Question

What are oviparous and viviparous animals?

Answer 1

Hint: Animals follow different modes of reproduction in which their offspring either undergoes embryonic changes inside a mother or it doesn't experience any changes. Due to this, animals can be either oviparous or viviparous.

Complete answer:
- Certain animals lay eggs to produce an offspring. This means that the offspring does not undergo any embryonic development inside the mother. They are known as oviparous animals.

- The eggs laid (by a female) by oviparous animals can be either fertilized (it has the capability of developing into a new individual) or unfertilized (it cannot develop into a new individual).

- The eggs produced by the oviparous animals are surrounded by an outer hard covering known as shell which protects the embryo.

- As oviparous animals lay eggs, the development of the embryo takes place outside the female’s body. The embryo develops inside the yolk of the egg, which is rich in fat and provides nourishment to the embryo.

- As the female lays eggs in an open environment, the chances of survival of young ones are less.

- A biologist named Thierry Lode divided oviparous reproduction into two parts. They were,

- Oviparity which involves external fertilization, that is, the oocytes present in the egg released by a female remains unfertilized unless a male fertilizes it, outside the body. It is seen in Mollusca (for instance, octopus), Echinodermata (for instance, sea urchins), etc.

- Oviparity which involves internal fertilization. In this, the male inserts the sperm inside a female, or the female takes up the sperm released by a male and produces an egg that contains a zygote. Oviparity is seen in the platypus, birds, some reptiles and fish, etc.

- Certain animals undergo embryonic development inside a mother’s womb. They are known as viviparous animals. They do not lay eggs rather they give birth to live young individuals.

- The eggs of a viviparous female lack a protective outer covering.

- In viviparous animals, the development of the embryo takes place inside the female’s body.

- The nourishment of the growing embryo is provided by the mother through the placenta.

- As the eggs are produced inside a mother’s body, the chances of survival of young one's increase.

Viviparous reproduction is divided into four parts. They are,
- Histotrophic viviparity: It involves the development of zygote inside the oviducts (it is the passage through which an ovum passes from the ovary to the uterine cavity. It is also known as a fallopian tube) of the female. This zygote draws nourishment from the other eggs which are produced by the ovary. For example, shark

- Hemotrophic viviparity: In this type, the growing embryo receives its nourishment from the mother through some form of the placenta. For example, frogs (the embryos draw nourishment through specialized gills).

- Placental viviparity: In this, the growing embryo receives its nourishment from the mother through the placenta. For example, human beings.

- Ovoviviparity: In this, the embryos develop inside the eggs which are present inside a mother’s body until they are ready to hatch and after that, they remain inside the mother’s body where they are nourished and then the females give birth to the young ones. For example, Some species of snakes, etc.

Note: Reproduction is the fundamental feature of life and each organism exists due to it. Animals show different modes of reproduction and depending on that mode of reproduction, that is, they either undergo embryonic changes inside a mother or they don't experience any change. This majorly affects their chances of survival.