text:
Why should evolution not be equated with progress?
My science textbook says this:

Evolution should not be equated with progress. In fact, there is no real 'progress' in the idea of evolution. Evolution is simply the generation of diversity and the shaping of the diversity by environmental factors. The only progressive trend in evolution seems to be that more and more complex body designs have emerged over time. However, again it is not as if older designs are inefficient! So many of the older and simpler designs still survive [..] In other words, human beings are not the pinnacle of evolution, but simply yet another species in the teeming spectrum of life.

I am not sure if I agree with this; after all, humans do seem to be more advanced than dogs. Many people have asked me why I thought this was true, so here is my answer: Today, humans could wipe out dogs from Earth if they wanted, but you can hardly imagine  a scenario in which dogs would do the same to humans.
What am I missing here?

Humans more advanced than dogs?  When you consider that dogs have better hearing, a far better sense of smell, often (depending on breed) much greater endurance, a digestive system able to accept a wider variety of food...

And if you still think humans are more advanced than dogs, I'd ;like to see YOU catch a frisbee in your mouth :-)

@jamesqf yes that was a new perspective for me. Yet dogs did'nt reach Mars or Pluto, humans did.

humans are the products of 4 billions years of evolution, just like every other living organisms, so either you and e-coli are equally advanced or advancement/progress is not equal to evolution. Evolution is also quite happy to have organisms evolve in a direction that will eventually drive them extinct, as long individual selective entity does better than its competitors. Evolution is less marching in a direction and more the drunkard's walk. Any advancement is due only to chance.

@Prashant Gokhale: Well, if that's your definition of "advanced".  And strictly speaking, humans haven't reached either Mars or Pluto, machines have :-)

@John:  Arguably it's not years of evolution, but the number of generations.  So figure a human can reproduce at 16, a dog at 2, then (assuming their last common ancestor also reproduced at 2, and the divergence was smooth), dogs are 4 times as "advanced" as humans.

Actually we try hard to wipe some pests out of one square mile, and usually cannot. When we do, we wipe out a significant part of biodiversity together. Is this to be advanced?

You know you can't say that humans are more advanced than dog cause humans haven't evolved from dogs so on what basis are you saying this? These are two totally different species , I don't think that is the right way to say it .

Related question "If evolution is progress, why fight extinction"

Your argument can be easily broken down by virus. And virus is not even universally considered to be a form of life.

Rolled back edit to block quote. The quoted text is from here, and includes the odd usage.

bacteria  can survive in many place where human can’t. Ex Thermus aquaticus . It can withstand high temperature. And it has high reproductive capability.

There was a similar question like " does it create complexity" and there werent any answers. So i argued that complexity or is a side effect of survival fitness, which is enhanced by increasing numbers of attributes to cope with increasing and multifaceted geographies and an increasingly biodiverse and fit competition environment.

I'm glad you've asked the question as it is a common layman misunderstanding.
Dog vs Human
Your example comparing humans and dogs is actually very central to the logical flaw that yields many to equate evolution with progress.
There are several issues when you say

humans do seem to be more advanced than dogs

Humans are not more evolved than dogs

Humans, dogs, jellyfish, oak tree, fungi, bacteria, .... we have all evolved during about 3.5 billion years. None of the extant lineages is more evolved than any other at least in terms of the number of years of evolution. Note, however, that what matters most when considering evolutionary time is the number of generations. Humans having a rather long generation time, it tends to make fewer generations. In this regard, one could expect a dog to have been through more generations than humans and could eventually be called more evolved but even there it is not that easy. See also Are we “more evolved” than present-day bacteria?

You are a human, be aware of your biases

As @Jamesqf rightly said in the comments, you did not feel like considering the dog's extraordinary sense of smell, better hearing, higher jumps, stronger jaws or protective fur. Not to mention, dogs can typically raise way more offsprings than humans can. Not to become personal but my 8 months old, 9 kg Cocker Spaniel runs 300 meters at the same time Usain Bolt runs 200 meters! You seem to have only considered things that make you human such as opposable thumbs and high cognitive abilities. Coming to cognitive abilities you will note that a puppy learns by association faster than a baby human. Dogs just plateau much quicker than humans.
Make sure that you understand that high cognitive abilities are not a goal or a direction of evolution. While it is hard to measure the evolution of intelligence for both a question of definition and question of measurement tools, it is very very likely that many lineages (incl. eventually the Homo lineage) have evolved toward reducing intelligence at some point (see this post).
You say humans could wipe out dogs from Earth however again it feels very human (and awkwardly combative and hostile) to consider the ability to kill as a measure of progress.

The illusion of considering two variables

You consider a correlation between two variables 1) how evolved a lineage is and 2) how advanced a lineage is. (As discussed in the first point, there is actually no variance in how evolved lineages are if we consider evolutionary time). You are determining those that are more evolved by how "advanced" you visualize the lineage. Your explanatory and response variables are therefore the same and you do not explain anything by saying 'humans are both more advanced and more evolved than dogs so evolution should equate progress'

Definition of progress
A big issue in your question is the definition of progress. For example, if you define progress as an increase of mean fitness (the concept of fitness in biology has nothing to do with bodybuilding, see here) over time, then yes evolution is in part to be equated with progress as increase in mean fitness over time is exactly what natural selection is doing (see the so-called Fundamental Theorem of Natural Selection).
Evolution ≠ Natural Selection
So, let's assume we define progress as an increase in mean fitness over time. As stated in the previous section, this is exactly what natural selection is doing. So, instead of saying Evolution should not be equated with progress, one could say Natural selection is to be equated with progress (as a reminder this assumes a very specific definition of progress)
You will note that I replace the term evolution with natural selection. It is often unclear to laymen but these two terms, while related, are different.
Evolution is a change of allele (loosely speaking, an allele is a variant of a gene) frequency over time. There are a number of mechanisms that can cause evolution, one of which is natural selection (which itself is caused by a fitness differential associated with genetic variance). But there is way more to evolution than just natural selection. Genetic drift, mutations, migration and other demographic elements are all important factors causing the evolution of populations.
You should have a look at Understanding Evolution by UC Berkeley. It is a very introductory online course on evolutionary biology that will teach you about the basic forces that cause evolution.

Well said, though I'd argue one point.  Evolutionary time should not be measured in years, but in generations.  Which means that bacteria, which can produce a new generation every few hours, are far more evolutionarily advanced than us primitive chordates ;-)

It would be misleading also to consider number of generations as the quantity of evolution but I agree with your point. I try not to get into complications but I edited my post. Feel free to edit it yourself if you would think of a better way of phrasing it. Thanks.

I always thought that what you propose here as other elements are categorically different and are not the alternative to natural selection. Without mutations or migration or etc. there would not be selection, as there would not be change. And selection then would work like a filter of that change, not the component of change itself.

I always enjoy and appreciate your answers. This is another good one. I do wonder, though, about equating natural selection with progress. You define it specifically, which helps, but over time, as well as the very word progress suggests an ongoing march over many generations in a constant environment. I wouldn't expect Darwin's finches to be any more fit now than they were in 1836, or in 1831, for that matter. Environments change. Sometimes selective pressures favor large beaks, other times small.  You're more knowledgable here, but I wondered what your thoughts were.

There are two issues here; defining "progress" and equating evolution with it. I'll take the second one first.
When we "equate evolution with progress" we are typically making specific claims (sometimes without thinking about it). We mean that progress is an important priority of evolution or even its goal. We mean that evolution always leads to progress. And when we say "don't equate evolution with progress" we're saying that neither of those things is implied in the Theory of Evolution, and in fact, there isn't much evidence for either.
Humans are more advanced than dogs (again, skipping the question of defining "progress" for now), but humans and dogs aren't the only organisms around. E.coli is as much the outcome of 4 billion years of evolution as we are, yet we didn't "progress" in the same way at all.
One way of looking at it is thinking of diffusion. When I release a dot of dye into the water, it expands outward. Is there a specific force pushing it outward? Are any of the molecules trying to go outward? No, and no; all the molecules are moving randomly, and it is statistics that make it so their overall movement is outward; there simply is more space to move outside of the dot than inside.
And if I put that dye on the right edge of a water container, it would expand leftward. Again, is there a leftward force? Do all the molecules want to go left? No, and no: all the molecules are moving randomly, they just can't go further right than they already are, so for a molecule by the edge any random movement right keeps them where they are and any random movement left takes them left. And the overall average of the molecule's positions will move leftward, even though no specific molecule has a leftward bent (if they did we might expect molecules to disappear from the right edge, and in a diffusion situation they don't). Moreover, if we took the leftmost molecule at a certain point and looked at its trajectory over time, it would sure look like it's deliberately moving leftward... But that deliberateness would be an illusion; out of trillions of molecules moving randomly the odds are good that one of them would have made only or mostly leftward movements, and obviously that's the kind of molecule that would end up being leftmost in the first place. That doesn't mean it is being pushed left, or that its next movement will be leftward.
So applied to evolution, for almost all measures of "progress" we can come up with - size, intelligence, behavioral complexity, structural complexity, whatever - if evolution was pushing any lineage randomly along those variables we would still expect the maximum and even average size/intelligence/complexity to increase over time, because it would be very hard for life to become smaller, dumber or simpler than E.coli (harder but not impossible ! And we see examples of such trajectories, in parasites especially).
Now, you will tell me, evolution isn't random! Through natural selection, it leads to adaptation. True; it leads to adaptation to the environment. Change the environment, you change the direction that evolution will "push" a given lineage. And in the case of things like complexity or intelligence (the usual markers for "progress" in evolution), those traits can be adaptive or not depending on the environment; complexity allows more variety in responding to the environment, intelligence allows more productive interactions with said environment, but both have a cost, in risks of errors, in energy consumption, and so on. And so while you might say this lineage over this time period (in this environment) shows a definite trend towards complexity or intelligence (or gaining flight, or losing sight...), it is impossible to say the same of Evolution as a whole.
One point of evidence that the increase in maximum "progress level" is the result of diffusion and not a specific progress-ward force, is that as the right side of the container that still contained dye, the biosphere still contains tons of (a majority of in fact!) "un-progressed" organisms. This would not be true if Evolution as a whole were pushing toward progress. (in fact, you might note that I am not quite correct here! In a naturalistic view of abiogenesis, living things (or not-technically-living ancestors to living things) must have existed that were themselves outcomes of evolution but were incredibly simple compared to today's amazing bacteria, and those could be thought to be the lower bound in complexity, and Evolution did move life as a whole away from it! So we could argue that Evolution does move towards a minimal level of "progress" (the amount sufficient to compete against a bacterium). It's just that we reached that level over 3 billion years ago).
And to get back to the first point about defining "progress", once you dig down into what that means it can become all the clearer that evolution doesn't push one way or another. Bacteria have more metabolic diversity than Eukaryotes could hope for. Humans are more intelligent than dogs but worse at smelling. It can be argued that from a Müller's Ratchet perspective, "complexity" in Eukaryotes is pretty much constant, and any progress in one domain is the result of tradeoffs in another domain. This doesn't mean humans aren't more "advanced" than dogs, but it does demonstrate you need to be more specific about what "advanced" means for that to be true.

It is also worth mentioning one result from the long term E. Coli experiment, sample are periodically taken and frozen, and when older samples are pitted against newer ones, sometimes the older ones outcompete the younger ones. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5788700/

When you say, humans are more advanced than dogs, from what perspective are you saying that from? Is it in the capacity to use intelligence, to build and create, to do the math, to climb trees? If it is any of these, you are right: humans are better at using intelligence to build and create, at doing the math and at climbing trees than dogs do. However, from the perspective of, say, hunting down a rabbit or detecting by smell some chemical component at very low concentrations in a suitcase, dogs are indubitably better.
So which is actually more advanced? The answer is none, they are just differently adapted to be better at some things - the things they needed to be better at to survive, and which evolution created and preserved. So evolution here simply means the constant modification of living organisms and the perseverance of those who become better adapted to the conditions they live in - this means that a bacteria today is as evolved as a human being, his dog or the tree that dog is peeing on. Now when we talk about progress, we're talking about something which function or capacity improves over a continuum. Evolution does make progress sometimes, such as the progression from initial photoreceptors to the organs of vision we have today (called eyes), and the increasing capacity of some bacteria strains to resist antibiotics - both are signs of progress, and both are made possible through the process of evolution.
At a larger level, we see that life, though evolution, has been progressively more able to create more and more complex organisms (complexity here meaning the amount of information necessary to describe the organism), through the principle of "complexity allows for the creation of more complexity". Today, there are indubitably more complex organisms that there was in the beginnings of life, and yes, we can say humans are one of the most (if not the most, because of brain complexity) complex beings alive, and also complex things in the universe. So we can say that evolution is a process which made possible the progress towards more and more complex things.
What I hope to have helped understand is that evolution and progress are correlated and interdependent, but not the same thing. Evolution is a process which allows for progress, but not always and not necessarily.
I am not including any sources or background because this question relates more to etymology and meaning than scientific research.
EDIT: interesting things you may like to watch about the progress and evolution of complexity:
https://www.youtube.com/watch?v=MTFY0H4EZx4
https://school.bighistoryproject.com/bhplive
https://www.ted.com/talks/david_christian_big_history

Okay so Ill answer the questions you asked me at the beggining of the answer.

1.For hunting a rabbit, humans are undoubtedly better, we have sophisticated equipment for that.

Moreover for smelling etc, we simply use the dogs for our own use. We can control dogs and use them for our work, but  dogs simply cant control us.

@Prashant Gokhale: Really?  You obviously haven't met my dogs, have you?  You might think about who goes out to work all day, and who gets to lounge around the house :-)

@jamesqf and we're not even talking about cats yet! :p

Indeed evolution cannot be equated with progress, but that book's reasoning is misstated.
The reason it cannot be equated is because of many distinctions between these 2 concepts, regardless of the fact that in many cases evolution is a vehicle or mechanism by which progress happens, by popular definitions of what we call progress at a given time. If survival and adaptation of a species in question, is what we would consider progress in whatever context, then evolution fuels that progress, and can reasonably be said to itself be progress in that context.
Now let's say that you consider a finely balanced Ecosystem, and some species quickly evolves to better hunt another species, then from a short term perspective of the subject species, evolution is progress, but knowing that this will cause a population explosion and shortly after, mass starvation, it is clear that this was not progress, even for the hunter species -- however, it still cannot be said that evolution did not occur, so clearly evolution does not equate with progress on sematic or functional levels (the latter simply because there can be shown many situations where that is clearly not the case).
Fun aside: Also consider that evolution cannot go backwards to pick another foregone path. But in some cases that would be required for progress being considered, like the perfection of human eyeballs, which are greatly evolved, but would/could have been much better if we didn't come from the water

Evolutionary biology cannot answer a question about "progress".  Opinions are strong.  For a good discussion see https://academic.oup.com/bioscience/article/50/5/451/264248 and note comment by Stephen Jay Gould, “Progress is a noxious, culturally embedded, untestable, nonoperational, intractable idea that must be replaced if we wish to understand the patterns of history” (Gould 1988, p. 319) and William Provine “the problem is that there is no ultimate basis in the evolutionary process from which to judge true progress” (Provine 1988, p. 63).
I believe this is because its mathematical formulation only looks backward.  It presumes a parameter "fitness" which has a value in a particular environment, especially in what that environment WAS not what it IS or WILL BE.  (For a clear treatment, not the usual overbearing textbook, see Gillespie, Population Genetics - A Concise Guide, 1998 https://public.wsu.edu/~gomulki/mathgen/materials/gillespie_book.pdf )
That does not mean the question cannot be answered.  But it requires a convincing definition of progress.  There already is one in common use among futurists.  And it leads to a convincing answer.  However, there is disagreement as to whether humans are on the path to an answer.
To obtain a definition of progress, only note which forms are most likely to remain viable in future environments.
This requires forecasting of future environments, a difficulty I will pass over.  While non-trivial, it is an entirely separate question.
Looking far enough into the future, it is extremely easy to forecast that Earth (and the sun and moon and rest of it) will eventually meet some end and not even be available as an environment.  It could be as simple as a focused gamma ray burst https://jatan.space/timeline-for-life-until-the-end-of-the-universe/ .  The only viable forms will be those which have left.
There is a famous puzzle, named after Enrico Fermi though he didn't formulate the puzzle exactly.  He just asked, "Where are all the Aliens?"
Putting aside those who claim they are among us and we don't know it, and looking only at physical evidence, while some might keep themselves secret we can't think of a reason why they all would.  We appear to be alone in the universe.  There appear to be some barriers that prevent life from leaving its home planet.  And I'm not talking about the long time travels required, etc.  Those are not actually insurmountable.  I worked for NASA for 45 years and studied this question often.  Difficult is not insurmountable.  Pass over that argument, it is a sidetrack.
None of the solutions to the so-called Fermi Paradox are the least bit impressive.  Not only to me, I never met anyone who was really impressed with any of them.  They pick favorites, but everyone is puzzled.  It is not obvious humans are capable of solving this problem.  For the most concise (not too long, but still comprehensive, and very colorful) see the animated video short https://www.youtube.com/watch?v=sNhhvQGsMEc&t=6s , or look up the original paper by Michael Hart, 1975, "Explanation for the Absence of Extraterrestrials on Earth."
If in the future humans become "advanced" enough to understand the problem and work out what its realistic features are, then we might be able to say if humans can solve it, or if dogs can solve it.  So there is potential to define objective progress in evolution.
It might require the evolution of life around red dwarfs to solve the problem.  Such life might have a concept of much longer time intervals, for example, or be much more cooperative.  We just don't know how such imponderable variables would affect evolution.  The issues with life around Red Dwarfs is discussed here https://www.space.com/14659-red-dwarf-stars-planets-habitable-zones.html and note that the timeline given earlier https://jatan.space/timeline-for-life-until-the-end-of-the-universe/ suggests that in 1 trillion years Red Dwarfs will be all that is left.  Thus the future environment has already been predicted with high confidence.
The ancestors of dogs evolved in surprising ways, achieving brains that rival our own.  I'm thinking of the whales and dolphins, that presumably evolved from some predator hunting in shallow lagoons and gradually returning to the sea.  https://evolution.berkeley.edu/evolibrary/article/evograms_03
In their present form they are unsuitable for spaceships.  Suppose over a billion years the sea dried up, and they gradually adapted, developed an urgent need to free themselves from dependence on one single planet that could be so rude as to lose its oceans, and developed an instinctive collective urge to find other planets, instilling cooperation far beyond the human level.  Then dogs might win.
I personally believe the Achilles heel of the Fermi dilemma is cooperation.  Much touted human cooperation is not what it appears.  More intelligent people cooperate less.  If you explain game theory to people they cooperate less (Nash Equilibrium and all that).  A global society might not be a highly cooperative one.  Interstellar travel might require global cooperation.  Forcing everyone to take just one approach to any given problem might be the ruin of any civilization.  It is certainly not the way of evolution.
But not knowing who is going to solve the Fermi Paradox, if any species ever, does not detract from its value in defining progress in an extremely objective manner.
And if you get past that, there is the end of what we call the universe.  Cosmologists, at least some of them, now think it is not really the end.  See Dyson et. al. Disturbing Implications of a Cosmological Constant https://arxiv.org/abs/hep-th/0208013 .
But there might be ten to the 100th years of not very interesting non-entropic processes until there is a repeat, or approximate repeat, of the initial conditions, a Poincare Recurrence as Poincare proved a theorem that this would eventually happen over a hundred years ago.  Who will survive that?  We can't say it's impossible.  We know next to nothing about non-entropic processes.  But it is possible to define progress even then.

Welcome to Biology.SE! It isn't clear that this adds anything to the existing answers or that it answers the OPs question. In addition, answers are much more likely to receive a favorable response if you include supporting references (primary literature is best). Without that support, your post is indistinguishable from opinion. ——— Please take the [tour] and then consult the help pages for additional advice on [Answer] effectively on this site and then either [edit] or delete your answer accordingly. Thanks!

I added references as you requested.  But the site would not let me add more than 8 links.  This is a really crummy site (first time I've tried to post here).  I have authored over 50 peer reviewed papers in half a dozen fields.  Including links for all references is par for the course.  Clean up your act.

Welcome. Because you are new here, certain restrictions apply, including, apparently, the number of links you can add. Further, I cannot  really see how this answers the question either?

@RobertShuler — If you have constructive suggestions about the site, please feel free to start a discussion about them on [meta]. I'm not sure why you're telling me to "clean up my act". Note that I'm just another user and I am trying to help brand new users such as yourself become productive members of this community ...

There is no real progress behind the idea of evolution.
Evolution is simply the generation of diversity and shaping of diversity by environmental selection.
The only progressive trend in evolution seems to be that more and more complex body designs has emerged over time. It doesn't means that the older designs are inefficient.
However, one of the simplest form of life (Bacteria) can even survive in harsh conditions such as hot springs or ice of Antarctica.
Therefore, Human beings aren't the pinnacle of evolution, but simply yet another species in teeming spectrum of evolving life.

SOURCE: NCERT Class 10 science textbook

priyanshu, I've downvoted your answer because it is a late answer that doesn't add to the information already present in other answers. We welcome contributions from new users, though.  You might try some unanswered questions. It's best if you avoid posting answers to a previously answered question unless your answer adds something to the post.


text:
Do we consume DNA and proteins of other organisms?
When we eat raw meat, e.g. chicken or fish, we are actually consuming the DNA, proteins etc. which are present in their cells.

Wouldn't this affect our cell functions as this DNA might enter our cells?
It is known that we get energy by eating them. Is it glucose or ATP or some other form of energy that is produced from them?

Or, to rephrase the question, why don't people who eat lots of sushi develop gills?

No, unless what we ate had the ability to infect our cells (viruses and some bacteria) 2. Proteins, complex carbohydrates, simple sugars, lipids, vitamins, ions...

We likely have the genes for making gills, however we do not express then in such a way during development as to have them form into functional gills. You won't develop new and novel organs after development and birth,.

While this is an obviously poorly phrased and researched question, it doesn't seem to be bad enough to warrant so many downvotes.

Yes, we are eating the DNA and proteins of an organism when we consume and digest its cells.
However, consuming the "raw flesh of hen or fish" in your example would not cause harm strictly due to the consumption of their DNA.
DNA has two basic components - a structural 'backbone' of alternating phosphate molecules and sugar molecules (called deoxyribose) and a nitrogenous base (a group of atoms that includes nitrogen) on each backbone unit. These basic components of DNA are common to the all organisms that contain DNA, like the hen and fish in your example.
When you digest the DNA in your food, specialized molecules (in this case nuclease, which digests DNA) produced by your digestive system break down DNA into its components. These components can then be rearranged to create 'human' molecules, such as human DNA.
In other words, you don't integrate fish or hen DNA directly into your human DNA; you break it down and rearrange it into human DNA, then integrate it into your body.
To answer your second question, we get energy by breaking down the proteins, carbohydrates, and fats (known as macromolecules) of other organisms. Much like DNA, these three macromolecules are broken down into their singular components. For carbohydrates, this would be glucose.
These components are then further broken down into energy (as a force) which powers cellular machinery to 'recharge' ADP (the 'discharged' version of ATP) back into ATP, a specialized molecule which can 'bring energy' to other parts of the body to power your body's processes.
ATP is not energy per se - energy is defined as the "capacity to cause change" (Campbell Biology, pg. 160) and do work. Energy is therefore a property rather than a distinct molecule.
Summary:

When we consume DNA of organisms, it does not inherently damage us as we break it down and rearrange it into completely 'humanized' molecules.
Glucose and ATP aren't energy per se - they are just molecules that contain lots of energy. ATP 'brings energy' to other parts of the body; glucose is broken down into energy to 'recharge' ATP. Energy is not a molecule - it is a property.

The second part of your question has been answered already, but you were right about your first point. I believe the previous answers are not completely correct concerning the total break down of nucleotide sequences.
It has been shown that RNA from ingested food (specifically rice miRNA) actually does enter mammalian cells and tissues and can influence gene expression [1].
A number of exogenous miRNAs from common foods where observed in Human blood plasma in this study [2].
I believe we still have to learn a lot about this kind of interaction with our food. It might be that miRNA is not the only component of our food that can survive digestion and influence human cells directly.

Nice find on miRNA!  From the two papers I think it's a bit early to hypothesize the same could be true for proteins or DNA though.

The lay summary of a newer paper says: "Experiments using mouse models show that the dietary uptake of microRNAs is barely significant, and certainly insufficient to affect physiological functions. Moreover, the microRNA molecules are broken down in the small intestine."

Please see also the even-newer paper, "Survey of 800 datasets from human tissue and body fluid reveals XenomiRs are likely artifacts", or its lay summary.

And some even newer papers: Chen et al 2021, PlosOne "Large-scale identification of extracellular plant miRNAs in mammals implicates their dietary intake", Li et al 2021 "A Timely Review of Cross-Kingdom Regulation of Plant-Derived MicroRNAs", Zhao et al 2018, PlosOne "Evidence for plant-derived xenomiRs based on a large-scale analysis of public small RNA sequencing data from human samples"

To add to adam's answer:
Protein and DNA molecules are simply too big to pass through cell membranes or through the wall of the gut.
In the process of digestion:
Proteins are broken down into amino acids.
Complex carbohydrates like starch are broken down into sugars.
Fats are broken down into fatty acids and glycerol.
These molecules are small enough to pass through the wall of the gut. These are essential food. Once through the wall of the gut, the body synthesizes "human" proteins, carbohydrates and fats from them.
DNA and RNA are broken down into nucleotides, which are small enough to pass through the wall of the gut. The mass of DNA is tiny compared to the mass of the above types of food. As far as I know nucleotides are not essential nutrients (that is to say, I believe our bodies can synthesize them from the above types of food.)
Incidentally one of the nucleotides of RNA, adenosine monophosphate (AMP) is the "discharged" form of ATP. According to https://en.wikipedia.org/wiki/Nucleotide all four of the nucleotides of RNA are used in monophosphate - triphosphate energy cycles, but the others are more specific.
It's important to remember that proteins, fats, sugars (and ATP) are not "energy" but simply molecules that are high in energy.
I would guess that there is far more of these RNA nucleotides free in the cell (involved in energetic pathways) than there is in the actual RNA used for protein transcription. And there is definitely more RNA than DNA.

"Protein and DNA molecules are simply too big to pass through cell membranes or through the wall of the gut." How about Prions? Kuru is the result of ingesting human tissue that carried the misfolded protein. Bovine Spongiform Encephalitis was transferred by eating affected cows. Our phagocytic cells are constantly taking in nucleic acids and processing them....

@AMR I was speaking in generalisations. Prions obviously do get through in small quantities (whether by passing through the gut membrane or through an open wound directly to the blood) but once through they are able to multiply. Calling me out on this is similar to calling someone out for the statement "sperm are too large to pass through condoms." The exceptions are rare, but the consequences are great.

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text:
What is the closest species to humans in animal kingdom?
I presumed chimpanzees were the closest relatives of us. However, after watching this TED Talk, it seems bonobos are closer to us both in skeleton and behavioral similarity than chimpanzees. I once read in The Magic of Reality that we share quite a lot of common FOXP2 gene letters with chimpanzees, but there isn't any mention on similarity between us and bonobos in that book. Here is the excerpt:

You can tell that FoxP2 is the same gene in all mammals because the
  great majority of the code letters are the same, and that is true of
  the whole length of the gene, not just this stretch of 80 letters. Of
  the total of 2,076 letters in FoxP2, the chimpanzee has 9 letters
  different from ours, while the mouse has 139 letters different.   And
  that pattern holds for other genes too. That explains why chimpanzees
  are very like us, while mice are less so. Chimpanzees are our close
  cousins, mice are our more distant cousins. 'Distant cousins' means
  that the most recent ancestor we share with them lived a long time
  ago.
Monkeys are closer to us than mice but further from us than
  chimpanzees.   Baboons and rhesus macaques are both monkeys, close
  cousins of each other, and with almost identical FoxP2 genes. They are
  exactly as distant from chimps as they are from us; and the number of
  DNA letters in FoxP2 that separate baboons from chimps is almost
  exactly the same (24) as the number of letters that separate baboons
  from us (23).

So which species is closest to us, chimpanzees or bonobos?

Others have given great answers, so I'll just support their answers with this diagram and a little further background on how to think about relatedness in evolutionary context.

Since the author in this excerpt makes no mention of Bonobos, I would imagine that, by chimpanzee, he really meant the genus Pan, which includes both Bonobos and Common Chimps. But that does not necessarily matter.
Relatedness, in modern taxonomy, depends purely on common ancestry, not necessarily on similarity of specific traits. As others have explained, we make theories about ancestry relationships based on many criteria and logic, not just variation in one gene. In this tree, you should think of A, B, and C as theoretical, extinct common ancestors of the species below them in the tree. The list of apes at the bottom represent the relevant extant species species only. Bonobos and Common Chimps have a more recent common ancestor (C) than either Bonobos and Humans (B) or Common Chimps and Humans (B). This is why @mgkrebs said that both qualify equally as most closely related, because the common ancestor of each pair is the same.
Few would disagree that Bonobos do seem to be more similar to humans than Chimps are to humans, but that actually does not mean they are more closely related evolutionarily! Theoretically there are two ways this could happen even if Bonobos and Chimps are equally related to humans, either our common ancestor with Chimps and Bonobos also shared the traits we have in common with Bonobos and Chimps changed, or Bonobos and Humans happened to develop these similarities independently. The former is a simpler explanation, but either are possible for each similarity. Again, the key in understanding this is in thinking about the theoretical ancestor species, B and C. The only way Humans could be more closely related to Bonobos than chimps is if the common ancestor, B, was a descendant of C, which seems extremely unlikely and as far as I know is not supported by the genetic research in this area.
Our common ancestor with Gorillas (A) on the other hand is much "earlier" than our common ancestor with Chimps and Bonobos, so Gorillas are less closely related to use than the group containing Bonobos and Chimps.

Chimpanzees and bonobos are equally close to us in time (which is the opportunity for evolutionary divergence).  Our most recent common ancestor with either species is the same, as our line split from their common line about 6 million years ago (estimates are generally in the 4-8 mya range).
The split between the common chimp and the bonobo is much more recent, probably less than one million years ago.
So in terms of general closeness to us, these two species qualify equally.  For any particular gene, either one might be closer, as our version may be unchanged from our common ancestor, while one of the two Pan (chimp) species may be the same and one different.  For most genes that have differences, we can expect that we are the odd man out, while the two Pan species share a common gene.

Looking at one gene is not enough. Since each gene is free to evolve (or not), there can be different sister taxon relationships depending on the gene studied. A better estimate is made using several genes or combining the results of several analyses.
According to Purvis (1995), the extant sister taxon of Homo sapiens is a clade with the bonobo (Pan paniscus) and chimpanzee (Pan troglodytes), with gorillas as an outgroup.
So the answer is that neither is closer.
Purvis, A. 1995. A Composite Estimate of Primate Phylogeny. Philosophical Transactions: Biological Sciences 348: 405-421.

I'm don't have enough experience with this particular area to know whether experts have come to a consensus about this (although both your question and a brief literature search suggests they have not). What I do know is that when you begin looking at these types of questions at this level of detail, the answer that you get will depend on the characters used and the modeling strategy. The fact that you may arrive at a different conclusion when looking at a small number of morphological (skeletal) and behavioral characters versus genetic characters (sequence homology of a particular family of genes) is not surprising. Even when using the same characters, different methods (maximum parsimony vs maximum likelihood vs Bayesian) may give you different results.
So the answer is probably "we don't know for sure" (I'd be happy to be proven wrong here). But either way, the different conclusions you cite are not necessarily contradictory. Any conclusion will simply have to be justified in terms of the assumptions made, the data (characters) involved, and the method used.

please don't guess ans an answer.

As someone has mentioned in this question, the closest species not directly linked to the Homo genus are the chimpanzees and the bonobos. Around 6 million years ago, humans diverged from both chimps and bonobos, making them (as far as we know now) both humanity's last common ancestor. The last common ancestor directly connected to the homo genus, however, is Australopithecus for approximately 3-4 million years ago, as shown by the Little Foot skeletal system in South Africa .

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text:
How can I preserve hair or saliva for future genome sequencing?
Suppose I want to preserve myself so that I can be reproduced as best as possible, in future or be simulated in future. At the moment full human genome sequencing is a bit expensive.
One could get some of my hair or saliva, but what can I do with it to best preserve it?
Would it need to be put in a freezer?
How long would the DNA of the hair or saliva be preserved for in a regular kitchen freezer?
How long would the DNA be preserved if the hair or saliva was not in a freezer?
Are there any issues of contamination?
Also, once the full genome sequencing has been done, is that all the info that could be gleaned from it genetically? can the hair/saliva be thrown out, or might it be possible that future human genome sequencing could pull more info from the sample?

Best of the two would be hair, since the saliva contains enzymes that degrade DNA. DNA is fairly stable, and the hairs could be kept at room temperature for future use. The problem with home freezers is that they defrost once in a while to lower the condensing ice that forms around it. These cycles of freeze-thaw are rather bad for everything you would want to keep in a lab. This is why we have non-defrosting freezers in labs.

@WilliamL how long would hair last at room temp? And how long in a non-defrosting freezer?

@barlop they've sequenced DNA from hair hundreds of years old.

As @MattDMo said, DNA from hair can last for very long in ambient conditions. Let's just say it could last for very very ... very long in a non-defrosting freezer. It just seems overkill much. Put your hair in a plastic bag (ziplock style) and put them in a binder/scrapbook (it will get creepy if you start a collection of those...).

Your biological information and your experiences are two entirely different things. You could make a cell for cell, protein for protein, base pair for base pair replica of yourself and that organism would be different as it will experience things differently than you have. Even identical twins are individuals. You can fool yourself into thinking that clone will be you, but they won't be, no more than a child will be you. They will carry more of your genetic code than a child or grandchild, but nurture plays a role in the person you develop into. Embrace your mortality, enjoy the ride.

Your old baby teeth might be a better-preserved source of DNA.

Full genome sequencing is only one of many experimental approaches. It's important in the field of genomics and useful in transcriptomics and proteomics.
It's best to extract DNA as soon as the sample has been removed from the living organism since all kinds of physiological processes start breaking down DNA in dead tissue. Kitchen refrigerators are not ideal for storing extracted DNA because they operate at about four degrees celsius. In the lab, minus eighty degree freezers are used. The lower the temperature, the better. Minus eighty degrees, however, is good enough.
Contamination is a big problem, so the more technical repeats you run, and the more biological repeats you have, the better your chances of getting reliable results. Biological repeats refer to, for example, taking three strands of your hair for analysis, while technical repeats refer to, for example, carrying out three PCR experiments on material from the same strand of hair. Once you've used tissue to extract DNA you don't keep remaining tissue because it gets contaminated during experimental preparation. That is why you may want to have biological repeats. It's also important to take precaution when removing the sample from the organism. This means wearing latex gloves and even using dilute ethanol to sterilize the sample before placing it in a sterile container. The problem is that ethanol can interfere with DNA extraction and be a contaminant itself. Balancing contamination prevention with quality results is important in the lab.
There are additional biological information such as DNA methylation events that occur intermittently on a genome and are inheritable. This information cannot be predicted from the sequence composition of your genome, but there are experiments meant for elucidating methylation patterns that can be carried out using uncontaminated biological samples (such as hair and saliva) stored in eppendorf tubes at minus eighty degrees celsius.

"Kitchen freezers are not ideal for storing extracted DNA because they operate at about four degrees celsius." That would be a kitchen refrigerator, as that is 4° above the freezing point for water. A kitchen freezer operates at -20°C. The issue with most consumer freezer's are that they have an automatic defrost cycle, so the temperature is not maintained constantly at -20°C, which can cause sample or reagent degradation.

@AMR - Now that is interesting...

@AliceD What? You think I am only a Biology hack? I know my way around household appliances! ;-)

@AliceD, also, I am pretty sure that -20°C is a holdover from 0°F, which is ~-18°C... so as you metric wonks like your base 10 numbers, you went with -20°C, because what is -2°C amongst friends....

@AMR - Now I'm curious - what is -2°C amongst friends? Did the F system precede °C?

@AliceD sorry, idiomatic usage. What is x, amongst friends, is an idiom for a trivial detail that can be ignored, though it can also be used as irony as well... but I will save you from that explanation. Fahrenheit was proposed in 1724, Celsius in the mid 1740s, and Kelvin in 1848, so Fahrenheit was first. But refrigerators were mainly developed in the US, and as we hold onto the Fahrenheit scale.... Interestingly, 0°F is the temperature of brine made of equal parts ice and salt (that is where the zero point baseline was defined). https://en.wikipedia.org/wiki/Fahrenheit

@AliceD it's more realistic to store your samples at minus 80 degrees celsius

If I had a substantial hair sample from my own head as a small child kept in a scrapbook made in the 1970's, sealed behind plastic, would this still contain my DNA? When I Googled it said hair DNA can remain up to 10,000 years but not sure if that's true.

In addition to -20 freezer, keeping your sample in 100% ethanol will help preserve your sample.
Cold temperatures help, because the bases (ATGC) in DNA can be damaged (deaminated) and even knocked out (depurinated) leaving abasic sites (and once that is lost no information can be recovered) and the DNA strand can be broken up into shorter and shorter pieces.
How long will a DNA sample survive in -20 freezer without other protection? Years. Decades if you are lucky. But it will probably be years.
How long will DNA in sample survive not in a freezer? Depends on ambient temperature, humidity and  and microbe activity. Anywhere from days to years,
Contamination is a huge huge problem. A saliva sample is going to be very very contaminated and is going to degrade fast. A hair sample would be okay. But there is a certain trick to pulling hair to getting the follicular cells. A biopsy, some nice human tissue is even better.
DNA extraction from the sample is destructive process. Once the extraction process is done, the sample is gone.

As a general rule, you'd want to keep the sample as cold and dry as possible. If a sample is wet, heat/thaw cycles can damage tissue integrity due to ice crystal formation.
In the future, a small hair sample would probably only be able to recreate a small part of who you were, because it excludes epigenetic factors (methylation can be different in different parts of the body) and the entire microbiome.


text:
is a musk deer's musk pod in its abdomen, its back, or its bottom/rear end?
I have read/heard different things about where a musk deer stores its perfume
Some links say it stores it in its abdomen just in front of its penis.  Others say the rectum(by which I suppose they mean the backside).
A) https://en.wikipedia.org/wiki/Deer_musk  "Deer musk is a substance with a persistent odor, obtained from a gland of the male musk deer situated in its back/rectal area. The substance has been extensively used as a perfume fixative, incense material, and medicine, since ancient times."
B) https://www.youtube.com/watch?v=r6CZKuSjlhI   7:40  "the fangs, but it's the other end of the deer that attracts more attention - the male's musk gland produces a scent that's irresistible to .. and perfume makers"
C) http://sandwalk.blogspot.co.uk/2009/10/are-you-sexually-attracted-to-male-musk.html   Only the mature male Moschus produces musk. The substance occurs in only one location on the deer's body: on its abdomen, just in front of its penis, is a hairy pouch known as the musk gland. This sac is about the size of a golf ball. It is composed of several layers of skin, with two openings immediately above the animal's urethra.
Quite a few links agree with 'C', that it's in the abdomen near the penis. Are wikipedia and national geographic wrong for putting the musk pod in the backside?

Here's another description of the musk sac. It mentions a musk sac that is "situated between the umbilicus and penis", as well as a caudal gland.

@AndersonGreen  I guess umbilicus is belly button. And since between the umbilicus and penis is the abdomen, it sounds like that's in agreement with  'C'  -  abdomen

does this image help? source

@WhatHiFi i guess maybe the answer is the back underside of a deer has its  penis  and scrotum and still near the back but a little bit further towards the front of the penis, is the stomach.  I will see if I can get to a farm and get a picture of the underside of a deer. will be a bit of a project.


text:
Why do mammals rarely have eyespots?
An eyespot is a marking to mimic the eyes. Many examples of eyespots can be found in fish, reptiles (including birds), and insects. Recently Radford 2020 has shown that artificial eyespots can reduce predations in cattle. However, apart from cats (tigers and servals), mammals, especially herbivores, rarely have this trait.
Why does mammals rarely have eyespots?

does this answer your question https://biology.stackexchange.com/questions/35532/why-do-some-bad-traits-evolve-and-good-ones-dont

A lot of mammals do have eyespots. Specifically "mid-guild" predators such as raccoons, coatimundis, ringtails, foxes, raccoon dogs, many opossums, skunks, red pandas, civets, etc. It's thought to be an anti-predator defense, with the eyespots or face mask being places further back on the head. A predator might mistake these eyespots for its actual eyes, and because they're placed further back they create the optical illusion that the animal's head belongs to a much larger animal than it actually does.

This is a photo of the gray four-eyed opossum (Philander opossum). It's called "four-eyed" because of the two eye spots it has just above it's eyes. It's thought that the position of these spots mimics the position of the eyes on a much larger predator, so if a predator like a raccoon or a coyote sees the opossum they'll mistake it for a much larger predator and they'll leave it alone.


text:
Is poison venomous and is venom poisonous?
I know the difference between poison and venom AND poisonous and venomous.
But I just want to know if an ingested venom would do harm to humans and if an injected poison would do harm to humans.
I really think that poison is both poisonous and venomous AND venom is both venomous and poisonous.

This wikipedia link might help you understand the difference. https://en.wikipedia.org/wiki/Venom     Read the first two sentences in particular.

I am fully aware of that. But what I am asking is that if poison is injected/venom is ingested would do harm to a person's health.

Related : http://biology.stackexchange.com/questions/53577/are-there-any-animals-there-are-both-poisonous-and-venomous

They had a tough time with venom on SE English Language and Usage here and here.

I think you are both confused about terminology, and asking a very broad question. An organism that produces venom is venomous. Poison is not venomous, the black mamba is venomous. Venom is not venomous.
According to the Wikipedia article on venom,

Venom is a form of toxin secreted by an animal for the purpose of causing harm to another.

A toxin is a poisonous substance produced by a living organism. The article goes on:

Venom is injected into victims by means of a bite, sting or other sharp body feature, which differentiates it from poison (that is absorbed, consumed or inhaled).

However, a toxin is a poison, and poisons are defined (by wiki) as

substances which cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism. (emphasis mine)

So, the definitions are kind of circular.
From what I understand of your question, you are wondering whether a venom would still be dangerous if it were, for example, ingested rather than injected, as well as whether a poison would still be dangerous if injected rather than ingested (or inhaled, or whatever), and this is where the "Too Broad" category gets applied. There are thousands if not millions of different types of toxins in the world, ranging from full proteins to peptide-based to small organic molecules to completely different structures, such as lipopolysaccharide (LPS, the component of Gram-negative bacteria that causes septic shock). Some may not survive the digestive tract, others might. Some can act through the skin, others can't be absorbed. Inhalation is the next best thing to injection, but probably not for every single one of them, so it's impossible to make broad statements about their efficacy and median lethal dose via different routes of exposure. The exact same thing applies to the "poisons" category - while something that is damaging when absorbed cutaneously, such as methyl mercury, is probably just as damaging directly injected into the bloodstream, it's impossible to say that with certainty about all poisons.

Most venoms contain a lot of enzymes. These enzymes can be split by the proteases in your stomach. So if they don't have any effect before reaching your stomach, they will probably digested like any other protein. Ofc. there are some proteins which resist digestion.
There are poisons which affect only certain cells in the digestive system, so injecting them probably would not have any effect or it can have a completely different effect. E.g. cholera toxin (if we can call it a poison) affect the glucose transport when injected, while it causes diarrhea when it is produced by the bacteria in the infected guts.
There are toxins which have the same effect from both ways. E.g. botulinum toxin can be deadly both injected and ingested. You probably heard of botox injections...
The effect can vary by delivery method as well. Injected can mean subcutan, intravenous, etc... while ingested can mean drinking, swallowing a capsule, which protects it from the proteases in the stomach, and so on... It depends on the dose as well.
I think MattDMo is right, the question is too broad because there are many different poisons and venoms and delivery methods.

To answer this question first we need to look at what is the definition of a venom and poison. This is somewhat difficult because the definition has changed slightly over the years, but looking over them we can learn of the similarities between the two.
"A venom is typically a mixture of compounds containing one or more toxins, which is produced in venom glands and injected into animal tissues via specialized morphological structures." This meaning that a venom is made and is injected into another organism (both plants and animals can do this).
"A poison is one or more compounds that are toxic. These toxins can be inhaled, absorbed, ingested, or injected. Plants and animals can produced organic poisons; however, poisons can also come directly from the environment." Example: Chlorine or Fluorine gas.
This is where it's tricky with the definitions. A venom can only be injected to be harmful, whereas a poison can be as well; however, a poison has a broader area of effect. Some snakes have venom that can be absorbed or toxins in their flesh making them poisonous to eat. So the issues are first what happened, was it injected or not, next could it have not been injected and still caused harm.
The best logical answer is that all venoms are poisons, but not all poisons are venoms. This is because both can be injected and cause harm, but venoms have to be injected when poisons don't. Like with the above, some snakes have toxins that are commonly injected so they are still called venoms even when they can be absorbed making them poisons by definition.
To conclude, it's a complicated issue that people are still trying to figure out. In the end the main difference between the two is that a venom needs to be injected, when a poison can but doesn't have to be.

Welcome to Biology.SE! Your answer sounds reasonable (although it isn't clear to me what it adds anything to the existing answers), however, it is likely to receive a more favorable response if you include supporting references (primary literature is best, but a textbook available online would seem sufficient for this question). In particular, the quotes you make must have references to the original sources. ——— Please also take the [tour] and then consult the help pages for additional advice on [Answer] effectively on this site and then edit your answer accordingly. Thanks!

Some substances can be both venom and/or poison.  According to Wikipedia, the source of all knowledge in this internet age, Blue Ring octopi are dangerous to humans if provoked because their venom contains the powerful neurotoxin tetrodotoxin.  According to the same reliable source, Pufferfish are dangerous to humans if eaten because their flesh contains the powerful neurotoxin tetrodotoxin*.
*Summations, not quotes.

Welcome to Biology.SE. The community is looking for more developed answers like the first ones in the list (they include references and citations).


text:
Are all hybrids infertile?
I'm familiar with the concept of hybrid infertility, but my question is: Are ALL hybrids infertile, or is it just so extremely unlikely that the chances are basically nil that they can actually produce a viable sperm/egg?
Thanks.

From today's news, an article about hybridizing between elephants and mastodons: https://gizmodo.com/ancient-elephants-and-mastodons-were-totally-down-with-1823328857#15196834320111&%7B%22sender%22:%22offer-0-WKRZx%22,%22displayMode%22:%22modal%22,%22recipient%22:%22opener%22,%22event%22:%22loaded%22,%22params%22:%7B%22width%22:735,%22height%22:854,%22iframeId%22:%22offer-0-WKRZx%22%7D%7D

Species definition
The whole problem is based upon your definition of hybrid and therefore your definition of species. If a hybrid is the offspring of two individuals belonging to different species and if we define species based on reproductive isolation, then a hybrid can, by definition, not be fertile.
However, we often call two lineages as being two different species even if they can reproduce. To get into more difficulties we could differentiate between pre-zygotic and post-zygotic reproductive isolation assisted reproduction.
You should definitely have a look at the post How could humans have interbred with Neanderthals if we're a different species? for a discussion on the concept of species.
In practice
In practice we often call two lineages as different species even though they are not reproductively isolated. In such cases, yes hybrids are fertile. In fact, hybrid can even have a very high fitness, a phenomenon called heterosis (aka. hybrid vigour). A historically important example is one described by Darwin in The Variation of Animals and Plants under Domestication; the hybrids between the common pheasant and domestic fowl are larger nd more resistant than both parents.
Note also, Haldane's rule that states if in a species hybrid only one sex is inviable or sterile, that sex is more likely to be the heterogametic sex. This is for example the case of the Yakalo (hybrid of yak and bison).
There are also cases where the hybrids are reproductively isolated from both parent species and end up creating a third species. This is called hybrid speciation.


text:
Are there any animal species other than humans & chimps that engage in tribal conflicts?
i.e., between tribes within the specie.
(For chimps, see, e.g., https://news.nationalgeographic.com/2016/01/160130-animals-insects-ants-war-chimpanzees-science.)
Am seeking examples to develop taxonomy of such conflicts, e.g., for resource acquisition, enslavement, etc.

this depends largely on how you define tribal conflict, ants for instance go to war.

Thx — elaborated q to clarify

That does not help clarify. You need to define "tribal conflict" otherwise this is just opinion.

In the introduction of an article by Gavrilets and Fortunato, the authors give (with references) some examples of intra-specific group conflicts:

Social organisms living in stable groups often engage in aggressive interactions with conspecifics from neighbouring groups over territory, mating opportunities and other resources... Examples include border patrols in chimpanzees, raiding parties in spider monkeys, clan wars in hyenas and between-group fights in lions, free-ranging dogs, meerkats, Capuchin monkeys, blue monkeys, black howler monkeys and ring-tail lemurs.

Whether these conflicts (or others, such as ant colony conflicts) meet your definition of "tribal conflicts" you will have to decide.

Thank you -very- much — an excellent article, on point.

Surprisingly, bonobos do. A study from researchers from the Max-Planck Institute for Evolutionary Anthropology back in 2008 and other research found that even though bonobos prefer to solve problems using sex, bonobos fight each other and even other great apes.
The same thing applies to bees. Australia's stingless bees go to war where thousands of worker bees perish and the young from the losing side are dragged out of the nest to die. Slave-making ants raid and attack other ant species. These intertribal conflicts seem to happen in nature due to in-group favoritism that causes certain creatures to favor members of their own phenotype when it comes to companionship and territory defense.


text:
In human anatomy what is the purpose of measuring shoulder abduction and shoulder adduction separately if they cover the same range of motion?
In human anatomy what is the purpose of measuring shoulder abduction and shoulder adduction separately if they cover the same range of motion?
For example, this video
Goniometry Shoulder Abduction & Adduction  uploaded by Kelly Watson
https://www.youtube.com/watch?v=WgTu6HsZZTE
mentions measuring shoulder abduction and adduction but it seems to me like maybe One would be something like 180 minus the other.
In the case of measuring knee extension and knee flexion that situation doesn't exist as extension is 0 degrees(leg straight), and possibly a few degrees if there is hyperextension.  And flexion is around 0(leg straight), to  150 degrees. So degrees of flexion and degrees of extension don't overlap. You can't substitute one for the other.
In the case of hip abduction and adduction, it's also the case that they don't overlap. For example this really clear video
Hip abduction and adduction ROM with a goniometer By MCCCPTAP
https://www.youtube.com/watch?v=CjotehYttpE
Shows where 0 is, and how hip abduction is one way from there and hip adduction is the other way, so there's no overlap. And it's useful to have a measure of each. They aren't interchangeable.
So, the shoulder abduction and shoulder adduction one seems strange to me.. What is the purpose of measuring each, if they overlap. And if they do overlap, then why the inconsistency if comparing shoulder abduction and adduction, to hip abduction and adduction?

interestingly this video https://www.youtube.com/watch?v=ih_OZB_ciT4 mentions that very rarely would you measure adduction.. unless they have a problem with their arm being at the side. But then wouldn't that still be within the abduction range? so still doesn't quite answer it

To answer this question of "In human anatomy what is the purpose of measuring shoulder abduction and shoulder adduction separately if they cover the same range of motion?"
Before looking at some example images of video clips showing movement I think it's easier to consider wrist flexion/extension, and knee flexion/extension, as the concepts are very analogous.
In the case if wrist flexion and wrist extension,  0 is neutral. And the wrist can move maybe 70 degrees either way.
In the case of the knee,  0 degrees is full extension. Some people have a few degrees of hyperextension. And basically the movement people do in a gym is moving through degrees of knee flexion, on a machine known as a knee extension machine.
So if we apply that to the case of the wrist, when people say that wrist extension typically has a ROM/range of motion of 70 degrees, they mean when measuring from 0.  A person could do wrist extension from a position of wrist flexion, and do e.g. 140 degrees of wrist extension.
So, degrees of extension and degrees of flexion do not overlap.
But the terms extension and flexion do not assume/necessitate starting from a particular position  of extension or flexion. They could start from any position of extension or flexion or neutral.
In the context of measurement with a goniometer, and measuring a person's range of motion, then it suggests starting from 0/neutral. But otherwise, just talking of the movements of extension and flexion, it doesn't require starting from zero.
So to answer the question of "In human anatomy what is the purpose of measuring shoulder abduction and shoulder adduction separately if they cover the same range of motion?"
If each starts from zero, then they don't cover the same range of motion.
If measuring a person's ROM/range of motion, as physiotherapists do, then one would  start from zero.
If not measuring a person's range of motion, e.g. if just interested in the movement then the movements can cover the same range. One might extend from a position of extension. One might extend from a position of flexion, and from there either stay in flexion, or go into extension.  Likewise one might flex from a position of flexion or extension or neutral/0.
Like forearm supination can start from a degree of pronation and finish at a degree of supination, or start from a degree of supination and finish at a degree of supination, or start from a degree of pronation and finish in a degree of pronation. A "long" forearm supination movement not measured from 0, would start from a high degree of pronation and finish at a degree of supination.

I think the term arm abduction/adduction normally refers to vertical abduction/adduction, but i'll mention horizontal abduction/adduction too.
A screenshot from this video on youtube, man with red dot on his shoulder, shows the furthest degree of (vertical) shoulder adduction.

That's  consistent with what I heard from somebody that told me "normal (vertical) shoulder adduction motion is 30 to 50 degrees. Normal range of motion for shoulder (vertical) abduction is 150 degrees. "
There is an image from https://www.anatomyexhibits.com/  showing 0-180 degrees of vertical shoulder abduction.
Without reproducing it here , it's like

And they have an image showing 0-30 degrees of shoulder vertical adduction
which you can imagine with a protractor showing 0-30 degrees beyond 0. So  the arm starts by the side at 0 (neutral position), then moves across the body like the first pic(the man with the red dot on his shoulder).
The full movement of adduction would go from a high degree of abduction, down to 0 degrees of abduction / 0 degrees of adduction, and through to a high degree of adduction(as far as the arm goes for adduction to the end of the movement).
So likewise, with the hips , degrees of hip adduction are different to degrees of hip abduction. Though the movements of abduction or adduction can pass through degrees of one or the other or both. And that applies with wrist extension and flexion too. But for measuring a person's ROM you'd start from 0.
And I notice that the anatomyexhibits link specifies, vertical shoulder abduction/adduction.   Horizontal shoulder Abduction/adduction  would be in the transverse plane (I have noticed a difference though where some eg anatomyexhibits, measure horizontal shoulder abduction/adduction with 0 out in front, whereas others measure it with 0 to the side).
e.g. this link https://www.researchgate.net/figure/Shoulder-horizontal-adduction-A-start-position-B-end-position_fig1_309743960
has horizontal shoulder adduction (or no doubt abduction), with 0 out to the side.

whereas anatomyexhibits.com has 0 out in the front
--
This 7sec video saying it shows shoulder adduction.. youtube.com/watch?v=2N6WhuGDZRs is showing it not from 0. it's showing it from 180 or nearly 180 degrees of shoulder abduction.
One strange exception I ran into is 43sec into Goniometry Shoulder Abduction & Adduction (by kelly) youtube.com/watch?v=WgTu6HsZZTE it shows adduction measured where 0 is arm up. That seems strange to me, normally  abduction and adduction are measured from the same 0 point.
This video by OTStudentVids shows Horizontal shoulder abduction and horizontal shoulder adduction and takes 0 as out to the side. https://www.youtube.com/watch?v=Zu0WPhfHCWc All makes sense, abduction is one way, and adduction is towards/ across the body.


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What is the difference between muscle fascicle and muscle bundle?

In the photo above (given by Bio teacher), the muscle bundle is shown to be as a bundle of fascicles, but in most web definitions I've seen, the two terms are used interchangeably. What is the correct name for the part labeled "muscle bundle" if there are in fact no distinctions between bundle and fascicle?

Short answer
Muscle fascicles are the building blocks of skeletal muscle.
Background
Skeletal muscle, or striated muscle is composed of many units called muscle fascicles. The fascicles are bound together by a type of connective tissue called fascia.
Fascicles in skeletal muscle are composed of muscle cells, called mycocytes. These cells are referred to as muscle fibers in skeletal muscle. Myocytes contain small strands called myofibrils, which are the contractile elements in the muscle cells. The myofibrils move as skeletal muscle contracts.
Putting it all back together, myofibrils are the contractile elements in muscle cells (muscle fibers); muscle fibers make-up muscle fascicles; and muscle fascicles are bound together by fascia to compose the skeletal muscle.
Hence the part labeled 'muscle bundle' is a muscle, made out of a bundle of fascicles.
Source: Penn Medicine

I'm confused. In your categorization, where is the single muscle cell (is that the fiber?) Should that be part of the explanation of the organizational structure?

@anongoodnurse - nice catch. Thanks. I added an explanation (you are right, as always :-) and I added some web links to wikipedia and other sites for background reading.


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How can mammalian red blood cells live without a nucleus?
Even though they have a shorter lifespan than other varieties of cells, I would think that 120 days without a nucleus is still quite a long time.

It depends on what you call "to live". RBCs cannot divide, for instance. They cannot synthesise proteins either, so they are decaying after their nucleus is expelled. But they produce ATP using anaerobic glycolysis (as they lack mitochondria), which you may take as a characteristic of "living".


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Why do veins undergo vasoconstriction during physical activity?
How would this help increase blood circulation?

Do you have a citation for this claim?

"As physical activity increases, the veins undergo vasoconstriction, driving more blood back to the heart and increasing circulation." –http://www.biosbcc.net/doohan/sample/htm/vessels.htm

I believe that the answer is in the same cited source (BioSBCC).
Veins are considered a blood reservoir and undergo constriction to mobilize blood.

[...] the veins act somewhat like a blood reservoir, containing 60% of the total blood volume at rest. [...] When the body needs to mobilize more blood for physical activity, the sympathetic nervous system induces vasoconstriction of veins.

The result is an increase in circulating blood volume. This changes cardiac output and arterial blood pressure (CV Physiology: Blood Volume).
I also recommend reading on Biology.SE: Where does extra blood come from to fill your muscles during exercise?

There does not need to be a change in circulating blood volume during exercise; the role of vasoconstriction is more subtle than that.
Vasoconstriction increases the stiffness of venous vessels leading back to the heart. This makes them act more like stiff tubes than elastic reservoirs. As a result, any extra blood pumped by the heart is more likely to return to the heart rather than to be stored in the venous vasculature. The importance of regulating venous return in concert with cardiac function has been appreciated at least since the work of Guyton and colleagues in the 1950s.
In exercise the effective muscle pump arising from the combination of muscle contraction and valves in the veins preventing backflow is also important; both the muscle pump and venoconstriction promote venous return to the heart.


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Is new idea equivalent to forming new synaptic connection?
We get new ideas quite frequently hence I am curious that is getting new idea equvant to formation of new synaptic connections? I am aware of neural plasticity but somehow doubt that it happens quite rapid.
Since that idea was missing before one creates it makes me believe that the structure of synaptic connection was not present earlier and once the new idea was formed then the structure to simulate/produce that idea was created.
If that's the case that that's lots of neurons being connected/disconnected in few seconds which don't seem physically possible.

Not an area I have much familiarity with, but you seem to be making a lot of assumptions rather than doing some research. 1) Why do you assume "neural plasticity" isn't something that happens "rapidly" — also what do you mean by rapid? 2) Why are you assuming that conscious awareness of new idea happens the moment the associated synapses form? 3) Are synapses really binary (present or absent) or are they instead something with a strength and if the latter how would that affect your question?

1) Why do you assume "neural plasticity" isn't something that happens "rapidly" I actually couldn't get a good reference for frequency of synaptic changes (synaptic plasticity) but my assumption is based on general morphology, if new ideas get created in seconds, would it imply morphing happens. 2) Why are you assuming that conscious awareness of new idea happens the moment the associated synapses form? Because to give rise to that awareness, a pathway that leads to thought must be present, if I haven't learned about addition, I would not naturally add two number (something is missing)

3) Are synapses really binary (present or absent) or are they instead something with a strength and if the latter how would that affect your question? With what I have learned so far that they are binary winner-takes-all, All-or-None activations. So either they are active or inactive.

There is a lot of debate over what "thoughts" are in terms of consciousness, and this has been referred to as the "hard problem". However, it seems pretty clear that in some form patterns of brain activity are the "stuff" that underlies a thought/idea: if you change patterns of brain activity, you change the thought.
Therefore, I would describe a "new" idea as a "new pattern of brain activity" rather than connections. While the exact timescale of a "pattern" should be is unclear, perhaps a few hundred milliseconds is a good guess (see for example Luczak et al 2015, and the recent paper by Davis et al 2020). Brain activity is constantly shifting, of course, so really every moment experienced is a new thought of some sort.
There are too many studies to name all of them that show that some consistent pattern of brain activity is associated with some thought. The review by Harris, 2005 is a favorite of mine, but there are many levels of analysis to approach these questions. You might find some more compelling work among the studies of the biological basis of perception.
One particularly elegant paper is Liu et al, 2012. They used some molecular tricks to identify neurons in a rodent brain that are activated during a fearful context, and they cause long-term expression of a protein in those specific cells that they then use to reactivate those same cells at a later time. Reactivating those cells causes the fear behavior to return, effectively triggering the same ideas.
Connections between cells can also change pretty rapidly, but this would be better described as memory rather than an initial thought or idea. This can involve de novo creation of synapses, but more often is studied as a change in synaptic strength. Weak synapses can be strengthened with certain input patterns, and we call this long-term potentiation. The idea of connections between neurons as the stuff of memory goes back some 100 years to Ramón y Cajal.

Davis, Z. W., Muller, L., Martinez-Trujillo, J., Sejnowski, T., & Reynolds, J. H. (2020). Spontaneous travelling cortical waves gate perception in behaving primates. Nature, 1-5.
Harris, K. D. (2005). Neural signatures of cell assembly organization. Nature Reviews Neuroscience, 6(5), 399-407.
Liu, X., Ramirez, S., Pang, P. T., Puryear, C. B., Govindarajan, A., Deisseroth, K., & Tonegawa, S. (2012). Optogenetic stimulation of a hippocampal engram activates fear memory recall. Nature, 484(7394), 381-385.
Luczak, A., McNaughton, B. L., & Harris, K. D. (2015). Packet-based communication in the cortex. Nature Reviews Neuroscience, 16(12), 745-755.

This is exactly the kind of answer I was looking for. It makes so much sense to have thoughts as a pattern of various neurons firing rather then having to change a physical synaptic connection! So once again correct me if I am wrong as I want to reiterate its is highly likely that thoughts are some pattern of neurons firing instead of formation of physical connections or Neural plasticity. Right?

@metron Yes that's correct.


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How does permanently modifying human DNA work? And how does it impact procreation?
So I read an article about a metabolic disease being treated with gene therapy, where they inserted corrective dna into the patient.
https://www.independent.co.uk/news/science/dna-permanent-change-cure-disease-experiment-california-brain-madeux-iv-hunter-syndrome-a8055696.html
How can this be permanent though? Wouldn't the other cells "take over" these modified cells when they reproduce, and eventually have back the same old dna?
Furthermore, will this affect offspring in any way? Will they inherit the new dna changes (if that part of the dna is passed on from the parent with the changed dna)?

It seems this therapy is targeted to liver cells. Cells that are affected will continue to express the inserted gene as long as they last, and any dividing cells will spread it to their daughter cells.
Genetic information is passed on to the next generation through germline cells: eggs and sperm. There won't be any effect on the next generation unless these cells or the cells that give rise to them have the inserted gene.

But what if, say, only half of the liver cells get the new dna, and the other half still have the old dna? Won't they kind of "battle it out" and one of them will take over?

@user62354 Why do you think they would "battle"?

Wouldn't they try to take up more space because of cell division? One cell becomes two, etc.?

If that were happening it would be called cancer.

I see, thanks for the input


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Does double stranded RNA (dsRNA) exist in eukaryotic cells?
I know it sounds like a stupid question. Obviously, tRNAs and rRNAs, for example, form loops and could therefore be considered as dsRNAs... but are they really considered as such?
Are there examples of RNAs, in eukaryotic cells, that could be considered exclusively as dsRNAs, or are dsRNAs considered as unique to certain viruses?
Thanks in advance for your help. I couldn't find a clear answer to that question in my textbooks and on the internet, so I hope you can help.

Yes, dsRNAs are present in eukaryotic cells and regulate various biological processes.
These nucleic acids are also present in the nucleus and regulate mitosis. Altering this nucleic acid could even lead to cell death.
(Reference: https://pubmed.ncbi.nlm.nih.gov/25504323/)

I attached the image of a research article as Peter Bernhard can't access this article. And I tried to add the whole article but couldn't do that because of size issues. I will remove this image because of copyright issues. I Will keep this in mind from now onwards. Thank you David.

I will keep it very very short and simple.
dsRNA is very critical in regulation of gene expression at translational level.
In our system we have specific miRNA (micro RNA) that are somewhat complementary to a specific  mRNA and miRNA-mRNA binding forms a double stranded molecule that is degraded by our system at a cellular level. So in a way it controls the translation of mRNA(s).
Further reading about miRNA-
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6085463/

Sure about  "at translational level" if it's mRNA being degraded - that doesn't make it "at transcriptional level"?

No. Transcriptional level would mean it interferes with DNA.

@PeterBernhard miRNAs bind mRNA and block ribosomes from tranlating it. So it is at a translational level.


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If species are reproductively isolated, then how are interspecific hybridisations carried out?
during fertilisation there is compatibility test done so that both sperms and eggs are of same species. the zona pellucida of egg bears sperm specific receptor proteins(ZP3 receptor proteins) which bind with species specific proteins (bindin) present on sperm. so during interspecific hybridisaton( for example mule which is hybrid of donkey and horse) how fertilisation between gametes of different species carried out? what is exactly the mechanism behind this?

Mules existed for quite a long time - maybe 5000 years? - before any of the relevant biology was known: https://en.wikipedia.org/wiki/Mule  Apparently there is enough similarity in sex pheromones &c that male donkeys are quite willing to mate with female horses.  But that's not saying much, since a couple of my female acquaintances who have donkeys have told me that they just don't ever bend over when they're in the same corral as a male.

Hello and welcome at Biology SE! Please take our tour to see how to ask good questions. Can you please clarify your question? Are you interested in the specific molecular mechanisms behind egg and sperm cell interactions or you would like to know how is it possible that different species can mate?

i want to know about specific molecular mechanism behind egg and sperm cell interaction during interspecific hybridisation processes.

Why do you think that molecular mechanism would be different compared to intraspecific matings?

i am not able to understand that how gametes of different species involved in fertilisation. what about species specificity? how is it compatible?


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Why would lethal genes evolve?
I've been reading through 'The Selfish Gene' by Dawkins. At a few places in the book he states that incest is damaging because it would give a very high chance of lethal recessive genes becoming active due to the high probability of both children having the gene compared to one child and one stranger from the same species.
However, this leaves me with the question why lethal genes would evolve in the first place. The only reason I can think of is that these genes have some secondary purpose and survive natural selection because of that.
Is this simply the entire story or are there things that I'm missing? It seems to me that the having possibility of getting healthy offspring from incest is beneficial to a species, if only because finding a mate would be easier, so those secondary effects would have to be pretty good.
Also I'd be curious if any research has been done which has found examples of side effects of these lethal genes that would make them preferable.

Hint: lethal recessive genes are recessive. If they weren't, we probably wouldn't be having this conversation. Natural selection has literally zero "motivation" to eliminate effectively unused genes. See also (on a macro scale but same principle): we still each have an appendix.

@LightnessRacesinOrbit but even recessive genes will now and then appear together right? So the motivation would be less than for a dominant gene, but there would still be a motivation. Unless incest is the only way to get the double those, but I don't see why that would be the case.

Sure but "now and then" is unlikely to make a huge dent in the gene's survival. It's basically a vestigial gene that, yes, may pop up from time to time to cause trouble (see also: appendicitis!), but on the whole isn't enough to trigger any evolutionary magicks.

Lethal genes evolve simply because of random deleterious mutations and absence of strong selection.
Recessive lethal genes
Random mutations can make a gene product non-functional or reduce its activity. However, in diploid organisms the other fully-functional copy of the gene can compensate for the non-functional allele.
Sometimes both the alleles can carry different mutations which can lead to complementation; this would not affect the gene activity. Also see:  Explain allelic complementation at molecular level. Let's not consider this case here.
So, the fitness of the heterozygotes would not be affected and they will continue to propagate. However, if both the alleles are affected then it would lead to lethality (or lets say reduced fitness). This can happen if two heterozygotes (with the same deleterious mutation) mate and give rise to a homozygote (with both the alleles affected). Since siblings (or other close kins) are genetically related, there is a good likelihood that both of them may be carrying a copy of a non-functional allele and homozygous offspring born out of such a mating may have reduced fitness.
Dominant lethal genes
There are some cases of dominant lethal alleles. Examples include the mutated genes responsible for Huntington's disease (or similar poly-Q disorders). Other examples include a mutant allele of a proto-oncogene that leads to its hyperactivity (and therefore cancer).
Dominant lethal alleles persist in the population primarily because of their late onset. In such cases an individual with such an allele would have already mated and produced offspring before the disease kills them.
Other reasons for the persistence of lethal genes
Another possibility (applicable to the case of cancer) is that the mutations are not in the germ cells and were acquired by somatic cells because of some external agent. These mutations would not be transmitted to the next generation.
Sometimes, the deleterious nature of the allele can exert its effect only under certain conditions. Let's say someone has a mutation that causes reduced immunity. Such a person would survive well if they remain in a sterile environment. In general, we can say that there is no strong selective pressure against the mutation.
Sometimes the reduced fitness because of a mutation under a certain condition can be overwhelmed by an increased fitness caused by it under some other condition. A very well known example is that of the haemoglobin allele that causes sickle-cell anaemia. However, the RBCs in the individuals affected by this disease are resistant to infection by the malarial parasite. The mortality due to malaria is much higher than that due to sickle cell anaemia. Therefore, in regions where malaria has high incidence (like Africa) this allele is positively selected.

I'd like to add that sometimes predicted LOF in homozygous genotypes is compensated but the mechanism of compensation is not clear yet - http://science.sciencemag.org/content/early/2016/03/02/science.aac8624, http://www.nature.com/nbt/journal/vaop/ncurrent/full/nbt.3514.html.

This is just loose terminology. By ‘lethal gene’ Dawkins means an essential gene with a mutation that renders it inactive. With a recessive gene, the one ‘good’ copy in the heterozygote provides enough gene-product to allow survival, in contrast to the situation in the homozygote where the total absence of gene-product is lethal.
With a rare mutation, the chances of two unrelated individuals being heterozygotes is small. However within a family, the chances are much higher. One sees this, for example, in inbred animals such as thoroughbred dogs.
Such recessive genes normally stay rare, and do not ‘evolve’ — there is no selective pressure to maintain them and they are lethal in the homozygote. Only in cases where there is some advantage to carrying only one copy of the gene is the heterozygote selected for. Examples of this are sickle-cell anaemia and beta-thalesaemia where the protection against malaria is provided in the heterozygote. (But I don’t think Dawkins mentions this.)

Sorry I did not notice your edit and thought of adding the sickle cell case myself. Hope there is no conflict regarding this :)

@WYSIWYG No problem!  I'm such a serial editor of my own posts that it's bound to happen.

They occur because there is no reason for them to be selected against. Except for a 25% chance of offspring not surviving, in the rare event that the other parent also has the mutation.
That recessive, lethal genes can persist in the population is surprisingly one of the reasons that diploid organisms that sexually reproduce are so successful and diverse. Diploidy means there are two copies of each gene, and that a mutation in one gene that doesn't immediately increase fitness won't necessarily be removed from the population. Even if it would be down right fatal if it occurred in both genes. Because its function can often be covered by the other, normal gene.
It might appear that a carrier of this mutated gene might be less fit to produce healthy offspring. But most organisms create many more offspring than can actually thrive. And what first appears to be a 'weak gene' can later go on to be the basis for a better mutation, often through recombination during meiosis of parts of the lethal gene with its normal counterpart.
In general this is one of the reasons that eukaryotes are so diverse. Because they have many mechanisms like this that don't only protect from mistakes in DNA, they often enable them to be beneficial.
Another such mechanism is that eukaryotes have a lot of introns in their DNA that are removed from their messenger RNA before it is translated into protein. This means that any random chunk of DNA integrating into their genome (a reasonably frequent event, evolutionarily speaking) is less likely to cause gene inactivation and more likely to simply be incorporated. Into an existing gene or even actually added as an extra gene. This encourages a very modular organisation of genes, gene regulation and proteins by enabling the evolution of functional motifs that are reused over and over again.

Any reference to add?

It would be beneficial to a population for a lethal gene to evolve in incestuous situations because genetic diversity is then promoted through natural selection. Genetic diversity is necessary for a species to evolve which would improve the chance of survival.

But there are so many species where these genes are not present that it seems unlikely to be such a big deal. It also seems like an unstable strategy: in a population where there are no genes preventing successful incestuous reproduction, were such genes to arise by chance they would quickly be eliminated, afaik in a matter of generations as they are so incredibly bad. For this to become stable you would have to evolve aversion to incest which would take longer than that. (I'm far from an expert so please correct me if I'm wrong)

To add to my other comment: It seems therefore to me that the only way such genes could actually evolve is because of secondary (dominant) effects which are beneficial enough to counter the lethal effects. Then I can understand that, over time, a species would 'learn' to select mates without the same lethal gene such that the offspring only has the beneficial effect.

This should be a comment, not an answer. You can always comment on your own posts, and once you have sufficient reputation you'll be able to comment on all posts.