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1

It is generally known that the smaller (or less complex) an organism is, the more "condensed" it's genome is. For example, bacteria (or some eukaryotes) have operons (http://en.wikipedia.org/wiki/Operon) or overlapping genes using different and they don't have introns, which alltogether saves a lot of space. There are many reasons for that. Available space ...


0

It's simplest to think about a haploid population with size $N$. Say there are two alleles, $A$ and $a$, with $A$ having frequency $p$ in this generation. Each $A$ individual will have some realized fitness (i.e., number of offspring) in this generation; let's call this number $w_A^{(i)}$ for the $i^\text{th}$ individual. The total number of $A$ individuals ...


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I really good intro to evolution book is The Evolution of Vertebrate Design by Leonard Radinski. Also, for a more math based approach you could look into Narrow Roads of Gene Land. These are collected papers of W.D Hamilton.


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You would want to do a search for "feature detection" in sensory systems. The answer to your question is quite broad but that should narrow it down.


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If the fitness of a heterozygote is $(1+s/2)$ and of a homozygote is $(1-s/2)$ then why is the probability for a given state $(1+s/2)^j(1-s/2)^{m-k}$ $$\binom mj (1/2)^j(1/2)^{m-j}= \binom mj (1/2)^m~~ ?$$ As you pointed out earlier, in the general case it need not be true that $p = q = 1/2$ but that is what the form of the probability above implies. So ...


2

You may consider consulting the H2DB database. The database is quite new, so the number of heritability estimates is not very high at the moment (currently 225 estimates for human, 838 estimates in total), but it's a start. The database is described in a paper by Kaminuma et al.(2)


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You are right that a person with an abnormal number of chromosomes will be unlikely to find an "equal" partner to mate with. This does not prevent a chromosome aberration from spreading though, and it is not necessary that the mutation is initially beneficial for it to spread. While it is true that many chromosomal aberrations may be detrimental and cause ...


5

Toilets have always been a great place to think about biology, I agree $\ddot \smile$. In short, urine contains the waste from our blood while defecation is just the stuff that we haven't digested. Kidneys are the organs responsible for draining wastes (mostly nitrogen-containing, or nitrogenous, wastes) from our blood. You're correct that the loss of ...


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I think one would not have a lot of success using a filter to do this, rather using a centrifugal gradient and comparing the fractions to a standard I think would be preferable. Nitrocellulose filters are made with precision but not very astounding accuracy which is the main reason they are commonly used at set sizes (like 0.2 and 0.4 microns) and not often ...


1

What do you call an acquired trait? A trait acquired during the lifetime of the individual through its relationship with the environment (especially culture and traditions in humans)? If you take any population of living organisms, the variance of quantitative trait in this population, also called phenotypic variance and denoted $V_P$ is the result of the ...


1

@Remi.b's list is excellent, but it should also include Gillespie's Population Genetics: A Concise Guide.


1

You either want a introductory book in evolutionary biology or a book that provide models/formulations of evolutionary processes In my first class of evolutionary biology I had this textbook: Futuyama, Evolution I think it gives a good start to the field and offers a good overview of the difference subfields. If you think you already knows enough about the ...


5

Short answer Yes that would work in the condition that the trait you select for (size) is heritable. Long answer The kind of selection you would apply is called truncated selection because you fix a limit in size (depends on your filter) under which individuals do not survive and above which individuals survive and reproduce equally. The response to ...


2

Is this the exact text from the book? The left side seems to represent the probability for "No coalescence in $k$ lines in $t$ generations (i.e. the $Pr(k)^t$ term), and at least one coalescence among those lines in generation $t+1$ (the $1-Pr(k)$ term)" which is the same event as "First coalescence event in $k$ lines is exactly in generation ...


1

One example of an active selection pressure's effect on human phenotype is in areas where malaria is endemic, the prevalence of sickle cell anemia is higher. Sickle cell anemia is highly protective against malaria, and less people die from sickle cell than die from malaria, so you see a rise of sickle cell in the population. This is a small degree of ...


4

Background I'd like to start by saying that traits phenotypic (loosely speaking phenotypic mean morphological) traits evolve because their variance is correlated with some genetic variance. If most of the phenotypic variance is genetically coded, you'd expect that the trait will change through if different variant of the trait influence fitness (which is a ...


1

The basic idea is that mutations improving different traits can occur in different individuals, and then be brought together by recombination. So the frequency of recombination roughly sets the maximum rate at which the population can acquire good mutations. Nick Barton and I calculated it, and found that a population can gain about one good mutation per ...


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I think the key work here is 'evolve'. Overall GC/AT ratios change by mutations, whose rate is constant. The probability that given a mutation event that one base will be substituted by another one has been modeled in several ways where the probabilities of different mutations may or may not be the same. Overall the GC content will tend to close to 50%. ...


7

No, they are of course not there to cause allergies. It is thought (although not directly proven in human) that IgE is important to fight parasites and worms. They bind to antigens from the parasites, which leads to the secretion of histamines. This causes a local immune reaction (which also is a problem in allergies) which is helpful to fight the parasites. ...


2

Some elements of response to your question. First, something about tRNA frequency. Even if there are six codons for a given amino acid, they are not equivalent because some will correspond to abundant tRNA, while others correspond to very minor tRNA. This has significant influence on the traduction speed, as the traduction will dramatically slow down on ...


2

I think the main issue you have is in this paragraph: But if mutations are rare, it seems unlikely that many (thousands of) properties of organisms get improved in a single generation. You'd need to get very lucky to randomly improve all the genes responsible for it. There are two basic misconceptions there: Mutations are not rare. They're actually ...


6

Has anyone calculated or simulated how the adaptation for many different traits can happen simultaneously? There are a lots of studies on the subject but I don't fully understand what is your issue. So I'll try to give some words hoping that helps a bit but it is possible that I'll totally miss the point you want to make. The mutation rate in humans is ...


1

Not in general -- there can be linkage disequilibrium among the loci. For instance, say that there are two di-allelic loci, $A/a$ and $B/b$, and that the frequencies of the $A$ and $B$ alleles are both $1/2$ and that they have the same effect on the trait, with no dominance. If all haplotypes in the population are either $Ab$ or $aB$ (with no $AB$ or $ab$ ...


1

To derive it, first use that $E[x(1-x)]= E[x-x^2]=E[x]-E[x^2]$ and that $E[x^2]=\text{Var}[x]+E[x]^2$ to rewrite the left-hand side: $$E\left[x_{t+1}(1-x_{t+1})\right] = E\left[x_{t+1}\right](1-E\left[x_{t+1}\right])-\text{Var}\left[x_{t+1}\right].$$ The equation for $p_{ij}$ is just saying that $2Nx_{t+1}$ is binomially distributed with $2N$ trials with ...


1

The notation at this site resembles that in your question but preserves the $\frac{x_t}{2N}$ notation for probability of selecting an allele. $$E[\frac{x_{t+1}}{2N})(1 - \frac{x_{t+1}}{2N} )|x_t] = (\frac{x_{t}}{2N})(1 - \frac{x_{t}}{2N}) (1 - \frac{1}{2N}) $$ The expression $(\frac{x_{t}}{2N})(1 - \frac{x_{t}}{2N}) $ is the probability of heterozygosity ...


2

A Biologist's guide to mathematical modeling in evolution and ecology (Otto) is a very good book that is presented for people that have highschool level in mathematics (It makes a good review in linear algebra for example). It is highly accessible and in the meantime it goes pretty far as it ends up talking about the application of diffusion equation in ...


3

There is a substantial variation in some human traits: hair colour, eye colour, height, weight, skin colour, build etc. etc. HOWEVER there is also considerable variation within other species, to suggest otherwise is naive (though quite common). We often feel like there is more variation within our own species because we are more aware of the subtle ...


3

Crossing or decussation is a lot more robust against wiring errors than their seemingly simpler same-sided wiring counterparts. See here for the research carried out to establish this and for more detail.


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This varies by the kind of animal or plant. I think one company would rarely do both. For plants Monsanto comes to mind. And Syngenta. I'm not sure for animals. For beef cattle in the US, this is done by individual ranchers (who may be corporations) that collectively share their genetic data creating a market which can predict the value of a bull. The ...


0

Well, the total genetic variance is just, by the definition of the variance, $$ \sigma^2 =\sum_{i,j} f_i f_j (w_{ij}-\bar{w})^2 $$ (using $f_i$ and $w_{ij}$ for frequency and fitness, respectively), and $$\bar{w} = \sum_{i,j} f_i f_j w_{ij}$$ is just the average fitness. You can calculate the additive genetic variance for different loci by simply assuming ...


1

Hopefully this syllogism will answer your question. Given the following premises: In the absence of selection, fitness of individuals are at a theoretical maximum. If a theoretical maximum fitness is achieved then effective population size is maximum. If there is an allele that confers both increased and decreased fitness you have a genetic conflict (e.g. ...


0

We might imagine living things that are very different from what we know. There is no conceptual reason for limiting life in its relation to water for example. Moreover, the definition of what is alive is really unclear. We classified more or less arbitrarily objects we know on earth as being living or not living but this does not give any clear definition ...


3

To a good first approximation $\overline{\Delta f} = 0$. Where $\overline{\Delta f}$ is the mean change in fitness down to any point or indel mutation. The reasons for this are as follows: In the genome of higher organisms, most of the genome is non-functional ("junk") so most mutations will not have any effect regardless of the change made. A substantial ...


1

http://link.springer.com/article/10.1007%2FBF00180642 study on the O2 production rate of one of the fastest growing species of cyanobacteria. The theory is not just someone's idea, its a conclusion made from trends which were discovered during the course of conducting countless experiments.


3

I don't believe you can produce a general function for this. It will depend on the exact gene and organism you are considering. From a molecular point of view, the vast majority of recessive mutations result from a change producing either a non-functional protein product or a truncated product that is cleaned up by the cell. We can reasonably assume that ...


1

[This is purely speculative] Assumptions: impact on fitness is measured by survival chance impact is because of protein coding genes Probability of a mutation at position $i$ $P(m=i\ |\ g)$ where $g$ is the genome with its annotations. Probability that activity of some protein changes by X-fold given mutation at $i^{th}$ position(s) in the genome: ...


2

What you say is true, but the answer as to how modern evolutionary theory understand this considers other ideas about living things which seem to allow so called 'neutral traits'. Neutral traits being those phenotypes which seem to have no particular relationship to fitness. Toungue rolling is an often mentioned example. Some folks argue that there is ...


2

The short answer is: Because of genetic drift. If a mutation does not influence the fitness in heterozygote individuals, then its frequency varies only through genetic drift while it reaches some high enough frequency. If by chance, the frequency of this new allele achieve a high enough level so that the homozygous for this allele given by $x^2$ where $x$ is ...


1

Another important point about evolution is, that rhere are many, many small steps - not huge leaps. E.g. going from a bacteria to something with four legs in one step will not happen - that is simply too much change at once, and it's probabillity is close to zero. But small steps happen all the time - if we take your example with a cephalopod: Imagine that ...


2

It is understood that Evolution basically involves three elements. Natural selection, genetic mutation, and time. The problem for Evolution, is that none of those three elements are creative. They absolutely are creative in that they create something new. Mutation introduces random errors, some of which may never have existed before in that combination ...


4

Where does the information come from? From the environment, and the previous history of interactions in that environment. The process of evolution can be viewed as an undirected search for "good" solutions (i.e. those that better support replication) to problems presented by the environment. There is a large amount of information (in the information-theory ...


1

We find valleys pretty. We find mountains pretty. We like sunshine and clouds. I'd say all these have some advantages. Trees you can climb. In valleys you have protection. From mountains you have a good view across the landscape. So yes it does make sense that we like nature. We like things that are good for us. Like fertile land and food.


1

evolution means unrolling http://www.etymonline.com/index.php?term=evolution Now if you imagine a tree with one root then the stem rolls out, branches roll out twigs and leaves roll out etc. Same with the roots on the other and to balance it out. And that's it. Evolution does not happen in a vacuum. It happens in and together with an environment. If the ...


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Your basic problem is indeed a fundamental misunderstanding of how DNA and by extension its evolution works. First of all, there is no such thing as "correct" or "error", there are only changes, some of them are better for the individual and some are worse. You also have a basic misunderstanding of the concept of information. An error does not decrease the ...


0

Bright colors can attract a sexual partner as they are beautiful and are often a sign of good health. So, if you have bright and beautiful colors, you'll attract a partner to reproduce more easily than other and your genes will pass to the next generations. So, some animals are "beautiful" because of sexual selection. For flowers, bright colors and perfume ...


10

You question, I'm afraid, betrays a deep misunderstanding of evolution. Genetic mutation is just errors in replication. So it creates nothing. It simply degrades. This is patently false. The vast majority of mutations are "errors", in that they produce a less fit organism. But once in a while, a mutation will confer an advantage, rather than an ...


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It's seems to me you forget something pretty important about evolution : it has nothing to do with improvement. All living organisms have the exact same time of evolution as they all derive from a common ancestor. They simply evolved through different paths, that's what explain the biodiversity we can observe today and no organism is better than others, not ...


5

Earwax, also called cerumen, is slightly acidic (1), with a pH of about 6, and acidic foods or substances taste sour. The composition of earwax, upon which its taste depends, is related to its functions. Earwax aids in cleaning and lubrication of the ear canal and has an antimicrobial effect. The antimicrobial effect is in part attributed to its acidity, ...


2

I think this is a little like writing a book. The most common advice is for aspiring writers to write every day and write a decent amount. Evolution creates by testing everything against its fitness - its ability to survive and reproduce. If something is advantageous, it stays in the corpus of genes and genetic solutions to problems. If something is ...


0

I'm not at a biologist, but I have a pet theory I'd like to throw into the ring: hermaphroditism tends to be unstable in a similar way to strong sex skews. Imagine species A where 90% of offspring are female; at moderate population density, the 10% male population will be more than sufficient to maintain the females, and having 90% of the population able to ...



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