Viviparity

Viviparity is a form of reproduction found in most mammals and in several other species. Viviparous animals give birth to living young that have been nourished in close contact with their mothers’ bodies. Humans, dogs, and cats are viviparous animals. Viviparous animals differ from egg-laying animals, such as birds and most reptiles. Egg-laying, or oviparous, animals obtain all nourishment as they develop from the yolk and the protein-rich albumen, or “white,” in the egg itself, not from direct contact with the mother, as is the case with viviparous young.

The offspring of both viviparous and oviparous animals develop from fertilized eggs, but the eggs of viviparous animals lack a hard outer covering or shell like the chicken egg. Viviparous young grow in the adult female until they are able to survive on their own outside her body. In many cases, the developing fetuses of viviparous animals are connected to a placenta in the mother’s body. The placenta is a special membranous organ with a rich blood supply that lines the uterus in pregnant mammals. It provides nourishment to the fetus through a supply line called an umbilical cord. The time between fertilization and birth of viviparous animals is called the gestation period.

All mammals except the platypus and the echidnas are viviparous. Only these two unusual mammals, called montremes, lay eggs. Some snakes, such as the Garter snake, are viviparous. So are some lizards and even a few insects. Ocean perch, some sharks, and a few popular aquarium fish, guppies, and mollies are also viviparous.

Although certain snakes give birth to live young, they are not viviparous. These snakes hatch from eggs which never leave the body of the parent snake. Because these young snakes hatch from eggs, and do not receive nourishment directly from the mother’s body, this type of reproduction is called ovoviviparity. It is considered a more primitive form of reproduction than viviparity.

Even some plants, such as the mangrove and the tiger lily, are described as viviparous because they produce seeds that germinate, or sprout, before they become detached from the parent plant.

See also Embryo and embryonic development.

Viviparity

Viviparity is a form of reproduction found in most mammals and in several other species . Viviparous animals give birth to living young that have been nourished in close contact with their mothers' bodies. Humans, dogs, and cats are viviparous animals. Viviparous animals differ from egg-laying animals, such as birds and most reptiles . Egg-laying, or oviparous , animals obtain all nourishment as they develop from the yolk and the protein-rich albumen, or "white," in the egg itself, not from direct contact with the mother, as is the case with viviparous young.

The offspring of both viviparous and oviparous animals develop from fertilized eggs, but the eggs of viviparous animals lack a hard outer covering or shell like the chicken egg. Viviparous young grow in the adult female until they are able to survive on their own outside her body. In many cases, the developing fetuses of viviparous animals are connected to a placenta in the mother's body. The placenta is a special membranous organ with a rich blood supply that lines the uterus in pregnant mammals. It provides nourishment to the fetus through a supply line called an umbilical cord. The time between fertilization and birth of viviparous animals is called the gestation period.

All mammals except the platypus and the echidnas are viviparous. Only these two unusual mammals, called montremes, lay eggs. Some snakes , such as the Garter snake, are viviparous. So are some lizards and even a few insects . Ocean perch , some sharks , and a few popular aquarium fish , guppies, and mollies are also viviparous.

Although certain snakes give birth to live young, they are not viviparous. These snakes hatch from eggs which never leave the body of the parent snake. Because these young snakes hatch from eggs, and do not receive nourishment directly from the mother's body, this type of reproduction is called ovoviviparity. It is considered a more primitive form of reproduction than viviparity.

Even some plants, such as the mangrove and the tiger lily, are described as viviparous because they produce seeds that germinate, or sprout, before they become detached from the parent plant .

See also Embryo and embryonic development.

vi·vip·a·rous / vīˈvip(ə)rəs; vi-/ • adj. Zool. (of an animal) bringing forth live young that have developed inside the body of the parent. Compare with oviparous and ovoviviparous. ∎  Bot. (of a plant) reproducing from buds that form plantlets while still attached to the parent plant, or from seeds that germinate within the fruit.DERIVATIVES: viv·i·par·i·ty / ˌvivəˈparitē; ˌvīvə-/ n.vi·vip·a·rous·ly adv.

viviparity
1. (in zoology) A form of reproduction in animals in which the developing embryo obtains its nourishment directly from the mother via a placenta or by other means. Viviparity occurs in some insects and other arthropods, in certain fishes, amphibians, and reptiles, and in the majority of mammals. Compare oviparity; ovoviviparity.

2. (in botany)
a. A form of asexual reproduction in certain plants, such as the onion, in which the flower develops into a budlike structure that forms a new plant when detached from the parent.

b. The development of young plants on the inflorescence of the parent plant, as seen in certain grasses and the spider plant.

viviparous Applied to:
a. a plant (e.g. mangroves) whose seeds germinate within and obtain nourishment from the fruit; or

b. a plant (e.g. some grasses) that reproduces vegetatively from shoots rather than an inflorescence.