Question

All cells of an organism find their lineage from a single fertilized cell. This single
fertilized cell is called what?

Answer 1

zygote is the answer...

Answer 2

This single fertilized cell is called 'Zygote'. The zygote undergoes division in two forms - mitosis and cleavage. In mitosis, the cell volume increases. In cleavage, the cell divides into numerous cells  and there is no increase in cell volume. This happens during the G1 and G2 phases of the cell cycle.