What does this variation of natural selection consist of? How does variation arise and spread through populat.
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The variation, could be frankly anything, because it arises from mutations. It could be anything from a different shell colour for a beetle, to a different beak shape for a bird.\n\nHow does it spread? Well, through mating. Organisms mate, they produce offspring. Some will have the mutation. Others won't. The mutation will only take a hold in the population, if it gives the particular organisms that have it, an advantage. So, it doesn't so much as spread, as that it outlasts the other variations.\n\nOf course, even this description doesn't do it justice. I suggest you really, look into the below sources and remember that the Wikipedia article is open to vandalism by Creationists and IDers that don't know what they're talking about.
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The term comes from oldish genetics vocabulary and it refers to the most common allele (in terms of proportion) for a given gene in a population. \nBefore modern population genetics research, it was believed that most genes (and associated characteristics) usually had one "normal" form (that would be the wild-type allele, present in most individuals) and another "mutant" form (the least common one). \nNow we know that natural populations are polymorphic (have usually several alleles) for any given gene, and there may be one or more than one more frequent alleles.
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1. Changes in allelic frequencies over time\n2. Change in a lineage of populations between generations
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Back to the old debate... nature or nurture?\nI think both, and the issue is a very complex one.
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it depends on how long youre talking about. natural selection will 'select' the more fit individuals that are better suited to their environment. therefore if competition exists between individuals those better adapted to the environment will win, thus natural selection picks it.
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Heh heh. Clever question. I always like to see a lateral thinker. The answer lies in appreciating that adaptation occurs for the population, not the individual.\n\nAdaptation in the sense that you refer to in your question is a population process. Imagine we have a population of one hundred animals, 50 are fast and 50 are slow. The slow ones get eaten. The slow individuals don't adapt because they are dead, and the fast individuals don't adapt because they don't need to.\n\nBut the population has adapted. We started with a population consisting of even numbers of fast and slow animals. Now we have a population consisting of 100% fast animals. That is because all the slow animals are dead.\n\n\nAnd because it is the population that has adapted it doesn't matter whether maladapted individuals survive. All that matters is  that sufficiently adapted individuals survive and produce offspring.\n\nThis is precisely what happens in the real world. There was a time when jack rabbits as a population were much slower than they are today. As all the slow animals succumbed to coyotes only the fast animals survived to produce young. As a result the jack rabbit population became faster and faster with every generation even though individuals rabbits were stuck with the genes they were born with.
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Mutation generates differences.  Most mutations are deleterious and natural selection tends to eliminate them quickly.  Many are neutral and are retained to some degree because there's nothing weeding them out.  A few are positive and variation is also lost in that case because selection will eliminate the other variations.\n\nThere is a process called frequency dependent selection whereby a trait is advantageous but only if its rare.  For example since hosts adapt to a certain kind of parasite, it is advantageous for a parasite to have rare characteristics.  That way the host is unlikely to have seen that model before and the parasite is likely to be successful.  In that case selection actually favors a lot of versions in a species because as soon as anything become really numerous it becomes deleterious.
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Natural selection is a mechanism of evolution which involves the "interaction" with environment. The fitness of an organism to their environment depends on it's phenotype, not genotype, since genotype doesn't "interact" with environment.\n\nAs for example, black heterozygote moth which lives in a polluted area (black sky), have the same fitness as black homozygote moth at the same condition.They're harder to be noticed by their predator, hence have a better chance to survive compared to those white moths. \nBoth of the moths have different genotype, but since the two genotypes are translated into one same phenotypes, it doesn't affect their fitness.\n\nAnd as conclusion, natural selection only works on phenotypes, since only phenotypes that have direct "interaction" to the environment.
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it's called population control...fits right in with natural selection!
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Complexity; what displays variation with out being random. You, for instance. I have answered both questions with the one explanation. A pile of sand on a beach is not complex; it displays variation, but it is random variation. You are a non random collection of variation. I sure wish yahoo answers would split biology into evolutionary and functional; then questions like this would be noticed, sooner or better.
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Wikipedia has a good summary:\nhttp://en.wikipedia.org/wiki/Origin_of_species\n\nAn extract from this wikipedia page:\nDarwin's theory of evolution is based on five key observations and inferences drawn from them, as summarized by the biologist Ernst Mayr:\n\nSpecies have great fertility. They make more offspring than can grow to adulthood. \nPopulations remain roughly the same size, with modest fluctuations. \nFood resources are limited, but are relatively constant most of the time. From these three observations it may be inferred that in such an environment there will be a struggle for survival among individuals. \nIn sexually reproducing species, generally no two individuals are identical. Variation is rampant. \nMuch of this variation is heritable. \nFrom this Darwin infers: In a world of stable populations where each individual must struggle to survive, those with the "best" characteristics will be more likely to survive, and those desirable traits will be passed to their offspring; and that these advantageous characteristics are inherited by following generations, becoming dominant among the population through time. This is natural selection.\n\nDarwin did not suggest that every variation and every character must have a selection value. However, he pointed out that, because of our ignorance of animal physiology and its relationship with the environment, it was extremely rash to set down any characters as valueless to their owners. It is even more important to notice that he did not suggest that every individual with a favorable variation must be selected, or that the selected or favored animals were better or higher, but merely that they were more adapted to their surroundings.\n\nDarwin further infers that natural selection, if carried far enough, makes changes in a population, eventually leading to new species. He puts forward myriad observations as demonstrations of this, and also claims that the fossil record can be interpreted as supporting these observations. Darwin imagined it might be possible that all life is descended from an original species from ancient times. Modern DNA evidence is consistent with this idea.
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Your argument has some assumptions, assertions, and logic that are not sound.\n\nFirst of all, you only multiply probabilities together when they are independent variables - it would be easy to argue that many of the items that you mentioned are interdependent.\n\nAlso, I think you misunderstand what evolution of species is proposing.  Evolution does NOT depend on luck - it is instead an observation that lucky organisms survive and pass on their properties to their descendants.\n\nConsider bacteria - almost all mutations are harmful but a few bacteria have lucky mutations that make them immune to penicillin.  If penicillin is used on bacteria, only these lucky ones survive - and most of their descendants inherit the the same immunity-mutation.  \n\nThe original mutation is luck - the environment then selects and a small set of traits due to beneficial mutations persists.  And THAT is not luck, that is selection.  That's why the process is called "Natural Selection".  \n\nSadly, this is why almost all bacteria were zapped by the early antibiotics, and now (only 60 years later) we have hundreds of resistant strains.
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No scientist propounds a creation theoryt of\nevolution.  The creation theories, of which there are\nmany came from religions long befoe science\ndeveloped as a separate activity from philosophy\nand religion. \n\nIgnore the long-winded answer from smiling4ever2\nit is without merit.  Note that he says that evolution\n takes place by chance.  No scientist ever claimed\nthat evolution takes place by chance.  Natural\nselection is an ANTIchance mechanism.  The\nproduction of variation by mutation and recombination is often referred to as random, but it\nis clearly not completely dependent on random \nchance.  What is meant is that new variations are\nnot directed toward solutions of whatever problem\nthe population is facing.  If the environment is\ndrying up and new adaptations for water conservation are needed, the new variations that\nappear are just as likely to be detrimental to saving \nwater as to be beneficial for it, or to have nothing\nat all to do with water balance.  Those few that\ndo fit the organism to a drier climate will be favored\nby natural selection and the others will not.
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True, in fact observations that the offspring from parents of different species (where offspring are possible) are sterile was one of the key lines of evidence that lead Darwin to evolution by natural selection. ie. that once two populations of the same species become different enough, they can't interbreed thus stay separate.  \n\nIt is now established though, through many observations, that bacteria have and do pick up chunks of DNA from unrelated species of bacteria. A lot of their DNA is very mobile. I guess it depends on what you call 'kind'.
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An organism will have offspring, each will be different. The offspring with the "differences" that give it the best chance of survival, will tend to live, and pass those traits on to there offspring. That's it, that's all evolution is.
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Spatial variation.  Temporal variation leads to section of the best allele for adapting to a single environment.  Though the environment changes over time, there is still only one environment to drive selection.  However, spatial variation within an environment leads to multiple different micro-environments.  Each of these micro-environments will drive selection of alleles which are best for adapting to each micro-environment, not the environment as a whole.  So, several different alleles will be selected for at the same time within the environment, which is polymorphism.
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Organisms do not 'evolve' in response to changes in their environment in order to adapt to that change. Through a process called random mutation, mutant genes are constantly being produced in a small percentage of any given population. If there is no change to the environment, these mutant genes are generally less able to survive than their parent/s. However if there is a sudden or dramatic change, the mutant may be favored over the 'normal' population, because its mutant gene is compatible with the new conditions. This mutant gene now becomes the norm thus ensuring the survival of  its offspring who have inherited this gene.