Unicellular organisms are immortal whereas multicellular organisms are not.Justify
Your friends are correct, However i would like to add that
The single cell organisms are said to be immortal because their progenies are exactly like them in the genetic make up. Offsprings are in fact the clones of their parents and full genetic composition is conserved.
@Others...Good work..keep posting!
An amoeba or a bacterium lives for a time, aging in the sense that it becomes older. But eventually, it divides, yielding two newborn cells. Nothing has died. Molecules and structures that constituted the old microbe serve as templates for creation of molecules and structures of two young ones. That's why one celled organisms are immortal.
Unicellular organisms always reproduce through division which can be budding, fission, etc. The parent cell divides itself to form daghter cells but do not directly give birth to another young one. Thus you don't see the death of any organism here. Whereas in most of the multicellular organisms, the parent gives birth to a young offspring, still existing to quite some time. Later we do see the death of this parent, which means it is mortal.