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Short answer Yes, men and women's brains are different before birth. Background First off, learning effects versus genetic differences is the familiar nature versus nurture issue. Several genes on the Y-chromosome, unique to males, are expressed in the pre-natal brain. In fact, about a third of the genes on the Y-chromosome are expressed in the male ...


70

The three "holes" are the result of the 3 carpels in coconut flowers, and three carpels is typical of the family Arecaceae (Palms). The "holes" are actually germination pores, where one is usually functional and the other two are plugged. The new coconunt shoot will emerge from the functional, open, germination pore. For further info and pictures, see this ...


68

If you compare placental mammals in how much time they need to start walking, you'll see that deer are no exception. Humans are an exception. Hypothesis of Obstetrical Dilemma The hypothesis of Obstetrical Dilemma states that humans are born premature. We very much think this is because if we were to be born more developed (like other mammals), our big ...


59

The question is relatively broad and one should take into account that the brain not only consists of neurons, but also glial cells (supportive cells) and pre-mitotic neuronal stem cells. Furthermore, as critical fellow-scientists have indicated, developmental stage is very important, as the developing embryonic brain is very different from the adult brain. ...


39

According to Cornell's All About Birds website, you will have to wait about a month for the nest to be cleared. The egg incubation period is 12–14 days. Following hatching, the nestlings will remain in the nest for another 13 days (i.e., the "nestling period" is 13 days). However, there are two caveats to this: A typical robin clutch size (i.e. the # of ...


35

Deer are hardly unique in this, The young of horses, cows, and I suspect most grazing species are able to walk soon after birth. The reason, of course, is evolutionary: flight is the species mechanism for avoiding predators, so if they weren't able to flee, they would become lunch for some predator. Other species have gone down an evolutionary route of ...


25

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 ...


20

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 ...


19

Summary: The idea that primary sexual determination defaults to female was proposed several decades ago and is primarily based on the observation that, in the absence of Sry, ovarian development takes hold. However, more recent models suggest that both ovary and testis development require complex genetic regulation and neither can really be said to occur by ...


17

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 ...


14

In utero, the growing little human is getting ready to be an independently functioning individual. While it is everything but that, it must be able to obtain fluids and nutrients through its mother's milk, and that from pretty much the first hour of its life. To develop proper kidney function, the growing fetus needs to ingest fluids just as it will do post ...


12

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 ...


12

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, ...


12

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 ...


11

To add to Christiaan's answer, I'll mention one striking example of long-distance neuronal migration in the adult mammalian brain: the so-called Rostral Migratory Stream found in rodents, in rabbits and both the squirrel and rhesus monkey. Neuronal precursors originating in the subventricular zone (SVZ) of the brain migrate to reach the main olfactory bulb ...


10

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 ...


10

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 ...


9

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 ...


9

That you use the word "learn" in your question leads me to think that you're under a common misconception that people have about biology. It can seem self-evident to us that certain skills, for animals or humans, are necessarily "learned", but often, this isn't the case. The first thing to note, there are a number of things that humans can learn, which they ...


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

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 ...


8

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 ...


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 E....


8

Q: We know neurons can organize into very complex networks, but how? The answer is your first guess: Neurons find other target neurons with specific chemical signals. Q: What are the names of said mechanisms? This process is called axon guidance, by which the growth cones of developing axons are directed to reach their targets. This process depends upon a ...


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

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 ...


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

The first differentiation in human embryogenesis is from early blastomeres into trophoblast, which forms the outer layer of the blastocyst, and inner cell mass (ICM). It may be unsurprising then that cells on the inside of the 8-16 cell stage morula differentiate into ICM whereas those on the outside differentiate into trophoblast. However it is currently ...


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