General characteristics of the viviparousAs a general trend, the offspring of the vipiraros embryo develops within the womb, specifically in the placenta. The placenta is the tissue that protects the fetus and is a membrane that allows all basic vital exchanges for fetal development (food, transportation of oxygen and breathing). In some cases, hatchlings are developed outside of the placenta, as it is the case with the marsupials (hatchlings continue its evolution in the marsupial pouch after the birth).
Biologists believe that the viviparism can be explained in relation to the evolution of the species. In this sense, the viviparism appeared as a mechanism for the protection of calves: being within the mother, were not exposed to the dangers of predatory animals.
Viviparous animals share similar mechanisms in the reproduction. In this way, after fertilization forms the embryo, which remains in the aforementioned structure, the placenta. With regard to pregnancy and the formation of the new be each species has its own processes. When breeding reaches the moment of ripening it is expelled through the vaginal canal of the female.
Special featuresWhile the viviparism is usually associated with mammals, we must remember that there are also viviparous plants. This strange phenomenon has an explanation, since these plants seeds germinate when they are still subject to the plant stem. The case of viviparous plants is exceptional in nature and, indeed, naturalists consider that these plants are doomed to disappear.
In relation to fish, some species are ovoviviparous, meaning that they are born from eggs, but these remain within the body and at the time of birth the young are already independent.
Article contributed by the team of collaborators.