Question

Is the chromosome number of zygot embryonal cells and adult of a particular organism always constant?how is the constancy maintained in these three stages?

Answer 1

$\color{blue}\huge\bold\star\underline\mathcal{Hey\:Mate}\star$

$yes!$
the chromosome number of zygote,embryonal cell and adult of a particular organism is always constant.

Meiosis is the cell division which happens during gametogenesis.This results in number of chromosomes getting halved in gametes.When fertilisation happens,the number of chromosomes becomes equal to that in somatic cells.After that mitosis takes place during rest of stages of life.
So,the constancy of chromosomal numbers maintained in these three stages.