"Organism" is a convenient label, but like most labels is not complete. A zygote is what it is, and it really does not matter what labels we pin on it.
One human cell is a human organism. It contains 22 autosomal pairs and 1 pair of sex chromosomes.
A human liver cell also contains all of these.
So does a heart cell.
So does a brain cell.
Any cell with a nucleus has these. A zygote has them too.
They are living organisms. They have human DNA so they are human organisms.
It's important to note though that any cell with a nucleus is still part of a holistic system. Even though we can examine a zygote's nature separately, in nature it cannot be separate from the body if it is to continue living. The same goes for any cell in the body, any tissue, or any organ.
So if you're looking at the zygote you also have to view it in relation to the rest of the body. As a cell it needs the body to live and cannot be apart from it for any meaningful amount of time.
Which in turn sort of answers the question. The zygote can't be a human organism if it's dead or separate from the body; it can't be put into a non-human organism to live because it will be attacked; the only place it can live is in-utero, in a human. That to me makes it a human organism.
Last edited by Orion; 01-22-10 at 12:22 AM.
There's a disturbing lack of biological knowledge around here.
If it's a cell then it's an organism. It has DNA/RNA, organelles, etc. So a cell is an organism. Hence a zygote is an organism. A zygote is a little different in that the DNA in it is not yet active, but it will be, so it's an organism.
Is it a human? Well, if it's not, then what species is it?
So yes, a zygote is a human organism. The real question is about when it gets dignity.
Who shall ascend the hill of the Lord? And who shall stand in his holy place? He who has clean hands and a pure heart, who does not lift up his soul to what is false, and does not swear deceitfully. Psalm 24
"True law is right reason in agreement with nature . . . Whoever is disobedient is fleeing from himself and denying his human nature [and] will suffer the worst penalties . . ." - Cicero