Question

Write the definition and any one significance of parthenogenesis.

Answer 1

Hint: In some plants, in some invertebrates such as water fleas, aphids, stick insects, some ants, bees and parasitic wasps, in vertebrates such as some reptiles, amphibians, fish and in some kind of birds, new individuals are produced without fusion of gametes, this type of reproduction is called parthenogenesis.

Complete answer:
Parthenogenesis is a type of asexual reproduction in which zygote develops without the fusion of female and male gametes (fertilization). The offspring produced are clones.
Parthenogenesis may be apomixis or automixis.
In apomixis parthenogenesis, egg cells are produced through mitosis and they develop directly into embryos. The new individuals produced are genetically similar to the mother. Whereas, in automixis parthenogenesis, the gametes undergo meiosis and are haploid. The haploid egg then transformed into the diploid cell by chromosome duplication or fusion with a polar body.
Parthenogenesis may be facultative parthenogenesis or obligate parthenogenesis.
In facultative parthenogenesis, the female reproduces either sexually or asexually. For example, Mayflies undergo parthenogenesis in absence of fertile males in the habitat. But in obligate parthenogenesis, the organism reproduce only by asexual means. For example some species of reptiles such as lizards are capable of obligate parthenogenesis.
Parthenogenesis can be introduced artificially in some animals by the use of various chemicals such as urea chloroform, sucrose and physical agents such as temperature, ultraviolet light, electrical shocks cause parthenogenesis.
There are several significance of parthenogenesis:
It is the simplest and easy process of reproduction.
It is an adaptation which allows organisms to reproduce when sexual reproduction is not possible due to environmental conditions.
It helps in the development of advantageous mutant characters

Note: Parthenogenesis is an adaptive strategy of adaptation which allows organisms to reproduce at the time when sexual reproduction cannot take place in the natural environmental conditions.