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1

I believe that evolution is driven by the needs of the organism to adapt not by the need to adapt for human beings consumption. meaning that some nitrogen gets back to the soil through the effect of nature e.g. fixation of nitrogen during storms and when fecal matter decomposes in soil and these I assume provide enough nitrogen for normal plant growth and ...


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I think you're looking at this the wrong way. Animals evolve to fill niches. Many, many land animals returned to the water as a place to live, including: whales, dolphins, porpoises, seals, sea lions, walruses, manatees, dugongs, otters, hippos, pygmy hippos, crocodiles, sea snakes, sea turtles, river turtles, river snakes, etc. etc. etc. Their ...


1

That definition is problematic and incomplete. Absolute fitness can be used in different ways, and can be calculated at different levels of organisation (individuals, genes etc). However, absolute fitness always relate to actual growth rate, actual numbers of offspring or other measures of fitness (so an absolute measure), while relative fitness is ...


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Welcome to Biology.SE! Definition of Absolute Fitness Let's forget about the wikipedia definition for a little while. There exists different definitions of fitness. They vary only slightly and usually it does not really matter. Let's talk only about absolute fitness at first. Absolute fitness can be calculated for a genotype for a haplotype for an ...


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That definition in the wikipedia is misleading at best. Contrary to what it seems to suggest there, absolute fitness is computed across a single generation, not within a single generation. For simplicity, let's look at an example using asexual haploids with discrete non-overlapping generations. If individuals with the A genotype produce an average of 3 ...


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There is little neurological evidence that finds a difference between men and women. However there are psychological studies that do find a small difference in mental strengths. This interesting TED talk debunking pyscological myths by a lecturer from the University of Liverpool discusses the pyscological differences between men and women. Males and ...


2

That is an interesting question. But rises some line of thought by analogy, e.g. why people won't evolve to produce their own ATP without mitochondria? (I mean of course Eukaryotas in general). I don't see any reason why multicellular organism cannot incorporate bacterial functionality either as happened with mitochondria, or as just separate cell type, that ...


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The evidence shows that the tusk is innervated, and acts as a sensory organ to the outside environment, as well as a mating tool. Sensory ability in the narwhal tooth organ system


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This question has been asked before: Is there an advantage to linear chromosomes? Firstly, I should state that the generalisation that ALL prokaryotes have circular genomes is incorrect. A growing number of prokaryotes have been discovered which have linear chromosomes, such as Borrelia burgdorferi ,which causes Lyme disease, members of the Streptomyces ...


3

Preamble. There is a lot of misunderstood science here and you are more than right for questioning the lecturers interpretation of these energy values; something the other answers do not discuss. The problem arises from a dodgy reference and a lot of conjecture. In summary. Light and sound cannot be compared energetically in a biological context. Our ears ...


5

Welcome to Biology.SE! Your question is very broad. Also, your post has the default of containing severals questions in it. Make sure in the future to restrict your post to only question, it will be much more likely that you receive a good answer then. I hope that I can give some indications about how to get some more knowledge in this answer. In this ...


4

http://phylot.biobyte.de/ performs the requisite task (generating a phylogenetic tree based on the specific organisms provided, using the NCBI taxonomy tables). For example, the input of tree elements Trichomonas vaginalis,Trypanosoma brucei,Homo sapiens,Fibroporia radiculosa,Paramecium tetraurelia,Tetrahymena thermophila,Cryptosporidium ...


0

here is an interesting article: The accumulation of radioactive iodine by Amphioxus summarizing the abstract: it's about cephalocordates that are not vertebrate, so they are close relatives (most related to the ancestors of) the vertebrate. The specific cephalocordate in question is amphioxus.The article talks about a specific gland called the "endostyle" ...


3

Classical thyroid hormones implement a very flexible signaling mechanism. Basically, they comprise two aromatic rings that are connected via an oxygen atom. Optionally, they may contain organic side chains and inorganic iodine atoms. In the case of iodothyronines, which are represented e.g. by the well-known thyroid hormones T4, T3 and 3,5-T2, the side ...


10

A gene being dominant does not necessarily imply the gene is also common. An easy counterexample is Huntington's disease. The gene is dominant, and only one mutant allele of huntingtin would result in development of the disease. However, the allele prevalence of the mutant is low in the general population. In the absence of a selective advantage of green ...


1

This question can be tackled in several ways, and also seems to contain a couple of misconceptions about ecological processes (e.g. problematic group-selection ideas and how species 'fit' into the ecosystem). However, I think it is most usefully answered from the perspective of life history theory and the evolution of life histories (see e.g. Roff, 2002 and ...


3

The way you pose the question, as in what mechanisms limit the fertility of predators, together with your comment about the distinction to the population dynamic aspect, strongly that what you are thinking about an adaptional mechanism here and asking about its characteristics, right? In that case, this is very similar to the kind of scenarios you find in ...


1

Reading this website (www.sharks-world.com/shark_reproduction) it seems that for most sharks the eggs develop inside the mother (ovoviviparity), and the young sharks ("pups") are born fully functional, but this is not true for all sharks (as you mention in your question). This persons blog (morgana249/modern reptiles give birth to live young) discusses ...


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In a given area there can be only a limited number of top predators due to resource limitations. Furthermore, as top predators are not hunted upon, a relatively high percentage of offspring will survive until adulthood. Hence, producing many offspring doesn't make sense as survival rates are high, while resources are limited. Producing many offspring is a ...


2

The thunder chimp's answer summarized the answer very well. To try to pull things together a bit, if you have seven minutes, check out this video. It shows a man chasing down a kudu. They both run for 8 hours, until the kudu literally collapses and the man calmly walks up to it and slays it. The video shows the evolutionary adaptions that the man has - he ...


1

If your first question means: why is later-life ageing usually a long and painful process of degradation (rather than why do we have existential agony) with diseases of ageing like osteoporosis, heart disease, dementia - then I can offer one answer. There is an absence (almost) of any selection pressure after reproductive age. Once individuals are past ...


3

Sorry to spoil the fun here, but male nipples are not completely useless. With stimulation and hormones, they can be used to make milk. I don't have a great peer reviewed source for this, because it is sort of common knowledge. I heard about it at a Le Leche Leage meeting when my son was small. This question could even be considered culturally biased


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As already pointed it out, there is no scientific consensus on the answer to this question. This is because it is hard to test proposed explanations and it's likely that several factors interacted. All of these have been claimed to be the explanation for the evolution of bipedalism: Freed hands for increased tool use. (Encyclopedia Britannica) Freed hands ...



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