produce) Development of an egg into a complete individual without fertilization is known as parthenogenesis. It was first discovered by Charles Bonnet in . Parthenogenesis is of two main types namely, Natural Parthenogenesis and Artificial Parthenogenesis. In certain animals, parthenogenesis occurs regularly, constantly and naturally in their life cycle and is known as natural parthenogenesis .
Natural parthenogenesis are of different types: a) Arrhenotoky: In this type only males are produced by parthenogenesis. eg: Apis (honey bee). b) Thelytoky: In this type only females are produced by parthenogenesis.eg: Solenobia c) Amphitoky: In this type parthenogenetic egg may develop into individuals of any sex. eg: Aphis gossypii Natural parthenogenesis may be of two types, viz., complete and incomplete.
Complete parthenogenesis is the only form of reproduction in certain animals and there is no biparental sexual reproduction. There are no male organisms and so, such individuals are represented by females only. Incomplete parthenogenesis is found in some animals in which both sexual reproduction and parthenogenesis occurs. e.g.
In honeybees; fertilized eggs (zygotes) develop into queen and workers, whereas unfertilized eggs develop into drones (male). In paedogenetic parthenogenesis (paedogenesis) the larvae produce a new generation of larvae by parthenogenesis. It occurs in the sporocysts and Redia larvae of liver fluke. It is also seen in the larvae of some insects.
e.g. Gall fly. In artificial parthenogenesis , the unfertilized egg (ovum) is induced to develop into a complete individual by physical or chemical stimuli. e.g., Annelid and seaurchin eggs.
XII Std Zoology Chapter XII Std Zoology Chapter Reproduction in Organisms