Fission. Sometimes the body of single organism divides into two or more than two organisms, process is termed fission. It is of two types.

(i) Binary fission. It is the simplest method of asexual reproduction generally found in unicellular organisms like Amoeba, Paramecium, Euglena etc. Binary means two and fission means breaking, thus this process involves the division of animal body into two parts.

After attaining an optimum size the adult undergoes division. It is completed in two steps. First the nuclear division followed by cleavage of cytoplasm into two parts each having a daughter nucleus. Amoeba and Paramecium divide in transverse plane and Euglena in longitudinal plane.

Binary Fission in Amoeba

(ii) Multiple fission. It is a type of asexual reproduction in which nucleus undergoes repeated divisions before the cytoplasm breaks to form a number of uninucleate daughter cells. Each body thus formed grows into a new individual. Multiple fission occurs in Amoeba and Plasmodium during the formation of merozoites (schizogony), sporozoites (sporogony) and male gametes (Gamogony). It is also quite common in Amoeba and other acellular organisms.

Spore formation in Amoeba.