Originally posted by Monique
Well, I wouldn't say one organism, but AG refers to that we are all made up of the same four letter code ACGT. All genetic diversity is based on the sequence of only those four letters. If you look at a mycoplasm or an elephant, both have the same foundation.
I'll try to explain it this way.
Humans start out as an egg. One egg cell, with two copies of your Genetic Code in it. That egg divides into two identical cells. Are those two cells two organisms, or one organism?
Over time this dividing continues and continues. When they are born, it is normal to consider them a 'person' who belongs to the human race. But are they really one organism? Or a collection of billions of organisms?
Over the course of the groing of their body, the billions of cellular organisms which make up their body die and are replaaced over and over again. But they remain. So, again I ask, are they billions of organisms, or are they one organism? If they are one organism, are they now a new organism?
Sometime further down the track, they have sex, get pregnant. Do you know what happens when they get pregnant? One of their cells divided in a slightly different way, so that it only had one copy of their DNA instead of two, and then an external source of DNA was added in a complimentary fashion to their own. That single cell then starts dividing. Just like everyother cell in their body. Is that cell an organism? Or is it just another part of the organism which is the human?
This is the modern version of the process which has made every single life form on earth. There is no distinct line from one organism to the next. Every single generation comes from a copy of the previous generation. Even within the generation, maintanence is achieved by copying and backing up. So don't try to say that copying is the thing which seperates them. As brought up in the human example, to maintain this organism that is known as a human, it is only achieveable by copying its parts millions of times over just to keep it in top condition....
THE POINT: There is no break in the continuous survival of the first strand of DNA, to all of the strands of DNA now Present. Every single one of them comes from the one origin, in a continuous process of copying.
Just because the DNA which programs a mouse has gone down a different path to the DNA which programs a bear, does not mean that either of them are any less related to the original ancestor as each of them are to their own parents.