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Fertilization, which is regarded as the part of the life process, where the male gametes unite with the female gametes. This union leads to the formation of a structure called a zygote. The zygote further develops into a foetus. This whole process of fertilization can take place inside the female body, or outside the female body. The process of fertilization outside the female body is known as external fertilization, and the process of fertilization inside the female body is known as internal fertilization. Animals are categorized as Oviparous, viviparous, and ovoviviparous on the basis of external and internal fertilization.
Also Read: Internal Fertilization: Oviparity, Ovoviviparity, Viviparity
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Keywords: Viviparous, Oviparous, Ovoviviparous, Fertilization, external and internal fertilization
Viviparous Animals
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Viviparous animals are those who give birth to young ones. The term means ‘life-bearing’, or ‘to bring forth alive’. Viviparous animals are also termed viviparous. Since they do not hatch eggs, thus embryonic development takes place inside the female reproductive system. Only when the foetus is fully developed, then the baby is delivered from the mother’s body. Here, the embryo directly attains the additional nutrients from the mother. The attainment of direct nutrition from the mother is known as Matrotrophy. For example, animals like whales, human beings, cats, dolphins, dogs, cows, goats, tigers, etc are Viviparous animals.
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Metamorphosis in Viviparous Animals
Every organism undergoes a sequential chain of changes from its embryonic stage to adulthood. This process is called Metamorphosis. When the offspring grows into an adult, it may not look alike the parents but may have some features similar to the parents. For example, a caterpillar changes to pupa and then to an adult silkworm. So, it passes through a series of changes while becoming an adult. Similar development happens with frogs, butterflies, etc.
Oviparous Animals
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The initial process of fertilization takes place inside the mother’s reproductive system, for Oviparous Animals. The female produces eggs, which are not retained inside the mother’s body throughout the embryonic development period. When the zygote is formed and it develops into a foetus, and the foetus attains full maturity, the female parent hatches the eggs. As there is a large number of eggs hatched at a time, it is considered to be an evolutionary reproduction method. Here the embryo draws its nutritional supplements from the yolk material which lies inside the egg, and which is deposited by the mother’s reproductive system. This method is different from that of atrophic and is known as Lecithotrophic. The eggs are protected from predators by the eggshell. Most amphibians, birds, and reptiles give birth to their young ones through this process. Insects, arachnids, monotremes, and mollusks are also examples of oviparous animals.
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Ovoviviparous Animals
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The ovoviviparous animals are those who fertilize the egg internally and then hatch the egg inside the mothers’ body in the mother’s womb. The mother retains the egg in the oviduct for a certain time, until they are fully developed to be laid outside, and survive in the external environment. The ovoviviparous animals do not have any umbilical cord attached or any placental appendage with the mother for nutritional needs or gas exchange. The offspring gets the nutritional supplement from the egg yolk. Ovoviviparity is also known as Aplacental viviparity.
There exists a specific outlet in species like sharks and rays, for gas exchange with the baby in the womb. There are some species, for whom, the egg yolk in the egg sac gives a lesser amount of nutrition, and is thus often replaced with the uterine secretion like trophic eggs in the uterus.
The advantage for the Ovoviviparous animals is that the delaying of the process of giving birth to the young ones makes the baby more mature and developed to defend itself against the adversities in the wild. They learn to fulfil their needs without the help of their mother.
Difference between Viviparous, Oviparous, Ovoviviparous
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| Viviparous Animals | Oviparous Animals | Ovoviviparous Animals |
|---|---|---|
| Reproductive Strategy | ||
| Directly gives birth to young ones. They do not hatch eggs | They hatch eggs, and their eggs attain maturity after it is being hatched out from the body. | They hatch eggs inside the mother’s body. When the baby is mature enough, |
| Fertilization | ||
| They undergo internal fertilization. The development of the zygote takes within the mother’s body. | They may undergo external or internal fertilization. The zygote develops outside the female’s body. | They undergo internal fertilization, and until the baby is fully developed, the new-borns are not given birth. |
| Embryo Nourishment | ||
| The embryo receives nourishment from the mother directly. | The embryo receives all its nutrition from the yolk of the egg, which is Lecithotrophic. | The Embryo receives nutrition from the yolk of the egg sac. |
| Examples | ||
| Human beings, cat, dog | Reptile amphibian | Rays, Snakes |
Things to remember
- The animals’ species are categorized as Oviparous, viviparous, and ovoviviparous, on the basis of the fertilization process they follow
- Oviparous animals are those who hatch eggs and the eggs mature when laid out of the mother’s body. The embryo receives the nutrients from the yolk, this process is known as Lecithotrophic.
- Viviparous animals are those who give birth to their young ones directly. They do not hatch eggs. The embryo receives nutrients from the mother, this process is called matrotrophic.
- Ovoviviparous animals are those who hatch eggs inside the mother’s body. They receive nutrients from the yolk in the egg sac.
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Sample Questions
Ques. Who are Oviparous Animals?
Ans. Oviparous Animals are those whose fertilization may take place internally or externally of the mothers’ reproductive system. Their embryo receives nourishment from the yolk of the egg.
Ques. From where does the embryo of Ovoviviparous draw the nourishment?
Ans. The embryos of Ovoviviparous animals receive their nutrition from the yolk of the egg sac.
Ques. Give some examples of Oviparous Animals.
Ans. Reptiles, Amphibians, birds are examples of oviparous animals.
Ques. Which Group of Animals have a better survival chance?
Ans. Viviparous animals have a better survival chance because the embryo is protected and drives their nourishment from their mother directly.
Ques. Is Human Being Viviparous?
Ans. Yes, Human beings are viviparous as they directly give birth to their young ones. They did not hatch eggs.
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