Gynogenesis
It is a special type of parthenogenesis occurring in a few turbellarians, nematodes and earth worms. In these animals, the egg is stimulated to develop by the penetration of the spermatozoon. After penetration, the sperm disintegrates without fusing with the egg nucleus. This process is said to be gynogenesis or pseudo fertilisation. Gynogenesis is more common in hermaphrodite animals.
Significance of Parthenogenesis
Fallowing are the some important significance of the parthenogenesis.
1. As a means of reproduction:
Parthenogenesis is a simple and easier means of reproduction. It ensures the continuity of a race when fertilization fails to occur.
2. Rapid Multiplication: Parthenogenesis favours the production of large number of individuals within a short period of time.
3. Elimination of Disadvantageous characters: sometimes mutation produces unfavorable characters. These are not useful to the possessor. Such organisms cannot compete with the fittest animals. Hence, parthenogenesis with unfavorable adaptations are eliminated from the population.
4. Persistence of Advantageous characters: Sometimes advantageous characters appear in the parthenogenesis by mutations.
5. Elimination of Variety: As the offspring are formed by the contribution of only one animal, the possibility for the development of variation is reduced. Hence, parthenogenesis cannot produce new varieties.
6. As a mean of sex determination: As the sex is determined by chromosomes, parthenogenesis is very useful in determining the ratio of males and females in a population. For example, in aphids all the unfertilized eggs develop into males and fertilized eggs into females.
7. Prevention of wastage of energy: Mating is an essential phenomenon in sexual reproduction. It involves the wastage of energy. Parthenogenesis does not require mating. Hence, most of the energy can be saved.
8. Polyploidy: Parthenogenesis favours for polyploidy.
9. Fertility: Parthenogenesis avoids sterility in the races.
10. Inheritance: Parthenogenesis supports the chromosome theory of inheritance.