In nature we can observe several reproductive strategies and one of them is oviparity. You should know that there are many animals that follow this same strategy, which appeared much earlier in evolutionary history than viviparous animals.
If you want to know what are oviparous animals, what this reproductive strategy consists of and some examples of oviparous animals, keep reading this article from our site. You will solve all your doubts and you will learn incredible things!
What are oviparous animals?
The definition of oviparous animals is very simple, since they are those that lay eggs and hatchonce the mother has expelled them from her body. Fertilization can be external or internal, but hatching always occurs in the external environment, never in the mother's womb.
The fish, amphibians, reptiles, and birds, including the occasional mammal, are oviparous. They usually lay their eggs in well-protected nests, where the embryo will develop inside the egg and then hatch. Some animals are ovoviviparous, that is, they incubate the eggs inside the body instead of in a nest, and the young are born alive directly from the body of the mother. We can see this in some types of sharks and snakes.
Being oviparous is an evolutionary strategy for reproduction. They can produce one or many eggs Each egg is a gamete made up of genetic material from the female (ovum) and genetic material from the male (sperm). The spermatozoa must find their way to the ovule, either in an internal environment (the female's body) when fertilization is internal, or in an external environment (for example, the aquatic environment) when fertilization is external.
Once the egg and sperm meet, we say that the egg has been fertilized and gives rise to an embryo that will develop inside the eggMany animals produce many but very fragile eggs. This has the advantage that, by producing so many offspring, it will be more likely that at least one will survive predators. Other animals produce very few but very large and strong eggs, this increases the probability that the development of the new individual will reach the end and hatch, giving rise to a very strong new individual, having more possibilities of escaping from predators once they are born..
Being oviparous has its drawbacks too. Unlike viviparous and ovoviviparous animals that carry their developing young inside them, oviparous animals must protect or conceal their eggs during their development, in structures called nests. Birds often sit on their eggs to keep them warm. In the case of animals that do not actively protect their nests, there is always the possibility that a predator will stumble upon it and devour it, so it is very important to select the place correctly and hide the eggs very well.
Differences between oviparous and viviparous animals
The main difference between oviparous and viviparous animals is that oviparous animals do not develop inside the mother, while Viviparous animals undergo all kinds of changes inside their mother. So oviparous animals lay eggs that develop and hatch into young individuals. While viviparous animals are born as live young individuals and do not lay eggs.
Birds, reptiles, amphibians, most fish, insects, molluscs, arachnids, and monotremes (mammals with reptilian characteristics) are oviparous animals. Most mammals are viviparous animals. For the avoidance of doubt, we show a list of characteristics that differentiate oviparous from viviparous animals:
Oviparous animals:
- Oviparous animals produce eggs that mature and hatch once they are expelled from the mother's body.
- Eggs can be laid fertilized or unfertilized.
- Fertilization can be external or internal.
- The development of the embryo takes place outside the female.
- The embryo receives nutrients from the egg yolk.
- The probability of survival is lower.
Viviparous Animals:
- Viviparous animals give birth to live, fully developed young animals.
- They don't lay eggs.
- Fertilization of the ovum is always internal.
- The development of the embryo occurs inside the mother.
- The embryo receives nutrients from the mother.
- The probability of survival is higher.
What are oviparous animals? - Examples
There are many types of animals that lay eggs, here are some of them:
- Birds: some birds lay only one or two eggs fertilized, while others lay many. Generally, birds that lay one or two eggs, such as cranes, do not survive long in the wild. These birds spend a lot of time caring for their young to help them survive. On the other hand, birds that lay many eggs, like the coot, have a higher survival rate, and don't need to stay as long with their young. As an example, we leave you this article on The reproduction of chickens.
- Amphibians and reptiles: Frogs, newts, and salamanders are all amphibians, living in and out of water, but they need it to keep them moist, and they also lay their eggs in it, since these eggs don't have a shell and they would dry out quickly in the air. Reptiles, such as lizards, crocodiles, lizards, turtles, and snakes, can live on land or in water and whether they lay eggs in or out of it depends on the species. Since they don't usually take care of their clutches, they lay many eggs so that the survival rate increases.
- Fish: all fish lay their eggs in the waterFemale fish release their eggs into the environment freely, place them on aquatic plants or throw them into a small dug hole. The male fish then releases the sperm onto the eggs. Some fish, such as cichlids, keep the eggs in their mouths after fertilization to protect them from predators. For more information, see How do fish reproduce?
- Arthropods: Most of the arachnids, myriapods, hexapods and crustaceans that make up the group of arthropods are oviparous. Spiders, centipedes, crabs or butterflies are some of the millions of arthropods that lay eggs, and lay hundreds of them Some lay eggs that were fertilized by internal fertilization and others, lay non-fertile eggs that will need to be externally fertilized, while others lay unfertilized eggs that still require sperm. Here you can see, for example, how spiders reproduce.
Examples of oviparous mammals
It is very rare for mammals to lay eggs. Only a small group called monotremes do. This group includes platypuses and echidnas We can only find them in Australia and some parts of Africa. These creatures lay eggs, but unlike other oviparous animals, monotremes feed their young with milk and also have hair.
