How animals reproduce

1

We will start by talking about sexual reproductions, that is, that type of reproduction in which a female is required to be fertilized by the male’s sperm in order to become pregnant. Within this type of reproduction, there are animals that practice the internal fertilization (as would be, for example, the case of people) or the external fertilization; here we tell you the differences:

• Internal fertilization: the sperm fertilizes the ovum when the male is inside the female’s body. Mammals, birds, insects and reptiles are the ones that carry out this type of fertilization; just like humans. The operation of this process consists of the male putting sperm into the egg to cause the embryo to become pregnant.

• External fertilization: this occurs when the entry of the sperm into the ovum takes place outside the female’s body; This occurs especially in marine animals such as fish and amphibians. The procedure is that the female puts different eggs in the water and it is the male who spreads his sperm over them until they become fertilized.

2

The animals that practice sexual reproduction can be differentiated according to whether they are viviparous animals or oviparous animals; this depends on how they have gestate the embryo since there are some who do it internally, that is, inside the mother’s belly the fetus develops (as in the case of people) and others who develop externally, in eggs.

Here are the differences:

• Viviparous animals: those that give birth to their young via are known as viviparous. They are the animals that form the embryo within the mother’s body and the fetus is fed by the umbilical cord that provides the food that the female takes. These animals are the mammals that are the ones that have their young with the natural process of childbirth and the duration of pregnancy as well as the number of young can be completely variable.

• Oviparous animals: apart from mammals, most animals carry out gestation external to the mother’s body, hatchling develops inside an egg that contain the embryo and different layers that protect the young. It is when animals break the shell that we can speak of the “birth” of these animals; As soon as they leave, it may happen that they are independent enough to go to live on their own without the help of the mother (for example, it is the case of fish or reptiles) or that, on the contrary, they need the care of their mother until they get a little bigger (as is the case with birds).

3

Depending on how the hatchlings come out From their respective places of fertilization (the mother’s belly or the eggs), animals can also be divided into different types according to their development, whether direct or indirect. This simply refers to whether or not the animals resemble their adult form, that is, if when they are born they seem the same as their mothers.

• Direct development: It is when newborns look like their parents as soon as they are born; that is to say, it shows that they are the same animal but, simply, that they are smaller. This is the case with humans, mammals, and some birds.

• Indirect development: This occurs when the calf that appears is very different in appearance from its mother. This is the case, for example, of frogs that when they are born are tadpoles, something like little fish and that later become frogs.

4

The asexual reproduction It is the one that does not need two members of the same species, but an animal can bring living beings into the world without the need to be fertilized by someone outside. The main characteristic of this type of reproduction is that genetics are not modified because there are not two channels but only one. There are several types of asexual reproductions:

• Bipartition: they are unicellular beings that are split in two to create a new living being.

• Gemmation: in a living being a lump appears spontaneously that causes a new being to appear. This is the case, for example, of marine sponges.

• Fragmentation: from a fragment of a living being another is created; for example, the arm of a starfish can produce the appearance of a new star.

5

Inside of asexual reproduction There are two phenomena that take place on Earth and that should be mentioned in a separate case because they are different modes of animal reproduction in which they do not need a second member to be able to have offspring:

• Hermaphroditism: this type of animal contains in itself the two sexes, the female and the male, so that they alone can generate an embryo without the need for any other member. This is the case, for example, of snails.

• Parthenogenesis: It consists in that an embryo develops from a part of the body without the need for it to be fertilized. This type of reproduction occurs mainly in arthropods (ants, spiders, etc.) although they also take place in fish or reptiles. The offspring they have is exactly the same as their genetic component because they do not have the intervention of any other organism.

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Advice

• You can find detailed information on the net about a specific type of reproduction.
• There are many reproduction books for sale that can help you.