what are the 3 condtions that must be true for natural selection to occur?
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Please take the time to\nvote for the best answer\n\nThank You!!\n\nI know this is for take yr pick\n\nConditions for natural selection\n\nThe excess fecundity, and consequent competition to survive, in every species provides the precondition for the process Darwin called natural selection. Natural selection is easiest to understand as a logical argument, leading from premises to conclusion. The argument requires the four conditions listed below.\n\n1. Reproduction. Entities must reproduce to form a new generation.\n\n2. Heredity. The offspring must tend to resemble their parents: roughly speaking, 'like must produce like'. This condition is provided by Mendelian inheritance.\n\n3. Variation in characteristics of the members of the population. \n\n4. Variation in the fitness of organisms associated with these characteristics. \n\nProvided these conditions are met for any property of a species, natural selection automatically results, as in the case of the peppered moth. If any are not, it does not. Thus entities, like planets, that do not reproduce cannot evolve by natural selection. But when the four conditions apply, the organisms with the property conferring higher fitness will leave more offspring, and the frequency of that type of organism will increase in the population. \n\nThe biologist Richard Dawkins argues that there is possibly only one condition for natural selection.
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By eliminating weak individuals in the prey population and causing natural selection to play its role in population genetics.  \n\nI knows its a vague answer but  I can't remember all the fancy terminology in population ecology.
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It's not "by chance," it's the result of natural selection and other selective pressures.  I'm sorry if evolution doesn't make sense to you, but the basic principles are effectively proven fact, and it makes sense to anyone who's every actually studied it.  It makes just as much sense as it did to say the Earth is round and revolves around the sun.  People had a really hard time accepting those facts because if you look out your window they Earth looks flat, and if you watch the sun move across the sky it looks like it's moving around us rather than the other way round.  Without having seen the scientific evidence to support these claims, people thought they didn't make sense, so they rejected them.  Now people are doing the same thing with evolution.  Of course it doesn't make sense if you don't understand it, but that doesn't mean it isn't true.  Or should we also reject quantum mechanics, atomic theory, the physical nature of an electron, and Einsteins theory of relativity.\n\nEvolution is a scientific theory that explains the origin of the diversity of species (note that it does not, and is not intended to explain the origin of life). The basic idea of evolution is that mutations result in genetic diversity in a population, and consequently different traits, and different selective pressures favor certain traits over others. In a diverse population, some individuals are better suited to the environment than others, and the individuals that are better suited are more likely to survive to reproduce and thus pass their genes on to the next generation. Consequently, the next generation will have more of the "good" genes and fewer of the "bad" genes than the generation before it. Because the environment is constantly changing, the definition of "good" and "bad" genes is also constantly changing. Something that used to be an advantage can become a disadvantage, and vice versa. More often, however, neutral traits will become either good or bad. Changes in environment can include not only changes in weather or resources, but also competition from other species.\n\nAs the environmental pressures change, the population of organisms changes with it. Over time, the little changes start to add up, and eventually the population will be so different from the ancestral state that it will be considered a different species. The diversity of species results from splitting of populations. If a population is separated by some geographical or reproductive barrier, the two subpopulations will likely evolve in different ways, to become two separate species. Eventually the two species may be reunited, but they will no longer be able to interbreed. Instead, they will compete with each other, and likely diverge even more.\n\nScience is not about finding a single piece of evidence to conclusively prove a theory. It's about constructing theories to fit the existing evidence and gathering new evidence that supports or refutes existing theories. Evolution is supported by a preponderance of evidence. While no one point conclusively proves it, when all the evidence is considered in the context of existing scientific knowledge evolution is a well substantiated theory. Intelligent design is not.  What follows are brief explanations of some of the evidence that supports the theory of evolution.\n\n1. Vestigial structures\n\nOne example of a vestigial structure in humans is the appendix. It has no function. Removing it is harmful only in so far as any surgery is associated with certain risks (so I wouldn't have it removed just for fun, but it's because of the surgery not the absence of the appendix). An appendix is found in several mammals. In humans it is small and has no known function. In rabbits and many other herbivores it is large and is used in the digestion of cellulose.\n\nAnother example of a vestigial structure is the hipbones of snakes. Snakes
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To become "selected against" the individual organism must die before it is able to reproduce. If it manages to reproduce, it will escape natural selection and perpetuate its DNA. Hence, not only the strongest survive. Only the very weakest and unfeasible of organisms die out.
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Genetic code,teeth, hair, claws, brains. reproduction: color, smell, size, shape, power.Good Luck!
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Hi. First off, its "deScent with modification".\nThat was Darwin's term for what is now known as genetic variability in a population, and a stage of his proposed evolutionary mechanism, natural selection.\nHe did not have the genetic background to explain the variations that he saw generation after generation (Mendel's works had been ignored at the time), but he noticed that in every new generation, the individuals showed varied characteristics: some traits where similar to their parents, but others were novel or maybe similar to those of older ancestors. \nThese variations occur because of 1) spontaneous mutations in the parental gametes; 2) recombination between homologous chromosomes during gamete formation (crossing over); 3) the combination of the parents' genotypes to form the genotype of the offspring (this is not strictly new material, only a new combination of preexisting ones).\n\nOnce there is a new generation of individuals that are growing and living together, some of those characteristics may result in better adjustment to the environment. The individuals with those "adaptively advantageous" traits will have higher probabilities of growing, maturing and reproducing more, with respect to other individuals. \nIf those advantageous characteristics are heritable, that is, if they are determined by the individual's combination of alleles (=the two versions of the same gene in each of us), when the individual is able to "pass them on" to more descendants those alleles will spread in the population, and eventually be present in most individuals. This, in a nutshell, is natural selection. NS leads to gradual adjustment of the population with respect to its environment.\nFrom a population genetics perspective, evolution is defined as _the change in allele frequencies_; thus, "descent with modification", coupled with evolutionary factors, leads to evolution of the population. \nIn addition to mutation and natural selection, this change in allele frequencies may be occasioned by migration (genetic flux among different populations), genetic drift (a random process) and selective mating (which strictly speaking only alters the proportion of combinations, but does not produce new material).\n\nSorry for the lengthy answer, but evolutionary processes need a little context to be understood. Good luck with your explanation!
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Natural Selection is a process where the weaker individuals are "culled out" and only the stronger ones survive.  A good example of this concerning bacteria is the overuse of antibiotics.  Eventually, the resilient individuals will survive antibiotic treatment and become resistant to that particular antibiotic.  Eventually, that population will grow enough and be untreatable with that particular treatment and another antibiotic will have to be used.  Some speculate (myself included) that this is how Bird Flu was created except on a viral level instead of bacterial.  In summary, new environment (heat, cold, antibiotics, etc.) weaker bacteria die off, strong ones survive and propagate and therefore, live on. . . thus adaptation.  Hope this helps.
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Natural selection involves mechanisms such as competition or predation to kill off some members of a species, allowing members that have certain genetic traits that make them stronger or better-suited for survival, and those traits will be passed on to future generations of that species.
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1. The trait must be genetic.\n\n2. There needs to be variation within the gene between different individuals (e.g. two or more alleles for a single gene).\n\n3. There needs to be differing fitness between alleles (e.g. one allele gives a reproductive advantage over another).
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Good question. \nAny candidate for a pre-biotic existence should have possessed the characteristics that make evolution possible, that is: \n- genetic information (heritable instructions)\n- ability to replicate and carry out those instructions\n- replication with some random variation (so that new traits could appear)\n\nThe "prebiotic RNA world" is one possible theory.\nThis hypothesis was independently proposed by Carl Woese,  Francis Crick, and Leslie Orgel. If you're interested go to the link, it's clear and well explained.
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Here's a little known fact - the theory of natural selection - very few on YA can describe it correctly yet it's very simple:\nThere are just 3 assumptions:\n\n1. Individual members of a species are not always exactly alike. A population of similar organisms displays variability.\n\n2. Organisms possess some mechanism by which offspring tend to be like their parents. That is, individual traits are heritable.\n\n3. Totally unrestricted breeding doesn't happen. No population can reproduce forever without limit. So clearly there must be some force at work to reduce populations.\n\nFrom these assumptions Darwin concluded the theory of natural selection - some of the variations between individuals are inherited by their offspring, and, in a world where not everyone can survive, some of these inherited characteristics give some individuals a better chance of survival.
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Darwin's Theory of Natural Selection, in a nutshell:\n\nThere are three observations about life\n1) Variation: Individuals of a species are not all identical.  \n2) Competition: More individuals are born than can possibly survive to reproduce.  \n3) Inheritance: Individuals pass on traits to their offspring.  \nGiven these three things, those individuals in a species that have traits that help them survive better and produce more offspring, will pass those very traits on to those offspring.  So in this way, beneficial traits become more frequent a population, and produce an overall change in the species over time.  \n\nThat's it.\n\nAs for the creation of new species:  If two subpopulations of a species get separated for long enough, then they will change in separate directions, and will eventually lose the ability to interbreed, resulting in (now) two separate species that will continue to change (evolve) in different directions.\n\nThe catchphrase "survival of the fittest" summarizes this idea ... but use it with caution.  It's not just about "surviving" but "surviving to reproduce."  For example, a peacock's tail doesn't really help him "survive" better ... in fact it probably makes him an easier prey for predators ... but it does attract the ladies.  So it makes those individuals with the flashiest tail more "fit" then their homelier cousins.\n\n-------------- A warning about 'tiffany g's answer ---------------\n\nBe careful with answers like 'tiffany g' who copy-paste web pages instead of giving you a link to them, and without giving you the source, so you can check it out.  She is copying from the web-site allaboutscience.org, a thinly disguised Christian/Creationist site.  \n\nMy objection is not with people presenting the Creationist side ... but rather the attempt to hide that fact.  For example, it is deliberately misleading for a site to call itself "allaboutscience.org" when it does not address science topics in general, but only topics like the Big Bang, Evolution, and evidence for the existence of Jesus.  (Watch out for "allaboutphilosophy.org" as well.)\n\nAs a glaring example of intellectual dishonesty, the citation/page finishes with Darwin's famous quote about the eye ... famous because it is always quoted out of context and omits Darwin's very next sentence.  Darwin did indeed write that the evolution of the eye "seems, I freely confess, absurd in the highest degree."  (Note the word "seems".)  But then Darwin continues ... "Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real."  (See second source, Darwin, Ch. 6.)\n\nIn other words, Darwin immediately refutes the "irreducible complexity" argument, by pointing out that all we need to do is show that the eye can come about through small, incremental changes that each confers a small advantage, no matter how small.  Every single case of "irreducible complexity" yet offered by Creationists has always been shown (usually quite easily) to be fully "reducible."\n\nCreationists love to quote out-of-context from Darwin's Chapter 6, because this is the chapter where Darwin considers possible objections or "difficulties" with the theory, and then refutes them. The Creationists love to quote Darwin's own-words description of the "difficulty", but then omit his
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1) Genetic variation among members of a population\n2) Inheritance of characteristics (or variations)\n3) Natural selection (survival of the fittest)\n4) Time
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Which god or goddess or that matter...\n\nNo, natural selection is just the norm of nature...
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The process of adaptation cannot be appreciated in a single organism, but only in a population. This is because adaptation is a RELATIVE condition, that is, relative with respect to a particular environment, and with respect to other individuals/species. \nNatural selection acts on the variation that arises naturally and randomly in each generation of individuals, so that those individuals best adapted to the extant environmental conditions leave more offspring which, presumably, will inherit these characteristics (assuming they're at least partly hereditary). Thus those "more adaptive" traits will spread in the population, and the population as a whole will be better adapted. \nHowever, as environmental conditions vary, some traits that were "better" may become "worse", and the population will evolve in a different direction.. or become extinct.\nThe changes in individuals that occur during their lifetime are _not_ adaptation, but a different phenomenon called ACCLIMATION.
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evolution is a slow moving process. too slow to observe within a lifespan or possibly even a few generations. it could take tens or hundreds of thousands of years for it to happen.
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The idea of evolution was not started by Darwin ... it actually goes back to the Greeks.  What Darwin's theory of natural selection did was provide the *mechanism* by which evolution occurred.\n\nIt consists of three basic observations:\n(1) Variation: All individuals within a species are NOT identical.  They vary in many different ways ... some are shorter, some taller.  Some are faster, some slower.  Some are hairier, some less hairy. etc.\n(2) Competition:  More offspring are born than can possibly survive to propagate.  If this were not true, then the world would be overwhelmed with overpopulation (of all species) within a few years.  This means that some will survive to pass on their genes, others will not.\n(3) Inheritance:  Every individual passes characteristics on to its offspring.  (Darwin did not know the mechanism for this inheritance ... what we now call "genetics", but it was clear that the offspring of a hairy individual, had a better chance of being hairy itself.)\n\nPutting these three things together, we realize that any characteristic, that is part of normal variation, that produces a slight advantage, will tend to get passed on through inheritance into offspring.  Therefore, advantageous characteristics will get passed on more within a species.\n\nOne important thing that a lot of people miss when you hear "survival of the fittest" ... it's not just survival ... it is SURVIVAL TO PROCREATE.  I.e. it doesn't matter if you survive if you don't have offspring.  E.g., a peacock's feathers don't help it survive, but it helps it to procreate (it attracts the ladies), and that is all that matters.\n\nAgain, the idea of *evolution* ... that organisms change over time ... is much bigger than the theory of natural selection.  Darwin's theory merely provides the missing piece of information of HOW that change occurs.