Thanks for your reply, Bioflex.
A lot has already been answered, but I'll put my way anyway:
But all i am asking is, do you think over enough time those not-dogs could change extensively in their body structure as to be considered as totally different animals? like maybe goats?
As I said, the name we give a type of animal, such as "dog" is arbitrary. Given enough time, changes could indeed be so great that "not-dogs" would appear to be a completely different animal. But, careful, expert examination would still show their ancestral relationship to dogs.
My problem lies in how one species can split into two or more speices on its own. I know viruses and algae can reproduce on their own but no matter how they split all the end up producing is another of their kind.
Consider the small differences you can find in any breeding population. Then if one of these differences makes the organism stronger, tougher, or able to digest better, over time the critters that carry this trait beget more offspring. Over more time, almost the whole population has this difference, so that it's no longer a "difference". Then, a refinement on the difference appears, again one that helps survival. Round 2.
Consider also that the original population may also not have survived unchanged. It is theorised that population change happens fastest when the environment changes, which would make sense.
Can you see that after hundreds of "rounds", the two populations would be substantially different? Perhaps no longer able to interbreed?
If i am correct fishes and reptiles cant interbreed so how do you prove a fish splitting to produce a reptile without these two having any kind of sexual interferance?
Again, you are asking why the two "end result" populations cannot interbreed. Isn't this exactly what the evolutionary scenario above would cause? The theory of evolution suggests that once both fish and reptiles descended from one ancestral population. These were neither modern fish nor modern reptiles. But those in deeper water evolved the differences that helped survival there, and those in the shallows benefited, from being able to, for instance, survive short times out of water, and put weight on their fins. Caedes has explained this very well.
i find it hard to accept that natural selection or speciation can link features of a girrafe from a fish. Its like saying evolution is the reason why dogs have tails like reptiles.
The postulated common ancestor of giraffes and fish is a long way back. But although they are very different, they do have some structures in common. Most notably, a backbone. They are both vertebrates. Now if you could find a mammal-like creature without a backbone, you could cast serious doubt on the theory!
Keep asking and reading, and good luck! Retro