The chromosome number has to be maintained in all the organisms. For this the asexual and sexual reproduction maintain a constant chromosome number by adopting different methods.

In asexual reproduction the organisms divide the chromosome first and then the cells. For example in binary fission the chromosomes are replicated and then tranfered to the daughter cells.

In case of sxual reproduction, gametes are formed which are haploid in nature and then unite to restore the normal diploid condition . Thus , mainataining the chromosome number in the organism. For example in humans the male and the female gamete carry 23 chromosomes. They unite to form zygite which restores the normal 46 chromosome number in the offspring.

Introduction:
Organisms, whether reproducing asexually or sexually, have mechanisms in place to maintain a constant chromosome number through several generations. This is crucial for maintaining genetic stability and preventing harmful mutations or imbalances in the genome. Let's explore how this is achieved, with the help of suitable examples.

Asexual Reproduction:
During asexual reproduction, a single parent produces offspring that are genetically identical to itself. The most common mechanisms for maintaining a constant chromosome number in asexual reproduction are:

1. Binary Fission: In organisms like bacteria, the parent cell divides into two identical daughter cells through a process called binary fission. Each daughter cell receives an exact copy of the parent's chromosome, ensuring a constant chromosome number.

2. Budding: In organisms like yeast, a small bud forms on the parent organism, which eventually grows and detaches to become a new individual. The bud receives a copy of the parent's chromosome, maintaining the same chromosome number.

3. Vegetative Propagation: In plants, specialized structures like rhizomes or runners produce new individuals that are genetically identical to the parent plant. These structures contain the same chromosome complement as the parent, ensuring a constant chromosome number.

Sexual Reproduction:
Sexual reproduction involves the fusion of gametes from two parents, leading to genetic diversity in the offspring. Despite the mixing of genetic material, organisms still maintain a constant chromosome number through the following mechanisms:

1. Meiosis: Meiosis is a specialized type of cell division that occurs in the cells responsible for producing gametes (sperm and egg cells). During meiosis, the chromosome number is halved, resulting in haploid gametes. When two haploid gametes fuse during fertilization, the chromosome number is restored to its original diploid state.

2. Sexual Life Cycle: Organisms have different variations of sexual life cycles, such as alternation of generations or haploid-dominant life cycles. These life cycles involve alternating between haploid and diploid stages, ensuring a constant chromosome number across generations.

Example: Fruit Flies (Drosophila melanogaster)
Fruit flies are a common example of organisms that reproduce sexually and maintain a constant chromosome number. They have four pairs of chromosomes, making a total of eight chromosomes. During meiosis, the cells producing sperm or eggs undergo two rounds of cell division, resulting in four haploid cells. When a haploid sperm fertilizes a haploid egg, the chromosome number is restored to eight in the resulting diploid zygote.

In conclusion, organisms maintain a constant chromosome number through several generations by employing mechanisms specific to their mode of reproduction. Asexual reproduction relies on processes like binary fission, budding, or vegetative propagation to ensure the offspring receive an identical chromosome complement. Sexual reproduction involves meiosis and specialized life cycles to halve and restore the chromosome number, respectively. Fruit flies exemplify how sexual reproduction maintains a constant chromosome number through meiosis and fertilization.