Question about evolution?

yes, it goes that if the two can breed and produce fertile offspring, then the are the same species.

Yes.

A finch is a finch, is a finch. Like a dog is a dog. If that bird loosed its feathers and beak, then gains scales and teeth-then you might have an argument for evolution. One would have to survey the exact cause. If the losses were due to genetic mutation (for what ever reason), and there were no gains-then you still have the same creature-or at least whats left of it.

Adaptation (or variation, speciation) happens today. It is observable. It is unfortunate that this phenomenon has been labeled 'micro-evolution'. By adding the term "micro" to "evolution" seems (in some minds) to lend some validity to the the theory. But evolution really means one species changing completely into another-like a lizard (or dinosaur) changing into a feathered bird. This does not happen, nor is there any evidence for it. Two black dogs can have a white puppy. Or, two grey squirrels can have a brown offspring. This does not mean that a cow can become a whale or a T-Rex can become a Mocking bird.

If they can still interbreed with the endangered variety, then the genome will not have been materially altered, and the tendency for the original beak will still be present.

However, if the population in the competing area is isolated for a long time, then genetic drift will reduce their ability to mate successfully with the original, large-beaked birds. At this point they will be cut adrift genetically speaking, and will go on to become a new species.

In a situation like this the beak issue is incidental. What counts is their genetic connectedness with their original species. Two colonies of beetles may become separated by a small stream, and in a relatively short time lose the ability to interbreed.

As soon as the two groups are genetically isolated, their adaptations to their respective environments are independent, and they will become completely different species in time. Genetic defects may eventually cause a change in chromosome number in one group.

This happened to us: other members of the Ape Clade have one more pair of chromosomes, but human chromosome 2 is actually a joined-together copy of two chimp chromosomes.

CD

Speciation is a difficult subject. In many respects you could say it's the same species. But you could also argue for it being different.

Generally, the ability of a mutated A and a wild-type A to mate and produce fertile offspring would be a good indication of same species or not.

It is even more difficult when speaking about bacteria. Because they mutate and evolve a lot quicker than birds, their DNA can be quite different even within the same 'species'.

So far only Super Atheist has given a decent answer - there is regular cross-species breeding, so this is not the factor which tells you whether individuals are from the same species. Horse and donkeys can mate, as can lions and tigers.

If scientists were able to give a definition of species which was always true, then you could perhaps answer your question. As of now, it is a question of semantics, not reality. The divisions you are discussing are artifical, and thus there will always be examples which do not conform to such generalised descriptions.

It depends on whether or not it can still produce fertile offspring with the "old" version of species A. If little time has passed, then members of the "new" species A will be able to produce fertile with the "old" members, and so they will be the same species.

After enough time, however, it is possible that members of the "new" species will no longer be able to reproduce with members of the "old" species, and in this case we would have an example of speciation.

Yes, same species, different breed.

Now apply this method to several thousand-millions of years and tell me if they are the same species after that.

My first thought was, No.

Do you have any idea how many billions of different species of birds exist on this planet?

well, we need to know more than that to determine its species, but one way to find out, are old A and new A mating? cause different species cant mate

I'm not a biologist, but I would say that as long as they can produce a fertile offspring, then they're of the same species.

Haha, Geisha! Great minds think alike.