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15

There is some evidence that fetal development under zero gravity conditions might be problematic. Wakayama S, Kawahara Y, Li C, Yamagata K, Yuge L, et al. (2009) Detrimental Effects of Microgravity on Mouse Preimplantation Development In Vitro. PLoS ONE 4(8): e6753. doi:10.1371/journal.pone.0006753 The paper is here. These authors studied aspects of ...


13

From a certain point of view you could argue that our bodies have an inherently limited lifespan; Telomeres are extensions to the end of chromosomes that prevent damage or loss of genetic information during cell division. Telomeres are not replaced (in normal cells), which gives rise to a replicative lifespan; the number of times a cell can divide before ...


12

Seeds are spread by many mechanisms Wind dispersal: When air currents used to spread seeds. Often these plants have evolved features to facilitate wind catching, for example dandelions. Aka, anemochory. Propulsion & bursting: When seeds are propelled from the plant in an such as in these videos. This is called Ballochory. Water: Similarly to wind ...


11

First of all: Yes, fluoride is toxic, but the toxicity depends largely on the form (soluble vs. unsoluble, which fluoride salt etc.) occurs. It also depends on the environment since insoluble salts which are subjected to strong acids can release fluorine ions. The certain toxic dose for adults is 32-64mg/kg body weight, a 75kg adult needs to take up between ...


8

Cell-cell adhesion is a well-regulated mechanism, cells don't just stick together randomly, this interaction is mediated by specific molecules on the cell surfaces. The responsible proteins for that are the Cell Adhesion Molecules (CAMs) like integrins, cadherins and selectins. Which of these CAMs are present on the surface of a cell determines if those ...


8

Short answer: Changing something (instead of everything) yes. There are several studies on the impact of environmental factors on life span. Of course it depends from organism to organism. Diet restriction for example has been shown to extend life span of worms and mice. Temperature is also working well, at least with microorganisms, the metabolism of ...


7

The answer is more or less yes. Normally Firebugs (Pyrrhocoris apterus) go through 5 nymph instar stages (as do most Hemiptera), where they resemble the adults more and more as they grow. Only adults are winged and have have functional reproductive organs. This type of metamorphosis is called hemimetabolous or simple metamorphosis (in contrast to ...


7

This is a very interesting question. Many people have researched this topic, and many still are. But regardless, I had never heard of Alan Turing's contributions, so thank you! First of all, I cannot actually find who first coined the term morphogen. Though people had hypothesized that chemicals could play a critical role in development through much of the ...


7

You may want to look into "Evolutionary - Developmental Biology", which deals with how an embryo develops into a grown organism. Thus, by combinatorial specifying the identity of particular body regions, Hox genes determine where limbs and other body segments will grow in a developing embryo or larva. A paragon of a toolbox gene is Pax6/eyeless, ...


7

In my experience (in common with the experience of everyone I've talked to who could be considered an expert on the subject), taking old wood and using that as a scion when grafting new trees rejuvenates them, and they grow as new trees. I'll take apple trees as an example. As you can see from the table here, there is a distinct age after which the tree ...


6

Cell differentiation, cell fate and cell mapping is an interplay of accessible evolutionary strategies/programmes and responses to dynamic environmental cues such as specialized hormones (e.g. morphogens) and physical parameters and constraints. That is putting it very broadly. It is a complex issue, if L. Wolpert's PLOS assays are any indication. I compiled ...


6

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 ...


6

No, fish scales are dermal (= formed in derma) bones like skull roof bones. Scales in reptiles are formed by epidermis and are made primarily of protein (from keratinocytes), being similar in derivation to hair, feather and nails. On the other hand, in reptiles one must differentiate between scales and osteoderms (= scutes). Scutes are widespread among ...


6

Oocytes, or immature female eggs, develop in the fetus's ovaries during pregnancy. This graph (U. New South Wales) shows the oocyte population over time in a human female: Although the x-scale is kind of confusing (months when negative, years when positive), you can see that the fetus has all the oocytes it will ever have at the peak 18-22 weeks after ...


6

There are legitimate case reports in credited journals of hyperdontia, or the condition of having supernumerary teeth. Such cases are often associated with congenital syndromes-- cleft lip and palate, trichorhinophalangeal syndrome, cleidocranial dysplasia, and Gardner's syndrome. I included a case report and a comprehensive review for you below. Case ...


5

Many genetic studies in this area have found that variation in serotonin receptors associates with differences in a number of personality traits. That one gene, or a very small number, turns up time and time again for something so complex as human personality makes me a bit suspicious. Other factors at play: Family dynamics Culture and cultural norms ...


5

The urogenital system as a cohesive functional unit probably evolved very early in vertebrate history. Hagfishes and lampreys have separate systems for reproduction and excretion. More derived groups of fishes use kidney tubules and ducts for sperm delivery outside the body (Helfman et al. 2009). The vertebrate nephron may be homologous to the invertebrate ...


5

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 ...


5

I don't know if this is what you mean, but take a look at BioNumbers. Also, mathematical constants like pi are different from physical constants. Mathematical constants are true in a mathematical (logic) sense, and do not need to be related to any physical quantity. They are derived by logic. Physical constants, on the other hand, typically describe an ...


5

That is highly unlikely. The article to which you linked specifically states: While watching other people exercise may increase your heart rate and have other physiological effects, nothing can replace the health benefits of getting off the couch. With proper nutrition, muscle is built through exercise by adding sarcomeres [to muscle cells which ...


5

It is impossible at present to reproduce all the conditions of a womb. A womb is more than a warm fluid-filled home for nine months. A few days after fertilization, the trophoblast portion of the conceptus attaches itself to the uterine wall where it develops into a placenta and umbilical cord while the rest (the epiblast) becomes the baby. Throughout the ...


5

Artificial amniotic fluid has been used on goats, and for premature human babies. In the 1996 experiment, Thomas Shaffer, a scientist at Temple University, used an oxygenated liquid in a clinical trial with thirteen infants born at twenty-three to twenty-four weeks who were not expected to survive, and seven babies were discharged healthy. Jonathan Knight, ...


5

This "undifferentiation" is actually possible and it is known as induced pluripotent stem cell (iPSC). The first "undifferentiation" cells i.e. iPSCs were mouse fibroblasts created in 2006 by researchers in Shina Yamanaka's lab who got the Nobel prize in 2012 for this work. You can find further reading on this topic on the according Wikipedia-Page or more ...


5

Resemblance between parent and offspring is certainly true. Some traits are more obvious than others, for example skin colour would be very obvious. As babies mature they will gradually begin to look more and more like their parents, the features of babies often change rapidly, for example pretty much every baby has a little nose, but by the time they are a ...


4

The problem you are looking for is called the "Nature vs nurture" debate. Lots of scientists have written lots of books and papers and done lots of studies on the subject. As you can see, the title of the debate already includes the two main concerning factors: nature (genes) and nurture (environment). These of course each include a variety of ways in which ...


4

This is a very general question. The "developmental sequences" are just genes like any other. Like all genes they are semi-randomly distributed through the genome. While there are gene-rich and gene-poor areas in the genome, with some exceptions --notably the homeobox genes--, genes are not grouped by function. As to how they are accessed sequentially, that ...


4

Wikipedia has a page listing cell types which classifies their origin as endodermal or ectodermal. I haven't been able to find a source for a complete lineage of all cell types, and I have gained the impression that there is no complete picture, except in some specific cases such as the haemopoietic lineage. Here is a TEDX talk by a researcher in the ...


4

Physalia and Siphonophorans in general are multicellular Metazoans. But the whole discussion is about modularity on the level of individuals: Siphonophorans are colonial organisms, which means they are composed of multiple individual polyps and medusae. This is in fact quite common among Hydrozoa, but in Siphonophora the degree of integrity and function ...


4

Not all cat predatory behavior is innate. Researchers found that cats predatory behavior for birds vs. mice depends to a significant degree on training by the mother: if the mother taught predatory behavior with birds, the kittens grew up to be better at catching birds than at catching mice and vice versa. Supportive data shows that aside from monkeys and ...


4

Indeed a very good question. I'm afraid it might remain without a proper anatomy-based answer, but my intuition would tend towards agreeing with "the smaller you get, the more deviation you'll find". Or rather, I would expect the same principle as in conservation of genetic patterns to apply here: the more central a tissue structure is to survival, i.e. the ...



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