Normally egg cell develops into zygote after fertilization by male gamate.In this normal fertilization after fertilization zygote formation occurs and egg develops into organism.
While one unusual method is followed by some insects and lizards aphids and aves in which egg develops into organism without fertilization is known as Parthenogenesis.There are various organisms which develops without fertilization through parthenogenesis, this organisms are called as Parthenogenone or Parthenote.
eg desert lizards and some insects
There are some intermediate condithions in parthenogenesis and fertilization example Partial parthenogenesis, gynogenesis, androgenesis.
1) Partial parthenogenesis:-
In some organisms egg may fertilize by part of male gamete or sperm called partial parthenogenesis. Example aster of sperm only involved or penetrate the egg cell and egg gets activated to produce organism.
2) Gynogenesis:-
The sperm penetrates completely in egg cell while it doesn't become part of fertilization called as Gyngenesis.
eg. Rhabditis abberance
3) Androgenesis:-
In this condition egg cell is fertilized by sperm and gets activated while egg nucleas not takes part in organisms development
eg ova of frogs and toads.
Parthenogenesis is of two types natural parthenogenesis and Artificial parthenogenesis
1) Natural Parthenogenesis:-
In some animals parthenogenesis occurs naturally on regular basis and constantly in their lyfe cycle known as Natural parthenogenesis.
Natural parthenogenesis is of two types one is complete and other is Incomplete Parthenogenesis.
1) Complete parhtenogenesis:-
Certain insects have no males ao thet completely depends on parhtenogenesis for their self-reproduction. This type of parthenogenesis is called complete or obligatory parthenogenesis.
eg Salamanders, Grasshoppers and Lizards.
2) Incomplete parthenogenesis:-
The life cycle of certain insects have two generations first is reproduction and followed by parthenogenesis both of which are alternate to each other.
In most of such a cases the diploid egg produces females and the unfertilized egg poduces males.this type of parthenogenesis is called as incomplete or partial or cyclic Parthenogenesis.
Complete and Incomplete type of natural parthenogenesis may be of following types
1) Haploid or arrhenotokous :-
In this haploid eggs are unfertilized and develops into haploid individuals. In this case haploids are males while diploids are females.
eg Bees and Wasps
2) Diploid or thylatokous:-
In this diploid parthenogenesis diploid eggs which are unfertilized are develops into young individuals.
Eg Aphids
2) Artificial Parthenogenesis:-
In this type of parthenogenesis eggs are activated by artificial means called Artificial parthenogenesis.
Physical means:-
Some physical means are employed to activate egg cells which mainly are
1) Temprature:-if eggs are exposed from 30 degree to 0-10 degree it induces parthenogenesis.
2) Electric shock:- Electric shock to egg cell induce parthenogenesis.
3) Ultraviolet light:- Ultraviolet light radiation has potential to induce egg developlent so used for parthenogenesis.,
Chemical means:-
normal eggs can be induced by exposing to certain chemicals .
eg Butyric acids, chloroform, Urea and sugar.
So this was all about parthenogenesis .
Nice.
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