Figure 20.2: Different types of Gametes.

The gametes are formed after meiotic divisions. In this process, diploid (2n) cells will give rise haploid (1n) gametes (Figure 20.3). In the process of sexual reproduction, the gametes fused with each other to form zygote (2n). This process is known as fertilization. The meiosis and fertilization are important event to maintain the number of chromosome constant over several generations (Figure 20.3). In addition, during crossing over,  exchange of genetic material between homologous chromosomes results in new combinations of genes. It results generation of genetic diversity and acquire of new phenotype.