Meiosis is the process of dividing cell from diploid form (2n) to haploid form (n), this process is very important in formation of gametes. Where there are no meiosis means no gamete formation then no fertilization. On absence of meiosis cells will end up to divide my mitosis ie to increase in numbers but will not qualify to be gamete then sexual reproduction will stop.
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By means of meiosis the chromosome number retain in species . If there is no meiosis then the number of chromosome become double after each generation and genetic makeup of species changes. During meiosis crossing over takes place which result in genetic variation.