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We don't know, and we never will. Science doesn't work that way. But evolution is the simplest hypothesis that is both falsifiable and consistent with lots of experimental data. Therefore it is the currently accepted scientific theory. I would agree that genetic similarities between current species does not in itself suggest that they evolved from a common ...


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Introduction Welcome to Biology.SE. Please see my comment for issues relating the form of your question. Below my answers are very short as it would take too long to give complete answer. I just redirect you toward a source of information. Questions Having said that, you do realize that the reason why you grow old is because of mutations, right? No, ...


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Although you don't mention it in your question, I guess you'd like examples of extinction in (more or less) constant environment? Then I guess you'd like cases of extinction due to the introduction of an overseas species out-competing the original one. Red squirrel is not extinct yet, but its sharp population decrease is mostly linked with competition with ...


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The first part of the question is interesting. Does an increased reproduction/mortality rate provide an evolutionary advantage? The concept of evolutionary advantage for a species needs to be used with much cautious as different definition of evolutionary advantage may exist. You should typically have a look at game theory beforehand to understand the ...


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As anongoodnurse has mentioned in the comments, an incomplete course can allow weakly resistant stains to expand their population. As you mentioned, the antibiotic does not cause the bacteria to mutate but it kills all strains that do not carry the mutation that provides the resistance. This mutation arises randomly (in certain cases it can be acquired by ...


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The concept that you hint at, has been studied at the example of the island of Australia, where marsupials often look quite similar as their counterparts in the same ecological niche, which live outside Australia and have a placenta, and are less related on the DNA level (e.g.: squirrel-like animals, wolf-like, and the now everywhere extinct saber-toothed ...


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Temperature affect pretty much all metabolic pathways. There are incentive in fishes as well to control their internal temperature. Control of Body temperature can be categorize along two axes, one concerning the source of heat and the other the magnitude of temperature variation. Please have a look at this post to understand the terms endo-, exo-, poikilo-,...


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A large part of the body of your question seems relatively unrelated to the main question which is a little confusing. I will focus on the question Is it possible for there to be a random un-mutation of genes? Yes, these are usually called reversed mutation. It is quite common though that a second mutation at a distinct locus may reverse the phenotypic ...


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It is vanishingly unlikely that when DNA sequences which are thousands and thousands of bases long are identical between two creatures, that those sequences have no common origin. That's like saying, "Your Honor, I didn't pirate that Justin Bieber track; I generated random 16 bit audio samples which just happen to match!" That is less likely than the ...


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I'm not an expert in this topic but I have read a reasonable amount on animal thermal regulation, especially in insects, so maybe I can give some insight into your question. First of all, an important thing I learned is that one must differentiate poikilotherms from homeotherms and endotherms from ectotherms. According to Randall et al (1997): Endotherms ...


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Cold/warm blooded are misleading categories The terms cold blooded and warm blooded is very misleading as it gives one the sensation that animals may warm up their internal temperature for the only reason of warming it up. The terms homeo-, poikilo-, exo- and endo- terms are much more useful in thinking about control of body temperature. Have a look at ...


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1) Reproduction is metabolically costly, so a high reproduction rate, such as that seen in fishes that lay thousands of eggs at a pop, is generally a strategy to compensate for a high mortality rate. On the other hand, bacteria, that can in some cases double every 20 minutes, have the advantage of rapidly evolving resistance to antimicrobial agents. 2) ...


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The main area-specific factors I can think of: Disease resistance. Local diseases put a lot of evolutionary pressure. So if your area is prone to some illness, you can expect higher immunity to it amongst the locals. For example, here on Earth most Africans are malaria-resistant (duffy negative), while most non-Africans are not. Food/water specific. If ...


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Many consider pubic hair to be a sort of protection or warmth, however this can only hold true for the vagina, since pubic hair doesn't offer any additional protective advantages to the male urethra. The most prevailing theory is that simply it is one of the odor producing parts of the body and humans (like most life forms in general) are simply aroused by ...


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First, the setting for this question is almost always related to explaining some aspect of broadly defined trait differences in extant (currently-living) species. The specific problem at hand is one in which someone is trying to explain what may drive the observed differences among competitors. It is unclear whether such differences are relatively recent (...


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The issue of IBD and IBS can indeed be confusing. The identity by state definition refers to the fact that at some point two individuals, even if they are not related to each other, present the same allele at a specific locus. Because of their un-relatedness this similarity probably arose from a similar mutational event. On the other side, with IBD two ...


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As I understand the main purpose of the gallbladder is to ensure the full digestion fatty or otherwise difficult or complex foods to digest in support of the liver. Both rats and mice breastfeed for about the same amount of time 4-5 weeks. Rats typically have a longer life cycle than mice. But there are more specific reasons why some mammals don't have or ...



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