Question

How does a single-celled fertilized egg grow into an adult in human beings?

Answer 1

In the growth process, a single-celled fertilised egg, i.e. a zygote divides and redivides to form a cluster of cells. This division is accompanied by another process i.e., specialisation of cells. The specialisation of cells leads to the formation of different parts of the body. This whole process is called differentiation. This process also gives rise to various tissues, and further, various organs and organ systems. Thus, the zygote grows into an embryo and an embryo develops into a baby, and a baby ultimately into an adult.