How does natural selection affect the population over time ?
407289
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.
1186604
One answer might be that they have gradually changed, or evolved,over a very long time to suit the places they live in and the food that is available to them.\n                 In the 19th centurya scientist named CHARLES DARWIN (1802-1882) put forward a theory, which he called 'natural selection'. to explain how these changes might happen.\n              According to darwon, individuals animals and plants sometimes have qualities that help them to survive.For example,in agreen forest, a green bug would pribably survive longer than a brown bug,because its appearence would help it to aviod being seen amd eaten.\n       The individuals that survive the longest are likely to have more babies,and will pass on their useful qualities to them.Over a very long time,each species will very gradually develop all the most useful qualities for surviving in its own habitat.
90708
Natural selection acts on all living organisms.  Every time a lion catches one zebra and another gets away, that's natural selection.  Every time a certain plant's seeds grow while another's don't, that's natural selection.  If the girl you like marries someone else, that's natural selection.  \n\nNatural selection is all about biological fitness (having positive traits).  The strong survive and reproduce.  The weak don't.  It's that simple.
328841
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.
23794
Evolution is a dynamic, ongoing process that can have direct, important impacts on human welfare. The evolution of insecticide resistance by pest species of insects and other arthropods provides a spectacular example.1 \n\nSince World War II, synthetic insecticides have been used to control insects and mites that cause immense crop losses, and by carrying malaria and other diseases, pose major threats to public health. However, many chemical control programs are failing or have failed altogether, because the pest species have evolved resistance. \nMore than 500 species have evolved resistance to at least one insecticide. Many pest species are now resistant to all, or almost all, of the available insecticides. Moveover, some species that had been uncommon have become serious pests, because insecticide use has extinguished their natural enemies. As insects have become more resistant, farmers have applied ever higher levels of insecticide to their crops, so that more than one billion pounds per year are now applied in the United States. Resistance has made it necessary to develop new insecticides, each at an average cost of 8 to 10 years and $20 to $40 million in research and development. Hence insect evolution has imposed a huge economic burden (about $118 million per year, just in the United States), and an increasing environmental burden of chemicals that can endanger human health and natural ecosystems. \nInsect resistance evolves rapidly because natural selection increases the rare mutations that are not advantageous under normal conditions, but happen to provide protection against harmful chemicals. Entomologists trained in evolutionary genetics have developed strategies for delaying the evolution of resistance. The most effective strategy, based both on evolutionary models and on evidence, is to provide the pest species with pesticide-free "refuges" in which susceptible genotypes can reproduce, thus preventing resistant genotypes from taking over. The intuitively appealing opposite strategy – trying to overwhelm the insect population with "saturation bombing" – simply hastens the evolution of resistance, because it increases the strength of natural selection. \nAlthough evolution of resistance can be delayed, it is probably inevitable in most cases. Thus modern pest management strategies combine pesticides with other tactics. For example, spider mites in almond orchards have been controlled by applying both a pesticide and predatory mites that had been selected for pesticide resistance in the laboratory. Crop varieties that are genetically resistant to certain insects have been developed both by traditional methods of selection and by genetic engineering. For instance, strains of several crops have been engineered to carry a bacterial gene for a protein (Bt-toxin) that is toxic to certain insects. Pest-resistant crop varieties have often been economically very profitable, but history has shown that if they are planted widely, the insect pest eventually evolves the capacity to attack them, so that it becomes necessary to develop new genetic strains that the pest is not yet adapted to. At least one pest species, the diamondback moth, has already adapted to Bt-toxin. Thus, the "arms race" between the insect evolution and human ingenuity presents a continuing challenge
272274
let's see...\nAccording to Darwin, natural selections is when species born with a trait that's slightly different from what they are supposed to be turn out to have a bigger advantage in life. Because it's successful, it breeds, and the trait is passed on to the next generation. Eventually, that trait dominates the species in a way that we identiy them as a new or different species. \nIn the case of hummingbirds, the flowers they feed on also evolve with the birds. As we all know, hummingbirds have prett long beaks. To 'protect' their nector (or something), flowers start to grow more in a 'tube' shape, which prevents species like bees to get the nector. In response, hummingbirds evolve by growing longer beaks so they can still get their food (drink?)
225222
Stabilizing selection. In the absence of pressures for species to change, the dominant pressure in natural selection is for the species to remain the same (this is largely because the vast majority of non-silent mutations are either neutral, or detrimental, for any given organism at any given time). This is because they have reached a local fitness maximum, and it takes a selection pressure to push them out of it.\n\nAs an analogy, think of a round-ish rock on the side of a steep mountain. Gravity forces the rock to roll downhill. But, imagine there is an upwards slope that the rock has to roll over to continue rolling downhill. If the rock's momentum (ie, the selection pressures on the organism) is not sufficient to roll it over the upslope (the local fitness maximum), then the rock will stay at that altitude (stabilizing selection).\n\nOkay, it's not an outstanding analogy, but it should get the idea across.\n\nOh, and to some of the other respondents, natural selection is NOT survival of the fittest; it's survival of the fit enough.
510995
Well, I don't think it would change much.  It's most significant contribution is  that it was the first formal study, observation and written explanation of the process of natural selection.  People had known about natural selection for centuries at least, but either didn't have the necessary scientific skills or inclination to write them in a book.  I guess Darwin had those skills and passion, and he gets credit for it.  He is often misunderstood as the person who "discovered" evolution, which is inaccurate.\n\nToday, natural selection and evolution are so obvious that I doubt many people even read that book any more.  (It's kind of boring and tedious.)
805249
Of course. It lead to genetic isolation, then evolution which gave us new species. Look at the ratities as an example.
310618
Theory of origin states that DNA can lead researchers to a specific date that the first of a species originally occured. Natural selection deals with the process by which random generation of attributes help one animal to survive and not another, thereby selecting on of the two to procreate. The two theories are not really related in a way that you can contrast them, as they deal with separate subjects, not arguing ones.
1147729
The answer is (1) selection and MUTATION because he realised that animals whose genes mutate and enable them to survive more succesfully:\n\n'Darwin concluded that species evolved over long periods due to what he called natural selection. There may be differences in the offspring of an organism. These differences are called mutations. We generally think of mutations as harmful, such as birth defects, but a mutation is simply an alteration of the genetic information of an organism. Some mutations are good. A child might be taller or stronger than his or her parents. \n\nDarwin’s theory suggested that organisms evolved to fit their environment based on natural selection. If a mutation was good, the organism lived and contributed the mutation to the gene pool of its offspring. If the mutation was bad, the organism was more likely to die before contributing to the gene pool. Over billions of years, these mutations slowly produced the world we know today. '\n\nHope this helps!
639448
thousands....changing always due to evolution
304671
It is very questionable that humans are evolving, at least in terms of largescale selections.  Where we are today with technology, rather than nature selecting the most fit of us, oftentimes we alter nature to allow everyone to live.  This obviously isnt true in all cases, but we are at least tampering and slowing down human evolution
342488
I think what you are referring to is "natural selection" aka "survival of the fittest"\n\nBasically the animal most suited to its environment due to mutation (the ones with genetic proclivity to have longer necks, stronger arms etc) will get more food/mates and will tend to, over a long period, tend to make the species move in that direction.\n\nBasic answer - if you need more drop me a line.
81667
Evolution is the gradual change in a group of organisms based on surroundings and circumstances that make one population more favorable. Since we do not know what future events might select for homo sapiens, we cannot predict how they will evolve. For example, if we had a full out nuclear war, perhaps a small group of humans would survive that were very tolerant to radiation. There is no way to know. That being said, humans have somewhat overcome evolution because of our advanced medicine- we can let people live who would otherwise be selected against, like people with debilating diseases.
849658
It's a gradual process, you'd never notice it.  It generally works like this: attractive people with talents that make money provide the resources for their children to be likewise successful.  These people are less likely to die than most people (better healthcare, less violent neighborhoods, etc.) and as such pass on their traits more readily.  It's an everyday process.\n\nThe modern trend in evolution is a focus away from disease resistance.  Once diseases would often kill people before they would have children, and so those that did have children would be on average 'healthier'.  In the advanced world today (Japan, western Europe, the US, etc.) this is less of an issue, so people with favorable traits in other respects but less 'genetic health' are more likely to pass on their genes.
1116290
DNA changes over a long period of time by different factors such as the temperature. For example, During the ice age, the organisms have tough skin, heavy fur to keep their body temperature warm. Then the earth warmed up so the these organisms no longer need the heavy fur to keep warm. Their children's children began to evolve to have less fur in order to not die of heat. The organism changes when its surroundings/environment change. Evolution is needed for the organisms to adapt and survive to the current living conditions presented upon them.