Clatify this for me(evolution)

mikeman · 2011-08-16T00:15:39

I'm currently reading Richard Dawkins book "The greatest show on earth", which I recommend to everyone, it's a really well written book. I haven't finished it yet, but I have some questions that the book doesn't seem to answer(at least, from what I read), or probably I missed them. Basically: 1)The whole mechanism of evolution is mutation+natural selection, am I correct? That is, let's take the eye or the lungs. They were first maybe a very simple organ for detecting light, and in the passage of many millenia, random mutations happened in the genes that "coded" that organ, and those mutations that helped the organism survive better remained, while others(the most) were discarded. It must follow that happened thousands or millions of "beneficial" mutations? Is that basically it, or am I missing something, is there a more sophisticated mechanism? 2)What I don't understand at all, since my days of highschool, is how completely new species arise. It is talked about in the book how we see evolution real-time in dog or flower breeding(it gives an example of foxes being bred in such a way that they give birth, after some generations, to foxes that look and behave more like dogs), it is talked about experiments in bacteria that show the same things. What I'm lost is if we know how new species arise. Does that happen due to mutation, that is, at some point happen a series of mutation that turn some population of a species to another species, genetically incompatible with the first one? When a species "splits" in half, with the halves being genetically incompatible so we can talk about different species? If so, what happens, do whole chromosomes get added or subtracted(as we know, different species have different number of chromosomes). Thanks in advance for any helpful answers.