The number of chromosomes in parents and offsprings of a particular species remains constant. due to

The number of individuals of a species in a particular ecosystem at a given time remains constant due to:

The number of individuals of a species in a particular ecosystem at a given time remains constant due to:

Do all individuals of a particular species have constant chromosome number ?

Number of chromosomes in the parent and progeny cells is same, it is known as

Transmission of characters from parents to offspring ……

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