Difference Between Oviparous and Viviparous Animals

Main Difference – Oviparous vs Viviparous Animals

Animals show different methods of production of young ones. Oviparous and viviparous are such two methods. The main difference between oviparous and viviparous animals is that oviparous animals do not undergo any embryonic development inside the mother whereas viviparous animals develop into a young animal inside the mother. This means oviparous animals lay eggs. These eggs develop and hatch into young individuals. In contrast, viviparous animals are born as live young individuals. Therefore, they do not lay eggs. Birds, reptiles, amphibians, most fish, insects, mollusks, arachnids, and monotremes are oviparous animals. Most mammals are viviparous animals.

Key Areas Covered

1. What are Oviparous Animals
      – Definition, Features, Examples
2. What are Viviparous Animals
      – Definition, Features, Examples
3. What are the Similarities Between Oviparous and Viviparous Animals
      – Outline of Common Features
4. What is the Difference Between Oviparous and Viviparous Animals
      – Comparison of Key Differences

Key Terms: Eggs, Embryo, External Fertilization, Internal Fertilization, Nests, Oviparous Animals, Reproduction, Viviparous Animals

What are Oviparous Animals

Oviparous animals refer to the animals that produce eggs; the maturation and hatching of young ones occur outside the female body. The fertilization of the egg may occur either internally or externally. Birds, reptiles, amphibians, most fish, insects, mollusks, arachnids, and monotremes are oviparous animals. Many birds, amphibians, reptiles and fish produce nests in order to protect their eggs. However, some sharks and snakes are oviparous animals whose eggs hatch inside the female body and live, young ones are expelled. A mute swan’s nest with eggs is shown in figure 1.

Figure 1: A Mute Swan’s Nest with Eggs

Oviparity can be considered as an evolutionary strategy of reproduction since a large number of eggs can be produced at a time. Each egg may serve as a gamete. Once fertilized, eggs develop into the embryo. Most of the eggs are small and fragile. But, some oviparous animals lay large eggs. Since small eggs are laid in large numbers, they can produce a large number of offspring as well. Moreover, a large egg may have a higher chance to survive. However, oviparous animals have to protect their eggs from predators. They have to sit on their eggs in order to keep them warm.

What are Viviparous Animals

Viviparous animals refer to the animals that give birth to developed live young individuals. These animals possess special organs which supply nutrients for the development of the embryo. This condition is referred to as matrotrophy. This means the embryo of the viviparous animals receives nutrients from the mother, rather than from the yolk. Some fish, amphibians, reptiles, and mammals show viviparity. But, birds do not show viviparity. Mammals also consist of mammary glands, which produce milk to feed the young ones. Humans are one of the examples of viviparous mammals. A human embryo inside the mother is shown in figure 2.

Figure 2: A Human Embryo

Typically, viviparous animals take a longer time to care for their young ones. Some young animals such as dolphins stay with their mother for years. Due to this caring of mothers, viviparous animals show a greater survival.

Similarities Between Oviparous and Viviparous Animals

• Both oviparous and viviparous are two methods of the production of young ones.
• Internal fertilization can occur in both oviparous and viviparous animals.

Difference Between Oviparous and Viviparous Animals

Definition

Oviparous Animals: Oviparous animals refer to the animals that produce eggs that mature and hatch after being expelled from the body.

Viviparous Animals: Viviparous animals refer to the animals that give birth to developed live young individuals.

Correspondence

Oviparous Animals: Oviparous animals lay either fertilized or unfertilized eggs.

Viviparous Animals: Viviparous animals give birth to young individuals.

Internal/External Fertilization

Oviparous Animals: Oviparous animals may undergo internal or external fertilization.

Viviparous Animals: Viviparous animals undergo internal fertilization.

Development of the Zygote

Oviparous Animals: The development of the zygote of oviparous animals occurs outside the female.

Viviparous Animals: The development of the zygote of viviparous animals occurs inside the female.

Nourishment of the Embryo

Oviparous Animals: The embryo of the oviparous animals receives nutrients from the yolk.

Viviparous Animals: The embryo of the viviparous animals receives nutrients from the mother.

Chances for Survival

Oviparous Animals: Since oviparous animals lay eggs on the environmental surfaces, the chances of survival are less.

Viviparous Animals: Since viviparous animals directly deliver young ones, the chances of survival are more.

Examples

Oviparous Animals: Birds, reptiles, amphibians, most fish, insects, mollusks, arachnids, and monotremes are oviparous animals.

Viviparous Animals: Most mammals are viviparous animals.

Conclusion

Oviparous and viviparous animals are two groups of animals that produce offspring differently. The main difference between oviparous and viviparous animals is the method of the development of the young ones. Oviparous animals such as birds lay fertilized or unfertilized eggs. The development of the embryo of oviparous animals occurs outside the female body. Viviparous animals such as humans develop the embryo inside the female body.

Reference:

1.“Oviparous – Definition and Examples.” Biology Dictionary, 28 Apr. 2017, Available here.
2.“Viviparity.” Viviparous, Animals, Eggs, and Egg – JRank Articles, Available here 

Image Courtesy:

1. “Cygnus olor, nests with eggs, Höckerschwan mit Nest 4” by Böhringer Friedrich – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Embryo week 9-10” by lunar caustic (CC BY-SA 2.0) via Flickr