Write a note on parthenogenesis.

Explanation

(i) Development of an egg into a complete individual without fertilization is known as parthenogenesis.
(ii) It was first discovered by Charles Bonnet in 1745. Parthenogenesis is of two main types namely, natural Parthenogenesis and artificial Parthenogenesis.
(iii) In certain animals, parthenogenesis occurs regurlay, constantly and naturall in their life cycle and is known as natural parthenogenesis.
Natural parthenogenesis are of different types:
a. Arrhenotoky, In this type only males are prodced by parthenogenesis. e.g. honey bees
b. Thelytoky: In this type of parthenogenesis only females are produced by parthenogenesis.
E.g: Solenobia
c. Amphitoky: In this type parthenogenetic egg may develop into individuals of an sex. E.g. Aphis.
(iv) Natural parthenogenesis may be of two types, viz., complete and incomplete.
Complete parthenoenesis is te only form of reproduction in certain animals and there is no biparental sexual reproduction. These are no male organisms and so, such individuals are represented by females. only.
(v) Incomplete parthenogenesis is found in some animals in which both sexual reproduction and parthenogenesis ocurs.
Eg. In honeybees, fertilized eggs (zygotes) develop into queen and workers, whereas unfertilized eggs develop into drones (male). (vii) It occurs in the sporocysts and Redial larvae of liver fluke. It is also seen in the larvae of some insects. E.g. Gall fly.
(viii) 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.