Major Differences Between Oviparous and Viviparous Animals: A Brief Overview
During reproduction, the sperm and egg fuse together to create the zygote. This process is known as fertilisation. It is of two types – external and internal fertilisation. External fertilisation mainly takes place in an aquatic environment.
Here, male and female members release their egg and sperm in the same area at the same time, and external environment fuel the fertilisation process. In case of internal fertilisation, seen usually in terrestrial animals, sperms are releases within the female body where it fuses with the egg. Based on internal fertilisation, organisms can be categorised into oviparous and viviparous.
In the sections below, we will discuss viviparous and oviparous animals along with differences.
Terrestrial organisms who lay eggs are called oviparous animals. The fertilisation process may take place internally or externally; however, embryonic development takes place in egg outside of the female’s body.
Some Features of Oviparous Animals are Given Below -
The eggshell acts as a protection for developing embryo from external world. Moreover, it acts as an incubator by regulating the inside temperature.
Usually, the fully developed embryo shares similar features with its parents. However, in some organisms, the characteristics of a fetus are different from that of adults. Consider the life cycle of a frog as an example. After hatching out of the egg, it is a tadpole. As it grows, it starts resembling an adult frog.
The chances of survival are meagre as an embryo is protected only by the eggshell and therefore very much exposed to predators and other external factors. Consequently, oviparous organisms lay many small eggs at a time to ensure successful survival.
Some oviparous organisms, however, lay large eggs in small numbers which have a hard-outer covering. It provides more protection to a developing embryo and ensures its survival until birth.
Examples of oviparous organisms include birds, reptiles, fish and amphibians etc.
The word viviparous has originated from Latin 'vivius' which means alive and 'parere' to bring forth. It refers to animals who give birth to alive young ones instead of eggs. Internal fertilisation takes place in both oviparous and viviparous animals. However, in viviparous animals, embryo development takes place within the female member of that species.
The Characteristics of Viviparous Animals are Given Below –
The embryo development within female takes weeks to months. For instance, in humans, the embryo takes around nine months to completely develop.
The female carries the embryo within her while it's still developing, which is why mammals have specially designed reproductive organs that have the ability to carry and support the development of the embryo within themselves. For instance, the fetus draws nutrition from its mother through a specially developed tissue called the plasma.
The offspring do not have the ability to feed itself after it is born. So, during the initial period, it drinks its mother's milk which contains essential nutrients. Accordingly, mammals have mammary glands that produce milk.
Unlike oviparous animals, viviparous animals do not produce a lot of young ones at the same time. It is because the chances of survival are high as embryo is fully protected inside mother's womb.
Examples of some terrestrial viviparous animals include humans, dogs, cats, tiger, lions, chimpanzee and so on. Some aquatic organisms are also viviparous; these include different species of sharks, dolphins, whales, sea otters and so on.
The table below shows main difference between Oviparous and viviparous animals. A quick glance through this table before examinations will help you revise the crucial points and definitions.
Difference Between Oviparous and Viviparous Animals