Why is evolutions primary mechanism mutation ?

You don't need some other force to evolve into mutation. Mutations happened from the beginning, as a result of imperfect reproduction. When something mutates, however, it usually doesn't affect the organism so much that it must figure out a radically new way to reproduce. If the change is so great that it prevents the new organism from reproducing, then it will not be passed on to any offspring.As an analogy, consider the ways in which languages change over time. English has changed greatly over the centuries. At no time in history, however, did anyone suddenly start speaking the English of 400 years in the future. Rather, the small changes built up over time, until certain dialects became so divergent from one another as to be nearly incomprehensible. Similarly, life can evolve, splitting up into new populations, and each population mutates in a different way, until you have radically different forms of life that descended from a common ancestor.

If one mutant dies, it may very well be a billion years before another similar mutation occurs. However, the rest of the population in which the mutant lives might not die. For example, if there is a population of black mice, and a mutation arises, causing the birth of a white mouse, the white mouse may stand out and be eaten by a predator. Likewise, the white mouse might blend in better with snow, and so it won't get eaten while most of the other mice do. In the second case, the white mouse might pass on its special new allele, providing it can find a mate that wasn't eaten after the snowstorm. The mate doesn't neccessarily have to have white hair, that is, it doesn't have to have the exact same mutation.In plants, however, sometimes hybridization can result in a new species that can't reproduce with either of its parent species. The population consists of a lone individual. In this case, the new plant may be able to breed with itself, reproducing asexually, as many plants do. Then it might reproduce sexually with its offspring, producing a bigger population. Long ago, when sex was first arising, it is likely that the first sexual organisms, some sort of single celled critters, were also able to reproduce both sexually and asexually. There might not have been a specified male or female either, in much the same way that there are hermaphroditic species today. Modern bacteria, including E. coli, are capable of a process called conjugation, in which genetic material is exchanged through cell-to-cell contact. Sexual reproduction may have had its origins with a similar process.The evolution of sex is not fully understood at this time. There is still a lot to figure out, and it is an area of study that is still growing. Sexual reproduction is thought to confer an advantage, however, so we have an idea about why it stayed around once it came into being. Sexual species are able to adapt to changing conditions faster, especially in their ability to evolve resistance to parasites or poisonous chemicals.

It doesn't have to be a "positive mutation", and if the mutation is in the zygote, then it will end up in all the cells in the whole organism.I can see what you mean about the animals mutating things that they seem to already know how to use. Usually, however, the mutations are so small that animals don't need to learn anything new, and if they did, they would have dealt with their mutation since their birth so they would be used to it. As an example, look at dogs. There are all sorts of dogs, with huge variation in size and shape, so much so that if I had to compare, say, the skulls from a greyhound, a chihuahua, and a bulldog, I might think they belong to different species. All this variation is caused by mutations, and then people selected for traits that they liked. Despite all this variation, dogs don't have any anatomy that they don't know how to deal with.Here is another example of a mutation. These cats are members of the Scottish fold breed. Their ears are folded backwards due to a mutation in just one gene, and people think its cute so they bred lots of them. The mutation probably occured sometime around 1961, because that is the year in which the first cat with folded ears was discovered. This change isn't an incredibly large change, just enough to be noticeable, but it doesn't affect the cat in such a dramatic way that it prevents them from reproducing.

If you want to learn more about evolution, I recently read The Blind Watchmaker, by Richard Dawkins. It is fairly long, but very interesting, and much easier reading than many textbooks. Dawkins has amazing talent in writing and does an excellent job of explaining how natural selection works, arguing that the Darwinian version of evolution is the only theory that can acceptably explain life on Earth. The Blind Watchmaker was a national bestseller. He has written other books as well, but I haven't read any of them yet. You should look into reading something by him.

Yeah, I remember in high school, my biology teacher practically called me a creationist when I told her she was wrong and that modern humans didn't evolve from Neanderthals. They gave me a really cursory description of natural selection, and didn't spend much time on it at all. I realize that there is a limited amount of time in the school year, but I think that we should have spent more time on evolution and less on stuff that we will forget right after the test, like memorizing all the enzymes and chemicals in photosynthesis. I guess the teachers aren't allowed to make their own curricula though. Florida isn't famous for its stellar school system either.But getting back on topic, I think the reason your teacher said that is because the environment tends to "choose" certain individuals as more fit than others, where fitness is determined by the number of viable offspring the organism produces. She might have misunderstood something about natural selection. Mutations occur more or less randomly. They occur all the time. It isn't a rare thing at all. They are simply products of an imperfect copying system. All the errors lead to variation within a population. As time goes on, some individuals end up with the ability to produce more viable offspring than others. These individuals are said to be more "fit". They pass on their mutations and eventually the whole population is full of these "fit" genes.You mentioned in another post that this sounds like it would make animals all the same. There are a few factors that prevent this, but the most important one is the environment. The environment is always changing, so what may work today might not work tommorow. If an area is invaded by a new plant species that outcompetes some native plant, the way kudzu outcompetes practically everything, animals dependent on the native plant may have to adapt to eating the new plant. Any that can't eat it will just starve to death or get sick and die from that or get eaten by something that likes to eat sick herbivores.Imagine a petri dish with millions of bacteria living in it. If you add an antibiotic, the bacteria will die. However, if only one out of those millions of bacteria has a mutation that lets it survive with the antibiotic, then it will start its own colony and all its offspring will probably also be resistant to the antibiotic. You could also add only a small amount of the antibiotic. Maybe some bacteria can deal with a little bit, but others can't. Then you could keep breeding bacteria that are stronger and stronger, until the antibiotic is useless for killing bacteria. But if you picked out a new antibiotic it might kill them all off.This is a simple example of a changing environment. You started out with bacteria that aren't resistant, and you end up with resistant bacteria. So selection didn't determine what has to mutate, it just picked out a particular individual who got lucky and had mutated.

I was in the IB program, so we used Campbell's Biology, which I feel handles evolution extremely well. Evolution is a central theme, as it should be. Those books are expensive though, and schools are underfunded, so we couldn't bring them home, and so not much reading got done. Most of the course was based around what the teacher at the front of the class was talking about, or what the IB guide told us we should be studying. The way the course was set up encouraged us to write a page of BS and then show it to the teacher and then we could just socialize for the rest of the period.When I got to college, I took Biology 1, and we used the same book, except it was the sixth edition instead of the second, third and fourth. We did much more reading and I learned much more, but I didn't really give evolution a lot of my time until I started reading books like The Blind Watchmaker on my own time.I'm now majoring in biology, and I agree with Dobzhansky. In a vertebrate anatomy class I'm taking now, evolution explains the anatomy of a given animal far better than any other explanation.Campbell's Biology isn't meant to be a high school text though. Nowadays, many textbooks are written by teams of editors rather than experts, and these textbooks are meant to sell to as many schools as possible at $50 a pop, instead of conveying useful information. Because of this system, the books are rife with errors and they result in a school system that allows people to graduate high school without being able to read.

All the known laws do agree with the theory of evolution.A very common argument against evolution is that it violates the Second Law of Thermodynamics. This states that entropy (most simply, a measure of chaos) must increase in a closed system. Opponents of evolution either ignore "in a closed system" or they take Earth to be a closed system. It isn't. Earth is an open system, getting energy from the Sun. The Sun puts out a tremendous amount of energy, relative to the amount of biomass in existence. If the Earth was a closed system, everything on it would gradually die out in the cold darkness.

And then everything on Earth will die.Either that, or the sun will expand and swallow up the Earth, in which case everything will die.The Sun hasn't run out of fuel yet, I just checked. It's really bright right now.

Imagine an environment in which only one species existed. Wouldn't this environment have many empty niches? For example, if one individual from that lonely species died, his body would have to rot, so bacteria would be there. Also, some other species could scavenge the body, like vultures. Also, what would feed that first species? Maybe it could be carnivorous, in which case it would probably eat herbivores. And those herbivores would in turn have to eat plants.There could be parasites on everything too. And maybe something that eats the parasites, the way some fish let other fish clean them off. Maybe a carnivorous plant could eat some insects too, taking over a previously empty niche.What about dung? There could be insects that eat or lay eggs in all the animals' dung.Humans have E. coli bacteria in their large intestines, and they help us absorb Vitamin K. Maybe the animals we are talking about would have something similar.You can see where this is going. In what seems like an environment with one species, I expanded that to nine. There is room for plenty of diversity.

It seems like a contributing factor can be a primary mechanism at the same time. Natural selection can select for certain alleles or combinations of genes, while mutations provide the novelty and variety that natural selection can act upon. They are two parts to the same whole.I don't know any scientists who treat Darwin the same way Christians treat Jesus. No one I know has a What Would Darwin Do bumper sticker. If they did, that wouldn't be very scientific since Darwin got so many things wrong, even though he got natural selection right. Pangenesis, a model for heredity, comes to mind. It isn't used anymore because the evidence doesn't support it. Many, but not all, Christians are not so open minded about the Bible, and this is where creationism comes from.Scientists working in fields related to evolution are, however, very cognizant of the contributions made by Darwin as well as the modern version of his theory, which has been modified and improved significantly in the last 150 years as evidence accumulates. There is still a lot of work to be done in biology and many questions to answer, but right now it seems like we've got evolution right for the most part.What questions about evolution do you feel are not addressed properly?

It seems to me that you've been told that evolution has holes and flaws, but no one who told you about them went into much more detail. If the creationists made some observation that goes against our current understanding of evolution, then we don't simply look beyond that observation, as though it wasn't there, we modify the theory, assuming the evidence is reliable. Nowadays, such observations that go against the theory of evolution rarely, if ever, are reliable. It gets harder and harder to trust information from creationists when they deliberately falsify evidence or when they themselves ignore evidence against their own beliefs.

Did it recently become illegal to use simpler, more familiar subjects to explain more complicated ones?I've seen a few fossil bats in museums. They are very rare. The ones I've seen were surprisingly well preserved, but they looked pretty similar to modern bats. The explanation given for their rarity was that bats tend to live in places where fossilization is rare, and when a bat dies it almost invariably is eaten by something or rots quickly. I think that fossil bats are interesting enough that people are probably looking for them, so if they are looking in the right places they may find more fossils in the future, despite their rarity.I don't see why any of the intermediates between non-flying bat ancestors and modern bats would be at a disadvantage compared to animals unable to fly. Even though their forelimbs may become less useful on the ground, the advantage from gliding is great enough to offset this. Early gliders may not have had highly modified forelimbs anyway, they may have just had loose skin that can be stretched out into a surface to catch the air. There are plenty of gliding animals alive today that are not as well-adapted to flight as bats, so the intermediate may have been somewhat similar to flying squirrels alive today.Bats don't have to give up the use of their forelimbs on the ground entirely before they can fly. Vampire bats can walk or run on all fours. This is how they often approach their prey. Flying foxes have a claw that they can hook onto things with as well. I found this image on Wikipedia:

You make a good point in that words can jump from one language to another. It might be taking the analogy too far to think of that concept as hybridization. I hadn't thought of that one and I agree that the analogy isn't perfect, but the evolution of language still has very strong similarities to the evolution of living things.One language can split into two or more groups, as English was split between Great Britain and America. After centuries of separation, the two languages have very obvious differences, but still retain many similarities, as would be the case between two populations within the same species which had been separated for many generations. If enough time has passed, the two populations may be able to interbreed, but may not produce fertile offspring, as horses and donkeys do. Similarly, someone with a thick British accent might have trouble understanding someone who speaks African American Vernacular. The ability to communicate effectively with someone speaking a different dialect is in this way analogous to the ability of animals to interbreed - one marks the separation between species, another marks the separation between dialects or languages. Languages change over time, as gene frequencies in populations also change over time. Both dialects and species are very fuzzily defined.