source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-5544 | rotational-dynamics, reference-frames
Now suppose that the particles are indeed stuck together to form a rigid body. We see that the body is moving so that: 1) the CofM remains fixed, 2) all the distances between the particles are fixed. (This second condition is what is meant by a $rigid$ body after all).
A motion with these two properties, (1) and (2), is precisely what is meant by the phrase ``a rotation about the CofM''
The following is multiple choice question (with options) to answer.
In what state of matter are particles rigidly fixed in space and held tightly to neighboring particles? | [
"solids",
"liquids",
"energies",
"Gases"
] | A | As shown in Figure above , each state of matter looks quite different at the molecular level. In the case of liquids and solids, the distances between particles are negligible relative to the size of each particle; they are essentially in direct contact with one another. In liquids, particles are free to move and exchange neighbors, resulting in the properties of a fluid. In solids, they are rigidly fixed in space and held tightly to neighboring particles. |
SciQ | SciQ-5545 | 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.
What is a network solid and consists of carbon atoms covalently bonded to one another in a repeating three-dimensional pattern? | [
"a diamond",
"an agate",
"a zirconium",
"a ruby"
] | A | Diamond is a network solid and consists of carbon atoms covalently bonded to one another in a repeating three-dimensional pattern. Each carbon atom makes four single covalent bonds in a tetrahedral geometry. |
SciQ | SciQ-5546 | taxonomy, history
Title: How many species did Carl Linnaeus classify? How many species did Carl Linnaeus (senior) classify? More than 13,000.
Plants: >9,000 names.
In Systema Naturae 10th edition, commonly taken as the starting point of modern taxonomy, Linnaeus is reported to have published around 6,000 plant names (I haven't counted, but Müller-Wille gives 5,900 and Stearn says "almost 6,000". The Wikipedia figure of 7,700 may come from a different edition of Systema Naturae).
However, that's just SN10. Luckily, a wonderful source has compiled the names from all of Linnaeus's work:
The Linnaean Plant Name Typification Project of the Natural History Museum says that Linnaeus published more than 9,000 valid plant names in his life (names that are still valid under current nomenclatural conventions), and they have many of them in a searchable database with references to where Linnaeus published them.
Animals: >4,200 names.
For SN10, different authors give 4,236 or 4,378 animal names. Stearn says "nearly 4,400", so perhaps he too was unsure. The total number Linnaues described in his life is probably higher, as he did write separate zoological publications like Fauna Svevica, but I couldn't find a source like the project bringing together all of his animal names.
Müller-Wille S. 2006. Linnaeus' herbarium cabinet: a piece of furniture and its function. Endeavour 30: 60–64.
Stearn WT. 1959. The Background of Linnaeus's Contributions to the Nomenclature and Methods of Systematic Biology.)
The following is multiple choice question (with options) to answer.
Linnaeus developed binomial nomenclature, which means each organism is assigned what? | [
"single name",
"complex name",
"two-part name",
"simple name"
] | C | Linnaeus developed binomial nomenclature , a way to give a scientific name to every organism. In this system, each organism receives a two-part name in which the first word is the genus (a group of species), and the second word refers to one species in that genus. For example, a coyote's species name is Canis latrans . Latrans is the species and Canis is the genus, a larger group that includes dogs, wolves, and other dog-like animals. Here is another example: the red maple, Acer rubra , and the sugar maple, Acer saccharum , are both in the same genus and they look similar ( Figure below ). Notice that the genus is capitalized and the species is not, and that the whole scientific name is in italics. Tigers (Panthera tigris) and lions (Panthera leo) have the same genus name, but are obviously different species. The names may seem strange, but the names are written in a language called Latin. |
SciQ | SciQ-5547 | • @flea, the French word is "poisson" (same spelling as that mathematician, if it helps). This undermines your assertion a wee bit. Aug 19, 2016 at 8:54
The following is multiple choice question (with options) to answer.
What do we call the mathematical field of study credited to french mathematician-philosopher rene descartes? | [
"Euclidean geometry",
"cartesian geometry",
"algebra",
"calculus"
] | B | The plot that we know of as a graph was the brainchild of the French mathematician-philosopher Rene Descartes (1596-1650). His studies in mathematics led him to develop what was known as “Cartesian geometry”, including the idea of our current graphs. The coordinates are often referred to as Cartesian coordinates. |
SciQ | SciQ-5548 | biochemistry, physiology, muscles, bioenergetics
Title: Location of t tubule in muscle Why do mammalian skeletal muscles have t-tubules at the junction of the anisotropic and isotropic band, whereas non-mammalian muscles and cardiac muscles have it at Z-line? What could have been the functional significance?
If skeletal muscle would have it at the Z-line then I think it would have been more effective in contraction of muscle fibre. So which arrangement is more efficient?
Also, why is a common arrangement (the more efficient one) not seen in all those muscle types? Interesting question. Indeed it is related to the working of cardiac muscles. First of all, lets have a look at the structure of a sarcomere of a cardiac muscle from here:
Here, what we can see is that the t-tubule is a depression formed in myocyte. It is important to know this fact here. Why? See this:
In contrast to skeletal muscle, cardiac muscle requires extracellular calcium ions for contraction to occur. Like skeletal muscle, the initiation and upshoot of the action potential in ventricular cardiomyocytes is derived from the entry of sodium ions across the sarcolemma in a regenerative process. However, an inward flux of extracellular calcium ions through L-type calcium channels sustains the depolarization of cardiac muscle cells for a longer duration. The reason for the calcium dependence is due to the mechanism of calcium-induced calcium release (CICR) from the sarcoplasmic reticulum that must occur during normal excitation-contraction (EC) coupling to cause contraction.
First, cardiac muscles don't work by external action potentials, they work on a cycle governed by themselves, known as the cardiac cell cycle.
Second, as is clear from above paragraph, these cells depend on extracellular Ca2+ ions for initiating contraction, a clear difference from skeletal muscles which need Ca2+ stored in SR. Hence, they require t-tubule at a place where a sarcomere ends. Obviously, having a depression in the middle of a sarcomere (i.e. between I- and A-band) would not work here.
Also, the structure of t-tubules is also different between the two. Compare my first image with the image below from here:
The following is multiple choice question (with options) to answer.
Where do skeletal muscles usually attach? | [
"end of bones",
"to dendrites",
"to cartilage",
"to the spine"
] | A | Many skeletal muscles are attached to the ends of bones where they meet at a joint. The muscles span the joint and connect the bones. When the muscles contract, they pull on the bones, causing them to move. |
SciQ | SciQ-5549 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
What do the cells in the front of a volvox typically develop to help swim towards light? | [
"tumors",
"vertebrates",
"sunspots",
"eyespots"
] | D | Each Volvox , shown in Figure above , is a colonial organism. It is made up of between 1,000 to 3,000 photosynthetic algae that are grouped together into a hollow sphere. The sphere has a distinct front and back end. The cells have eyespots, which are more developed in the cells near the front. This enables the colony to swim towards light. |
SciQ | SciQ-5550 | human-biology, senses
Olfaction (smell, as carried out by neurons in the nasal epithelium; e.g. smell of vanilla, and smell of bad food)
Gustation (taste, as carried out by neurons on the tongue; e.g. salt, sugar)
Antigen chemosensing (chemical sensing, as carried out by, for instance, immune antigen receptors on B cells)
Hormonal signaling chemosensing (chemical sensing of hormones such as insulin, as carried out for instance by myocytes)
Starch sensing? (amylase in saliva can be used as a test for digestable starch)
Visual system, at the retina?
Visible light (sensing electromagnetic radiation on the order of a few hundred nanometers in wavelength)
Internal methanol sensing (the visual system as a sensor for methanol, which disproportionately affects myelin surrounding the optic nerve)
Pressure sensing (see phosphenes)
The vestibular system
Gravity sensing
Balance
Coordination
Motion sensor
Head position sensor
Spatial orientation
Skin
thermosensation (touching a hot kettle!)
Nociception (pain sensing)
allergen sensing
sensor for gamma rays, X-rays and UV light (indicated by radiation burns, development of skin cancer, sunburns, etc.)
Bones and muscles?
Kinesthetic and bodily proprioception
Brain/mind/mental/social senses?
mental pain
boredom
mental or spiritual distress
sense of self and other, including friendship, power, place in social hierarchy, reputation, companionship
motivation and love (oxytocin, dopamine, etc. in limbic systems and other neural correlates)
I'm sure some would agree, and some would disagree about the specific cases I provide. Thus the definition of senses, or sensing, seems to be opinion-based or at the very least very sensitive to an agreed-upon operational definition, for which there is none.
The following is multiple choice question (with options) to answer.
What bodily system handles taking in oxygen, getting rid of carbon dioxide, aiding in speech production and sensing odors? | [
"circulatory system",
"pulmonary system",
"nervous system",
"respiratory system"
] | D | CHAPTER REVIEW 22.1 Organs and Structures of the Respiratory System The respiratory system is responsible for obtaining oxygen and getting rid of carbon dioxide, and aiding in speech production and in sensing odors. From a functional perspective, the respiratory system can be divided into two major areas: the conducting zone and the respiratory zone. The conducting zone consists of all of the structures that provide passageways for air to travel into and out of the lungs: the nasal cavity, pharynx, trachea, bronchi, and most bronchioles. The nasal passages contain the conchae and meatuses that expand the surface area of the cavity, which helps to warm and humidify incoming air, while removing debris and pathogens. The pharynx is composed of three major sections: the nasopharynx, which is continuous with the nasal cavity; the oropharynx, which borders the nasopharynx and the oral cavity; and the laryngopharynx, which borders the oropharynx, trachea, and esophagus. The respiratory zone includes the structures of the lung that are directly involved in gas exchange: the terminal bronchioles and alveoli. The lining of the conducting zone is composed mostly of pseudostratified ciliated columnar epithelium with goblet cells. The mucus traps pathogens and debris, whereas beating cilia move the mucus superiorly toward the throat, where it is swallowed. As the bronchioles become smaller and smaller, and nearer the alveoli, the epithelium thins and is simple squamous epithelium in the alveoli. The endothelium of the surrounding capillaries, together with the alveolar epithelium, forms the respiratory membrane. This is a blood-air barrier through which gas exchange occurs by simple diffusion. |
SciQ | SciQ-5551 | radioactivity, statistics, randomness, half-life
Title: What happens to a radioactive material's atom when it disintegrates? Suppose you initial had radioactive $2^n$ atoms (where $n$ is an integer). Now after a number of halflives the number of left out atoms becomes 1. Now what will happen to it will it disintegrate and the leftover would be half an atom? Now if the reaction stops then the statement "The decaying radioactive atom would never end" then it'll be wrong. Radioactive decay is a stochastic process. This means that there is random chance involved, so the exponential model used to represent radioactive does not say exactly how many atoms of the original substance will be left at a given time, rather it tells you the expected value of atoms remaining. If you begin with n=1 atom, after some time the exponential model gives you n=0.5. This does not mean there are 0.5 atoms remaining, it rather means that there is a 0.5 chance that the atom has not decayed yet.
The following is multiple choice question (with options) to answer.
The atom often (but not always) turns into a different what during the decay process? | [
"aspect",
"element",
"reaction",
"concept"
] | B | When an atomic nucleus decays, it does so by releasing one or more particles. The atom often (but not always) turns into a different element during the decay process. The amount of radiation given off by a certain sample of radioactive material depends on the amount of material, how quickly it decays, and the nature of the decay product. Big, rapidly decaying samples are most dangerous. |
SciQ | SciQ-5552 | molecular-biology, molecular-genetics, development, sex
Quote from a Review (Yao 2005):
We have just begun to glimpse into the mechanisms underlying ovarian development. Convincing evidence challenges us to reconsider the existing paradigm that describes ovarian development as a default system. The default concept was first proposed in the early 1950s when Jost performed the groundbreaking experiments to demonstrate mechanisms of sex differentiation of reproductive tracts (Jost, 1947, 1953, 1970). The term “default” was not originally intended to describe the developmental status of the ovary. Instead, it is referred to the female reproductive tract or the Mullerian duct based on the fact that the female reproductive tract forms in both XX and XY individuals in the absence of gonads. Indeed, now it has become evident that early ovarian development is an active process involving intrinsic cell fate decisions and complex crosstalks between germ cells and somatic cells. Most intriguingly, the appearance of testicular structures in XX individuals where Sry and its downstream components are absent further raises the improbable question: Could the testicular development be default after all?
The following is multiple choice question (with options) to answer.
Females are not influenced by the male sex hormone testosterone during embryonic development because they lack what? | [
"x chromosome",
"m chromosome",
"y chromosome",
"z chromosome"
] | C | Unlike males, females are not influenced by the male sex hormone testosterone during embryonic development. This is because they lack a Y chromosome. As a result, females do not develop male reproductive organs. By the third month of fetal development, most of the internal female organs have formed. Immature eggs also form in the ovary before birth. Whereas a mature male produces sperm throughout his life, a female produces all the eggs she will ever make before birth. |
SciQ | SciQ-5553 | pressure
Title: What is the principle behind the expansion and contraction of balloon in the bottle used for lung model
The picture above describes inhalation and exhalation, the balloons present the lungs which deflate during exhalation when the elastic bottom(diaphragm) is release and vice versa for inhalation what is the principle behind the conservation of pressure in the balloons and in the bottle
Air (or any fluid) in equilibrium exerts an equal pressure in all directions.
Any difference in pressure between the gas jar and the balloons will cause the balloons to expand or contract.
As the balloon expands, the elastic force acts so as to return the balloon to its natural shape.
The pressure exerted by the gas is inversely proportional to the volume it occupies (bigger volume means fewer particles per unit volume, so less force on the container).
Using this, it is simple to understand how the model works. As the elastic membrane is pulled down, the volume of the chamber increases, thereby reducing the air pressure inside the chamber. Therefore, the force of the air in the balloons (atmospheric pressure) is greater than the pressure in the chamber, so the balloon expands.
As the balloon expands, the elastic force increases, eventually compensating for the difference in pressure between the atmosphere and the chamber.
When the membrane is released, the reverse happens. The volume of the chamber decreases, so the pressure in the chamber increases, which forces the balloons to contract.
The following is multiple choice question (with options) to answer.
Pressure relationships inspiration (or inhalation) and expiration (or exhalation) are dependent on the differences in pressure between the atmosphere and these? | [
"bones",
"enzymes",
"salts",
"lungs"
] | D | Pressure Relationships Inspiration (or inhalation) and expiration (or exhalation) are dependent on the differences in pressure between the atmosphere and the lungs. In a gas, pressure is a force created by the movement of gas molecules that are confined. For example, a certain number of gas molecules in a two-liter container has more room than the same number of gas molecules. |
SciQ | SciQ-5554 | evolution, zoology, taxonomy, phylogenetics
The apomorphy that defines the tetrapods is "paired limbs". You have Amphibia to the left and Amniota to the right, whose apomorphy is " egg with extraembrionic membranes". Inside them, you have Reptilia, whose apomorphies are "skull with upper and lower fenestra and beta-keratin in epidermis". Turtles came from an ancestor with these characteristics. So, turtles belong to the monophyletic group of "Reptiles".
Post scriptum: You wrote that "turtles (specifically sea turtles) live on both land and water, very much like amphibians". Just a curiosity: the reason why sea turtles leave the water (sea) from time to time shows exactly that they are not amphibians! Amphibians, being non-amniotes, have eggs that survive under water (actually, with few exceptions, they need to be under water). Turtles, on the other hand, are amniotes, and the amniotic egg cannot be laid under water. That's why the turtles have to leave the water to lay eggs: because, contrary to the amphibians, they cannot lay eggs under water.
The following is multiple choice question (with options) to answer.
Female monotremes share what external opening with reptiles and birds? | [
"cloaca",
"vagina",
"urethra",
"anus"
] | A | Female monotremes lack a uterus and vagina. Instead, they have a cloaca with one external opening, like the cloaca of reptiles and birds. The opening is used to excrete wastes as well as lay eggs. The eggs of monotremes have a leathery shell, like the eggs of reptiles. Female monotremes have mammary glands but not nipples. They secrete milk to feed their young from a patch on their belly. This form of reproduction is least risky for the mother but most risky for the offspring. |
SciQ | SciQ-5555 | quantum-mechanics, wavefunction, atomic-physics, quantum-electrodynamics, collision
Title: How does the collision between two atoms work? Considering the quantum mechanical model for an atom, what exactly happens when two atoms (say, two Ca2+ ions in a Brownian motion) collide with each other? As I know, this collision is not like a regular elastic or inelastic collision between two macroscopic objects. Is it mainly due to the coulombic repulsion between the electrons of the two atoms? And, how is the trajectory of the two atoms after collision determined, and what factors contribute to it? Are these trajectories and the angle by which the atoms get deviated deterministic, or fuzzy just as the atoms themselves? One can make a simplistic quantum model of the two atoms by treating them as point particles with appropriately fuzzy, but as high-information as possible, positions and momenta directed toward each other. You do not need relativistic quantum field theory in this case - though you might need at least a crude version if you want to also include photon emission, namely a coupled EM field, but not a full QFT for the electrons and such, just the EM, because if this is meant to simulate a chemical process, this is suitably low-energy that we aren't creating or destroying any known massive particles.
And you are right in your hunch: The collision will be, as you say, fuzzy. The available information in position falls steadily with time as the probability distributions broaden during approach and then even more in collision - if one starts out broader than the other it will spill over the other on each side. Moreover, the positions after collision will be entangled, or correlated: you cannot simply and totally faithfully write down two separate wave functions
$$\psi_\mathbf{r}(\mathbf{r}_\mbox{atom 1})$$
and
$$\psi_\mathbf{r}(\mathbf{r}_\mbox{atom 2})$$
to describe their fuzzy positions independently after collision. Instead, you need a six-dimensional wave function
$$\psi_{\mathbf{r}_1, \mathbf{r}_2}(\mathbf{r}_\mbox{atom 1}, \mathbf{r}_\mbox{atom 2})$$
The following is multiple choice question (with options) to answer.
Collisions between hydrogen atoms demonstrate one form of what? | [
"destructive fusion",
"nuclear fusion",
"nuclear radiation",
"nuclear reaction"
] | B | Collisions between hydrogen atoms demonstrate one form of nuclear fusion. |
SciQ | SciQ-5556 | biochemistry, photosynthesis
Title: When is Water Produced During Photosynthesis? The formula for photosynthesis is: $$6CO_2+12H_2O \rightarrow C_6H_{12}O_6+6O_2+6H_2O$$
I can count the carbons, the waters on the reactant side, the oxygens, and the glucose, but I cannot seem to locate where in either light or dark reaction 6 water molecules were produced again. Where and when were they produced? Some of the water that's split is regenerated when the hydroxyl radicals (reactive oxygen species) are converted to hydrogen peroxide, water, etc. by superoxide dismutases and antioxidative mechanisms in the chloroplast (peroxisomes/catalases, etc. take care of this). There's also some evidence that the presence of mannitol, ascorbate and glutathione protect against ROS produced in chloroplasts as well. So you input water, and in an effort to avoid oxidative damage, you do get some water generated. However, the balanced equation doesn't reflect this because it's not an actual product of photosynthesis.
About ROS and protective elements
Extra Reading on ROS in photosynthetic systems
I think that's a very obscure fact, and despite the reality of things, it's actually difficult to query the literature. Good question.
The following is multiple choice question (with options) to answer.
Fluid-filled thylakoids are the site of glucose production in the second stage of what process? | [
"birth",
"glycolysis",
"photosynthesis",
"measurements"
] | C | The interior space that surrounds the thylakoids is filled with a fluid called stroma . This is where carbon dioxide is used to produce glucose, the second part of photosynthesis. |
SciQ | SciQ-5557 | biochemistry, neuroscience, brain, neuroanatomy
Title: The human brain in numbers I: neurons Even though knowing the number of neurons in a functional unit or with the same function is not of main importance, it may be interesting to know their orders of magnitude, especially in the human brain. For example:
|------------------|------------------|
| cerebellum | 100,000,000,000 |
| cortex | 20,000,000,000 |
| telencephalon | 10,000,000,000 |
| brainstem | 1,000,000,000 |
| sensory neurons | |
| haptic | 500,000,000 |
| visual | 100,000,000 |
| auditory | 2,000 |
| limbic system | |
| amygdala | 10,000,000 |
|------------------|------------------|
The following is multiple choice question (with options) to answer.
What are the basic units of structure and function in living organisms? | [
"lipids",
"proteins",
"molecules",
"cells"
] | D | All living things consist of one or more cells. Cells are the basic units of structure and function of living organisms. |
SciQ | SciQ-5558 | soft-question, biophysics, biology
Title: Does physics explain why the laws and behaviors observed in biology are as they are? Does physics explain why the laws and behaviors observed in biology are as they are? I feel like biology and physics are completely separate and although physics determine what's possible in biology, we have no idea how physics determine every facets of biology. We know roughly how forces in physics may impact biological systems, but not every little connections and relations that exist between physics and biology. Am I wrong? To get more insight into a question like this, you might like to ponder the relationship between logic gates and programming languages in the case of computers. This is a lot simpler than the physics—biology question, but begins to open up some of the issues. When a computer runs a program, certainly lots of logic gates and memory elements etc. are enacting the process described by the program. But the logic gates do not themselves tell you much about the structure and nature of a high-level programming language such as Java or Python. In a similar way, further study of atoms and molecules will not in itself reveal much about the immune system in mammals, or the social structure of an ant colony, and things like that.
This "answer" is really a brief comment on what is, in the end, quite a deep issue concerning the whole nature and structure of scientific knowledge. Another useful thing to ponder is the relationship between the concepts involved when one moves from the equations of particle physics to many-body physics. There is every reason to consider that the motions of a non-linear many-body system are all consistent with the description offered by the Standard Model of particle physics for all the various fields and interactions. However, the low-level description does not in itself tell us how to formulate a field theory which correctly captures the main elements of the collective behaviour.
The following is multiple choice question (with options) to answer.
What concept can be applied to biology, because the structure of an organism, or part of an organism, depends on its function? | [
"motion follows function",
"form follows use",
"form follows function",
"attachment follows function"
] | C | An important concept in biology is that form follows function. In other words, the structure of an organism, or part of an organism, depends on its function. Apply this concept to plants, and explain why plants have different types of cells and tissues. |
SciQ | SciQ-5559 | human-biology
Title: Does sweat contain DNA information? I was reading this article : Perspiration
The first question which came to my mind after reading the composition of sweat was whether it contains any information about the DNA or not?
I haven't had much interaction with biology since 12th grade (2010), so kindly answer in layman's terms and detail as well. The Wikipedia page you linked says that sweat is composed of a liquid similar to blood plasma. As all DNA in humans is stored in the nucleus of a cell, it seems unlikely that the sweat itself would contain any DNA.
However, when someone sweats significantly, I can't imagine that no skin cells end up in the sweat. In any case in which this occurs, then the DNA in the cell is in the sweat. Additionally, with small amounts of sweat, I can't imagine how it would be collected without getting any skin cells in it.
This source confirms that sweat contains DNA in some form. Additionally, I think the following quote from here shows that it is stored in cells:
In every case, what is being tested is the DNA contained in cells of human tissue
The following is multiple choice question (with options) to answer.
Is sweat an exocrine or endocrine substance? | [
"both",
"exocrine",
"exocrine",
"neither"
] | B | Epithelial tissue from epithelium. Below this is dermis, thicker and with blood vessels. Two specialized epithelia: • pseudostratified • transitional Pseudostratified epithelia lines the trachea (where it is ciliated)and the male urethra (where it is non ciliated), looks stratified but not. Transitional epithelia found only in bladder and urinary system. As it stretches it appears to go from 6 to 3 cell layers deep. Glandular epithelia (gland: group of cells that excretes something. mostly derived from epithelium. Glands are classified into endocrine and exocrine by where they excrete. Endocrine glands secrete hormones into the blood without use of ducts. Exocrine glands secrete onto the body surface or into a cavity, thru a duct. Exocrine substances include sweat, mucous, oil, and saliva. An exocrine gland is the liver, which secretes bile. |
SciQ | SciQ-5560 | nuclear-physics
Title: Why are elements with even atomic number more abundant? In reading this article about the origins of elements, I found the following diagram:
What strikes me about this image is the very consistent zig-zagging of the line that appears to indicate that elements/isotopes with an even number are more abundant.
Am I correct? What's going on here? I will add to the answer from @BowlofRed https://physics.stackexchange.com/a/158270/36194 that the nuclear pairing interaction lowers the energy in nuclei where the number of like nucleons is even: thus for instance there are more isotopes with even rather than odd number of neutrons. This also favors the formation of even-proton-numbered nuclei over the neighbouring odd ones.
The following is multiple choice question (with options) to answer.
Nuclei with even numbers of protons, neutrons, or both are more likely to be this? | [
"stable",
"unstable",
"solid",
"ionic"
] | A | The nuclei that are to the left or to the right of the band of stability are unstable and exhibit radioactivity. They change spontaneously (decay) into other nuclei that are either in, or closer to, the band of stability. These nuclear decay reactions convert one unstable isotope (or radioisotope) into another, more stable, isotope. We will discuss the nature and products of this radioactive decay in subsequent sections of this chapter. Several observations may be made regarding the relationship between the stability of a nucleus and its structure. Nuclei with even numbers of protons, neutrons, or both are more likely to be stable (see Table 21.1). Nuclei with. |
SciQ | SciQ-5561 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
Some prokaryotes form spores for survival called what? | [
"gymnosperms",
"endospores",
"rhizomes",
"buds"
] | B | Many organisms form spores for reproduction. Some prokaryotes form spores for survival. Called endospores , they form inside prokaryotic cells when they are under stress. The stress could be UV radiation, high temperatures, or harsh chemicals. Endospores enclose the DNA and help it survive under conditions that may kill the cell. Endospores are commonly found in soil and water. They may survive for long periods of time. |
SciQ | SciQ-5562 | cell-biology, terminology
Title: What is the difference between cytosol and cytoplasm? I've generally seen cytosol defined as the solution inside cells minus the organelles, cytoskeleton, etc and cytoplasm as the cytosol plus the organelles, cytoskeleton, etc. This naturally leads to the impression that cytosol is the cytoplasm minus all the solids. The problem here is that there are all sorts of other large molecules in the cells which could be thought of as solid. Are they also part of the cytosol or are they suspended in it? (I.e. are they part of the cytosol or are they non-cytosol components of the cytoplasm?)
Basically, I'm asking if the precise definition of cytosol is just anything in the cell that's not behind an endomembrane (save the exoskeleton) or if the dividing line is something else.
Subquestion: things can get even more terminologically confused because the cytosol is sometimes called the matrix. What the heck is the preferred terminology with this stuff? IMO, the definitive answer to this question is given in a paper by J. S Clegg. He traced the origin of the term cytosol to a book chapter by H. A. Lardy, and confirmed by email that Lardy had indeed coined the term. Their definition of cytosol is as follows:
... that portion of the cell which is found in the supernatant fraction after centrifuging the homogenate at 105 000 x g for 1 hour.
The following is multiple choice question (with options) to answer.
What is the liquid inside the central vacuole called? | [
"chloroplasm",
"cytoplasm",
"cell sap",
"osmotic fluid"
] | C | The central vacuole contains large amounts of a liquid called cell sap, which differs in composition to the cell cytosol. Cell sap is a mixture of water, enzymes, ions, salts, and other substances. Cell sap may also contain toxic byproducts that have been removed from the cytosol. Toxins in the vacuole may help to protect some plants from being eaten. |
SciQ | SciQ-5563 | nutrition, hematology, metabolism
Title: How does a glucose molecule enter the cell from blood vessel? The transporters in the plasma membrane of the cells promote the entry of glucose molecules from the extracellular matrix to the cytosol of the cell. Could someone explain how does the nutrient molecule enter the extracellular space from the blood vessel?
For instance, in the context of the pancreas, the walls of the blood vessel is fenestrated. The literature also provides evidence for the presence of connexon in the endothelium of the capillaries.
My doubt is, the nutrient molecule that diffuses from the blood vessel reaches the cytosol of the cell through
Diffusing through connexon ?(or)
Does it reach the interstitial matrix(the fluid surrounding the cells) and then uptaken by the transporters present in the plasma membrane of the cell? I think I understand your question, Natasha. In short, your own answer #2 is correct.
There are 3 spaces, and 2 pathways for glucose to pass from one to the next:
intracapillary plasma
extracellular fluid
the cytosol.
Ways glucose gets into the cell:
(2->3) To get from the ECF to the cytosol , glucose always needs a transport protein. These are the GLUTs. In two cases, the small intestine and kidney, these are part of a secondary active transport system based on the Na/K-ATPase. In the pancreas, it's GLUT2.
(1->2) To get from the capillary plasma to the ECF requires filtration, the process of applying hydrostatic pressure to the plasma and literally squeezing it like a sponge. The boundary of the "blood sponge" is the basement membrane. The membrane holds in the proteins, and lets anything dissolved in the watery serum (like glucose) through.
The Filtration Constant Kf is proportional to the percentage of the BM that is exposed in a given capillary, which varies by the type and other factors like histamine release.
The following is multiple choice question (with options) to answer.
Cancer cells take up glucose for what reason? | [
"energy",
"heating",
"food",
"reproduction"
] | A | Despite its dangers, radioactivity has several uses. For example, it can be used to determine the ages of ancient rocks and fossils. It can also be used as a source of power to generate electricity. Radioactivity can even be used to diagnose and treat diseases, including cancer. Cancer cells grow rapidly and take up a lot of glucose for energy. Glucose containing radioactive elements can be given to patients. Cancer cells take up more of the glucose than normal cells do and give off radiation. The radiation can be detected with special machines like the one in the Figure below . The radiation may also kill cancer cells. You can learn more about medical uses of radiation at this URL: http://www. youtube. com/watch?v=v_8xM-mLxJ8. |
SciQ | SciQ-5564 | zoology, entomology
Title: How do insects know what is edible? What is the current scientific consensus on how insects innately know what is food and not food? If they are introduced to new food sources do they experiment with eating the new food? Could you teach a preying mantis to eat beef? Insect feeding behaviour is generally triggered by one or more conditions which may include colour, shape, chemical traces or temperature.
Insects generally locate food based on some combination of olfactory, thermal and visual queues (colour and shape). If their minimum criteria are met to specified tolerance, they will attempt to feed on whatever is nearby using their usual feeding method.
When these conditions appear on the 'wrong' target, it attracts insects and triggers feeding attempts. Insects can be triggered to feed on atypical food sources if the relevant aspects of their environment match those of their normal feeding environments. For example, here is a report from a professor of entomology recollecting his observations of being bitten by pea aphids while handling plants, which he assumes is because of the scent on his hands.
We can exploit this in various ways for research. One is for artificial blood-feeding of insects: most systems, like the Hemotek membrane feeding system, warm blood to the body temperature of the host. They do not normally resemble a target host in any other way. Some blood-feeding insects have very specific requirements for temperature (for example they will only feed on blood if it is heated to the body temperature of birds; the same blood heated to mammalian body temperature will be ignored) but we do not need to make the target look or smell like the natural host. Other species may need olfactory cues, which can be provided by researchers rubbing the membranes on their forearms before placing them on the feeding system, or by breathing on cages as you add the food.
A second way we exploit this is for insect traps. Although not all traps work this way, some work by mimicking the host and attracting insects that are looking for a meal. This can be via olfactory/chemical mimicry (for example carbon dioxide baited traps - try Googling "CO2-baited traps") or visual. Different degrees of visual 'deception' may be needed; for instance to attract tsetse flies, colour is important but shape is not:
The following is multiple choice question (with options) to answer.
Birds and insects perform what function for flowering plants? | [
"condensation",
"pollination",
"irrigation",
"vegetation"
] | B | Insects and birds pollinate flowering plants, including crop plants. |
SciQ | SciQ-5565 | molecular-genetics, terminology, cancer, mutations
Title: Are all mutagens carcinogens? Not all carcinogens are mutagens. Alcohol and estrogen, for example, does not damage DNA.
It's one of the assumptions of the Ames test that mutagenicity implies carcinogenicity, but is this always the case? I assumed that it was, but then I saw one of the comments here. I did some more research but the internet seems to be reluctant to be definitive on the subject. This guy claims 'no', but I'd prefer sources or at least a response that handles counterexamples like HPV. This paper claims 'yes', but doesn't list any specific examples. Some mutagens might be more specific to genes involved in cell cycle regulation, so I could see how a weak mutagen is a powerful carcinogen.
My question is, can you go the other way? Are there mutagens that just do not cause cancer? If they do not exist or are not known to exist, are they even possible? Short answer
All mutagens are potential carcinogens unless the mutagen is highly specific to a site. As noted in the question, carcinogens need not be mutagenic.
The following is multiple choice question (with options) to answer.
Most carcinogens produce mutations in genes that control what? | [
"cell cycle",
"proteins cycle",
"digestive cycle",
"ubiquitous cycle"
] | A | Most carcinogens produce mutations in genes that control the cell cycle. |
SciQ | SciQ-5566 | homework-and-exercises, special-relativity, doppler-effect
in order that the wavelength of one photon be twice that of the other?
So given the formula above, the remainig mathematical task is to solve
$2 = \lambda_{\text{towards}} / \lambda_{\text{away}} = \left(\lambda_s \sqrt{ \frac{1 + \beta}{1 - \beta} } \right) / \left(\lambda_s \sqrt{ \frac{1 - \beta}{1 + \beta} } \right) = \left( \frac{1 + \beta}{1 - \beta} \right)$
for $\beta$.
The result is of course:
$\beta = 1/3$, i.e. $v = c/3$ (referring to the detector and source moving towards each other).
Then the answer is the speed needed to shift down wavelength by 25% for one detector, and up 25% for the other.
No: since
$\sqrt{ \frac{1 - 1/3}{1 + 1/3} } = \sqrt{ \frac{2/3}{4/3} } = \sqrt{1/2}$
and correspondingly
$\sqrt{ \frac{1 + 1/3}{1 - 1/3} } = \sqrt{ \frac{4/3}{2/3} } = \sqrt{2}$,
the "shifts" involved are rather:
"down by 29.289... %" and "up by 41.42... %", respectively.
The following is multiple choice question (with options) to answer.
What type of equations allows calculation of the wavelength of any moving object? | [
"disc wave",
"debroglie wave",
"fluctuations wave",
"develpoment wave"
] | B | The deBroglie wave equations allows calculation of the wavelength of any moving object. |
SciQ | SciQ-5567 | periodic-trends, periodic-table
Title: How long the block starting with element 121 will be? I remember from my chemistry classes that (after the initial irregularities) a new block of elements starts every two periods. After the initial s-block and p-block following it shortly, we have d-block starting at period IV, and f-block starting at period VI.
Now that Element 118 has been discovered, we're about to open period VIII and we're two elements short of a new block.
What block will it be? How many groups, what name etc? As you noted, this is a very appropriate question in light of the IUPAC announcement that we have just finished filling Period 7!
The names of the subshells s, p, d, and f are named after the old spectroscopic terms sharp, principal, diffuse, and fundamental. We ran out of fancy names after that, so the subsequent subshells are named in alphabetical order - g, h, and so on - which means that after the 8s block is filled, we would theoretically have a 5g block.
The orbitals in the g subshell would be labelled with the quantum number $l = 4$, so $m_l$ would take integer values between $-4$ and $4$ (inclusive) giving a total of nine g-orbitals. Each g-orbital could hold two electrons with opposite spins, so the g-block would have $18$ electrons.
However, it is worth noting that the electronic configurations may or may not obey the aufbau principle fully. Whether the 5g orbitals will actually be filled or not will certainly not be easy to determine, considering how short the half-lives of those elements are likely to be.
Wikipedia has an article which talks about it.
The following is multiple choice question (with options) to answer.
Each new horizontal row of the periodic table corresponds to the beginning of a new period because a new principal energy level is being filled with what? | [
"photons",
"protons",
"neutrons",
"electrons"
] | D | When ordered by atomic number, the discrepancies within Mendeleev’s table disappeared. Tellurium has an atomic number of 52, while iodine has an atomic number of 53. So even though tellurium does indeed have a greater atomic mass than iodine, it is properly placed before iodine in the periodic table. Mendeleev and Moseley are credited with being most responsible for the modern periodic law : When elements are arranged in order of increasing atomic number, there is a periodic repetition of their chemical and physical properties. The result is the periodic table as we know it today. Each new horizontal row of the periodic table corresponds to the beginning of a new period because a new principal energy level is being filled with electrons. Elements with similar chemical properties appear at regular intervals, within the vertical columns called groups . |
SciQ | SciQ-5568 | newtonian-mechanics, energy, work
Title: Types of energy and work I am learning about energy and work, and am a beginner to this topic. Energy is defined as the ability to do work. In some cases, the ability to do work directly follows the type of energy. For instance, heat energy can be used to do work through isothermal expansion of gas, for instance.
Is there a relationship/concept between how easy it is to get a type of energy to do work? Some types of energy might make them more suitable to do work, whereas others might involve a more indirect/contrived route. Energy defined as the ability to do work; this does not mean that only work is done, it means that work can be done.
Here is an expanded definition that should help.
The energy of a system is a property of the system that is increased (decreased) by the following mechanisms:
work done on (or done by) the system from its surroundings
heat added to (or removed from) the system from its surroundings
mass transfer into (or from) the system to its surroundings.
"How easy it is to get a type of energy to do work" depends how the system interacts with the surrounding.
For example, if a system comprised of a gas has a higher pressure than its surroundings and can move a boundary (say a piston), the system can lose energy by doing work on the surroundings as the gas expands. Or if the gas is in a closed container (fixed volume) and has a higher temperature than its surroundings, the gas can lose energy by transferring heat to the surroundings. A liquid can have a decrease in its energy, with a decrease in its temperature, by evaporation (mass transfer from the liquid).
The details of energy transfer is addressed by the laws of thermodynamics (e.g., the first and second laws).
The following is multiple choice question (with options) to answer.
What kind of energy is specifically defined as the energy that is available to do work? | [
"used",
"new",
"old",
"free"
] | D | 6.2 Potential, Kinetic, Free, and Activation Energy Energy comes in many different forms. Objects in motion do physical work, and kinetic energy is the energy of objects in motion. Objects that are not in motion may have the potential to do work, and thus, have potential energy. Molecules also have potential energy because the breaking of molecular bonds has the potential to release energy. Living cells depend on the harvesting of potential energy from molecular bonds to perform work. Free energy is a measure of energy that is available to do work. The free energy of a system changes during energy transfers such as chemical reactions, and this change is referred to as ∆G. The ∆G of a reaction can be negative or positive, meaning that the reaction releases energy or consumes energy, respectively. A reaction with a negative ∆G that gives off energy is called an exergonic reaction. One with a positive ∆G that requires energy input is called an endergonic reaction. Exergonic reactions are said to be spontaneous, because their products have less energy than their reactants. The products of endergonic reactions have a higher energy state than the reactants, and so these are nonspontaneous reactions. However, all reactions (including spontaneous -∆G reactions) require an initial input of energy in order to reach the transition state, at which they’ll proceed. This initial input of energy is called the activation energy. |
SciQ | SciQ-5569 | hydrology, geography, rivers, salinity, estuary
Title: Are there any saltwater rivers on Earth? I'm curious if there are any saltwater rivers on Earth. These would presumably arise if a saltwater lake had a river outlet to the ocean.
However, all the saltwater lakes I looked at (Caspian Sea, Dead Sea, Great Salt Lake Utah), apparently don't have any river outlets.
Do any exist? And the obvious follow up, why or why not?
Edit: For the purposes of this question, undersea flows don't count. They are fascinating, but I'm interested if any "regular surface rivers" exist as saltwater rivers. The water in any river draining the sea is infinitely recycle-able (from rain replenishment), whereas the salt from any terrestrial source is not. So salty rivers, if any, won't exist permanently. Saltwater lakes gain their salinity precisely because they have no outlet, so salt just gets concentrated by evaporation. I don't think there are any truly saline rivers throughout their entire length.
The nearest approximations I can think of are:
Rare ephemeral runoff from emergent salt domes in desert areas.
Freshwater rivers that drain into arid areas where combined evaporation and infiltration gradually reduces the flow to zero. These are more 'very brackish' than truly saline. The Amu Darya in Uzbekistan is one such example. I don't know the salinity of the Jordan as it enters the Dead Sea, but the river is reduced to almost nothing, whilst there are hypersaline springs, and sewage effluent from Amman draining into it.
The only river I can think of that is very highly mineralized from source to sea is only about 3 kilometres long. It is an unnamed river from the volcanic crater on Savo Island, in the Solomon Islands (Southwest Pacific). It is also acidic and boiling hot - quite literally, for most of it's length.
The following is multiple choice question (with options) to answer.
Only a small percent of earth's water is what type, as opposed to saltwater? | [
"groundwater",
"rainwater",
"fresh",
"runoff"
] | C | Only a very small percentage of Earth’s water is fresh, liquid water on the surface. But that tiny fraction of water is vital. It is needed by humans, plants, and many other living things. Liquid freshwater flows over Earth’s surface in streams and rivers. It also forms ponds, lakes, and wetlands. People use freshwater for drinking, washing, and industry. They also use it for fun. How do you use freshwater for fun?. |
SciQ | SciQ-5570 | ornithology, kidney
Back to worrying about the mammal-centric thinking: there is a causal implication in both the original and my edited version that is not warranted, which is that the anatomy of the loops of Henle is somehow determining the nitrogen excretion strategy that birds use. It's equally reasonable to presume that birds don't need long loops of Henle since they evolved an alternative excretion mechanism that makes it unnecessary to concentrate urine to a great degree.
The "trick" of that alternative excretion mechanism is using uric acid and excreting a paste. Because uric acid crystalizes and comes out of solution, it doesn't "count" toward osmolarity of the urine, it's excreted as a solid. Birds don't need to remove water to crystalize uric acid, and don't need to use water to flush it out at all, it falls out of solution on its own because it's not very soluble. You could add a bunch of extra water and it would still stay mostly solid rather than dissolving.
So back to your original question: how do birds concentrate their urine? Well, pretty much the same way we do as far as the kidney goes. They also pull some water back in through the cloaca before urine is released, similar to how mammals pull water in from stool in the large intestine. The important difference is not how birds concentrate their urine (because urine concentration isn't a goal/need in itself), but rather how birds excrete nitrogen waste. By not flushing soluble nitrogenous waste with water in the first place, they don't have as much urine to concentrate, so it's less important for them to be very efficient in doing so.
The following is multiple choice question (with options) to answer.
The kidneys work with the urinary system to remove what? | [
"nutrients",
"ions",
"wastes",
"water"
] | C | The kidneys play many vital roles in homeostasis . They work with many other organ systems to do this. For example, they work with the circulatory system to filter blood, and with the urinary system to remove wastes. |
SciQ | SciQ-5571 | reproduction, asexual-reproduction
Title: can self-fertilization in flowers be called asexual reproduction? Suppose a flower having both male and female reproductive parts is self-fertilized then can this be called asexual reproduction...?I'm quite confused cause in this case the fusion of male and female gametes do take place but again the gametes are from the same parent....please help. According to this article from Berkeley, asexual reproduction is:
Any reproductive process that does not involve meiosis or syngamy
Using this definition of asexual reproduction and knowing self-fertilization involves meiosis and syngamy, it is not asexual.
The following is multiple choice question (with options) to answer.
What is asexual reproduction in which an egg develops without being fertilized called? | [
"binary fission",
"metamorphosis",
"budding",
"parthenogenesis"
] | D | |
SciQ | SciQ-5572 | water, atmospheric-science, molecules, humidity
Commentary 3: Physics explanation based on molecule movement will be greatly appreciated. While you are at it - I have a hypothesis why humidity of the atmosphere is seldom 100 %. Water molecules are lighter than nitrogen (or average air) molecules and thus water vapour rises upward due to buoyancy. Depending on the temperature and vicinity of open water surfaces, the rate at which water molecules float upward may be faster than the rate of evaporation, resulting in a temporary steady state where relative humidity is below 100 %. The water vapour in the atmosphere is not lost to the space, however. At some point it cools down so much that it condenses. Thus clouds are made, which float until they can't support their own weight (by whatever means, up-drafts, buoyancy...) at which point the liquid water obeys gravity and falls down again. This greatly enhances evaporation rates while cooling the atmosphere down, and thus relative humidity rises to near 100 % while it's raining. Once the rain is done and the excess water is either absorbed or evaporates again, the cycle starts up again. Water molecules are lost to the upper layers of the atmosphere faster than evaporation can supply them, and thus relative humidity falls below 100 % again. How far below depends on the temperature, major air currents, open bodies of water, and so on. With neither evaporation nor condensation is the system then you can regard the water vapor and the dry air as distinct systems each subject to the same boundary conditions and conclude that they will have the same behavior.
Thus the absolute fraction of water will be the same at both ends and the relative humidity will vary.
The following is multiple choice question (with options) to answer.
What does water vapor in the atmosphere cool and condense into? | [
"puddles",
"clouds",
"oceans",
"rain"
] | B | Figure below shows the role of the atmosphere in the water cycle. Water vapor rises from Earth’s surface into the atmosphere. As it rises, it cools. The water vapor may then condense into water droplets and form clouds. If enough water droplets collect in clouds they may fall as rain. This how freshwater gets from the atmosphere back to Earth's surface. |
SciQ | SciQ-5573 | dating
Title: Can we carbon-date the remains of homo floresiensis found in 2003? According to the Wikipedia article on the species Homo floresiensis, the remains discovered in 2003 consist of unfossilized bones. I would assume that means they are still composed of the original organic material left behind when the human specimen died thousands of years ago. Shoudn't that mean radiocarbon dating would be a good method to date the reamains?
Many articles on Homo floresiensis also discuss how the remains were originally dated to ~12,000 years ago, but that this estimate was later revised to 60–100,000 years ago. However, everything I can find indicates that mostly geological dating methods were used, not radiometric dating.
Why not? The Wikipedia entry on carbon dating says that it can only be used reliably to date specimens up to ~50,000 years, but could carbon dating then at least place a lower limit on the age of these remains? And why wouldn't it have been used back when they thought the specimens were only ~12,000 years old? ScienceMag says:
The following is multiple choice question (with options) to answer.
Carbon-14 dating is a method of what kind of dating? | [
"metamorphic",
"orbital",
"radiometric",
"stratigraphy"
] | C | The best-known method of radiometric dating is carbon-14 dating . A living thing takes in carbon-14 (along with stable carbon-12). As the carbon-14 decays, it is replaced with more carbon-14. After the organism dies, it stops taking in carbon. That includes carbon-14. The carbon-14 that is in its body continues to decay. So the organism contains less and less carbon-14 as time goes on. We can estimate the amount of carbon-14 that has decayed by measuring the amount of carbon-14 to carbon-12. We know how fast carbon-14 decays. With this information, we can tell how long ago the organism died. |
SciQ | SciQ-5574 | bacteriology, ph, gut-bacteria
Any one of these is enough to have a bactericidal or bacteriostatic effect! This is also why cells that do live in slightly alkaline or acidic environments have to specialize, and they have narrow windows of pH that they can survive under, because they have to compensate so much to counteract the protonation or lack-thereof in their environments.
The following is multiple choice question (with options) to answer.
Friendly bacteria live mostly in the large intestine and part of the small intestine, because what organ is too acidic? | [
"skin",
"rectum",
"stomach",
"liver"
] | C | Your large intestine is not just made up of cells. It is also an ecosystem , home to trillions of bacteria known as the "gut flora" ( Figure below ). But don't worry, most of these bacteria are helpful. Friendly bacteria live mostly in the large intestine and part of the small intestine. The acidic environment of the stomach does not allow bacterial growth. |
SciQ | SciQ-5575 | energy, temperature, potential-energy
Title: When water turns to steam at 100 degrees Celsius why does both the internal and potential energy increase? I thought during this transition only the potential energy increases as energy is used to weaken the van Der Waal forces between the molecules. And that the internal energy is only dependent on the change in kinetic energy . So why does internal energy increase? Thankyou for the help. In simple terms the internal energy can be thought of as the sum of the kinetic energy and the potential energy of the molecules.
The kinetic energy of the molecules depends on the temperature - a higher temperature means that the molecules have more kinetic energy.
The potential energy of the molecules depends on the bonds (interactions) between them - breaking bonds requires work to be done and that means that there is a increase in the potential energy.
So converting water at $100\;^\circ$C into steam at $100\;^\circ$C makes no change to the kinetic energy of the molecules but increases the potential energy of the molecules (bonds are broken) and so the internal energy of steam is greater than that of water.
The following is multiple choice question (with options) to answer.
The addition of heat changes liquid water to what? | [
"ice",
"water vapor",
"rainwater",
"distilled water"
] | B | |
SciQ | SciQ-5576 | biochemistry, physiology, muscles
Title: How is ATP involved in muscle contraction? The sliding filament mechanism as explained by my text does not elaborate on how ATP is involved in the cross bridge binding and contraction process. How does muscle contraction utilize ATP?
In my text explains this is the procedure for a contraction:
Ach released by motor neuron cross cleft and binds to motor end
plate
AP generated in response to binding of Ach gated channels and propagates down T tuble
T tuble triggers Ca2+ from sarcoplasmic reticulum
Ca2+ binds onto tropinin on actin filament and removes tropomyosin
This opens up sites for myosin to attach to actin using protein heads
Actin filament is pulled toward the center of sarcomere, causing contraction
I see that the action potential definitely needs ATP in order to be generated, aside from that I am surprised that the actual contraction via cross bridge binding does not seem to need ATP.
ATP prepares myosin for binding with actin by moving it to a
higher-energy state and a "cocked" position.
Once the myosin forms a cross-bridge with actin, the Pi disassociates
and the myosin undergoes the power stroke, reaching a lower energy
state when the sarcomere shortens.
ATP must bind to myosin to break the cross-bridge and enable the
myosin to rebind to actin at the next muscle contraction.
The following is multiple choice question (with options) to answer.
What is the most widely accepted theory explaining how muscle fibers contract? | [
"sliding carbon theory",
"sliding pigment theoery",
"sliding filament theory",
"sliding tritium theory"
] | C | The most widely accepted theory explaining how muscle fibers contract is called the sliding filament theory . According to this theory, myosin filaments use energy from ATP to “walk” along the actin filaments with their cross bridges. This pulls the actin filaments closer together. The movement of the actin filaments also pulls the Z lines closer together, thus shortening the sarcomere. |
SciQ | SciQ-5577 | electric-circuits, electric-current, voltage, power
Title: Understanding voltage and power in the fluid analogy for DC circuits I am trying to understand electric circuits (ie voltage, current, power, and resistance). For the most part, everything makes perfect sense, but for some reason I do not feel as if I understand the proper definition of power. Yes, I understand the formula's $V=IR$ and $P=IV$, but I am a strong believer that you do not truly understand something until you can explain it to someone else in layman's terms (which I cannot confidently do at this point in time).
Perhaps I can explain my confusion using the water analogy (which I'm not particularly fond of, but will use anyone for illustrative purposes). I understand that if water is flowing through a hose (or pipe), the amount of water at a specific spot per second is analogous to electrical current, the pressure to voltage, and the width of the pipe to resistance.
Now let's imagine two hoses... one has twice the resistance (meaning it has smaller physical width than the other). But we also make sure that both hoses have the same current (meaning that the smaller hose has twice the voltage (water pressure)).
If we were to hit some toy windmills with the water coming out of each of these hoses (from the same distance of course), it is my understanding that they would start spinning at the same speed, or another way to put this might be that the work done upon them is the same.
Now this is where my confusion starts, because in this situation, the current is the same for both hoses, but the power (watts) is doubled for the hose that requires double the voltage to maintain the same current (due to it having twice the resistance).
The following is multiple choice question (with options) to answer.
Power in electricity is the voltage multiplied by what? | [
"wattage",
"the current",
"power",
"amperes"
] | B | ; Power in electricity is the voltage multiplied by the current. |
SciQ | SciQ-5578 | theoretical-chemistry, crystal-structure, software, nanotechnology, boron-family
Beta_12.cif file:
data_Beta_12_str
_audit_creation_date 2021-09-18
_audit_creation_method 'Materials Studio'
_symmetry_space_group_name_H-M 'PMM2'
_symmetry_Int_Tables_number 25
_symmetry_cell_setting orthorhombic
loop_
_symmetry_equiv_pos_as_xyz
x,y,z
-x,-y,z
x,-y,z
-x,y,z
_cell_length_a 2.5600
_cell_length_b 20.0000
_cell_length_c 4.2600
_cell_angle_alpha 90.0000
_cell_angle_beta 90.0000
_cell_angle_gamma 90.0000
loop_
_atom_site_label
_atom_site_type_symbol
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_U_iso_or_equiv
_atom_site_adp_type
_atom_site_occupancy
B1 B 0.00000 0.00000 0.83833 0.00000 Uiso 1.00
B2 B 0.00000 0.00000 0.50500 0.00000 Uiso 1.00
B3 B 0.00000 0.00000 0.17167 0.00000 Uiso 1.00
B4 B -0.50000 0.00000 0.68718 0.00000 Uiso 1.00
B5 B -0.50000 0.00000 0.35385 0.00000 Uiso 1.00
loop_
_geom_bond_atom_site_label_1
_geom_bond_atom_site_label_2
_geom_bond_distance
_geom_bond_site_symmetry_2
_ccdc_geom_bond_type
B1 B2 1.420 . S
B1 B4 1.433 . S
B1 B4 1.433 1_655 S
B1 B3 1.420 1_556 S
B2 B3 1.420 . S
B2 B4 1.497 . S
The following is multiple choice question (with options) to answer.
What are the vertical columns of similar chemical properties on the periodic table? | [
"Family",
"zones",
"Pods",
"groups"
] | D | |
SciQ | SciQ-5579 | ocean, waves
Title: What causes waves to form the characteristic "breaking" shape as they approach the shoreline? We all know that as waves approach the shallow shores, the waves begin to form a characteristic shape. The upper portion of these breaking waves appears to curl forward and downwards over the bottom segment of the wave, before breaking into "white wash". The image below illustrates what this characteristic shape looks like:
The following is multiple choice question (with options) to answer.
What forms the changing shapes of sand dunes? | [
"humidity",
"temperature",
"wind",
"magnetism"
] | C | Since we can observe wind forming sand dunes with these patterns now, we have a good explanation for how the Navajo sandstone formed. The Navajo sandstone is a rock formed from ancient sand dunes. The rock shows that the ancient wind direction changed from time to time. |
SciQ | SciQ-5580 | cell-biology, mitochondria, mitosis
Title: Are cells guaranteed to get at least one mitochondrion when they divide? If mitochondria exist at random within a cell, isn't there a possibility that cell division will result in a daughter cell with no mitochondria? If not, what is the process for guaranteeing at least one is present in each daughter cell? If so, what happens to that cell?
Isn't there a possibility that cell division will result in a daughter
cell with no mitochondria?
Yes, there is always the possibility. However, there must be a strong negative selection pressure against eukaryotic life that cannot achieve the proper partitioning of mitochondria, so you can imagine that there are mechanisms in place to prevent this case.
Mitochondria are both passively and actively partitioned to daughter cells. This is understood to occur through the cytoskeleton and with the control of mitochondrial fusion and fission at key stages of the cell cycle, prior to mitosis and cytokinesis!
Here is a great review from several years ago that addresses your question well.
The following is multiple choice question (with options) to answer.
What is the process in which one cell divides to form two new cells called? | [
"cell contribution",
"Cell Formation",
"cell direction",
"cell division"
] | D | Cell division is part of the life cycle of virtually all cells. Cell division is the process in which one cell divides to form two new cells. |
SciQ | SciQ-5581 | organic-chemistry, biochemistry, synthesis, photochemistry
Title: Is photosynthesis endothermic and exothermic at the same time? ... somehow? Photosynthesis is obviously an endothermic reaction, I mean, what would be the point otherwise, right? This is probably just sheer and utter stupidity on my behalf, but why does Wikipedia say the heat of formation of glucose is negative? As you can probably see I'm on a quest of understanding enthalpy as a concept and I'm still quite new, but some sort of ultranoob clarification would be very much welcome. Consider that when $1$ molecule of glucose forms, this happens at the cost of $6$ molecules of $\ce{CO2}$ and $6$ molecules of $\ce{H2O}$ :
$
\ce{6CO2(g) + 6H2O(l) -> C6H12O6(s) + 6O2(g)}
$
Considering that at $25\ \mathrm{^\circ C}$ and $1\ \text{atm}$
$
\Delta H_{\text{f},\ce{CO2}}^\circ=-393.5\ \text{kJ/mol}
$
$
\Delta H_{\text{f},\ce{H2O}}^\circ=-285.8\ \text{kJ/mol}
$
$
\Delta H_{\text{f},\ce{C6H12O6}}^\circ=-1273.3\ \text{kJ/mol}
$
You get, by summing the enthalpies of formation for each of the involved species and considering that for $\ce{O2}$ that enthalpy is zero:
$
\Delta H_\text{r}^\circ=6\times393.5\ \text{kJ/mol}+6\times285.8\ \text{kJ/mol}-1273.3\ \text{kJ/mol}=2802.5\ \text{kJ/mol}
$
The following is multiple choice question (with options) to answer.
What reaction is considered the reverse of photosynthesis? | [
"cellular digestion",
"cellular decay",
"cellular transfer",
"cellular respiration"
] | D | Many important biological processes involve redox reactions, which frequently store and release energy. For example, photosynthesis involves the reduction of carbon dioxide into glucose and the oxidation of water into oxygen. This process stores the energy of sunlight in the bonds of sugars. The reverse reaction, cellular respiration, converts the energy in glucose into ATP. Cellular respiration involves the oxidation of glucose to carbon dioxide and the reduction of oxygen gas to water. This process depends on the reduction of NAD + to the electron carrier NADH, and the reverse oxidation of NADH to NAD + . The reduction of NAD + leads to the formation of a proton (H + ) gradient, which drives the synthesis of ATP. NADH (nicotinamide adenine dinucleotide) and NADPH (Nicotinamide adenine dinucleotide phosphate) are electron carriers in biological systems. The term redox state is often used to describe the balance between NAD + /NADH and NADP + /NADPH (Nicotinamide adenine dinucleotide phosphate). |
SciQ | SciQ-5582 | organic-chemistry, molecules, carbohydrates
Title: When oxygen is connected only to carbon, are then the oxygen and carbon connected with a double bond? My teacher showed us three molecules: a carbohydrate molecule, a protein molecule, and a lauric acid molecule. I noticed that, when an oxygen atom is connected to one carbon atom and isn't connected to any other atom, then the oxygen and carbon atoms are connected with a double bond. Is my hypothesis correct, and has anyone ever found it before? Over 150 years ago August Kekulé had a dream about how atoms might form molecules. You might find it interesting to read about it.
Chemistry is largely about valence, the number of connections that each atom is able to make with other atoms.
In the cases you are talking about, with co-valent bonds, you can imagine each carbon atom as having 4 arms reaching out, each oxygen having two arms, and each hydrogen having 1 arm.
If an oxygen atom is connected to only one other atom, then that connection must use both arms, holding hands with 2 of the carbon atom's arms (just as you noticed), forming a double bond.
The carbon's other two arms could be connected to another oxygen atom, forming CO2 (carbon dioxide), or to 2 Hydrogen atoms, forming CH2O (formaldehyde).
Or it could double bond to another carbon atom, which in turn has two more arms to connect to something else, such as C2H5OH (drinking alcohol).
Molecules based on carbon are so common and potentially so complicated, that there is a whole field (organic chemistry) based on it.
If you are at all interested in chemistry, the concept of valence will be essential to your understanding.
The following is multiple choice question (with options) to answer.
What are composed of an oxygen atom that forms single bonds with two carbon atoms? | [
"acids",
"sugars",
"solvents",
"ethers"
] | D | Ethers are composed of an oxygen atom that forms single bonds with two carbon atoms. Ethers are relatively unreactive making them good solvents for other organic compounds, such as in the formation of anesthetics. |
SciQ | SciQ-5583 | cell-biology
Title: How do we look inside the cell? My sister is in 9th grade biology and her teacher avoided answering the question of how we actually study the inside of a cell. I haven't taken biology in a while but I'd like to give her an answer.
Can someone roughly summarize how we actually learn about what goes on inside a cell? Just mentioning a few of the most common or used techniques would be fine.
Note: I hope this isn't a bad question. It's a bit vague. But I didn't want to leave her without a decent answer. Techniques to look at whole cells are: Light microscopy (cells, large organelles), electron microscopy (detailed analysis of subcellular structures and even proteins) and confocal fluorescence miscroscopy (look at particular cellular planes, reconstruct 3D images).
And of course you can analyze the insides by Biochemistry by breaking the cell membranes and look at individual proteins and DNA/RNA by extraction and electrophoresis followed by Western / Northern / Southern blotting, or isolate organelles by centrifugation.
It is a broad question, and I just gave the most obvious examples of techniques (not anywhere near exhaustive). By googling the bold-out terms you may provide some details to your sis.
The following is multiple choice question (with options) to answer.
Where do cells come from? | [
"preexisting cells",
"mutations",
"sexual reproduction",
"nuclear fission"
] | A | No matter what the cell, all cells come from preexisting cells through the process of cell division. This is one of the core concepts of the Cell Theory. The cell may be the simplest bacterium or a complex muscle, bone, or blood cell. The cell may comprise the whole organism, or be just one cell of trillions. But whatever type of cell it is, it comes from a preexisting cell. And the new cell is genetically identical to its parent cell - that is, it has exactly the same DNA. |
SciQ | SciQ-5584 | molecular-biology, molecular-genetics, development, sex
Quote from a Review (Yao 2005):
We have just begun to glimpse into the mechanisms underlying ovarian development. Convincing evidence challenges us to reconsider the existing paradigm that describes ovarian development as a default system. The default concept was first proposed in the early 1950s when Jost performed the groundbreaking experiments to demonstrate mechanisms of sex differentiation of reproductive tracts (Jost, 1947, 1953, 1970). The term “default” was not originally intended to describe the developmental status of the ovary. Instead, it is referred to the female reproductive tract or the Mullerian duct based on the fact that the female reproductive tract forms in both XX and XY individuals in the absence of gonads. Indeed, now it has become evident that early ovarian development is an active process involving intrinsic cell fate decisions and complex crosstalks between germ cells and somatic cells. Most intriguingly, the appearance of testicular structures in XX individuals where Sry and its downstream components are absent further raises the improbable question: Could the testicular development be default after all?
The following is multiple choice question (with options) to answer.
What are the female gametes that form in the ovaries? | [
"spermatozoa",
"sperm",
"eggs",
"genes"
] | C | Eggs are female gametes that form in the ovaries and are released into the fallopian tubes. |
SciQ | SciQ-5585 | evolution, embryology, chromosome, polyploidy
Polyploidy is an important evolutionary mechanism which was and is probably responsible for a great deal of biological diversity.
Polyploidy arises easily in both animals and plants, but reproductive strategies might prevent it from propagating in certain circumstances, rather than any reduction in fitness resulting from the genome duplication.
Polyploidy may be more prevalent in animals than previously expected, and the imbalance in data arises from the fact that cytogenetics (i.e. chromosome counting) of large populations of wild specimens is a very common practise in botany, and very uncommon in zoology.
In addition, there are now several new suspected factors involved in ploidy which are currently being investigated:
The following is multiple choice question (with options) to answer.
What are plants in the diploid generation called? | [
"keratinocytes",
"haplocytes",
"sporophytes",
"monocots"
] | C | Plants in the diploid generation are called sporophytes . They form from the fertilization of gametes. They reproduce asexually. They have a structure called a sporangium that produces haploid spores by meiosis. Spores develop into the haploid generation. Then the cycle repeats. |
SciQ | SciQ-5586 | thermodynamics, statistical-mechanics, entropy
Title: When heat flows from hot to cold, do individual particles share energy or is it just a statistical effect? I'm struggling to get a clear understanding of why heat flows from hot to cold. I understand that temperature reflects the average kinetic energy of the particles, and that kinetic energy transfers from the hot object to the cold one until thermal equilibrium is reached, but is this transfer at the particle level or only at a macroscopic level? Does kinetic energy average out between two interacting particles or is it just the distribution of energies in the population of particles throughout the whole space (i.e. a statistical effect)? In general, you will have particles moving at different speeds inside any body. Temperature is determined by the statistical distribution of velocity, but individual particles might have very different velocities. So when you have two bodies at different temperatures, individual particles colliding might exchange kinetic energy in either direction. However, on average kinetic energy will flow from hot body to cold body. So you are right in saying that it is a statistical effect.
The following is multiple choice question (with options) to answer.
Through what do moving particles transfer thermal energy? | [
"fluid",
"gas",
"plasma",
"tissue"
] | A | Moving particles transfer thermal energy through a fluid by forming convection currents. |
SciQ | SciQ-5587 | biochemistry, molecular-biology, photosynthesis
how is it controlled that the correct number of H2O molecules are lysed so that excess electrons aren't generated?
This is achieved by a complicated interplay of the enzymatic components within the PSII. In summary, utilizing the four stable oxidation states of manganese core in the redox center ($\ce{Mn}^{(2-5)+}$, four separate states of the center ($S1\rightarrow 4$) are formed. These states cyclically shunt one electron during each step, until a water molecule is bound to $S4$ which is then directly converted to $\ce{O2}$ by $P680+$, formed in PSII due to photon absorption, which is a strong reducing agent. Since the final step occurs only with water molecule bound to $S4$, which in turn is formed only by the cyclical transition between the various states of the redox center with systematic sequential loss of electrons, the overall process is very tightly constrained to extract only the limited number of electrons preventing any troublesome redox intermediates.
See here for some basic treatment of photosynthesis.
The following is multiple choice question (with options) to answer.
What is the name for the water-splitting step of photosynthesis? | [
"hydrolysis",
"peristalsis",
"photolysis",
"cellular respiration"
] | C | |
SciQ | SciQ-5588 | equilibrium, entropy, free-energy, mixtures
Title: Is the entropy change positive or negative in this reaction? Suppose I have a reversible reaction
\begin{align}
\ce{A(g) + B(g) <=> C(g)}\\
\end{align}
with equilibrium constant K.
Its ΔΗ is positive throughout.
Now, suppose I start with 1 mole each of gases A and B, and zero (negligible) moles of C. The temperature is constant.
According to $\Delta G = RT\ln(Q/K)$ , $\Delta G$ will be highly negative at my initial conditions and will increase (become less negative) as reaction proceeds forward.
Also, using the same expression, $$\Delta S = \frac{\Delta H}{T} - R \ln\left(\frac{Q}{K}\right)$$
Hence, $\Delta S$ is highly positive initially and decreases as the reaction proceeds forward. When $\Delta S = \Delta H/T$ (at $Q=K$) , no net reaction takes place further and equilibrium is maintained.
I understand it.
But how is $\Delta S$ positive? How can it be explained theoretically?
Theoretically, shouldn't $\Delta S$ be negative as number of gaseous moles decrease on going forward?
Or is this type of reaction not possible?
Source:https://chem.libretexts.org/Bookshelves/General_Chemistry/Book%3A_ChemPRIME_(Moore_et_al.)/16%3A_Entropy_and_Spontaneous_Reactions/16.10%3A_Entropy_Changes_in_Gaseous_Reactions
But how is dS positive? How can it be explained theoretically?
The following is multiple choice question (with options) to answer.
The entropy change is positive as the solid state changes into which state? | [
"chemical",
"gas",
"mixture",
"liquid"
] | D | The entropy change is positive as the solid state changes into the liquid state. If the transition went from the liquid to the solid state, the numerical value for would be the same, but the sign would be reversed since we are going from a less ordered to a more ordered situation. |
SciQ | SciQ-5589 | thermodynamics, soft-question, terminology
Title: Proper name for a thermodynamic process with constant internal energy $U$ Back in the day I learned that a few special thermodynamical processes have special names.
For example, if one keeps $P$ constant, the process is called isobaric, if one keeps $T, V$ or $S$ constant, one gets, correspondingly, isothermic, isochoric or isentropic processes. Similarly, if one keeps $\dfrac{\mathrm{d} \ln P}{\mathrm{d} \ln \rho}$ constant during the process, it is called polytropic, and if $\delta Q = 0$ at any time, the process is called adiabatic.
Now, the question: what is the process called, if one keeps internal energy $U$ constant? A process where the energy is kept constant is called isoenergetic (or, if you prefer, iso-energetic).
It also seems from the literature that a flow where the energy is constant when following a fluid particle is usually called an isoenergetic flow.
Similarly, when the enthalpy is kept constant, the process (or the flow) is said to be isenthalpic (or isoenthalpic). And so on.
Notice that if there is some subtlety and you keep a constant internal energy $U=\text{cte}$ but not a constant energy $E=U+E_{\text{m}}$, by modifying the mechanical energy $E_{\text{m}}$, you should refrain from using standard names like isoenergetic and explain precisely what happens.
The following is multiple choice question (with options) to answer.
The process when heat is released is referred to as what? | [
"geothermal",
"endothermic",
"exothermic",
"insular"
] | C | Heat involves the transfer of thermal energy between two bodies that are at different temperatures. If you held a flask containing a reaction that releases energy, you would be able to feel the heat being transferred from the reaction into your hand. A process in which heat is released is referred to as exothermic . Conversely, reactions that absorb energy will remove energy from the surroundings, causing the container to feel cold. For example, dissolving ammonium nitrate in water will significantly lower the water temperature. Processes that absorb energy from their surroundings are called endothermic . |
SciQ | SciQ-5590 | neuroscience, brain
Title: What is in the space between neurons in a brain? When neuron animations are displayed, there are frequently seen neurons, axons arranged in a lattice with a lot of empty space between. I'm interested if there is indeed empty space in the brain, or if it is filled with some sort of fluid? I've checked an article on cerebrospinal fluid but am not sure that it is present all throughout the brain.
The reason I'm asking is that I'm thinking of neurotransmitters- they are released in synapses, but I'm not sure how they stay there - are they suspended in some liquid as well? Not so empty, actually.
The human brain has a mass of ~1.5kg, and volume ~1200cc (a little bigger for men, a little smaller for women). So is heavier than water by a good margin.
While it has Cerebrospinal fluid, that only occupies the subarachnoid space (the space below the skull and above the cortex, contained between two layers: pia matter and arachnoid membrane) and the ventricular system (several spaces inside the brain, remnants of the embryological development of the brain).
Neuron density may vary widely, depending mainly on the particular characteristics of neuron cell types and their interconnections. But besides neurons, there's a lot of infrastructure inside the brain. For example:
Astroglia: They are a type of glial cells which participate in the formation of the blood-brain barrier (supporting the endothelial cells), nourishing of neurons, maintenance of ion and neurotransmitter concentrations, among others. They also keep in place most of the tissue.
Microglia: Small cells with immune (phagocitic) functions inside the brain.
Radial glia: A more specialized precursor cell, that also participates in neuronal migration in the brain.
Oligodendrocites: Cells responsible for the insulation (myelination) of axons.
Neuroepithelial cells: The stem cells in the brain.
The following is multiple choice question (with options) to answer.
What is a large space that helps the organism digest & move nutrients around the cnidarian body? | [
"gastrovascular cavity",
"thorax",
"vacuole",
"abdominal wall"
] | A | Unlike the sponges which evolved prior to cnidarians, the cnidarians are made up of true tissues. The inside of a cnidarian is called the gastrovascular cavity , a large space that helps the organism digest and move nutrients around the body. The cnidarians also have nerve tissue organized into a net-like structure, known as a nerve-net, with connected nerve cells dispersed throughout the body. Cnidarians do not have true organs, however. |
SciQ | SciQ-5591 | human-biology, virology, pathology
Title: Why is rabies incurable? I'm still not sure about the mechanics that lead to rabies being incurable. I know that it can be treated before any symptoms show up, but why is it that once symptoms show the person is a dead man walking? This is because rabies is a viral infection of nervous tissue that propagates through peripheral nerves into the brain and causes brain tissue inflammation (encephalitis).
As long as the virus is in the brain there is no way to get rid of it. The main trade-off here is that everything that would kill the virus will be as (or even more) aggressive against the brain tissue, and impairment of the latter will lead to really heavy deficits in vital functions like breathing and thermoregulation.
The first manifestations of rabies are those due to brain damage. This means, the virus is already there and the brain is already fatally damaged.
The following is multiple choice question (with options) to answer.
An infection of the brain is called? | [
"encephalitis",
"influenza",
"tuberculosis",
"syphilis"
] | A | Bacteria and viruses can infect the brain or spinal cord. An infection of the brain is called encephalitis. An infection of the membranes that cover the brain and spinal cord is called meningitis. A vaccine is available to prevent meningitis caused by viruses (see Figure below ). |
SciQ | SciQ-5592 | geophysics, plate-tectonics, earth-history, continent
Title: Why Do Supercontinents Form? It would seem, on the face of it, improbable that the continental land-masses would accumulate into a single composite, yet it has happened numerous times, and is expected to again in the future.
There must likely then be some aspect of plate tectonics which favors these arrangements.
Can anyone provide an explanation?
EDIT: This is not, as I see it, a duplicate of the 'What are the causes of the supercontinent cycle?' question. This question goes to what process drives the formation of any & all supercontinent formations, which I assert should be improbable, made more improbable by their recurrence, not so much the cycle itself. The other question did not address this more fundamental aspect, or in any case receive a pertinent account of its resolution. If anyone wants to engage on this, or doesn't see the distinction, please do so in the comments or a chat. I think the mechanisms that you're looking for are subduction, paired with the "stickiness" of continental crust.
The subduction of oceanic crust under continental crust inevitably creates a net movement of crustal material toward a continental plate. Any oceanic plate that is carrying continental material will therefore always drag that continent toward the continental plate that it is subducting underneath, always resulting in eventual collision.
If an oceanic plate has subduction occurring on both sides, the ocean will inevitably narrow until it closes, thereby causing the continental plates on either side to collide.
In every case, subduction inevitably pulls continents together.
Furthermore, once continental plates collide, they have a tendency to stick together for long periods of time, increasing the likelihood that all continental material will eventually accumulate there.
The following is multiple choice question (with options) to answer.
The converging of continental plates can form what kind of geological feature? | [
"shores",
"plains",
"mountains",
"streams"
] | C | When two continental plates converge, they smash together and create mountains. |
SciQ | SciQ-5593 | zoology, marsupials
Title: Do male marsupials have a pouch? Do male marsupials have a pouch, or is it a female organ only (like the womb)? In most marsupials, only the females have a pouch. However, males of the water opossum and the extinct tasmanian tiger (or thylacine) also have a pouch. The males of both the thylacine and water opposum used/use their pouch to keep their genitalia from getting entangled in vegetation.
The following is multiple choice question (with options) to answer.
Mammals generally lack a cloaca and have a separate opening for the what? | [
"tissues tract",
"physical tract",
"urinary tract",
"digestive tract"
] | D | |
SciQ | SciQ-5594 | evolution, ornithology, palaeontology
One thing those many, many bird and proto-bird fossils also made clear is that the traits of modern birds (feathers, wings, toothless beaks, etc) didn't evolve in a simple line from non-bird to bird. Many of those traits evolved convergently in several lineages, were lost in some, maybe regained in others, and feathers in particular turn out to be a widespread dinosaur feature that cannot be considered a uniquely bird trait anymore (unless we want to call T-rexes "birds"). Still, saying "beaks evolved several times" or "feathers evolved several times" doesn't mean that birds, let alone modern birds, evolved from several different ancestors. It can mean that the common ancestor of birds had lots of variously bird-like more-or-less distant cousins living around the same time.
The following is multiple choice question (with options) to answer.
Chordates are defined by a set of four characteristics that are shared by these animals at some point during their? | [
"death",
"development",
"response",
"birth"
] | B | Chordates are defined by a set of four characteristics that are shared by these animals at some point during their development. In some chordates, all four traits are present in the adult animal and serve important functions. However, in many chordates, including humans, some traits are present only during the embryonic stage. After that, these traits may disappear. |
SciQ | SciQ-5595 | biochemistry, photosynthesis
Title: When is Water Produced During Photosynthesis? The formula for photosynthesis is: $$6CO_2+12H_2O \rightarrow C_6H_{12}O_6+6O_2+6H_2O$$
I can count the carbons, the waters on the reactant side, the oxygens, and the glucose, but I cannot seem to locate where in either light or dark reaction 6 water molecules were produced again. Where and when were they produced? Some of the water that's split is regenerated when the hydroxyl radicals (reactive oxygen species) are converted to hydrogen peroxide, water, etc. by superoxide dismutases and antioxidative mechanisms in the chloroplast (peroxisomes/catalases, etc. take care of this). There's also some evidence that the presence of mannitol, ascorbate and glutathione protect against ROS produced in chloroplasts as well. So you input water, and in an effort to avoid oxidative damage, you do get some water generated. However, the balanced equation doesn't reflect this because it's not an actual product of photosynthesis.
About ROS and protective elements
Extra Reading on ROS in photosynthetic systems
I think that's a very obscure fact, and despite the reality of things, it's actually difficult to query the literature. Good question.
The following is multiple choice question (with options) to answer.
What is produced during the light reactions in photosynthesis? | [
"nitrogen",
"oxygen",
"waste",
"carbon"
] | B | Photosynthesis begins with the light reactions. It is during these reactions that the energy from sunlight is absorbed by the pigment chlorophyll in the thylakoid membranes of the chloroplast. The energy is then temporarily transferred to two molecules, ATP and NADPH, which are used in the second stage of photosynthesis. ATP and NADPH are generated by two electron transport chains . During the light reactions, water is used and oxygen is produced. These reactions can only occur during daylight as the process needs sunlight to begin. |
SciQ | SciQ-5596 | neuroscience, neurophysiology, neuroanatomy, neurology
Conceptually, rather than thinking about extra parts, all of your same questions apply just as much to what is "normal". There is no evidence that brain development has any assumption built in that there will be 4 limbs or 5 digits on a hand, rather, connections are made with the nervous system as the limbs and digits develop, and these connections carry information between the CNS and sensory neurons and motor neurons, and the brain develops in response to those connections.
The following is multiple choice question (with options) to answer.
Nerves of the hands, arms, feet, legs, and trunk are part of what system? | [
"cardiovascular system",
"peripheral nervous system",
"urinary system",
"circulatory system"
] | B | There are other nerves in your body that are not found in the brain or spinal cord. The peripheral nervous system (PNS) ( Figure below ) contains all the nerves in the body that are found outside of the central nervous system. They include nerves of the hands, arms, feet, legs, and trunk. They also include nerves of the scalp, neck, and face. Nerves that send and receive messages to the internal organs are also part of the peripheral nervous system. |
SciQ | SciQ-5597 | newtonian-mechanics, momentum
Title: What is the significance of momentum? I just want to get an idea what momentum is. I know the mathematical meaning that momentum is $mv$ where $v$ is velocity. But I don't know its significance. Like I know that Acceleration is how velocity is changing with respect to time, I wanted to get feel of what momentum really is? Momentum is what makes it "tough" to stop moving things.
If you stand with an apple in each hand, then you feel their weight. If you throw one of them upwards and catch it again, it feels "heavier" in that moment. What you feel in addition to the weight is the momentum.
Stopping a motion can be an easy or tough task depending on the momentum, which encompasses both the speed $v$ to decelerate from as well as the mass $m$ that resists this deceleration.
At the same time there happens to exist a conservation law regarding momentum. All momentum before equals all after any event; momentum is always conserved $\sum P_{before}=\sum p_{after}$. So apart from the physical significance of momentum, it also happens to be a very useful tool.
That's why we see it and learn about it and use it all the time.
The following is multiple choice question (with options) to answer.
Generally, momentum implies a tendency to continue on course—to move in the same direction—and is associated with great mass and speed. momentum, like energy, is important because it is what? | [
"conserved",
"invisible",
"sequences",
"endless"
] | A | Introduction to Linear Momentum and Collisions We use the term momentum in various ways in everyday language, and most of these ways are consistent with its precise scientific definition. We speak of sports teams or politicians gaining and maintaining the momentum to win. We also recognize that momentum has something to do with collisions. For example, looking at the rugby players in the photograph colliding and falling to the ground, we expect their momenta to have great effects in the resulting collisions. Generally, momentum implies a tendency to continue on course—to move in the same direction—and is associated with great mass and speed. Momentum, like energy, is important because it is conserved. Only a few physical quantities are conserved in nature, and studying them yields fundamental insight into how nature works, as we shall see in our study of momentum. |
SciQ | SciQ-5598 | 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.
Which types of muscles cause bones to move when they retract? | [
"bone muscles",
"active muscles",
"skeletal muscles",
"working muscles"
] | C | Skeletal muscles are attached to the skeleton and cause bones to move when they contract. |
SciQ | SciQ-5599 | 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.
Which is the final step of cell division? | [
"Mitosis",
"genesys",
"electrolysis",
"cytokinesis"
] | D | Cytokinesis is the final step in cell division. It often occurs concurrently with telophase, though it is a separate process. Cytokinesis ( Figure below ) differs between plant and animal cells. In animal cells, the plasma membrane pinches inward along the cell’s equator until two cells are formed. Specifically, a cleavage furrow containing a contractile ring develops in approximately the middle of the cell (similar to the position of the metaphase plate), essentially pinching off the two nuclei and forming separate cells. In plant cells, a cell plate forms along the cells equator. A new membrane grows along each side of the cell plate, with a new cell wall forming on the outside of each new membrane. |
SciQ | SciQ-5600 | homework, plant-physiology, plant-anatomy
and 'Vascular Plants = Winning! - Crash Course Biology #37'
https://youtu.be/h9oDTMXM7M8?t=373
[5] Osmosis (water compensating solutes) "In Da Club - Membranes & Transport: Crash Course Biology #5"
https://youtu.be/dPKvHrD1eS4?list=PL3EED4C1D684D3ADF&t=148
Ian (and dad <= all errors and approximations are his :) ).
The following is multiple choice question (with options) to answer.
What are xylem and phloem responsible for transporting to the cells of leaves? | [
"light and gas",
"water and blood",
"water and minerals",
"air and dirt"
] | C | Veins are made primarily of xylem and phloem. They transport water and minerals to the cells of leaves and carry away dissolved sugar. |
SciQ | SciQ-5601 | dna, chromosome
Title: Are human chromosomes connected or separate molecules? Do the 46 human chromosomes form a single unbroken DNA helix? Or is it rather that a human's genome consists of 46 disconnected helices?
If it is the former, does the common numbering scheme for the chromosomes have any correlation to their actual ordering in the one large strand?
If is the latter, is there a convention on how the chromosomes are ordered in genomic datasets? Also, is there a clear understanding of how sister chromosomes "find" each other in Meiosis I?
Generally, during periods when Mitosis/Meiosis are not occurring, what's a good physical picture for how the chromosomes are physically arranged (e.g. a bowl of 46 spaghetti noodles, or maybe the sister chromosomes always stay close together, etc)
thanks! Each chromosome is a pair of distinct, separate DNA molecules. A chromosome of an eukaryotic cell nucleus is a (long) helix of two linear molecules and so has two ends, which are called telomeres. DNA naturally forms a double helix with its complementary DNA molecule, and the double helix can further curl in what are called supercoils.
In humans, the chromosomes occur in 23 pairs (totaling 46). Except for the sex chromosome pair, each member of the pair is identical in appearance in a karyotype (picture) and each such pair has a number assigned from 1 to 22; the numbering generally follows the size of the chromosome, with chromosome 1 being the longest. In mammals, the sex chromosomes in a male are quite different in size and are labelled X and Y; a female has two identical X chromosomes.
The following is multiple choice question (with options) to answer.
What kind of cell is a cell with two chromosomes? | [
"neurotic cell",
"mutated cell",
"diploid cell",
"haploid cells"
] | C | |
SciQ | SciQ-5602 | terminology
Fermentors commonly have all or some the following elements: Agitator (of simple design), pH meter, temperature control (jacketed vessels are common), pipes for transferring nutrients, water, etc., and a sampling port (maybe). It may be made out of wood or clay, but if it is made from steel, plastic, glass, or other modern materials, that certainly wouldn't disqualify the term fermenter, but I would probably not call an oak barrel or a clay pot a bioreactor.
Bioreactors generally have the same things as fermenters, but bioreactors also usually have some or all of the following additional elements: oxygen probe, air or oxygen pump(s) and diffuser(s), other gas ports, additional ports/pipes for pH monitoring and control (often a programmable computer controlled pump is used for multiple solutions), electrolyte balance, radial or axial impellors- which operate at hundreds or thousand of RPMs, a vapor condensor (maybe), spectophotometer (for cell density measurements), nutrient processing data, and any variety of data measurement and/or recording is the often the point of interest, or when growth of tricky or finicky cells is necessary (especially like hybridomas, phytoplankton, or perhaps generally eukaryotic cell culturing). Also, there are different kinds of bioreactors like wave bioreactors (often in bioreactor bags on shaker tables instead of having an impellor).
The following is multiple choice question (with options) to answer.
Which term literally means 'spore in a vessel'? | [
"germination",
"cyanobacteria",
"sporangia",
"Carboid"
] | C | to the embryo as it develops into the new generation of sporophyte. This distinguishing feature of land plants gave the group its alternate name of embryophytes. Sporangia in Seedless Plants The sporophyte of seedless plants is diploid and results from syngamy (fusion) of two gametes. The sporophyte bears the sporangia (singular, sporangium): organs that first appeared in the land plants. The term “sporangia” literally means “spore in a vessel,” as it is a reproductive sac that contains spores Figure 25.3. Inside the multicellular sporangia, the diploid sporocytes, or mother cells, produce haploid spores by meiosis, where the 2n chromosome number is reduced to 1n (note that many plant sporophytes are polyploid: for example, durum wheat is tetraploid, bread wheat is hexaploid, and some ferns are 1000-ploid). The spores are later released by the sporangia and disperse in the environment. Two different types of spores are produced in land plants, resulting in the separation of sexes at different points in the lifecycle. Seedless nonvascular plants produce only one kind of spore and are called homosporous. The gametophyte phase is dominant in these plants. After germinating from a spore, the resulting gametophyte produces both male and female gametangia, usually on the same individual. In contrast, heterosporous plants produce two morphologically different types of spores. The male spores are called microspores, because of their smaller size, and develop into the male gametophyte; the comparatively larger megaspores develop into the female gametophyte. Heterospory is observed in a few seedless vascular plants and in all seed plants. |
SciQ | SciQ-5603 | evolution, human-evolution
Title: Is evolution a fact? Richard Dawkins in one of his videos says that Evolution is a fact and not just a theory.
He goes on to say that man and chimpanzees both evolve from apes.
Is this correct (Is evolution a fact and did humans & chimps evolve from apes)? A tiny bit of terminology
Fact
In popular culture, the term fact means "something that is true". I would consider a theory as being the closest concept in science to what is called a fact in the population culture.
In natural sciences, the term fact is rarely used but would have the same meaning than the one in popular culture. The reason we are not often using this concept is that in science (nor in any other field of knowledge) one can never definitely know the truth. We can only have evidence that are congruent with a hypothesis or body of statements. In such case we talk about theory (see below).
Theory
In popular culture, "theory" is used to mean what the natural sciences call a "hypothesis."
In the natural sciences, a theory is a body of thoughts/statements that is very well supported by loads of evidence. In science, a theory is not a hypothesis. For example: Theory of evolution, Theory of general relativity, transition state theory, etc. Note by the way that various definitions of theory are in use (ref.). The below answer respects the definition that I gave above.
The scientific terminology presented above is actually a matter of philosophy and not science. If you need more information about the definitions of "theory", "fact" and other related terms, you may want to ask on Philosophy.SE. Stephen Jay Gould summarized the concepts of theory and facts nicely when saying
[..] facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts.
In the answer below, I am using the scientific terminology.
Your questions
Is evolution true?
Evolution is what is called a theory in natural science (The Theory of Evolution a.k.a. modern evolutionary synthesis), and it is extremely well-supported. Evolution is NOT a hypothesis. In other words, we have a lot of supporting evidence that living beings have evolved and are evolving.
Did both humans and chimpanzees evolve from apes?
The following is multiple choice question (with options) to answer.
Human culture is related to evolutionary theory in the discipline of what? | [
"psychopathology",
"astrology",
"ethnology",
"sociobiology"
] | D | |
SciQ | SciQ-5604 | quantum-field-theory, particle-physics, statistical-mechanics, condensed-matter
Some of these examples are admittedly more contrived than others, but I hope they work together to help convince you that higher orders in perturbation theory are not merely a textbook exercise.
The following is multiple choice question (with options) to answer.
Which forces hold particles together in more ordered states? | [
"natural",
"intermolecular",
"gravitational",
"particular"
] | B | Chemical energy, the energy stored in molecules and atoms, is one type of potential energy. Certain reactions can cause this energy to be released as heat. Other reactions require an input of energy, in which case the products will store more potential energy than the reactants. When we studied phase changes, we saw a relationship between energy and the state of matter. To melt a solid or boil a liquid, energy needs to be added in order to break up the intermolecular forces holding particles together in more ordered states. The reverse processes, condensation and freezing, release energy, because more favorable intermolecular interactions are formed. |
SciQ | SciQ-5605 | human-physiology, digestion, stomach
The stomach accomplishes much of its function by mechanically breaking down the swallowed food particles and mixing them with acid and enzymes into a sort of slurry. To do this, there are three major layers of muscle surround the stomach - from the outside, the longitudinal layer, the circular layer, and the oblique layer. The stomach also has two holes in it - the gastroesophageal opening, coming from the esophagus with the swallowed food/saliva mix, and the pylorus, where the food/acid/enzyme slurry exits into the duodenum, which is the beginning of the small intestine.
Due to the three layers of (rather strong) muscle, the stomach doesn't have a lot of expansion capability once it is filled completely to capacity. Fortunately, this almost never occurs (despite how we may feel after a large meal) because material is always leaving the stomach on its way to enzymatic digestion in the intestines. Additionally, once the stomach is filled to a certain extent, hormones such as leptin are secreted that give you the feeling of being sated, or full, triggering the brain to make you stop eating.
Of course, as we can see with the current epidemic of obesity around the world, the stomach can change its size over time. However, this is a rather slow process (weeks to months to years) of adapting to continuously consuming large meals.
But what would happen if you completely ignored these internal warnings, or were being force-fed, or whatever? Instead of rupturing (the biological equivalent of "exploding"), food would most likely be expelled either into the small intestine or back into the esophagus and back up the way it came down, i.e. causing vomiting.
The following is multiple choice question (with options) to answer.
What is the movement of muscle in the digestive system called? | [
"apoptosis",
"labor contractions",
"acid reflux",
"peristalsis"
] | D | The organs of the digestive system are lined with muscles. The muscles contract, or tighten, to push food through the system ( Figure below ). The muscles contract in waves. The waves pass through the digestive system like waves through a slinky. This movement of muscle contractions is called peristalsis . Without peristalsis, food would not be able to move through the digestive system. Peristalsis is an involuntary process, which means that it occurs without your conscious control. |
SciQ | SciQ-5606 | human-biology, cancer, medicine
Title: Why are only few cigarette smokers prone to cancer? It's tacit that only a few populace of smokers get cancer. What spares the others from it or what specifically cause cancer in those populace? See this Washington Post Article Cigarette smokers are most certainly prone to cancer. See Cecil Medicine, Chapter 183, on the epidemiology of cancer, exposure to tobacco is the most important environmental risk factor for cancer development, at least in the US:
Exposure to tobacco is the single largest cause of cancer in the United States... All forms of tobacco can cause cancer. Cigarette smoking causes cancer of the lip, oral cavity, nasal cavity, paranasal sinuses, pharynx (nasal, oral, and hypopharnyx), larynx, lung, esophagus (squamous cell and adenocarcinoma), stomach, colorectum, pancreas, liver, kidney (adenocarcinoma and renal pelvis), urinary bladder, uterine cervix, and myeloid leukemia.
Cancer may be identified or the cause of death in fewer smokers than might be expected, though, because smoking is an even greater risk factor for cardiovascular disease, and death due to cardiovascular disease.
Cancer is an unlikely phenomenon in an individual cell, but becomes more likely at the organism level, and even more likely over time. Though tobacco may be the most important environmental risk factor for cancer, age is actually a stronger predictor of cancer (see again, Cecil Chapter 183. Autopsy studies give us a quite remarkable example, this one shows incidental prostate cancer in nearly 60% of men over 80 who died from other causes. That figure is not out of the ordinary. Live long enough and you are likely to develop cancer.
Death due to heart disease may account for the lower than expected rates of cancer diagnoses and deaths in smokers. Nothing prevents cancer as well as dying from something else. And as discussed in the blog in the Washington Post you linked to, up to 2/3 of smokers die from smoking related causes
The following is multiple choice question (with options) to answer.
Smoking increases the risk of cancer from what radioactive gas that can also be detected with a test kit for your home? | [
"carbon dioxide",
"arsenic",
"carbon monoxide",
"radon"
] | D | Radon is also radioactive and can easily be inhaled into the lungs. Over time, this internal radon exposure can lead to the development of lung cancer. The incidence of lung cancer in smokers exposed to radon is much higher than that in non-smokers exposed to radon since smoking has already produced some lung damage, and the radon simply makes the damage worse. Radon exposure is highest in homes lacking good air circulation to move the gas out of the residence. There are a number of inexpensive approaches to decreasing your exposure to radon. A good start is to test your living area for radon with a radon test kit. |
SciQ | SciQ-5607 | physiology, cardiology, blood-circulation
Title: What is the quality rate of intrinsic autoregulation in the heart? Autoregulation is the maintenance of constant blood flow to an organ in spite of fluctuations in Blood pressure.
It involves the relaxation of myocardium and contraction.
It is local.
I know that autoregulation is best done in the brain, well in kidneys and badly in skeletal muscle.
I am interested how it is in the heart.
I think it should be at least good.
Brain can be thought more important.
However, I am not sure.
How good is the autoregulation of the blood flow in the heart? My conjecture: Intrinsic regulation is done in the heart the second best, after the brain.
This idea is based on the fact that the brain controls heart's some autonomic functions.
It is an open research question how the autonomic nervous system affects the intrinsic functions of the heart - and the reverse is true too.
To answer this question, we need to understand the autonomic regulation of the heart better i.e. the inner-physiology of the heart's electrical activity.
The following is multiple choice question (with options) to answer.
What is the main function of the cardiovascular system? | [
"to transport",
"digestion",
"respiration",
"implanatation"
] | A | Many ecosystems have changed because of human actions. The human species is responsible for a range of environmental problems. |
SciQ | SciQ-5608 | acid-base, hydrogen, protons
Title: Is water hydronium and hydroxide? In our chemistry lesson when learning about the Bronsted-Lowry definition for acids and bases, we came across the reaction...
H2O + H2O -> H3O+ + OH-
...Where water is amphiprotic which means it acts as an acid and base. Does this mean that water is a combination of hydronium and hydroxide? How is it not harmful to drink then? If there are arrows going both ways then that means it’s in equilibrium between the right side (products) and the left side (reactants).
It doesn’t mean that water is a mix of H3O+ and -OH, a vast majority of water will stay H2O, and the small amount of H3O+ or -OH wouldn’t be anywhere near a concentration to hurt you
I think the purpose of that was to show that water has the potential to form H3O+ and -OH in itself in an attempt to teach you about acid base equilibrium
The following is multiple choice question (with options) to answer.
When something is described as "hydrophilic", you can determine something about how it interacts with what? | [
"iron",
"air",
"hydrogen",
"water"
] | D | hydrophilic heads are directed outward, in contact with the water. Each micelle may contain thousands of lipid molecules. Polar lipids may also form a monolayer, a layer one molecule thick on the surface of the water. The polar heads face into water, and the nonpolar tails stick up into the air. Bilayers are double layers of lipids arranged so that the hydrophobic tails are sandwiched between an inner surface and an outer surface consisting of hydrophilic heads. The hydrophilic heads are in contact with water on either side of the bilayer, whereas the tails, sequestered inside the bilayer, are prevented from having contact with the water. Bilayers like this make up every cell membrane (Figure 17.6 "Schematic Diagram of a Cell Membrane"). Figure 17.5 Spontaneously Formed Polar Lipid Structures in Water: Monolayer, Micelle, and Bilayer. |
SciQ | SciQ-5609 | genetics, homework, human-genetics
Title: What are sex linked traits? Which of the two definitions of sex-linked trait is correct?
Traits controlled by genes present on the non-homologous region of sex chromosomes are called sex-linked traits.
Bodily traits controlled by genes present on the non-homologous regions of sex chromosomes are called sex-linked traits. Here by bodily traits I mean traits that are not involved with sex of an organism.
I read the first definition in the book Competition Science Visionand also from Instant notes genetics (page 163).
The following is an excerpt from the latter
Sex linkage is not displayed by genes which map to a small segment of X chromosome, the pseudoautosomal region, the part of X chromosome that pairs with Y chromosome in meiosis.
The second definition is made up but sounds potentially intuitive to me. The first definition is correct.
A sex-linked trait is a trait affected by a locus on a sex chromosome.
If you google sex-linked trait, you will find this same definition (not the exact same words) over and over again.
The definition of sex-linked trait is NOT restricted to traits that are not unrelated to primary or secondary sexual organs. Any phenotypic trait can be sex-linked as long as the causal locus is on a sexual chromosome.
The following is multiple choice question (with options) to answer.
What human traits are controlled by more than one gene? | [
"maladaptive traits",
"polygenic traits",
"autolysis traits",
"mutant traits"
] | B | Many human traits are controlled by more than one gene. These traits are called polygenic traits (or characteristics). The alleles of each gene have a minor additive effect on the phenotype. There are many possible combinations of alleles, especially if each gene has multiple alleles. Therefore, a whole continuum of phenotypes is possible. |
SciQ | SciQ-5610 | neuroscience, pathology, human-genetics, neurology
Presumably, genes in the first category contribute most to the shared phenotype of Down syndrome, and genes in the second category contribute most to the variation. Perhaps alleles that produce mRNA transcripts at the low end of normal for those genes are less susceptible to the effects of chromosome duplication.
A case study: Amyloid precursor protein
One protein of interest in particular is the amyloid precursor protein, APP, which is also associated with Alzheimer's disease (which shares some phenotypic characteristics with Down syndrome). APP expression varies widely among tissue types and individuals. Therefore, although APP mRNA levels are significantly elevated in Down syndrome individuals, the distributions between controls and Down syndrome are very overlapping; for example, see Figure 2B from the Antonarakis 2016 review.
3. Interactions with genes on other chromosomes
The third contributor to the variation of symptoms is the interaction of duplicated chromosome 21 genes with alleles located on other chromosomes. Just for an example where some of the genetic basis is understood, Down syndrome individuals are susceptible to certain leukemias, which are also associated with specific alleles on other chromosomes (Antonarakis, 2016). It seems that trisomy 21 affects histone modification in the areas of those alleles (Lane et al., 2014) and promotes proliferation of B-cells. Therefore, Down syndrome interacts with those other oncogenes to produce a greater combined risk. Individual with Down syndrome but not possessing the other alleles are less susceptible to the increased risk of leukemia
Similar interactions are likely with other systems that are influenced by Down syndrome, though the full molecular basis of all of those interactions are not fully understood. The Down Syndrome Genomes Project aims to, among other things, discover these other alleles outside of chromosome 21 that contribute to Down syndrome symptoms, which may also help understanding of the contribution of those alleles to other disorders (Antonarakis, 2016).
The following is multiple choice question (with options) to answer.
Most chromosomal disorders involve which chromosomes? | [
"ribosomes",
"protosomes",
"sex chromosomes",
"autosomes"
] | C | Most chromosomal disorders involve the sex chromosomes. Can you guess why? The X and Y chromosomes are very different in size. The X is much larger than the Y. This difference in size creates problems. It increases the chances that the two chromosomes will fail to separate properly during meiosis. |
SciQ | SciQ-5611 | 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.
Carbonic anhydrase plays what role to achieve a variety of results involving different organs? | [
"enzyme",
"inhibition",
"blocker",
"sequence"
] | A | About 67 percent of the water, Na+, and K+ entering the nephron is reabsorbed in the PCT and returned to the circulation. Almost 100 percent of glucose, amino acids, and other organic substances such as vitamins are normally recovered here. Some glucose may appear in the urine if circulating glucose levels are high enough that all the glucose transporters in the PCT are saturated, so that their capacity to move glucose is exceeded (transport maximum, or Tm). In men, the maximum amount of glucose that can be recovered is about 375 mg/min, whereas in women, it is about 300 mg/min. This recovery rate translates to an arterial concentration of about 200 mg/dL. Though an exceptionally high sugar intake might cause sugar to appear briefly in the urine, the appearance of glycosuria usually points to type I or II diabetes mellitus. The transport of glucose from the lumen of the PCT to the interstitial space is similar to the way it is absorbed by the small intestine. Both glucose and Na+ bind simultaneously to the same symport proteins on the apical surface of the cell to be transported in the same direction, toward the interstitial space. Sodium moves down its electrochemical and concentration gradient into the cell and takes glucose with it. Na+ is then actively pumped out of the cell at the basal surface of the cell into the interstitial space. Glucose leaves the cell to enter the interstitial space by facilitated diffusion. The energy to move glucose comes from the Na+/K+ ATPase that pumps Na+ out of the cell on the basal surface. Fifty percent of Cl– and variable quantities of Ca++, Mg++, and HPO 24 − are also recovered in the PCT. Recovery of bicarbonate (HCO3–) is vital to the maintenance of acid–base balance, since it is a very powerful and fast-acting buffer. An important enzyme is used to catalyze this mechanism: carbonic anhydrase (CA). This same enzyme and reaction is used in red blood cells in the transportation of CO2, in the stomach to produce hydrochloric acid, and in the pancreas to produce HCO3– to buffer acidic chyme from the stomach. In the kidney, most of the CA is located within the cell, but a small amount is bound to the brush border of the membrane on the apical surface of the cell. In the lumen of the PCT,. |
SciQ | SciQ-5612 | paleontology, taphonomy
Title: How are organic walled microfossils preserved in the fossil record? Organic walled microfossils have no hard mineralised parts, how are they preserved in the fossil record? Organic-walled microfossils (wether they be dinoflagellates, pollens, spores or "acritarchs") all have in common to contain an organic compound known as sporopollenin (for the spores and pollens) or dinosporin (for dinoflagellates and, I believe, acritarchs as well). Both compounds have chemical and structural similarities but have appeared independently.
Those compound are incredibly resistant. To give you an idea, to collect siliceous microfossils we first dissolve the sediments with HCl (hydrochloric acid) to get rid of carbonate microfossils. Palynologists (who study such organic-walled microfossils) uses HF (hydrofluoric acid) to get rid of both carbonate and siliceous microfossils (e.g. Doher 1980). Sporopollenin therefore resist to HF, which has a pH of ca. 3. In addition to this, they are also unusually resistant to microbiological degradation (e. g. Gunnison & Alexander 1975).
They are however not resistant to oxydation, hence, probably, why we don't find more of them in the sediments. Additionally, to break sporopollenin walls (in order to study the inner side of those walls) ultrasound can be used (e. g. Lennie 1968).
"Organic-walled" doesn't mean no hard part, it just means no "mineral" hard part.
Sources:
Doher, I., 1980. Palynomorph preparation procedures currently used in the paleontology and stratigraphy laboratories, U.S. Geological Survey. Geological Survey circular, 830: 1-29.
Gunnison, D., Alexander, M., 1975. Basis for the resistance of several algae to microbial decomposition. Applied Microbiology, 29: 729-738.
Lennie, C. R., 1968. Palynological Techniques used in New Zealand. New Zealand Journal of Geology and Geophysics, 11: 1211-1221.
The following is multiple choice question (with options) to answer.
What is it called when minerals replace the organic material to create fossils? | [
"carbonization",
"permineralization",
"spongin",
"petrification"
] | B | Some fossils are created when minerals replace the organic material. This is called permineralization. |
SciQ | SciQ-5613 | galaxy, mass, density
Title: Is the object mass distribution different for galaxies of different diameter? Let's say we compare two elliptic/spiral galaxies with the bigger having a diameter 100 times the smaller.
Now we count every separated object inside them and classify them into mass categories e.g. $10^i$kg with $i = -40..50$.
(Finally we divided the number of each category by the total number of counted objects)
Q: Will the proportion of each mass category (in mean) be different for different galaxy diameter sizes?
E.g. have galaxies with a large diameter a higher proportion of more massive objects?
Or for example let's pick a random star inside the small and large galaxy. How likely will it be a red dwarf or a blue giant? Is the Probability different for a small/large galaxy?
Big galaxies might have bigger black holes in their center. Would it change if we just count the objects which are at least e.g. 10% of the diameter away from the center? What are the objects in a galaxy
First of all, we need to discuss what are these 'objects' composing the galaxy referred by the question. The total mass of a Galaxy will be divided between
Dark matter
Stars
Gas & Dust
Other non luminous objects such as planets, asteroids, black holes...
The following is multiple choice question (with options) to answer.
Smaller sized galaxies are known as what? | [
"nebula",
"dwarf galaxies",
"black holes",
"constellations"
] | B | Dwarf galaxies are small galaxies containing “only” a few million to a few billion stars. Most dwarf galaxies are irregular in shape. However, there are also dwarf elliptical galaxies and dwarf spiral galaxies . Dwarf galaxies are the most common type in the Universe. However, because they are relatively small and dim, we don’t see as many dwarf galaxies as we do their full-sized cousins. |
SciQ | SciQ-5614 | biochemistry
Specific Force Deficit in Skeletal Muscles of Old Rats Is Partially
Explained by the Existence of Denervated Muscle Fibers
Association of adiponectin and resistin with adipose tissue
compartments, insulin resistance and dyslipidaemia
Shifts in the Distribution of Mass Densities Is a Signature of
Caloric Restriction in Caenorhabditis elegans
The following is multiple choice question (with options) to answer.
What is the name of the supportive structed that helps move a worm's muscles? | [
"spongin",
"pollenation",
"exoskeleton",
"hydroskeleton"
] | D | Segmented worms have a well-developed body cavity filled with fluid. This fluid-filled cavity serves as a hydroskeleton , a supportive structure that helps move the worm's muscles. Only the most primitive worms (the flatworms) lack a body cavity. |
SciQ | SciQ-5615 | biochemistry, cell-biology, metabolism, photosynthesis
Title: How are ions 'pumped' across a membrane during electron transport? A number of sites (including this one) that provide descriptions of photosynthesis state that high energy electrons 'pump' ions across a membrane. What is the actual 'pumping' mechanism? I've looked at Wikipedia and at a number of YouTube lectures/tutorials but so far have only found statements as to the where and when but not the how of this important process. Short answer:
Electrons flow through membranes by floating through kind of channels made out of iron-sulfur clusters.
Long answer:
Let's take a look at the electron transport chain in the inner mitochodrial membrane. There is a proton gradient across the membrane building up a potential difference by pumping protons across the membrane as electeons flow through the respiratory chain. They (electrons) like to flow throught the respiratory chain because they can go from enzyme to enzyme each with a lower standart free energy. These enymes together form one big complex within the inner membrane with Fe-S clusters enabeling electrons to flow through the membrane by giving them a kind of a power stroke (see here).
This as an simplyfied answer on a example.
The following is multiple choice question (with options) to answer.
What type of transport occurs when substances cross the plasma membrane without any input of energy from the cell? | [
"active transport",
"wave diffusion",
"physical transport",
"passive transport"
] | D | Passive transport occurs when substances cross the plasma membrane without any input of energy from the cell. No energy is needed because the substances are moving from an area where they have a higher concentration to an area where they have a lower concentration. Concentration refers to the number of particles of a substance per unit of volume. The more particles of a substance in a given volume, the higher the concentration. A substance always moves from an area where it is more concentrated to an area where it is less concentrated. It’s a little like a ball rolling down a hill. It goes by itself without any input of extra energy. |
SciQ | SciQ-5616 | mycology, olfaction
Title: When something "smells moldy" what are we really smelling? When things smell moldy -- it could be clean clothes left in a heap, a damp basement, old books stored in elevated humidity -- they can smell moldy.
There are distinct smells for each of these.
Are we smelling the mold spores themselves, or are there other molecules released by molds that causes the "moldy smell" we perceive? The vast majority of the things you smell are odorants, or volatile molecules; not spores. They are light compounds that have high vapor pressure (are airborne), and that interact with your chemoreceptors in your nose (can be smelled). The most-often reported microbial volatile organic compounds in living environments according to this study are as follows:
2-Methyl-1-propanol
3-Methyl-1-butanol
3-Methyl-2-butanol
2-Pentanol
3-Octanol
1-Octen-3-ol
2-Octen-1-ol
3-Methylfuran
2-Hexanone
2-Heptanone
3-Octanone
2-Methylisoborneol
2-Isopropyl-3-methoxy-pyrazine
Geosmin
Dimethyl disulphide
Geosmin is probably the most moldy-smelling and is detected very sensitively by olfactory systems of animals that want to avoid contaminated food. To me it smells muddy, or earthy, like soil after a rain shower. In our lab, about half the people find it a pleasant smell. It can be smelled in wine, it's the earthy taste found in vegetables, it's the smell of dead bacteria, and so on and so on. The term petrichor describes the odor and geosmin is a major contributing odorant for this.
The following is multiple choice question (with options) to answer.
A mold is an imprint of an organism left in what? | [
"magma",
"fossil",
"band",
"rock"
] | D | Fossils may form in other ways. With complete preservation, the organism doesn't change much. As seen below, tree sap may cover an organism and then turn into amber. The original organism is preserved so that scientists might be able to study its DNA. Organisms can also be completely preserved in tar or ice. Molds and casts are another way organisms can be fossilized. A mold is an imprint of an organism left in rock. The organism's remains break down completely. Rock that fills in the mold resembles the original remains. The fossil that forms in the mold is called a cast. Molds and casts usually form in sedimentary rock. With compression, an organism's remains are put under great pressure inside rock layers. This leaves behind a dark stain in the rock. |
SciQ | SciQ-5617 | fluid-dynamics, differentiation, density, flow
I can understand the picture of each particle having its own position, velocity, etc. that involves spatial or time coordinates, but I am confused as to the discussion of particles carrying density, and how particles could change density as they flow. (Note that I understand the explanation of incompressible fluid flow given if the density of a particle can change, I am just confused as to what this really means).
So my question then is the following: What do we mean by particles in the Lagrangian description of fluid flow, and how could the density of these particles be changing? (I am new to looking at fluid dynamics, so if this is a really simple or too broad of a question I will gladly close the question. I hate bad or ignorant questions on this site). When we use the term "fluid particle" in this context, what we really mean is "fluid parcel," consisting of many many atoms/molecules, present in the limit of a very small spatial volume containing these atoms/molecules. If, at a given location is space, the density is not changing with time within a fixed tiny control volume (parcel), this means that the number of molecules/atoms within the control volume is not changing, and $\partial \rho/\partial t=0$.
If we are following the motion of a fluid parcel in a Lagrangian sense, what we mean is that the number of atoms/molecules within the moving parcel is constant, but the volume of the parcel can be increasing or decreasing, and the fluid density can be changing as a result. If the volume of the Lagrangian parcel does not change in a Lagrangian sense, we say that the density is constant with time following the motion of the parcel, and we represent this as $D\rho/Dt=0$
So, a Lagrangian parcel contains a fixed number of material "particles" within a tiny moving (and potentially changing parcel volume), while an Eulerian parcel consists of a fixed tiny parcel with a fixed and stationary spatial volume (and potentially changing number of "particles" within the parcel).
The following is multiple choice question (with options) to answer.
Particles of different densities exert different amounts of what? | [
"pressure",
"energy",
"force",
"resistance"
] | A | Christopher Auyeung. Particles of different densities exert different amounts of pressure . CC BY-NC 3.0. |
SciQ | SciQ-5618 | botany, plant-physiology, plant-anatomy
*No others are known, but could definitely exist.
Bibliography
Crafts, A. S. “Phloem Anatomy, Exudation, and Transport of Organic Nutrients in Cucurbits.” Plant Physiology 7, no. 2 (1932): 183–225.
Fischer, A. “Das Siebröhrensystem von Cucurbita.” Berichte Deutsche Botanische Gesell 1 (1883): 276–279.
Fischer, A. “Neue Beiträge Zur Kenntniss Der Siebröhren.” Berichte Über Die Verhandlungen Der Königlich-Sächsischen Gesellschaft Der Wissenschaften Zu Leipzig, Mathematisch-Physische Klasse 38 (1886): 291–336.
Fischer, A. Untersuchungen Über Das Siebröhren System Der Cucurbitaceen. Berlin, 1884.
Turgeon, R. and Oparka, K. “The Secret Phloem of Pumpkins.” Proceedings of the National Academy of Sciences 107, no. 30 (2010): 13201 –13202.
Walz, C. and Giavalisco, P. and Schad, M. and Juenger, M. and Klose, J. and Kehr, J. “Proteomics of Curcurbit Phloem Exudate Reveals a Network of Defence Proteins.” Phytochemistry 65, no. 12 (2004): 1795–1804.
Zhang, B. and Tolstikov, V. and Turnbull, C. and Hicks, L. M. and Fiehn, O. “Divergent Metabolome and Proteome Suggest Functional Independence of Dual Phloem Transport Systems in Cucurbits.” Proceedings of the National Academy of Sciences 107, no. 30 (2010): 13532.
The following is multiple choice question (with options) to answer.
Plants generally transport carbohydrates from leaves to roots and other nonphotosynthetic organs in the form of what? | [
"chloride",
"glucose",
"sucrose",
"potassium"
] | C | |
SciQ | SciQ-5619 | evolution, botany, ecology, plant-physiology, plant-anatomy
Title: Why do some plant species have lobed leaves, while similar species in the same habitat don't? Some plants have lobed leaves, like the English oak (Quercus robur), while other plants growing the same deciduous woodland habitats, and very often growing alongside oaks, such as the European beech (Fagus sylvaticus) don't have lobes. Here are two two leaves side by side for comparison:
These two species should be subject to most of the same evolutionary pressures. Why would one evolve lobed leaves, whilst the other has only tiny serrations? This is a question for which, I think at the moment, we don't have a clear answer.
It is important to bear in mind that the leaf plays a number of important roles in the plant (photosynthesis, thermoregulation etc.) so leaf shapes probably evolved through a process of successive trade-offs. This may make it difficult to identify the exact selection processes operating on any one species. In contrast, something like the eye has a well-defined single function, which in principle at least, makes it easier to understand the link between form and function.
From Niklas (1988):
Life history and optimisation theory suggest that the number of
phenotypic solutions that allow for different equally successful trait
combinations increases as the number of trade-offs increases – a
conclusion that applies to traits within the leaf (e.g. for shape) as
well as to leaf–branch relationships.
However, there are a number of ideas to explain leaf shape diversity which include:
Thermoregulation
It has been shown that by adding lobes to leaves, the rate of heat transfer across a leaf is greater than that of an unlobed leaf of the same area (e.g. Gurevitch and Schuepp 1990). So, lobed leaves may be selected for under certain environmental conditions.
hydromechanical constraints
Lobed leaves may have greater hydraulic efficiency. For smaller veins, hydraulic pressure increases as they present an increased resistance to water flow. This places stress on the deliate outer leaf tissues. If lobed leaves have relatively less mesophyll tissue than large, highly conductive veins, they may have reduced hydraulic resistance compared unlobed leaves (Sack and Tyree 2005).
The following is multiple choice question (with options) to answer.
Monocots and eudicots differ in what type of a leaf's tissue? | [
"circulatory",
"structural",
"vascular",
"reproductive"
] | C | |
SciQ | SciQ-5620 | 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.
What kind of reproduction, in general, relies on sets of cells that are precursors for eggs and sperm? | [
"fusion",
"asexual",
"binary fission",
"sexual"
] | D | |
SciQ | SciQ-5621 | optics, refraction, geometric-optics, lenses, telescopes
I've neglected the convex lens for the sake of simplicity.
It can be seen that the image $A'B'$ is formed at the midpoint of focal length on the same side of object $AB$ (image formed by the convex lens). I also verified it using the thin lens formula $\frac 1 v -\frac 1 u=\frac 1 f$. So for an object at the focal point of a diverging lens, the image forms midway between the object and the lens. But this is contradictory to what is being explained in my textbook, and in the answer linked above regarding Galilean telescopes.
In short, my question is - How does a diverging lens in a Galilean telescope form an image at infinity when its object is at its focal plane? The first (convex) lens produces an image that is to the right of the diverging lens i.e. this acts as a virtual object for the diverging lens. So the rays look like the diagram below. I've drawn a point object to keep the diagram simple. This could for example be an image of a distant star.
When we say there is a virtual object we mean that to the left of the lens the light rays are converging as if they were coming to a focus at the point where the virtual object is. I've drawn those converging rays as solid blur lines to the left of the lens and as dashed line to the right of the lens to show how they would come to a focus at the object if the diverging lens was not there.
Now the diverging lens makes the rays diverge, which in this case means it reduces their convergence. With the diverging lens in place the light rays look like this:
The following is multiple choice question (with options) to answer.
A lens of what shape causes rays of light to diverge, or spread apart, as they pass through it? | [
"concave",
"flat",
"convex",
"elongated"
] | A | A concave lens is thicker at the edges than it is in the middle. You can see the shape of a concave lens in the Figure below . From the diagram, it’s clear that the lens causes rays of light to diverge, or spread apart, as they pass through it. Note that the image formed by a concave lens is on the same side of the lens as the object. It is also smaller than the object and right-side up. However, it isn’t a real image. It is a virtual image. Your brain “tricks” you into seeing an image there. The light rays actually pass through the glass to the other side and spread out in all directions. You can explore the formation of images by a concave lens at this URL: http://phet. colorado. edu/sims/geometric-optics/geometric-optics_en. html. |
SciQ | SciQ-5622 | neuroscience
Title: Nervous system : Nerve signals If the electrical signals from all the various organs throughout the body eventually connect to the nerves in the spinal column traveling up to the brain, how does the brain differentiate the different signals. Is the nerve in the spinal column like an electrical conduit with many wires inside? Yes is the simple answer. A nerve will go up to a specific part of the brain which the brain knows corresponds to a certain region of the body. It isn't perfect though e.g. pain in the diaphragm confuses the brain which doesn't recognise that pain must be coming from there so instead tells the body there is shoulder pain, however this is useful in medicine. Another infamous example is pain from heart disease (angina) which causes pain in the jaw and arm. Perhaps even more interestingly, if a nerve is cut and then grows back linking to the wrong nerve it may lead to the completely wrong part of the body being identified when touched. Also if the brain itself is stimulated in these corresponding areas, a person will feel he or she is indeed being touched in a certain part of the body.
The following is multiple choice question (with options) to answer.
What is the complex network of nervous tissue that carries electrical messages throughout the body? | [
"lymphatic system",
"nervous system",
"respiratory system",
"circulatory system"
] | B | A small child darts in front of your bike as you race down the street. You see the child and immediately react. You put on the brakes, steer away from the child, and yell out a warning, all in just a split second. How do you respond so quickly? Such rapid responses are controlled by your nervous system. The nervous system is a complex network of nervous tissue that carries electrical messages throughout the body. It includes the brain and spinal cord, the central nervous system , and nerves that run throughout the body, the peripheral nervous system (see Figure below ). To understand how nervous messages can travel so quickly, you need to know more about nerve cells. |
SciQ | SciQ-5623 | molecular-biology, cell-biology
This rate decreases dramatically as radius of the cell increases. For example a cell with double the diameter (2 micrometers) has a volume eight times larger, so collisions between any two molecules take 8 times ($2^3$) as long to occur (in other words, it takes molecules 8 times longer to "find" each other). This is one reason why there is a kind of upper limit on the size of an individual cell. Bigger organisms are bigger because they have more cells, not because they have larger cells.
The field of biology concerned with how likely it is for a reaction to occur is called enzyme kinetics. A related field, which deals with how frequently molecules collide is called statistical mechanics.
The following is multiple choice question (with options) to answer.
Crowding and resource limitation can have a profound effect on the rate of what? | [
"population stagnation",
"cultural advances",
"population growth",
"technology advances"
] | C | |
SciQ | SciQ-5624 | molecular-genetics, human-genome
Title: Criteria for the numbering of human chromosomes What were the criteria devised for the numbering convention employed in human chromosomes? When was it fixed?
Correct me if I am wrong; it appears that chromosome pairs 1 to 22 were originally ordered in terms of perceived structural size, which ended up fitting neatly with the quantity of base pairs (but not with the quantity of genes).
The sex chromosomes in turn were arbitrarily assigned as "pair 23".
Is this sound?
Thanks in advance. Why do you think it was "fixed?" Here's a nice review of the history of human cytogenetics, which included not only the original image from 1956 but points out a report which comments on the standardization of chromosome number. The autosomes were indeed numbered by length, and the sex chromosomes are traditionally put at the end as they are "numbered" 23 but clearly function quite differently. Gene content was decades away from being known at the time, and honestly isn't even known now. It's also just as arbitrary; simple size is easy enough and makes for rather nice pictures.
The following is multiple choice question (with options) to answer.
X and y are the labels of what specialized human chromosomes? | [
"exotic chromosomes",
"protein chromosomes",
"carb chromosomes",
"sex chromosomes"
] | D | The 24 human chromosomes. The autosomes are numbered 1 - 22, based on size, with chromosome 1 being the largest. The X and Y sex chromosomes are shown in the box. |
SciQ | SciQ-5625 | physical-chemistry, atoms, isotope, neutrons
Title: Z:#Neutrons Ratio Is there a fixed ratio that can be used to calculate the number of neutrons in the nucleus of the most stable isotope of an element by knowing the atomic number?
Side question: if Z is the symbol for atomic number, are there symbols for the number of neutrons and/or atomic mass? The symbols $Z$, $N$, and $A$ are typically used to describe a nucleus:
$Z$ : atomic number (= number of protons)
$N$ : neutron number
$A$ : mass number ($A = Z + N$)
There is no fixed $Z:N$ ratio throughout the whole periodic table for stable isotopes, but a belt of stability in the Chart of Nuclides.
The following is multiple choice question (with options) to answer.
Isotopes are named for their number of ______ plus neutrons? | [
"electrons",
"protons",
"atoms",
"nuclei"
] | B | Isotopes are named for their number of protons plus neutrons. If a carbon atom had 7 neutrons, what would it be named?. |
SciQ | SciQ-5626 | evolution, mycology
Title: Why are some fungi poisonous? There are many poisonous fungi in nature. For example Amanita Phalloides.
What reasons could a fungus need poison for? Some species, like venomous snakes, use poison to kill other species as prey. But what about fungi? I can't think of any purpose for poison in fungi. If poison has no real function in fungi shouldn't evolution get rid of it? The same reason some plants are poisonous: to stop animals from eating them.
The visible part of the fungus is called, rather misleadingly, the fruiting body. It exists to produce and spread spores and thus produce the next fungal generation. Getting eaten, rather obviously, inhibits its ability to do this. Being poisonous discourages animals from eating the fruiting body and thus permits it to complete its life cycle.
The following is multiple choice question (with options) to answer.
Because fungi feed on decaying and dead matter, they play what important role by releasing essential elements into the environment? | [
"producers",
"carnivores",
"consumers",
"decomposers"
] | D | CHAPTER SUMMARY 24.1 Characteristics of Fungi Fungi are eukaryotic organisms that appeared on land more than 450 million years ago. They are heterotrophs and contain neither photosynthetic pigments such as chlorophyll, nor organelles such as chloroplasts. Because fungi feed on decaying and dead matter, they are saprobes. Fungi are important decomposers that release essential elements into the environment. External enzymes digest nutrients that are absorbed by the body of the fungus, which is called a thallus. A thick cell wall made of chitin surrounds the cell. Fungi can be unicellular as yeasts, or develop a network of filaments called a mycelium, which is often described as mold. Most species multiply by asexual and sexual reproductive cycles and display an alternation of generations. Another group of fungi do not have a sexual cycle. Sexual reproduction involves plasmogamy (the fusion of the cytoplasm), followed by karyogamy (the fusion of nuclei). Meiosis regenerates haploid individuals, resulting in haploid spores. |
SciQ | SciQ-5627 | physical-chemistry, thermodynamics, gas-laws
Title: What will happen to the entropy and free energy of the gasses when the partition is removed?
Consider a container of volume $ 5.0$ L that is divided into two compartments of
equal size. In the left compartment there is nitrogen at $1.0$ $atm$ and $25 °C$; in the
right compartment there is hydrogen at the same temperature and pressure. What
will happen when the partition is removed?
$A) $The entropy decreases, and the free energy decreases.
$B)$ The entropy increases, and the free energy decreases.
$C) $The entropy increases, and the free energy increases.
$D) $The entropy decreases, and the free energy increases.
Logic tells that upon removing the partition, randomness increases and hence entropy increases. I am confused about free energy. First law of thermodynamics has to be applied , I think. But I can't seem to get the right direction. A Spontaneous process is characterized by an increase in the total entropy (for both system and surroundings).
Spontaneous processes are characterized by a decrease in free energy (analogous to the decrease in gravitational potential energy occurring for a ball rolling downhill).
The following is multiple choice question (with options) to answer.
If the temperature of a gas sample is decreased, what happens to the volume? | [
"increases",
"decreases",
"expands",
"stays the same"
] | B | If the temperature of a gas sample is decreased, the volume decreases as well. |
SciQ | SciQ-5628 | If the maximum number of fish caught is $$m$$, then the total number of fish caught is no more than $$m+(m-1)+...+(m-6)$$. So there is one fisherman that caught at least 18 fish. Repeat this process for the second and third highest number of fish caught and you should be good.
I should add that this is a common proof technique in combinatorics and graph theory. To show that something with a certain property exists, choose the "extremal" such something, and prove that property holds for the extremal object. For instance, to show in a graph where each vertex has degree at least $$d$$ there is a path of length at least $$d$$, and one proof starts by simply showing a maximal path has length at least $$d$$.
• If the most fish caught is $18$ that gives a tight result - there is a little work to check what happens if the largest number of fish caught is greater than $18$ Sep 30 '18 at 15:12
• @MarkBennet right, my thought was to iterate, i.e. After you choose the max $m$, replace $100$ with $100-m$ and $7$ fishers with $6$, this gives a bound on the second highest, etc. Thanks for pointing this out Sep 30 '18 at 15:15
• Not a problem - it actually gets a bit easier. This works and was my first way of doing it. Sep 30 '18 at 15:26
• Thank you for your solution. I accept Mark's solution because it is more accessible for kinds about 14 years.
– Aqua
Sep 30 '18 at 15:45
• @greedoid no prob! I would accept marks as well :) Sep 30 '18 at 15:45
I think I have a solution. First note that if $$r_4 \geq 15$$ then we have:
$$r_5 \geq 16$$
$$r_6 \geq 17$$
$$r_8 \geq 18$$
so $$r_5 + r_6 + r_7 \geq 16 + 17 +18 = 51$$ which is impossible.
Therefore $$r_4 < 15$$
The following is multiple choice question (with options) to answer.
Most food chains and webs have a maximum of how many trophic levels? | [
"10",
"4",
"6",
"3"
] | B | A trophic level is a feeding position in a food chain or food web. Most food chains and webs have a maximum of four trophic levels. There is less energy and biomass at higher trophic levels. |
SciQ | SciQ-5629 | 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 refers to the development and nourishment of an embryo within the mother’s body but not inside an egg? | [
"adolescence",
"ovulation",
"birth",
"vivipary"
] | D | Vivipary refers to the development and nourishment of an embryo within the mother’s body but not inside an egg. Birth may be followed by a period of parental care of the offspring. This reproductive strategy occurs in almost all mammals including humans. |
SciQ | SciQ-5630 | 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.
What kind of anaerobe is yeast? | [
"facultative",
"mutualistic",
"obligate",
"aerobic"
] | A | Yeast is a facultative anaerobe. This means that alcohol fermentation takes place only if: a. the temperature is close to 37°C b. the atmosphere does not contain oxygen c. sugar is provided to the cells d. light is provided to the cells. |
SciQ | SciQ-5631 | classical-mechanics, home-experiment, equilibrium
You can possibly liken your pile of stones like this where a very, very small push will not disturb them but a small push will?
A good example of balance is the bird on the end of a finger which is in stable equilibrium.
The following is multiple choice question (with options) to answer.
Bones are far from static, or unchanging. instead, they are what? | [
"dynamic",
"stable",
"continuous",
"fluid"
] | A | Bones are far from static, or unchanging. Instead, they are dynamic, living tissues that are constantly being reshaped. Under the direction of osteocytes, osteoblasts continuously build up bone, while osteoclasts continuously break it down. You can watch an animated video of these processes in bone at http://www. youtube. com/watch?v=yENNqRJ2mu0 . |
SciQ | SciQ-5632 | physiology, hematology
Title: What is the function of clot retraction? I am thinking how clot retraction and fibrinolysis work together.
I think that clot retraction is a process that gets clot towards fibrinolysis process.
Fibrinolysis process then lyses the clot.
However, I am not sure if it is so simple.
Some seems to be discussing about how to differentiate start of fibrinolysis from clot retraction morphologically.
So they probably seem to be at this stage similar processes visually, but not functionally.
What is the function of clot retraction? The platelets in the clot contain contractile proteins. They bring the edges of the wound together, which also reduces the chance of further bleeding. The contraction process also supports the wound healing process as it brings the ends of the wound together.
For more information see this article: "Mechanics and contraction dynamics of single platelets and implications for clot stiffening"
The following is multiple choice question (with options) to answer.
After entering the circulation, approximately one-third of platelets migrate to what organ for storage, to be released in response to any blood vessel rupture? | [
"kidneys",
"spleen",
"bladder",
"lungs"
] | B | Platelets You may occasionally see platelets referred to as thrombocytes, but because this name suggests they are a type of cell, it is not accurate. A platelet is not a cell but rather a fragment of the cytoplasm of a cell called a megakaryocyte that is surrounded by a plasma membrane. Megakaryocytes are descended from myeloid stem cells (see Figure 18.4) and are large, typically 50–100 µm in diameter, and contain an enlarged, lobed nucleus. As noted earlier, thrombopoietin, a glycoprotein secreted by the kidneys and liver, stimulates the proliferation of megakaryoblasts, which mature into megakaryocytes. These remain within bone marrow tissue (Figure 18.12) and ultimately form platelet-precursor extensions that extend through the walls of bone marrow capillaries to release into the circulation thousands of cytoplasmic fragments, each enclosed by a bit of plasma membrane. These enclosed fragments are platelets. Each megakarocyte releases 2000–3000 platelets during its lifespan. Following platelet release, megakaryocyte remnants, which are little more than a cell nucleus, are consumed by macrophages. Platelets are relatively small, 2–4 µm in diameter, but numerous, with typically 150,000–160,000 per µL of blood. After entering the circulation, approximately one-third migrate to the spleen for storage for later release in response to any rupture in a blood vessel. They then become activated to perform their primary function, which is to limit blood loss. Platelets remain only about 10 days, then are phagocytized by macrophages. Platelets are critical to hemostasis, the stoppage of blood flow following damage to a vessel. They also secrete a variety of growth factors essential for growth and repair of tissue, particularly connective tissue. Infusions of concentrated platelets are now being used in some therapies to stimulate healing. |
SciQ | SciQ-5633 | fluid-statics, surface-tension
So, it would be very helpful if you could explain why does a metal paper clip float even though it has an acute contact angle with water.
Please note that the question Surface tension: the paper clip experiment is not same as this one. It doesn't discuss about the obtuse contact angles observed between metal paper clip and water which is the central theme of this question. When there is no wetting, the contact angle is obtuse. When wetting takes place, the contact angle becomes acute. A certain amount of pressure is needed to break the surface of the liquid so that wetting takes place. If wetting were to take place, the paperclip would sink (likewise it would sink if there were no surface tension).
When wetting does not take place, the contact angle is obtuse. The paper clip can float because wetting does not take place (or only a small amount of wetting takes place) - the clip is light enough that does not push hard enough on the surface of the water to break surface tension. This is undoubtedly helped by contaminants, such as oils picked up from fingers (it is opposite to capillary action, in which wetting does take place).
The following is multiple choice question (with options) to answer.
What causes a small scrap of paper placed on top of the water droplet to float , although the object is denser (heavier) than the water? | [
"transfusion",
"surface tension",
"van der waals force",
"diffusion"
] | B | a small scrap of paper onto a droplet of water, the paper floats on top of the water droplet, although the object is denser (heavier) than the water. This occurs because of the surface tension that is created by the water molecules. Cohesion and surface tension keep the water molecules intact and the item floating on the top. It is even possible to “float” a steel needle on top of a glass of water if you place it gently, without breaking the surface tension (Figure 2.11). |
SciQ | SciQ-5634 | human-anatomy
Title: Why is a penis an organ? According to Wikipedia an "An organ is a group of tissues with similar functions". I don't know anything about anatomy but it doesn't seem to me that a penis can be delimited somewhere to form a "group". Therefore I do not understand why a penis is considered an organ.
Can you explain it to me ? Frankly, that's a terrible definition by Wikipedia.
Merriam-Webster defines an organ as:
a differentiated structure (such as a heart, kidney, leaf, or stem) consisting of cells and tissues and performing some specific function in an organism
or
bodily parts performing a function or cooperating in an activity
The important defining feature of an organ is not that the tissues have similar functions but that, together, the tissues comprise a functional whole that achieves some end goal.
For the penis, it consists of multiple tissues with different functions:
(from https://www.ncbi.nlm.nih.gov/books/NBK525966/figure/article-20668.image.f1/ - original from Gray's Anatomy)
The different tissues pictured here: the fibrous envelope, the corpora cavernosa, the septum pectiniforme, the urethra and blood vessels, the nervous tissue in the skin: all of these tissues have different individual functions: structural, erectile, carrying urine or semen, etc.
The key that unifies them into an organ is that the functions of the penis at the organism level (principally sexual function) are not served by any of these tissues alone, but rather by their combination in a full structure: an organ.
Ultimately, organ definitions are somewhat opinion-based: people are lumpers and splitters, so you might find conflicting definitions for which groupings of tissues reflect distinct organs, but I think by most standards you would find the penis to be considered a distinct organ, affiliated with but distinct from the primary sex organs and associated glands.
The following is multiple choice question (with options) to answer.
What is the term for a structure composed of more than one type of tissue? | [
"organ",
"system",
"cortex",
"marrow"
] | A | Like animals, plants have organs that are specialized to carry out complex functions. An organ is a structure composed of more than one type of tissue. A tissue, in turn, is a group of cells of the same kind that do the same job. In this lesson, you will read about the tissues that do the important work of plants. The cells that make up plant tissues are described first. |
SciQ | SciQ-5635 | 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 pair of bean-shaped organs situated just above the waist? | [
"lungs",
"kidneys",
"aorta",
"pancreas"
] | B | The kidneys are a pair of bean-shaped organs just above the waist. A cross-section of a kidney is shown in Figure below . The function of the kidney is to filter blood and form urine. Urine is the liquid waste product of the body that is excreted by the urinary system. Nephrons are the structural and functional units of the kidneys. A single kidney may have more than a million nephrons!. |
SciQ | SciQ-5636 | zoology, species-identification, ornithology, behaviour
Title: What is this crow eating, and is it a common part of the corvid diet? Here's a picture (by Rob Curtis) of a crow carrying and eating the corpse of what looks a bit like a small hawk or falcon:
Other pictures clearly show the crow is eating the dead bird. This image shows the underside of the head and beak; this one shows its legs, which are grayish.
What bird is being eaten?
Is this bird a usual part of the corvid diet? Or did the crow just opportunistically scavenge a dead bird? Crows are omnivorous, and will eat almost anything they find or can kill.
In this case the prey looks like a Yellow-Shafted Flicker.
The following is multiple choice question (with options) to answer.
What part of a bird is adapted for the food it eats? | [
"head",
"beak",
"teeth",
"eye"
] | B | Bird beaks are generally adapted for the food they eat. For example, the sharp, hooked beak of a raptor is well suited for killing and tearing apart prey. The long beak of the hummingbird in Figure below co-evolved with the tube-shaped flowers from which it sips nectar. |
SciQ | SciQ-5637 | 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.
What is the inner cell mass formed by the cells of the blastocyst called? | [
"xerophyte",
"ectoderm",
"embryoblast",
"amniotic cavity"
] | C | The cells of the blastocyst form an inner cell mass and an outer cell layer, as shown in Figure below . The inner cell mass is called the embryoblast . These cells will soon develop into an embryo. The outer cell layer is called the trophoblast . These cells will develop into other structures needed to support and nourish the embryo. |
SciQ | SciQ-5638 | that the dart will land in section A. She throws darts, one at a time, aiming each at the bull’s-eye. Exercise 15. p ´(8)2 = 64p Answer: Area of large circle = Area of small circle = p ´(2)2 = 4p So the probability of the point being in the small circle is. If you have ever watched a professional darts player on TV, when he or she is looking to win the game they know what to hit to checkout high scores. A dart hits the circular dartboard shown below at a random point. The shape is a circle. Figure 1 shows the layout and scor-ing system. What distribution does X follow? State the name and parameters. 1 Answer to Playing darts. I created this for a lesson observation - the PP and worksheet are adaptations of other resources I found online and tes - so thank you for the help! I had done a number of lessons on probability leading up to this lesson with my 11 set 3 group - roughly E/D grade students. Introduce electrons in atoms by dropping darts! Lab provides a discussion of probability and electron density. I have the answer, but I don't know how to get to the answer. 1 The answer is around 0. Geometric Probability : Example : Suppose you are considering the probability of hitting a target on a dart board. There is a 25% chance it will land in section B. 3 Matthew throws three darts. FREE Rd Sharma for class 10 Math, Chapter 1 - Real Numbers from (Rd Sharma). txt) or read online for free. area of square = 4×4 = 16. The best we can say is how likely they are to happen, using the idea of probability. (Same picture from #1) A point in the figure selected at random. Write the probability as a fraction, decimal, or percent. If the probability of winning is 20% what are the odds of winning? CLASSIC PROBABILITY 9. In most dart games, each player throws three darts per turn. Uniform distributions are very common for initial studies of probability. But the question could have been given an equivalent restatement: A factory produces cubes with face-area between 0 and 1 square-feet; what is the probability that a randomly chosen cube has face-area between 0 and 1/4 square-feet?. 2 Theoretical Probability, pages 68-75 26 16 13 10 13 26 13 18 Answers
The following is multiple choice question (with options) to answer.
What does the distribution of darts on a dartboard shows the difference between? | [
"accuracy and precision",
"equilibrium and precision",
"Aim and precision",
"production and precision"
] | A | The distribution of darts on a dartboard shows the difference between accuracy and precision. |
SciQ | SciQ-5639 | biochemistry, gas-laws
Title: What is the state of aggregation (gas, liquid) of oxygen in blood? Atmospheric oxygen is in O2 and a gas. Then we inhale the air, our efficient lungs do the magic to filter out the oxygen and push them into the blood stream.
When we say hemo and globin transport the oxygen using the iron ions. In what state oxygen is transported in the blood? as a gas or a liquid or an ion? It is hard for me to conceive of the idea that oxygen would be in gaseous form in the blood. "GAS in blood?" e.g. Arterial Blood Gas Test
Also, how does the lungs convert the gas into something that is compatible to be in blood?
References:
Amount of Oxygen in the Blood Regarding the state of oxygen in blood: It is in solution in the blood plasma (which mostly consists of water), in the form of single molecules. Think of water which you leave exposed to air: carbon dioxide will be captured and dissolved (along with the other gases in air), but these molecules are not gaseous or liquid, but rather "in solution", which is different from the "classical" states.
Back to oxygen: As your reference already states, most of the oxygen in solution will bind to hemoglobin. The actual state of oxygen in that complex has been debated, but it is believed to be reduced by the hemoglobin iron to the superoxide anion, coordinated to Fe$^{3+}$. See Wikipedia on this.
Also, the lungs do not "convert" the atmospheric oxygen to anything, they rather allow, due to their very large surface area, the quick exchange of oxygen/carbon dioxide in solution and in the air.
The following is multiple choice question (with options) to answer.
What gas do the lungs give up as they take in oxygen? | [
"carbon dioxide",
"carbon monoxide",
"nitrogen",
"methane"
] | A | Pulmonary circulation is the part of the circulatory system that carries blood between the heart and lungs (the term “pulmonary” means “of the lungs”). It is illustrated in Figure below . Deoxygenated blood leaves the right ventricle through pulmonary arteries, which transport it to the lungs. In the lungs, the blood gives up carbon dioxide and picks up oxygen. The oxygenated blood then returns to the left atrium of the heart through pulmonary veins. |
SciQ | SciQ-5640 | cell-division
Title: Why doesn't cellular, replicative senescence (or the hayflick limit) constrain the normal development of an organism? The wikipedia article on cellular senescence states:
Cellular senescence is the phenomenon by which normal diploid cells cease to divide. In culture, fibroblasts can reach a maximum of 50 cell divisions before becoming senescent. This phenomenon is known as "replicative senescence", or the Hayflick limit.
The following is multiple choice question (with options) to answer.
What is the term for the last stage of life before adulthood? | [
"old age",
"pre-pubescence",
"childhood",
"adolescence"
] | D | For the first year after birth, a baby is called an infant . Childhood begins at age two and continues until adolescence. Adolescence is the last stage of life before adulthood. |
SciQ | SciQ-5641 | bond
SO, when you're thinking about breaking $\ce{H-F}$ bond, you gotta take into consideration what happens with the products. In the example with organic chemistry and leaving groups that you have pointed out, fluorine is the worst leaving group for the precisely the same reason--it cannot stabilize the negative charge well, so it doesn't "want" to leave. However, if you try to do a, say, $S_N2$ reaction in a protic solution (not the best way to go around, but doable), then $\ce{F-}$ will be a much better leaving group than $\ce{I-}$, b/c $\ce{F-}$ will instantly "catch" a hydrogen from the solution and stop being nucleophilic, which according to Le'Chatelie'r principle shifts the equilibrium to where $\ce{F-}$ is a leaving group.
The following is multiple choice question (with options) to answer.
Breaking of weak bonds, which tend to form between positive and negative charges, does not require much what? | [
"time",
"energy",
"catalyzation",
"heat"
] | B | Hydrogen Bonds Ionic and covalent bonds are strong bonds that require considerable energy to break. However, not all bonds between elements are ionic or covalent bonds. Weaker bonds can also form. These are attractions that occur between positive and negative charges that do not require much energy to break. Two weak bonds that occur frequently are hydrogen bonds and van der Waals interactions. These bonds give rise to the unique properties of water and the unique structures of DNA and proteins. When polar covalent bonds containing a hydrogen atom form, the hydrogen atom in that bond has a slightly positive charge. This is because the shared electron is pulled more strongly toward the other element and away from the hydrogen nucleus. Because the hydrogen atom is slightly positive (δ+), it will be attracted to neighboring negative partial charges (δ–). When this happens, a weak interaction occurs between the δ+ charge of the hydrogen atom of one molecule and the δ– charge of the other molecule. This interaction is called a hydrogen bond. This type of bond is common; for example, the liquid nature of water is caused by the hydrogen bonds between water molecules (Figure 2.7). Hydrogen bonds give water the unique properties that sustain life. If it were not for hydrogen bonding, water would be a gas rather than a liquid at room temperature. |
SciQ | SciQ-5642 | 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 two organs secrete fluids that aid in digestion? | [
"kidney and gall bladder",
"pancreas and liver",
"stomach and lung",
"spleen and bladder"
] | B | The pancreas and liver secrete fluids that aid in digestion. |
SciQ | SciQ-5643 | electromagnetism, photons, collision
Title: Collision of light waves & matter When light or electromagnetic wave hits an obstacle, what happens? Are the reactions times always negligible?
By reaction I mean all that happens after the hit like reflection for example. There are several things that can happen, depending on the nature of the obstacle.
The simplest case is if, classically, we think that the obstacle is not too much smaller than the wavelength of the light. Then, the light wave can be reflected, absorbed, or diffracted.
Most people are familiar with reflection, the light more or less bounces off the obstacle. The reflected light wave will still travel at the speed of light.
Absorption happens when the material absorbs the energy of the light, and changes its form, usually to heat. This happens as the light travels just below the surface (exactly how far depends on how absorbing the material is.).
Diffraction happens because light is a wave, and happens when light passes close to the edge of an obstacle. The wave tends to spread out into the region where we would think the obstacle should cast a shadow. Again, the diffracted light continues to travel at the speed of light.
Finally, if we have an 'obstacle' that isn't really an obstacle, but lets light pass through, then the light will be slowed down by an amount that depends on the refractive index of the material. This is what causes bending of light in lenses, liquids, etc. The speed can change by a large factor -- there are plenty of materials with refractive indicies several times that of air.
The direct answer to your question depends on what you mean by negligible, exactly. What is negligible? The speed of light is very very high (300,000 km/s), so the time required for a reflected beam to complete a return path, or the extra time taken for light to go through a lens or liquid is correspondingly tiny. But if you are looking on very large distances, or with very precise times, then the effects can be seen.
Extra -- the other case, where the obstacle is smaller than the wavelength of the light, and is a single atom or molecule, the answer becomes different, as you have to take into account the atomic structure. But that's a whole course in atomic physics to explain it all.
The following is multiple choice question (with options) to answer.
When light meets matter, it may be reflected, transmitted, or what? | [
"absorbed",
"diffracted",
"diffuse",
"reflected"
] | A |
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