Phases of fertilization

Reproduction is one of the most important functions carried out by living beings throughout their lives, being necessary for species to survive in the world, and none of them become extinct. Reproduction can be of different types, one of them being sexual, consisting of a process where the call is very important. fertilization. For all this, in this lesson from a PROFESSOR we are going to offer you a summary of the stages of fertilization.

Fertilization is a reproductive process in which two gametes, one male and one female, merge during the sexual act, achieving, thanks to this union, the formation of a new being, which will have the fused genome of both parents, being a single being.

Fertilization may vary to a lesser or greater extent depending on the kind of living being, being very different for example between animals and plants, although it can also vary within groups of living beings, the fertilization of a viviparous animal and that of a oviparous animal.

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Fertilization varies with each species, there are truly unique methods, but there are a number of phases that are common in all living beings that carry out fertilization. These phases are as follows:

1. The contact between sperm and egg in which they are recognized, that is, between the sex cells of the male parent and the female parent. This phase is relevant to be sure that the cells of both parents are of the same species.
2. Contact regulation between both cells, since only a male gamete must be the one that fertilizes a single female gamete. Therefore, the ovum only allows the entry of one, closing itself so that no more enter.
3. The genome of both parents is fused, This is something very important, because thanks to this fusion a new genetic code is created, totally new, unlike, for example, asexual reproduction, where the genetic code is identical to that of the parent.
4. Formation of the zygote, that is, the result of the union of the female and male gametes, and the beginning of its development.

To continue with this lesson on phases of fertilizationWe must talk about the different types of fertilization that exist, since although all fertilizations have similarities, there are some types with unique characteristics. Some of these types of fertilization are the following:

Cross fertilization

It is what happens when the encounter between the female and male gametes takes place in different individuals, and can even fertilize each other. In this type of fertilization the reproductive organs they are far from each other, there is no contact. Some examples are plants that reproduce using pollen from a distant plant, or some kinds of fish that shed their sex cells in water.

Selfing

It is the type of fertilization that happens when both gametes come from the same individual, so it could be said that the individual fertilizes himself. An example of this type of reproduction is animals hermaphrodites or flowering plants that do not open. In some cases, living beings can mix self-fertilization and cross-fertilization, angiosperm plants being a clear example. It is also known as asexual reproduction.

Internal fertilization

The male gametes are introduced into the mother through the sexual organs, reaching the place where the female gametes are found and initiating fertilization. Therefore we can say that internal fertilization is one in which the union of sex cells occurs inside the mother. This kind of fertilization can be of different kinds:

• Viviparous: Internal fertilization in which there is a development of the embryo within the mother. Characteristic of most mammals.
• Oviparous: Internal fertilization in which there is an external development of the embryo that lives inside an egg. Characteristic of many invertebrates, birds, and some reptiles and mammals.
• Ovoviviparous: Internal fertilization in which development is incomplete when leaving the mother's body.

External fertilization

It is a type of fertilization that takes place outside the mother's body, generally in the water, where the sexual cells are expelled to the outside. Generally, the mother lays her eggs under water, and the male deposits his sperm in them. This type of fertilization is characteristic of fish, although it can also be carried out by some species of amphibians.