Question

Unicellular organisms are immortal whereas multicellular organisms are not.Justify

Answer 1

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...

Answer 2

Unicellular organisms undergo asexual reproduction thus the parent cell divides and forms new daughter cells [thus we can understand that the parent cell has not undergone natural death it is now present in the form of the daughter cells] but the genetic and structural constituition of parent cell is retained in the daughter cells.