Natural selection is the gradual process by which heritable biological traits become either more or less common in a population as a function of the effect of inherited traits on the differential reproductive success of organisms interacting with their environment. It is a key mechanism of evolution.
There we go! Natural selection isn't evolution, it's the key mechanism. Calling Natural selection, evolution is like calling the engine of a car, the car. Of course, without the engine the car would never move (unless you pushed it) but there would have to be some force causing the car to move. So, like evolution, without it's engine (natural selection) it wouldn't go anywhere. There would have to be something forcing it to happen. An example of forced evolution, would be dogs. Dogs are a common cousin of wolves. They are very very close cousins, within the years of the rise of man-kind. Distant wolves were able to utilize humans for their own benefits. For example, wolves that were considered pleasant to look at, were kept as pets, and as such were fed, fed = good, so naturally those wolves were bred to look pleasant, and pleasant features were artificially selected by humans. Wolves who could smell really well, were bred for their hunting capabilities, wolves who could fight or protect were also bred. Of course we have TONS of breeds of dogs now, but they generally all come from decisions of usefulness at different times and from different places as Wolves are very common around the world.
Natural selection would be like... A unique animal with a small tail can't climb as high as the same unique animal with a longer tail. The longer tail animal is able to live healthier because they can climb higher to get their food. This healthiness is noticed by it's unique kind, and now it has the ability to produce offspring. So naturally over time, having a long tail is important. The flip side to that, is perhaps the shorter tail animal has larger hands, and is able to move things on the ground, or fight off other animals. That could be used for it's advantage and another adaptation is born. No where, would having larger hands or longer tails suddenly equate to wings or fins. But there is nothing saying that fish couldn't develop stronger fins that could be used to go on land, or those same extremities be useful for keeping air-time when jumping, give that 3 billion years to develop and probably wings occurs. But hey, birds and insects with wings have been a thing for a lot longer than just as recent as 3 billion. So perhaps it was just a more direct adaptation. I'm sure if you research the history and evolutionary process of common birds you'll find a good answer.
This is the difference between Natural and Artificial selection just so we are clear on that.
as if it explains the origin of the diversity of life? By definition it is a selective process (selecting from already existing information), so is not a creative process. It might explain the survival of the fittest (why certain genes benefit creatures more in certain environments), but not the arrival of the fittest (where the genes and creatures came from in the first place). The death of individuals not adapted to an environment and the survival of those that are suited does not explain the origin of the traits that make an organism adapted to an environment. E.g., how do minor back-and-forth variations in finch beaks explain the origin of beaks or finches? How does natural selection explain goo-to-you evolution?
Well I mean I had to google what goo-to-you stood for and I find that hilarious. Natural selection doesn't explain evolution and it never will. Because natural selection is a tool and an engine for the process of evolution. That's like saying, the paint brush doesn't explain the painting, therefore the painting had to not been created by a paintbrush. Of course, who made the paintbrush? Where did the paint come from? These are all very valid questions. Of course where and who can go back pretty far... but the question that everyone is stuck on, is "why". Why does the paintbrush push colours across a page? Why does the universe have life in it? Why is the universe a "thing".
The honest answer... Why doesn't matter. Why is the least important scientific exploration out there. No one cares WHY the sun sets or rises or rotates through the solar system, what people care about is HOW. Some people care about the where and the who and the what, but most people care about HOW. HOW does it benefit me that the sun rises, well if I learn HOW the sun rises, perhaps I can take advantage of it and use it for my personal advancement. As you know, the sun doesn't rise, the Earth just rotates (something that was discovered, and the guy who discovered it got sent to jail for it as you know Galileo Galilei. http://www.biography.com/people/galileo-9305220)
The concept of why, really doesn't help. Why does the Earth rotate around the Sun, well because of the gravitational pull! Well... that's more of HOW does it rotate. Why is still unanswered, and it still doesn't matter. Why is important in our lives, Why do I have to go to school, why did this bad thing happen to me, why do we die, why do we love, why why why. But what is more important to why, is how. How do I go to school, how do I avoid bad things, or how do I good things, or how does bad things happen to me, how do we die, how do we love. Etc..
Minor back and forth variations explains HOW birds gained beaks, and how an ancestor animal evolved into a finch. It's hard to explain WHY, and honestly, why does why matter :P
For instance, a challenger might say, ‘Mosquitoes have evolved resistance to DDT in just 40 years. If that’s not evolution happening before our eyes, what is?’ Most Christian responses focus on the amount of change. For instance, they will say, ‘Well, that’s just variation within a kind.’ Or they reply, ‘But the mosquito’s still a mosquito, isn’t it? It hasn’t turned into anything else.’
That's a dumb example. Mosquitoes haven't evolved a resistance to DDT, the same way a child hasn't evolved a resistance to measles. The reason I say this, is because it isn't evolving. Mosquitoes who have stronger resistances to the DDT reproduce, and therefore there is a HIGHER (not 100%) chance that their offspring will as well, be resistant to DDT. Humans have also driven a lot of artificial selection (as I defined above). So Mosquitoes being resistant to a chemical such as DDT, is an act of artificial evolution, and not natural solution. We have NO IDEA if this is an evolution of a new species, since it hasn't been 500 million years of us spraying mosquitoes with DDT. But you did, I bet it would change a lot.
The other reason why this example isn't correct, is that it doesn't take into account ENVIRONMENT. An animal with a long tail thrives in an environment with TALL trees, if the trees aren't tall, it won't thrive. So as the environment around the animals changes, the things that make the animals thrive changes, and in that change you get different animals based on their natural selection.
Let me represent this in a particularly simple way.
You have a person who walks up stairs every day, and you have a person who walks down stairs everyday. Assuming they exert the same effort to do so, and are the same weight and eat the same things and are just as desirable to women of the same interest (women who walk up and down stairs respectively). After 500 million years of reproducing people that can walk up and down, the people who walk down stairs are realllllly good at it, and people who walk up stairs are reaaaaaalllly good at it. Perhaps they are not good with the reverse, so people who walk up might not be comfortable walking down as the people who walk down do and the people who walk down are probably not as comfortable walking up.
NOW, let's assume a huge Volcano erupts in the middle of North America, and for some reason everyone is in the general area so they have to run from this massive volcano or they will die. But the catch is, they have to run downhill to survive.
You will have a LOT of people who could only go uphill, die in that situation because they could not last as long as the people who have been training for 500 million years. The breed of down-hillers lives on, while the breed of up-hillers dies out.
Now let's assume you have an actual event, where insects are on the top of trees, and birds with long beaks eat them. The trees will grow, just because trees do that. So the birds happily live on just flying and eating insects, and there are also insects who live deep underground. The insects at the top of the trees might like eating leaves who knows. Come up with a good reason if you have to.
There might an animal that eats the birds who eat the insects, and there might be an animal that eats the rodents that eat the insects deep underground. Both animals will survive, and they might be the same animal at the start, but one adaptation is, well I can't eat if I keep trying to get insects underground, and I climb better than my brother over there (now multiply that by a few hundred million years and now you have two very different adaptations of the same ancestor who are now classified as different species due to their unique attributes).