Question

How do organisms, whether reproduced asexually or sexually maintain constant chromosome numbers throughout several generations?

Answer 1

In case of asexually reproducing organisms, mitosis is the method used for cell division and reproduction in cells. This process starts with one replication and one division of the chromosome material. The whole set of chromosomes is replicated and transferred to the next generation. This results in the chromosome numbers in the two cells produced, being the same as in the parent cell. Example: Reproduction in Amoebaby binary fission or Plasmodium by multiple fission.

Sexually reproducing organisms undergo meiosis wherein the chromosome number is halved to form gametes. In this way, the new offspring receives one set of chromosome from each parent. The gametes then fuse together to form the zygote which restores the diploid chromosome number in the newly formed offspring. Example: Reproduction in human beings where there are 46 chromosomes in a diploid individual. Each parent contributes 23 chromosomes in the form of gametes. The two gametes fuse to form the zygote which again has 46 chromosomes.