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Viviparous Oviparous Embryo Development

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Fertilization in the animal kingdom is classified as external and internal fertilization.

External fertilization is a process in which the fusion of sperm and egg takes place outside the female body.

Embryo development, in the case of external fertilization, takes place in an external environment.

Internal fertilization is a process in which the fusion of sperm and egg takes place inside the female body, while embryo development may take place outside or inside the environment.

Based on embryo development in internally fertilized animals, they are classified into oviparous and viviparous animals.

Refer to the official website of Vedantu or download the app for an elaborate and easy explanation.

Oviparous and Viviparous Animals

Oviparous animals don't give birth to their off-springs directly. The development of an embryo takes place outside the female body. 

That is internal or external fertilization but external embryonic development in these animals.

All egg-laying animals/mammals are oviparous animals, and this feature is called oviparity.

The yolk present provides all nutrients to the off-springs in an egg.

Eggshells are made up of calcium carbonate.

Some animals’ eggs are fragile (Reptiles), and some develop hard shells (Birds).

Eggs are vulnerable to predators.

In oviparous animals, like fish, fertilization occurs in floating water, where the female and male gametes meet. Then the metamorphosis takes place.

Example: All birds are egg-laying, egg-laying mammals are Echidna and Platypus, reptiles, amphibians, fishes. 

Viviparous animals are the ones that give birth to their off-springs directly. Embryonic development takes place inside the female body, and this feature is called viviparity.

Viviparity comes from a Latin word viviparous in which vivus means living, and patio means to give birth to.

In viviparous animals, both fertilization and embryonic development are internal.

Since the development of an embryo is internal, young ones are protected.

Example: All mammals (Cow, Humans, dogs, etc.). 

They feed their young ones.


The young ones take nutrients directly from the mother but not the yolk.

If the zygote develops in oviducts, then it is known as phototrophic viviparity.

If the nutrients are provided by the placenta, then it is known as chemotrophic viviparity.

Placental viviparity is the advanced embryo development of animals. It is seen in humans. Embryonic development takes place in the uterus; all nutrients required for the embryo are provided through the umbilical cord.

Reproductive modes in viviparous animals vary in two basic traits: those are, i) stages of development at which the young ones are born. ii) the mode at which the foetus receives nutritional energy for its further development.

Viviparous females have a larger body size, reproductive investment, and high hatching success rate than oviparous animals.

Sex does not determine whether the animals are viviparous or oviparous.

In some reptiles, sex is determined by the temperature, in some snakes, and in most of the reptiles, genotype sex determination is present.

Metamorphosis in Oviparous and Viviparous Animals

There are two types of embryonic development, direct and indirect development:

Direct development: Direct development of the young ones thus resembling the adult. E.g., Hen, monkey, cow, human.

In indirect development, the young ones don't resemble adults. Eg. Silkworm, frog, butterfly.

Metamorphosis is a process in which young ones transform into an adult.

Example: Larva transformation into a butterfly. Tadpole to the frog.

Metamorphosis of a Frog

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The frog has four stages during metamorphosis, they are:

  1. Egg-laying, the egg masses are laid in a pond.

  2. Hatching a tadpole from eggs in the pond.

  3. Froglets formation from tadpoles. Legs form and the body shrinks.

  4. The development of lungs and back legs takes place.

  5. Tail shrinks, the frog is developed.

Metamorphosis in Butterfly

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Butterfly metamorphosis is the process of transformation of the egg into an adult butterfly.

It has four main steps:

  1. Egg: 

Female adult butterflies lay eggs on plants, which later becomes food for caterpillars. 

  1. Caterpillar: 

This is the second stage of metamorphosis, also called a larval stage. During its development, it sheds skin about four to five times.

  1. Pupa: 

This is the third stage of metamorphosis, the transition stage. The butterflies' pupas are called  chrysalis. This stage is long and can range from a few weeks to years.

  1. Adult: 

It is the last stage where the butterfly is fully developed. It is also called the reproductive stage in the butterfly life cycle.


Animals wherein the embryos develop in the eggs and remain in the body of the mother until they are capable of hatching. This mode of reproduction is the same as viviparity, but the only difference is the connection to the placenta of the mother and receiving nourishment. Yolk sac supplies are replaced with secretions from the uterus in some of the species.

Ovoviviparous Animals

The species of animals that exhibit ovoviviparity come under the classification of ovoviviparous animals. The animals, including some species of fish like manta rays, some amphibians like Surinam toad, and reptiles such as garter snakes are ovoviviparous. By making a delay in birth even after hatching, the young ones become capable of defending and feeding themselves during the time they take birth. The number of offspring that the ovoviviparous mother gives birth to simultaneously is dependent on the species. Some species give birth to two or three, while others like a guppy give birth to around 200 babies at once in the stretch of a few hours.

Embryo Development 

Oxygen is not provided for the developing eggs of Ovoviviparous insects, however, a brooding chamber is. In the case of lizards, fish and snakes, oxygen is provided along with nutrition to the progeny in the oviduct. Most nutrition is provided by the yolk that is present in the eggs. The eggshell has a lesser thickness and is reduced in size due to a membrane. Internal fertilization is also a term used in the case of ovoviviparous animals referring to fusion if gametes are within the body of the female, then incubation to the eggs is provided within the oviduct. After the eggs are ready to hatch, the female gives birth to young ones, and they start moving independently and are capable of defending themselves. In some species, the young ones are at the larval stage when they are born, and later metamorphosis happens.

Difference Between Oviparous, Viviparous, and Ovoviviparous Animals








Egg-laying animals

Give birth to young ones

The egg develops inside the female body



External fertilization

Internal or external fertilization

Internal fertilization


Embryo development

Indirect development

Direct development

Direct development



Amphibians, birds, reptiles, fishes.

Humans, cows, dogs, cats, etc.

Snakes, insects and some sharks,


  • Oviparous animals are the ones who lay eggs and do not give birth to their off-springs directly.

  • Oviparous animals are birds, reptiles, amphibians, etc.

  • Viviparous animals are the ones that give live birth and do not lay eggs.

  • Viviparous animals are humans, cats, dogs, etc.

  • Echidna and Platypus are two egg-laying mammals.

  • Ovoviviparous animals are those wherein the embryos develop in the eggs and remain in the body of the mother until they are capable of hatching.

  • In ovoviviparous animals, embryonic development takes place in female oviducts.

  • Some examples of ovoviviparous are manta rays, Surinam toad, garter snakes, etc.  

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FAQs on Viviparous Oviparous Embryo Development

1. How can I score good marks in Class 12 board exams?

Each student aspires to score a good grade in board exams as one should. Boards exams are an important step in your career journey and hold your way forward in the correct path. Students can achieve their desired marks in Class 12 if they work hard and diligently. Students can follow a few simple tips to achieve a good grade which is mentioned below:

  • Read thoroughly: Nothing is as important as reading the chapter thoroughly and with your entire focus. Reading through a chapter helps with the chronology of the topics and also helps in answering one-mark questions.

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Class 12 Biology is far more interesting than the common notion of it being a boring subject. Class 12 Biology includes topics about the human body and its functions in depth. Students will find it interesting as they will get to know what happens inside the human body. Students might find a few topics hard to understand at first but as they will read and understand a few times they will get comfortable with the subject. Over the years, students have scored excellent grades in Class 12. If students get the right guidance and have a passion and interest in the subject then will have no difficulty in studying it. Vedantu provides a detailed comprehensive explanation to help the students with the subject, check out the website or download the app and attain the information for free.

3. What should a timetable for a Class 12 student include?

The timetable is a necessity for students of Class 12 as they can afford no time to spare. A timetable for Class 12 should be such that it utilizes every second of their time and helps them achieve their desired results. 

The following things should be kept in mind while designing the timetable:

  • The timetable must be practical: The practicality of the timetable is very important because if the timetable is not practical enough to be followed by the students then its sole purpose is destroyed. 

  • Regular breaks: The timetable should include the break time as well. Not including break time can either extend your breaks for 2 hours or extend your working hours. If the breaks are extended, students will find less time to cover the syllabus and if the working hours are extended then students might get frustrated easily. Each student session should be no more than 40 minutes as studies have shown that a human brain cannot focus on something for more than 40 minutes at a stretch.

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The NCERT books are the bible for students that are going to appear for board exams. I observed over the years that most of the questions asked in board exams are from the NCERT book itself. These questions either come from the book exercise at the end of each chapter, book examples, activities mentioned in the book, or from in between the chapters. Hence, if students give their 100 percent in learning and revising the NCERT they can secure good marks in Class 12.

5. What do you understand by the term viviparous?

Viviparous term is used for those animals in the Animalia kingdom that give birth to their offspring. In an animal that belongs to the viviparous group, fertilization, and development of the embryo take place inside the female reproductive system. For example dogs, cats, human beings, elephants, etc. The mother delivers the baby once the development of the baby is complete.