometer to determine the molar mass of compounds. In order to go from the empirical formula to the molecular formula, follow these steps:. |
SciQ | SciQ-5131 | speciation
Title: Does too much Genetical Modification leads to formation of new species? I think Genetical Modification can be termed as 'Artificial Mutation'.
Is it possible that genes can be modified so much that it leads to the introduction of new Species i.e Can integration of large no. of Helpful mutations lead to quick evolution? yes it possible, in one article show a study for Mycoplasma genitalium which have 525 gene, however only 382 genes are essential for biological functions, they take out the nature gene and place the ' artifical gene' which synthsis in vitro, to test if the M. genitalium will survival when the No. of gene lower than 382. If it survival it will be a new species.
The following is multiple choice question (with options) to answer.
What is the term for much bigger evolutionary changes that result in new species? | [
"breaking away",
"macroevolution",
"regression",
"recalibration"
] | B | Macroevolution refers to much bigger evolutionary changes that result in new species. Macroevolution may happen:. |
SciQ | SciQ-5132 | 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 are the effects of light on plant morphology called? | [
"electrogenesis",
"Megasporogenesis",
"Microsporogenesis",
"photomorphogenesis"
] | D | |
SciQ | SciQ-5133 | electromagnetism
Title: Region of most and least intense magnetic field
It's a unmagnetized iron screw placed in the north pole of a U shaped magnet. I believe the region of least intense magnetic field is at the far left of the board. From what I understand the screw becomes magnetized and it's south pole is where it's touching the north of the magnetic, is it correct to assume the most intense magnetic field will be where the screw is touching the magnet due to there being direct contact between them?
Consider these images showing the magnetic field lines of a horse-shoe magnet. Magnetic intensity at any point in its field is directly proportional to its magnetic flux.So the region where the field lines are more densely packed have a higher intensity than where the field lines are loosely packed. If possible, draw the field lines for your own case and you will realize where the magnetic intensity is most and least.
The following is multiple choice question (with options) to answer.
In a magnet, what are the regions called that are the strongest? | [
"positives",
"plates",
"negatives",
"poles"
] | D | A magnet is an object that attracts certain materials such as iron. All magnets have north and south magnetic poles. The poles are regions where the magnet is strongest. |
SciQ | SciQ-5134 | molecular-biology, neurotransmitter, muscles, receptor
Is the membrane continuous along these tubules, or does the tubule just end somewhere inside the muscle fiber?
The membranes are continuous.
When the muscle is twitching... is this neurological of nature, or is it related to a molecular cause in the muscle itself?
Most things you'd call a muscle twitch are at the whole-muscle-group scale, involving the coordinated contraction of many individual motor units, so it's basically neurological.
When the muscle is cramping... I'm almost certain this arises in the muscle. What causes it? A malfunction with regard to the calcium ions?
A muscle cramp is a colloquialism for a couple of things that are quite different from each other. Overall, as with the previous question, if someone's experiencing a muscle cramp that means it's a fairly macroscopic phenomenon and it likely involves a whole group of muscle filaments, so it's neurological. Most spasms and cramps are neurologically mediated.
The connections with electrolyte balances (cramps from low sodium, potassium, magnesium, or calcium) also hint at the neurological basis because neurons act on each other (and on muscles) by forming or dissipating ion gradients. You may know that low dietary calcium can lead to muscle cramps; if this was relevant to the calcium release within the myocyte (from the sarcoplasmic reticulum) then the calcium-starved muscles wouldn't be expected to chronically contract (which requires calcium) but to chronically relax.
That being said, there's a lot of room for feedback mechanisms. So, let's say a person experiences a muscle tear; the tear is small enough that it doesn't compromise the function of the entire muscle group. In this case it's adaptive for the local damage to 'signal' to the rest of the muscle group to initiate spasm so as to stabilize the damaged structures as they're repaired. In this scenario the local damage would 'inform' a neurological (and/or endocrine) response that actually effects the spasm.
Lastly, and on a slightly different subject, what are the microlesions in the muscles that occur during strength training, and what is the overcompensation that happens?
The following is multiple choice question (with options) to answer.
What kind of muscle cells undergo twitch-type contractions with long refractory periods followed by brief relaxation periods, allowing the heart to fill with blood for the next cycle? | [
"smooth muscle",
"nervous muscle",
"cardiac muscle",
"skeletal muscle"
] | C | Cardiac muscle undergoes aerobic respiration patterns, primarily metabolizing lipids and carbohydrates. Myoglobin, lipids, and glycogen are all stored within the cytoplasm. Cardiac muscle cells undergo twitch-type contractions with long refractory periods followed by brief relaxation periods. The relaxation is essential so the heart can fill with blood for the next cycle. The refractory period is very long to prevent the possibility of tetany, a condition in which muscle remains involuntarily contracted. In the heart, tetany is not compatible with life, since it would prevent the heart from pumping blood. |
SciQ | SciQ-5135 | mass, newtonian-gravity, statics
Title: How do you weigh a box on a scale whose limit is too low? As you will see I know nothing about physics and after being asked to solve a physics problem in a recent interview wanted to ask it of professionals and see what the response would be:
I have a set of domestic scales (actually just one scale) that weigh up to the maximum weight of 5kg and a large package that weighs more than 5kgs but less than 10kgs. How can I tell the exact weight using the inadequate scales.
The package is a long item akin to a steal girder but not in weight obviously.
I know that stack exchange has rules about this type of question so please treat it as light entertainment from someone in awe of your intellect. You put the package horizontally across three scales and add up the weight you see. If the center scale registers more than the limit, move the box, or put some pieces of paper under the scales which are registering a small weight to redistribute the weight.
A more physics-y question would be how to determine the weight when you have only one scale. This can be done by tilting the package at a small angle, by placing one end on a scale (perhaps propped up on something light, like your shoe, so that the weight momentum flow goes through the scale to the floor). To weigh this way requires knowing where the CM of the box is, and this can be determined by balancing it precisely on the edge of the scale (or on your finger, or on something else narrow).
Then the weight registered by the scale (minus the weight of the shoe) is the ratio of the length of the box to the distance from the end which is on the floor to the center of mass. If this is still too heavy, you can tilt the box up to 45 degrees, which will cut down the weight registered by the scale further by a factor of .707, which can be undone by multiplying by 1.414.
The following is multiple choice question (with options) to answer.
What is a factor in determining weight but not mass? | [
"function",
"location",
"material",
"gravity"
] | B | Mass is independent of location, while weight depends on location. |
SciQ | SciQ-5136 | physical-chemistry, everyday-chemistry, thermodynamics
As a comparison to this example, let's check out two liquids that do mix.
3. Water and ethanol
For the water, we have basically the same situation as before -- water molecules forming good bonds to each other. The ethanol, though, has an -OH group that can form bonds to the water in the same way that the water does (though not as well). This means that ethanol that mixes with water (and vice versa) will tend to stay mixed, and given that the liquids are being mixed around just by random motions, means that you'll get one mixing with the other just as a matter of statistics.
The following is multiple choice question (with options) to answer.
What occurs when two nonpolar liquids are mixed? | [
"refracted - nonpolar interactions",
"polar-nonpolar interactions",
"sediment - nonpolar interactions",
"nonpolar-nonpolar interactions"
] | D | Nonpolar-nonpolar interactions occur when two nonpolar liquids are mixed. An example of this is the interaction between toluene and octane (see Figures above and below ). The interactions between a molecule of toluene and a molecule of octane are relatively weak, but so are the toluene-toluene and octane-octane interactions. Because no strong intermolecular forces (like those between water molecules) need to be broken for mixing to occur, no strong interactions need to be formed in order for mixing to be a favorable process. Toluene and octane will form a homogeneous mixture. The phrase "like dissolves like" applies to these mixtures as well. In this case, nonpolar dissolves nonpolar. |
SciQ | SciQ-5137 | cardiology, embryology, pain, central-nervous-system
Title: At what stage is the nervous system developed enough to interpret neuronal signals as 'pain'? According to this article in Live Science, one of the reasons the fetus can't feel pain until 19 weeks is because the nervous system isn't fully developed.
But according to this article, the heart starts beating at day 16.
And according to this article, the nervous system controls the rate beating of the heart.
Then my question is, **how can it be assured that the nervous system isn't developed until 19 weeks, when the nervous system controls the heart beating rate since day 16? First, there is some confusion on your part about heart cells and pain perception. Heart cells generate an action potential intrinsically; they do not need the central nervous system to beat (your second article explains this; read the part about the importance of calcium.) So yes, long before a fetus can feel pain, the heart is beating, because there must be circulation of nutrients throughout the embryo.
Secondly, the vagus nerve and sympathetic nerves can affect heart rate (the former by slowing it down when firing). These nerves start to reach their endpoints late in week 4 of development. So 19 days is not correct.
Cardiac sympathetic system
Although the primitive human heart starts to beat at 21 to 22 d, heart development continues to day 50, and it is near the end of this period, during the fifth week, that thoracic neural crest cells migrate from the neural tube through the somites and form aggregations (ganglia) near the dorsal aorta. [emphasis mine]
To experience pain, however, requires maturation of certain parts of the brain, most importantly, part of the thalamus and the cerebral cortex:
Current theories of pain consider an intact cortical system to be both necessary and sufficient for pain experience. In support are functional imaging studies showing that activation within a network of cortical regions correlate with reported pain experience. Furthermore, cortical activation can generate the experience of pain even in the absence of actual noxious stimulation. These observations suggest thalamic projections into the cortical plate are the minimal necessary anatomy for pain experience. These projections are complete at 23 weeks' gestation. [emphasis mine]
The following is multiple choice question (with options) to answer.
Although much of the heart's basic structure is complete by the end of the fifth week, what fetal structures remain until birth or shortly after? | [
"heart shunts",
"renal arteries",
"blood shunts",
"umbilical arteries"
] | C | The five regions of the primitive heart tube develop into recognizable structures in a fully developed heart. The truncus arteriosus will eventually divide and give rise to the ascending aorta and pulmonary trunk. The bulbus cordis develops into the right ventricle. The primitive ventricle forms the left ventricle. The primitive atrium becomes the anterior portions of both the right and left atria, and the two auricles. The sinus venosus develops into the posterior portion of the right atrium, the SA node, and the coronary sinus. As the primitive heart tube elongates, it begins to fold within the pericardium, eventually forming an S shape, which places the chambers and major vessels into an alignment similar to the adult heart. This process occurs between days 23 and 28. The remainder of the heart development pattern includes development of septa and valves, and remodeling of the actual chambers. Partitioning of the atria and ventricles by the interatrial septum, interventricular septum, and atrioventricular septum is complete by the end of the fifth week, although the fetal blood shunts remain until birth or shortly after. The atrioventricular valves form between weeks five and eight, and the semilunar valves form between weeks five and nine. |
SciQ | SciQ-5138 | waves, pressure, acoustics, density
Title: Why does sound not move through a wall? I'm learning a bit about sound and was wondering:
If the speed of sound is determined by the amount of matter the source is surrounded with, why doesn't it go through a wall?
Example:
Speed of sound in air is 343 m/s but in water, it moves at 1500 m/s because of the increase of matter surrounding it. And since iron has more tightly packed matter, it moves even faster because it's moving the matter to move the vibrations.
If this is true, why doesn't the sound go through walls? Is it because it loses its "strength" for the amount it travels? Sound doesn't go through walls? Please tell my neighbor.
In electromagnetism, a medium has a property called an "impedance" which is related to the index of refraction and the speed of waves in the medium. At an interface between two media, the relative impedances determine how much of an incoming wave is transmitted or reflected, so that the entire power of the incoming wave goes somewhere. At an "impedance-matched" interface the reflection coefficient goes to zero. In signal cables and waveguides for electromagnetic waves this leads to people adding "terminating resistors" in various places, so that an incoming signal doesn't get reflected back from a cable junction. Conversely, at a junction with an impedance mis-match, the reflection coefficient is generally nonzero and not all of the power is transmitted.
You can do the same sort of analysis for sound waves moving from one medium to another. The reflection and transmission coefficients can depend on the frequency of the wave, as well, which is why my neighbor complains when I have my music turned up too loud: they can hear the low-frequency bass sounds just fine through the wall, but the high-frequency components (that they'd need to follow the lyrics) don't reach them.
The following is multiple choice question (with options) to answer.
Because sound waves must move through a medium, there are no sound waves in a what? | [
"gas",
"solid",
"vacuum",
"liquid"
] | C | Sound Auditory stimuli are sound waves, which are mechanical, pressure waves that move through a medium, such as air or water. There are no sound waves in a vacuum since there are no air molecules to move in waves. The speed of sound waves differs, based on altitude, temperature, and medium, but at sea level and a temperature of 20º C (68º F), sound waves travel in the air at about 343 meters per second. As is true for all waves, there are four main characteristics of a sound wave: frequency, wavelength, period, and amplitude. Frequency is the number of waves per unit of time, and in sound is heard as pitch. High-frequency (≥15.000Hz) sounds are higher-pitched (short wavelength) than low-frequency (long wavelengths; ≤100Hz) sounds. Frequency is measured in. |
SciQ | SciQ-5139 | ph
Here, the addition of any $\ce{HA}$ will produce $\ce{H^+}$ and $\ce{A^-}$ in an aqueous solution (the blood), and decrease the $\ce{pH}$. $\ce{A^-}$ is only a base insomuch as it can form $\ce{HA}$ by combining with $\ce{H^+}$. This can occur if you add (or, as occurs in the kidney, reabsorb) $\ce{A^-}$ with some counter ion other than a proton. Then you can drive the equilibrium to to the left, towards $\ce{HA}$, decreasing $\ce{[H^+]}$. Otherwise, $\ce{A^-}$ derived from $\ce{HA}$ will not drive the equilibrium one way or the other. $\ce{H^+}$ will still dissociate as determined by the $\ce{K_a}$.
The following is multiple choice question (with options) to answer.
Bicarbonate is the second most abundant anion in the blood. its principal function is to maintain your body’s acid-base balance by being part of these? | [
"stream systems",
"buffer systems",
"compound systems",
"curb systems"
] | B | Bicarbonate Bicarbonate is the second most abundant anion in the blood. Its principal function is to maintain your body’s acid-base balance by being part of buffer systems. This role will be discussed in a different section. Bicarbonate ions result from a chemical reaction that starts with carbon dioxide (CO2) and water, two molecules that are produced at the end of aerobic metabolism. Only a small amount of CO2 can be dissolved in body fluids. Thus, over 90 percent of the CO2 is converted into bicarbonate ions, HCO3–, through the following reactions:. |
SciQ | SciQ-5140 | 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.
What process involves two cell divisions and produces four haploid cells? | [
"mutations",
"meiosis",
"Klerokinesis",
"Mitosis"
] | B | Meiosis involves two cell divisions and produces four haploid cells. |
SciQ | SciQ-5141 | dna, homework, transcription, translation
Title: How to find the amino acid in the DNA protein 3' A T A G T A C C G C A T G T A C G G G C G A G A C A T T C G A G C A T T C A T 5'
This a Template DNA.
How to find the number of amino acids amino acids in the protein encoded by the above gene?
The answer is $7$.
My Try:
First I converted the above DNA to RNA and got
5' U A U C A U G G C G U A C A U G C C C G C U C U G U A A G C U C G U A A G U A 3'
Then I found the start codon which is A U G
5' U A U C |A U G| G C G U A C A U G C C C G C U C U G U A A G C U C G U A A G U A 3'
From here I am not understanding how to proceed.
Can anyone please explain how to solve this? Then you just have to read the codon until you reach a stop codon. There are three stop codon UAA, UGA and UAG. So, in your example..
Start Stop
5' U A U C | A U G | G C G | U A C | A U G | C C C | G C U | C U G | U A A | G C U C G U A A G U A 3'
Your protein is therefore 7 amino acids long (incuding the starting methionine). The genetic code is
Therefore the 7 amino acids are
Met Ala Tyr Met Pro Ala Leu
In case you are confused about having an AUG codon in the middle of an open reading frame, then you should have a look at the post Effect of a doubling of the start codon in a gene.
Of course, I assumed that the region is indeed transcribed and that the first AUG is indeed the start codon and not just a methionine in the middle of an open reading frame.
The following is multiple choice question (with options) to answer.
What happens to a chain of amino acids after it reaches a stop codon? | [
"digestion stops",
"released from the ribosome",
"metabolism begins",
"stays in ribosome"
] | B | The chain of amino acids keeps growing until a stop codon is reached. Then the chain is released from the ribosome. |
SciQ | SciQ-5142 | 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.
How many electrons can be accommodated in the first electron shell's orbital? | [
"3",
"2",
"1",
"none"
] | B | |
SciQ | SciQ-5143 | ecology, statistics, species, species-distribution
Title: How do I compare the variance of a distribution of species in one area versus another? It's possible that this question is better suited for stack overflow, but I think the ecologists on this site might be better equipped to answer it.
I'm trying to study two geographically-isolated populations of the same species. Inspecting the distributions, I see that both are bimodal (there's some seasonality to their occurrence), but the peaks in one population are much higher and much narrower (i.e., the variance of the local peaks is smaller).
What sort of statistical test would be appropriate to determine whether these differences are significant? These are just some preliminary ideas...
I think you should look at the seasonal distributions separately, since the bimodal distribution is the outcome of two fairly separate processes. The two distributions might also be controlled by different mechanisms, so that e.g. winter distributions might be more sensitive to yearly climate. If you want to look at population differences and reasons for these I think it is therefore more useful to study seasonal distributions separately. An exploratory analysis could be to compare distribution percentiles (north/south and east/west coordinates) to look at range edges, or to use a fixed number of edge observations to establish borders. The weighted centre-point of population distributions can be used to look for differences in overall position. If you have grid occurences, percentage overlap between species/populations could maybe also be useful.
If you haven't already, you look also look at Maxent, which is a widely used software for modelling species distributions and habitats. Look at Elith et al. (2011) for an overview. If you want to look at changes over time (even if this doesn't seem to be your main point) you should also check out dynamic occupancy models that use occurrence records to model species distribution while taking detectability into account, e.g. MacKenzie et al. (2009).
The following is multiple choice question (with options) to answer.
Species distributions are a consequence of both ecological and evolutionary what? | [
"fluctuations",
"particles",
"isolation",
"interactions"
] | D |
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