(N/A) $\Rightarrow$ All organisms,even the smallest or the largest,start their life as a single cell called the $Zygote$.
$\Rightarrow$ The $Zygote$ is produced by the fertilization of male and female gametes and is a unicellular structure.
$\Rightarrow$ Due to constant cell division and differentiation of the $Zygote$,a complex multicellular body structure is formed.
$\Rightarrow$ Growth and reproduction of cells are fundamental characteristics and requirements of all living organisms.
$\Rightarrow$ All cells reproduce by dividing into two; each parental cell gives rise to two daughter cells each time they divide. These newly formed daughter cells can themselves grow and divide.
$\Rightarrow$ In other words,cycles of growth and division allow a single cell to form a structure consisting of millions of cells.
$\Rightarrow$ The total number of cells in an adult human is approximately $10^{14}$.