Why does each species have a constant number of chromosomes?

The number of chromosomes is a sign of belonging to a particular species. Chromosomes:
1) store hereditary information;
2) reproduce it in the process of cell division;
3) participate in the implementation of genetic information.
Each chromosome (each pair of chromosomes) is duplicated during mitosis (cell division), so the number of chromosomes remains the same (at first it doubles exactly, then when dividing cells in each new cell, half of this doubled amount, ie, the initial amount, remains. leads to a change in the number of chromosomes, which leads to diseases, difficulties in reproduction, often ends in death, therefore the number of chromosomes is constant.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.