Question

gametes must be produced by meiosis for sexual reproduction.why is it so ?

Answer 1

Male and female gametes are produced by meiosis. It's necessary as number of chromosomes are halved in gametes and when they unite to form zygote which later on develop into organism will have deploid number of chromosomes, as their parents have.

Answer 2

Answer: the correct answer is-

Gametes are the haploid, reproductive cells that are produced by sexually reproducing organisms. They must be produced by a process of cell division that is called meiosis.

It is a reductional division as a diploid parent ( having 2n chromosome) cell produces four haploid daughter cells ( called gametes such as sperms and eggs) having half the number of chromosomes as compared to their parent cell.

Gametes are produced by each parent ( that is male and female gamete) and then they unit/ fuse together to form zygote ( which is diploid) that ultimately develops into the whole organism.

Thus, haploid sex cells ( gametes) must be produced through meiosis, which is a reductional cell division so that upon fertilization ( fusion of male and female gamete), they can produce a diploid organism.