Parthenogenesis is a form of asexual reproduction where growth and development of embryos can occur without fertilization. It was first recognized in 1745 and experiments in the early 1900s and 1930s stimulated both natural and artificial parthenogenesis in various species. There are two main types of natural parthenogenesis - complete (obligate) where reproduction relies exclusively on parthenogenesis, and incomplete (cyclic) where sexual and parthenogenetic generations alternate. Parthenogenesis occurs naturally in many invertebrates as well as some vertebrates and can be induced artificially.

1. PARTHENOGENESIS
_ Dr Zaid Wani

2. History
• Parthenogenesis was first recognized in 1745 by
CHARLES BONNET
• JACQUES LOEB stimulated parthenogenesis in sea
urchin and frog eggs by artificial means in 1900.
• G.PINCUS in 1936 artificially produced the first
known parthenogenetic offspring in a mammal
{rabbit}.

3. Definition
• Parthenogenesis is a natural form of asexual
reproduction.
• Growth and development of embryos occur
without fertilization.
• It is a component of apomixis.

4. Occurrence
• Parthenogenesis is found in many
invertebrates such as rotifers and arthropods.
• Crustaceans , insects and arachnids {spider,
mites}
• some vertebrates {rock lizards and birds}.
• Snails, Sharks, Amphibians

5. Types of parthenogenesis
I. Natural parthenogenesis:
1 Complete { obligate } parthenogenesis
2 Incomplete {cyclic} parthenogenesis
• 3 Paedogenetic parthenogenesis
II. Artificial parthenogenesis.

6. I. Natural Parthenogenesis
In certain animals the parthenogenesis occurs
regularly, constantly and naturally in their life
cycles and is known as the natural
parthenogenesis.
• The natural parthenogenesis may be of two
types, viz., complete or incomplete

7. Complete Parthenogenesis:
• Certain insects have no sexual phase and no
males. They depend exclusively on the
parthenogenesis for the self-reproduction.
• This type of parthenogenesis is known as the
complete parthenogenesis or obligatory
parthenogenesis.
• Examples : Rotifers, Caucasian Rock Lizard.

8. Incomplete parthenogensis:
• The life cycle of certain insects includes two
generations, the sexual generation and
parthenogenetic generation, both of which alternate to
each other.
• In such cases, the diploid eggs produce females and the
un-fertilised eggs produce males.
• This type of parthenogenesis is known as the partial or
incomplete or cyclic parthenogenesis.
• Examples : Aphids, Honeybees, Rotifers, Birds.

10. The complete or incomplete type of natural
parthenogenesis may be of following two types:
• 1. Haploid or arrhenotokous parthenogenesis.
• 2. Diploid or thelytokous parthenogenesis.

11. • Haploid or arrhenotokous parthenogenesis:
In the arrhenotokous parthenogenesis the
haploid eggs are not fertilised by the sperms and
develop into the haploid individuals. Eg,
Honeybees
• Diploid or thelytokous parthenogenesis:
In the diploid parthenogenesis, the young
individuals develop from the un-fertilised
diploid eggs.

12.  Types:
(i) Ameiotic Parthenogenesis:
• Sometimes during the oogenesis, first meiotic or
reduction division does not occur but second meiotic
division occurs as usual.
• Such eggs contain diploid number of chromosomes and
develop into new individuals without the fertilisation.
• This type of parthenogenesis is known as apomictic or
ameiotic parthenogenesis and occurs in weevils and
long-horned grasshoppers.

14. ii) Meiotic Parthenogenesis:
• Certain eggs develop by the usual process of
oogenesis but at certain stages diplosis or
doubling of chromosome number and production
of diploid eggs occur.
• Such eggs develop into the diploid individuals
and this phenomenon is known as the meiotic
parthenogenesis.

15. Paedogenetic parthenogenisis:
• Larvae of some insects lays eggs which
develop parthenogenetically into new
generation of larvae. Eg , Dipterous insects.

16. Artificial Parthenogenesis
• The eggs which always develop into the young
individuals by the fertilisation sometimes may
develop parthenogenetically under certain
artificial conditions.
• The artificial parthenogenesis may be induced
by various chemical and physical means.

17. Significance
1. The parthenogenesis serves as the means for the
determination of sex in the honey bees, wasps, etc.
2. The parthenogenesis is the most simple, stable and
easy process of reproduction.
3. The parthenogenesis eliminates the variation from
the populations.
4. The parthenogenesis is the best way of high rate of
multiplication in certain insects, e.g., aphids.

18. 5. The parthenogenesis causes the polyploidy in the
organisms.
6. The parthenogenesis encourages advantageous
mutant characters.
7. No need for the organisms to waste their energy in
the process of mating.

19. THANK YOU