How does meiosis contribute to evolution?

Meiosis contributes to evolution by introducing genetic variation through recombination and independent assortment of chromosomes.

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 eukaryotes, including humans. The key aspect of meiosis that contributes to evolution is the generation of genetic diversity.

During the first division of meiosis, homologous chromosomes pair up and exchange genetic material in a process known as crossing over or recombination. This results in new combinations of genes on each chromosome, which can lead to new traits in offspring. This genetic variation is the raw material upon which natural selection can act. If a new trait increases an organism's fitness, it is more likely to be passed on to the next generation, leading to evolutionary change.

In addition to recombination, meiosis also introduces variation through the independent assortment of chromosomes. This is the random distribution of maternal and paternal chromosomes into gametes. Each gamete receives a unique combination of chromosomes, which means that each offspring produced by sexual reproduction has a unique genetic makeup. This further increases the genetic diversity within a population.

Moreover, meiosis ensures the constant chromosome number across generations. By halving the chromosome number in gametes, it allows the restoration of the diploid number upon fertilisation. This prevents the chromosome number from doubling each generation, which would be unsustainable.

In summary, meiosis contributes to evolution by generating genetic variation through recombination and independent assortment of chromosomes. This variation provides the raw material for natural selection to act upon, driving evolutionary change. Furthermore, meiosis maintains the constant chromosome number across generations, ensuring the stability of species over time.