”Parthenogenesis is a form of asexual reproduction in which female gamete of egg cell develops without any fertilization.
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Parthenogenesis Meaning
Animals, including such as wasps, bees and ants, that have no sex chromosome. These organisms reproduce by parthenogenesis. Some reptiles and fish are also capable of reproducing in this manner. Many plant are also capable of reproducing by parthenogenesis.
A few organism that reproduce by parthenogenesis also reproduce sexually. This types o parthenogenesis is know as facultative parthenogenesis, and organism including such as water fleas, crayfish, snakes, sharks, and komodo dragon reproduce through this process.
Types of parthenogenesis
Basically there are two types of parthenogenesis
- Natural parthenogenesis
- Artificial parthenogenesis
Natural parthenogenesis
In some organism, Parthenogenesis occurs naturally in their life cycles. This is know as naturally parthenogenesis.
The naturally parthenogenesis may be of two types, Viz., Complete parthenogenesis and Incomplete parthenogenesis.
1. Complete Parthenogenesis
Certain insects have no no sexual phase and no males. Such organism depend exclusively on the parthenogenesis for the self-reproduction. This is know as complete parthenogenesis. It is found in some species of Bdelloid rotifers, Grasshoppers, Cockroaches, Salamanders, Typhlina brahmina, Lacerta Saxicola armeniaca (caucasian rock lizard), etc.
2. Incomplete Parthenogenesis
It is also called as cyclic parthenogenesis. The life cycle of few insects has two generation. One is the sexual generation and other is parthenogenesis generation. In such insects, diploid eggs produce female and the unfertilized eggs produce male. Example- Honey Bee, Aphid, Turkey, Bird, Wasp, and Ants.
Artificial Parthenogenesis
In this, the fertilised eggs might sometimes developed parthenogenetically by various chemicals and physical means. Chemicals like Salts, Weak acids, Organic solvents, Chloroform, Urea, Strychnine, Sucrose, and Physical stimuli like Changes in temperature and pH, Electric shock, Ultra-violet light, and Mechanical stimulus. Example Annelids, Starfish, Hen, Frog, Rabbit, Mollusca, etc.
1. Physical Means
The following physical means cause by the parthenogenesis
a. Temperature:- The range of temperature may induce parthenogenesis in the eggs. For instant, when the egg is transferred from -30 to -10 degree Celsius, the parthenogenesis is induced.
b. Electric shocks:- Can cause parthenogenesis.
c. Ultraviolet light:- Can cause parthenogenesis.
d. when an egg is pricked by a needle, the development occurs parthenogenetically.
2. Chemical Means
The following chemicals that are responsible for the parthenogenesis of egg are:
a. Chloroform
b. Strychnine
c. Urea and Sucrose
d. Acids such as butyric acid, lactic acid, oleic acid, and other fatty acids;
e. Fat Solvents, e.g., toluene, alcohol, benzene, and acetone;
f. Chlorides of K, Ca, Na, Mg, etc.;
g. Hypertonic and Hypotonic sea water
Significance of Parthenogenesis
There are some advantage and some disadvantage of parthenogenesis are:
Advantages
- It is most simple, stable and easy process of reproduction. Example- Aphids(insects).
- The avoids the wastage of germplasm as sperm and ova. An adult organism is devoted exclusively to feeding and reproduction so is a mode of high reproduction.
- The parthenogenesis is the best way to high rate of multiplication in certain insects, e.g., aphids.
- The parthenogenesis causes the polyploidy in the organism.
- Parthenogenesis is a means of sex determination in some animals such as honeybees. Thus it support the chromosomal theory of sex determination.
Disadvantage
- It stops the changes of a new combination of genes and thus avoids selection in the population. It decreases the changes of adaptability followed by extinction.
Example of Parthenogenesis
Example of parthenogenesis are- bees, wasps, aunts.