Modes of Reproduction in Animals

In the animal kingdom, animals can reproduce in two different ways:

• Asexual reproduction: in asexual reproduction, identical offsprings originate from a single parent, which can occur in different ways. Hermaphroditic species fall into this group.
• Sexual reproduction: the other form of reproduction is sexual, which occurs through the copulation of the genetic material of two individuals. In sexual reproduction, fertilization can occur externally or internally. In the first case, we have as an example fish, amphibians and many invertebrates. The second case is typical of most reptiles, birds and mammals. For its part, the development of the zygote can also occur inside or outside the female, although the nutrition of the embryo can be dependent or independent of the mother.

Learn more in our article about types of animal reproduction. You can also watch the video below to learn more about sexual and asexual reproduction.

The mode of reproduction of each animal is established depending on where the development of the embryo occurs. This can occur inside or outside the body of the parent. The three different modes of reproduction are as follows:

• Oviparous animals
• Ovoviviparous animals
• Viviparous animals

Fertilization in oviparous animals can occur internally or externally to the body, but the development of the embryo will always take place outside the body of the female.

This is why the characteristics of the egg are essential for it to develop outside of their parent. Therefore, some oviparous produce dry eggs that are capable of resisting contact with the air, since they have a protective cover (shell), as is the case of birds and reptiles. The largest egg in this type of reproduction that we find today is that of the ostrich (Struthio camelus).

Other groups of oviparous, such as most fish, some reptiles, amphibians and insect, produce smaller eggs that are not calcified. In many cases this process occurs in an aquatic environment. Some oviparous animals leave their eggs once they are expelled, allowing their young to face the dangers of life alone. Others will take care of them until a certain age, by protecting them and even providing them with food once they're born.

Within the oviparous, we also find two primitive mammals that reproduce this way: the platypus (Ornithorhynchus anatinus) and the echidna, such as the species Tachyglossus aculeatus.

Examples of oviparous animals

Some examples of oviparous animals are:

• Birds: ostriches, chickens, ducks, geese, penguins, parrots, hummingbirds, storks.
• Fish: anchovies, piranhas, eels, salmon, tuna.
• Reptiles: snakes, lizards like the Komodo dragon, turtles, crocodiles.
• Insects: ants, bees, beetles, flies.
• Mollusks and crustaceans: snails, octopuses, crabs.
• Mammals: platypus and echidna.

Ovoviviparous is when animals are born from eggs, but fertilization is internal and embryonic growth also occurs within the parent.

The hatching of the egg can occur within the maternal organism, so that the birth of the offspring can come out directly from the parent's body or the egg can be expelled outside, opening immediately or shortly afterwards. As in the case of oviparous animals, the nutrition of the offspring depends on the egg, which is why it is essential in this regard.

This group is made up of several types of invertebrates, some fish, such as the white shark (Carcharodon carcharias), and certain reptiles, such as the Trioceros jacksonii chameleon species.

Examples of ovoviviparous animals

Some examples of ovoviviparous animals are:

• Reptiles: rattlesnake, some lizards.
• Amphibians: some species of salamanders.
• Fish: white shark, manta ray.
• Insects: certain species of flies.

Viviparous animals are those whose fertilization is internal and the embryo develops within the body of their parent. However, in this case, it is the parent that provides them with the nutrition and protection throughout the process.

Here we find almost all mammals, including bats. Marsupials are also viviparous. However, their reproductive system differs from the rest since the embryo is born without being fully developed and the process culminates in the marsupial bag. This is the case of the koala (Phascolarctos cinereus).

As in the previous classifications of animals according to their reproduction, there are exceptions. An example is the fat-tailed scorpion (Androctonus crassicauda).

Examples of viviparous animals

Some examples of viviparous animals are:

• Mammals: all except the platypus and echidna.
• Fish: some sharks, such as hammerhead.
• Reptiles: some snakes, such as boas and certain lizards.
• Amphibians: some species of salamanders.

The classification of animals according to their reproduction is a complex process, since, as we have seen in this article, there are always exceptions within the animal kingdom. Therefore, absolute categorizations cannot be established to define each group as oviparous, ovoviviparous or viviparous. There are always exceptions.

For example, did you know that it is actually the father seahorse that carries the young after fertilization? Once the egg is fertilized, the mother's job is done and she swims away. In this case, it's the father who carries and cares for their young until they are old enough to survive on their own. To learn more, read our article about the 10 best animal dads.

If you want to read similar articles to Modes of Reproduction in Animals, we recommend you visit our Facts about the animal kingdom category.