How does meiosis ensure the stability of an organism's chromosome number?

Meiosis ensures the stability of an organism's chromosome number by halving the number of chromosomes during gamete formation.

Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell. This process is crucial for sexual reproduction in eukaryotic organisms, as it ensures that the offspring will have the correct number of chromosomes. If this did not occur, the chromosome number would double with each generation, leading to instability and potentially harmful mutations.

The process of meiosis involves two rounds of cell division, known as meiosis I and meiosis II. During meiosis I, homologous chromosomes pair up and exchange genetic material in a process known as crossing over. This is followed by the separation of these homologous pairs, each going into a different daughter cell. This effectively halves the chromosome number from diploid (2n) to haploid (n).

In meiosis II, the sister chromatids of each chromosome are separated, resulting in four haploid daughter cells. These cells, known as gametes in animals and spores in plants and fungi, are used in sexual reproduction. When two gametes fuse during fertilisation, the diploid number of chromosomes is restored, ensuring the stability of the chromosome number in the offspring.

In addition to maintaining the chromosome number, meiosis also increases genetic diversity through the process of crossing over and independent assortment. Crossing over allows for the exchange of genetic material between homologous chromosomes, creating new combinations of genes. Independent assortment refers to the random distribution of chromosomes into gametes, which means that each gamete carries a unique combination of genes.

In summary, meiosis is a vital process that ensures the stability of an organism's chromosome number by halving the number of chromosomes during gamete formation. This not only maintains the chromosome number from generation to generation but also contributes to genetic diversity, which is key for the survival and evolution of species.