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13

I will start with a quote from François Jacob, a French geneticist: The sole ambition of a bacterium is to make two bacteria. The same reasoning can be extended to all life on Earth, including humans. There is no purpose to human existence, in the same way that there is no purpose for life at all. Life is there because it can. It works, chemically, ...


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. ...


7

This is quite common. It is most likely dried rheum (also know by slang terms such as "sleep", "eye boogers", "eye crusties", etc.). Rheum is the result of dried mucus, tears (and the salt and minerals therein), as well as dead blood and skin cells. Essentially it is all the stuff that’s normally in your eye that eventually dries up making the contents ...


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, ...


5

The dynamic-dominance hypothesis of handedness states that the essential factor that distinguishes dominant from nondominant arm performance is the facility governing the control of limb dynamics. Sainburg (1) writes that It should be noted that dominant arm advantages do not apply to all tasks, or all aspects of tasks. Healey et al. (1986) examined an ...


5

In men, gout is associated with a higher risk of death from all causes. This would imply that their life expectancy is shorter. From a review by Kim et al. (1): Among men who did not have pre-existing coronary heart disease, the increased mortality risk is due primarily to an elevated risk of cardiovascular death, particularly from coronary heart ...


4

I think CT is an abbreviation for connective tissue. Some examples of its use in that fashion: http://en.wikipedia.org/wiki/Connective_tissue http://www.vetmed.vt.edu/education/curriculum/vm8054/Labs/Lab5/Lab5.htm http://www.pitt.edu/~sshostak/biosci1450/hislec03.html


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 ...


4

To learn obstructive/restrictive lung diseases, I find it easiest to think in extremes at first, with vivid descriptions of why. So in obstructive lung diseases, like COPD/emphysema: Total volume increases because so many of the walls of the alveoli have been destroyed, they are like giant floppy bags instead of nice firm bubbles. There's more empty ...


4

First of all, I should quote the sentence from the MOST reliable ophthalmology sourcing in the world - American Academy of Ophthalmology: Section 11 - "Lens and Cataract" "The equatorial diameter of the unfixed human lens measures 2 mm at 12 weeks and 6 mm at 35 weeks. Both the growth and the maturation of lenticular fibers continue throughout life." The ...


4

No. In fact the lens of the eye, which is nearly optically perfect in humans, does not change or grow after it is fully formed around week 26 of gestation. Interestingly this is why one of the cues for identifying young children is having small faces with large eyes. This also the case for puppies and cats and other animals, who are mostly cuter when they ...


4

Summary: A fall from "any height" may be survivable, depending on what you hit, but with an expectation of severe injuries. A water impact at terminal velocity will in all likelyhood result in immediate death. The Serbian Flight attendant Vesna Vulović holds the Guiness World Record for surviving a fall without a parchute with an estimated fall height ...


3

That's an interesting question. And it is also a common misunderstanding of evolutionary processes. Thanks to @Chris comment, we know/can assume that high mortality rate is not a consequence of industrialization but has ever been before the era of modern medicine. Women don't let themselves die in order to improve the species. Those women that carry the ...


3

A Google search for "Huntingtons disease gene discovery" yielded this page at the Nature Education Scitable website. The following citations are provided regarding the molecular basis of HD: Huntingtin (HTT) was the first disease-associated gene to be molecularly mapped to a human chromosome (Gusella et al., 1983)2. Ten years later, scientists ...


3

Purpose requires a sentient being to have intent. There is no biological reason to suppose there is any purposeful intent behind life. If you hold otherwise, perhaps inquire of the fellow or lady or other you suppose is responsible. Just because a child can give an answer to a question doesn't mean that the answer is accurate, or that the question truly ...


3

The endothelial cells in small blood vessels take in more glucose even if insulin level is high (insulin level increases as a feedback reaction in type II diabetes or after treatment in type I diabetes), because they don't have insulin receptors. Thus they form surface glycoproteins which causes the basement membrane to become thicker yet less strong. This ...


2

I'm pretty sure this doesn't exist. If it did, that would be awesome. The following is 100% pure speculation with nothing to back this up at all (as a disclaimer). Phosphorus-31 (the stable isotope) is NMR active, which means that you could theoretically use an MRI machine to visualize phosphorus. A quick google search shows scientists attempting to use ...


2

I wasn't sure when I first read this, but this is actually a very interesting question. Right now there seem to be two completely divorced lines of inquiry that researchers are pursuing with respect to the antimalarial drugs. One group of researchers is working on working out the mechanism by which say, chloroquine and its ilk bind to and interfere with ...


2

Quoting a great biologist Peter Medawar : It is by no means difficult to imagine a genetic endowment which can favor young animals only at the expense of their elders; or rather at their own expense when they, themselves, grow old. A gene or combination of genes that promotes this state of affairs will, under certain numerically definable ...


2

nuhcole is mostly correct. Airborne particles first pass through the nasal passageways and/or mouth and throat and many are caught, but those that enter the lungs become trapped in mucus. Your cilia act like a constant escalator, bringing up that mucus from your lungs 24/7. You reflexively swallow it without even realizing it. That is why when you are ...


2

Human females have one of the worst chidbirth experiences. This is because of our extremely high cranial capacity compared to the apes. This had an obvious evolutionary advantage and made us what we are today. However this creates problems as the braincase has to pass the pelvic cavity during childbirth. The wider hips in women compensate for this but still ...


2

cool pics! Firstly, Formadahyde is a terribly toxic substance. Skin Contact: CORROSIVE. Contact can cause pain, redness, burns, and blistering. Permanent scarring can result. Can be absorbed through the skin. Formaldehyde causes organ failure and scarring if ingested. In this case, since you don't have burning or blistering, it seems like a ...


2

Question is two years old, and the answer is approx 20 yo, but I believe both are still pertinent: According to Jared Diamond on pg 12 of his Harper paper version (1993 -- but reissued in 2006) of The Third Chimpanzee, we replace intestinal lining epithelium every few days, urinary bladder lining every two months, and replace every red blood cell about every ...


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)


2

Small or relatively small amounts of the antigen can cause an allergy, when you have IgE antibodies which fit to this antigen. They will then cause a local immune reaction and cause the secretion of histamine. For the desensitation therapy large amounts of antigen are given (which is not without risk). The mechanism behind this therapy is not completely ...


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

According to an article in Vision Research Volume 50 issue 2 : "The face’s vertical distance between the eyes and the mouth is approximately 36% of its length, and the horizontal distance between the eyes is approximately 46% of the face’s width." The article can be found at: http://www.sciencedirect.com/science/article/pii/S0042698909005045


1

In the developing embryo you have the three germ layers: Endoderm, mesoderm and ectoderm. From these layers all cell lineages of the body develop and can be traced back through their differentiation and migration to this three layers. Have a look on the image below, which illustrates this pretty nicely: The figure is part of this PhD thesis, which also ...


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 ...


1

Let us say this myopic patient has amplitude of accommodation of 8D. The patient accommodates 8D beyond far point, thus his near point is 1/6+8=0.07m (7.1cm). If we compare the case with emmetropic eye with accommodation amplitude of 8D, the near point is 1/8=0.12m (12cm). So, yes, near point of myopic person is different from an emmetropic one. But, you ...



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