I read the Wikipedia article about Cell Potency       Totipotency is the ability of a single cell to divide and produce all of the differentiated cells in an organism.   while pluripotency means     a stem cell that has the potential to differentiate into any of the three germ layers: endoderm, mesoderm, or ectoderm.   I don't quite understand the difference, then, between a totipotent and a pluripotent cell.
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Both develop into specialized cells.Then how are they different?
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is the multiplication of number of chromosomal sets from 2n to 3n (triploidy), 4n (tetraploidy) and so on. It is quite common in plants, for example many crops like wheat or Brassica forms. It seems to be rarer in animals but still it is present among some amphibian species like Xenopus.  As I know in mammals polyploidy is lethal (I don't mean tissue - limited polyploidy). I understand that triploidy is harmful due to stronger influence of maternal or paternal epigenetic traits that cause abnormal development of placenta, but why there is no tetraploid mammals?
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I can't seem to find a satisfactory answer to this anywhere on the web. While  poses a related question, I don't think it sufficiently answers mine...  During the opening chapters of Jedi Search, Luke addresses the new Senate on the need to find new Jedi talent, or Force sensitive individuals. During this proposal, he cites that the most fruitful leads of Jedi potential are in the descendants of Jedi Knights: as Force sensitivity is hereditary. The book even discusses the notion that Leia should be comparatively well attuned to the Force, due to her being the child of Anakin Skywalker.  I understand that the concept of the Jedi as a totally celibate and monastic order was something that was retconned into the lore after Episode II: Attack of the Clones, and that there are examples of entire nuclear Jedi families exist (such as Andur Sunrider and Plo Koon)...  But if Force-manipulative ability is passed down genetically (as a potentially mutative property of their genetic makeup), why would the Jedi order be so numerous if they practice Chastity?  Even if procreation is not expressly forbidden (as in the pre-retcon Expanded Universe): why would Jedi need special permission to produce more Jedi potential children?  How are more Jedi created, if not through procreation? Has their profusion been deliberately retarded, and if so why? is there another explanation for their (pre-empirical) plenitude?
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As far as I know, DNA is the construction protocol of all organisms on Earth.  Does it change when influenced by time and environment (physical laws)?  As parents with schizophrenia are more likely to have children with schizophrenia and an individual with no genetic predisposition for schizophrenia can suffer from such a condition because of drug abuse or environmental influence, does this prove that human DNA is changing during our lifespan?
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From :     Human embryos have a tail that measures about one-sixth of the size of the embryo itself. As the embryo develops into a fetus, the tail is absorbed by the growing body.   How are we sure that it is a real tail and is not a superficial resemblance of something else?  I ask this because some creationist guy challenged me in this regard.
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I was told that these three phases have the same meanings, but I want to know if there are any differences between them:   sort of kind of somewhat
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In the picture below, which I obviously do not own:     it depicts two different phylogenic trees, one which is based on molecular comparisons and another one which is based on body-plan grades. My question is which is more common or accepted in the current Biology world?  Image reference:
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I'm not a professional in biology nor a student, but I'm curious about this. To be more specific: why doesn't a plant virus affect animal cells?  I suspect that different kinds of cells have different ways to replicate DNA and that this is the reason for the specialization of viruses.  I wonder if someone in the field can explain this to me. Thanks.
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I am reading a field biology manual that is directing me to do a power analysis, and I find the phrasing very confusing. It says: Determine sampling requirement to be 80% confident you are within 10% of the objective. (More concretely: how many survey plots do I need to be 80% confident of whether I am within 10% of having 65 trees per hectare?) It's phrased like a power analysis, but is confidence a synonym for power, and is being with 10% an indication of the alpha? *Can anyone suggest what the statement means mathematically (e.g., B = 0.8)? *Can anyone recommend an R package for this?
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For a proposition, such as:     P: Socrates is a man   Then not P is also a proposition:     Not P: Socrates is not a man   But do the same goes for properties? One can argue in the following way:    red is a property of red flags, or of red apples; but not red is not a property; for no thing instantiates not redness; that is not redness does not cohere in some substrate - here a flag, or apple; even though whiteness, which is an example of not redness, coheres in a white wall.  Q. Is this right?  All this, I think, takes it for granted that properties cohere in some substrate or substance - this is a commitment to a specific ontology; we may choose something else; the obvious choice being a world where all that there is are bundles of properties, and no substrate or substance to which to hang them on; there, existence is also a property - a property which all existing entities have.   Q. Given this ontological commitment; then is not P also a property?
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Let $I$ be the unit interval, and define the torus using the usual identifications on $I \times I$. I've shown that $I \times I - \{x\}$ (where $x$ is a point not on the boundary of $I \times I$) is homotopy equivalent to its boundary (and that it even retracts onto its boundary). Let $p: I \times I \rightarrow I \times I /\sim$ be the canonical quotient map. Using the retraction above, call it $r$, is there a way I can explicitly show that $p(I \times I - \{x\})$ is homotopy equivalent to $p(\text{boundary of } I \times I)$, i.e., that torus minus a point to a figure-eight?  More generally, if $A \subset X$, and $X$ is homotopy equivalent to $A$ (or $X$ retracts to $A$), for which maps $p$ can I say that $p[X]$ is homotopy equivalent to $p[A]$?   Hints appreciated!
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Background  The standard definition of species refers to the concept of . If two lineages are found to be reproductively isolated, then we consider these two lineages to belong to different species. My question concerns evolved reproductive isolation in Drosophila sp. following labs due to experimental evolution.  Question  Have we ever demonstrated that two Drosophila sp. lineages that could initially interbreed (in nature or in labs) evolved through artificial selection (and drift and mutations) in labs to finally not be able to interbreed anymore either due pre- or post- zygotic isolation (see )? Or, in other words, have we ever demonstrated that two drosophila lineages evolved to become different species (reproductive isolation definition) in labs experiments?  If not, have we ever observed some partial reproductive isolation such as inbreeding depression for example?    Note: This question is motivated by @LotusBiology that could not receive the answers she/he was waiting for because he/she failed to ask questions that are possibly answerable! So I wanted to ask this question that somehow addresses  question he/she asked (now on-hold)  For more information about the concept of species, please have a look at
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I made an answer on the Scifi.SE that can be read . It is about how the characters in the story Jurassic Park might have gotten DNA for all the species shown.  In my answer, I said this:     Apes and Humans, for example, share over 99% of their genes. That means the difference between our species is less than 1% of our genes. In fact, all life on Earth shares about 50% of it's genes.   but in the original posting (before someone edited it) I chose to use the word DNA instead of genes.  He left this comment in the section to explain the edit:     Sorry, I'm a biologist, I can't help it. Humans and apes share 99% similarity in the coding sequences of their DNA, the ~5% that codes for genes, not on all the DNA. I simplified this to genes for the answer.   I have a basic high school understanding of DNA and genes, so I'm afraid I fail to see the difference between using "DNA" or using "genes" in my statement. I understand that genes are specific sequences of DNA that are used by the cell in some way. I understand that DNA is more generic, including all of the strands, whether they are used or not, whether they seem to code for something or not.  So is it wrong then to say that apes and humans share 99% of their DNA or is it equally correct to say "genes"?
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In propositional logic, the statement "If pigs can fly, then elephants can lay eggs." validates to true because the antecedent validates to false.  In other words, given $a \rightarrow b$, if a is false, the entire statement is true. Why?  Just because the antecendent is false doesn't mean that another fact depends on it, right?
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Hello guys I have this problem which has been really bugging me. And it goes as follows:  Using induction, we want to prove that all human beings have the same hair colour. Let       S(n) be the statement that “any group of n human beings has the same hair colour”.  Clearly S(1) is true: in any group of just one, everybody has the same hair colour.  Now assume S(k), that in any group of k everybody has the same hair colour. If we replace any one in the group with someone else, they still make a total of k and hence have the same hair colour. This works for any initial group of people, meaning that any group of k + 1 also has the same hair colour. Therefore S(k + 1) is true.  I cant seem to figure out where the problem lies in this proof. I have tried a few things and I have concluded the base case is correct. But other than that I can't seem to disprove this proof.
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When it comes to getting a tenure-track position where one has both a lot of resources and academic freedom to do what one wants to do (so having a tenure-track position in a top university might be more useful because one may get more resources at a top university).   Or in short, when one wants to maximize one's chances of becoming a "top scientist".  There are obviously numerous factors, and "rank/prestige" should not be considered as a factor in itself. That said, the period after one gets a PhD is an extremely important time for building up connections, and those are easier to get at a top university.
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The top 25% is the top quartile. The top 10% is the top decile. The top 1% is the top percentile.  Is there an equivalent for the top 0.5%  i.e. 1-in-200?