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22

1. Sheep are fearless 2. English common names are misleading when it comes to the genetic differences between goats and sheep You posted a picture of Mountain Goats (Oreamnos americanus), which are a different genus than Domestic Goats (Capra aegagrus). Both Capra and Oreamnos are members of the Subfamily Caprinae, as are Domestic Sheep (Ovis aries). ...


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 ...


12

For humans, our blood and other tissues have a salinity which is less than that of sea water. There is an old chestnut that our blood has a comparable salinity to sea water - its just a classic example of textbook error. The major reason we need to drink and excrete (sweat, breath and urine) water is to rid the system of waste- i.e. water soluble chemicals ...


8

You should also bear in mind that the fact that they are great climbers does not make them fearless. For example, if I were to find myself floating 500 meters above the ground, I would be terrified. The fact that birds do not appear to be scared in the same situation does not make them fearless, it just makes them fliers. Similarly, I am sure a fish would ...


8

Among the great apes, chimpanzees and gorillas live in very hierarchical, male-dominated clans that are often in violent conflict with other clans. Bonobos, on the other hand, lead very peaceful lives, and are female-dominated, using sexual contact as a manner of communication to reduce tension within and between groups. Orangutans are largely solitary ...


7

At the very least, I know that male primates also have nipples like female, though they are very close relatives to human. On the other hand, in some of my dissection labs, I noticed that male pigs also have nipples just like the female ones. It seems to be the case that most male mammals have nipples, which probably has to do with mammals being ...


7

In mammals there are only two species (known, there may well be others) where males lactate. They are both species of bats and this paper discusses the evolutionary mechanisms that could underlie male lactation. I have ignored human cases because they are more of an unusual occurrence (often brought on by severe dietary stress) rather than an evolved ...


7

Well, technically yes, but most adult dolphins do not have hair: Unlike most mammals, dolphins do not have hair, except for a few hairs around the tip of their rostrum (beak) which they lose shortly before or after birth. The only exception to this is the Boto river dolphin, which has persistent small hairs on the rostrum. Whales do, and depending on ...


6

It sounds pretty much like a fox squirrel (or better: as masked face fox squirrel which are found in Alabama). They look like this (taken from this website): There seems to be quite some variation in terms of fur color, some animals are more greyish: Taken from here, this website also contains some additional information.


5

The number of mammary glands a species has is related to litter size. The relationship generally follows the "one-half rule," which states that the average litter size is equal to half the number of mammaries. The number of mammaries also tends to put an upper limit on litter size. It's not necessarily a hard limit, but survival tends to drop noticeably when ...


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 ...


4

I'm wondering if it is safe to assume that the approximate number of cells per unit mass in a mammal will remain fairly constant throughout its lifespan. Not exactly. When a tissue is put under stress, it can respond in four main ways: Hypertrophy - individual cells get larger. E.g. stressed muscle cells get bigger. Atrophy - invidivual cells get ...


4

For what concerns amino acids, mice rapidly reject meals that are not balanced in essential amino acids and continue to look for other kind of foods. This behavior is called aversion response and it is an adaptive phenomena that can be observed already 20 minutes after exposure to the unbalanced food. The mechanism involves brain sensing of uncharged tRNAs. ...


4

From Wikipedia: Sloths go to the ground to urinate and defecate about once a week, digging a hole and covering it afterwards. They go to the same spot each time and are vulnerable to predation while doing so. The reason for this risky behaviour is unknown, although some believe that it is to avoid making noise while defecating from up high that would ...


4

GULO encodes L-gulonolactone oxidase which catalyses a step in the biosynthetic pathway to ascorbic acid (vitamin C). I did a BLAST search at NCBI using the mouse GULO protein as probe, excluding mammals, and I saw highly significant hits in reptiles, birds, sea urchins, fungi and bacteria. I conclude that this enzyme, (or very close relatives) is ...


4

Until someone has a better method to determine this, and I'm willing to go with idea of that this question is not answerable, I put forward the two likely forms of selection criteria: Which mammal has the highest percentage of keratin in it's body for the highest density, and which has the highest percentage of gas (over the day) for the lowest. I also ...


3

These poisons prevent recirculation of vitamin K and thus formation of prothrombin which is essential for coagulation of blood and are required for maintaining the integrity of capillaries. The depletion of vitamin K is slow and in a couple of days internal hemorrhage occurs extensively and the animal dies of shock. Early recognition of poisoning in humans ...


3

Cats, dogs and bears all belong to the Carnivora clade of mammals, but they are not the only ones belonging to this clade. For instance, cats are more closely related to mongoose and hyenas than to dogs or bears, who in turn are more closely related to raccoons, weasels, and walruses. Their common ancestors likely displayed various adaptations to a ...


3

Most mammalian males have nipples. The duck-billed platypus does not have nipples but you begin to see development of nipples in marsupials (Park and Lindberg 2004) like the opossum and kangaroo. Development of a complete nipple begins in the eutherian (placental) mammals. The mammary glands develop early in the embryo along a pair of ridges called the ...


3

Bats distinguish day and night the same way that other animals do, with an internal circadian clock and by environmental cues (dawn and dusk). Most bats (over 1000 different species total) are nocturnal, meaning that they are out of their roost and foraging at night. This includes that vast majority of bats, which also echolocate. Some bats, notably ...


3

As it happens someone has just published a theory about this. To save you following the link, I reproduce the abstract below. I must admit that I had never realised that lactose is synthesised within the organelles of the secretory pathway (β4-galactosyltransferase is a Golgi enzyme and α-lactalbumin is, of course, a whey protein, so is in transit through ...


3

Whether using quantitative models, or "animal models", I think this is a useful quote to keep in mind: A model is a lie that helps you see the truth. -- Howard Skipper As for evidence that using mice models for human nutrition is justified -- I believe there has been a good deal of research that has provided useful insight on the influence of ...


3

There's an issue with what you mean when saying "cold blooded". The correct words you may want to use are homeotherm, poikilothermic, ectotherm, and endotherm. In short… Source of heat endo = inside exo = outside Variance in warmth Poikilo = varies homeo = does not vary Any combination of these two axes exist. For example: If the temperature ...


2

My impression is that the use of mice as human models for anything is primarily the result of historical precedent. A lot of work has been done to breed different lines of mice for particular purposes, and a lot of related methodology has therefore been established. Similarly, a lot of comparative genetic/genomic work has been done to characterize ...


2

This is not my field so I am sure there are other examples, but certain neurons will definitely be larger in adulthood than in infancy. There are motor neurons that connect the spine to, for example, the toes. These will grow in length as an animal grows. So, in a human infant they will be a few centimeters long and can reach lengths of over a meter in an ...


2

I think this would depend entirely on the diet of the host and donor mammal. Assuming they are of similar size and diet, I don't see any reason why this wouldn't work. The gut tends to absorb more or less everything in the food. If the diet of the two mammals differed significantly, I could see some problems with eating the correct foods. Herbivores with ...


2

You say "snout" but you might more specifically mean "muzzle" if you're focusing on the teeth aspect. Ram Manohar M hypothesizes some good reasons that make sense but for some other examples of snouts, here's a fun link that describes a few uses: Tapir: "nose and upper lip form a trunk he uses to grip, handy for grabbing and cleaning branches and plucking ...


2

Obviously there is an evolutionary advantage for those animals which has a long snout/muzzle. That is why they are still around. For carnivores the canine is the most important tooth and it is positioned strategically at the front corners of the jaw. Canines are meant to pierce and is essential for holding on to the prey and preventing from escaping. They ...


2

I'd say that unihemispheric sleep and adaptations like it really are sleep - the brain activity on one side of the brain gives a characteristic sleep pattern. It certainly must satisfy the needs of an aquatic mammal like a dolphin or a whale since they have to be partially conscious to breathe by surfacing regularly. It does seem to affect the brain ...


2

UV rays cause damage is by thinning the walls of surface blood vessels, leading to bruising, bleeding, and the appearance of blood vessels through the skin. Longwave UV radiation (UV-A) accounts for up to 95% of the UV radiation that reaches the earth's surface. Although UV-A is less intense than UV-B, it is more prevalent and can penetrate deeper into the ...



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