Multicellular organisms grow and develop with the involvement of mitotic cell division. Meiosis occurs in them to form gametes in their reproductive phase of life cycle.
Significance of Mitosis
(i) Multicellular plants and animals start life as single cells. The process of mitosis gives rise to many cells which differentiate to form tissues, organs and organ-systems of the organism.
(ii) It results in increase in size and growth of an organ.
(iii) Cellular reproduction is used to form new cells to renew certain tissues and to replace worn out cells.
(iv) Mitosis is also involved in asexual reproduction in some unicellular and multicellular organisms. Eg: Asexual reproduction in amoeba and hydra takes place through mitosis.
Significance of Meiosis
(i) Meiosis is the mechanism by which conservation of specific chromosome number of each species is achieved across generations in sexually reproducing organisms.
(ii) Meiosis also increases the genetic variability in the population of organisms from one generation to the next. Variations are very important for the process of evolution.